TY - JOUR TI - Molybdenum disulfide and water interaction parameters AU - Heiranian, M. AU - Wu, Y. AU - Aluru, N.R. T2 - Journal of Chemical Physics AB - Understanding the interaction between water and molybdenum disulfide (MoS2) is of crucial importance to investigate the physics of various applications involving MoS2 and water interfaces. An accurate force field is required to describe water and MoS2 interactions. In this work, water-MoS2 force field parameters are derived using the high-accuracy random phase approximation (RPA) method and validated by comparing to experiments. The parameters obtained from the RPA method result in water-MoS2 interface properties (solid-liquid work of adhesion) in good comparison to the experimental measurements. An accurate description of MoS2-water interaction will facilitate the study of MoS2 in applications such as DNA sequencing, sea water desalination, and power generation. DA - 2017/// PY - 2017/// DO - 10.1063/1.5001264 VL - 147 IS - 10 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85029438448&partnerID=MN8TOARS ER - TY - JOUR TI - Antibody Subclass Detection Using Graphene Nanopores AU - Barati Farimani, A. AU - Heiranian, M. AU - Min, K. AU - Aluru, N.R. T2 - Journal of Physical Chemistry Letters AB - Solid-state nanopores are promising for label-free protein detection. The large thickness, ranging from several tens of nanometers to micrometers and larger, of solid-state nanopores prohibits atomic-scale scanning or interrogation of proteins. Here, a single-atom thick graphene nanopore is shown to be highly capable of sensing and discriminating between different subclasses of IgG antibodies despite their minor and subtle variation in atomic structure. Extensive molecular dynamics (MD) simulations, rigorous statistical analysis with a total aggregate simulation time of 2.7 μs, supervised machine learning (ML), and classification techniques are employed to distinguish IgG2 from IgG3. The water flux and ionic current during IgG translocation reveal distinct clusters for IgG subclasses facilitating an additional recognition mechanism. In addition, the histogram of ionic current for each segment of IgG can provide high-resolution spatial detection. Our results show that nanoporous graphene can be used to detect and distinguish antibody subclasses with good accuracy. DA - 2017/// PY - 2017/// DO - 10.1021/acs.jpclett.7b00385 VL - 8 IS - 7 SP - 1670-1676 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85016962617&partnerID=MN8TOARS ER - TY - JOUR TI - Sustainable polymeric material for the facile and repetitive removal of oil-spills through the complementary use of both selective-absorption and active-filtration processes AU - Rather, A.M. AU - Jana, N. AU - Hazarika, P. AU - Manna, U. T2 - Journal of Materials Chemistry A AB - Superhydrophobic cotton (SHC) with exemplary physical and chemical durability is capable of removing repeatedly diverse types of oil contaminants, through both the selective absorption and gravity-driven active-filtration processes. DA - 2017/// PY - 2017/// DO - 10.1039/c7ta07982f VL - 5 IS - 44 SP - 23339-23348 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85034240678&partnerID=MN8TOARS ER - TY - JOUR TI - Exceptional control on physical properties of a polymeric material through alcoholic solvent-mediated environment-friendly Michael addition reaction AU - Rather, A.M. AU - Jana, N. AU - Begum, S. AU - Srivastava, H.K. AU - Manna, U. T2 - Green Chemistry AB - An eco-friendly approach to synthesize the polymeric materials with various controlled physical properties is explored in this work through appropriate selection of the reaction medium (i.e. alcoholic solvent). DA - 2017/// PY - 2017/// DO - 10.1039/c7gc02286g VL - 19 IS - 19 SP - 4527-4532 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85030712501&partnerID=MN8TOARS ER - TY - JOUR TI - A general and facile chemical avenue for the controlled and extreme regulation of water wettability in air and oil wettability under water AU - Parbat, D. AU - Gaffar, S. AU - Rather, A.M. AU - Gupta, A. AU - Manna, U. T2 - Chemical Science AB - The controlled modulation of both oil (under water) and water (in air) wettability is an emerging approach to develop several functional materials for various prospective applications including oil/water separation, anti-corrosive coatings, underwater robotics, protein crystallization, drug delivery, open microfluidics, water harvesting etc. Here, we report a 'reactive' and covalently cross-linked coating through a facile and robust Michael addition reaction, which is suitable for the controlled and extreme regulation of both water and oil wettability in air and under water respectively. Along with extremes (super-philicity and super-phobicity) of water (in air) and oil (under water) wettability, this single multilayer construction was also able to display special liquid wettability (i.e.; extremely liquid repellent-but with controlled adhesive properties) both in air and under water, after strategic post chemical modifications, again through 1,4-conjugate addition reaction. The super-wetting properties in the materials were able to withstand various physical and chemical insults including adhesive tape test, sand drop test, and exposure to extremes of pH, salt, and surfactant contaminated aqueous media. Moreover, this approach also allowed the decoration of various flexible and rigid substrates (i.e.; wood, Al-foil, synthetic fabric etc.) with various bio-inspired wettability properties including (1) non-adhesive superhydrophobicity (lotus leaf), (2) adhesive superhydrophobicity (rose petal), (3) underwater superoleophobicity (fish scale) etc. This single polymeric coating-which is capable of displaying several bio-inspired interfaces both in air and under water, even after harsh physical/chemical insults-would be useful in various prospective and relevant applications for practical scenarios. DA - 2017/// PY - 2017/// DO - 10.1039/c7sc02296d VL - 8 IS - 9 SP - 6542-6554 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85027891795&partnerID=MN8TOARS ER - TY - JOUR TI - 'Reactive' nano-complex coated medical cotton: A facile avenue for tailored release of small molecules AU - Rather, A.M. AU - Mahato, S. AU - Maji, K. AU - Gogoi, N. AU - Manna, U. T2 - Nanoscale AB - Here, the medical-cotton that coated with amine ‘reactive’ nanocomplex was exploited in tailoring the release rate (from 1 day to 100 days) of post-loaded small molecules through appropriate modulation of water wettability. DA - 2017/// PY - 2017/// DO - 10.1039/c7nr03990e VL - 9 IS - 42 SP - 16154-16165 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85032935077&partnerID=MN8TOARS ER - TY - JOUR TI - Stretchable and durable superhydrophobicity that acts both in air and under oil AU - Rather, A.M. AU - Manna, U. T2 - Journal of Materials Chemistry A AB - A facile and robust Michael addition reaction is strategically exploited here, to develop a highly stretchable (150% deformation) superhydrophobic material. This material strongly repels aqueous phase both in air and under oil and with impeccable physical/chemical durability, and is appropriate for rapid separation of both heavy and light oils from complex aqueous phases with above 99% efficiency. DA - 2017/// PY - 2017/// DO - 10.1039/c7ta04073c VL - 5 IS - 29 SP - 15208-15216 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85026221342&partnerID=MN8TOARS ER - TY - JOUR TI - Strategic Formulation of Graphene Oxide Sheets for Flexible Monoliths and Robust Polymeric Coatings Embedded with Durable Bioinspired Wettability † AU - Das, A. AU - Deka, J. AU - Rather, A.M. AU - Bhunia, B.K. AU - Saikia, P.P. AU - Mandal, B.B. AU - Raidongia, K. AU - Manna, U. T2 - ACS Applied Materials and Interfaces AB - Artificial bioinspired superhydrophobicity, which is generally developed through appropriate optimization of chemistry and hierarchical topography, is being recognized for its immense prospective applications related to environment and healthcare. Nevertheless, the weak interfacial interactions that are associated with the fabrication of such special interfaces often provide delicate biomimicked wettability, and the embedded antifouling property collapses on exposure to harsh and complex aqueous phases and also after regular physical deformations, including bending, creasing, etc. Eventually, such materials with potential antifouling property became less relevant for practical applications. Here, a facile, catalyst-free, and robust 1,4-conjugate addition reaction has been strategically exploited for appropriate covalent integration of modified graphene oxide to developing polymeric materials with (1) tunable mechanical properties and (2) durable antifouling property, which are capable of performing both in air and under oil. Furthermore, this approach provided a facile basis for (3) engineering a superhydrophobic monolith into arbitrary free-standing shapes and (4) decorating various flexible (metal, synthetic plastic, etc.) and rigid (glass, wood, etc.) substrates with thick and durable three-dimensional superhydrophobic coatings. The synthesized superhydrophobic monoliths and polymeric coatings with controlled mechanical properties are appropriate to withstand different physical insults, including twisting, creasing, and even physical erosion of the material, without compromising the embedded antiwetting property. The materials are also equally resistant to various harsh chemical environments, and the embedded antifouling property remained unperturbed even after continuous exposure to extremes of pH (pH 1 and pH 11), artificial sea water for a minimum of 30 days. These flexible and formable free-standing monoliths and stable polymeric coatings that are extremely water-repellent both in air and under oil, are of utmost importance owing to their suitability in practical circumstances and robust nature. DA - 2017/// PY - 2017/// DO - 10.1021/acsami.7b14028 VL - 9 IS - 48 SP - 42354-42365 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85037744278&partnerID=MN8TOARS ER - TY - JOUR TI - Unveiling the Role of CeO2 Atomic Layer Deposition Coatings on LiMn2O4 Cathode Materials: An Experimental and Theoretical Study AU - Sarkar, Susmita AU - Patel, Rajankumar L. AU - Liang, Xinhua AU - Park, Jonghyun T2 - ACS Applied Materials & Interfaces AB - An atomic layer deposition (ALD) coating on active materials of a lithium ion battery is a more effective strategy for improving battery performance than other coating technologies. However, substantial uncertainty still remains about the underlying physics and role of the ALD coating in improving battery performance. Although improvement in the stability and capacity of CeO2 thin film coated particles for batteries has been reported, a detailed and accurate description of the mechanism has not been provided. We have developed a multiphysics-based model that takes into consideration stress mechanics, diffusion of lithium ion, and dissolution of transition-metal ions of spinel LiMn2O4 cathode. The model analyzes how different coating thicknesses affect diffusion-induced stress generation and, ultimately, crack propagation. Experimentally measured diffusivity and dissolution rates were incorporated into the model to account for a trade-off between delayed transport and prevention of side reactions. Along with experimental results, density functional theory results are used to explain how a change in volume, due to dissolution of active material, can affect battery performance. The predicted behavior from the model is well-matched with experimental results obtained on coated and uncoated LiMn2O4–Li foil cells. The proposed approach and explanations will serve as important guidelines for thin film coating strategies for various battery materials. DA - 2017/9/13/ PY - 2017/9/13/ DO - 10.1021/acsami.7b06988 UR - http://dx.doi.org/10.1021/acsami.7b06988 ER - TY - CONF TI - Insect Residue Height for Different Conditions and Coatings AU - Carter, D. T2 - GEM Consortium Annual Board Meeting Technical Presentation Competition C2 - 2017/9/8/ C3 - GEM Consortium Annual Board Meeting Technical Presentation Competition DA - 2017/9/8/ PY - 2017/9/8/ ER - TY - CONF TI - High-speed schlieren and 10-Hz Kr PLIF for the new AFRL mach-6 Ludwieg tube hypersonic wind tunnel AU - Lam, K.-Y. AU - Pickles, J.D. AU - Narayanaswamy, V. AU - Carter, C.D. AU - Kimmel, R.L. C2 - 2017/// C3 - AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting DA - 2017/// DO - 10.2514/6.2017-0550 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85017211937&partnerID=MN8TOARS ER - TY - CONF TI - Sharp-fin induced shock wave/turbulent boundary layer interactions in an axisymmetric configuration AU - Pickles, J.D. AU - Mettu, B.R. AU - Subbareddy, P.K. AU - Narayanaswamy, V. C2 - 2017/// C3 - 47th AIAA Fluid Dynamics Conference, 2017 DA - 2017/// DO - 10.2514/6.2017-4314 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85081176764&partnerID=MN8TOARS ER - TY - CONF TI - Parametric study of forced ignition in laminar and turbulent methane jets AU - Ley, K. AU - Narayanaswamy, V. C2 - 2017/// C3 - 53rd AIAA/SAE/ASEE Joint Propulsion Conference, 2017 DA - 2017/// DO - 10.2514/6.2017-4770 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85088061673&partnerID=MN8TOARS ER - TY - CONF TI - Experimental investigation of shock boundary layer interactions in axisymmetric isolator geometries AU - Funderburk, M.L. AU - Narayanaswamy, V. C2 - 2017/// C3 - 53rd AIAA/SAE/ASEE Joint Propulsion Conference, 2017 DA - 2017/// DO - 10.2514/6.2017-5052 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85088202935&partnerID=MN8TOARS ER - TY - CONF TI - Numerical investigation of scoop effect on film cooling for cylindrical inclined hole AU - Ji, Y. AU - Singh, P. AU - Ekkad, S.V. AU - Zang, S. AB - Film cooling behavior of a single cylindrical hole inclined at an angle of 35° with respect to a flat surface is numerically predicted in this study. Adiabatic film cooling effectiveness has been presented to evaluate the influence of the scoop placed on the coolant entry side. The effect of blowing ratio (0.65, 1, 1.5 and 2) and the length-to-diameter ratio (1.7 and 4.4) are examined. Three-dimensional Reynolds-averaged Navier-Stokes analysis with SST turbulence model is used for the computations. It has been found that both centerline and laterally averaged adiabatic film cooling effectiveness are enhanced by the scoop and the enhancement increases with the blowing ratio in the investigated range of variables. The scoop was more effective for the higher length-to-diameter ratio cases (L/D = 4.4) because of better velocity distribution at the film hole exit, which makes coolant reattach at a more upstream location after blowing off from the wall. C2 - 2017/// C3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) DA - 2017/// DO - 10.1115/IMECE2017-70184 VL - 8 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85040975494&partnerID=MN8TOARS ER - TY - CONF TI - Numerical & experimental investigations for flow fields under non-reacting & reacting conditions through a lean premixed fuel nozzle AU - Kedukodi, S. AU - Park, S. AU - Gadiraju, S. AU - Ekkad, S. AU - Kim, Y. AU - Srinivasan, R. AB - Numerical methods coupled with experimental benchmarking approaches, are typically used as effective tools for solving engineering problems due to their significant time saving benefits. In this paper, the swirling flow through an industrial lean-premixed fuel nozzle as used in actual gas turbine combustors is numerically analyzed and compared with experimental observations. The analysis is performed under both non-reacting and reacting conditions for a specific Reynolds number. The reacting experiments were performed using compressed methane as the fuel and air as the oxidizer. A specific inlet Reynolds number flow was studied to understand the combustor flow field with an overall equivalence ratio of 0.65 and 6% pilot fuel. Steady state simulations were performed using Fluent solver using Realizable k-ε turbulence model. The reacting flow was simulated using Flamelet Generation Manifold (FGM) model to simulate partially premixed combustion. The non-reacting simulations predicted the combustor flow profiles with certain deviation from Particle Image Velocimetry (PIV) data within the central recirculation region. This deviation may be attributed to the inherent limitations of turbulence model in predicting the central vortex accurately. However, the simulated flow fields were in very good agreement with PIV data under reacting conditions. Additionally, the study was also extended to investigate the sensitivity of inlet swirl on the jet impingement location along the combustor wall. It was found that reaction significantly modifies the jet impingement location for lower inlet swirl angles and showed negligible impact under non-reacting conditions. The presented studies in this paper provide a comprehensive summary of modified flow features under non-reacting and reacting conditions and also demonstrates the sensitivity of inlet swirl changes on the location of liner wall impingement. This study is believed to offer a strong base for future studies involving heat transfer characterization along the combustor walls under reacting conditions; and also provide valuable information to the gas turbine combustor design community towards improved liner wall designs using simplistic numerical modeling approaches. C2 - 2017/// C3 - Proceedings of the ASME Turbo Expo DA - 2017/// DO - 10.1115/GT2017-64911 VL - 5C-2017 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85029086182&partnerID=MN8TOARS ER - TY - JOUR TI - Isothermal coherent structures and turbulent flow produced by a gas turbine combustor lean pre-mixed swirl fuel nozzle AU - Gomez-Ramirez, David AU - Ekkad, Srinath V. AU - Moon, Hee-Koo AU - Kim, Yong AU - Srinivasan, Ram T2 - Experimental Thermal and Fluid Science AB - The steady and unsteady isothermal fluid dynamics generated by an industrial low emission, lean premixed, fuel swirl nozzle designed by Solar Turbines Incorporated were investigated in this study. The experiments were carried out in a model optical can combustor operating at atmospheric pressures. Non-time resolved, planar Particle Image Velocimetry (PIV) measurements were taken at Reynolds numbers with respect to the nozzle throat diameter of ∼50 000, ∼100 000, and ∼180 000. The time-averaged velocity fields were approximately self-similar, with the highest mass flow exhibiting a central recirculation zone (CRZ) with a slightly larger diameter. The results were analyzed using a methodology based on Proper Orthogonal Decomposition (POD) to extract the periodic structures in the flow and obtain the underlying stochastic turbulence field. This distinction between stochastic and coherent fluctuations is critical to properly model combustor flows. Coherent flow instabilities such as the precessing vortex core (PVC) and the propagation of axial/radial vortices were observed to significantly contribute to the mixing between the nozzle exit flow and the recirculated mass flow. Over 30% of the total fluctuation (difference between instantaneous and time-averaged velocity fields) kinetic energy was attributed to coherent structures throughout the inner shear layer between the swirling jet exiting the nozzle and the CRZ. Stochastic variability was prevalent close the liner wall and throughout the combustor domain after the swirling jet impinged on the wall, with <20% of the total fluctuation attributed to coherent structures. The normalized coherent and stochastic flow fields were also approximately self-similar with Reynolds number. DA - 2017/2// PY - 2017/2// DO - 10.1016/j.expthermflusci.2016.10.010 VL - 81 SP - 187-201 J2 - Experimental Thermal and Fluid Science LA - en OP - SN - 0894-1777 UR - http://dx.doi.org/10.1016/j.expthermflusci.2016.10.010 DB - Crossref ER - TY - CONF TI - Heat transfer enhancement by criss-cross pattern formed by 45° Angled rib turbulators in a straight square duct AU - Singh, P. AU - Ji, Y. AU - Zhang, M. AU - Ekkad, S.V. AB - The need for higher turbine efficiency has been constantly pushing the turbine inlet temperatures to elevated levels. Hot gas path temperatures are much higher than the typical blade material yield temperature. Efficient internal cooling technologies are required for safe operation of gas turbine. Several internal cooling technologies have been developed in order to enhance the heat transfer from relatively hotter walls of turbine blade. For mid-chord region of turbine blade, rib turbulators are typically installed in multi-pass channels. Rib turbulators trip the boundary layer, induce secondary flows which enhance near wall shear as well as enhance turbulent mixing when they interact with surrounding walls. Research has been carried out on several aspects of rib turbulated passages in order to achieve higher thermal hydraulic performance. Generally, rib turbulators are installed on two opposite walls of serpentine passages in order to enhance heat transfer from both pressure and suction sides of blade through coolant flowing through complicated paths. Typical arrangement of rib turbulators were parallel to each other or having some offset from each other. In the present study, an attempt has been made to arrange 45° angled ribs in a way that they form a Criss-Cross pattern. Two ribbed configurations with Criss-Cross pattern - Inline and staggered, have been studied where the baseline case was smooth duct with no rib turbulators. The effective rib-pitch-to-rib-height ratio (p/e) was 8.6 and rib-height-to-channel-hydraulic diameter ratio (e/dh) was 0.1. The channel had a total length of 20 hydraulic diameters and the rib turbulators were installed at a distance of six hydraulic diameters from the inlet of the test section to allow flow development. Detailed heat transfer coefficients were measured using transient liquid crystal thermography employing 1D semi-infinite conduction model. Globally averaged Nusselt numbers are calculated from the detailed measurements and thermal hydraulic performance of configurations have been reported with respect to Reynolds number. The aim of this study was to develop a cooling configuration which has higher thermal-hydraulic performance compared to other traditional rib configurations. It has been found that the heat transfer characteristics of the inline and staggered configurations were similar to each other and ranged between three times D-B correlation to 2.7 times, for Reynolds number ranging from 30000 to 60000. Inline configuration had relatively lower frictional losses, however the thermal hydraulic performances of both the configurations were similar. C2 - 2017/// C3 - ASME 2017 Heat Transfer Summer Conference, HT 2017 DA - 2017/// DO - 10.1115/HT2017-4908 VL - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85032891330&partnerID=MN8TOARS ER - TY - JOUR TI - Heat Transfer Performance of a Transonic Turbine Blade Passage in the Presence of Leakage Flow Through Upstream Slot and Mateface Gap With Endwall Contouring AU - Roy, Arnab AU - Jain, Sakshi AU - Ekkad, Srinath V. AU - Ng, Wing AU - Lohaus, Andrew S. AU - Crawford, Michael E. AU - Abraham, Santosh T2 - Journal of Turbomachinery AB - Comparison of heat transfer performance of a nonaxisymmetric contoured endwall to a planar baseline endwall in the presence of leakage flow through stator–rotor rim seal interface and mateface gap is reported in this paper. Heat transfer experiments were performed on a high turning turbine airfoil passage at Virginia Tech's transonic blow down cascade facility under design conditions for two leakage flow configurations—(1) mateface blowing only, (2) simultaneous coolant injection from the upstream slot and mateface gap. Coolant to mainstream mass flow ratios (MFRs) were 0.35% for mateface blowing only, whereas for combination blowing, a 1.0% MFR was chosen from upstream slot and 0.35% MFR from mateface. A common source of coolant supply to the upstream slot and mateface plenum made sure the coolant temperatures were identical at both upstream slot and mateface gap at the injection location. The contoured endwall geometry was generated to minimize secondary aerodynamic losses. Transient infrared thermography technique was used to measure endwall surface temperature and a linear regression method was developed for simultaneous calculation of heat transfer coefficient (HTC) and adiabatic cooling effectiveness, assuming a one-dimensional (1D) semi-infinite transient conduction. Results indicate reduction in local hot spot regions near suction side as well as area averaged HTC using the contoured endwall compared to baseline endwall for all coolant blowing cases. Contoured geometry also shows better coolant coverage further along the passage. Detailed interpretation of the heat transfer results along with near endwall flow physics has also been discussed. DA - 2017/10/3/ PY - 2017/10/3/ DO - 10.1115/1.4037909 VL - 139 IS - 12 LA - en OP - SN - 0889-504X 1528-8900 UR - http://dx.doi.org/10.1115/1.4037909 DB - Crossref ER - TY - JOUR TI - Film Cooling Performance of Tripod Antivortex Injection Holes Over the Pressure and Suction Surfaces of a Nozzle Guide Vane AU - Ramesh, Sridharan AU - LeBlanc, Christopher AU - Narzary, Diganta AU - Ekkad, Srinath AU - Anne Alvin, Mary T2 - Journal of Thermal Science and Engineering Applications AB - Film cooling performance of the antivortex (AV) hole has been well documented for a flat plate. The goal of this study is to evaluate the same over an airfoil at three different locations: leading edge suction and pressure surface and midchord suction surface. The airfoil is a scaled up first stage vane from GE E3 engine and is mounted on a low-speed linear cascade wind tunnel. Steady-state infrared (IR) technique was employed to measure the adiabatic film cooling effectiveness. The study has been divided into two parts: the initial part focuses on the performance of the antivortex tripod hole compared to the cylindrical (CY) hole on the leading edge. Effects of blowing ratio (BR) and density ratio (DR) on the performance of cooling holes are studied here. Results show that the tripod hole clearly provides higher film cooling effectiveness than the baseline cylindrical hole case with overall reduced coolant usage on the both pressure and suction sides of the airfoil. The second part of the study focuses on evaluating the performance on the midchord suction surface. While the hole designs studied in the first part were retained as baseline cases, two additional geometries were also tested. These include cylindrical and tripod holes with shaped (SH) exits. Film cooling effectiveness was found at four different blowing ratios. Results show that the tripod holes with and without shaped exits provide much higher film effectiveness than cylindrical and slightly higher effectiveness than shaped exit holes using 50% lesser cooling air while operating at the same blowing ratios. Effectiveness values up to 0.2–0.25 are seen 40-hole diameters downstream for the tripod hole configurations, thus providing cooling in the important trailing edge portion of the airfoil. DA - 2017/1/24/ PY - 2017/1/24/ DO - 10.1115/1.4035290 VL - 9 IS - 2 LA - en OP - SN - 1948-5085 1948-5093 UR - http://dx.doi.org/10.1115/1.4035290 DB - Crossref ER - TY - JOUR TI - Experimental study of heat transfer augmentation in a two-pass channel featuring V-shaped ribs and cylindrical dimples AU - Singh, Prashant AU - Ekkad, Srinath T2 - Applied Thermal Engineering AB - Higher turbine inlet temperature requirements in modern gas turbine airfoils necessitate the development of high performance internal cooling designs for increasing turbine durability and performance. The internal cooling passages of turbine airfoils feature ribs which promote turbulent mixing, increase in near wall shear and hence lead to heat transfer augmentation. One other method of increasing heat transfer enhancement is by adding depressions (commonly called “dimples”) on the walls of internal cooling passages. Earlier studies have investigated different shapes of rib turbulators and dimples, however, the limitations in manufacturability of dimple in actual turbine airfoils has been a concern in the past. Recent advancements in the field of additive manufacturing, e.g. Direct Metal Laser Sintering (DMLS), opens endless possibilities for the development of novel cooling features which can be incorporated in actual engines. The present study investigates the heat transfer and pressure drop characteristics of a two-pass channel (AR = 1) featuring ribs-alone, dimples-alone and combination of ribs and dimples. The ribs are V-shaped with rib-height-to-hydraulic diameter ratio of 0.125 and rib-pitch-to-rib height ratio of 16. Dimples are cylindrical in shape and have a depth-to-print diameter ratio of 0.3. The heat transfer coefficient was measured using transient Liquid Crystal Thermography and detailed Nusselt numbers have been reported and analyzed. Also, static pressure measurements were carried out at several locations to determine the total pressure drop across the two pass channel and the local variation of pressure coefficient. The experiments were carried out for a wide range of Reynolds number (19,500–69,000) to cover the full spectrum typically found in both land-based and air-breathing engines. It has been observed that the combination of ribs and dimples resulted in higher heat transfer augmentation as well as higher thermal hydraulic performance when compared with ribs alone and dimples alone configurations for the range of Reynolds number studied. DA - 2017/4// PY - 2017/4// DO - 10.1016/j.applthermaleng.2017.01.098 VL - 116 SP - 205-216 J2 - Applied Thermal Engineering LA - en OP - SN - 1359-4311 UR - http://dx.doi.org/10.1016/j.applthermaleng.2017.01.098 DB - Crossref ER - TY - JOUR TI - Investigation of isothermal convective heat transfer in an optical combustor with a low-emissions swirl fuel nozzle AU - Gomez-Ramirez, David AU - Kedukodi, Sandeep AU - Ekkad, Srinath V. AU - Moon, Hee-Koo X. AU - Kim, Yong AU - Srinivasan, Ram T2 - Applied Thermal Engineering AB - Modern combustor design optimization is contingent on the accurate characterization of the combustor flame side heat loads. The present work focuses on the experimental measurement of the isothermal (non-reacting) convective heat transfer along a fused silica optical can combustor liner for Reynolds numbers ranging between 11,500 and 138,000. The model combustor was equipped with the SoLoNOx swirl fuel nozzle from Solar Turbines Incorporated, subjecting the liner walls to realistic isothermal flow and turbulence fields. Infrared (IR) imaging through fused silica was demonstrated, and a novel estimation of the three-dimensional conduction heat losses for steady state constant heat flux experiments was developed. A maximum heat transfer augmentation of ∼18 was observed with respect to fully developed turbulent pipe flow correlations. Contrary to other investigations, the augmentation magnitude and distribution are shown to be approximately constant with Reynolds number (particularly away from the impingement location). Particle Image Velocimetry (PIV) was included to support the heat transfer measurements, suggesting that peak heat transfer occurred 0.12 nozzle diameters upstream of the jet reattachment point along the liner. Reynolds-Averaged Navier Stokes (RANS) computations are shown to yield peak heat transfer predictions within 17.4% of the experimental results when using the realizable k-ε turbulence model and enhanced wall treatment. The measurements were further analyzed in the context of results from other heat transfer studies on gas turbine combustors. DA - 2017/3// PY - 2017/3// DO - 10.1016/j.applthermaleng.2016.11.154 VL - 114 SP - 65-76 J2 - Applied Thermal Engineering LA - en OP - SN - 1359-4311 UR - http://dx.doi.org/10.1016/j.applthermaleng.2016.11.154 DB - Crossref ER - TY - CONF TI - Flow field and wall temperature measurements for reacting flow in a lean premixed swirl stabilized can combustor AU - Park, S. AU - Gomez-Ramirez, D. AU - Gadiraju, S. AU - Kedukodi, S. AU - Ekkad, S. AU - Moon, H.-K. AU - Kim, Y. AU - Srinivasan, R. AB - Designing gas turbine combustors requires accurate measurement and prediction of the violent, high-temperature environment in reacting flow. One important factor in combustor design is the heat load on the inner surface of the combustor liner during combustion. To properly analyze the heat load, the mechanisms of thermal energy transfer must be investigated. Of these, the convective heat transfer has not been fully characterized, representing an important challenge in the field of combustor research. The flow field is closely related to the combustion dynamics from the swirling flame in modern burners, and has a direct impact on the convective heat transfer. Most of the flow field measurements reported in the literature have relied on custom research nozzles. However, the development of modern low emission, lean-premixed combustors requires experimental results from realistic industrial fuel nozzles. This paper experimentally investigates the effects of combustor operating conditions on the reacting flow in an optical single can combustor. The swirling flow was generated by an industrial lean pre-mixed, axial swirl fuel nozzle manufactured by Solar Turbines Incorporated. Planar particle image velocimetry (PIV) data were acquired and analyzed to understand the characteristics of the flow field. Experiments were conducted at Reynolds numbers ranging between 50000 and 110000 (with respect to the nozzle diameter, DN); equivalence ratios between 0.55 and 0.78; and pilot fuel split ratios of 0 to 6%. Characterizing the impingement location on the liner, and the turbulent kinetic energy (TKE) distribution were a fundamental part of the investigation. Self-similar characteristics were observed at reacting conditions. Jet impingement locations on the liner were at x ≈ 1.16 DN for seven different reacting cases, and it was observed that the impingement location was not significantly affected by the combustion parameters studied. However, non-reacting flow was significantly different in flame structure and impingement locations. Combustor liner wall temperature distributions were measured in reacting condition with an infrared camera for a single case. The temperature profile was explained qualitatively with the flow features measured with PIV. Peak wall temperature close to impingement location on the liner wall reached about 900 K, and peak heat flux was measured as ≈ 23 kW/m2 at x ≈ 2.3 DN. C2 - 2017/// C3 - Proceedings of the ASME Turbo Expo DA - 2017/// DO - 10.1115/GT2017-64837 VL - 5C-2017 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85029116922&partnerID=MN8TOARS ER - TY - JOUR TI - Effect of endwall contouring on a transonic turbine blade passage: Heat transfer performance AU - Panchal, K.V. AU - Abraham, S. AU - Roy, A. AU - Ekkad, S.V. AU - Ng, W. AU - Lohaus, A.S. AU - Crawford, M.E. T2 - Journal of Turbomachinery AB - Effect of turbine endwall contouring on its aerodynamic performance has been widely studied, but only a few studies are available in the open literature investigating its effect on heat transfer performance; especially at transonic exit Mach number conditions. In this paper, we report a study of effect of contouring on endwall heat transfer performance of a high-turning high-pressure (HP) turbine blade passage operating under transonic exit conditions. The paper describes comparison of heat transfer performance of two contoured endwall geometries, one aerodynamically optimized (AO) and the other heat transfer optimized (HTO), with a baseline, noncontoured geometry. The endwall geometries were experimentally investigated at Virginia Tech's transient, blow down, transonic linear cascade facility at three exit Mach numbers, Mex= 0.71, 0.88(design) and 0.95, for their heat transfer performance. Endwall surface temperatures were measured using infrared (IR) thermography and local heat transfer coefficient (HTC) values were calculated using measured temperatures. A camera matrix model-based data postprocessing technique was developed to relate the two-dimensional images captured by IR camera to three-dimensional endwall contours. The measurement technique and the methodology for postprocessing of the heat transfer coefficient data have been presented in detail. Discussion and interpretation of experimental results have been augmented using aerodynamic CFD simulations of the geometries. Both the contoured endwalls demonstrated a significant reduction in the overall average heat transfer coefficient values of the order of 10%. The surface Stanton number distributions also indicated a reduction in the level of hot spots for most of the endwall surface. However, at some locations an increase was also observed, especially in the area near the leading edge (LE). The results indicate that the endwall contouring could significantly improve heat transfer performance of turbine passages. DA - 2017/// PY - 2017/// DO - 10.1115/1.4034411 VL - 139 IS - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84988703612&partnerID=MN8TOARS ER - TY - JOUR TI - A transient liquid crystal image technique for local heat transfer distributions near a sharp 180° turn of a two-pass smooth square channel AU - Ekkad, S.V. AU - Han, J.-C. T2 - Journal of Flow Visualization and Image Processing AB - Local heat transfer distributions are presented near a sharp 180° turn of a two-pass smooth square channel using a transient technique and encapsulated liquid crystal coating. Detailed distributions of the local Nusselt numbers are given for three flow Reynolds numbers of 10,000, 25,000, and 50,000. Results show that the Nusselt numbers are much higher in the region immediately downstream of the turn compared with upstream values for all three Reynolds numbers. The regional averaged results are compared with published heat transfer data. DA - 2017/// PY - 2017/// DO - 10.1615/jflowvisimageproc.v24.i1-4.90 VL - 24 IS - 1-4 SP - 127-140 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85045919409&partnerID=MN8TOARS ER - TY - CONF TI - Experimental investigation of rotating rib roughened two-pass square duct with two different channel orientations AU - Singh, P. AU - Ekkad, S.V. AB - Effects of rotation on heat transfer on leading and trailing sides of gas turbine blades has been extensively studied in the past. It has been established for typical two-pass channel that radially outward flow (first pass) has higher heat transfer on trailing side and lower heat transfer on leading side and vice versa for radially inward flow (second pass). Rotation induces three forces on the coolant flow — Coriolis, Centrifugal and Buoyancy forces. The direction of Coriolis force depends on the relative angle between the coolant flow and the rotation direction, because of which the direction of Coriolis force is different in individual passes — which in turn results in non-uniform distribution of high heat transfer regions on leading and trailing walls. The present study is focused on utilizing the Coriolis force favorably in both the passes by rotating the typical arrangement of two-pass channels by 90°. Firstly, smooth two pass duct (Model A-smooth) having typical arrangement of coolant flow and rotation direction is studied. The second configuration is the corresponding ribbed channel (Model A-ribbed) featuring V-shaped ribs on both leading and trailing walls. The rib-height-to-channel hydraulic diameter ratio was 0.125, rib pitch-to-rib height ratio was 8, and channel aspect ratio was unity. Model B was obtained by rotating the Model A by 90° and changing the coolant inlet port as well. Model B had three configurations — (a) smooth duct, (b) single sided ribbed duct, and (c) double sided ribbed duct. Detailed heat transfer coefficients were measured by transient liquid crystal thermography under rotating conditions. In order to match the direction of Buoyancy force as it exists in actual engines, colder air was passed during the transient experiment. The heat transfer experiments were carried out at a Reynolds number of 20000 and Rotation numbers of 0, 0.05 and 0.1. The Nusselt numbers have been reported in two forms, (a) normalized with respect to Dittus-Boelter correlation for developed turbulent flow in circular duct, (b) normalized with corresponding Nusselt number obtained from smooth channel experiments. The effects of Coriolis force and centrifugal force on heat transfer has been discussed in detail. A new model has been proposed based on the understanding and findings of the present study, which has positive effects of rotation on both leading and trailing walls. C2 - 2017/// C3 - Proceedings of the ASME Turbo Expo DA - 2017/// DO - 10.1115/GT2017-64225 VL - 5A-2017 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85029022270&partnerID=MN8TOARS ER - TY - CONF TI - Experimental based empirical model of the initial onset of sand deposits on hastelloy-X from 1000°C to 1100°C using particle tracking AU - Boulanger, A. AU - Hutchinson, J. AU - Ng, W.F. AU - Ekkad, S.V. AU - Keefe, M.J. AU - Xu, W. AU - Barker, B.J. AU - Hsu, K. AB - Deposition experiments are performed on a Hastelloy-X coupon using Arizona Road Test Dust (ARD). A statistical empirical model of the initial onset of ARD deposits is developed from the experimental data. The initial onset of deposits are a quadratic function of local surface temperature and impact velocity components (normal and tangential). A prominent observation is that tangential impact velocity has a significant non-linear, independent effect on deposits relative to normal impact velocity and local surface temperatures. All experiments use 20–40 μm ARD on a bare metal surface over a 1000–1100°C range. Unlike prior mass-based deposit studies, initial deposits for this study are quantified using a Coverage Ratio (CR), which is the area covered by deposits relative to the total area available. The empirical CR model has a strong correlation to coupon surface temperature and impact velocity vectors and is a foundation for future numerical or experimental model comparisons. C2 - 2017/// C3 - Proceedings of the ASME Turbo Expo DA - 2017/// DO - 10.1115/GT2017-64480 VL - 2D-2017 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85028971325&partnerID=MN8TOARS ER - TY - JOUR TI - Experimental and numerical investigation of heat transfer inside two-pass rib roughened duct (AR = 1:2) under rotating and stationary conditions AU - Singh, Prashant AU - Li, Weihong AU - Ekkad, Srinath V. AU - Ren, Jing T2 - International Journal of Heat and Mass Transfer AB - Heat transfer enhancement inside ribbed channels for turbine blades is a critical phenomenon that impacts overall performance and life of the gas turbine. Present study investigates heat and fluid flow in a rectangular duct with heat transfer enhancement features, under rotating and stationary conditions. The heat transfer data obtained experimentally has been explained using numerical prediction of flow features. Detailed heat transfer coefficients have been measured on the walls of two-pass rectangular duct (AR = 1:2) featuring V-shaped rib turbulators, using transient liquid crystal thermography (TLCT). The first pass and second pass featured nine V-shaped ribs each and the bend featured a 90° rib connecting the blade tip underside and the two-pass divider wall. The flow in the first pass was developing in nature. The rib-pitch to rib-height ratio (p/e) was 9.625 and the rib-height to channel hydraulic diameter (e/dh) was 0.125. The baseline case for the rib roughened duct was geometrically identical smooth duct (with no heat transfer enhancement features). Stationary experiments were carried out for Reynolds numbers ranging from 25000 to 75000. The rotation experiments were carried out at 400 RPM (Ro = 0.036) and 700 RPM (Ro = 0.063), at Reynolds number of 25000 (Ro=Ωdh/V,Re=Vdh/ν). Also, numerical simulations were performed for a similar test model under similar flow conditions, using realizable k-∊ turbulence model. Detailed discussion on rib induced secondary flows and rotational effects on heat transfer in smooth and rib roughened duct are presented in this paper using results obtained from detailed heat transfer measurements from experiments and fluid dynamics predictions from numerical simulations. DA - 2017/10// PY - 2017/10// DO - 10.1016/j.ijheatmasstransfer.2017.05.085 VL - 113 SP - 384-398 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2017.05.085 DB - Crossref ER - TY - JOUR TI - Effects of spent air removal scheme on internal-side heat transfer in an impingement-effusion system at low jet-to-target plate spacing AU - Singh, Prashant AU - Ekkad, Srinath V. T2 - International Journal of Heat and Mass Transfer AB - Present study reports detailed measurements of heat transfer coefficient for jet impingement in an impingement-effusion system at low jet-to-target plate spacing. The heat transfer coefficients were measured experimentally by transient liquid crystal thermography. Heat transfer experiments were carried out at three jet Reynolds numbers – 3500, 6000 and 9000. The jet plate featured 8 × 9 circular jets with normalized streamwise (x/dj) and spanwise (y/dj) spacing of 6. The configurations are divided into two segments based on the characteristics of target surface. The first target surface was smooth without effusion holes, and the second target surface was smooth with effusion holes. The arrangement of effusion holes was staggered with respect to jet plate and the ratio of effusion hole diameter to jet hole diameter was unity. For the smooth target surface without effusion holes, three crossflow schemes were studied – minimum, intermediate and maximum. For the smooth target surface with effusion holes, four different crossflow schemes were studied – zero, minimum, intermediate and maximum. Interesting heat transfer characteristics are reported for different crossflow schemes as it was found that low z/dj (=1) played an important role in the spent air removal from the system. Discharge coefficient of jets is also reported for wide range of plenum pressure ratio. Also reported are the pumping power requirements for each configuration across full range of flow conditions. It has been found that the minimum crossflow scheme (with and without effusion holes) has been the most efficient configuration and the maximum crossflow scheme with target surface without effusion holes has been the least efficient configuration. DA - 2017/5// PY - 2017/5// DO - 10.1016/j.ijheatmasstransfer.2016.12.104 VL - 108 SP - 998-1010 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.12.104 DB - Crossref ER - TY - JOUR TI - Characterization of heat transfer enhancement and frictional losses in a two-pass square duct featuring unique combinations of rib turbulators and cylindrical dimples AU - Singh, Prashant AU - Pandit, Jaideep AU - Ekkad, Srinath V. T2 - International Journal of Heat and Mass Transfer AB - Transient heat transfer experiments using liquid crystal thermography have been carried out on a two-pass square channel for testing several unique combinations of ribs and cylindrical dimples. Four different rib shapes, viz. 45° angled, V, W and M have been studied. In compound channels, the rib pitch accommodates cylindrical dimples arranged in the shape of the rib, hence following the direction of rib induced secondary flows. For each rib shape, three different configurations – rib alone, dimple alone and rib–dimpled compound cases were studied. The rib-height-to-channel hydraulic diameter ratio was 0.125 and rib-pitch-to-rib-height ratio was 16. The dimple-depth-to-print diameter ratio was 0.3. The experiments were carried out for a wide range of Reynolds number (19,500–69,000), covering a spectrum typically found in both land-based and air-breathing engines. A total of 52 experiments were carried out to measure detailed heat transfer coefficient on the bottom wall of the two-pass channel. A transient liquid crystal thermography technique was used for heat transfer measurement. Static pressure measurements were carried out to measure the overall pressure drop in the two pass channel. From globally averaged Nusselt number and overall pressure drop, thermal-hydraulic performance of the 13 configurations were determined, compared and analyzed. It has been observed that 45° angled and V compound configurations resulted in higher heat transfer augmentation as well as higher thermal hydraulic performance when compared with their corresponding ribs alone and dimples alone configurations. DA - 2017/3// PY - 2017/3// DO - 10.1016/j.ijheatmasstransfer.2016.09.037 VL - 106 SP - 629-647 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.09.037 DB - Crossref ER - TY - CONF TI - Application of proper orthogonal decomposition to high speed imaging for the study of combustion oscillations AU - Gadiraju, S. AU - Park, S. AU - Gomez-Ramirez, D. AU - Ekkad, S.V. AU - Todd Lowe, K. AU - Moon, H.