TY - JOUR TI - Single-layer MoS2 nanopores as nanopower generators AU - Feng, J. AU - Graf, M. AU - Liu, K. AU - Ovchinnikov, D. AU - Dumcenco, D. AU - Heiranian, M. AU - Nandigana, V. AU - Aluru, N.R. AU - Kis, A. AU - Radenovic, A. T2 - Nature AB - Blue energy is a desirable renewable resource, involving the osmotic transport of ions through a membrane from seawater to fresh water; here, nanopores have been created in two-dimensional molybdenum-disulfide membranes, and shown to generate a substantial osmotic power output. Osmotic power generation is a promising renewable energy source. This study demonstrates the use of single-layer molybdenum disulfide (MoS2) nanopores as osmotic nanogenerators. The transport of water through a membrane scales inversely with membrane thickness, so atomically thin materials should provide the ideal medium to host the nanopores in an osmotic power generator. Aleksandra Radenovic and colleagues produced nanopores in two-dimensional MoS2 and, using a salt gradient across a single nanopore, generated a power output per area orders of magnitude greater than that previously reported for nanotubes. They also show that a chemical potential gradient across a single nanopore in MoS2 can generate enough power to operate a single-layer MoS2 transistor. Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as ‘blue energy’1,2,3. Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient4 or by an osmotic potential resulting from a salt concentration gradient5. For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness5,6,7. Here we demonstrate the use of single-layer molybdenum disulfide (MoS2) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to 106 watts per square metre—a current that can be attributed mainly to the atomically thin membrane of MoS2. Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment8,9,10,11—for example, a piezoelectric zinc oxide nanowire array8 or single-layer MoS2 (ref. 12). We use our MoS2 nanopore generator to power a MoS2 transistor, thus demonstrating a self-powered nanosystem. DA - 2016/// PY - 2016/// DO - 10.1038/nature18593 VL - 536 IS - 7615 SP - 197-200 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84978127640&partnerID=MN8TOARS ER - TY - JOUR TI - Nano-electro-mechanical pump: Giant pumping of water in carbon nanotubes AU - Farimani, A.B. AU - Heiranian, M. AU - Aluru, N.R. T2 - Scientific Reports AB - A fully controllable nano-electro-mechanical device that can pump fluids at nanoscale is proposed. Using molecular dynamics simulations, we show that an applied electric field to an ion@C60 inside a water-filled carbon nanotube can pump water with excellent efficiency. The key physical mechanism governing the fluid pumping is the conversion of electrical energy into hydrodynamic flow with efficiencies as high as 64%. Our results show that water can be compressed up to 7% higher than its bulk value by applying electric fields. High flux of water (up to 13,000 molecules/ns) is obtained by the electro-mechanical, piston-cylinder-like moving mechanism of the ion@C60 in the CNT. This large flux results from the piston-like mechanism, compressibility of water (increase in density of water due to molecular ordering), orienting dipole along the electric field and efficient electrical to mechanical energy conversion. Our findings can pave the way towards efficient energy conversion, pumping of fluids at nanoscale, and drug delivery. DA - 2016/// PY - 2016/// DO - 10.1038/srep26211 VL - 6 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84969951823&partnerID=MN8TOARS ER - TY - JOUR TI - Facile Synthesis of Tunable and Durable Bulk Superhydrophobic Material from Amine "reactive" Polymeric Gel AU - Rather, A.M. AU - Manna, U. T2 - Chemistry of Materials AB - Materials with extremes of water wettability are of potential interest in various fundamental and applied contexts. However, often, poor chemical and physical durabitity of conventional thin special wettable materials stands in the way of prospective applications of this property at practical settings. A chemically “reactive” polymeric gel material is introduced here, and advantage is taken of the robust and facile 1,4-Michael addition reaction between acrylate and primary amine groups to develop a chemically cross-linked and bulk (including interior and surface) superhydrophobic material. A mixture of dipentaerythritol pentaacrylate and branched poly(ethylenimine) (BPEI) can rapidly form a self-standing gel network. On removal of solvent molecules, the synthesized gel network provides a highly porous and reactive polymeric matrix that can be further modified with a variety of small molecules to tailor the liquid water wettability on the synthesized material. This approach provides a facile and rapid process to fabricate a bulk (internally) superhydrophobic material of arbitrary size that can take complex shapes. This property of the material remains intact even after various standard chemical and physical insults. This synthetic strategy could be useful in developing advanced and multifunctional materials to further broadening the applications of this anti-wetting property, including oil/water separation, self-cleaning, sustaining and slow drug release, etc. DA - 2016/// PY - 2016/// DO - 10.1021/acs.chemmater.6b03862 VL - 28 IS - 23 SP - 8689-8699 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85006257596&partnerID=MN8TOARS ER - TY - CONF TI - Study of Cetacean Fluke Structures effect on Hydrodynamic Performance AU - Carter, D. AU - Bart-Smith, H. T2 - Virginia-North Carolina Alliance of Louis Stokes Alliance for Minority Participation Research Symposium C2 - 2016/4/4/ C3 - Virginia-North Carolina Alliance of Louis Stokes Alliance for Minority Participation Research Symposium, April 4th DA - 2016/4/4/ PY - 2016/4/4/ ER - TY - CONF TI - Study of Cetacean Fluke Structures effect on Hydrodynamic Performance AU - Carter, D. AU - Bart-Smith, H. T2 - National Conference of Louis Stokes Alliance for Minority Participation C2 - 2016/2/23/ C3 - National Conference of Louis Stokes Alliance for Minority Participation DA - 2016/2/23/ PY - 2016/2/23/ ER - TY - CONF TI - Sharp-fin induced shock wave/turbulent boundary layer interactions in an axisymmetric configuration AU - Pickles, J.D. AU - Subbareddy, P.K. AU - Narayanaswamy, V. C2 - 2016/// C3 - 46th AIAA Fluid Dynamics Conference DA - 2016/// DO - 10.2514/6.2016-3340 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85088071146&partnerID=MN8TOARS ER - TY - CONF TI - Experimental investigation of shock boundary layer interactions to unravel inlet unstart physics AU - Funderburk, M.L. AU - Narayanaswamy, V. C2 - 2016/// C3 - 46th AIAA Fluid Dynamics Conference DA - 2016/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84980347810&partnerID=MN8TOARS ER - TY - JOUR TI - Heat Transfer Optimization for Thermoelectric Power Generation with Automobile Waste Heat Recovery Applications AU - Pandit, Jaideep AU - Ekkad, Srinath V. AU - Huxtable, Scott T. AU - Ma, Ting T2 - Annual Review of Heat Transfer AB - This chapter describes the considerations in optimizing the heat exchanger performance of thermoelectric power generators (TEGs) for use in waste heat recovery from automotive exhaust gases. Thermoelectric devices have been in development since the early twentieth century with much of the research focus on improvement in thermoelectric material properties. However, the effective transfer of heat to and from the TEG also has a significant impact on the overall device performance. Strategies and efforts to improve heat transfer for automotive TEG systems are described in this chapter. DA - 2016/// PY - 2016/// DO - 10.1615/AnnualRevHeatTransfer.2016015353 VL - 19 IS - 1 SP - 241–277 SN - 1049-0787 UR - http://dx.doi.org/10.1615/AnnualRevHeatTransfer.2016015353 ER - TY - JOUR TI - Effect of Endwall Contouring on a Transonic Turbine Blade Passage: Heat Transfer Performance AU - Panchal, Kapil V. AU - Abraham, Santosh AU - Roy, Arnab AU - Ekkad, Srinath V. AU - Ng, Wing AU - Lohaus, Andrew S. AU - Crawford, Michael 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 - 2016/9/20/ PY - 2016/9/20/ DO - 10.1115/1.4034411 VL - 139 IS - 1 LA - en OP - SN - 0889-504X 1528-8900 UR - http://dx.doi.org/10.1115/1.4034411 DB - Crossref ER - TY - CONF TI - Preliminary experimental investigation of initial onset of sand deposition in the turbine section of gas turbines AU - Boulanger, A. AU - Patel, H. AU - Hutchinson, J. AU - DeShong, W. AU - Xu, W. AU - Ng, W. AU - Ekkad, S. AB - Particle ingestion into modern gas turbine engines is known to reduce performance and may damage many primary gas path components through erosion or deposition mechanisms. Many studies have been conducted that evaluate the effects of particulate ingestion in primary and secondary gas path components. However, modern gas turbines have gas path temperatures that are above most previous studies. As a result, this study performed particle deposition experiments at the Virginia Tech Aerothermal Rig facility at engine representative temperatures. Arizona Test Dust of 20 to 40 μm was chosen to represent the particle ingested into rotorcraft turbine engines in desert and sandy environments. The experimental setup impinged air and sand particles on a flat Hastelloy X coupon. The gas and sand mixture impacted the coupon at varying angles measured between the gas flow direction and coupon face, hereby referred to as coupon angle. For this study, gas and sand particles maintained a constant flow velocity of about 70 m/s and a temperature of about 1100°C. The coupon angle was varied between 30° to 90° for all experiments. The experimental results indicate sand deposition increased linearly from about 975 °C to 1075 °C for all coupon angles. A multiple linear regression model is used to estimate the amount of deposition that will occur on the test coupon as a function of gas path temperature and coupon angle. The model is adequate in explaining about 67% of the deposition that occurs for the tests. The remaining percentage could be explained with other factors such as particle injection rates and exact surface temperature where the deposits occur. C2 - 2016/// C3 - Proceedings of the ASME Turbo Expo DA - 2016/// DO - 10.1115/GT2016-56059 VL - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84991396783&partnerID=MN8TOARS ER - TY - CONF TI - Gas turbine combustor rig development and initial observations at cold and reacting flow conditions AU - Gomez-Ramirez, D. AU - Kedukodi, S. AU - Gadiraju, S. AU - Ekkad, S.V. AU - Moon, H.-K. AU - Kim, Y. AU - Srinivasan, R. AB - The present paper describes the first phase of the design and development of a realistic, high-pressure, full-scale research gas turbine combustor at Virginia Tech. The final test rig will be capable of operating at inlet temperatures of 650 K, pressures up to 9.28 Bar (120 psig), maximum air inlet flow rates of 1.27 kg/s (2.8 lbm/s), and allow for variations in the geometry of the combustor model. The first phase consists of a low-pressure (atmospheric) optical combustor for heat transfer and flow-field measurements at isothermal and reacting conditions. The combustor model is equipped with an industrial low emission fuel injector from Solar Turbines Incorporated, used in their land based gas turbine Taurus-60. The primary objective of the developed rig is to provide additional insight into the heat transfer processes that occur within gas turbine combustors, primarily the convective component, which has not been characterized. A future phase of the test rig development will incorporate a pressure vessel that will allow for the operation of the combustor simulator at higher pressures. In the present publication, the design methodology and considerations, as well as the challenges encountered during the design of the first phase of the simulator are briefly discussed. An overview is given on the design of the instrumentation and process piping surrounding the test rig, including ASME codes followed as well as the instrumentation and equipment selected. A detailed description of the test section design is given, highlighting the design for high temperature operation. As an example of the capabilities of the rig, representative measurements are presented. Characterization of the isothermal flow field using planar Particle Image Velocimetry (PIV) at a Reynolds number of 50 000 was performed and compared with flame imaging data at the same inlet conditions operating at an equivalence ratio of 0.7. The data suggests that the flame location follows the maximum turbulent kinetic energy as measured in the isothermal field. Representative data from the computational efforts are also presented and compared with the experimental measurements. Future work will expand on both reacting and isothermal PIV and heat transfer measurements, as well as computational validations. C2 - 2016/// C3 - Proceedings of the ASME Turbo Expo DA - 2016/// DO - 10.1115/GT2016-57825 VL - 5B-2016 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84991629023&partnerID=MN8TOARS ER - TY - JOUR TI - Experimental and numerical study of heat transfer due to developing flow in a two-pass rib roughened square duct AU - Singh, Prashant AU - Ravi, Bharath Viswanath AU - Ekkad, Srinath V. T2 - International Journal of Heat and Mass Transfer AB - Experimental and numerical study of flow and heat transfer in a two-pass channel featuring different rib geometries has been carried out. The thermal hydraulic performance of four different rib geometries – 45° angled, V, W and M-shaped ribs, have been reported and analyzed. The tests were performed over a Reynolds number range from 19,500 to 69,000. The channel aspect ratio was 1:1 (square), the rib-pitch-to-rib-height ratio (p/e) was 16 and the rib-height-to-channel hydraulic diameter ratio (e/Dh) was 0.125. The detailed Nusselt number distributions on the ribbed wall were obtained using transient liquid crystal thermography. Numerical simulations (using ANSYS Fluent) have been carried out to resolve the complex flow field peculiar to rib turbulator shapes, for detailed understanding of the experimentally measured heat transfer coefficients. For the numerical simulations, realizable version of k-ε model was chosen because of its ability to predict separated flows behind ribs. Also, CFD simulations have been validated with experimentally obtained pressure measurements at several locations in the two pass channel. In addition to flow validation, the numerically obtained heat transfer results are validated and compared with the experiments and discussion has been presented on the role of secondary flows, turbulent kinetic energy etc., on heat transfer augmentation due to the presence of the ribs. DA - 2016/11// PY - 2016/11// DO - 10.1016/j.ijheatmasstransfer.2016.07.015 VL - 102 SP - 1245-1256 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.07.015 DB - Crossref ER - TY - CONF TI - Effects of rotation on heat transfer due to jet impingement on cylindrical dimpled target surface AU - Singh, P. AU - Ekkad, S. AB - One way to enhance the thermal efficiency of simple gas turbines cycle is by using recuperation to recover some of the exhaust heat. Therefore, this study aims to introduce a new integrated approach to evaluate the techno-economic value of recuperator retrofit on existing industrial gas turbines. The original engines are designed for combined cycles so that the pressure ratios are moderate to secure suitable exhaust temperatures. The developed model is described and implemented for two gas turbines, and the obtained characteristics are evaluated against the actual data. This approach will help the users to select the suitable gas turbine models with favorable recuperator characteristics based on a technical and economic perspective. Besides, the performance results are used to select the optimum thermodynamic and geometrical characteristics of TEMA tubular heat exchanger so that the generated design alternatives are optimized using multi-decision process principle in order to ensure the highest techno-economic value. One of the unique features of the new method is that it depends only on the velocity of recuperator streams to derive the rest of the heat exchanger design and performance characteristics. Moreover, this paper includes a sensitivity study to investigate the effects of power setting, utilization factor and operation availability on the selected recuperator features. C2 - 2016/// C3 - Proceedings of the ASME Turbo Expo DA - 2016/// DO - 10.1115/GT2016-56145 VL - 5B-2016 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84991573843&partnerID=MN8TOARS ER - TY - JOUR TI - Analysis of film cooling performance of advanced tripod hole geometries with and without manufacturing features AU - Ramesh, Sridharan AU - Ramirez, David Gomez AU - Ekkad, Srinath V. AU - Alvin, Mary Anne T2 - International Journal of Heat and Mass Transfer AB - The present study evaluates the film cooling performance of a set of manufacturable tripod hole designs, with and without shaped exits. The tripod holes with realistic manufacturing features included rounded corners at the hole inlet and outlet, as well as a webbing between the tripod holes. Standard cylindrical and shaped cylindrical (10° fan + laidback) holes were also studied for comparative analysis. Transient heat transfer experiments with a mainstream Red ≈ 3200 were conducted on a flat plate test rig. Different hole geometries were tested at equal mass flow rates, corresponding to a range of blowing ratios equal to 0.5, 1.0, and 2.0 for the cylindrical hole. IR (Infrared) thermography was used to evaluate adiabatic film cooling effectiveness, heat transfer coefficient, and the normalized heat flux on the flat surface. Results showed that the presence of rounded corners or webbing did not lower the performance of the tripod cooling holes. Both tripod hole geometries, with and without manufacturing features, yielded higher film cooling effectiveness compared to the cylindrical holes and slightly higher effectiveness than the shaped holes, while consuming 50% less coolant when operating at the same blowing ratio. The heat transfer coefficient measurements and the overall heat flux ratios further corroborated the thermal advantages of the tripod hole design over traditional cylindrical and shaped holes. DA - 2016/3// PY - 2016/3// DO - 10.1016/j.ijheatmasstransfer.2015.11.033 VL - 94 SP - 9-19 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2015.11.033 DB - Crossref ER - TY - JOUR TI - A Diagnostic Technique for Particle Characterization Using Laser Light Extinction AU - Barboza, Kris AU - Ma, Lin AU - Todd Lowe, K. AU - Ekkad, Srinath AU - Ng, Wing T2 - Journal of Engineering for Gas Turbines and Power AB - Increased operations of aircraft, both commercial and military in hostile desert environments have increased the risk of micro-sized particle ingestion into engines. The probability of increased sand and dust ingestion results in increased life cycle costs in addition to increased potential for performance loss. Thus, the ability to accurately assess the amount of inlet debris would be useful for engine diagnostics and prognostic evaluation. Previous engine monitoring studies were based on the particle measurements performed a posteriori. Thus, there exists a need for in situ quantification of ingested particles. This paper describes the initial development of a line-of-sight optical technique to characterize the ingested particles at concentrations similar to those experienced by aircraft in brownout conditions using laser extinction with the end goal of producing an onboard aircraft diagnostic sensor. By measuring the amount of light that is transmitted due to the effects of scattering and absorption in the presence of particles over a range of concentrations, a relationship between particle diameters and the laser light extinction was obtained. This relationship was then used to obtain information on diameters and number densities of ingested particles. The particle size range of interest was chosen to be between 1 and 10 μm and the size distribution function was assumed to be lognormal. Tests were performed on polystyrene latex spheres of sizes 1.32 μm, 3.9 μm, and 5.1 μm in water dispersions to measure diameters and concentrations. Measurements were performed over multiple wavelengths to obtain information on the size distribution and number density of particles. Results of tests presented in this paper establish the validity of the laser extinction technique to provide real time information of ingested particles and will serve as an impetus to carry out further research using this technique to characterize particles. DA - 2016/5/17/ PY - 2016/5/17/ DO - 10.1115/1.4033468 VL - 138 IS - 11 LA - en OP - SN - 0742-4795 1528-8919 UR - http://dx.doi.org/10.1115/1.4033468 DB - Crossref ER - TY - JOUR TI - Sensitivity of different impingement structures to rotation AU - Yang, L. AU - Tyagi, K. AU - Ren, J. AU - Ekkad, S. AU - Jiang, H.-D. T2 - Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics DA - 2016/// PY - 2016/// VL - 37 IS - 1 SP - 37-40 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964686315&partnerID=MN8TOARS ER - TY - CONF TI - Experimental investigation of heat transfer augmentation by different jet impingement hole shapes under maximum crossflow AU - Singh, P. AU - Ravi, B.V. AU - Ekkad, S. AB - To achieve higher overall efficiency in gas turbine engines, hot gas path components are subjected to high heat transfer loads due to higher turbine inlet temperatures. Jet impingement has been extensively used especially as an internal cooling technique in the leading edge and mid-chord region of first stage vanes, which are subjected to highest heat loads. With the advent of additive manufacturing methods such as Direct Metal Laser Sintering (DMLS), designers are not limited to designing round or race track holes for impingement. The present study is focused on exploring new jet hole shapes, in an arrangement, typical of mid-chord region in a double wall cooling configuration. Transient liquid crystal experiments are carried out to study heat transfer augmentation by jet impingement on smooth target where the spent air is allowed to exit in one direction, thus imposing maximum crossflow condition. The averaged Reynolds number (based on jet hydraulic diameter) is varied from 2500 to 10000. The jet plate has a square array of jets with 7 jets in one row (total number of jets = 49), featuring hole shapes — Racetrack and V, where the baseline case is the round hole. The non-dimensional streamwise (x/dj) and spanwise (y/dj) spacing is 6 and the normalized jet-to-target-plate spacing (z/dj) is 4 and the nozzle aspect ratio (L/dj) is also 4. The criteria for the hole shape design was to keep the effective area of different hole shapes to be the same, which resulted in slightly different hydraulic diameters. The jet-to-target plate spacing (z) has been adjusted accordingly so as to maintain a uniform z/dj of 4, across all three configurations studied. Heat transfer coefficients are measured using a transient Liquid Crystal technique employing a one-dimensional semi-infinite model. Flow experiments are carried out to measure static pressures in the plenum chamber, to calculate the discharge coefficient, for a range of plenum absolute pressure-to-ambient pressure ratios. Detailed normalized Nusselt number contours have been presented, to identify the regions of high heat transfer augmentation locally, so as to help the designers in the organization of jet hole shapes and their patterns in an airfoil depending upon the active heat loads. C2 - 2016/// C3 - Proceedings of the ASME Turbo Expo DA - 2016/// DO - 10.1115/GT2016-57874 VL - 5B-2016 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84991628479&partnerID=MN8TOARS ER - TY - CONF TI - Analysis on impact of turbulence parameters and swirl angle variation on isothermal gas turbine combustor flows AU - Kedukodi, S. AU - Gomez-Ramirez, D. AU - Ekkad, S.V. AU - Moon, H.-K. AU - Kim, Y. AU - Srinivasan, R. AB - The current computational study deals with the isothermal fluid flow and heat transfer analysis of a gas turbine combustor subject to different boundary conditions. A 90 degree sector model was studied computationally in order to identify the impingement and peak heat transfer locations along the combustor liner in addition to heat transfer augmentation. Validation experiments were carried out for the full scale industrial swirler-fuel nozzle using PIV and IR thermography to obtain flow and heat transfer data. Inlet conditions into the swirler were set to a Reynolds number of 50000 and the outlet was set to atmospheric conditions. The swirler vanes provided a radially varying swirl to the flow entering into the combustor. The k-w SST turbulence model was employed to investigate the effects of different inlet turbulence parameters on the accuracy of the simulation, i.e., calculations with experimental inlet turbulent kinetic energy and deduced dissipation rate profiles, and prescribed constant turbulent intensity and length scale. It was observed that the former provided conforming results with the experiments at specific locations and improved convergence, while both cases showed discrepancy in velocity profiles within the central recirculation region of the combustor. The peak heat transfer and impingement location along the liner were in excellent agreement with the experimental data. However the peak magnitude prediction was over-predicted up to 27%. This discrepancy was attributed to the limitations of two-equation turbulence model predictions near the stagnation region. An additional study was performed to investigate the effect of different inlet swirl angles on the impingement location. It was observed that a higher swirl angle shifts the impingement location upstream. Overall, the present study provides a probe into the capability of steady RANS models to predict combustor swirling flows and wall heat transfer; and also aids in using the steady state results as initialization data for the future scale resolved turbulence model based simulations. In spite of the quantitative discrepancies, the liner heat transfer trends are expected to provide valuable insight to the industrial community in the design of combustor liners based on less expensive computational tools. C2 - 2016/// C3 - ASME 2016 Heat Transfer Summer Conference, HT 2016, collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels DA - 2016/// DO - 10.1115/HT2016-7134 VL - 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85002934475&partnerID=MN8TOARS ER - TY - JOUR TI - Effect of pulse current on the mechanical properties and fracture behaviors of Al-Mg alloys AU - Fan, R. AU - Zhao, K. AU - Ren, D. AU - Zikry, M.A. T2 - Zhongguo Kexue Jishu Kexue/Scientia Sinica Technologica AB - The influence of pulse electric current to aluminum’s flow stress and elongation under high electric energy density (0.150 J/mm3) and low energy density (0.105 J/mm3) are investigated. Since the temperatures generated by electric current are identical under same energy density with different electric conditions, non-Joule heating effect under electrically assisted forming can be proven. The results show that pulse current help to reduce aluminum’s flow stress and increase its elongation. Under the same energy density, as the density of pulse current increased, although the maximum flow stress remains unchanged, the instant stress drop due to pulse current increases as well as its elongation. Stress recovery model is proposed to estimate the stress drop under tension. The number of fracture dimple continues to decrease until completely disappearance as the density of pulse current increases; the increase of elongation results from the suppression of the nucleation and growth of voids by pulse current. DA - 2016/// PY - 2016/// DO - 10.1360/N092016-00098 VL - 46 IS - 7 SP - 717-721 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84982859304&partnerID=MN8TOARS ER - TY - CONF TI - Modeling Filtration Performance of Nanofiber Media, Nanofibers AU - Saleh, A.M. AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - Applications, and Related Technologies (NART) C2 - 2016/9/13/ CY - Raleigh, North Carolina DA - 2016/9/13/ PY - 2016/9/13/ ER - TY - CONF TI - Structural Simulation of Nanofibrous Materials with Different Fiber Rigidities AU - Venkateshan, D.G. AU - Yousefi, S. AU - Tahir, M.A. AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - Nanofibers, Applications, and Related Technologies (NART) C2 - 2016/9/13/ CY - Raleigh, North Carolina DA - 2016/9/13/ PY - 2016/9/13/ ER - TY - CONF TI - Modeling Water Droplet Equilibrium Shape on Fibers with Trilobal Cross-Sections AU - Ameri, M.M. AU - Tafreshi, H.V. T2 - Nanofibers, Applications, and Related Technologies (NART) C2 - 2016/9/13/ CY - Raleigh, North Carolina DA - 2016/9/13/ PY - 2016/9/13/ ER - TY - CONF TI - Electrospun Mats with Orthogonal Fibers for Aerosol Filtration and/or Water Repellency Applications: A Computational Study AU - Bucher, T.M. AU - Ameri, M.M. AU - Tafreshi, H.V. T2 - Nanofibers, Applications, and Related Technologies (NART) C2 - 2016/9/13/ CY - Raleigh, North Carolina DA - 2016/9/13/ PY - 2016/9/13/ ER - TY - CONF TI - Modeling Detachment of A Droplet from A Fiber Crossover AU - Amrei, M.M. AU - Tafreshi, H.V. T2 - American Filtration and Separation Society C2 - 2016/5/9/ CY - Houston, Texas DA - 2016/5/9/ PY - 2016/5/9/ ER - TY - CONF TI - Modeling Performance of Pleated Filters under Dust-Loading Condition AU - Saleh, A. AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - American Filtration and Separation Society C2 - 2016/5/9/ CY - Houston, Texas DA - 2016/5/9/ PY - 2016/5/9/ ER - TY - JOUR TI - Wetting states of superhydrophobic surfaces made of polygonal pores or posts AU - Hemeda, A. A. AU - Amrei, M. M. AU - Tafreshi, H.V. T2 - Journal of Applied Physics AB - In this work, a mathematical framework is developed to describe some of the important intermediate wetting states of a superhydrophobic surface between the two extreme states of Cassie and Wenzel. The superhydrophobic surfaces considered here are comprised of sharp-edged polygonal pores or posts. Two different critical pressures are defined in this work, and used to distinguish pinned, partially pinned, and de-pinned air–water interfaces from one another. This information, in particular, is used to develop predictive expressions for the critical pressure and wetted area of the surfaces. Good agreement is observed between the predictions of our expressions and those obtained from numerical calculations or experiment. The work presented here compares the pressure-dependent performances of the superhydrophobic surfaces having different pore or post designs with one another. DA - 2016/5/7/ PY - 2016/5/7/ DO - 10.1063/1.4948336 VL - 119 IS - 17 SP - 175304 SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4948336 ER - TY - JOUR TI - Modeling effects of fiber rigidity on thickness and porosity of virtual electrospun mats AU - Venkateshan, D.G. AU - Tahir, M.A. AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - Materials & Design AB - Despite the widespread applications of electrospun fibers, there is still no accurate method to measure the thickness or porosity of thin electrospun mats. The current study is devised to develop a modeling approach toward solving this problem by simulating the 3-D structure of nanofiber mats. The uniqueness of our algorithm is in its ability to capture how the fibers conform to the geometry of the surface on which they deposit. This feature is important for predicting how the thickness of a nanofiber mat grows as fibers continue to deposit on the collector. Our algorithm is implemented in a C ++ computer program, and is used to study the effects of fiber rigidity, fiber diameter(s), and fiber orientation on the thickness and porosity of electrospun mats. Contrary to the common belief, it was shown that reducing fiber diameter, while maintaining the total weight of the material constant, does not necessarily lead to an increase in the thickness and porosity of the resulting mat. The thickness and porosity of electrospun mats were shown to depend on fibers' tendency to bend at the fiber–fiber crossovers, which may vary depending on the properties of the fibers and the electrospinning process conditions. DA - 2016/4// PY - 2016/4// DO - 10.1016/j.matdes.2016.01.105 VL - 96 SP - 27–35 SN - 0264-1275 UR - http://dx.doi.org/10.1016/j.matdes.2016.01.105 KW - Electrospinning KW - Modeling electrospun mats KW - Fibrous materials KW - Nanofibers ER - TY - JOUR TI - An analytical approach to predict pressure drop and collection efficiency of dust-load pleated filters AU - Saleh, A.M. AU - Tafreshi, H. Vahedi AU - Pourdeyhimi, B. T2 - Separation and Purification Technology AB - In this work, a series of first-principle analytical expressions are derived to predict the instantaneous pressure drop and collection efficiency of pleated filters under dust loading condition. Both the depth and surface filtration regimes are formulated for filters with triangular and rectangular pleats. The analytical expressions derived in this paper can be used in the early stages of designing a pleated filter to circumvent the need for conducting CPU-intensive numerical calculations. The predictions of our analytical expressions are compared with those reported in previous studies and good agreement is observed. DA - 2016/3// PY - 2016/3// DO - 10.1016/j.seppur.2016.01.034 VL - 161 SP - 80-87 J2 - Separation and Purification Technology LA - en OP - SN - 1383-5866 UR - http://dx.doi.org/10.1016/j.seppur.2016.01.034 DB - Crossref KW - Filtration theory KW - Mathematical modeling KW - Filter media ER - TY - JOUR TI - Liquid–Infused Surfaces with Trapped Air (LISTA) for Drag Force Reduction AU - Hemeda, A. A. AU - Tafreshi, H. Vahedi T2 - Langmuir AB - Superhydrophobic (SHP) surfaces are known for their drag-reducing attributes thanks to their ability to trap air in their surface pores and thereby reduce the contact between water and the frictional solid area. SHP surfaces are prone to failure under elevated pressures or because of air-layer dissolution into the surrounding water. Slippery liquid-infused porous surfaces (SLIPS) or liquid-infused surfaces (LIS) in which the trapped air is replaced with a lubricant have been proposed in the literature as a way of eliminating the air dissolution problem as well as improving the surface stability under pressure. While an LIS surface has been shown to reduce drag for flow of water-glycerol mixture (ref 18), no significant drag reduction has yet been reported for the flow of water (a lower viscosity fluid) over LIS. In this concern, we have designed a new surface in which a layer of air is trapped underneath the infused lubricant to reduce the frictional forces preventing the LIS to provide drag reduction for water or any fluid with a viscosity less than that of the lubricant. Drag reduction performance of such surfaces, referred to here as liquid-infused surfaces with trapped air (LISTA), is predicted by solving the biharmonic equation for the water-oil-air three-phase system in transverse grooves with enhanced meniscus stability thanks to double-reentry designs. For the arbitrary dimensions considered in our proof-of-concept study, LISTA designs showed 20-37% advantage over their LIS counterparts. DA - 2016/3/15/ PY - 2016/3/15/ DO - 10.1021/acs.langmuir.5b04754 VL - 32 IS - 12 SP - 2955-2962 J2 - Langmuir LA - en OP - SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/acs.langmuir.5b04754 DB - Crossref ER - TY - JOUR TI - Flow-enhanced kinetics of uranyl (UO2) transport into nano-porous silica gel AU - Dodd, Brandon M. AU - Tafreshi, Hooman V. AU - Tepper, Gary C. T2 - Materials & Design AB - Uranyl transport into nanoporous silica gel is limited in a static aqueous solution by slow natural diffusion to the open bonding sites. In order to make this process faster, the diffusion dependence was eliminated using pressure driven fluid flow. Uranyl transport and adsorption within nanoporous silica gel was measured using time-dependent fluorescent measurements in an aqueous solution. The transport kinetics was measured under two different conditions: static solution in a standard cuvette and flowing solution through the silica gel. It was determined that the kinetics of uranyl uptake within nanoporous silica gel depends strongly on the liquid flow velocity. Above a certain velocity, the adsorption kinetics increased by at least two orders of magnitude (from about 40 min to 2 s) in comparison to a static solution. In a static solution, the kinetics depends on the porosity of the silica gel, but this dependence was not observed when the liquid flow velocity exceeded a certain value. Flow-enhanced adsorption kinetics has potential applications for fast detection of trace levels of uranyl in water. DA - 2016/9// PY - 2016/9// DO - 10.1016/j.matdes.2016.05.107 VL - 106 SP - 330-335 J2 - Materials & Design LA - en OP - SN - 0264-1275 UR - http://dx.doi.org/10.1016/j.matdes.2016.05.107 DB - Crossref KW - Silica gel KW - Transport kinetics KW - Uranyl KW - Detection KW - Fluorescence ER - TY - CONF TI - On the Underwater Performance of Superhydrophobic Fibrous Coatings AU - Tafreshi, H.V. T2 - American Filtration and Separation Society C2 - 2016/5/9/ C3 - American Filtration and Separation Society CY - Houston, Texas DA - 2016/5/9/ PY - 2016/5/9/ ER - TY - JOUR TI - Novel Approach to Measuring the Droplet Detachment Force from Fibers AU - Amrei, M. M. AU - Venkateshan, D. G. AU - D’Souza, N. AU - Atulasimha, J. AU - Tafreshi, H. Vahedi T2 - Langmuir AB - Determining the force required to detach a droplet from a fiber or from an assembly of fibers is of great importance to many applications. A novel technique is developed in this work to measure this force experimentally by using ferrofluid droplets in a magnetic field. Unlike previous methods reported in the literature, our technique does not require air flow or a mechanical object to detach the droplet from the fiber(s); therefore, it simplifies the experiment and also allows one to study the capillarity of the droplet-fiber system in a more isolated environment. In this article, we investigated the effects of the relative angle between intersecting fibers on the force required to detach a droplet from the fibers in the in-plane or out-of-plane direction. The in-plane and through-plane detachment forces were also predicted via numerical simulation and compared with the experimental results. Good agreement was observed between the numerical and experimental results. It was found that the relative angle between intersecting fibers has no significant effect on the detachment force in the out-of-plane direction. However, the detachment force in the in-plane direction depends strongly on the relative angle between the fibers, and it increases as this angle increases. DA - 2016/12/8/ PY - 2016/12/8/ DO - 10.1021/acs.langmuir.6b03198 VL - 32 IS - 50 SP - 13333-13339 J2 - Langmuir LA - en OP - SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/acs.langmuir.6b03198 DB - Crossref ER - TY - JOUR TI - Failure pressures and drag reduction benefits of superhydrophobic wire screens AU - Venkateshan, D.G. AU - Amrei, M.M AU - Hemeda, A.A. AU - Cullingsworth, Z. AU - Corbett, J. AU - Tafreshi, H.V. T2 - Colloids and Surfaces A: Physicochemical and Engineering Aspects AB - This work presents a detailed study on the failure pressure of spray-coated superhydrophobic wire screens in terms of their geometric and wetting properties. Such information is needed in designing fluid–fluid or fluid–air separation/barrier media as well as drag reducing and self-cleaning surfaces, amongst many others. Good agreement has been observed between the results of our numerical simulations and the experimental data for failure pressure. In addition, the wetted area of the screens was calculated and used to predict their drag reduction benefits when used in a Couette flow configuration under different operating pressures. Interestingly, it was found that operating pressure in the Couette configuration does not significantly affect the drag reducing effects of the screens. DA - 2016/12// PY - 2016/12// DO - 10.1016/j.colsurfa.2016.09.087 VL - 511 SP - 247–254 SN - 0927-7757 UR - http://dx.doi.org/10.1016/j.colsurfa.2016.09.087 KW - Superhydrophobic wire screens KW - Breakthrough pressure KW - Wetting KW - Air-water interface KW - Slip length ER - TY - CONF TI - An Investigation into Piezoelectrically Induced Bistability AU - Lee, A.J. AU - Moosavian, A. AU - Inman, D.J. T2 - 27th International Conference on Adaptive Structures and Technologies C2 - 2016/10/3/ C3 - 27th International Conference on Adaptive Structures and Technologies CY - Lake George, NY DA - 2016/10/3/ PY - 2016/10/3/ ER - TY - JOUR TI - A Concentric Tube Continuum Robot with Piezoelectric Actuation for MRI-Guided Closed-Loop Targeting AU - Su, H. AU - Li, G. AU - Rucker, D.C. AU - Webster, R.J., III AU - Fischer, G.S. T2 - Annals of Biomedical Engineering DA - 2016/// PY - 2016/// ER - TY - JOUR TI - Verification of the flexoelectricity in barium strontium titanate through d33 meter AU - Shu, Longlong AU - Wang, Tong AU - Jiang, Xiaoning AU - Huang, Wenbin T2 - AIP Advances AB - Flexoelectricity is a newly arising electromechanical property that couples strain gradient to polarization. This physical property widely exists in most of the solid dielectrics but has quite weak response that often overlooked. Recently, barium strontium titanate (BST), a well-known ferroelectrics, has been reported to be a promising flexoelectric material, and thus triggered the associated studies on flexoelectricity to a new height. However, part of the researchers argued the observed flexoelectricity in BST is either by residual piezoelectricity or centric symmetry breaking during the densification process. In this paper, we would verify the flexoelectricity in BST ceramics by many comparison experiments. Our experimental result suggested the observed polarization in BST material is likely to be induced by strain gradient through flexoelectricity. DA - 2016/12// PY - 2016/12// DO - 10.1063/1.4968524 VL - 6 IS - 12 SP - 125003 J2 - AIP Advances LA - en OP - SN - 2158-3226 UR - http://dx.doi.org/10.1063/1.4968524 DB - Crossref ER - TY - JOUR TI - 3 Dimensional-Printed Micro-Container with Graphene Current Collector and Manganese Oxide Thin-Film as Cathodes of Li-Batteries AU - Gill, Waqas A. AU - Ali, Dima AU - Choi, Daniel S. AU - Park, Jung-Rae AU - Ryu, Jong Eun AU - Kim, Young Keun T2 - Nanoscience and Nanotechnology Letters DA - 2016/12/1/ PY - 2016/12/1/ DO - 10.1166/nnl.2016.2273 VL - 8 IS - 12 SP - 1095-1098 J2 - Nanosci Nanotechnol Lett LA - en OP - SN - 1941-4900 1941-4919 UR - http://dx.doi.org/10.1166/nnl.2016.2273 DB - Crossref ER - TY - JOUR TI - Scalable nanoparticle assembly on carbon nanotubes using flash-induced dewetting AU - Espich, Taylor AU - Salcedo, Eduardo AU - Kulkarni, Ameya AU - Sung Choi, Daniel AU - Ryu, Jong Eun T2 - Journal of Composite Materials AB - Nanoparticle assembly through a novel photothermal dewetting was demonstrated on a macro-scale carbon nanotube (CNT) film. Intense pulsed Xe-light (IPL) was applied to transform a gold (Au) thin-film on CNT into nanoparticles (NPs). Au films measuring 3, 6, and 9 nm were completely dewetted by 10, 20, and 35 J/cm 2 of IPL intensities, respectively. The means of NP diameters after dewetting were 7.25 nm (standard deviation, σ = 2.23 nm), 13.07 nm ( σ = 2.38 nm), and 21.02 nm ( σ = 5.86 nm) for the 3, 6, and 9 nm of Au films, respectively. On the other hand, the means of Au NPs formed by furnace annealing were 13.16 nm ( σ = 1.78 nm) and 20.98 nm ( σ = 15.60 nm) for 6 and 9 nm of Au films, respectively. The 6 and 9 nm of Au films on CNTs were annealed in a furnace at 300 and 400℃, respectively. The distributions of NPs induced by IPL were not significantly different from the result of conventional furnace annealing ( p values = 0.45 and 0.96 for 6 and 9 nm Au films, respectively). Finally, thermodynamic stability of IPL dewetted NPs was evaluated by comparing the samples treated with multiple IPL up to five times and with extended thermal annealing up to 10 h. DA - 2016/12/6/ PY - 2016/12/6/ DO - 10.1177/0021998316682310 VL - 51 IS - 9 SP - 1299-1305 J2 - Journal of Composite Materials LA - en OP - SN - 0021-9983 1530-793X UR - http://dx.doi.org/10.1177/0021998316682310 DB - Crossref KW - Carbon nanotubes KW - nanoparticles KW - IPL KW - Xenon flash annealing KW - dewetting KW - photothermal ER - TY - JOUR TI - Retraction notice to Processing, characterization and failure analysis of a novel thin sheet metal [Mater. Des. 86(2016) 752–760] AU - Rabiei, Afsaneh T2 - Materials & Design DA - 2016/7// PY - 2016/7// DO - 10.1016/J.MATDES.2016.04.035 VL - 101 SP - 366 J2 - Materials & Design LA - en OP - SN - 0264-1275 UR - http://dx.doi.org/10.1016/J.MATDES.2016.04.035 DB - Crossref ER - TY - JOUR TI - Effects of noise on symmetric intrinsic localized modes AU - Perkins, Edmon AU - Kimura, Masayuki AU - Hikihara, Takashi AU - Balachandran, Balakumar T2 - Nonlinear Dynamics DA - 2016/// PY - 2016/// VL - 85 IS - 1 SP - 333-341 ER - TY - JOUR TI - Nonlinear Control of a Robot Manipulator with a Nonholonomic Jerk Constraint AU - Rubio-Hervas, J.R. AU - Reyhanoglu, M. T2 - Asian Journal of Control AB - Abstract We study the control of a prismatic‐prismatic‐revolute (PPR) robot manipulator subject to a nonholonomic jerk constraint, i.e., a third‐order nonintegrable design constraint. The mathematical model is obtained using the method of Lagrange multipliers. The control inputs are two forces and a torque applied to the prismatic joints and the revolute joint, respectively. The control objective is to control the robot end‐effector movement while keeping the transverse jerk component as zero. The main result of the paper is the construction of a feedback control algorithm that transfers the manipulator from any initial equilibrium configuration to the zero equilibrium configuration in finite time. The effectiveness of the algorithm is illustrated through a simulation example. DA - 2016/7// PY - 2016/7// DO - 10.1002/asjc.1254 VL - 18 IS - 4 SP - 1566-1573 KW - Higher-order nonholonomic constraints KW - robot manipulators ER - TY - CONF TI - Teaching and Learning of Engineering Topics with Software Tools AU - Xu, C. AU - Wentworth, S. AU - Mousavinezhad, H. T2 - ASEE Annual Conference & Exposition. ASEE Annual Conference & Exposition C2 - 2016/// CY - New Orleans, CA DA - 2016/// ER - TY - CONF TI - Modeling and control of a flexible-structure-mounted manipulator AU - Reyhanoglu, Mahmut AU - Hoffman, Derek T2 - 2016 IEEE International Conference on Advanced Intelligent Mechatronics (AIM) AB - This paper studies the modeling and control problem for a robot manipulator consisting of a flexible first link and rigid second link. A nonlinear dynamical model is first derived using a Lagrangian formulation. A Lyapunov-based feedback control law is then introduced to achieve a slew maneuver of the rigid link while suppressing bending vibrations in the flexible link. The asymptotic stability of the closed-loop system is proven using LaSalle's invariance principle. Computer simulation results are included to illustrate the effectiveness of the proposed control design. C2 - 2016/7// C3 - 2016 IEEE International Conference on Advanced Intelligent Mechatronics (AIM) DA - 2016/7// DO - 10.1109/AIM.2016.7576892 PB - IEEE SN - 9781509020652 UR - http://dx.doi.org/10.1109/AIM.2016.7576892 DB - Crossref ER - TY - CONF TI - Robust and adaptive nonlinear regulation of thermoacoustic oscillations in Rijke-type systems AU - MacKunis, William AU - Reyhanoglu, Mahmut AU - Kidambi, Krishna Bhavithavya AU - Hervas, Jaime Rubio T2 - 2016 IEEE International Conference on Advanced Intelligent Mechatronics (AIM) AB - Nonlinear control of self-excited oscillations in a Rijke-type thermoacoustic system is considered. A commonly used thermoacoustic model with a number of monopole-like actuators is first introduced. The model is expressed in a nonlinear control-oriented form, which includes unmodeled nonlinearities and parametric uncertainty in both the thermoacoustic dynamics and in the actuator dynamics. A robust and adaptive nonlinear control law is developed to compensate for the parametric uncertainty and unmodeled nonlinearities. Challenges in the control design include input-multiplicative parametric uncertainty. This challenge is mitigated through careful algebraic manipulation in the regulation error system development along with a Lyapunov-based adaptive law. A rigorous Lyapunov-based stability analysis is used to prove that the nonlinear controller achieves asymptotic regulation of an uncertain thermoacoustic system with multiple modes. C2 - 2016/7// C3 - 2016 IEEE International Conference on Advanced Intelligent Mechatronics (AIM) DA - 2016/7// DO - 10.1109/aim.2016.7576873 PB - IEEE SN - 9781509020652 UR - http://dx.doi.org/10.1109/aim.2016.7576873 DB - Crossref ER - TY - JOUR TI - Nonlinear control of fixed-wing UAVs in presence of stochastic winds AU - Rubio Hervas, Jaime AU - Reyhanoglu, Mahmut AU - Tang, Hui AU - Kayacan, Erdal T2 - Communications in Nonlinear Science and Numerical Simulation AB - This paper studies the control of fixed-wing unmanned aerial vehicles (UAVs) in the presence of stochastic winds. A nonlinear controller is designed based on a full nonlinear mathematical model that includes the stochastic wind effects. The air velocity is controlled exclusively using the position of the throttle, and the rest of the dynamics are controlled with the aileron, elevator, and rudder deflections. The nonlinear control design is based on a smooth approximation of a sliding mode controller. An extended Kalman filter (EKF) is proposed for the state estimation and filtering. A case study is presented: landing control of a UAV on a ship deck in the presence of wind based exclusively on LADAR measurements. The effectiveness of the nonlinear control algorithm is illustrated through a simulation example. DA - 2016/4// PY - 2016/4// DO - 10.1016/j.cnsns.2015.08.026 VL - 33 SP - 57-69 J2 - Communications in Nonlinear Science and Numerical Simulation LA - en OP - SN - 1007-5704 UR - http://dx.doi.org/10.1016/j.cnsns.2015.08.026 DB - Crossref KW - Nonlinear control KW - State estimation KW - Extended Kalman filter ER - TY - CONF TI - Combined plant and controller performance analysis and optimization for an energy-harvesting tethered wing AU - NikpoorParizi, Parvin AU - Deodhar, Nihar AU - Vermillion, Christopher T2 - 2016 American Control Conference (ACC) AB - This paper presents a combined plant and controller analysis and optimization for a tethered rigid wing with on-board rotors, flying in crosswind patterns. Specifically, we use a 3-D model of the tethered wing to assess the influence of critical design parameters on both quality of flight and energy generation performance, as quantified by the “Loyd Factor” [1], which compares energy generation performance to a theoretical upper bound established by Miles Loyd [2]. Recognizing that the optimal performance occurs when the system is on the verge of instability, we demonstrate how a combined optimization of the plant and controller can aid in further pushing the boundaries of the system. The results of this combined optimization show a critical trade-off between robustness and energy generation performance, wherein the attainment of peak performance not only requires operation on the verge of instability but also results in the shrinking of the set of parameters for which the system is stable. C2 - 2016/7// C3 - 2016 American Control Conference (ACC) DA - 2016/7// PY - 2016/7/5/ DO - 10.1109/acc.2016.7525564 PB - IEEE SN - 9781467386821 UR - http://dx.doi.org/10.1109/acc.2016.7525564 ER - TY - CONF TI - Disturbance and Performance-Weighted Iterative Learning Control With Application to Modulated Tool Path-Based Manufacturing AU - DiMarco, Christopher AU - Vermillion, Christopher AU - Ziegert, John C. T2 - ASME 2016 Dynamic Systems and Control Conference AB - Single-point metal turning processes can create chip nests that are hazards to both parts and machine tools. This is mitigated by a process called Modulated Tool Path (MTP) machining, which superimposes an oscillation in the tool tip feed direction in order to break these chips and provide an adequate surface finish. MTP machining is highly sensitive