TY - JOUR TI - Effect of Rotation on Detailed Heat Transfer Distribution for Various Rib Geometries in Developing Channel Flow AU - Lamont, Justin A. AU - Ekkad, Srinath V. AU - Anne Alvin, Mary T2 - Journal of Heat Transfer AB - The effects of Coriolis force and centrifugal buoyancy have a significant impact on heat transfer behavior inside rotating internal serpentine coolant channels for turbine blades. Due to the complexity of added rotation inside such channels, detailed knowledge of the heat transfer will greatly enhance the blade designer's ability to predict hot spots so coolant may be distributed more effectively. The effects of high rotation numbers are investigated on the heat transfer distributions for different rib types in near entrance and entrance region of the channels. It is important to determine the actual enhancement derived from turbulating channel entrances where heat transfer is already high due to entrance effects and boundary layer growth. A transient liquid crystal technique is used to measure detailed heat transfer coefficients (htc) for a rotating, short length, radially outward coolant channel with rib turbulators. Different rib types such as 90 deg, W, and M-shaped ribs are used to roughen the walls to enhance heat transfer. The channel Reynolds number is held constant at 12,000 while the rotation number is increased up to 0.5. Results show that in the near entrance region, the high performance W and M-shaped ribs are just as effective as the simple 90 deg ribs in enhancing heat transfer. The entrance effect in the developing region causes significantly high baseline heat transfer coefficients thus reducing the effective of the ribs to further enhance heat transfer. Rotation causes increase in heat transfer on the trailing side, while the leading side remains relatively constant limiting the decrement in leading side heat transfer. For all rotational cases, the W and M-shaped ribs show significant effect of rotation with large differences between leading and trailing side heat transfer. DA - 2013/10/25/ PY - 2013/10/25/ DO - 10.1115/1.4025211 VL - 136 IS - 1 LA - en OP - SN - 0022-1481 1528-8943 UR - http://dx.doi.org/10.1115/1.4025211 DB - Crossref ER - TY - JOUR TI - Study of Microparticle Rebound Characteristics Under High Temperature Conditions AU - Reagle, C. J. AU - Delimont, J. M. AU - Ng, W. F. AU - Ekkad, S. V. T2 - Journal of Engineering for Gas Turbines and Power AB - Large amounts of tiny microparticles are ingested into gas turbines over their operating life, resulting in unexpected wear and tear. Knowledge of such microparticle behavior at gas turbine operating temperatures is limited in published literature. In this study, Arizona road dust (ARD) is injected into a hot flow field to measure the effects of high temperature and velocity on particle rebound from a polished 304 stainless steel (SS) coupon. The results are compared with baseline (27 m/s) measurements at ambient (300 K) temperature made in the Virginia Tech Aerothermal Rig, as well as previously published literature. Mean coefficient of restitution (COR) was shown to decrease with the increased temperature/velocity conditions in the VT Aerothermal Rig. The effects of increasing temperature and velocity led to a 12% average reduction in COR at 533 K (47 m/s), 15% average reduction in COR at 866 K (77 m/s), and 16% average reduction in COR at 1073 K (102 m/s) compared with ambient results. The decrease in COR appeared to be almost entirely a result of increased velocity that resulted from heating the flow. Trends show that temperature plays a minor role in energy transfer between particle and impact surface below a critical temperature. DA - 2013/10/21/ PY - 2013/10/21/ DO - 10.1115/1.4025346 VL - 136 IS - 1 LA - en OP - SN - 0742-4795 1528-8919 UR - http://dx.doi.org/10.1115/1.4025346 DB - Crossref ER - TY - CONF TI - Study of microparticle rebound characteristics under high temperature conditions AU - Reagle, C.J. AU - Delimont, J.M. AU - Ng, W.F. AU - Ekkad, S.V. AB - Large amounts of tiny microparticles are ingested into gas turbines over their operating life, resulting in unexpected wear and tear. Knowledge of such microparticle behavior at gas turbine operating temperatures is limited in published literature. In this study, Arizona Road Dust (ARD) is injected into a hot flow field to measure the effects of high temperature and velocity on particle rebound from a polished 304 Stainless Steel (SS) coupon. The results are compared with baseline (27m/s) measurements at ambient (300°K) temperature made in the Virginia Tech Aerothermal Rig, as well as previously published literature. Mean Coefficient of Restitution (COR) was shown to decrease with the increased temperature/velocity conditions in the VT Aerothermal Rig. The effects of increasing temperature and velocity led to a 12% average reduction in COR at 533°K (47m/s), 15% average reduction in COR at 866°K (77m/s), and 16% average reduction in COR at 1073°K (102m/s) compared with ambient results. The decrease in COR appeared to be almost entirely a result of increased velocity that resulted from heating the flow. Trends show that temperature plays a minor role in energy transfer between particle and impact surface below a critical temperature. C2 - 2013/// C3 - Proceedings of the ASME Turbo Expo DA - 2013/// DO - 10.1115/GT2013-95083 VL - 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890244778&partnerID=MN8TOARS ER - TY - CONF TI - Heat transfer in multiple parallel high aspect ratio ducts with triangular trench enhancement features AU - Lamont, J. AU - Chatterjee, K. AU - Ekkad, S.V. AU - Ledezma, G. AU - Kaminski, C. AU - Tolpadi, A. AB - Detailed heat transfer coefficient distributions and pressure drop have been obtained for high aspect ratio (AR = Width/Height = 12.5) ducts with triangular trench enhancement features oriented normal to the coolant flow direction. Numerical and experimental approaches analyze the performance of triangular trenches for six geometrically identical ducts branching from a common plenum. The numerical approach is based on a Reynolds Averaged Navier Stokes (RANS) turbulence model with an unstructured mesh. A transient liquid crystal (TLC) technique is used to experimentally calculate Nu on the ducts surfaces. Reynolds number (Re = 7080, 14800, and 22400, with respect to the duct hydraulic diameter are explored. As Computational Fluid Dynamics (CFD) and TLC results are both detailed, qualitative and quantitative comparisons are made. Experimental results show the closest and furthest ducts from the entrance of the plenum are considerably affected, as recirculation zones develop which partially choke the inlet the respective ducts. Results from the experiments are compared to CFD predictions from Duct 4. In addition, the experimental data are recalculated with the maximum bias in TLC temperature to indicate an improved matching between CFD and experimental methods to demonstrate that CFD captures the wall heat transfer coefficient trends similar to experimental results. The triangular trenches enhance heat transfer in the ducts two-fold compared to smooth wall Dittus-Boelter Nusselt number correlation for flow in tubes. C2 - 2013/// C3 - ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 DA - 2013/// DO - 10.1115/HT2013-17325 VL - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84892995827&partnerID=MN8TOARS ER - TY - JOUR TI - Heat Transfer Enhancement in Narrow Diverging Channels AU - Lamont, Justin AU - Ramesh, Sridharan AU - Ekkad, Srinath V. AU - Tolpadi, Anil AU - Kaminski, Christopher AU - Salamah, Samir T2 - Journal of Turbomachinery AB - Detailed heat transfer coefficient distributions have been obtained for narrow diverging channels with and without enhancement features. The cooling configurations considered include rib turbulators and concavities (or dimples) on the main heat transfer surfaces. All of the measurements are presented at a representative Reynolds number of 28,000. Pressure drop measurements for the overall channel are also presented to evaluate the heat transfer enhancement geometry with respect to the pumping power requirements. The test models were studied for wall heat transfer coefficient measurements using the transient liquid crystal technique. The model wall inner surfaces were sprayed with thermochromic liquid crystals and a transient test was used to obtain the local heat transfer coefficients from the measured color change. An analysis of the results shows that the choice of designs is limited by the available pressure drop, even if the design provides significantly higher heat transfer coefficients. Dimpled surfaces provide appreciably high heat transfer coefficients and a reasonable pressure drop, whereas ribbed ducts provide significantly higher heat transfer coefficients and a higher overall pressure drop. DA - 2013/6/5/ PY - 2013/6/5/ DO - 10.1115/1.4007740 VL - 135 IS - 4 LA - en OP - SN - 0889-504X 1528-8900 UR - http://dx.doi.org/10.1115/1.4007740 DB - Crossref ER - TY - JOUR TI - Comparison of Flow and Heat Transfer Distributions in a Can Combustor for Radial and Axial Swirlers Under Cold Flow Conditions AU - Carmack, Andrew AU - Ekkad, Srinath AU - Kim, Yong AU - Moon, Hee-Koo AU - Srinivasan, Ram T2 - Journal of Thermal Science and Engineering Applications AB - A comparison study between axial and radial swirler performance in a gas turbine can combustor was conducted by investigating the correlation between combustor flow field geometry and convective heat transfer at cold flow conditions for Reynolds numbers of 50,000 and 80,000. Flow velocities were measured using particle image velocimetry (PIV) along the center axial plane and radial cross sections of the flow. It was observed that both swirlers produced a strong rotating flow with a reverse flow core. The axial swirler induced larger recirculation zones at both the backside wall and the central area as the flow exits the swirler, and created a much more uniform rotational velocity distribution. The radial swirler however, produced greater rotational velocity as well as a thicker and higher velocity reverse flow core. Wall heat transfer and temperature measurements were also taken. Peak heat transfer regions directly correspond to the location of the flow as it exits each swirler and impinges on the combustor liner wall. DA - 2013/7/15/ PY - 2013/7/15/ DO - 10.1115/1.4023890 VL - 5 IS - 3 LA - en OP - SN - 1948-5085 1948-5093 UR - http://dx.doi.org/10.1115/1.4023890 DB - Crossref ER - TY - CONF TI - Tripod hole geometry performance for a vane suction surface near throat location AU - Ramesh, S. AU - LeBlanc, C. AU - Ekkad, S.V. AU - Alvin, M.A. AB - Film cooling performance depends strongly on the hole exit geometry, blowing ratio, and hole location. The goal of this study is to evaluate film cooling geometries that can provide better protection over the suction surface of the airfoil beyond the throat region. This study compares the performance of standard cylindrical; fan-shaped (10° flare/laidback); tripod hole geometry (15° breakout angle); and tripod holes with shaped exits (5° flare on 15° tripod). Film cooling holes are located just upstream of the throat region on the suction side of an airfoil. The airfoil is a scaled up first stage vane from GE E3 engine and is mounted on a low speed linear cascade wind tunnel. A range of blowing ratios from 0.5 to 2.0 was covered for a cylindrical hole, while ensuring all other hole geometries run under similar mass flow rate conditions. Steady state IR (Infra-Red) technique was employed to measure adiabatic film cooling effectiveness. Results show that the tripod holes with and without shaped exits provide much higher film effectiveness than cylindrical and slightly higher effectiveness than shaped exit holes using 50% lesser cooling air while operating at the same blowing ratios. Effectiveness values up to 0.2–0.25 are seen 40-hole diameters downstream for the tripod hole configurations thus providing cooling in the important trailing edge portion of the airfoil. C2 - 2013/// C3 - Proceedings of the ASME Turbo Expo DA - 2013/// DO - 10.1115/GT2013-94459 VL - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890183573&partnerID=MN8TOARS ER - TY - CONF TI - Thermo-mechanical analysis of various film cooling hole geometries AU - Ramesh, S. AU - Leblanc, C. AU - Ekkad, S. AU - Alvin, M.A. AB - Tripod hole film cooling designs can provide improved cooling with reduced coolant usage. It is essential to determine the impact of strong cooling near hole locations due to increased thermal gradients around the hole region. In this paper, efforts have been made to predict the same using a numerical analysis. Local temperature distribution on the blade surface causes different rates of expansion, resulting in a differential strain, furthering the impact of the numerical study and creating a need to understand the thermo-mechanical behavior of blade design. The thermal stresses that are generated near the film cooling holes are compared for different cooling hole shapes and eventually weigh the thermal advantage of a tripod hole over the cylindrical standard design. Standard k-ε was used to validate the CFD results, ensuring by a fine mesh of 5 million tetrahedrons. Validation includes comparison of the experimental results, with a numerical one where similar blade material and working temperatures are used. Upon validation, CFD was run again at engine temperature conditions with Haynes230 alloy as the blade material. Surface temperature contour enabled structural analysis using a finite element approach. Equivalent stresses (Von-Mises stresses) on the blade emerging from the analysis provided more information about stress dependency on blowing ratio. C2 - 2013/// C3 - ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 DA - 2013/// DO - 10.1115/HT2013-17423 VL - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893025970&partnerID=MN8TOARS ER - TY - CONF TI - Numerical modeling of fluid flow and thermal behavior in geothermal heat exchangers AB - Geothermal heat exchangers are highly dependent on the local heat exchange capacity and ground thermal properties. The ability to simulate performance and testing of geothermal heat exchangers is limited. Therefore thermal conductivity tests are usually required for correct sizing of geothermal heat exchange systems. To better understand these tests in relation to energy piles, a 3D finite element model was created using the COMSOL software to simulate the thermal conductivity test of a 12inch (30cm) energy pile. The finite element simulation was created and validated using experimental data to expand the comparisons made between geothermal boreholes and energy piles. In this study, the numerical finite element model has been recreated using the commercial computational fluid dynamics (CFD) software ANSYS which incorporates fluid flow effects. Confirming that the CFD model can accurately model the thermal conductivity test provides an additional tool that will be valuable in modeling geothermal heat exchangers. Results show that parametric variations in terms of fluid flow rate and fluid selection are easier to evaluate using the CFD model compared to the finite element model. Results are also compared with discrete thermal conductivity measurements obtained from real geothermal heat exchangers. C2 - 2013/// C3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) DA - 2013/// DO - 10.1115/IMECE2013-65098 VL - 6 B UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84903452518&partnerID=MN8TOARS ER - TY - JOUR TI - Multi-Layer Mini-Channel and Ribbed Mini-Channel Based High Performance Cooling Configurations for Automotive Inverters—Part A: Design and Evaluation AU - Parida, Pritish R. AU - Ekkad, Srinath V. AU - Ngo, Khai T2 - Journal of Thermal Science and Engineering Applications AB - Necessitated by the dwindling supply of petroleum resources, various new automotive technologies have been actively developed from the perspective of achieving energy security and diversifying energy sources. Hybrid electric vehicles and electric vehicles are a few such examples. Such diversification requires the use of power control units essentially for power control, power conversion, and power conditioning applications such as variable speed motor drives (dc–ac conversion), dc–dc converters and other similar devices. The power control unit of a hybrid electric vehicle or electric vehicle is essentially the brain of the hybrid system as it manages the power flow between the electric motor generator, battery and gas engine. Over the last few years, the performance of this power control unit has been improved and size has been reduced to attain higher efficiency and performance, causing the heat dissipation as well as heat density to increase significantly. Efforts are constantly being made to reduce this size even further. As a consequence, a better high performance cooler/heat exchanger is required to maintain the active devices temperature within optimum range. Cooling schemes based on multiple parallel channels are a few solutions which have been widely used to dissipate transient and steady concentrated heat loads and can be applied to existing cooling system with minor modifications. The aim of the present study has therefore been to study the various cooling options based on mini-channel and rib-turbulated mini-channel cooling for application in a hybrid electric vehicle and other similar consumer products, and perform a parametric and optimization study on the selected designs. Significant improvements in terms of thermal performance, reduced overall pressure drop, and volume reduction have been shown both experimentally and numerically. This paper is the first part in a two part submission and focuses on the design and evaluation of mini-channel and rib-turbulated mini-channel cooling configurations. The second part of this paper discusses the manufacturing and testing of the cooling device. DA - 2013/6/25/ PY - 2013/6/25/ DO - 10.1115/1.4023604 VL - 5 IS - 3 LA - en OP - SN - 1948-5085 1948-5093 UR - http://dx.doi.org/10.1115/1.4023604 DB - Crossref ER - TY - JOUR TI - Foreword AU - Phinney, L.M. AU - Ekkad, S. T2 - Journal of Heat Transfer DA - 2013/// PY - 2013/// DO - 10.1115/1.4023545 VL - 135 IS - 6 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84878309195&partnerID=MN8TOARS ER - TY - JOUR TI - Film-Cooling Performance of Antivortex Hole on a Flat Plate AU - LeBlanc, Christopher AU - Narzary, Diganta P. AU - Ekkad, Srinath T2 - Journal of Turbomachinery AB - Improved film cooling performance and coolant flow usage have a significant effect on overall engine performance. In the current study, film cooling performance of an improved antivortex or tripod hole geometry is evaluated on a flat plate surface with steady-state IR (infrared thermography) technique and compared to traditional baseline geometry. The baseline geometry is a simple cylindrical hole design inclined at 30 deg from the surface with pitch-to-diameter ratio of 3.0. The proposed improvement is a tripod design where the two side holes, also of the same diameter, branch out from the root of the main hole at 15 deg angle with a larger pitch-to-diameter ratio of 6.0 between the main holes. The third geometry studied is the same tripod design embedded in a trench to enhance two-dimensional film performance. The mainstream Reynolds number is 3110 based on the coolant hole inlet diameter. Two secondary fluids, air and carbon dioxide, were used to study the effects of coolant-to-mainstream density ratio (DR = 0.95 and 1.45) on film cooling effectiveness. Several blowing ratios in the range 0.5–4.0 were investigated independently at the two density ratios. Results indicate significant improvement in effectiveness with the tripod holes compared to cylindrical holes at all the blowing ratios studied. The trenched design shows improved effectiveness in the trench region and reduced effectiveness in the downstream region. At any given blowing ratio, the tripod hole designs use 50% less coolant and provide at least 30%–40% overall averaged higher cooling effectiveness. The use of relatively dense secondary fluid improves effectiveness immediately downstream of the antivortex holes but leads to poor performance downstream. DA - 2013/9/13/ PY - 2013/9/13/ DO - 10.1115/1.4023436 VL - 135 IS - 6 LA - en OP - SN - 0889-504X 1528-8900 UR - http://dx.doi.org/10.1115/1.4023436 DB - Crossref ER - TY - CONF TI - Experimental investigation of heat transfer across a thermoelectric generator for waste heat recovery from automobile exhaust AU - Pandit, J. AU - Thompson, M. AU - Ekkad, S.V. AU - Huxtable, S. AB - The study investigates the temperature gradients achieved across a thermoelectric generator by using the exhaust gases from a vehicle as a heat source and the radiator coolant as the cold sink. Various heat transfer enhancement features are employed in order to achieve as high a temperature gradient as possible. Effect of flow Reynolds numbers and inlet temperatures are examined to create a body of data predicting total power output from the TEG. Data is normalized against results from baseline heat exchanger designs investigated in the past. The experiments are carried out at 1/5th scale of the previously examined geometry. Impingement geometry is employed on the coolant side to enhance heat transfer. The experimental test sections are fabricated using metal 3D printing. Water is used instead of radiator coolant and heated air is used for exhaust gases. The results from the experiments provide valuable data which can be used for system level optimization. C2 - 2013/// C3 - ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 DA - 2013/// DO - 10.1115/HT2013-17438 VL - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84892966336&partnerID=MN8TOARS ER - TY - CONF TI - Experimental and computational evaluation of flow characteristics for advanced film cooling hole geometries AU - Gomez-Ramirez, D. AU - Srinivasan, S. AU - Ramesh, S. AU - Miranda, M. AU - Ekkad, S.V. AU - Alvin, M.A. AB - Film cooling is crucial in the field of gas turbines to protect the blade surfaces from the hot combustion gases. Several hole geometries have been studied in the past in an effort to optimize the cooling effectiveness of the holes while maintaining the structural integrity of the blade and low manufacturing costs. To understand the cooling effectiveness of the various hole geometries, the flow structures that develop as the coolant jet interacts with the hot mainstream must be understood. The present paper compares the results obtained from 2D Particle Image Velocimetry (PIV) measurements with CFD predictions using standard Reynolds-Averaged Navier Stokes (RANS) models with a commercially available code. The study is conducted for flat plate film cooling via conventional cylindrical holes, shaped holes (10° flare/laidback), and a tripod anti-vortex hole (AV) design. A constant blowing ratio (BR) of 0.5 was used for all the experiments, except for an additional measurement for the AV design at a BR of 1.0. Computational fluid dynamic (CFD) calculations were made with a standard k-epsilon model and compared to PIV results. The results show the counter-rotating vortices developing for cylindrical and shaped holes up to 5D and 3D respectively from the hole exit. AV holes showed no vortex formation, further supporting its higher cooling performance. Moreover, the present results indicate no separation of the coolant jet for AV or shaped holes as expected, while cylindrical holes displayed a small separation with a vertical extent of ∼0.1D. The CFD model was able to capture the main structures of the flow, but further efforts will concentrate in improving the representation of the flow normal to the flat plate surface. C2 - 2013/// C3 - ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 DA - 2013/// DO - 10.1115/HT2013-17463 VL - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84892957601&partnerID=MN8TOARS ER - TY - CONF TI - Effect of upstream purge slot on a transonic turbine blade passage: Part 2 - Heat transfer performance AU - Roy, A. AU - Blot, D.M. AU - Ekkad, S.V. AU - Ng, W.F. AU - Lohaus, A.S. AU - Crawford, M.E. AB - Heat transfer experiments with and without upstream purge cooling were carried out for a high turning (127°) airfoil passage in the presence of an upstream purge slot in a transonic linear cascade. Different coolant to mainstream mass flow ratios (MFR) were investigated at cascade design exit Mach number (0.88) and design incidence angle. The experiments were performed at Virginia Tech’s transient transonic blow down facility. A transient Infrared thermography technique was employed to measure the endwall surface temperature. Heat transfer coefficient (HTC) and film cooling effectiveness (ETA) were calculated from measured temperature assuming a 1-D semi-infinite transient conduction through a solid with convective boundary condition. In this experiment, the blade span increases in the mainstream flow direction in order to match realistic inlet/exit airfoil surface Mach number distribution. Results indicate strong interactions between coolant flow and cross passage secondary flow where significant coolant coverage is observed at higher leakage flow rates through the purge slot. The backward facing step created by the purge slot seems to be the driving factor on influencing endwall HTC compared to with or without blowing cases. Three-dimensional viscous CFD has also been performed for further insight of flow characteristics and to support experimental data. Aerodynamic measurements at cascade exit plane are provided in the companion paper GT2013-94951 [1], “Effect of upstream purge slot on a transonic turbine blade passage: Part – 1 – Aerodynamic performance”. C2 - 2013/// C3 - Proceedings of the ASME Turbo Expo DA - 2013/// DO - 10.1115/GT2013-94581 VL - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890218479&partnerID=MN8TOARS ER - TY - CONF TI - Effect of upstream purge slot on a transonic turbine blade passage: Part 1 - Aerodynamic performance AU - Blot, D.M. AU - Roy, A. AU - Ekkad, S.V. AU - Ng, W. AU - Lohaus, A.S. AU - Crawford, M.E. AB - In this paper, detailed experimental results of total pressure loss and secondary flow field are presented for a high turning (127°) airfoil passage in presence of an upstream purge slot (with and without coolant injection). The experiments were performed at Virginia Tech’s quasi 2D linear turbine cascade operating at transonic conditions. Measurements were made at design exit Mach number 0.88 and design incidence angle. The selected coolant to mainstream mass flow ratio (MFR) was set at 1.0%. In order to match engine representative inlet/exit blade loading, a diverging endwall was utilized where the span increased from the inlet to the exit at a 13 degree angle. A 5-hole probe traverse was used to measure exit total pressure. Pressure loss coefficients were calculated both along pitchwise and spanwise directions at 0.1 axial chord downstream of the blade trailing edge. CFD studies were conducted to compliment the experimental results. The backward facing step present with the upstream slot affects the approaching boundary layer and influences the passage horse-shoe vortex strength. The addition of coolant from the purge slot further increased the aerodynamic losses. However, the backward facing step of the upstream slot seems to be the predominant factor in affecting pressure losses when compared to with or without blowing cases. These results provide further understanding of the passage secondary flow characteristics and aid towards improved design of endwall passages. The heat transfer experiments, designed to find the heat transfer coefficient and the film cooling effectiveness are described in detail in part II of this paper [1]. C2 - 2013/// C3 - Proceedings of the ASME Turbo Expo DA - 2013/// DO - 10.1115/GT2013-94591 VL - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890181493&partnerID=MN8TOARS ER - TY - CONF TI - Comparison of data processing techniques for convective heat transfer measurements in a transient transonic hot wind tunnel AU - Xue, S. AU - Roy, A. AU - Ng, W.F. AU - Ekkad, S.V. AB - The present study compares two data processing techniques of calculating convective heat transfer coefficient (HTC) for experiments carried out at the Virginia Tech transonic wind tunnel facility. The discussion starts from the physical models and basic assumptions of the two methods denoted as Curve Fitting and Linear Regression, and is followed by application of both methods with the same set of experimental data for a comparative analysis. The linear regression method is found to be superior to the curve fitting method in eliminating the errors caused due to the transient starting up effect of the hot blow down. C2 - 2013/// C3 - ASME 2013 Gas Turbine India Conference, GTINDIA 2013 DA - 2013/// DO - 10.1115/GTINDIA2013-3733 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84896611165&partnerID=MN8TOARS ER - TY - CONF TI - A review of hole geometry and coolant density effect on film cooling AU - Ekkad, S. AU - Han, J.-C. AB - Improved film cooling hole geometries and effect of coolant density on film cooling have been a focus since the 1970s. One of the first studies on modifying hole exit to improve film cooling effectiveness and quantifying coolant density effect was from Prof. Goldstein’s group [1]. This paper traces the development and implementation of hole exit geometries as well as coolant density study from this landmark paper and its impact on future studies of advanced hole geometries under realistic engine-like coolant to mainstream density ratio conditions. This work is not intended to be a comprehensive review of the literature. It is aimed at providing an overview of the influence of ref. [1] over the past 4 decades. C2 - 2013/// C3 - ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 DA - 2013/// DO - 10.1115/HT2013-17250 VL - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893010995&partnerID=MN8TOARS ER - TY - JOUR TI - 75th Anniversary Special Issues AU - Phinney, L.M. AU - Ekkad, S.V. T2 - Journal of Thermal Science and Engineering Applications DA - 2013/5/17/ PY - 2013/5/17/ DO - 10.1115/1.4023582 VL - 5 IS - 2 SP - 020301 SN - 1948-5085 1948-5093 UR - http://dx.doi.org/10.1115/1.4023582 ER - TY - CONF TI - Test capabilities in the CCAPS/CSDL augmentor development facility AU - Blanchard, R. AU - Wickersham, A. AU - Yeaton, I. AU - Fleischman, C. AU - Ekkad, S. AU - Ng, W. AU - Vandsburger, U. AU - Ma, L. AU - Lowe, T. AB - The Commonwealth Center for Aerospace and Propulsion Systems (CCAPS) has developed an augmentor development test facility at Virginia Tech’s Combustion System Dynamics Lab (CSDL) that will enable rapid evaluation of augmentor concepts as well as the development of diagnostic techniques for measuring heat release, species concentrations, flame speeds, pressure loss, and other quantities relevant to augmentor performance. This paper provides an overview of the rig’s design and capabilities and the diagnostic techniques that are being developed. C2 - 2013/// C3 - 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013 DA - 2013/// DO - 10.2514/6.2013-32 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85086949414&partnerID=MN8TOARS ER - TY - CONF TI - Effect of hole exit shaping on film cooling performance for tripod hole injection over a flat surface AU - LeBlanc, C.N. AU - Ramesh, S. AU - Ekkad, S.V. AU - Alvin, M.A. AB - The effect of hole exit shaping on both heat transfer coefficient and film cooling effectiveness of tripod injection holes is examined experimentally on a flat plate. Previously, it has been clearly proven that tripod hole configurations provide at least 50–60% more cooling effectiveness while using 50% less coolant than standard cylindrical and shaped hole exit geometries. Temperature data is collected using infrared thermography at different operating conditions to determine the benefit of shaping the hole exits for an already proven tripod hole configuration. The test rig consists of a rectangular test section with a main stream flow at 7.9 m/s and coolant flow injected through the bottom surface through the film cooling injection holes. A unique transient IR technique has been used to determine both the adiabatic film effectiveness and heat transfer coefficient from a single test. Two different exit shaping have been considered, one with a 5° flare and layback and one with a 10° flare and layback. Results show that exit shaping improves the performance of these tripod holes compared to the cylindrical hole exits. The 10° flare and layback exit performs slightly better than the 5° flare and layback exit. C2 - 2013/// C3 - Proceedings of the ASME Turbo Expo DA - 2013/// DO - 10.1115/GT2013-94456 VL - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890154225&partnerID=MN8TOARS ER - TY - CONF TI - Effect of endwall contouring in presence of upstream leakage flow in a transonic turbine blade passage: Heat transfer measurements AU - Roy, A. AU - Blot, D. AU - Ekkad, S. AU - Ng, W.F. AU - Lohaus, A.S. AU - Crawford, M.E. AB - Described in this paper is the design of and initial ground test results from a small spacecraft propulsion system. The system consists of a 25 N PMMA and nitrous oxide main hybrid thruster and multiple 1 N ethylene and nitrous oxide bipropellant reaction control thrusters (although only a single reaction control thruster has been tested). The primary objective of the propulsion system development project is to develop an inexpensive system that uses environmentally benign propellants and has performance comparable to the hydrazine and nitrogen tetraoxide bipropellants systems commonly used. Ground test results (using a non flight-weight configuration) show that reliable ignition and efficient and stable combustion have been achieved in the reaction control thruster. Ground testing of the main thruster is underway but is not complete at the point in time. C2 - 2013/// C3 - 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference DA - 2013/// DO - 10.2514/6.2013-3635 VL - 1 PartF UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85071590348&partnerID=MN8TOARS ER - TY - CONF TI - Biomass/coal co-pyrolysis and co-combustion characterization AU - Liu, G. AU - Agarwal, G. AU - Lattimer, B. AU - Ekkad, S. C2 - 2013/// C3 - 8th US National Combustion Meeting 2013 DA - 2013/// VL - 3 SP - 2584-2591 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84943399074&partnerID=MN8TOARS ER - TY - CONF TI - High Performance Yacht Design with Abaqus AU - Fong, Rey-Yie AU - Tsai, Ray AU - Lin, Yu-Chieh AU - Ou, Chia-Chuan C2 - 2013/// C3 - SIMULIA Community Conference DA - 2013/// ER - TY - BOOK TI - Transport Category Aircraft Certification Flight Test Guide DA - 2013/// PY - 2013/// ER - TY - BOOK TI - Civil Airplane Flight Test Introduction for Special Flight Service and Ground Support Condition DA - 2013/// PY - 2013/// ER - TY - CONF TI - The mechanics and stability of gold nanoparticle-oligo-ligand-DNA systems AU - McLaughlin, L.A. AU - Zikry, M.A. C2 - 2013/// C3 - Materials Research Society Symposium Proceedings DA - 2013/// DO - 10.1557/opl.2013.501 VL - 1513 SP - 6-11 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84899757656&partnerID=MN8TOARS ER - TY - CONF TI - Microstructural behavior of energetic crystalline aggregates AU - Labarbera, D. AU - Zikry, M.A. C2 - 2013/// C3 - Materials Research Society Symposium Proceedings DA - 2013/// DO - 10.1557/opl.2013.503 VL - 1526 SP - 24-29 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84900318964&partnerID=MN8TOARS ER - TY - CONF TI - High dynamic range high sensitivity FBG interrogation AU - Stan, N. AU - Bailey, D. AU - Chadderdon, S. AU - Selfridge, R.H. AU - Schultz, S.M. AU - Webb, S. AU - Peters, K.J. AU - Zikry, M. AB - We present a fiber Bragg grating (FBG) interrogation method using a micro-controller board and optical filter that achieves high strain sensitivity and high dynamic range. This interrogation method allows high sensitivity detection of ultrasonic waves superimposed on low-frequency (on the order of 100Hz) vibrations of arbitrary magnitude. One possible application is in-situ structural health monitoring of windmill blades exposed to strong winds by using FBG sensors for detection of ultrasonic waves. Interrogator operation is based on the edge filtering method using a broadband source, fiber Fabry-Perot filter and a micro-controller board which acts as a control feedback loop that locks the filter wavelength to the mid-reflection point on the FBG spectrum. Wavelength locking method allows high sensitivity for edge filtering of high-frequency waves, while the feedback signal is the measurement of low-frequency vibration with high dynamic range. The concept of the interrogator operation and different implementations are described and discussed with experimental results. C2 - 2013/// C3 - Proceedings of SPIE - The International Society for Optical Engineering DA - 2013/// DO - 10.1117/12.2009875 VL - 8694 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84878401441&partnerID=MN8TOARS ER - TY - JOUR TI - Convective Air Mass Transfer in Submerged Superhydrophobic Surfaces: Turbulent Flow AU - Barth, C.A. AU - Tafreshi, H.V. AU - Gad-el-Hak, M. T2 - Bulletin of the American Physical Society DA - 2013/// PY - 2013/// VL - 58 IS - 18 SP - 349 SN - 0003-0503 ER - TY - CONF TI - Modeling Depth and Surface Dust-Loading in Pleated Air Filters AU - Fotovati, S. AU - Saleh, A. AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - American Filtration and Separation Society C2 - 2013/5/6/ CY - Bloomington, Minnesota DA - 2013/5/6/ PY - 2013/5/6/ ER - TY - JOUR TI - Convective Mass Transfer From Submerged Superhydrophobic Surfaces AU - Barth, Christina AU - Samaha, Mohamed AU - Tafreshi, Hooman AU - Gad-el-Hak, Mohamed T2 - International Journal of Flow Control AB - Longevity of entrapped air is an outstanding problem for using superhydrophobic coatings in submersible applications. Under pressure and flowing water, the air micropockets eventually dissolve into the ambient water or burst and diminish. Herein, we analyze from first principles a simple mass transfer problem. We introduce an effective slip to a Blasius boundary layer, and solve the hydrodynamic equations. A slowly evolving, non-similar solution is found. We then introduce the hydrodynamic solution to the two-dimensional problem of alternating solid-water and air-water interfaces to determine the convective mass transfer of air's dissolution into water. This situation simulates spanwise microridges, which is one of the geometries used for producing superhydrophobic surfaces. The mass-transfer problem has no similarity solution but is solvable using approximate integral methods. A mass-transfer solution is achieved as a function of the surface geometry (or gas area fraction), Reynolds number, and Schmidt n... DA - 2013/6// PY - 2013/6// DO - 10.1260/1756-8250.5.2.79 VL - 5 IS - 2 SP - 79-88 J2 - International Journal of Flow Control LA - en OP - SN - 1756-8250 UR - http://dx.doi.org/10.1260/1756-8250.5.2.79 DB - Crossref ER - TY - JOUR TI - On the effects of fiber orientation in permeability of fibrous media to power-law fluids AU - Emami, B. AU - Fotovati, S. AU - Amrei, M.M. AU - Tafreshi, H. Vahedi T2 - International Journal of Heat and Mass Transfer AB - In this note, for the first time, the flow of power-law fluids is numerically simulated in 3-D fibrous structures resembling the internal microstructure of fibrous hygiene products to study the effects of fibers’ in-plane and through-plane orientations on the media’s permeability. It was found that while the permeability of a fibrous material to a power-law fluid hardly depends on the in-plane orientation of the fibers, it increases with increasing the fibers’ through-plane orientation. Moreover, we developed a simple analytical expression that can be used together with the empirical correlation of Davies (1973) [16], modified with an equation derived by Banks (1987) [17], to predict the permeability of anisotropic fibrous media to power-law non-Newtonian fluids. The predictions of our formulation are compared with our numerical simulations and good agreement is observed. DA - 2013/5// PY - 2013/5// DO - 10.1016/j.ijheatmasstransfer.2013.01.025 VL - 60 SP - 375-379 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.01.025 DB - Crossref KW - Filtration KW - Non-Newtonian fluids KW - Transport processes KW - Porous media KW - Fibrous media KW - Nonwoven materials ER - TY - JOUR TI - Modeling performance of thin fibrous coatings with orthogonally layered nanofibers for improved aerosol filtration AU - Bucher, T.M. AU - Tafreshi, H. Vahedi AU - Tepper, G.C. T2 - Powder Technology AB - Advances in nanofiber fabrication techniques (e.g., electrospinning) have come to allow control over fiber distribution and orientation such that an ordered coating with fibers arranged in layers orthogonal to one another can potentially be produced. Such coatings can serve as a nano-sieve that can be designed and placed on the downstream side of a conventional nonwoven fibrous filter to enhance its performance (collection efficiency for a given pressure drop). This paper presents a thorough analysis of the performance characteristics of these thin coatings to guide the fabrication process in terms of the coatings' microstructural properties. In particular, we have found a correlation such that, for coatings composed of a given fiber size, there exists a corresponding particle size for which a coating's performance becomes independent of variations in fiber-to-fiber spacing (i.e., coating's non-homogeneity). We have also found that a coating's performance improves when its mass is distributed across more than one pair of orthogonal layers. DA - 2013/11// PY - 2013/11// DO - 10.1016/j.powtec.2013.07.023 VL - 249 SP - 43-53 J2 - Powder Technology LA - en OP - SN - 0032-5910 UR - http://dx.doi.org/10.1016/j.powtec.2013.07.023 DB - Crossref KW - Aerosol KW - Nanofiber KW - Nanofiber coating KW - Aerosol filtration KW - Modeling filtration KW - Electrospinning ER - TY - JOUR TI - Convective Mass Transfer From Submerged Superhydrophobic Surfaces: Turbulent Flow AU - Barth, Christina AU - Samaha, Mohamed AU - Tafreshi, Hooman AU - Gad-el-Hak, Mohamed T2 - International Journal of Flow Control AB - Superhydrophobic surfaces have received considerable attention in recent years. The surface has a strong water-repellent characteristic that could produce slip flow and drag reduction. The coating traps air within its micropores, such that a submerged moving body experiences shear-free and no-slip regions over, respectively, the air pockets and the solid surface. This, in turn, holds promise for a broad range of applications. Longevity of the entrapped air is an outstanding problem for these coatings. Under pressure and flowing water, the air micropockets eventually dissolve into the ambient water or burst and diminish. Herein, we analyze from first principles an air mass transfer problem. Using integral methods, we extend our prior laminar flow solution to turbulent flows. We introduce an effective slip to the turbulent boundary layer characterized by a modified 1/7-power law velocity profile. We then introduce the hydrodynamic solution to the two-dimensional problem of alternating solid-water and air-wa... DA - 2013/9// PY - 2013/9// DO - 10.1260/1756-8250.5.3-4.143 VL - 5 IS - 3-4 SP - 143-152 J2 - International Journal of Flow Control LA - en OP - SN - 1756-8250 UR - http://dx.doi.org/10.1260/1756-8250.5.3-4.143 DB - Crossref ER - TY - JOUR TI - Dual-scale 3-D approach for modeling radiative heat transfer in fibrous insulations AU - Arambakam, R. AU - Tafreshi, H. Vahedi AU - Pourdeyhimi, B. T2 - International Journal of Heat and Mass Transfer AB - Abstract In this work, a dual-scale computationally-affordable 3-D method is developed to simulate the transfer of radiative heat through fibrous media comprised of fibers with different diameters and orientations. The simulations start by generating a virtual fibrous material with specified microstructural properties and then compute the radiative properties of each fiber (i.e., effective phase function, as well as scattering and absorption coefficients) in the structure using the Mie Scattering theory. Considering independent scattering formulations for our fibrous media (media with high porosities), the radiative properties of the insulation material are computed by summing up the radiative properties of each individual fiber, after transforming the phase function values from the fiber’s local 3-D coordinates system to a fixed global coordinates system. The radiative properties of the media are then used in the Radiative Transfer Equation (RTE) equation, an integro-differential equation obtained for computing the attenuation and augmentation of an InfraRed ray’s energy as it travels through a fibrous medium. Using the Discrete Ordinate Method (DOM), the RTE is then discretized into a system of twenty four coupled partial differential equations and solved numerically using the FlexPDE program to obtain the rate of heat transfer through the entire thickness of the media. Studying media with different microstructural properties, it was quantitatively shown that increasing solid volume fraction, thickness, or fibers’ through-plane orientation increases the rate of heat transfer through insulation. With regard to the role of fiber diameter, it was found that there exists a fiber diameter for which radiation heat transfer through a fibrous media is minimal, ranging between 3 and 10 μm for glass fibers operating in a temperature range of about 340–750 K. DA - 2013/9// PY - 2013/9// DO - 10.1016/j.ijheatmasstransfer.2013.05.047 VL - 64 SP - 1109-1117 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.05.047 DB - Crossref KW - Radiative heat transfer KW - Dual-scale modeling KW - Insulation media KW - Fibrous media ER - TY - BOOK TI - Civil Airplane Flight Test Introduction for Special Flight Service and Ground Support Condition A3 - Chen, M. DA - 2013/// PY - 2013/// PB - Shanghai Jiaotong University Press SN - 9787313096944 ER - TY - BOOK TI - Transport Category Aircraft Certification Flight Test Guide AU - Chen, M. DA - 2013/// PY - 2013/// PB - Shanghai Jiaotong University Press ER - TY - JOUR TI - On applications and limitations of one-dimensional capillarity formulations for media with heterogeneous wettability AU - Bucher, T.M. AU - Vahedi Tafreshi, H. T2 - Applied Physics Letters AB - Force-balance-based one-dimensional algebraic formulations that are often used in characterizing the capillarity of a multi-component system (e.g., predicting capillary height rise in porous media) are discussed. It is shown that such formulations fail to provide accurate predictions when the distribution of wetting (or non-wetting) surfaces is not homogeneous. A more general mathematical formulation is suggested and used to demonstrate that for media with heterogeneous wettability, hydrophilic (or hydrophobic) surfaces clustered in groups will have less contribution to the overall capillarity of the system. DA - 2013/// PY - 2013/// DO - 10.1063/1.4811167 VL - 102 IS - 24 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84879824357&partnerID=MN8TOARS ER - TY - JOUR TI - Novel method to characterize superhydrophobic coatings AU - Samaha, M.A. AU - Vahedi Tafreshi, H. AU - Gad-el-Hak, M. T2 - Journal of Colloid and Interface Science AB - Superhydrophobic coatings possess a strong water-repellent characteristic, which, among several other potential applications, enhances the mobility of water droplets over the surface. The coating traps air within its micropores, such that a submerged moving body experiences shear-free and no-slip regions over, respectively, the air pockets and the solid surface. This, in turn, may lead to significant skin-friction reduction. The coating maintains its superhydrophobicity as long as the air remains entrapped. It is therefore of great interest to precisely measure the amount of trapped air, which is particularly difficult to estimate for coatings with disordered microstructures. A novel method to measure the effective thickness and gas volume fraction of superhydrophobic coatings with either ordered or random microroughness is advanced. The technique is applied to both aerogel and electrospun fibrous coatings. The experiments utilize a sensitive weighing scale (down to 10−4 gm) and height gauge (down to 10 μm) to determine the buoyancy force on an immersed, coated glass-slide substrate. The measured force is used to calculate the volume fraction of entrapped air. The coating’s effective thickness also follows from the same calculations. The sensitivity of our particular scale enables the measuring of thicknesses down to 3 μm, which is not readily possible with conventional thickness gauges. Smaller thicknesses could be measured using more sensitive scales. DA - 2013/// PY - 2013/// DO - 10.1016/j.jcis.2012.12.066 VL - 395 IS - 1 SP - 315-321 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875504535&partnerID=MN8TOARS KW - Superhydrophobic coatings KW - Fibers KW - Aerogel KW - Buoyancy force KW - Effective thickness KW - Gas volume fraction KW - Coating's thickness ER - TY - JOUR TI - A simple simulation method for designing fibrous insulation materials AU - Arambakam, R. AU - Vahedi Tafreshi, H. AU - Pourdeyhimi, B. T2 - Materials and Design AB - Conductive heat in a fibrous material travels through both the air (interstitial fluid) and the fibers (solid phase). The numerical simulations reported in this paper are devised to study the effective thermal conductivity of fibrous media with different microstructural parameters. Simulations were conducted in 3-D fibrous geometries resembling the microstructure of a fibrous material. Assuming that the heat transfer through the interstitial fluid is independent of the geometrical parameters of the solid phase (for when the porosity is held constant), the energy equation was solved only for the solid structures, and the resulting values were used to predict the effective thermal conductivity of the whole media. This treatment allows us to drastically reduce the computational cost of such simulations. The results indicate that heat conduction through the solid fibrous structure increases by increasing the material’s solid volume fraction, fiber diameter, and fibers’ through-plane orientations. The in-plane orientation of the fibers, on the other hand, did not show any significant influence on the material’s conductivity. It was also shown that the microstructural parameters of fibrous insulations have negligible influence on the material’s performance if the conductivity of the solid phase is close to that of the interstitial fluid. DA - 2013/// PY - 2013/// DO - 10.1016/j.matdes.2012.07.058 VL - 44 SP - 99-106 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84865316039&partnerID=MN8TOARS KW - Conductive heat transfer KW - Fibrous materials KW - Insulation materials KW - Numerical simulation ER - TY - JOUR TI - Predicting longevity of submerged superhydrophobic surfaces with parallel grooves AU - Emami, B. AU - Hemeda, A.A. AU - Amrei, M.M. AU - Luzar, A. AU - Gad-el-Hak, M. AU - Vahedi Tafreshi, H. T2 - Physics of Fluids AB - A mathematical framework is developed to predict the longevity of a submerged superhydrophobic surface made up of parallel grooves. Time-dependent integro-differential equations predicting the instantaneous behavior of the air–water interface are derived by applying the balance of forces across the air–water interface, while accounting for the dissolution of the air in water over time. The calculations start by producing a differential equation for the initial steady-state shape and equilibrium position of the air–water interface at t = 0. Analytical and/or numerical solutions are then developed to solve the time-dependent equations and to compute the volume of the trapped air in the grooves over time until a Wenzel state is reached as the interface touches the groove's bottom. For demonstration, a superhydrophobic surface made of parallel grooves is considered, and the influence of the groove's dimensions on the longevity of the surface under different hydrostatic pressures is studied. It was found that for grooves with higher width-to-depth ratios, the critical pressure (pressure at which departure from the Cassie state starts) is higher due to stronger resistance to deflection of the air–water interface from the air trapped in such grooves. However, grooves with higher width-to-depth ratios reach the Wenzel state faster because of their greater air–water interface areas. DA - 2013/// PY - 2013/// DO - 10.1063/1.4811830 VL - 25 IS - 6 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84880126879&partnerID=MN8TOARS ER - TY - JOUR TI - 3-D microscale simulation of dust-loading in thin flat-sheet filters: A comparison with 1-D macroscale simulations AU - Saleh, A.M. AU - Hosseini, S.A. AU - Vahedi Tafreshi, H. AU - Pourdeyhimi, B. T2 - Chemical Engineering Science AB - In this work, a microscale approach is undertaken to simulate the instantaneous pressure drop and collection efficiency of fibrous media exposed to particle loading, i.e., filter aging. The air flow field through 3-D disordered geometries representing the internal microstructure of a fibrous filter is obtained by numerically solving Stokes' equations. A Lagrangian approach is used to track the trajectory of particles through our virtual filter media and determine the filter's collection efficiency under different dust-load conditions. The calculations were conducted using the ANSYS CFD code enhanced with a series of in-house C++ subroutines. To better illustrate the value of such CPU-intensive 3-D microscale modeling, we compared the results of our simulations with those obtained from a 1-D macroscale model developed based on some of the pioneering studies reported in the literature. It was found that while the 1-D macroscale models can provide fast predictions for the pressure drop and collection efficiency of a given filter, they require a series of empirical correction factors or case-specific assumptions that limit their usage for design and development of new filter media. The 3-D microscale simulation methods, in contrast, are self-sufficient as they are developed based on first principles. With the current rate of progress in developing high-speed computers, it is expected that 3-D microscale simulations will be the preferred method of filter design in the near future. DA - 2013/// PY - 2013/// DO - 10.1016/j.ces.2013.06.007 VL - 99 SP - 284-291 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84879724263&partnerID=MN8TOARS KW - Aerosol KW - CFD KW - Filtration KW - Separations KW - Porous media KW - Fibrous media ER - TY - CONF TI - Power harvesting prediction of piezoelectric stack actuator from a shock event AU - Lee, A.J. AU - Wang, Y. AU - Inman, D.J. AB - This paper is to study free response of a spinning, cyclic symmetric rotor assembled to a flexible housing via multiple bearings. In particular, the rotor spins at a constant speed ω3, and the housing is excited via a set of initial displacements. The focus is to study ground-based response of the rotor through theoretical and numerical analyses. The paper consists of three parts. The first part is to briefly summarize an equation of motion of the coupled rotor-bearing-housing systems for the subsequent analyses. The equation of motion, obtained from prior research [1], employs a ground-based and a rotor-based coordinate system to the housing and the rotor, respectively. As a result, the equation of motion takes the form of a set of ordinary differential equations with periodic coefficients of frequency ω3. To better understand its solutions, a numerical model is introduced as an example. In this example, the rotor is a disk with four radial slots and the housing is a square plate with a central shaft. The rotor and housing are connected via two ball bearings. The second part of the paper is to analyze the rotor’s response in the rotor-based coordinate system theoretically. When the rotor is at rest, let ωH be the natural frequency of a coupled rotor-bearing-housing mode whose response is dominated by the housing. The theoretical analysis then indicates that response of the spinning rotor will possess frequency components ωH ± ω3 demonstrating the interaction of the spinning rotor and the housing. The theoretical analysis further shows that this splitting phenomenon results from the periodic coefficients in the equation of motion. The numerical example also confirms this splitting phenomenon. The last part of the paper is to analyze the rotor’s response in the ground-based coordinate system. A coordinate transformation shows that the ground-based response of the spinning rotor consists of two major frequency branches ωH − (k + 1) ω3 and ωH − (k − 1) ω3, where k is an integer determined by the cyclic symmetry and vibration modes of interest. The numerical example also confirms this derivation. C2 - 2013/// C3 - Proceedings of the ASME Design Engineering Technical Conference DA - 2013/// DO - 10.1115/DETC2013-12776 VL - 8 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84896950608&partnerID=MN8TOARS ER - TY - JOUR TI - Superomniphobic Surfaces for Effective Chemical Shielding AU - Pan, Shuaijun AU - Kota, Arun K. AU - Mabry, Joseph M. AU - Tuteja, Anish T2 - Journal of the American Chemical Society AB - Superomniphobic surfaces display contact angles >150° and low contact angle hysteresis with essentially all contacting liquids. In this work, we report surfaces that display superomniphobicity with a range of different non-Newtonian liquids, in addition to superomniphobicity with a wide range of Newtonian liquids. Our surfaces possess hierarchical scales of re-entrant texture that significantly reduce the solid-liquid contact area. Virtually all liquids including concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces. Consequently, they serve as effective chemical shields against virtually all liquids--organic or inorganic, polar or nonpolar, Newtonian or non-Newtonian. DA - 2013/// PY - 2013/// DO - 10.1021/ja310517s VL - 135 IS - 2 SP - 578–581 SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja310517s ER - TY - JOUR TI - Design of Ordered Wrinkled Patterns with Dynamically Tuned Properties AU - Yagüe, Jose Luis AU - Yin, Jie AU - Boyce, Mary C. AU - Gleason, Karen K. T2 - Physics Procedia AB - The formation of patterned surfaces is a common tool to engineer materials. The capability to design and reproduce detailed features is a key factor to fulfill requirements for functional surfaces. Generation of wrinkles via buckling of a stiff film on a compliant surface is an inexpensive, easy and reliable method to yield a patterned surface. The wrinkling method has been exploited in a wide variety of areas, including photovoltaics, microfluidics, adhesion, and anti-fouling systems. Here we show the ability to obtain deterministically ordered herringbone patterns. In a biaxially pre-stretched PDMS sample a thin film of a stiff coating is deposited by initiated chemical vapor deposition (iCVD). iCVD is a solvent- free technique that yields a conformal thin coating on virtually any substrate, giving a controllable thickness and tunable structural, mechanical, thermal, wetting, and swelling properties. Sequential release of the film-substrate system shows the transition from 1-D ripples to an ordered herringbone pattern. Wrinkle features can be controlled adjusting the film thickness, the initial load and the release process. Moreover, the surface topography can be dynamically tuned by applying a controlled mechanical stimulus. These properties make these materials excellent candidates for flexible applications. DA - 2013/// PY - 2013/// DO - 10.1016/j.phpro.2013.07.043 VL - 46 SP - 40-45 J2 - Physics Procedia LA - en OP - SN - 1875-3892 UR - http://dx.doi.org/10.1016/j.phpro.2013.07.043 DB - Crossref KW - iCVD KW - buckling KW - patterning ER - TY - BOOK TI - Metal Foams 2013 A3 - Rabiei, A. DA - 2013/// PY - 2013/// VL - 3 PB - MDPI. ER - TY - CHAP TI - Hydroforming Tribology AU - Ngaile, Gracious T2 - Encyclopedia of Tribology PY - 2013/// DO - 10.1007/978-0-387-92897-5_1067 SP - 1765–1774 PB - Springer US SN - 9780387928968 9780387928975 UR - http://dx.doi.org/10.1007/978-0-387-92897-5_1067 ER - TY - CONF TI - Noise-influenced dynamics of a vertically excited pendulum AU - Perkins, Edmon AU - Balachandran, Balakumar T2 - American Society of Mechanical Engineers C2 - 2013/// C3 - ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference DA - 2013/// SP - V07BT10A025-V07BT10A025 ER - TY - JOUR TI - Noise-influenced transient energy localization in an oscillator array AU - Perkins, Edmon AU - Chabalko, Chris AU - Balachandran, Balakumar T2 - Nonlinear Theory and Its Applications, IEICE DA - 2013/// PY - 2013/// VL - 4 IS - 3 SP - 232-243 ER - TY - CONF TI - Control and stabilization of a third-order nonholonomic system AU - Hervas, J.R. AU - Reyhanoglu, M. T2 - 2013 13th International Conference on Control, Automation and Systems (ICCAS 2013) AB - We study the control of a simplified model of a PPR robot manipulator subject to a third-order nonholonomic constraint. The model consists of a base body, which can translate and rotate freely in the plane, and a massless arm at the tip of which the end-effector is attached. It is assumed that two forces and a torque applied to the manipulator are available as control inputs. The objective is to control the robot end-effector movement while keeping the transverse jerk component is 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. C2 - 2013/// C3 - Proceedings of the 2013 13th International Conference on Control, Automation and Systems (ICCAS 2013) CY - Gwangju, South Korea DA - 2013/// PY - 2013/10/20/ DO - 10.1109/ICCAS.2013.6703856 SP - 17–22 PB - IEEE ER - TY - CONF TI - Thrust-vector control of a three-axis stabilized spacecraft with fuel slosh dynamics AU - Rubio Hervas, Jaime AU - Reyhanoglu, Mahmut AU - Tang, Hui T2 - 2013 13th International Conference on Control, Automaton and Systems (ICCAS) AB - The thrust vector control problem is studied for an upper-stage rocket with fuel slosh dynamics. The sloshing propellant is modeled as a multi-mass-spring system. The coupled equations of motion of the spacecraft and the fuel are expressed in terms of the three dimensional spacecraft translational velocity vector, the attitude, the angular velocity, and the internal coordinates representing the slosh modes. A Lyapunov-based nonlinear feedback control law is proposed to control the translational velocity vector and the attitude of the spacecraft, while attenuating the sloshing modes. A simulation example is included to illustrate the effectiveness of the control law. C2 - 2013/10// C3 - 2013 13th International Conference on Control, Automation and Systems (ICCAS 2013) CY - Gwangju, South Korea DA - 2013/10// PY - 2013/10/20/ DO - 10.1109/iccas.2013.6704015 PB - IEEE SN - 9788993215052 UR - http://dx.doi.org/10.1109/iccas.2013.6704015 ER - TY - CONF TI - Observer-based nonlinear control of slosh in liquid container transfer via a PPR robot AU - Rubio Hervas, Jaime AU - Reyhanoglu, Mahmut T2 - 2013 13th International Conference on Control, Automaton and Systems (ICCAS) AB - This paper studies the problem of observer-based control of slosh in liquid container transfer via a PPR robot. The control inputs for the PPR robot are two forces and a torque applied to the prismatic joints and the revolute joint, respectively. The control objective is point-to-point transfer of an open liquid container while suppressing the sloshing modes. A full-state feedback that uses a reduced-order observer for the estimation of the slosh state is proposed to achieve the objective. The effectiveness of the proposed observer-based control law is illustrated through a computer simulation. C2 - 2013/10// C3 - 2013 13th International Conference on Control, Automation and Systems (ICCAS 2013) CY - Gwangju, South Korea DA - 2013/10// PY - 2013/10/20/ DO - 10.1109/iccas.2013.6704018 PB - IEEE SN - 9788993215052 UR - http://dx.doi.org/10.1109/iccas.2013.6704018 ER - TY - JOUR TI - Nonlinear modeling and control of slosh in liquid container transfer via a PPR robot AU - Reyhanoglu, Mahmut AU - Rubio Hervas, Jaime T2 - Communications in Nonlinear Science and Numerical Simulation AB - This paper studies the point-to-point liquid container transfer control problem for a PPR robot. The robot manipulator is represented as three rigid links, and the liquid slosh dynamics are included using a multi-mass-spring model. It is assumed that two forces and a torque applied to the prismatic joints and the revolute joint, respectively, are available as control inputs. The objective is to control the robot end-effector movement while suppressing the sloshing modes. A nonlinear mathematical model that reflects all of these assumptions is first introduced. Then, Lyapunov-based feedback controllers are designed to achieve the control objective. Two cases are considered: partial-state feedback that does not use slosh state information and full-state