-K. AU - Kim, Y. AU - Srinivasan, R. AB - The flame structure and characteristics generated by an industrial low emission, lean premixed, fuel swirl nozzle were analyzed for understanding combustion oscillations. The experimental facility is located at the Advanced Propulsion and Power Laboratory (APPL) at Virginia Tech. The experiments were carried out in a model optical can combustor operating at atmospheric pressures. Low-frequency oscillations (<100 Hz) were observed during the reaction as opposed to no reaction, cold flow test cases. The objective of this paper is to understand the frequency and magnitude of oscillations due to combustion using high-speed imaging and associate them with corresponding structure or feature of the flame. Flame images were obtained using a Photron Fastcam SA4 high-speed camera at 500 frames per second. The experiments were conducted at equivalence ratios of 0.65, 0.75; different Reynolds numbers of 50K, 75K; and three pilot fuel to main fuel ratios of 0%, 3%, 6%. In this study, Reynolds number was based on the throat diameter of the fuel nozzle. Since the time averaged flame images are not adequate representation of the flame structures, proper orthogonal decomposition (POD) was applied to the flame images to extract the dominant features. The spatiotemporal dynamics of the images can be decomposed into their constituent modes of maximum spatial variance using POD so that the dominant features of the flame can be observed. The frequency of the dominant flame structures, as captured by the POD modes of the flame acquisitions, were consistent with pressure measurements taken at the exit of the combustor. Thus, the oscillations due to combustion can be visualized using POD. POD was further applied to high-speed images taken during instabilities. Specifically, the instabilities discussed in this paper are those encountered when the equivalence ratio is reduced to the levels approaching lean blowout (LBO). As the equivalence ratio is reduced to near blowout regime, it triggers low-frequency high amplitude instabilities. These low-frequency instabilities are visible as the flapping of the flame. The frequencies of the dominant POD modes are consistent with pressure measurements recorded during these studies. C2 - 2017/// C3 - Proceedings of the ASME Turbo Expo DA - 2017/// DO - 10.1115/GT2017-64602 VL - Part F130041-4B UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85030695776&partnerID=MN8TOARS ER - TY - JOUR TI - A new cooling design for rib roughened two-pass channel having positive effects of rotation on heat transfer enhancement on both pressure and suction side internal walls of a gas turbine blade AU - Singh, Prashant AU - Li, Weihong AU - Ekkad, Srinath V. AU - Ren, Jing T2 - International Journal of Heat and Mass Transfer AB - This paper presents a new cooling design for a typical two-pass channel of a high pressure stage turbine blade. Gas turbine blades are subjected to elevated heat loads on the pressure and suction walls. In order to enhance heat transfer from the surfaces to the relatively colder internal air (gas), rib turbulators are installed on the opposite walls of two-pass channel. Combination of Coriolis force and centrifugal buoyancy force result in increase in heat transfer on trailing walls (along the pressure surface, and radially outward coolant flow) and leading walls (along the suction surface, radially inward flow) and vice versa. This leads to non-uniform cooling in both the passes and hence a non-optimum usage of cooling potential. The present study is focused on utilizing the Coriolis force favorably in both the passes by rotating the typical arrangement of two-pass channels by 90°. Detailed heat transfer coefficients were measured by transient liquid crystal thermography under rotating conditions. In order to match the direction of Buoyancy force as it exists in actual engines, colder air was passed during the transient experiment. The heat transfer experiments were carried out at a Reynolds number of 20000 and Rotation numbers of 0 and 0.1. The Nusselt numbers have been reported in two forms, (a) normalized with respect to Dittus-Boelter correlation for developed turbulent flow in circular duct, (b) normalized with corresponding Nusselt number obtained from smooth channel experiments. In order to understand the heat transfer characteristics of both traditional and new design, numerical simulations were also carried out for all configurations and at all experimental conditions to obtain flow and heat transfer predictions. A combined experimental and numerical discussion has been provided to explain the findings of the present study and to support the proposed design. It has been reported that the new design has 11% higher heat transfer enhancement at 8% lower pumping power compared to the traditional two pass rib roughened duct. DA - 2017/12// PY - 2017/12// DO - 10.1016/j.ijheatmasstransfer.2017.07.128 VL - 115 SP - 6-20 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2017.07.128 DB - Crossref ER - TY - JOUR TI - Microfluidic channel for characterizing normal and breast cancer cells AU - TruongVo, TN AU - Kennedy, RM AU - Chen, H AU - Chen, A AU - Berndt, A AU - Agarwal, M AU - Zhu, L AU - Nakshatri, H AU - Wallace, J AU - Na, S AU - others T2 - Journal of Micromechanics and Microengineering DA - 2017/// PY - 2017/// VL - 27 IS - 3 SP - 035017 ER - TY - CONF TI - Novel Approach to Measuring Droplet Detachment Force from Fibers AU - Amrei, M.M. AU - Tafreshi, H.V. T2 - Virginia Soft Matter Symposium C2 - 2017/9/4/ CY - James Madison University DA - 2017/9/4/ PY - 2017/9/4/ ER - TY - CONF TI - Droplet interactions with smooth and rough fibers AU - Davoudi, M. AU - Amrei, M.M. AU - Chase, G.G. AU - Tafreshi, H.V. T2 - American Filtration and Separations Society C2 - 2017/4/10/ CY - Louisville, Kentucky DA - 2017/4/10/ PY - 2017/4/10/ ER - TY - CONF TI - Modelling Drag Reduction and Droplet Mobility over Superhydrophobic wire screen AU - Venkateshan, D.G. AU - Tafreshi, H.V. T2 - Virginia Soft Matter Symposium C2 - 2017/9/4/ CY - James Madison University DA - 2017/9/4/ PY - 2017/9/4/ ER - TY - JOUR TI - Modeling Cassie droplets on superhydrophobic coatings with orthogonal fibrous structures AU - Aziz, H. AU - Amrei, M.M. AU - Dotivala, A. AU - Tang, C. AU - Tafreshi, H.Vahedi T2 - Colloids and Surfaces A: Physicochemical and Engineering Aspects AB - Superhydrophobic coatings comprised of orthogonally layered fibers are studied in this paper in terms of their ability to accommodate water droplets in the non-wetting Cassie state. The effects of microstructural properties of these coatings on droplet contact angles and Cassie state stability are investigated via numerical simulation. More specifically, mathematical expressions are derived to predict whether or not such fibrous coatings can provide sufficient capillary forces for the droplet to remain in the Cassie state. For comparison, similar coatings comprised of parallel fibers are also studied, as a droplet may only interact with the first layer of fibers (parallel fibers) when the fiber spacing is smaller than some critical spacing value. Considerable differences were observed between droplet contact angles on coatings made of orthogonally layered fibers and those having multiple layers of parallel fibers. Our numerical simulations conducted using the Surface Evolver finite element code indicated that apparent contact angle of a droplet can be different in longitudinal and transverse directions, and they both increase by decreasing the diameter of the fibers or by increasing their spacing. It was also found that contact angle in the longitudinal direction is more sensitive to the spacing or the diameter of the fibers. It was also found that a droplet may achieve higher contact angles on a coating with orthogonally layered fibers than on its parallel-fiber counterpart. DA - 2017/1// PY - 2017/1// DO - 10.1016/j.colsurfa.2016.10.031 VL - 512 SP - 61-70 J2 - Colloids and Surfaces A: Physicochemical and Engineering Aspects LA - en OP - SN - 0927-7757 UR - http://dx.doi.org/10.1016/j.colsurfa.2016.10.031 DB - Crossref KW - Superhydrophobic surfaces KW - Fibrous coatings KW - Wetting ER - TY - JOUR TI - Effects of roughness on droplet apparent contact angles on a fiber AU - Amrei, M.M. AU - Davoudi, M. AU - Chase, G.G. AU - Tafreshi, H. Vahedi T2 - Separation and Purification Technology AB - This paper reports on our investigation of the effects of surface roughness on the equilibrium shape and apparent contact angles of a droplet deposited on a fiber. In particular, the shape of a droplet on a roughened fiber is studied via the energy minimization method implemented in the surface evolver finite element code. Sinusoidal roughness varying in both the longitudinal and radial directions is considered in the simulations to study the effects of surface roughness on the most stable shape of a droplet on a fiber (corresponding a global minimum energy state). It is found that surface roughness delays droplet shape transition from a symmetric barrel to a clamshell or an asymmetric barrel profile. A phase diagram that includes the effects of fiber roughness on droplet configurations—symmetric barrel, clamshell, and asymmetric barrel—is presented for the first time. It is also found that droplet apparent contact angle tends to decrease on rough fibers. Likewise, roughness tends to increase the force required to detach a droplet from a fiber but the effect diminishes as droplet size increases relative to the size of surface roughness. The results presented in our study have been compared with experimental data or those from prior studies whenever possible, and good agreement has been observed. DA - 2017/6// PY - 2017/6// DO - 10.1016/j.seppur.2017.02.049 VL - 180 SP - 107-113 J2 - Separation and Purification Technology LA - en OP - SN - 1383-5866 UR - http://dx.doi.org/10.1016/j.seppur.2017.02.049 DB - Crossref KW - Droplet-fiber interactions KW - Droplet shape modeling KW - Surface roughness KW - Droplet contact angle ER - TY - JOUR TI - Control and characterization of a bistable laminate generated with piezoelectricity AU - Lee, Andrew J AU - Moosavian, Amin AU - Inman, Daniel J T2 - Smart Materials and Structures AB - Extensive research has been conducted on utilizing smart materials such as piezoelectric and shape memory alloy actuators to induce snap through of bistable structures for morphing applications. However, there has only been limited success in initiating snap through from both stable states due to the lack of actuation authority. A novel solution in the form of a piezoelectrically generated bistable laminate consisting of only macro fiber composites (MFC), allowing complete configuration control without any external assistance, is explored in detail here. Specifically, this paper presents the full analytical, computational, and experimental results of the laminate's design, geometry, bifurcation behavior, and snap through capability. By bonding two actuated MFCs in a [0MFC/90MFC]T layup and releasing the voltage post cure, piezoelectric strain anisotropy and the resulting in-plane residual stresses yield two statically stable states that are cylindrically shaped. The analytical model uses the Rayleigh–Ritz minimization of total potential energy and finite element analysis is implemented in MSC Nastran. The [0MFC/90MFC]T laminate is then manufactured and experimentally characterized for model validation. This paper demonstrates the adaptive laminate's unassisted forward and reverse snap through capability enabled by the efficiencies gained from simultaneously being the actuator and the primary structure. DA - 2017/8/1/ PY - 2017/8/1/ DO - 10.1088/1361-665x/aa7165 VL - 26 IS - 8 SP - 085007 UR - http://dx.doi.org/10.1088/1361-665x/aa7165 KW - bistable KW - laminate KW - piezoelectric KW - macro fiber composite KW - morphing ER - TY - CONF TI - Piezoelectrically strained bistable laminates with macro fiber composites AU - Lee, A.J. AU - Moosavian, A. AU - Inman, D.J. AB - The bistability and snap through capability of an unsymmetric laminate consisting of only Macro Fiber Composites (MFC) are investigated. The non-linear analysis predicts two cylindrically stable configurations when strain anisotropy is piezoelectrically induced within a [0MFC/90MFC]T laminate. This is achieved by bonding two MFCs in their actuated states and releasing the voltage post cure to create in-plane residual stresses. The minimization of total potential energy with the Rayleigh-Ritz method are used to analytically model the resulting laminate. A finite element analysis is conducted in MSC Nastran using the piezoelectric-thermal analogy approach to verify the analytical results. The effects of adhesive properties, bonding cure cycles, MFC layup, and its geometry on the curvatures, displacements, and bifurcation voltages are characterized. Finally, the snap through and reverse snap through capabilities with piezoelectric actuation are demonstrated. This adaptive laminate functions as both the actuator and the primary structure and allows large deformations under a non-continuous energy input. Its snap through capability allows full configuration control necessary in morphing applications. C2 - 2017/// C3 - Proceedings of SPIE - The International Society for Optical Engineering DA - 2017/// DO - 10.1117/12.2257680 VL - 10164 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85024118119&partnerID=MN8TOARS KW - MFC KW - bistable KW - laminate KW - piezoelectric KW - actuation KW - snap-through KW - bifurcation ER - TY - JOUR TI - A piezoelectrically generated bistable laminate for morphing AU - Lee, A.J. AU - Moosavian, A. AU - Inman, D.J. T2 - Materials Letters AB - This letter presents the analytical and experimental results of piezoelectrically generating bistability via Macro Fiber Composite (MFC) actuators. Two stable configurations are exhibited when piezoelectric strain anisotropy is induced within a [0MFC/90MFC]T laminate. This is achieved by bonding two MFCs in their actuated states and releasing the voltage post cure to create in-plane residual stresses. The resulting shapes are cylindrical and can be snapped through and back with only piezoelectric actuation. A [0MFC/90MFC]T laminate is modeled, manufactured, and experimentally characterized. This adaptive laminate functions as both the actuator and the primary structure and its snap through capability allows full configuration control necessary in morphing, without continuous energy input or any mechanical assistance. DA - 2017/// PY - 2017/// DO - 10.1016/j.matlet.2017.01.005 VL - 190 SP - 123-126 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85008422611&partnerID=MN8TOARS KW - Piezoelectric materials KW - Bistable KW - Laminates KW - Structural KW - Composite materials ER - TY - CONF TI - A parametric study on a bio-inspired continuously morphing trailing edge AU - Moosavian, A. AU - Chae, E.J. AU - Pankonien, A.M. AU - Lee, A.J. AU - Inman, D.J. AB - Inspired by the wave-like camber variation in the trailing edge feathers of large birds, the aerodynamic impact of similar variations in the geometry of morphing wings is investigated. The scope of this problem is reduced by exploring parametrically generated geometries derived from an existing morphing wing design, namely the Spanwise Morphing Trailing Edge (SMTE), which is actuated via conformally integrated Macro Fiber Composites (MFCs). Utilizing this design, the deformation of the trailing edge of the SMTE is parameterized as a function of the spanwise location using a sinusoidal relationship. The aerodynamic responses are then obtained using Computational Fluid Dynamics (CFD) simulations, while the efficacy of the proposed approach is explored using a Pareto-like frontier approach. C2 - 2017/// C3 - Proceedings of SPIE - The International Society for Optical Engineering DA - 2017/// DO - 10.1117/12.2257582 VL - 10162 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85020192159&partnerID=MN8TOARS KW - bio-inspired design KW - morphing trailing edge KW - wave-shaped varying camber KW - macro fiber composites ER - TY - CONF TI - Precision control of nanoparticle monolayer assembly: Optimizing rate and crystal quality AU - Bedewy, M. AU - Hu, J. AU - Hart, A.J. AB - We study the critical factors that govern the 2D-crystal quality of self-assembled nanoparticles using convective assembly (“blade-casting”) technique. The goal is to improve crystal quality by both maximizing monolayer coverage and optimizing crystal width. We find that crystal quality is enhanced by air plasma treatment on substrate surface, while the monolayer domain size increases with assembly at higher substrate temperature. In addition, we correlate the meniscus shape to array thickness obtained at different deposition stages. Our results provide insights toward scalable production of well-ordered nanoparticle monolayers for applications including biosensors, optically-active surfaces, and nanocomposites. C2 - 2017/// C3 - 2017 IEEE 17th International Conference on Nanotechnology, NANO 2017 DA - 2017/// DO - 10.1109/NANO.2017.8117489 SP - 286-289 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85041200868&partnerID=MN8TOARS ER - TY - JOUR TI - Biosynthesis of Gold Nanoparticles and Gold/Prodigiosin Nanoparticles with Serratia marcescens Bacteria AU - Dozie-Nwachukwu, S.O. AU - Obayemi, J.D. AU - Danyuo, Y.T. AU - Etuk-Udo, G. AU - Chi, Y. AU - Hu, J. AU - Anuku, N. AU - Odusanya, O.S. AU - Malatesta, K. AU - Soboyejo, W.O. T2 - Waste and Biomass Valorization DA - 2017/// PY - 2017/// DO - 10.1007/s12649-016-9734-7 VL - 8 IS - 6 SP - 2045-2059 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85008204222&partnerID=MN8TOARS KW - Serratia marcescens KW - Gold nanoparticles KW - Cell-free extract KW - Biomass KW - Dynamic light scattering KW - Prodigiosin ER - TY - JOUR TI - Adhesion of ligand-conjugated biosynthesized magnetite nanoparticles to triple negative breast cancer cells AU - Obayemi, J.D. AU - Hu, J. AU - Uzonwanne, V.O. AU - Odusanya, O.S. AU - Malatesta, K. AU - Anuku, N. AU - Soboyejo, W.O. T2 - Journal of the Mechanical Behavior of Biomedical Materials AB - This paper presents the results of an experimental study of the adhesion forces between components of model conjugated magnetite nanoparticle systems for improved selectivity in the specific targeting of triple negative breast cancer. Adhesion forces between chemically synthesized magnetite nanoparticles (CMNPs), biosynthesized magnetite nanoparticles (BMNPs), as well as their conjugated systems and triple negative breast cancer cells (MDA-MB-231) or normal breast cells (MCF 10A) are elucidated at a nanoscale. In all cases, the BMNPs had higher adhesion forces (to breast cancer cells and normal breast cells) than CMNPs. The adhesion of LHRH-conjugated BMNPs or BSA-conjugated BMNPs to cancer cells is shown to be about 6 times to that of normal breast cells. The increase in adhesion forces between luteinizing hormone-releasing hormone, LHRH- or EphA2, a breast specific antibody(BSA)-conjugated BMNPs to breast cancer cells is attributed to van der Waals interactions between the peptides/antibodies from the conjugated nanoparticles and the over-expressed receptors (revealed using immunofluorescence staining) on the surfaces of the breast cancer. The implications of the results are discussed for the selectivity and specificity of breast cancer targeting by ligand-conjugated BMNPs. DA - 2017/// PY - 2017/// DO - 10.1016/j.jmbbm.2017.02.004 VL - 68 SP - 276-286 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85013191493&partnerID=MN8TOARS KW - Chemically synthesized magnetite nanoparticles (CMNPs) KW - Biosynthesized magnetite nanoparticles (BMNPs) KW - Luteinizing hormone-releasing hormone (LHRH) KW - Breast specific antibody (BSA) KW - Ephrin type-A receptor 2 (EphA2) ER - TY - JOUR TI - MRI-Guided Telesurgery System Using a Fabry-Perot Interferometry Force Sensor and a Pneumatic Haptic Device AU - Su, H. AU - Shang, W. AU - Li, G. AU - Fischer, G.S. T2 - Annals of Biomedical Engineering DA - 2017/// PY - 2017/// ER - TY - JOUR TI - Fiber Optic Force Sensors for MRI-Guided Interventions and Rehabilitation AU - Su, H. AU - Iordorchita, I. AU - Tokuda, J. AU - Hata, N. AU - Liu, X. AU - Fischer, G.S. T2 - IEEE Sensors Journal DA - 2017/// PY - 2017/// ER - TY - JOUR TI - Increased piezoelectric response in functional nanocomposites through multiwall carbon nanotube interface and fused-deposition modeling three-dimensional printing – CORRIGENDUM AU - Kim, Hoejin AU - Torres, Fernando AU - Islam, Tariqul AU - Islam, Didarul AU - Chavez, Luis A. AU - Rosales, Carlos A. Garcia AU - Wilburn, Bethany R. AU - Stewart, Calvin M. AU - Noveron, Juan C. AU - Tseng, Tzu-Liang B. AU - Lin, Yirong T2 - MRS Communications DA - 2017/// PY - 2017/// DO - 10.1557/mrc.2017.129 VL - 7 IS - 4 SP - 974-974 ER - TY - JOUR TI - Increased piezoelectric response in functional nanocomposites through multiwall carbon nanotube interface and fused-deposition modeling three-dimensional printing AU - Kim, H. AU - Torres, F. AU - Islam, M.T. AU - Islam, M.D. AU - Chavez, L.A. AU - Garcia Rosales, C.A. AU - Wilburn, B.R. AU - Stewart, C.M. AU - Noveron, J.C. AU - Tseng, T.-L.B. AU - Lin, Y. T2 - MRS Communications DA - 2017/// PY - 2017/// DO - 10.1557/mrc.2017.126 VL - 7 IS - 4 SP - 960-966 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85034586130&partnerID=MN8TOARS ER - TY - JOUR TI - Analysis of thermoelastic characteristics in a thick walled FGM cylinder AU - Tanvir, A. N. M. AU - Islam, Md. Didarul AU - Ahmed, Faisal T2 - AIP Conference Proceedings AB - This study is concerned with the behavior of stress and strain in a thick walled functionally graded material (FGM) cylinder under internal pressure. The incompatible eigenstrain and equivalent eigenstrain developed in the cylinder, are taken into account. As a demonstration, a TiC/Al2O3 FGM cylinder is considered and different components of stress and strain are presented in order to study the effects of internal pressure, temperature difference (between room and sintering temperature), cylinder wall thickness and material distribution. The numerical result presented here shows that the thermoelastic characteristic like stress and strain of an FGM cylinder is significantly influenced by some of the above-mentioned parameters and can be controlled by properly controlling these parameters. DA - 2017/// PY - 2017/// DO - 10.1063/1.5018548 VL - 1919 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85040996392&partnerID=MN8TOARS ER - TY - CONF TI - Stochastic Effects on a Chaotic Duffing Oscillator AU - Perkins, Edmon T2 - International Microelectronics Assembly and Packaging Society, 13th International Conference and Exhibition on Device Packaging C2 - 2017/// CY - Fountain Hills, AZ DA - 2017/// PY - 2017/3/5/ ER - TY - CONF TI - Frequency response of p-mode intrinsic localized mode AU - Perkins, Edmon T2 - 9th European Nonlinear Dynamics Conference C2 - 2017/// CY - Budapest, Hungary DA - 2017/// PY - 2017/6/25/ ER - TY - JOUR TI - Effects of noise on the frequency response of the monostable Duffing oscillator AU - Perkins, Edmon T2 - Physics Letters A DA - 2017/// PY - 2017/// VL - 381 IS - 11 SP - 1009-1013 ER - TY - JOUR TI - Flexoelectric characterization of BaTiO3-0.08Bi(Zn1/2Ti1/2)O3 AU - Huang, Shujin AU - Kim, Taeyang AU - Hou, Dong AU - Cann, David AU - Jones, Jacob L. AU - Jiang, Xiaoning T2 - Applied Physics Letters AB - Flexoelectricity, the linear coupling between the strain gradient and the induced electric polarization, has been widely studied as a substitution for piezoelectricity among ceramic lead-free materials. Its potential in micro/nano-scale sensing has especially gained attention, outweighing the performance of cutting edge lead-based piezoelectric materials. In this letter, the flexoelectric coefficient of lead-free ceramic BaTiO3-0.08Bi(Zn1/2Ti1/2)O3 (BT-8BZT) was investigated in the transverse mode. The thermal dependence of flexoelectricity in BT-8BZT was investigated at temperatures ranging from 25 °C to 200 °C, and the results were compared with those of BaxSr1-xTiO3 (BST) ceramics. The effective μ12 of BT-8BZT is ∼25 μC/m at room temperature and can remain as high as ∼13 μC/m at 200 °C. This result suggests that BT-8BZT can be effectively used for micro/nano-sensing within a broad range of temperatures. DA - 2017/5/29/ PY - 2017/5/29/ DO - 10.1063/1.4984212 VL - 110 IS - 22 SP - 222904 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4984212 DB - Crossref ER - TY - BOOK TI - Dynamical Systems: Analytical and Computational Techniques A3 - Reyhanoglu, Mahmut AB - There has been a considerable progress made during the recent past on mathematical techniques for studying dynamical systems that arise in science and engineering. This progress has been, to a large extent, due to our increasing ability to mathematically model physical processes and to analyze and solve them, both analytically and numerically. With its eleven chapters, this book brings together important contributions from renowned international researchers to provide an excellent survey of recent advances in dynamical systems theory and applications. The first section consists of seven chapters that focus on analytical techniques, while the next section is composed of four chapters that center on computational techniques. DA - 2017/3/15/ PY - 2017/3/15/ DO - 10.5772/63189 PB - InTech SN - 9789535130154 9789535130161 UR - http://dx.doi.org/10.5772/63189 ER - TY - CONF TI - A dynamic neural network-based sliding mode observer method for a class of uncertain dynamic systems AU - Stebler, Shane AU - MacKunis, William AU - Ramos-Pedroza, Natalie AU - Reyhanoglu, Mahmut T2 - 2017 IEEE Conference on Control Technology and Applications (CCTA) AB - A dynamic neural network (DNN)-based observer design is presented, which amalgamates an adaptive neural network-based technique with a finite-time sliding mode estimation method. The proposed observer design is motivated by practical quadrotor unmanned aerial vehicle tracking control applications, where direct sensor measurements of translational and rotational rates are not available for feedback. While sliding mode estimation strategies are well established as an effective means to compensate for bounded disturbances and dynamic model uncertainty, the proposed observer design employs a feedforward adaptive DNN-based estimation term in addition to a robust, high-gain feedback sliding mode element. The use of the DNN-based term in the estimator design is motivated by the desire to improve transient performance and reduce steady state error. In addition, the proposed sliding mode estimator design is proven to compensate for input-multiplicative parametric model uncertainty. To the best of the authors' knowledge, this is the first DNN-based sliding mode estimator result to rigorously prove asymptotic state estimation in the presence of parametric actuator uncertainty. A Lyapuov-based stability analysis is utilized to prove that the proposed DNN-based observer achieves asymptotic estimation of the quadrotor altitude and attitude rates in the presence of model uncertainty and bounded disturbances (e.g., sensor noise). Numerical simulation results are also provided to demonstrate the improved performance that is achieved by incorporating the adaptive DNN in the observer. C2 - 2017/8// C3 - 2017 IEEE Conference on Control Technology and Applications (CCTA) CY - Mauna Lai, Hawaii DA - 2017/8// PY - 2017/8/27/ DO - 10.1109/CCTA.2017.8062431 PB - IEEE SN - 9781509021826 UR - http://dx.doi.org/10.1109/CCTA.2017.8062431 ER - TY - CONF TI - Robust quaternion-based nonlinear output feedback control of a quadrotor hover system AU - Hoffman, Derek AU - Rehan, Muhammad AU - MacKunis, William AU - Reyhanoglu, Mahmut T2 - 2017 IEEE 56th Annual Conference on Decision and Control (CDC) AB - A robust nonlinear output feedback control method is presented, which achieves three degree of freedom (3-DOF) attitude control of a hover system test bed. The proposed control method formally incorporates the practical limitations in the voltage control inputs to the control actuators (i.e., the quadrotor propellers). In addition, the control law is designed to compensate for uncertainty in the hover system dynamic model, including input-multiplicative parametric uncertainty resulting from uncertain drag and friction coefficients in the propellers' dynamic model. To reduce the computational requirement in the closed-loop system, constant feedforward estimates of the input-multiplicative uncertainty are utilized in lieu of adaptive parameter estimates. Eschewing the high-gain feedback requirement that is characteristic of standard sliding mode observer methods, the proposed control method utilizes a bank of dynamic filters, which operates as a velocity estimator in the closed-loop system. A rigorous error system development and Lyapunov-based stability analysis are presented to prove that the proposed output feedback control law achieves asymptotic 3-DOF attitude control in the presence of parametric input uncertainty and unmodeled dynamics. Experimental results are provided to demonstrate the performance of the attitude control method using the Quanser 3-DOF hover system test bed. C2 - 2017/12// C3 - 2017 IEEE 56th Annual Conference on Decision and Control (CDC) CY - Melbourne, Victoria, Australia DA - 2017/12// PY - 2017/12/12/ DO - 10.1109/CDC.2017.8264379 PB - IEEE SN - 9781509028733 UR - http://dx.doi.org/10.1109/CDC.2017.8264379 ER - TY - JOUR TI - Learning Control of Fixed-Wing Unmanned Aerial Vehicles Using Fuzzy Neural Networks AU - Kayacan, Erdal AU - Khanesar, Mojtaba Ahmadieh AU - Rubio-Hervas, Jaime AU - Reyhanoglu, Mahmut T2 - International Journal of Aerospace Engineering AB - A learning control strategy is preferred for the control and guidance of a fixed-wing unmanned aerial vehicle to deal with lack of modeling and flight uncertainties. For learning the plant model as well as changing working conditions online, a fuzzy neural network (FNN) is used in parallel with a conventional P (proportional) controller. Among the learning algorithms in the literature, a derivative-free one, sliding mode control (SMC) theory-based learning algorithm, is preferred as it has been proved to be computationally efficient in real-time applications. Its proven robustness and finite time converging nature make the learning algorithm appropriate for controlling an unmanned aerial vehicle as the computational power is always limited in unmanned aerial vehicles (UAVs). The parameter update rules and stability conditions of the learning are derived, and the proof of the stability of the learning algorithm is shown by using a candidate Lyapunov function. Intensive simulations are performed to illustrate the applicability of the proposed controller which includes the tracking of a three-dimensional trajectory by the UAV subject to time-varying wind conditions. The simulation results show the efficiency of the proposed control algorithm, especially in real-time control systems because of its computational efficiency. DA - 2017/// PY - 2017/// DO - 10.1155/2017/5402809 VL - 2017 SP - 1-12 J2 - International Journal of Aerospace Engineering LA - en OP - SN - 1687-5966 1687-5974 UR - http://dx.doi.org/10.1155/2017/5402809 DB - Crossref ER - TY - CONF TI - Iterative In-Situ 3D Layout Optimization of a Reconfigurable Ocean Current Turbine Array Using Bayesian Optimization AU - Baheri, Ali AU - Ramaprabhu, Praveen AU - Vermillion, Chris T2 - ASME 2017 Dynamic Systems and Control Conference AB - In this paper, we present an online approach for optimizing the 3D layout of an ocean current turbine (OCT) array. Unlike towered turbines, most OCT concepts for Gulf Stream energy harvesting involve tethered systems. The replacement of towers with tethers provides the opportunity for OCTs to adjust their locations within some domain by paying out/in tether to adjust depth and manipulating control surfaces (elevators and rudders) to adjust longitudinal and lateral positions. The ability to adjust the OCT positions online provides the capacity to reconfigure the array layout in response to changing flow conditions; however, successful online array layout reconfiguration requires optimization schemes that are not only effective but also enable fast convergence to the optimal configuration. To address the above needs, we present a reconfigurable layout optimization algorithm with two novel features. First, we describe the location of each turbine through a small set of basis parameters; the number of basis parameters does not grow with increasing array size, thereby leading to an optimization that is not only computationally tractable but is also highly scalable. Secondly, we use Bayesian Optimization to optimize these basis parameters. Bayesian Optimization is a very powerful iterative optimization technique that, at every iteration, fuses a best-guess model of a complex function (array power as a function of basis parameters, in our case) with a characterization of the model uncertainty in order to determine the next evaluation point. Using a low-order analytical wake interaction model, we demonstrate the effectiveness of the proposed optimization approach for various array sizes. C2 - 2017/// C3 - ASME 2017 Dynamic Systems and Control Conference : October 11-13, 2017, Tysons, Virginia, USA. CY - Tysons, Virginia DA - 2017/// PY - 2017/10/11/ DO - 10.1115/dscc2017-5230 VL - 3 PB - American Society of Mechanical Engineers ER - TY - JOUR TI - Design of cut unit geometry in hierarchical kirigami-based auxetic metamaterials for high stretchability and compressibility AU - Tang, Yichao AU - Yin, Jie T2 - Extreme Mechanics Letters AB - We studied the mechanical response of a recently developed new class of mechanical metamaterials based on the paper art of cutting, kirigami. Specially, the geometrical and structural design of representative cut units, via combined line cut, cut-out, and hierarchy of the structure, was explored for achieving both extreme stretchability and/or compressibility in kirigami metamaterials through experiments, alongside geometrical modeling and finite element simulations. The kirigami design was tested on constituent materials including non-stretchable copy papers and highly stretchable silicone rubber to explore the role of constituent material properties. The cut unit in the shape of solid rectangles with the square shape as a special case was demonstrated for achieving the extreme stretchability via rigid rotation of cut units. We found that compared to the square cut units, the theoretically predicted maximum stretchability via unit rotation in rectangle units (aspect ratio 2:1) increased dramatically from about 41% to 124% for the level 1 cut structure without hierarchy, and from about 62% to 156% for the level 2 hierarchical cut structure, which was validated by both experiments and simulations. To demonstrate the achievement of both extreme stretchability and compressibility, we replaced the solid square cut units with porous squares and re-entrant lattice shapes in silicone rubber based metamaterials. We found that a porous structure can enable an extreme compressibility of as high as 81%. DA - 2017/4// PY - 2017/4// DO - 10.1016/j.eml.2016.07.005 VL - 12 SP - 77-85 J2 - Extreme Mechanics Letters LA - en OP - SN - 2352-4316 UR - http://dx.doi.org/10.1016/j.eml.2016.07.005 DB - Crossref KW - Kirigami KW - Auxetic metamaterial KW - Hierarchy KW - High stretchability KW - Compressibility ER - TY - JOUR TI - Origami and kirigami inspired self-folding for programming three-dimensional shape shifting of polymer sheets with light AU - Zhang, Qiuting AU - Wommer, Jonathon AU - O’Rourke, Connor AU - Teitelman, Joseph AU - Tang, Yichao AU - Robison, Joshua AU - Lin, Gaojian AU - Yin, Jie T2 - Extreme Mechanics Letters AB - Origami and kirigami guided programmable shape shifting is explored via self-folding and spontaneous buckling of a thin sheet of shape memory polymer with light. By patterning the sheet with printed black ink lines as actuating hinges, we show that the folding angle can be well controlled by tuning the ink line width, which is predicted by both a simplified localized bilayer folding model and corresponding finite element method (FEM) simulation. Inspired by the approach of paper origami and kirigami combining folding and cutting, we then explored the design of prescribed patterned creases (i.e. ink lines) and/or cuts in the polymer thin sheet for programming a library of light-responsive three-dimensional (3-D) surfaces in a controlled fashion. Through the design of prescribed straight and curved crease patterns in origami, we demonstrated the generation of light-driven self-folding cylinders, helices, and pyramids with zero Gaussian curvature, as well as spontaneous formation of saddles with negative Gaussian curvature through localized curved folding induced global buckling. The quantitative underlying mechanism governing the geometry of the different self-folded 3-D structures is revealed through simple geometrical modeling and FEM simulations. Lastly, through kirigami combining both folding and cutting in the form of line cuts or cut-outs, we demonstrated the spontaneous formation of light-responsive, more complex pop-up kirigami structures. DA - 2017/2// PY - 2017/2// DO - 10.1016/j.eml.2016.08.004 VL - 11 SP - 111-120 J2 - Extreme Mechanics Letters LA - en OP - SN - 2352-4316 UR - http://dx.doi.org/10.1016/j.eml.2016.08.004 DB - Crossref KW - Origami and kirigami KW - Self-folding KW - Buckling KW - Programmable matter KW - Light-responsive ER - TY - JOUR TI - Radio frequency-mediated local thermotherapy for destruction of pancreatic tumors using Ni–Au core–shell nanowires AU - Hopkins, X. AU - Gill, W. AU - Kringel, R. AU - Wang, G. AU - Hass, J. AU - Acharya, S. AU - Park, J. AU - Jeon, I.-T. AU - An, B.H. AU - Lee, J. AU - Ryu, J. AU - Hill, R. AU - McIlroy, D. AU - Kim, Y.K. AU - Choi, D. T2 - Nanotechnology AB - We present a novel method of radio frequency (RF)-mediated thermotherapy in tumors by remotely heating nickel (Ni)–gold (Au) core–shell nanowires (CSNWs). Ectopic pancreatic tumors were developed in nude mice to evaluate the thermotherapeutic effects on tumor progression. Tumor ablation was produced by RF-mediated thermotherapy via activation of the paramagnetic properties of the Ni–Au CSNWs. Histopathology demonstrated that heat generated by RF irradiation caused significant cellular death with pyknotic nuclei and nuclear fragmentation dispersed throughout the tumors. These preliminary results suggest that thermotherapy ablation induced via RF activation of nanowires provides a potential alternative therapy for cancer treatment. DA - 2017/1/20/ PY - 2017/1/20/ DO - 10.1088/1361-6528/28/3/03LT01 VL - 28 IS - 3 SP - 03LT01 KW - RF-mediated thermotherapy KW - magnetic core-shell nanowire KW - RF radiation KW - cancer ER - TY - CONF TI - Context-Dependent Bayesian Optimization in Real-Time Control; A Case Study in Airborne Wind Energy Systems AU - Baheri, Ali AU - Vermillion, Chris T2 - NIPS Workshop on Bayesian Optimization C2 - 2017/// C3 - Proceedings of BayesOpt 2017 CY - Long Beach, CA DA - 2017/// PY - 2017/12/9/ ER - TY - JOUR TI - Laboratory-Scale Flight Characterization of a Multitethered Aerostat for Wind Energy Generation AU - Deodhar, Nihar AU - Bafandeh, Alireza AU - Deese, Joe AU - Smith, Brian AU - Muyimbwa, Tim AU - Vermillion, Christopher AU - Tkacik, Peter T2 - AIAA Journal AB - Tethered lifting bodies have attracted significant attention from surveillance, communications, and (most recently) wind energy domains. As with many aerospace systems, the costs of full-scale testing act as a bottleneck to development, especially when accurate dynamic models do not exist, as is the case with a number of lifting-body designs that deviate from the traditional aerostat shape. This paper demonstrates the efficacy of using a laboratory-scale water channel-based test platform for the dynamic characterization of tethered systems with rigid lifting bodies, focusing on a lighter-than-air wind energy system as a case study. The platform overcomes the financial burden of full-scale testing, which simultaneously alleviates the short-term need for high-fidelity dynamic models and aids in the long-term development of high-fidelity models. In this paper, it is shown how a dimensional analysis provides a qualitative correlation between full-scale and th-scale flight behavior, as well as how this laboratory-scale platform is used to evaluate different lifting-body designs. DA - 2017/6// PY - 2017/6// DO - 10.2514/1.j054407 VL - 55 IS - 6 SP - 1823-1832 J2 - AIAA Journal LA - en OP - SN - 0001-1452 1533-385X UR - http://dx.doi.org/10.2514/1.j054407 DB - Crossref ER - TY - JOUR TI - Experimentally Infused Plant and Controller Optimization Using Iterative Design of Experiments—Theoretical Framework and Airborne Wind Energy Case Study AU - Deodhar, Nihar AU - Deese, Joseph AU - Vermillion, Christopher T2 - Journal of Dynamic Systems, Measurement, and Control AB - This research presents an iterative framework for optimizing the plant and controller for complex systems by fusing expensive but valuable experiments with cheap yet less accurate simulations. At each iteration, G-optimal design is used to generate experiments and simulations within a prescribed design space that is shrunken in size after each successful iteration. The shrinking of the design space is determined through statistical characterization of a response surface model, and further shrinking is achieved at successive iterations through a numerical model correction factor that is driven by the results of experiments. An initial validation of this iterative design optimization framework was performed on an airborne wind energy (AWE) system, where tethers and an aerostat are used in place of a tower to elevate the turbine to high altitudes. Using a unique lab-scale setup for the experiments, the aforementioned iterative methodology was used to optimize the center of mass location and pitch angle set point for the airborne wind energy system. The optimum configuration yielded a substantial improvement in system responses as compared to a numerically optimized configuration. The framework was recently extended to include four variables (horizontal and vertical stabilizer areas, center of mass location, and pitch angle set point). DA - 2017/8/29/ PY - 2017/8/29/ DO - 10.1115/1.4037014 VL - 140 IS - 1 LA - en OP - SN - 0022-0434 1528-9028 UR - http://dx.doi.org/10.1115/1.4037014 DB - Crossref ER - TY - JOUR TI - Nested Plant/Controller Co-Design Using G-Optimal Design and Extremum Seeking: Theoretical Framework and Application to an Airborne Wind Energy System * *This work was supported by NSF grant number 1453912, entitled CAREER: Efficient Experimental Optimization for High Performance Airborne Wind Energy Systems. AU - Deese, Joe AU - Deodhar, Nihar AU - Vermillion, Chris T2 - IFAC-PapersOnLine AB - This paper presents a unique nested optimization framework for the co-design of a physical system (plant) and controller, which leverages optimal Design of Experiments (DoE) techniques for the plant optimization and extremum seeking for the control system optimization. At each iteration of the optimization, candidate plant parameters are generated by using G-optimal DoE. Unlike gradient-based approaches, the use of optimal DoE enables efficient global exploration of a plant design space that can contain multiple local optima. For each candidate plant design, the corresponding controller optimization is performed in real time, using extremum seeking. This enables the real-time adjustment of controller parameters during the course of simulations or experiments, thereby expediting the overall optimization process. The co-design process is carried out iteratively, where sub-optimal plant designs are rejected based on a response surface characterization and hypothesis testing. The co-design framework was validated in simulation for a Buoyant Airborne Turbine (BAT). Here, the optimized plant parameters were a reference area scale factor (scales the horizontal and vertical stabilizer areas uniformly) and center of mass location, whereas the optimized control parameter was the pitch angle setpoint. After four complete iterations, the flight performance index improved and the feasible plant design space (i.e., the locus of plant design parameters that could possibly be optimal, based on hypothesis testing) shrunk by 99%. DA - 2017/7// PY - 2017/7// DO - 10.1016/j.ifacol.2017.08.1182 VL - 50 IS - 1 SP - 11965-11971 J2 - IFAC-PapersOnLine LA - en OP - SN - 2405-8963 UR - http://dx.doi.org/10.1016/j.ifacol.2017.08.1182 DB - Crossref KW - Optimization KW - co-design KW - energy systems KW - wind energy KW - airborne wind energy ER - TY - CONF TI - Impact performance and damage behavior of composite sandwich structures In arctic condition AU - Tan, K.T. AU - Elamin, M. AU - Li, B. C2 - 2017/// C3 - 32nd Technical Conference of the American Society for Composites 2017 DA - 2017/// VL - 2 SP - 1309-1314 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85047767450&partnerID=MN8TOARS ER - TY - CONF TI - Effect of low temperature on impact behavior of composite sandwich structures AU - Elamin, M. AU - Li, B. AU - Tan, K.T. C2 - 2017/// C3 - ICCM International Conferences on Composite Materials DA - 2017/// VL - 2017-August UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85053168143&partnerID=MN8TOARS ER - TY - CHAP TI - Nonlinear Dynamics and Control of Aerial Robots AU - Reyhanoglu, Mahmut AU - Rehan, Muhammad T2 - Aerial Robots - Aerodynamics, Control and Applications AB - Aerial robotics is one of the fastest growing industry and has a number of evolving applications. Higher agility make aerial robots ideal candidate for applications like rescue missions especially in difficult to access areas. This chapter first derives the complete nonlinear dynamics of an aerial robot consisting of a quadcopter with a two-link robot manipulator. Precise control of such an aerial robot is a challenging task due to the fact that the translational and rotational dynamics of the quadcopter are strongly coupled with the dynamics of the manipulator. We extend our previous results on the control of quadrotor UAVs to the control of aerial robots. In particular, we design a backstepping and Lyapunov-based nonlinear feedback control law that achieves point-to-point control of the areal robot. The effectiveness of this feedback control law is illustrated through a simulation example. PY - 2017/9/6/ DO - 10.5772/intechopen.69641 OP - PB - InTech SN - 9789535134633 9789535134640 UR - http://dx.doi.org/10.5772/intechopen.69641 DB - Crossref ER - TY - CONF TI - Motion planning for a knife-edge on the surface of a hyperboloid AU - Rehan, Muhammad AU - Reyhanoglu, Mahmut AU - McClamroch, Harris T2 - 2017 11th Asian Control Conference (ASCC) AB - This paper presents a motion planning strategy for a knife-edge moving on the surface of a hyperboloid. First, kinematics equations for the knife-edge are developed without the use of local coordinates so that the mathematical model is globally defined and have no singularities or ambiguities. Then, a novel motion planning algorithm has been constructed using the concept of ruled surfaces. The computer simulations demonstrate the effectiveness of the algorithm for any initial and final position/direction of the knife-edge on the surface of the hyperboloid. C2 - 2017/12// C3 - 2017 11th Asian Control Conference (ASCC) DA - 2017/12// DO - 10.1109/ASCC.2017.8287363 PB - IEEE SN - 9781509015733 UR - http://dx.doi.org/10.1109/ASCC.2017.8287363 DB - Crossref ER - TY - CONF TI - Geometric tracking control of a three-dimensional revolute joint robot AU - Hoffman, Derek AU - Reyhanoglu, Mahmut T2 - 2017 11th Asian Control Conference (ASCC) AB - This paper studies the tracking control of a three-dimensional revolute joint robot consisting of a rotating base and two rigid rotating links with bounded unstructured uncertainties to all three degrees of freedom. The configuration space of the system is considered as a direct product of three one-sphere (S 1 ) configuration spaces to provide a global formulation. Following a Lagrangian formulation, a nonlinear tracking control law is designed in terms of global coordinates. The proposed controller is mathematically proven to provide uniformly ultimately bounded stability, and simulations demonstrate its performance. C2 - 2017/12// C3 - 2017 11th Asian Control Conference (ASCC) DA - 2017/12// DO - 10.1109/ASCC.2017.8287245 PB - IEEE SN - 9781509015733 UR - http://dx.doi.org/10.1109/ASCC.2017.8287245 DB - Crossref ER - TY - CONF TI - Finite-time control of a compliant base robot manipulator AU - Reyhanoglu, Mahmut AU - Hoffman, Derek T2 - 2017 11th Asian Control Conference (ASCC) AB - The control design of a two-link robotic manipulator with a translationally compliant base is investigated. The equations of motion are derived using a Lagrangian formulation. A notch-filtered finite-time control law is designed to avoid natural frequency excitation via the control input. The control algorithm's performance is then observed through simulation, aiming to demonstrate effectiveness on a benchmark robotic manipulator system. C2 - 2017/12// C3 - 2017 11th Asian Control Conference (ASCC) DA - 2017/12// DO - 10.1109/ASCC.2017.8287365 PB - IEEE SN - 9781509015733 UR - http://dx.doi.org/10.1109/ASCC.2017.8287365 DB - Crossref ER - TY - CONF TI - Dynamic neural network-based sliding mode estimation of quadrotor systems AU - Stebler, S. AU - Campobasso, M. AU - Kidambi, K. AU - MacKunis, W. AU - Reyhanoglu, M. T2 - 2017 American Control Conference (ACC) AB - A dynamic neural network (DNN)-based observer design is presented, which amalgamates an adaptive neural network-based technique with a sliding mode estimation method. The proposed observer design is motivated by practical quadrotor tracking control applications, where direct sensor measurements of translational and rotational rates are not available for feedback. While sliding mode estimation strategies are well established as an effective means to compensate for bounded disturbances and dynamic model uncertainty, the proposed observer design employs a feedforward adaptive DNN-based estimation term in addition to a robust, high-gain feedback sliding mode element. The use of the DNN-based term in the estimator design is motivated by the desire to improve transient performance and reduce steady state error. The DNN-based feedforward term could also offer the advantage of reducing the control effort that would be required when the proposed observer design is operating as part of a closed-loop control system. A Lyapuov-based stability analysis is utilized to prove that the proposed DNN-based observer achieves asymptotic estimation of the quadrotor altitude and attitude rates in the presence of model uncertainty and bounded disturbances (e.g., sensor noise). Numerical simulation results are also provided to demonstrate the improved performance that is achieved by incorporating the adaptive DNN in the observer. C2 - 2017/5// C3 - 2017 American Control Conference (ACC) DA - 2017/5// DO - 10.23919/ACC.2017.7963344 PB - IEEE SN - 9781509059928 UR - http://dx.doi.org/10.23919/ACC.2017.7963344 DB - Crossref ER - TY - JOUR TI - Synthetic Jet Actuator-Based Aircraft Tracking Using a Continuous Robust Nonlinear Control Strategy AU - Ramos-Pedroza, N. AU - MacKunis, W. AU - Reyhanoglu, M. T2 - International Journal of Aerospace Engineering AB - A robust nonlinear control law that achieves trajectory tracking control for unmanned aerial vehicles (UAVs) equipped with synthetic jet actuators (SJAs) is presented in this paper. A key challenge in the control design is that the dynamic characteristics of SJAs are nonlinear and contain parametric uncertainty. The challenge resulting from the uncertain SJA actuator parameters is mitigated via innovative algebraic manipulation in the tracking error system derivation along with a robust nonlinear control law employing constant SJA parameter estimates. A key contribution of the paper is a rigorous analysis of the range of SJA actuator parameter uncertainty within which asymptotic UAV trajectory tracking can be achieved. A rigorous stability analysis is carried out to prove semiglobal asymptotic trajectory tracking. Detailed simulation results are included to illustrate the effectiveness of the proposed control law in the presence of wind gusts and varying levels of SJA actuator parameter uncertainty. DA - 2017/// PY - 2017/// DO - 10.1155/2017/4934281 VL - 2017 SP - 1-13 J2 - International Journal of Aerospace Engineering LA - en OP - SN - 1687-5966 1687-5974 UR - http://dx.doi.org/10.1155/2017/4934281 DB - Crossref ER - TY - JOUR TI - Knife-Edge Motion on a Surface as a Nonholonomic Control Problem AU - McClamroch, Harris AU - Reyhanoglu, Mahmut AU - Rehan, Muhammad T2 - IEEE Control Systems Letters AB - This letter studies a new formulation for the kinematics of a knife-edge moving on an arbitrary smooth surface in ${\mathbb {R}^{3}}$ . The kinematics equations for a knife-edge, viewed as a rigid body, are constrained by the requirement that the knife-edge maintain contact with the surface. They describe the constrained translation of the point of contact of the knife-edge on the surface and the constrained attitude of the knife-edge as a rigid body. These equations for the knife-edge kinematics in ${\mathbb {R}}^{3}$ are expressed in a geometric form, without the use of local coordinates; they are globally defined without singularities or ambiguities. The kinematics equations can be expressed in several simplified forms and written as a drift-free nonlinear control system. Comments are made about interesting motion planning and path planning problems. The kinematics equations are specialized for two specific surfaces defined in ${ {\mathbb {R}}^{3}}$ , namely, a flat plane and the surface of a sphere. Results for the flat plane are compared with standard results obtained using local coordinates; results for the sphere, in contrast, require full attention to the 3-D geometry. DA - 2017/7// PY - 2017/7// DO - 10.1109/lcsys.2017.2700441 VL - 1 IS - 1 SP - 26-31 J2 - IEEE Control Syst. Lett. OP - SN - 2475-1456 UR - http://dx.doi.org/10.1109/lcsys.2017.2700441 DB - Crossref KW - Nonholonomic KW - geometric formulation ER - TY - JOUR TI - Non-additive impacts of covalent cross-linking on the viscoelastic nanomechanics of ionic polyelectrolyte complexes AU - Han, Biao AU - Ma, Tianzhu AU - Vergara, John H. AU - Palmese, Giuseppe R. AU - Yin, Jie AU - Lee, Daeyeon AU - Han, Lin T2 - RSC Advances AB - This study elucidates the influences of adding covalent cross-linking on the nanomechanical viscoelasticity of ionically cross-linked polyelectrolyte networks. DA - 2017/// PY - 2017/// DO - 10.1039/c7ra08514a VL - 7 IS - 84 SP - 53334-53345 J2 - RSC Adv. LA - en OP - SN - 2046-2069 UR - http://dx.doi.org/10.1039/c7ra08514a DB - Crossref ER - TY - JOUR TI - Self-similar Hierarchical Wrinkles as a Potential Multifunctional Smart Window with Simultaneously Tunable Transparency, Structural Color, and Droplet Transport AU - Lin, Gaojian AU - Chandrasekaran, Prashant AU - Lv, Cunjing AU - Zhang, Qiuting AU - Tang, Yichao AU - Han, Lin AU - Yin, Jie T2 - ACS Applied Materials & Interfaces AB - Smart window has immense potential for energy savings in architectural and vehicular applications, while most studies focus on the tunability of a single property of optical transmittance. Here we explore harnessing dynamically tunable hierarchical wrinkles for design of a potential multifunctional smart window with combined structural color and water droplet transport control. The self-similar hierarchical wrinkles with both nanoscale and microscale features are generated on a prestrained poly(dimethylsiloxane) elastomer through sequential strain release and multistep oxygen plasma treatment. We show that the hierarchically wrinkled elastomer displays both opaqueness and iridescent structural color. We find that restretching/releasing the elastomer leads to the reversible and repeatable switch from opaqueness to transparency, arising from the flattening of large wrinkles (micrometer scale), while a nonvanishing structural color occurs due to the nondisappearing small wrinkles (nanoscale). The unique features of combined reversible large wrinkles and irreversible small wrinkles during hierarchical wrinkling are well reproduced by corresponding finite element simulation. The criteria for generating self-similar hierarchical wrinkles is revealed through a simplified theoretical model and validated by experiments. In addition to its tunable optical property, we further show its ability in control of water droplet transport on demand through mechanical stretching and release. We find that an initially pinned water droplet on the tilted hierarchically wrinkled surface starts to slide when the surface is stretched, and becomes pinned again upon strain release. Such a process is reversible and repeatable. The hierarchically wrinkled surface could find broad potential applications not only in multifunctional smart windows with additional features of aesthetics and water collection, but in microfluidics, design of slippery surfaces, and directional water transportation. DA - 2017/7/25/ PY - 2017/7/25/ DO - 10.1021/acsami.7b05056 VL - 9 IS - 31 SP - 26510-26517 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/acsami.7b05056 DB - Crossref KW - hierarchical wrinkles KW - smart window KW - tunable optical properties KW - water droplet transport control KW - multifunctionality ER - TY - JOUR TI - Cuts Guided Deterministic Buckling in Arrays of Soft Parallel Plates for Multifunctionality AU - Lin, Gaojian AU - Ge, Dengteng AU - Tang, Yichao AU - Xia, Yu AU - Wu, Gaoxiang AU - Han, Lin AU - Yang, Shu AU - Yin, Jie T2 - ACS Applied Materials & Interfaces AB - Harnessing buckling instability in soft materials offers an effective strategy to achieve multifunctionality. Despite great efforts in controlling the wrinkling behaviors of film-based systems and buckling of periodic structures, the benefits of classical plate buckling in soft materials remain largely unexplored. The challenge lies in the intrinsic indeterminate characteristics of buckling, leading to geometric frustration and random orientations. Here, we report the controllable global order in constrained buckling of arrays of parallel plates made of hydrogels and elastomers on rigid substrates. By introducing patterned cuts on the plates, the randomly phase-shifted buckling in the array of parallel plates transits to a prescribed and ordered buckling with controllable phases. The design principle for cut-directed deterministic buckling in plates is validated by both mechanics model and finite element simulation. By controlling the contacts and interactions between the buckled parallel plates, we demonstrate on-demand reconfigurable electrical and optical pathways, and the potential application in design of mechanical logic gates. By varying the local stimulus within the plates, we demonstrate that microscopic pathways can be written, visualized, erased, and rewritten macroscopically into a completely new one for potential applications such as soft reconfigurable circuits and logic devices. DA - 2017/8/17/ PY - 2017/8/17/ DO - 10.1021/acsami.7b09466 VL - 9 IS - 34 SP - 29345-29354 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/acsami.7b09466 DB - Crossref KW - cut-directed deterministic buckling KW - hydrogel KW - constrained buckling of plates KW - multifunctionality KW - reconfigurable electrical and optical pathways ER - TY - JOUR TI - Spontaneous Periodic Delamination of Thin Films To Form Crack-Free Metal and Silicon Ribbons with High Stretchability AU - Zhang, Qiuting AU - Tang, Yichao AU - Hajfathalian, Maryam AU - Chen, Chunxu AU - Turner, Kevin T. AU - Dikin, Dmitriy A. AU - Lin, Gaojian AU - Yin, Jie T2 - ACS Applied Materials & Interfaces AB - Design of electronic materials with high stretchability is of great importance for realizing soft and conformal electronics. One strategy of realizing stretchable metals and semiconductors is to exploit the buckling of materials bonded to elastomers. However, the level of stretchability is often limited by the cracking and fragmentation of the materials that occurs when constrained buckling occurs while bonded to the substrate. Here, we exploit a failure mechanism, spontaneous buckling-driven periodic delamination, to achieve high stretchability in metal and silicon films that are deposited on prestrained elastomer substrates. We find that both globally periodic buckle-delaminated pattern and ordered cracking patterns over large areas are observed in the spontaneously buckle-delaminated thin films. The geometry of periodic delaminated buckles and cracking periodicity can be predicted by theoretical models. By patterning the films into ribbons with widths smaller than the predicted cracking periodicity, we demonstrate the design of crack-free and spontaneous delaminated ribbons on highly prestrained elastomer substrates, which provides a high stretchability of about 120% and 400% in Si and Au ribbons, respectively. We find that the high stretchability is mainly attributed to the largely relaxed strain in the ribbons via spontaneous buckling-driven delamination, as made evident by the small maximum tensile strain in both ribbons, which is measured to be over 100 times smaller than that of the substrate prestrain. DA - 2017/12/14/ PY - 2017/12/14/ DO - 10.1021/acsami.7b15693 VL - 9 IS - 51 SP - 44938-44947 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/acsami.7b15693 DB - Crossref KW - crack-free ribbons KW - extreme stretchability KW - spontaneous periodic buckle-delamination KW - metal and silicon thin films KW - crack fragmentation ER - TY - JOUR TI - Tunable cobalt nanoparticle synthesis by intense pulse flash annealing AU - Mosey, Aaron AU - Gaire, Babu AU - Kim, Jeongwhan AU - Ryu, Jong Eun AU - Cheng, Ruihua T2 - AIP Advances AB - Magnetically susceptible materials can serve as a basis for the directed assembly of nanoscale network devices which can be used to extract energy from phase change materials. So far, matrix production cost has been a prohibitive factor in the realization of real world applications. Here we report a cost-effective method to synthesize magnetic nanoparticles. Samples were fabricated by sputtering magnetic thin films on carbon nanotube substrates followed by xenon intense pulsed light flash annealing. The results indicate that spatially ordered magnetic spheres can be tuned by various parameters such as initial thin film thickness, xenon lamp exposure excitation energy, local surface geometries, and the presence of an external magnetic field during annealing. DA - 2017/1/25/ PY - 2017/1/25/ DO - 10.1063/1.4975044 VL - 7 IS - 5 SP - 056308 J2 - AIP Advances LA - en OP - SN - 2158-3226 UR - http://dx.doi.org/10.1063/1.4975044 DB - Crossref ER - TY - JOUR TI - Poly(vinylidene fluoride) derived fluorine-doped magnetic carbon nanoadsorbents for enhanced chromium removal AU - Cao, Yonghai AU - Huang, Jiangnan AU - Peng, Xiangfang AU - Cao, Dapeng AU - Galaska, Alexandra AU - Qiu, Song AU - Liu, Jiurong AU - Khan, Mojammel A. AU - Young, David P. AU - Ryu, Jong Eun AU - Feng, Hongbo AU - Yerra, Narendranath AU - Guo, Zhanhu T2 - Carbon AB - Newly designed fluorine-doped magnetic carbon (F-MC) was synthesized in situ though a facile one-step pyrolysis-carbonization method. Poly(vinylidene fluoride) (PVDF) served as the precursor for both carbon and fluorine. 