to the amplitude and frequency of this oscillation, both of which can often be diminished by standard machine tool controllers. These controllers are also unresponsive to iteration-varying disturbances such as temperature fluctuations, which can cause positional and velocity-related inaccuracies. This paper presents a library-based variant of Iterative Learning Control (ILC) called Disturbance and Performance-Weighted ILC (DPW-ILC), which is designed to improve the accuracy of machine tool trajectories that are highly oscillatory in nature, as well as provide robustness to varying, but measurable disturbances. DPW-ILC has been shown in simulation to provide a tremendous accuracy benefit over standard ILC techniques, specifically in the presence of two separate types of temperature-based disturbances. C2 - 2016/10/12/ C3 - ASME 2016 Dynamic Systems and Control Conference : October 12-14, 2016, Minneapolis, Minnesota, USA CY - Minneapolis, Minnesota DA - 2016/10/12/ PY - 2016/10/12/ DO - 10.1115/dscc2016-9898 VL - 2 PB - American Society of Mechanical Engineers SN - 9780791850701 UR - http://dx.doi.org/10.1115/dscc2016-9898 ER - TY - JOUR TI - Micro-capacitor with vertically grown silver nanowires and bismuth ferric oxide composite structures on silicon substrates AU - Choi, Daniel AU - An, Boo Hyun AU - Mansouri, Mariam AU - Ali, Dima AU - Khalil, Malathe AU - Xu, Ke AU - Nwoke, Dominic AU - Park, Jung-Rae AU - Shankar, Akash AU - Ryu, Jong Eun T2 - Journal of Composite Materials AB - We have designed and demonstrated a complementary metal-oxide-semiconductor compatible process for fabricating high capacitance micro-capacitors based on vertically grown silver nanowires on silicon substrates. Array of silver nanowires with high-aspect ratio were electrochemically grown in the pores of anodized aluminum oxide film, which was pre-formed through anodization of aluminum thin film deposited on titanium/silicon oxide/silicon substrates. High dielectric bismuth ferric oxide layer was electrodeposited to fill the gap between silver nanowires after anodized aluminum oxide film was removed. It was found that the micro-capacitor based on the silver nanowires/bismuth ferric oxide composite film possessed higher capacitance by approximately one order of magnitude from the COMSOL simulation results from the flat Ag thin-film capacitor and the silver nanowire capacitor. DA - 2016/7/28/ PY - 2016/7/28/ DO - 10.1177/0021998316656767 VL - 51 IS - 7 SP - 965-969 J2 - Journal of Composite Materials LA - en OP - SN - 0021-9983 1530-793X UR - http://dx.doi.org/10.1177/0021998316656767 DB - Crossref KW - Micro-capacitor KW - silver nanowires KW - nanocomposites KW - energy storage ER - TY - CONF TI - Effects of fuel quantity on soot formation process for biomass-based renewable diesel fuel combustion AU - Jing, W. AU - Wu, Z. AU - Roberts, W.L. AU - Fang, T. C2 - 2016/// C3 - ASME 2016 Internal Combustion Engine Fall Technical Conference, ICEF 2016 DA - 2016/// DO - 10.1115/ICEF20169380 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85012013277&partnerID=MN8TOARS ER - TY - JOUR TI - Projecting long-term non-Fickian diffusion behavior in polymeric composites based on short-term data: a 5-year validation study AU - Grace, Landon R. T2 - Journal of Materials Science DA - 2016/1// PY - 2016/1// DO - 10.1007/S10853-015-9407-0 VL - 51 IS - 2 SP - 845–853 SN - 0022-2461 1573-4803 UR - http://dx.doi.org/10.1007/S10853-015-9407-0 KW - Moisture absorption KW - Hindered diffusion KW - Bismaleimide KW - Laminate ER - TY - JOUR TI - Optimization of excess system capability for increased evolvability AU - Watson, J. D. AU - Allen, J. D. AU - Mattson, C. A. AU - Ferguson, S. M. T2 - Structural and Multidisciplinary Optimization DA - 2016/1/9/ PY - 2016/1/9/ DO - 10.1007/S00158-015-1378-X VL - 53 IS - 6 SP - 1277-1294 J2 - Struct Multidisc Optim LA - en OP - SN - 1615-147X 1615-1488 UR - http://dx.doi.org/10.1007/S00158-015-1378-X DB - Crossref KW - Evolvability KW - Reconfigurability KW - Flexibility KW - Excess KW - Complex systems KW - Multi-objective optimization ER - TY - JOUR TI - Can numerical modeling help understand the fate of tau protein in the axon terminal? AU - Kuznetsov, I.A. AU - Kuznetsov, A.V. T2 - Computer Methods in Biomechanics and Biomedical Engineering AB - In this paper, we used mathematical modeling to investigate the fate of tau protein in the axon terminal. We developed a comprehensive model of tau transport that accounts for transport of cytosolic tau by diffusion, diffusion transport of microtubule (MT)-bound tau along the MT lattice, active motor-driven transport of MT-bound tau via slow axonal transport mechanism, and degradation of tau in the axon due to tau's finite half-life. We investigated the effect of different assumptions concerning the fate of tau in the terminal on steady-state transport of tau in the axon. In particular, we studied two possible scenarios: (i) tau is destroyed in the terminal and (ii) there is no tau destruction in the terminal, and to avoid tau accumulation we postulated zero flux of tau at the terminal. We found that the tau concentration and percentage of MT-bound tau are not very sensitive to the assumption concerning the fate of tau in the terminal, but the tau's flux and average velocity of tau transport are very sensitive to this assumption. This suggests that measuring the velocity of tau transport and comparing it with the results of mathematical modeling for different assumptions concerning tau's fate in the terminal can provide information concerning what happens to tau in the terminal. DA - 2016/1/25/ PY - 2016/1/25/ DO - 10.1080/10255842.2014.994119 VL - 19 IS - 2 SP - 115–125 SN - 1025-5842 1476-8259 UR - http://dx.doi.org/10.1080/10255842.2014.994119 KW - neuron KW - tau protein KW - diffusion KW - slow axonal transport KW - mathematical modeling ER - TY - JOUR TI - Collisional broadening of Kr (4p6S01→→5p[32]2) transition with combustion species as collision partners AU - Zelenak, Dominic AU - Sealy, William AU - Narayanaswamy, Venkateswaran T2 - Journal of Quantitative Spectroscopy and Radiative Transfer AB - Abstract Collisional broadening of krypton 4 p 6 S 0 1 → → 5 p [ 3 2 ] 2 transition centered at 107.3 nm caused by common combustion species is investigated in this work. The present work investigates the compositional and thermodynamic dependencies of the collisional parameters between collision partners with similar electronic energy level gaps. In this situation, the classical expression of dispersive energy during collisions cannot be simplified to obtain closed form equations for the collisional parameters. The broadening parameters, namely collisional full width at half maximum (wc) and collisional shift (δc) are obtained through a two-photon excitation scan of krypton (Kr) present in a mixture containing krypton and the collision partner at 295 K and 101 kPa. The compositional scaling of wc and δc are compared with scaling at situations corresponding to both large and small perturber electronic energy level gaps as compared to the absorber’s electronic energy level gap. In the Kr PLIF system, wc scaling corresponds to a situation where the perturber electronic energy level gap is significantly larger than absorber energy level gap, whereas δc scaling corresponds to when the absorber electronic energy level gap is significantly larger than the perturber electronic energy level gap. Further, contributions from non-dispersive forces are computed to be significantly smaller than dispersive forces, which results to the observed tight scaling. The observed compositional scaling is shown to be consistent with a different collisional partner system (NO as the absorber and combustion species as perturbers), indicating that the scaling obtained with the krypton system is general to situations with perturbers and absorbers having similar electronic energy level spacing. DA - 2016/5// PY - 2016/5// DO - 10.1016/J.JQSRT.2016.01.017 VL - 174 SP - 28-38 J2 - Journal of Quantitative Spectroscopy and Radiative Transfer LA - en OP - SN - 0022-4073 UR - http://dx.doi.org/10.1016/J.JQSRT.2016.01.017 DB - Crossref KW - Spectroscopy KW - Lineshape KW - Kr-PLIF KW - Collisional broadening ER - TY - JOUR TI - Failure analysis of mixed mode crack growth in heavy duty truck frame rail AU - Rao, Vinay N. AU - Eischen, Jeffrey W. T2 - Case Studies in Engineering Failure Analysis AB - A failure analysis investigation was performed on a fractured heavy duty truck frame rail obtained during endurance track testing. The fracture observed was on the frame web within the torque rod connection to the rear drive axle of the vehicle. This section of frame experiences multi-axial loading conditions including out-of-plane bending, twisting and shear under road loads. Metallographic examination revealed micro-cracks on the edges of an open hole located in an area of high stress concentration. This manufacturing defect acted as a stress raiser and resulted in fatigue crack initiation. Simulation of crack growth on frame rail using dynamic loads from a full vehicle model was completed. After careful analysis it was concluded that the failure occurred due to an aggressively drilled open hole which created small crack initiations in a high stress-state location of the frame. This resulted in extensive curvilinear crack growth under dynamic loads of the vehicle. DA - 2016/4// PY - 2016/4// DO - 10.1016/j.csefa.2016.03.002 VL - 5-6 SP - 67-74 J2 - Case Studies in Engineering Failure Analysis LA - en OP - SN - 2213-2902 UR - http://dx.doi.org/10.1016/j.csefa.2016.03.002 DB - Crossref ER - TY - CONF TI - Computer and Information Technology Tools in Signals & Systems AU - Xu, Cheryl AU - Mousavinezhad, S. T2 - 2016 ASEE Annual Conference & Exposition AB - Abstract Computer and Information Technology Tools in Signals & Systems ABSTRACT. Signals and Systems course is a junior-level course offered in engineering programs including Electrical/Computer Engineering, Computer Science and Mechanical Engineering. There are several excellent textbooks available for the subject matter but students still have difficulty in grasping many seemingly abstract concepts like various transform methods (Fourier, Laplace and z), modeling of signals & systems in time/frequency domains, discrete power spectrum, energy spectral density, bandwidth, filter input/output relations, Parseval’s theorem, convolution, signal-to-noise ratio, and transfer (system) function. Software packages like MATLAB, MATHCAD and WFILTER are useful computer IT tools so problems, examples can be presented in the class and simulations discussed after analytical results are obtained for the given problem. In our school we have offered a Signals & Systems course with pre-requisites of circuits I & II as well as differential equations (which is a co-requisite.) Since Matlab/Mathcad programs are available in our computer laboratory, these are used throughout the course. The textbook (third edition) by Kamen & Heck are used for the course and students can access the accompanying website at Georgia Tech. It should be noted that some class examples use Mathcad but the textbook uses Matlab. In our school we also have an elective course in analog and digital filters using the software tool called WFilter accompanying the textbook. As engineering educators teaching undergraduate courses we are all aware that these tools should be used at the right time, right place. Usually a problem is worked out using the analytical approach as much as possible, then software tools are used for presenting calculations, plots and extension of the problem using simulations. Since many advanced courses such as Control Systems, Analog and Digital Communication Systems, and Digital Signal Processing use the Signals & Systems course as pre-requisite and background information, it is very critical that students have a good understanding of the basic concepts before doing the simulations and “number crunching” on the computer and their graphics calculators. Authors have broad backgrounds in Mechanical Engineering as well as Electrical/Computer Engineering and use practical examples in the class to discuss the difficult concepts. Many techniques learned in the Signals & Systems course are applicable to all engineering systems such as: Electrical, Mechanical, and Chemical. The course starts by presenting many different kinds of signals including analog, digital (discrete-time), energy, power, periodic, deterministic and random. The linear, time invariant systems are presented next. Signals are analyzed in the frequency domain by using transform tools of Fourier Analysis (integral and series), discrete-time Fourier series, discrete-time Fourier transform, discrete Fourier transform (also FFT), Laplace transform and z-transform. By using the system (transfer) function the response of a given system is computed in both time & frequency domains. C2 - 2016/7/7/ C3 - 2016 ASEE Annual Conference & Exposition Proceedings DA - 2016/7/7/ DO - 10.18260/p.26552 PB - ASEE Conferences UR - http://dx.doi.org/10.18260/p.26552 DB - Crossref ER - TY - CONF TI - Nonlinear tracking control and structural vibration suppression for aircraft using synthetic jet actuators AU - Ramos-Pedroza, Natalie AU - Kidambi, Krishna Bhavithavya AU - MacKunis, William AU - Reyhanoglu, Mahmut T2 - 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV) AB - A synthetic jet actuator (SJA)-based control method is developed, which is rigorously proven to achieve accurate aircraft trajectory tracking control while simultaneously regulating limit cycle oscillations (LCO) in aircraft wings. To achieve the result, innovative tracking error system development is utilized along with a robust-inverse control structure. The robust-inverse control structure is utilized to compensate for the parametric uncertainty and nonlinearity inherent in the SJA mathematical model without the use of adaptive parameter estimation or function approximation schemes. After recasting the dynamics in a form amenable to control design, a nonlinear control law is developed, which achieves asymptotic trajectory tracking in the presence of external disturbances and structural disturbances due to LCO. A Lyapunov-based stability analysis is utilized to prove semi-global asymptotic trajectory tracking in the presence of LCO disturbances and parametric uncertainty in the SJA actuator model. Numerical simulation results are provided to demonstrate the capability of the proposed SJA-based control method to achieve simultaneous trajectory tracking and LCO regulation. C2 - 2016/11// C3 - 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV) DA - 2016/11// DO - 10.1109/icarcv.2016.7838797 PB - IEEE SN - 9781509035496 UR - http://dx.doi.org/10.1109/icarcv.2016.7838797 DB - Crossref ER - TY - CONF TI - Nonlinear output feedback tracking control of a quadrotor UAV in the presence of uncertainty AU - Stebler, Shane AU - MacKunis, William AU - Reyhanoglu, Mahmut T2 - 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV) AB - A nonlinear output feedback control method is presented, which achieves asymptotic altitude and attitude trajectory tracking of a quadrotor system in the presence of model uncertainty and unknown external disturbances. To address a practical scenario where velocity measurements are not available, a bank of dynamic filters is utilized, which acts as a velocity observer in the closed-loop system. A primary focus of the proposed control method is detailed development that shows how a computationally minimal strategy can be utilized to compensate for multiple sources of uncertainty without the use of adaptive parameter estimation or function approximators. A rigorous Lyapunov-based stability analysis is utilized to prove semi-global asymptotic trajectory tracking in the presence of parametric uncertainty and unmodelled external disturbances. Numerical simulation results are also provided to demonstrate the performance of the proposed control law. C2 - 2016/11// C3 - 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV) DA - 2016/11// DO - 10.1109/icarcv.2016.7838569 PB - IEEE SN - 9781509035496 UR - http://dx.doi.org/10.1109/icarcv.2016.7838569 DB - Crossref ER - TY - CONF TI - Observer-based sliding mode control of a 3-DOF hover system AU - Reyhanoglu, Mahmut AU - Damen, Remon AU - MacKunis, William T2 - 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV) AB - A sliding mode control (SMC) strategy is presented for a quadrotor-based hover system, which achieves asymptotic attitude regulation in the presence of electrical and physical constraints. A sliding mode observer is employed to estimate the angular velocities. In addition, the proposed control design incorporates the input voltage constraints inherent in practical systems. A rigorous Lyapunov-based analysis is provided to prove asymptotic regulation of the hover system attitude to a desired set point. Computer simulation results are also provided, which demonstrate the capability of the control law to achieve asymptotic attitude regulation when applied to the complete nonlinear system dynamics. C2 - 2016/11// C3 - 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV) DA - 2016/11// DO - 10.1109/ICARCV.2016.7838643 PB - IEEE SN - 9781509035496 UR - http://dx.doi.org/10.1109/ICARCV.2016.7838643 DB - Crossref ER - TY - CONF TI - Nonlinear modeling and control of a two-link hybrid manipulator AU - Reyhanoglu, Mahmut AU - Hoffman, Derek AU - de Wit, Jop T2 - 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV) AB - The slew maneuver problem is studied for a robot manipulator consisting of a flexible first link and rigid second link. A nonlinear dynamical model is first derived using a Lagrangian formulation. A notch-filtered finite-time control law is then introduced to achieve fast and precise slewing maneuvers without residual vibrations. The results are applied to a benchmark two-link system and a simulation example is included to illustrate the effectiveness of the proposed control technique. C2 - 2016/11// C3 - 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV) DA - 2016/11// DO - 10.1109/ICARCV.2016.7838809 PB - IEEE SN - 9781509035496 UR - http://dx.doi.org/10.1109/ICARCV.2016.7838809 DB - Crossref ER - TY - CONF TI - Nonlinear control of thermoacoustic oscillations in Rijke-type systems AU - MacKunis, William AU - Reyhanoglu, Mahmut AU - Kidambi, Krishna Bhavithavya AU - Hervas, Jaime Rubio T2 - 2016 16th International Conference on Control, Automation and Systems (ICCAS) AB - This paper presents a robust and adaptive nonlinear controller to asymptotically regulate thermoacoustic oscillations in a Rijke-type system in the presence of dynamic model uncertainty and unknown disturbances. A mathematical model that includes unmodelled nonlinearities and parametric uncertainty is first introduced. A robust and adaptive non-linear control law is then developed to compensate for the parametric uncertainty and unmodelled nonlinearities. Results of Monte Carlo-type simulations are included to demonstrate the effectiveness of the control law. C2 - 2016/10// C3 - 2016 16th International Conference on Control, Automation and Systems (ICCAS) DA - 2016/10// DO - 10.1109/ICCAS.2016.7832470 PB - IEEE SN - 9788993215113 UR - http://dx.doi.org/10.1109/ICCAS.2016.7832470 DB - Crossref ER - TY - CONF TI - Passivity-based quaternion feedback control of a hover system AU - Damen, Remon AU - Reyhanoglu, Mahmut AU - MacKunis, William AU - Hervas, Jaime Rubio T2 - 2016 16th International Conference on Control, Automation and Systems (ICCAS) AB - A passivity-based quaternion feedback control strategy is presented for a hover system (quadrotor UAV test bed), which achieves asymptotic attitude regulation. The proposed control design incorporates the input voltage constraints inherent in practical UAV systems. A rigorous Lyapunov-based analysis is provided to prove asymptotic regulation of the hover system attitude to a desired set point. Computer simulation results are also provided, which demonstrate the capability of the control law to achieve asymptotic attitude regulation when applied to the complete nonlinear system dynamics. C2 - 2016/10// C3 - 2016 16th International Conference on Control, Automation and Systems (ICCAS) DA - 2016/10// DO - 10.1109/ICCAS.2016.7832321 PB - IEEE SN - 9788993215113 UR - http://dx.doi.org/10.1109/ICCAS.2016.7832321 DB - Crossref ER - TY - JOUR TI - Nanomechanics of layer-by-layer polyelectrolyte complexes: a manifestation of ionic cross-links and fixed charges AU - Han, Biao AU - Chery, Daphney R. AU - Yin, Jie AU - Lu, X. Lucas AU - Lee, Daeyeon AU - Han, Lin T2 - Soft Matter AB - This study investigates the roles of two distinct features of ionically cross-linked polyelectrolyte networks – ionic cross-links and fixed charges – in determining their nanomechanical properties. DA - 2016/// PY - 2016/// DO - 10.1039/c5sm01430a VL - 12 IS - 4 SP - 1158-1169 J2 - Soft Matter LA - en OP - SN - 1744-683X 1744-6848 UR - http://dx.doi.org/10.1039/c5sm01430a DB - Crossref ER - TY - JOUR TI - Programmable Kiri-Kirigami Metamaterials AU - Tang, Yichao AU - Lin, Gaojian AU - Yang, Shu AU - Yi, Yun Kyu AU - Kamien, Randall D. AU - Yin, Jie T2 - Advanced Materials AB - Programmable kirigami metamaterials with controllable local tilting orientations on demand through prescribed notches are constructed through a new approach of kiri-kirgami, and their actuation of pore opening via both mechanical stretching and temperature, along with their potential application as skins for energy-saving buildings, is discussed. DA - 2016/12/27/ PY - 2016/12/27/ DO - 10.1002/adma.201604262 VL - 29 IS - 10 SP - 1604262 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 UR - http://dx.doi.org/10.1002/adma.201604262 DB - Crossref ER - TY - JOUR TI - Reinforcement of Cu nanoink sintered film with extended carbon nanofibers for large deformation of printed electronics AU - Kim, Jeonghwan AU - Shankar, Akash AU - Zhu, Jiahua AU - Choi, Daniel S AU - Guo, Zhanhu AU - Ryu, Jong E T2 - Journal of Composite Materials AB - Metallic nanoparticle inks (nanoinks) have attracted great interest in the manufacturing of printed flexible electronics. However, sintering pure nanoinks in ambient conditions results in micro-cracks and pores within the sintered film, which deteriorate the mechanical and electrical characteristics of the sintered nanoinks. To alleviate these problems, we demonstrate the use of very long carbon nanofiber (average length 200 µm) to reinforce the sintered nanoink films. In this study, different weight fractions of carbon nanofiber are dispersed into the Cu nanoink to improve the mechanical bending characteristics. Scanning electron micrographs show improved dispersion of oxidized carbon nanofiber in the nanoink compared to the as-received carbon nanofiber. The composite nanoinks are stencil printed on polyethylene terephthalate film and sintered by intense pulsed light using Xe-flash. The electrical measurements show 90%, 65%, and 66% improved electrical conductivity in the composite nanoink film (0.7% of oxidized carbon nanofiber) compared to the pure Cu nanoink under the 7.5 cm, 5.0 cm, and 2.5 cm of bending radii, respectively. DA - 2016/7/28/ PY - 2016/7/28/ DO - 10.1177/0021998316656394 VL - 51 IS - 7 SP - 997-1003 J2 - Journal of Composite Materials LA - en OP - SN - 0021-9983 1530-793X UR - http://dx.doi.org/10.1177/0021998316656394 DB - Crossref KW - Printed electronics KW - flexible electronics KW - carbon nanofiber KW - nanoink KW - intense pulsed light KW - photonic sintering KW - nanofiber reinforcement ER - TY - CONF TI - Real-time altitude optimization of airborne wind energy systems using Lyapunov-based switched extremum seeking control AU - Bafandeh, Alireza AU - Vermillion, Chris T2 - 2016 American Control Conference (ACC) 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 evaluate the stability and convergence of this control algorithm for the application at hand. Achievement of the optimal altitude to maximize energy production requires use of energy in order to search for the optimal altitude, which is continually and randomly varying. The simultaneous desires to optimize altitude and minimize control energy consumption are balanced in this paper through a variant of extremum seeking 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 vs. altitude) is subject to continual variations, this application represents a challenging case study in LSES control. Using real wind shear data, 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 extremum seeking strategies. C2 - 2016/7// C3 - 2016 American Control Conference (ACC) DA - 2016/7// DO - 10.1109/acc.2016.7526144 PB - IEEE SN - 9781467386821 UR - http://dx.doi.org/10.1109/acc.2016.7526144 DB - Crossref ER - TY - CONF TI - A Framework for Fused Experimental/Numerical Plant and Control System Optimization Using Iterative G-Optimal Design of Experiments AU - Deodhar, Nihar AU - Vermillion, Christopher T2 - ASME 2016 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference AB - This paper presents a methodology for optimally fusing experiments and numerical simulations in the design of a combined plant and control system. The proposed methodology uses G-optimal Design of Experiments to balance the need for experimental data with the expense of collecting a multitude of experimental results. Specifically, G-optimal design is used to first select a batch of candidate experimental configurations, then determine which of those points to test experimentally and which to numerically simulate. The optimization process is carried out iteratively, where the set of candidate design configurations is shrunken at each iteration using a Z-test, and the numerical model is corrected according to the most recent experimental results. The methodology is presented on a model of an airborne wind energy system, wherein both the center of mass location (plant parameter) and trim pitch angle (controller parameter) are critical to system performance. C2 - 2016/8/21/ C3 - Volume 2A: 42nd Design Automation Conference DA - 2016/8/21/ DO - 10.1115/detc2016-60488 PB - American Society of Mechanical Engineers SN - 9780791850107 UR - http://dx.doi.org/10.1115/detc2016-60488 DB - Crossref ER - TY - CONF TI - Lab-Scale Experimental Crosswind Flight Control System Prototyping for an Airborne Wind Energy System AU - Cobb, Mitchell AU - Vermillion, Christopher AU - Fathy, Hosam T2 - ASME 2016 Dynamic Systems and Control Conference AB - This paper presents an original experimental setup for controlling and measuring the crosswind flight of airborne wind energy systems in a laboratory environment. Execution of cross-wind flight patterns, which is achieved in this work through the asymmetric motion of three tethers, enables dramatic increases in energy generation compared with stationary operation. Achievement of crosswind flight in the 1:100-scale experimental framework described herein allows for rapid, inexpensive, and dynamically scalable characterization of new control algorithms without recourse to expensive full-scale prototyping. This work is the first example of successful lab-scale control and measurement of crosswind motion for an airborne wind energy system. Specifically, this paper presents the experimental setup, crosswind flight control strategy, and experimental results for a model of the Altaeros Buoyant Airborne Turbine (BAT). The results demonstrate that crosswind flight control can achieve nearly 50 percent more power production then stationary operation, while also demonstrating the potential of the experimental framework for further algorithm development. C2 - 2016/10/12/ C3 - Volume 1: Advances in Control Design Methods, Nonlinear and Optimal Control, Robotics, and Wind Energy Systems; Aerospace Applications; Assistive and Rehabilitation Robotics; Assistive Robotics; Battery and Oil and Gas Systems; Bioengineering Applications; Biomedical and Neural Systems Modeling, Diagnostics and Healthcare; Control and Monitoring of Vibratory Systems; Diagnostics and Detection; Energy Harvesting; Estimation and Identification; Fuel Cells/Energy Storage; Intelligent Transportation DA - 2016/10/12/ DO - 10.1115/dscc2016-9737 PB - American Society of Mechanical Engineers SN - 9780791850695 UR - http://dx.doi.org/10.1115/dscc2016-9737 DB - Crossref ER - TY - CONF TI - Spatio-temporal optimization through model predictive control: A case study in airborne wind energy AU - Bin-Karim, Shamir AU - Bafandeh, Alireza AU - Vermillion, Christopher T2 - 2016 IEEE 55th Conference on Decision and Control (CDC) AB - This paper presents a model predictive control (MPC)-based spatio-temporal optimization strategy that is applied to the problem of optimizing the altitude of an airborne wind energy (AWE) system. Altitude optimization for AWE systems represents a challenging problem under which the wind speed at the operating altitude dictates the net power produced by the system. The wind speed varies with both time and altitude and is typically only instantaneously observable at the operating altitude of the AWE system. The MPC strategy proposed in this work avoids the need for a computationally expensive Markov process model for characterizing the wind speed and is structured in a way that the need for instantaneous power maximization (termed exploitation) is balanced with the need to maintain an accurate map of wind speed vs. altitude (termed exploration). The MPC strategy is calibrated through data-driven statistical characterizations of the wind profile and is validated through real wind speed vs. altitude data. C2 - 2016/12// C3 - 2016 IEEE 55th Conference on Decision and Control (CDC) DA - 2016/12// DO - 10.1109/cdc.2016.7798913 PB - IEEE SN - 9781509018376 UR - http://dx.doi.org/10.1109/cdc.2016.7798913 DB - Crossref ER - TY - CONF TI - Reversible dielectric property degradation in moisture-contaminated fiber-reinforced laminates AU - Rodriguez, Luis A. AU - García, Carla AU - Fittipaldi, Mauro AU - Grace, Landon R. T2 - PROCEEDINGS OF PPS-31: The 31st International Conference of the Polymer Processing Society – Conference Papers AB - The potential for recovery of dielectric properties of three water-contaminated fiber-reinforced laminates is investigated using a split-post dielectric resonant technique at X-band (10 GHz). The three material systems investigated are bismaleimide (BMI) reinforced with an eight-harness satin weave quartz fabric, an epoxy resin reinforced with an eight- harness satin weave glass fabric (style 7781), and the same epoxy reinforced with a four-harness woven glass fabric (style 4180). A direct correlation between moisture content, dielectric constant, and loss tangent was observed during moisture absorption by immersion in distilled water at 25 °C for five equivalent samples of each material system. This trend is observed through at least 0.72% water content by weight for all three systems. The absorption of water into the BMI, 7781 epoxy, and 4180 epoxy laminates resulted in a 4.66%, 3.35%, and 4.01% increase in dielectric constant for a 0.679%, 0.608%, and 0.719% increase in water content by weight, respectively. Likewise, a significant increase was noticed in loss tangent for each material. The same water content is responsible for a 228%, 71.4%, and 64.1% increase in loss tangent, respectively. Subsequent to full desorption through drying at elevated temperature, the dielectric constant and loss tangent of each laminate exhibited minimal change from the dry, pre-absorption state. The dielectric constant and loss tangent change after the absorption and desorption cycle, relative to the initial state, was 0.144 % and 2.63% in the BMI, 0.084% and 1.71% in the style 7781 epoxy, and 0.003% and 4.51% in the style 4180 epoxy at near-zero moisture content. The similarity of dielectric constant and loss tangent in samples prior to absorption and after desorption suggests that any chemical or morphological changes induced by the presence of water have not caused irreversible changes in the dielectric properties of the laminates. C2 - 2016/// C3 - DA - 2016/// DO - 10.1063/1.4942332 PB - AIP Publishing LLC UR - http://dx.doi.org/10.1063/1.4942332 DB - Crossref KW - Dielectric constant KW - Loss Tangent ER - TY - CONF TI - Optimization of injection molding parameters for poly(styrene-isobutylene-styrene) block copolymer AU - Fittipaldi, Mauro AU - Garcia, Carla AU - Rodriguez, Luis A. AU - Grace, Landon R. T2 - PROCEEDINGS OF PPS-31: The 31st International Conference of the Polymer Processing Society – Conference Papers AB - Poly(styrene-isobutylene-styrene) (SIBS) is a widely used thermoplastic elastomer in bioimplantable devices due to its inherent stability in vivo. However, the properties of the material are highly dependent on the fabrication conditions, molecular weight, and styrene content. An optimization method for injection molding is herein proposed which can be applied to varying SIBS formulations in order to maximize ultimate tensile strength, which is critical to certain load-bearing implantable applications. The number of injection molded samples required to ascertain the optimum conditions for maximum ultimate tensile strength is limited in order to minimize experimental time and effort. Injection molding parameters including nozzle temperature (three levels: 218, 246, and 274 °C), mold temperature (three levels: 50, 85, and 120 °C), injection speed (three levels: slow, medium and fast) and holding pressure time (three levels: 2, 6, and 10 seconds) were varied to fabricate dumbbell specimens for tensile testing. A three-level L9 Taguchi method utilizing orthogonal arrays was used in order to rank the importance of the different injection molding parameters and to find an optimal parameter setting to maximize the ultimate tensile strength of the thermoplastic elastomer. Based on the Taguchi design results, a Response Surface Methodology (RSM) was applied in order to build a model to predict the tensile strength of the material at different injection parameters. Finally, the model was optimized to find the injection molding parameters providing maximum ultimate tensile strength. Subsequently, the theoretically-optimum injection molding parameters were used to fabricate additional dumbbell specimens. The experimentally-determined ultimate tensile strength of these samples was found to be in close agreement (1.2%) with the theoretical results, successfully demonstrating the suitability of the Taguchi Method and RSM for optimizing injection molding parameters of SIBS. C2 - 2016/// C3 - DA - 2016/// DO - 10.1063/1.4942269 PB - AIP Publishing LLC UR - http://dx.doi.org/10.1063/1.4942269 DB - Crossref KW - Taguchi Method KW - Response Surface Methodology KW - SIBS KW - Injection Molding Opthnization ER - TY - JOUR TI - Lipid diffusion and swelling in a phase separated biocompatible thermoplastic elastomer AU - Fittipaldi, Mauro AU - Grace, Landon R. T2 - Journal of the Mechanical Behavior of Biomedical Materials AB - Lipid uptake was analyzed via gravimetric measurements in a biocompatible poly(styrene-block-isobutylene-block-styrene) (SIBS) copolymer. Absorption followed Fickian diffusion behavior very closely, although some deviation was noticed once saturation was reached. Diffusion parameters of three different SIBS formulations were calculated and used to predict the behavior of a fourth type based on molecular weight and relative polystyrene content. SIBS with lower polystyrene content and molecular weight showed lower physical stability and developed surface cracks that propagated with exposure to the lipid medium. Saturation lipid content varied from 45% to 63% by weight and was inversely related to polystyrene content, suggesting most of the plasticization is occurring in the isobutylene phase of SIBS. Moreover, swelling of specimens was monitored throughout the immersion in the lipid medium and ranged from 32% to 58%. Swelling in formulations with lower hard phase (polystyrene) was significantly higher than the swelling in SIBS with higher hard phase content. This is consistent with lipid-induced plasticization occurring in the soft (polyisobutylene) segments, relaxing the polymer network and leading to increased swelling and lipid uptake. The biocompatibility and tailorability of SIBS through control of hard/soft phase ratio offer significant advantages for in vivo applications. However, the lipophilic nature of the material and the associated degradation may render the polymer unusable in certain applications. The predictive model of lipid uptake introduced here will allow more accurate evaluation of lipid susceptibility during the preliminary design phase of SIBS-based in vivo structures. DA - 2016/12// PY - 2016/12// DO - 10.1016/J.JMBBM.2016.07.016 VL - 64 SP - 1-9 J2 - Journal of the Mechanical Behavior of Biomedical Materials LA - en OP - SN - 1751-6161 UR - http://dx.doi.org/10.1016/J.JMBBM.2016.07.016 DB - Crossref KW - SIBS KW - Lipids KW - Plasticization KW - Gravimetric KW - Diffusion ER - TY - CHAP TI - Dynamic Failure Mechanisms in Woven Ceramic Fabric Reinforced Metal Matrix Composites During Ballistic Impact AU - McWilliams, Brandon A. AU - Yu, Jian H. AU - Pankow, Mark T2 - Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems, Volume 9 AB - The complex interaction of dynamic stress waves during ballistic impact provides the opportunity to simultaneously observe the high strain rate loading response under various triaxialities including tension, compression, and shear. In this work the dynamic failure mechanisms of woven ceramic fabric reinforced aluminum metal matrix composites (MMC) during ballistic impact are experimentally investigated. In addition to experimental characterization, an orthotropic elastic-plastic constitutive model with hydrostatic pressure dependent yield is implemented in an explicit finite element code to quantify the stress states present during the progressive damage and failure of the MMC during the penetration and perforation process. PY - 2016/// DO - 10.1007/978-3-319-21765-9_20 SP - 155-159 OP - PB - Springer International Publishing SN - 9783319217642 9783319217659 UR - http://dx.doi.org/10.1007/978-3-319-21765-9_20 DB - Crossref KW - Metal matrix composites KW - Penetration mechanics KW - Dynamic failure mechanisms KW - Failure modeling KW - High strain rate behavior ER - TY - CHAP TI - Simulation of High Rate Failure Mechanisms in Composites During Quasi-static Testing AU - Pankow, Mark AU - McWilliams, Brandon A. T2 - Conference Proceedings of the Society for Experimental Mechanics Series AB - High Rate testing is often difficult to perform, requires specialized equipment and often had results that are difficult to interpret. Being able to simulate the same failure mechanisms at high rates would enable rapid material selection. In this experimental investigation, the mechanical response is determined of different hybrid composites materials. A modified through-the-thickness tests has been used to force a high order of failure mode that is similar to those seen in high speed impact. Failure is observed in the samples and stresses on the surface are determine to help with failure envelope measurements. The details of a comparison between 2D fabrics vs. 3D woven fabrics has been under taken and a comparison will be presented showing the similarities and differences in response. A discussion of the comparison between the high rate testing and the low-rate testing will be investigated and discussion on the applications of the testing will be examined for failure envelope prediction. PY - 2016/// DO - 10.1007/978-3-319-21762-8_52 SP - 445-450 OP - PB - Springer International Publishing SN - 9783319217611 9783319217628 UR - http://dx.doi.org/10.1007/978-3-319-21762-8_52 DB - Crossref KW - Composites KW - Penetration mechanics KW - Dynamic failure mechanisms KW - High strain rate behavior ER - TY - JOUR TI - Do Isoflux Boundary Conditions Inhibit Oscillatory Double-Diffusive Convection? AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - Transport in Porous Media DA - 2016/3/17/ PY - 2016/3/17/ DO - 10.1007/S11242-016-0666-2 VL - 112 IS - 3 SP - 609-618 J2 - Transp Porous Med LA - en OP - SN - 0169-3913 1573-1634 UR - http://dx.doi.org/10.1007/S11242-016-0666-2 DB - Crossref KW - Double-diffusive convection KW - Isoflux boundary conditions KW - Oscillatory instability ER - TY - JOUR TI - Announcing the 2015 Measurement Science and Technology outstanding paper awards AU - Peters, Kara AU - Yang, Wuqiang AU - Tadigadapa, Srinivas AU - Jakoby, Bernhard T2 - Measurement Science and Technology DA - 2016/5/17/ PY - 2016/5/17/ DO - 10.1088/0957-0233/27/7/070101 VL - 27 IS - 7 SP - 070101 SN - 0957-0233 1361-6501 UR - http://dx.doi.org/10.1088/0957-0233/27/7/070101 ER - TY - JOUR TI - Substrate Effects on Growth of MoS2 Film by Laser Physical Vapor Deposition on Sapphire, Si and Graphene (on Cu) AU - Jagannadham, K. AU - Cui, J. AU - Zhu, Y. T2 - Journal of Electronic Materials DA - 2016/10/28/ PY - 2016/10/28/ DO - 10.1007/S11664-016-5060-X VL - 46 IS - 2 SP - 1010-1021 J2 - Journal of Elec Materi LA - en OP - SN - 0361-5235 1543-186X UR - http://dx.doi.org/10.1007/S11664-016-5060-X DB - Crossref KW - Molybdenum disulfide KW - graphene KW - laser deposition ER - TY - JOUR TI - Thrombin-Responsive Transcutaneous Patch for Auto-Anticoagulant Regulation AU - Zhang, Yuqi AU - Yu, Jicheng AU - Wang, Jinqiang AU - Hanne, Nicholas J. AU - Cui, Zheng AU - Qian, Chenggen AU - Wang, Chao AU - Xin, Hongliang AU - Cole, Jacqueline H. AU - Gallippi, Caterina M. AU - Zhu, Yong AU - Gu, Zhen T2 - Advanced Materials AB - A thrombin-responsive closed-loop patch is developed for prolonged heparin delivery in a feedback-controlled manner. This microneedle-based patch can sense activated thrombin and subsequently releases heparin to prevent coagulation in the blood flow. This “smart” heparin patch can be transcutaneously inserted into skin without drug leakage and can sustainably regulate blood coagulation in response to thrombin. DA - 2016/11/25/ PY - 2016/11/25/ DO - 10.1002/ADMA.201604043 VL - 29 IS - 4 SP - 1604043 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 UR - http://dx.doi.org/10.1002/ADMA.201604043 DB - Crossref ER - TY - CONF TI - Predicting and accelerating chemistry in high speed reacting flows AU - Wignall, T.J. AU - Patton, C.H. AU - Echekki, T. AU - Edwards, J.R. C2 - 2016/// C3 - 54th AIAA Aerospace Sciences Meeting DA - 2016/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85007578694&partnerID=MN8TOARS ER - TY - CONF TI - LES model assessment for high speed combustion AU - Patton, C.H. AU - Wignall, T.J. AU - Edwards, J.R. AU - Echekki, T. C2 - 2016/// C3 - 54th AIAA Aerospace Sciences Meeting DA - 2016/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85007417906&partnerID=MN8TOARS ER - TY - CONF TI - Improved 4D data assimilation for large eddy simulation of high speed turbulent combustion AU - Edwards, J.R. AU - Luo, L. AU - Patton, C.H. AU - Wignall, T.J. AU - Echekki, T. C2 - 2016/// C3 - 46th AIAA Fluid Dynamics Conference DA - 2016/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84980367676&partnerID=MN8TOARS ER - TY - JOUR TI - Tunable superomniphobic surfaces for sorting droplets by surface tension AU - Movafaghi, S. AU - Wang, W. AU - Metzger, A. AU - Williams, D. D. AU - Williams, J. D. AU - Kota, A. K. T2 - Lab on a Chip AB - Utilizing tunable superomniphobic surfaces with flower-like TiO2 nanostructures, we fabricated a simple device that can sort droplets by surface tension. DA - 2016/// PY - 2016/// DO - 10.1039/c6lc00673f VL - 16 IS - 17 SP - 3204-3209 J2 - Lab Chip LA - en OP - SN - 1473-0197 1473-0189 UR - http://dx.doi.org/10.1039/c6lc00673f DB - Crossref ER - TY - JOUR TI - Superhydrophobic Coatings with Edible Materials AU - Wang, Wei AU - Lockwood, Karsten AU - Boyd, Lewis M. AU - Davidson, Matthew D. AU - Movafaghi, Sanli AU - Vahabi, Hamed AU - Khetani, Salman R. AU - Kota, Arun K. T2 - ACS Applied Materials & Interfaces AB - We used FDA-approved, edible materials to fabricate superhydrophobic coatings in a simple, low cost, scalable, single step process. Our coatings display high contact angles and low roll off angles for a variety of liquid products consumed daily and facilitate easy removal of liquids from food containers with virtually no residue. Even at high concentrations, our coatings are nontoxic, as shown using toxicity tests. DA - 2016/7/14/ PY - 2016/7/14/ DO - 10.1021/acsami.6b06958 VL - 8 IS - 29 SP - 18664-18668 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/acsami.6b06958 DB - Crossref KW - superhydrophobic KW - edible KW - coating KW - nontoxic KW - wax KW - FDA ER - TY - JOUR TI - Free-Standing, Flexible, Superomniphobic Films AU - Vahabi, Hamed AU - Wang, Wei AU - Movafaghi, Sanli AU - Kota, Arun K. T2 - ACS Applied Materials & Interfaces AB - Fabrication of most superomniphobic surfaces requires complex process conditions or specialized and expensive equipment or skilled personnel. In order to circumvent these issues and make them end-user-friendly, we developed the free-standing, flexible, superomniphobic films. These films can be stored and delivered to the end-users, who can readily attach them to virtually any surface (even irregular shapes) and impart superomniphobicity. The hierarchical structure, the re-entrant texture, and the low solid surface energy render our films superomniphobic for a wide variety of liquids. We demonstrate that our free-standing, flexible, superomniphobic films have applications in enhanced chemical resistance and enhanced weight bearing. DA - 2016/8/22/ PY - 2016/8/22/ DO - 10.1021/acsami.6b06333 VL - 8 IS - 34 SP - 21962-21967 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/acsami.6b06333 DB - Crossref KW - superomniphobic KW - free-standing KW - flexible KW - enhanced chemical resistance KW - enhanced weight-bearing capacity ER - TY - JOUR TI - Durable gels with ultra-low adhesion to ice AU - Beemer, Darryl L. AU - Wang, Wei AU - Kota, Arun K. T2 - Journal of Materials Chemistry A AB - Building on principles of adhesion mechanics, we developed novel PDMS gels with ultra-low adhesion to ice and outstanding mechanical durability. DA - 2016/// PY - 2016/// DO - 10.1039/c6ta07262c VL - 4 IS - 47 SP - 18253-18258 J2 - J. Mater. Chem. A LA - en OP - SN - 2050-7488 2050-7496 UR - http://dx.doi.org/10.1039/c6ta07262c DB - Crossref ER - TY - JOUR TI - Hemodynamic Performance and Thrombogenic Properties of a Superhydrophobic Bileaflet Mechanical Heart Valve AU - Bark, David L. AU - Vahabi, Hamed AU - Bui, Hieu AU - Movafaghi, Sanli AU - Moore, Brandon AU - Kota, Arun K. AU - Popat, Ketul AU - Dasi, Lakshmi P. T2 - Annals of Biomedical Engineering AB - In this study, we explore how blood-material interactions and hemodynamics are impacted by rendering a clinical quality 25 mm St. Jude Medical Bileaflet mechanical heart valve (BMHV) superhydrophobic (SH) with the aim of reducing thrombo-embolic complications associated with BMHVs. Basic cell adhesion is evaluated to assess blood-material interactions, while hemodynamic performance is analyzed with and without the SH coating. Results show that a SH coating with a receding contact angle (CA) of 160° strikingly eliminates platelet and leukocyte adhesion to the surface. Alternatively, many platelets attach to and activate on pyrolytic carbon (receding CA = 47), the base material for BMHVs. We further show that the performance index increases by 2.5% for coated valve relative to an uncoated valve, with a maximum possible improved performance of 5%. Both valves exhibit instantaneous shear stress below 10 N/m2 and Reynolds Shear Stress below 100 N/m2. Therefore, a SH BMHV has the potential to relax the requirement for antiplatelet and anticoagulant drug regimens typically required for patients receiving MHVs by minimizing blood-material interactions, while having a minimal impact on hemodynamics. We show for the first time that SH-coated surfaces may be a promising direction to minimize thrombotic complications in complex devices such as heart valves. DA - 2016/4/20/ PY - 2016/4/20/ DO - 10.1007/s10439-016-1618-2 VL - 45 IS - 2 SP - 452-463 J2 - Ann Biomed Eng LA - en OP - SN - 0090-6964 1573-9686 UR - http://dx.doi.org/10.1007/s10439-016-1618-2 DB - Crossref KW - Shear stress KW - Superhydrophobic KW - Thrombosis KW - Turbulence KW - Blood KW - Bileaflet mechanical heart valve ER - TY - JOUR TI - Hemocompatibility of Superhemophobic Titania Surfaces AU - Movafaghi, Sanli AU - Leszczak, Victoria AU - Wang, Wei AU - Sorkin, Jonathan A. AU - Dasi, Lakshmi P. AU - Popat, Ketul C. AU - Kota, Arun K. T2 - Advanced Healthcare Materials AB - The hemocompatibility of superhemophobic surfaces is investigated and compared with that of hemophobic surfaces and hemophilic surfaces. This analysis indicates that only those superhemophobic surfaces with a robust Cassie-Baxter state display significantly lower platelet adhesion and activation. It is envisioned that the understanding gained through this work will lead to the fabrication of improved hemocompatible, superhemophobic medical implants. DA - 2016/12/21/ PY - 2016/12/21/ DO - 10.1002/adhm.201600717 VL - 6 IS - 4 SP - 1600717 J2 - Adv. Healthcare Mater. LA - en OP - SN - 2192-2640 UR - http://dx.doi.org/10.1002/adhm.201600717 DB - Crossref ER - TY - JOUR TI - Zones of material separation in simulations of cutting AU - Pan, H. AU - Liu, J. AU - Choi, Y. AU - Xu, C. AU - Bai, Y. AU - Atkins, T. T2 - International Journal of Mechanical Sciences AB - FEM simulations of orthogonal cutting are reported in which both the Johnson–Cook (JC) constitutive relation and the Johnson–Cook separation (fracture or damage) criterion are used. Results demonstrate that the damaged regions, in which separation of material occurs at the tool tip, form thin boundary layers on the top of the machined surface and on the underside of the chip. Damage was calculated in terms of the parameters of the Johnson–Cook fracture criterion appropriate for A2024-T351 aluminium alloy. The size of the damaged layers is some 35 μm and appears to be independent of the uncut chip thickness t0 over the range investigated (50f/SiC composites incorporated with boron nitride nanotubes AU - Zhu, G. AU - Dong, S. AU - Ni, D. AU - Xu, C. AU - Wang, D. T2 - RSC Advances AB - SiCf/BNNTs–SiC hierarchical composites were fabricated via firstly in situ growth of BNNTs on SiC fibers using boron powder as a raw material and then matrix densification by chemical vapor infiltration and polymer impregnation/pyrolysis methods. DA - 2016/// PY - 2016/// DO - 10.1039/c6ra16496j VL - 6 IS - 86 SP - 83482-83492 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84986302081&partnerID=MN8TOARS ER - TY - JOUR TI - Mechanical response and microstructure of 2D carbon fiber reinforced ceramic matrix composites with SiC and Ti3SiC2fillers AU - Yang, J. AU - Dong, S. AU - Xu, C. T2 - Ceramics International AB - 2D carbon fiber reinforced ceramic matrix composites are prepared by PIP process using SiC and Ti3SiC2 as separate fillers. The effect of SiC and Ti3SiC2 fillers on mechanical property, fracture behavior and microstructure of the final composites is studied. The force–displacement curve shows no apparent delamination in Cf/Ti3SiC2–SiC composites during three-point flexural test, compared to Cf/SiC composites in which the through-thickness crack is much more devious. The ultimate force of Cf/Ti3SiC2–SiC composites is much lower than Cf/SiC composites. The thermal expansion mismatch and chemical reactions between carbon fiber and the matrix make the fiber–matrix interface bonding stronger in Cf/Ti3SiC2–SiC composites. It can infer that the carbon fibers׳ strength can be damaged by the chemical reactions. The thermal expansion mismatch and chemical reactions are two important factors that influence the mechanical properties and microstructure of the final composites. DA - 2016/// PY - 2016/// DO - 10.1016/j.ceramint.2015.10.088 VL - 42 IS - 2 SP - 3019-3027 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84949965271&partnerID=MN8TOARS KW - Composites KW - Electron microscopy KW - Mechanical properties KW - SiC KW - Fibers ER - TY - JOUR TI - High electrical conductivity and anisotropy of aligned carbon nanotube nanocomposites reinforced by silicon carbonitride AU - Yang, J. AU - Downes, R. AU - Schrand, A. AU - Park, J.G. AU - Liang, R. AU - Xu, C. T2 - Scripta Materialia AB - Aligned carbon nanotube (CNT) sheets reinforced with silicon carbonitride were prepared by the infiltration and pyrolysis of liquid polysilazane into mechanically