feedback that uses both robot state and slosh state measurements or estimations. Computer simulations are included to illustrate the effectiveness of the proposed control laws. DA - 2013/6// PY - 2013/6// DO - 10.1016/j.cnsns.2012.10.006 VL - 18 IS - 6 SP - 1481-1490 J2 - Communications in Nonlinear Science and Numerical Simulation LA - en OP - SN - 1007-5704 UR - http://dx.doi.org/10.1016/j.cnsns.2012.10.006 DB - Crossref KW - Lyapunov method KW - Nonlinear control KW - Liquid slosh ER - TY - JOUR TI - Intracellular delivery of top-down fabricated tunable nano-plasmonic resonators AU - Ota, Sadao AU - Wang, Sheng AU - Ryu, Jongeun AU - Wang, Yuan AU - Chen, Yong AU - Zhang, Xiang T2 - Nanoscale AB - Engineered plasmonic structures fabricated using top-down technologies have demonstrated huge enhancements in the optical response of molecules, including Raman scattering. However, providing a sufficient number of such top-down fabricated nanostructures in solution has been a nontrivial task which has limited their potential in intracellular applications. Here we report the development of a protocol for the intracellular delivery of tunable nanoplasmonic resonators fabricated via scalable top-down techniques. This offers excellent possibilities towards the real-time parallel optical detection of intracellular molecular events. DA - 2013/// PY - 2013/// DO - 10.1039/c3nr02910g VL - 5 IS - 21 SP - 10179 J2 - Nanoscale LA - en OP - SN - 2040-3364 2040-3372 UR - http://dx.doi.org/10.1039/c3nr02910g DB - Crossref ER - TY - CONF TI - Soot measurements in high-pressure laminar diffusion flames AU - Steinmetz, S.A. AU - Fang, T. AU - Roberts, W.L. C2 - 2013/// C3 - Fall Technical Meeting of the Eastern States Section of the Combustion Institute 2013 DA - 2013/// SP - 318-323 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84946216954&partnerID=MN8TOARS ER - TY - CONF TI - Soot measurements in diluted high pressure laminar ethylene co-flow flames AU - Steinmetz, S.A. AU - Fang, T.G. AU - Roberts, W.L. C2 - 2013/// C3 - Proceedings of the 9th Asia-Pacific Conference on Combustion, ASPACC 2013 DA - 2013/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84905457491&partnerID=MN8TOARS ER - TY - CONF TI - Comparison of spray combustion for Jet-A and diesel in a constant volume chamber AU - Jing, W. AU - Roberts, W.L. AU - Fang, T. C2 - 2013/// C3 - Fall Technical Meeting of the Eastern States Section of the Combustion Institute 2013 DA - 2013/// SP - 477-482 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84946237266&partnerID=MN8TOARS ER - TY - CHAP TI - Fusion of Global and Local Measurements of Damage in Bonded Joints AU - Webb, Sean C. AU - Shin, Peter AU - Peters, Kara T2 - Fracture and Fatigue, Volume 7 AB - In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor embedded at the adhesive layer of a single composite lap joint subjected to harmonic excitation after fatigue loading. After a fully-reversed cyclic fatigue loading is applied to the composite lap joint, the full spectral response of the sensor is interrogated in reflection at 100 kHz during two states: with and without an added harmonic excitation. The dynamic response of the FBG sensor indicates strong nonlinearities as damage progresses. The short-time Fourier transform (STFT) is computed for the extracted peak wavelength information to reveal time-dependent frequencies and amplitudes of the dynamic FBG sensor response. Pulsed-phase thermography indicates a progression in defect size at the adhesive layer that strongly suggests non-uniform loading of the FBG sensor. These imaging results are applied to finite element modeling of the joint to simulate the non-linearities in the structural response. PY - 2013/7/23/ DO - 10.1007/978-3-319-00765-6_3 SP - 13-19 OP - PB - Springer International Publishing SN - 9783319007649 9783319007656 UR - http://dx.doi.org/10.1007/978-3-319-00765-6_3 DB - Crossref ER - TY - CHAP TI - Thermal Output Observations from Fe-Ni-Cr Metal Foil Strain Gages AU - Kieffer, T. P. AU - Zhu, Y. T2 - Advancement of Optical Methods in Experimental Mechanics, Volume 3 PY - 2013/8/8/ DO - 10.1007/978-3-319-00768-7_48 SP - 379-387 OP - PB - Springer International Publishing SN - 9783319007670 9783319007687 UR - http://dx.doi.org/10.1007/978-3-319-00768-7_48 DB - Crossref ER - TY - JOUR TI - The science of rotator cuff tears: translating animal models to clinical recommendations using simulation analysis AU - Mannava, Sandeep AU - Plate, Johannes F. AU - Tuohy, Christopher J. AU - Seyler, Thorsten M. AU - Whitlock, Patrick W. AU - Curl, Walton W. AU - Smith, Thomas L. AU - Saul, Katherine R. T2 - Knee Surgery, Sports Traumatology, Arthroscopy DA - 2013/7// PY - 2013/7// DO - 10.1007/S00167-012-2145-9 VL - 21 IS - 7 SP - 1610–1619 SN - 0942-2056 1433-7347 UR - http://dx.doi.org/10.1007/S00167-012-2145-9 KW - Rotator cuff KW - Tear KW - Repair KW - Animal model KW - Computational model KW - Botulinum neurotoxin KW - Ageing KW - Review ER - TY - CONF TI - On the nonlinear modeling of systems with higher-order nonholonomic constraints AU - Hervas, Jaime Rubio AU - Reyhanoglu, Mahmut T2 - 2013 13th International Conference on Control, Automaton and Systems (ICCAS) AB - This paper studies the nonlinear modeling problem for systems with higher-order nonholonomic constraints using tools from theoretical mechanics. A general control systems approach is developed for such systems. The applicability of the theoretical development is illustrated through a point mass moving on a constant-torsion space curve. C2 - 2013/10// C3 - 2013 13th International Conference on Control, Automation and Systems (ICCAS 2013) DA - 2013/10// DO - 10.1109/iccas.2013.6704064 PB - IEEE SN - 9788993215052 UR - http://dx.doi.org/10.1109/iccas.2013.6704064 DB - Crossref ER - TY - CONF TI - Robust nonlinear aircraft tracking control using synthetic jet actuators AU - MacKunis, W. AU - Subramanian, S. AU - Mehta, S. AU - Ton, C. AU - Curtis, J. W. AU - Reyhanoglu, M. T2 - 2013 IEEE 52nd Annual Conference on Decision and Control (CDC) AB - A robust, nonlinear tracking control strategy is presented for an aircraft equipped with synthetic jet actuators (SJA). The control law is designed to be easily implementable, requiring no observers, function approximators, or adaptive laws. By exploiting minimal knowledge of the structure of the nonlinear SJA dynamic model, a matrix decomposition technique is exploited to compensate for the input-multiplicative parametric uncertainty inherent in the SJA dynamics. The control law is shown to yield global asymptotic trajectory tracking in the presence of parametric uncertainty, actuator nonlinearity, and unknown, nonlinear external disturbances. A rigorous Lyapunov-based stability analysis is utilized to prove the theoretical result, and numerical simulation results are provided to demonstrate the performance of the proposed control law. C2 - 2013/12// C3 - 52nd IEEE Conference on Decision and Control DA - 2013/12// DO - 10.1109/cdc.2013.6759885 PB - IEEE SN - 9781467357173 9781467357142 9781479913817 UR - http://dx.doi.org/10.1109/cdc.2013.6759885 DB - Crossref ER - TY - CONF TI - Estimation of debris hazard areas due to a space vehicle breakup at high altitudes AU - Reyhanoglu, Mahmut AU - Alvarado, Juan AU - Carmi, Avishy T2 - 2013 9th Asian Control Conference (ASCC) AB - With the recent developments in the Commercial Space Transportation industry, there has been a surge of interest in the analyses of the debris hazard areas due to a space vehicle breakup and the risk posed to the aircraft in the national airspace system as well as to the people and the property on the ground. The focus of this paper is to study the problem of estimation of the extent of the airspace containing falling debris due to a space vehicle breakup. A precise computation of propagation of debris to the ground is not practical for many reasons. There is insufficient knowledge of the initial state vector; ambient wind conditions; and key parameters, including the ballistic coefficient distributions. In addition, propagation of all debris pieces to the ground would require extensive computer time. In this paper, a computationally efficient covariance propagation method is employed for the estimation of debris dispersion. C2 - 2013/6// C3 - 2013 9th Asian Control Conference (ASCC) DA - 2013/6// DO - 10.1109/ascc.2013.6606025 PB - IEEE SN - 9781467357692 9781467357678 UR - http://dx.doi.org/10.1109/ascc.2013.6606025 DB - Crossref ER - TY - CONF TI - Controllability and stabilizability of higher-order nonholonomic systems AU - Hervas, Jaime Rubio AU - Reyhanoglu, Mahmut T2 - 2013 9th Asian Control Conference (ASCC) AB - This paper studies the nonlinear modeling and control problem for systems with higher-order nonholonomic constraints using tools from differential geometry. A number of control-theoretic properties such as nonintegrability, controllability, and stabilizability are first derived. The applicability of the theoretical development is illustrated through a third-order nonholonomic system example: a planar PPR robot manipulator subject to a jerk constraint. In particular, it is shown that although the system is not asymptotically stabilizable to a given equilibrium configuration using a time-invariant continuous feedback, it is strongly accessible and small-time locally controllable at any equilibrium. C2 - 2013/6// C3 - 2013 9th Asian Control Conference (ASCC) DA - 2013/6// DO - 10.1109/ascc.2013.6606065 PB - IEEE SN - 9781467357692 9781467357678 UR - http://dx.doi.org/10.1109/ascc.2013.6606065 DB - Crossref ER - TY - JOUR TI - Estimation of debris dispersion due to a space vehicle breakup during reentry AU - Reyhanoglu, Mahmut AU - Alvarado, Juan T2 - Acta Astronautica AB - This paper studies the problem of the estimation of the extent of the airspace containing falling debris due to a space vehicle breakup. A precise propagation of debris to the ground is not practical for many reasons. There is insufficient knowledge of the initial state vector, ambient wind conditions, and the key parameters including the ballistic coefficients. In addition, propagation of all debris pieces to the ground would require extensive computer time. In this paper, a covariance propagation method is introduced for the estimation of debris dispersion due to a space vehicle breakup. The falling debris is simulated, and the data are analyzed to derive the probability of debris evolution in different altitude layers over time. The concept of positional probability ellipsoids is employed for the visualization of the results. Through a case study, it is shown that while the results of the covariance propagation method are in close agreement with those of the Monte Carlo method, the covariance propagation method is much more computationally efficient than the Monte Carlo method. DA - 2013/5// PY - 2013/5// DO - 10.1016/j.actaastro.2013.01.018 VL - 86 SP - 211-218 J2 - Acta Astronautica LA - en OP - SN - 0094-5765 UR - http://dx.doi.org/10.1016/j.actaastro.2013.01.018 DB - Crossref KW - Monte Carlo simulation KW - Covariance propagation KW - Estimation KW - Reentry debris dispersion ER - TY - CONF TI - A Critical Assessment of Airborne Wind Energy Systems AU - Samson, J. AU - Katebi, R. AU - Vermillion, C. T2 - 2nd IET Renewable Power Generation Conference (RPG 2013) AB - This paper focuses on the different types design of Airborne Wind Energy Systems (AWES) and their control architecture. The main focus of this paper will be on a novel lighter than air system developed by Altaeros Energies. AWES combines cutting edge innovation with practical engineering design to produce a system capable of rivalling conventional wind energy generation. Closed-form control strategies provide greater transparency and make tuning and debugging in real-time much easier. Control architecture of this type will be presented for the Altaeros system. This paper contributes to existing literature by focusing on the Altaeros design, discussing the relative advantages and disadvantages that this system holds over other airborne systems and conventional wind generation. C2 - 2013/// C3 - 2nd IET Renewable Power Generation Conference (RPG 2013) DA - 2013/// DO - 10.1049/cp.2013.1852 PB - Institution of Engineering and Technology SN - 9781849197588 UR - http://dx.doi.org/10.1049/cp.2013.1852 DB - Crossref ER - TY - CONF TI - Reference governor design for computationally efficient attitude and tether tension constraint enforcement on a lighter-than-air wind energy system AU - Kalabic, Uros AU - Vermillion, Chris AU - Kolmanovsky, Ilya T2 - 2013 European Control Conference (ECC) AB - In this paper, we propose a reference governor-based approach to guarantee enforcement of critical flight constraints on the Altaeros tethered, lighter-than-air wind energy system. While the high-altitude flight made available by the tethered system leads to significant increases in power production over traditional, tower-mounted systems, the freedom of motion resulting from the tethers and aerodynamic shell introduces critical attitude and tether tension constraints. To date, methods considered for enforcing these constraints have relied upon heuristic static maps or model predictive control (MPC). The former cannot guarantee transient constraint satisfaction, whereas the latter is computationally burdensome given Altaeros's current microcontroller capabilities. The approach pursued in this paper uses a reference governor, which is a computationally simple add-on to the existing controller that enforces transient and steady-state constraints. The methodology proposed in this paper is demonstrated through simulations on linear and nonlinear models of the longitudinal dynamics of the Altaeros system with wind gust disturbances. C2 - 2013/7// C3 - 2013 European Control Conference (ECC) DA - 2013/7// DO - 10.23919/ecc.2013.6669490 PB - IEEE SN - 9783033039629 UR - http://dx.doi.org/10.23919/ecc.2013.6669490 DB - Crossref ER - TY - CONF TI - Altitude and Crosswind Motion Control for Optimal Power-Point Tracking in Tethered Wind Energy Systems With Airborne Power Generation AU - Vermillion, Chris T2 - ASME 2013 Dynamic Systems and Control Conference AB - This paper presents a control strategy that combines altitude and crosswind motion control for tethered wind energy systems with airborne turbines and generators. The proposed algorithm adjusts altitude and induces an appropriate level of crosswind motion to present the system with an apparent wind speed that most closely meets, but does not exceed, the rated wind speed of the on-board turbine(s), thereby tracking the turbine’s optimal power point. The adjustment of both altitude and motion control, along with the reduction in crosswind motion and altitude when the rated wind speed is exceeded, differentiates the proposed control architecture from other strategies proposed in the literature. Initial control laws and simulation results are presented for the Altaeros lighter-than-air wind energy system. C2 - 2013/10/21/ C3 - Volume 3: Nonlinear Estimation and Control; Optimization and Optimal Control; Piezoelectric Actuation and Nanoscale Control; Robotics and Manipulators; Sensing; System Identification (Estimation for Automotive Applications, Modeling, Therapeutic Control in Bio-Systems); Variable Structure/Sliding-Mode Control; Vehicles and Human Robotics; Vehicle Dynamics and Control; Vehicle Path Planning and Collision Avoidance; Vibrational and Mechanical Systems; Wind Energy Systems and Control DA - 2013/10/21/ DO - 10.1115/dscc2013-3796 PB - American Society of Mechanical Engineers SN - 9780791856147 UR - http://dx.doi.org/10.1115/dscc2013-3796 DB - Crossref ER - TY - JOUR TI - Electricity in the Air: Tethered Wind Energy Systems AU - Vermillion, Chris AU - Fagiano, Lorenzo T2 - Mechanical Engineering AB - This article summarizes the fundamental dynamics and control attributes and challenges faced by stationary and crosswind airborne wind energy (AWE) systems. AWE systems have undergone rapid and steady technological development over the past decade, with several organizations demonstrating basic economic and technical viability of their concepts. The theoretical and numerical analyses performed so far indicate that crosswind systems have the potential to achieve a power curve similar in shape to that of current commercial wind turbines, with rated power of 2–5 MW. The ongoing development activities are increasing the viability of the concept; yet, several technical issues remain and need to be addressed, to definitively show that this technology can be scaled up to industrial size. The expert analysis suggests that AWE technologies are at the dawn of their development, and there is significant untapped potential for the use of innovative solutions in multiple fields such as materials, power electronics, and aerodynamics, to tackle problems. These challenges present a wealth of opportunities for future, multidisciplinary research and development activities. DA - 2013/9/1/ PY - 2013/9/1/ DO - 10.1115/1.2013-sep-5 VL - 135 IS - 09 SP - S13-S21 LA - en OP - SN - 0025-6501 1943-5649 UR - http://dx.doi.org/10.1115/1.2013-sep-5 DB - Crossref ER - TY - CHAP TI - Lighter-Than-Air Wind Energy Systems AU - Vermillion, Chris AU - Glass, Ben AU - Rein, Adam T2 - Airborne Wind Energy AB - Several wind energy concepts utilize airborne systems that contain lighterthan-air gas, which supplements aerodynamic lift and expands these systems’ available operating regimes. While lighter-than-air systems can incorporate the traction and crosswind flight motions of their heavier-than-air counterparts, several lighterthan-air concepts have also been designed to deliver large amounts of power under completely stationary operation and remain aloft during periods of intermittent wind. This chapter provides an overview of the history of LTA airborne wind energy concepts, including the design drivers and principal design constraints. The focus then turns to the structural and aerodynamic design principles behind lighterthan air systems, along with fundamental flight dynamic principles that must be addressed. A prototype design developed by Altaeros Energies is examined as an example of the application of these principles. The chapter closes with suggestions for future research to enable commercially-viable LTA systems. PY - 2013/// DO - 10.1007/978-3-642-39965-7_30 SP - 501-514 OP - PB - Springer Berlin Heidelberg SN - 9783642399640 9783642399657 UR - http://dx.doi.org/10.1007/978-3-642-39965-7_30 DB - Crossref ER - TY - JOUR TI - Measuring the coefficient of restitution of high speed microparticle impacts using a PTV and CFD hybrid technique AU - Reagle, C J AU - Delimont, J M AU - Ng, W F AU - Ekkad, S V AU - Rajendran, V P T2 - Measurement Science and Technology AB - A novel particle tracking velocimetry (PTV)/computational fluid dynamics (CFD) hybrid method for measuring coefficient of restitution (COR) has been developed which is relatively simple, cost-effective, and robust. A laser and camera system is used in the Virginia Tech Aerothermal Rig to measure velocity trajectories of microparticles. The method solves for particle impact velocity at the impact surface using a CFD solution and Lagrangian particle tracking. The methodology presented here attempts to characterize a difficult problem by a combination of established techniques, PTV and CFD, which have not been used in this capacity before. Erosion and deposition are functions of particle/wall interactions and COR is a fundamental property of these interactions. COR depends on impact velocity, angle of impact, temperature, particle composition, and wall material. Two sizes of Arizona road dust and one size of glass beads are impacted on to a 304 stainless steel coupon. The particles are entrained into a free jet of 27 m s−1 at room temperature. Impact angle was varied from 85° to 25° depending on particle. Mean results collected using this new technique compare favorably with trends established in literature. The utilization of this technique to measure COR of microparticle sand will help develop a computational model and serve as a baseline for further measurements at elevated air and wall temperatures. DA - 2013/9/4/ PY - 2013/9/4/ DO - 10.1088/0957-0233/24/10/105303 VL - 24 IS - 10 SP - 105303 J2 - Meas. Sci. Technol. OP - SN - 0957-0233 1361-6501 UR - http://dx.doi.org/10.1088/0957-0233/24/10/105303 DB - Crossref KW - particle tracking velocimetry KW - microparticle KW - coefficient of restitution ER - TY - JOUR TI - Non-fickian three-dimensional hindered moisture absorption in polymeric composites: Model development and validation AU - Grace, L.R. AU - Altan, M.C. T2 - Polymer Composites AB - A new, three-dimensional, anisotropic non-Fickian diffusion model is developed to characterize moisture absorption in polymeric composites. The new hindered diffusion model extends the classical Fickian theory to include the effects of the interaction of diffusing molecules with the chemical and physical structure of polymeric composites. The numerical solution of the hindered diffusion model is obtained for a three-dimensional, anisotropic domain by using a forward-time, centered-space finite difference technique. The moisture weight gain over time predicted by the model is shown to mimic a wide variety of anomalous absorption behavior, often exhibited by anisotropic composite laminates. The accuracy of the numerical solutions is verified by comparing the results to known analytical solutions of a one-dimensional, “Langmuir-type” diffusion model and for the limiting case of the three-dimensional Fickian model. The utility of the proposed hindered diffusion model is demonstrated by accurately recovering the absorption behavior of three different material systems reported in