2.5% F content with core-shell structure was obtained over F-MC, which was used as a adsorbent for the Cr(VI) removal. To our best knowledge, this is the first time to report that the fluorine doped material was applied for the Cr(VI) removal, demonstrating very high removal capacity (1423.4 mg g−1), higher than most reported adsorbents. The unexpected performance of F-MC can be attributed to the configuration of F dopants on the surface. The observed pseudo-second-order kinetic study indicated the dominance of chemical adsorption for this process. High stability of F-MC after 5 recycling test for the Cr(VI) removal was also observed, indicating that F-MC could be used as an excellent adsorbent for the toxic heavy metal removal from the wastewater. DA - 2017/5// PY - 2017/5// DO - 10.1016/j.carbon.2017.01.033 VL - 115 SP - 503-514 J2 - Carbon LA - en OP - SN - 0008-6223 UR - http://dx.doi.org/10.1016/j.carbon.2017.01.033 DB - Crossref ER - TY - JOUR TI - Reduction in Migratory Phenotype in a Metastasized Breast Cancer Cell Line via Downregulation of S100A4 and GRM3 AU - Chen, Andy AU - Wang, Luqi AU - Li, Bai-Yan AU - Sherman, Jesse AU - Ryu, Jong E. AU - Hamamura, Kazunori AU - Liu, Yunlong AU - Nakshatri, Harikrishna AU - Yokota, Hiroki T2 - Scientific Reports AB - Abstract To investigate phenotypic and genotypic alterations before and after bone metastasis, we conducted genome-wide mRNA profiling and DNA exon sequencing of two cell lines (TMD and BMD) derived from a mouse xenograft model. TMD cells were harvested from the mammary fat pad after transfecting MDA-MB-231 breast cancer cells, while BMD cells were isolated from the metastasized bone. Compared to BMD cells, TMD cells exhibited higher cellular motility. In contrast, BMD cells formed a spheroid with a smoother and more circular surface when co-cultured with osteoblasts. In characterizing mRNA expression using principal component analysis, S100 calcium-binding protein A4 (S100A4) was aligned to a principal axis associated with metastasis. Partial silencing of S100A4 suppressed migratory capabilities of TMD cells, while Paclitaxel decreased the S100A4 level and reduced TMD’s cellular motility. DNA mutation analysis revealed that the glutamate metabotropic receptor 3 (GRM3) gene gained a premature stop codon in BMD cells, and silencing GRM3 in TMD cells altered their spheroid shape closer to that of BMD cells. Collectively, this study demonstrates that metastasized cells are less migratory due in part to the post-metastatic downregulation of S100A4 and GRM3. Targeting S100A4 and GRM3 may help prevent bone metastasis. DA - 2017/6/14/ PY - 2017/6/14/ DO - 10.1038/s41598-017-03811-9 VL - 7 IS - 1 SP - 3459-3460 J2 - Sci Rep LA - en OP - SN - 2045-2322 UR - http://dx.doi.org/10.1038/s41598-017-03811-9 DB - Crossref ER - TY - JOUR TI - Altitude Optimization of Airborne Wind Energy Systems via Switched Extremum Seeking—Design, Analysis, and Economic Assessment AU - Bafandeh, Alireza AU - Vermillion, Chris T2 - IEEE Transactions on Control Systems Technology AB - This paper applies a Lyapunov-based switched extremum seeking (LSES) control algorithm to the application of altitude optimization of airborne wind energy systems. We perform an economic analysis to evaluate the effectiveness of the control scheme. Finding the altitude with the highest energy yield requires energy to be consumed in the search for this optimal altitude. The simultaneous desires to optimize altitude and minimize control energy consumption are balanced in this paper through a variant of ES control, where the periodic perturbation signal is reduced when convergence upon an optimal altitude is detected. The signal is reinstated when the wind speed begins to deviate from its instantaneous optimal value. Because the wind shear profile (wind speed versus altitude) is subject to continual variations, this application represents a challenging case study in LSES control. Using real wind shear data acquired over a 25-day period, the results presented in this paper show that the LSES controller is successful in significantly increasing the net energy production over fixed-altitude and standard ES strategies. The economic advantage of the approach is illustrated through a comparison of achievable wind energy penetration with and without LSES-based altitude optimization in place, using real load demand data. DA - 2017/11// PY - 2017/11// DO - 10.1109/tcst.2016.2632534 VL - 25 IS - 6 SP - 2022-2033 J2 - IEEE Trans. Contr. Syst. Technol. OP - SN - 1063-6536 1558-0865 UR - http://dx.doi.org/10.1109/tcst.2016.2632534 DB - Crossref KW - Airborne wind energy (AWE) KW - economic assessment KW - extremum seeking (ES) control KW - Lyapunov technique KW - optimization. ER - TY - JOUR TI - Real-time control using Bayesian optimization: A case study in airborne wind energy systems AU - Baheri, Ali AU - Bin-Karim, Shamir AU - Bafandeh, Alireza AU - Vermillion, Christopher T2 - Control Engineering Practice AB - This paper presents a framework by which a data-driven optimization technique known as Bayesian Optimization can be used for real-time optimal control. In particular, Bayesian Optimization is applied to the real-time altitude optimization of an Airborne Wind Energy (AWE) system, for the purpose of maximizing net energy production. Determining the optimal operating altitude of an AWE system is challenging, as the wind speed constantly varies with both time and altitude. Furthermore, without expensive auxiliary equipment, the wind speed is only measurable at the AWE system’s operating altitude. In this work, Gaussian Process modeling and Bayesian Optimization are used in real-time to optimize the AWE system’s operating altitude efficiently, without the use of auxiliary wind profiling equipment. Specifically, the underlying objective function is modeled by a Gaussian Process (GP); then, Bayesian Optimization utilizes the predictive uncertainty information from the GP to determine the best subsequent operating altitude. In the AWE application, context-dependent Bayesian Optimization is used to handle the time-varying nature of the wind shear profile (wind speed vs. altitude). Using real wind data, our method is validated against three baseline approaches. Our simulation results show that the Bayesian Optimization method is successful in significantly increasing power production over these baselines. DA - 2017/12// PY - 2017/12// DO - 10.1016/j.conengprac.2017.09.007 VL - 69 SP - 131-140 J2 - Control Engineering Practice LA - en OP - SN - 0967-0661 UR - http://dx.doi.org/10.1016/j.conengprac.2017.09.007 DB - Crossref KW - Bayesian Optimization KW - Optimal control KW - Energy systems KW - Wind energy KW - Airborne wind energy systems ER - TY - CONF TI - Insights from an experimental study on the crosswind flight of a lab-scale buoyant air turbine AU - Kehs, Michelle AU - Cobb, Mitchell AU - Fathy, Hosam K. AU - Vermillion, Chris T2 - 2017 American Control Conference (ACC) AB - This paper presents an experimental investigation into the crosswind motion of a lab-scale buoyant air turbine under a variety of flow conditions. A buoyant air turbine consists of a horizontal-axis turbine placed inside a helium-filled shroud and connected to the ground by tethers. Because of this setup, the system can reach higher altitudes where winds are typically stronger. Furthermore, there is an opportunity to improve power production by executing crosswind flight. This paper builds directly on (i) previous work that uses a water channel to develop a lab-scale setup that is dynamically equivalent to a full-scale system and (ii) previous work that uses this setup to execute crosswind motion induced by a square wave roll set-point trajectory. The water channel setup allows for many tests to be run at a relatively low cost. In this paper, we use the water channel to run crosswind experiments at a variety of flow speeds and with a variety of control parameters. These experimental conditions are selected using the G-optimal Design of Experiments. To the best of the authors' knowledge, this is the first time that such a variety of crosswind flight conditions have been tested on a lab-scale buoyant air turbine. Results show that (i) crosswind motion can be achieved at a variety of flow speeds, (ii) roll set-points with periods between 4 and 6 seconds are most effective out of the conditions tested, and (iii) at low flow speeds, the system can oscillate, even when unprompted by a periodic roll set-point trajectory. C2 - 2017/5// C3 - 2017 American Control Conference (ACC) DA - 2017/5// DO - 10.23919/acc.2017.7963809 PB - IEEE SN - 9781509059928 UR - http://dx.doi.org/10.23919/acc.2017.7963809 DB - Crossref ER - TY - CONF TI - Altitude optimization of Airborne Wind Energy systems: A Bayesian Optimization approach AU - Baheri, Ali AU - Vermillion, Christopher T2 - 2017 American Control Conference (ACC) AB - This study presents a data-driven approach for optimizing the operating altitude of Airborne Wind Energy (AWE) systems to maximize net energy production. Determining the optimal operating altitude of an AWE system is challenging, as the wind speed constantly varies with both time and altitude. Furthermore, without expensive auxiliary equipment, the wind speed is only measurable at the AWE system's operating altitude. The work presented in this paper shows how tools from machine learning can be blended with real-time control to optimize the AWE system's operating altitude efficiently, without the use of auxiliary wind profiling equipment. Specifically, Bayesian Optimization, which is a data-driven technique for finding the optimum of an unknown and expensive-to-evaluate objective function, is applied to the real-time control of an AWE system. The underlying objective function is modeled by a Gaussian Process (GP); then, Bayesian Optimization utilizes the predictive uncertainty information from the GP to decide the best subsequent operating altitude. In the AWE application, conventional Bayesian Optimization is extended to handle the time-varying nature of the wind shear profile (wind speed vs. time). Using real wind data, our method is validated against three baseline approaches. Our simulation results show that the Bayesian Optimization method is successful in dramatically increasing power production over these baselines. C2 - 2017/5// C3 - 2017 American Control Conference (ACC) DA - 2017/5// DO - 10.23919/acc.2017.7963143 PB - IEEE SN - 9781509059928 UR - http://dx.doi.org/10.23919/acc.2017.7963143 DB - Crossref ER - TY - JOUR TI - Constraint Enforcement for a Lighter-than-Air Wind-Energy System: An Application of Reference Governors with Chance Constraints AU - Kalabić, Uroš AU - Vermillion, Christopher AU - Kolmanovsky, Ilya T2 - IFAC-PapersOnLine AB - This paper considers the application of a reference governor scheme to a lighter-than-air wind-energy system subject to wind turbulence. The turbulence is treated as the output of the von Kármán model, which can be represented by a linear filter with a normally distributed disturbance input. The conventional reference governor, which enforces constraints robustly, has to be heuristically tuned in order to be applied to stochastic systems. In this work, the reference governor is generalized to the stochastic setting in order to handle stochastic disturbances. A simulation is presented, which shows satisfactory constraint enforcement with properties that are superior to the heuristically-tuned reference governor results of the authors’ previous work. DA - 2017/7// PY - 2017/7// DO - 10.1016/j.ifacol.2017.08.1962 VL - 50 IS - 1 SP - 13258-13263 J2 - IFAC-PapersOnLine LA - en OP - SN - 2405-8963 UR - http://dx.doi.org/10.1016/j.ifacol.2017.08.1962 DB - Crossref KW - Aerospace control KW - Renewable energy systems KW - Constraints KW - Predictive control ER - TY - CONF TI - Fused local-global control of spatiotemporally-varying systems: A case study in airborne wind energy AU - Bafandeh, Alireza AU - Bin-Karim, Shamir AU - Vermillion, Chris T2 - 2017 IEEE Conference on Control Technology and Applications (CCTA) AB - This paper presents a real-time altitude optimization technique for airborne wind energy (AWE) systems that fuses a coarse, global optimization with a fine, local optimization. The ultimate goal is to maximize net energy consumption by operating at an altitude where the wind speed is closest to the turbine's rated wind speed. Without the use of auxiliary wind profiling equipment, this results in a challenging real-time optimization that must be performed over a spatiotemporally varying, partially observable environment. As a result of computational complexity, global optimization techniques must be performed over a very coarse grid. Local optimization techniques alone, on the other hand, are unlikely to yield convergence to the globally-optimal altitude trajectory. The fused control strategy proposed in this work overcomes the limitations that both strategies pose when used in isolation. Unlike traditional hierarchical control architectures, where the upper-level controller prescribes a setpoint to the lower-level, our proposed upper-level controller passes an advisory input to the lower level. This advisory input prevents the AWE system from getting stuck in non-global optima while still giving the lower level controller freedom to explore. We demonstrate the effectiveness of the proposed controller using real wind data. C2 - 2017/8// C3 - 2017 IEEE Conference on Control Technology and Applications (CCTA) DA - 2017/8// DO - 10.1109/ccta.2017.8062512 PB - IEEE SN - 9781509021826 UR - http://dx.doi.org/10.1109/ccta.2017.8062512 DB - Crossref ER - TY - CONF TI - Iterative learning-based waypoint optimization for repetitive path planning, with application to airborne wind energy systems AU - Cobb, Mitchell AU - Barton, Kira AU - Fathy, Hosam AU - Vermillion, Chris T2 - 2017 IEEE 56th Annual Conference on Decision and Control (CDC) AB - This paper presents an iterative learning approach for optimizing waypoints in repetitive path following applications. Our proposed algorithm consists of two key features: First, a recursive least squares fit is used to construct an estimate of the behavior of the performance index. Secondly, an iteration-to-iteration waypoint adaptation law is used to update waypoints in the direction of optimal performance. This waypoint update law parallels the mathematical structure of a traditional iterative learning control (ILC) update but replaces the tracking error term with an error between the present and estimated optimal waypoint sequences. The proposed methodology is applied to the crosswind path optimization of an airborne wind energy (AWE) system, where the goal is to maximize the average power output over a figure-8 path. In validating the tools from this work, we introduce a simplified 2-dimensional analog to the more complex 3-dimensional AWE system, which distills the problem to its core elements. Using this model, we demonstrate that the proposed waypoint adaptation strategy successfully achieves convergence to near-optimal figure-8 paths for a variety of initial conditions. C2 - 2017/12// C3 - 2017 IEEE 56th Annual Conference on Decision and Control (CDC) DA - 2017/12// DO - 10.1109/cdc.2017.8264051 PB - IEEE SN - 9781509028733 UR - http://dx.doi.org/10.1109/cdc.2017.8264051 DB - Crossref ER - TY - JOUR TI - Heat Transfer Measurements inside Narrow Channels with Ribs and Trenches AU - Srinivasan, Shreyas AU - Ekkad, Srinath V. AU - Tolpadi, Anil T2 - Heat Transfer Engineering AB - Detailed heat transfer coefficient distributions are obtained for high aspect ratio (width/height = 12.5) duct with rib and trench enhancement features oriented normal to the coolant flow direction. A transient thermochromic liquid crystal technique has been used to experimentally measure heat transfer coefficients from which Nusselt numbers are calculated on the duct surface featuring heat transfer enhancement features. Reynolds number (calculated based on duct hydraulic diameter) ranging from 7100 to 22400 were experimentally investigated. Detailed measurements of heat transfer provided insight into the role of protruding ribs and trenches on the fluid dynamics in the duct. Experimentally obtained Nusselt numbers are normalized by Dittus-Boelter correlation for developed turbulent flow in circular duct. The triangular trenches provide heat transfer enhancement ratios up to 1.9 for low Reynolds numbers. The in-line rib configuration shows similar levels to the trench whereas staggered rib configuration provides heat transfer enhancement ratios up to 2.2 for a low Reynolds number of 7100. DA - 2017/7/13/ PY - 2017/7/13/ DO - 10.1080/01457632.2017.1341198 VL - 39 IS - 9 SP - 750-759 J2 - Heat Transfer Engineering LA - en OP - SN - 0145-7632 1521-0537 UR - http://dx.doi.org/10.1080/01457632.2017.1341198 DB - Crossref ER - TY - JOUR TI - Experimental investigation of the onset of sand deposits on Hastelloy-X between 1,000°C and 1,100°C AU - Boulanger, A. AU - Hutchinson, J. AU - Ng, W.F. AU - Ekkad, S.V. AU - Keefe, M.J. AU - Xu, W. AU - Barker, B. AU - Hsu, K. T2 - The Aeronautical Journal AB - ABSTRACT Deposit formation on turbine hardware in propulsion turbine engines can occur in many arid regions globally. Characterising crystalline deposits on metallic substrates can aid in component resilience and health monitor algorithms during particle ingestion. This study has developed two statistical empirical models for prediction from acquired experimental data for the onset of deposits. The prediction models are for crystalline particulate (Arizona Road Test Dust) deposits on a flat rectangular Hastelloy-X test coupon. Particle impingement angles varied between 20° and 80° in experimental flow temperatures of 1,000–1,100°C. Averaged deposits are methodically quantified through normalised particle deposit tallies per area and percent coverage of the surface using microscopic imaging and image processing programs. Deposit accumulation is a quadratic function of both near-surface coupon temperature and coupon angle. DA - 2017/6/21/ PY - 2017/6/21/ DO - 10.1017/AER.2017.48 VL - 121 IS - 1242 SP - 1187-1199 J2 - Aeronaut. j. LA - en OP - SN - 0001-9240 2059-6464 UR - http://dx.doi.org/10.1017/AER.2017.48 DB - Crossref KW - Sand KW - deposition KW - turbines KW - Arizona Road Dust ER - TY - JOUR TI - Numerical study on thermoelectric–hydraulic performance of a thermoelectric power generator with a plate-fin heat exchanger with longitudinal vortex generators AU - Ma, Ting AU - Lu, Xing AU - Pandit, Jaideep AU - Ekkad, Srinath V. AU - Huxtable, Scott T. AU - Deshpande, Samruddhi AU - Wang, Qiu-wang T2 - Applied Energy AB - In this paper, the effect of longitudinal vortex generators (LVGs) on the performance of a thermoelectric power generator (TEG) with a plate-fin heat exchanger is investigated. A fluid-thermal-electric multi-physics coupled model for the TEG is established on the COMSOL® platform, in which the Seebeck, Peltier, Thomson, and Joule heating effects are taken into account. The equivalent thermal–electrical properties of the thermoelectric (TE) module are used in the numerical simulation. The results indicate that the LVGs produce complex three-dimensional vortices in the cross section downstream from the LVGs, thus enhancing the heat transfer and electric performance compared to a TEG without LVGs. Under baseline operating conditions, the heat input and open circuit voltage of the TEG with LVGs are increased by 41–75% compared to a TEG with smooth channel. The simulations also show that the Reynolds number and hot-side inlet temperature have significant effects on the net power and thermal efficiency of the TEG, but the cold-side temperature has a smaller effect. Additionally, the performance of the TEG under a constant heat transfer coefficient boundary condition is almost the same as the performance under a constant temperature boundary condition. Overall, this work demonstrates that LVGs have great potential to enhance the performance of TEGs for waste heat recovery from vehicle exhaust. DA - 2017/1// PY - 2017/1// DO - 10.1016/J.APENERGY.2016.01.078 VL - 185 SP - 1343-1354 J2 - Applied Energy LA - en OP - SN - 0306-2619 UR - http://dx.doi.org/10.1016/J.APENERGY.2016.01.078 DB - Crossref KW - Thermoelectric power generator KW - Longitudinal vortex generator KW - Equivalent thermal-electrical properties KW - Heat transfer enhancement KW - Plate-fin heat exchanger ER - TY - JOUR TI - Flexible polydimethylsiloxane/multi-walled carbon nanotubes membranous metacomposites with negative permittivity AU - Sun, Kai AU - Xie, Peitao AU - Wang, Zhongyang AU - Su, Tongming AU - Shao, Qian AU - Ryu, JongEun AU - Zhang, Xihua AU - Guo, Jiang AU - Shankar, Akash AU - Li, Jianfeng AU - Fan, Runhua AU - Cao, Dapeng AU - Guo, Zhanhu T2 - Polymer AB - Metacomposites with negative electromagnetic parameters can be promising substitute for periodic metamaterials. In this paper, we devoted to fabricating flexible metacomposite films, which have great potential applications in the field of wearable cloaks, sensing, perfect absorption and stretchable electronic devices. The conductivity and the complex permittivity were investigated in flexible polydimethylsiloxane (PDMS)/multi-walled carbon nanotubes (MWCNTs) membranous nanocomposites, which were fabricated via in-situ polymerization process. With the increase of conductive one-dimension carbon nanotubes concentration, there was a percolation transition observed in conduction due to the formation of continuous networks. The dielectric dispersion behavior was also analyzed in the spectra of complex permittivity. It is indicated that the conduction and polarization make a combined effect on the dielectric loss in flexible PDMS/MWCNTs composites. The negative permittivity with a dielectric resonance was obtained, and was attributed to the induced electric dipoles. DA - 2017/9// PY - 2017/9// DO - 10.1016/j.polymer.2017.07.083 VL - 125 SP - 50-57 J2 - Polymer LA - en OP - SN - 0032-3861 UR - http://dx.doi.org/10.1016/j.polymer.2017.07.083 DB - Crossref KW - Flexible metamaterials KW - Negative permittivity KW - Metacomposites ER - TY - JOUR TI - Tunable and weakly negative permittivity in carbon/silicon nitride composites with different carbonizing temperatures AU - Cheng, Chuanbing AU - Fan, Runhua AU - Wang, Zhongyang AU - Shao, Qian AU - Guo, Xingkui AU - Xie, Peitao AU - Yin, Yansheng AU - Zhang, Yuliang AU - An, Liqiong AU - Lei, Yanhua AU - Ryu, Jong Eun AU - Shankar, Akash AU - Guo, Zhanhu T2 - Carbon AB - Despite the exotic electromagnetic properties have been demonstrated in metamaterials to date, how to effectively adjust negative electromagnetic parameters remains a challenge. Tunable negative permittivity is essential for the metamaterials to satisfy a variety of practical applications, such as capacitor, microwave absorbing and shielding. Here, we fabricated a random metamaterial, carbon/silicon nitride (C/Si3N4) composite, using a feasible impregnation-pyrolysis method. The microstructure and dielectric property of the composites with different heat treatment temperatures (HTTs) and carbon contents were investigated. The amorphous carbon membrane adhered on the rod-like Si3N4 grains. The negative permittivity behavior combined with inductive character was obtained in the composites, which was attributed to the low frequency plasmonic state generated from the formative conducting carbon networks. The magnitude of negative permittivity is demonstrated to be successfully adjusted by controlling the HTT and carbon content. The result is in good agreement with the analysis of Drude model. Interestingly, a weakly negative permittivity behavior was observed in the measured frequency, showing small negative values of permittivity between −50 and −10, which was ascribed to a moderate carrier concentration provided by the carbon networks. This work provides an effective way to achieve the tunable and weakly negative permittivity in random metamaterials. DA - 2017/12// PY - 2017/12// DO - 10.1016/j.carbon.2017.09.037 VL - 125 SP - 103-112 J2 - Carbon LA - en OP - SN - 0008-6223 UR - http://dx.doi.org/10.1016/j.carbon.2017.09.037 DB - Crossref KW - Amorphous carbon KW - Metamaterial KW - Negative permittivity KW - Dielectric property KW - Silicon nitride ER - TY - JOUR TI - Pulsed light sintering of silver nanoparticles for large deformation of printed stretchable electronics AU - Shankar, Akash AU - Salcedo, Eduardo AU - Berndt, Aaron AU - Choi, Daniel AU - Ryu, Jong Eun T2 - Advanced Composites and Hybrid Materials DA - 2017/11/3/ PY - 2017/11/3/ DO - 10.1007/s42114-017-0012-3 VL - 1 IS - 1 SP - 193-198 J2 - Adv Compos Hybrid Mater LA - en OP - SN - 2522-0128 2522-0136 UR - http://dx.doi.org/10.1007/s42114-017-0012-3 DB - Crossref KW - Stretchable electronics KW - Conductive ink KW - Nanoink KW - Printed electronics KW - Photonic sintering ER - TY - JOUR TI - Effect of crossflow regulation by varying jet diameters in streamwise direction on jet impingement heat transfer under maximum crossflow condition AU - Ji, Yongbin AU - Singh, Prashant AU - Ekkad, Srinath V. AU - Zang, Shusheng T2 - Numerical Heat Transfer, Part A: Applications AB - Jet impingement heat transfer has been studied numerically for a maximum crossflow condition using a 3 × 9 array of jets. Five-hole configurations have been studied for jet average Reynolds numbers ranging from 10,000 to 20,000. Crossflow has been mitigated by varying the jet diameters in the streamwise direction to reduce the impact of crossflow on downstream jet impingement. The design criteria for all five configurations were to keep the average of the jet diameters equal to the constant jet diameter configuration (baseline). It has been found that the configuration with increasing and then decreasing jet diameters provided higher levels of heat transfer with more uniform cooling when compared to the traditional constant diameter configuration and other configurations. DA - 2017/10/18/ PY - 2017/10/18/ DO - 10.1080/10407782.2017.1394136 VL - 72 IS - 8 SP - 579-599 J2 - Numerical Heat Transfer, Part A: Applications LA - en OP - SN - 1040-7782 1521-0634 UR - http://dx.doi.org/10.1080/10407782.2017.1394136 DB - Crossref ER - TY - JOUR TI - Numerical investigation of turbulent flow and heat transfer in two-pass ribbed channels AU - Ravi, Bharath Viswanath AU - Singh, Prashant AU - Ekkad, Srinath V. T2 - International Journal of Thermal Sciences AB - In this study, the heat transfer and friction characteristics of four different rib geometries- 45° angled, V-shaped, W-shaped and M-shaped ribs in a two-pass stationary channel have been numerically investigated. The aspect ratio (Height to Width) of the cooling channel was 1:1 (square). The rib pitch-to-rib height ratio (p/e) and the rib-height-to-channel hydraulic diameter ratio (e/Dh) were 16 and 0.125 respectively. The Reynolds number was varied from 20,000 to 70,000. For the computations, the Reynolds averaged Navier–Stokes (RANS) equations were solved with the commercial software ANSYS Fluent using the realizable version of k-ε (RKE) model. The heat transfer results were benchmarked with experiments on a test rig with similar geometries and flow conditions. Detailed analysis of the flow characteristics in the two-pass channel was carried out so as to understand the interaction of the rib-induced secondary flows and the bend-induced secondary flows and their contribution to heat transfer enhancement. The heat transfer enhancement provided by V-shaped ribs was 7% higher than 45° ribs, 28% higher than W-shaped ribs and 35% higher than M-shaped ribs. However, the pressure penalty for V-shaped ribs was 19% higher than 45° ribs, 24% higher than W-shaped ribs and 28% higher than M-shaped ribs. On comparing the overall thermal hydraulic performance, V-shaped and 45° ribs were observed to perform significantly better than W-shaped and M-shaped ribs. DA - 2017/2// PY - 2017/2// DO - 10.1016/J.IJTHERMALSCI.2016.09.034 VL - 112 SP - 31-43 J2 - International Journal of Thermal Sciences LA - en OP - SN - 1290-0729 UR - http://dx.doi.org/10.1016/J.IJTHERMALSCI.2016.09.034 DB - Crossref KW - Internal cooling KW - Two-pass channel KW - Ribs KW - Heat transfer KW - CFD ER - TY - CONF TI - The effect of lipid absorption on the mechanical properties of poly(styrene-block-isobutylene-block-styrene) for use in biomedical applications AU - Damley-Strnad, Alexandra AU - Fittipaldi, Mauro AU - Morales, Brigitte AU - Grace, Landon R. T2 - PROCEEDINGS OF PPS-32: The 32nd International Conference of the Polymer Processing Society - Conference Papers AB - The decrease in tensile strength and increase in specimen weight due to lipid diffusion in a biocompatible thermoplastic elastomer was studied and quantified. Mechanical and viscoelastic properties of poly(styrene-isobutylene-styrene) (SIBS) block copolymer are critical to determine feasibility of certain load bearing in vivo applications. Moreover, changes of these properties due to the presence of lipids must be well understood for long-term bio implantation. Dumbbell specimens were thermoformed via injection molding and weights were recorded. Lipid uptake in the body was simulated by specimen immersion in palm and castor oils at 25 °C and 37 °C. After only 96 hours of immersion at body temperature (37 °C), dumbbell weight increased by 6% and 0.3% for palm oil and castor oil, respectively. These values correspond to a reduction in ultimate tensile strength of approximately 30% and 10%, respectively. These results restrict the use of this biocompatible polymer in certain critical components due to the high concentration of lipids in vivo. Based on these significant and rapid reductions in tensile strength in the presence of lipids, it is of vital importance to fully understand the bio-durability and lipid uptake characteristics of SIBS for future design and performance prediction of implantable devices. Further, the results highlight the necessity of improving lipid resistance in order to fully exploit the biocompatibility of SIBS. C2 - 2017/// C3 - DA - 2017/// DO - 10.1063/1.5016760 PB - Author(s) UR - http://dx.doi.org/10.1063/1.5016760 DB - Crossref KW - SIBS KW - Lipid Absorption KW - Tensile Strength KW - Bio-degradation ER - TY - JOUR TI - Modeling, construction and experimental validation of actuated rolling dynamics of the cylindrical Transforming Roving-Rolling Explorer (TRREx) AU - Edwin, L. AU - Mazzoleni, A. AU - Gemmer, T. AU - Ferguson, S. T2 - Acta Astronautica AB - Planetary surface exploration technology over the past few years has seen significant advancements on multiple fronts. Robotic exploration platforms are becoming more sophisticated and capable of embarking on more challenging missions. More unconventional designs, particularly transforming architectures that have multiple modes of locomotion, are being studied. This work explores the capabilities of one such novel transforming rover called the Transforming Roving-Rolling Explorer (TRREx). Biologically inspired by the armadillo and the golden-wheel spider, the TRREx has two modes of locomotion: it can traverse on six wheels like a conventional rover on benign terrain, but can transform into a sphere when necessary to negotiate steep rugged slopes. The ability to self-propel in the spherical configuration, even in the absence of a negative gradient, increases the TRREx's versatility and its concept value. This paper describes construction and testing of a prototype cylindrical TRREx that demonstrates that “actuated rolling” can be achieved, and also presents a dynamic model of this prototype version of the TRREx that can be used to investigate the feasibility and value of such self-propelled locomotion. Finally, we present results that validate our dynamic model by comparing results from computer simulations made using the dynamic model to experimental results acquired from test runs using the prototype. DA - 2017/3// PY - 2017/3// DO - 10.1016/J.ACTAASTRO.2016.11.006 VL - 132 SP - 43-53 J2 - Acta Astronautica LA - en OP - SN - 0094-5765 UR - http://dx.doi.org/10.1016/J.ACTAASTRO.2016.11.006 DB - Crossref ER - TY - JOUR TI - Development of a Non-isothermal Forging Process for Hollow Axle Shafts AU - Pang, Hao AU - Lowrie, James AU - Ngaile, Gracious T2 - Procedia Engineering AB - This paper presents a novel non-isothermal forging process for a hollow axle shaft. The process consists of three operations: i) partially heat the initial tubular stock via induction heating, ii) deform the heated section into a solid, rod-like structure by upsetting the workpiece, and iii) shape the new ‘solid’ section into a flange by further upsetting the workpiece. The commercial finite element software Deform 2D is used to simulate the process and evaluate its feasibility. It is determined that the non-isothermal forming process does not require excessive forming loads and can be completed using the presses that are currently employed for axle shaft forging. Furthermore, the strains encountered in the process are reasonable for a hot forming process and the dimensional accuracy of the final product is acceptable. Future optimization of this process may lead to improved strain distributions and forming loads. DA - 2017/// PY - 2017/// DO - 10.1016/J.PROENG.2017.10.804 VL - 207 SP - 454-459 J2 - Procedia Engineering LA - en OP - SN - 1877-7058 UR - http://dx.doi.org/10.1016/J.PROENG.2017.10.804 DB - Crossref KW - non-isothermal KW - forging process KW - hollow shaft ER - TY - JOUR TI - Analytical modeling of hydrodynamic lubrication in a multiple-reduction drawing die AU - Lowrie, James AU - Ngaile, Gracious T2 - Journal of Manufacturing Processes AB - The hydrodynamic lubrication regime is reported to exist in numerous metal forming applications, such as wire drawing and hydrostatic extrusion, but it is difficult to achieve in the drawing of large diameter rods due to the relatively low drawing speeds common for larger parts. By creating a stable fluid film between the workpiece and the die during the drawing process friction and die wear could be significantly reduced, leading to energy savings, increased achievable reductions, and increased die life. An analytical model of the hydrodynamic drawing process is proposed which considers the geometry of the workpiece and die, as well as, the material properties (including work hardening effects), and (temperature dependent) fluid properties to determine the fluid film thickness over the reduction die. This model is then used to analyze several case studies, including a multiple reduction die with high pressure lubricant supplied to the space between the dies. It is shown that a stable fluid film can be established for low drawing speeds through the combination of a multiple reduction die and a supply of lubricant at high pressures to the inlet of the dies. DA - 2017/6// PY - 2017/6// DO - 10.1016/J.JMAPRO.2017.05.003 VL - 27 SP - 291-303 J2 - Journal of Manufacturing Processes LA - en OP - SN - 1526-6125 UR - http://dx.doi.org/10.1016/J.JMAPRO.2017.05.003 DB - Crossref KW - Drawing KW - Hydrodynamic lubrication KW - Non-Isothermal KW - Analytical model ER - TY - JOUR TI - Controllable curvature from planar polymer sheets in response to light AU - Hubbard, Amber M. AU - Mailen, Russell W. AU - Zikry, Mohammed A. AU - Dickey, Michael D. AU - Genzer, Jan T2 - Soft Matter AB - The ability to change shape and control curvature in 3D structures starting from planar sheets can aid in assembly and add functionality to an object. Herein, we convert planar sheets of shape memory polymers (SMPs) into 3D objects with controllable curvature by dictating where the sheets shrink. Ink patterned on the surface of the sheet absorbs infrared (IR) light, resulting in localized heating, and the material shrinks locally wherever the temperature exceeds the activation temperature, Ta. We introduce two different mechanisms for controlling curvature within SMP sheets. The ‘direct’ mechanism uses localized shrinkage to induce curvature only in regions patterned with ink. The ‘indirect’ mechanism uses localized shrinkage in regions patterned with ink to induce curvature in neighboring regions without ink through a balance of internal stresses. Finite element analysis predicts the final shape of the polymer sheets with excellent qualitative agreement with experimental studies. Results from this study show that curvature can be controlled by the distribution and darkness of the ink pattern on the polymer sheet. Additionally, we utilize the direct and indirect curvature mechanisms to demonstrate the formation and actuation of gripper devices, which represent the potential utility of this approach. DA - 2017/// PY - 2017/// DO - 10.1039/C7SM00088J VL - 13 IS - 12 SP - 2299-2308 J2 - Soft Matter LA - en OP - SN - 1744-683X 1744-6848 UR - http://dx.doi.org/10.1039/C7SM00088J DB - Crossref ER - TY - JOUR TI - Computationally efficient analysis of particle transport and deposition in a human whole-lung-airway model. Part II: Dry powder inhaler application AU - Kolanjiyil, Arun V. AU - Kleinstreuer, Clement AU - Sadikot, Ruxana T. T2 - Computers in Biology and Medicine AB - Pulmonary drug delivery is becoming a favored route for administering drugs to treat both lung and systemic diseases. Examples of lung diseases include asthma, cystic fibrosis and chronic obstructive pulmonary disease (COPD) as well as respiratory distress syndrome (ARDS) and pulmonary fibrosis. Special respiratory drugs are administered to the lungs, using an appropriate inhaler device. Next to the pressurized metered-dose inhaler (pMDI), the dry powder inhaler (DPI) is a frequently used device because of the good drug stability and a minimal need for patient coordination. Specific DPI-designs and operations greatly affect drug-aerosol formation and hence local lung deposition. Simulating the fluid-particle dynamics after use of a DPI allows for the assessment of drug-aerosol deposition and can also assist in improving the device configuration and operation. In Part I of this study a first-generation whole lung-airway model (WLAM) was introduced and discussed to analyze particle transport and deposition in a human respiratory tract model. In the present Part II the drug-aerosols are assumed to be injected into the lung airways from a DPI mouth-piece, forming the mouth-inlet. The total as well as regional particle depositions in the WLAM, as inhaled from a DPI, were successfully compared with experimental data sets reported in the open literature. The validated modeling methodology was then employed to study the delivery of curcumin aerosols into lung airways using a commercial DPI. Curcumin has been implicated to possess high therapeutic potential as an antioxidant, anti-inflammatory and anti-cancer agent. However, efficacy of curcumin treatment is limited because of the low bioavailability of curcumin when ingested. Hence, alternative drug administration techniques, e.g., using inhalable curcumin-aerosols, are under investigation. Based on the present results, it can be concluded that use of a DPI leads to low lung deposition efficiencies because large amounts of drugs are deposited in the oral cavity. Hence, the output of a modified DPI has been evaluated to achieve improved drug delivery, especially needed when targeting the smaller lung airways. This study is the first to utilize CF-PD methodology to simulate drug-aerosol transport and deposition under actual breathing conditions in a whole lung model, using a commercial dry-powder inhaler for realistic inlet conditions. DA - 2017/5// PY - 2017/5// DO - 10.1016/J.COMPBIOMED.2016.10.025 VL - 84 SP - 247-253 J2 - Computers in Biology and Medicine LA - en OP - SN - 0010-4825 UR - http://dx.doi.org/10.1016/J.COMPBIOMED.2016.10.025 DB - Crossref KW - Lung KW - Airflow KW - Whole lung-airway modeling KW - Computational fluid-particle dynamics (CF-PD) KW - Particle deposition KW - Pharmaceutical aerosols KW - Dry powder inhaler (DPI) KW - Curcumin ER - TY - JOUR TI - Ultrasound-triggered noninvasive regulation of blood glucose levels using microgels integrated with insulin nanocapsules AU - Di, Jin AU - Yu, Jicheng AU - Wang, Qun AU - Yao, Shanshan AU - Suo, Dingjie AU - Ye, Yanqi AU - Pless, Matthew AU - Zhu, Yong AU - Jing, Yun AU - Gu, Zhen T2 - Nano Research DA - 2017/3/6/ PY - 2017/3/6/ DO - 10.1007/S12274-017-1500-Z VL - 10 IS - 4 SP - 1393-1402 J2 - Nano Res. LA - en OP - SN - 1998-0124 1998-0000 UR - http://dx.doi.org/10.1007/S12274-017-1500-Z DB - Crossref KW - controlled drug delivery KW - focused ultrasound KW - diabetes KW - nanocapsule KW - microgel ER - TY - JOUR TI - Overview of Composite Metal Foams and Their Properties and Performance AU - Marx, Jacob AU - Rabiei, Afsaneh T2 - Advanced Engineering Materials AB - This paper reviews the background and evolution of composite metal foam (CMF) from its inception until now. A broad understanding of the processing and basic mechanical, microstructural, and physical properties of different types of composite metal foams is discussed in the first part of the paper. In the second part, some recent studies on high strain rate properties, ballistic performance, radiation attenuation, and thermal properties of composite metal foams are discussed and compared with other bulk and control materials. These properties suggest many potential applications for this novel material in a broad range of engineering structures from ballistic armors to trains', cars', buses', helicopters' crashworthiness systems, and many others such as nuclear casks and thermal insulating units. DA - 2017/3/13/ PY - 2017/3/13/ DO - 10.1002/adem.201600776 VL - 19 IS - 11 SP - 1600776 J2 - Adv. Eng. Mater. LA - en OP - SN - 1438-1656 UR - http://dx.doi.org/10.1002/adem.201600776 DB - Crossref ER - TY - JOUR TI - A Miniature Water Surface Jumping Robot AU - Jiang, Fei AU - Zhao, Jianguo AU - Kota, Arun K. AU - Xi, Ning AU - Mutka, Matt W. AU - Xiao, Li T2 - IEEE Robotics and Automation Letters AB - Many small insects such as water striders can leap from water surface. Inspired by their jumping capability, we present the design of a novel, miniature, water surface jumping robot in this paper. Jumping from water surface is more challenging than jumping from ground due to the liquid water surface. We address this problem by using carbon fiber strip to store energy, two wings to flap the water surface, a hollow body to initially support the robot, and an intermittent gear train to charge and release energy. With such a design, the final robot weighs around 12.5 g and has a maximum size of 10 cm. Experimental results show that the robot can jump up to 9.5 cm in height, which is close to the predicted results from a dynamic model developed by us to capture the hydrodynamic behaviors of the robot during the whole jumping process. The research presented in this paper offers a new design of tiny robots for mimicking the water-jumping capability of aquatic insects. The robot, if equipped with sensors, can be employed for aquatic environmental monitoring of water quality. DA - 2017/7// PY - 2017/7// DO - 10.1109/lra.2017.2662738 VL - 2 IS - 3 SP - 1272-1279 J2 - IEEE Robot. Autom. Lett. OP - SN - 2377-3766 2377-3774 UR - http://dx.doi.org/10.1109/lra.2017.2662738 DB - Crossref KW - Kinematics KW - mechanism design of mobile robots KW - biologically inspired robotics ER - TY - JOUR TI - Metamorphic Superomniphobic Surfaces AU - Wang, Wei AU - Salazar, Joshua AU - Vahabi, Hamed AU - Joshi-Imre, Alexandra AU - Voit, Walter E. AU - Kota, Arun K. T2 - Advanced Materials AB - Superomniphobic surfaces are extremely repellent to virtually all liquids. By combining superomniphobicity and shape memory effect, metamorphic superomniphobic (MorphS) surfaces that transform their morphology in response to heat are developed. Utilizing the MorphS surfaces, the distinctly different wetting transitions of liquids with different surface tensions are demonstrated and the underlying physics is elucidated. Both ex situ and in situ wetting transitions on the MorphS surfaces are solely due to transformations in morphology of the surface texture. It is envisioned that the robust MorphS surfaces with reversible wetting transition will have a wide range of applications including rewritable liquid patterns, controlled drug release systems, lab-on-a-chip devices, and biosensors. DA - 2017/5/9/ PY - 2017/5/9/ DO - 10.1002/adma.201700295 VL - 29 IS - 27 SP - 1700295 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 UR - http://dx.doi.org/10.1002/adma.201700295 DB - Crossref KW - shape memory polymers KW - superomniphobic surfaces KW - wetting transition ER - TY - JOUR TI - Metallic superhydrophobic surfaces via thermal sensitization AU - Vahabi, Hamed AU - Wang, Wei AU - Popat, Ketul C. AU - Kwon, Gibum AU - Holland, Troy B. AU - Kota, Arun K. T2 - Applied Physics Letters AB - Superhydrophobic surfaces (i.e., surfaces extremely repellent to water) allow water droplets to bead up and easily roll off from the surface. While a few methods have been developed to fabricate metallic superhydrophobic surfaces, these methods typically involve expensive equipment, environmental hazards, or multi-step processes. In this work, we developed a universal, scalable, solvent-free, one-step methodology based on thermal sensitization to create appropriate surface texture and fabricate metallic superhydrophobic surfaces. To demonstrate the feasibility of our methodology and elucidate the underlying mechanism, we fabricated superhydrophobic surfaces using ferritic (430) and austenitic (316) stainless steels (representative alloys) with roll off angles as low as 4° and 7°, respectively. We envision that our approach will enable the fabrication of superhydrophobic metal alloys for a wide range of civilian and military applications. DA - 2017/6/19/ PY - 2017/6/19/ DO - 10.1063/1.4989577 VL - 110 IS - 25 SP - 251602 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4989577 DB - Crossref ER - TY - JOUR TI - Superhemophobic titania nanotube array surfaces for blood contacting medical devices AU - Bartlet, Kevin AU - Movafaghi, Sanli AU - Kota, Arun AU - Popat, Ketul C. T2 - RSC Advances AB - Appropriate hemocompatible response for blood-contacting medical devices is necessary to prevent device failure. DA - 2017/// PY - 2017/// DO - 10.1039/c7ra03373g VL - 7 IS - 56 SP - 35466-35476 J2 - RSC Adv. LA - en OP - SN - 2046-2069 UR - http://dx.doi.org/10.1039/c7ra03373g DB - Crossref ER - TY - JOUR TI - Fabrication of Nanostructured Omniphobic and Superomniphobic Surfaces with Inexpensive CO2 Laser Engraver AU - Pendurthi, Anudeep AU - Movafaghi, Sanli AU - Wang, Wei AU - Shadman, Soran AU - Yalin, Azer P. AU - Kota, Arun K. T2 - ACS Applied Materials & Interfaces AB - Superomniphobic surfaces (i.e., surfaces that are extremely repellent to both high surface tension liquids like water and low surface tension liquid like oils) can be fabricated through a combination of surface chemistry that imparts low solid surface energy with a re-entrant surface texture. Recently, surface texturing with lasers has received significant attention because laser texturing is scalable, solvent-free, and can produce a monolithic texture on virtually any material. In this work, we fabricated nanostructured omniphobic and superomniphobic surfaces with a variety of materials using a simple, inexpensive and commercially available CO2 laser engraver. Further, we demonstrated that the nanostructured omniphobic and superomniphobic surfaces fabricated using our laser texturing technique can be used to design patterned surfaces, surfaces with discrete domains of the desired wettability, and on-surface microfluidic devices. DA - 2017/7/25/ PY - 2017/7/25/ DO - 10.1021/acsami.7b06924 VL - 9 IS - 31 SP - 25656-25661 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/acsami.7b06924 DB - Crossref KW - superomniphobic KW - laser ablation KW - CO2 laser KW - re-entrant texture KW - nanostructure ER - TY - JOUR TI - Coalescence-Induced Self-Propulsion of Droplets on Superomniphobic Surfaces AU - Vahabi, Hamed AU - Wang, Wei AU - Davies, Seth AU - Mabry, Joseph M. AU - Kota, Arun K. T2 - ACS Applied Materials & Interfaces AB - We utilized superomniphobic surfaces to systematically investigate the different regimes of coalescence-induced self-propulsion of liquid droplets with a wide range of droplet radii, viscosities, and surface tensions. Our results indicate that the nondimensional jumping velocity Vj* is nearly constant (Vj* ≈ 0.2) in the inertial-capillary regime and decreases in the visco-capillary regime as the Ohnesorge number Oh increases, in agreement with prior work. Within the visco-capillary regime, decreasing the droplet radius R0 results in a more rapid decrease in the nondimensional jumping velocity Vj* compared to increasing the viscosity μ. This is because decreasing the droplet radius R0 increases the inertial-capillary velocity Vic in addition to increasing the Ohnesorge number Oh. DA - 2017/8/16/ PY - 2017/8/16/ DO - 10.1021/acsami.7b09344 VL - 9 IS - 34 SP - 29328-29336 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/acsami.7b09344 DB - Crossref KW - inertial-capillary KW - visco-capillary KW - superomniphobic KW - coalescence KW - jumping droplet ER - TY - JOUR TI - High-speed polarized light microscopy for in situ, dynamic measurement of birefringence properties AU - Wu, Xianyu AU - Pankow, Mark AU - Shadow Huang, Hsiao-Ying AU - Peters, Kara T2 - Measurement Science and Technology AB - A high-speed, quantitative polarized light microscopy (QPLM) instrument has been developed to monitor the optical slow axis spatial realignment during controlled medium to high strain rate experiments at acquisition rates up to 10 kHz. This high-speed QPLM instrument is implemented within a modified drop tower and demonstrated using polycarbonate specimens. By utilizing a rotating quarter wave plate and a high-speed camera, the minimum acquisition time to generate an alignment map of a birefringent specimen is 6.1 ms. A sequential analysis method allows the QPLM instrument to generate QPLM data at the high-speed camera imaging frequency 10 kHz. The obtained QPLM data is processed using a vector correlation technique to detect anomalous optical axis realignment and retardation changes throughout the loading event. The detected anomalous optical axis realignment is shown to be associated with crack initiation, propagation, and specimen failure in a dynamically loaded polycarbonate specimen. The work provides a foundation for detecting damage in biological tissues through local collagen fiber realignment and fracture during dynamic loading. DA - 2017/12/8/ PY - 2017/12/8/ DO - 10.1088/1361-6501/aa9084 VL - 29 IS - 1 SP - 015203 J2 - Meas. Sci. Technol. OP - SN - 0957-0233 1361-6501 UR - http://dx.doi.org/10.1088/1361-6501/aa9084 DB - Crossref KW - polarized light microscopy KW - dynamic property testing KW - optical methods ER - TY - CONF TI - Effects of thermal energy harvesting on the human - Clothing - environment microsystem AU - Myers, A.C. AU - Jur, J.S. AB - The objective of this work is to perform an in depth investigation of garment-based thermal energy harvesting. The effect of human and environmental factors on the working efficiency of a thermal energy harvesting devices, or a thermoelectric generator (TEG), placed on the body is explored.. Variables that strongly effect the response of the TEG are as follows: skin temperature, human motion or speed, body location, environmental conditions, and the textile properties surrounding the TEG. In this study, the use of textiles for managing thermal comfort of wearable technology and energy harvesting are defined. By varying the stitch length and/or knit structure, one can manipulate the thermal conductivity of the garment in a specific location. Another method of improving TEG efficiency is through the use of a heat spreader, which increases the effective collection area of heat on the TEG hot side. Here we show the effect of a TEG on the thermal properties of a garment with regard to two knit stitches, jersey and 1 × 1 rib. C2 - 2017/// C3 - IOP Conference Series: Materials Science and Engineering DA - 2017/// DO - 10.1088/1757-899X/254/7/072015 VL - 254 M1 - 7 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85034955383&partnerID=MN8TOARS ER - TY - JOUR TI - A Wearable Hydration Sensor with Conformal Nanowire Electrodes AU - Yao, Shanshan AU - Myers, Amanda AU - Malhotra, Abhishek AU - Lin, Feiyan AU - Bozkurt, Alper AU - Muth, John F. AU - Zhu, Yong T2 - Advanced Healthcare Materials AB - A wearable skin hydration sensor in the form of a capacitor is demonstrated based on skin impedance measurement. The capacitor consists of two interdigitated or parallel electrodes that are made of silver nanowires (AgNWs) in a polydimethylsiloxane (PDMS) matrix. The flexible and stretchable nature of the AgNW/PDMS electrode allows conformal contact to the skin. The hydration sensor is insensitive to the external humidity change and is calibrated against a commercial skin hydration system on an artificial skin over a wide hydration range. The hydration sensor is packaged into a flexible wristband, together with a network analyzer chip, a button cell battery, and an ultralow power microprocessor with Bluetooth. In addition, a chest patch consisting of a strain sensor, three electrocardiography electrodes, and a skin hydration sensor is developed for multimodal sensing. The wearable wristband and chest patch may be used for low-cost, wireless, and continuous monitoring of skin hydration and other health parameters. DA - 2017/1/27/ PY - 2017/1/27/ DO - 10.1002/ADHM.201601159 VL - 6 IS - 6 SP - 1601159 J2 - Adv. Healthcare Mater. LA - en OP - SN - 2192-2640 UR - http://dx.doi.org/10.1002/ADHM.201601159 DB - Crossref ER - TY - JOUR TI - The role of the surface morphology and segmented cracks on the damage forms of laser re-melted thermal barrier coatings in presence of a molten salt (Na2SO4 + V2O5) AU - Fan, Z. AU - Wang, K. AU - Dong, X. AU - Wang, R. AU - Duan, W. AU - Mei, X. AU - Wang, W. AU - Cui, J. AU - Zhang, S. AU - Xu, C. T2 - Corrosion Science AB - Hot corrosion behaviour of yttria-stabilized zirconia thermal barrier coatings (TBCs) with various segmented cracks and surface morphologies, obtained using ultrasonic-assisted laser re-melting, was investigated during exposure to Na2SO4 + V2O5 salt at 1100 °C. It is demonstrated, that the damage types of TBCs were significantly affected by segmented cracks and surface morphology. Four main damage mechanisms: (i) chemical reaction, (ii) Coefficient thermal mismatch stress, (iii) oxidation of bond coating and (iv) intergranular corrosion, based on the observed transport behaviour of oxygen and molten salt, stress-tolerance and self-healing of various segmented cracks, were discussed to account for the failure behaviour. DA - 2017/// PY - 2017/// DO - 10.1016/j.corsci.2016.11.011 VL - 115 SP - 56-67 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85006810370&partnerID=MN8TOARS KW - Ceramic KW - Molten salts KW - High temperature corrosion KW - Intergranular corrosion KW - Oxidation ER - TY - JOUR TI - Study on coexistence of brittle and ductile fractures in nano reinforcement composites under different loading conditions AU - Qiao, Y. AU - Liu, J. AU - Jia, Y. AU - Xu, C. AU - An, L. AU - Bai, Y. T2 - International Journal of Fracture DA - 2017/// PY - 2017/// DO - 10.1007/s10704-016-0174-y VL - 204 IS - 2 SP - 205-224 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85007238098&partnerID=MN8TOARS KW - Brittle fracture KW - Ductile fracture KW - Particulate reinforced material ER - TY - CONF TI - Study of chip morphology and chip formation mechanism during machining of magnesium-based metal matrix composites AU - Davis, B. AU - Dabrow, D. AU - Ju, L. AU - Li, A. AU - Xu, C. AU - Huang, Y. AB - Magnesium (Mg) and its alloys are among the lightest metallic structural materials, making them very attractive for use in the aerospace and automotive industries. Recently, Mg has been used in metal matrix composites (MMCs), demonstrating significant improvements in mechanical performance. However, the machinability of Mg-based MMCs is still largely elusive. In this study, Mg-based MMCs are machined using a wide range of cutting speeds in order to elucidate both the chip morphology and chip formation mechanism. Cutting speed is found to have the most significant influence on both the chip morphology and chip formation mechanism, with the propensity of discontinuous, particle-type chip formation increasing as the cutting speed increases. Saw-tooth chips are found to be the primary chip morphology at low cutting speeds (lower than 0.5 m/s), while discontinuous, particle-type chips prevail at high cutting speeds (higher than 1.0 m/s). Using in situ high speed imaging, the formation of the saw-tooth chip morphology is found to be due to crack initiation at the free surface. However, as the cutting speed (and strain rate) increases, the formation of the discontinuous, particle-type chip morphology is found to be due to crack initiation at the tool tip. In addition, the influences of tool rake angle, particle size, and particle volume fracture are investigated and found to have little effect on the chip morphology and chip formation mechanism. C2 - 2017/// C3 - ASME 2017 12th International Manufacturing Science and Engineering Conference, MSEC 2017 collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing DA - 2017/// DO - 10.1115/MSEC2017-3052 VL - 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85027731034&partnerID=MN8TOARS ER - TY - JOUR TI - Study of Chip Morphology and Chip Formation Mechanism during Machining of Magnesium-Based Metal Matrix Composites AU - Davis, B. AU - Dabrow, D. AU - Ju, L. AU - Li, A. AU - Xu, C. AU - Huang, Y. T2 - Journal of Manufacturing Science and Engineering, Transactions of the ASME AB - Magnesium (Mg) and its alloys are among the lightest metallic structural materials, making them very attractive for use in the aerospace and automotive industries. Recently, Mg has been used in metal matrix composites (MMCs), demonstrating significant improvements in mechanical performance. However, the machinability of Mg-based MMCs is still largely elusive. In this study, Mg-based MMCs are machined using a wide range of cutting speeds in order to elucidate both the chip morphology and chip formation mechanism. Cutting speed is found to have the most significant influence on both the chip morphology and chip formation mechanism, with the propensity of discontinuous, particle-type chip formation increasing as the cutting speed increases. Saw-tooth chips are found to be the primary chip morphology at low cutting speeds (lower than 0.5 m/s), while discontinuous, particle-type chips prevail at high cutting speeds (higher than 1.0 m/s). Using in situ high-speed imaging, the formation of the saw-tooth chip morphology is found to be due to crack initiation at the free surface. However, as the cutting speed (and strain rate) increases, the formation of the discontinuous, particle-type chip morphology is found to be due to crack initiation at the tool tip. In addition, the influences of tool rake angle, particle size, and particle volume fracture are investigated and found to have little effect on the chip morphology and chip formation mechanism. DA - 2017/// PY - 2017/// DO - 10.1115/1.4037182 VL - 139 IS - 9 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85025092741&partnerID=MN8TOARS KW - magnesium KW - metal matrix composite KW - machining KW - chip morphology KW - chip formation mechanism ER - TY - BOOK TI - Intelligent systems: Modeling, optimization, and control AU - Shin, Y.C. AU - Xu, C. AB - Providing a thorough introduction to the field of soft computing techniques, Intelligent Systems: Modeling, Optimization, and Control covers every major technique in artificial intelligence in a clear and practical style. This book highlights current research and applications, addresses issues encountered in the development of applied systems, and describes a wide range of intelligent systems techniques, including neural networks, fuzzy logic, evolutionary strategy, and genetic algorithms. The book demonstrates concepts through simulation examples and practical experimental results. Case studies are also presented from each field to facilitate understanding. DA - 2017/// PY - 2017/// DO - 10.1201/9781420051773 SE - 1-433 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85052533159&partnerID=MN8TOARS ER - TY - JOUR TI - Enhanced cyclic oxidation resistance through the self-healing of segmented cracks using nano-Al2O3/Ni-20 wt%Al particles in laser re-melted thermal barrier coatings AU - Fan, Z. AU - Wang, K. AU - Dong, X. AU - Wang, R. AU - Duan, W. AU - Mei, X. AU - Wang, W. AU - Zhang, S. AU - Xu, C. T2 - Materials Letters AB - This paper introduces a novel and effective self-healing method of segmented cracks in laser re-melted ZrO2-7 wt% Y2O3 thermal barrier coatings (TBCs). The method uses pressure sintering of nano-Al2O3/Ni-20 wt%Al particles at 1150 °C for 12 h. After treatment to facilitate self-healing, a very dense and metallurgically bonded nano-Al2O3 reinforced Ni-matrix sealed film formed in the segmented gaps. Cyclic oxidation results indicate that dense sealed films can effectively suppress the growth of thermally grown oxides (TGO) and prevent the formation of other brittle and fragile oxides (i.e., spinels) at the top coat/bond coat (TC/BC) interface. Using the pressure-sintering effect, any aluminums contained in the sealed particles or films becomes prone to diffusion into the TC/BC interface to facilitate the formation of a thin-continuous TGO during the initial oxidation. This results in a significantly enhanced anti-oxidation effect of laser re-melted TBCs. DA - 2017/// PY - 2017/// DO - 10.1016/j.matlet.2017.04.116 VL - 201 SP - 156-160 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85018757034&partnerID=MN8TOARS KW - Laser processing KW - TBCs KW - Oxidation KW - Sintering KW - TGO ER - TY - SOUND TI - Wireless Temperature Measurement Based on Radio Frequency (RF) Technology AU - Xu, C. AU - Daniel, J. DA - 2017/// PY - 2017/// ER - TY - SOUND TI - Thermal and Oxidation Stability of BNNT and BNNT Composites AU - Xu, C. AU - Ajayi, T. AU - Morales, J. DA - 2017/// PY - 2017/// N1 - Invited RN - Invited ER - TY - JOUR TI - Pearl-Chain Formation of Discontinuous Carbon Fiber Under Electrical Field AU - Daniel, J. AU - Ju, L. AU - Yang, J. AU - Sun, X. AU - Gupta, N. AU - Schrand, A. AU - Xu, C. T2 - Journal of Manufacturing and Materials Processing AB - The purpose of this paper is to develop a theoretical derivation on aligning discontinuous carbon fiber with an applied electric field, and prove the theory with experiment. A principle with regard to the occurrence of carbon fiber alignment is presented after an introduction of the electromechanical quantities of dielectrics. Based on this principle, an estimation of the polarizability tensor is employed to calculate the required electric field to achieve fiber alignment in liquid solution (e.g., water, resin, etc.). Individual carbon fiber is modeled as a polarizable dielectric cylinder in liquid resin and its motion under direct current (DC) electrical field is decomposed into a polarization effect and rotation effect. A value of 20.12 V/mm is required to align short carbon fibers (0.15 mm) long in liquid resin and is experimentally validated. Finally, an expression to include weight percentage as a means of controlling pearl-chain formation is derived to change the composite’s electrical conductivity. DA - 2017/// PY - 2017/// DO - 10.3390/jmmp1020022 VL - 1 IS - 2 SP - 22 KW - polarization KW - carbon fiber alignment KW - pearl-chain formation ER - TY - SOUND TI - Non-Destructive Testing of Composite Materials at High Temperature (2000oC) AU - Xu, C. AU - Peebles, J. DA - 2017/// PY - 2017/// ER - TY - SOUND TI - Metamaterial Enabling RF Transparency – Ceramic Composite Design for High Temperature Application AU - Macdonald, J. AU - Xu, C. DA - 2017/// PY - 2017/// ER - TY - BOOK TI - Effect of Processing Conditions on Electric and Dielectric Properties of Polymer-Derived SiC Ceramics AU - Xu, C. AU - Wang, K. DA - 2017/// PY - 2017/// PB - Materials Science & Technology ER - TY - CONF TI - Photoacoustic transduction efficiency evaluation of candle soot nanoparticles/PDMS composites AU - Chang, W. Y. AU - Zhang, X. A. AU - Kim, J. AU - Huang, W. B. AU - Chang, C. H. AU - Jiang, X. N. AB - Carbon-based materials have been considered as an efficient light-absorption component of film-type laser ultrasound transducers. Our previously designed laser ultrasound patch composed of candle soot nanoparticles and polydimethylsiloxane (CS/PDMS) composites showed high photoacoustic transducer efficiency than other carbon-based composites. In this study, we demonstrate that the carbon volume fraction and the thickness of clustered carbon nanoparticles of CS/PDMS composites are highly related to the photoacoustic transduction efficiency. This study builds upon our previous study to characterize optical properties of the CS/PDMS composites in both experimental measurements and finite difference time domain (FDTD) analysis in the visible wavelength range. C2 - 2017/// C3 - 2017 ieee 17th international conference on nanotechnology (ieee-nano) DA - 2017/// DO - 10.1109/nano.2017.8117338 SP - 439-442 ER - TY - BOOK TI - High frequency piezo-composite micromachined ultrasound transducer array technology for biomedical imaging AU - Jiang, X. AU - Li, S. AU - Kim, J. AU - Ma, J. AB - In this monograph, the authors reports the current advancement in high frequency piezoelectric crystal micromachined ultrasound transducers and arrays and their biomedical applications. Piezoelectric ultrasound transducers operating at high frequencies (> 20 MHz) are of increasing demand in recent years for medical imaging and biological particle manipulation involved therapy. The performances of transducers greatly rely on the properties of the piezoelectric materials and transduction structures, including piezoelectric coefficient (d), electromechanical coupling coefficient (k), dielectric permittivity (e) and acoustic impedance (Z).Piezo-composite structures are preferred because of their relatively high electromechanical coupling coefficient and low acoustic impedance. A number of piezo-composite techniques have been developed, namely “dice and fill,” “tape-casting,” “stack and bond,” “interdigital phase bonding,” “laser micromachining” and “micro-molding”. However, these techniques are either difficult to achieve fine features or not suitable for manufacturing of high frequency ultrasound transducers (> 20 MHz). The piezo-composite micromachined ultrasound transducers (PC-MUT) technique discovered over the last 10 years or so has demonstrated high performance high frequency piezo-composite ultrasound transducers.In this monograph, piezoelectric materials used for high frequency transducers is introduced first. Next, the benefits and theory of piezo composites is presented, followed by the design criteria and fabrication methods. Biomedical applications using piezo composites micromachined ultrasound transducers (PC-MUT) and arrays will also be reported, in comparison with other ultrasound transducer techniques. The final part of this monograph describes challenges and future perspectives of this technique for biomedical applications. DA - 2017/// PY - 2017/// DO - 10.1115/1.860441 PB - New York, NY, USA: ASME Press ER - TY - JOUR TI - Plasma textiles as fibrous filter media AU - Jasper, Warren J. AU - Rasipuram, Srinivasan C. T2 - FIBROUS FILTER MEDIA AB - Plasma textiles are a new class of compact filters which provide enhanced submicron particle filtration for particle diameters ranging from 30 to 300 nm without exhibiting a most penetrating particle size (MPPS). Unlike traditional passive respiratory filters, plasma textiles are active tunable filters which can be manufactured from woven, nonwoven, or knitted fabrics. They are embedded with high-voltage electrodes to produce in-situ room temperature/cold plasma. Simultaneous charging and capture of incoming submicron particles are achieved by a corona discharge that is initiated by applying high voltages beyond 6 kV. Both the woven and the nonwoven plasma textiles provide filtration efficiencies close to 100% for ultra-fine particles, indicating that electrostatic forces dominate at higher voltages. The maximum filtration efficiency obtained with the woven plasma textile exceeds HEPA specification and the nonwoven plasma textile exceeds the filtration efficiency of ULPA filters. DA - 2017/// PY - 2017/// DO - 10.1016/b978-0-08-100573-6.00011-3 SP - 191-210 ER - TY - CONF TI - Sensitivity analysis of interfacial momentum closure terms in two phase flow and boiling simulations using MCFD solver AU - Liu, Y. AU - Rollins, C. AU - Dinh, N. AU - Luo, H. AB - In this paper, a general workflow for the global Sensitivity Analysis (SA) has been proposed based on the coupling of VUQ toolkit DAKOTA and Multiphase Computational Fluid Dynamics (MCFD) solver boilEulerFoam. A surrogate model is first constructed based on sampling simulations from boilEulerFoam. This surrogate is based on Gaussian Processes Model (GPM) and is validated and proved to have good properties. The Morris Screening method is then applied based on the surrogate to those interfacial momentum closure terms for SA, including drag, lift, turbulent dispersion, wall lubrication, and virtual mass. Two different cases are considered, one is on low-pressure adiabatic flow, and the other is on high pressure boiling flow. Each case has its experimental background with data support. The radial void fraction distribution, gas velocity, relative velocity and liquid temperature (only for high pressure boiling case) are chosen as the Quantities of Interest (QoIs) which are of key interests for two-phase flow simulation and boiling crisis prediction. The interfacial force coefficient of each closure term is chosen as the input parameter. For the boiling case, the bubble diameter effect is also analyzed. Three remarks are drawn from this work on SA. First, it demonstrates the feasibility of surrogate model in the VUQ work for models in MCFD solver. The computational cost can be significantly reduced by employing the surrogate model. Secondly, through the Morris Sensitivity measurements, the importance of interfacial forces on different QoIs and regions can be analyzed and ranked for the two cases. Such analysis is also helpful for further model parameter calibration. Last but not least, the limitation of current work and the desired future work are discussed. C2 - 2017/// C3 - Proceedings of the ASME Summer Heat Transfer Conference, 2017, vol 2 DA - 2017/// DO - 10.1115/ht2017-4963 ER - TY - JOUR TI - Numerical Simulation of Aero-Optical Effects in a Supersonic Cavity Flow AU - Zilberter, Ilya A. AU - Edwards, Jack R. AU - Wittich, Donald J., III T2 - AIAA JOURNAL AB - A hybrid large-eddy simulation/Reynolds-averaged Navier–Stokes turbulence model is applied to compute the wave-front aberrations in an optical beam passing through a supersonic open cavity flow. The turbulence model blends a Reynolds-averaged Navier–Stokes-type closure near solid walls with a subgrid model in the freestream based on the ratios of estimated inner and outer turbulent length scales. The cavity geometry is modeled using an immersed boundary method, and an auxiliary flat-plate simulation is performed to replicate the effects of the wind-tunnel boundary layer on the computed optical path difference. Two-dimensional proper orthogonal decomposition modes of the optical wave front are computed; these compare favorably with wind-tunnel data, despite uncertainties about inflow turbulence levels and boundary-layer thicknesses over the wind-tunnel window. Dynamic mode decomposition of a planar wave front spanning the entire cavity reveals that wave-front distortions are driven by shear-layer oscillation at the Rossiter frequencies; these disturbances create eddy shocklets that propagate into the freestream and create additional optical path disturbances. DA - 2017/9// PY - 2017/9// DO - 10.2514/1.j055402 VL - 55 IS - 9 SP - 3095-3108 SN - 1533-385X ER - TY - CONF TI - Modular electric generator rapid deployment DC microgrid AU - Pritchard, E. AU - Mackey, L. AU - Zhu, D. AU - Gregory, D. AU - Norris, G. AB - The development of a rapidly deployable modular electric generator based on plug-in hybrid vehicle DC architectures provides a highly reliable DC microgrid for use in applications with unstable infrastructure or highly sensitive loads. The result is the commercial production of early stage prototype units built by Schneider Electric with onboard energy storage, combustion generator and rapid interconnects for loads, renewable energy and grid connection. C2 - 2017/// C3 - 2017 IEEE Second International Conference on DC Microgrids (ICDCM) DA - 2017/// DO - 10.1109/icdcm.2017.8001030 SP - 106-110 ER - TY - CONF TI - Exploring architecture selection and system evolvability AU - White, S. AU - Ferguson, S. AB - For engineered systems, one of the first decisions a designer must make is the architecture that will solve the established high level function. In most cases, this can be accomplished in a multitude of ways, with each original architecture having strengths and weaknesses. This paper explores how the architecture choice for a system impacts the ability to evolve and meet future needs. The lessons learned from this paper are extracted from a case study where three systems that perform the same task via different architectural solutions are considered. These systems are them compared to understand how well they adhere to, or violate, the Empirically-Derived Principles for Designing Products with Flexibility for Future Evolution introduced by Tilstra et al. C2 - 2017/// C3 - Proceedings of the asme international design engineering technical conferences and computers and information in engineering conference, 2017, vol 2b DA - 2017/// DO - 10.1115/detc2017-68290 ER - TY - CONF TI - A case study of evolvability and excess on the B-52 stratofortress and FA-18 hornet AU - Long, D. AU - Ferguson, S. AB - The moment a system is put into service it begins to lose value as technological and societal changes accrue while the system is frozen in the state it was constructed. System decision makers are faced with the choice of accepting a decline in performance, updating the design, or retiring the system. Each time a decision maker faces these alternatives, the value of the available options must be evaluated to determine the preferred course of action. A design that can adapt to changes with minimal cost should provide more value over a longer period than a system that is initially less costly, but less adaptable. This is especially desirable for systems that have large initial costs and/or a lengthy development cycle. The purpose of this paper is to evaluate the United States Air Force (USAF) B-52 Stratofortress and the United States Navy (USN) F/A-18 Hornet to characterize the changes in desired capabilities and what system attributes allowed them to either successfully adapt or prevented them from adapting. These observations allow the development of heuristics that designers can use during system design to enhance system lifetime value. C2 - 2017/// C3 - Proceedings of the asme international design engineering technical conferences and computers and information in engineering conference, 2017, vol 4 DA - 2017/// DO - 10.1115/detc2017-68287 ER - TY - JOUR TI - Study on Random Decrement Signature Under Different Triggering Level and Length of Time History AU - Wu, Jinzhi AU - Zheng, Xiujuan AU - Hu, Jie AU - Zhang, Yigang AU - Yuan, Fuh-Gwo T2 - TOPICS IN MODAL ANALYSIS & TESTING, VOL 10 AB - Random Decrement Technique (RDT) is a widely used method to extract free decay response data by averaging time segments obtained under certain triggering condition from structural vibration response. And thus, different triggering condition will inevitably lead to different Random Decrement Signature (RDS) and different modal parameters. The quality of RDS has significant influence on the modal parameter identification results. Based on three assessments criteria for RDS’s quality, statistical analysis of change law of RDS with different triggering level and length of time history are carried out by a SDOF system and a 6-DOF system. A multi-triggering method is proposed, by which a better RDS can be obtained. Numerical simulation and the practical engineering application verified the recommended method and values. DA - 2017/// PY - 2017/// DO - 10.1007/978-3-319-54810-4_17 SP - 159-166 SN - 2191-5652 KW - Random decrement technique KW - Triggering level KW - Length of time history KW - Modal parameters KW - Space truss ER - TY - JOUR TI - Shoulder Strength Requirements for Upper Limb Functional Tasks: Do Age and Rotator Cuff Tear Status Matter? AU - Santago, Anthony C., II AU - Vidt, Meghan E. AU - Li, Xiaotong AU - Tuohy, Christopher J. AU - Poehling, Gary G. AU - Freehill, Michael T. AU - Saul, Katherine R. T2 - JOURNAL OF APPLIED BIOMECHANICS AB - Understanding upper limb strength requirements for daily tasks is imperative for early detection of strength loss that may progress to disability due to age or rotator cuff tear. We quantified shoulder strength requirements for 5 upper limb tasks performed by 3 groups: uninjured young adults and older adults, and older adults with a degenerative supraspinatus tear prior to repair. Musculoskeletal models were developed for each group representing age, sex, and tear-related strength losses. Percentage of available strength used was quantified for the subset of tasks requiring the largest amount of shoulder strength. Significant differences in strength requirements existed across tasks: upward reach 105° required the largest average strength; axilla wash required the largest peak strength. However, there were limited differences across participant groups. Older adults with and without a tear used a larger percentage of their shoulder elevation ( p < .001, p < .001) and external rotation ( p < .001, p = .017) strength than the young adults, respectively. Presence of a tear significantly increased percentage of internal rotation strength compared to young ( p < .001) and uninjured older adults ( p = .008). Marked differences in strength demand across tasks indicate the need for evaluating a diversity of functional tasks to effectively detect early strength loss, which may lead to disability. DA - 2017/12// PY - 2017/12// DO - 10.1123/jab.2016-0116 VL - 33 IS - 6 SP - 446-452 SN - 1543-2688 KW - functional task KW - simulation KW - upper limb KW - reserve strength ER - TY - CONF TI - Additive vacuum electronics electron beam melting of copper AU - Gamzina, D. AU - Luhmann, N. C. AU - Ledford, C. AU - Horn, Timothy AU - Karakaut, I. AU - Lin, L. AU - Frigola, P. AB - The construction of vacuum electronic devices is an artisan process; it requires extremes of high precision machining and assembly and the tolerances and feature sizes become more exacting as the frequency increases. Merging of copper additive manufacturing and electropolishing technologies will produce low-cost, high-throughput fabrication techniques for construction of fully integrated vacuum electronic devices. Technology demonstrations at two frequencies (S-Band and W-band) will address the demand for fast turnaround manufacturing of travelling wave tube amplifiers in legacy military systems as well as in the emerging high frequency applications. C2 - 2017/// C3 - 2017 eighteenth international vacuum electronics conference (ivec) DA - 2017/// DO - 10.1109/ivec.2017.8289495 ER - TY - JOUR TI - How dense core vesicles are delivered to axon terminals - a review of modeling approaches AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. T2 - Modeling of Microscale Transport in Biological Processes DA - 2017/// PY - 2017/// SP - 335-352 ER - TY - CONF TI - Cooperative output regulation of multi-agent systems with switched leader dynamics via smooth switching AU - Yuan, C. Z. AU - Wu, F. AU - Duan, C. AB - This paper deals with the leader-following cooperative output regulation problem for heterogeneous multi-agent systems by considering a switched leader dynamics. The switched leader dynamics is composed by multiple linear models and a switching rule governing the switches among them, which is capable of generating more diverse and sophisticated reference signals so as to enhance the multi-agent system’s capability in coping with more complicated coordination tasks. A novel distributed switching control scheme, namely, the smooth switching control strategy, is proposed to achieve cooperative output regulation performance. Distributed switching stability of the overall network is established using multiple Lyapunov functions from the switching control theory. Moreover, under the proposed design framework, the overall cooperative switching output regulation problem can be decomposed into several independent switching stabilization subproblems, and the associated switching control synthesis conditions for each subproblems are formulated as a set of linear matrix inequalities (LMIs) plus linear algebraic equations. As a result, stabilizing switching rules for the leader and distributed switching protocols for the follower agents can be jointly synthesized via semi-definite programming. A numerical example has been used to demonstrate the effectiveness of the proposed approach. C2 - 2017/// C3 - Proceedings of the ASME 10th Annual Dynamic Systems and Control Conference, 2017, vol 2 DA - 2017/// DO - 10.1115/dscc2017-5055 ER - TY - CONF TI - A New low cost, efficient, self-driving personal rapid transit system AU - Hollar, S. AU - Brain, M. AU - Nayak, A. A. AU - Stevens, A. AU - Patil, N. AU - Mittal, H. AU - Smith, W. J. AB - The market demand for a low-cost transportation system that operates efficiently in a circulatory environment is significant. In this paper, we propose a solution, EcoPRT, a two person, electric, autonomous, low cost, adaptable system that solves the circulatory problem, being ideal for areas that are too far to walk but too short to drive. The key advantages of the proposed system are: narrow footprint, low weight, low cost, no delays en route, and adaptable installation. A pilot run of the vehicle is expected during the first part of 2017 on the campus of NC State University. To date an operating prototype and test track have been completed. An overview of the mechanical and electrical vehicle design is presented. Additionally, we discuss the major navigation and sensing subsystems including the development of a low-cost 3D LIDAR unit for navigation and collision avoidance. Further, three different solutions for vision-based navigation are compared qualitatively for effectiveness. In summary, a functional platform vehicle is presented on which we expect to further develop and refine an effective, low cost, automated transportation solution. C2 - 2017/// C3 - 2017 28th ieee intelligent vehicles symposium (iv 2017) DA - 2017/// DO - 10.1109/ivs.2017.7995753 SP - 412-417 ER - TY - JOUR TI - Side-chain engineering of perylenediimide-vinylene polymer acceptors for high-performance all-polymer solar cells AU - Guo, Yikun AU - Li, Yunke AU - Awartani, Omar AU - Han, Han AU - Zhang, Guangye AU - Ade, Harald AU - Yan, He AU - Zhao, Dahui T2 - MATERIALS CHEMISTRY FRONTIERS AB - The performance of a PDI-vinylene polymer acceptor in an all-PSC is optimized by side-chain engineering. The best average PCE of 7.40% is obtained with a medium side-chain length. DA - 2017/7/1/ PY - 2017/7/1/ DO - 10.1039/c6qm00355a VL - 1 IS - 7 SP - 1362-1368 SN - 2052-1537 ER - TY - JOUR TI - Optical modeling of fiber organic photovoltaic structures using a transmission line method AU - Moshonas, N. AU - Stathopoulos, N. A. AU - O'Connor, B. T. AU - Bedeloglu, A. Celik AU - Savaidis, S. P. AU - Vasiliadis, S. T2 - APPLIED OPTICS AB - An optical model has been developed and evaluated for the calculation of the external quantum efficiency of cylindrical fiber photovoltaic structures. The model is based on the transmission line theory and has been applied on single and bulk heterojunction fiber-photovoltaic cells. Using this model, optimum design characteristics have been proposed for both configurations, and comparison with experimental results has been assessed. DA - 2017/12/1/ PY - 2017/12/1/ DO - 10.1364/ao.56.009351 VL - 56 IS - 34 SP - 9351-9358 SN - 2155-3165 ER - TY - JOUR TI - On buckling and postbuckling behavior of nanotubes AU - She, Gui-Lin AU - Yuan, Fuh-Gwo AU - Ren, Yi-Ru AU - Xiao, Wan-Shen T2 - INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE AB - For the first time, the size-dependent thermal buckling and post-buckling behavior of nanotubes made of functionally graded materials (FGMs) with porosities is investigated by using a refined beam theory. This non-classical nanotube model is based on Eringen nonlocal elasticity model which incorporates the small scale effect. Two types of porosity distribution, including even and uneven distribution, are taken into account. The material properties of the nanotubes are temperature-dependent and vary in the radial direction. The size-dependent governing differential equations are derived by employing the generalized variation principle and solved by using a two-step perturbation method. The effects of small scale parameter, porosity volume fraction, the volume fraction index and boundary conditions on thermal buckling and post-buckling of FGM nanotubes are studied by several numerical examples. It can be concluded that the porosity volume fraction and small scale parameter change the buckling and post-buckling behavior of the nanotubes. DA - 2017/12// PY - 2017/12// DO - 10.1016/j.ijengsci.2017.09.005 VL - 121 SP - 130-142 SN - 1879-2197 KW - Functionally graded materials KW - Porous material KW - Nanotube KW - Thermal buckling KW - Post-buckling KW - A two-step perturbation method ER - TY - JOUR TI - Intrinsic coincident full-Stokes polarimeter using stacked organic photovoltaics and architectural comparison of polarimeter techniques AU - Yang, Ruonan AU - Sen, Pratik AU - O'Connor, B. T. AU - Kudenov, M. W. T2 - POLARIZATION SCIENCE AND REMOTE SENSING VIII AB - An intrinsic coincident full-Stokes polarimeter is demonstrated by using stain-aligned polymer-based organic photovoltaics (OPVs) which can preferentially absorb certain polarized states of incident light. The photovoltaic-based polarimeter is capable of measuring four stokes parameters by cascading four semitransparent OPVs in series along the same optical axis. Two wave plates were incorporated into the system to modulate the S3 stokes parameter so as to reduce the condition number of the measurement matrix. The model for the full-Stokes polarimeter was established and validated, demonstrating an average RMS error of 0.84%. The optimization, based on minimizing the condition number of the 4-cell OPV design, showed that a condition number of 2.4 is possible. Performance of this in-line polarimeter concept was compared to other polarimeter architectures, including Division of Time (DoT), Division of Amplitude (DoAm), Division of Focal Plane (DoFP), and Division of Aperture (DoA) from signal-to-noise ratio (SNR) perspective. This in-line polarimeter concept has the potential to enable both high temporal (as compared with a DoT polarimeter) and high spatial resolution (as compared with DoFP and DoA polarimeters). We conclude that the intrinsic design has the same ~√2 SNR advantage as the DoAm polarimeter, but with greater compactness. DA - 2017/// PY - 2017/// DO - 10.1117/12.2273885 VL - 10407 SP - SN - 1996-756X KW - polarimetry KW - polarimetric imaging KW - polarization-selective devices KW - photovoltaic KW - polymer active devices KW - signal-to-noise ratio KW - condition number KW - frobenius norm ER - TY - JOUR TI - Interaction of delaminations and matrix cracks in a CFRP plate, Part II: Simulation using an enriched shell finite element model AU - McElroy, Mark W. AU - Gutkin, Renaud AU - Pankow, Mark T2 - COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING AB - Numerical simulations are presented of a recently developed test which creates multiple delaminations in a CFRP laminate specimen that grow and interact via transverse matrix cracks [1]. A novel shell element enriched with the Floating Node Method, and a damage algorithm based on the Virtual Crack Closure Technique, were used to successfully simulate the tests. Additionally, a 3D high mesh fidelity model based on cohesive zones and continuum damage mechanics was used to simulate the tests and act as a representative of other similar state-of-the-art high mesh fidelity modeling techniques to compare to the enriched shell element. The enriched shell and high mesh fidelity models had similar levels of accuracy and generally matched the experimental data. With runtimes of 36 min for the shell model and 55 h for the high mesh fidelity model, the shell model is 92 times faster than the high-fidelity simulation. DA - 2017/12// PY - 2017/12// DO - 10.1016/j.compositesa.2017.10.006 VL - 103 SP - 252-262 SN - 1878-5840 KW - Laminates KW - Delamination KW - Fracture KW - Finite element analysis (FEA) ER - TY - JOUR TI - Interaction of delaminations and matrix cracks in a CFRP plate, Part I: A test method for model validation AU - McElroy, Mark AU - Jackson, Wade AU - Olsson, Robin AU - Hellstrom, Peter AU - Tsampas, Spyros AU - Pankow, Mark T2 - COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING AB - Isolating and observing the damage mechanisms associated with low-velocity impact in composites using traditional experiments can be challenging, due to damage process complexity and high strain rates. In this work, a new test method is presented that provides a means to study, in detail, the interaction of common impact damage mechanisms, namely delamination, matrix cracking, and delamination-migration, in a context less challenging than a real impact event. Carbon fiber reinforced polymer specimens containing a thin insert in one region were loaded in a biaxial-bending state of deformation. As a result, three-dimensional damage processes, involving delaminations at no more than three different interfaces that interact with one another via transverse matrix cracks, were observed and documented using ultrasonic testing and X-ray computed tomography. The data generated by the test is intended for use in numerical model validation. Simulations of this test are included in Part II of this paper. DA - 2017/12// PY - 2017/12// DO - 10.1016/j.compositesa.2017.09.011 VL - 103 SP - 314-326 SN - 1878-5840 KW - Laminates KW - Delamination KW - Transverse cracking KW - Mechanical testing ER - TY - JOUR TI - Evaluation of 3D Additively Manufactured Canine Brain Models for Teaching Veterinary Neuroanatomy AU - Schoenfeld-Tacher, Regina M. AU - Horn, Timothy J. AU - Scheviak, Tyler A. AU - Royal, Kenneth D. AU - Hudson, Lola C. T2 - JOURNAL OF VETERINARY MEDICAL EDUCATION AB - Physical specimens are essential to the teaching of veterinary anatomy. While fresh and fixed cadavers have long been the medium of choice, plastinated specimens have gained widespread acceptance as adjuncts to dissection materials. Even though the plastination process increases the durability of specimens, these are still derived from animal tissues and require periodic replacement if used by students on a regular basis. This study investigated the use of three-dimensional additively manufactured (3D AM) models (colloquially referred to as 3D-printed models) of the canine brain as a replacement for plastinated or formalin-fixed brains. The models investigated were built based on a micro-MRI of a single canine brain and have numerous practical advantages, such as durability, lower cost over time, and reduction of animal use. The effectiveness of the models was assessed by comparing performance among students who were instructed using either plastinated brains or 3D AM models. This study used propensity score matching to generate similar pairs of students. Pairings were based on gender and initial anatomy performance across two consecutive classes of first-year veterinary students. Students' performance on a practical neuroanatomy exam was compared, and no significant differences were found in scores based on the type of material (3D AM models or plastinated specimens) used for instruction. Students in both groups were equally able to identify neuroanatomical structures on cadaveric material, as well as respond to questions involving application of neuroanatomy knowledge. Therefore, we postulate that 3D AM canine brain models are an acceptable alternative to plastinated specimens in teaching veterinary neuroanatomy. DA - 2017/// PY - 2017/// DO - 10.3138/jvme.0416-080r VL - 44 IS - 4 SP - 612-619 SN - 1943-7218 KW - gross anatomy education KW - neuroanatomy KW - 3D additive manufacturing KW - physical models KW - veterinary students KW - propensity score matching ER - TY - JOUR TI - Anomalous Tensile Detwinning in Twinned Nanowires AU - Cheng, Guangming AU - Yin, Sheng AU - Chang, Tzu-Hsuan AU - Richter, Gunther AU - Gao, Huajian AU - Zhu, Yong T2 - PHYSICAL REVIEW LETTERS AB - In spite of numerous studies on mechanical behaviors of nanowires (NWs) focusing on the surface effect, there is still a general lack of understanding on how the internal microstructure of NWs influences their deformation mechanisms. Here, using quantitative in situ transmission electron microscopy based nanomechanical testing and molecular dynamics simulations, we report a transition of the deformation mechanism from localized dislocation slip to delocalized plasticity via an anomalous tensile detwinning mechanism in bitwinned metallic NWs with a single twin boundary (TB) running parallel to the NW length. The anomalous tensile detwinning starts with the detwinning of a segment of the preexisting TB under no resolved shear stress, followed by the propagation of a pair of newly formed TB and grain boundary leading to a large plastic deformation. An energy-based criterion is proposed to describe this transition of the deformation mechanism, which depends on the volume ratio between the two twin variants and the cross-sectional aspect ratio. DA - 2017/12/21/ PY - 2017/12/21/ DO - 10.1103/physrevlett.119.256101 VL - 19 IS - 25 SP - SN - 1079-7114 ER - TY - JOUR TI - The development of a dynamic single effect, lithium bromide absorption chiller model with enhanced generator fidelity AU - Misenheimer, Corey T. AU - Terry, Stephen D. T2 - ENERGY CONVERSION AND MANAGEMENT AB - Single effect, lithium bromide absorption chillers offer the ability to utilize low-pressure steam to produce chilled water for satisfying various comfort cooling needs. Previous attempts have been made to characterize dynamic and steady-state absorption chiller operation. Though these models perform adequately, they are based on hot water driven absorption chillers. Commercially available absorption chillers often can run on both hot water and low-pressure steam. In this paper, the mathematical framework for a dynamic single effect, lithium bromide absorption chiller model capable of using low-pressure steam is presented. The transient thermodynamic FORTRAN model is grounded on mass, energy, and species balances, and builds on prior modeling efforts. Well-known correlations for heat transfer coefficients are used to describe both tube-side and shell-side heat transfer rates in each primary chiller component. To account for the absorption chiller unit receiving steam, a heat transfer model for condensation inside horizontal tubes based on distinct internal condensation flow regimes is incorporated within the generator. This heat transfer model is used with two-phase flow pressure drop equations to establish steam temperature, quality, and pressure along the generator tube bundle. Steam consumption trends are established as a function of fluctuating external conditions. These trends reasonably align with information made available online by the manufacturer, though some deviation does occur at low chiller capacities and cooling water temperatures. Additionally, the transient response of internal and external parameters from a step increase in heat input supplied to the generator mimics results of other dynamic absorption chiller models found throughout literature. DA - 2017/10/15/ PY - 2017/10/15/ DO - 10.1016/j.enconman.2017.08.005 VL - 150 SP - 574-587 SN - 1879-2227 KW - Absorption KW - Lithium KW - Bromide KW - Chiller KW - Steam KW - Refrigerant ER - TY - JOUR TI - Role of Polymer Segregation on the Mechanical Behavior of All Polymer Solar Cell Active Layers AU - Balar, Nrup AU - Xiong, Yuan AU - Ye, Long AU - Li, Sunsun AU - Nevola, Daniel AU - Dougherty, Daniel B. AU - Hou, Jianhui AU - Ade, Harald AU - Brendan T. O'Connor, T2 - ACS APPLIED MATERIALS & INTERFACES AB - An all-polymer bulk heterojunction (BHJ) active layer that removes the use of commonly used small molecule electron acceptors is a promising approach to improve the thermomechanical behavior of organic solar cells. However, there has been limited research on their mechanical properties. Here, we report on the mechanical behavior of high-performance blade-coated all-polymer BHJ films cast using eco-friendly solvents. The mechanical properties considered include the elastic modulus, crack onset strain, and cohesive fracture energy. We show that the mechanical behavior of the blend is largely unaffected by significant changes in the segregation characteristics of the polymers, which was varied systematically through solvent formulation. In comparison to a polymer:fullerene BHJ counterpart, the all-polymer films were found to have lower stiffness and increased ductility. Yet, the fracture energy of the all-polymer films is not significantly improved compared to that of the polymer:fullerene films. This study highlights that improved mechanical behavior of all-polymer systems cannot be assumed, and that details of the molecular structure, molecular weight, and film morphology play an important role in both the optoelectronic and mechanical properties. Furthermore, we show that simple composite modeling provides a predictive tool for the mechanical properties of the polymer blend films, providing a framework to guide future optimization of the mechanical behavior. DA - 2017/12/20/ PY - 2017/12/20/ DO - 10.1021/acsami.7b13719 VL - 9 IS - 50 SP - 43886-43892 SN - 1944-8244 KW - all-polymer solar cell KW - polymer blend film KW - fracture energy KW - crack onset strain KW - multilength scale morphology ER - TY - JOUR TI - Observation of zone folding induced acoustic topological insulators and the role of spin-mixing defects AU - Deng, Yuanchen AU - Ge, Hao AU - Tian, Yuan AU - Lu, Minghui AU - Jing, Yun T2 - PHYSICAL REVIEW B AB - This article reports on the experimental realization of a flow-free, pseudospin-based acoustic topological insulator designed using the strategy of zone folding. Robust sound one-way propagation is demonstrated with the presence of non-spin-mixing defects. On the other hand, it is shown that spin-mixing defects, which break the geometric symmetry and therefore the pseudo-time-reversal symmetry, can open up nontrivial band gaps within the edge state frequency band, and their width can be tailored by the extent of the defect. This provides a possible route for realizing tunable acoustic topological insulators. DA - 2017/11/27/ PY - 2017/11/27/ DO - 10.1103/physrevb.96.184305 VL - 96 IS - 18 SP - SN - 2469-9969 ER - TY - JOUR TI - Investigation of the effective density of arbitrarily shaped plate-type acoustic metamaterials without mass attached AU - Huang, Tai-Yun AU - Jing, Yun T2 - WAVE MOTION AB - The effective densities of arbitrarily shaped plate-type acoustic metamaterials (AMMs) without mass attached are studied in this paper. Acoustic impedances of three different shaped plates, i.e. circle, triangle, and hexagon, are calculated by the meshless boundary method and the effective densities are calculated using the lumped model. To validate the accuracy of this framework, the numerical results are compared with the analytical solution as well as the finite element method (FEM) for circular plates and are compared with FEM for the other two shapes. In general, good agreements can be found provided that a sufficient number of edge points and collocation points are used in the meshless boundary method. For the triangular shape, some discrepancies are found at the low-frequency region and this might have been because of the sharp corners of the triangle. The framework studied in this paper can provide an accurate and efficient method for designing plate-type AMMs with an arbitrary shape. DA - 2017/11// PY - 2017/11// DO - 10.1016/j.wavemoti.2017.07.003 VL - 74 SP - 124-133 SN - 1878-433X KW - Acoustic metamaterials KW - Meshless boundary method ER - TY - JOUR TI - Inefficient Ribosomal Skipping Enables Simultaneous Secretion and Display of Proteins in Saccharomyces cerevisiae AU - Cruz-Teran, Carlos A. AU - Tiruthani, Karthik AU - Mischler, Adam AU - Rao, Balaji M. T2 - ACS SYNTHETIC BIOLOGY AB - The need for recombinant expression of soluble protein slows the validation of engineered proteins isolated from combinatorial libraries and limits the number of protein variants evaluated. To overcome this bottleneck, we describe a system for simultaneous cell surface display and soluble secretion of proteins in Saccharomyces cerevisiae based on inefficient ribosomal skipping. Ribosomal skipping mediated by “self-cleaving” 2A peptides produces two proteins from a single open reading frame. Incorporation of the F2A peptide sequence—with ∼50% efficiency of ribosomal skipping—between the protein of interest and the yeast cell wall protein Aga2 results in simultaneous expression of both the solubly secreted protein and the protein–Aga2 fusion that is tethered to the yeast cell surface. We show that binding proteins derived from the Sso7d scaffold and the homodimeric enzyme glucose oxidase can be simultaneously secreted solubly and expressed as yeast cell surface fusions using the F2A-based system. Furthermore, a combinatorial library of Sso7d mutants can be screened to isolate binders with higher affinity for a model target (lysozyme), and the pool of higher affinity binders can be characterized in soluble form. Significantly, we show that both N- and C-terminal fusions to Aga2 can be simultaneously secreted solubly and displayed on the cell surface; this is particularly advantageous because protein functionality can be affected by the specific position of Aga2 in the protein fusion. We expect that the F2A-based yeast surface display and secretion system will be a useful tool for protein engineering and enable efficient characterization of individual clones isolated from combinatorial libraries. DA - 2017/11// PY - 2017/11// DO - 10.1021/acssynbio.7b00144 VL - 6 IS - 11 SP - 2096-2107 SN - 2161-5063 KW - yeast surface display KW - secretion KW - ribosomal skipping KW - 2A peptide KW - Sso7d KW - glucose oxidase ER - TY - JOUR TI - High-Speed Interrogation of Multiplexed Fiber Bragg Gratings With Spectral Distortion AU - Van Hoe, Bram AU - Oman, Kyle G. AU - Van Steenberge, Geert AU - Stan, Nikola AU - Schultz, Stephen M. AU - Peters, Kara J. T2 - IEEE SENSORS JOURNAL AB - Fiber Bragg grating (FBG) sensors can be multiplexed in large numbers to monitor the performance of large structures. This paper addresses the collection of FBG reflection spectra from wavelength division multiplexed sensors at fast acquisition rates. The spectral and temporal resolution is first derived as a function of the tunable filter and measurement system properties. The method is applied to impact loading investigations of a stiffened composite skin panel. The reflected spectrum of each FBG in an array, embedded in the panel, is collected at 100 kHz during the impact events with a spectral resolution down to 40 pm. Visualization of the FBG responses to these impact events, including the presence of spectral distortion in some FBG spectra, is presented. Future analyses based on the full-spectral data sets can enable the assessment of the localized progression of internal damage in such structures. DA - 2017/11/1/ PY - 2017/11/1/ DO - 10.1109/jsen.2017.2750327 VL - 17 IS - 21 SP - 6941-6947 SN - 1558-1748 KW - Bragg gratings KW - delamination KW - nondestructive testing KW - tunable filters KW - sensor systems ER - TY - JOUR TI - Growth of defect-free GaAsSbN axial nanowires via self-catalyzed molecular beam epitaxy AU - Sharma, Manish AU - Deshmukh, Prithviraj AU - Kasanaboina, Pavan AU - Reynolds, C. Lewis, Jr. AU - Liu, Yang AU - Iyer, Shanthi T2 - SEMICONDUCTOR SCIENCE AND TECHNOLOGY AB - Bandgap reduction of 10% by incorporation of a dilute amount of N is reported for the first time, in axial GaAsSb nanowires (NWs) grown on Si (111) via Ga-assisted molecular beam epitaxy. Impact of N incorporation on the surface morphology, NW growth kinetics, and their structural and optical properties were examined. Dilute nitride NWs with Sb composition of 7 at% did not exhibit any noticeable planar