stretched CNTs. The resultant nanocomposites contained a high volume fraction of CNTs (60 vol%), and due to alignment, reached an electrical conductivity of up to 2.2 × 105 S m− 1. The electrical conductivity was anisotropic based upon the CNT alignment and changed from 3.3 to 9.2 after the pyrolysis process. The high electrical conductivity of the nanocomposites contributes to their potential application in electromagnetic interference shielding. DA - 2016/// PY - 2016/// DO - 10.1016/j.scriptamat.2016.06.023 VL - 124 SP - 21-25 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84978035561&partnerID=MN8TOARS KW - Carbon nanotubes KW - Ceramic matrix composites KW - Electrical properties KW - Scanning electron microscopy KW - Alignment ER - TY - JOUR TI - Fully Printed Halide Perovskite Light-Emitting Diodes with Silver Nanowire Electrodes AU - Bade, S.G.R. AU - Li, J. AU - Shan, X. AU - Ling, Y. AU - Tian, Y. AU - Dilbeck, T. AU - Besara, T. AU - Geske, T. AU - Gao, H. AU - Ma, B. AU - Hanson, K. AU - Siegrist, T. AU - Xu, C. AU - Yu, Z. T2 - ACS Nano AB - Printed organometal halide perovskite light-emitting diodes (LEDs) are reported that have indium tin oxide (ITO) or carbon nanotubes (CNTs) as the transparent anode, a printed composite film consisting of methylammonium lead tribromide (Br-Pero) and poly(ethylene oxide) (PEO) as the emissive layer, and printed silver nanowires as the cathode. The fabrication can be carried out in ambient air without humidity control. The devices on ITO/glass have a low turn-on voltage of 2.6 V, a maximum luminance intensity of 21014 cd m(-2), and a maximum external quantum efficiency (EQE) of 1.1%, surpassing previous reported perovskite LEDs. The devices on CNTs/polymer were able to be strained to 5 mm radius of curvature without affecting device properties. DA - 2016/// PY - 2016/// DO - 10.1021/acsnano.5b07506 VL - 10 IS - 2 SP - 1795-1801 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84961221465&partnerID=MN8TOARS KW - halide perovskites KW - printed electronics KW - light-emitting diodes KW - composites KW - flexible electronics KW - moisture ER - TY - JOUR TI - Effect of drilling allowance on TBC delamination, spatter and re-melted cracks characteristics in laser drilling of TBC coated superalloys AU - Fan, Z. AU - Dong, X. AU - Wang, K. AU - Duan, W. AU - Wang, R. AU - Mei, X. AU - Wang, W. AU - Cui, J. AU - Yuan, X. AU - Xu, C. T2 - International Journal of Machine Tools and Manufacture AB - Laser drilling of inclined holes on Ni-based superalloys coated with thermal barrier coatings (TBC) was studied using numerical simulation and experiments. Two types of drilling, three steps-laser drilling (TSLD) method and the one step laser drilling (OSLD), were employed for making comparison. The simulation results demonstrate that relatively strong vortex effect of assist gas at hole entrance and the drilling allowance of the substrate hole can deflect the trajectories of melt flow from leading edge TBC wall. This phenomenon may isolate leading edge of the hole from the ejecting molten material. Thus, shearing stress effect was prevented. The characteristics of TBC delamination, spatter at the TBC leading edge and re-melted cracks along the TBC trailing edge are investigated by comparing the characteristics of the melt flow obtained via simulation and experiment. The combined results suggest that the TBC/substrate multilayer can avoid these defects applying the TSLD technology. DA - 2016/// PY - 2016/// DO - 10.1016/j.ijmachtools.2016.03.008 VL - 106 SP - 1-10 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84962911187&partnerID=MN8TOARS KW - Laser drilling KW - Thermal barrier coating KW - Drilling allowance KW - TBC delamination KW - Spatter KW - Re-melted cracks ER - TY - JOUR TI - Development of a Wireless Temperature Sensor Using Polymer-Derived Ceramics AU - Zhao, R. AU - Shao, G. AU - Li, N. AU - Xu, C. AU - An, L. T2 - Journal of Sensors AB - A temperature sensor has been developed using an embedded system and a sensor head made of polymer-derived SiAlCN ceramics (PDCs). PDC is a promising material for measuring high temperature and the embedded system features low-power consumption, compact size, and wireless transmission. The developed temperature sensor has been experimentally tested to demonstrate the possibility of using such sensors for real world applications. DA - 2016/// PY - 2016/// DO - 10.1155/2016/8624817 VL - 2016 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84971280268&partnerID=MN8TOARS ER - TY - JOUR TI - Characterization and Alignment of Carbon Nanofibers under Shear Force in Microchannel AU - Yang, J. AU - Dong, S. AU - Webster, D. AU - Gilmore, J. AU - Xu, C. T2 - Journal of Nanomaterials AB - This work presents a novel method to align CNFs by using shear forces in microchannels. Effect of two different microchannel sizes (1 mm × 0.1 mm and 1 mm × 0.2 mm) on CNFs alignment is investigated. SEM images of CNFs preform display significant alignment by both microchannels, which can be interpreted using a second-order alignment tensor and a manual angle meter. In the second-order alignment tensor description, an elongated ellipse can signify high degree of alignment in the direction of the major axis. When the microchannel size is 1 mm × 0.2 mm, the lengths of major and minor axes of the ellipse are 0.982 to 0.018. An angle meter manually shows that 85% of the CNFs are aligned in the direction between 60° and 90° when the microchannel is 1 mm × 0.2 mm. Both methods can demonstrate that better alignment of CNFs can be obtained using the 1 mm × 0.2 mm microchannel. DA - 2016/// PY - 2016/// DO - 10.1155/2016/1052478 VL - 2016 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84962675850&partnerID=MN8TOARS ER - TY - SOUND TI - Three-Dimensional Multi-Reinforced Ceramic Composites with Enhanced Through-Thickness Thermal Conductivity AU - Xu, C. AU - Yang, J. DA - 2016/// PY - 2016/// N1 - Invited RN - Invited ER - TY - SOUND TI - Strong and Flexible Ceramic Composites with High In-Plane Thermal Conductivity for Hypersonic Applications AU - Xu, C. DA - 2016/// PY - 2016/// N1 - Invited RN - Invited ER - TY - SOUND TI - High Conductive Ceramic Thin Film with Unique Mechanical Property AU - Xu, C. DA - 2016/// PY - 2016/// N1 - Invited RN - Invited ER - TY - JOUR TI - Microstructural Modeling of Coupled Electromagnetic-Thermo-Mechanical Response of Energetic Aggregates to Infrared Laser Radiation and Dynamic Fracture AU - Brown, J. A. AU - Bond, D. M. AU - Zikry, M. A. T2 - MRS ADVANCES DA - 2016/// PY - 2016/// DO - 10.1557/adv.2015.56 VL - 1 IS - 17 SP - 1197-1202 SN - 2059-8521 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85041287988&partnerID=MN8TOARS ER - TY - JOUR TI - Human and Environment Influences on Thermoelectric Energy Harvesting Toward Self-Powered Textile-Integrated Wearable Devices AU - Myers, Amanda AU - Hodges, Ryan AU - Jur, Jesse S. T2 - MRS ADVANCES AB - The study of on-body energy harvesting is most often focused on improving and optimizing the energy harvester. However, other factors play a critical factor in the energy harvesting integration techniques of the harvester to close-to body materials of the wearable device. In addition, one must recognize the wide array of human factors and ergonomic factors that lead a variation of the energy harvesting. In this work, key affecting variables at varying on-body locations are investigated for commercial thermoelectric generators (TEGs) integrated within a textile-based wearable platform. For this study, a headband and an armband is demonstrated with five TEGs connected in series in a flexible form factor via Pyralux®. These platforms enable comparison of the amount of energy harvested from the forehead versus the upper arm during various external conditions and movement profiles, e.g. running, walking, and stationary for periods of up to 60 minutes. During these tests, ambient temperature, ambient humidity, accelerometry, and instantaneous power are recorded live during the activity and correlated to the energy harvested. Human factors such as skin temperature and application pressure were also analyzed. Our analysis demonstrates that vigorous movement can generate over 100 μW of instantaneous power from the headband and up to 35 μW from the armband. During the stationary movement profile, the instantaneous power levels of both the headband and the armband decreased to a negligible value. Our studies show that for higher intensities of movement, air convection on the cool side of the TEG is the dominating variable whereas the temperature gradient has a significant effect when the subject is stationary. This work demonstrates key materials and design factors in on-body thermoelectric energy harvesting that allows for a strategic approach to improving the integration of the TEGs. DA - 2016/// PY - 2016/// DO - 10.1557/adv.2016.316 VL - 1 IS - 38 SP - 2665-2670 SN - 2059-8521 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85041362992&partnerID=MN8TOARS ER - TY - JOUR TI - Biothermal Convection and Nanofluid Bioconvection AU - Kuznetsov, A. V. T2 - Handbook of Fluid Dynamics, 2nd Edition DA - 2016/// PY - 2016/// ER - TY - CONF TI - H-infinity state-feedback control of linear systems with time-varying input delays AU - Yuan, C. Z. AU - Wu, F. AB - In this paper, we will address the state-feedback control synthesis problem for linear systems with time-varying input delays under the integral quadratic constraint (IQC) framework. A new exact-memory control scheme is first proposed, which consists of a standard linear state-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. With this controller structure, the resulting 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. The corresponding results on memoryless state-feedback control are also derived for cases when input-delay information is not available for feedback control. A numerical example has been used to illustrate the effectiveness of the proposed approach. C2 - 2016/// C3 - 2016 ieee 55th conference on decision and control (cdc) DA - 2016/// DO - 10.1109/cdc.2016.7798332 SP - 586-591 ER - TY - JOUR TI - Temperature Abatement Using Hollow Spheres in Liquid Piston Compressor for Ocean Compressed Air Energy Storage System AU - Ramakrishnan, Kishore Ranganath AU - Ro, Paul. I. AU - Patil, Vikram. C. T2 - OCEANS 2016 MTS/IEEE MONTEREY AB - This paper deals with a novel technique to curb the temperature raise during compression in a liquid piston compressor used in Ocean Compressed Air Energy Storage (OCAES) system. Hollow spheres made of various materials, viz. Silicon Carbide (SiC), High Density Polyethylene (HDPE), and Polypropylene (PP) were made to float on the top surface of the liquid column. It was observed that the temperature abatement in each of the three cases was very evident. The heat transfer does not depend on the material of the sphere, but the fact that there is a solid surface between water and air itself plays an important role along with the size of the sphere. The heat transfer per unit area from the simulation and the analytical model have been compared and the values are found to be very similar. Also, polytropic index of the compression process was evaluated in case without and with SiC spheres, and it was found to be closer to the isothermal index of 1 when the spheres are used. DA - 2016/// PY - 2016/// DO - 10.1109/oceans.2016.7761341 SP - KW - Ocean energy KW - Energy storage KW - Liquid Piston compressor KW - Temperature abatement ER - TY - JOUR TI - End-To-End Efficiency of Liquid Piston based Ocean Compressed Air Energy Storage AU - Patil, Vikram C. AU - Ro, Paul I. AU - Ranganath, Kishore R. T2 - OCEANS 2016 MTS/IEEE MONTEREY AB - Intermittent ocean energy resources need energy storage system for their optimal utilization. Ocean compressed air energy storage (OCAES) is a promising way for a utility scale energy storage. In this paper, a liquid piston based ocean compressed air energy storage is analyzed for end-to-end efficiency. An analytical model for end-to-end efficiency based on efficiencies of individual components in the liquid piston based OCAES is presented. Numerical analysis based on the analytical model and experimental data is done using Monte Carlo simulations. End-To-End efficiency of the liquid piston based OCAES is observed to be highly dependent on the polytropic index of compression and expansion. End-to-End efficiency increases from 24% to 72% with decrease in polytropic index from 1.4 to 1. Experimentally observed polytropic index shows 45% end-to-end efficiency. Comparison of results with end-to-end efficiency of existing compressed air energy storage systems indicates that the isothermal liquid piston based OCAES shows significantly higher end-to-end efficiency. DA - 2016/// PY - 2016/// DO - 10.1109/oceans.2016.7761399 SP - KW - Ocean Energy KW - Energy Storage KW - Compressed Air KW - End-to-End Efficiency ER - TY - CONF TI - A new hybrid LFT control method for missile autopilot design AU - Yuan, C. Z. AU - Wu, F. AB - This paper presents a new hybrid gain-scheduling control method for missile autopilot design. The nonlinear missile dynamics is first converted to a switched linear fractional transformation (LFT) model for controller design and synthesis purpose. Then, by using multiple Lyapunov functions and average dwell time (ADT) techniques, a new hybrid gain-scheduling autopilot is designed, which consists of a switching dynamic output-feedback LFT controller and a controller state jump dynamics. The associated control synthesis conditions guaranteeing weighted ℒ 2 stability are formulated in terms of a finite number of linear matrix inequalities (LMIs), which can be solved effectively via convex optimization without parameter-space gridding. Nonlinear simulation studies show the effectiveness of the proposed approach. C2 - 2016/// C3 - Proceedings of the 35th chinese control conference 2016 DA - 2016/// DO - 10.1109/chicc.2016.7554273 SP - 5852-5857 ER - TY - CONF TI - Modeling of harmonic measurement radiated by a plane circular piston in fluids AU - An, Z. W. AU - Wang, Z. C. AU - Li, H. Y. AU - Jiang, X. N. AB - In recent years, the use of nonlinear ultrasound in medical and industrial applications has increased rapidly. Harmonic signals, generated from nonlinear distortion of ultrasonic wave propagation in fluid or solid media, play an important role not only in ultrasonic medical imaging to provide higher resolution and higher contrast to tissue ratio, but also in nondestructive testing of fatigue cracks to provide higher sensitivity. We present a finite element model that embodies all the factors (diffraction, attenuation, receiver integration and tone-burst excitation) mentioned previously to describe the nonlinear characteristics of the ultrasonic field radiated by a plane circular piston source in fluids more accurately. A computer controlled ultrasonic system (RAM-5000 SNAP, Ritec Inc.) was used to verify the numerical predictions. The fundamental and the second harmonic versus axial distance are compared, and a reasonable agreement is achieved. C2 - 2016/// C3 - Proceedings of 2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA) DA - 2016/// DO - 10.1109/spawda.2016.7830007 SP - 288-292 ER - TY - JOUR TI - On the size-dependent elasticity of penta-twinned silver nanowires AU - Chang, Tzu-Hsuan AU - Cheng, Guangming AU - Li, Chengjun AU - Zhu, Yong T2 - EXTREME MECHANICS LETTERS AB - Penta-twinned metallic NWs have recently received much attention due to their excellent mechanical properties. However, their elasticity size effect remains not well understood due to the large discrepancy in the reported experimental and simulation results. This paper reports an experimental effort to address the discrepancy about the size-dependent Young’s modulus of penta-twinned Ag NWs. Two independent experiments on the same NW, in-situ resonance test and tensile test in a scanning electron microscope, were used to measure the Young’s moduli. The cross-sectional shape of the Ag NWs was found to transit from pentagon to circle with decreasing NW diameter, which can modify the Young’s modulus as much as 8% (for resonance test) and 19% (for tensile test) for the tested diameter range. This work confirmed that the Young’s modulus of penta-twinned Ag NWs increases with decreasing NW diameter. DA - 2016/9// PY - 2016/9// DO - 10.1016/j.eml.2016.03.007 VL - 8 SP - 177-183 SN - 2352-4316 KW - Nanowires KW - Nanomechanics KW - Elasticity size effect ER - TY - CONF TI - Modelling and experimental comparison of fluid structure coupling for thin sheet metal tanks using statistical energy analysis AU - Shende, K. V. AU - Keltie, R. AB - Acoustic response of flat surfaces in contact with a fluid volume is of some interest for the design of automotive fuel tanks, fluid containers and underwater applications [1]. As this response can be related to the surface vibration response in the linear domain, the effect of fluid structure coupling on the vibration response of the structure is studied in this paper. Advances in the computational abilities have increased the focus of analysis-led approaches in the design of thin sheet metal tanks. Conventional finite element (FE) based approaches are useful at low frequencies but are highly sensitive to geometrical details and local effects at higher frequencies. With changing input parameters, finite element approaches could prove to be computationally expensive during the initial design phase of such structures. Statistical Energy Analysis (SEA) is an energy based approach and was used to study the fluid structure coupling effect on the vibration characteristics of a simple rectangular parallelepiped thin sheet metal tank. A thin steel tank (thickness/min. characteristic dimension <0.01) was excited by a broad band uniform power spectral density white noise signal and the spatial and frequency averaged acceleration responses were compared. Some parameters like the damping loss factor and the excitation force were calculated from the experimental measurements and used as input for SEA simulations. Coupling loss factors were calculated from tests and the trend lines were found to be in agreement with the theoretical calculations. The SEA simulation model results were compared with the conventional FE based approach for reference. Variance studies were used to compute the envelope for the SEA simulation response for a 90% confidence interval. The SEA and the test results comparison was quantified by a correlation coefficient which indicated a moderately strong correlation (>0.5) between the SEA and experimental results. C2 - 2016/// C3 - Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 2016, Vol 8 DA - 2016/// DO - 10.1115/detc2016-59071 ER - TY - CONF TI - Effects of fuel quantity on soot formation process for biomass-based renewable diesel fuel combustion AU - Jing, W. AU - Wu, Z. Y. AU - Roberts, W. L. AU - Fang, Tiegang 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. C2 - 2016/// C3 - Proceedings of the ASME Internal Combustion Engine Division Fall Technical Conference (ICEF) DA - 2016/// DO - 10.1115/icef2016-9380 ER - TY - JOUR TI - Editorial for the focus issue on "Nanomechanics'' in Extreme Mechanics Letters AU - Zhu, Yong AU - Gianola, Daniel AU - Zhu, Ting T2 - EXTREME MECHANICS LETTERS DA - 2016/9// PY - 2016/9// DO - 10.1016/j.eml.2016.07.008 VL - 8 SP - 125-126 SN - 2352-4316 ER - TY - CONF TI - Dynamic IQC-based analysis and synthesis of networked control systems AU - Yuan, C. Z. AU - Wu, F. AB - This paper presents a new control design approach for networked control systems under the integral quadratic constraint (IQC) framework. In order to apply the IQC and dissipation theory, the networked control system with network-induced time-varying delays is first transformed to an equivalent linear fractional transformation (LFT) model. As such, dynamic IQCs can be used to capture the input-output behavior of the delay nonlinearities. Then, a novel full-information feedback control law is proposed, which utilizes both plant states and the IQC dynamic states, as well as the network-induced delay amounts, as feedback information. Robust ℓ2 stability analysis of the resulting closed loop is performed via dynamic IQCs. Based on the analysis results, the synthesis conditions for the proposed full-information feedback controller are established in a linear matrix inequality (LMI) form, which can be solved effectively using existing convex optimization algorithms. Finally, a servo motor control system is used to demonstrate the effectiveness of the proposed IQC-based control design scheme. C2 - 2016/// C3 - 2016 american control conference (acc) DA - 2016/// DO - 10.1109/acc.2016.7526507 SP - 5346-5351 ER - TY - CONF TI - Design optimization and analysis of a prescribed vibration system AU - Malinga, B. AU - Ferguson, S. M. AU - Buckner, G. D. AB - Advances in technology that come with increased system complexity have accentuated the intricacy of decision making in engineering design. This has stimulated a great deal of research in ways to incorporate decision analysis and multi-attribute decision-making theory in engineering problems. In this research, Conjoint Value Analysis is incorporated into a scheme that optimizes the design of a multi-attribute Prescribed Vibration System. The influence of designer preferences is investigated by comparing design alternatives that result from different preference rankings. Monte Carlo-based uncertainty and sensitivity studies are performed to support the design process by providing additional information on the candidate designs. By understanding how small changes in the values of optimized parameters influence the system attributes, sensitivity analysis and uncertainty analyses can be used as a design robustness measure. The overall choice of the design is therefore based not only on the performance objectives but also on the resulting system robustness, which is very valuable considering manufacturing variations and tolerance stacks. C2 - 2016/// C3 - Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 2016, Vol 2b DA - 2016/// DO - 10.1115/detc2016-60096 SP - 353-360 ER - TY - JOUR TI - Bringing PLOS Genetics Editors to Preprint Servers AU - Barsh, Gregory S. AU - Bergman, Casey M. AU - Brown, Christopher D. AU - Singh, Nadia D. AU - Copenhaver, Gregory P. T2 - PLOS GENETICS DA - 2016/12// PY - 2016/12// DO - 10.1371/journal.pgen.1006448 VL - 12 IS - 12 SP - SN - 1553-7404 ER - TY - JOUR TI - Van der Waals Force Isolation of Monolayer MoS2 AU - Gurarslan, Alper AU - Jiao, Shuping AU - Li, Tai-De AU - Li, Guoqing AU - Yu, Yiling AU - Gao, Yang AU - Riedo, Elisa AU - Xu, Zhiping AU - Cao, Linyou T2 - ADVANCED MATERIALS AB - Monolayer MoS2 can effectively screen the vdW interaction of underlying substrates with external systems by >90% because of the substantial increase in the separation between the substrate and external systems due to the presence of the monolayer. This substantial screening of vdW interactions by MoS2 monolayer is different from what reported at graphene. 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 - 2016/12/7/ PY - 2016/12/7/ DO - 10.1002/adma.201601581 VL - 28 IS - 45 SP - 10055-10060 SN - 1521-4095 ER - TY - CONF TI - Nanocomposite transducer with a laser ultarsound transmitter and a piezoelectric receiver AU - Kim, J. AU - Chang, W. Y. AU - Huang, S. J. AU - Jiang, X. N. AB - Laser ultrasound transducers, converting the laser pulses into acoustic waves with high frequency, broadband and high pressure amplitude, is attractive to many biomedical and industrial applications. In this paper, nanocomposites consisting of carbon nanomaterials, PDMS and PVDF were incorporated into a transducer structure for ultrasound transmitting and receiving. The prototyped nanocomposite transducers were characterized by conducting pulse-echo tests. The obtained center frequency is 12 MHz, -6 dB fractional bandwidth is 138%, and the signal-to-noise ratio of 42 dB with an excitation of ~5 mJ of 532 nm, 6 ns pulsed laser. These initial findings strongly suggest that laser ultrasound transducers are promising for advanced ultrasound imaging applications. C2 - 2016/// C3 - 2016 IEEE 16th International Conference on Nanotechnology (IEEE-nano) DA - 2016/// DO - 10.1109/nano.2016.7751440 SP - 191-192 ER - TY - JOUR TI - Lumped-parameter electromyogram-driven musculoskeletal hand model: A potential platform for real-time prosthesis control AU - Crouch, Dustin L. AU - Huang, He T2 - JOURNAL OF BIOMECHANICS AB - Simple, lumped-parameter musculoskeletal models may be more adaptable and practical for clinical real-time control applications, such as prosthesis control. In this study, we determined whether a lumped-parameter, EMG-driven musculoskeletal model with four muscles could predict wrist and metacarpophalangeal (MCP) joint flexion/extension. Forearm EMG signals and joint kinematics were collected simultaneously from 5 able-bodied (AB) subjects. For one subject with unilateral transradial amputation (TRA), joint kinematics were collected from the sound arm during bilateral mirrored motion. Twenty-two model parameters were optimized such that joint kinematics predicted by EMG-driven forward dynamic simulation closely matched measured kinematics. Cross validation was employed to evaluate the model kinematic predictions using Pearson׳s correlation coefficient (r). Model predictions of joint angles were highly to very highly positively correlated with measured values at the wrist (AB mean r=0.94, TRA r=0.92) and MCP (AB mean r=0.88, TRA r=0.93) joints during single-joint wrist and MCP movements, respectively. In simultaneous multi-joint movement, the prediction accuracy for TRA at the MCP joint decreased (r=0.56), while r-values derived from AB subjects and TRA wrist motion were still above 0.75. Though parameters were optimized to match experimental sub-maximal kinematics, passive and maximum isometric joint moments predicted by the model were comparable to reported experimental measures. Our results showed the promise of a lumped-parameter musculoskeletal model for hand/wrist kinematic estimation. Therefore, the model might be useful for EMG control of powered upper limb prostheses, but more work is needed to demonstrate its online performance. DA - 2016/12/8/ PY - 2016/12/8/ DO - 10.1016/j.jbiomech.2016.10.035 VL - 49 IS - 16 SP - 3901-3907 SN - 1873-2380 KW - Wrist KW - Simulation KW - Amputation KW - Parameter KW - Optimization ER - TY - CONF TI - Effect of flow rate and particle size on heat transfer to dense granular flows AU - Watkins, M. F. AU - Gould, R. D. AB - The increasing demand for renewable energy sources necessitates the development of more efficient technologies. Concentrated solar power (CSP) towers exhibit promising qualities, as temperatures greater than 1000°C are possible. The heat transfer fluid implemented to capture the sun’s energy significantly impacts the overall performance of a CSP system. Current fluids, such as molten nitrate salts and steam, have limitations; molten salts are limited by their small operational temperature range while steam requires high pressures and is unable to act as an effective storage medium. As a result, a new heat transfer fluid composed of ceramic particles is being investigated, as ceramic particles demonstrate no practical limit on operation temperature and have the ability to act as a storage medium. This study sought to further investigate the use of dense granular flows as a new heat transfer fluid. Previous work validated the use of such flows as a heat transfer fluid; the present work examined the effect of flow rate, as well as the particle size and type on the heat transfer to the particle fluid. Three different types of particles were tested, along with two different diameter particles. Of the three materials tested, the particle type did not appear to effect the heat transfer. Particle diameter, however, did effect the heat transfer, as a smaller diameter particle yielded slightly higher heat transfer to the fluid. Flow rates ranging from 30 to 200 kg/m2-s were tested. Initially, the heat transfer to the flow, characterized by the convective heat transfer coefficient, decreased with increasing flow rate. However, at approximately 80 kg/m2-s, the heat transfer coefficient began to increase with increasing flow rate. These results indicate that a dense granular flow consisting of small diameter particles and traveling at very slow or fast flow rates yields the best wall to “fluid” heat transfer. C2 - 2016/// C3 - Proceedings of the ASME 10th International Conference on Energy Sustainability, 2016, vol 1 DA - 2016/// DO - 10.1115/es2016-59258 ER - TY - JOUR TI - Dynamic IQC-Based Control of Uncertain LFT Systems With Time-Varying State Delay AU - Yuan, Chengzhi AU - Wu, Fen T2 - IEEE TRANSACTIONS ON CYBERNETICS AB - This paper presents a new exact-memory delay control scheme for a class of uncertain systems with time-varying state delay under the integral quadratic constraint (IQC) framework. The uncertain system is described as a linear fractional transformation model including a state-delayed linear time-invariant (LTI) system and time-varying structured uncertainties. The proposed exact-memory delay controller consists of a linear state-feedback control law and an additional term that captures the delay behavior of the plant. We first explore the delay stability and the L 2 -gain performance using dynamic IQCs incorporated with quadratic Lyapunov functions. Then, the design of exact-memory controllers that guarantee desired L 2 -gain performance is examined. The resulting delay control synthesis conditions are formulated in terms of linear matrix inequalities, which are convex on all design variables including the scaling matrices associated with the IQC multipliers. The IQC-based exact-memory control scheme provides a novel approach for delay control designs via convex optimization, and advances existing control methods in two important ways: 1) better controlled performance and 2) simplified design procedure with less computational cost. The effectiveness and advantages of the proposed approach have been demonstrated through numerical studies. DA - 2016/12// PY - 2016/12// DO - 10.1109/tcyb.2015.2503741 VL - 46 IS - 12 SP - 3320-3329 SN - 2168-2275 KW - Integral quadratic constraints (IQCs) KW - linear fractional transformation (LFT) KW - linear matrix inequalities (LMIs) KW - time-varying state delay KW - uncertain systems ER - TY - JOUR TI - Dynamic Fracture of Aluminum-Bonded Composites AU - Khanikar, Prasenjit AU - Wu, Qifeng AU - Zikry, M. A. T2 - JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME AB - A dislocation density-based crystal plasticity framework, a nonlinear computational finite-element methodology adapted for nucleation of crack on cleavage planes, and rational crystallographic orientation relations were used to predict the failure modes associated with the high strain rate behavior of aluminum-bonded composites. A bonded aluminum composite, suitable for high strain-rate damage resistance application, was modeled with different microstructures representing precipitates, dispersed particles, and grain boundary (GB) distributions. The dynamic fracture approach is used to investigate crack nucleation and growth as a function of the different microstructural characteristics of each alloy in bonded composites with and without pre-existing cracks. The nonplanar and irregular nature of the crack paths were mainly due to the microstructural features, such as precipitates and dispersed particles distributions and orientations, ahead of the crack front. The evolution of dislocation density and the subsequent formation of localized plastic slip contributed to the blunting of the propagating crack(s). Extensive geometrical and thermal softening resulted in localized plastic slip and had a significant effect on crack path orientations and directions along cleavage planes. DA - 2016/7// PY - 2016/7// DO - 10.1115/1.4033036 VL - 138 IS - 3 SP - SN - 1528-8889 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84971467668&partnerID=MN8TOARS KW - high strain-rate fracture KW - AA2195-AA2139 aluminum composite KW - dislocation density KW - crystal plasticity KW - nonlinear finite-element method ER - TY - CONF TI - Discrete element studies of gravity-driven dense granular flows in vertical cylindrical tubes AU - Chilamkurti, Y. N. AU - Gould, R. D. AB - The current paper focusses on the characterization of gravity-driven dry granular flows in cylindrical tubes. With a motive of using dense particulate media as heat transfer fluids (HTF), the main focus was to address the characteristics of flow regimes with a packing fraction of ∼60%. In a previous work [1], experimental and computational studies were conducted to understand the effects of different geometrical parameters on the flow physics. The current paper is an extension of that work to gain more insights into the granular flow physics. The three-dimensional computer simulations were conducted by implementing the Discrete Element Method (DEM) for the Lagrangian modelling of particles. Hertz-Mindilin models were used for the soft-particle formulations of inter-particulate contacts. Simulations were conducted to examine the particulate velocities and flow rates to understand the rheology in the dense flow regime. Past studies suggested the existence of a Gaussian mean velocity profile for dense gravity-driven granular flows. These observations were further analyzed by studying the influence of geometrical parameters on the same. The current work thus focusses on studying the rheology of dense granular flows and obtaining a better understanding of the velocity profiles, the wall friction characteristics, and the particle-wall contact behavior. C2 - 2016/// C3 - Proceedings of the ASME Power Conference, 2016 DA - 2016/// DO - 10.1115/power2016-59159 ER - TY - JOUR TI - Analysis on the anisotropic electromechanical properties of lead magnoniobate titanate single crystal for ring type ultrasonic motors AU - Shi, Xiang AU - Huang, Wenbin AU - Li, Fei AU - Li, Zhenrong AU - Xu, Zhuo AU - Jiang, Xiaoning AU - Wei, Xiaoyong T2 - AIP ADVANCES AB - This work discussed the optimized cut of single crystal lead magnoniobate titanate (PMNT) for use of ring type travelling wave ultrasonic motors (USMs), according to anisotropic analysis on electromechanical properties. The selection criterion of crystal orientation relies on the circular uniformity of the induced travelling wave amplitude on the stator surface. By calculating the equivalent elastic coefficient c11 and lateral piezoelectric constant d31, the optimal crystal orientations were proposed for PMNT single crystals poled along different directions. For single crystal poled along &lt;001&gt;c directions, the optimal orientation lies along [001]c with d31=-1335pC/N and k31=0.87. The crystallographic orientation [025]c is the optimized orientation for single crystals poled along &lt;011&gt;c direction with d31=199pC/N and k31=0.55. The optimal orientation of 1R configuration is [332¯]c with a large enhancement of d31 = 1201 and k31=0.92. DA - 2016/11// PY - 2016/11// DO - 10.1063/1.4967823 VL - 6 IS - 11 SP - SN - 2158-3226 ER - TY - JOUR TI - Turbulence/chemistry interactions in a ramp-stabilized supersonic hydrogen-air diffusion flame AU - Fulton, Jesse A. AU - Edwards, Jack R. AU - Cutler, Andrew AU - McDaniel, Jim AU - Goyne, Christopher T2 - COMBUSTION AND FLAME AB - Hybrid large-eddy / Reynolds-averaged Navier–Stokes simulations of turbulence / chemistry interactions occurring within a ramp-injected, hydrogen-fueled scramjet combustor are presented in this work. The experimental geometry is one of several studied at the Universty of Virginia as part of the National Center for Hypersonic Combined Cycle Propulsion and consists of an isolator, a combustor, and an extender section. Data collected includes coherent anti-Stokes Raman spectroscopy (CARS) measurements of major species composition and temperature at several streamwise planes, stereoscopic particle image velocimetry (PIV) measurements, hydroxyl planar-induced fluorescence (OH-PLIF) imagery, wall pressure distributions, and line-of-sight profiles of temperature and water concentration obtained using tunable diode laser spectroscopy (TDLAS). This paper focuses on an equivalence ratio of 0.17, which does not produce enough heat release to force a shock train into the isolator. The computational methods utilize a hybrid fourth-order central-difference / upwind strategy to enable accurate resolution of turbulent structures and employ a nine-species hydrogen oxidation mechanism. Generally accurate predictions of temperature, velocity, and nitrogen mole fraction are achieved through a ‘laminar chemistry’ assumption for the filtered species production rates, though results do improve slightly with the use of a simple turbulence / chemistry subgrid closure model. The predictions are most sensitive to the choice of isolator inflow boundary condition, with the use of a recycling / rescaling technique to sustain turbulent fluctuations resulting in an ‘over-mixing’ effect immediately downstream of the fuel injector. Turbulence–chemistry interactions in the flameholding region are examined from the standpoint of laminar flamelet theory. A region of high scalar dissipation rate, coincident with the breakdown of the fuel plume and the interaction of a reflected shock wave with the plume, inhibits flame propagation, forming a ‘hole’ in the flame. Advection of cooler fluid downstream into regions of moderate scalar dissipation enlarges the ‘hole’, but eventually the flame reconnects. These results point to one potential disadvantage of fuel-air mixing technologies that enhance axial vorticity – even if conditions for combustion are favorable, high strain rates generated by the interaction and breakdown of vortex pairs can lead to flame suppression. DA - 2016/12// PY - 2016/12// DO - 10.1016/j.combustflame.2016.09.017 VL - 174 SP - 152-165 SN - 1556-2921 KW - Supersonic combustion KW - Large-eddy simulation ER - TY - JOUR TI - The stabilization of partially-premixed jet flames in the presence of high potential electric fields AU - Kribs, James D. AU - Shah, Parth V. AU - Hutchins, Andrew R. AU - Reach, William A. AU - Muncey, Richard D. AU - June, M. Sean AU - Saveliev, Alexei AU - Lyons, Kevin M. T2 - JOURNAL OF ELECTROSTATICS AB - Numerous research efforts have focused on flame stabilization and emissions. Based on initial experiments, specific mechanisms resulting from DC electric fields were chosen to be investigated, namely the chemical, thermal, and ionization mechanisms. Numerical simulations were performed on premixed propane-ozone-air flames to characterize ozone effects on flame speed resulting from the formation of ozone in high potential electric fields. These results were compared against partially premixed flame experiments to observe the dominant influences within leading edge stabilization within high potential electric fields. It was found that the electromagnetic or ionization influences, serve as the dominant effect on the combustion zone. DA - 2016/12// PY - 2016/12// DO - 10.1016/j.elstat.2016.08.002 VL - 84 SP - 1-9 SN - 1873-5738 KW - Jet flame stability KW - Plasma excitation KW - Ozone formation KW - High potential electric field ER - TY - JOUR TI - Regulation in free amino acid profile and protein synthesis pathway of growing pig skeletal muscles by low-protein diets for different time periods AU - Li, Y. H. AU - Wei, H. K. AU - Li, F. N. AU - Kim, S. W. AU - Wen, C. Y. AU - Duan, Y. H. AU - Guo, Q. P. AU - Wang, W. L. AU - Liu, H. N. AU - Yin, Y. L. T2 - JOURNAL OF ANIMAL SCIENCE AB - The objective of the study was to explore the extent to which the dietary CP level can be reduced for maintaining muscle protein deposition in growing pigs as well as the related mechanism and whether the response to dietary protein restriction is diversely modified throughout the 2 trial periods. A total of 36 pigs (9.57 ± 0.64 kg initial BW) were individually penned and fed 1 of 3 diets for 10 or 25 d. During each period, the diets contained 20, 17, and 14% CP, respectively. Both the 17% CP diet and the 14% CP diet were supplemented with Lys, Met, Thr, and Trp to provide the same total concentrations as those in the 20% CP diet. Results showed that feeding the 14% CP diet for 10 or 25 d seriously impaired ( < 0.05) growth performance of the pigs compared with those fed the 20 or 17% CP diets. Pigs fed the 20% CP diet for 25 d had a higher ( < 0.05) serum content of urea nitrogen than those fed the 17 and 14% CP diets. In addition, the free AA (FAA) profile in skeletal muscle of the pigs was evidently changed ( < 0.05) by the low-protein diets for 25 d; of note, the 14% CP diet increased ( < 0.05) the size of muscle FAA pool compared with the 20% CP diet. Meanwhile, on d 25, reducing dietary CP levels also influenced ( < 0.05) mRNA levels of specific AA transceptors expressed in skeletal muscle, especially revealing the striking differences between the 14 and 20% CP diet-fed pigs. Most importantly, we observed a globally decreased ( < 0.05) activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway in skeletal muscle of pigs fed the 14% CP diet, whereas only partial inhibition was observed for those fed the 17% CP diet compared with those fed the 20% CP diet. However, feeding the low-protein diets for 10 d had minimal effects on serum parameters, muscle FAA profile, and muscle mTORC1 pathway of the pigs. Taken together, our results indicate that supplementing with limiting AA to the 14% CP diet is not highly effective for the pigs in restoring protein synthesis and muscle growth, whereas the 17% CP diet likely maintains the pigs' muscle mass, which were regulated, at least in part, by mediating AA transceptors expression, FAA profile, and activation of the mTORC1 pathway. DA - 2016/12// PY - 2016/12// DO - 10.2527/jas.2016-0917 VL - 94 IS - 12 SP - 5192-5205 SN - 1525-3163 KW - amino acid transceptor KW - free amino acids KW - growing pig KW - low-protein diet KW - mammalian target of rapamycin complex 1 pathway KW - skeletal muscle ER - TY - JOUR TI - Optics of Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII): delay lines and alignment AU - Dhabal, Arnab AU - Rinehart, Stephen A. AU - Rizzo, Maxime J. AU - Mundy, Lee AU - Fixsen, Dale AU - Sampler, Henry AU - Mentzell, Eric AU - Veach, Todd AU - Silverberg, Robert F. AU - Furst, Stephen AU - Dow, Thomas AU - Ade, Peter AU - Tucker, Carole T2 - OPTICAL AND INFRARED INTERFEROMETRY AND IMAGING V AB - We present the optics of Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) as it gets ready for launch. BETTII is an 8-meter baseline far-infrared (30-90 μm) interferometer mission with capabilities of spatially resolved spectroscopy aimed at studying star formation and galaxy evolution. The instrument collects light from its two arms, makes them interfere, divides them into two science channels (30-50 μm and 60-90 μm), and focuses them onto the detectors. It also separates out the NIR light (1-2.5 μm) and uses it for tip-tilt corrections of the telescope pointing. Currently, all the optical elements have been fabricated, heat treated, coated appropriately and are mounted on their respective assemblies. We are presenting the optical design challenges for such a balloon borne spatio- spectral interferometer, and discuss how they have been mitigated. The warm and cold delay lines are an important part of this optics train. The warm delay line corrects for path length differences between the left and the right arm due to balloon pendulation, while the cold delay line is aimed at introducing a systematic path length difference, thereby generating our interferograms from where we can derive information about the spectra. The details of their design and the results of the testing of these opto-mechanical parts are also discussed. The sensitivities of different optical elements on the interferograms produced have been determined with the help of simulations using FRED software package. Accordingly, an alignment plan is drawn up which makes use of a laser tracker, a CMM, theodolites and a LUPI interferometer. DA - 2016/// PY - 2016/// DO - 10.1117/12.2230218 VL - 9907 SP - SN - 0277-786X KW - spatio-spectral interferometry KW - far infra-red KW - delay line KW - capacitive sensor KW - interferometric simulation KW - metrology KW - alignment ER - TY - JOUR TI - Fiber-optic temperature profiling for thermal protection system heat shields AU - Black, Richard J. AU - Costa, Joannes M. AU - Zarnescu, Livia AU - Hackney, Drew A. AU - Moslehi, Behzad AU - Peters, Kara J. T2 - OPTICAL ENGINEERING AB - To achieve better designs for spacecraft heat shields for missions requiring atmospheric aero-capture or entry/reentry, reliable thermal protection system (TPS) sensors are needed. Such sensors will provide both risk reduction and heat-shield mass minimization, which will facilitate more missions and enable increased payloads and returns. This paper discusses TPS thermal measurements provided by a temperature monitoring system involving lightweight, electromagnetic interference-immune, high-temperature resistant fiber Bragg grating (FBG) sensors with a thermal mass near that of TPS materials together with fast FBG sensor interrogation. Such fiber-optic sensing technology is highly sensitive and accurate, as well as suitable for high-volume production. Multiple sensing FBGs can be fabricated as arrays on a single fiber for simplified design and reduced cost. Experimental results are provided to demonstrate the temperature monitoring system using multisensor FBG arrays embedded in a small-size super-light ablator (SLA) coupon which was thermally loaded to temperatures in the vicinity of the SLA charring temperature. In addition, a high-temperature FBG array was fabricated and tested for 1000°C operation, and the temperature dependence considered over the full range (cryogenic to high temperature) for which silica fiber FBGs have been subjected. DA - 2016/11// PY - 2016/11// DO - 10.1117/1.oe.55.11.114101 VL - 55 IS - 11 SP - SN - 1560-2303 KW - thermal protection systems KW - thermal protection system KW - temperature sensing KW - fiber-optic sensing KW - fiber Bragg gratings ER - TY - JOUR TI - Fiber Bragg gratings as transient thermal gradient sensors AU - Hackney, Drew A. AU - Peters, Kara J. AU - Black, Richard J. AU - Costa, Joannes M. AU - Moslehi, Behzad T2 - OPTICAL ENGINEERING AB - We experimentally subject a fiber Bragg grating to an unknown, variable temperature gradient. We use the full-spectral response of the grating to determine the magnitude of the gradient over the length of the grating via the full width at quarter maximum bandwidth. The experimental bandwidth and spectrum deformation were compared with a numerical model consisting of an analytical heat transfer model, a finite element analysis model, and the transfer matrix (T-matrix) method. The numerical model showed excellent agreement with the experimental results when the T-matrix method was modified to include the slope of the gradient in addition to the magnitude of the gradient. DA - 2016/11// PY - 2016/11// DO - 10.1117/1.oe.55.11.114102 VL - 55 IS - 11 SP - SN - 1560-2303 KW - fiber Bragg grating KW - full spectrum KW - temperature gradient KW - transfer matrix method ER - TY - JOUR TI - A cryogenic target for Compton scattering experiments at HI gamma S AU - Kendellen, D. P. AU - Ahmed, M. W. AU - Baird, E. AU - Feldman, G. AU - Perreau, N. AU - Wallace, P. W. AU - Weller, H. R. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Abstract We have developed a cryogenic target for use at the High Intensity γ-ray Source (HIγS). The target system is able to liquefy 4He at 4 K, hydrogen at 20 K, and deuterium at 23 K to fill a 0.3 L Kapton cell. Liquid temperatures and condenser pressures are recorded throughout each run in order to ensure that the target's areal density is known to ∼ 1 %. The target is being utilized in a series of experiments which probe the electromagnetic polarizabilities of the nucleon. DA - 2016/12/21/ PY - 2016/12/21/ DO - 10.1016/j.nima.2016.10.016 VL - 840 SP - 174-180 SN - 1872-9576 KW - Cryogenic target KW - Liquid helium KW - Liquid deuterium KW - Compton scattering KW - Nucleon polarizabilities ER - TY - CONF TI - Parametric study of a fluidic artificial muscle actuated electrohydraulic system AU - Chapman, E. AU - Jenkins, T. AU - Bryant, M. AB - Fluidic artificial muscles have the potential for a wide range of uses; from injury rehabilitation to high-powered hydraulic systems. Their modeling to date has largely been quasi-static and relied on the operator to adjust pressure so as to control force output and utilization while little work has been done to analyze the kinematics of the driving-systems involved in their operation. This paper utilizes an established electro-hydraulic model to perform a study of the components of a fluidic artificial muscle actuated climbing robot. Its purpose is to determine the effect of the robotic subsystems on function and efficiency for a small-scale system in order to extrapolate more general design and analysis schemes for future use. Its results indicate that important aspects to consider in design of the hydraulic system are system payload, operating pressure, pump selection, and FAM construction. C2 - 2016/// C3 - Proceedings of the asme conference on smart materials adaptive DA - 2016/// DO - 10.1115/smasis2016-9044 ER - TY - JOUR TI - Muscle Forces and Their Contributions to Vertical and Horizontal Acceleration of the Center of Mass During Sit-to-Stand Transfer in Young, Healthy Adults AU - Caruthers, Elena J. AU - Thompson, Julie A. AU - Chaudhari, Ajit M. W. AU - Schmitt, Laura C. AU - Best, Thomas M. AU - Saul, Katherine R. AU - Siston, Robert A. T2 - JOURNAL OF APPLIED BIOMECHANICS AB - Sit-to-stand transfer is a common task that is challenging for older adults and others with musculoskeletal impairments. Associated joint torques and muscle activations have been analyzed two-dimensionally, neglecting possible three-dimensional (3D) compensatory movements in those who struggle with sit-to-stand transfer. Furthermore, how muscles accelerate an individual up and off the chair remains unclear; such knowledge could inform rehabilitation strategies. We examined muscle forces, muscleinduced accelerations, and interlimb muscle force differences during sit-to-stand transfer in young, healthy adults. Dynamic simulations were created using a custom 3D musculoskeletal model; static optimization and induced acceleration analysis were used to determine muscle forces and their induced accelerations, respectively. The gluteus maximus generated the largest force (2009.07 ± 277.31 N) and was a main contributor to forward acceleration of the center of mass (COM) (0.62 ± 0.18 m/s 2 ), while the quadriceps opposed it. The soleus was a main contributor to upward (2.56 ± 0.74 m/s 2 ) and forward acceleration of the COM (0.62 ± 0.33 m/s 2 ). Interlimb muscle force differences were observed, demonstrating lower limb symmetry cannot be assumed during this task, even in healthy adults. These findings establish a baseline from which deficits and compensatory strategies in relevant populations (eg, elderly, osteoarthritis) can be identified. DA - 2016/10// PY - 2016/10// DO - 10.1123/jab.2015-0291 VL - 32 IS - 5 SP - 487-503 SN - 1543-2688 KW - musculoskeletal modeling KW - OpenSim KW - knee ER - TY - JOUR TI - Multi-frequency ferromagnetic resonance investigation of nickel nanocubes encapsulated in diamagnetic magnesium oxide matrix AU - Nellutla, S. AU - Nori, S. AU - Singamaneni, S. R. AU - Prater, J. T. AU - Narayan, J. AU - Smirnov, A. I. T2 - Journal of Applied Physics DA - 2016/// PY - 2016/// VL - 120 IS - 22 ER - TY - JOUR TI - Loss-induced Enhanced Transmission in Anisotropic Density-near-zero Acoustic Metamaterials AU - Shen, Chen AU - Jing, Yun T2 - SCIENTIFIC REPORTS AB - Abstract Anisotropic density-near-zero (ADNZ) acoustic metamaterials are investigated theoretically and numerically in this paper and are shown to exhibit extraordinary transmission enhancement when material loss is induced. The enhanced transmission is due to the enhanced propagating and evanescent wave modes inside the ADNZ medium thanks to the interplay of near-zero density, material loss, and high wave impedance matching in the propagation direction. The equi-frequency contour (EFC) is used to reveal whether the propagating wave mode is allowed in ADNZ metamaterials. Numerical simulations based on plate-type acoustic metamaterials with different material losses were performed to demonstrate collimation and subwavelength imaging enabled by the induced loss in ADNZ media. This work provides a different way for manipulating acoustic waves. DA - 2016/11/25/ PY - 2016/11/25/ DO - 10.1038/srep37918 VL - 6 SP - SN - 2045-2322 ER - TY - CONF TI - Laser-generated-focused ultrasound transducers for microbubble-mediated, dual-excitation sonothrombolysis AU - Kim, J. AU - Chang, W. Y. AU - Lindsey, B. D. AU - Dayton, P. A. AU - Dai, X. M. AU - Stavas, J. M. AU - Jiang, X. N. AB - A laser-generated-focused ultrasound (LGFU) transducer generates high-pressure (up to 20 MPa), high-frequency (>10 MHz) shock waves with a tight focal spot. In this work, we aim to demonstrate the feasibility of using LGFU transducers for sonothrombolysis in vitro. A carbon black LGFU transducer was designed, fabricated and characterized. The prototyped LGFU was applied with in-vitro thrombolysis tests involving microbubble contrast agent (MCA). A conventional piezo ultrasound transducer was used as a secondary excitation source to enhance the cavitation effect by dual-frequency excitation. The in vitro test results showed that microbubble-mediated LGFU treatment can yield the lytic rate of approximately 2 mg/min, suggesting that LGFU transducers may be useful in precision high lytic rate sonothrombolysis. C2 - 2016/// C3 - 2016 ieee international ultrasonics symposium (ius) DA - 2016/// DO - 10.1109/ultsym.2016.7728473 ER - TY - JOUR TI - Laminar/turbulent airflow and microsphere deposition in a patient-specific airway geometry using an open-source solver AU - Vaish, Mayank AU - Kleinstreuer, Clement AU - Kolanjiyil, Arun V. AU - Saini, Nadish AU - Pillalamarri, Narasimha R. T2 - INTERNATIONAL JOURNAL OF BIOMEDICAL ENGINEERING AND TECHNOLOGY AB - Using the open-source software OpenFOAM as the solver, airflow and microsphere transport have been simulated in a patient-specific lung-airway model. A suitable transitional turbulence model was validated and implemented to accurately simulate airflow fields, as the laryngeal jet occurring in the throat region may induce turbulence immediately downstream. Furthermore, a modified eddy interaction model with a generalised near-wall correction factor is presented that more accurately simulates the particle trajectories and subsequent deposition phenomena which are especially affected by near-wall velocity fluctuations. Particle depositions in the realistic lung-airway configuration are compared with those in an idealised upper airway model. The results indicate that for microsphere deposition in turbulent airflow regions, selection of an appropriate near-wall correction factor can reduce the problem of subject variability for different lung-airway configurations. Open-source solvers for lung-aerosol dynamics simulations, such as OpenFOAM, are predictive tools which are basically cost-free, flexible, largely user-friendly, and portable. DA - 2016/// PY - 2016/// DO - 10.1504/ijbet.2016.079145 VL - 22 IS - 2 SP - 145-161 SN - 1752-6426 KW - OpenFOAM solver KW - patient-specific geometry and idealised configuration KW - modified eddy interaction model KW - microsphere transport and deposition KW - practical Stokes number range ER - TY - JOUR TI - EX VIVO PORCINE ARTERIAL AND CHORIOALLANTOIC MEMBRANE ACOUSTIC ANGIOGRAPHY USING DUAL-FREQUENCY INTRAVASCULAR ULTRASOUND PROBES AU - Martin, K. Heath AU - Lindsey, Brooks D. AU - Ma, Jianguo AU - Nichols, Timothy C. AU - Jiang, Xiaoning AU - Dayton, Paul A. T2 - ULTRASOUND IN MEDICINE AND BIOLOGY AB - The presence of blood vessels within a developing atherosclerotic plaque has been found to be correlated with increased plaque vulnerability and ensuing cardiac events, however, detection of coronary intraplaque neovascularization poses a significant challenge in the clinic. We describe here a new in vivo intravascular ultrasound imaging method using a dual-frequency transducer to visualize contrast flow in microvessels with high specificity. This method uses a specialized transducer capable of exciting contrast agents at a low frequency (5.5 MHz) while detecting their nonlinear superhamonics at a much higher frequency (37 MHz). In vitro evaluation of the approach was performed in a microvascular phantom to produce 3-D renderings of simulated vessel patterns and to determine image quality metrics as a function of depth. Furthermore, we describe the ability of the system to detect microvessels both ex vivo using porcine arteries and in vivo using the chorioallantoic membrane of a developing chicken embryo with optical confirmation. Dual-frequency contrast-specific imaging was able to resolve vessels similar in size to those found in vulnerable atherosclerotic plaques at clinically relevant depths. The results of this study add to the support for further evaluation and translation of contrast-specific imaging in intravascular ultrasound for the detection of vulnerable plaques in atherosclerosis. DA - 2016/9// PY - 2016/9// DO - 10.1016/j.ultrasmedbio.2016.04.008 VL - 42 IS - 9 SP - 2294-2307 SN - 1879-291X KW - Ultrasonography KW - Vasa vasorum KW - Dual frequency KW - Superharmonic KW - Acoustic angiography KW - Intravascular ultrasound KW - Microbubble KW - Contrast KW - Atherosclerosis ER - TY - CONF TI - Bubble tracking simulations of turbulent two-phase flows AU - Fang, J. AU - Bolotnov, I. A. AB - Bubbly flow is quite common in various natural and engineering phenomena. In particular, nuclear engineers are interested in fundamental understanding of the bubbly flow behavior due to its importance in cooling light water reactor cores. Given the extreme conditions and complex support structures in nuclear reactor cores, it is very challenging to study the flow behavior using high-fidelity experiments. Typically validated computational codes are chosen as practical tools for the thermal-hydraulic and safety analyses. As the new generations of nuclear reactors are being developed, more advanced modeling techniques are required to design safe and efficient systems. Different from most simulation approaches, direct numerical simulation (DNS) employs no turbulence closure assumptions, which makes it a promising tool for model development. The major bottleneck of DNS was and remains to be the high computational cost, increasing exponentially with the Reynolds number. However, thanks to the on-going improvements in computer power, these computationally expensive simulations are becoming more and more affordable. Coupled with level-set interface tracking method (ITM), DNS can be used for the high-fidelity studies of two-phase bubbly flows with unprecedented details. Meanwhile, another concern that arises is how one can best take advantage of the ‘big data’ generated from large-scale DNS and translate it into new knowledge. The traditional level-set method utilizes a signed distance field to distinguish different phases while the interface is modeled by the zero level-set. Although level-set method can distinguish gas bubbles from the liquid phase, it cannot recognize and track individual bubbles which hinders the collection of useful bubble information. As a result, the bubble tracking capability has to be developed to improve the data extraction efficiency. In the present work, a marker field is created and advected for bubble distinction and extraction of detailed bubble parameters from the simulations. Each bubble in the flow gets assigned a unique ID, based on which the code will collect the corresponding bubble information. It has been demonstrated that bubble tracking capability can significantly improve the data extraction efficiency for level-set based two-phase flow simulations. Statistical analysis tools are also developed to post-process the recorded information about the bubbles to study the dependencies/correlations of bubble behavior with bubble local conditions. For example, in the pressurized water reactor (PWR) subchannel geometry investigated in this paper, bubbles are observed to experience different relative velocity when presenting at different distance from fuel rod surfaces. With proper grouping criterion, statistical analysis would allow introducing variable drag coefficient for bubbles based on their positions. These new insights are contributing to more accurate modeling of the multiphase computational fluid dynamic (M-CFD) simulations, and better prediction of two-phase flow behavior in engineering systems. Together with the analysis tools, bubble tracking capability will open a new door to study and understand two-phase flows. C2 - 2016/// C3 - Proceedings of the asme fluids engineering division summer meeting, 2016, vol 1b DA - 2016/// DO - 10.1115/fedsm2016-1005 ER - TY - CONF TI - Aggregate control of clustered networks with inter-cluster time delays AU - Boker, A. M. AU - Yuan, C. Z. AU - Wu, F. AU - Chakrabortty, A. AB - We address a control problem for networks that have multiple dense clusters with sparse interconnection structure. By making use of the time-scale separation properties of such networks, we design state-feedback controllers at the cluster level to guarantee stability in the presence of time varying delays in the inter-cluster feedback channels. Applying results from singular perturbation theory, we show that when these individual controllers are implemented on the actual network model, the closed-loop response is close to that obtained from the approximate models, provided that the clustering is strong and the time delay is below the maximum limit. The design procedure is demonstrated by a simulation example. C2 - 2016/// C3 - 2016 american control conference (acc) DA - 2016/// DO - 10.1109/acc.2016.7526506 SP - 5340-5345 ER - TY - CONF TI - Adaptive windowing in mechanically-steered intravascular ultrasound imaging: Ex vivo and in vivo studies with contrast enhancement AU - Lindsey, B. D. AU - Dayton, P. A. AU - Jiang, X. N. AB - Intravascular ultrasound (IVUS) is utilized frequently in vascular diseases such as coronary artery disease and peripheral vascular disease. Many techniques-including but not limited to IVUS-seek to characterize plaques in coronary artery disease in order to determine which are likely to rupture. Biologists have recently identified the development of intra-plaque vasa vasorum, small vessels which supply the coronaries with oxygen and nutrients, as a potential indicator of plaque vulnerability. By imaging plaques with penetrating vasa vasorum, high resolution contrast-enhanced ultrasound imaging may allow identification of vulnerable plaques prior to rupture. Here we present processing techniques for improving spatial resolution and image contrast in mechanically steered ultrasound imaging based on minimum variance (MV) beamforming and the phase coherence factor (PCF). In tissue-mimicking phantom studies, PCF processing improved CTR by a mean of 4.2 dB, while combined MV and PCF processing improved spatial resolution by 41.7%. These processing strategies may improve image quality in both conventional B-mode IVUS and contrast-enhanced IVUS. C2 - 2016/// C3 - 2016 ieee international ultrasonics symposium (ius) DA - 2016/// DO - 10.1109/ultsym.2016.7728433 ER - TY - CONF TI - A dual-frequency endoscopic transducer for imaging vascular invasion in pancreatic cancer AU - Lindsey, B. D. AU - Dayton, P. A. AU - Kim, J. AU - Jiang, X. N. AB - Pancreatic adenocarcinoma is among the most deadly of cancers, with surgery being typically the only curative option. Tumor resectability is typically determined via endoscopic ultrasound imaging, however, many patients who may be eligible for resection are not offered surgery due to the difficulty in determining vascular or lymphatic invasion. Contrast-enhanced ultrasound imaging may address this problem. We describe the development of a single element dual-frequency transducer for rotational endoscopic imaging designed to operate at 4/20 MHz to image microbubble superharmonics. The ability of the developed transducer to image in a tissue mimicking phantom at depths from 1.0 cm (CTR = 21.6 dB) to 2.5 cm (CTR = 11.4 dB) is demonstrated. The completed 4-Fr transducer is also capable of imaging microbubbles in a 200 µm-diameter tube through the wall of a ∼1 cm-diameter porcine artery, suggesting such a device may be suitable for direct visualization of small vessels from within the lumen of larger vessels such as the portal vein. C2 - 2016/// C3 - 2016 ieee international ultrasonics symposium (ius) DA - 2016/// DO - 10.1109/ultsym.2016.7728435 ER - TY - CONF TI - A dual-frequency co-linear array for prostate acoustic angiography AU - Li, S. B. AU - Kim, J. AU - Wang, Z. C. AU - Jiang, X. N. AU - Kasoji, S. AU - Lindsey, B. AU - Dayton, P. A. AB - Approximately 80% of men who reach 80-years of age will have some form of prostate cancer. The challenge remains to differentiate indolent from aggressive disease. Based on recent research, acoustic angiography, a novel contrast enhanced ultrasound imaging technique, can provide high-resolution visualization of tissue microvasculature and has demonstrated the ability to differentiate vascular characteristics between healthy and tumor tissue. We hypothesize that transrectal acoustic angiography may enhance assessment of prostate cancer. In this paper, we describe the development of a dual layer co-linear array ultrasound transducer for transrectal acoustic angiography. The KLM model and Field II were used for the element design and acoustic field simulation, respectively. The probe consists of 64 transmit elements with a center frequency of 3 MHz and 128 receive elements with a center frequency of 15 MHz. The dimensions of the array are 18 mm in azimuth and 8 mm in elevation. The pitch is 280 μm for transmitting (TX) elements and 140 μm for receiving (RX) elements. Pulse-echo test of TX/RX elements were conducted and compared with the simulation results. Real-time contrast imaging was tested using a Verasonics system. Non-linear responses from microbubble contrast agents at a depth of 18 mm were clearly observed. The axial beam width (-6 dB) and CTR were calculated from the measured signals to be 400 μm and 20 dB, respectively. These results suggest that the prototype co-linear array is capable of performing dual-frequency superharmonic imaging of microbubbles for prostate cancer assessment. C2 - 2016/// C3 - 2016 ieee international ultrasonics symposium (ius) DA - 2016/// DO - 10.1109/ultsym.2016.7728718 ER - TY - JOUR TI - Split Hopkinson bar measurement using high-speed full-spectrum fiber Bragg grating interrogation AU - Seng, Frederick AU - Hackney, Drew AU - Goode, Tyler AU - Shumway, LeGrand AU - Hammond, Alec AU - Shoemaker, George AU - Pankow, Mark AU - Peters, Kara AU - Schultz, Stephen T2 - APPLIED OPTICS AB - The development and validation of a high-speed, full-spectrum measurement technique is described for fiber Bragg grating (FBG) sensors. A FBG is surface-mounted to a split-Hopkinson tensile bar specimen to induce high strain rates. The high strain gradients and large strains that indicate material failure are analyzed under high strain rates up to 500 s-1. The FBG is interrogated using a high-speed full-spectrum solid-state interrogator with a repetition rate of 100 kHz. The captured deformed spectra are analyzed for strain gradients using a default interior point algorithm in combination with the modified transfer matrix approach. This paper shows that by using high-speed full-spectrum interrogation of an FBG and the modified transfer matrix method, highly localized strain gradients and discontinuities can be measured without a direct line of sight. DA - 2016/9// PY - 2016/9// DO - 10.1364/ao.55.007179 VL - 55 IS - 25 SP - 7179-7185 SN - 2155-3165 ER - TY - JOUR TI - Robust switching output-feedback control of time-varying polytopic uncertain systems AU - Yuan, Chengzhi AU - Wu, Fen T2 - INTERNATIONAL JOURNAL OF CONTROL AB - The problem of designing a globally optimal robust output feedback controller for time-varying polytopic uncertain systems is a well-known non-convex optimisation problem. In this paper, new sufficient conditions for both robust H2 and H∞ switching output-feedback control syntheses are proposed in terms of bilinear matrix inequalities (BMIs) under the multiple Lyapunov function framework. This set of synthesis conditions is further reduced to a special type of BMIs, which can be solved effectively using linear matrix inequality optimisation plus a line search. The associated robust output-feedback controller is constructed as a switching-type full-order dynamic output-feedback controller, consisting of a family of linear time-invariant subcontrollers and a min-switching logic. The proposed approach features the important property of computational efficiency with stringent performance. Its effectiveness and advantages have been demonstrated through extensive numerical studies. DA - 2016/// PY - 2016/// DO - 10.1080/00207179.2016.1154607 VL - 89 IS - 11 SP - 2262-2276 SN - 1366-5820 KW - Min-switching control KW - polytopic uncertainties KW - output feedback KW - linear matrix inequalities (LMIs) ER - TY - JOUR TI - On the evaluation of effective density for plate- and membrane-type acoustic metamaterials without mass attached AU - Huang, Tai-Yun AU - Shen, Chen AU - Jing, Yun T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA AB - The effective densities of plate- and membrane-type acoustic metamaterials (AMMs) without mass attached are studied theoretically and numerically. Three models, including the analytic model (based on the plate flexural wave equation and the membrane wave equation), approximate model (under the low frequency approximation), and the finite element method (FEM) model, are first used to calculate the acoustic impedance of square and clamped plates or membranes. The effective density is then obtained using the resulting acoustic impedance and a lumped model. Pressure transmission coefficients of the AMMs are computed using the obtained densities. The effect of the loss from the plate is also taken into account. Results from different models are compared and good agreement is found, particularly between the analytic model and the FEM model. The approximate model is less accurate when the frequency of interest is above the first resonance frequency of the plate or membrane. The approximate model, however, provides simple formulae to predict the effective densities of plate- or membrane-type AMMs and is accurate for the negative density frequency region. The methods presented in this paper are useful in designing AMMs for manipulating acoustic waves. DA - 2016/8// PY - 2016/8// DO - 10.1121/1.4960590 VL - 140 IS - 2 SP - 908-916 SN - 1520-8524 ER - TY - JOUR TI - Narrow band flame emission from dieseline and diesel spray combustion in a constant volume combustion chamber AU - Wu, Zengyang AU - Jing, Wei AU - Zhang, Weibo AU - Roberts, William L. AU - Fang, Tiegang T2 - FUEL AB - In this paper, spray combustion of diesel (No. 2) and diesel-gasoline blend (dieseline: 80% diesel and 20% gasoline by volume) were investigated in an optically accessible constant volume combustion chamber. Effects of ambient conditions on flame emissions were studied. Ambient oxygen concentration was varied from 12% to 21% and three ambient temperatures were selected: 800 K, 1000 K and 1200 K. An intensified CCD camera coupled with bandpass filters was employed to capture the quasi-steady state flame emissions at 430 nm and 470 nm bands. Under non-sooting conditions, the narrow-band flame emissions at 430 nm and 470 nm can be used as indicators of CH∗ (methylidyne) and HCHO∗ (formaldehyde), respectively. The lift-off length was measured by imaging the OH∗ chemiluminescence at 310 nm. Flame emission structure and intensity distribution were compared between dieseline and diesel at wavelength bands. Flame emission images show that both narrow band emissions become shorter, thinner and stronger with higher oxygen concentration and higher ambient temperature for both fuels. Areas of weak intensity are observed at the flame periphery and the upstream for both fuels under all ambient conditions. Average flame emission intensity and area were calculated for 430 nm and 470 nm narrow-band emissions. At a lower ambient temperature the average intensity increases with increasing ambient oxygen concentration. However, at the 1200 K ambient temperature condition, the average intensity is not increasing monotonically for both fuels. For most of the conditions, diesel has a stronger average flame emission intensity than dieseline for the 430 nm band, and similar phenomena can be observed for the 470 nm band with 800 K and 1200 K ambient temperatures. However, for the 1000 K ambient temperature cases, dieseline has stronger average flame emission intensities than diesel for all oxygen concentrations at 470 nm band. Flame emissions for the two bands have a smaller average emission area under higher ambient oxygen concentration and temperature for both fuels, while dieseline has a slightly larger average flame emission area than diesel for most cases. The experimental findings were further analyzed and discussed based on an empirical model of the distributions of air and fuel. Both experiment results and theoretical model show that dieseline has wider 430 nm and 470 nm band emissions than diesel under all conditions. DA - 2016/12/1/ PY - 2016/12/1/ DO - 10.1016/j.fuel.2016.08.022 VL - 185 SP - 829-846 SN - 1873-7153 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84982090895&partnerID=MN8TOARS KW - Dieseline KW - Spray combustion KW - Lift-off length KW - Flame structure KW - Chemiluminescence ER - TY - JOUR TI - Multi-sample Arabidopsis Growth and Imaging Chamber (MAGIC) for long term imaging in the ZEISS Lightsheet Z.1 AU - Balaguer, Maria Angels de Luis AU - Ramos-Pezzotti, Marina AU - Rahhal, Morjan B. AU - Melvin, Charles E. AU - Johannes, Eva AU - Horn, Timothy J. AU - Sozzani, Rosangela T2 - DEVELOPMENTAL BIOLOGY AB - Time-course imaging experiments on live organisms are critical for understanding the dynamics of growth and development. Light-sheet microscopy has advanced the field of long-term imaging of live specimens by significantly reducing photo-toxicity and allowing fast acquisition of three-dimensional data over time. However, current light-sheet technology does not allow the imaging of multiple plant specimens in parallel. To achieve higher throughput, we have developed a Multi-sample Arabidopsis Growth and Imaging Chamber (MAGIC) that provides near-physiological imaging conditions and allows high-throughput time-course imaging experiments in the ZEISS Lightsheet Z.1. Here, we illustrate MAGIC's imaging capabilities by following cell divisions, as an indicator of plant growth and development, over prolonged time periods. To automatically quantify the number of cell divisions in long-term experiments, we present a FIJI-based image processing pipeline. We demonstrate that plants imaged with our chamber undergo cell divisions for >16 times longer than those with the glass capillary system supplied by the ZEISS Z1. DA - 2016/11/1/ PY - 2016/11/1/ DO - 10.1016/j.ydbio.2016.05.029 VL - 419 IS - 1 SP - 19-25 SN - 1095-564X KW - Arabidopsis root KW - Light sheet KW - 3D printing KW - Time-lapse imaging ER - TY - JOUR TI - Modeling of submicron particle filtration in an electret monolith filter with rectangular cross-section microchannels AU - Wu, Guojiang AU - Miao, Zhengqing AU - Jasper, Warren J. AU - Kuznetsov, Andrey V. T2 - AEROSOL SCIENCE AND TECHNOLOGY AB - Electret monolith filters have the advantage of low pressure drop and high filtration efficiency. In such filters, the filtration of submicron aerosol particles occurs as air passes through millions of microchannels. This article investigates the flow and filtration mechanisms in a representative rectangular microchannel of an electret monolith filter. An improved incompressible lattice Boltzmann method with Bhatnagar–Gross–Krook (traditionally shortened as LBGK) and lattice velocity D3Q15 model is employed to simulate no-slip and slip flows in the rectangular microchannels of a monolith filter. We considered mono-disperse submicron particles and one-way coupling (particle motion was affected by the flow, but the presence of particles did not affect the flow). Based on flow computations, the effects of key dimensionless parameters (Reynolds number, Knudsen number, Stokes number and the dimensionless length of the channel) on the total capture efficiency of mono-disperse submicron particles were investigated. Our results indicate that the optimal monolith filter should be characterized by a Knudsen number between 0.022 and 0.044, and that the dimensionless length of the channel should be between 4 and 8.Copyright © 2016 American Association for Aerosol Research DA - 2016/// PY - 2016/// DO - 10.1080/02786826.2016.1218437 VL - 50 IS - 10 SP - 1033-1043 SN - 1521-7388 ER - TY - JOUR TI - Mechanical stresses at the cathode–electrolyte interface in lithium-ion batteries AU - Kim, Sangwook AU - Huang, Hsiao-Ying Shadow T2 - Journal of Materials Research DA - 2016/10/19/ PY - 2016/10/19/ DO - 10.1557/jmr.2016.373 VL - 31 IS - 22 SP - 3506-3512 J2 - J. Mater. Res. LA - en OP - SN - 0884-2914 2044-5326 UR - http://dx.doi.org/10.1557/jmr.2016.373 DB - Crossref ER - TY - JOUR TI - Low-Power Wearable Systems for Continuous Monitoring of Environment and Health for Chronic Respiratory Disease AU - Dieffenderfer, James AU - Goodell, Henry AU - Mills, Steven AU - McKnight, Michael AU - Yao, Shanshan AU - Lin, Feiyan AU - Beppler, Eric AU - Bent, Brinnae AU - Lee, Bongmook AU - Misra, Veena AU - Zhu, Yong AU - Oralkan, Omer AU - Strohmaier, Jason AU - Muth, John AU - Peden, David AU - Bozkurt, Alper T2 - IEEE JOURNAL OF BIOMEDICAL AND HEALTH INFORMATICS AB - We present our efforts toward enabling a wearable sensor system that allows for the correlation of individual environmental exposures with physiologic and subsequent adverse health responses. This system will permit a better understanding of the impact of increased ozone levels and other pollutants on chronic asthma conditions. We discuss the inefficiency of existing commercial off-the-shelf components to achieve continuous monitoring and our system-level and nano-enabled efforts toward improving the wearability and power consumption. Our system consists of a wristband, a chest patch, and a handheld spirometer. We describe our preliminary efforts to achieve a submilliwatt system ultimately powered by the energy harvested from thermal radiation and motion of the body with the primary contributions being an ultralow-power ozone sensor, an volatile organic compounds sensor, spirometer, and the integration of these and other sensors in a multimodal sensing platform. The measured environmental parameters include ambient ozone concentration, temperature, and relative humidity. Our array of sensors also assesses heart rate via photoplethysmography and electrocardiography, respiratory rate via photoplethysmography, skin impedance, three-axis acceleration, wheezing via a microphone, and expiratory airflow. The sensors on the wristband, chest patch, and spirometer consume 0.83, 0.96, and 0.01 mW, respectively. The data from each sensor are continually streamed to a peripheral data aggregation device and are subsequently transferred to a dedicated server for cloud storage. Future work includes reducing the power consumption of the system-on-chip including radio to reduce the entirety of each described system in the submilliwatt range. DA - 2016/9// PY - 2016/9// DO - 10.1109/jbhi.2016.2573286 VL - 20 IS - 5 SP - SN - 2168-2208 KW - Environmental and physiological sensing KW - wearable asthma monitoring ER - TY - JOUR TI - Laser synthesis of a copper-single-walled carbon nanotube nanocomposite via molecular-level mixing and non-equilibrium solidification AU - Tu, Jay F. AU - Rajule, Nilesh AU - Molian, Pal AU - Liu, Yi T2 - JOURNAL OF PHYSICS D-APPLIED PHYSICS AB - A copper–single-walled carbon nanotube (Cu–SWCNT) metal nanocomposite could be an ideal material if it can substantially improve the strength of copper while preserving the metal's excellent thermal and electrical properties. However, synthesis of such a nanocomposite is highly challenging, because copper and SWCNTs do not form intermetallic compounds and are insoluble; as a result, there are serious issues regarding wettability and fine dispersion of SWCNTs within the copper matrix. In this paper we present a novel wet process, called the laser surface implantation process (LSI), to synthesize Cu–SWCNT nanocomposites by mixing SWCNTs into molten copper. The LSI process includes drilling several microholes on a copper substrate, filling the microholes with SWCNTs suspended in solution, and melting the copper substrate to create a micro-well of molten copper. The molten copper advances radially outward to engulf the microholes with pre-deposited SWCNTs to form the Cu–SWCNT implant upon solidification. Rapid and non-equilibrium solidification is achieved due to copper's excellent heat conductivity, so that SWCNTs are locked in position within the copper matrix without agglomerating into large clusters. This wet process is very different from the typical dry processes used in powder metallurgy. Very high hardness improvement, up to 527% over pure copper, was achieved, confirmed by micro-indentation tests, with only a 0.23% SWCNT volume fraction. The nanostructure of the nanocomposite was characterized by TEM imaging, energy-dispersive x-ray spectroscopy mapping and spectroscopy measurements. The SWCNTs were found to be finely dispersed within the copper matrix with cluster sizes in the range of nanometers, achieving the goal of molecular-level mixing. DA - 2016/12/14/ PY - 2016/12/14/ DO - 10.1088/0022-3727/49/49/495301 VL - 49 IS - 49 SP - SN - 1361-6463 KW - metal composite KW - carbon nanotubes KW - nanostructure KW - copper nanocomposites KW - molecular level mixing KW - laser surface implantation KW - laser synthesis ER - TY - JOUR TI - Hybrid Switched Gain-Scheduling Control for Missile Autopilot Design AU - Yuan, Chengzhi AU - Liu, Yang AU - Wu, Fen AU - Duan, Chang T2 - JOURNAL OF GUIDANCE CONTROL AND DYNAMICS AB - This paper presents a new hybrid switched gain-scheduling control method for missile autopilot design via dynamic output feedback. For controller design purpose, the nonlinear missile plant model is first converted to a switched linear fractional transformation system. Then, the new hybrid switched gain-scheduling autopilot is designed, which consists of a switching dynamic output–feedback linear fractional transformation controller and a supervisor enforcing a controller state reset at each switching time instant. The proposed hybrid control scheme is shown to provide a systematic yet simple framework for missile autopilot design. Specifically, the control synthesis conditions that guarantee weighted stability performance are formulated in terms of a finite number of linear matrix inequalities, which can be solved effectively via convex optimization without parameter-space gridding. Furthermore, stringent controlled performance and strong robustness against parameter perturbations are achieved using this new control approach, whereas no parameter variation information is required for both controller synthesis and implementation. The advantages of the proposed design approach over existing methods will be shown through nonlinear simulations for the missile autopilot design over a wide range of operating conditions. DA - 2016/10// PY - 2016/10// DO - 10.2514/1.g001791 VL - 39 IS - 10 SP - 2352-2363 SN - 1533-3884 ER - TY - JOUR TI - Experimental investigation of primary and corner shock boundary layer interactions at mild back pressure ratios AU - Funderburk, M. AU - Narayanaswamy, V. T2 - PHYSICS OF FLUIDS AB - Unstart of rectangular inlets occurs as a result of interactions between shock-induced separation units along the floor/ceiling, corner, and sidewalls. While a significant body of literature exists regarding the individual flow interactions at the inlet floor/ceiling (called primary separation) and sidewalls, limited efforts have focused on the mean and dynamic features of the corner separation. Experiments are conducted to investigate primary and corner shock boundary layer interactions (SBLI) with the objectives of elucidating the flow interactions that occur in the corner, and characterizing the interaction between the corner and primary separation units at mild back pressure ratios. Surface streakline flow visualization and high-frequency wall static pressure measurements are performed along the centerline and corner regions of shock-induced flow separation generated by a 12° compression ramp in a Mach 2.5 flow. Sidewall fences that extend upstream of the leading edge of the flat plate generate corner separation of adequate size to determine the mean flow structures, characterize the unsteady motions, and investigate the mechanisms that drive the unsteadiness of primary and corner SBLI. Results show that the corner and primary SBLI units differ fundamentally in both their mean and unsteady features and their response to upstream and downstream flow perturbations. These observations suggest that the two behave as independent units at this relatively low shock-induced back pressure ratio. DA - 2016/8// PY - 2016/8// DO - 10.1063/1.4960963 VL - 28 IS - 8 SP - SN - 1089-7666 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84983745346&partnerID=MN8TOARS ER - TY - JOUR TI - Evaluation of System Evolvability Based on Usable Excess AU - Allen, Jeffrey D. AU - Mattson, Christopher A. AU - Ferguson, Scott M. T2 - JOURNAL OF MECHANICAL DESIGN AB - Complex, large-scale engineered systems are an integral part of modern society. The cost of these systems is often high, while their ability to react to emergent requirements can be low. This paper proposes evolvability, based on usable excess, as a possible metric to promote system longevity. An equation for the usability of excess, previously defined only in terms of quantity, is improved to include the attributes of type, location, and form as well as quantity. A methodology for evaluating a system's evolvability is also presented. Using an automated assembly line as an example, we show that system evolvability can be modeled as a function of usable excess. DA - 2016/9// PY - 2016/9// DO - 10.1115/1.4033989 VL - 138 IS - 9 SP - SN - 1050-0472 KW - evolvability KW - evolve KW - reconfigurability KW - reconfigure KW - system design KW - automated assembly line KW - excess KW - complex engineered systems ER - TY - JOUR TI - Design and validation of the mounting structure for BETTII balloon-based telescope with thin-walled optics AU - Furst, Stephen AU - Dow, Tom AU - Garrard, Ken AU - Sohn, Alex AU - Fixsen, Dale AU - Rinehart, Stephen AU - Mentzell, Eric AU - Veach, Todd AU - Rizzo, Maxime AU - Dhabal, Arnab T2 - JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS AB - The NASA Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) system is designed to study the infrared emissions from star formation and active galactic nuclei through a double-Fourier Michelson interferometer located on a balloon at an altitude of 37 km. The BETTII external optics include a pair of identical beam-reducing, four-mirror telescopes, each with a 522-mm aperture, nonrotationally symmetric primary mirror. These telescopes were designed and assembled at the North Carolina State University Precision Engineering Consortium and are composed entirely of thin-walled aluminum components. The mounting structure is designed to be light weight and stiff to reduce thermal equilibration time in the rarified air at the edge of space and to maintain robust alignment of the optical elements. The mounts also prevent deformation of the large optical elements via custom-built kinematic Kelvin couplings and fixed-load clamps; the maximum form error of the optical surfaces are 300 nm RMS. This work details the design of the thin mirrors and mounting structure as well as validation of the mount assembly process, mount stiffness, and the kinematic couplings. DA - 2016/4// PY - 2016/4// DO - 10.1117/1.jatis.2.2.024001 VL - 2 IS - 2 SP - SN - 2329-4221 KW - light-weight optics KW - diamond turning optics KW - optical mounting KW - kinematic coupling KW - Balloon Experimental Twin Telescope for Infrared Interferometry ER - TY - JOUR TI - Bio-inspired online variable recruitment control of fluidic artificial muscles AU - Jenkins, Tyler E. AU - Chapman, Edward M. AU - Bryant, Matthew T2 - SMART MATERIALS AND STRUCTURES AB - This paper details the creation of a hybrid variable recruitment control scheme for fluidic artificial muscle (FAM) actuators with an emphasis on maximizing system efficiency and switching control performance. Variable recruitment is the process of altering a system's active number of actuators, allowing operation in distinct force regimes. Previously, FAM variable recruitment was only quantified with offline, manual valve switching; this study addresses the creation and characterization of novel, on-line FAM switching control algorithms. The bio-inspired algorithms are implemented in conjunction with a PID and model-based controller, and applied to a simulated plant model. Variable recruitment transition effects and chatter rejection are explored via a sensitivity analysis, allowing a system designer to weigh tradeoffs in actuator modeling, algorithm choice, and necessary hardware. Variable recruitment is further developed through simulation of a robotic arm tracking a variety of spline position inputs, requiring several levels of actuator recruitment. Switching controller performance is quantified and compared with baseline systems lacking variable recruitment. The work extends current variable recruitment knowledge by creating novel online variable recruitment control schemes, and exploring how online actuator recruitment affects system efficiency and control performance. Key topics associated with implementing a variable recruitment scheme, including the effects of modeling inaccuracies, hardware considerations, and switching transition concerns are also addressed. DA - 2016/12// PY - 2016/12// DO - 10.1088/0964-1726/25/12/125016 VL - 25 IS - 12 SP - SN - 1361-665X KW - McKibben muscle KW - fluidic artificial muscle KW - hydraulic artificial muscle KW - actuator KW - variable recruitment KW - bio-inspired KW - switching control ER - TY - JOUR TI - Asymptotic analysis of steady two-reactant premixed flames using a step-function reaction rate model AU - Echekki, Tarek T2 - COMBUSTION AND FLAME AB - A step-function reaction rate model is used to study the problem of steady, 1D, planar two-reactant premixed flames. The analysis yields leading order solutions for the flame structure and the dependence of the flame speed on reaction and transport parameters. The results for the flame speed reproduce the same scaling obtained using activation energy asymptotics. Two analytical solutions are derived for the cases of stoichiometric and far from stoichiometric flames. These solutions constitute the first closed-form solutions of the flame structure at non-unity Lewis numbers for the reactants. Comparisons between numerical solutions based on an Arrhenius reaction rate with the analytical solutions show an excellent agreement. DA - 2016/10// PY - 2016/10// DO - 10.1016/j.combustflame.2016.07.027 VL - 172 SP - 280-288 SN - 1556-2921 UR - https://doi.org/10.1016/j.combustflame.2016.07.027 KW - Asymptotic analysis KW - Differential diffusion effects KW - Preferential diffusion effects ER - TY - CONF TI - Analysis and control of genetic regulatory systems with switched drug inputs AU - Oduola, W. AU - Li, X. F. AU - Duan, C. AU - Qian, L. J. AU - Wu, F. AU - Dougherty, E. R. AB - Because cancer usually involves multiple genes and pathways, combination therapy is considered as a promising approach for cancer treatment. However, when multiple drugs are taken by a patient simultaneously, toxicity becomes a concern. A potential solution is to give the drugs sequentially rather than simultaneously. In this study, we try to explore the feasibility of such an approach. Specifically, this study investigates the response of genetic regulatory networks to sequential (switched) drug inputs. The switching mechanism is based on the combination of a state-dependent and time-driven switching function. The design of the switching strategy ensures that the genetic regulatory network will be stabilized and satisfies a decay rate performance index. Simulation results using a mTOR pathway model show the effectiveness of the proposed method. C2 - 2016/// C3 - 2016 3rd IEEE EMBS International Conference on Biomedical and Health Informatics DA - 2016/// DO - 10.1109/bhi.2016.7455952 SP - 533-536 ER - TY - JOUR TI - Hydroxyapatite coating on PEEK implants: Biomechanical and histological study in a rabbit model AU - Durham, John W., III AU - Montelongo, Sergio A. AU - Ong, Joo L. AU - Guda, Teja AU - Allen, Matthew J. AU - Rabiei, Afsaneh T2 - MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS AB - A bioactive two-layer coating consisting of hydroxyapatite (HA) and yttria-stabilized zirconia (YSZ) was investigated on cylindrical polyetheretherketone (PEEK) implants using ion beam assisted deposition (IBAD). Post-deposition heat treatments via variable frequency microwave annealing with and without subsequent autoclaving were used to crystallize the as-deposited amorphous HA layer. Microstructural analysis, performed by TEM and EDS, showed that these methods were capable of crystallizing HA coating on PEEK. The in vivo response to cylindrical PEEK samples with and without coating was studied by implanting uncoated PEEK and coated PEEK implants in the lateral femoral condyle of 18 rabbits. Animals were studied in two groups of 9 for observation at 6 or 18weeks post surgery. Micro-CT analysis, histology, and mechanical pull-out tests were performed to determine the effect of the coating on osseointegration. The heat-treated HA/YSZ coatings showed improved implant fixation as well as higher bone regeneration and bone-implant contact area compared to uncoated PEEK. The study offers a novel method to coat PEEK implants with improved osseointegration. DA - 2016/11/1/ PY - 2016/11/1/ DO - 10.1016/j.msec.2016.06.049 VL - 68 SP - 723-731 SN - 1873-0191 KW - Coating KW - Hydroxyapatite KW - Ion beam assisted deposition KW - Polyetheretherketone KW - Osseointegration ER - TY - JOUR TI - High Performance Organic Solar Cells Processed by Blade Coating in Air from a Benign Food Additive Solution AU - Ye, L. AU - Xiong, Y. AU - Yao, H. AU - Dinku, A.G. AU - Zhang, H. AU - Li, S. AU - Ghasemi, M. AU - Balar, N. AU - Hunt, A. AU - O'Connor, B.T. AU - Hou, J. AU - Ade, H. T2 - Chemistry of Materials AB - Solution processable conjugated organic materials have gained tremendous interest motivated by their potential of low cost, lightweight and especially easy manufacturing of large-area and flexible electronics. Toxic halogen-containing solvents have been widely used in the processing of organic electronics, particularly organic photovoltaics (OPVs). To transition this technology to more commercially attractive manufacturing approaches, removing these halogenated solvents remains one of the key challenges. Our morphological (hard/soft X-ray scattering) and calorimetric characterizations reveal that using o-methylanisole, a certified food additive, as processing solvent can achieve similar crystalline properties and domain spacing/purity with that achieved by widely used binary halogenated solvents (chlorobenzene and 1,8-diiodooctane), thus yielding comparable photovoltaic performance in spin-casted films. To move a step forward, we further present the potential of o-methylanisole as processing solvent in the blade-coating of several cases of OPVs in air. Remarkably, this single nonhazardous solvent yields ∼8.4% and ∼5.2% efficiency in OPVs by respectively blade-coating PBDT-TSR:PC71BM and all-polymeric PBDT-TS1:PPDIODT in ambient air, which are among the highest values for the respective kind of device. We postulate this simple nonhazardous solvent approach will also be applicable in the large area roll-to-roll coating and industrial scale printing of high-efficiency OPVs in air. DA - 2016/// PY - 2016/// DO - 10.1021/acs.chemmater.6b03083 VL - 28 IS - 20 SP - 7451-7458 SN - 1520-5002 ER - TY - JOUR TI - Helical coil buckling mechanism for a stiff nanowire on an elastomeric substrate AU - Chen, Youlong AU - Liu, Yilun AU - Yan, Yuan AU - Zhu, Yong AU - Chen, , Xi T2 - JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS AB - When a stiff nanowire is deposited on a compliant soft substrate, it may buckle into a helical coil form when the system is compressed. Using theoretical and finite element method (FEM) analyses, the detailed three-dimensional coil buckling mechanism for a silicon nanowire (SiNW) on a polydimethylsiloxane (PDMS) substrate is studied. A continuum mechanics approach based on the minimization of the strain energy in the SiNW and elastomeric substrate is developed. Due to the helical buckling, the bending strain in SiNW is significantly reduced and the maximum local strain is almost uniformly distributed along SiNW. Based on the theoretical model, the energy landscape for different buckling modes of SiNW on PDMS substrate is given, which shows that both the in-plane and out-of-plane buckling modes have the local minimum potential energy, whereas the helical buckling model has the global minimum potential energy. Furthermore, the helical buckling spacing and amplitudes are deduced, taking into account the influences of the elastic properties and dimensions of SiNWs. These features are verified by systematic FEM simulations and parallel experiments. As the effective compressive strain in elastomeric substrate increases, the buckling profile evolves from a vertical ellipse to a lateral ellipse, and then approaches to a circle when the effective compressive strain is larger than 30%. The study may shed useful insights on the design and optimization of high-performance stretchable electronics and 3D complex nano-structures. DA - 2016/10// PY - 2016/10// DO - 10.1016/j.jmps.2016.05.020 VL - 95 SP - 25-43 SN - 1873-4782 KW - Helical buckling KW - Energy landscape KW - Nanowires KW - Continuum mechanics approach KW - Stretchable electronics ER - TY - JOUR TI - Experimental-computational study of fibrous particle transport and deposition in a bifurcating lung model AU - Chen, Xiaole AU - Zhong, Wenqi AU - Tom, Josin AU - Kleinstreuer, Clement AU - Feng, Yu AU - He, Xiaopu T2 - PARTICUOLOGY AB - Experiments carried out using a lung model with a single horizontal bifurcation under different steady inhalation conditions explored the orientation of depositing carbon fibers, and particle deposition fractions. The orientations of deposited fibers were obtained from micrographs. Specifically, the effects of the sedimentation parameter (γ), fiber length, and flow rate on orientations were analyzed. Our results indicate that gravitational effect on deposition cannot be neglected for 0.0228 < γ < 0.247. The absolute orientation angle of depositing fibers decreased linearly with increasing γ for values 0.0228 < γ < 0.15. Correspondence between Stokes numbers and γ suggests these characteristics can be used to estimate fiber deposition in the lower airways. Computer simulations with sphere-equivalent diameter models for the fibers explored deposition efficiency vs. Stokes number. Using the volume-equivalent diameter model, our experimental data for the horizontal bifurcation were replicated. Results for particle deposition using a lung model with a vertical bifurcation indicate that body position also affects deposition. DA - 2016/8// PY - 2016/8// DO - 10.1016/j.partic.2016.02.002 VL - 28 SP - 102-113 SN - 2210-4291 KW - Lung aerosol dynamics KW - Image-processing method KW - Fiber deposition data KW - Computer simulations KW - Deposited fiber orientations ER - TY - JOUR TI - Design of an Orthotropic Piezoelectric Composite Material Phased Array Transducer for Damage Detection in a Concrete Structure AU - Wang, Ziping AU - Luo, Ying AU - Zhao, Guoqi AU - Xu, Bai Qiang AU - Yuan, Fuh-Gwo T2 - RESEARCH IN NONDESTRUCTIVE EVALUATION AB - In order to verify the feasibility and effectiveness of the sensor used in complex concrete materials, an innovative application of ultrasonic phased array detection for a concrete structure was investigated. Comparing with the traditional piezoelectric composites, orthotropic piezoelectric composite material (OPCM) can be used as transducers in damage detection show clear advantages because of their high sensitivity and directivity along the polarization direction. A low frequency ultrasonic phased array transducer consisting of 16 OPCM elements is studied. The optimal array parameters, such as the phased array element interval, the array element width, and number of elements, are obtained by studying the total displacement changes as various parameters change at the focus point in the concrete structure. This configuration allowed the variation and control of the wave field directivity in the concrete structure during the measurements. The measurements were taken on concrete specimens using a precise time-delay device. The experimental measurements were compared to theoretical calculations to investigate the influence of different array element parameters. The results show that an OPCM phased array transducer can be used to detect damage in a concrete block. DA - 2016/// PY - 2016/// DO - 10.1080/09349847.2015.1122129 VL - 27 IS - 4 SP - 204-215 SN - 1432-2110 KW - Concrete structure KW - damage detection KW - orthotropic piezoelectric composite material KW - phased array transducer ER - TY - JOUR TI - Defect mediated room temperature ferromagnetism and resistance minima study in epitaxial ZnGa0.002Al0.02O transparent conducting oxide films AU - Temizer, N. K. AU - Nori, S. AU - Kumar, D. AU - Narayan, J. T2 - Journal of Physics. D, Applied Physics DA - 2016/// PY - 2016/// VL - 49 IS - 34 ER - TY - JOUR TI - Comparisons of Two Test Methods for Evaluating the Radiant Protective Performance of Wildland Firefighter Protective Clothing Materials AU - Hummel, Alex AU - Watson, Kyle AU - Barker, Roger T2 - PERFORMANCE OF PROTECTIVE CLOTHING AND EQUIPMENT, 10TH VOL: RISK REDUCTION THROUGH RESEARCH AND TESTING DA - 2016/// PY - 2016/// DO - 10.1520/stp159320160012 VL - 1593 SP - 178-194 SN - 0066-0558 KW - Radiant Protective Performance KW - stored energy tester KW - wildlands KW - protective clothing ER - TY - JOUR TI - Carboxymethylated lignins with low surface tension toward low viscosity and highly stable emulsions of crude bitumen and refined oils AU - Li, Shuai AU - Ogunkoya, Dolanimi AU - Fang, Tiegang AU - Willoughby, Julie AU - Rojas, Orlando J. T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - Kraft and organosolv lignins were subjected to carboxymethylation to produce fractions that were soluble in water, displayed a minimum surface tension as low as 34mN/m (25°C) and a critical aggregation concentration of ∼1.5wt%. The carboxymethylated lignins (CML), which were characterized in terms of their degree of substitution ((31)P NMR), elemental composition, and molecular weight (GPC), were found suitable in the formulation of emulsions with bitumens of ultra-high viscosity, such as those from the Canadian oil sands. Remarkably, the interfacial features of the CML enabled fuel emulsions that were synthesized in a very broad range of internal phase content (30-70%). Cryo-replica transmission electron microscopy, which was used here the first time to assess the morphology of the lignin-based emulsions, revealed the droplets of the emulsion stabilized with the modified lignin. The observed drop size (diameters<2μm) was confirmed by light scattering, which revealed a normal size distribution. Such characteristics led to stable emulsified systems that are amenable for a wide range of applications. Emulsification with CML afforded bitumen emulsions with very high colloidal stability (no change was noted for over one month) and with a strong shear thinning behavior. Both features indicate excellent prospects for storage, transport and spraying, which are relevant in operations for power generation, which also take advantage of the high heating value of the emulsion components. The ability of CML to stabilize emulsions and to contribute in their combustion was tested