literature. First, it is shown that the hindered diffusion model can accurately predict the moisture absorption data for unidirectional glass-reinforced epoxy plates of varying dimensions exposed to a relative humidity of 80%. Second, the one-dimensional version of the model is applied to experimental moisture absorption data for isotropic epoxy resin samples of different thicknesses. Anomalous effects due to sample thickness reported in the original article are accurately captured. Third, the proposed model is shown to be more accurate than a two-stage diffusion model applied to moisture absorption data obtained from a woven 3-ply carbon fiber reinforced bismaleimide composite. POLYM. COMPOS., 34:1144–1157, 2013. © 2013 Society of Plastics Engineers DA - 2013/6/3/ PY - 2013/6/3/ DO - 10.1002/PC.22523 VL - 34 IS - 7 SP - 1144-1157 J2 - Polym. Compos. LA - en OP - SN - 0272-8397 UR - http://dx.doi.org/10.1002/PC.22523 DB - Crossref ER - TY - JOUR TI - Age-related degenerative functional, radiographic, and histological changes of the shoulder in nonhuman primates AU - Plate, Johannes F. AU - Bates, Christopher M. AU - Mannava, Sandeep AU - Smith, Thomas L. AU - Jorgensen, Matthew J. AU - Register, Thomas C. AU - Stehle, John R. AU - High, Kevin P. AU - Shively, Carol A. AU - Kaplan, Jay R. AU - Saul, Katherine R. AU - Tuohy, Christopher J. T2 - Journal of Shoulder and Elbow Surgery AB - Background Nonhuman primates have similar shoulder anatomy and physiology compared to humans, and may represent a previously underutilized model for shoulder research. This study sought to identify naturally occurring bony and muscular degeneration in the shoulder of nonhuman primates and to assess relationships between structural and functional aspects of the shoulder and measures of physical function of the animals. We hypothesized that age-related degenerative changes in the shoulders of nonhuman primates would resemble those observed in aging humans. Methods Middle-aged (n = 5; ages 9.4-11.8 years) and elderly (n = 6; ages 19.8-26.4 years) female vervet monkeys were studied for changes in mobility and shoulder function, and radiographic and histologic signs of age-related degeneration. Results Four out of 6 (4/6) elderly animals had degenerative changes of the glenoid compared to 0/5 of the middle-aged animals (P = .005). Elderly animals had glenoid retroversion, decreased joint space, walked slower, and spent less time climbing and hanging than middle-aged vervets (P < .05). Physical mobility and shoulder function correlated with glenoid version angle (P < .05). Supraspinatus muscles of elderly animals were less dense (P = .001), had decreased fiber cross-sectional area (P < .001), but similar amounts of nuclear material (P = .085). Degenerative rotator cuff tears were not observed in any of the eleven animals. Discussion and conclusion The vervet monkey naturally undergoes age-related functional, radiographic and histological changes of the shoulder, and may qualify as an animal model for selected translational research of shoulder osteoarthritis. Nonhuman primates have similar shoulder anatomy and physiology compared to humans, and may represent a previously underutilized model for shoulder research. This study sought to identify naturally occurring bony and muscular degeneration in the shoulder of nonhuman primates and to assess relationships between structural and functional aspects of the shoulder and measures of physical function of the animals. We hypothesized that age-related degenerative changes in the shoulders of nonhuman primates would resemble those observed in aging humans. Middle-aged (n = 5; ages 9.4-11.8 years) and elderly (n = 6; ages 19.8-26.4 years) female vervet monkeys were studied for changes in mobility and shoulder function, and radiographic and histologic signs of age-related degeneration. Four out of 6 (4/6) elderly animals had degenerative changes of the glenoid compared to 0/5 of the middle-aged animals (P = .005). Elderly animals had glenoid retroversion, decreased joint space, walked slower, and spent less time climbing and hanging than middle-aged vervets (P < .05). Physical mobility and shoulder function correlated with glenoid version angle (P < .05). Supraspinatus muscles of elderly animals were less dense (P = .001), had decreased fiber cross-sectional area (P < .001), but similar amounts of nuclear material (P = .085). Degenerative rotator cuff tears were not observed in any of the eleven animals. The vervet monkey naturally undergoes age-related functional, radiographic and histological changes of the shoulder, and may qualify as an animal model for selected translational research of shoulder osteoarthritis. DA - 2013/8// PY - 2013/8// DO - 10.1016/j.jse.2012.11.004 VL - 22 IS - 8 SP - 1019-1029 J2 - Journal of Shoulder and Elbow Surgery LA - en OP - SN - 1058-2746 UR - http://dx.doi.org/10.1016/j.jse.2012.11.004 DB - Crossref KW - Animal model KW - vervet monkey KW - shoulder KW - rotator cuff KW - osteoarthritis KW - aging KW - degeneration ER - TY - JOUR TI - Biomechanical Contributions of Posterior Deltoid and Teres Minor in the Context of Axillary Nerve Injury: A Computational Study AU - Crouch, Dustin L. AU - Plate, Johannes F. AU - Li, Zhongyu AU - Saul, Katherine R. T2 - The Journal of Hand Surgery AB - Purpose To determine whether transfer to only the anterior branch of the axillary nerve will restore useful function after axillary nerve injury with persistent posterior deltoid and teres minor paralysis. Methods We used a computational musculoskeletal model of the upper limb to determine the relative contributions of posterior deltoid and teres minor to maximum joint moment generated during a simulated static strength assessment and to joint moments during 3 submaximal shoulder movements. Movement simulations were performed with and without simulated posterior deltoid and teres minor paralysis to identify muscles that may compensate for their paralysis. Results In the unimpaired limb model, teres minor and posterior deltoid accounted for 16% and 14% of the total isometric shoulder extension and external rotation joint moments, respectively. During the 3 movement simulations, posterior deltoid produced as much as 20% of the mean shoulder extension moment, whereas teres minor accounted for less than 5% of the mean joint moment in all directions of movement. When we paralyzed posterior deltoid and teres minor, the mean extension moments generated by the supraspinatus, long head of triceps, latissimus dorsi, and middle deltoid increased to compensate. Compensatory muscles were not fully activated during movement simulations when posterior deltoid and teres minor were paralyzed. Conclusions Reconstruction of the anterior branch of the axillary nerve only is an appropriate technique for restoring shoulder abduction strength after isolated axillary nerve injury. When shoulder extension strength is compromised by extensive neuromuscular shoulder injury, reconstruction of both the anterior and posterior branches of the axillary nerve should be considered. Clinical relevance By quantifying the biomechanical role of muscles during submaximal movement, in addition to quantifying muscle contributions to maximal shoulder strength, we can inform preoperative planning and permit more accurate predictions of functional outcomes. To determine whether transfer to only the anterior branch of the axillary nerve will restore useful function after axillary nerve injury with persistent posterior deltoid and teres minor paralysis. We used a computational musculoskeletal model of the upper limb to determine the relative contributions of posterior deltoid and teres minor to maximum joint moment generated during a simulated static strength assessment and to joint moments during 3 submaximal shoulder movements. Movement simulations were performed with and without simulated posterior deltoid and teres minor paralysis to identify muscles that may compensate for their paralysis. In the unimpaired limb model, teres minor and posterior deltoid accounted for 16% and 14% of the total isometric shoulder extension and external rotation joint moments, respectively. During the 3 movement simulations, posterior deltoid produced as much as 20% of the mean shoulder extension moment, whereas teres minor accounted for less than 5% of the mean joint moment in all directions of movement. When we paralyzed posterior deltoid and teres minor, the mean extension moments generated by the supraspinatus, long head of triceps, latissimus dorsi, and middle deltoid increased to compensate. Compensatory muscles were not fully activated during movement simulations when posterior deltoid and teres minor were paralyzed. Reconstruction of the anterior branch of the axillary nerve only is an appropriate technique for restoring shoulder abduction strength after isolated axillary nerve injury. When shoulder extension strength is compromised by extensive neuromuscular shoulder injury, reconstruction of both the anterior and posterior branches of the axillary nerve should be considered. DA - 2013/2// PY - 2013/2// DO - 10.1016/j.jhsa.2012.11.007 VL - 38 IS - 2 SP - 241-249 J2 - The Journal of Hand Surgery LA - en OP - SN - 0363-5023 UR - http://dx.doi.org/10.1016/j.jhsa.2012.11.007 DB - Crossref KW - Biomechanics KW - deltoid KW - nerve KW - shoulder KW - simulation ER - TY - JOUR TI - Normal aging alters in vivo passive biomechanical response of the rat gastrocnemius-Achilles muscle–tendon unit AU - Plate, Johannes F. AU - Wiggins, Walter F. AU - Haubruck, Patrick AU - Scott, Aaron T. AU - Smith, Thomas L. AU - Saul, Katherine R. AU - Mannava, Sandeep T2 - Journal of Biomechanics AB - Predisposition to Achilles tendon (AT) ruptures in middle-aged individuals may be associated with age-related changes to inherent passive biomechanical properties of the gastrocnemius-Achilles (GC-AT) muscle-tendon unit, due to known muscle-tendon structural changes in normal aging. The goal of this study was to determine whether the passive biomechanical response of the GC-AT muscle-tendon unit was altered with age in 6 young (8 months) and 6 middle-aged (24 months) F344xBN hybrid rats from the National Institute on Aging colony. Fung's quasilinear viscoelastic (QLV) model was used to determine in vivo history and time-dependent load-relaxation response of the GC-AT. Effective stiffness and modulus were also estimated using linear regression analysis. Fung's QLV revealed a significantly decreased magnitude of the relaxation response (parameter C, p=0.026) in middle-aged animals compared to young animals (0.108±0.007 vs. 0.144±0.015), with similar time-dependent viscous GC-AT properties (τ(1), τ(2)). The product of elastic parameters (A*B), which represents the initial slope of the elastic response, was significantly increased by 50% in middle-aged rats (p=0.014). Estimated GC-AT stiffness increased 28% at peak tensions in middle-aged rats (2.7±0.2 N/mm) compared to young rats (1.9±0.2 N/mm; p=0.036). While the limitations of this animal model must be considered, the changes we describe could be associated with the observation that GC-AT pathology and injury is more common in middle-aged individuals. Further studies are necessary to characterize the load-to-failure behavior of AT in middle-aged compared to young animals. DA - 2013/2// PY - 2013/2// DO - 10.1016/j.jbiomech.2012.11.007 VL - 46 IS - 3 SP - 450-455 J2 - Journal of Biomechanics LA - en OP - SN - 0021-9290 UR - http://dx.doi.org/10.1016/j.jbiomech.2012.11.007 DB - Crossref KW - Achilles tendon rupture KW - Passive biomechanical properties KW - Quasilinear viscoelastic KW - Fung QLV KW - Aging ER - TY - JOUR TI - Use of a shock tube to determine the bi-axial yield of an aluminum alloy under high rates AU - Justusson, B. AU - Pankow, M. AU - Heinrich, C. AU - Rudolph, M. AU - Waas, A.M. T2 - International Journal of Impact Engineering AB - This paper presents a method for extracting the bi-axial rate dependent mechanical properties of thin homogenous materials, using a shock tube, demonstrated here using an aluminum alloy sheet. Rate dependence determination techniques such as Split Hopkinson Pressure Bar (SHPB) have long been used for determining uniaxial properties. Recent advances have led to modification of the SHPB to include a bulge cell to develop a so called “dynamic bulge test”. Due to the relative fixed nature of the SHPB, it is difficult to obtain lower strain rate response without significantly modifying the test fixture. Using shock wave loading, and a flat, circular thin plate specimen, a state of biaxial tensile stress is created at the center of the crown during intermediate to high rates of loading. An inverse modeling technique in conjunction with a finite element (FE) simulation technique is used to determine the rate dependent constitutive properties of the plate material. This work demonstrates the applicability of the shock loading method for extracting rate dependent properties of materials available in thin sheet form by using commercial grade aluminum. A finite element model of the shock response is used to determine the strain rate dependent mechanical properties using an optimization algorithm and an inverse modeling method. The results were found to be in agreement with previous literature and good correlation between the model and experimental results are presented here. DA - 2013/8// PY - 2013/8// DO - 10.1016/J.IJIMPENG.2013.01.012 VL - 58 SP - 55-65 J2 - International Journal of Impact Engineering LA - en OP - SN - 0734-743X UR - http://dx.doi.org/10.1016/J.IJIMPENG.2013.01.012 DB - Crossref KW - Shock KW - Mechanical properties KW - Strain rate KW - Multiaxial response ER - TY - JOUR TI - Gradient trajectory analysis in a Jet flow for turbulent combustion modelling AU - Gampert, M. AU - Schaefer, P. AU - Narayanaswamy, V. AU - Peters, N. T2 - Journal of Turbulence AB - Abstract Based on planar high-speed Rayleigh scattering measurements of the mixture fraction Z of propane discharging from a turbulent round jet into co-flowing carbon dioxide at nozzle-based Reynolds numbers Re 0 = 3000–8600, we use scalar gradient trajectories to investigate the local structure of the turbulent scalar field with a focus on the scalar turbulent/non-turbulent interface. The latter is located between the fully turbulent part of the jet and the outer flow. Using scalar gradient trajectories, we partition the turbulent scalar field into these three regions according to an approach developed by Mellado et al. (J.P. Mellado, L. Wang, and N. Peters, Gradient trajectory analysis of a scalar field with external intermittency, J. Fluid Mech. 626 (2009), pp. 333–365.). Based on these different regions, we investigate in a next step zonal statistics of the scalar probability density function (pdf) P(Z) as well as the scalar difference along the trajectory ΔZ and its mean scalar value Zm , where the latter two quantities are used to parameterize the scalar profile along gradient trajectories. We show that the scalar pdf P(Z) can be reconstructed from zonal gradient trajectory statistics of the joint pdf P(Zm , ΔZ). Furthermore, on the one hand we relate our results for the scalar turbulent/non-turbulent interface to the findings made in other experimental and numerical studies of the turbulent/non-turbulent interface, and on the other hand discuss them in the context of the flamelet approach and the modelling of pdfs in turbulent non-premixed combustion. Finally, we compare the zonal statistics for P(Z) with the composite model of Effelsberg and Peters (E. Effelsberg and N. Peters, A composite model for the conserved scalar pdf, Combust. Flame 50 (1983), pp. 351–360) and observe a very good qualitative and quantitative agreement. Keywords: jet flowgradient trajectoryturbulent/non-turbulent interfacescalar pdfflamelet theory Acknowledgements This work was funded by the Research School “BrenaRo” and the Cluster of Excellence “Tailor-Made Fuels from Biomass,” which is funded by the Excellence Initiative of the German Federal state governments to promote science and research at German universities. DA - 2013/1// PY - 2013/1// DO - 10.1080/14685248.2012.747688 VL - 14 IS - 1 SP - 147-164 J2 - Journal of Turbulence LA - en OP - SN - 1468-5248 UR - http://dx.doi.org/10.1080/14685248.2012.747688 DB - Crossref KW - jet flow KW - gradient trajectory KW - turbulent/non-turbulent interface KW - scalar pdf KW - flamelet theory ER - TY - JOUR TI - Conditional statistics of the turbulent/non-turbulent interface in a jet flow AU - Gampert, Markus AU - Narayanaswamy, Venkat AU - Schaefer, Philip AU - Peters, Norbert T2 - Journal of Fluid Mechanics AB - Abstract Using two-dimensional high-speed measurements of the mixture fraction $Z$ in a turbulent round jet with nozzle-based Reynolds numbers $R{e}_{0} $ between 3000 and 18 440, we investigate the scalar turbulent/non-turbulent (T/NT) interface of the flow. The mixture fraction steeply changes from $Z= 0$ to a final value which is typically larger than 0.1. Since combustion occurs in the vicinity of the stoichiometric mixture fraction, which is around $Z= 0. 06$ for typical fuel/air mixtures, it is expected to take place largely within the turbulent/non-turbulent interface. Therefore, deep understanding of this part of the flow is essential for an accurate modelling of turbulent non-premixed combustion. To this end, we use a composite model developed by Effelsberg & Peters ( Combust. Flame , vol. 50, 1983, pp. 351–360) for the probability density function (p.d.f.) $P(Z)$ which takes into account the different contributions from the fully turbulent as well as the turbulent/non-turbulent interface part of the flow. A very good agreement between the measurements and the model is observed over a wide range of axial and radial locations as well as at varying intermittency factor $\gamma $ and shear. Furthermore, we observe a constant mean mixture fraction value in the fully turbulent region. The p.d.f. of this region is thus of non-marching character, which is attributed physically to the meandering nature of the fully turbulent core of the jet flow. Finally, the location and in particular the scaling of the thickness $\delta $ of the scalar turbulent/non-turbulent interface are investigated. We provide the first experimental results for the thickness of the interface over the above-mentioned Reynolds number range and observe $\delta / L\sim R{ e}_{\lambda }^{- 1} $ , where $L$ is an integral length scale and $R{e}_{\lambda } $ the local Reynolds number based on the Taylor scale $\lambda $ , meaning that $\delta \sim \lambda $ . This result also supports the assumption often made in modelling of the stoichiometric scalar dissipation rate ${\chi }_{st} $ being a Reynolds-number-independent quantity. DA - 2013/8/29/ PY - 2013/8/29/ DO - 10.1017/JFM.2013.327 VL - 731 SP - 615-638 J2 - J. Fluid Mech. LA - en OP - SN - 0022-1120 1469-7645 UR - http://dx.doi.org/10.1017/JFM.2013.327 DB - Crossref KW - jets KW - shear layer turbulence KW - turbulent/non-turbulent interface ER - TY - JOUR TI - Ultrasound-Triggered Regulation of Blood Glucose Levels Using Injectable Nano-Network AU - Di, Jin AU - Price, Jennifer AU - Gu, Xiao AU - Jiang, Xiaoning AU - Jing, Yun AU - Gu, Zhen T2 - Advanced Healthcare Materials AB - The integration of an injectable insulin-encapsulated nano-network with a focused ultrasound system (FUS) can remotely regulate insulin release both in vitro and in vivo. A single subcutaneous injection of the nano-network with intermittent FUS administration facilitates reduction of the blood glucose levels in type 1 diabetic mice for up to 10 d. 