defects, as revealed by the absence of satellite twin peaks in the selected-area diffraction pattern and high-resolution transmission electron microscopy imaging. Point defects were also minimal in as-grown dilute nitride NWs, as ascertained from the comparison of low-temperature photoluminescence spectra as well as the shape and shift of Raman modes, with in situ annealed NWs in different ambients. Evidence of enhanced incorporation of N was found in the NWs in situ annealed in N ambient, but with deteriorated optical quality due to simultaneous creation of N-induced defects. The lack of any noticeable defects in the as-grown GaAsSbN NWs demonstrates the advantage of the vapor–liquid–solid mechanism responsible for growth of axial configuration over the vapor–solid growth mechanism for core–shell NWs as well as their thin film counterpart, which commonly exhibit N-induced point defects. DA - 2017/12// PY - 2017/12// DO - 10.1088/1361-6641/aa90b0 VL - 32 IS - 12 SP - SN - 1361-6641 KW - GaAsSbN KW - MBE KW - VLS KW - N-plasma annealing ER - TY - JOUR TI - Experiments and Computations on the Lift of Accelerating Flat Plates at Incidence AU - Stevens, P. R. R. J. AU - Babinsky, H. AU - Manar, F. AU - Mancini, P. AU - Jones, A. R. AU - Nakata, T. AU - Phillips, N. AU - Bomphrey, R. J. AU - Gozukara, A. C. AU - Granlund, K. O. AU - Ol, M. V. T2 - AIAA JOURNAL AB - This paper discusses the force history and flow topology of accelerating flat-plate wings. The work is a collaborative effort to study fundamental, unsteady low-Reynolds-number flows. The motion kinematics is designed to be relevant to the micro air vehicle flight regime. A combination of experimental and computational techniques is used to obtain data for comparison. There is a striking correlation of lift history data and flow topology from both experimental and computational data sets. It is found that the leading/trailing-edge vortex core separation during the initial part of a surge motion can be reasonably well approximated by , and the leading/trailing-edge vortex relative advection velocity is estimated to be . This leading/trailing-edge vortex relative advection velocity is a useful measure of how quickly the trailing-edge vortex moves away from the leading-edge vortex, which can influence lift for accelerating flat plates at high incidence angles. DA - 2017/10// PY - 2017/10// DO - 10.2514/1.j055323 VL - 55 IS - 10 SP - 3255-3265 SN - 1533-385X ER - TY - JOUR TI - Enhanced total internal reflection using low-index nanolattice materials AU - Zhang, Xu A. AU - Chen, Yi-An AU - Bagal, Abhijeet AU - Chang, Chih-Hao T2 - OPTICS LETTERS AB - Low-index materials are key components in integrated photonics and can enhance index contrast and improve performance. Such materials can be constructed from porous materials, which generally lack mechanical strength and are difficult to integrate. Here we demonstrate enhanced total internal reflection (TIR) induced by integrating robust nanolattice materials with periodic architectures between high-index media. The transmission measurement from the multilayer stack illustrates a cutoff at about a 60° incidence angle, indicating an enhanced light trapping effect through TIR. Light propagation in the nanolattice material is simulated using rigorous coupled-wave analysis and transfer matrix methods, which agrees well with experimental data. The demonstration of the TIR effect in this Letter serves as a first step towards the realization of multilayer devices with nanolattice materials as robust low-index components. These nanolattice materials can find applications in integrated photonics, antireflection coatings, photonic crystals, and low-k dielectric. DA - 2017/10/15/ PY - 2017/10/15/ DO - 10.1364/ol.42.004123 VL - 42 IS - 20 SP - 4123-4126 SN - 1539-4794 ER - TY - JOUR TI - Design of novel plug-type triggers for composite square tubes: enhancement of energy-absorption capacity and inducing failure mechanisms AU - Jiang, Hongyong AU - Ren, Yiru AU - Gao, Binhua AU - Xiang, Jinwu AU - Yuan, Fuh-Gwo T2 - INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES AB - To improve their energy-absorption capacity and induce failure mechanisms, the plug-type triggers of composite square tubes are designed and compared. A progressive failure model verified by the axial quasi-static loading test is proposed. Six different plug initiators including circle convex plug initiator, two types of square convex plug initiators, two types of groove-like plug initiators, and ditch-like plug initiator are given. To understand the triggering mechanism, the crashworthiness of chamfered square tubes is compared. Further, the influence of width of ditch plug-initiator towards energy-absorption characteristics and failure modes is investigated. Results show that well agreements in the failure and energy-absorption mechanisms between the simulation and experiment are identified. Three types of convex plug initiators can reduce the initial peak load and induce the out-ward petaling and splaying mode. The progressive inward-folding mode is similarly triggered by both two groove plug initiators. The ditch plug initiators are recommended as the best plug design with reasonably induced failure modes and an increase of 31.9% in total energy absorption. Comparing with non-plug initiator, square tubes crushed by narrower ditch plug initiator possess higher energy-absorption capacity, with an increase of 51.9% in SEA. DA - 2017/10// PY - 2017/10// DO - 10.1016/j.ijmecsci.2017.06.050 VL - 131 SP - 113-136 SN - 1879-2162 KW - Plug initiator KW - Energy-absorption capacity KW - Composite square tube KW - Triggering mechanism KW - Failure mechanism ER - TY - CONF TI - Control design for high-fidelity cyber-physical systems with applications to experimental fluid-structure interaction studies AU - Waghela, R. AU - Bryant, M. AB - A cyber-physical system (CPS) combines active actuation, sensing, and a control algorithm to virtually replicate a physical structure with desired inertia, stiffness, and damping properties. The interaction of a CPS with a fluid flow can be used to study complex fluid-structure interaction phenomena. This paper highlights some of the control design challenges associated with the design of CPS and elaborates on issues pertaining to performance and lag. A model for including the interaction force and a potential work-around to inertia compensation are presented. Finally, a case study compares classical PID control with H∞ based model-matching control design. C2 - 2017/// C3 - Proceedings of the asme conference on smart materials adaptive DA - 2017/// DO - 10.1115/smasis2017-3740 ER - TY - JOUR TI - Constitutive modeling of jugular vein-derived venous valve leaflet tissues AU - Kaul, Nayyan AU - Huang, Hsiao-Ying Shadow T2 - Journal of the Mechanical Behavior of Biomedical Materials AB - Venous valve tissues, though used in vein reconstruction surgeries and bioprosthetic valves with moderate success, have not been extensively studied with respect to their structure. Their inherent anisotropic, non-linear behavior combined with severe diseases which affect veins, such as chronic venous insufficiency, warrant understanding the structure and material behavior of these tissues. Hence, before any bioprosthetic grafts may be used in place of tissues, it is of the utmost importance to understand the mechanical and structural properties of these tissues as this may lead to higher success rates for valve replacement surgeries. The longevity of the bioprosthetics may also increase if the manufactured grafts behave the same as native valves. Building on the scant information about the uniaxial and biaxial mechanical properties of jugular venous valves and wall tissues from previous studies, the current focus of our investigation lies in understanding the material behavior by establishing a phenomenological strain energy-based constitutive relation for the tissues. We used bovine veins to study the behavior of valve leaflet tissue and adjoining wall tissue (from the proximal and distal ends of the veins) under different biaxial testing protocols. We looked at the behavior of numerical partial derivatives of the strain energy to select a suitable functional form for the strain energy for wall and valve tissues. Using this strain energy descriptor, we determined the Cauchy stress and compared it with experimental results under additional sets of displacement-controlled biaxial testing protocols to find material specific model parameters by the Powell's method algorithm. Results show that whereas wall tissue strain energy can be explained using a polynomial non-linear function, the valve tissue, due to higher non-linearities, requires an exponential function. This study may provide useful information for the primary stages of bioprosthetic designs and replacement surgeries and may support future studies investigating structural models. It may also support the study of valvular diseases by providing a way to understand material properties and behavior and to form a continuum model when required for numerical analyses and computational simulations. DA - 2017/11// PY - 2017/11// DO - 10.1016/j.jmbbm.2017.06.037 VL - 75 SP - 50-57 J2 - Journal of the Mechanical Behavior of Biomedical Materials LA - en OP - SN - 1751-6161 UR - http://dx.doi.org/10.1016/j.jmbbm.2017.06.037 DB - Crossref KW - Constitutive model KW - Phenomenological model KW - Venous valve KW - Chronic venous insufficiency KW - Biaxial testing KW - Biomechanics ER - TY - JOUR TI - Barely visible impact damage imaging using non-contact air-coupled transducer/laser Doppler vibrometer system AU - Harb, M. S. AU - Yuan, F. G. T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - The aim of this study is to investigate the capability of the zero-lag cross-correlation imaging condition of an A 0 Lamb wave mode in imaging a barely visible impact damage in a carbon fiber–reinforced polymer composite using a fully non-contact-guided wave-based non-destructive inspection system. A 16-ply (45/0/-45/90) 2s carbon fiber–reinforced polymer laminate was impacted at three different locations with different impact energies using a drop ball at three drop heights causing three barely visible impact damages with different sizes. The A 0 Lamb wave mode is generated inside the laminate using a circular air-coupled transducer and detected along the damaged region using a laser Doppler vibrometer. The measured wavefield is then decomposed into a forward and backward propagating wavefields by applying a frequency–wavenumber filtering post-processing technique. The decomposed wavefields are then cross-correlated in the frequency domain using zero-lag cross-correlation imaging condition producing a detailed cumulative damage image. The images obtained in frequency domain highlight the three damaged areas with higher zero-lag cross-correlation values compared to other parts of the inspected areas. The experimental investigation has shown a good correlation between the zero-lag cross-correlation imaging condition and C-scan images, which demonstrate a strong capability of guided wave zero-lag cross-correlation imaging condition technique in approximating the location and size of relatively small barely visible impact damages in thin composite structures. DA - 2017/11// PY - 2017/11// DO - 10.1177/1475921716678921 VL - 16 IS - 6 SP - 663-673 SN - 1741-3168 KW - Lamb waves KW - barely visible impact damage KW - delamination KW - composite KW - zero-lag cross-correlation imaging condition KW - non-destructive inspection ER - TY - JOUR TI - Almost output regulation of switched linear dynamics with switched exosignals AU - Yuan, Chengzhi AU - Wu, Fen T2 - INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL AB - Summary For systems with switched linear dynamics and affected by persistent switched exosignals, we propose a new hybrid control approach to achieve not only closed‐loop stability but also tracking and/or rejection of persistent references/disturbances generated by multiple exosystems, namely, output regulation. It is assumed that both controlled plant and exosystem are described by switched linear models. The proposed hybrid controller/output regulator is specified as a switching impulsive system, where the controller states will undergo impulsive jumps at each switching instant. Based on the average dwell time switching technique, it has been shown how to completely reduce the synthesis problem of the hybrid controller to a set of linear matrix equations and linear matrix inequalities. Both continuous‐time and discrete‐time cases are discussed. To demonstrate its usefulness, the proposed hybrid control method has been applied to solve the output regulation problem for a mechanical system. Copyright © 2017 John Wiley & Sons, Ltd. DA - 2017/11/10/ PY - 2017/11/10/ DO - 10.1002/rnc.3735 VL - 27 IS - 16 SP - 3197-3217 SN - 1099-1239 KW - almost output regulation KW - switched linear systems KW - hybrid control ER - TY - JOUR TI - Weight reduction of heavy-duty truck components through hollow geometry and intensive quenching AU - Lowrie, James AU - Pang, Hao AU - Ngaile, Gracious T2 - JOURNAL OF MANUFACTURING PROCESSES AB - Increasing environmental awareness has put pressure on heavy duty truck manufacturers to improve the fuel economy and reduce the emissions of their vehicles. Light weighting efforts are a useful tool in meeting these goals. As a demonstration of how light weighting practices can be applied to the power trains of heavy duty vehicles, this paper focuses on reducing the weight of the rear axle shaft. Two methods are focused on, i) hollow shaft geometry and ii) intensive quenching, as possible avenues to shed mass from the shaft. Load mapping is used to establish a finite element model which can be used to evaluate the light weight designs and techniques proposed in the paper. It is discovered that weight savings of around 26% can be achieved by changing the traditionally solid axle shaft into a hollow shaft. The intensive quenching process is shown to be superior to the oil quenching process in regards to both residual stresses and strength, allowing for material removal accounting for 3% of the shaft weight. Additionally, the compressive residual stresses created on the surface of the part during the intensive quenching process may also serve to slow crack initiation and increase fatigue life. Further optimization of the intensive quenching process may provide additional weight reduction opportunities. DA - 2017/8// PY - 2017/8// DO - 10.1016/j.jmapro.2017.04.021 VL - 28 SP - 523-530 SN - 1526-6125 KW - Heavy duty powertrain KW - Light weighting KW - Hollow shaft KW - Intensive quench ER - TY - JOUR TI - Toward computationally efficient combustion DNS with complex fuels via principal component transport AU - Owoyele, Opeoluwa AU - Echekki, Tarek T2 - COMBUSTION THEORY AND MODELLING AB - We investigate the potential of accelerating chemistry integration during the direct numerical simulation (DNS) of complex fuels based on the transport equations of representative scalars that span the desired composition space using principal component analysis (PCA). The transport of principal components (PCs) can reduce the number of transported scalars and improve the spatial and temporal resolution requirements. The strategy is demonstrated using DNS of a premixed methane–air flame in a 2D vortical flow and is extended to the 3D geometry to demonstrate the resulting enhancement in the computational efficiency of PC transport. The PCs are derived from a priori PCA of the same composition space using DNS. This analysis is used to construct and tabulate the PCs’ chemical source terms in terms of the PCs using artificial neural networks (ANN). Comparison of DNS based on a full thermo-chemical state and DNS based on PC transport with six PCs shows excellent agreement even for terms that are not included in the PCA reduction. The transported PCs reproduce some of the salient features of strongly curved and strongly strained flames. The results also show a significant reduction of two orders of magnitude in the computational cost of the simulations, which enables an extension of the solution approach to 3D DNS under similar computational requirements. DA - 2017/// PY - 2017/// DO - 10.1080/13647830.2017.1296976 VL - 21 IS - 4 SP - 770-798 SN - 1741-3559 UR - http://dx.doi.org/10.1080/13647830.2017.1296976 KW - turbulent flames KW - direct numerical simulation KW - principal component analysis KW - low-dimensional manifolds ER - TY - JOUR TI - Spotted Gar and the Evolution of Innate Immune Receptors AU - Wcisel, Dustin J. AU - Ota, Tatsuya AU - Litman, Gary W. AU - Yoder, Jeffrey A. T2 - JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION AB - The resolution of the gar genome affords an opportunity to examine the diversification and functional specialization of immune effector molecules at a distant and potentially informative point in phylogenetic development. Although innate immunity is effected by a particularly large number of different families of molecules, the focus here is to provide detailed characterization of several families of innate receptors that are encoded in large multigene families, for which orthologous forms can be identified in other species of bony fish but not in other vertebrate groups as well as those for which orthologs are present in other vertebrate species. The results indicate that although teleost fish and the gar, as a holostean reference species, share gene families thought previously to be restricted to the teleost fish, the manner in which the members of the multigene families of innate immune receptors have undergone diversification is different in these two major phylogenetic radiations. It appears that both the total genome duplication and different patterns of genetic selection have influenced the derivation and stabilization of innate immune genes in a substantial manner during the course of vertebrate evolution. DA - 2017/11// PY - 2017/11// DO - 10.1002/jez.b.22738 VL - 328 IS - 7 SP - 666-684 SN - 1552-5015 ER - TY - JOUR TI - Scalar conservation and boundedness in simulations of compressible flow AU - Subbareddy, Pramod K. AU - Kartha, Anand AU - Candler, Graham V. T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - With the proper combination of high-order, low-dissipation numerical methods, physics-based subgrid-scale models, and boundary conditions it is becoming possible to simulate many combustion flows at relevant conditions. However, non-premixed flows are a particular challenge because the thickness of the fuel/oxidizer interface scales inversely with Reynolds number. Sharp interfaces can also be present in the initial or boundary conditions. When higher-order numerical methods are used, there are often aphysical undershoots and overshoots in the scalar variables (e.g. passive scalars, species mass fractions or progress variable). These numerical issues are especially prominent when low-dissipation methods are used, since sharp jumps in flow variables are not always coincident with regions of strong variation in the scalar fields: consequently, special detection mechanisms and dissipative fluxes are needed. Most numerical methods diffuse the interface, resulting in artificial mixing and spurious reactions. In this paper, we propose a numerical method that mitigates this issue. We present methods for passive and active scalars, and demonstrate their effectiveness with several examples. DA - 2017/11/1/ PY - 2017/11/1/ DO - 10.1016/j.jcp.2017.08.001 VL - 348 SP - 827-846 SN - 1090-2716 KW - Numerical methods KW - Compressible flow KW - Boundedness KW - Reacting flow KW - Scalar excursions KW - Multispecies ER - TY - JOUR TI - High-speed 3D digital image correlation of low-velocity impacts on composite plates AU - Flores, Mark AU - Mollenhauer, David AU - Runatunga, Vipul AU - Beberniss, Timothy AU - Rapking, Daniel AU - Pankow, Mark T2 - COMPOSITES PART B-ENGINEERING DA - 2017/12/15/ PY - 2017/12/15/ DO - 10.1016/j.compositesb.2017.07.078 VL - 131 SP - 153-164 SN - 1879-1069 KW - Low-velocity impact KW - Damage threshold strain KW - High-speed photography ER - TY - CONF TI - Heat transfer to vertical dense granular flows at high operating temperatures AU - Watkins, M. F. AU - Gould, R. D. AB - Ceramic particles as a heat transfer fluid for concentrated solar power towers offers a variety of advantages over traditional heat transfer fluids. Ceramic particles permit the use of very high operating temperatures, being limited only by the working temperatures of the receiver components, as well as demonstrate the potential to be used for thermal energy storage. A variety of system configurations utilizing ceramic particles are currently being studied, including upward circulating beds of particles, falling particle curtains, and flows of particles over an array of absorber tubes. The present work investigates the use of gravity-driven dense granular flows through cylindrical tubes, which demonstrate solid packing fractions of approximately 60%. Previous work demonstrated encouraging results for the use of dense flows for heat transfer applications and examined the effect of various parameters on the overall heat transfer for low temperatures. The present work examined the heat transfer to dense flows at high operating temperatures more characteristic of concentrated solar power tower applications. For a given flow rate, the heat transfer coefficient was examined as a function of the mean flow temperature by steadily increasing the input heat flux over a series of trials. The heat transfer coefficient increased almost linearly with temperature below approximately 600°C. Above 600°C, the heat transfer coefficient increased at a faster rate, suggesting an increased radiation heat transfer contribution. C2 - 2017/// C3 - Proceedings of the asme 11th international conference on energy sustainability, 2017 DA - 2017/// DO - 10.1115/es2017-3272 ER - TY - JOUR TI - Dynamic Output Feedback Control for Continuous-Time T-S Fuzzy Systems Using Fuzzy Lyapunov Functions AU - Liu, Yang AU - Wu, Fen AU - Ban, Xiaojun T2 - IEEE TRANSACTIONS ON FUZZY SYSTEMS AB - A novel relaxation approach is proposed for the analysis and dynamic output feedback control of continuous-time Takagi–Sugeno (T–S) fuzzy systems using fuzzy Lyapunov functions. Previous relaxation methods for T–S fuzzy systems have some drawbacks in relaxing quadratic functions depending on normalized fuzzy weighting functions. They often introduce conservatism or lead to computational difficulty in analysis and control synthesis. Different from previous works, the proposed approach employs linear fractional transformation mechanism and full-block $S$ -procedure to reduce the conservatism in analysis. Furthermore, the relaxation technique proposed in this paper can be used in solving the controller synthesis problem effectively. As a result, a design procedure of a nonparallel distributed compensation output feedback controller, which ensures asymptotic stability and optimizes ${\mathcal L}_2$ gain performance of the closed-loop systems, is provided. Several examples have been used to illustrate the advantages and efficiency of the proposed method extensively. DA - 2017/10// PY - 2017/10// DO - 10.1109/tfuzz.2016.2598852 VL - 25 IS - 5 SP - 1155-1167 SN - 1941-0034 KW - Continuous-time Takagi-Sugeno (T-S) fuzzy systems KW - full-block S-procedure KW - fuzzy Lyapunov functions KW - linear fractional transformation KW - output feedback control KW - relaxation method ER - TY - JOUR TI - Design for excess capability to handle uncertain product requirements in a developing world setting AU - Allen, Jeffrey D. AU - Mattson, Christopher A. AU - Thacker, Kendall S. AU - Ferguson, Scott M. T2 - RESEARCH IN ENGINEERING DESIGN DA - 2017/10// PY - 2017/10// DO - 10.1007/s00163-017-0253-8 VL - 28 IS - 4 SP - 511-527 SN - 1435-6066 KW - Developing world KW - Excess KW - Evolvability KW - Adaptability KW - Reconfigurability KW - Reconfigure KW - System design KW - Improved cookstove ER - TY - JOUR TI - Damage Imaging of an Isotropic Plate Using Matching Pursuit Algorithm AU - Kim, H. W. AU - Yuan, F. G. T2 - SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2017 AB - A matching pursuit (MP) algorithm is effective tool to decompose the overlapped wave packets in a signal so that each wave mode can be identified. For the successful separations of the wave packets, an atom function should be properly designed, that can well resemble the physical features of the signal of interest. In this paper, a novel atom function for the MP algorithm is proposed based on the wave propagating model due to an excitation of a Hann-windowed toneburst signal, which performs very accurately compared to the MP algorithm with the existing Gaussian-type atom functions. The decomposed wave packets, including the directly scattered wave from damage as well as the reverberant waves from the free edges of the plate, via the MP method are employed in the damage imaging algorithm, highlighting the damaged location with higher intensity than the conventional algorithm utilizing only a direct reflected wave. The proposed approach is verified from the experiment where four piezoelectric wafers can accurately identify the damage location in a plate. DA - 2017/// PY - 2017/// DO - 10.1117/12.2258691 VL - 10168 SP - SN - 1996-756X KW - matching pursuit KW - damage imaging KW - Hann-window toneburst KW - piezoelectric wafer KW - Lamb wave ER - TY - JOUR TI - Correlating Crack Onset Strain and Cohesive Fracture Energy in Polymer Semiconductor Films AU - Balar, Nrup AU - Brendan T. O'Connor, T2 - MACROMOLECULES AB - Polymer semiconductors are an attractive material system for flexible and stretchable electronic devices owing to their potentially favorable mechanical attributes. Establishing the thermomechanical behavior of polymer semiconductors is thus an important consideration to ensure successful operation in these applications. One of the most common mechanical characterization methods for these materials is to manipulate the thin films while on an elastomer substrate. A primary measurement with this approach is the film’s crack onset strain (COS), a measure of ductility. It is simple and effective; however, it is a highly qualitative view of film mechanical stability, particularly in flexible device applications. Alternatively, cohesive fracture energy (Gc) provides a direct quantitative measure of the mechanical integrity of the film. While fracture energy provides important insight into mechanical stability, it typically requires a more complex measurement method than the film on elastomer tests. Here, we compare the COS using film on elastomer testing, with cohesive fracture energy measured using four-point bending for a range of polymer semiconductor films. The polymers considered have a range of molecular structures and molecular packing characteristics providing a broad representative sample set. The values of Gc ranged from 0.4 to 18 J/m2 while COS ranged from 2% to over 100%. We show that COS of the films can be correlated with Gc providing support that COS is a valuable measurement to probe the mechanical toughness of polymer semiconductor films. We also discuss the physical characteristics each measurement highlights and the complementary nature of these measurements. DA - 2017/11/14/ PY - 2017/11/14/ DO - 10.1021/acs.macromol.7b01282 VL - 50 IS - 21 SP - 8611-8618 SN - 1520-5835 ER - TY - JOUR TI - Composition-independent mean temperature measurements in laminar diffusion flames using spectral lineshape information AU - Zelenak, D. AU - Narayanaswamy, V. T2 - EXPERIMENTS IN FLUIDS DA - 2017/10// PY - 2017/10// DO - 10.1007/s00348-017-2430-y VL - 58 IS - 10 SP - SN - 1432-1114 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85029953501&partnerID=MN8TOARS ER - TY - JOUR TI - Composition and structure of porcine digital flexor tendon-bone insertion tissues AU - Chandrasekaran, Sandhya AU - Pankow, Mark AU - Peters, Kara AU - Huang, Hsiao-Ying Shadow T2 - Journal of Biomedical Materials Research Part A AB - Tendon-bone insertion is a functionally graded tissue, transitioning from 200 MPa tensile modulus at the tendon end to 20 GPa tensile modulus at the bone, across just a few hundred micrometers. In this study, we examine the porcine digital flexor tendon insertion tissue to provide a quantitative description of its collagen orientation and mineral concentration by using Fast Fourier Transform (FFT) based image analysis and mass spectrometry, respectively. Histological results revealed uniformity in global collagen orientation at all depths, indicative of mechanical anisotropy, although at mid-depth, the highest fiber density, least amount of dispersion, and least cellular circularity were evident. Collagen orientation distribution obtained through 2D FFT of histological imaging data from fluorescent microscopy agreed with past measurements based on polarized light microscopy. Results revealed global fiber orientation across the tendon-bone insertion to be preserved along direction of physiologic tension. Gradation in the fiber distribution orientation index across the insertion was reflective of a decrease in anisotropy from the tendon to the bone. We provided elemental maps across the fibrocartilage for its organic and inorganic constituents through time-of-flight secondary ion mass spectrometry (TOF-SIMS). The apatite intensity distribution from the tendon to bone was shown to follow a linear trend, supporting past results based on Raman microprobe analysis. The merit of this study lies in the image-based simplified approach to fiber distribution quantification and in the high spatial resolution of the compositional analysis. In conjunction with the mechanical properties of the insertion tissue, fiber, and mineral distribution results for the insertion from this may potentially be incorporated into the development of a structural constitutive approach toward computational modeling. Characterizing the properties of the native insertion tissue would provide the microstructural basis for developing biomimetic scaffolds to recreate the graded morphology of a fibrocartilaginous insertion. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3050-3058, 2017. DA - 2017/8/19/ PY - 2017/8/19/ DO - 10.1002/jbm.a.36162 VL - 105 IS - 11 SP - 3050-3058 J2 - J. Biomed. Mater. Res. LA - en OP - SN - 1549-3296 UR - http://dx.doi.org/10.1002/jbm.a.36162 DB - Crossref KW - tendon-bone insertion KW - collagen fiber orientation KW - fast fourier transform KW - time-of-flight secondary ion mass spectrometry ER - TY - CONF TI - Comparative assessment of different types of ocean compressed air energy storage systems based on exergy analysis AU - Patil, V. C. AU - Ro, P. I. AB - Ocean compressed air energy storage (OCAES) is a promising large-scale energy storage concept. Different types of OCAES viz. - Diabatic, adiabatic and isothermal are possible based on the handling of heat in the system. In diabatic OCAES, compressed air is cooled in a cooler and heated using external heat source before transport to the expander. In Adiabatic OCAES, heat from the compressed air is stored in a thermal energy storage (TES) and reused to reheat compressed air before sending it to the expander. In Isothermal OCAES, air is compressed and expanded isothermally which results in the least compression work and highest expansion work. These OCAES configurations are assessed using exergy analysis in this paper. The exergy efficiency of individual components, exergy flow and overall efficiencies of diabatic, adiabatic and isothermal OCAES are presented. Results show that adiabatic OCAES shows improved efficiency over diabatic OCAES by storing thermal exergy of compressed air in TES and isothermal OCAES shows significantly higher efficiency over adiabatic and diabatic OCAES. C2 - 2017/// C3 - Proceedings of the ASME Power Conference Joint with ICOPE-17, 2017, vol 2 DA - 2017/// DO - 10.1115/power-icope2017-3630 ER - TY - CONF TI - Characterizing particle-wall contact behavior and fluctuations in gravity-driven dense granular flows in cylindrical tubes using dem AU - Chilamkurti, Y. N. AU - Gould, R. D. C2 - 2017/// C3 - Proceedings of the ASME Power Conference Joint with ICOPE-17, 2017, vol 2 DA - 2017/// ER - TY - JOUR TI - A spectral profile multiplexed FBG sensor network with application to strain measurement in a Kevlar woven fabric AU - Guo, Guodong AU - Hackney, Drew AU - Pankow, Mark AU - Peters, Kara T2 - SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2017 AB - A spectral profile division multiplexed fiber Bragg grating (FBG) sensor network is described in this paper. The unique spectral profile of each sensor in the network is identified as a distinct feature to be interrogated. Spectrum overlap is allowed under working conditions. Thus, a specific wavelength window does not need to be allocated to each sensor as in a wavelength division multiplexed (WDM) network. When the sensors are serially connected in the network, the spectrum output is expressed through a truncated series. To track the wavelength shift of each sensor, the identification problem is transformed to a nonlinear optimization problem, which is then solved by a modified dynamic multi-swarm particle swarm optimizer (DMS-PSO). To demonstrate the application of the developed network, a network consisting of four FBGs was integrated into a Kevlar woven fabric, which was under a quasi-static load imposed by an impactor head. Due to the substantial radial strain in the fabric, the spectrums of different FBGs were found to overlap during the loading process. With the developed interrogating method, the overlapped spectrum would be distinguished thus the wavelength shift of each sensor can be monitored. DA - 2017/// PY - 2017/// DO - 10.1117/12.2260114 VL - 10168 SP - SN - 1996-756X KW - fiber Bragg grating KW - sensor multiplexing KW - particle swarm optimizer ER - TY - CONF TI - The adhesive effect on ultrasonic Lamb wave detection sensitivity of remotely-bonded fiber Bragg grating sensors AU - Wee, J. AU - Hackney, D. A. AU - Bradford, P. D. AU - Peters, Kara AB - Fiber Bragg grating (FBG) sensors are excellent transducers for ultrasonic signal detection in structural health monitoring (SHM) application. While the FBG sensors are typically bonded directly on the surface of a structure to collect signals, one of the major challenges arises from demodulating relevant information from the low amplitude signal. The authors have experimentally demonstrated that the ultrasonic wave detection sensitivity of FBG sensors can be increased by bonding optical fiber away from the FBG location. This configuration is referred to here as remote bonding. However the mechanism causing this phenomenon has not been explored. In this work, we simulate the previous experimental work through a transient analysis based on the finite element method, and the output FBG response is calculated through the transfer matrix method. We first model an optical fiber bonded on the surface of an aluminum plate with an adhesive. The consistent input signal is excited to the plate, which is detected by the directly and remotely-bonded FBGs. The effect of the presence of the adhesive around the FBG is investigated by analyzing strain and displacement along the length of the FBGs at the locations of direct and remote bonding cases, and the consequent output FBG responses. The result demonstrates that the sensitivity difference between the direct and remote bonding cases is originated from shear lag effect due to adhesive. C2 - 2017/// C3 - Sensors and smart structures technologies for civil, mechanical, and aerospace systems 2017 DA - 2017/// DO - 10.1117/12.2260009 VL - 10168 ER - TY - JOUR TI - Temperature controlled interlayer disorder in ultrathin films of alpha-sexithiophene AU - Hoffman, Benjamin C. AU - Mcafee, Terry AU - Pazoki, Sara AU - Apperson, Aubrey AU - Brendan T. O'Connor, AU - Dougherty, Daniel B. T2 - THIN SOLID FILMS AB - The surface potential difference between the first and second layer of α-sexithiophene (6T) films on silane passivated SiO2 is observed using Kelvin Probe Force Microscopy. The relative surface potential between the first two layers changes sign depending on whether the films are grown at 70 °C or 120 °C substrate temperature. Complementary wide angle X-ray scattering observations show that this difference can be interpreted as the result of a higher concentration of interlayer hole traps due to poor out-of-plane ordering in films deposited at lower temperature. Molecular sliding and shifts in tilt angle are proposed as the microscopic origin of out-of-plane disorder leading to trapped charges. DA - 2017/11/30/ PY - 2017/11/30/ DO - 10.1016/j.tsf.2017.09.011 VL - 642 SP - 182-187 SN - 0040-6090 ER - TY - JOUR TI - Pop-up assembly of 3D structures actuated by heat shrinkable polymers AU - Cui, Jianxun AU - Adams, J. G. M. AU - Zhu, Yong T2 - SMART MATERIALS AND STRUCTURES AB - Folding 2D sheets into desired 3D structures is a promising fabrication technique that can find a wide range of applications. Compressive buckling provides an attractive strategy to actuate the folding and can be applied to a broad range of materials. Here a new and simple method is reported to achieve controlled compressive buckling, which is actuated by a heat shrinkable polymer sheet. The buckling deformation is localized at the pre-defined creases in the 2D sheet, resulting in sharp folding. Two approaches are developed to actuate the transformation, which follow similar geometric rules. In the first approach, the 2D precursor is pushed from outside, which leads to a 3D structure surrounded by the shrunk polymer sheet. Assembled 3D structures include prisms/pyramids with different base shapes, house roof, partial soccer ball, Miura-ori structure and insect wing. In the second approach, the 2D precursor is pulled from inside, which leads to a 3D structure enclosing the shrunk polymer sheet. Prisms/pyramids with different base shapes are assembled. The assembled structures are further tessellated to fabricate cellular structures that can be used as thermal insulator and crash energy absorber. They are also stacked vertically to fabricate complex multilayer structures. DA - 2017/12// PY - 2017/12// DO - 10.1088/1361-665x/aa9552 VL - 26 IS - 12 SP - SN - 1361-665X KW - origami KW - kirigami KW - controlled buckling KW - heat shrinkable polymer ER - TY - JOUR TI - Numerical Simulations of Turbulent Flow over Airfoils Near and During Static Stall AU - Ke, Jianghua AU - Edwards, Jack R. T2 - JOURNAL OF AIRCRAFT AB - Reynolds-averaged Navier–Stokes and hybrid large-eddy/Reynolds-averaged Navier–Stokes simulations of turbulent flow past an Aérospatiale A-Airfoil near stall at , , and a NACA 0012 airfoil under static stall conditions (, , ) are described in this paper. In the flow past the A-Airfoil, comparisons with surface skin-friction coefficient and pressure coefficient distribution are generally in good agreement with experimental measurements. Comparisons with experimental velocity profile data and Reynolds-stress data are also generally favorable. Leading-edge laminar separation and turbulent reattachment is predicted when the Menter–Langtry correlation-based transition model is used in combination with either Reynolds-averaged Navier–Stokes or large-eddy/Reynolds-averaged Navier–Stokes strategies, but the level of trailing-edge separation is underpredicted, relative to experimental data and to results obtained without the inclusion of transition model. For the case of flow past a NACA 0012 airfoil under static stall conditions, results from the large-eddy/Reynolds-averaged Navier–Stokes simulations exhibit a sensitivity to mesh refinement, with finer spanwise mesh resolution leading to light stall, characterized primarily by trailing-edge separation, and coarser spanwise mesh resolution leading to deep stall, characterized by the presence of a stabilized leading-edge vortex. Calculations that include wind-tunnel wall effects show better general agreement with experimental measurements but also display the aforementioned sensitivity to spanwise mesh refinement. DA - 2017/9// PY - 2017/9// DO - 10.2514/1.c034186 VL - 54 IS - 5 SP - 1960-1978 SN - 1533-3868 ER - TY - JOUR TI - Mechanisms of signal coupling to optical fiber for FBG sensor detection of Lamb waves AU - Wee, Junghyun AU - Hackney, Drew AU - Bradford, Philip AU - Peters, Kara T2 - 2017 25TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS (OFS) AB - One of the major challenges when using fiber Bragg grating sensors (FBGs) to detect Lamb wave or acoustic emission signals in structures is the low sensitivity of these sensors to surface waves propagating in the structure. The authors have previously demonstrated that remote bonding of the optical fiber away from the FBG can increase the measured signal amplitude. In this paper we investigate the potential mechanisms for this increase through finite element simulations and demonstrate that the shear lag effect through the adhesive is the major source of the signal amplitude difference between the direct and remote bonding cases. DA - 2017/// PY - 2017/// DO - 10.1117/12.2263278 VL - 10323 SP - SN - 1996-756X KW - Lamb wave detection KW - fiber Bragg grating KW - structural health monitoring KW - adhesive bonding ER - TY - JOUR TI - IR-MALDESI Mass Spectrometry Imaging at 50 Micron Spatial Resolution AU - Bokhart, Mark T. AU - Manni, Jeffrey AU - Garrard, Kenneth P. AU - Ekelof, Mans AU - Nazari, Milad AU - Muddiman, David C. T2 - JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY AB - High spatial resolution in mass spectrometry imaging (MSI) is crucial to understanding the biology dictated by molecular distributions in complex tissue systems. Here, we present MSI using infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) at 50 μm resolution. An adjustable iris, beam expander, and an aspherical focusing lens were used to reduce tissue ablation diameters for MSI at high resolution. The laser beam caustic was modeled using laser ablation paper to calculate relevant laser beam characteristics. The minimum laser spot diameter on the tissue was determined using tissue staining and microscopy. Finally, the newly constructed optical system was used to image hen ovarian tissue with and without oversampling, detailing tissue features at 50 μm resolution. Graphical Abstract ᅟ. DA - 2017/10// PY - 2017/10// DO - 10.1007/s13361-017-1740-x VL - 28 IS - 10 SP - 2099-2107 SN - 1879-1123 KW - Mass spectrometry imaging KW - IR-MALDESI KW - Tissue imaging KW - Spatial resolution KW - Laser focusing ER - TY - JOUR TI - Highly anisotropic magneto-transport and field orientation dependent oscillations in aligned carbon nanotube/epoxy composites AU - Wells, Brian AU - Kumar, Raj AU - Reynolds, C. Lewis, Jr. AU - Peters, Kara AU - Bradford, Philip D. T2 - APPLIED PHYSICS LETTERS AB - Carbon nanotubes (CNTs) have been widely investigated as additive materials for composites with potential applications in electronic devices due to their extremely large electrical conductivity and current density. Here, highly aligned CNT composite films were created using a sequential layering fabrication technique. The degree of CNT alignment leads to anisotropic resistance values which varies &gt;400× in orthogonal directions. Similarly, the magnetoresistance (MR) of the CNT composite differs depending upon the relative direction of current and the applied magnetic field. A suppression of negative to positive MR crossover was also observed. More importantly, an overall positive magnetoresistance behavior with localized +/− oscillations was discovered at low fields which persists up to room temperature when the current (I) and in-plane magnetic field (B) were parallel to the axis of CNT (B∥I∥CNT), which is consistent with Aharonov-Bohm oscillations in our CNT/epoxy composites. When the current, applied magnetic field, and nanotube axis are aligned, the in-plane MR is positive instead of negative as observed for all other field, current, and tube orientations. Here, we provide in-depth analysis of the conduction mechanism and anisotropy in the magneto-transport properties of these aligned CNT-epoxy composites. DA - 2017/12/25/ PY - 2017/12/25/ DO - 10.1063/1.4999503 VL - 111 IS - 26 SP - SN - 1077-3118 ER - TY - JOUR TI - Effects of thermo-mechanical behavior and hinge geometry on folding response of shape memory polymer sheets AU - Mailen, Russell W. AU - Dickey, Michael D. AU - Genzer, Jan AU - Zikry, Mohammed T2 - JOURNAL OF APPLIED PHYSICS AB - Shape memory polymer (SMP) sheets patterned with black ink hinges change shape in response to external stimuli, such as absorbed thermal energy from an infrared (IR) light. The geometry of these hinges, including size, orientation, and location, and the applied thermal loads significantly influence the final folded shape of the sheet, but these variables have not been fully investigated. We perform a systematic study on SMP sheets to fundamentally understand the effects of single and double hinge geometries, hinge orientation and spacing, initial temperature, heat flux intensity, and pattern width on the folding behavior. We have developed thermo-viscoelastic finite element models to characterize and quantify the stresses, strains, and temperatures as they relate to SMP shape changes. Our predictions indicate that hinge orientation can be used to reduce the total bending angle, which is the angle traversed by the folding face of the sheet. Two parallel hinges increase the total bending angle, and heat conduction between the hinges affects the transient folding response. IR intensity and initial temperatures can also influence the transient folding behavior. These results can provide guidelines to optimize the transient folding response and the three-dimensional folded structure obtained from self-folding polymer origami sheets that can be applied for myriad applications. DA - 2017/11/21/ PY - 2017/11/21/ DO - 10.1063/1.5000040 VL - 122 IS - 19 SP - SN - 1089-7550 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85034607215&partnerID=MN8TOARS ER - TY - JOUR TI - Effects of Fuel Quantity on Soot Formation Process for Biomass-Based Renewable Diesel Fuel Combustion AU - Jing, Wei AU - Wu, Zengyang AU - Roberts, William L. AU - Fang, Tiegang T2 - JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME AB - Soot formation process was investigated for biomass-based renewable diesel fuel, such as biomass to liquid (BTL), and conventional diesel combustion under varied fuel quantities injected into a constant volume combustion chamber. Soot measurement was implemented by two-color pyrometry under quiescent type diesel engine conditions (1000 K and 21% O2 concentration). Different fuel quantities, which correspond to different injection widths from 0.5 ms to 2 ms under constant injection pressure (1000 bar), were used to simulate different loads in engines. For a given fuel, soot temperature and KL factor show a different trend at initial stage for different fuel quantities, where a higher soot temperature can be found in a small fuel quantity case. but a higher KL factor is observed in a large fuel quantity case generally. Another difference occurs at the end of combustion due to the termination of fuel injection. Additionally, BTL flame has a lower soot temperature, especially under a larger fuel quantity (2 ms injection width). Meanwhile, average soot level is lower for BTL flame, especially under a lower fuel quantity (0.5 ms injection width). BTL shows an overall low sooting behavior with low soot temperature compared to diesel; however, trade-off between soot level and soot temperature needs to be carefully selected when different loads are used. DA - 2017/10// PY - 2017/10// DO - 10.1115/1.4036292 VL - 139 IS - 10 SP - SN - 1528-8919 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85020430438&partnerID=MN8TOARS ER - TY - JOUR TI - Consensus for multi-agent systems with time-varying input delays AU - Yuan, Chengzhi AU - Wu, Fen T2 - INTERNATIONAL JOURNAL OF SYSTEMS SCIENCE AB - This paper addresses the consensus control problem for linear multi-agent systems subject to uniform time-varying input delays and external disturbance. A novel state-feedback consensus protocol is proposed under the integral quadratic constraint (IQC) framework, which utilises not only the relative state information from neighbouring agents but also the real-time information of delays by means of the dynamic IQC system states for feedback control. Based on this new consensus protocol, the associated IQC-based control synthesis conditions are established and fully characterised as linear matrix inequalities (LMIs), such that the consensus control solution with optimal H∞ disturbance attenuation performance can be synthesised efficiently via convex optimisation. A numerical example is used to demonstrate the proposed approach. DA - 2017/// PY - 2017/// DO - 10.1080/00207721.2017.1363927 VL - 48 IS - 14 SP - 2956-2966 SN - 1464-5319 KW - Multi-agent systems KW - cooperative control KW - decentralised control KW - time-delay systems KW - linear matrix inequalities ER - TY - JOUR TI - Computational analysis of aerosol-dynamics in a human whole-lung airway model AU - Kolanjiyil, Arun V. AU - Kleinstreuer, Clement T2 - JOURNAL OF AEROSOL SCIENCE AB - Prediction of the air-particle dynamics in human lungs can reveal critical deposition sites of toxins or can determine best physical parameters for direct drug delivery and associated inhaler devices. However, the sheer complexity of the human lung, featuring a total of 16 million airways, prohibits a full-scale study. So, as an alternative, a physiologically realistic and computationally efficient computer simulation model has been developed. The configuration of the new whole-lung airway model (WLAM) consists of subject-specific upper airways from nose/mouth to, say, generation 3, which are then connected to adjustable triple bifurcation units (TBUs). These TBUs are in series and parallel to cover the remaining generations, based on morphometric measurements of human lung casts. Actual transient airflow, fluid-particle dynamics and alveolar tissue dynamics have been implemented to evaluate the impact of all respiratory airways under realistic inlet conditions. Specifically, the expanding and contracting motion of the alveoli mimic inhalation and exhalation in the alveolar region. Particle transport and deposition depend on the lung-airway geometry, particle characteristics, and inhalation flow frequency. Considering inhalation/exhalation in form of a square-wave breathing profile at 15 L/min with different tidal volumes and 3 μm-size microspheres as a WLAM test case, significantly higher deposition was observed in the alveolar region than in the upper airways. For short and light breathing conditions, multiple breathing cycles are required to exhale all the suspended particles. Particle deposition patterns differ for inhalation vs. exhalation, as well as in subsequent breathing cycles. During later cycles, the suspended particles tend to travel to distal airways. The model predictions agree well with in vivo results. The new WLAM can be used for local, segmental and total deposition predictions of inhaled toxic or therapeutic aerosols, and for providing inhaler-design guidelines to improve drug-aerosol targeting. DA - 2017/12// PY - 2017/12// DO - 10.1016/j.jaerosci.2017.10.001 VL - 114 SP - 301-316 SN - 1879-1964 KW - Whole-lung airway model KW - Particle deposition KW - Lung air-particle dynamics KW - Local and total lung depositions KW - Actual breathing modes KW - Alveolar region ER - TY - JOUR TI - Biaxial mechanical properties of bovine jugular venous valve leaflet tissues AU - Huang, Hsiao-Ying Shadow AU - Lu, Jiaqi T2 - Biomechanics and Modeling in Mechanobiology DA - 2017/6/19/ PY - 2017/6/19/ DO - 10.1007/s10237-017-0927-1 VL - 16 IS - 6 SP - 1911-1923 J2 - Biomech Model Mechanobiol LA - en OP - SN - 1617-7959 1617-7940 UR - http://dx.doi.org/10.1007/s10237-017-0927-1 DB - Crossref KW - Anisotropy KW - Tissue biomechanics KW - Biaxial testing KW - Chronic venous insufficiency ER - TY - JOUR TI - Using Resampling Residuals for Estimating Confidence Intervals of the Effective Viscosity and Forchheimer Coefficient AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2017/9// PY - 2017/9// DO - 10.1007/s11242-017-0892-2 VL - 119 IS - 2 SP - 451-459 SN - 1573-1634 KW - Brinkman-Forchheimer equation KW - Least-squares error minimization KW - Bootstrapping KW - Parameter determination ER - TY - JOUR TI - Tether enabled spacecraft systems for ultra long wavelength radio astronomy AU - Gemmer, Thomas AU - Yoder, Christopher D. AU - Reedy, Jacob AU - Mazzoleni, Andre P. T2 - ACTA ASTRONAUTICA AB - This paper describes a proposed CubeSat mission to perform unique experiments involving interferometry and tether dynamics. A 3U CubeSat is to be placed in orbit where it will separate into three 1U CubeSats connected by a total of 100 m of tether. The separation between the three units will allow for the demonstration of high resolution radio interferometry. The increased resolution will provide access to the Ultra-Long Wavelength (ULW) scale of the electromagnetic spectrum, which is largely unexplored. During and after completion of the primary experiment, the CubeSat will be able to gather data on tethered dynamics of a space vehicle. Maneuvers to be performed and studied include direct testing of tether deployment and tethered formation flying. Tether deployment is a vital area where more data is needed as this is the phase where many tethered missions have experienced complications and failures. There are a large number of complex dynamical responses predicted by the theory associated with the deployment of an orbiting tethered system. Therefore, it is imperative to conduct an experiment that provides data on what dynamic responses actually occur. DA - 2017/9// PY - 2017/9// DO - 10.1016/j.actaastro.2016.11.009 VL - 138 SP - 530-535 SN - 1879-2030 ER - TY - JOUR TI - Simulating tubulin-associated unit transport in an axon: using bootstrapping for estimating confidence intervals of best-fit parameter values obtained from indirect experimental data AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. T2 - PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES AB - In this paper, we first develop a model of axonal transport of tubulin-associated unit (tau) protein. We determine the minimum number