with light fuels (kerosene, diesel, and jet fuel) after formulation of high internal phase systems (70% oil) that enabled operation of a fuel engine. A significant finding is that under certain conditions and compared to the respective pure fuel, combustion of the O/W emulsions stabilized by CML presented lower NOx and CO emissions and maintained a relatively high combustion efficiency. The results highlight the possibilities in high volume application for lignin biomacromolecules. DA - 2016/11/15/ PY - 2016/11/15/ DO - 10.1016/j.jcis.2016.07.063 VL - 482 SP - 27-38 SN - 1095-7103 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84979781362&partnerID=MN8TOARS KW - Lignin KW - Bitumen-in-water emulsion KW - Colloidal stability KW - Fuel emulsions KW - High heating value KW - Exhaust emission KW - Combustion efficiency ER - TY - JOUR TI - Analytical Modeling of Hydrodynamic Lubrication in a Multiple-Reduction Drawing Die AU - Lowrie, James AU - Ngaile, Gracious T2 - 44TH NORTH AMERICAN MANUFACTURING RESEARCH CONFERENCE, NAMRC 44 AB - The hydrodynamic lubrication regime is reported to exist in numerous metal forming applications, such as wire drawing and hydrostatic extrusion, but it has not been achievable 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 proposed 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 elevated lubricant pressure in the inlet of the dies. DA - 2016/// PY - 2016/// DO - 10.1016/j.promfg.2016.08.058 VL - 5 SP - 707-723 SN - 2351-9789 KW - Hydrodynamic Lubrication KW - Drawing KW - Analytical Modeling ER - TY - JOUR TI - A reconstructed discontinuous Galerkin method for magnetohydrodynamics on arbitrary grids AU - Halashi, Behrouz Karami AU - Luo, Hong T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - A reconstructed discontinuous Galerkin (rDG) method, designed not only to enhance the accuracy of DG methods but also to ensure the nonlinear stability of the rDG method, is developed for solving the Magnetohydrodynamics (MHD) equations on arbitrary grids. In this rDG(P1P2) method, a quadratic polynomial solution (P2) is first obtained using a Hermite Weighted Essentially Non-oscillatory (WENO) reconstruction from the underlying linear polynomial (P1) discontinuous Galerkin solution to ensure linear stability of the rDG method and to improves efficiency of the underlying DG method. By taking advantage of handily available and yet invaluable information, namely the first derivatives in the DG formulation, the stencils used in reconstruction involve only Von Neumann neighborhood (adjacent face-neighboring cells) and thus are compact. The first derivatives of the quadratic polynomial solution are then reconstructed using a WENO reconstruction in order to eliminate spurious oscillations in the vicinity of strong discontinuities, thus ensuring the nonlinear stability of the rDG method. The HLLD Riemann solver introduced in the literature for one-dimensional MHD problems is adopted in normal direction to compute numerical fluxes. The divergence free constraint is satisfied using the Locally Divergence Free (LDF) approach. The developed rDG method is used to compute a variety of 2D and 3D MHD problems on arbitrary grids to demonstrate its accuracy, robustness, and non-oscillatory property. Our numerical experiments indicate that the rDG(P1P2) method is able to capture shock waves sharply essentially without any spurious oscillations, and achieve the designed third-order of accuracy: one order accuracy higher than the underlying DG method. DA - 2016/12/1/ PY - 2016/12/1/ DO - 10.1016/j.jcp.2016.08.055 VL - 326 SP - 258-277 SN - 1090-2716 KW - Discontinuous Galerkin KW - Magnetohydrodynamics KW - HLLD Riemann solver KW - Arbitrary grid KW - HWENO ER - TY - CONF TI - A novel hybrid heating method for elevated temperature mechanical testing of miniature specimens AU - Li, L. AU - Ngaile, G. AU - Hassan, T. AB - The lack of robust testing systems to generate uniform elevated temperatures on specimens in material tests is hindering the advancement of small specimen testing technology (SSTT). The purpose of this study is to develop a novel hybrid heating method combining coil heating and electric-resistance specimen heating to uniformly heat micro specimens in material tests. In a hybrid heating process, two heating coils are used to heat the local temperatures on the specimen ends, and electric current is conducted through the specimen to generate Joule heat and compensate the heat transfer effects of natural convection and radiation around the specimen center area. In this way, a highly uniform temperature distribution can be generated on the specimen between the heating coils. In this study, Thermal-Electrical and Transient Thermal FEA simulations are applied to analyze the temperature distributions and preheating times on the micro specimens under coil heating, electric-resistance specimen heating, and hybrid heating respectively. According to the simulation results, it can be concluded that hybrid heating method can provide the ability to generate highly uniform elevated temperature conditions on different micro tubular specimens with short preheating times. C2 - 2016/// C3 - Proceedings of the ASME 11th International Manufacturing Science and Engineering Conference, 2016, vol 1 DA - 2016/// DO - 10.1115/msec2016-8852 ER - TY - JOUR TI - A hybrid reconstructed discontinuous Galerkin and continuous Galerkin finite element method for incompressible flows on unstructured grids AU - Pandare, Aditya K. AU - Luo, Hong T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - A hybrid reconstructed discontinuous Galerkin and continuous Galerkin method based on an incremental pressure projection formulation, termed rDG ( P n P m ) + CG ( P n ) in this paper, is developed for solving the unsteady incompressible Navier–Stokes equations on unstructured grids. In this method, a reconstructed discontinuous Galerkin method ( rDG ( P n P m ) ) is used to discretize the velocity and a standard continuous Galerkin method ( CG ( P n ) ) is used to approximate the pressure. The rDG ( P n P m ) + CG ( P n ) method is designed to increase the accuracy of the hybrid DG ( P n ) + CG ( P n ) method and yet still satisfy Ladyženskaja–Babuška–Brezzi (LBB) condition, thus avoiding the pressure checkerboard instability. An upwind method is used to discretize the nonlinear convective fluxes in the momentum equations in order to suppress spurious oscillations in the velocity field. A number of incompressible flow problems for a variety of flow conditions are computed to numerically assess the spatial order of convergence of the rDG ( P n P m ) + CG ( P n ) method. The numerical experiments indicate that both rDG ( P 0 P 1 ) + CG ( P 1 ) and rDG ( P 1 P 2 ) + CG ( P 1 ) methods can attain the designed 2nd order and 3rd order accuracy in space for the velocity respectively. Moreover, the 3rd order rDG ( P 1 P 2 ) + CG ( P 1 ) method significantly outperforms its 2nd order rDG ( P 0 P 1 ) + CG ( P 1 ) and rDG ( P 1 P 1 ) + CG ( P 1 ) counterparts: being able to not only increase the accuracy of the velocity by one order but also improve the accuracy of the pressure. DA - 2016/10/1/ PY - 2016/10/1/ DO - 10.1016/j.jcp.2016.07.002 VL - 322 SP - 491-510 SN - 1090-2716 KW - Reconstructed discontinuous Galerkin KW - Incompressible flows KW - Projection method ER - TY - JOUR TI - A direct discontinuous Galerkin method for the compressible Navier-Stokes equations on arbitrary grids AU - Cheng, Jian AU - Yang, Xiaoquan AU - Liu, Xiaodong AU - Liu, Tiegang AU - Luo, Hong T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - A Direct Discontinuous Galerkin (DDG) method is developed for solving the compressible Navier–Stokes equations on arbitrary grids in the framework of DG methods. The DDG method, originally introduced for scalar diffusion problems on structured grids, is extended to discretize viscous and heat fluxes in the Navier–Stokes equations. Two approaches of implementing the DDG method to compute numerical diffusive fluxes for the Navier–Stokes equations are presented: one is based on the conservative variables, and the other is based on the primitive variables. The importance of the characteristic cell size used in the DDG formulation on unstructured grids is examined. The numerical fluxes on the boundary by the DDG method are discussed. A number of test cases are presented to assess the performance of the DDG method for solving the compressible Navier–Stokes equations. Based on our numerical results, we observe that DDG method can achieve the designed order of accuracy and is able to deliver the same accuracy as the widely used BR2 method at a significantly reduced cost, clearly demonstrating that the DDG method provides an attractive alternative for solving the compressible Navier–Stokes equations on arbitrary grids owning to its simplicity in implementation and its efficiency in computational cost. DA - 2016/12/15/ PY - 2016/12/15/ DO - 10.1016/j.jcp.2016.09.049 VL - 327 SP - 484-502 SN - 1090-2716 KW - Direct discontinuous Galerkin method KW - Compressible Navier-Stokes equations KW - Arbitrary grids ER - TY - JOUR TI - A Vinylene-Bridged Perylenediimide-Based Polymeric Acceptor Enabling Efficient All-Polymer Solar Cells Processed under Ambient Conditions AU - Guo, Yikun AU - Li, Yunke AU - Awartani, Omar AU - Zhao, Jingbo AU - Han, Han AU - Ade, Harald AU - Zhao, Dahui AU - Yan, He T2 - ADVANCED MATERIALS AB - All-polymer solar cells with 7.57% power conversion efficiency are achieved via a new perylenediimide-based polymeric acceptor. Furthermore, the device processed in ambient air without encapsulation can still reach a high power conversion efficiency (PCE) of 7.49%, which is a significant economic advantage from an industrial processing perspective. These results represent the highest PCE achieved from perylenediimide-based polymers. 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 - 2016/10/12/ PY - 2016/10/12/ DO - 10.1002/adma.201602387 VL - 28 IS - 38 SP - 8483-8489 SN - 1521-4095 KW - air processibility KW - all-polymer solar cells KW - PDI-based polymeric acceptors ER - TY - JOUR TI - Tuning thermal conductivity in molybdenum disulfide by electrochemical intercalation AU - Zhu, Gaohua AU - Liu, Jun AU - Zheng, Qiye AU - Zhang, Ruigang AU - Li, Dongyao AU - Banerjee, Debasish AU - Cahill, David G. T2 - NATURE COMMUNICATIONS AB - Thermal conductivity of two-dimensional (2D) materials is of interest for energy storage, nanoelectronics and optoelectronics. Here, we report that the thermal conductivity of molybdenum disulfide can be modified by electrochemical intercalation. We observe distinct behaviour for thin films with vertically aligned basal planes and natural bulk crystals with basal planes aligned parallel to the surface. The thermal conductivity is measured as a function of the degree of lithiation, using time-domain thermoreflectance. The change of thermal conductivity correlates with the lithiation-induced structural and compositional disorder. We further show that the ratio of the in-plane to through-plane thermal conductivity of bulk crystal is enhanced by the disorder. These results suggest that stacking disorder and mixture of phases is an effective mechanism to modify the anisotropic thermal conductivity of 2D materials. Molybdenum disulfide shows potential for use in nanoelectronics and optoelectronics. Here, the authors use electrochemical intercalation to tune its structural and compositional features, and show that the thermal conductivity can be effectively modified over a considerable range. DA - 2016/10/21/ PY - 2016/10/21/ DO - 10.1038/ncomms13211 VL - 7 SP - SN - 2041-1723 UR - http://dx.doi.org/10.1038/ncomms13211 ER - TY - JOUR TI - The effects of twins on the large strain deformation and fracture of hexagonal close packed crystalline materials AU - Ziaei, S. AU - Zikry, M. A. T2 - ACTA MATERIALIA AB - We investigated how twin modes in hexagonal close packed materials can affect large inelastic strain behavior and fracture. We considered the two twin mode systems of (112¯1)[1¯1¯26] and (0001) [1¯1¯20] in zircaloy-2, with each mode having 24 unique twin systems. We then incorporated these twin and parent slip systems with a dislocation-density crystalline plasticity, a non-linear finite-element, and fracture framework that accounts for crack nucleation and propagation. We investigated how these twin modes affect the interrelated effects of crack nucleation and propagation, dislocation density and inelastic slip evolution, stress accumulation, and lattice rotation. The predictions indicate that twin modes significantly affect local deformation and fracture behavior, and, therefore, are essential for the accurate representation of behavior at different physical scales in heterogeneous crystalline hexagonal close packed systems. DA - 2016/11// PY - 2016/11// DO - 10.1016/j.actamat.2016.08.059 VL - 120 SP - 435-442 SN - 1873-2453 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84986587922&partnerID=MN8TOARS KW - HCP crystals KW - Twins KW - Fracture KW - Dislocation-densities KW - Orientation effects ER - TY - JOUR TI - The Onset of Convection in a Sloping Layered Porous Medium: Effects of Local Thermal Non-equilibrium and Heterogeneity AU - Nield, D. A. AU - Kuznetsov, A. V. AU - Barletta, A. AU - Celli, M. T2 - TRANSPORT IN POROUS MEDIA DA - 2016/8// PY - 2016/8// DO - 10.1007/s11242-016-0728-5 VL - 114 IS - 1 SP - 87-97 SN - 1573-1634 KW - Sloping layer KW - Local thermal non-equilibrium KW - Porous medium KW - Instability KW - Natural convection ER - TY - CONF TI - Silver nanowire based wearable sensors for multimodal sensing AU - Lin, F. Y. AU - Yao, S. S. AU - McKnight, M. AU - Zhu, Y. AU - Bozkurt, A. AB - We present multifunctional sensors based on highly stretchable silver nanowire conductors, which can be conformally attached to human skin for multimodal sensing. The wearable sensors were integrated with an interface circuit with wireless capability in the form of a chest patch. The capabilities of electrocardiography, strain/motion sensing and skin impedance sensing were demonstrated. Additionally, the impedance sensor with the interface circuit was packaged into a wrist watch for skin impedance monitoring. C2 - 2016/// C3 - Ieee topical conference on biomedical wireless technologies networks and DA - 2016/// DO - 10.1109/biowireless.2016.7445561 SP - 55-58 ER - TY - JOUR TI - Sensitivity of contact-free fiber Bragg grating sensors to ultrasonic Lamb waves AU - Wee, Junghyun AU - Hackney, Drew AU - Peters, Kara AU - Wells, Brian AU - Bradford, Philip T2 - SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2016 AB - Networks of fiber Bragg grating (FBG) sensors can serve as structural health monitoring (SHM) systems for large-scale structures based on the collection of ultrasonic waves. The demodulation of structural Lamb waves requires a high signal-to-noise ratio because Lamb waves have a low amplitude. This paper investigates the signal transfer between Lamb waves propagating in an aluminum plate collected by an optical fiber containing a FBG. The fiber is bonded to the plate at locations away from the FBG. The Lamb waves are converted into longitudinal and flexural traveling waves propagating along the optical fiber, which are then transmitted to the Bragg grating. The signal wave amplitude is measured for different distances between the bond location and the Bragg grating. Bonding the optical fiber away from the FBG location and closer to the signal source produces a significant increase in signal amplitude, here measured to be 5.1 times that of bonding the Bragg grating itself. The arrival time of the different measured wave coupling paths are also calculated theoretically, verifying the source of the measured signals. The effect of the bond length to Lamb wavelength ratio is investigated, showing a peak response as the bond length is reduced compared to the wavelength. This study demonstrates that coupling Lamb waves into guided traveling waves in an optical fiber away from the FBG increases the signal-to-noise ratio of Lamb wave detection, as compared to direct transfer of the Lamb wave to the optical fiber at the location of the FBG. DA - 2016/// PY - 2016/// DO - 10.1117/12.2218924 VL - 9803 SP - SN - 1996-756X KW - contact-free fiber Bragg grating KW - Lamb wave KW - traveling wave ER - TY - JOUR TI - Networking of optical fiber sensors for extreme environments AU - Peters, Kara T2 - SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2016 AB - One of the major benefits of optical fiber sensors for applications to structural health monitoring and other structural measurements is their inherent multiplexing capabilities, meaning that a large number of sensing locations can be achieved with a single optical fiber. It has been well demonstrated that point wise sensors can be multiplexed to form sensor networks or optical fibers integrated with distributed sensing techniques. The spacing between sensing locations can also be tuned to match different length scales of interest. This article presents an overview of directions to adapt optical fiber sensor networking techniques into new applications where limitations such as available power or requirements for high data acquisition speeds are a driving factor. In particular, the trade-off between high fidelity sensor information vs. rapid signal processing or data acquisition is discussed. DA - 2016/// PY - 2016/// DO - 10.1117/12.2225296 VL - 9803 SP - SN - 1996-756X KW - Fiber Bragg gratings KW - multiplexing KW - sensor networks ER - TY - JOUR TI - Mechanical Force-Triggered Drug Delivery AU - Zhang, Yuqi AU - Yu, Jicheng AU - Bomba, Hunter N. AU - Zhu, Yong AU - Gu, Zhen T2 - CHEMICAL REVIEWS AB - Advanced drug delivery systems (DDS) enhance treatment efficacy of different therapeutics in a dosage, spatial, and/or temporal controlled manner. To date, numerous chemical- or physical-based stimuli-responsive formulations or devices for controlled drug release have been developed. Among them, the emerging mechanical force-based stimulus offers a convenient and robust controlled drug release platform and has attracted increasing attention. The relevant DDS can be activated to promote drug release by different types of mechanical stimuli, including compressive force, tensile force, and shear force as well as indirect formats, remotely triggered by ultrasound and magnetic field. In this review, we provide an overview of recent advances in mechanically activated DDS. The opportunities and challenges regarding clinical translations are also discussed. DA - 2016/10/12/ PY - 2016/10/12/ DO - 10.1021/acs.chemrev.6b00369 VL - 116 IS - 19 SP - 12536-12563 SN - 1520-6890 ER - TY - JOUR TI - Improving actuation efficiency through variable recruitment hydraulic McKibben muscles: modeling, orderly recruitment control, and experiments AU - Meller, Michael AU - Chipka, Jordan AU - Volkov, Alexander AU - Bryant, Matthew AU - Garcia, Ephrahim T2 - BIOINSPIRATION & BIOMIMETICS AB - Hydraulic control systems have become increasingly popular as the means of actuation for human-scale legged robots and assistive devices. One of the biggest limitations to these systems is their run time untethered from a power source. One way to increase endurance is by improving actuation efficiency. We investigate reducing servovalve throttling losses by using a selective recruitment artificial muscle bundle comprised of three motor units. Each motor unit is made up of a pair of hydraulic McKibben muscles connected to one servovalve. The pressure and recruitment state of the artificial muscle bundle can be adjusted to match the load in an efficient manner, much like the firing rate and total number of recruited motor units is adjusted in skeletal muscle. A volume-based effective initial braid angle is used in the model of each recruitment level. This semi-empirical model is utilized to predict the efficiency gains of the proposed variable recruitment actuation scheme versus a throttling-only approach. A real-time orderly recruitment controller with pressure-based thresholds is developed. This controller is used to experimentally validate the model-predicted efficiency gains of recruitment on a robot arm. The results show that utilizing variable recruitment allows for much higher efficiencies over a broader operating envelope. DA - 2016/10// PY - 2016/10// DO - 10.1088/1748-3190/11/6/065004 VL - 11 IS - 6 SP - SN - 1748-3190 KW - McKibben muscle KW - hydraulic artificial muscle (HAM) KW - variable recruitment KW - energy efficiency KW - robotics KW - fluid power KW - hydraulic control systems ER - TY - JOUR TI - Design optimization of a prescribed vibration system using conjoint value analysis AU - Malinga, Bongani AU - Buckner, Gregory D. T2 - ENGINEERING OPTIMIZATION AB - This article details a novel design optimization strategy for a prescribed vibration system (PVS) used to mechanically filter solids from fluids in oil and gas drilling operations. A dynamic model of the PVS is developed, and the effects of disturbance torques are detailed. This model is used to predict the effects of design parameters on system performance and efficiency, as quantified by system attributes. Conjoint value analysis, a statistical technique commonly used in marketing science, is utilized to incorporate designer preferences. This approach effectively quantifies and optimizes preference-based trade-offs in the design process. The effects of designer preferences on system performance and efficiency are simulated. This novel optimization strategy yields improvements in all system attributes across all simulated vibration profiles, and is applicable to other industrial electromechanical systems. DA - 2016/// PY - 2016/// DO - 10.1080/0305215x.2016.1157687 VL - 48 IS - 12 SP - 2090-2113 SN - 1029-0273 KW - vibration KW - shale shaker KW - system optimization KW - multi-attribute KW - conjoint value analysis ER - TY - JOUR TI - Deposition, heat treatment and characterization of two layer bioactive coatings on cylindrical PEEK AU - Durham, John W., III AU - Rabiei, Afsaneh T2 - SURFACE & COATINGS TECHNOLOGY AB - Polyether ether ketone (PEEK) rods were coated via ion beam asssisted deposition (IBAD) at room temperature. The coating consists of a two-layer design of yttria-stabilized zirconia (YSZ) as a heat-protection layer, and hydroxyapatite (HA) as a top layer to increase bioactivity. A rotating substrate holder was designed to deposit an even coating on the cylindrical surface of PEEK rods; the uniformity is verified by cross-sectional measurements using scanning electron microscopy (SEM). Deposition is followed by heat treatment of the coating using microwave annealing and autoclaving. Transmission electron microscopy (TEM) showed a dense, uniform columnar grain structure in the YSZ layer that is well bonded to the PEEK substrate, while the calcium phosphate layer was amorphous and pore-free in its as-deposited state. Subsequent heat treatment via microwave energy introduced HA crystallization in the calcium phosphate layer and additional autoclaving further expanded the crystallization of the HA layer. Chemical composition evaluation of the coating indicated the Ca/P ratios of the HA layer to be near that of stoichiometric HA, with minor variations through the HA layer thickness. The adhesion strength of as-deposited HA/YSZ coatings on smooth, polished PEEK surfaces was mostly unaffected by microwave heat treatment, but decreased with additional autoclave treatment. Increasing surface roughness showed improvement of bond strength. DA - 2016/9/15/ PY - 2016/9/15/ DO - 10.1016/j.surfcoat.2015.12.045 VL - 301 SP - 106-113 SN - 0257-8972 KW - Hydroxyapatite KW - Polyether ether ketone KW - Adhesion KW - Ion beam assisted deposition ER - TY - JOUR TI - Computationally efficient analysis of particle transport and deposition in a human whole-lung-airway model. Part I: Theory and model validation AU - Kolanjiyil, Arun V. AU - Kleinstreuer, Clement T2 - COMPUTERS IN BIOLOGY AND MEDICINE AB - Computational predictions of aerosol transport and deposition in the human respiratory tract can assist in evaluating detrimental or therapeutic health effects when inhaling toxic particles or administering drugs. However, the sheer complexity of the human lung, featuring a total of 16 million tubular airways, prohibits detailed computer simulations of the fluid-particle dynamics for the entire respiratory system. Thus, in order to obtain useful and efficient particle deposition results, an alternative modeling approach is necessary where the whole-lung geometry is approximated and physiological boundary conditions are implemented to simulate breathing. In Part I, the present new whole-lung-airway model (WLAM) represents the actual lung geometry via a basic 3-D mouth-to-trachea configuration while all subsequent airways are lumped together, i.e., reduced to an exponentially expanding 1-D conduit. The diameter for each generation of the 1-D extension can be obtained on a subject-specific basis from the calculated total volume which represents each generation of the individual. The alveolar volume was added based on the approximate number of alveoli per generation. A wall-displacement boundary condition was applied at the bottom surface of the first-generation WLAM, so that any breathing pattern due to the negative alveolar pressure can be reproduced. Specifically, different inhalation/exhalation scenarios (rest, exercise, etc.) were implemented by controlling the wall/mesh displacements to simulate realistic breathing cycles in the WLAM. Total and regional particle deposition results agree with experimental lung deposition results. The outcomes provide critical insight to and quantitative results of aerosol deposition in human whole-lung airways with modest computational resources. Hence, the WLAM can be used in analyzing human exposure to toxic particulate matter or it can assist in estimating pharmacological effects of administered drug-aerosols. As a practical WLAM application, the transport and deposition of asthma drugs from a commercial dry-powder inhaler is discussed in Part II. DA - 2016/12/1/ PY - 2016/12/1/ DO - 10.1016/j.compbiomed.2016.10.020 VL - 79 SP - 193-204 SN - 1879-0534 KW - Lung KW - Airflow KW - Whole lung airway modeling KW - Computational fluid dynamics KW - Particle deposition ER - TY - JOUR TI - Analysis of effects of loading and postural demands on upper limb reaching in older adults using statistical parametric mapping AU - Li, Xiaotong AU - Santago, Anthony C., II AU - Vidt, Meghan E. AU - Saul, Katherine R. T2 - JOURNAL OF BIOMECHANICS AB - Continuous time-series data are frequently distilled into single values and analyzed using discrete statistical methods, underutilizing large datasets. Statistical parametric mapping (SPM) allows hypotheses over the entire spectrum, but consistency with discrete analyses of kinematic data is unclear. We applied SPM to evaluate effect of load and postural demands during reaching on thoracohumeral kinematics in older and young adults, and examined consistency between one-dimensional SPM and discrete analyses of the same dataset. We hypothesized that older adults would choose postures that bring the humerus anterior to the frontal plane (towards flexion) even for low demand tasks, and that SPM would reveal differences persisting over larger temporal portions of the reach. Ten healthy older (72.4±3.1yrs) and 16 young (22.9±2.5yrs) adults reached upward and forward with high and low loads. SPM and discrete t-tests were used to analyze group effects for elevation plane, elevation, and axial rotation joint angles and velocity. Older adults used more positive (anterior) elevation plane and less elevated postures to initiate and terminate reaching (p<0.008), with long duration differences during termination. When reaching upward, differences in elevation persisted over longer temporal periods at midreach for high loads (32–58% of reach) compared to low load (41–45%). SPM and discrete analyses were consistent, but SPM permitted clear identification of temporal periods over which differences persisted, while discrete methods allowed analysis of extracted values, like ROM. This work highlights the utility of SPM to analyze kinematics time series data, and emphasizes importance of task selection when assessing age-related changes in movement. DA - 2016/9/6/ PY - 2016/9/6/ DO - 10.1016/j.jbiomech.2016.06.018 VL - 49 IS - 13 SP - 2806-2816 SN - 1873-2380 KW - Aging KW - Older adults KW - Kinematics KW - Upper limb KW - Statistical parametric mapping KW - Reaching ER - TY - JOUR TI - An Integrated System for Superharmonic Contrast-Enhanced Ultrasound Imaging: Design and Intravascular Phantom Imaging Study AU - Li, Yang AU - Ma, Jianguo AU - Martin, K. Heath AU - Yu, Mingyue AU - Ma, Teng AU - Dayton, Paul A. AU - Jiang, Xiaoning AU - Shung, K. Kirk AU - Zhou, Qifa T2 - IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING AB - Objective: Superharmonic contrast-enhanced ultrasound imaging, also called acoustic angiography, has previously been used for the imaging of microvasculature. This approach excites microbubble contrast agents near their resonance frequency and receives echoes at nonoverlapping superharmonic bandwidths. No integrated system currently exists could fully support this application. To fulfill this need, an integrated dual-channel transmit/receive system for superharmonic imaging was designed, built, and characterized experimentally. Method: The system was uniquely designed for superharmonic imaging and high-resolution B-mode imaging. A complete ultrasound system including a pulse generator, a data acquisition unit, and a signal processing unit were integrated into a single package. The system was controlled by a field-programmable gate array, on which multiple user-defined modes were implemented. A 6-, 35-MHz dual-frequency dual-element intravascular ultrasound transducer was designed and used for imaging. Result: The system successfully obtained high-resolution B-mode images of coronary artery ex vivo with 45-dB dynamic range. The system was capable of acquiring in vitro superharmonic images of a vasa vasorum mimicking phantom with 30-dB contrast. It could detect a contrast agent filled tissue mimicking tube of 200 μm diameter. Conclusion: For the first time, high-resolution B-mode images and superharmonic images were obtained in an intravascular phantom, made possible by the dedicated integrated system proposed. The system greatly reduced the cost and complexity of the superharmonic imaging intended for preclinical study. Significant: The system showed promise for high-contrast intravascular microvascular imaging, which may have significant importance in assessment of the vasa vasorum associated with atherosclerotic plaques. DA - 2016/9// PY - 2016/9// DO - 10.1109/tbme.2015.2506639 VL - 63 IS - 9 SP - 1933-1943 SN - 1558-2531 KW - Acoustic angiography KW - biomedical electronics KW - field-programmable gate arrays (FPGA) KW - intravascular ultrasound (IVUS) KW - microbubble contrast agent (MCA) KW - ultrasonic imaging KW - ultrasonic transducer ER - TY - JOUR TI - Acoustic Holographic Rendering with Two-dimensional Metamaterial-based Passive Phased Array AU - Xie, Yangbo AU - Shen, Chen AU - Wang, Wenqi AU - Li, Junfei AU - Suo, Dingjie AU - Popa, Bogdan-Ioan AU - Jing, Yun AU - Cummer, Steven A. T2 - SCIENTIFIC REPORTS AB - Acoustic holographic rendering in complete analogy with optical holography are useful for various applications, ranging from multi-focal lensing, multiplexed sensing and synthesizing three-dimensional complex sound fields. Conventional approaches rely on a large number of active transducers and phase shifting circuits. In this paper we show that by using passive metamaterials as subwavelength pixels, holographic rendering can be achieved without cumbersome circuitry and with only a single transducer, thus significantly reducing system complexity. Such metamaterial-based holograms can serve as versatile platforms for various advanced acoustic wave manipulation and signal modulation, leading to new possibilities in acoustic sensing, energy deposition and medical diagnostic imaging. DA - 2016/10/14/ PY - 2016/10/14/ DO - 10.1038/srep35437 VL - 6 SP - SN - 2045-2322 ER - TY - JOUR TI - A quantitative damage imaging technique based on enhanced CCRTM for composite plates using 2D scan AU - He, J. Z. AU - Yuan, F. G. T2 - Smart Materials & Structures AB - A two-dimensional (2D) non-contact areal scan system was developed to image and quantify impact damage in a composite plate using an enhanced zero-lag cross-correlation reverse-time migration (E-CCRTM) technique. The system comprises a single piezoelectric wafer mounted on the composite plate and a laser Doppler vibrometer (LDV) for scanning a region in the vicinity of the PZT to capture the scattered wavefield. The proposed damage imaging technique takes into account the amplitude, phase, geometric spreading, and all of the frequency content of the Lamb waves propagating in the plate; thus, a reflectivity coefficients of the delamination is calculated and potentially related to damage severity. Comparisons are made in terms of damage imaging quality between 2D areal scans and 1D line scans as well as between the proposed and existing imaging conditions. The experimental results show that the 2D E-CCRTM performs robustly when imaging and quantifying impact damage in large-scale composites using a single PZT actuator with a nearby areal scan using LDV. DA - 2016/// PY - 2016/// DO - 10.1088/0964-1726/25/10/105022 VL - 25 IS - 10 ER - TY - JOUR TI - A piezoelectric shear stress sensor 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 - SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2016 AB - In this paper, a piezoelectric sensor with a floating element was developed for shear stress measurement. The piezoelectric sensor was designed to detect the pure shear stress, suppressing effects of normal stress components, by applying opposite poling vectors to the piezoelectric elements. The sensor was first calibrated in the lab by applying shear forces where it demonstrated high sensitivity to shear stress (91.3 ± 2.1 pC/Pa) due to the high piezoelectric coefficients of 0.67Pb(Mg1∕3Nb2∕3)O3-0.33PbTiO3 (PMN-33%PT, d31=-1330 pC/N). The sensor also exhibited negligible sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the device. The usable frequency range of the sensor is up to 800 Hz. DA - 2016/// PY - 2016/// DO - 10.1117/12.2219185 VL - 9803 SP - SN - 1996-756X KW - PMN-33% PT crystal KW - bimorph piezoelectric structures KW - floating element KW - electromechanical symmetry ER - TY - JOUR TI - A hybrid reconstructed discontinuous Galerkin method for compressible flows on arbitrary grids AU - Cheng, Jian AU - Liu, Tiegang AU - Luo, Hong T2 - COMPUTERS & FLUIDS AB - A new reconstructed Discontinuous Galerkin (rDG) method based on a hybrid least-squares recovery and reconstruction, named P1P2(HLSr), is developed for solving the compressible Euler and Navier-Stokes equations on arbitrary grids. The development of the new hybrid rDG method is motivated by the observation that the original least-squares reconstruction does not have the property of the 2-exactness. As a remedy, the new hybrid reconstruction obtains a quadratic polynomial solution from the underlying linear DG solution by use of a hybrid recovery and reconstruction strategy. The resultant hybrid rDG method combines the simplicity of the reconstruction-based DG method and the accuracy of the recovery-based DG method, and has the desired property of 2-exactness. A number of test cases for a variety of flow problems are presented to assess the performance of the new P1P2(HLSr) method. Numerical experiments demonstrate that this hybrid rDG method is able to achieve the designed optimal 3rd order of accuracy for both inviscid and viscous flows and outperform the rDG methods based on either Green-Gauss or least-squares reconstruction. DA - 2016/11/5/ PY - 2016/11/5/ DO - 10.1016/j.compfluid.2016.04.001 VL - 139 SP - 68-79 SN - 1879-0747 KW - Reconstructed methods KW - Discontinuous Galerkin methods KW - Arbitrary grids ER - TY - JOUR TI - A comprehensive finite element model for lithium–oxygen batteries AU - Ayers, Martin W. AU - Huang, Hsiao-Ying Shadow T2 - Journal of Materials Research DA - 2016/9/22/ PY - 2016/9/22/ DO - 10.1557/jmr.2016.306 VL - 31 IS - 18 SP - 2728-2735 J2 - J. Mater. Res. LA - en OP - SN - 0884-2914 2044-5326 UR - http://dx.doi.org/10.1557/jmr.2016.306 DB - Crossref ER - TY - JOUR TI - A Comparative Study of Rosenbrock-Type and Implicit Runge-Kutta Time Integration for Discontinuous Galerkin Method for Unsteady 3D Compressible Navier-Stokes equations AU - Liu, Xiaodong AU - Xia, Yidong AU - Luo, Hong AU - Xuan, Lijun T2 - COMMUNICATIONS IN COMPUTATIONAL PHYSICS AB - Abstract A comparative study of two classes of third-order implicit time integration schemes is presented for a third-order hierarchical WENO reconstructed discontinuous Galerkin (rDG) method to solve the 3D unsteady compressible Navier-Stokes equations: — 1) the explicit first stage, single diagonally implicit Runge-Kutta (ESDIRK3) scheme, and 2) the Rosenbrock-Wanner (ROW) schemes based on the differential algebraic equations (DAEs) of Index-2. Compared with the ESDIRK3 scheme, a remarkable feature of the ROW schemes is that, they only require one approximate Jacobian matrix calculation every time step, thus considerably reducing the overall computational cost. A variety of test cases, ranging from inviscid flows to DNS of turbulent flows, are presented to assess the performance of these schemes. Numerical experiments demonstrate that the third-order ROW scheme for the DAEs of index-2 can not only achieve the designed formal order of temporal convergence accuracy in a benchmark test, but also require significantly less computing time than its ESDIRK3 counterpart to converge to the same level of discretization errors in all of the flow simulations in this study, indicating that the ROW methods provide an attractive alternative for the higher-order time-accurate integration of the unsteady compressible Navier-Stokes equations. DA - 2016/10// PY - 2016/10// DO - 10.4208/cicp.300715.140316a VL - 20 IS - 4 SP - 1016-1044 SN - 1991-7120 KW - Implicit time integration KW - Rosenbrock-Wanner KW - discontinuous Galerkin KW - WENO KW - Navier-Stokes ER - TY - JOUR TI - Wide field-of-view fluorescence imaging with optical-quality curved microfluidic chamber for absolute cell counting AU - Shourav, M. K. AU - Kim, K. AU - Kim, S. AU - Kim, J. K. T2 - Micromachines DA - 2016/// PY - 2016/// VL - 7 IS - 7 ER - TY - JOUR TI - Variable Buoyancy System for Unmanned Multi-Domain Vehicles AU - MacLeod, Marc AU - Bryant, Matthew T2 - ACTIVE AND PASSIVE SMART STRUCTURES AND INTEGRATED SYSTEMS 2016 AB - This paper presents the system design, construction, and testing of an active variable buoyancy system (VBS) actuator with applications to unmanned multi-domain vehicles. Unmanned multi-domain vehicles require nontraditional VBS designs because of their unique operation requirements. We present a VBS actuator design that targets multi-domain vehicle design objectives of high endurance, stealth, and underwater loitering. The design features a rigid ballast tank with an inner elastic bladder connected to a hydraulic pump and a proportionally controlled vent valve. The system working fluid is obtained from the ambient surrounding water and the elastic bladder separates the water from pressurized gas, thus preventing any gas from escaping during a venting operation. An analytic model of the VBS characterizing the system dynamics is derived. Ballast tank prototype design and construction is discussed. A VBS test platform vehicle is presented, featuring two ballast tanks, motor, pump, and RF receiver for control. DA - 2016/// PY - 2016/// DO - 10.1117/12.2219289 VL - 9799 SP - SN - 1996-756X KW - actuators KW - buoyancy systems KW - marine vehicles KW - multi-domain KW - unmanned aerial vehicles ER - TY - JOUR TI - Toward efficient aeroelastic energy harvesting through limit cycle shaping AU - Kirschmeier, Benjamin AU - Bryant, Matthew T2 - ACTIVE AND PASSIVE SMART STRUCTURES AND INTEGRATED SYSTEMS 2016 AB - Increasing demand to harvest energy from renewable resources has caused significant research interest in unsteady aerodynamic and hydrodynamic phenomena. Apart from the traditional horizontal axis wind turbines, there has been significant growth in the study of bio-inspired oscillating wings for energy harvesting. These systems are being built to harvest electricity for wireless devices, as well as for large scale mega-watt power generation. Such systems can be driven by aeroelastic flutter phenomena which, beyond a critical wind speed, will cause the system to enter into limitcycle oscillations. When the airfoil enters large amplitude, high frequency motion, leading and trailing edge vortices form and, when properly synchronized with the airfoil kinematics, enhance the energy extraction efficiency of the device. A reduced order dynamic stall model is employed on a nonlinear aeroelastic structural model to investigate whether the parameters of a fully passive aeroelastic device can be tuned to produce limit cycle oscillations at desired kinematics. This process is done through an optimization technique to find the necessary structural parameters to achieve desired structural forces and moments corresponding to a target limit cycle. Structural nonlinearities are explored to determine the essential nonlinearities such that the system’s limit cycle closely matches the desired kinematic trajectory. The results from this process demonstrate that it is possible to tune system parameters such that a desired limit cycle trajectory can be achieved. The simulations also demonstrate that the high efficiencies predicted by previous computational aerodynamics studies can be achieved in fully passive aeroelastic devices. DA - 2016/// PY - 2016/// DO - 10.1117/12.2218437 VL - 9799 SP - SN - 1996-756X KW - Limit cycle oscillations KW - energy harvesting KW - leading edge vortex ER - TY - JOUR TI - Spray combustion of biomass-based renewable diesel fuel using multiple injection strategy in a constant volume combustion chamber AU - Jing, Wei AU - Wu, Zengyang AU - Roberts, William L. AU - Fang, Tiegang T2 - FUEL AB - Effect of a two-injection strategy associated with a pilot injection on the spray combustion process was investigated under conventional diesel combustion conditions (1000 K and 21% O2 concentration) for a biomass-based renewable diesel fuel, i.e., biomass to liquid (BTL), and a regular No. 2 diesel in a constant volume combustion chamber using multiband flame measurement and two-color pyrometry. The spray combustion flame structure was visualized by using multiband flame measurement to show features of soot formation, high temperature and low temperature reactions, which can be characterized by the narrow-band emissions of radicals or intermediate species such as OH, HCHO, and CH. The objective of this study was to identify the details of multiple injection combustion, including a pilot and a main injection, and to provide further insights on how the two injections interact. For comparison, three injection strategies were considered for both fuels including a two-injection strategy (Case TI), single injection strategy A (Case SA), and single injection strategy B (Case SB). Multiband flame results show a strong interaction, indicated by OH∗ emissions between the pilot injection and the main injection for Case TI while very weak connection is found for the narrow-band emissions acquired through filters with centerlines of 430 nm and 470 nm. A faster flame development is found for the main injection of Case TI compared to Cases SA and SB, which could be due to the high temperature environment and large air entrainment from the pilot injection. A lower soot level is observed for the BTL flame compared to the diesel flame for all three injection types. Case TI has a lower soot level compared to Cases SA and SB for the BTL fuel, while the diesel fuel maintains a similar soot level among all three injection strategies. Soot temperature of Case TI is lower for both fuels, especially for diesel. Based on these results, it is expected that the two-injection strategy could be effective in reducing soot and NOx (due to lower combustion temperature) simultaneously compared to either of the single injection strategies. DA - 2016/10/1/ PY - 2016/10/1/ DO - 10.1016/j.fuel.2016.05.039 VL - 181 SP - 718-728 SN - 1873-7153 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84969269086&partnerID=MN8TOARS KW - Biomass to liquid KW - BTL KW - Diesel KW - Spray combustion KW - Multiple-injection strategy KW - Two-color pyrometry ER - TY - JOUR TI - Scramjet Combustion Efficiency Measurement via Tomographic Absorption Spectroscopy and Particle Image Velocimetry AU - Busa, Kristin M. AU - Rice, Brian E. AU - McDaniel, James C. AU - Goyne, Christopher P. AU - Rockwell, Robert D. AU - Fulton, Jesse A. AU - Edwards, Jack R. AU - Diskin, Glenn S. T2 - AIAA JOURNAL AB - The combustion efficiency of a scramjet is a metric that evaluates the overall performance of the engine. Until recently, combustion efficiency was measured using indirect approaches such as a one-dimensional control volume calculation or a calorimeter and wall pressure tap measurements. A novel nonintrusive direct approach for the measurement of combustion efficiency is presented that combines the optical diagnostic techniques tunable diode laser absorption tomography and stereoscopic particle image velocimetry. Experimental results are presented for measurements of the University of Virginia’s Supersonic Combustion Facility in both the scram and ram-modes of operation. The tunable-diode-laser-absorption-tomography/stereoscopic-particle-image-velocimetry method directly measures the converted hydrogen (via water vapor) mass flow rate exiting the dual-mode scramjet and compares this to the facility-measured injected hydrogen fuel mass flow rate. A complementary computational fluid dynamics study was performed and results are available for the scram-mode operating condition. The results reported show excellent agreement between the tunable-diode-laser-absorption-tomography/stereoscopic-particle-image-velocimetry-measured combustion efficiency and the computational-fluid-dynamics-predicted combustion efficiency for the scram-mode of operation, which are both near 99%. The tunable-diode-laser-absorption-tomography/stereoscopic-particle-image-velocimetry-measured combustion efficiency for the ram-mode of operation is shown to be lower than that of the scram-mode operation: at 79%. DA - 2016/8// PY - 2016/8// DO - 10.2514/1.j054662 VL - 54 IS - 8 SP - 2463-2471 SN - 1533-385X ER - TY - JOUR TI - Performance and emission testing of a bi-fuel outboard spark-ignition engine AU - Bohon, Steven AU - Fang, Tiegang T2 - INTERNATIONAL JOURNAL OF ENGINE RESEARCH AB - With the increasing concern about the future availability of gasoline and continuously stringent engine emission regulatory standards, the need for an alternative to gasoline as a primary engine fuel is becoming increasingly important. One proposed alternative is to use natural gas due to its availability, low cost, and generally reduced engine emissions. However, due to volumetric efficiency losses, the conversion of a standard spark-ignition engine originally operating on gasoline to run on natural gas has been shown to produce considerable power reductions. Additionally, improperly tuned natural gas conversion kits could potentially increase certain emissions’ quantities compared to gasoline. This work reports the results of an experiment designed to characterize the performance and emissions of a commonly used gasoline outboard boat motor converted to run on natural gas. Reported are the comparisons between gasoline and natural gas for the widely used engine operating parameters for gauging engine performance related to power output and harmful emissions, including oxides of nitrogen, unburned hydrocarbons, and carbon monoxide, for comparison of the two test fuels. The results indicate that operation on natural gas greatly reduces harmful hydrocarbon and carbon monoxide emissions at the cost of reduced engine power output and potentially increased oxides of nitrogen emissions. DA - 2016/6// PY - 2016/6// DO - 10.1177/1468087415597095 VL - 17 IS - 5 SP - 576-592 SN - 2041-3149 KW - Outboard engine KW - spark-ignition engine KW - compressed natural gas KW - bi-fuel engine KW - emissions KW - performance ER - TY - JOUR TI - Membrane- and plate-type acoustic metamaterials AU - Huang, Tai-Yun AU - Shen, Chen AU - Jing, Yun T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA AB - Over the past decade there has been a great amount of research effort devoted to the topic of acoustic metamaterials (AMMs). The recent development of AMMs has enlightened the way of manipulating sound waves. Several potential applications such as low-frequency noise reduction, cloaking, angular filtering, subwavelength imaging, and energy tunneling have been proposed and implemented by the so-called membrane- or plate-type AMMs. This paper aims to offer a thorough overview on the recent development of membrane- or plate-type AMMs. The underlying mechanism of these types of AMMs for tuning the effective density will be examined first. Four different groups of membrane- or plate-type AMMs (membranes with masses attached, plates with masses attached, membranes or plates without masses attached, and active AMMs) will be reviewed. The opportunities, limitations, and challenges of membrane- or plate-type AMMs will be also discussed. DA - 2016/6// PY - 2016/6// DO - 10.1121/1.4950751 VL - 139 IS - 6 SP - 3239-3249 SN - 1520-8524 ER - TY - JOUR TI - Fabrication and structural properties of AlN submicron periodic lateral polar structures and waveguides for UV-C applications AU - Alden, D. AU - Guo, W. AU - Kirste, R. AU - Kaess, F. AU - Bryan, I. AU - Troha, T. AU - Bagal, A. AU - Reddy, P. AU - Hernandez-Balderrama, Luis H. AU - Franke, A. AU - Mita, S. AU - Chang, C. -H. AU - Hoffmann, A. AU - Zgonik, M. AU - Collazo, R. AU - Sitar, Z. T2 - APPLIED PHYSICS LETTERS AB - Periodically poled AlN thin films with submicron domain widths were fabricated for nonlinear applications in the UV-VIS region. A procedure utilizing metalorganic chemical vapor deposition growth of AlN in combination with laser interference lithography was developed for making a nanoscale lateral polarity structure (LPS) with domain size down to 600 nm. The Al-polar and N-polar domains were identified by wet etching the periodic LPS in a potassium hydroxide solution and subsequent scanning electron microscopy (SEM) characterization. Fully coalesced and well-defined vertical interfaces between the adjacent domains were established by cross-sectional SEM. AlN LPSs were mechanically polished and surface roughness with a root mean square value of ∼10 nm over a 90 μm × 90 μm area was achieved. 