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 - 2013/11/19/ PY - 2013/11/19/ DO - 10.1002/ADHM.201300490 VL - 3 IS - 6 SP - 811-816 J2 - Adv. Healthcare Mater. LA - en OP - SN - 2192-2640 UR - http://dx.doi.org/10.1002/ADHM.201300490 DB - Crossref ER - TY - JOUR TI - Superoleophobic surfaces: design criteria and recent studies AU - Kota, Arun K. AU - Mabry, Joseph M. AU - Tuteja, Anish T2 - Surface Innovations AB - Surfaces that display contact angles greater than 150° along with a low contact angle hysteresis for low surface tension liquids such as oils and alcohols are known as superoleophobic surfaces. Such surfaces are of interest for a diverse array of applications including self-cleaning, nonfouling, stain-free clothing and spill-resistant protective wear, drag reduction, microrobots for aqueous and chemical environments and icephobicity. Recently, significant advances have been made in understanding the criteria required to design superoleophobic surfaces. In this article, the authors discuss the roles of surface energy and roughness, the critical role of re-entrant texture and the role of hierarchical structure in fabricating superoleophobic surfaces. On the basis of this understanding, the authors also discuss two design parameters that allow for the systematic design of superoleophobic surfaces. The authors also summarize the recent studies on superoleophobic surfaces and emphasize the need for careful and diligent characterization. Finally, the authors conclude with the major challenges and opportunities for research on superoleophobic surfaces. DA - 2013/6// PY - 2013/6// DO - 10.1680/si.12.00017 VL - 1 IS - 2 SP - 71-83 J2 - Surface Innovations LA - en OP - SN - 2050-6252 2050-6260 UR - http://dx.doi.org/10.1680/si.12.00017 DB - Crossref KW - hierarchical KW - rough surface KW - superhydrophobicity KW - superoleophobicity KW - surface chemistry ER - TY - JOUR TI - Superomniphobic surfaces: Design and durability AU - Kota, Arun K. AU - Choi, Wonjae AU - Tuteja, Anish T2 - MRS Bulletin DA - 2013/5// PY - 2013/5// DO - 10.1557/mrs.2013.101 VL - 38 IS - 5 SP - 383-390 J2 - MRS Bull. LA - en OP - SN - 0883-7694 1938-1425 UR - http://dx.doi.org/10.1557/mrs.2013.101 DB - Crossref ER - TY - JOUR TI - High-efficiency, ultrafast separation of emulsified oil–water mixtures AU - Kota, Arun K AU - Tuteja, Anish T2 - NPG Asia Materials AB - Multiple oil spill disasters over the last few years have highlighted the challenges of effective oil–water separation. The separation of oil–water micro- and nano-emulsions (emulsions with dispersed droplet sizes in the micro- or nano-meter range) can be particularly difficult.1, 2 Shi et al.3 from the Chinese Academy of Sciences in Suzhou and Beijing have now developed ultrathin carbon nanotube membranes that can separate a wide range of oil–water micro- and nano-emulsions with separation efficiency >99.9%. Perhaps more significantly, the separation fluxes are 2–3 orders of magnitude higher than those obtained with current commercially available separation membranes. DA - 2013/8// PY - 2013/8// DO - 10.1038/am.2013.34 VL - 5 IS - 8 SP - e58-e58 J2 - NPG Asia Mater LA - en OP - SN - 1884-4049 1884-4057 UR - http://dx.doi.org/10.1038/am.2013.34 DB - Crossref ER - TY - JOUR TI - Amphiphilic Colloidal Surfactants Based on Electrohydrodynamic Co-jetting AU - Yoon, Jaewon AU - Kota, Arun AU - Bhaskar, Srijanani AU - Tuteja, Anish AU - Lahann, Joerg T2 - ACS Applied Materials & Interfaces AB - A novel synthetic route for the preparation of amphiphilic Janus particles based on electrohydrodynamic cojetting has been developed. In this approach, selective encapsulation of hydrophobic fluorodecyl-polyhedral oligomeric silsesquioxane (F-POSS) in one compartment and a poly(vinyl alcohol) in the second compartment results in colloidal particles with surfactant-like properties including the self-organization at oil–water and air–water interfaces. Successful localization of the respective polymers in different compartments of the same particle is confirmed by a combination of fluorescence microscopy, vibrational spectroscopy, and ζ-potential measurements. We believe that this straightforward synthetic approach may lead to a diverse class of surface-active colloids that will have significant relevance ranging from basic scientific studies to immediate applications in areas, such as pharmaceutical sciences or cosmetics. DA - 2013/10/24/ PY - 2013/10/24/ DO - 10.1021/am403516h VL - 5 IS - 21 SP - 11281-11287 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/am403516h DB - Crossref KW - electrohydrodynamic cojetting KW - amphiphilic particles KW - polymers ER - TY - JOUR TI - Ballistic impact damages of 3-D angle-interlock woven composites based on high strain rate constitutive equation of fiber tows AU - Luan, K. AU - Sun, B. AU - Gu, B. T2 - International Journal of Impact Engineering AB - This paper reports the ballistic impact damage of three-dimensional angle-interlock woven composite (3DAWC) under a hemispherical rigid projectile penetration on the basis of high strain rate constitutive equations of fiber tows and multi-scale geometrical model of the 3DAWC. The constitutive equations of the Twaron® fiber tows (poly paraphenylene terepthalamide, PPTA) under high strain rates have been established to characterize the mechanical behaviors under impact loading. The Twaron® fiber tows were assumed as transversely isotropic viscoelastic material to derive the constitutive equations. The maximum strain failure criterion was adopted for defining the failure of the PPTA fiber tows. A user-defined subroutine UMAT (FORTRAN user-material subroutine) was written for combining both the constitutive equations and the failure criterion in numerical calculation. Based on a micro-scale geometrical model of the 3DAWC, the UMAT for the PPTA fiber tows was combined with a commercial available finite element method (FEM) software package LS-DYNA to calculate the ballistic impact damage when the 3DAWC panel penetrated under a hemispherical–cylindrical steel projectile. It was found that the FEM simulation agrees well with the experimental results. The impact damage morphologies and damage propagations, the energy absorptions and the stress distributions in the 3DAWC panel were presented to elucidate the ballistic penetration damage mechanisms for optimizing the ballistic protection capacity of the 3-D woven composite material. DA - 2013/// PY - 2013/// DO - 10.1016/j.ijimpeng.2013.02.003 VL - 57 SP - 145-158 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875133847&partnerID=MN8TOARS KW - 3-D angle-interlock woven composite (3DAWC) KW - Poly paraphenylene terepthalamide (PPTA) filament yarn KW - User-defined material subroutine (UMAT) KW - Multi-scale finite element model KW - Ballistic penetration damage ER - TY - JOUR TI - Editorial AU - Ngaile, Gracious AU - Kinsey, Brad L. AU - Kapoor, Shiv G. T2 - Journal of Manufacturing Processes DA - 2013/4// PY - 2013/4// DO - 10.1016/J.JMAPRO.2013.02.005 VL - 15 IS - 2 SP - 181-182 J2 - Journal of Manufacturing Processes LA - en OP - SN - 1526-6125 UR - http://dx.doi.org/10.1016/J.JMAPRO.2013.02.005 DB - Crossref ER - TY - JOUR TI - Part 1: Analytical modeling of symmetric multi-nose tube hydroforming AU - Alzahrani, Bandar AU - Ngaile, Gracious AU - Yang, Chen T2 - Journal of Manufacturing Processes AB - Part 1 of this series of papers presents an analytical model for a multi-nose tube hydroforming process based on a mechanistic approach. In this process, the tube is surrounded by a number of evenly distributed circular dies. The model was established based on equilibrium conditions, yielding criteria, geometrical relationships, and a volume constancy condition. The system of equations was derived and solved for various process parameters. The model validation was performed using finite element analysis and experiments. The model has the ability to predict process parameters such as stresses, strains, internal pressure, geometry variables, and thinning rate distribution. The model could be applied to regular planar tube hydroforming of polygonal shapes such as square, pentagon, or octagon. Details for establishing governing relationships for polygonal shape hydroforming from the multi-nose analytical model are given in Part 2 of this series of papers. DA - 2013/4// PY - 2013/4// DO - 10.1016/J.JMAPRO.2013.01.004 VL - 15 IS - 2 SP - 273-286 J2 - Journal of Manufacturing Processes LA - en OP - SN - 1526-6125 UR - http://dx.doi.org/10.1016/J.JMAPRO.2013.01.004 DB - Crossref KW - Multi-nose KW - Tube hydroforming KW - Finite element analysis KW - Analytical modeling ER - TY - JOUR TI - Part 2: Analytical modeling of regular planar polygon tube hydroforming as a special case of symmetric multi-nose tube hydroforming AU - Alzahrani, Bandar AU - Ngaile, Gracious T2 - Journal of Manufacturing Processes AB - Part 2 of this series of papers presents an analytical model for regular planar polygon tube hydroforming (THF) as a special case of the analytical model for symmetric multi-nose tube hydroforming. The governing equations derived for multi-nose THF in Part 1 were evaluated by taking the limit of die geometric variables, resulting in a new set of governing equations for regular polygon THF. The model was validated using finite element analysis and a THF experiment, where good agreement was obtained. The model is able to predict field variables such as stresses and strain distribution, thinning rate distribution, and deformed shape at a particular pressure. DA - 2013/4// PY - 2013/4// DO - 10.1016/J.JMAPRO.2013.01.002 VL - 15 IS - 2 SP - 287-297 J2 - Journal of Manufacturing Processes LA - en OP - SN - 1526-6125 UR - http://dx.doi.org/10.1016/J.JMAPRO.2013.01.002 DB - Crossref KW - Multi-nose KW - Polygon tube hydroforming KW - Finite element analysis KW - Analytical modeling ER - TY - JOUR TI - Aerodynamic effects on the accuracy of an end-over-end kick of an American football AU - Lee, W. M. AU - Mazzoleni, A. P. AU - Zikry, M. A. T2 - Sports Engineering DA - 2013/2/13/ PY - 2013/2/13/ DO - 10.1007/S12283-012-0110-Y VL - 16 IS - 2 SP - 99-113 J2 - Sports Eng LA - en OP - SN - 1369-7072 1460-2687 UR - http://dx.doi.org/10.1007/S12283-012-0110-Y DB - Crossref ER - TY - JOUR TI - Modeling the heterogeneous effects of retained austenite on the behavior of martensitic high strength steels AU - Wu, Q. AU - Shanthraj, P. AU - Zikry, M. A. T2 - International Journal of Fracture DA - 2013/9/6/ PY - 2013/9/6/ DO - 10.1007/S10704-013-9879-3 VL - 184 IS - 1-2 SP - 241-252 J2 - Int J Fract LA - en OP - SN - 0376-9429 1573-2673 UR - http://dx.doi.org/10.1007/S10704-013-9879-3 DB - Crossref KW - Dislocation-density KW - Crystal plasticity KW - Martensitic steel KW - Retained austenite KW - Failure ER - TY - JOUR TI - Ultralow Thermal Conductivity of Atomic/Molecular Layer-Deposited Hybrid Organic–Inorganic Zincone Thin Films T2 - Nano Letters AB - Atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques with atomic level control enable a new class of hybrid organic–inorganic materials with improved functionality. In this work, the cross-plane thermal conductivity and volumetric heat capacity of three types of hybrid organic–inorganic zincone thin films enabled by MLD processes and alternate ALD–MLD processes were measured using the frequency-dependent time-domain thermoreflectance method. We revealed the critical role of backbone flexibility in the structural morphology and thermal conductivity of MLD zincone thin films by comparing the thermal conductivity of MLD zincone films with an aliphatic backbone to that with aromatic backbone. Much lower thermal conductivity values were obtained in ALD/MLD-enabled hybrid organic–inorganic zincone thin films compared to that of the ALD-enabled W/Al2O3 nanolaminates reported by Costescu et al. [Science 2004, 303, 989–990], which suggests that the dramatic material difference between organic and inorganic materials may provide a route for producing materials with ultralow thermal conductivity. DA - 2013/11/13/ PY - 2013/11/13/ DO - 10.1021/nl403244s UR - http://dx.doi.org/10.1021/nl403244s KW - Atomic layer deposition KW - molecular layer deposition KW - hybrid organic-inorganic material KW - thermal conductivity ER - TY - JOUR TI - Thermoelectric Transport Across Nanoscale Polymer–Semiconductor–Polymer Junctions T2 - The Journal of Physical Chemistry C AB - There is an increasing interest in the thermoelectric (TE) properties of hybrid organic–inorganic structures, such as molecular junctions, organic–inorganic multilayers, and nanocomposites, owing to the recent success in nanostructuring of inorganic materials for high-efficiency thermoelectrics and the ability to synthesize hybrid materials in close analog to inorganic counterparts with much lower cost and greater flexibility. Compared to inorganic counterparts, the development of hybrid inorganic-polymer structures for TE applications are in a nascent stage, where theoretical understanding is very much needed and many potential nanoscale structures are yet to be explored. In this work, we study quasi-one-dimensional TE transport in a nanoscale polymer–semiconductor–polymer (PSP) junction, where a semiconductor quantum dot (QD) is trapped between two bulk polymers with aligned polymer chains. The Holstein small polaron model, which can be used for strong electron–phonon interaction in polymers beyond the perturbation theory, is used to model the transport in such a nanoscale PSP junction. We then use the Green’s function method along with the Landauer formula to calculate the TE properties of a nanoscale PSP junction, including the electrical conductance G, the Seebeck coefficient S, and the power factor GS2. Due to the sharp distribution of electron density of states in the polymer leads and the discrete energy levels in a QD, simultaneous enhancement of the Seebeck coefficient and the electrical conductance in nanoscale PSP junctions can be achieved when the energy levels are appropriately aligned, compared to metal–molecule–metal junctions. The theoretical approach to study nanoscale PSP junctions can be readily extended to the study of QD–polymer nanocomposites. The quantitative results obtained in this work can shed some light in material selection for the synthesis of hybrid inorganic–polymer nanocomposites, where theoretical guidance is much in need. DA - 2013/11/27/ PY - 2013/11/27/ DO - 10.1021/jp4084019 UR - http://dx.doi.org/10.1021/jp4084019 ER - TY - JOUR TI - Simultaneous measurement of thermal conductivity and heat capacity of bulk and thin film materials using frequency-dependent transient thermoreflectance method T2 - Review of Scientific Instruments AB - The increasing interest in the extraordinary thermal properties of nanostructures has led to the development of various measurement techniques. Transient thermoreflectance method has emerged as a reliable measurement technique for thermal conductivity of thin films. In this method, the determination of thermal conductivity usually relies much on the accuracy of heat capacity input. For new nanoscale materials with unknown or less-understood thermal properties, it is either questionable to assume bulk heat capacity for nanostructures or difficult to obtain the bulk form of those materials for a conventional heat capacity measurement. In this paper, we describe a technique for simultaneous measurement of thermal conductivity κ and volumetric heat capacity C of both bulk and thin film materials using frequency-dependent time-domain thermoreflectance (TDTR) signals. The heat transfer model is analyzed first to find how different combinations of κ and C determine the frequency-dependent TDTR signals. Simultaneous measurement of thermal conductivity and volumetric heat capacity is then demonstrated with bulk Si and thin film SiO2 samples using frequency-dependent TDTR measurement. This method is further testified by measuring both thermal conductivity and volumetric heat capacity of novel hybrid organic-inorganic thin films fabricated using the atomic∕molecular layer deposition. Simultaneous measurement of thermal conductivity and heat capacity can significantly shorten the development∕discovery cycle of novel materials. DA - 2013/3// PY - 2013/3// DO - 10.1063/1.4797479 UR - http://dx.doi.org/10.1063/1.4797479 ER - TY - CONF TI - A novel principal component analysis-based acceleration scheme for LES-ODT: An a priori study AU - Mirgolbabaei, H. AU - Echekki, T. C2 - 2013/// C3 - 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013 DA - 2013/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84881421712&partnerID=MN8TOARS ER - TY - JOUR TI - Virtualisation of stress distribution in heart valve tissue AU - Huang, Siyao AU - Huang, Hsiao-Ying Shadow T2 - Computer Methods in Biomechanics and Biomedical Engineering AB - This study presents an image-based finite element analysis incorporating histological photomicrographs of heart valve tissues. We report stress fields inside heart valve tissues, where heterogeneously distributed collagen fibres are responsible for transmitting forces into cells. Linear isotropic and anisotropic tissue material property models are incorporated to quantify the overall stress distributions in heart valve tissues. By establishing an effective predictive method with new computational tools and by performing virtual experiments on the heart valve tissue photomicrographs, we clarify how stresses are transferred from matrix to cell. The results clearly reveal the roles of heterogeneously distributed collagen fibres in mitigating stress developments inside heart valve tissues. Moreover, most local peak stresses occur around cell nuclei, suggesting that higher stress may be mediated by cells for biomechanical regulations. DA - 2013/3/12/ PY - 2013/3/12/ DO - 10.1080/10255842.2013.763937 VL - 17 IS - 15 SP - 1696-1704 J2 - Computer Methods in Biomechanics and Biomedical Engineering LA - en OP - SN - 1025-5842 1476-8259 UR - http://dx.doi.org/10.1080/10255842.2013.763937 DB - Crossref KW - heart valve tissue KW - finite element method KW - collagen fibre architecture KW - stress analysis ER - TY - CONF TI - Polymer-derived ceramic sensors for temperature measurement in harsh environment AU - Freese, D. AU - Shao, G. AU - Xu, C. AB - Development of an ultra-high temperature sensor advocates numerous applications in a variety of diverse fields. Combustion turbine engine advancements are predominately the benefactors of high temperature measurement capabilities; founded upon the principle of higher combustion reaction efficiency. The interior combustion chamber of a gas turbine is an extremely hostile environment for any typical material, especially a measurement component. Implementing the conductive properties and high temperature stability of a polymer derived ceramic (PDC) offers a solution to this predicament. Complementing the virtuous mechanical properties of the unique ceramic is micro-machinability and tunable electric characteristics established from the precursor compounds. The thermo-electric qualities of the PDC prepare formulation of a relationship between the changing temperatures of the research environment with respect to the internal resistance of the ceramic. An elected measurement system will actively monitor a PDC sensory circuit as well as reference thermocouple temperature. Series of response experiments were performed to characterize the functionality of the sensor within the high temperature environment. C2 - 2013/// C3 - Proceedings of the ASME Turbo Expo DA - 2013/// DO - 10.1115/GT2013-96031 VL - 4 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890205551&partnerID=MN8TOARS ER - TY - JOUR TI - Experimental investigation on the machinability of SiC nano-particles reinforced magnesium nanocomposites during micro-milling processes AU - Li, J. AU - Liu, J. AU - Liu, J. AU - Ji, Y. AU - Xu, C. T2 - International Journal of Manufacturing Research AB - This paper experimentally investigates the machinability of magnesium metal matrix composites (Mg-MMCs) with high volume fractions of SiC nano-particles using micro-milling process. The nanocomposites containing 5 vol.%, 10 vol.% and 15 vol.% reinforcements of SiC nano-particles were studied and compared with pure magnesium. The milling was carried out at different feedrates and spindle speeds chosen according to design of experiment (DOE) method. Cutting forces, surface morphology and surface roughness were measured to understand the machinability of the four different materials. Based on response surface methodology (RSM) design, experimental models and related contour plots were developed to build a connection between material properties and cutting parameters. Those models can be used to predict the cutting force, the surface roughness, and then optimise the machining conditions with the required cutting forces and surface roughness. DA - 2013/// PY - 2013/// DO - 10.1504/IJMR.2013.051840 VL - 8 IS - 1 SP - 64-84 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84873342204&partnerID=MN8TOARS ER - TY - JOUR TI - Design, fabrication, and characterization of linear multiplexed electrospray atomizers micro-machined from metal and polymers AU - Lojewski, B. AU - Yang, W. AU - Duan, H. AU - Xu, C. AU - Deng, W. T2 - Aerosol Science and Technology AB - Multiplexed electrospray is a promising aerosol generation technique to produce high throughput quasi-monodisperse droplets in the nanometer and micron size range. Here we report the design, fabrication, analysis, and performance of a linear electrospray (LINES) system. The fabrication of the nozzle array is based on a precision computer numerical control (CNC) micromachining platform with 1-micron resolution. This rapid prototyping approach offers the flexibility of creating devices from a wide range of materials including metals and polymers with packing densities on par with silicon microfabrication at 20 sources/cm for LINES devices and 460 sources/cm2 for the two-dimensional array. The LINES device uses a slot extractor design to simplify alignment and enhance operation robustness. We also used dummy nozzles (posts without fluidic channels) to offset edge effect on electric field and improved droplet size uniformity. We derived the approximate spray expansion model from charge conservation and Gauss’... DA - 2013/// PY - 2013/// DO - 10.1080/02786826.2012.734936 VL - 47 IS - 2 SP - 146-152 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876791780&partnerID=MN8TOARS ER - TY - JOUR TI - Cutting force prediction on micromilling magnesium metal matrix composites with nanoreinforcements AU - Liu, J. AU - Li, J. AU - Xu, C. T2 - Journal of Micro and Nano-Manufacturing AB - Due to its light weight, high creep, and wear resistance, magnesium metal matrix composites (Mg-MMCs) with nanosized reinforcements are promising for various industrial applications, especially those with high volume fractions of reinforcements. The machinability of Mg-MMCs and related cutting process modeling are important to study. In this paper, an analytical cutting force model is developed to predict cutting forces of Mg-MMC reinforced with SiC nanoparticles in micromilling process. This model is different from previous ones by encompassing the behaviors of nanoparticle reinforcements in three cutting scenarios, i.e., shearing, ploughing, and elastic recovery. By using the enhanced yield strength in the cutting force model, three major strengthening factors are incorporated, including load-bearing effect, enhanced dislocation density strengthening effect, and Orowan strengthening effect. In this way, material properties, such as the particle size and volume fraction as significant factors affecting the cutting forces, are explicitly considered. To validate the model, experiments based on various cutting conditions using two types of end mills (diameters as 100 μm and 1 mm) were conducted on pure Mg, Mg-MMCs with volume fractions of 5 vol. %, 10 vol. %, and 