of parameters necessary to reproduce published experimental results, reducing the number of parameters from 18 in the full model to eight in the simplified model. We then address the following questions: Is it possible to estimate parameter values for this model using the very limited amount of published experimental data? Furthermore, is it possible to estimate confidence intervals for the determined parameters? The idea that is explored in this paper is based on using bootstrapping. Model parameters were estimated by minimizing the objective function that simulates the discrepancy between the model predictions and experimental data. Residuals were then identified by calculating the differences between the experimental data and model predictions. New, surrogate 'experimental' data were generated by randomly resampling residuals. By finding sets of best-fit parameters for a large number of surrogate data the histograms for the model parameters were produced. These histograms were then used to estimate confidence intervals for the model parameters, by using the percentile bootstrap. Once the model was calibrated, we applied it to analysing some features of tau transport that are not accessible to current experimental techniques. DA - 2017/5/1/ PY - 2017/5/1/ DO - 10.1098/rspa.2017.0045 VL - 473 IS - 2201 SP - SN - 1471-2946 KW - neuron KW - tau protein KW - Alzheimer's disease KW - bootstrapping KW - resampling residuals KW - mathematical modelling ER - TY - JOUR TI - SENSITIVITY ANALYSIS IN PORO-ELASTIC AND PORO-VISCO-ELASTIC MODELS WITH RESPECT TO BOUNDARY DATA AU - Banks, H. T. AU - Bekele-Maxwell, K. AU - Bociu, L. AU - Noorman, M. AU - Guidoboni, G. T2 - QUARTERLY OF APPLIED MATHEMATICS AB - In this article we consider poro-elastic and poro-visco-elastic models inspired by problems in medicine and biology, and we perform sensitivity analysis on the solutions of these fluid-solid mixture problems with respect to the imposed boundary data, which are the main drivers of the system. Moreover, we compare the results obtained in the elastic case vs. visco-elastic case, as it is known that structural viscosity of biological tissues decreases with age and disease. Sensitivity analysis is the first step towards optimization and control problems associated with these models, which is our ultimate goal. DA - 2017/12// PY - 2017/12// DO - 10.1090/qam/1475 VL - 75 IS - 4 SP - 697-735 SN - 1552-4485 KW - Sensitivity KW - poro-elastic KW - poro-visco-elastic KW - biological tissues KW - complex-step method ER - TY - JOUR TI - Piezoelectric Floating Element Shear Stress Sensor for the Wind Tunnel Flow Measurement AU - Kim, Taeyang AU - Saini, Aditya AU - Kim, Jinwook AU - Gopalarathnam, Ashok AU - Zhu, Yong AU - Palmieri, Frank L. AU - Wohl, Christopher J. AU - Jiang, Xiaoning T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - A piezoelectric (PE) sensor with a floating element was developed for direct measurement of flow induced shear stress. The PE sensor was designed to detect the pure shear stress while suppressing the effect of normal stress generated from the vortex lift up by applying opposite poling vectors to the PE elements. During the calibration stage, the prototyped sensor showed a high sensitivity to shear stress (91.3 ± 2.1 pC/Pa) due to the high PE coefficients (d31 = -1330 pC/N) of the constituent 0.67Pb(Mg 1/3 Nb 2/3 )O 3 - 0.33PbTiO 3 (PMN-33%PT) single crystal. By contrast, the sensor showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the sensing structure. The usable frequency range of the sensor is up to 800 Hz. In subsonic wind tunnel tests, an analytical model was proposed based on cantilever beam theory with an end-tip-mass for verifying the resonance frequency shift in static stress measurements. For dynamic stress measurements, the signal-to-noise ratio (SNR) and ambient vibration-filtered pure shear stress sensitivity were obtained through signal processing. The developed PE shear stress sensor was found to have an SNR of 15.8 ± 2.2 dB and a sensitivity of 56.5 ± 4.6 pC/Pa in the turbulent flow. DA - 2017/9// PY - 2017/9// DO - 10.1109/tie.2016.2630670 VL - 64 IS - 9 SP - 7304-7312 SN - 1557-9948 KW - Bimorph piezoelectric (PE) structures KW - electromechanical symmetry KW - floating element (FE) KW - PMN-33% PT crystal KW - shear stress ER - TY - JOUR TI - Nanostructured antireflective in-plane solar harvester AU - Tippens, Jared AU - Bagal, Abhijeet AU - Zhang, Xu A. AU - Chang, Chih-Hao T2 - OPTICS EXPRESS AB - In this work, we demonstrate a two-dimensional nano-hole array that can reduce reflection losses while passively trapping and harvesting incident light. The surface structure is designed to scavenge a small portion of incident light that would typically be lost due to Fresnel reflection, while the majority of light transmits unobstructed like a regular window. The trapping mechanism is dependent on angle and wavelength, and can be designed to selectively trap narrow wavelength bands using the constructed theoretical models. We demonstrate that structures with periods of 275 nm and 325 nm can trap different wavelength range within the visible spectrum, while simultaneously suppressing reflection losses. The trapping effect can be observed visually, and can be converted to a current output using a photovoltaic (PV) cell on the glass edge. The fabrication of such materials employs a simple replication process, and can be readily scaled up for large-scale manufacturing. The demonstrated solar harvester can be potentially be widely deployed in residential and commercial buildings as multifunctional windows for solar energy harvesting, scavenging, spectra splitting, and anti-glare properties. DA - 2017/8/7/ PY - 2017/8/7/ DO - 10.1364/oe.25.00a840 VL - 25 IS - 16 SP - A840-A850 SN - 1094-4087 ER - TY - JOUR TI - Impact of natural organic matter and inorganic solutes on energy recovery from five real salinity gradients using reverse electrodialysis AU - Kingsbury, R. S. AU - Liu, F. AU - Zhu, S. AU - Boggs, C. AU - Armstrong, M. D. AU - Call, D. F. AU - Coronell, O. T2 - JOURNAL OF MEMBRANE SCIENCE AB - “Blue energy” technologies such as reverse electrodialysis (RED) have received significant research attention over the last several years as a means of generating clean electricity from natural salinity gradients (e.g., seawater and river water). To date, however, knowledge of RED is largely based on synthetic sodium chloride solutions that simulate natural waters. Accordingly, in this work we measured the RED performance of five real water pairs, including seawater, river water, desalination brine, saline wastewater from a pickling plant, and treated wastewater. We compared the performance of each real water pair with that of synthetic control waters to investigate the individual impacts of inorganic constituents (e.g., multivalent ions) and natural organic matter (NOM). Our results indicate that the presence of NOM has a larger impact on power density than ionic composition. Specifically, NOM reduced power densities by up to 43%, while inorganic constituents reduced power densities by up to 8% compared to control waters. Furthermore, UV-absorbing NOM present in the dilute compartment of the RED stack was strongly associated with reduced membrane permselectivity and energy efficiency. Taken together, our findings highlight the important role of organic matter in determining the RED performance of real waters. DA - 2017/11/1/ PY - 2017/11/1/ DO - 10.1016/j.memsci.2017.07.038 VL - 541 SP - 621-632 SN - 1873-3123 KW - Reverse electrodialysis KW - Salinity gradient energy KW - Ion exchange membranes KW - Natural organic matter KW - Blue energy ER - TY - JOUR TI - Dual-Frequency Transducer with a Wideband PVDF Receiver for Contrast-Enhanced, Adjustable Harmonic Imaging AU - Kim, Jinwook AU - Lindsey, Brooks D. AU - Li, Sibo AU - Dayton, Paul A. AU - Jiang, Xiaoning T2 - HEALTH MONITORING OF STRUCTURAL AND BIOLOGICAL SYSTEMS 2017 AB - Acoustic angiography is a contrast-enhanced, superharmonic microvascular imaging method. It has shown the capability of high-resolution and high-contrast-to-tissue-ratio (CTR) imaging for vascular structure near tumor. Dual-frequency ultrasound transducers and arrays are usually used for this new imaging technique. Stacked-type dual-frequency transducers have been developed for this vascular imaging method by exciting injected microbubble contrast agent (MCA) in the vessels with low-frequency (1-5 MHz), moderate power ultrasound burst waves and receiving the superharmonic responses from MCA by a high-frequency receiver (>10 MHz). The main challenge of the conventional dual-frequency transducers is a limited penetration depth (<25 mm) due to the insufficient receiving sensitivity for highfrequency harmonic signal detection. A receiver with a high receiving sensitivity spanning a wide superharmonic frequency range (3rd to 6th) enables selectable bubble harmonic detection considering the required penetration depth. Here, we develop a new dual-frequency transducer composed of a 2 MHz 1-3 composite transmitter and a polyvinylidene fluoride (PVDF) receiver with a receiving frequency range of 4-12 MHz for adjustable harmonic imaging. The developed transducer was tested for harmonic responses from a microbubble-injected vessel-mimicking tube positioned 45 mm away. Despite the long imaging distance (45 mm), the prototype transducer detected clear harmonic response with the contrast-to-noise ratio of 6-20 dB and the -6 dB axial resolution of 200-350 μm for imaging a 200 um-diameter cellulose tube filled with microbubbles. DA - 2017/// PY - 2017/// DO - 10.1117/12.2258571 VL - 10170 SP - SN - 0277-786X KW - Dual-frequency transducer KW - PVDF transducer KW - P(VDF-TrFE) copolymer KW - Acoustic angiography KW - superharmonic imaging KW - contrast imaging ER - TY - JOUR TI - Compact, Highly Efficient, and Fully Flexible Circularly Polarized Antenna Enabled by Silver Nanowires for Wireless Body-Area Networks AU - Jiang, Zhi Hao AU - Cui, Zheng AU - Yue, Taiwei AU - Zhu, Yong AU - Werner, Douglas H. T2 - IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS AB - A compact and flexible circularly polarized (CP) wearable antenna is introduced for wireless body-area network systems at the 2.4 GHz industrial, scientific, and medical (ISM) band, which is implemented by employing a low-loss composite of polydimethylsiloxane (PDMS) and silver nanowires (AgNWs). The circularly polarized radiation is enabled by placing a planar linearly polarized loop monopole above a finite anisotropic artificial ground plane. By truncating the anisotropic artificial ground plane to contain only 2 by 2 unit cells, an integrated antenna with a compact form factor of 0.41λ 0 × 0.41λ 0 × 0.045λ 0 is obtained, all while possessing an improved angular coverage of CP radiation. A flexible prototype was fabricated and characterized, experimentally achieving S 11 <;- 15 dB, an axial ratio of less than 3 dB, a gain of around 5.2 dBi, and a wide CP angular coverage in the targeted ISM band. Furthermore, this antenna is compared to a conventional CP patch antenna of the same physical size, which is also comprised of the same PDMS and AgNW composite. The results of this comparison reveal that the proposed antenna has much more stable performance under bending and human body loading, as well as a lower specific absorption rate. In all, the demonstrated wearable antenna offers a compact, flexible, and robust solution which makes it a strong candidate for future integration into body-area networks that require efficient off-body communications. DA - 2017/8// PY - 2017/8// DO - 10.1109/tbcas.2017.2671841 VL - 11 IS - 4 SP - 920-932 SN - 1940-9990 KW - Off-body communications KW - polydimethylsiloxane (PDMS) KW - silver nanowires (AgNWs) KW - wearable antenna KW - wireless body-area networks ER - TY - JOUR TI - Tunable Asymmetric Transmission via Lossy Acoustic Metasurfaces AU - Li, Yong AU - Shen, Chen AU - Xie, Yangbo AU - Li, Junfei AU - Wang, Wenqi AU - Cummer, Steven A. AU - Jing, Yun T2 - PHYSICAL REVIEW LETTERS AB - In this study, we show that robust and tunable acoustic asymmetric transmission can be achieved through gradient-index metasurfaces by harnessing judiciously tailored losses. We theoretically prove that the asymmetric wave behavior stems from loss-induced suppression of high order diffraction. We further experimentally demonstrate this novel phenomenon. Our findings could provide new routes to broaden applications for lossy acoustic metamaterials and metasurfaces. DA - 2017/7/18/ PY - 2017/7/18/ DO - 10.1103/physrevlett.119.035501 VL - 119 IS - 3 SP - SN - 1079-7114 ER - TY - JOUR TI - Three-dimensional colloidal interference lithography AU - Nagai, Hironori AU - Poteet, Austen AU - Zhang, Xu A AU - Chang, Chih-Hao T2 - Nanotechnology AB - Light interactions with colloidal particles can generate a variety of complex three-dimensional (3D) intensity patterns, which can be utilized for nanolithography. The study of particle-light interactions can add more types of intensity patterns by manipulating key factors. Here we investigate a novel 3D nanolithography technique using colloidal particles under two-beam coherent illuminations. The fabricated 3D nanostructures are hollow, nested within periodic structures, and possess multiple chamber geometry. The effects of incident angles and particle size on the fabricated nanostructures were examined. The relative phase shift between particle position and interference pattern is identified as another significant parameter influencing the resultant nanostructures. A numerical model has been developed to show the evolution of nanostructure geometry with phase shifts, and experimental studies confirm the simulation results. Through the introduction of single colloidal particles, the fabrication capability of Lloyd's mirror interference can now be extended to fabrication of 3D nanostructure with complex shell geometry. The fabricated hollow nanostructures with grating background could find potential applications in the area of photonics, drug delivery, and nanofluidics. DA - 2017/2/23/ PY - 2017/2/23/ DO - 10.1088/1361-6528/aa5e3f VL - 28 IS - 12 SP - 125302 J2 - Nanotechnology OP - SN - 0957-4484 1361-6528 UR - http://dx.doi.org/10.1088/1361-6528/aa5e3f DB - Crossref KW - nanolithography KW - three-dimensional nanostructures KW - colloids KW - self-assembly KW - interference lithography ER - TY - JOUR TI - Surprising Effects upon Inserting Benzene Units into a Quaterthiophene-Based D-A Polymer-Improving Non-Fullerene Organic Solar Cells via Donor Polymer Design AU - Chen, Shangshang AU - Yao, Huatong AU - Li, Zhengke AU - Awartani, Omar M. AU - Liu, Yuhang AU - Wang, Zheng AU - Yang, Guofang AU - Zhang, Jianquan AU - Ade, Harald AU - Yan, He T2 - ADVANCED ENERGY MATERIALS AB - Benzene units are inserted into the backbone of a quaterthiophene-based polymer named PffBT4T, and the resulting polymer, PffBT4T-B, exhibits remarkably tight alkyl chain interdigitation, which can expel the ITIC-Th molecules from the polymer domains thus forming more pure and crystalline ITIC-Th domains. As a result, PffBT4T-B-based non-fullerene organic solar cells achieve a high power conversion efficiency of 9.4%. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2017/6/21/ PY - 2017/6/21/ DO - 10.1002/aenm.201602304 VL - 7 IS - 12 SP - SN - 1614-6840 KW - alkyl chain interdigitation KW - donor polymer design KW - organic solar cells KW - small-molecular acceptor ER - TY - JOUR TI - Large-Area Nanolattice Film with Enhanced Modulus, Hardness, and Energy Dissipation AU - Bagal, Abhijeet AU - Zhang, Xu A. AU - Shahrin, Rahnuma AU - Dandley, Erinn C. AU - Zhao, Junjie AU - Poblete, Felipe R. AU - Oldham, Christopher J. AU - Zhu, Yong AU - Parsons, Gregory N. AU - Bobko, Christopher AU - Chang, Chih-Hao T2 - Scientific Reports AB - We present an engineered nanolattice material with enhanced mechanical properties that can be broadly applied as a thin film over large areas. The nanolattice films consist of ordered, three-dimensional architecture with thin-shell tubular elements, resulting in favorable modulus-density scaling (n ~ 1.1), enhanced energy dissipation, and extremely large material recoverability for strains up to 20% under normal compressive loading. At 95.6% porosity, the nanolattice film has demonstrated modulus of 1.19 GPa and specific energy dissipation of 325.5 kJ/kg, surpassing previously reported values at similar densities. The largest length scale in the reported nanolattice is the 500 nm unit-cell lattice constant, allowing the film to behave more like a continuum material and be visually unobservable. Fabricated using three-dimensional colloidal nanolithography and atomic layer deposition, the process can be scaled for large-area patterning. The proposed nanolattice film can find applications as a robust multifunctional insulating film that can be applied in integrated photonic elements, optoelectronic devices, and microcircuit chips. DA - 2017/8/22/ PY - 2017/8/22/ DO - 10.1038/S41598-017-09521-6 VL - 7 IS - 1 J2 - Sci Rep LA - en OP - SN - 2045-2322 UR - http://dx.doi.org/10.1038/S41598-017-09521-6 DB - Crossref ER - TY - JOUR TI - Dynamic Modeling, Analysis, and Testing of a Variable Buoyancy System for Unmanned Multidomain Vehicles AU - MacLeod, Marc AU - Bryant, Matthew T2 - IEEE JOURNAL OF OCEANIC ENGINEERING AB - This paper presents the system design and dynamic model of an active variable buoyancy system (VBS) actuator with applications to unmanned multidomain vehicles. Unmanned multidomain vehicles have a unique concept of operations that require nontraditional VBS designs. We present a VBS actuator design that focuses on vehicle design objectives of high endurance, stealth, and loitering while underwater. The design consists of an elastic bladder housed within a rigid ballast tank, hydraulic pump, and proportionally controlled vent valve. Ambient surrounding water is the system working fluid and the elastic bladder serves to separate the gas-water interface, eliminating the risk of the compressed gas escaping when venting the water during extreme pitch maneuvers. A nonlinear analytic model of the VBS is derived and used to examine the parameter design space and the effects on water flow rate, actuation force, and energy efficiency. The VBS actuator design is shown to require a smaller, denser energy storage device than a comparable buoyancy system that uses consumable compressed air. A vehicle model is studied that features forward and aft VBS actuators, which enables vehicle pitch control by shifting the center of gravity along the vehicle's longitudinal axis. The coupling between the VBS actuator dynamics and vehicle dynamics is presented and discussed. A proof-of-concept demonstration is presented and compared to the analytical system model. DA - 2017/7// PY - 2017/7// DO - 10.1109/joe.2016.2586802 VL - 42 IS - 3 SP - 511-521 SN - 1558-1691 KW - Actuators KW - marine vehicles KW - multidomain KW - unmanned aerial vehicles KW - variable buoyancy systems ER - TY - JOUR TI - Dual-Frequency Piezoelectric Endoscopic Transducer for Imaging Vascular Invasion in Pancreatic Cancer AU - Lindsey, Brooks D. AU - Kim, Jinwook AU - Dayton, Paul A. AU - Jiang, Xiaoning T2 - IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL AB - Cancers of the pancreas have the poorest prognosis among all cancers, as many tumors are not detected until surgery is no longer a viable option. Surgical viability is typically determined via endoscopic ultrasound imaging. However, many patients who may be eligible for resection are not offered surgery due to diagnostic challenges in determining vascular or lymphatic invasion. In this paper, we describe the development of a dual-frequency piezoelectric transducer for rotational endoscopic imaging designed to transmit at 4 MHz and receive at 20 MHz in order to image microbubble-specific superharmonic signals. Imaging performance is assessed in a tissue-mimicking phantom at depths from 1 cm [contrast-to-tissue ratio (CTR) = 21.6 dB] to 2.5 cm (CTR = 11.4 dB), in ex vivo porcine vessels, and in vivo in a rodent. The prototyped 1.1-mm aperture transducer demonstrates contrast-specific imaging of microbubbles in a 200-μm-diameter tube through the wall of a 1-cm-diameter porcine artery, suggesting such a device may enable direct visualization of small vessels from within the lumen of larger vessels such as the portal vein or superior mesenteric vein. DA - 2017/7// PY - 2017/7// DO - 10.1109/tuffc.2017.2702010 VL - 64 IS - 7 SP - 1078-1086 SN - 1525-8955 KW - Acoustic angiography KW - endoscope KW - high frequency KW - interventional imaging KW - microbubble KW - superharmonic ER - TY - JOUR TI - Announcing the 2016 Measurement Science and Technology Outstanding Paper Awards AU - Foss, John AU - Peters, Kara AU - Yang, Wuqiang T2 - MEASUREMENT SCIENCE AND TECHNOLOGY DA - 2017/7// PY - 2017/7// DO - 10.1088/1361-6501/aa726e VL - 28 IS - 7 SP - SN - 1361-6501 ER - TY - JOUR TI - A Methodology to Synthesize Gearbox and Control Design for Increased Power Production and Blade Root Stress Mitigation in a Small Wind Turbine AU - Nejadkhaki, Hamid Khakpour AU - Lall, Amrita AU - Hall, John F. T2 - JOURNAL OF MECHANICAL DESIGN AB - Large wind turbines typically have variable rotor speed capability that increases power production. However, the cost of this technology is more significant for small turbines, which have the highest cost-per-watt of energy produced. This work presents a low-cost system for applications where cost and reliability are of concern. The configuration utilizes the fixed-speed squirrel cage induction generator. It is combined with a variable ratio gearbox (VRG) that is based on the automated-manual automotive transmission. The design is simple, low cost and implements reliable components. The VRG increases efficiency in lower wind speeds through three discrete rotor speeds. In this study, it is implemented with active blades. The contribution of this work is a methodology that synthesizes the selection of the gearbox ratios with the control design. The design objectives increase the power production while mitigating the blade stress. Top-down dynamic programming reduces the computational expense of evaluating the performance of multiple gearbox combinations. The procedure is customizable to the wind conditions at an installation site. A case study is presented to demonstrate the ability of the strategy. It employs a 300 kW wind turbine drivetrain model that simulates power production. Two sets of wind data representing low and high wind speed installation sites were used as the input. The results suggest a VRG can improve energy production by up to 10% when the system operates below the rated wind speed. This is also accompanied by a slight increase in the blade-root stress. When operating above the rated speed, the stress decreases through the optimal selection of gear combinations. DA - 2017/8// PY - 2017/8// DO - 10.1115/1.4036998 VL - 139 IS - 8 SP - SN - 1050-0472 KW - variable ratio gearbox design KW - design customization KW - multidisciplinary optimization KW - design automation KW - blade stress analysis KW - wind turbine design ER - TY - JOUR TI - Transit Time Difference Flowmeter for Intravenous Flow Rate Measurement Using 1-3 Piezoelectric Composite Transducers AU - Kim, Taeyang AU - Kim, Jinwook AU - Jiang, Xiaoning T2 - IEEE SENSORS JOURNAL AB - The flow rate of injected medication implemented by intravenous (IV) systems must be accurately monitored and meticulously controlled to prevent medical accidents. In this paper, an ultrasonic flowmeter (UF) with 1-3 piezoelectric composite transducers was designed, fabricated, and tested on a variety of flow rates of mimic medical injections. The transducer wedge for the angled beam propagation and an acoustic impedance matching layer were included in the design for transmission enhancement. To ensure an accurate measurement of flow rate, the effect of the flow distributions inside the IV tube was taken into account. The developed UF exhibited the capability of detecting low flow rates (<;0.005 m/s), with 1%-2% discrepancy compared with the reference rate of infusion. DA - 2017/9/1/ PY - 2017/9/1/ DO - 10.1109/jsen.2017.2727340 VL - 17 IS - 17 SP - 5741-5748 SN - 1558-1748 KW - Intravenous (IV) flow rate KW - transit time difference KW - ultrasonic flowmeter KW - 1-3 composite transducer ER - TY - JOUR TI - Strong polymer molecular weight-dependent material interactions: impact on the formation of the polymer/fullerene bulk heterojunction morphology AU - Kim, Joo-Hyun AU - Gadisa, Abay AU - Schaefer, Charley AU - Yao, Huifeng AU - Gautam, Bhoj R. AU - Balar, Nrup AU - Ghasemi, Masoud AU - Constantinou, Iordania AU - So, Franky AU - Brendan T. O'Connor, AU - Gundogdu, Kenan AU - Hou, Jianhui AU - Ade, Harald T2 - JOURNAL OF MATERIALS CHEMISTRY A AB - The morphological evolution is initiated by L–L or L–S phase separation (left) and further developed by molecular mobility, governed by polymer–solvent interactions which determine the final domain size of the BHJ layer (right). DA - 2017/7/7/ PY - 2017/7/7/ DO - 10.1039/c7ta03052e VL - 5 IS - 25 SP - 13176-13188 SN - 2050-7496 ER - TY - CONF TI - Significance of randomness in establishing hotspots in crystals AU - Chen, M. AU - Steer, M. B. AU - Zikry, Mohammed AB - Microwave scattering in random mediums is known to result in localized energy concentrations known as hotspots. However, the mechanics behind this effect are not well understood. Abstractions are needed to manage the complexity required to develop understanding through simulation and lead to the establishment of the parameters for a microwave system to neutralize energetic materials. Here, two random contributions of rotation and translation are separately simulated. It is observed that the individual effects both contribute to localization, and the combined effect is greater than the sum of the individuals. C2 - 2017/// C3 - Southeastcon 2017 DA - 2017/// DO - 10.1109/secon.2017.7925394 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85019680119&partnerID=MN8TOARS ER - TY - JOUR TI - Precise Manipulation of Multilength Scale Morphology and Its Influence on Eco-Friendly Printed All-Polymer Solar Cells AU - Ye, Long AU - Xiong, Yuan AU - Li, Sunsun AU - Ghasemi, Masoud AU - Balar, Nrup AU - Turner, Johnathan AU - Gadisa, Abay AU - Hou, Jianhui AU - Brendan T. O'Connor, AU - Ade, Harald T2 - ADVANCED FUNCTIONAL MATERIALS AB - Significant efforts have lead to demonstrations of nonfullerene solar cells (NFSCs) with record power conversion efficiency up to ≈13% for polymer:small molecule blends and ≈9% for all‐polymer blends. However, the control of morphology in NFSCs based on polymer blends is very challenging and a key obstacle to pushing this technology to eventual commercialization. The relations between phases at various length scales and photovoltaic parameters of all‐polymer bulk‐heterojunctions remain poorly understood and seldom explored. Here, precise control over a multilength scale morphology and photovoltaic performance are demonstrated by simply altering the concentration of a green solvent additive used in blade‐coated films. Resonant soft X‐ray scattering is used to elucidate the multiphasic morphology of these printed all‐polymeric films and complements with the use of grazing incidence wide‐angle X‐ray scattering and in situ spectroscopic ellipsometry characterizations to correlate the morphology parameters at different length scales to the device performance metrics. Benefiting from the highest relative volume fraction of small domains, additive‐free solar cells show the best device performance, strengthening the advantage of single benign solvent approach. This study also highlights the importance of high volume fraction of smallest domains in printed NFSCs and organic solar cells in general. DA - 2017/9/6/ PY - 2017/9/6/ DO - 10.1002/adfm.201702016 VL - 27 IS - 33 SP - SN - 1616-3028 KW - green solvents KW - multilength morphology KW - nonfullerene solar cells KW - polymer blends KW - solvent additives ER - TY - JOUR TI - Lamb Wave-based BVID Imaging for a Curved Composite Sandwich Panel AU - He, Jiaze AU - Yuan, Fuh-Gwo T2 - 43RD REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION AB - Composite sandwich structures, consisting of a low density core sandwiched between two laminated facesheets, have been widely used in various aerospace structures. A new Lamb wave-based imaging condition, which will be referred to as the inverse incident wave energy (IIWE) imaging criterion, is proposed in this paper to resolve the situations where the incident wave energy weakly penetrates into the damaged area in the upper facesheet region. Current imaging conditions by analyzing wavefield reconstructed from laser Doppler vibrometer (LDV) scanning have been proven to be adequate for imaging damage in layered composite laminates. In this research, those current imaging conditions were applied and compared in the composite foam structures for barely visible impact damage (BVID). A piezoelectric wafer was used to excite Lamb waves into the structure and a LDV was used to scan the potential damaged areas in the upper facesheet of the panel. A BVID site in a curved composite sandwich foam aileron was inspected using various wavefield analysis methods and the damage images were compared with C-scan images. A few imaging conditions that are effective for this BVID site are identified when the incident waves have difficulties penetrating into the damaged region. DA - 2017/// PY - 2017/// DO - 10.1063/1.4974606 VL - 1806 SP - SN - 0094-243X ER - TY - JOUR TI - Intravascular forward-looking ultrasound transducers for microbubble-mediated sonothrombolysis AU - Kim, Jinwook AU - Lindsey, Brooks D. AU - Chang, Wei-Yi AU - Dai, Xuming AU - Stavas, Joseph M. AU - Dayton, Paul A. AU - Jiang, Xiaoning T2 - SCIENTIFIC REPORTS AB - Abstract Effective removal or dissolution of large blood clots remains a challenge in clinical treatment of acute thrombo-occlusive diseases. Here we report the development of an intravascular microbubble-mediated sonothrombolysis device for improving thrombolytic rate and thus minimizing the required dose of thrombolytic drugs. We hypothesize that a sub-megahertz, forward-looking ultrasound transducer with an integrated microbubble injection tube is more advantageous for efficient thrombolysis by enhancing cavitation-induced microstreaming than the conventional high-frequency, side-looking, catheter-mounted transducers. We developed custom miniaturized transducers and demonstrated that these transducers are able to generate sufficient pressure to induce cavitation of lipid-shelled microbubble contrast agents. Our technology demonstrates a thrombolysis rate of 0.7 ± 0.15 percent mass loss/min in vitro without any use of thrombolytic drugs. DA - 2017/6/14/ PY - 2017/6/14/ DO - 10.1038/s41598-017-03492-4 VL - 7 SP - SN - 2045-2322 ER - TY - JOUR TI - Increasing the operational capability of a horizontal axis wind turbine by its integration with a vertical axis wind turbine AU - Govind, Bala T2 - APPLIED ENERGY AB - A major difficulty encountered by a horizontal axis wind turbine is the limit of aerodynamic torque that it can withstand at high wind speeds. A novel strategy is proposed to improve the operational capability of a prototype scale system by increasing its rated wind speed for power generation. This is achieved by integrating its drivetrain with that of a vertical axis wind turbine supported on a common tower. Excess torque is transferred from the horizontal axis rotor to the vertical axis rotor’s drivetrain by coupling them using a continuously variable transmission. In this article, firstly, the concepts of motion transfer that facilitate this combined operation are discussed. A combination of a 12-kW horizontal axis rotor and a 10-kW vertical axis wind turbine is studied to estimate the increased benefit of increments in rated wind speed. Performance of this hybrid system is predicted at potential wind sites and is shown to exceed the standalone mechanical power output of both subsystems under different wind regimes. The critical criterion of the system’s aerodynamic feasibility is then investigated. Turbulence modelling is performed for a configuration which involves a combination of the NREL Phase VI rotor and a NACA 0021 profiled vertical axis H-rotor. A 3-D simulation, using a validated k-ω (Shear Stress Transport) computational fluid dynamics model helps confirm the ability of both turbines to operate aerodynamically independent of each other. Further, by this methodology, a safe clearance between the two rotors is pre-determined. Analysis of turbulent flow scenarios reveals the characteristic effects of aerodynamic torque ripple experienced by the vertical axis wind turbine and its impact on combined power output. Parameters outlined in this article will be of assistance in the practical implementation of the integrated axes wind turbine. DA - 2017/8/1/ PY - 2017/8/1/ DO - 10.1016/j.apenergy.2017.04.070 VL - 199 SP - 479-494 SN - 1872-9118 KW - Horizontal axis wind turbine KW - Vertical axis wind turbine KW - Hybrid wind turbine design KW - Motion transfer KW - Computational fluid dynamics KW - Turbulence modelling ER - TY - JOUR TI - High temperature transducer using aluminum nitride single crystal for laser ultrasound detection AU - Kim, Taeyang AU - Kim, Jinwook AU - Jiang, Xiaoning T2 - NONDESTRUCTIVE CHARACTERIZATION AND MONITORING OF ADVANCED MATERIALS, AEROSPACE, AND CIVIL INFRASTRUCTURE 2017 AB - In this work, a new ultrasound nondestructive testing (NDT) method based on laser-generated Lamb wave detection was proposed for high temperature (HT) NDT. Lamb waves were introduced to a stainless steel plate by the Nd:YAG pulsed laser at one point and detected by aluminum nitride (AlN) transducer at a distant position. The fundamental symmetric (S0) and antisymmetric (A0) mode Lamb waves were successfully propagated in the thin stainless steel plate. The time-of- flight (TOF) of the S0 and A0 mode waves proportionally increased with the distance (D) between the laser source and the sensor, and almost no attenuation of the amplitude was observed. For the HT NDT experiment, AlN single crystal was adopted as the ultrasonic sensor material due to its high thermal resistance of the dielectric and piezoelectric constants at the elevated temperature up to 800 °C. The combination of non-contact, portable laser source as a Lamb wave generator and temperature-robust NDT sensor made of AIN has shown its great capability to detect the Lamb waves at elevated temperatures. DA - 2017/// PY - 2017/// DO - 10.1117/12.2259975 VL - 10169 SP - SN - 0277-786X KW - Pulsed Nd: YAG laser KW - Lamb wave KW - AlN KW - high temperature NDT ER - TY - JOUR TI - Bi-directional ultrasonic wave coupling to FBGs in continuously bonded optical fiber sensing AU - Wee, Junghyun AU - Hackney, Drew AU - Bradford, Philip AU - Peters, Kara T2 - APPLIED OPTICS AB - Fiber Bragg grating (FBG) sensors are typically spot-bonded onto the surface of a structure to detect ultrasonic waves in laboratory demonstrations. However, to protect the rest of the optical fiber from any environmental damage during real applications, bonding the entire length of fiber, called continuous bonding, is commonly done. In this paper, we investigate the impact of continuously bonding FBGs on the measured Lamb wave signal. In theory, the ultrasonic wave signal can bi-directionally transfer between the optical fiber and the plate at any adhered location, which could potentially produce output signal distortion for the continuous bonding case. Therefore, an experiment is performed to investigate the plate-to-fiber and fiber-to-plate signal transfer, from which the signal coupling coefficient of each case is theoretically estimated based on the experimental data. We demonstrate that the two coupling coefficients are comparable, with the plate-to-fiber case approximately 19% larger than the fiber-to-plate case. Finally, the signal waveform and arrival time of the output FBG responses are compared between the continuous and spot bonding cases. The results indicate that the resulting Lamb wave signal output is only that directly detected at the FBG location; however, a slight difference in signal waveform is observed between the two bonding configurations. This paper demonstrates the practicality of using continuously bonded FBGs for ultrasonic wave detection in structural health monitoring (SHM) applications. DA - 2017/9/1/ PY - 2017/9/1/ DO - 10.1364/ao.56.007262 VL - 56 IS - 25 SP - 7262-7268 SN - 2155-3165 ER - TY - JOUR TI - Analysis of a Novel Technique for Temperature Rise Abatement in Liquid Piston Compressors-External Gas Injection AU - Bhaskaran, Hari Subramaniam AU - Ro, Paul AU - Park, Joong-Kyoo AU - Ramakrishnan, Kishore Ranganath T2 - JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS AB - This paper analyses a novel heat transfer enhancement technique that can be used in compressors to limit the temperature rise during compression. This technique is based on the injection of external high-pressure gas into the chamber during the compression process. The impact of different factors on the effectiveness of this technique has been studied using experimental and computational methods. In the first set of trials, the location and angle of injection of the external air was varied. It was observed that the heat transfer coefficient governing the heat transfer rate from the chamber varied greatly with change in location and angle of injection. In the second set of experiments, the source pressure of the injected gas was varied from 100.66 kPa to 551.58 kPa. It was observed that the temperature rise of air in the chamber was reduced with an increase in source pressure. Additionally, the increase in chamber pressure was steeper in the higher source pressure cases. In the third set of experiments, the injection profile of the injected gas was varied. This parameter did not greatly impact the effectiveness of external gas injection. In the last set of experiments, the time of initiation of injection was varied. Earlier injection had a positive impact on reducing the temperature rise in the chamber. However, the pressure in the chamber was seen to increase more rapidly in the runs with early injection. Considering that these factors could have a positive/negative impact on the temperature and pressure in the chamber (work required for compression), it may be required to optimize the injection of external high-pressure gas depending on the application. DA - 2017/6// PY - 2017/6// DO - 10.1115/1.4035969 VL - 9 IS - 2 SP - SN - 1948-5093 ER - TY - JOUR TI - A review on mechanics and mechanical properties of 2D materials-Graphene and beyond AU - Akinwande, Deji AU - Brennan, Christopher J. AU - Bunch, J. Scott AU - Egberts, Philip AU - Felts, Jonathan R. AU - Gao, Huajian AU - Huang, Rui AU - Kim, Joon-Seok AU - Li, Teng AU - Li, Yao AU - Liechti, Kenneth M. AU - Lu, Nanshu AU - Park, Harold S. AU - Reed, Evan J. AU - Wang, Peng AU - Yakobson, Boris I. AU - Zhang, Teng AU - Zhang, Yong-Wei AU - Zhou, Yao AU - Zhu, Yong T2 - EXTREME MECHANICS LETTERS AB - Since the first successful synthesis of graphene just over a decade ago, a variety of two-dimensional (2D) materials (e.g., transition metal-dichalcogenides, hexagonal boron-nitride, etc.) have been discovered. Among the many unique and attractive properties of 2D materials, mechanical properties play important roles in manufacturing, integration and performance for their potential applications. Mechanics is indispensable in the study of mechanical properties, both experimentally and theoretically. The coupling between the mechanical and other physical properties (thermal, electronic, optical) is also of great interest in exploring novel applications, where mechanics has to be combined with condensed matter physics to establish a scalable theoretical framework. Moreover, mechanical interactions between 2D materials and various substrate materials are essential for integrated device applications of 2D materials, for which the mechanics of interfaces (adhesion and friction) has to be developed for the 2D materials. Here we review recent theoretical and experimental works related to mechanics and mechanical properties of 2D materials. While graphene is the most studied 2D material to date, we expect continual growth of interest in the mechanics of other 2D materials beyond graphene. DA - 2017/5// PY - 2017/5// DO - 10.1016/j.eml.2017.01.008 VL - 13 SP - 42-77 SN - 2352-4316 ER - TY - JOUR TI - Thermoelectric transport in hybrid materials incorporating metallic nanowires in polymer matrix AU - Liu, Bin AU - Lu, Tingyu AU - Wang, Biao AU - Liu, Jun AU - Nakayama, Tsuneyoshi AU - Zhou, Jun AU - Li, Baowen T2 - APPLIED PHYSICS LETTERS AB - We propose a type of thermoelectric materials incorporating metallic nanowires in insulating polymers. It is shown that the hybridization of poor thermoelectric materials such as metal and polymer can achieve high performance of thermoelectricity. The electrical conductivity of such hybrid materials is controllable by the volume fraction of metallic nanowires which is above a percolation critical value. Meanwhile, the Seebeck coefficient shows a weak dependence on the volume fraction. Low thermal conductivities required for achieving the high figure of merit can be fulfilled from both the low thermal conductivity of polymer and the interfacial thermal resistance between nanowires and polymer. In this regard, we propose the concept “electron-percolation thermal-insulator,” providing a guide to design efficient hybrid thermoelectric materials. DA - 2017/3/13/ PY - 2017/3/13/ DO - 10.1063/1.4978602 VL - 110 IS - 11 SP - SN - 1077-3118 UR - http://dx.doi.org/10.1063/1.4978602 ER - TY - JOUR TI - Thermal buckling and post-buckling analysis of functionally graded beams based on a general higher-order shear deformation theory AU - She, Gui-Lin AU - Yuan, Fuh-Gwo AU - Ren, Yi-Ru T2 - APPLIED MATHEMATICAL MODELLING AB - In the present work, attention is focused on the prediction of thermal buckling and post-buckling behaviors of functionally graded materials (FGM) beams based on Euler–Bernoulli, Timoshenko and various higher-order shear deformation beam theories. Two ends of the beam are assumed to be clamped and in-plane boundary conditions are immovable. The beam is subjected to uniform temperature rise and temperature dependency of the constituents is also taken into account. The governing equations are developed relative to neutral plane and mid-plane of the beam. A two-step perturbation method is employed to determine the critical buckling loads and post-buckling equilibrium paths. New results of thermal buckling and post-buckling analysis of the beams are presented and discussed in details, the numerical analysis shows that, for the case of uniform temperature rise loading, the post-buckling equilibrium path for FGM beam with two clamped ends is also of the bifurcation type for any arbitrary value of the power law index and any various displacement fields. DA - 2017/7// PY - 2017/7// DO - 10.1016/j.apm.2017.03.014 VL - 47 SP - 340-357 SN - 1872-8480 KW - Functionally graded beams KW - Buckling KW - Post-buckling KW - A two-step perturbation method ER - TY - JOUR TI - Preparation, characterization and in vitro response of bioactive coatings on polyether ether ketone AU - Durham, John W., III AU - Allen, Matthew J. AU - Rabiei, Afsaneh T2 - JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS AB - Polyether ether ketone (PEEK) is a highly heat-resistant thermoplastic with excellent strength and elastic modulus similar to human bone, making it an attractive material for orthopedic implants. However, the hydrophobic surface of PEEK implants induces fibrous encapsulation which is unfavorable for stable implant anchorage. In this study, PEEK was coated via ion-beam-assisted deposition (IBAD) using a two-layer design of yttria-stabilized zirconia (YSZ) as a heat-protection layer, and hydroxyapatite (HA) as a top layer to improve osseointegration. Microstructural analysis of the coatings showed a dense, uniform columnar grain structure in the YSZ layer and no delamination from the substrate. The HA layer was found to be amorphous and free of porosities in its as-deposited state. Subsequent heat treatment via microwave energy followed by autoclaving crystallized the HA layer, confirmed by SEM and XRD analysis. An in vitro study using MC3T3 preosteoblast cells showed improved bioactivity in heat-treated sample groups. Cell proliferation, differentiation, and mineralization were analyzed by MTT assay and DNA content, osteocalcin expression, and Alizarin Red S (AR-S) content, respectively. Initial cell growth was increased, and osteogenic maturation and mineralization were accelerated most on coatings that underwent a combined microwave and autoclave heat treatment process as compared to uncoated PEEK and amorphous HA surfaces. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 560–567, 2017. DA - 2017/4// PY - 2017/4// DO - 10.1002/jbm.b.33578 VL - 105 IS - 3 SP - 560-567 SN - 1552-4981 KW - bioactive coatings KW - hydroxyapatite KW - PEEK KW - physical vapor deposition KW - crystallinity ER - TY - JOUR TI - Microstructural characterization of trabecular bone using ultrasonic backscattering and diffusion parameters AU - Du, Hualong AU - Mohanty, Kaustav AU - Mullera, Marie T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA AB - Finite differences time domain methods were utilized to simulate ultrasound propagation and scattering in anisotropic trabecular bone structures obtained from high resolution Computed Tomography (CT). The backscattered signals were collected and the incoherent contribution was extracted. The diffusion constant was calculated for propagations along and across the main direction of anisotropy, and was used to characterize the anisotropy of the trabecular microstructures. In anisotropic structures, the diffusion constant was significantly different in both directions, and the anisotropy of the diffusion constant was strongly correlated to the structural anisotropy measured on the CT images. These results indicate that metrics based on diffusion can be used to quantify the anisotropy of complex structures such as trabecular bone. DA - 2017/5// PY - 2017/5// DO - 10.1121/1.4982824 VL - 141 IS - 5 SP - EL445-EL451 SN - 1520-8524 ER - TY - JOUR TI - Microstructural Modeling of Intergranular Fracture in Tricrystals With Random Low- and High-Angle Grain Boundaries AU - Bond, David M. AU - Zikry, Mohammed A. T2 - JOM DA - 2017/5// PY - 2017/5// DO - 10.1007/s11837-017-2291-0 VL - 69 IS - 5 SP - 856-862 SN - 1543-1851 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85014528940&partnerID=MN8TOARS ER - TY - JOUR TI - Lamb-wave-based two-dimensional areal scan damage imaging using reverse-time migration with a normalized zero-lag cross-correlation imaging condition AU - He, Jiaze AU - Yuan, Fuh-Gwo T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - This article presents a two-dimensional, non-contact, areal scanning system to image and quantify multiple sites of damage in isotropic plates using reverse-time migration with a normalized zero-lag cross-correlation imaging condition. The hybrid system composed of a single piezoelectric actuator mounted onto the structure and a laser Doppler vibrometer for two-dimensional scan. The laser Doppler vibrometer scanned a region in the vicinity of the lead zirconate titanate actuator to capture the scattered wavefield introduced by the damage. The proposed damage imaging technique takes into account the amplitude, phase, and all the frequency content of the single-mode Lamb waves propagating in the plate; thus, the size of multiple sites of damage can be imaged without bias, regardless of the damage locations. Damage image quality was used as a metric to compare two-dimensional areal scans and linear scans as well as to compare the proposed method with existing imaging conditions. The experimental results show that the two-dimensional reverse-time migration/normalized zero-lag cross-correlation technique is capable of imaging and quantification of multiple damage sites in an aluminum plate using a single lead zirconate titanate actuator and a nearby, areal laser Doppler vibrometer scan. DA - 2017/7// PY - 2017/7// DO - 10.1177/1475921716674373 VL - 16 IS - 4 SP - 444-457 SN - 1741-3168 KW - Lamb waves KW - reverse-time migration KW - dispersion compensation KW - two-dimensional array KW - laser Doppler vibrometer ER - TY - JOUR TI - Interrogation of a spectral profile division multiplexed FBG sensor network using a modified particle swarm optimization method AU - Guo, Guodong AU - Hackney, Drew AU - Pankow, Mark AU - Peters, Kara T2 - MEASUREMENT SCIENCE AND TECHNOLOGY AB - This paper applies the concept of spectral profile division multiplexing to track each Bragg wavelength shift in a serially multiplexed fiber Bragg grating (FBG) network. Each sensor in the network is uniquely characterized by its own reflected spectrum shape, thus spectral overlapping is allowed in the wavelength domain. In contrast to the previous literature, spectral distortion caused by multiple reflections and spectral shadowing between FBG sensors, that occur in serial topology sensor networks, are considered in the identification algorithm. To detect the Bragg wavelength shift of each FBG, a nonlinear optimization function based on the output spectrum is constructed and a modified dynamic multi-swarm particle swarm optimizer is employed. The multiplexing approach is experimentally demonstrated on data from multiplexed sensor networks with up to four sensors. The wavelength prediction results show that the method can efficiently interrogate the multiplexed network in these overlapped situations. Specifically, the maximum error in a fully overlapped situation in the specific four sensor network demonstrated here was only 110 pm. A more general analysis of the prediction error and guidelines to optimize the sensor network are the subject of future work. DA - 2017/5// PY - 2017/5// DO - 10.1088/1361-6501/aa637f VL - 28 IS - 5 SP - SN - 1361-6501 KW - fiber Bragg grating sensor KW - sensor multiplexing KW - particle swarm optimizer ER - TY - JOUR TI - Improved Performance of All-Polymer Solar Cells Enabled by Naphthodiperylenetetraimide-Based Polymer Acceptor AU - Guo, Yikun AU - Li, Yunke AU - Awartani, Omar AU - Han, Han AU - Zhao, Jingbo AU - Ade, Harald AU - Yan, He AU - Zhao, Dahui T2 - ADVANCED MATERIALS AB - A new polymer acceptor, naphthodiperylenetetraimide-vinylene (NDP-V), featuring a backbone of altenating naphthodiperylenetetraimide and vinylene units is designed and applied in all-polymer solar cells (all-PSCs). With this polymer acceptor, a new record power-conversion efficiencies (PCE) of 8.59% has been achieved for all-PSCs. The design principle of NDP-V is to reduce the conformational disorder in the backbone of a previously developed high-performance acceptor, PDI-V, a perylenediimide-vinylene polymer. The chemical modifications result in favorable changes to the molecular packing behaviors of the acceptor and improved morphology of the donor-acceptor (PTB7-Th:NDP-V) blend, which is evidenced by the enhanced hole and electron transport abilities of the active layer. Moreover, the stronger absorption of NDP-V in the shorter-wavelength range offers a better complement to the donor. All these factors contribute to a short-circuit current density (J sc ) of 17.07 mA cm-2 . With a fill factor (FF) of 0.67, an average PCE of 8.48% is obtained, representing the highest value thus far reported for all-PSCs. DA - 2017/7/12/ PY - 2017/7/12/ DO - 10.1002/adma.201700309 VL - 29 IS - 26 SP - SN - 1521-4095 KW - all-polymer solar cells KW - polymeric acceptors KW - power conversion efficiency ER - TY - JOUR TI - High-Efficiency Nonfullerene Organic Solar Cells: Critical Factors that Affect Complex Multi-Length Scale Morphology and Device Performance AU - Ye, Long AU - Zhao, Wenchao AU - Li, Sunsun AU - Mukherjee, Subhrangsu AU - Carpenter, Joshua H. AU - Awartani, Omar AU - Jiao, Xuechen AU - Hou, Jianhui AU - Ade, Harald T2 - ADVANCED ENERGY MATERIALS AB - Organic solar cells (OSCs) made of donor/acceptor bulk‐heterojunction active layers have been of widespread interest in converting sunlight to electricity. Characterizing of the complex morphology at multiple length scales of polymer:nonfullerene small molecular acceptor (SMA) systems remains largely unexplored. Through detailed characterizations (hard/soft X‐ray scattering) of the record‐efficiency polymer:SMA system with a close analog, quantitative morphological parameters are related to the device performance parameters and fundamental morphology–performance relationships that explain why additive use and thermal annealing are needed for optimized performance are established. A linear correlation between the average purity variations at small length scale (≈10 nm) and photovoltaic device characteristics across all processing protocols is observed in ≈12%‐efficiency polymer:SMA systems. In addition, molecular interactions as reflected by the estimated Flory–Huggins interaction parameters are used to provide context of the room temperature morphology results. Comparison with results from annealed devices suggests that the two SMA systems compared show upper and lower critical solution temperature behavior, respectively. The in‐depth understanding of the complex multilength scale nonfullerene OSC morphology may guide the device optimization and new materials development and indicates that thermodynamic properties of materials systems should be studied in more detail to aid in designing optimized protocols efficiently. DA - 2017/4/5/ PY - 2017/4/5/ DO - 10.1002/aenm.201602000 VL - 7 IS - 7 SP - SN - 1614-6840 ER - TY - JOUR TI - A fully coupled thermo-viscoelastic finite element model for self-folding shape memory polymer sheets AU - Mailen, Russell W. AU - Dickey, Michael D. AU - Genzer, Jan AU - Zikry, Mohammed A. T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - ABSTRACT The thermo‐mechanical response of heat activated shape memory polymers (SMPs) has been investigated using a thermo‐viscoelastic finite element analysis that accounts for external and internal heat sources. SMPs can be thermally stimulated by external heat sources, such as temperature and surface heat flux, or from internal viscous heating. Viscous heating can significantly affect the response of SMP sheets by increasing the temperature during pre‐strain, which accelerates stress relaxation. This stress relaxation results in a slower shrinking rate when the SMP is reheated. Viscous heating also causes an increase in temperatures during unconstrained recovery. The predicted results elucidate how the coupled thermo‐mechanical loading conditions affect folding and unfolding of SMP sheets in response to localized heating in a hinged region. A parametric study of sheet thickness, hinge width, degree of pre‐strain, and hinge surface temperature is also conducted. The validated results can provide guidelines for the design of functional, self‐folding structures. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1207–1219 DA - 2017/8/15/ PY - 2017/8/15/ DO - 10.1002/polb.24372 VL - 55 IS - 16 SP - 1207-1219 SN - 1099-0488 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85019544264&partnerID=MN8TOARS KW - modeling KW - viscoelastic properties KW - stimuli-sensitive polymers KW - viscous heating KW - shape memory ER - TY - JOUR TI - Ultrathin Acoustic Metasurface-Based Schroeder Diffuser AU - Zhu, Yifan AU - Fan, Xudong AU - Liang, Bin AU - Cheng, Jianchun AU - Jing, Yun T2 - PHYSICAL REVIEW X AB - Schroeder diffuser is a classical design, proposed over 40 years ago, for artificially creating optimal and predictable sound diffuse reflection. It has been widely adopted in architectural acoustics and it has also shown substantial potential in noise control, ultrasound imaging, microparticle manipulation, among others. The conventional Schroeder diffuser, however, has a considerable thickness on the order of one wavelength, severely impeding its applications for low frequency sound. In this paper, a new class of ultra-thin and planar Schroeder diffusers are proposed based on the concept of acoustic metasurface. Both numerical and experimental results demonstrate satisfactory sound diffuse reflection produced from the metasurface-based Schroeder diffuser despite it being one order of magnitude thinner than the conventional one. The proposed design not only offer promising building blocks with great potential to profoundly impact architectural acoustics and related fields, but also constitutes a major step towards real-world applications of acoustic metasurfaces. DA - 2017/6/5/ PY - 2017/6/5/ DO - 10.1103/physrevx.7.021034 VL - 7 IS - 2 SP - SN - 2160-3308 ER - TY - JOUR TI - Time-Based Switching Control of Genetic Regulatory Networks: Toward Sequential Drug Intake for Cancer Therapy AU - Oduola, Wasiu Opeyemi AU - Li, Xiangfang AU - Duan, Chang AU - Qian, Lijun AU - Wu, Fen AU - Dougherty, Edward R. T2 - CANCER INFORMATICS AB - As cancer growth and development typically involves multiple genes and pathways, combination therapy has been touted as the standard of care in the treatment of cancer. However, drug toxicity becomes a major concern whenever a patient takes 2 or more drugs simultaneously at the maximum tolerable dosage. A potential solution would be administering the drugs in a sequential or alternating manner rather than concurrently. This study therefore examines the feasibility of such an approach from a switched system control perspective. Particularly, we study how genetic regulatory systems respond to sequential (switched) drug inputs using the time-based switching mechanism. The design of the time-driven drug switching function guarantees the stability of the genetic regulatory system and the repression of the diseased genes. Simulation results using proof-of-concept models and the proliferation and survival pathways with sequential drug inputs show the effectiveness of the proposed approach. DA - 2017/5/10/ PY - 2017/5/10/ DO - 10.1177/1176935117706888 VL - 16 SP - SN - 1176-9351 KW - Genetic regulatory network KW - switched systems KW - drug effect modeling ER - TY - JOUR TI - Real-time estimation of helicopter rotor blade kinematics through measurement of rotation induced acceleration AU - Allred, C. Jeff AU - Churchill, David AU - Buckner, Gregory D. T2 - MECHANICAL SYSTEMS AND SIGNAL PROCESSING AB - This paper presents a novel approach to monitoring rotor blade flap, lead-lag and pitch using an embedded gyroscope and symmetrically mounted MEMS accelerometers. The central hypothesis is that differential accelerometer measurements are proportional only to blade motion; fuselage acceleration and blade bending are inherently compensated for. The inverse kinematic relationships (from blade position to acceleration and angular rate) are derived and simulated to validate this hypothesis. An algorithm to solve the forward kinematic relationships (from sensor measurement to blade position) is developed using these simulation results. This algorithm is experimentally validated using a prototype device. The experimental results justify continued development of this kinematic estimation approach. DA - 2017/7// PY - 2017/7// DO - 10.1016/j.ymssp.2017.01.003 VL - 91 SP - 183-197 SN - 0888-3270 KW - Kinematics KW - Estimation KW - Helicopter KW - Accelerometer KW - Neural network KW - Rotor Blade ER - TY - JOUR TI - Raman spectra of (K, Na)(Nb,Ta)O-3 single crystal AU - Sang, Shijing AU - Yuan, Zhongyuan AU - Zheng, Limei AU - Sun, Enwei AU - Qi, Xudong AU - Zhang, Rui AU - Jiang, Xiaoning AU - Li, Shiyang AU - Du, Juan T2 - JOURNAL OF ALLOYS AND COMPOUNDS AB - The Raman scattering spectra for lead-free piezoelectric single crystal (K,Na)(Nb,Ta)O3 (KNNT) were intensively investigated to explore its crystallographic structure. For the [011]C oriented sample, 12 Raman peaks were identified from the room temperature Raman spectrum. The υ3, υ4 and υ6 modes which should be Raman silent in normal perovskites were observed due to the low symmetry (Pm) of KNNT single crystal. The temperature dependent Raman spectra indicated that the orthorhombic-tetragonal phase transition happened at about 68 °C, and the Curie temperature (TC) is about 225 °C. The merging of 2 υ5 modes at TC was ascribed to the vanishing of polarization. The backscattering polarized Raman spectra of KNNT single crystals with different orientations were analyzed. The Raman modes were identified using polarized selection rules based on group theory. DA - 2017/5/15/ PY - 2017/5/15/ DO - 10.1016/j.jallcom.2016.12.166 VL - 704 SP - 804-808 SN - 1873-4669 KW - Sodium potassium tantalate niobate KW - Lead free KW - Single crystal KW - Raman scattering KW - Temperature dependence KW - Polarization selection rules ER - TY - JOUR TI - Oscillatory coalescence of droplets in an alternating electric field AU - Choi, Suhwan AU - Saveliev, Alexei V. T2 - PHYSICAL REVIEW FLUIDS AB - Experiments show that a pair of droplets in an alternating electric field coalesce through a repeated sequence: dipole-dipole attraction, the formation of liquid bridge, the repulsion of equipotential droplets, the elongation and breakup of the bridge. DA - 2017/6/8/ PY - 2017/6/8/ DO - 10.1103/physrevfluids.2.063603 VL - 2 IS - 6 SP - SN - 2469-990X ER - TY - JOUR TI - Musculoskeletal model-based control interface mimics physiologic hand dynamics during path tracing task AU - Crouch, Dustin L. AU - Huang, He T2 - JOURNAL OF NEURAL ENGINEERING AB - We investigated the feasibility of a novel, customizable, simplified EMG-driven musculoskeletal model for estimating coordinated hand and wrist motions during a real-time path tracing task.A two-degree-of-freedom computational musculoskeletal model was implemented for real-time EMG-driven control of a stick figure hand displayed on a computer screen. After 5-10 minutes of undirected practice, subjects were given three attempts to trace 10 straight paths, one at a time, with the fingertip of the virtual hand. Able-bodied subjects completed the task on two separate test days.Across subjects and test days, there was a significant linear relationship between log-transformed measures of accuracy and speed (Pearson's r = 0.25, p < 0.0001). The amputee subject could coordinate movement between the wrist and MCP joints, but favored metacarpophalangeal joint motion more highly than able-bodied subjects in 8 of 10 trials. For able-bodied subjects, tracing accuracy was lower at the extremes of the model's range of motion, though there was no apparent relationship between tracing accuracy and fingertip location for the amputee. Our result suggests that, unlike able-bodied subjects, the amputee's motor control patterns were not accustomed to the multi-joint dynamics of the wrist and hand, possibly as a result of post-amputation cortical plasticity, disuse, or sensory deficits.To our knowledge, our study is one of very few that have demonstrated the real-time simultaneous control of multi-joint movements, especially wrist and finger movements, using an EMG-driven musculoskeletal model, which differs from the many data-driven algorithms that dominate the literature on EMG-driven prosthesis control. Real-time control was achieved with very little training and simple, quick (~15 s) calibration. Thus, our model is potentially a practical and effective control platform for multifunctional myoelectric prostheses that could restore more life-like hand function for individuals with upper limb amputation. DA - 2017/6// PY - 2017/6// DO - 10.1088/1741-2552/aa61bc VL - 14 IS - 3 SP - SN - 1741-2552 KW - electromyogram KW - prosthesis control KW - musculoskeletal model KW - dynamic simulation KW - amputation ER - TY - JOUR TI - Imaging of local porosity/voids using a fully non-contact air-coupled transducer and laser Doppler vibrometer system AU - Hudson, Tyler B. AU - Hou, Tan-Hung AU - Grimsley, Brian W. AU - Yuan, Fuh-Gwo T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - This study exploits the feasibility of imaging zones of local porosity/voids simulated by introducing microspheres during layup of a unidirectional carbon fiber–reinforced polymer composite panel. A fully non-contact hybrid system primarily composed of an air-coupled transducer and a laser Doppler vibrometer was used for imaging the local porosity/void zones from the guided wave response. To improve image resolution, several preprocessing techniques are performed. The wavefield reconstructed from the laser Doppler vibrometer measurements was first “denoised” using a one-dimensional wavelet transform in the time domain followed by a two-dimensional wavelet transform in the spatial domain. From the total wavefield, the much weaker backscattered waves were separated from the stronger incident wave by frequency–wavenumber domain filtering. In order to further enhance the signal-to-noise ratio and sharpen the image, the attenuation of incident wave propagation to the damage site was compensated through two proposed weight functions. Finally, a zero-lag cross-correlation was performed for imaging the zone where the compensated incident and backscattered waves were in phase. This improved imaging condition, the “denoised” weighted zero-lag cross-correlation, was proposed and tested for defect imaging in the composite panel with eight intentionally introduced zones of high porosity/voids of varying diameters (1.59–6.35 mm) and depths (0.36–1.08 mm). As expected, the sensitivity of the non-contact air-coupled transducer/laser Doppler vibrometer hybrid system was limited by the wavelength of the excitation signal. The system incorporated with the denoised weighted zero-lag cross-correlation imaging condition for guided wave interrogation gave similar image quality in comparison with that by the immersion C-scan. DA - 2017/3// PY - 2017/3// DO - 10.1177/1475921716668843 VL - 16 IS - 2 SP - 164-173 SN - 1741-3168 KW - Non-contact inspection KW - air-coupled transducer KW - laser Doppler vibrometer KW - frequency-wavenumber filtering KW - porosity KW - voids KW - structural health monitoring KW - non-destructive evaluation ER - TY - JOUR TI - Flexoelectric characterization of BaTiO3-0.08Bi(Zn1/2Ti1/2)O-3 AU - Huang, S. J. AU - Kim, T. AU - Hou, D. AU - Cann, D. AU - Jones, J. L. AU - Jiang, X. N. T2 - Applied Physics Letters DA - 2017/// PY - 2017/// VL - 110 IS - 22 ER - TY - JOUR TI - Flexible Inorganic Ferroelectric Thin Films for Nonvolatile Memory Devices AU - Yu, Hyeonggeun AU - Chung, Ching-Chang AU - Shewmon, Nate AU - Ho, Szuheng AU - Carpenter, Joshua H. AU - Larrabee, Ryan AU - Sun, Tianlei AU - Jones, Jacob L. AU - Ade, Harald AU - O'Connor, Brendan T. AU - So, Franky T2 - Advanced Functional Materials AB - Next‐generation wearable electronics call for flexible nonvolatile devices for ubiquitous data storage. Thus far, only organic ferroelectric materials have shown intrinsic flexibility and processability on plastic substrates. Here, it is shown that by controlling the heating rate, ferroelectric hafnia films can be grown on plastic substrates. The resulting highly flexible capacitor with a film thickness of 30 nm yields a remnant polarization of 10 µC cm −2 . Bending tests show that the film ferroelectricity can be retained under a bending radius below 8 mm with up to 1000 bending cycles. The excellent flexibility is due to the extremely thin hafnia film thickness. Using the ferroelectric film as a gate insulator, a low voltage nonvolatile vertical organic transistor is demonstrated on a plastic substrate with an extrapolated date retention time of up to 10 years. DA - 2017/4/12/ PY - 2017/4/12/ DO - 10.1002/ADFM.201700461 VL - 27 IS - 21 SP - 1700461 J2 - Adv. Funct. Mater. LA - en OP - SN - 1616-301X UR - http://dx.doi.org/10.1002/ADFM.201700461 DB - Crossref KW - ferroelectric materials KW - flexible electronics KW - hafnia films KW - low-temperature processes KW - nonvolatile memory ER - TY - JOUR TI - Effect of Hypoeutectic Boron Additions on the Grain Size and Mechanical Properties of Ti-6Al-4V Manufactured with Powder Bed Electron Beam Additive Manufacturing AU - Mahbooba, Zaynab AU - West, Harvey AU - Harrysson, Ola AU - Wojcieszynski, Andrzej AU - Dehoff, Ryan AU - Nandwana, Peeyush AU - Horn, Timothy T2 - JOM AB - In additive manufacturing, microstructural control is feasible via processing parameter alteration. However, the window for parameter variation for certain materials, such as Ti-6Al-4V, is limited, and alternative methods must be employed to customize microstructures. Grain refinement and homogenization in cast titanium alloys has been demonstrated through the addition of hypoeutectic concentrations of boron. This work explores the influence of 0.00 wt.%, 0.25 wt.%, 0.50 wt.%, and 1.0 wt.% boron additions on the microstructure and bulk mechanical properties of Ti-6Al-4V samples fabricated in an Arcam A2 electron beam melting (EBM) system with commercial processing parameters for Ti-6Al-4V. Analyses of EBM fabricated Ti-6Al-4V + B indicate that the addition of 0.25–1.0 wt.% boron progressively refines the grain structure, and it improves hardness and elastic modulus. Despite a reduction in size, the β grain structure remained columnar as a result of directional heat transfer during EBM fabrication. DA - 2017/3// PY - 2017/3// DO - 10.1007/s11837-016-2210-9 VL - 69 IS - 3 SP - 472-478 SN - 1543-1851 ER - TY - JOUR TI - A Predictive Framework for Dislocation-Density Pile-Ups in Crystalline Systems With Coincident Site Lattice and Random Grain Boundaries AU - Bond, David M. AU - Zikry, Mohammed A. T2 - JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME AB - Evolving dislocation-density pile-ups at grain-boundaries (GBs) spanning a wide range of coincident site lattice (CSL) and random GB misorientations in face-centered cubic (fcc) bicrystals and polycrystalline aggregates has been investigated. A dislocation-density GB interaction scheme coupled to a dislocation-density-based crystalline plasticity formulation was used in a nonlinear finite element (FE) framework to understand how different GB orientations and GB-dislocation-density interactions affect local and overall behavior. An effective Burger's vector of residual dislocations was obtained for fcc bicrystals and compared with molecular dynamics (MDs) predictions of static GB energy, as well as dislocation-density transmission at GB interfaces. Dislocation-density pile-ups and accumulations of residual dislocations at GBs and triple junctions (TJs) were analyzed for a polycrystalline copper aggregate with Σ1, Σ3, Σ7, Σ13, and Σ21 CSLs and random high-angle GBs to understand and predict the effects of GB misorientation on pile-up formation and evolution. The predictions indicate that dislocation-density pile-ups occur at GBs with significantly misoriented slip systems and large residual Burger's vectors, such as Σ7, Σ13, and Σ21 CSLs and random high-angle GBs, and this resulted in heterogeneous inelastic deformations across the GB and local stress accumulations. GBs with low misorientations of slip systems had high transmission, no dislocation-density pile-ups, and lower stresses than the high-angle GBs. This investigation provides a fundamental understanding of how different representative GB orientations affect GB behavior, slip transmission, and dislocation-density pile-ups at a relevant microstructural scale. DA - 2017/4// PY - 2017/4// DO - 10.1115/1.4035494 VL - 139 IS - 2 SP - SN - 1528-8889 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85012899751&partnerID=MN8TOARS ER - TY - JOUR TI - Turbulence effects on the autoignition of DME in a turbulent co-flowing jet AU - Echekki, Tarek AU - Ahmed, Samer F. T2 - COMBUSTION AND FLAME AB - Dimethyl ether (DME) autoignition in turbulent co-flowing jets with preheated air is studied using the one-dimensional turbulence (ODT) model. We investigate the effects of molecular and turbulent transport on the autoignition process at different jet Reynolds numbers and two air preheat conditions. Statistics for the cases considered show that the overall effects of turbulence and molecular transport can serve to delay or accelerate autoignition depending upon where ignition starts, the presence of 2-stage or single-stage ignition and the variations in ignition delay times in mixture fraction space. For the higher temperature air preheat cases, the classical view that autoignition is delayed by turbulence is established. For the lower preheat air temperature cases, we show that low-temperature chemistry associated with first-stage ignition can help accelerate the autoignition process and the transition to high-temperature chemistry. This acceleration can reduce the ignition delay time by as much as a factor of 2. Given this work and previous work by the authors based on a different fuel, n-heptane, we find that the ignition delay map based on homogeneous ignition for different mixture fractions can provide a preview of the ignition scenarios for the co-flowing jet configuration regardless of the choice of fuel considered. DA - 2017/4// PY - 2017/4// DO - 10.1016/j.combustflame.2016.12.022 VL - 178 SP - 70-81 SN - 1556-2921 UR - https://doi.org/10.1016/j.combustflame.2016.12.022 KW - Turbulent jet ignition KW - The one-dimensional turbulence model KW - Autoignition KW - DME fuel ER - TY - JOUR TI - Solution-Processed Cu2Se Nanocrystal Films with Bulk-Like Thermoelectric Performance AU - Forster, Jason D. AU - Lynch, Jared J. AU - Coates, Nelson E. AU - Liu, Jun AU - Jang, Hyejin AU - Zaia, Edmond AU - Gordon, Madeleine P. AU - Szybowski, Maxime AU - Sahu, Ayaskanta AU - Cahill, David G. AU - Urban, Jeffrey J. T2 - SCIENTIFIC REPORTS AB - Abstract Thermoelectric power generation can play a key role in a sustainable energy future by converting waste heat from power plants and other industrial processes into usable electrical power. Current thermoelectric devices, however, require energy intensive manufacturing processes such as alloying and spark plasma sintering. Here, we describe the fabrication of a p-type thermoelectric material, copper selenide (Cu 2 Se), utilizing solution-processing and thermal annealing to produce a thin film that achieves a figure of merit, ZT, which is as high as its traditionally processed counterpart, a value of 0.14 at room temperature. This is the first report of a fully solution-processed nanomaterial achieving performance equivalent to its bulk form and represents a general strategy to reduce the energy required to manufacture advanced energy conversion and harvesting materials. DA - 2017/6/5/ PY - 2017/6/5/ DO - 10.1038/s41598-017-02944-1 VL - 7 SP - SN - 2045-2322 UR - http://dx.doi.org/10.1038/s41598-017-02944-1 ER - TY - JOUR TI - Simulating increased Lamb wave detection sensitivity of surface bonded fiber Bragg grating AU - Wee, J. AU - Hackney, D. A. AU - Bradford, P. D. AU - Peters, K. J. T2 - SMART MATERIALS AND STRUCTURES DA - 2017/4// PY - 2017/4// DO - 10.1088/1361-665x/aa646b VL - 26 IS - 4 SP - SN - 1361-665X KW - fiber Bragg gratings KW - Lamb wave detection KW - adhesive bonding ER - TY - JOUR TI - Probabilistic fatigue damage prognosis using surrogate models trained via three-dimensional finite element analysis AU - Leser, Patrick E. AU - Hochhalter, Jacob D. AU - Warner, James E. AU - Newman, John A. AU - Leser, William P. AU - Wawrzynek, Paul A. AU - Yuan, Fuh-Gwo T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - Utilizing inverse uncertainty quantification techniques, structural health monitoring (SHM) can be integrated with damage progression models to form a probabilistic prediction of a structure’s remaining useful life (RUL). However, damage evolution in realistic structures is physically complex. Accurately representing this behavior requires high-fidelity models which are typically computationally prohibitive. In this paper, high-fidelity fatigue crack growth simulation times are reduced by three orders of magnitude using a model based on a set of surrogate models trained via three-dimensional finite element analysis. The developed crack growth modeling approach is experimentally validated using SHM-based damage diagnosis data. A probabilistic prediction of RUL is formed for a metallic, single-edge notch tension specimen with a fatigue crack growing under mixed-mode conditions. DA - 2017/5// PY - 2017/5// DO - 10.1177/1475921716643298 VL - 16 IS - 3 SP - 291-308 SN - 1741-3168 KW - Damage prognosis KW - remaining useful life KW - uncertainty quantification KW - Bayesian inference KW - surrogate modeling KW - machine learning KW - fatigue crack growth KW - finite element analysis ER - TY - JOUR TI - Power-Required Flight Testing of Unmanned Aerial Systems Using Non-Steady-State Flight AU - Soltmann, Lars M. AU - Hall, Charles E., Jr. T2 - JOURNAL OF AIRCRAFT AB - Power-required flight testing has traditionally been done using the classic power independent of weight, velocity independent of weight method. This method is well suited for manned aircraft but has some shortcomings when applied to unmanned systems that are remotely piloted and/or operating on small test ranges. Maximum-likelihood estimation was used to identify the lift and drag models of two test aircraft using data acquired through acceleration and deceleration runs. The calculated power-required data were reduced using the classic technique to remove weight and air density effects. Flight-test data were collected using a Raspberry Pi single-board computer because of its low cost, weight, and good performance. Data points using the classic flight-test method were also collected for comparison against the dynamic method. Because of the small test range used, a third of all points collected using the classic method had to be eliminated because of assumption violations. The flight-test results show good agreement between the deceleration runs and the classic method. The acceleration runs generally had a poorer overall fit and a larger spread due to excessive sensor noise caused by imbalances in the motor/prop combination. Overall, the dynamic power analysis was much easier to perform and required significantly less time and airspace. DA - 2017/5// PY - 2017/5// DO - 10.2514/1.c033982 VL - 54 IS - 3 SP - 1162-1171 SN - 1533-3868 ER - TY - JOUR TI - PARTICLE-FILTER BASED UPSCALING FOR TURBULENT REACTING FLOW SIMULATIONS AU - Srivastava, Shubham AU - Echekki, Tarek T2 - INTERNATIONAL JOURNAL FOR MULTISCALE COMPUTATIONAL ENGINEERING AB - The particle filter is used to couple a coarse-grained (CG) deterministic solution for a reacting flow with a fine-grained (FG) stochastic solution. The proposed method investigates the feasibility of implementing a multiscale approach for turbulent reacting flows based on large-eddy simulation (LES) coupled with a low-dimensional fine-grained stochastic solution for the subfilter scales reaction and transport. In this study, a model for the turbulent transport in the FG solution is implemented using the linear-eddy model (LEM), which combines a deterministic implementation for reaction, diffusion, and large-scale transport with a stochastic implementation for fine-scale transport. The solution for the continuity and momentum (the Burgers' equation) equations are implemented in 1D. The filtered densities obtained through the FG and the CG solutions are combined using the particle filter to obtain an updated density for the coarse solution that combines the effects of heat release (from the FG solution) and flow dynamics (from the CG solution). The results demonstrate that the particle filter may be a viable tool to couple deterministic CG solutions and stochastic FG solutions in reacting flow applications. DA - 2017/// PY - 2017/// DO - 10.1615/intjmultcompeng.2017017084 VL - 15 IS - 1 SP - 1-17 SN - 1940-4352 KW - turbulent reacting flows KW - particle filter KW - large-eddy simulation KW - multiscale modeling ER - TY - JOUR TI - Oxidation-induced failure in semi-crystalline organic thin films AU - Zhao, Bingxiao AU - Zikry, M. A. T2 - INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES AB - Polymer oxidation is a major degradation mechanism in organic solar cells. However, microstructural details of diffusion-reaction processes and oxidation-induced failure in structured semi-crystalline active layers are difficult to be predicted or measured, due to material heterogeneities, such as different material phases, crystallinities, nano-film thickness. Hence, a diffusion-reaction process has been coupled to a crystalline-amorphous material model and fracture algorithm within a nonlinear microstructurally-based finite element (FEM) framework to investigate and predict heterogeneous oxidative degradation and embrittlement failure in semi-crystalline organic thin films due to the interrelated effects of diffusion, reaction, stress accumulations, and crystalline packing order. The edge-on packing oriented film was more susceptible to oxidation than the face-on oriented packing film due to higher local stresses and reaction accumulations that resulted in higher decrease of local toughness and extensive film cracking in the amorphous phase. The coupled effects of mechanical stresses and oxygen diffusion-reaction accelerated degradation mechanisms and resulted in film cracking and delamination occurring at lower nominal strains in comparison with the case without oxidation embrittlement. Degradation was dominated by the reaction process and exposure time, as opposed to the diffusion process due to the nano-sized films. This predictive framework can be used to understand fundamental local oxidative degradation mechanisms and the morphological effects on long term durability of semi-crystalline organic thin films. DA - 2017/3/15/ PY - 2017/3/15/ DO - 10.1016/j.ijsolstr.2017.01.008 VL - 109 SP - 72-83 SN - 1879-2146 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85009488974&partnerID=MN8TOARS KW - Semi-crystalline organic thin films KW - Polymer oxidation KW - Microstructural failure mechanisms KW - Delamination KW - Multi-physics coupling KW - Organic electronics ER - TY - JOUR TI - On the origin and behavior of irradiation-induced c-component dislocation loops in magnesium AU - Xu, Weizong AU - Zhang, Yongfeng AU - Cheng, Guangming AU - Mathaudhu, Suveen N. AU - Scattergood, Ronald O. AU - Koch, Carl C. AU - Lavernia, Enrique J. AU - Zhu, Yuntian T2 - ACTA MATERIALIA AB - C-component dislocation loops are one of the unique defects in hexagonal close-packed (hcp) crystals that promote the accelerated growth and void formation under irradiation. Here, we report in situ observation of c-component dislocation loop formation in Mg under electron irradiation with emphasis on their atomic structures. Aberration-corrected scanning transmission electron microscopy imaging is utilized to reveal four possible types of double-layer loops, which were identified as different types of stacking fault and dislocation core structures. Triple- and quadruple-layer c-component dislocation loops were also observed. The formation mechanisms of the four types of double-layer loops were revealed via molecular dynamics simulations. The experimentally observed formation rate of the single- and double-layer dislocation loops is controlled by their formation energies. Our direct experimental observations in combination with molecular dynamics simulations provide fundamental insight into the mechanisms governing nucleation and growth of the c-component dislocation loops as well as their interactions, which could potentially help with future development of irradiation-resistant materials. DA - 2017/6/1/ PY - 2017/6/1/ DO - 10.1016/j.actamat.2017.04.015 VL - 131 SP - 457-466 SN - 1873-2453 KW - In situ transmission electron microscopy KW - C-component dislocation loop KW - Atomic structure KW - Magnesium KW - Stacking faults ER - TY - JOUR TI - Numerical investigation of the interaction, transport and deposition of multicomponent droplets in a simple mouth-throat model AU - Chen, Xiaole AU - Feng, Yu AU - Zhong, Wenqi AU - Kleinstreuer, Clement T2 - JOURNAL OF AEROSOL SCIENCE AB - A basic analysis of inhaled multicomponent droplet-vapor interaction and subsequent aerosol deposition is very important for the understanding of natural phenomena as well as for health-care related applications. Employing a highly idealized mouth-throat (MT) model as a test bed, the transport and deposition mechanisms of a water-droplet are simulated, considering ethanol, sodium chloride and fluorescein as components. The flow-field equations are solved with a validated transition SST model which can predict the effects of flow rate, relative humidity (RH), and wet vs. dry airway walls on aerosol deposition efficiency (DE). The simulation results indicate that the hygroscopic growth of sodium chloride particles is sensitive to the saturation pressure of water vapor. A high flow rate decreases the RH in the airways as well as the average growth ratios of deposited and escaped droplets; but, still increases the DE. When compared to a dry boundary condition, the wet airway-wall increases the DE up to 4.6% when RH=30% and the flow rate is 60 L/min. It also increases the average growth ratio of deposited droplets notably, i.e., larger than 0.5 for most conditions, while its effect on the average growth ratio of deposited droplets is not apparent. A high inlet RH can significantly enhance the hygroscopic growth of the droplets and DE, especially when it is larger than the RH threshold for the hygroscopic component. Besides, it can elevate the growth ratios of deposited and escaped droplets at the same time, which could be utilized to reduce the deposition of submicron hygroscopic aerosol in the upper airway. DA - 2017/3// PY - 2017/3// DO - 10.1016/j.jaerosci.2016.12.001 VL - 105 SP - 108-127 SN - 1879-1964 KW - Multicomponent droplet inhalation KW - droplet-vapor interaction KW - airway-wall condition KW - hygroscopic growth KW - deposition efficiency ER - TY - JOUR TI - Nonlinear analysis of bending, thermal buckling and post-buckling for functionally graded tubes by using a refined beam theory AU - She, Gui-Lin AU - Yuan, Fuh-Gwo AU - Ren, Yi-Ru T2 - COMPOSITE STRUCTURES AB - Nonlinear bending, thermal buckling and post-buckling analysis for functionally graded materials (FGMs) tubes with two clamped ends by using a refined beam theory are investigated. The theory satisfies the traction-free boundary conditions on the inner and outer surfaces of the tube and also takes into account the transverse shear effects without artificially introducing shear correction factors. The material properties of FGM tubes are assumed to be temperature-dependent and vary in the radial direction. The asymptotic solutions of the FGM tubes under nonlinear bending and thermal post-buckling are solved by using a two-step perturbation method. The analytical solutions of Timoshenko beam and Euler beam are also presented. Detailed parametric studies are performed to investigate effects of inner-to-outer radius ratio, volume fraction as well as shear deformation on nonlinear bending, thermal buckling and post-buckling characteristics of the FGM tubes. DA - 2017/4/1/ PY - 2017/4/1/ DO - 10.1016/j.compstruct.2017.01.013 VL - 165 SP - 74-82 SN - 1879-1085 KW - Functionally graded tubes KW - Refined circular tube model KW - Nonlinear bending KW - Buckling KW - Post-buckling ER - TY - JOUR TI - New Developments in Multibody System Dynamics and Its Applications 2015 AU - Rui, Xiaoting AU - Zhang, Chuanzeng AU - Wang, Shimin AU - Wu, Fen T2 - ADVANCES IN MECHANICAL ENGINEERING DA - 2017/3/16/ PY - 2017/3/16/ DO - 10.1177/1687814017695685 VL - 9 IS - 3 SP - SN - 1687-8140 ER - TY - JOUR TI - Lipid-induced degradation in biocompatible poly(Styrene-Isobutylene-Styrene) (SIBS) thermoplastic elastomer AU - Fittipaldi, Mauro AU - Grace, Landon R. T2 - JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS AB - The thermoplastic elastomer Poly(Styrene-block-Isobutylene-block-Styrene) (SIBS) is highly biocompatible, which has led to its use in several commercially-available implants. However, lipid-induced degradation has been previously identified as a primary cause of failure in long-term SIBS implants subject to mechanical loading. Thus, understanding the mechanisms and extent of lipid-induced damage and the role of styrene-isobutylene ratio and molecular weight is critical to improving longevity of SIBS-based implants in order to fully exploit the biocompatibility advantages. Samples of four different SIBS formulations were fabricated via compression molding, immersed to lipid saturation contents from 5 to 80% by weight, and tested in uniaxial tension, stress relaxation, and dynamic creep modes. Degradation mechanisms were investigated via infrared spectroscopy, chromatography, and microscopy. No evidence of lipid-induced chemical interactions or chain scissoring was observed. However, a decrease in tensile strength, loss of dynamic creep performance and faster relaxation with increasing lipid content is attributed to strong internal straining. The magnitude of these losses is inversely proportional to both molecular weight and styrene content, suggesting that selection of these variables during the design phase should be based not only on the mechanical requirements of the application, but the expected degree of lipid exposure. DA - 2017/4// PY - 2017/4// DO - 10.1016/j.jmbbm.2017.01.031 VL - 68 SP - 80-87 SN - 1878-0180 KW - Biocompatible KW - Lipids KW - Degradation KW - Relaxation KW - Polymer KW - Diffusion ER - TY - JOUR TI - Human and environmental analysis of wearable thermal energy harvesting AU - Myers, Amanda AU - Hodges, Ryan AU - Jur, Jesse S. T2 - ENERGY CONVERSION AND MANAGEMENT AB - In considering wearable energy harvesting, one must recognize the wide array of factors that lead to variations of energy harvesting. The objective of this work is to define analytical methods to study the effect of environmental and human factors on thermal energy generator (TEG) performance in a variety of use case scenarios. A test method for evaluating the performance of a TEG in a wearable form is developed and demonstrated using both in-lab and out-of-lab procedures. The fabrication procedure of an energy harvesting wearable device demonstrates a method of integrating rigid devices into a flexible substrate. The wearable device is used in a human trial which covered a series of activities in different environmental conditions. The results of these trials demonstrate the significant effect of movement, or convection, on thermal energy harvesting. Humidity levels do not have a significant correlation to power; however, wet bulb temperature must be taken into consideration due to the additional cooling effect of evaporation on temperature. The data collected indicates that while dry-bulb temperature does not have the greatest effect on TEG power generation, wet-bulb temperature is indicative of TEG performance. Additionally, user generated movement is the main consideration when designing a wearable device with TEGs as it had the largest effects on power generation. The results of this work quantify how a wearable device will perform throughout daily activities, allowing the definition of an operational scenario of a self-powered wearable device while choosing the most appropriate design for a particular application. This work also provides a foundation for exploring how textiles can enable the design of unique wearable devices. This will lead to further investigation into quantifying the effect that the construction of a textile has on TEG performance as well as on consumer comfort. DA - 2017/7/1/ PY - 2017/7/1/ DO - 10.1016/j.enconman.2017.04.002 VL - 143 SP - 218-226 SN - 1879-2227 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85017181906&partnerID=MN8TOARS KW - Wearable technology KW - Energy harvesting KW - Thermoelectric devices KW - Environmental to human correlations ER - TY - JOUR TI - Exact-memory and memoryless control of linear systems with time-varying input delay using dynamic IQCs AU - Yuan, Chengzhi AU - Wu, Fen T2 - AUTOMATICA AB - Input delay is an important type of actuator nonlinearity in control systems. In this paper, we will address the output-feedback control synthesis problem for linear systems with time-varying input delay under the integral quadratic constraint (IQC) framework. A new exact-memory control scheme is first proposed, which consists of a standard linear output-feedback control law and an internal delay loop. The delay loop is embedded in the controller structure so as to reproduce the input delay behavior of the plant. By using quadratic Lyapunov functions incorporated with dynamic IQC multipliers, the resulting dynamic output-feedback delay control synthesis problem is fully characterized by a set of linear matrix inequalities (LMIs), which are convex on all design variables including the scaling factors associated with the IQC multipliers. Moreover, the corresponding result on memoryless control is also derived for the case when the plant input-delay information is not available for feedback control. An application to network systems has been used to illustrate the effectiveness and usefulness of the proposed approach. DA - 2017/3// PY - 2017/3// DO - 10.1016/j.automatica.2016.11.015 VL - 77 SP - 246-253 SN - 1873-2836 KW - Time-varying input delay KW - Integral quadratic constraints (IQCs) KW - Output-feedback control KW - Linear matrix inequalities (LMIs) ER - TY - JOUR TI - Design and optimization of an OPFC ultrasonic linear phased array transducer AU - Wang, Ziping AU - Luo, Ying AU - Zhao, Guoqi AU - Yuan, Fuh-Gwo T2 - INTERNATIONAL JOURNAL OF MECHANICS AND MATERIALS IN DESIGN DA - 2017/3// PY - 2017/3// DO - 10.1007/s10999-015-9317-y VL - 13 IS - 1 SP - 57-69 SN - 1573-8841 KW - OPFC KW - Ultrasonic phased array KW - Transducer KW - Array optimization KW - Damage detection ER - TY - JOUR TI - Controlling the self-folding of a polymer sheet using a local heater: the effect of the polymer-heater interface AU - Cui, Jianxun AU - Yao, Shanshan AU - Huang, Qijin AU - Adams, John G. M. AU - Zhu, Yong T2 - SOFT MATTER AB - Self-folding of a pre-strained shape memory polymer (SMP) sheet was demonstrated using local joule heating. Folding is caused by shrinkage variation across the thickness of the SMP sheet. The folding direction can be controlled by the interfacial interaction between the heater and the SMP sheet. When the heater is placed on the SMP sheet with no constraint (weak interface), the SMP sheet folds toward the heater. Temperature gradient across the SMP thickness gives rise to the shrinkage variation. By contrast, when the heater is fixed to the SMP sheet (strong interface), the SMP sheet can fold away from the heater. In this case shrinkage variation is dictated by the constraining effect of the heater. In either mode, 180 degrees folding can be achieved. The folding angle can be controlled by varying the heater width and folding time. This method is simple and can be used to fold structures with sharp angles in a sequential manner. A variety of structures were folded as demonstrations, including digital numbers 0–9, a cube, a boat, and a crane. DA - 2017/6/7/ PY - 2017/6/7/ DO - 10.1039/c7sm00568g VL - 13 IS - 21 SP - 3863-3870 SN - 1744-6848 ER - TY - JOUR TI - CHARACTERIZATION OF THE LUNG PARENCHYMA USING ULTRASOUND MULTIPLE SCATTERING AU - Mohanty, Kaustav AU - Blackwell, John AU - Egan, Thomas AU - Muller, Marie T2 - ULTRASOUND IN MEDICINE AND BIOLOGY AB - The purpose of the study described here was to showcase the application of ultrasound to quantitative characterization of the micro-architecture of the lung parenchyma to predict the extent of pulmonary edema. The lung parenchyma is a highly complex and diffusive medium for which ultrasound techniques have remained qualitative. The approach presented here is based on ultrasound multiple scattering and exploits the complexity of ultrasound propagation in the lung structure. The experimental setup consisted of a linear transducer array with an 8-MHz central frequency placed in contact with the lung surface. The diffusion constant D and transport mean free path L* of the lung parenchyma were estimated by separating the incoherent and coherent intensities in the near field and measuring the growth of the incoherent diffusive halo over time. Significant differences were observed between the L* values obtained in healthy and edematous rat lungs in vivo. In the control rat lung, L* was found to be 332 μm (±48.8 μm), whereas in the edematous lung, it was 1040 μm (±90 μm). The reproducibility of the measurements of L* and D was tested in vivo and in phantoms made of melamine sponge with varying air volume fractions. Two-dimensional finite difference time domain numerical simulations were carried out on rabbit lung histology images with varying degrees of lung collapse. Significant correlations were observed between air volume fraction and L* in simulation (r = -0.9542, p < 0.0117) and sponge phantom (r = -0.9932, p < 0.0068) experiments. Ex vivo measurements of a rat lung in which edema was simulated by adding phosphate-buffered saline revealed a linear relationship between the fluid volume fraction and L*. These results illustrate the potential of methods based on ultrasound multiple scattering for the quantitative characterization of the lung parenchyma. DA - 2017/5// PY - 2017/5// DO - 10.1016/j.ultrasmedbio.2017.01.011 VL - 43 IS - 5 SP - 993-1003 SN - 1879-291X KW - Quantitative ultrasound KW - Multiple scattering KW - Lung parenchyma KW - Interstitial syndrome KW - Edema KW - Fibrosis ER - TY - JOUR TI - An equivalent dissipation rate model for capturing history effects in non-premixed flames AU - Kundu, Prithwish AU - Echekki, Tarek AU - Pei, Yuanjiang AU - Som, Sibendu T2 - COMBUSTION AND FLAME AB - The effects of strain rate history on turbulent flames have been studied in the past decades with 1D counter flow diffusion flame (CFDF) configurations subjected to oscillating strain rates. In this work, these unsteady effects are studied for complex hydrocarbon fuel surrogates at engine relevant conditions with unsteady strain rates experienced by flamelets in a typical spray flame. Tabulated combustion models are based on a steady scalar dissipation rate (SDR) assumption and hence cannot capture these unsteady strain effects; even though they can capture the unsteady chemistry. In this work, 1D CFDF with varying strain rates are simulated using two different modeling approaches: steady SDR assumption and unsteady flamelet model. Comparative studies show that the history effects due to unsteady SDR are directly proportional to the temporal gradient of the SDR. A new equivalent SDR model based on the history of a flamelet is proposed. An averaging procedure is constructed such that the most recent histories are given higher weights. This equivalent SDR is then used with the steady SDR assumption in 1D flamelets. Results show a good agreement between tabulated flamelet solution and the unsteady flamelet results. This equivalent SDR concept is further implemented and compared against 3D spray flames (Engine Combustion Network Spray A). Tabulated models based on steady SDR assumption under-predict autoignition and flame lift-off when compared with an unsteady Representative Interactive Flamelet (RIF) model. However, equivalent SDR model coupled with the tabulated model predicted autoignition and flame lift-off very close to those reported by the RIF model. This model is further validated for a range of injection pressures for Spray A flames. The new modeling framework now enables tabulated models with significantly lower computational cost to account for unsteady history effects. DA - 2017/2// PY - 2017/2// DO - 10.1016/j.combustflame.2016.10.001 VL - 176 SP - 202-212 SN - 1556-2921 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84995562566&partnerID=MN8TOARS KW - Flamelet history KW - Engine combustion network KW - Tabulation ER - TY - JOUR TI - An enhanced performance of a horizontal diamagnetic levitation mechanism-based vibration energy harvester for low frequency applications AU - Palagummi, Sri Vikram AU - Yuan, Fuh-Gwo T2 - JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES AB - This article identifies and studies key parameters that characterize a horizontal diamagnetic levitation mechanism–based low frequency vibration energy harvester with the aim of enhancing performance metrics such as efficiency and volume figure of merit. The horizontal diamagnetic levitation mechanism comprises three permanent magnets and two diamagnetic plates. Two of the magnets, lifting magnets, are placed co-axially at a distance such that each attracts a centrally located magnet, floating magnet, to balance its weight. This floating magnet is flanked closely by two diamagnetic plates which stabilize the levitation in the axial direction. The influence of the geometry of the floating magnet, the lifting magnet, and the diamagnetic plate is parametrically studied to quantify their effects on the size, stability of the levitation mechanism, and the resonant frequency of the floating magnet. For vibration energy harvesting using the horizontal diamagnetic levitation mechanism, a coil geometry and eddy current damping are critically discussed. Based on the analysis, an efficient experimental system is setup which showed a softening frequency response with an average system efficiency of 25.8% and a volume figure of merit of 0.23% when excited at a root mean square acceleration of 0.0546 m/s 2 and at a frequency of 1.9 Hz. DA - 2017/3// PY - 2017/3// DO - 10.1177/1045389x16651152 VL - 28 IS - 5 SP - 578-594 SN - 1530-8138 KW - energy harvesting KW - diamagnetic levitation KW - low frequency KW - nonlinear ER - TY - CONF TI - A convenient low order thermal model for heat transfer characteristics of single floored low-rise residential buildings AU - Anand, N. AU - Gould, R. D. AB - A low order thermal model is introduced to determine the thermal characteristics of a Low-Rise Residential (LRR) building and then predict the energy usage by its Heating Ventilation & Air Conditioning (HVAC) system according to future weather conditions. The LRR buildings are treated as a simple lump and the model is derived using the lumped capacitance model for transient heat transfer from bodies. Most contemporary HVAC systems have a thermostat control, which has an offset temperature, and user defined set point temperatures, which defines when the HVAC system will switch on and off. The aim is to predict, with minimal error, the inside air temperature, which is used to determine the switching on and off, of the HVAC system. To validate this lumped capacitance model we have used the EnergyPlus simulation engine, which simulates the thermal behavior of buildings with considerable accuracy. We have predicted using the low order model the inside air temperature of a single family house located in three different climate zones (Detroit, Raleigh & Austin) and different orientations for summer and winter seasons. The prediction error between the model and EnergyPlus is less than 10% for almost all the cases with the exception of Austin in summer. Possible factors responsible for error in prediction are also noted in this work, paving way for future research. C2 - 2017/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2016, vol. 6b DA - 2017/// DO - 10.1115/imece2016-65254 ER - TY - JOUR TI - A Parallel, High-Order Direct Discontinuous Galerkin Methods for the Navier-Stokes Equations on 3D Hybrid Grids AU - Cheng, Jian AU - Liu, Xiaodong AU - Liu, Tiegang AU - Luo, Hong T2 - COMMUNICATIONS IN COMPUTATIONAL PHYSICS AB - Abstract A parallel, high-order direct Discontinuous Galerkin (DDG) method has been developed for solving the three dimensional compressible Navier-Stokes equations on 3D hybrid grids. The most distinguishing and attractive feature of DDG method lies in its simplicity in formulation and efficiency in computational cost. The formulation of the DDG discretization for 3D Navier-Stokes equations is detailed studied and the definition of characteristic length is also carefully examined and evaluated based on 3D hybrid grids. Accuracy studies are performed to numerically verify the order of accuracy using flow problems with analytical solutions. The capability in handling curved boundary geometry is also demonstrated. Furthermore, an SPMD (single program, multiple data) programming paradigm based on MPI is proposed to achieve parallelism. The numerical results obtained indicate that the DDG method can achieve the designed order of accuracy and is able to deliver comparable results as the widely used BR2 scheme, clearly demonstrating that the DDG method provides an attractive alternative for solving the 3D compressible Navier-Stokes equations. DA - 2017/5// PY - 2017/5// DO - 10.4208/cicp.oa-2016-0090 VL - 21 IS - 5 SP - 1231-1257 SN - 1991-7120 KW - Direct discontinuous Galerkin method KW - compressible Navier-Stokes equations KW - hybrid grids ER - TY - JOUR TI - What mechanisms of tau protein transport could be responsible for the inverted tau concentration gradient in degenerating axons? AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. T2 - MATHEMATICAL MEDICINE AND BIOLOGY-A JOURNAL OF THE IMA AB - In tauopathies, such as Alzheimer's disease (AD), microtubule (MT)-associated protein tau detaches from MTs and aggregates, eventually forming insoluble neurofibrillary tangles. In a healthy axon, the tau concentration increases toward the axon terminal, but in a degenerating axon, the tau concentration gradient is inverted and the highest tau concentration is in the soma. In this article, we developed a mathematical model of tau transport in axons. We calibrated and tested the model by using published distributions of tau concentration and tau average velocity in a healthy axon. According to published research, the inverted tau concentration gradient may be one of the reasons leading to AD. We therefore used the model to investigate what modifications in tau transport can lead to the inverted tau concentration gradient. We investigated whether tau detachment from MTs due to tau hyperphosphorylation can cause the inverted tau concentration gradient. We found that the assumption that most tau molecules are detached from MTs does not consistently predict the inverted tau concentration gradient; the predicted tau distribution becomes more uniform if the axon length is increased. We then hypothesized that in degenerating axons some tau remains bound to MTs and participates in the component ‘a’ of slow axonal transport but that the rate of tau reversals from anterograde to retrograde motion increases. We demonstrated that this hypothesis results in a tau distribution where the tau concentration has its maximum value at the axon hillock and its minimum value at the axon terminal, in agreement with what is observed in AD. Our results thus suggest that defects in active transport of tau may be a contributing factor to the onset of neural degeneration. DA - 2017/3// PY - 2017/3// DO - 10.1093/imammb/dqv041 VL - 34 IS - 1 SP - 125-150 SN - 1477-8602 KW - neuron KW - tau protein KW - diffusion KW - motor-driven transport KW - Alzheimer's disease KW - mathematical modelling ER - TY - JOUR TI - Utilization of the bootstrap method for determining confidence intervals of parameters for a model of MAP1B protein transport in axons AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. T2 - JOURNAL OF THEORETICAL BIOLOGY AB - This paper develops a model of axonal transport of MAP1B protein. The problem of determining parameter values for the proposed model utilizing limited available experimental data is addressed. We used a global minimum search algorithm to find parameter values that minimize the discrepancy between model predictions and published experimental results. By analyzing the best fit parameter values it was established that some processes can be dropped from the model without losing accuracy, thus a simplified version of the model was formulated. In particular, our analysis suggests that reversals in MAP1B transport are infrequent and can be neglected. The detachment of anterogradely-biased MAP1B from microtubules (MTs) and the attachment of retrogradely-biased MAP1B to MTs can also be neglected. An analytical solution for the simplified model was obtained. Confidence intervals for the determined parameters were found by bootstrapping model residuals. The resultant analysis heavily constrained the values of some parameters while showing that some could vary without significantly impacting model error. For example, our analysis suggests that, above a certain threshold value, the kinetic constant determining the rate of MAP1B transition from the retrograde pausing state to the off-track state has little impact on model error. On the contrary, the kinetic constant describing MAP1B transition