3.8 μm wide and 650 nm thick AlN LPS waveguides were fabricated. The achieved domain sizes, surface roughness, and waveguides are suitable for second harmonic generation in the UVC spectrum. DA - 2016/6/27/ PY - 2016/6/27/ DO - 10.1063/1.4955033 VL - 108 IS - 26 SP - SN - 1077-3118 ER - TY - CONF TI - Exploring the relationship between excess and system evolutions using a stress-test AU - Cansler, E. Z. AU - Ferguson, S. M. AU - Mattson, C. A. AB - Engineers understand that attaining a full service life can add value to an engineered system. Ensuring that this is possible requires that excess be embedded within the design to enable system evolution when new or changed requirements are placed on it during the service phase. However, since future needs are by definition unknown, knowing with certainty which excesses to embed is impossible. To address that challenge, this paper draws on an excess mapping method developed in previous work that demonstrated how to map component relationships based on excess interactions. This method is now used in a stress test approach to explore how a system design is affected when faced with various possible evolution scenarios. This study has two results: first, a judgment of whether the current system design possesses sufficient excess for it to respond to future needs. Second, quantitative estimates of excesses to add if the current design excess is judged to be insufficient. A demonstrative example is presented using a dart gun, which determines that the system as designed is likely adequate for a variety of possible future needs. C2 - 2016/// C3 - International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 2015, vol 7 DA - 2016/// DO - 10.1115/detc2015-47603 ER - TY - JOUR TI - Experimental observation of ultrasound fast and slow waves through three-dimensional printed trabecular bone phantoms AU - Meziere, F. AU - Juskova, P. AU - Woittequand, J. AU - Muller, M. AU - Bossy, E. AU - Boistel, Renaud AU - Malaquin, L. AU - Derode, A. T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA AB - In this paper, ultrasound measurements of 1:1 scale three-dimensional (3D) printed trabecular bone phantoms are reported. The micro-structure of a trabecular horse bone sample was obtained via synchrotron x-ray microtomography, converted to a 3D binary data set, and successfully 3D-printed at scale 1:1. Ultrasound through-transmission experiments were also performed through a highly anisotropic version of this structure, obtained by elongating the digitized structure prior to 3D printing. As in real anisotropic trabecular bone, both the fast and slow waves were observed. This illustrates the potential of stereolithography and the relevance of such bone phantoms for the study of ultrasound propagation in bone. DA - 2016/2// PY - 2016/2// DO - 10.1121/1.4939297 VL - 139 IS - 2 SP - EL13-EL18 SN - 1520-8524 ER - TY - JOUR TI - Electrochemical Effects in Thermoelectric Polymers AU - Chang, William B. AU - Fang, Haiyu AU - Liu, Jun AU - Evans, Christopher M. AU - Russ, Boris AU - Popere, Bhooshan C. AU - Patel, Shrayesh N. AU - Chabinyc, Michael L. AU - Segalman, Rachel A. T2 - ACS MACRO LETTERS AB - Conductive polymers such as PEDOT:PSS hold great promise as flexible thermoelectric devices. The thermoelectric power factor of PEDOT:PSS is small relative to inorganic materials because the Seebeck coefficient is small. Ion conducting materials have previously been demonstrated to have very large Seebeck coefficients, and a major advantage of polymers over inorganics is the high room temperature ionic conductivity. Notably, PEDOT:PSS demonstrates a significant but short-term increase in Seebeck coefficient which is attributed to a large ionic Seebeck contribution. By controlling whether electrochemistry occurs at the PEDOT:PSS/electrode interface, the duration of the ionic Seebeck enhancement can be controlled, and a material can be designed with long-lived ionic Seebeck enhancements. DA - 2016/4// PY - 2016/4// DO - 10.1021/acsmacrolett.6b00054 VL - 5 IS - 4 SP - 455-459 SN - 2161-1653 UR - http://dx.doi.org/10.1021/acsmacrolett.6b00054 ER - TY - JOUR TI - Design of elliptically-vibrating ultrasonic actuator for nanocoining AU - Dow, Thomas A. AU - Nowak, John AU - Kessing, Jonas R. T2 - PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY AB - Nanocoining is a method of rapidly creating a cylindrical mold surface covered with features smaller than the wavelength of light. This mold can then be used in a roll-to-roll process to make surfaces whose functionality depends on the wavelength of the illumination. The die replaces the typical diamond tool used to produce overlapping grooves for applications such as reflective signs. The die has a face area approximately 20 μm2 that has been patterned in an FIB. It is mounted on a 2D ultrasonic actuator and follows an elliptical path that matches the surface speed of the moving workpiece during the short contact time and creates approximately 6000 features per impact. The spacing of die indents is controlled by the speed of the diamond turning machine axes such that a small overlap exists from previous indents as the die spirals around and along the mold surface. Because the die is small, the indentations must occur rapidly to make nanocoining a feasible process. This work focuses on the design and control of a nominally 40 kHz, 2D resonant actuator that is suitable for this process. A controller to automatically track resonance is described to maintain the elliptical motion during indentation. Methods of tuning the behavior of the actuator and maintaining a constant indent depth are proposed. Finally, 500 nm pitch feature indents were created on a brass workpiece at 40 kHz and scanning electron microscope (SEM) images of the features are provided. DA - 2016/7// PY - 2016/7// DO - 10.1016/j.precisioneng.2016.03.007 VL - 45 SP - 301-310 SN - 1873-2372 KW - Nanocoining KW - Ultrasonic transducer KW - Nanoindentation KW - Structured surfaces KW - Diamond die KW - Bio-inspired technology ER - TY - JOUR TI - Control approach development for variable recruitment artificial muscles AU - Jenkins, Tyler E. AU - Chapman, Edward M. AU - Bryant, Matthew T2 - ACTIVE AND PASSIVE SMART STRUCTURES AND INTEGRATED SYSTEMS 2016 AB - This study characterizes hybrid control approaches for the variable recruitment of fluidic artificial muscles with double acting (antagonistic) actuation. Fluidic artificial muscle actuators have been explored by researchers due to their natural compliance, high force-to-weight ratio, and low cost of fabrication. Previous studies have attempted to improve system efficiency of the actuators through variable recruitment, i.e. using discrete changes in the number of active actuators. While current variable recruitment research utilizes manual valve switching, this paper details the current development of an online variable recruitment control scheme. By continuously controlling applied pressure and discretely controlling the number of active actuators, operation in the lowest possible recruitment state is ensured and working fluid consumption is minimized. Results provide insight into switching control scheme effects on working fluids, fabrication material choices, actuator modeling, and controller development decisions. DA - 2016/// PY - 2016/// DO - 10.1117/12.2222201 VL - 9799 SP - SN - 1996-756X KW - McKibben muscle KW - fluidic artificial muscle KW - hydraulic artificial muscle KW - actuator KW - variable recruitment KW - bio-inspired KW - hybrid control KW - switching control ER - TY - JOUR TI - An enhanced CCRTM (E-CCRTM) damage imaging technique using a 2-D areal scan for composite plates AU - He, Jiaze AU - Yuan, Fuh-Gwo T2 - NONDESTRUCTIVE CHARACTERIZATION AND MONITORING OF ADVANCED MATERIALS, AEROSPACE, AND CIVIL INFRASTRUCTURE 2016 AB - A two-dimensional (2-D) non-contact areal scan system was developed to image and quantify impact damage in a composite plate using an enhanced zero-lag cross-correlation reverse-time migration (E-CCRTM) technique. The system comprises a single piezoelectric actuator mounted on the composite plate and a laser Doppler vibrometer (LDV) for scanning a region to capture the scattered wavefield in the vicinity of the PZT. The proposed damage imaging technique takes into account the amplitude, phase, geometric spreading, and all of the frequency content of the Lamb waves propagating in the plate; thus, the reflectivity coefficients of the delamination can be calculated and potentially related to damage severity. Comparisons are made in terms of damage imaging quality between 2-D areal scans and linear scans as well as between the proposed and existing imaging conditions. The experimental results show that the 2-D E-CCRTM performs robustly when imaging and quantifying impact damage in large-scale composites using a single PZT actuator with a nearby areal scan using LDV. DA - 2016/// PY - 2016/// DO - 10.1117/12.2218684 VL - 9804 SP - SN - 1996-756X KW - RTM KW - damage imaging KW - time-reversal KW - ZLCC KW - BVID KW - 2-D scan KW - non-contact KW - LDV ER - TY - JOUR TI - An efficient low frequency horizontal diamagnetic levitation mechanism based vibration energy harvester AU - Palagummi, S. AU - Yuan, F. G. T2 - ACTIVE AND PASSIVE SMART STRUCTURES AND INTEGRATED SYSTEMS 2016 AB - This article identifies and studies key parameters that characterize a horizontal diamagnetic levitation (HDL) mechanism based low frequency vibration energy harvester with the aim of enhancing performance metrics such as efficiency and volume figure of merit (FoMv). The HDL mechanism comprises of three permanent magnets and two diamagnetic plates. Two of the magnets, aka lifting magnets, are placed co-axially at a distance such that each attract a centrally located magnet, aka 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 are 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 HDL 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 FoMv of 0.23% when excited at a root mean square acceleration of 0.0546 m/s2 and at frequency of 1.9 Hz. DA - 2016/// PY - 2016/// DO - 10.1117/12.2218914 VL - 9799 SP - SN - 1996-756X KW - Energy harvesting KW - magnetic levitation KW - diamagnetism KW - low frequency KW - nonlinear ER - TY - JOUR TI - An anisotropic ultrasonic transducer for Lamb wave applications AU - Zhou, Wensong AU - Li, Hui AU - Yuan, Fuh-Gwo T2 - SMART STRUCTURES AND SYSTEMS AB - An anisotropic ultrasonic transducer is proposed for Lamb wave applications, such as passive damage or impact localization based on ultrasonic guided wave theory. This transducer is made from a PMNPT single crystal, and has different piezoelectric coefficients $d_{31}$ and $d_{32}$, which are the same for the conventional piezoelectric materials, such as Lead zirconate titanate (PZT). Different piezoelectric coefficients result in directionality of guided wave generated by this transducer, in other words, it is an anisotropic ultrasonic transducer. And thus, it has different sensitivity in comparison with conventional ultrasonic transducer. The anisotropic one can provide more information related to the direction when it is used as sensors. This paper first shows its detailed properties, including analytical formulae and finite elements simulations. Then, its application is described. DA - 2016/6// PY - 2016/6// DO - 10.12989/sss.2016.17.6.1055 VL - 17 IS - 6 SP - 1055-1065 SN - 1738-1584 KW - ultrasonic transducer KW - anisotropic KW - sensing property KW - ultrasonic applications ER - TY - JOUR TI - Aeroelastic modeling of a Piezo-Solar tensioned energy harvesting ribbon AU - Chatterjee, Punnag AU - Bryant, Matthew T2 - ACTIVE AND PASSIVE SMART STRUCTURES AND INTEGRATED SYSTEMS 2016 AB - A multifunctional compliant structure is proposed that can harvest electrical power from both incident sunlight and ambient mechanical energy including wind flow or vibration. The proposed energy harvesting device consists of a slender, ribbon-like, flexible thin film solar cell that is laminated with piezoelectric patches at either ends and mounted in the cross flow of wind in a clamped-clamped end condition with an adjustable axial preload. Taking this motivation forward a system model of the energy harvester is developed which captures the structural response of the solar ribbon and couples it with Theodorsen unsteady aerodynamics to predict the flutter boundary conditions as a function of applied axial preload tension. The model also accounts for geometric and material discontinuities, by effective use of Transfer Matrix Method (TMM) modeling technique both in bending and torsional degrees of freedom. This paper also derives TMM technique for torsional vibrations with an applied axial load from first principles, verifies the method and presents its applicability for the proposed energy harvester. The paper also points out that the flutter instability arises out of different structural modes at different values applied axial tension, with the help of a sample modal convergence plot. The analysis also presents the possibility to tune the solar ribbon to operate at an optimal reduced frequency by adjusting the applied axial preload. DA - 2016/// PY - 2016/// DO - 10.1117/12.2222109 VL - 9799 SP - SN - 1996-756X KW - Transfer Matrix Method (TMM) KW - aeroelastic flutter KW - piezo solar ribbon KW - hybrid energy harvesting KW - applied axial load KW - Theodorsen unsteady aerodynamics KW - reduced frequency KW - discontinuous structure ER - TY - JOUR TI - A hybrid incremental projection method for thermal-hydraulics applications AU - Christon, Mark A. AU - Bakosi, Jozsef AU - Nadiga, Balasubramanya T. AU - Berndt, Markus AU - Francois, Marianne M. AU - Stagg, Alan K. AU - Xia, Yidong AU - Luo, Hong T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - A new second-order accurate, hybrid, incremental projection method for time-dependent incompressible viscous flow is introduced in this paper. The hybrid finite-element/finite-volume discretization circumvents the well-known Ladyzhenskaya–Babuška–Brezzi conditions for stability, and does not require special treatment to filter pressure modes by either Rhie–Chow interpolation or by using a Petrov–Galerkin finite element formulation. The use of a co-velocity with a high-resolution advection method and a linearly consistent edge-based treatment of viscous/diffusive terms yields a robust algorithm for a broad spectrum of incompressible flows. The high-resolution advection method is shown to deliver second-order spatial convergence on mixed element topology meshes, and the implicit advective treatment significantly increases the stable time-step size. The algorithm is robust and extensible, permitting the incorporation of features such as porous media flow, RANS and LES turbulence models, and semi-/fully-implicit time stepping. A series of verification and validation problems are used to illustrate the convergence properties of the algorithm. The temporal stability properties are demonstrated on a range of problems with 2≤CFL≤100. The new flow solver is built using the Hydra multiphysics toolkit. The Hydra toolkit is written in C++ and provides a rich suite of extensible and fully-parallel components that permit rapid application development, supports multiple discretization techniques, provides I/O interfaces, dynamic run-time load balancing and data migration, and interfaces to scalable popular linear solvers, e.g., in open-source packages such as HYPRE, PETSc, and Trilinos. DA - 2016/7/15/ PY - 2016/7/15/ DO - 10.1016/j.jcp.2016.04.061 VL - 317 SP - 382-404 SN - 1090-2716 KW - FVM KW - FEM KW - Incompressible flow KW - Monotonicity-preserving advection KW - Projection method KW - Mixed-topology meshes KW - Thermal-hydraulics ER - TY - JOUR TI - A direct numerical simulation study on the possibility of macroscopic turbulence in porous media: Effects of different solid matrix geometries, solid boundaries, and two porosity scales AU - Uth, M. -F. AU - Jin, Y. AU - Kuznetsov, A. V. AU - Herwig, H. T2 - PHYSICS OF FLUIDS AB - In this study, we address the question of whether turbulent structures in a porous medium are restricted in size by the pore scale or whether the size of eddies may exceed the pore scale, leading to the formation of macroscopic coherent structures. Based on direct numerical simulations in porous media, we conclude that the size of turbulent eddies is restricted by the pore size, leading to the pore scale prevalence hypothesis (PSPH). We prove this hypothesis by considering four different porous matrices. In particular, we simulated turbulent flow in a two-dimensional matrix, a three-dimensional unbounded matrix, a three-dimensional matrix bounded by two parallel solid walls, and a three-dimensional matrix with two characteristic pore scales. The obtained results for the four simulated porous matrices support the PSPH. However, there is a partly open question of whether turbulent structures can reach the size of the largest pore scale if the solid matrix is characterized by more than one length scale. DA - 2016/6// PY - 2016/6// DO - 10.1063/1.4949549 VL - 28 IS - 6 SP - SN - 1089-7666 ER - TY - CONF TI - robust gain-scheduling output feedback control of state-delayed lft systems using dynamic IQCS AU - Yuan, C. Z. AU - Wu, F. AU - Duan, C. AB - This paper is concerned with the robust gain-scheduling output feedback control problem for a class of linear parameter-varying systems with time-varying state delay. The controlled plant under consideration is described as a linear fractional transformation (LFT) model of scheduling parameters. Dynamic integral quadratics (IQCs) are employed to characterize the input-output behavior of the state-delay nonlinearity. The robust stability and the L2-gain performance are first analyzed using quadratic Lyapunov function. Then, the design of dynamic output-feedback controllers robust against the plant state-delay nonlinearity and gain-scheduled by parameters is examined. The synthesis conditions of such robust gain-scheduling controllers are formulated in terms of linear matrix inequalities (LMIs) plus a line search, which can be solved effectively using existing algorithms. A numerical example has been used to demonstrate the effectiveness and advantages of the proposed approach. C2 - 2016/// C3 - Proceedings of the ASME 8th Annual Dynamic Systems and Control Conference, 2015, vol 3 DA - 2016/// DO - 10.1115/dscc2015-9686 ER - TY - JOUR TI - Unstable Forced Convection in a Plane Porous Channel With Variable-Viscosity Dissipation AU - Barletta, A. AU - Celli, M. AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - Fully developed and stationary forced convection in a plane-parallel porous channel is analyzed. The boundary walls are modeled as impermeable and subject to external heat transfer. Different Biot numbers are defined at the two boundary planes. It is shown that the combined effects of temperature-dependent viscosity and viscous heating may induce flow instability. The instability takes place at the lowest parametric singularity of the basic flow solution. The linear stability analysis is carried out analytically for the longitudinal modes and numerically for general oblique modes. It is shown that longitudinal modes with vanishingly small wave number are selected at the onset of instability. DA - 2016/3// PY - 2016/3// DO - 10.1115/1.4031868 VL - 138 IS - 3 SP - SN - 1528-8943 KW - heat transfer KW - variable-viscosity KW - porous media KW - viscous dissipation KW - convective instability ER - TY - JOUR TI - Thermal Conductivity in the Radial Direction of Deformed Polymer Fibers AU - Lu, Yanfu AU - Liu, Jun AU - Xie, Xu AU - Cahill, David G. T2 - ACS MACRO LETTERS AB - Thermal conductivity of polymer fibers in the axial direction has been extensively studied while thermal conductivity in the radial direction Λ remains unknown. In this work, polymer fibers with different molecular arrangements (crystalline, liquid crystalline, and amorphous) were plastically deformed. Λ was measured at engineering strains ε = 0.2-2.3 using time-domain thermoreflectance. Λ decreases with increasing strains for polyethylene (PE) and poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers and is independent of strain for poly(methyl methacrylate) (PMMA) fibers. The extrapolated thermal conductivity at zero strain is Λ0 ≈ 0.27 Wm-1 K-1 for crystalline PE, Λ0 ≈ 0.29 Wm-1 K-1 for liquid crystalline PBO, and Λ0 ≈ 0.18 Wm-1 K-1 for amorphous PMMA. Λ of PE drops to Λ ≈ 0.14 Wm-1 K-1 at ε = 1.9; Λ of PBO drops to Λ ≈ 0.12 Wm-1 K-1 at ε = 2.1. We attribute the decrease of Λ with ε in crystalline and liquid crystalline fibers to structural disorder induced by plastic deformation. The combination of structural disorder and phonon focusing effects produces a thermal conductivity in deformed PE and PBO fibers that is lower than amorphous PMMA. DA - 2016/6// PY - 2016/6// DO - 10.1021/acsmacrolett.6b00048 VL - 5 IS - 6 SP - 646-650 SN - 2161-1653 UR - http://dx.doi.org/10.1021/acsmacrolett.6b00048 ER - TY - JOUR TI - Soot particle size measurements in ethylene diffusion flames at elevated pressures AU - Steinmetz, Scott A. AU - Fang, Tiegang AU - Roberts, William L. T2 - COMBUSTION AND FLAME AB - Soot particle size is investigated in laminar nitrogen-diluted ethylene coflow diffusion flames at 4, 8, 12 and 16 atm. Line of sight attenuation and scattering are used to measure two-dimensional soot volume fraction and particle size fields for the first time at elevated pressures. Soot volume fraction dependence on pressure is consistent with the observations of similar studies, scaling approximately with the square of pressure. Scattering intensity is analyzed through Rayleigh and Rayleigh–Debye–Gans polydisperse fractal aggregate theories to provide two estimates of particle size. An increase in overall particle sizes with pressure is found, consistent with similar one-dimensional studies. Particle diameters in the annulus of the flame increase faster with pressure than those on centerline. Contrary to previous studies, the dependence of particle size on pressure was found to taper off between 8 and 12 atm, with little observed growth beyond 12 atm. The measurements provide additional data for one of the International Sooting Flame (ISF) workshop’s target pressurized flames. DA - 2016/7// PY - 2016/7// DO - 10.1016/j.combustflame.2016.02.034 VL - 169 SP - 85-93 SN - 1556-2921 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964931690&partnerID=MN8TOARS KW - Soot KW - High pressure KW - Particle KW - Aggregate KW - Scattering ER - TY - CONF TI - Simulating variability of rework cost and market performance estimates in product redesign AU - Von Hagel, K. A. AU - Ferguson, S. M. AB - When considering the redesign of an existing product, designers must consider possible engineering and marketing ramifications. Ideal changes capture a large portion of the market and have a low risk of change propagation that results in reduced cost to the manufacturer. Engineering change tools such as the Change Prediction Method and market research models such as Hierarchical Bayes Mixed Logit allow designers to estimate the cost of the redesign process and market shares of preference. Variability in the inputs of the Change Prediction Method (impact and likelihood values) results in a range of redesign cost values. Assumptions regarding model form and the randomness used in model fitting also lead to variations when estimating market performance. When the variability associated with these techniques is considered, focus should shift from a point-estimate to a region-estimate. This paper explores the region-estimate produced for proposed redesigns when considering rework cost and market share of preference. C2 - 2016/// C3 - International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 2015, vol 2A DA - 2016/// DO - 10.1115/detc2015-47598 ER - TY - JOUR TI - Significantly Increasing the Ductility of High Performance Polymer Semiconductors through Polymer Blending AU - Scott, Joshua I. AU - Xue, Xiao AU - Wang, Ming AU - Kline, R. Joseph AU - Hoffman, Benjamin C. AU - Dougherty, Daniel AU - Zhou, Chuanzhen AU - Bazan, Guillermo AU - Brendan T. O'Connor, T2 - ACS APPLIED MATERIALS & INTERFACES AB - Polymer semiconductors based on donor–acceptor monomers have recently resulted in significant gains in field effect mobility in organic thin film transistors (OTFTs). These polymers incorporate fused aromatic rings and have been designed to have stiff planar backbones, resulting in strong intermolecular interactions, which subsequently result in stiff and brittle films. The complex synthesis typically required for these materials may also result in increased production costs. Thus, the development of methods to improve mechanical plasticity while lowering material consumption during fabrication will significantly improve opportunities for adoption in flexible and stretchable electronics. To achieve these goals, we consider blending a brittle donor–acceptor polymer, poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b′]dithiophen-2-yl)-alt-[1,2,5]thiadiazolo[3,4-c]pyridine] (PCDTPT), with ductile poly(3-hexylthiophene). We found that the ductility of the blend films is significantly improved compared to that of neat PCDTPT films, and when the blend film is employed in an OTFT, the performance is largely maintained. The ability to maintain charge transport character is due to vertical segregation within the blend, while the improved ductility is due to intermixing of the polymers throughout the film thickness. Importantly, the application of large strains to the ductile films is shown to orient both polymers, which further increases charge carrier mobility. These results highlight a processing approach to achieve high performance polymer OTFTs that are electrically and mechanically optimized. DA - 2016/6/8/ PY - 2016/6/8/ DO - 10.1021/acsami.6b01852 VL - 8 IS - 22 SP - 14037-14045 SN - 1944-8244 KW - polymer semiconductors KW - blend films KW - vertical segregation KW - ductility KW - thin film transistors ER - TY - JOUR TI - Point of impact: the effect of size and speed on puncture mechanics AU - Anderson, P. S. L. AU - LaCosse, J. AU - Pankow, M. T2 - INTERFACE FOCUS AB - The use of high-speed puncture mechanics for prey capture has been documented across a wide range of organisms, including vertebrates, arthropods, molluscs and cnidarians. These examples span four phyla and seven orders of magnitude difference in size. The commonality of these puncture systems offers an opportunity to explore how organisms at different scales and with different materials, morphologies and kinematics perform the same basic function. However, there is currently no framework for combining kinematic performance with cutting mechanics in biological puncture systems. Our aim here is to establish this framework by examining the effects of size and velocity in a series of controlled ballistic puncture experiments. Arrows of identical shape but varying in mass and speed were shot into cubes of ballistic gelatine. Results from high-speed videography show that projectile velocity can alter how the target gel responds to cutting. Mixed models comparing kinematic variables and puncture patterns indicate that the kinetic energy of a projectile is a better predictor of penetration than either momentum or velocity. These results form a foundation for studying the effects of impact on biological puncture, opening the door for future work to explore the influence of morphology and material organization on high-speed cutting dynamics. DA - 2016/6// PY - 2016/6// DO - 10.1098/rsfs.2015.0111 VL - 6 IS - 3 SP - SN - 2042-8901 KW - puncture KW - cutting KW - velocity KW - energy KW - prey capture ER - TY - JOUR TI - Performance and Design Comparison of a Bulk Thermoelectric Cooler With a Hybrid Architecture AU - Antonik, Margaret AU - O'Connor, Brendan T. AU - Ferguson, Scott T2 - Journal of Thermal Science and Engineering Applications AB - This paper compares the economic viability and performance outcomes of two different thermoelectric device architectures to determine the advantages and appropriate use of each configuration. Hybrid thermoelectric coolers (TECs) employ thin-film thermoelectric materials sandwiched between a plastic substrate and form a corrugated structure. Roll-to-roll (R2R) manufacturing and low-cost polymer materials offer a cost advantage to the hybrid architecture at the sacrifice of performance capabilities while conventional bulk devices offer increased performance at a higher cost. Performance characteristics and cost information are developed for both hybrid and conventional bulk single-stage thermoelectric modules. The design variables include device geometry, electrical current input, and thermoelectric material type. The tradeoffs between cooling performance and cost will be explored, and the thermoelectric system configuration is analyzed for both hybrid and conventional bulk TECs. DA - 2016/3/1/ PY - 2016/3/1/ DO - 10.1115/1.4032637 VL - 8 IS - 2 SP - LA - en OP - SN - 1948-5085 1948-5093 UR - http://dx.doi.org/10.1115/1.4032637 DB - Crossref ER - TY - JOUR TI - Output feedback control of linear fractional transformation systems subject to actuator saturation AU - Ban, Xiaojun AU - Wu, Fen T2 - INTERNATIONAL JOURNAL OF SYSTEMS SCIENCE AB - In this paper, the control problem for a class of linear parameter varying (LPV) plant subject to actuator saturation is investigated. For the saturated LPV plant depending on the scheduling parameters in linear fractional transformation (LFT) fashion, a gain-scheduled output feedback controller in the LFT form is designed to guarantee the stability of the closed-loop LPV system and provide optimised disturbance/error attenuation performance. By using the congruent transformation, the synthesis condition is formulated as a convex optimisation problem in terms of a finite number of LMIs for which efficient optimisation techniques are available. The nonlinear inverted pendulum problem is employed to demonstrate the effectiveness of the proposed approach. Moreover, the comparison between our LPV saturated approach with an existing linear saturated method reveals the advantage of the LPV controller when handling nonlinear plants. DA - 2016/// PY - 2016/// DO - 10.1080/00207721.2015.1110213 VL - 47 IS - 15 SP - 3646-3655 SN - 1464-5319 KW - Linear fractional transformation systems KW - actuator saturation KW - gain-scheduling KW - output feedback KW - disturbance attenuation KW - L-2 gain ER - TY - JOUR TI - Non-linearity of apparent mass for multi-element bodies AU - Granlund K., Ol M. AU - L., Bernal T2 - AIAA Journal DA - 2016/// PY - 2016/// VL - 54 IS - 2 SP - 771-776 ER - TY - CONF TI - Modeling noncompensatory choices with a compensatory model for a product design search AU - Shin, J. AU - Ferguson, S. AB - Market-based product design has typically used compensatory models that assume a simple additive part-worth rule. However, marketing literature has demonstrated that consumers use various heuristics called noncompensatory choices to simplify their choice decisions. This study aims to explore the suitability of compensatory modeling of these noncompensatory choices for the product design search. This is motivated by the limitations of the existing Bayesian-based noncompensatory mode, such as the screening rule assumptions, probabilistic representation of noncompensatory choices, and discontinuous choice probability functions in the Bayesian-based noncompensatory model. Results from using compensatory models show that noncompensatory choices can lead to distinct segments with extreme part-worths. In addition, the product design search problem suggests that the compensatory model would be preferred due to small design errors and inexpensive computational burden. C2 - 2016/// C3 - International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 2015, vol 2A DA - 2016/// DO - 10.1115/detc2015-47632 ER - TY - JOUR TI - Thermal gradient induced flexoelectric effects in bulk Ba0.67Sr0.33TiO3 AU - Kim, Taeyang AU - Huang, Wenbin AU - Huang, Shujin AU - Jiang, Xiaoning T2 - APPLIED PHYSICS LETTERS AB - Flexoelectric effect, denoting electric field gradient induced mechanical strain or mechanical strain gradient induced electric polarization, is a universal phenomenon in all dielectrics. Although research on the topic of flexoelectricity under stress fields and electric fields has advanced significantly, information regarding the phenomenon under thermal fields is rather limited. In this letter, the flexoelectricity field of Ba0.67Sr0.33TiO3 (BST) was investigated by generating temperature gradients along the lengths of samples with symmetric geometry. An electric field gradient induced by a thermal gradient was analyzed based on the temperature-dependent dielectric property of BST. The strain was then experimentally verified due to the electric field gradient. Experimental results suggest converse flexoelectric effect of BST samples with symmetric geometry in a thermal field. This result was not only consistent with the theoretical prediction, but it also followed the scaling effect of flexoelectricity. DA - 2016/5/9/ PY - 2016/5/9/ DO - 10.1063/1.4949358 VL - 108 IS - 19 SP - SN - 1077-3118 ER - TY - JOUR TI - The Effect of Spatially Nonuniform Internal Heating on the Onset of Convection in a Horizontal Fluid Layer AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - In this paper, we investigated the onset of natural convection in a horizontal fluid layer due to nonuniform internal heat generation, which is relevant to a number of geophysical situations. We investigated a number of special cases, which we believe are paradigmatic. Those include linear, quadratic, concentrated, and exponential source strength distributions. Our results show that those situations that lead to a reduction/increase in the size of the region in which the basic temperature gradient is destabilizing lead to an increase/decrease in stability. DA - 2016/6// PY - 2016/6// DO - 10.1115/1.4032837 VL - 138 IS - 6 SP - SN - 1528-8943 KW - instability KW - natural convection KW - internal heating ER - TY - JOUR TI - Study on a flexoelectric microphone using barium strontium titanate AU - Kwon, S. R. AU - Huang, W. B. AU - Zhang, S. J. AU - Yuan, F. G. AU - Jiang, X. N. T2 - JOURNAL OF MICROMECHANICS AND MICROENGINEERING AB - In this study, a flexoelectric microphone was, for the first time, designed and fabricated in a bridge structure using barium strontium titanate (Ba0.65Sr0.35TiO3) ceramic and tested afterwards. The prototyped flexoelectric microphone consists of a 1.5 mm × 768 μm × 50 μm BST bridge structure and a silicon substrate with a cavity. The sensitivity and resonance frequency were designed to be 0.92 pC/Pa and 98.67 kHz, respectively. The signal to noise ratio was measured to be 74 dB. The results demonstrate that the flexoelectric microphone possesses high sensitivity and a wide working frequency range simultaneously, suggesting that flexoelectricity could be an excellent alternative sensing mechanism for microphone applications. DA - 2016/4// PY - 2016/4// DO - 10.1088/0960-1317/26/4/045001 VL - 26 IS - 4 SP - SN - 1361-6439 KW - flexoelectricity KW - microphone KW - barium strontium titanate KW - micro-bridge ER - TY - JOUR TI - Streamwise Oscillation of Airfoils into Reverse Flow AU - Granlund, Kenneth O. AU - Ol, Michael V. AU - Jones, Anya R. T2 - AIAA JOURNAL AB - A NACA 0012 airfoil is oscillated in streamwise direction in a constant freestream and at a fixed incidence angle such that reverse flow occurs cyclically. Force measurements reveal that lift is close to unsteady theory while advancing into the freestream, if the angle of attack permits attached flow. Lift is augmented at large angles of attack, where the flow is separated under steady conditions, and does not become appreciatively negative in flow reversal for either attached or separated flow, contrary to one unsteady theory but supported by another. Dye flow visualization reveals a coherent vortical structure upstream of the leading edge before flow reversal, which is believed to attenuate negative lift. DA - 2016/5// PY - 2016/5// DO - 10.2514/1.j054674 VL - 54 IS - 5 SP - 1628-1636 SN - 1533-385X ER - TY - CONF TI - Performance comparison of a bulk thermoelectric cooler with a hybrid device architecture AU - Antonik, M. AU - Ferguson, S. M. AU - O'Connor, B. T. AB - This paper compares the economic viability and performance outcomes of two different thermoelectric device architectures to determine the advantages and appropriate use of each configuration. Hybrid thermoelectric coolers employ thin-film thermoelectric materials sandwiched between a plastic substrate and formed into a corrugated structure. Roll-to-roll manufacturing and low-cost polymer materials offer a cost advantage to the hybrid architecture at the sacrifice of performance capabilities while conventional bulk devices offer increased performance at a higher cost. Performance characteristics and cost information are developed for both hybrid and conventional bulk single-stage thermoelectric modules. The design variables include device geometry, electrical current input, and thermoelectric material type. The trade-offs between cooling performance and cost will be explored and the thermoelectric system configuration analyzed for both hybrid and conventional bulk thermoelectric coolers. C2 - 2016/// C3 - International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 2015, vol 2b DA - 2016/// DO - 10.1115/detc2015-47610 ER - TY - JOUR TI - New punch design for the elimination of punch ejection load through manipulation of the elastic strain field in the punch nose AU - Lowrie, James AU - Ngaile, Gracious T2 - JOURNAL OF MANUFACTURING PROCESSES AB - The extreme tribological conditions present during both the forward stroke and the punch ejection stroke of a backward cup extrusion process can adversely affect the quality of the extruded part and diminish the life of the punches. A novel punch design based on the segmentation of the extrusion punch into a main body and a nose cone insert is proposed to reduce or eliminate the pressure between the punch and work piece during the punch removal stroke. This is facilitated by manipulating the elastic strain field at the punch nose. With the aid of the finite element analysis, a parametric study on the segmented elastic punch assembly was carried out to establish optimal conditions and punch design guidelines. Experiments were carried out to determine the effectiveness of the segmented elastic punch. A significant reduction in the punch ejection load was observed along with a reduction in material pickup on the punch and galling on the surface of the part. The elastic deflection of the punch also allowed the researchers to discover that a significant amount of damage could occur during the punch ejection stroke. DA - 2016/4// PY - 2016/4// DO - 10.1016/j.jmapro.2016.01.008 VL - 22 SP - 49-59 SN - 1526-6125 KW - Punch design KW - Extrusion KW - Punch load KW - Tribology ER - TY - JOUR TI - Experimental and computational studies on the thermal behavior and fire retardant properties of composite metal foams AU - Chen, Shuo AU - Marx, Jacob AU - Rabiei, Afsaneh T2 - INTERNATIONAL JOURNAL OF THERMAL SCIENCES AB - A comprehensive experimental and computational evaluation of thermal behavior and fire retardant properties of composite metal foams (CMFs) is reported in this study. Thermal behavior characterizations were carried out through specific heat, effective thermal conductivity, and coefficient of thermal expansion analyses using differential scanning calorimetry, high temperature guarded-comparative-longitudinal heat flow technique, and thermomechanical analyzer (TMA), respectively. The experimental results were compared with analytical results obtained from, respectively, rule of mixture, Brailsford and Major's model, and modified Turner's model for verification. United States Nuclear Regulatory Commission (USNRC) standards were employed as regulatory standards and criteria for fire retardant property study. The results revealed a superior thermal resistance and fire survivability of CMFs compared to 304L stainless steel. A physics-based three-dimensional model accounting for heat conduction was built using Finite Element Analysis to validate the reliability of the experimental results. The model led to a good reproduction of the experimentally measured data when comparing CMF to bulk stainless steel. This research indicates that one of the potential applications of lightweight CMFs can be in nuclear spent fuel casks replacing conventional structural and radiation shielding materials with demonstrated benefits of excellent thermal isolation, fire retardant, light weight and energy absorption capabilities. DA - 2016/8// PY - 2016/8// DO - 10.1016/j.ijthermalsci.2016.03.005 VL - 106 SP - 70-79 SN - 1778-4166 KW - Composite metal foams KW - Specific heat KW - Effective thermal conductivity KW - Coefficient of thermal expansion KW - Flame retardant ER - TY - CONF TI - Experimental and computational studies of gravity-driven dense granular flows AU - Chilamkurti, Y. N. AU - Gould, R. D. AB - The current paper focusses on the characterization of gravity-driven dry granular flows in cylindrical tubes. With a motive of using dense particulate media as heat transfer fluids (HTF), the study was primarily focused to address the characteristics of flow regimes with a packing fraction of ∼60%. Experiments were conducted to understand the effects of different flow parameters, including: tube radius, tube inclination, tube length and exit diameter. These studies were conducted on two types of spherical particles — glass and ceramic — with mean diameters of 150 μm and 300 μm respectively. The experimental data was correlated with the semi-empirical equation based on Beverloo’s law. In addition, the same flow configuration was studied through three-dimensional computer simulations by implementing the Discrete Element Method for the Lagrangian modelling of particles. A soft-particle formulation was used with Hertz-Mindilin contact models to resolve the interaction forces between particles. The simulation results were used to examine the velocity, shear rate and packing fraction profiles to study the detailed flow dynamics. Curve-fits were developed for the mean velocity profiles which could be used in developing hydrodynamic analogies for granular flows. The current work thus identifies the basic features of gravity driven dense granular flows that could form a basis for defining their rheology. C2 - 2016/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2015, vol 7a DA - 2016/// DO - 10.1115/imece2015-50762 ER - TY - JOUR TI - Embedded Ni-Ti particles for the detection of fatigue crack growth in AA7050 AU - Leser, W. P. AU - Newman, J. A. AU - Hochhalter, J. D. AU - Gupta, V. K. AU - Yuan, F. G. T2 - FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES AB - Abstract A multi‐functional aluminium alloy 7050 (AA7050) containing embedded Ni–Ti shape memory alloy particles to detect fatigue crack growth is proposed. The regions of intense strain near the tip of a growing fatigue crack cause nearby Ni–Ti particles to undergo a solid‐state phase transformation from austenite to martensite, releasing a detectable acoustic emission signal that can be used to locate the crack in the monitored component. The AA7050/Ni–Ti composite was made by vacuum hot pressing Ni–Ti powder between rolled AA7050 plates. The effect of hot pressing temperature and subsequent heat treatments (solutionizing and peak ageing) on the Ni–Ti particles was studied. A successful proof‐of‐concept was demonstrated for AA7050 with embedded particles that emit a measureable and repeatable acoustic emission signal in the presence of a fatigue crack, allowing for quick diagnosis of fatigue crack damage in this material. DA - 2016/6// PY - 2016/6// DO - 10.1111/ffe.12413 VL - 39 IS - 6 SP - 686-695 SN - 1460-2695 KW - acoustic emission KW - aluminium 7050 KW - digital image correlation KW - fatigue KW - multi-functional KW - shape memory alloy ER - TY - CONF TI - Electrohydraulic modeling of a fluidic artificial muscle actuation system for robot locomotion AU - Chapman, E. AU - Macleod, M. AU - Bryant, M. AB - Fluidic artificial muscles have the potential for a wide range of uses; from injury rehabilitation to high-powered hydraulic systems. Their modeling to date has largely been quasi-static and relied on the operator to adjust pressure so as to control force output and utilization while little work has been done to date to analyze the kinematics of the driving-systems involved in their operation. This paper establishes a combined electro-hydraulic model of a fluidic artificial muscle actuated climbing robot to establish a method for studying the relationships between muscle size, robot size and function, and system design. The study indicates a strong relationship between appropriate system component selection and not only system efficiency but individual component effectiveness. The results of the study show that robot mass, operating pressure, muscle size, and motor-pump selection have noteworthy impacts on the efficiency and thereby longevity of the robot for performing its task. C2 - 2016/// C3 - ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, 2015, vol 1 DA - 2016/// DO - 10.1115/smasis2015-8834 ER - TY - CONF TI - Dense granular flows as a new heat transfer fluid for concentrated solar power AU - Watkins, M. F. AU - Gould, R. D. AB - The increasing interest in concentrated solar power as a new form of renewable energy necessitates an improvement in overall system efficiency. Current heat transfer fluids employed to capture the concentrated heat demonstrate limited working temperature ranges. This study sought to investigate the use of dense granular flows as a possible new heat transfer fluid, as ceramic particles present virtually no restriction on working temperature. A bench-scale system simulating a single tube of a concentrated solar power central receiver was constructed and used to evaluate the heat transfer properties of the flow at low temperatures. Ceramic particles, 270μm in diameter, were gravity-fed through a vertical tube, resulting in granular flows with particle packing fractions of approximately 60%. Radial temperature profiles were measured and used to calculate the mean temperature of the fluid at different axial tube locations. The heat transfer coefficient was then calculated based on the input heat flux and measured wall and mean temperatures. The effect of the mass flow rate on the heat transfer coefficient was examined by using different orifices at the tube exit. As expected, the heat transfer coefficient increased with increasing flow rate. Heat transfer coefficients ranging from 330 to 380 W/m2-K were obtained for bulk temperatures ranging from 40 to 70°C. Previous works demonstrated comparable heat transfer coefficients at higher bulk temperatures. Thus, our preliminary heat transfer coefficient results demonstrate the potential of dense flows of ceramic particles for obtaining beneficial heat transfer properties at extremely high operating temperatures. C2 - 2016/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2015, vol 8b DA - 2016/// DO - 10.1115/imece2015-51069 ER - TY - JOUR TI - Computational transport, phase change and deposition analysis of inhaled multicomponent droplet-vapor mixtures in an idealized human upper lung model AU - Feng, Yu AU - Kleinstreuer, Clement AU - Castro, Nicolas AU - Rostami, Ali T2 - JOURNAL OF AEROSOL SCIENCE AB - Numerous inhalable aerosols consist of multiple nano-to-microscale solid or liquid particles with dissolved or embedded compounds, as well as associated vapors. In general, of interest are the transport and conversion phenomena leading to local particle/droplet/vapor depositions. Selected examples include inhalation of aerosols from use of inhalers, cigarettes and electronic cigarettes. In this study the focus is on hygroscopic growth of nano-size multi-component droplets and droplet–vapor interactions during transport with subsequent deposition in a human upper lung-airway model. For that purpose a comprehensive and efficient computational fluid–particle dynamics model has been developed. It is capable of simultaneously analyzing multi-component droplet–vapor and airflow interactions with evaporation and condensation effects for different sets of inhalation conditions. Selecting inhaled electronic cigarette (EC) aerosols as an application, the simulation results include detailed transport, deposition and absorption data for different constituents (i.e., water, propylene glycol, glycerol and nicotine) in both vapor and liquid forms for an idealized human upper lung airway geometry, i.e., from mouth to generation 3. Results indicate that liquid–vapor phase change induces hygroscopic growth of droplets, which in turn impacts significantly the deposition concentrations of aerosols via inertial impaction, secondary flows, Brownian motion, and the vapor-specific absorption rates. Parametric sensitivity analyses were performed to evaluate the influence of different inhalation flow waveforms on EC-aerosol transport, interaction, and deposition. DA - 2016/6// PY - 2016/6// DO - 10.1016/j.jaerosci.2016.03.001 VL - 96 SP - 96-123 SN - 1879-1964 KW - Hygroscopic droplet growth KW - Multi-component droplet-vapor interaction modeling KW - Multi-component mixture plus discrete-droplet (MCM-DD) model KW - Inhaled droplet-reduction (IDR) method KW - Electronic cigarettes ER - TY - JOUR TI - Asymmetric acoustic transmission through near-zero-index and gradient-index metasurfaces AU - Shen, Chen AU - Xie, Yangbo AU - Li, Junfei AU - Cummer, Steven A. AU - Jing, Yun T2 - APPLIED PHYSICS LETTERS AB - We present a design of acoustic metasurfaces yielding asymmetric transmission within a certain frequency band. The design consists of a layer of gradient-index metasurface and a layer of low refractive index metasurface. Incident waves are controlled in a wave vector dependent manner to create strong asymmetric transmission. Numerical simulations show that the approach provides high transmission contrast between the two incident directions within the designed frequency band. This is further verified by experiments. Compared to previous designs, the proposed approach yields a compact and planar device. Our design may find applications in various scenarios such as noise control and therapeutic ultrasound. DA - 2016/5/30/ PY - 2016/5/30/ DO - 10.1063/1.4953264 VL - 108 IS - 22 SP - SN - 1077-3118 ER - TY - JOUR TI - Anisotropic Thermal Transport in Thermoelectric Composites of Conjugated Polyelectrolytes/Single-Walled Carbon Nanotubes AU - Mai, Cheng-Kang AU - Liu, Jun AU - Evans, Christopher M. AU - Segalman, Rachel A. AU - Chabinyc, Michael L. AU - Gahill, David G. AU - Bazan, Guillermo C. T2 - MACROMOLECULES AB - We report a method to determine the thermal conductivities of polymer composites with single-walled carbon nanotubes (SWNTs) using time-domain thermoreflectance. Both through-plane and in-plane thermal conductivities were determined. Two types of CPEs used in these studies are of the same conjugated backbone but with either cationic (CPE-PyrBIm4) or anionic (CPE-Na) pendant functionalities. The CPE-Na/SWNT composites are p-type conductors, whereas the CPE-PyrBIm4/SWNT counterparts exhibit n-type charge transport. The CPE/SWNT films were prepared through a filtration method that preferentially aligns the SWNTs in the in-plane direction. Attaching the composites onto glass substrates with a precoated heat transducer allows one to measure the through-plane thermal conductivity of materials with rough surfaces. The in-plane thermal conductivity can be measured by embedding thick samples into epoxy followed by microtoming to expose the relatively smooth cross sections. The thermal conductivity along the in-plane direction is found to be higher than that along the through-plane direction. Indeed, the anisotropy factor of thermal conductivity in these composites is approximately an order of magnitude, favoring in-plane direction. DA - 2016/7/12/ PY - 2016/7/12/ DO - 10.1021/acs.macromol.6b00546 VL - 49 IS - 13 SP - 4957-4963 SN - 1520-5835 UR - http://dx.doi.org/10.1021/acs.macromol.6b00546 ER - TY - CONF TI - An optimization-based approach for prosthesis dynamic modeling and parameter identification AU - Yang, T. AU - Wu, F. AU - Liu, M. AU - Huang, H. AB - In this paper, we propose an effective approach to model the prosthetic leg dynamics for amputees wearing active-transfemoral prosthesis (ATP) which is self-powered. To accommodate unexpected effects of thigh on knee joints, the dynamic prosthesis model has been derived using both the thigh-knee-shank and the knee-shank configurations. Correlated with the amputee’s walking data, a nonlinear optimization problem is then formulated to identify the model parameters and the gains of the PD controller which is used to control the input torque for the ATP, while reducing measurement errors of the data. Moreover, the identified models are validated by comparing the predicted dynamics with experimental measurements. The advantages of proposed method in terms of simplicity, flexibility, and accuracy are demonstrated by the high correlation coefficients and the low root-mean-square errors. C2 - 2016/// C3 - Proceedings of the ASME 8th Annual Dynamic Systems and Control Conference, 2015, vol 1 DA - 2016/// DO - 10.1115/dscc2015-9637 ER - TY - JOUR TI - Adaptive windowing in contrast-enhanced intravascular ultrasound imaging AU - Lindsey, Brooks D. AU - Martin, K. Heath AU - Jiang, Xiaoning AU - Dayton, Paul A. T2 - ULTRASONICS AB - Intravascular ultrasound (IVUS) is one of the most commonly-used interventional imaging techniques and has seen recent innovations which attempt to characterize the risk posed by atherosclerotic plaques. One such development is the use of microbubble contrast agents to image vasa vasorum, fine vessels which supply oxygen and nutrients to the walls of coronary arteries and typically have diameters less than 200μm. The degree of vasa vasorum neovascularization within plaques is positively correlated with plaque vulnerability. Having recently presented a prototype dual-frequency transducer for contrast agent-specific intravascular imaging, here we describe signal processing approaches based on minimum variance (MV) beamforming and the phase coherence factor (PCF) for improving the spatial resolution and contrast-to-tissue ratio (CTR) in IVUS imaging. These approaches are examined through simulations, phantom studies, ex vivo studies in porcine arteries, and in vivo studies in chicken embryos. In phantom studies, PCF processing improved CTR by a mean of 4.2dB, while combined MV and PCF processing improved spatial resolution by 41.7%. Improvements of 2.2dB in CTR and 37.2% in resolution were observed in vivo. Applying these processing strategies can enhance image quality in conventional B-mode IVUS or in contrast-enhanced IVUS, where signal-to-noise ratio is relatively low and resolution is at a premium. DA - 2016/8// PY - 2016/8// DO - 10.1016/j.ultras.2016.04.022 VL - 70 SP - 123-135 SN - 1874-9968 KW - Intravascular ultrasound KW - Contrast-enhanced ultrasound KW - Adaptive beamforming KW - Phase coherence factor KW - High frequency ultrasound KW - Superharmonic ER - TY - JOUR TI - Acoustic properties of glass fiber assembly-filled honeycomb sandwich panels AU - Yang, Yong AU - Li, Binbin AU - Chen, Zhaofeng AU - Sui, Ni AU - Chen, Zhou AU - Saeed, Muhammad-Umar AU - Li, Yufang AU - Fu, Renli AU - Wu, Cao AU - Jing, Yun T2 - COMPOSITES PART B-ENGINEERING AB - A new composite structure (glass fiber assembly-filled honeycomb sandwich panel) is prepared in order to improve the acoustic properties. Effect of glass fiber assembly with different filling shapes (random and fiber ball), fiber diameter, fiber content and air-layer on acoustic properties are explored. Sound absorption coefficient (SAC) and sound transmission loss (STL) are determined by a B&K impedance tube. The experiment results indicate that the first resonance frequency of SAC disappears along with the improvement of the second resonance frequency by reducing the fiber diameter or increasing the fiber content. STL can be improved by the increase of the fiber content. Random glass fiber assembly with the fine fibers has the best STL in the all testing samples. The advantage of glass fiber assembly for improving the STL of honeycomb sandwich panel is particularly clear at frequencies below 4.5 kHz. Especially, the STL difference reaches the maximum at around 20 dB at frequencies below 3.0 kHz. DA - 2016/7/1/ PY - 2016/7/1/ DO - 10.1016/j.compositesb.2016.04.046 VL - 96 SP - 281-286 SN - 1879-1069 KW - Honeycomb KW - Layered structures KW - Physical properties KW - Acoustic emission ER - TY - CONF TI - A model of neuropeptide transport in various types of nerve terminals containing en passant boutons: The effect of the rate of neuropeptide production in the neuron soma AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. AB - After being synthesized in the soma, neuropeptides are packaged in dense core vesicles (DCVs) and transported toward nerve terminals. It is known, from published experimental results, that in terminals with type Ib boutons DCVs circulate in the terminal, undergoing repeated anterograde and retrograde transport, while in type III terminals DCVs do not circulate in the terminal. Our goal here is to investigate whether the increased DCV production in the soma can lead to the appearance of DCV circulation in type III boutons. For this purpose we developed a mathematical model that simulates DCV transport in various terminals. Our model reproduces some important experimental results, such as those concerning DCV circulation in type Ib and type III terminals. We used the developed model to make testable predictions. The model predicts that an increased DCV production rate in the soma leads to increased DCV circulation in type Ib boutons and to the appearance of DCV circulation in type III boutons. The model also predicts that there are different stages in the development of DCV circulation in the terminals after they were depleted of DCVs due to neuropeptide release. C2 - 2016/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2015, vol 3 DA - 2016/// DO - 10.1115/imece2015-50439 ER - TY - CONF TI - A dual frequency ivus transducer with a lateral mode transmitter for contrast enhanced intravascular ultrasound imaging AU - Wang, Z. C. AU - Martin, K. H. AU - Dayton, P. A. AU - Jiang, X. N. AB - Recent studies suggest that dual frequency intravascular ultrasound (IVUS) transducers are promising in contrast ultrasound for molecular imaging or vasa vasorum (VV) assessment to identify vulnerable plaques. Low frequency (1–3 MHz) acoustic waves are widely used for contrast imaging because it can excite microbubbles more effectively. However, conventional thickness mode 1–3 MHz transducers are not suitable for IVUS since bulky transducer size is not permitted in fine IVUS catheters used for coronary interventions (approx. 