15 vol. %. The experimental results show a good agreement with the predicted cutting force value. DA - 2013/// PY - 2013/// DO - 10.1115/1.4023286 VL - 1 IS - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84894092314&partnerID=MN8TOARS KW - magnesium metal matrix composite KW - nanoparticle reinforcement KW - minimum chip thickness KW - particle size KW - volume fraction ER - TY - CONF TI - Analytical modeling and experimental validation of force ripple and friction force for general direct drive systems AU - Zhao, R. AU - Xu, C. AB - In this paper, we present a systematic modeling method of direct drive systems. Experiments are designed to decouple and model friction and force ripple separately, which are two major sources of tracking error. Three different optimization methods, least square method, nonlinear least square method and particle swarm optimization are used for parameter optimization. The analytical form of the model makes it easy to use in engineering practices. All results are obtained and verified experimentally. The method presented in this paper can also be used to model other mechanical systems. C2 - 2013/// C3 - ASME 2013 International Manufacturing Science and Engineering Conference Collocated with the 41st North American Manufacturing Research Conference, MSEC 2013 DA - 2013/// DO - 10.1115/MSEC2013-1058 VL - 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890282920&partnerID=MN8TOARS ER - TY - CONF TI - A Biomechanical Study of Directional Mechanical Properties of Porcine Skin Tissues AU - Huang, Hsiao-Ying Shadow AU - Huang, Siyao AU - Gettys, Taylor AU - Prim, Peter AU - Harrysson, Ola AB - Skin is a multilayered composite material and composed principally of the proteins collagen, elastic fibers, and fibroblasts. The direction-dependent material properties of skin tissue is important for physiological functions like skin expansion. The current study has developed methods to characterize the directional biomechanical properties of porcine skin tissues. It is observed that skin tissue has a nonlinear anisotropy biomechanical behavior, where the parameters of material stiffness is 378 ±160 kPa in the preferred-fiber direction and 65.96±40.49 kPa in the cross-fiber direction when stretching above 30% strain equibiaxially. The results from the current study will help optimize functional skin stretching for patients requiring large surface area skin grafts and reconstructions due to burns or other injuries. C2 - 2013/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition CY - San Diego, CA DA - 2013/// DO - 10.1115/IMECE2013-63829 ER - TY - SOUND TI - Polymer Derived Ceramic Sensors for Ultra-High Temperature Application AU - Shao, G. AU - Freese, D. AU - Xu, C. AU - An, L. DA - 2013/// PY - 2013/// ER - TY - JOUR TI - Unsteady pitching flat plates AU - Granlund, Kenneth O. AU - Ol, Michael V. AU - Bernal, Luis P. T2 - JOURNAL OF FLUID MECHANICS AB - Abstract Direct force measurements and qualitative flow visualization were used to compare flow field evolution versus lift and drag for a nominally two-dimensional rigid flat plate executing smoothed linear pitch ramp manoeuvres in a water tunnel. Non-dimensional pitch rate was varied from 0.01 to 0.5, incidence angle from 0 to 90°, and pitch pivot point from the leading to the trailing edge. For low pitch rates, the main unsteady effect is delay of stall beyond the steady incidence angle. Shifting the time base to account for different pivot points leads to collapse of both lift/drag history and flow field history. For higher rates, a leading edge vortex forms; its history also depends on pitch pivot point, but linear shift in time base is not successful in collapsing lift/drag history. Instead, a phenomenological algebraic relation, valid at the higher pitch rates, accounts for lift and drag for different rates and pivot points, through at least 45° incidence angle. DA - 2013/10// PY - 2013/10// DO - 10.1017/jfm.2013.444 VL - 733 SP - SN - 1469-7645 KW - low-dimensional models KW - nonlinear dynamical systems KW - separated flows KW - vortex flows KW - wakes/jets ER - TY - JOUR TI - Experiments on free-to-pivot hover motions of flat plates AU - Granlund, K. AU - Ol, M. AU - Bernal, L. T2 - Journal of Fluids and Structures DA - 2013/// PY - 2013/// VL - 40 SP - 337-355 ER - TY - JOUR TI - Decoupled Implicit Method for Aerothermodynamics and Reacting Flows AU - Candler, Graham V. AU - Subbareddy, Pramod K. AU - Nompelis, Ioannis T2 - AIAA JOURNAL AB - We propose a new implicit computational fluid dynamics method for steady-state compressible reacting flows. The concept is to decouple the total mass, momentum, and energy conservation equations from the species mass and internal energy equations and to solve the two equation sets sequentially. With certain approximations to the implicit system, it is possible to dramatically reduce the cost of the solution with little to no penalty on the convergence properties. Importantly, the cost of the decoupled implicit problem scales linearly with the number of species, as opposed to the quadratic scaling for the conventional fully coupled method. Furthermore, the new approach reduces the memory requirements by a significant factor. The decoupled implicit method shows promise for the application to aerothermodynamics problems and reacting flows. DA - 2013/5// PY - 2013/5// DO - 10.2514/1.j052070 VL - 51 IS - 5 SP - 1245-1254 SN - 0001-1452 ER - TY - CONF TI - Robust control of switched linear systems via min of quadratics AU - Yuan, C. Z. AU - Wu, F. AB - In this paper, we will investigate the robust switching control problem for switched linear systems by using a class of composite quadratic functions, the min (of quadratics) function, to improve performance and enhance control design flexibility. The robustness is reflected in two prospectives including the ℋ ∞ performance and arbitrary switching of subsystems. A hysteresis min-switching strategy is employed to orchestrate the switching among a collection of controllers. The synthesis conditions for both state feedback and output feedback control problems are derived in terms of a set of linear matrix inequalities (LMIs) with linear search over scalar variables. The proposed min function based approach unifies the existing single Lyapunov function based method and multiple Lyapunov function based method in a general framework, and the derived LMI conditions cover the existing LMI conditions as special cases. Numerical studies are included to demonstrate the advantages of the proposed control design approach. C2 - 2013/// C3 - Proceedings of the ASME 2013 Dynamic Systems and Control Conference (DSCC2013), vol. 1 DA - 2013/// DO - 10.1115/dscc2013-3715 ER - TY - JOUR TI - Design, fabrication and characterization of a bi-frequency co-linear array (7.5MHz/15MHz) AU - Wang, Zhuochen AU - Li, Sibo AU - Jiang, Xiaoning AU - Liu, Ruibin AU - Geng, Xuecang T2 - 2013 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS) AB - Ultrasound imaging with high resolution and large field of depth is important in disease diagnosis, surgery guidance and post-surgery assessment. Conventional ultrasound imaging arrays work at a particular frequency, with -6dB fractional bandwidth of <; 100%, limiting the resolution or field of depth in many ultrasound imaging cases. This paper presented design of a 7.5 MHz / 15 MHz bi-frequency co-linear array prototype with a wide bandwidth of 5MHz-20 MHz, which can be significant in a broad range of biomedical ultrasound imaging applications. To demonstrate the concept, a 32-element 1-D linear sub-array was fabricated, followed by element characterization and beamforming tests using a Verasonics system. Beam steering at +/- 40 degree was achieved without obvious side lobes. The initial results suggest great potential of this bi-frequency co-linear array for medical imaging with high resolution and large field of depth. DA - 2013/// PY - 2013/// DO - 10.1109/ultsym.2013.0131 SP - 504-507 SN - 1948-5719 KW - bi-frequency ultrasound KW - composite transducer KW - broadband ultrasound KW - co-linear array ER - TY - CONF TI - The heart of a successful education - one journey through graduate school AU - Albers, L. AU - Bottomley, L. C2 - 2013/// C3 - Proceedings of the American Society for Engineering Education DA - 2013/// ER - TY - CONF TI - The creation, evolution and impact of a GK-12 outreach model AU - Albers, Lynn AU - Bottomley, Laura AU - Parry, Elizabeth C2 - 2013/// C3 - Proceedings of the American Society for Engineering Education DA - 2013/// ER - TY - JOUR TI - NEW RESULTS ON CONTINUOUS-TIME SWITCHED LINEAR SYSTEMS WITH ACTUATOR SATURATION AU - Duan, Chang AU - Wu, Fen T2 - ASME 2013 DYNAMIC SYSTEMS AND CONTROL CONFERENCE, VOL 2 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 (NDI) description of the saturated systems and the minimal switching rule, a set of switched output feedback controllers is designed to minimize 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 (BMIs) and can be solved by numerical search coupled with linear matrix inequality (LMI) optimization. Compared to the previous method based on polytopic differential inclusion (PDI), the proposed approach has good scalability and potentially renders better performance. Numerical examples are provided to verify effectiveness of the proposed approach. DA - 2013/// PY - 2013/// DO - 10.1115/dscc2013-3789 SP - ER - TY - RPRT TI - Balancing biomass harvesting and drying tactics with delivered payment practice AU - Roise, J. P. AU - Catts, G. AU - Hazel, D. AU - A. Hobbs A., AU - Hopkins, C. A3 - Greenville, S.C.: US Endowment for Forestry and Community DA - 2013/// PY - 2013/// PB - Greenville, S.C.: US Endowment for Forestry and Community ER - TY - JOUR TI - Nondestructive inspection in adhesive-bonded joint CFRP using pulsed phase thermography AU - Shin, P. H. AU - Webb, S. C. AU - Peters, K. J. T2 - THERMOSENSE: THERMAL INFRARED APPLICATIONS XXXV AB - Many forms of damages in fiber reinforcement polymer (FRP) composites are difficult to detect because they occurs in subsurface layers of the composites. One challenging need for inspection capabilities is in adhesively bonded joints between composite components, a common location of premature failure in aerospace structures. This paper investigates pulsed phase thermography (PPT) imaging of fatigue damage in these adhesively bonded joints. Simulated defects were created to calibrate parameters for fatigue loading conditions, PPT imaging parameters, and a damage sizing algorithm for carbon fiber reinforced polymer (CFRP) single lap joints. Afterwards, lap joint specimens were fabricated with varying quality of manufacturing. PPT imaging of the pristine specimens revealed defects such as air bubbles, adhesive thickness variations, and weak bonding surface between the laminate and adhesive. Next, fatigue testing was performed and acquired PPT imaging data identified fatigue induced damage prior to final failure cycles. After failure of each sample, those images were confirmed by visual inspections of failure surface. DA - 2013/// PY - 2013/// DO - 10.1117/12.2018414 VL - 8705 SP - SN - 0277-786X KW - Pulsed Phase Thermography KW - single lap joints KW - adhesively bonded joints ER - TY - JOUR TI - Nanoparticle Mass Transfer From Lung Airways to Systemic Regions-Part II: Multi-Compartmental Modeling AU - Kolanjiyil, Arun V. AU - Kleinstreuer, Clement T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME AB - This is the second article of a two-part paper, combining high-resolution computer simulation results of inhaled nanoparticle deposition in a human airway model (Kolanjiyil and Kleinstreuer, 2013, “Nanoparticle Mass Transfer From Lung Airways to Systemic Regions—Part I: Whole-Lung Aerosol Dynamics,” ASME J. Biomech. Eng., 135(12), p. 121003) with a new multicompartmental model for insoluble nanoparticle barrier mass transfer into systemic regions. Specifically, it allows for the prediction of temporal nanoparticle accumulation in the blood and lymphatic systems and in organs. The multicompartmental model parameters were determined from experimental retention and clearance data in rat lungs and then the validated model was applied to humans based on pharmacokinetic cross-species extrapolation. This hybrid simulator is a computationally efficient tool to predict the nanoparticle kinetics in the human body. The study provides critical insight into nanomaterial deposition and distribution from the lungs to systemic regions. The quantitative results are useful in diverse fields such as toxicology for exposure-risk analysis of ubiquitous nanomaterial and pharmacology for nanodrug development and targeting. DA - 2013/12// PY - 2013/12// DO - 10.1115/1.4025333 VL - 135 IS - 12 SP - SN - 1528-8951 KW - multicompartment modeling KW - animal test data KW - model validations KW - nanoparticle bio-kinetics KW - temporal accumulations KW - human organs ER - TY - JOUR TI - Nanoparticle Mass Transfer From Lung Airways to Systemic Regions-Part I: Whole-Lung Aerosol Dynamics AU - Kolanjiyil, Arun V. AU - Kleinstreuer, Clement T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME AB - This is a two-part paper describing inhaled nanoparticle (NP) transport and deposition in a model of a human respiratory tract (Part I) as well as NP-mass transfer across barriers into systemic regions (Part II). Specifically, combining high-resolution computer simulation results of inhaled NP deposition in the human airways (Part I) with a multicompartmental model for NP-mass transfer (Part II) allows for the prediction of temporal NP accumulation in the blood and lymphatic systems as well as in organs. An understanding of nanoparticle transport and deposition in human respiratory airways is of great importance, as exposure to nanomaterial has been found to cause serious lung diseases, while the use of nanodrugs may have superior therapeutic effects. In Part I, the fluid-particle dynamics of a dilute NP suspension was simulated for the entire respiratory tract, assuming steady inhalation and planar airways. Thus, a realistic airway configuration was considered from nose/mouth to generation 3, and then an idealized triple-bifurcation unit was repeated in series and parallel to cover the remaining generations. Using the current model, the deposition of NPs in distinct regions of the lung, namely extrathoracic, bronchial, bronchiolar, and alveolar, was calculated. The region-specific NP-deposition results for the human lung model were used in Part II to determine the multicompartmental model parameters from experimental retention and clearance data in human lungs. The quantitative, experimentally validated results are useful in diverse fields, such as toxicology for exposure-risk analysis of ubiquitous nanomaterial as well as in pharmacology for nanodrug development and targeting. DA - 2013/12// PY - 2013/12// DO - 10.1115/1.4025332 VL - 135 IS - 12 SP - SN - 1528-8951 KW - computational fluid-particle dynamics KW - multicompartment modeling KW - nanoparticle kinetics KW - nanoparticle deposition KW - toxic nanoparticles KW - nanodrugs ER - TY - JOUR TI - High-temperature (> 1000 degrees C) acoustic emission sensor AU - Johnson, Joseph A. AU - Kim, Kyungrim AU - Zhang, Shujun AU - Wu, Di AU - Jiang, Xiaoning T2 - NONDESTRUCTIVE CHARACTERIZATION FOR COMPOSITE MATERIALS, AEROSPACE ENGINEERING, CIVIL INFRASTRUCTURE, AND HOMELAND SECURITY 2013 AB - Piezoelectric crystals have shown promising results as acoustic emission sensors, but are often hindered by the loss of electric properties above temperatures in the 500-700°C range. Yttrium calcium oxyborate, (YCOB), however, is a promising high temperature piezoelectric material due to its high resistivity at high temperatures and its relatively stable electromechanical and piezoelectric properties across a broad temperature range. In this paper, a piezoelectric acoustic emission sensor was designed, fabricated, and tested for use in high temperature applications using a YCOB single crystal. An acoustic wave was generated by a Hsu-Nielsen source on a stainless steel bar, which then propagated through the substrate into a furnace where the YCOB acoustic emission sensor is located. Charge output of the YCOB sensor was collected using a lock-in charge amplifier. The sensitivity of the YCOB sensor was found to have small to no degradation with increasing temperature up to 1000 °C. This oxyborate crystal showed the ability to detect zero order symmetric and antisymmetric modes, as well as distinguishable first order antisymmetric modes at elevated temperatures up to 1000 °C. DA - 2013/// PY - 2013/// DO - 10.1117/12.2009301 VL - 8694 SP - SN - 1996-756X KW - Acoustic emission KW - sensor KW - high temperature KW - YCOB KW - hsu-nielsen ER - TY - CONF TI - DDPM-DEM simulations of particulate flows in human tracheobronchial airways AU - Feng, Y. AU - Kleinstreuer, C. C2 - 2013/// C3 - ASME 2013 International Mechanical Engineering Congress & Exposition DA - 2013/// ER - TY - JOUR TI - Correlation of population density to designated urban areas AU - Southwell, J. T. AU - Hall, C. E. AU - Burke, D. A. T2 - Journal of Aerospace Information Systems DA - 2013/// PY - 2013/// VL - 10 IS - 1 SP - 40-46 ER - TY - JOUR TI - Copper-Encapsulated Vertically Aligned Carbon Nanotube Arrays AU - Stano, Kelly L. AU - Chapla, Rachel AU - Carroll, Murphy AU - Nowak, Joshua AU - McCord, Marian AU - Bradford, Philip D. T2 - ACS APPLIED MATERIALS & INTERFACES AB - A new procedure is described for the fabrication of vertically aligned carbon nanotubes (VACNTs) that are decorated, and even completely encapsulated, by a dense network of copper nanoparticles. The process involves the conformal deposition of pyrolytic carbon (Py-C) to stabilize the aligned carbon-nanotube structure during processing. The stabilized arrays are mildly functionalized using oxygen plasma treatment to improve wettability, and they are then infiltrated with an aqueous, supersaturated Cu salt solution. Once dried, the salt forms a stabilizing crystal network throughout the array. After calcination and H2 reduction, Cu nanoparticles are left decorating the CNT surfaces. Studies were carried out to determine the optimal processing parameters to maximize Cu content in the composite. These included the duration of Py-C deposition and system process pressure as well as the implementation of subsequent and multiple Cu salt solution infiltrations. The optimized procedure yielded a nanoscale hybrid material where the anisotropic alignment from the VACNT array was preserved, and the mass of the stabilized arrays was increased by over 24-fold because of the addition of Cu. The procedure has been adapted for other Cu salts and can also be used for other metal salts altogether, including Ni, Co, Fe, and Ag. The resulting composite is ideally suited for application in thermal management devices because of its low density, mechanical integrity, and potentially high thermal conductivity. Additionally, further processing of the material via pressing and sintering can yield consolidated, dense bulk composites. DA - 2013/11/13/ PY - 2013/11/13/ DO - 10.1021/am402964e VL - 5 IS - 21 SP - 10774-10781 SN - 1944-8252 KW - carbon nanotube KW - nanocomposites KW - copper KW - CNT array KW - thermal management ER - TY - JOUR TI - Analytical comparison between Nixon-Logvinenko's and Jung-Brown's theories of slow neurofilament transport in axons AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. T2 - MATHEMATICAL BIOSCIENCES AB - This paper develops analytical solutions describing slow neurofilament (NF) transport in axons. The obtained solutions are based on two theories of NF transport: Nixon–Logvinenko’s theory that postulates that most NFs are incorporated into a stationary cross-linked network and only a small pool is slowly transported and Jung–Brown’s theory that postulates a single dynamic pool of NFs that are transported according to the stop-and-go hypothesis. The simplest two-kinetic state version of the model developed by Jung and Brown was compared with the theory developed by Nixon and Logvinenko. The model for Nixon–Logvinenko’s theory included stationary, pausing, and running NF populations while the model used for Jung–Brown’s theory only included pausing and running NF populations. Distributions of NF concentrations resulting from Nixon–Logvinenko’s and Jung-Brown’s theories were compared. In previous publications, Brown and colleagues successfully incorporated slowing of NF transport into their model by assuming that some kinetic constants depend on the distance from the axon hillock. In this paper we defined the average rate of NF transport as the rate of motion of the center of mass of radiolabeled NFs. We have shown that for this definition, if all kinetic rates are assumed constant, Jung–Brown’s theory predicts a constant average rate of NF transport. We also demonstrated that Nixon–Logvinenko’s theory predicts slowing of NF transport even if all kinetic rates are assumed constant, and the obtained slowing agrees well with published experimental data. DA - 2013/10// PY - 2013/10// DO - 10.1016/j.mbs.2013.08.001 VL - 245 IS - 2 SP - 331-339 SN - 1879-3134 KW - Slow axonal transport KW - Neurofilaments KW - Stop-and-go hypothesis KW - Neurons KW - Molecular motors KW - Exact solution ER - TY - JOUR TI - An unsteady airfoil theory applied to pitching motions validated against experiment and computation AU - Ramesh, Kiran AU - Gopalarathnam, Ashok AU - Edwards, Jack R. AU - Ol, Michael V. AU - Granlund, Kenneth T2 - Theoretical and Computational Fluid Dynamics DA - 2013/1/16/ PY - 2013/1/16/ DO - 10.1007/s00162-012-0292-8 VL - 27 IS - 6 SP - 843-864 J2 - Theor. Comput. Fluid Dyn. LA - en OP - SN - 0935-4964 1432-2250 UR - http://dx.doi.org/10.1007/s00162-012-0292-8 