from a pausing to a running state has great impact on model error. DA - 2017/4/21/ PY - 2017/4/21/ DO - 10.1016/j.jtbi.2017.02.017 VL - 419 SP - 350-361 SN - 1095-8541 KW - Neuron KW - Slow axonal transport KW - Parameter determination KW - Resampling residuals KW - Bootstrapping ER - TY - JOUR TI - Turbulence modeling for flows in wall bounded porous media: An analysis based on direct numerical simulations AU - Jin, Y. AU - Kuznetsov, A. V. T2 - PHYSICS OF FLUIDS AB - Various models are available for simulating turbulent flows in porous media. Models based on the eddy viscosity assumption are often adopted to close the Reynolds stress term. In order to validate the assumptions behind such turbulence models, we studied the dynamics of macroscopic momentum and turbulence kinetic energy in porous media flows by utilizing Direct Numerical Simulation (DNS). The generic porous matrix is composed of regularly arranged spheres. The resulting periodic porous medium is bounded by two walls. The DNS analyses with a Lattice Boltzmann method were performed for various values of the applied pressure gradient, pore size to channel width ratio, and porosity. The DNS results were averaged over time and volume to obtain macroscopic results. The results show that the macroscopic shear Reynolds stress in all Representative Elementary Volumes (REVs), independent of their location, is negligibly small, although the mean velocity gradient takes nonzero values near the wall. The turbulence kinetic energy production rate is generally balanced by the dissipation rate in each REV. The DNS results support a zero-equation turbulence model that accounts for the fact that turbulent structures are restricted in size by the pore scale. The DNS results also suggest that the Brinkman term, which expresses the diffusion of momentum, has an important effect near the wall where the gradient of the shear stress is large. Therefore, the Brinkman term should be taken into account in the macroscopic momentum equation as a component of the total drag. A preliminary macroscopic model for calculating turbulent porous media flows has been proposed and compared with our DNS results. DA - 2017/4// PY - 2017/4// DO - 10.1063/1.4979062 VL - 29 IS - 4 SP - SN - 1089-7666 ER - TY - JOUR TI - Tracking control of hybrid systems with state-triggered jumps and stochastic events and its application AU - Yang, Ting AU - Wu, Fen AU - Zhang, Lixian T2 - IET CONTROL THEORY AND APPLICATIONS AB - This study addresses the tracking control problem for a class of hybrid systems with both state-triggered jumps and stochastic events. The outputs of the plant are required to follow exactly the time-varying reference trajectories which are generated by the corresponding hybrid system. Since the jump times of the plant do not coincide with those of the references, the tracking error in terms of Euclidean distance will exhibit ‘peaking phenomena’, and is not suitable for this kind of situation. By invoking a novel definition of the tracking error which is insensitive to state-triggered jumps and stochastic events, sufficient conditions for asymptotic stability are obtained. Exploiting the asymptotic stability criteria and the proposed non-Euclidean measure of the tracking error, the tracking control problem of a simplified flexible single-link robotic arm is successfully solved by the hybrid controller. DA - 2017/4/25/ PY - 2017/4/25/ DO - 10.1049/iet-cta.2016.1086 VL - 11 IS - 7 SP - 1024-1033 SN - 1751-8652 KW - asymptotic stability KW - tracking KW - trajectory control KW - stochastic systems KW - hybrid systems KW - state-triggered jumps KW - stochastic events KW - tracking control problem KW - time-varying reference trajectories KW - Euclidean distance KW - peaking phenomena KW - tracking error KW - asymptotic stability criteria KW - non-Euclidean measure KW - flexible single-link robotic arm KW - hybrid controller ER - TY - JOUR TI - Research on nonlinear bending behaviors of FGM infinite cylindrical shallow shells resting on elastic foundations in thermal environments AU - She, Gui-Lin AU - Yuan, Fuh-Gwo AU - Ren, Yi-Ru T2 - COMPOSITE STRUCTURES AB - This paper pays attention to predicting the nonlinear bending behaviors of functionally graded materials (FGM) infinite cylindrical shallow shells with a two-parameter elastic foundation by using a two-step perturbation method. The shells are subjected to uniform temperature rise and temperature dependency of the constituents is also taken into account. Two ends of the shells are assumed to be clamped or pinned and in-plane boundary conditions are immovable. The governing equations are derived based on physical neutral surface concept and high order shear deformation theory. The explicit expressions between the transverse load and the deflection are obtained by perturbation method. In numerical examples, some comparisons are shown to verify the correctness of the present research and solution method. It can be concluded that FGM cylindrical shallow shells subjected to uniform bending loadings will bring about snap-through buckling and jump changes, and the foundation can enhance the stability of the shells. DA - 2017/6/15/ PY - 2017/6/15/ DO - 10.1016/j.compstruct.2017.03.010 VL - 170 SP - 111-121 SN - 1879-1085 KW - Functionally graded materials KW - Cylindrical shallow shells KW - A two-step perturbation method KW - Snap-through buckling ER - TY - CONF TI - Output feedback control for fuzzy systems subject to actuator saturation based on fuzzy Lyapunov functions AU - Ban, X. J. AU - Liu, Y. AU - Huang, X. L. AU - Wu, F. AB - In this paper, a novel fuzzy gain-scheduling output feedback control method is presented for T-S fuzzy systems subject to actuator saturation. To deal with saturation nonlinearity, the dead-zone function of control input is treated as an additional controller input. With the help of set conclusion condition, the controller can be synthesised based on fuzzy Lyapunov functions to guarantee the exponential stability of the closed-loop system in a larger region and a better L2 gain performance. Moreover, the full block S-procedure, which is widely used in robust control theory, is introduced to relax the synthesis conditions for T-S fuzzy systems to reduce the conservatism caused by quadratic terms in the conditions. Finally, a numerical example is provided to illustrates the effectiveness of the proposed control method. C2 - 2017/// C3 - Proceedings of the ASME 9th Annual Dynamic Systems and Control Conference, 2016, Vol 1 DA - 2017/// DO - 10.1115/dscc2016-9879 ER - TY - JOUR TI - Morphological considerations of organic electronic films for flexible and stretchable devices AU - Brendan T. O'Connor, AU - Awartani, Omar M. AU - Balar, Nrup T2 - MRS BULLETIN DA - 2017/2// PY - 2017/2// DO - 10.1557/mrs.2017.6 VL - 42 IS - 2 SP - 108-114 SN - 1938-1425 KW - electronic material KW - elastic properties KW - fracture KW - morphology KW - polymers ER - TY - JOUR TI - Mechanics of Crystalline Nanowires: An Experimental Perspective AU - Zhu, Yong T2 - APPLIED MECHANICS REVIEWS AB - A wide variety of crystalline nanowires (NWs) with outstanding mechanical properties have recently emerged. Measuring their mechanical properties and understanding their deformation mechanisms are of important relevance to many of their device applications. On the other hand, such crystalline NWs can provide an unprecedented platform for probing mechanics at the nanoscale. While challenging, the field of experimental mechanics of crystalline nanowires has emerged and seen exciting progress in the past decade. This review summarizes recent advances in this field, focusing on major experimental methods using atomic force microscope (AFM) and electron microscopes and key results on mechanics of crystalline nanowires learned from such experimental studies. Advances in several selected topics are discussed including elasticity, fracture, plasticity, and anelasticity. Finally, this review surveys some applications of crystalline nanowires such as flexible and stretchable electronics, nanocomposites, nanoelectromechanical systems (NEMS), energy harvesting and storage, and strain engineering, where mechanics plays a key role. DA - 2017/1// PY - 2017/1// DO - 10.1115/1.4035511 VL - 69 IS - 1 SP - SN - 0003-6900 ER - TY - JOUR TI - Hydration Sensing: A Wearable Hydration Sensor with Conformal Nanowire Electrodes (Adv. Healthcare Mater. 6/2017) AU - Yao, Shanshan AU - Myers, Amanda AU - Malhotra, Abhishek AU - Lin, Feiyan AU - Bozkurt, Alper AU - Muth, John F. AU - Zhu, Yong T2 - Advanced Healthcare Materials AB - A wearable skin hydration sensor is developed by Y. Zhu, J. F. Muth, and co-workers in article number 1601159. The sensor is made of silver nanowires inlaid in a silicone substrate, which renders the sensor flexible and stretchable. Integrated systems with multimodal sensing capability (e.g., hydration, strain/motion and electrophysiological sensing) are demonstrated in two form factors — wristband and chest patch. Image design by Shanshan Yao. DA - 2017/3// PY - 2017/3// DO - 10.1002/ADHM.201770031 VL - 6 IS - 6 J2 - Adv. Healthcare Mater. LA - en OP - SN - 2192-2640 UR - http://dx.doi.org/10.1002/ADHM.201770031 DB - Crossref ER - TY - JOUR TI - Computational Aerodynamic Modeling Tools for Aircraft Loss of Control AU - Frink, Neal T. AU - Murthy, Patrick C. AU - Atkins, Harold L. AU - Viken, Sally A. AU - Petrilli, Justin L. AU - Gopalarathnam, Ashok AU - Paul, Ryan C. T2 - JOURNAL OF GUIDANCE CONTROL AND DYNAMICS AB - This paper summarizes the status of ongoing NASA research supported over the past eight years to advance computational capabilities for modeling civil aircraft loss of control due to airframe damage or wing stall. The research is motivated by a desire to exploit the capabilities of computational methods to create augmented flight simulation models that improve pilot training for such loss-of-control scenarios. Flight of aircraft with either airframe damage or operating near and beyond the stall boundary encounters additional nonlinear aerodynamic influences on stability and control from dynamic motions that, if not included in flight simulation models, may lead to incorrect pilot responses. In the present work, both low- and high-fidelity computational methods are explored for analyzing such nonlinearities. The challenge of creating nonlinear reduced-order models from high-fidelity computational data is also addressed. At the beginning, few guidelines were available for computing or modeling the dynamic stability characteristics of civil aircraft in nonlinear stalled flight regimes. To accelerate progress, additional resources were leveraged through participation in two NATO task groups consisting of a diverse international body of computational aerodynamicists and flight simulation experts. As a result, a large body of knowledge has been generated, documenting the state of the art for computing and modeling the highly nonlinear stability characteristics of an unmanned air combat vehicle. This knowledge was infused directly into the NASA loss-of-control work through parallel application studies with the NASA Generic Transport Model. From this, it is concluded that the Reynolds-averaged Navier–Stokes formulation should suffice for capturing the representative behavior of civil aircraft stall for training purposes. Furthermore, promising approaches have been identified for creating nonlinear reduced-order models from computational data that can potentially augment flight simulation models for loss-of-control scenarios. DA - 2017/4// PY - 2017/4// DO - 10.2514/1.g001736 VL - 40 IS - 4 SP - 789-803 SN - 1533-3884 ER - TY - JOUR TI - A reconstructed discontinuous Galerkin method for the compressible Navier-Stokes equations on three-dimensional hybrid grids AU - Liu, Xiaodong AU - Xuan, Lijun AU - Xia, Yidong AU - Luo, Hong T2 - COMPUTERS & FLUIDS AB - A reconstructed discontinuous Galerkin (rDG(P1P2)) method, originally introduced for the compressible Euler equations, is developed for the solution of the compressible Navier–Stokes equations on 3D hybrid grids. In this method, a piecewise quadratic polynomial solution is obtained from the underlying piecewise linear DG solution using a hierarchical Weighted Essentially Non-Oscillatory (WENO) reconstruction. The reconstructed quadratic polynomial solution is then used for the computation of the inviscid fluxes and the viscous fluxes using the second formulation of Bassi and Reay (Bassi–Rebay II). The developed rDG(P1P2) method is used to compute a variety of flow problems to assess its accuracy, efficiency, and robustness. The numerical results demonstrate that the rDG(P1P2) method is able to achieve the designed third-order of accuracy at a cost slightly higher than its underlying second-order DG method, outperform the third order DG method in terms of both computing costs and storage requirements, and obtain reliable and accurate solutions to the direct numerical simulation (DNS) of compressible turbulent flows. DA - 2017/7/18/ PY - 2017/7/18/ DO - 10.1016/j.compfluid.2017.04.027 VL - 152 SP - 217-230 SN - 1879-0747 KW - Discontinuous Galerkin method KW - WENO reconstruction KW - Unstructured grids KW - Compressible Navier-Stokes equation ER - TY - JOUR TI - A Novel Hybrid Heating Method for Mechanical Testing of Miniature Specimens at Elevated Temperature AU - Li, Lin AU - Ngaile, Gracious AU - Hassan, Tasnim T2 - JOURNAL OF MICRO AND NANO-MANUFACTURING AB - A novel hybrid heating method which combines the conventional electric-resistance specimen heating with microcoil heating of specimen ends to achieve uniform heating over the gauge length is presented. Resistive heating of a miniature specimen develops a parabolic temperature profile with lowest temperature at the grip ends because of the heat loss to the gripper. Coil heating at the specimen ends compensates for this heat loss resulting in uniform temperature distribution over the central segment of the specimen. Thermo-electric finite element simulations were carried out to analyze the transient and steady temperature distribution in miniature specimens followed by experimental validation. DA - 2017/6// PY - 2017/6// DO - 10.1115/1.4035954 VL - 5 IS - 2 SP - SN - 2166-0476 ER - TY - JOUR TI - Structured Identification of Reduced-Order Models of Power Systems in a Differential-Algebraic Form AU - Nabavi, Seyedbehzad AU - Chakrabortty, Aranya T2 - IEEE TRANSACTIONS ON POWER SYSTEMS AB - In a recent paper, we proposed a system identification method for constructing reduced-order models for the electro-mechanical dynamics of large power systems, divided into multiple coherent clusters, using Synchrophasors. Every cluster in the actual model was represented as an aggregate generator in the reduced-order model. An aggregate network graph connected one aggregate generator to another. In this paper, we extend this identification approach to differential-algebraic (DAE) models. First, every cluster is associated with a unique terminal bus, referred to as the pilot bus, that couples its internal network to the rest of the system. The proposed algorithm uses Synchrophasor measurements from the pilot buses to identify the dynamic model of the aggregate generator for each cluster using nonlinear least squares while retaining the identity of all the pilot buses. The resulting reduced-order model is in the form of a nonlinear electric circuit described by aggregate differential and algebraic equations. We illustrate our results using two case studies, one for the IEEE 9-bus power system and another for the IEEE 39-bus power system. We also discuss how these reduced-order DAE models may be useful for designing shunt controllers at the pilot buses by using Synchrophasor feedback. DA - 2017/1// PY - 2017/1// DO - 10.1109/tpwrs.2016.2554154 VL - 32 IS - 1 SP - 198-207 SN - 1558-0679 KW - Model reduction KW - nonlinear least squares KW - swing equation KW - synchrophasors KW - system identification ER - TY - JOUR TI - Soot, organics, and ultrafine ash from air-and oxy-fired coal combustion AU - Andersen, Myrrha E. AU - Modak, Nabanita AU - Winterrowd, Christopher K. AU - Lee, Chun Wai AU - Roberts, William L. AU - Wendt, Jost O. L. AU - Linak, William P. T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - Pulverized bituminous coal was burned in a 10 W externally heated entrained flow furnace under air-combustion and three oxy-combustion inlet oxygen conditions (28, 32, and 36%). Experiments were designed to produce flames with practically relevant stoichiometric ratios (SR = 1.2–1.4) and constant residence times (2.3 s). Size-classified fly ash samples were collected, and measurements focused on the soot, elemental carbon (EC), and organic carbon (OC) composition of the total and ultrafine (<0.6 µm) fly ash. Results indicate that although the total fly ash carbon, as measured by loss on ignition, was always acceptably low (<2%) with all three oxy-combustion conditions lower than air-combustion, the ultrafine fly ash for both air-fired and oxy-fired combustion conditions consists primarily of carbonaceous material (50–95%). Carbonaceous components on particles <0.6 µm measured by a thermal optical method showed that large fractions (52–93%) consisted of OC rather than EC, as expected. This observation was supported by thermogravimetric analysis indicating that for the air, 28% oxy, and 32% oxy conditions, 14–71% of this material may be OC volatilizing between 100 °C and 550 °C with the remaining 29–86% being EC/soot. However, for the 36% oxy condition, OC may comprise over 90% of the ultrafine carbon with a much smaller EC/soot contribution. These data were interpreted by considering the effects of oxy-combustion on flame attachment, ignition delay, and soot oxidation of a bituminous coal, and the effects of these processes on OC and EC emissions. Flame aerodynamics and inlet oxidant composition may influence emissions of organic hazardous air pollutants (HAPs) from a bituminous coal. During oxy-coal combustion, judicious control of inlet oxygen concentration and placement may be used to minimize organic HAP and soot emissions. DA - 2017/// PY - 2017/// DO - 10.1016/j.proci.2016.08.073 VL - 36 IS - 3 SP - 4029-4037 SN - 1873-2704 KW - Oxy-coal combustion KW - Ultrafine fly ash KW - Loss on ignition KW - Elemental carbon KW - Organic carbon ER - TY - JOUR TI - Plastic Deformation of Polymer Blends as a Means to Achieve Stretchable Organic Transistors AU - Sun, Tianlei AU - Scott, Joshua I. AU - Wang, Ming AU - Kline, Regis Joseph AU - Bazan, Guillermo C. AU - Brendan T. O'Connor, T2 - ADVANCED ELECTRONIC MATERIALS AB - Intrinsically stretchable semiconductors will facilitate the realization of seamlessly integrated stretchable electronics. In this study, a new approach to achieve intrinsically stretchable semiconductors is introduced by blending a rigid high‐performance donor–acceptor polymer semiconductor poly[4‐(4,4‐dihexadecyl‐4H‐cyclopenta[1,2‐b:5,4‐b′]dithiopen‐2‐yl)‐alt[1,2,5]thiadiazolo[3,4‐c]pyridine] with a ductile polymer semiconductor poly(3‐hexylthiophene). Under large tensile strains of up to 75%, the polymers are shown to orient in the direction of strain, and when the strain is reduced, the polymers reversibly deform. During cyclic strain, the local packing order of the polymers is shown to be remarkably stable. The saturated field effect charge mobility is shown to be consistently above 0.04 cm 2 V −1 s −1 for up to 100 strain cycles with strain ranging from 10% to 75% when the film is printed onto a rigid test bed. At the 75% strain state, the charge mobility is consistently above 0.15 cm 2 V −1 s −1 . Ultimately, the polymer blend process introduced here results in an excellent combination of device performance and stretchability providing an effective approach to achieve intrinsically stretchable semiconductors. DA - 2017/1// PY - 2017/1// DO - 10.1002/aelm.201600388 VL - 3 IS - 1 SP - SN - 2199-160X ER - TY - JOUR TI - Microbubble mediated dual-frequency high intensity focused ultrasound thrombolysis: An In vitro study AU - Suo, Dingjie AU - Jin, Zhiyang AU - Jiang, Xiaoning AU - Dayton, Paul A. AU - Jing, Yun T2 - Applied Physics Letters AB - High intensity focused ultrasound (HIFU) has recently emerged as a promising alternative approach for thrombolysis. However, the high acoustic energy required by HIFU could elicit thermal damage bioeffects, impeding the clinical translation of this technique. This paper investigates the use of dual-frequency focused ultrasound (DFFU) mediated by microbubbles (MBs) to minimize the acoustic power required for thrombolysis in vitro. It was found that MBs, with sufficient concentration, could significantly lower the power threshold for thrombolysis for both DFFU and single-frequency focused ultrasound (SFFU). In addition, SFFU needs about 96%–156% higher energy to achieve the same thrombolysis efficiency as that of DFFU. The thrombolysis efficiency is also found to increase with the duty cycle. The measured cavitation signals reveal that the enhanced inertial cavitation is likely responsible for the improved thrombolysis under DFFU and MBs. DA - 2017/1/9/ PY - 2017/1/9/ DO - 10.1063/1.4973857 VL - 110 IS - 2 SP - 023703 SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4973857 ER - TY - JOUR TI - Electrical switching of antiferromagnets via strongly spin-orbit coupled materials AU - Li, Xi-Lai AU - Duan, Xiaopeng AU - Semenov, Yuriy G. AU - Kim, Ki Wook T2 - JOURNAL OF APPLIED PHYSICS AB - Electrically controlled ultra-fast switching of an antiferromagnet (AFM) is shown to be realizable by interfacing it with a material of strong spin-orbit coupling. The proximity interaction between the sublattice magnetic moments of a layered AFM and the spin-polarized free electrons at the interface offers an efficient way to manipulate antiferromagnetic states. A quantitative analysis, using the combination with a topological insulator as an example, demonstrates highly reliable 90° and 180° rotations of AFM magnetic states under two different mechanisms of effective torque generation at the interface. The estimated switching speed and energy requirement are in the ps and aJ ranges, respectively, which are about two-three orders of magnitude better than the ferromagnetic counterparts. The observed differences in the magnetization dynamics may explain the disparate characteristic responses. Unlike the usual precessional/chiral motions in the ferromagnets, those of the AFMs can essentially be described as a damped oscillator with a more direct path. The impact of random thermal fluctuations is also examined. DA - 2017/1/14/ PY - 2017/1/14/ DO - 10.1063/1.4974027 VL - 121 IS - 2 SP - SN - 1089-7550 ER - TY - JOUR TI - Efficient Charge Transfer and Fine-Tuned Energy Level Alignment in a THF- Processed Fullerene- Free Organic Solar Cell with 11.3% Efficiency AU - Zheng, Zhong AU - Awartani, Omar M. AU - Gautam, Bhoj AU - Liu, Delong AU - Qin, Yunpeng AU - Li, Wanning AU - Bataller, Alexander AU - Gundogdu, Kenan AU - Ade, Harald AU - Hou, Jianhui T2 - ADVANCED MATERIALS AB - Fullerene-free organic solar cells show over 11% power conversion efficiency, processed by low toxic solvents. The applied donor and acceptor in the bulk heterojunction exhibit almost the same highest occupied molecular orbital level, yet exhibit very efficient charge creation. DA - 2017/2/2/ PY - 2017/2/2/ DO - 10.1002/adma.201604241 VL - 29 IS - 5 SP - SN - 1521-4095 ER - TY - JOUR TI - Contrast Enhanced Superharmonic Imaging for Acoustic Angiography Using Reduced Form-Factor Lateral Mode Transmitters for Intravascular and Intracavity Applications AU - Wang, Zhuochen AU - Martin, K. Heath AU - Huang, Wenbin AU - Dayton, Paul A. AU - Jiang, Xiaoning T2 - IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL AB - Techniques to image the microvasculature may play an important role in imaging tumor-related angiogenesis and vasa vasorum associated with vulnerable atherosclerotic plaques. However, the microvasculature associated with these pathologies is difficult to detect using traditional B-mode ultrasound or even harmonic imaging due to small vessel size and poor differentiation from surrounding tissue. Acoustic angiography, a microvascular imaging technique that utilizes superharmonic imaging (detection of higher order harmonics of microbubble response), can yield a much higher contrast-to-tissue ratio than second harmonic imaging methods. In this paper, two dual-frequency transducers using lateral mode transmitters were developed for superharmonic detection and acoustic angiography imaging in intracavity applications. A single element dual-frequency intravascular ultrasound transducer was developed for concept validation, which achieved larger signal amplitude, better contrast-to-noise ratio (CNR), and pulselength compared to the previous work. A dual-frequency [Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] array transducer was then developed for superharmonic imaging with dynamic focusing. The axial and lateral sizes of the microbubbles in a 200- [Formula: see text] tube were measured to be 269 and [Formula: see text], respectively. The maximum CNR was calculated to be 22 dB. These results show that superharmonic imaging with a low frequency lateral mode transmitter is a feasible alternative to thickness mode transmitters when the final transducer size requirements dictate design choices. DA - 2017/2// PY - 2017/2// DO - 10.1109/tuffc.2016.2619687 VL - 64 IS - 2 SP - 311-319 SN - 1525-8955 KW - Dual frequency KW - lateral mode transducer KW - superharmonic KW - ultrasound transducer ER - TY - JOUR TI - Thrombin-responsive transcutaneous patch for auto-anticoagulant regulation AU - Zhang, Y. Q. AU - Yu, J. C. AU - Wang, J. Q. AU - Hanne, N. J. AU - Cui, Z. AU - Qian, C. G. AU - Wang, C. AU - Xin, H. L. AU - Cole, J. H. AU - Gallippi, C. M. AU - Zhu, Y. AU - Gu, Z. T2 - Advanced Materials AB - A thrombin-responsive microneedle-based transcutaneous patch is developed by C. M. Gallippi, Y. Zhu, Z. Gu, and co-workers, as demonstrated in article 1604043. The anticoagulant drug heparin is loaded into the hyaluronic acid needles through a thrombin cleavable peptide linker. This heparin patch can sense the thrombin level in blood vessels and autoregulate blood coagulation in a long-term manner. Cover design credit: Yuqi Zhang. DA - 2017/// PY - 2017/// DO - 10.1002/adma.201770028 VL - 29 IS - 4 ER - TY - JOUR TI - Piezoelectric d(36) in-plane shear-mode of lead-free BZT-BCT single crystals for torsion actuation AU - Berik, P. AU - Chang, W. -Y. AU - Jiang, X. T2 - APPLIED PHYSICS LETTERS AB - We report the study of piezoelectric direct torsion actuation mechanism using lead-free piezoelectric d36 in-plane shear-mode BZT-BCT single crystals. The generated angle of twist of the piezoelectric torsion actuator was obtained from the transverse deflection measurement using a laser vibrometer. The bi-morph torsional actuator, consisting of two lead-free piezoelectric BZT-BCT in-plane shear-mode single crystals with a giant piezoelectric d36 shear strain coefficient of 1590 pC/N, provided a rate of twist of 34.12 mm/m under a quasi-static 15 V drive. The experimental benchmark was further modelled and verified by the ANSYS software using three dimensional (3D) piezoelectric finite elements. The experimental results revealed that lead-free piezoelectric BZT-BCT d36-mode single crystal is a superior candidate for piezoelectric torsion actuation. This lead-free piezoelectric BZT-BCT d36-mode torsion actuator can be effectively applied in torsional deformation control by taking into account the environmental considerations. DA - 2017/1/30/ PY - 2017/1/30/ DO - 10.1063/1.4975587 VL - 110 IS - 5 SP - SN - 1077-3118 ER - TY - JOUR TI - Panchromatic Sequentially Cast Ternary Polymer Solar Cells AU - Ghasemi, Masoud AU - Ye, Long AU - Zhang, Qianqian AU - Yan, Liang AU - Kim, Joo-Hyun AU - Awartani, Omar AU - You, Wei AU - Gadisa, Abay AU - Ade, Harald T2 - ADVANCED MATERIALS AB - A sequential-casting ternary method is developed to create stratified bulk heterojunction (BHJ) solar cells, in which the two BHJ layers are spin cast sequentially without the need of adopting a middle electrode and orthogonal solvents. This method is found to be particularly useful for polymers that form a mechanically alloyed morphology due to the high degree of miscibility in the blend. DA - 2017/1/25/ PY - 2017/1/25/ DO - 10.1002/adma.201604603 VL - 29 IS - 4 SP - SN - 1521-4095 ER - TY - JOUR TI - Nanostructure diffraction analysis of a copper/single walled carbon nanotube nanocomposite synthesized by Laser Surface Implanting AU - Tu, Jay F. AU - Rajule, Nilesh AU - Liu, Yi AU - Martin, James T2 - CARBON AB - A new wet process, denoted as Laser Surface Implanting (LSI), has been developed to synthesize a Copper-Single Wall Carbon NanoTube (Cu-SWCNT) metal nanocomposite by dispersing SWCNTs into molten copper, followed by rapid and non-equilibrium solidification to form the Cu-SWCNT nanocomposite such that dispersed SWCNTs could locked in positions without agglomerating into large clusters. However, the nanometer sizes of the SWCNT clusters inside this nanocomposite make it extremely difficult to obtain TEM images with discernable SWCNT clusters in the copper matrix. In this paper, TEM images and their diffraction patterns for annealed pure copper, quenched pure copper (by the same synthesis process without introducing SWCNTs), and Cu-SWCNT nanocomposite are compared. It is concluded that TEM images with discernable SWCNT clusters are rare. Therefore, diffraction patterns are better tools to identify SWCNTs within the copper matrix. The indexed diffraction patterns confirm that the copper fcc lattice is preserved. However, the Cu-SWCNT nanocomposite samples also exhibit ordered diffuse scattering, consisting of at least two polyhedra of diffuse-scattering bounded by the {110}* and {200}* family of reciprocal lattice planes, respectively. In addition several samples exhibit super-lattice Bragg diffraction indicative expanded unit cells. It thus appears that the SWCNTs are incorporated into the Cu matrix with precise arrangements commensurate with specific Cu lattice planes. DA - 2017/3// PY - 2017/3// DO - 10.1016/j.carbon.2016.11.004 VL - 113 SP - 1-9 SN - 1873-3891 ER - TY - JOUR TI - Flexoelectricity in low densification materials and its implication AU - Shu, L. L. AU - Yong, Z. H. AU - Jiang, X. N. AU - Xie, Z. Q. AU - Huang, W. B. T2 - Journal of Alloys and Compounds AB - Coupling between the strain gradient and the electric polarization, also named flexoelectricity, is a fundamental but often overlooked property in solid dielectrics. The past ten years has witnessed its great potential in sensing and actuating applications, especially in nanomaterials or nanostructures. The recently discovered giant flexoelectricity in barium strontium titanate (BST) perovskite above its Curie temperature has boosted the research interests on flexoelectricity to a new height. The possible interpretation of the enhanced flexoelectricity in BST was initially attributed to the non-crystalline polar-phases or polar nano-regions existing in the perovskites, then to the inner micro strain generated from the material densification process. In this paper, we analyzed the origin of flexoelectricity in this kind of materials by using both analytical mechanics method and finite element simulation method. Our results suggested the inner micro defect generated during the material densification process would weaken the flexoelectricity of the materials. The observed polarization in the studied materials was likely induced by other mechanisms rather than the pure flexoelectricity. DA - 2017/// PY - 2017/// DO - 10.1016/j.jallcom.2016.10.298 VL - 695 SP - 1555-1560 ER - TY - JOUR TI - Dynamic Polarization Microscopy for In-Situ Measurements of Collagen Fiber Realignment During Impact AU - Wu, Xianyu AU - Huang, Hsiao-Ying Shadow AU - Pankow, Mark AU - Peters, Kara T2 - MECHANICS OF BIOLOGICAL SYSTEMS AND MATERIALS, VOL 6 AB - The long term goal of this work is to better understand the tendon-to-bone insertion injury due to medium strain rate impact (e.g. sports activity). Specifically, we imaged collagen fiber realignment during impact, to investigate the ability of the tendon-to-bone insertion to these survive harsh dynamic events. A polarized light microscopy (PLM) setup was built in the lab and used to monitor the birefringence property changes of a known material under changing stress conditions. Initially polycarbonate dogbone specimens were tested quasi-statically to validate the setup and analysis algorithm. Polarized light retardation and alignment direction images are generated to quantitatively analyze the birefringence property change under different stress and compared to theoretical predictions. To perform dynamic experiments a drop weight tower was modified for medium strain rate testing (10–100 %/s) and the PLM setup is being incorporated for imaging. Several dynamic experiments have been conducted using this modified drop tower on porcine tendon specimens. A high-speed camera is used to record their dynamic response and deformation. DA - 2017/// PY - 2017/// DO - 10.1007/978-3-319-41351-8_9 SP - 61-66 SN - 2191-5652 KW - Polarized light microscopy KW - Impact KW - Tendon-to-bone insertion KW - Drop tower KW - Mechanical testing ER - TY - JOUR TI - Modeling of 3D woven composites using the digital element approach for accurate prediction of kinking under compressive loads AU - Joglekar, Shreyas AU - Pankow, Mark T2 - COMPOSITE STRUCTURES AB - Model definition accuracy dictates the reliability of a predictive analysis for 3D woven composites (3DWC). The traditional modeling approach is based on analysis of ideal geometry with user specified imperfections. In that case, co-relating the actual imperfections arising from manufacturing processes with that of the model becomes an iterative process. In this study, a digital element (DE) approach is implemented for creating the woven architecture of the composite. This technique simulates the individual fibers and their interactions allowing the user to create a reference unit cell with imperfect geometry induced during manufacturing stages of 3DWCs. Thus the response and strength analysis account for the unique weaving signature and provide better predictions without the necessity to run iterative analysis procedures required for idealized geometry models. X-ray CT images or detailed statistical data for variations in specimen geometry are not required which makes this approach more attractive in terms of cost and creation time. A representative model created using the DE approach is used for prediction of compressive failure of 3DWC without having to seed imperfections for failure initiation. The analysis also captures the formation of a kink band as observed in experimental tests. Results of this study are compared with the experimental results and simulation results of idealized geometry reported previously in literature. DA - 2017/1/15/ PY - 2017/1/15/ DO - 10.1016/j.compstruct.2016.10.070 VL - 160 SP - 547-559 SN - 1879-1085 KW - 3D woven composites KW - Kink band formation KW - Realistic geometry modeling ER - TY - JOUR TI - Frequency dispersion of flexoelectricity in PMN-PT single crystal AU - Shu, Longlong AU - Wan, Meiqian AU - Jiang, Xiaoning AU - Li, Fei AU - Zhou, Naigen AU - Huang, Wenbin AU - Wang, Tong T2 - AIP ADVANCES AB - The mechanism of the recent discovered enhanced flexoelectricity in perovskites has brought about numerous controversies which still remain unclear. In this paper, we employed relaxor 0.68Pb(Mg2/3Nb1/3)O3 -0.32PbTiO3 (PMN-PT) single crystals for study. The observed flexoelectric coefficient in PMN-PT single crystal reaches up to 100 μC/m, and in a relative low frequency range, exhibits an abnormal frequency dispersion phenomenon with a positive relationship with frequency. Such frequency dispersion regulation is different from the normal relaxation behavior that usually occur a time delay, and hence proves the flexoelectricity acting more like bulk effect rather than surface effect in this kind of materials. DA - 2017/1// PY - 2017/1// DO - 10.1063/1.4973684 VL - 7 IS - 1 SP - SN - 2158-3226 ER - TY - JOUR TI - Exploring how optimal composite design is influenced by model fidelity and multiple objectives AU - Joglekar, Shreyas AU - Von Hagel, Kayla AU - Pankow, Mark AU - Ferguson, Scott T2 - COMPOSITE STRUCTURES AB - This paper explores how optimal configuration of a composite panel is influenced by the choice of analysis model – analytic or computational – and the consideration of multiple objectives. While past research has explored aspects of this problem separately – composite ply orientation, multiple load scenarios, and multiple performance objectives – there has been limited work addressing the interactions between these factors. Three loading scenarios are considered in this work, and it is demonstrated that for certain scenarios an analytical model likely over-predicts composite performance. Further, for complex loading scenarios it is impossible to develop an analytical model. However, this work also demonstrates that the use of analytical models can be advantageous. Analytical models can provide similar estimates to computational models for some loading cases at significantly reduced computational expense. More importantly, it is also shown how solutions from the analytical model, which can be relatively cheap to find computationally, can be used to seed the initial designs of a Finite Element-based optimization. Run time reductions as large as 80% are demonstrated when these informed seeded designs are used, even when the designs were created for a different set of loading scenarios. DA - 2017/1/15/ PY - 2017/1/15/ DO - 10.1016/j.compstruct.2016.10.089 VL - 160 SP - 964-975 SN - 1879-1085 KW - Composite panel design KW - Multi-objective optimization KW - Finite element model KW - Analytic model KW - Solution seeding ER - TY - JOUR TI - Characteristics of spray from a GDI fuel injector for naphtha and surrogate fuels AU - Wang, Libing AU - Badra, Jihad A. AU - Roberts, William L. AU - Fang, Tiegang T2 - FUEL AB - Characterization of the spray angle, penetration, and droplet size distribution is important to analyze the spray and atomization quality. In this paper, the spray structure development and atomization characterization of two naphtha fuels, namely light naphtha (LN) and whole naphtha (WN) and two reference fuel surrogates, i.e. toluene primary reference fuel (TPRF) and primary reference fuel (PRF) were investigated using a gasoline direct injection (GDI) fuel injector. The experimental setup included a fuel injection system, a high-speed imaging system, and a droplet size measurement system. Spray images were taken by using a high-speed camera for spray angle and penetration analysis. Sauter mean diameter, Dv(10), Dv(50), Dv(90), and particle size distribution were measured using a laser diffraction technique. Results show that the injection process is very consistent for different runs and the time averaged spray angles during the measuring period are 103.45°, 102.84°, 102.46° and 107.61° for LN, WN, TPRF and PRF, respectively. The spray front remains relatively flat during the early stage of the fuel injection process. The peak penetration velocities are 80 m/s, 75 m/s, 75 m/s and 79 m/s for LN, WN, TPRF and PRF, respectively. Then velocities decrease until the end of the injection and stay relatively stable. The transient particle size and the time-averaged particle size were also analyzed and discussed. The concentration weighted average value generally shows higher values than the arithmetic average results. The average data for WN is usually the second smallest except for Dv90, of which WN is the biggest. Generally the arithmetic average particle sizes of PRF are usually the smallest, and the sizes does not change much with the measuring locations. For droplet size distribution results, LN and WN show bimodal distributions for all the locations while TPRF and PRF shows both bimodal and single peak distribution patterns. The results imply that droplet size distribution is skewed to the larger side for locations close the axis and is skewed to the smaller side for distance away from the axis. DA - 2017/2/15/ PY - 2017/2/15/ DO - 10.1016/j.fuel.2016.11.015 VL - 190 SP - 113-128 SN - 1873-7153 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84996565995&partnerID=MN8TOARS KW - Gasoline direct injection (GDI) KW - Naphtha KW - Surrogate KW - Spray penetration KW - Spray angle KW - Particle size distribution ER - TY - JOUR TI - Volumetric flame synthesis of mixed tungsten-molybdenum oxide nanostructures AU - Farmahini-Farahani, Moien AU - Saveliev, Alexei V. AU - Merchan-Merchan, Wilson T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - Mixed-metal (Mo/W) oxide nanostructures were synthesized volumetrically in the oxygen-rich zone of a counter-flow diffusion flame. High purity Mo and W wires were used to generate Mo and W oxide vapors that are transformed into mixed-metal oxide nanostructures while transported by the gas flow in the upward direction toward the stagnation plane. The Mo wire was inserted in a lower position within the flame volume than the W wire. Samples of generated nanomaterials collected thermophoretically from the flame volume at various axial positions allowed tracing of the particle evolution. The following synthesis stages were identified. MoO3 structures are first formed in the lower part of the flame. As they are carried by the gas flow, W oxide vapors deposit on the surfaces of the early formed MoO3 nanostructures. W atoms diffuse at the interfaces of the MoO3 structures to form mixed W–Mo oxide nanoparticles. Fully grown structures, collected near the stagnation plane (SP), are nanocubes exhibiting well-defined edges with sizes less than 100 nm. Energy-dispersive X-ray spectroscopy elemental mapping revealed that the mature structures have uniform distribution of W, Mo, and O atoms. The measured lattice spacing showed expanded lattice distance of MoO3 which may be attributed to the incorporation of W atoms in the MoO3 crystal and formation of W–Mo oxide structures. DA - 2017/// PY - 2017/// DO - 10.1016/j.proci.2016.08.054 VL - 36 IS - 1 SP - 1055-1063 SN - 1873-2704 KW - Flame synthesis KW - Nanostructures KW - Mixed-metal oxides ER - TY - JOUR TI - Sound insulation of multi-layer glass-fiber felts: Role of morphology AU - Yang, Yong AU - Li, Binbin AU - Chen, Zhaofeng AU - Sui, Ni AU - Chen, Zhou AU - Xu, Tengzhou AU - Li, Yufang AU - Fu, Renli AU - Jing, Yun T2 - TEXTILE RESEARCH JOURNAL AB - Glass-fiber felts have emerged as a popular material for noise reduction. This paper investigates the effect of various morphologies (micro-layer, macro-layer and air-layer) of glass-fiber felts on sound insulation. The sound transmission loss is measured by a Brüel & Kjár (B&K) impedance tube. The results show that the sound insulation of glass-fiber felts can be improved by increasing the number of macro-layers. The comparison between the macro- and micro-layer of glass-fiber felts on sound insulation is systematically carried out. Notably, the sound transmission loss of glass-fiber felts with similar areal density and thickness favors macro-layer structures over micro-layer structures. A simple model is established to explain this phenomenon. In addition, the sound transmission loss exhibits period fluctuations due to the presence of the air-layer between glass-fiber felts, which can be theoretically explained by the resonance effect. It is found that sound transmission loss can be improved by increasing the number of air-layers. DA - 2017/2// PY - 2017/2// DO - 10.1177/0040517516629142 VL - 87 IS - 3 SP - 261-269 SN - 1746-7748 KW - sound insulation KW - glass-fiber felt KW - multi-layer KW - air-layer ER - TY - JOUR TI - Soft electrothermal actuators using silver nanowire heaters AU - Yao, Shanshan AU - Cui, Jianxun AU - Cui, Zheng AU - Zhu, Yong T2 - NANOSCALE AB - Low-voltage and extremely flexible electrothermal bimorph actuators were fabricated in a simple, efficient and scalable process. The bimorph actuators were made of flexible silver nanowire (AgNW) based heaters, which exhibited a fast heating rate of 18 °C s-1 and stable heating performance with large bending. The actuators offered the largest bending angle (720°) or curvature (2.6 cm-1) at a very low actuation voltage (0.2 V sq-1 or 4.5 V) among all types of bimorph actuators that have been reported to date. The actuators can be designed and fabricated in different configurations that can achieve complex patterns and shapes upon actuation. Two applications of this type of soft actuators were demonstrated towards biomimetic robotics - a crawling robot that can walk spontaneously on ratchet surfaces and a soft gripper that is capable of manipulating lightweight and delicate objects. DA - 2017/3/21/ PY - 2017/3/21/ DO - 10.1039/c6nr09270e VL - 9 IS - 11 SP - 3797-3805 SN - 2040-3372 ER - TY - JOUR TI - Modeling Hybrid Nuclear Systems With Chilled-Water Storage AU - Misenheimer, Corey T. AU - Terry, Stephen D. T2 - JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME AB - Air-conditioning loads during the warmer months of the year are large contributors to an increase in the daily peak electrical demand. Traditionally, utility companies boost output to meet daily cooling load spikes, often using expensive and polluting fossil fuel plants to match the demand. Likewise, heating, ventilation, and air conditioning (HVAC) system components must be sized to meet these peak cooling loads. However, the use of a properly sized stratified chilled-water storage system in conjunction with conventional HVAC system components can shift daily energy peaks from cooling loads to off-peak hours. This process is examined in light of the recent development of small modular nuclear reactors (SMRs). In this study, primary components of an air-conditioning system with a stratified chilled-water storage tank were modeled in FORTRAN 95. A basic chiller operation criterion was employed. Simulation results confirmed earlier work that the air-conditioning system with thermal energy storage (TES) capabilities not only reduced daily peaks in energy demand due to facility cooling loads but also shifted the energy demand from on-peak to off-peak hours, thereby creating a more flattened total electricity demand profile. Thus, coupling chilled-water storage-supplemented HVAC systems to SMRs is appealing because of the decrease in necessary reactor power cycling, and subsequently reduced associated thermal stresses in reactor system materials, to meet daily fluctuations in cooling demand. Also, such a system can be used as a thermal sink during reactor transients or a buffer due to renewable intermittency in a nuclear hybrid energy system (NHES). DA - 2017/1// PY - 2017/1// DO - 10.1115/1.4033858 VL - 139 IS - 1 SP - SN - 0195-0738 ER - TY - JOUR TI - Intrinsic coincident full-Stokes polarimeter using stacked organic photovoltaics AU - Yang, Ruonan AU - Sen, Pratik AU - O'Connor, B. T. AU - Kudenov, M. W. T2 - APPLIED OPTICS AB - An intrinsic coincident full-Stokes polarimeter is demonstrated by using strain-aligned polymer-based organic photovoltaics (OPVs) that can preferentially absorb certain polarized states of incident light. The photovoltaic-based polarimeter is capable of measuring four Stokes parameters by cascading four semitransparent OPVs in series along the same optical axis. This in-line polarimeter concept potentially ensures high temporal and spatial resolution with higher radiometric efficiency as compared to the existing polarimeter architecture. Two wave plates were incorporated into the system to modulate the S3 Stokes parameter so as to reduce the condition number of the measurement matrix and maximize the measured signal-to-noise ratio. Radiometric calibration was carried out to determine the measurement matrix. The polarimeter presented in this paper demonstrated an average RMS error of 0.84% for reconstructed Stokes vectors after normalized to S0. A theoretical analysis of the minimum condition number of the four-cell OPV design showed that for individually optimized OPV cells, a condition number of 2.4 is possible. DA - 2017/2/20/ PY - 2017/2/20/ DO - 10.1364/ao.56.001768 VL - 56 IS - 6 SP - 1768-1774 SN - 2155-3165 ER - TY - JOUR TI - Hypoxia and H2O2 Dual-Sensitive Vesicles for Enhanced Glucose-Responsive Insulin Delivery AU - Yu, Jicheng AU - Qian, Chenggen AU - Zhang, Yuqi AU - Cui, Zheng AU - Zhu, Yong AU - Shen, Qundong AU - Ligler, Frances S. AU - Buse, John B. AU - Gu, Zhen T2 - NANO LETTERS AB - A glucose-responsive closed-loop insulin delivery system mimicking pancreas activity without long-term side effect has the potential to improve diabetic patients' health and quality of life. Here, we developed a novel glucose-responsive insulin delivery device using a painless microneedle-array patch containing insulin-loaded vesicles. Formed by self-assembly of hypoxia and H2O2 dual-sensitive diblock copolymer, the glucose-responsive polymersome-based vesicles (d-GRPs) can disassociate and subsequently release insulin triggered by H2O2 and hypoxia generated during glucose oxidation catalyzed by glucose specific enzyme. Moreover, the d-GRPs were able to eliminate the excess H2O2, which may lead to free radical-induced damage to skin tissue during the long-term usage and reduce the activity of GOx. In vivo experiments indicated that this smart insulin patch could efficiently regulate the blood glucose in the chemically induced type 1 diabetic mice for 10 h. DA - 2017/2// PY - 2017/2// DO - 10.1021/acs.nanolett.6b03848 VL - 17 IS - 2 SP - 733-739 SN - 1530-6992 KW - Drug delivery KW - diabetes KW - insulin KW - glucose-responsive KW - hypoxia-sensitive KW - H2O2-sensitive ER - TY - JOUR TI - Gain-scheduling control of T-S fuzzy systems with actuator saturation AU - Liu, Yang AU - Ban, Xiaojun AU - Wu, Fen AU - Lam, H. K. T2 - JOURNAL OF INTELLIGENT & FUZZY SYSTEMS AB - This paper presents a gain-scheduling output feedback control design method for T-S fuzzy systems with actuator saturation. Different from existing control design methods for T-S fuzzy systems, the basic idea of the proposed approach is to transform the T-S fuzzy model with saturation nonlinearity into the form of linear fractional transformation (LFT). Instead of commonly used fuzzy controllers, a gain-scheduled output feedback controller in the LFT form is introduced to stabilize the saturated T-S fuzzy system with guaranteed H∞ performance. The problem of establishing regional stability and performance of the closed-loop nonlinear system are tackled by using robust control techniques. As a result, the conservatism introduced by dealing with the quadratic terms of normalized fuzzy weighting functions can be avoided. The proposed controller synthesis problem is cast as a convex optimization in terms of linear matrix inequalities (LMIs) and can be solved efficiently. An example of balancing the inverted pendulum with bounded actuation is provided to illustrate the effectiveness of the proposed design method. DA - 2017/// PY - 2017/// DO - 10.3233/jifs-16546 VL - 32 IS - 3 SP - 2579-2589 SN - 1875-8967 KW - T-S fuzzy systems KW - actuator saturation KW - gain-scheduling control KW - linear fractional transformation ER - TY - JOUR TI - Analytical and numerical investigation on a new compact thermoelectric generator AU - Ming, Tingzhen AU - Yang, Wei AU - Huang, Xiaoming AU - Wu, Yongjia AU - Li, Xiaohua AU - Liu, Jun T2 - ENERGY CONVERSION AND MANAGEMENT AB - In order to improve the performance and maximize the efficiency of energy conversion of thermoelectric generator (TEG), a mathematical model to predict the maximum energy conversion efficiency of TEG is developed. Then, a new compact thermoelectric generator (C-TEG) and a dimensional optimized TEG (DO-TEG) are proposed in this article. The compact thermoelectric generator is designed via logical intersection angle selection and layout, thus to improve the electric performance per unit volume. Finally, we compared the output electric performance of C-TEG and traditional thermoelectric generator (T-TEG) and that of DO-TEG under design and off-design conditions via numerical simulations. The results indicate that C-TEG has an excellent electric performance whose voltage, power, and efficiency decrease slightly whereas the output voltage, work, and efficiency compared with that of T-TEG have been significantly improved, with the amplitude increasing with the increase of resistant value of external loads. DA - 2017/1/15/ PY - 2017/1/15/ DO - 10.1016/j.enconman.2016.11.043 VL - 132 SP - 261-271 SN - 1879-2227 UR - http://dx.doi.org/10.1016/j.enconman.2016.11.043 KW - Thermoelectric power generator (TEG) KW - Specific voltage KW - Specific power KW - Specific efficiency ER - TY - JOUR TI - Thermal radiation modeling using the LES-ODT framework for turbulent combustion flows AU - Ben Rejeb, Sami AU - Echekki, Tarek T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - A novel multiscale Monte-Carlo Ray Tracing (MCRT) model in the large eddy simulation–one-dimensional turbulence (LES–ODT) framework for participating gray media is developed. LES–ODT is based on a hybrid simulation of the large scales within LES and 1D ODT fine-resolution solutions embedded in the LES. Radiation is solved within the ODT domain at the subgrid scale where a combination of stochastic and deterministic solutions allows the treatment of different processes governing the transport and chemistry for scalars and momentum. The MCRT model is implemented in a non-homogeneous auto-ignition isotropic turbulence simulation and compared to direct numerical simulations (DNS) of the same configuration. This configuration exhibits complex coupling between turbulent transport and molecular processes, diffusion, reaction and radiation, under highly transient conditions. Implementation in the LES–ODT framework is performed for different cases of optical thicknesses. Results of the simulations are compared to DNS statistics. The comparison of the different statistics shows a satisfactory agreement. DA - 2017/1// PY - 2017/1// DO - 10.1016/j.ijheatmasstransfer.2016.09.074 VL - 104 SP - 1300-1316 SN - 1879-2189 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84989184566&partnerID=MN8TOARS KW - One-dimensional turbulence KW - Large-eddy simulation KW - Combustion KW - Radiative heat transfer KW - Monte-Carlo Ray Tracing ER -