3-French). In this paper, a dual frequency (2.25 MHz/30 MHz) IVUS transducer with a lateral mode transmitter (2.25 MHz) and a thickness mode high frequency receiver (30 MHz) was designed, fabricated and characterized. In contrast detection tests, superharmonic microbubble responses flown through a 200 μm diameter tube was successfully detected with a contrast to noise ratio (CNR) of 13 dB and an axial resolution (−6 dB) of 0.1 μs (150 μm). The results showed that this dual frequency IVUS transducer with a lateral mode transmitter can be used to detect super-harmonic signal (12th to 15th harmonic) ideal for superharmonic imaging of microvascular structures. C2 - 2016/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2015, vol 3 DA - 2016/// DO - 10.1115/imece2015-51131 ER - TY - JOUR TI - A direct correlation of x-ray diffraction orientation distributions to the in-plane stiffness of semi-crystalline organic semiconducting films AU - Zhao, Bingxiao AU - Awartani, Omar AU - O'Connor, Brendan AU - Zikry, Mohammed A. T2 - APPLIED PHYSICS LETTERS AB - Large charge mobilities of semi-crystalline organic semiconducting films could be obtained by mechanically aligning the material phases of the film with the loading axis. A key element is to utilize the inherent stiffness of the material for optimal or desired alignment. However, experimentally determining the moduli of semi-crystalline organic thin films for different loading directions is difficult, if not impossible, due to film thickness and material anisotropy. In this paper, we address these challenges by presenting an approach based on combining a composite mechanics stiffness orientation formulation with a Gaussian statistical distribution to directly estimate the in-plane stiffness (transverse isotropy) of aligned semi-crystalline polymer films based on crystalline orientation distributions obtained by X-ray diffraction experimentally at different applied strains. Our predicted results indicate that the in-plane stiffness of an annealing film was initially isotropic, and then it evolved to transverse isotropy with increasing mechanical strains. This study underscores the significance of accounting for the crystalline orientation distributions of the film to obtain an accurate understanding and prediction of the elastic anisotropy of semi-crystalline polymer films. DA - 2016/5/2/ PY - 2016/5/2/ DO - 10.1063/1.4948533 VL - 108 IS - 18 SP - SN - 1077-3118 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84968866659&partnerID=MN8TOARS ER - TY - JOUR TI - A Novel Laser Ultrasound Transducer Using Candle Soot Carbon Nanoparticles AU - Huang, Wenbin AU - Chang, Wei-Yi AU - Kim, Jinwook AU - Li, Sibo AU - Huang, Shujin AU - Jiang, Xiaoning T2 - IEEE TRANSACTIONS ON NANOTECHNOLOGY AB - As a novel composite material for laser ultrasound transducer, candle soot nanoparticles polydimethylsiloxane (CSPs-PDMS) has been demonstrated to generate high frequency, broadband, and high-amplitude ultrasound waves. In this study, we investigated the mechanism of the high-optoacoustic conversion efficiency exhibited by the composite. A thermal-acoustic coupling model was proposed for analyzing the performance of the composite. The theoretical result matches well with the experimental observation. The acoustic beam profile was compared with Field II simulation results. The 4.41 × 10 -3 energy conversion coefficient and 21 MHz--6 dB frequency bandwidth of the composite suggest that CSPs-PDMS composites is promising for a broad range of ultrasound therapy and non-destructive testing applications. DA - 2016/5// PY - 2016/5// DO - 10.1109/tnano.2016.2536739 VL - 15 IS - 3 SP - 395-401 SN - 1941-0085 KW - Broadband ultrasound KW - candle soot KW - high frequency ultrasound KW - nano-particles composite KW - optoacoustic ER - TY - CONF TI - 40-MHz micromachined PMN-PT composite ultrasound array for medical imaging AU - Li, S. B. AU - Huang, W. B. AU - Chang, W. Y. AU - Jiang, X. N. AB - Ultrasonography is well known as a relatively low cost and non-invasive modality for real-time imaging. In recent years, various high frequency array transducers have been developed and used for ophthalmology, dermatology, and small animal studies. This paper reports the development of a 48-element 40-MHz ultrasonic array using micromachined lead magnesium niobate-lead titanate (PMN-PT) single crystal 1–3 composite material. Array elements with a pitch of 100-micron were interconnected via a customized flexible circuit. Pulse-echo test showed an average center frequency of 40 MHz and a −6 dB fractional bandwidth of 52%. The −20 dB pulse length was evaluated as 120 ns. The electrical and acoustical separation showed the crosstalk less than - 24 dB. An image of a steel wire target phantom was acquired by stacking multiple A-lines. The results demonstrate resolutions exceeding 70 μm axially and 800 μm laterally. Those results imply the great potential of the developed array transducer for the high frequency medical imaging. C2 - 2016/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2015, vol 3 DA - 2016/// DO - 10.1115/imece2015-52540 ER - TY - JOUR TI - Wicking Enhancement in Three-Dimensional Hierarchical Nanostructures AU - Wang, Zhiting AU - Zhao, Junjie AU - Bagal, Abhijeet AU - Dandley, Erinn C. AU - Oldham, Christopher J. AU - Fang, Tiegang AU - Parsons, Gregory N. AU - Chang, Chih-Hao T2 - LANGMUIR AB - Wicking, the absorption of liquid into narrow spaces without the assistance of external forces, has drawn much attention due to its potential applications in many engineering fields. Increasing surface roughness using micro/nanostructures can improve capillary action to enhance wicking. However, reducing the structure length scale can also result in significant viscous forces to impede wicking. In this work, we demonstrate enhanced wicking dynamics by using nanostructures with three-dimensional (3D) hierarchical features to increase the surface area while mitigating the obstruction of liquid flow. The proposed structures were engineered using a combination of interference lithography and hydrothermal synthesis of ZnO nanowires, where structures at two length scales were independently designed to control wicking behavior. The fabricated hierarchical 3D structures were tested for water and ethanol wicking properties, demonstrating improved wicking dynamics with intermediate nanowire lengths. The experimental data agree with the derived fluid model based on the balance of capillary and vicious forces. The hierarchical wicking structures can be potentially used in applications in water harvesting surfaces, microfluidics, and integrated heat exchangers. DA - 2016/8/16/ PY - 2016/8/16/ DO - 10.1021/acs.langmuir.6b01864 VL - 32 IS - 32 SP - 8029-8033 SN - 0743-7463 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84982307197&partnerID=MN8TOARS ER - TY - JOUR TI - What can trigger the onset of Parkinson's disease - A modeling study based on a compartmental model of alpha-synuclein transport and aggregation in neurons AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. T2 - MATHEMATICAL BIOSCIENCES AB - The aim of this paper is to develop a minimal model describing events leading to the onset of Parkinson's disease (PD). The model accounts for α-synuclein (α-syn) production in the soma, transport toward the synapse, misfolding, and aggregation. The production and aggregation of polymeric α-syn is simulated using a minimalistic 2-step Finke–Watzky model. We utilized the developed model to analyze what changes in a healthy neuron are likely to lead to the onset of α-syn aggregation. We checked the effects of interruption of α-syn transport toward the synapse, entry of misfolded (infectious) α-syn into the somatic and synaptic compartments, increasing the rate of α-syn synthesis in the soma, and failure of α-syn degradation machinery. Our model suggests that failure of α-syn degradation machinery is probably the most likely cause for the onset of α-syn aggregation leading to PD. DA - 2016/8// PY - 2016/8// DO - 10.1016/j.mbs.2016.05.002 VL - 278 SP - 22-29 SN - 1879-3134 KW - Neuron KW - alpha-synuclein KW - Parkinson's disease KW - Multi-compartment model KW - Mathematical modeling ER - TY - CONF TI - Simulation of high rate failure mechanisms in composites during quasi-static testing AU - Pankow, M. AU - McWilliams, B. A. C2 - 2016/// C3 - Mechanics of composite and multifunctional materials, vol 7 DA - 2016/// SP - 445-450 ER - TY - JOUR TI - Silver decorated polymer supported semiconductor thin films by UV aided metalized laser printing AU - Halbur, Jonathan C. AU - Padbury, Richard P. AU - Jur, Jesse S. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - A facile ultraviolet assisted metalized laser printing technique is demonstrated through the ability to control selective photodeposition of silver on flexible substrates after atomic layer deposition pretreatment with zinc oxide and titania. The photodeposition of noble metals such as silver onto high surface area, polymer supported semiconductor metal oxides exhibits a new route for nanoparticle surface modification of photoactive enhanced substrates. Photodeposited silver is subsequently characterized using low voltage secondary electron microscopy, x-ray diffraction, and time of flight secondary ion mass spectroscopy. At the nanoscale, the formation of specific morphologies, flake and particle, is highlighted after silver is photodeposited on zinc oxide and titania coated substrates, respectively. The results indicate that the morphology and composition of the silver after photodeposition has a strong dependency on the morphology, crystallinity, and impurity content of the underlying semiconductor oxide. At the macroscale, this work demonstrates how the nanoscale features rapidly coalesce into a printed pattern through the use of masks or an X-Y gantry stage with virtually unlimited design control. DA - 2016/5// PY - 2016/5// DO - 10.1116/1.4947011 VL - 34 IS - 3 SP - SN - 1520-8559 ER - TY - JOUR TI - Robust H-2 and H-infinity switched feedforward control of uncertain LFT systems AU - Yuan, Chengzhi AU - Wu, Fen T2 - INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL AB - This paper presents a new robust switched feedforward control scheme for a class of uncertain systems described in a standard linear fractional transformation form. First, the analysis conditions for switching stability are derived by using a piecewise Lyapunov function incorporated with the min-switching control technique. Based on the analysis results, the synthesis conditions are then formulated as a special type of bilinear matrix inequalities, which can be solved by means of linear matrix inequalities and line search. Both robust and feedforward control problems are considered. The proposed robust switched control scheme outperforms existing robust feedforward control approaches for uncertain systems based on single quadratic Lyapunov function, and leads to less conservative control design. Numerical examples will be used to illustrate the effectiveness and advantages of the proposed results. Copyright © 2015 John Wiley & Sons, Ltd. DA - 2016/6// PY - 2016/6// DO - 10.1002/rnc.3380 VL - 26 IS - 9 SP - 1841-1856 SN - 1099-1239 KW - robust feedforward control KW - switching control KW - uncertain LFT systems KW - H-2 and H-infinity performance ER - TY - JOUR TI - Relationship between maximum isometric joint moment and functional task performance in patients with brachial plexus injury: A pilot study AU - Crouch, Dustin L. AU - Santago, Anthony C., II AU - Plate, Johannes F. AU - Li, Zhongyu AU - Saul, Katherine R. T2 - GAIT & POSTURE AB - We evaluated whether subjects with brachial plexus injury (BPI) adapted their movements to reduce the mechanical demand on their impaired upper extremity. In 6 subjects with unilateral BPI with C5 and C6 involvement, we measured bilateral maximum isometric shoulder and elbow strength, and computed joint kinematics and net muscle-generated joint moments during 7 unimanual functional tasks. Compared to the unimpaired extremity, maximum strength in shoulder abduction, extension, and external rotation was 60% (p = 0.02), 49% (p = 0.02), and 75% (p = 0.02) lower, respectively, on the impaired side. Significant kinematic and kinetic differences were observed only when reaching to the back of the head. However, because of substantially reduced strength in their impaired upper extremities, subjects used a significantly higher percentage of their maximum strength during several tasks and along several directions of movement. The peak percentage of maximal strength subjects used across tasks was 32% (p = 0.03) and 29% (p = 0.03) more on their impaired side in shoulder extension and external rotation, respectively. Subjects had less reserve strength available for performing upper extremity tasks and, therefore, may be less adaptive to strength declines due to injury progression and normal aging. Quantitatively measuring maximal strength may help clinicians ensure that patients maintain sufficient upper extremity strength to preserve long-term functional ability. DA - 2016/2// PY - 2016/2// DO - 10.1016/j.gaitpost.2015.12.038 VL - 44 SP - 238-244 SN - 1879-2219 KW - Nerve KW - Shoulder KW - Simulation KW - Strength KW - Kinematics ER - TY - JOUR TI - Quantitative Analysis of Three-Dimensional Distribution and Clustering of Intramuscular Fat in Muscles of the Rotator Cuff AU - Santago, Anthony C., II AU - Vidt, Meghan E. AU - Tuohy, Christopher J. AU - Poehling, Gary G. AU - Freehill, Michael T. AU - Jordan, Jennifer H. AU - Kraft, Robert A. AU - Saul, Katherine R. T2 - ANNALS OF BIOMEDICAL ENGINEERING AB - The purpose of this study was to (1) develop and present a technique to quantitatively assess three-dimensional distribution and clustering of intramuscular fat and (2) use the technique to compare spatial characteristics of intramuscular fat in rotator cuff muscles of older adults with and without a supraspinatus tear. Moran’s Index (I), an existing quantitative measure of clustering, was extended for use with MRI to allow comparisons across individuals with different size muscles. Sixteen older adults (>60 years) with (N = 6) and without (N = 10) a degenerative supraspinatus tear participated. Following 3D Dixon MRIs of the shoulder, which separates fat from water, rotator cuff muscles were segmented and sectioned and fat% and Moran’s I were calculated to assess distribution and clustering, respectively. Moran’s I ranged was 0.40–0.92 and 0.39–0.76 for the tear and control subjects, respectively. Compared to uninjured controls, tear subjects demonstrated increased fat distribution (p = 0.036) and clustering (p = 0.020) distally in the supraspinatus. Tear subjects had more pronounced distribution (p < 0.001) and clustering distally (p < 0.001) than proximally. Other rotator cuff muscles exhibited different patterns of fat clustering and distribution. This technique, which we applied to quantify spatial characteristics of intramuscular fat, can be applied to assess clustering of fat in other pathologies and tissues. DA - 2016/7// PY - 2016/7// DO - 10.1007/s10439-015-1488-z VL - 44 IS - 7 SP - 2158-2167 SN - 1573-9686 KW - Rotator cuff tear KW - Spatial characteristics of fat KW - MRI KW - Moran's Index KW - Fat percentage ER - TY - JOUR TI - Microstructural modeling of transgranular and intergranular fracture in crystalline materials with coincident site lattice grain-boundaries: Sigma 3 and Sigma 17b bicrystals AU - Wu, Q. AU - Zikry, M. A. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The competing microstructural failure mechanisms of transgranular (TG) and intergranular (IG) fracture, in martensitic steel bicrystals with coincident site lattice (CSL) boundaries of Σ3 and Σ17b, have been investigated, using a dislocation-density-based crystalline plasticity formulation and a recently developed overlapping fracture method. A dislocation-density grain boundary (GB) interaction scheme was coupled within a dislocation-density based crystal plasticity formulation to investigate how different types of CSL GBs affect dislocation-density evolution, plastic deformation, dislocation pile-up formation, TG and IG fracture, and fracture toughness. The computational predictions indicate that the bicrystal, with a Σ3 boundary, transitioned from IG to TG fracture, with large dislocation density generation and plastic deformation on the TG fracture planes. Bicrystals with the Σ17b boundary failed due to intergranular fracture and rupture, with much lower, in comparison with the Σ3 boundary case, dislocation density generation and plastic deformation. These predictions, which are consistent with experimental observations, indicate that Σ3 boundary is resistant to IG fracture with a higher fracture toughness than the Σ17b boundary case. More significantly, the computational framework can potentially be used as a guideline for GB engineering for failure-resistant materials. DA - 2016/4/20/ PY - 2016/4/20/ DO - 10.1016/j.msea.2016.02.039 VL - 661 SP - 32-39 SN - 1873-4936 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84960079801&partnerID=MN8TOARS KW - Coincident site lattice KW - Grain boundary KW - Dislocation-density KW - Transgranular KW - Intergranular KW - Fracture ER - TY - JOUR TI - Intrinsic coincident linear polarimetry using stacked organic photovoltaics AU - Roy, S. Gupta AU - Awartani, O. M. AU - Sen, P. AU - O'Connor, B. T. AU - Kudenov, M. W. T2 - OPTICS EXPRESS AB - Polarimetry has widespread applications within atmospheric sensing, telecommunications, biomedical imaging, and target detection. Several existing methods of imaging polarimetry trade off the sensor's spatial resolution for polarimetric resolution, and often have some form of spatial registration error. To mitigate these issues, we have developed a system using oriented polymer-based organic photovoltaics (OPVs) that can preferentially absorb linearly polarized light. Additionally, the OPV cells can be made semitransparent, enabling multiple detectors to be cascaded along the same optical axis. Since each device performs a partial polarization measurement of the same incident beam, high temporal resolution is maintained with the potential for inherent spatial registration. In this paper, a Mueller matrix model of the stacked OPV design is provided. Based on this model, a calibration technique is developed and presented. This calibration technique and model are validated with experimental data, taken with a cascaded three cell OPV Stokes polarimeter, capable of measuring incident linear polarization states. Our results indicate polarization measurement error of 1.2% RMS and an average absolute radiometric accuracy of 2.2% for the demonstrated polarimeter. DA - 2016/6/27/ PY - 2016/6/27/ DO - 10.1364/oe.24.014737 VL - 24 IS - 13 SP - 14737-14747 SN - 1094-4087 ER - TY - JOUR TI - Increasing signal amplitude in fiber Bragg grating detection of Lamb waves using remote bonding AU - Wee, Junghyun AU - Wells, Brian AU - Hackney, Drew AU - Bradford, Philip AU - Peters, Kara T2 - APPLIED OPTICS AB - Networks of fiber Bragg grating (FBG) sensors can serve as structural health monitoring systems for large-scale structures based on the collection of ultrasonic waves. The demodulation of structural Lamb waves using FBG sensors requires a high signal-to-noise ratio because the Lamb waves are of low amplitudes. This paper compares the signal transfer amplitudes between two adhesive mounting configurations for an FBG to detect Lamb waves propagating in an aluminum plate: a directly bonded FBG and a remotely bonded FBG. In the directly bonded FBG case, the Lamb waves create in-plane and out-of-plane displacements, which are transferred through the adhesive bond and detected by the FBG sensor. In the remotely bonded FBG case, the Lamb waves are converted into longitudinal and flexural traveling waves in the optical fiber at the adhesive bond, which propagate through the optical fiber and are detected by the FBG sensor. A theoretical prediction of overall signal attenuation also is performed, which is the combination of material attenuation in the plate and optical fiber and attenuation due to wave spreading in the plate. The experimental results demonstrate that remote bonding of the FBG significantly increases the signal amplitude measured by the FBG. DA - 2016/7/20/ PY - 2016/7/20/ DO - 10.1364/ao.55.005564 VL - 55 IS - 21 SP - 5564-5569 SN - 2155-3165 ER - TY - JOUR TI - Harvesting Waste Heat in Unipolar Ion Conducting Polymers AU - Chang, William B. AU - Evans, Christopher M. AU - Popere, Bhooshan C. AU - Russ, Boris M. AU - Liu, Jun AU - Newman, John AU - Segalman, Rachel A. T2 - ACS MACRO LETTERS AB - The Seebeck effect in unipolar ion-conducting, solid-state polymers is characterized. The high Seebeck coefficient and sign in polymer ion conductors is explained via analysis of thermogalvanic multicomponent transport. A solid-state, water-processeable, flexible device based on these materials is demonstrated, showcasing the promise of polymers as thermogalvanic materials. Thermogalvanic materials based on ion-conducting polymer membranes show great promise in the harvesting of waste heat. DA - 2016/1// PY - 2016/1// DO - 10.1021/acsmacrolett.5b00829 VL - 5 IS - 1 SP - 94-98 SN - 2161-1653 UR - http://dx.doi.org/10.1021/acsmacrolett.5b00829 ER - TY - JOUR TI - Fully-implicit orthogonal reconstructed Discontinuous Galerkin method for fluid dynamics with phase change AU - Nourgaliev, R. AU - Luo, H. AU - Weston, B. AU - Anderson, A. AU - Schofield, S. AU - Dunn, T. AU - Delplanque, J-R T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - A new reconstructed Discontinuous Galerkin (rDG) method, based on orthogonal basis/test functions, is developed for fluid flows on unstructured meshes. Orthogonality of basis functions is essential for enabling robust and efficient fully-implicit Newton–Krylov based time integration. The method is designed for generic partial differential equations, including transient, hyperbolic, parabolic or elliptic operators, which are attributed to many multiphysics problems. We demonstrate the method's capabilities for solving compressible fluid–solid systems (in the low Mach number limit), with phase change (melting/solidification), as motivated by applications in Additive Manufacturing (AM). We focus on the method's accuracy (in both space and time), as well as robustness and solvability of the system of linear equations involved in the linearization steps of Newton-based methods. The performance of the developed method is investigated for highly-stiff problems with melting/solidification, emphasizing the advantages from tight coupling of mass, momentum and energy conservation equations, as well as orthogonality of basis functions, which leads to better conditioning of the underlying (approximate) Jacobian matrices, and rapid convergence of the Krylov-based linear solver. DA - 2016/1/15/ PY - 2016/1/15/ DO - 10.1016/j.jcp.2015.11.004 VL - 305 SP - 964-996 SN - 1090-2716 KW - Discontinuous Galerkin method KW - High-order space-time discretization KW - Fully-implicit solvers KW - Newton-Krylov algorithm KW - Fluid dynamics KW - Phase-change ER - TY - JOUR TI - Excess Identification and Mapping in Engineered Systems AU - Cansler, Ethan Z. AU - White, Samantha B. AU - Ferguson, Scott M. AU - Mattson, Christopher A. T2 - JOURNAL OF MECHANICAL DESIGN AB - A system must continue to meet stakeholder needs throughout its service life to maintain value. Excess that is embedded into components during the design phase can enable in-service system evolution when new or changed requirements are introduced. However, while the concept of excess has been established in the literature, it is not clear how to identify and quantify the set of excesses in a particular design. This paper uses component properties and functional flow information to map and quantify the excess that exists within a system. Understanding the functional flow relationships between components allows for the bottlenecks at component interfaces to be identified. Those flows that do not limit the potential evolvability of a system can be removed from consideration, allowing for critical interface parameters to be highlighted and their capabilities quantified. The method is demonstrated on a consumer heat gun, where quantifying the excess within components allows for a reduced map to be created with irrelevant flows removed. Finally, changes to the system are explored to demonstrate how knowledge of component excess can be used to initially validate a proposed evolution. DA - 2016/8// PY - 2016/8// DO - 10.1115/1.4033884 VL - 138 IS - 8 SP - SN - 1050-0472 ER - TY - CONF TI - Dynamic failure mechanisms in woven ceramic fabric reinforced metal matrix composites during ballistic impact AU - McWilliams, B. A. AU - Yu, J. H. AU - Pankow, M. C2 - 2016/// C3 - Residual stress, thermomechanics & infrared imaging, hybrid techniques and inverse problems, vol 9 DA - 2016/// SP - 155-159 ER - TY - JOUR TI - Coupled infrared laser-thermo-mechanical response of RDX-PCTFE energetic aggregates AU - Brown, Judith A. AU - Zikry, M. A. T2 - COMPUTATIONAL MECHANICS DA - 2016/4// PY - 2016/4// DO - 10.1007/s00466-015-1241-3 VL - 57 IS - 4 SP - 611-628 SN - 1432-0924 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84961114701&partnerID=MN8TOARS KW - Energetic materials KW - Crystal plasticity KW - Electromagnetic-thermo-mechanical coupling KW - Defects KW - Hot spot formation ER - TY - JOUR TI - Can self-report instruments of shoulder function capture functional differences in older adults with and without a rotator cuff tear? AU - Vidt, Meghan E. AU - Santago, Anthony C., II AU - Hegedus, Eric J. AU - Marsh, Anthony P. AU - Tuohy, Christopher J. AU - Poehling, Gary G. AU - Freehill, Michael T. AU - Miller, Michael E. AU - Saul, Katherine R. T2 - JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY AB - Rotator cuff tears (RCT) are prevalent in older individuals and may compound age-associated functional declines. Our purpose was to determine whether self-report measures of perceived functional ability are valid for older patients with RCT. Twenty five subjects participated (12M/13F; age=63.9±3.0years); 13 with RCT and 12 controls (CON). Participants completed self-report measures of shoulder function (SST, ASES, WORC) and health-related quality of life (SF-36). Isometric joint moment and range of motion (ROM) were measured at the shoulder. Relationships among functional self-reports, and between these measures and joint moment and ROM were assessed; group differences for total and subcategory scores were evaluated. There were significant correlations among self-reports (rs=0.62-0.71, p⩽0.02). For RCT subjects, ASES was associated with all joint moments except adduction (p⩽0.02); SST, ASES, and WORC were associated with abduction and external rotation ROM (p⩽0.04). For RCT subjects, SST and WORC were associated with SF-36 physical function subcategory scores (p⩽0.05). The RCT group scored worse than CON on all functional self-reports (p<0.01) and WORC and ASES subcategories (p<0.01). In conclusion, SST, ASES, and WORC demonstrate utility and discriminant validity for older individuals by distinguishing those with RCT, but this work suggests prioritizing ASES given its stronger association with functional group strength. DA - 2016/8// PY - 2016/8// DO - 10.1016/j.jelekin.2015.06.009 VL - 29 SP - 90-99 SN - 1873-5711 KW - Self report KW - Aged KW - Rotator cuff KW - Upper extremity KW - Activities of daily living KW - Strength KW - Range of motion ER - TY - JOUR TI - Atomically Thin MoS2 Narrowband and Broadband Light Superabsorbers AU - Huang, Lujun AU - Li, Guoqing AU - Gurarslan, Alper AU - Yu, Yiling AU - Kirste, Ronny AU - Guo, Wei AU - Zhao, Junjie AU - Collazo, Ramon AU - Sitar, Zlatko AU - Parsons, Gregory N. AU - Kudenov, Michael AU - Cao, Linyou T2 - ACS NANO AB - We present a combined theoretical and experimental effort to enable strong light absorption (>70%) in atomically thin MoS2 films (≤4 layers) for either narrowband incidence with arbitrarily prespecified wavelengths or broadband incidence like solar radiation. This is achieved by integrating the films with resonant photonic structures that are deterministically designed using a unique reverse design approach based on leaky mode coupling. The design starts with identifying the properties of leaky modes necessary for the targeted strong absorption, followed by searching for the geometrical features of nanostructures to support the desired modes. This process is very intuitive and only involves a minimal amount of computation, thanks to the straightforward correlations between optical functionality and leaky modes as well as between leaky modes and the geometrical feature of nanostructures. The result may provide useful guidance for the development of high-performance atomic-scale photonic devices, such as solar cells, modulators, photodetectors, and photocatalysts. DA - 2016/8// PY - 2016/8// DO - 10.1021/acsnano.6b02195 VL - 10 IS - 8 SP - 7493-7499 SN - 1936-086X KW - MoS2 KW - two-dimensional materials KW - light absorption KW - leaky mode KW - resonant photonics ER - TY - JOUR TI - A cyber expert system for auto-tuning powered prosthesis impedance control parameters AU - Huang, H. AU - Crouch, D. L. AU - Liu, M. AU - Sawicki, G. S. AU - Wang, D. T2 - Annals of Biomedical Engineering DA - 2016/// PY - 2016/// DO - 10.1007/s10439-015-1464-7 VL - 44 IS - 5 SP - 1613-1624 ER - TY - JOUR TI - Thermal Stress and High Temperature Effects on Power Devices in a Fault-Resilient NPC IGCT-Based Converter AU - Rocha, Anderson Vagner AU - Bhattacharya, Subhashish AU - Moghaddam, Giti Karimi AU - Gould, Richard D. AU - Paula, Helder AU - Cardoso Filho, Braz de Jesus T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - The integrated gate-commutated thyristor and presspack power diodes have been successfully applied in medium-voltage neutral point-clamped converters in the power range from hundreds of kilowatt to tenths of megawatt. Responsible for driving key processes in the industry, high reliability and availability are crucial for these converters, since their repair or replacement after failure events may take too long. Given the vital importance of such equipment for the drive systems, they are equipped with protection schemes that are usually reliable, but not infallible. If the protection scheme of the converter does not work properly in a short-circuit situation, serious damages may be expected on its power semiconductor devices. In this paper, the power semiconductors thermal behavior is investigated using finite-element models in the COMSOL Multiphysics software. Three-dimensional thermal models of the power devices were raised by industrial radiography techniques, aiming to expand the information provided by the manufacturers. The authors show how these results can be used in a real equipment to attenuate the catastrophic effects of the protection scheme malfunction, so limiting the damage pattern within the converter to their least complex power devices. DA - 2016/4// PY - 2016/4// DO - 10.1109/tpel.2015.2452262 VL - 31 IS - 4 SP - 2800-2807 SN - 1941-0107 KW - Fault-resilience KW - integrated gate-commutated thyristor (IGCT) KW - medium voltage (MV) KW - neutral point-clamped (NPC) converter KW - presspack KW - reliability KW - thermal management ER - TY - JOUR TI - The effects of a rotator cuff tear on activities of daily living in older adults: A kinematic analysis AU - Vidt, Meghan E. AU - Santago, Anthony C. AU - Marsh, Anthony P. AU - Hegedus, Eric J. AU - Tuohy, Christopher J. AU - Poehling, Gary G. AU - Freehill, Michael T. AU - Miller, Michael E. AU - Saul, Katherine R. T2 - JOURNAL OF BIOMECHANICS AB - Rotator cuff tears (RCT) in older individuals may compound age-associated physiological changes and impact their ability to perform daily functional tasks. Our objective was to quantify thoracohumeral kinematics for functional tasks in 18 older adults (mean age=63.3±2.2), and compare findings from nine with a RCT to nine matched controls. Motion capture was used to record kinematics for 7 tasks (axilla wash, forward reach, functional pull, hair comb, perineal care, upward reach to 90°, upward reach to 105°) spanning the upper limb workspace. Maximum and minimum joint angles and motion excursion for the three thoracohumeral degrees of freedom (elevation plane, elevation, axial rotation) were identified for each task and compared between groups. The RCT group used greater minimum elevation angles for axilla wash and functional pull (p≤0.0124) and a smaller motion excursion for functional pull (p=0.0032) compared to the control group. The RCT group also used a more internally rotated maximum axial rotation angle than controls for functional reach, functional pull, hair comb, and upward reach to 105° (p≤0.0494). The most differences between groups were observed for axial rotation, with the RCT group using greater internal rotation to complete functional tasks, and significant differences between groups were identified for all three thoracohumeral degrees of freedom for functional pull. We conclude that older adults with RCT used more internal rotation to perform functional tasks than controls. The kinematic differences identified in this study may have consequences for progression of shoulder damage and further functional impairment in older adults with RCT. DA - 2016/2/29/ PY - 2016/2/29/ DO - 10.1016/j.jbiomech.2016.01.029 VL - 49 IS - 4 SP - 611-617 SN - 1873-2380 KW - Upper limb KW - Thoracohumeral KW - Kinematics KW - Aging KW - Rotator cuff tear ER - TY - JOUR TI - System Efficiency of Miniature Horizontal-Axis Wind Turbines With and Without Gear Transmission AU - Xu, Fujun AU - Yuan, Fuh-Gwo AU - Hu, Jingzhen T2 - JOURNAL OF ENERGY ENGINEERING AB - In this paper, two miniature horizontal-axis wind-turbine systems (MHAWTs) with and without gear transmission consisting of commercially available off-the-shelf components were designed for harvesting energy from ambient airflow to power wireless sensors. The basic performance of the MHAWTs was tested at various wind speeds (2–8 m/s) and resistive loads (10–500 Ω). The maximum output powers of the MHAWT with and without gear were 8.6 and 11 mW at the wind speed of 4 m/s, which suggested that both MHAWTs enabled powering low-power wireless sensors in natural airflow environment. To analyze the system efficiency and predict the optimal resistive load of the MHAWTs, an equivalent-circuit model was used. According to this model, the maximum system efficiency of the MHAWT system was predicted to be 14.8%. The actual maximum system efficiency of the MHAWTs with and without gears was tested as 8.4% and 7.5% at the wind speed of 8 and 6.5 m/s. In addition, the predicted optimal resistive loads of the MHAWTs with and without gear were 128 and 34 Ω, which correlated well with the tested results. The equivalent-circuit model is well suited to estimating and optimizing the performance of the MHAWTs. DA - 2016/3// PY - 2016/3// DO - 10.1061/(asce)ey.1943-7897.0000276 VL - 142 IS - 1 SP - SN - 1943-7897 KW - Miniature wind turbine KW - Wireless sensor KW - Equivalent-circuit model KW - Energy harvesting ER - TY - JOUR TI - Structural, magnetic and magnetotransport properties of bi-epitaxial La0.7Sr0.3MnO3 (110) thin films integrated on Si (001) AU - Punugupati, Sandhyarani AU - Kumar, Raj AU - Nori, Sudhakar AU - Hunte, Frank AU - Narayan, Jagdish T2 - ACTA MATERIALIA AB - We report the growth of bi-epitaxial La0.7Sr0.3MnO3 (110) thin films on Si (001) substrate with cubic yttria stabilized zirconia (c-YSZ)/SrTiO3 (STO) buffer layers by pulsed laser deposition. The La0.7Sr0.3MnO3 and STO thin films were grown with a single [110] out-of-plane orientation and with two in-plane domain variants, which is confirmed by XRD and detailed TEM studies. The growth of STO on c-YSZ can be explained by the paradigm of domain matching epitaxy. The epitaxial relationship between STO and c-YSZ can be written as [110] (001) c-YSZ ‖ [1¯11¯] (110) STO (or) [110] (001) c-YSZ ‖ [1¯12¯] (110) STO. The La0.7Sr0.3MnO3 thin films are ferromagnetic with Curie temperature 324 K and showed metal to insulator transition at 285 K. The La0.7Sr0.3MnO3 thin films showed hysteresis loops in magnetoresistance when magnetic field is applied along both in-plane (110) and out-of-plane [110] directions. The highest magnetoresistance obtained in this study is −32% at 50 K and 50 kOe for in-plane configuration, whereas the room-temperature magnetoresistance is −4% at 10 kOe and −17% at 50 kOe. The hysteresis in the magnetoresistance and the controlled domain boundaries in bi-epitaxial La0.7Sr0.3MnO3 films integrated on Si can offer significant advantages over the polycrystalline counterparts. DA - 2016/3// PY - 2016/3// DO - 10.1016/j.actamat.2015.12.054 VL - 106 SP - 40-47 SN - 1873-2453 KW - La0.7Sr0.3MnO3 (110) KW - Bi-epitaxial KW - Magnetoresistance KW - Out-of-plane ER - TY - JOUR TI - Steady Viscous Flow Between Two Porous Disks With Stretching Motion AU - Fang, Tiegang AU - He, Xin T2 - JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME AB - In this work, an exact solution to the steady-state Navier–Stokes (NS) equations is presented for viscous flows between two stretchable disks with mass transpiration effects. The governing momentum equations were converted into an ordinary differential equation by a similarity transformation technique. The similarity equation was solved numerically and the effects of Reynolds number and the mass transpiration parameter were investigated. At very low Reynolds numbers (i.e., R → 0), a creeping flow was observed with a parabolic radial velocity profile and a cubic function profile for the vertical velocity. With the increase of the Reynolds number, the flow shows a boundary layer behavior near the wall with a constant velocity core flow in the centerline region between the two disks for mass suction or lower mass injection. The effects of the mass transpiration on the flow are quite different and interesting. With strong suction, the radial profiles also show boundary layer type characteristics with a core flow. But for large mass injection, the radial velocity approaches to a linear profile under higher Reynolds number. These results are a rare case of an exact solution to the NS equations and are useful as a benchmark problem for the validation of three-dimensional (3D) numerical computation code. DA - 2016/1// PY - 2016/1// DO - 10.1115/1.4030805 VL - 138 IS - 1 SP - SN - 1528-901X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84939865333&partnerID=MN8TOARS KW - Navier-Stokes equation KW - exact solution KW - stretchable disk KW - similarity solution KW - mass transpiration ER - TY - JOUR TI - Solid Tumor Embolotherapy in Hepatic Arteries with an Anti-reflux Catheter System AU - Xu, Zelin AU - Jernigan, Shaphan AU - Kleinstreuer, Clement AU - Buckner, Gregory D. T2 - ANNALS OF BIOMEDICAL ENGINEERING DA - 2016/4// PY - 2016/4// DO - 10.1007/s10439-015-1411-7 VL - 44 IS - 4 SP - 1036-1046 SN - 1573-9686 KW - Liver cancer KW - Transient particle-hemodynamics KW - Embolization KW - Particle-reflux KW - Infusion-stop point KW - Excessive particle capture ER - TY - JOUR TI - Microstructural Behavior and Failure Mechanisms of Organic Semicrystalline Thin Film Blends AU - Zhao, Bingxiao AU - Awartani, Omar AU - O'Connor, Brendan AU - Zikry, Mohammed A. T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - Organic thin film blends of P3HT semiconducting polymers and PCBM fullerenes have enabled large-scale semiconductor fabrication pertaining to flexible and stretchable electronics. However, molecular packing and film morphologies can significantly alter mechanical stability and failure behavior. To further understand and identify the fundamental mechanisms affecting failure, a multiphase microstructurally based formulation and nonlinear finite-element fracture methodology were used to investigate the heterogeneous deformation and failure modes of organic semicrystalline thin film blends. The multiphase formulation accounts for the crystalline and amorphous behavior, polymer tie-chains, and the PCBM aggregates. Face-on packing orientations resulted in extensive inelastic deformation and crystalline rotation, and this was characterized by ductile failure modes and interfacial delamination. For edge-on packing orientations, brittle failure modes and film cracking were due to lower inelastic deformation and higher film stress in comparison with the face-on orientations. The higher crystallinity of P3HT and larger PCBM aggregates associated with larger domain sizes, strengthened the film and resulted in extensive film cracking. These predictions of ductile and brittle failure are consistent with experimental observations for P3HT:PCBM films. The proposed predictive framework can be used to improve organic film ductility and strength through the control of molecular packing orientations and microstructural mechanisms. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 896–907 DA - 2016/5/1/ PY - 2016/5/1/ DO - 10.1002/polb.23991 VL - 54 IS - 9 SP - 896-907 SN - 1099-0488 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84954289843&partnerID=MN8TOARS KW - flexible material systems KW - interfacial delamination KW - microstructural failure mechanisms KW - modeling KW - organic thin films KW - P3HT: PCBM ER - TY - JOUR TI - In Situ Nanomechanical Testing of Crystalline Nanowires in Electron Microscopes AU - Zhu, Yong T2 - JOM DA - 2016/1// PY - 2016/1// DO - 10.1007/s11837-015-1614-2 VL - 68 IS - 1 SP - 84-93 SN - 1543-1851 ER - TY - JOUR TI - Evolution of Irradiation-Induced Vacancy Defects in Boron Nitride Nanotubes AU - Cheng, Guangming AU - Yao, Shanshan AU - Sang, Xiahan AU - Hao, Boyi AU - Zhang, Dongyan AU - Yap, Yoke Khin AU - Zhu, Yong T2 - SMALL AB - Irradiation-induced vacancy defects in multiwalled (MW) boron nitride nanotubes (BNNTs) are investigated via in situ high-resolution transmission electron microscope operated at 80 kV, with a homogeneous distribution of electron beam intensity. During the irradiation triangle-shaped vacancy defects are gradually generated in MW BNNTs under a mediate electron current density (30 A cm(-2)), by knocking the B atoms out. The vacancy defects grow along a well-defined direction within a wall at the early stage as a result of the curvature induced lattice strain, and then develop wall by wall. The orientation or the growth direction of the vacancy defects can be used to identify the chirality of an individual wall. With increasing electron current density, the shape of the irradiation-induced vacancy defects changes from regular triangle to irregular polygon. DA - 2016/2/10/ PY - 2016/2/10/ DO - 10.1002/smll.201502440 VL - 12 IS - 6 SP - 818-824 SN - 1613-6829 KW - boron nitride KW - nanotubes KW - electron irradiation KW - TEM KW - irradiation-induced defects KW - vacancy defects ER - TY - JOUR TI - Designing unit cell in three-dimensional periodic nanostructures using colloidal lithography AU - Min, Joong-Hee AU - Zhang, Xu A. AU - Chang, Chih-Hao T2 - OPTICS EXPRESS AB - Colloidal phase-shift lithography, the illumination of a two-dimensional (2D) ordered array of self-assembled colloidal nanospheres, is an effective method for the fabrication of periodic three-dimensional (3D) nanostructures. In this work, we investigate the design and control of the unit-cell geometry by examining the relative ratio of the illumination wavelength and colloidal nanosphere diameter. Using analytical and finite-difference time-domain (FDTD) modeling, we examine the effect of the wavelength-diameter ratio on intensity pattern, lattice constants, and unit-cell geometry. These models were validated by experimental fabrication for various combination of wavelength and colloid diameter. The developed models and fabrication tools can facilitate the design and engineering of 3D periodic nanostructure for photonic crystals, volumetric electrodes, and porous materials. DA - 2016/1/25/ PY - 2016/1/25/ DO - 10.1364/oe.24.00a276 VL - 24 IS - 2 SP - A276-A284 SN - 1094-4087 ER - TY - JOUR TI - Collisional broadening of Kr (4p(6) S-0(1) -> -> 5p [3/2](2)) transition with combustion species as collision partners AU - Zelenak, D. AU - Sealy, W. AU - Narayanaswamy, V. T2 - Journal of Quantitative Spectroscopy & Radiative Transfer DA - 2016/// PY - 2016/// VL - 174 SP - 28-38 ER - TY - JOUR TI - Anisotropic Elastic Modulus of Oriented Regioregular Poly(3-hexylthiophene) Films AU - Awartani, Omar M. AU - Zhao, Bingxiao AU - Currie, Tyler AU - Kline, R. Joseph AU - Zikry, Mohammed A. AU - Brendan T. O'Connor, T2 - MACROMOLECULES AB - Specific morphological features of polymer semiconductors are often promoted in devices to optimize optoelectronic behavior. Less studied is the role of morphology on the mechanical properties of the film, such as elastic modulus, which is an important property for the development of flexible and stretchable devices. To gain insight into the morphological origin of elasticity in polymer semiconductors and its relationship to charge transport, we study the anisotropic in-plane elastic modulus of strain-aligned regioregular poly(3-hexylthiophene) (P3HT) films and compare the results to previously measured field effect charge mobility. The film morphology is varied through the amount of applied strain and post strain thermal annealing. Morphological characterization includes UV–vis optical spectroscopy and X-ray diffraction. The elastic modulus is measured using a buckling-based measurement technique. The elastic modulus of the film is found to decrease as the film is plastically strained. Thermally annealing the strained films results in a large in-plane elastic modulus anisotropy, where the modulus increases in the direction of backbone alignment and decreases in the transverse direction. The measured elastic modulus is compared to the film morphology, showing a dependence on both in-plane polymer chain alignment and local aggregate order. Comparing the elastic modulus to field effect mobility shows that they are not necessarily correlated, which has important implication for flexible organic electronic device design. DA - 2016/1/12/ PY - 2016/1/12/ DO - 10.1021/acs.macromol.5b02680 VL - 49 IS - 1 SP - 327-333 SN - 1520-5835 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84954288748&partnerID=MN8TOARS ER - TY - JOUR TI - A Nonlinear Gain-Scheduling Compensation Approach Using Parameter-Dependent Lyapunov Functions AU - Wu, Fen AU - Song, Xun AU - Ren, Zhang T2 - JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME AB - This paper addresses the gain-scheduling control design for nonlinear systems to achieve output regulation. For gain-scheduling control, the linear parameter-varying (LPV) model is obtained by linearizing the plant about zero-error trajectories upon which an LPV controller is based. A key in this process is to find a nonlinear output feedback compensator such that its linearization matches with the designed LPV controller. Then, the stability and performance properties of LPV control about the zero-error trajectories can be inherited when the nonlinear compensator is implemented. By incorporating the exosystem, nominal input, and measured output information into the LPV model, the LPV control synthesis problem is formulated as linear matrix inequalities (LMIs) using parameter-dependent Lyapunov functions (PDLFs). Moreover, explicit formulae for the construction of the nonlinear gain-scheduled compensator have been derived to meet the linearization requirement. Finally, the validity of the proposed nonlinear gain-scheduling control approach is demonstrated through a ball and beam example. DA - 2016/1// PY - 2016/1// DO - 10.1115/1.4031845 VL - 138 IS - 1 SP - SN - 1528-9028 ER - TY - JOUR TI - A Gain-Scheduling Control Approach for Takagi-Sugeno Fuzzy Systems Based on Linear Parameter-Varying Control Theory AU - Liu, Yang AU - Ban, Xiaojun AU - Wu, Fen AU - Lam, H. K. T2 - JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME AB - Due to the universal approximation capability of Takagi–Sugeno (T–S) fuzzy models for nonlinear dynamics, many control issues have been investigated based on fuzzy control theory. In this paper, a transformation procedure is proposed to convert fuzzy models into linear fractional transformation (LFT) models. Then, T–S fuzzy systems can be regarded as a special case of linear parameter-varying (LPV) systems which proved useful for nonlinear control problems. The newly established connection between T–S fuzzy models and LPV models provides a new perspective of the control problems for T–S fuzzy systems and facilitates the fuzzy control designs. Specifically, an output feedback gain-scheduling control design approach for T–S fuzzy systems is presented to ensure globally asymptotical stability and optimize H∞ performance of the closed-loop systems. The control synthesis problem is cast as a convex optimization problem in terms of linear matrix inequalities (LMIs). Two examples have been used to illustrate the efficiency of the proposed method. DA - 2016/1// PY - 2016/1// DO - 10.1115/1.4031914 VL - 138 IS - 1 SP - SN - 1528-9028 ER - TY - JOUR TI - Thermal Conductivity, Heat Capacity, and Elastic Constants of Water Soluble Polymers and Polymer Blends AU - Xie, Xu AU - Li, Dongyao AU - Tsai, Tsung-Han AU - Liu, Jun AU - Braun, Paul V. AU - Cahill, David G. T2 - MACROMOLECULES AB - We use time-domain thermoreflectance (TDTR), and the generation and detection of longitudinal and surface acoustic waves, to study the thermal conductivity, heat capacity, and elastic properties of thin films of poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), polyacrylamide (PAM), poly(vinylpyrrolidone) (PVP), methyl cellulose (MC), poly(4-styrenesulfonic acid) (PSS), poly(N-acryloylpiperidine) (PAP), poly(methyl methacrylate) (PMMA), and a polymer blend of PVA/PAA. The thermal conductivity of six water-soluble polymers in the dry state varies by a factor of ≈2, from 0.21 to 0.38 W m–1 K–1, where the largest values appear among polymers with a high concentration of hydrogen bonding (PAA, PAM, PSS). The longitudinal elastic constants range from 7.4 to 24.5 GPa and scale linearly with the shear elastic constants, suggesting a narrow distribution of Possion’s ratio 0.35 < ν < 0.40. The thermal conductivity increases with the average sound velocity, as expected based on the model of the minimum thermal conductivity. The thermal conductivity of polymer blends of PVA (0.31 W m–1 K–1) and PAA (0.37 W m–1 K–1) is in agreement with a simple rule of mixtures. DA - 2016/2/9/ PY - 2016/2/9/ DO - 10.1021/acs.macromol.5b02477 VL - 49 IS - 3 SP - 972-978 SN - 1520-5835 UR - http://dx.doi.org/10.1021/acs.macromol.5b02477 ER - TY - JOUR TI - Preliminary Investigation of the Process Capabilities of Hydroforging AU - Alzahrani, Bandar AU - Ngaile, Gracious T2 - MATERIALS AB - Hydroforging is a hybrid forming operation whereby a thick tube is formed to a desired geometry by combining forging and hydroforming principles. Through this process hollow structures with high strength-to-weight ratio can be produced for applications in power transmission systems and other structural components that demands high strength-to-weight ratio. In this process, a thick tube is deformed by pressurized fluid contained within the tube using a multi-purpose punch assembly, which is also used to feed tube material into the die cavity. Fluid pressure inside the thick tube is developed by volume change governed by the movement of the punch assembly. In contrast to the conventional tube hydroforming (THF), the hydroforging process presented in this study does not require external supply of pressurized fluid to the deforming tube. To investigate the capability of hydroforging process, an experimental setup was developed and used to hydroforge various geometries. These geometries included hollow flanged vessels, hexagonal flanged parts, and hollow bevel and spur gears. DA - 2016/1// PY - 2016/1// DO - 10.3390/ma9010040 VL - 9 IS - 1 SP - SN - 1996-1944 KW - hybrid process KW - hydroforging KW - tube hydroforming process KW - lightweight ER - TY - JOUR TI - New results on switched linear systems with actuator saturation AU - Duan, Chang AU - Wu, Fen T2 - INTERNATIONAL JOURNAL OF SYSTEMS SCIENCE AB - This paper further studies the analysis and control problems of continuous-time switched linear systems subject to actuator saturation. Using the norm-bounded differential inclusion description of the saturated systems and the minimal switching rule, a set of switched output feedback controllers is designed to minimise the disturbance attenuation level defined by the regional L2 gain over a class of energy-bounded disturbances. The synthesis conditions are expressed as bilinear matrix inequalities, and can be solved by numerical search coupled with linear matrix inequality optimisation. Compared to the previous method based on polytopic differential inclusion, the proposed approach has good scalability and potentially renders better performance. Numerical examples are provided to verify the effectiveness of the proposed approach. DA - 2016/4/3/ PY - 2016/4/3/ DO - 10.1080/00207721.2014.911386 VL - 47 IS - 5 SP - 1008-1020 SN - 1464-5319 KW - switching control KW - output feedback control KW - actuator saturation KW - linear matrix inequalities (LMIs) ER - TY - JOUR TI - Mechanism of the Transition From In-Plane Buckling to Helical Buckling for a Stiff Nanowire on an Elastomeric Substrate AU - Chen, Youlong AU - Zhu, Yong AU - Chen, , Xi AU - Liu, Yilun T2 - JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME AB - In this work, the compressive buckling of a nanowire partially bonded to an elastomeric substrate is studied via finite-element method (FEM) simulations and experiments. The buckling profile of the nanowire can be divided into three regimes, i.e., the in-plane buckling, the disordered buckling in the out-of-plane direction, and the helical buckling, depending on the constraint density between the nanowire and the substrate. The selection of the buckling mode depends on the ratio d/h, where d is the distance between adjacent constraint points and h is the helical buckling spacing of a perfectly bonded nanowire. For d/h > 0.5, buckling is in-plane with wavelength λ = 2d. For 0.27 < d/h < 0.5, buckling is disordered with irregular out-of-plane displacement. While, for d/h < 0.27, buckling is helical and the buckling spacing gradually approaches to the theoretical value of a perfectly bonded nanowire. Generally, the in-plane buckling induces smaller strain in the nanowire, but consumes the largest space. Whereas the helical mode induces moderate strain in the nanowire, but takes the smallest space. The study may shed useful insights on the design and optimization of high-performance stretchable electronics and three-dimensional complex nanostructures. DA - 2016/4// PY - 2016/4// DO - 10.1115/1.4032573 VL - 83 IS - 4 SP - SN - 1528-9036 ER - TY - JOUR TI - Mathematical models of alpha-synuclein transport in axons AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. T2 - COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING AB - To investigate possible effects of diffusion on α-synuclein (α-syn) transport in axons, we developed two models of α-syn transport, one that assumes that α-syn is transported only by active transport, as part of multiprotein complexes, and a second that assumes an interplay between motor-driven and diffusion-driven α-syn transport. By comparing predictions of the two models, we were able to investigate how diffusion could influence axonal transport of α-syn. The predictions obtained could be useful for future experimental work aimed at elucidating the mechanisms of axonal transport of α-syn. We also attempted to simulate possible defects in α-syn transport early in Parkinson's disease (PD). We assumed that in healthy axons α-syn localizes in the axon terminal while in diseased axons α-syn does not localize in the terminal (this was simulated by postulating a zero α-syn flux into the terminal). We found that our model of a diseased axon predicts the build-up of α-syn close to the axon terminal. This build-up could cause α-syn accumulation in Lewy bodies and the subsequent axonal death pattern observed in PD ('dying back' of axons). DA - 2016/4/3/ PY - 2016/4/3/ DO - 10.1080/10255842.2015.1043628 VL - 19 IS - 5 SP - 515-526 SN - 1476-8259 KW - neuron KW - alpha-synuclein KW - motor-driven transport KW - diffusion KW - Parkinson's disease KW - mathematical modeling ER - TY - JOUR TI - Lamb Waves Based Fast Subwavelength Imaging Using a DORT-MUSIC Algorithm AU - He, Jiae AU - Yuan, Fuh-Gwo T2 - 42ND ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: INCORPORATING THE 6TH EUROPEAN-AMERICAN WORKSHOP ON RELIABILITY OF NDE AB - A Lamb wave-based, subwavelength imaging algorithm is developed for damage imaging in large-scale, plate-like structures based on a decomposition of the time-reversal operator (DORT) method combined with the multiple signal classification (MUSIC) algorithm in the space-frequency domain. In this study, a rapid, hybrid non-contact scanning system was proposed to image an aluminum plate using a piezoelectric linear array for actuation and a laser Doppler vibrometer (LDV) line-scan for sensing. The physics of wave propagation, reflection, and scattering that underlies the response matrix in the DORT method is mathematically formulated in the context of guided waves. The singular value decomposition (SVD) and MUSIC-based imaging condition enable quantifying the damage severity by a ‘reflectivity’ parameter and super-resolution imaging. With the flexibility of this scanning system, a considerably large area can be imaged using lower frequency Lamb waves with limited line-scans. The experimental results showed that the hardware system with a signal processing tool such as the DORT-MUSIC (TR-MUSIC) imaging technique can provide rapid, highly accurate imaging results as well as damage quantification with unknown material properties. DA - 2016/// PY - 2016/// DO - 10.1063/1.4940494 VL - 1706 SP - SN - 0094-243X ER - TY - JOUR TI - Elastic drug delivery: could treatments be triggered by patient movement? AU - Zhang, Yuqi AU - Yu, Jicheng AU - Zhu, Yong AU - Gu, Zhen T2 - NANOMEDICINE AB - NanomedicineVol. 11, No. 4 EditorialFree AccessElastic drug delivery: could treatments be triggered by patient movement?Yuqi Zhang, Jicheng Yu, Yong Zhu & Zhen GuYuqi Zhang Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill & North Carolina State University, Raleigh, NC 27695, USASearch for more papers by this author, Jicheng Yu Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill & North Carolina State University, Raleigh, NC 27695, USASearch for more papers by this author, Yong Zhu Department of Mechanical & Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USASearch for more papers by this author & Zhen Gu*Author for correspondence: E-mail Address: zgu@email.unc.edu Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill & North Carolina State University, Raleigh, NC 27695, USASearch for more papers by this authorPublished Online:19 Jan 2016https://doi.org/10.2217/nnm.15.197AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinkedInReddit Keywords: drug deliverymechanical-responsivenanoparticlewearable devicesFirst draft submitted: 22 October 2015; Accepted for publication: 12 November 2015; Published online: 19 January 2016Nanoparticle-based drug delivery systems have drawn extensive attention for treating a broad range of diseases during the last few decades [1,2]. In order to enhance therapeutic efficacy, reduce side effects and prolong action time, vast efforts have been dedicated to the development of on-demand, precise drug release. In light of this, numerous stimuli-responsive designs have been exploited, including external triggers like mechanical force, temperature, light, ultrasound, electric current and magnetic field as well as internal factors like pH, redox, enzymes, ATP and hypoxia [3–8]. Compared with other stimuli-responsive designs, the macroscopic mechanical force-mediated approach, as one of the most promising strategies, possesses several advantages. It can be generated on-demand during the patients’ daily movement, such as tension in bone joints, tendons and muscles, or compression in cartilage and bones. Therefore, a self-administrated therapy can be readily achieved without requirement of additional instrumentations. In addition, in contrast to the inaccurate internal factors due to the complicated physiological environment, the degree of stretch or compression is more conveniently controlled by the patient themselves, leading to a precise dosage-, spatial- and temporal-controllable administration of drug release.Physical deformation of drug carriers supported on an elastomer substrate caused by stretch or compression is one of the most important strategies for mechanical force-triggered release. Mooney group designed a compression-responsive system for controlled release of growth factor [9]. Inspired by the natural extracellular matrices, they developed a hydrogel with reversible binding of drug as synthetic extracelluar matrices. The physical-loaded hydrogel could respond to repeated compression stimulus and as a result released free drug. Afterward, the matrices could be refilled by free drug during relaxation via dissociation of previously bound drug. Using VEGF as a model drug in in vivo studies, they demonstrated that the implanted hydrogels allowed an increase in VEGF concentration near implantation site as applying mechanical signals, subsequently leading to a local enhanced vascularization. In another case, Jeong group developed a strain-sensitive patch consisting of arrays of microcapsules onto a rubbery substrate for drug release [10]. When stretch was applied to the elastomer substrate, the volume of the stretchable microcapsules encapsulating cargoes decreased accordingly with the substrate, then pumping out the preloaded molecules. Under different degrees of mechanical stretching, the release rate and amount of cargoes could be adjusted. This patch has the potential to respond to body motions, even to the mechanical stretching of organs, muscles and tendons when it is implanted into body.We have recently developed a multipurpose wearable, tensile strain-triggered drug delivery device, which comprised of a stretchable elastomer and microgel depots containing drug-loaded nanoparticles [11]. The drugs can be continuously released from the nanoparticles and temporarily stored in the microgels. When applying a tensile strain, the drugs were released from micro-depots due to the enlarged surface area for diffusion and Poisson's ratio-induced compression toward the microgels. Therefore, a sustained drug release can be conveniently achieved by daily body motion, while a pulsatile release is able to be controlled through intentional administration. We demonstrated that this device could be simply attached to a finger joint, and stretched to trigger the drug release when the finger is flexed for multiple cycles, which allowed patients to control the dose and release timing of antibacterial drug on their own.Furthermore, we integrated this stretch-sensitive device with a microneedle array patch for on-demand transcutaneous insulin delivery [3], which allowed the blood glucose level of mice to decline quickly to a normoglycemic range within 0.5 h. Meanwhile, the obvious pulsatile and continuous reduction in blood glucose level were observed when applying a strain with an interval of 4 h. Based on this technology, the diabetic patients can easily maintain normoglycemia through simple joint movement instead of a traditional painful insulin injection. This skin-mountable device can be further extended for anti-inflammatory, anti-infective drug or painkiller delivery. More importantly, this facile strategy allows immediate medical treatment in emergency situation by patient's simple body movement.Besides the direct drug release via changing diffusion area or pumping out caused by physical deformation, tension or compression can also generate energy to change the physical properties of drug carriers. For example, Pioletti group exploited dissipation properties of hydrogel as an internal heat source to trigger the thermal-sensitive drug release instead of additional external heat source [12]. Self heating was quickly produced after 5 min cyclic mechanical loading. The increased temperature further caused the shrinkage of thermal-responsive nanoparticles entrapped in the hydrogel and subsequent drug release.In addition, mechanical stretch or compression is able to tune the molecular conformation and intermolecular interaction between host molecule and guest molecule, resulting in a force-triggered drug release [13,14]. Based on this phenomenon, Ariga group reported a mechanically controlled monolayer formed by a steroid cyclophane molecule with a cyclic core linked to four steroid moieties via the flexible L-lysine spacer [13]. The applied compression could lead to a cavity-forming conformation of the cyclophane. Therefore, the hydrophobic model drug was easily trapped in this hydrophobic cavity. In contrast, expansion of the monolayer could release the encapsulated drug through the molecular transformation from cavity to planarity. Similarly, they developed a mechanical stimulus-activated β-cyclodextrin (CyD)-crosslinked alginate gel [15]. As applying mild mechanical compression, the model drug ondansetron, the entrapped guest, could be released from the host CyD moieties, due to the change in inclusion ability of CyD. The host–guest interactions dominated by van der Waals interactions and hydrogen bonds in a gel matrix can be more easily broken than covalent bonds, which provide a convenient on-demand administration of medicines operated intentionally by the patient.The research and development of patients’ movement-controlled drug delivery systems hold promise in improving patients’ compliance by providing a self-directed and on-demand treatment. Nonetheless, there are still many remaining challenges for clinical development. For example, the current systems cannot precisely control the release dose of therapeutics. A fundamental study on the dynamic relationships between the phase transitions of materials and the relevant release profile should be closely investigated. Moreover, regarding the different movement extent and ability for different individuals, how to generate a personalized platform and consistently apply the mechanical trigger signal are difficult tasks ahead that need to be addressed. Integration of this device with other wearable modalities to monitor the real-time physiological signals (e.g., electrocardiograph, blood glucose levels or body temperature [16,17]) and motion signals [18,19] might be able to provide feedback to guide the precise, personalized drug delivery. Last but not least, good biocompatibility and biodegradability for materials is extremely important for further translation of the elastic drug delivery system. Tailoring materials mimicking the structures and composites of natural systems offer a promising strategy [5,20].Financial & competing interests disclosureThe authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.No writing assistance was utilized in the production of this manuscript.References1 Jiang T, Mo R, Bellotti A, Zhou J, Gu Z. Gel–liposome‐mediated co‐delivery of anticancer membrane‐associated proteins and small‐molecule drugs for enhanced therapeutic efficacy. Adv. Funct. Mater. 24(16), 2295–2304 (2014).Crossref, CAS, Google Scholar2 Sun W, Jiang T, Lu Y, Reiff M, Mo R, Gu Z. Cocoon-like self-degradable dna nanoclew for anticancer drug delivery. J. Am. Chem. 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Engl. 49(43), 7904–7908 (2010).Crossref, Medline, CAS, Google Scholar8 Zhang Y, Yin Q, Yin L, Ma L, Tang L, Cheng J. Chain‐shattering polymeric therapeutics with on‐demand drug‐release capability. Angew. Chem. Int. Ed. Engl. 52(25), 6435–6439 (2013).Crossref, Medline, CAS, Google Scholar9 Lee KY, Peters MC, Anderson KW, Mooney DJ. Controlled growth factor release from synthetic extracellular matrices. Nature 408(6815), 998–1000 (2000).Crossref, Medline, CAS, Google Scholar10 Hyun DC, Moon GD, Park CJ, Kim BS, Xia Y, Jeong U. Strain‐controlled release of molecules from arrayed microcapsules supported on an elastomer substrate. Angew. Chem. Int. Ed. Engl. 50(3), 724–727 (2011).Crossref, Medline, CAS, Google Scholar11 Di J, Yao S, Ye Y et al. Stretch-triggered drug delivery from wearable elastomer films containing therapeutic depots. ACS Nano 9(9), 9407–9415 (2015).Crossref, Medline, CAS, Google Scholar12 Moghadam MN, Kolesov V, Vogel A, Klok H-A, Pioletti DP. Controlled release from a mechanically-stimulated thermosensitive self-heating composite hydrogel. Biomaterials 35(1), 450–455 (2014).Crossref, Medline, CAS, Google Scholar13 Ariga K, Terasaka Y, Sakai D, Tsuji H, Kikuchi J-I. Piezoluminescence based on molecular recognition by dynamic cavity array of steroid cyclophanes at the air-water interface. J. Am. Chem. Soc. 122(32), 7835–7836 (2000).Crossref, CAS, Google Scholar14 Michinobu T, Shinoda S, Nakanishi T et al. Mechanical control of enantioselectivity of amino acid recognition by cholesterol-armed cyclen monolayer at the air-water interface. J. Am. Chem. Soc. 128(45), 14478–14479 (2006).Crossref, Medline, CAS, Google Scholar15 Izawa H, Kawakami K, Sumita M, Tateyama Y, Hill JP, Ariga K. β-Cyclodextrin-crosslinked alginate gel for patient-controlled drug delivery systems: regulation of host–guest interactions with mechanical stimuli. J. Mater. Chem. B 1(16), 2155–2161 (2013).Crossref, CAS, Google Scholar16 Myers AC, Huang H, Zhu Y. Wearable silver nanowire dry electrodes for electrophysiological sensing. RSC Adv. 5(15), 11627–11632 (2015).Crossref, CAS, Google Scholar17 Kim D-H, Lu N, Ma R et al. Epidermal electronics. Science 333(6044), 838–843 (2011).Crossref, Medline, CAS, Google Scholar18 Yao S, Zhu Y. Wearable multifunctional sensors using printed stretchable conductors made of silver nanowires. Nanoscale 6(4), 2345–2352 (2014).Crossref, Medline, CAS, Google Scholar19 Yao S, Zhu Y. Nanomaterial‐enabled stretchable conductors: strategies, materials and devices. Adv. Mater. 27(9), 1480–1511 (2015).Crossref, Medline, CAS, Google Scholar20 Mitragotri S, Anderson DG, Chen X et al. Accelerating the translation of nanomaterials in biomedicine. ACS Nano 9(7), 6644–6654 (2015).Crossref, Medline, CAS, Google ScholarFiguresReferencesRelatedDetailsCited ByExternal stimuli-responsive drug delivery systemsMechanical on-off gates for regulation of drug release in cutaneous or musculoskeletal tissue repairsMaterials Science and Engineering: C, Vol. 115Biomechano-Interactive Materials and Interfaces7 June 2018 | Advanced Materials, Vol. 30, No. 31Nanomaterial‐Enabled Wearable Sensors for Healthcare30 November 2017 | Advanced Healthcare Materials, Vol. 7, No. 1 Vol. 11, No. 4 Follow us on social media for the latest updates Metrics History Published online 19 January 2016 Published in print February 2016 Information© Future Medicine LtdKeywordsdrug deliverymechanical-responsivenanoparticlewearable devicesFinancial & competing interests disclosureThe authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.No writing assistance was utilized in the production of this manuscript.PDF download DA - 2016/// PY - 2016/// DO - 10.2217/nnm.15.197 VL - 11 IS - 4 SP - 323-325 SN - 1748-6963 KW - drug delivery KW - mechanical-responsive KW - nanoparticle KW - wearable devices ER - TY - JOUR TI - Damage Modes Recognition and Hilbert-Huang Transform Analyses of CFRP Laminates Utilizing Acoustic Emission Technique AU - WenQin, Han AU - Ying, Luo AU - AiJun, Gu AU - Yuan, Fuh-Gwo T2 - APPLIED COMPOSITE MATERIALS DA - 2016/4// PY - 2016/4// DO - 10.1007/s10443-015-9454-3 VL - 23 IS - 2 SP - 155-178 SN - 1573-4897 KW - CFRP KW - Acoustic emission KW - Peak frequency KW - EMD KW - HHT ER - TY - JOUR TI - Assessments of Fatty Infiltration and Muscle Atrophy From a Single Magnetic Resonance Image Slice Are Not Predictive of 3-Dimensional Measurements AU - Vidt, Meghan E. AU - Santago, Anthony C., II AU - Tuohy, Christopher J. AU - Poehling, Gary G. AU - Freehill, Michael T. AU - Kraft, Robert A. AU - Marsh, Anthony P. AU - Hegedus, Eric J. AU - Miller, Michael E. AU - Saul, Katherine R. T2 - ARTHROSCOPY-THE JOURNAL OF ARTHROSCOPIC AND RELATED SURGERY AB - Purpose To (1) determine whether standard clinical muscle fatty infiltration and atrophy assessment techniques using a single image slice for patients with a rotator cuff tear (RCT) are correlated with 3-dimensional measures in older individuals (60+ years) and (2) to determine whether age-associated changes to muscle morphology and strength are compounded by an RCT. Methods Twenty older individuals were studied: 10 with an RCT of the supraspinatus (5 men and 5 women) and 10 matched controls. Clinical imaging assessments (Goutallier and Fuchs scores and cross-sectional area ratio) were performed for participants with RCTs. Three-dimensional measurements of rotator cuff muscle and fat tissues were obtained for all participants using magnetic resonance imaging (MRI). Isometric joint moment was measured at the shoulder. Results There were no significant associations between single-image assessments and 3-dimensional measurements of fatty infiltration for the supraspinatus and infraspinatus muscles. Compared with controls, participants with RCTs had significantly increased percentages of fatty infiltration for each rotator cuff muscle (all P ≤ .023); reduced whole muscle volume for the supraspinatus, infraspinatus, and subscapularis muscles (all P ≤ .038); and reduced fat-free muscle volume for the supraspinatus, infraspinatus, and subscapularis muscles (all P ≤ .027). Only the teres minor (P = .017) fatty infiltration volume was significantly greater for participants with RCTs. Adduction, flexion, and external rotation strength (all P ≤ .021) were significantly reduced for participants with RCTs, and muscle volume was a significant predictor of strength for all comparisons. Conclusions Clinical scores using a single image slice do not represent 3-dimensional muscle measurements. Efficient methods are needed to more effectively capture 3-dimensional information for clinical applications. Participants with RCTs had increased fatty infiltration percentages that were likely driven by muscle atrophy rather than increased fat volume. The significant association of muscle volume with strength production suggests that treatments to preserve muscle volume should be pursued for older patients with RCTs. Level of Evidence Level II, diagnostic study, with development of diagnostic criteria on the basis of consecutive patients with universally applied reference gold standard. To (1) determine whether standard clinical muscle fatty infiltration and atrophy assessment techniques using a single image slice for patients with a rotator cuff tear (RCT) are correlated with 3-dimensional measures in older individuals (60+ years) and (2) to determine whether age-associated changes to muscle morphology and strength are compounded by an RCT. Twenty older individuals were studied: 10 with an RCT of the supraspinatus (5 men and 5 women) and 10 matched controls. Clinical imaging assessments (Goutallier and Fuchs scores and cross-sectional area ratio) were performed for participants with RCTs. Three-dimensional measurements of rotator cuff muscle and fat tissues were obtained for all participants using magnetic resonance imaging (MRI). Isometric joint moment was measured at the shoulder. There were no significant associations between single-image assessments and 3-dimensional measurements of fatty infiltration for the supraspinatus and infraspinatus muscles. Compared with controls, participants with RCTs had significantly increased percentages of fatty infiltration for each rotator cuff muscle (all P ≤ .023); reduced whole muscle volume for the supraspinatus, infraspinatus, and subscapularis muscles (all P ≤ .038); and reduced fat-free muscle volume for the supraspinatus, infraspinatus, and subscapularis muscles (all P ≤ .027). Only the teres minor (P = .017) fatty infiltration volume was significantly greater for participants with RCTs. Adduction, flexion, and external rotation strength (all P ≤ .021) were significantly reduced for participants with RCTs, and muscle volume was a significant predictor of strength for all comparisons. Clinical scores using a single image slice do not represent 3-dimensional muscle measurements. Efficient methods are needed to more effectively capture 3-dimensional information for clinical applications. Participants with RCTs had increased fatty infiltration percentages that were likely driven by muscle atrophy rather than increased fat volume. The significant association of muscle volume with strength production suggests that treatments to preserve muscle volume should be pursued for older patients with RCTs. DA - 2016/1// PY - 2016/1// DO - 10.1016/j.arthro.2015.06.035 VL - 32 IS - 1 SP - 128-139 SN - 1526-3231 ER - TY - JOUR TI - The Onset of Convection in a Horizontal Porous Layer with Spatially Non-Uniform Internal Heating AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2016/1// PY - 2016/1// DO - 10.1007/s11242-015-0610-x VL - 111 IS - 2 SP - 541-553 SN - 1573-1634 KW - Porous medium KW - Instability KW - Natural convection KW - Internal heating ER - TY - JOUR TI - The Effect of Pulsating Throughflow on the Onset of Convection in a Horizontal Porous Layer AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2016/2// PY - 2016/2// DO - 10.1007/s11242-015-0622-6 VL - 111 IS - 3 SP - 731-740 SN - 1573-1634 KW - Pulsating throughflow KW - Porous medium KW - Thermal instability KW - Horizontal layer ER - TY - JOUR TI - Pulsed phase thermography imaging of fatigue-loaded composite adhesively bonded joints AU - Shin, Peter H. AU - Webb, Sean C. AU - Peters, Kara J. T2 - NDT & E INTERNATIONAL AB - We applied pulsed phase thermography to image and size damage in adhesively bonded joints. Specifically, the initiation and propagation of fatigue-induced damage in single lap joints with carbon fiber epoxy adherends was investigated. Lap joint specimens with various levels of manufacturing defects were fabricated and loaded in low-cycle fatigue. A calibration specimen with artificial defects was used to design a threshold algorithm for sizing of the damaged regions. The dominant failure mode in specimens without manufacturing defects was fiber-failure, whereas joints failing prematurely demonstrated adhesive failure. Imaging of the lap joints after regular number of fatigue cycles revealed that manufacturing defects could be detected and the resulting, imminent adhesive failure could be identified prior to joint failure. Additionally, the extent of this damage could be accurately estimated through the sizing algorithm. Due to the brittle nature of fiber-failure, it could not be detected prior to failure of the joint, however this was not critical, as the goal was to identify premature failure of the adhesively bonded joint. DA - 2016/4// PY - 2016/4// DO - 10.1016/j.ndteint.2015.11.008 VL - 79 SP - 7-16 SN - 1879-1174 KW - Pulsed phase thermography KW - Adhesively bonded joints KW - Fatigue ER - TY - JOUR TI - Nanomaterial-Enabled Dry Electrodes for Electrophysiological Sensing: A Review AU - Yao, Shanshan AU - Zhu, Yong T2 - JOM DA - 2016/4// PY - 2016/4// DO - 10.1007/s11837-016-1818-0 VL - 68 IS - 4 SP - 1145-1155 SN - 1543-1851 ER - TY - JOUR TI - Lamb wave-based subwavelength damage imaging using the DORT-MUSIC technique in metallic plates AU - He, Jiaze AU - Yuan, Fuh-Gwo T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - A Lamb wave-based, subwavelength imaging algorithm is developed for damage imaging in a metallic plate based on a decomposition of the time-reversal operator method together with a multiple signal classification imaging condition in the space-frequency domain. In this study, a hybrid non-contact inspection system was proposed to image damage in an aluminum plate using a piezoelectric linear array for actuation and a laser Doppler vibrometer line-scan perpendicular to the piezoelectric array for sensing. The physics of incident waves, reflection, and reflected waves that underlie the transfer matrix in the decomposition of the time-reversal operator method is mathematically formulated in the context of guided waves based on the first-order Born approximation. Singular value decomposition is then employed to decompose the experimentally measured transfer matrix into three matrices, detailing the incident wave propagation from the linear actuator array, reflection from the damage, and followed by reflected waves toward the linear sensing array for each small damage. The singular value decomposition and multiple signal classification imaging condition enable providing insight on both the damage “reflectivity” and detecting damage smaller than a wavelength (subwavelength). With the flexibility of this inspection system, a considerably large area can be imaged using lower frequency Lamb waves with rapid line-scans. The experimental results showed that the hardware system with a signal processing tools such as the decomposition of the time-reversal operator with multiple signal classification (time-reversal with multiple signal classification) imaging technique can provide robust, highly accurate imaging results as well as providing damage reflectivity estimation with unknown material properties. DA - 2016/1// PY - 2016/1// DO - 10.1177/1475921715623359 VL - 15 IS - 1 SP - 65-80 SN - 1741-3168 KW - Decomposition of the time-reversal operator KW - time-reversal KW - multiple signal classification KW - subwavelength imaging KW - super-resolution KW - low frequency KW - non-contact KW - laser Doppler vibrometer ER - TY - JOUR TI - Hybrid almost output regulation of linear impulsive systems with average dwell-time AU - Yuan, Chengzhi AU - Wu, Fen T2 - NONLINEAR ANALYSIS-HYBRID SYSTEMS AB - This paper deals with the hybrid almost output regulation problem for a class of linear systems with average dwell-time impulses. The proposed hybrid output regulator is constructed as a linear impulsive system that undergoes synchronous impulses with the controlled plant. Lyapunov-based sufficient conditions of the output regulability and weighted L2 performance for the linear impulsive systems are first derived. Based on the analysis results, the hybrid synthesis problem is formulated in terms of linear matrix equations plus a set of linear matrix inequalities (LMIs). With this hybrid synthesis scheme, both flow and jump dynamics of the hybrid regulator can be jointly designed by solving a convex optimization problem in minimizing the weighted L2 gain from the perturbation signal to the error output. A numerical example is used to demonstrate the proposed approach. DA - 2016/5// PY - 2016/5// DO - 10.1016/j.nahs.2015.11.001 VL - 20 SP - 82-94 SN - 1878-7460 KW - Linear impulsive systems KW - Hybrid control KW - Output regulation KW - Average dwell-time KW - Convex optimization ER - TY - JOUR TI - Hepatic-directed therapies in patients with neuroendocrine tumors AU - Kennedy, A. S. T2 - Hematology-Oncology Clinics of North America DA - 2016/// PY - 2016/// VL - 30 IS - 1 SP - 193- ER - TY - JOUR TI - Electrochemical effects in thermoelectric polymers AU - Chang W., Fang H. AU - Liu J., Evans C. AU - Russ B., Popere B. AU - Patel S., Chabinyc M. AU - R., Segalman T2 - ACS Macro Letters DA - 2016/// PY - 2016/// VL - 5 SP - 455-459 ER - TY - JOUR TI - Dynamic modeling and mobility analysis of the transforming roving-rolling explorer (TRREx) as it Traverses Rugged Martian Terrain AU - Edwin, Lionel E. AU - Mazzoleni, Andre P. T2 - ACTA ASTRONAUTICA AB - All planetary surface exploration missions thus far have employed traditional rovers with a rocker-bogie suspension. These rovers can navigate moderately rough and flat terrain, but are not designed to traverse rugged terrain with steep slopes. The fact is, however, that the most scientifically interesting missions require exploration platforms with capabilities for navigating such types of rugged terrain. This issue motivates the development of new kinds of rovers that take advantage of the latest advances in robotic technologies to traverse rugged terrain efficiently. This work analyzes one such rover concept called the Transforming Roving–Rolling Explorer (TRREx) that is principally aimed at addressing the above issue. Biologically inspired by the way the armadillo curls up into a ball when threatened, and the way the golden wheel spider uses the dynamic advantages of a sphere to roll down hills when escaping danger, the TRREx rover can traverse like a traditional 6-wheeled rover over conventional terrain, but can also transform itself into a sphere, when necessary, to travel down steep inclines, or navigate rough terrain. This paper investigates the mobility of the TRREx when it is in its rolling mode, i.e. when it is a sphere and can steer itself through actuations that shift its center of mass to achieve the desired direction of roll. A mathematical model describing the dynamics of the rover in this spherical configuration is presented, and actuated rolling is demonstrated through computer simulation. Parametric analyzes that investigate the rover’s mobility as a function of its design parameters are also presented. This work highlights the contribution of the spherical rolling mode to the enhanced mobility of the TRREx rover and how it could enable challenging surface exploration missions in the future. DA - 2016/// PY - 2016/// DO - 10.1016/j.actaastro.2015.10.017 VL - 120 SP - 103-120 SN - 1879-2030 KW - Mars KW - Rover KW - Transforming KW - Dynamics KW - Terrain KW - Modeling ER - TY - JOUR TI - Design, Fabrication, and Characterization of a Bifrequency Colinear Array AU - Wang, Zhuochen AU - Li, Sibo AU - Czernuszewicz, Tomasz J. AU - Gallippi, Caterina M. AU - Liu, Ruibin AU - Geng, Xuecang AU - Jiang, Xiaoning T2 - IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL AB - Ultrasound imaging with high resolution and large penetration depth has been increasingly adopted in medical diagnosis, surgery guidance, and treatment assessment. Conventional ultrasound works at a particular frequency, with a [Formula: see text] fractional bandwidth of [Formula: see text], limiting the imaging resolution or depth of field. In this paper, a bifrequency colinear array with resonant frequencies of 8 and 20 MHz was investigated to meet the requirements of resolution and penetration depth for a broad range of ultrasound imaging applications. Specifically, a 32-element bifrequency colinear array was designed and fabricated, followed by element characterization and real-time sectorial scan (S-scan) phantom imaging using a Verasonics system. The bifrequency colinear array was tested in four different modes by switching between low and high frequencies on transmit and receive. The four modes included the following: 1) transmit low, receive low; 2) transmit low, receive high; 3) transmit high, receive low; and 4) transmit high, receive high. After testing, the axial and lateral resolutions of all modes were calculated and compared. The results of this study suggest that bifrequency colinear arrays are potential aids for wideband fundamental imaging and harmonic/subharmonic imaging. DA - 2016/2// PY - 2016/2// DO - 10.1109/tuffc.2015.2506000 VL - 63 IS - 2 SP - 266-274 SN - 1525-8955 KW - Bifrequency ultrasound KW - colinear array KW - composite transducer ER - TY - JOUR TI - Damage imaging using non-contact air-coupled transducer/laser Doppler vibrometer system AU - Harb, Mohammad Said AU - Yuan, Fuh-Gwo T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - In this work, a rapid imaging technique is proposed for imaging damage in metallic plates using a zero-lag cross-correlation imaging condition in the frequency domain. A fully non-contact, single-side access, hybrid inspection system employing air-coupled transducer (ACT) for the generation of anti-symmetric Lamb wave mode and laser Doppler vibrometer (LDV) for dynamic visualization of the Lamb wavefield is used to experimentally verify the proposed technique on three identical aluminum plates with same notch geometry but with various orientations at different locations. The notches (10 mm × 5 mm) are grooved in the aluminum plates using electric discharge machining with a maximum depth of 40% of plate’s thickness and with the following orientations 90°, 60°, and 45° with respect to the horizontal axis. A damage image is constructed by cross-correlating the forward and backward propagating wavefields in the aluminum plates which are separated by analyzing the actual laser Doppler vibrometer measured wavefield using a frequency–wavenumber filtering post-processing technique. The experimental results demonstrate a strong capability of guided wave zero-lag cross-correlation imaging condition technique in localizing, sizing, and detecting the orientation of relatively small defects in the isotopic material. DA - 2016/3// PY - 2016/3// DO - 10.1177/1475921716636336 VL - 15 IS - 2 SP - 193-203 SN - 1741-3168 KW - Lamb waves KW - damage imaging KW - zero-lag cross-correlation imaging condition KW - non-destructive inspection KW - air-coupled transducer KW - laser Doppler vibrometer ER - TY - JOUR TI - Assessment of a hybrid finite element and finite volume code for turbulent incompressible flows AU - Xia, Yidong AU - Wang, Chuanjin AU - Luo, Hong AU - Christon, Mark AU - Bakosi, Jozsef T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - Hydra-TH is a hybrid finite-element/finite-volume incompressible/low-Mach flow simulation code based on the Hydra multiphysics toolkit being developed and used for thermal-hydraulics applications. In the present work, a suite of verification and validation (V&V) test problems for Hydra-TH was defined to meet the design requirements of the Consortium for Advanced Simulation of Light Water Reactors (CASL). The intent for this test problem suite is to provide baseline comparison data that demonstrates the performance of the Hydra-TH solution methods. The simulation problems vary in complexity from laminar to turbulent flows. A set of RANS and LES turbulence models were used in the simulation of four classical test problems. Numerical results obtained by Hydra-TH agreed well with either the available analytical solution or experimental data, indicating the verified and validated implementation of these turbulence models in Hydra-TH. Where possible, some form of solution verification has been attempted to identify sensitivities in the solution methods, and suggest best practices when using the Hydra-TH code. DA - 2016/2/15/ PY - 2016/2/15/ DO - 10.1016/j.jcp.2015.12.022 VL - 307 SP - 653-669 SN - 1090-2716 KW - Incompressible flow KW - Turbulence model KW - RANS KW - LES ER - TY - JOUR TI - Particle- and crack-size dependency of lithium-ion battery materials LiFePO₄ AU - Stamps, Michael A. AU - Eischen, Jeffrey W. AU - Huang, Hsiao-Ying Shadow T2 - AIMS Materials Science AB - Lithium-ion batteries have become a widely-used commodity for satisfying the world’s mobile power needs. However, the mechanical degradation of lithium-ion batteries initiated by micro cracks is considered to be a bottleneck for advancing the current technology. This study utilizes a finite element method-based virtual crack closure technique to obtain particle- and crack-size-dependent estimates of mixed-mode energy release rates and stress intensity factors. Interfacial cracks in orthotropic bi-materials are considered in the current study, whereas the crack extension along the interface is assumed. The results show that energy release rate, stress intensity factor, and the propensity of crack extension are particle- and crack-size- dependent. In particular, our results show that for smaller plate-like LiFePO4 particles (100 nm × 45 nm), a crack has lesser tendency to extend if crack-to-particle size is less than 0.2, and for 200 nm × 90 nm particles, similar results are obtained for crack-to-particle sizes of less than 0.15. However, for larger particles (500 nm × 225 nm), it requires an almost flawless particle to have no crack extension. Therefore, the current study provides insight into the fracture mechanics of LiFePO4 and the associated crack-to-particle size dependency to prevent crack extensions. DA - 2016/// PY - 2016/// DO - 10.3934/matersci.2016.1.190 VL - 3 IS - 1 SP - 190-203 SN - 2372-0484 UR - http://dx.doi.org/10.3934/matersci.2016.1.190 KW - Lithium-ion batteries KW - cracks KW - finite element method KW - virtual crack closure technique KW - LiFePO4 ER - TY - JOUR TI - Fabrication and design of metal nano-accordion structures using atomic layer deposition and interference lithography AU - Min, J. -H. AU - Bagal, A. AU - Mundy, J. Z. AU - Oldham, C. J. AU - Wu, B. -I. AU - Parsons, G. N. AU - Chang, C. -H. T2 - NANOSCALE AB - Fabricated free-standing platinum nano-accordion structures with a wide variety of cross-sectional profiles using a combination of ALD and IL. DA - 2016/// PY - 2016/// DO - 10.1039/c5nr08566g VL - 8 IS - 9 SP - 4984-4990 SN - 2040-3372 ER - TY - JOUR TI - A Novel Ultrasound Technique for Non-Invasive Assessment of Cell Differentiation AU - Huang, Wenbin AU - Kim, Jinwook AU - Kim, Kyngrim AU - Bakshi, Saurabh AU - Williams, John AU - Matthieu, Pattie AU - Loboa, Elizabeth AU - Shung, Koping Kirk AU - Zhou, Qifa AU - Jiang, Xiaoning T2 - IEEE SENSORS JOURNAL AB - A novel technique for the characterization of mammalian cells during cell culture was studied using a lead magnesium niobate-lead titanate single crystal piezoelectric resonator. Tests were conducted to observe changes in material properties of human adipose derived stem cells during both proliferation and osteogenic differentiation. The resonator electrical impedance was recorded as a function of the cell acoustic impedance, an indicator of cell viscoelasticity. Observed electrical impedance change (in percentage) from day 1 to day 14 for human adipose derived stem cells undergoing chemical-induced osteogenic differentiation was ~1.7× that observed for proliferating stem cells maintained in complete growth medium. DA - 2016/1// PY - 2016/1// DO - 10.1109/jsen.2015.2477340 VL - 16 IS - 1 SP - 61-68 SN - 1558-1748 KW - Lead magnesium niobate-lead titanate piezoelectric resonator KW - in-situ cell differentiation monitoring KW - electrical impedance measurement KW - osteogenic differentiation ER - TY - JOUR TI - A 3D collision avoidance strategy for UAV with physical constraints AU - Lihua, Zhu AU - Xianghong, Cheng AU - Fuh-Gwo, Yuan T2 - MEASUREMENT AB - The main goal of this research effort is to find a flyable collision-free path for an unmanned aerial vehicle (UAV) in a dynamic environment. Given that the UAV path planning needs to adapt in near real-time to the dynamic nature of the operational scenario, and to react rapidly to updates in the situational awareness, a modified artificial potential field (MAPF) approach is utilized to provide collision avoidance in view of pop-up threats and a random set of moving obstacles. To ensure a practically reachable trajectory, this paper proposes a constraint reference frame to develop MAPF so that the decomposed forces from MAPF can be matched with the physical constraints of the UAV for online adjustment. Simulations and experimental results provide promising validation in terms of the efficiency and scalability of the proposed approach. DA - 2016/1// PY - 2016/1// DO - 10.1016/j.measurement.2015.09.006 VL - 77 SP - 40-49 SN - 1873-412X KW - UAV KW - Collision avoidance path planning KW - Physical constraints KW - MAPF ER - TY - JOUR TI - Non-contact ultrasonic technique for Lamb wave characterization in composite plates AU - Harb, M. S. AU - Yuan, F. G. T2 - ULTRASONICS AB - A fully non-contact single-sided air-coupled and laser ultrasonic non-destructive system based on the generation and detection of Lamb waves is implemented for the characterization of A0 Lamb wave mode dispersion in a composite plate. An air-coupled transducer (ACT) radiates acoustic pressure on the surface of the composite and generates Lamb waves within the structure. The out-of-plane velocity of the propagating wave is measured using a laser Doppler vibrometer (LDV). In this study, the non-contact automated system focuses on measuring A0 mode frequency–wavenumber, phase velocity dispersion curves using Snell’s law and group velocity dispersion curves using Morlet wavelet transform (MWT) based on time-of-flight along different wave propagation directions. It is theoretically demonstrated that Snell’s law represents a direct link between the phase velocity of the generated Lamb wave mode and the coincidence angle of the ACT. Using Snell’s law and MWT, the former three dispersion curves of the A0 mode are easily and promptly generated from a set of measurements obtained from a rapid ACT angle scan experiment. In addition, the phase velocity and group velocity polar characteristic wave curves are also computed to analyze experimentally the angular dependency of Lamb wave propagation. In comparison with the results from the theory, it is confirmed that using the ACT/LDV system and implementing simple Snell’s law method is highly sensitive and effective in characterizing the dispersion curves of Lamb waves in composite structures as well as its angular dependency. DA - 2016/1// PY - 2016/1// DO - 10.1016/j.ultras.2015.08.011 VL - 64 SP - 162-169 SN - 1874-9968 KW - Air-coupled ultrasound KW - Snell's law KW - Lamb waves KW - Dispersion curves KW - Composites ER - TY - JOUR TI - Guided torsional wave generation of a linear in-plane shear piezoelectric array in metallic pipes AU - Zhou, Wensong AU - Yuan, Fuh-Gwo AU - Shi, Tonglu T2 - ULTRASONICS AB - Cylindrical guided waves based techniques are effective and promising tools for damage detection in long pipes. The essential operations are generation and reception of guided waves in the structures utilizing transducers. A novel in-plane shear (d36 type) PMNT wafer is proposed to generate and receive the guided wave, especially the torsional waves, in metallic pipes. In contrast to the traditional wafer, this wafer will directly introduce in-plane shear deformation when electrical field is conveniently applied through its thickness direction. A single square d36 PMNT wafer is bonded on the surface of the pipe positioned collinearly with its axis, when actuated can predominantly generate torsional (T) waves along the axial direction, circumferential shear horizontal (C-SH) waves along circumferential direction, and other complex cylindrical Lamb-like wave modes along other helical directions simultaneously. While a linear array of finite square size d36 PMNT wafers was equally spaced circumferentially, when actuated simultaneously can nearly uniform axisymmetric torsional waves generate in pipes and non-symmetric wave modes can be suppressed greatly if the number of the d36 PMNT wafer is sufficiently large. This paper first presents the working mechanism of the linear d36 PMNT array from finite element analysis (FEA) by examining the constructive and destructive displacement wavefield phenomena in metallic pipes. Furthermore, since the amplitude of the received fundamental torsional wave signal strongly depends on frequency, a series of experiments are conducted to determine the frequency tuning curve for the torsional wave mode. All results indicate the linear d36 PMNT array has potential for efficiently generating uniform torsional wavefield of the fundamental torsional wave mode, which is more effective in monitoring structural health in metallic pipes. DA - 2016/2// PY - 2016/2// DO - 10.1016/j.ultras.2015.10.021 VL - 65 SP - 69-77 SN - 1874-9968 KW - Guided wave KW - Piping structure KW - In-plane shear transducers KW - Torsional wave mode KW - Frequency tuning curve ER -