DB - Crossref KW - Unsteady aerodynamics KW - Airfoil aerodynamics KW - Leading-edge vortex ER - TY - JOUR TI - The Onset of Double-Diffusive Convection in a Vertical Cylinder With Vertical Throughflow AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - The effect of vertical throughflow on the onset of convection, induced by an applied vertical temperature gradient in a vertical cylinder is studied analytically using linear stability theory. This problem is important to hydrologists to investigate under what conditions convection is taking place in a well or borehole. The effect of double diffusion is included. Both nonoscillatory and oscillatory situations are studied. DA - 2013/3// PY - 2013/3// DO - 10.1115/1.4007859 VL - 135 IS - 3 SP - SN - 1528-8943 KW - throughflow KW - thermal instability KW - vertical cylinder KW - double diffusion ER - TY - JOUR TI - Temperature-dependent material properties of Z-shaped MEMS thermal actuators made of single crystalline silicon AU - Ouyang, Jing AU - McDonald, Margaret AU - Zhu, Yong T2 - JOURNAL OF MICROMECHANICS AND MICROENGINEERING AB - MEMS thermal actuators have been employed in a broad range of applications, often operating in different environments (e.g. vacuum, air or liquid). Since the involved heat dissipation mechanisms are different in different operating environments, the device performances are expected to be different. In this paper, we report experimental measurement and multiphysics modeling of device performance metrics of a recently introduced thermal actuator, the Z-shaped thermal actuator, including temperature distribution, electric resistance and displacement in both air and vacuum environments. The temperature measurement was based on Raman scattering in air. Fully 3D multiphysics (coupled thermo-electro-mechanical) simulations were performed to treat both air and vacuum environments. Heat conduction through air to neighboring devices is important, while heat convection to air is negligible. The experimental and modeling results agreed well, which demonstrated the accuracy of the temperature-dependent material properties used in the modeling. Fully 3D multiphysics modeling combined with valid material property parameters will enable the exploration of the design space and the optimization of performances of the MEMS thermal actuators for different operating environments. DA - 2013/12// PY - 2013/12// DO - 10.1088/0960-1317/23/12/125036 VL - 23 IS - 12 SP - SN - 1361-6439 ER - TY - JOUR TI - Semi-Batch Deoxygenation of Canola- and Lard-Derived Fatty Acids to Diesel-Range Hydrocarbons AU - Ford, Jeffrey P. AU - Thapaliya, Nirajan AU - Kelly, M. Jason AU - Roberts, William L. AU - Lamb, H. Henry T2 - ENERGY & FUELS AB - Fatty acids (FAs) derived via thermal hydrolysis of food-grade lard and canola oil were deoxygenated in the liquid phase using a commercially available 5 wt % Pd/C catalyst. Online quadrupole mass spectrometry and gas chromatography were used to monitor the effluent gases from the semi-batch stirred autoclave reactors. Stearic, oleic, and palmitic acids were employed as model compounds. A catalyst lifetime exceeding 2200 turnovers for oleic acid deoxygenation was demonstrated at 300 °C and 15 atm under 10% H2. The initial decarboxylation rate of palmitic acid under 5% H2 decreases sharply with increasing initial concentration; in contrast, the initial decarbonylation rate increases linearly, indicative of first-order kinetics. Scale-up of diesel-range hydrocarbon production was investigated by increasing the reactor vessel size, initial FA concentration, and FA/catalyst mass ratio. Lower CO2 selectivity and batch productivity were observed at the larger scales (600 and 5000 mL), primarily because of the higher initial FA concentration (67 wt %) employed. Because unsaturated FAs must be hydrogenated before deoxygenation can proceed at an appreciable rate, the additional batch time required for FA hydrogenation reduces the batch productivity for unsaturated feedstocks. Low-temperature hydrogenation of unsaturated feedstocks (using Pd/C or another less-expensive catalyst) prior to deoxygenation is recommended. DA - 2013/12// PY - 2013/12// DO - 10.1021/ef4016763 VL - 27 IS - 12 SP - 7489-7496 SN - 1520-5029 ER - TY - JOUR TI - Note on a New Blackbody Fraction Function Used for Surfaces With a Linear Emissivity in a Wavelength Interval AU - Jing, Wei AU - Fang, Tiegang T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - In this note, a new blackbody radiation fraction function is proposed for calculating the emissive power or total emissivity of a surface that has an emissivity depending linearly on wavelength in a wavelength interval. This new fraction function is expressed as a function of the product of wavelength and temperature and the numerical values are tabulated. Based on the new defined fraction function, the emissive power in a given wavelength interval can be calculated very conveniently combined with the traditional blackbody radiation fraction function. This new function can be used in many practical applications with good accuracy without numerical integration. DA - 2013/5// PY - 2013/5// DO - 10.1115/1.4023393 VL - 135 IS - 5 SP - SN - 1528-8943 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877622228&partnerID=MN8TOARS KW - blackbody radiation KW - fraction function KW - emissivity ER - TY - JOUR TI - Exploring the Effectiveness of Using Graveyard Data When Generating Design Alternatives AU - Foster, Garrett AU - Ferguson, Scott T2 - JOURNAL OF COMPUTING AND INFORMATION SCIENCE IN ENGINEERING AB - The objective of this paper is to demonstrate that unique alternative designs can be efficiently found by searching the discarded data (or graveyard) from a multiobjective genetic algorithm (MOGA). Motivation for using graveyard data to generate design alternatives arises from the computational cost associated with real-time design space exploration of multiobjective optimization problems. The effectiveness of this approach is explored by comparing (1) the uniqueness of alternatives found using graveyard data and those generated using an optimization-based search, and (2) how alternative generation near the Pareto frontier is impacted. Two multiobjective case study problems are introduced—a two bar truss and an I-beam design optimization. Results from these studies indicate that using graveyard data allows for the discovery of alternative designs that are at least 70% as unique as alternatives found using an optimization-based alternative identification approach, while saving a significant number of functional evaluations. Additionally, graveyard data are shown to be better suited for alternative generation near the Pareto frontier than standard sampling techniques. Finally, areas of future work are also discussed. DA - 2013/12// PY - 2013/12// DO - 10.1115/1.4024913 VL - 13 IS - 4 SP - SN - 1944-7078 KW - design alternatives KW - multiobjective optimization KW - multiobjective genetic algorithms KW - design space exploration KW - MGA ER - TY - JOUR TI - Diamagnetic to ferromagnetic switching in VO2 epitaxial thin films by nanosecond excimer laser treatment AU - Molaei, R. AU - Bayati, R. AU - Nori, S. AU - Kumar, D. AU - Prater, J. T. AU - Narayan, J. T2 - Applied Physics Letters DA - 2013/// PY - 2013/// VL - 103 IS - 25 ER - TY - JOUR TI - Critical Invalidation of Temperature Dependence of Nanofluid Thermal Conductivity Enhancement AU - Han, Kisoo AU - Lee, Wook-Hyun AU - Kleinstreuer, Clement AU - Koo, Junemo T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - Of interest is the accurate measurement of the enhanced thermal conductivity of certain nanofluids free from the impact of natural convection. Owing to its simplicity, wide range of applicability and short response time, the transient hot-wire method (THWM) is frequently used to measure the thermal conductivity of fluids. In order to gain a sufficiently high accuracy, special care should be taken to assure that each measurement is not affected by initial heat supply delay, natural convection, and signal noise. In this study, it was found that there is a temperature limit when using THWM due to the incipience of natural convection. The results imply that the temperature-dependence of the thermal conductivity enhancement observed by other researchers might be misleading when ignoring the impact of natural convection; hence, it could not be used as supporting evidence of the effectiveness of micromixing due to Brownian motion. Thus, it is recommended that researchers report how they keep the impact of the natural convection negligible and check the integrity of their measurements in the future researches. DA - 2013/5// PY - 2013/5// DO - 10.1115/1.4023544 VL - 135 IS - 5 SP - SN - 1528-8943 KW - transient hot-wire method KW - thermal conductivity KW - nanofluids KW - natural convection ER - TY - JOUR TI - An Historical and Topical Note on Convection in Porous Media AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - This note deals with three main themes. The first is a discussion of the early literature on convection in porous media. The second is a brief overview of current analytical modeling of single-phase convection in saturated porous media and in composite fluid/porous-medium domains. The third is a brief discussion of some pertinent recent studies involving nanofluids, cellular porous materials, bidisperse and tridisperse porous media. DA - 2013/6// PY - 2013/6// DO - 10.1115/1.4023567 VL - 135 IS - 6 SP - SN - 1528-8943 KW - single-phase convection KW - saturated porous media KW - fluid/porous-medium domains KW - nanofluids KW - cellular porous materials KW - bidisperse porous media ER - TY - JOUR TI - Scalar gradient trajectory measurements using high-frequency cinematographic planar Rayleigh scattering AU - Gampert, Markus AU - Narayanaswamy, Venkat AU - Peters, Norbert T2 - EXPERIMENTS IN FLUIDS DA - 2013/12// PY - 2013/12// DO - 10.1007/s00348-013-1621-4 VL - 54 IS - 12 SP - SN - 1432-1114 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84886400214&partnerID=MN8TOARS ER - TY - JOUR TI - Performance Prediction and Demonstration of a Miniature Horizontal Axis Wind Turbine AU - Xu, Fujun AU - Yuan, Fuh-Gwo AU - Liu, Lei AU - Hu, Jingzhen AU - Qiu, Yiping T2 - JOURNAL OF ENERGY ENGINEERING AB - A miniature wind turbine (MWT) has received great attention recently for powering low-power devices. In this paper, a physics-based comprehensive model for predicting the performance of a miniature horizontal axis wind turbine (MHAWT) was established. The turbine rotor performance was investigated and an approximation of the power coefficient of the turbine rotor was made. Incorporation of the approximation with the equivalent circuit model, which was proposed in accordance with the principles of the MHAWT, in addition to its overall system performance versus the resistive load and ambient wind speed, was predicted. To demonstrate predictive modeling capability, the MHAWT system comprised of commercially available off-the-shelf components was designed and its performance was experimentally tested. The results matched well with those by prediction modeling, which implies that the proposed model holds promise in estimating and optimizing the performance of the MWT. DA - 2013/9// PY - 2013/9// DO - 10.1061/(asce)ey.1943-7897.0000125 VL - 139 IS - 3 SP - 143-152 SN - 1943-7897 KW - Miniature wind turbine KW - Energy harvesting KW - Physics-based model KW - Wireless sensor ER - TY - JOUR TI - Nitrogen-diluted methane flames in the near-and far-field AU - Kribs, J. AU - Moore, N. AU - Hasan, T. AU - Lyons, K. T2 - Journal of Energy Resources Technology DA - 2013/// PY - 2013/// VL - 135 IS - 4 ER - TY - JOUR TI - Modelling of axonal cargo rerouting in a dendrite AU - Kuznetsov, A. V. T2 - MATHEMATICAL MEDICINE AND BIOLOGY-A JOURNAL OF THE IMA AB - Journal Article Modelling of axonal cargo rerouting in a dendrite Get access A.V. Kuznetsov A.V. Kuznetsov Department of Mechanical and Aerospace Engineering, North Carolina State University, Campus Box 7910, Raleigh, NC 27695-7910, USA avkuznet@eos.ncsu.edu Search for other works by this author on: Oxford Academic Google Scholar Mathematical Medicine and Biology: A Journal of the IMA, Volume 30, Issue 3, September 2013, Pages 273–285, https://doi.org/10.1093/imammb/dqs021 Published: 01 June 2012 Article history Received: 31 December 2011 Revision received: 29 March 2012 Accepted: 11 April 2012 Published: 01 June 2012 DA - 2013/9// PY - 2013/9// DO - 10.1093/imammb/dqs021 VL - 30 IS - 3 SP - 273-285 SN - 1477-8602 KW - neurons KW - intracellular transport KW - axons and dendrites KW - axonal cargo KW - cargo targeting ER - TY - JOUR TI - Modeling the heterogeneous effects of retained austenite on the behavior of martensitic high strength steels AU - Wu, Q. AU - Shanthraj, P. AU - Zikry, Mohammed T2 - International Journal of Fracture DA - 2013/// PY - 2013/// DO - 10.1007/978-3-319-04397-5_16 VL - 184 IS - 1-2 SP - 241–252 ER - TY - JOUR TI - Flexoelectric nano-generator: Materials, structures and devices AU - Jiang, Xiaoning AU - Huang, Wenbin AU - Zhang, Shujun T2 - NANO ENERGY AB - Flexoelectricity, as a fundamental electromechanical coupling effect between electric polarization and mechanical strain gradient, or vice versa between electric polarization gradient and mechanical gradient, exists in various categories of materials including solid materials, liquid crystals, polymers, and biomembranes. Dependence of electric or mechanical gradients on geometry requires the adoption of specific structures for different flexoelectric mode applications. Scaling effect associated with gradient suggests that flexoelectric effect can be more significant in micro/nano systems, comparable to or even exceed piezoelectricity. In this review, flexoelectricity in those studied materials will be summarized and compared. Applications in sensors, actuators, capability of tuning the ferroelectric thin film properties, and roles in bio-system mechanosensitivity and mechanotranduction of flexoelectricity will be introduced respectively. Especially, flexoelectricity nano-generator enlightens a new technique for energy harvesting. Comparison with piezoelectric nano-generator suggests that flexoelectric counterpart can yield enhanced performance with specific nanostructures and provide a wider materials choice. DA - 2013/11// PY - 2013/11// DO - 10.1016/j.nanoen.2013.09.001 VL - 2 IS - 6 SP - 1079-1092 SN - 2211-3282 KW - Flexoelectricity KW - Nanogenerator KW - Energy harvesting ER - TY - CONF TI - Damage identification for composite structures using a cross-correlation reverse-time migration technique AU - He, J. AU - Yuan, F. G. C2 - 2013/// C3 - Structural Health Monitoring 2013, Vols 1 and 2 DA - 2013/// SP - 2185-2193 ER - TY - CONF TI - Comparison of 2D and 3D composites to confined crush loading AU - Pankow, M. AU - Yen, C. F. AU - Waas, A. M. C2 - 2013/// C3 - Proceedings of the American Society for Composites DA - 2013/// ER - TY - CONF TI - Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber bragg grating sensors AU - Webb, S. AU - Shin, P. AU - Peters, K. AU - Zikry, M. AU - Schultz, S. AU - Selfridge, R. C2 - 2013/// C3 - Structural Health Monitoring 2013, Vols 1 and 2 DA - 2013/// SP - 1953-1960 ER - TY - JOUR TI - A microelectromechanical system for thermomechanical testing of nanostructures AU - Chang, Tzu-Hsuan AU - Zhu, Yong T2 - APPLIED PHYSICS LETTERS AB - We report an integrated microelectromechanical system (MEMS) with an on-chip heater for in-situ mechanical testing of nanostructures from room to elevated temperatures. Multiphysics simulation is used to predict the temperature distribution in air and vacuum conditions. The temperature simulation in air agrees well with the measurement based on Raman spectroscopy. Mechanical testing of single crystalline silicon nanowires is carried out to investigate the brittle-to-ductile transition, demonstrating the efficacy of the MEMS stage. The stage reported here could be applied to investigate the temperature effect on mechanical properties at the nanoscale. DA - 2013/12/23/ PY - 2013/12/23/ DO - 10.1063/1.4858962 VL - 103 IS - 26 SP - SN - 1077-3118 ER - TY - CONF TI - Tissue- and cell-levels stress distribution of heart valve tissue during diastole AU - Huang, Siyao AU - Huang, Hsiao-Ying Shadow AB - Heart valves are inhomogeneous microstructure with nonlinear anisotropic properties and constantly experience different stress states during cardiac cycles. However, how tissue-level mechanical forces can translate into altered cellular stress states remains unclear, and associated biomechanical regulation in the tissue has not been fully understood. In the current study, we use an image-based finite element method to investigate factors contributing the stress distributions at both tissue- and cell-levels inside the healthy heart valve tissues. Effects of tissue microstructure, inhomogeneity, and anisotropic material property at different diastole states are discussed to provide a better understanding of structure-mechanics-property interactions, which alters tissue-to-cell stress transfer mechanisms in heart valve tissue. To the best of the authors’ knowledge, this is the first study reporting on the evolution of stress fields at both the tissue- and cellular-levels in valvular tissue, and thus contributes toward refining our collective understanding of valvular tissue micromechanics while providing a computational tool enabling further study of valvular cell-tissue interactions. C2 - 2013/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition CY - San Diego, CA DA - 2013/// DO - 10.1115/imece2013-63229 ER - TY - JOUR TI - Stress Evolution on the Phase Boundary in LiFePO4Particles AU - ChiuHuang, Cheng-Kai AU - Shadow Huang, Hsiao-Ying T2 - Journal of The Electrochemical Society AB - It is commonly thought that diffusion-induced stress is one of the main factors causing loss of capacity in electrode materials. To understand stress evolution on the phase boundary during the lithiation process, we develop a finite element model adopting lithium ion concentration-dependent anisotropic material properties and volume misfits. Increased mechanical stresses on the phase boundaries are observed during the lithiation process. When the particle is more fully lithiated, larger stresses occur on the free surfaces and these may be related to the cracks on the ac-plane. The C-rate dependent strain energy evolution is also studied. The result shows that with the same amount of lithiation, particles experience different strain energies due to varied C-rate discharging. The high elastic energy from the high C-rate model suggests that the system becomes unstable, and a homogeneous phase transformation path is more plausible for the system. The current study provides a connection between diffusion-induces stresses on the phase boundary and the cracking propensity on free surfaces. Thus, the study could be used to better understand the mechanisms that cause particle fracture and capacity loss. DA - 2013/// PY - 2013/// DO - 10.1149/2.079311jes VL - 160 IS - 11 SP - A2184-A2188 J2 - J. Electrochem. Soc. LA - en OP - SN - 0013-4651 1945-7111 UR - http://dx.doi.org/10.1149/2.079311jes DB - Crossref ER - TY - CONF TI - Gain-scheduling compensator synthesis for output regulation of nonlinear systems AU - Song, X. AU - Ren, Z. AU - Wu, F. AB - This paper addresses the gain-scheduling output regulation synthesis problem for nonlinear systems. For gain-scheduling control, the linear parameter-varying (LPV) model is obtained from nonlinear plant by plant linearization about zero-error trajectories upon which an LPV controller is synthesized. In practical engineering application, a key issue is to find a nonlinear output feedback compensator related to the designed LPV controller which can guarantee that the closed-loop system of nonlinear plant and compensator linearizes to the interconnection of LPV model and LPV controller. So the stability and performance about the zero-error trajectories can be inherited when the nonlinear compensator is implemented. By incorporating equilibrium input and measured output into the auxiliary LPV model, the compensator synthesis problem is reformulated as linear matrix inequalities (LMIs) which can be solved efficiently using the interior-point method. Consequently the proposed output feedback compensator can satisfy the linearization requirement. Finally, the validity of the proposed approach is demonstrated through a ball and beam design example. C2 - 2013/// C3 - 2013 american control conference (acc) DA - 2013/// DO - 10.1109/acc.2013.6580791 SP - 6078-6083 ER - TY - CONF TI - Exploring lithium-ion intensity and distribution via a Time-of-Flight Secondary Ion Mass Spectroscopy AU - ChiuHuang, Cheng-Kai AU - Zhou, Chuanzhen AU - Huang, Hsiao-Ying Shadow AB - For high rate-capability and low cost lithium-ion batteries, the prevention of capacity loss is one of major challenges facing by lithium-ion batteries today. During electrochemical processes, lithium ions diffuse from and insert into battery electrodes accompanied with the phase transformation, where ionic diffusivity and concentration are keys to the resultant battery capacity. In the current study, we first compare voltage vs. capacity curves at different C-rates (1C, 2C, 6C, 10C). Second, lithium-ion distributions and intensity are quantified via the Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). The result shows that voltage vs. capacity relations are C-rate dependent and larger hystereses are observed in the higher C-rate samples. Detailed quantification of lithium-ion intensity for the 1C sample is conducted. It is observed that lithium-ions are distributed uniformly inside the electrode. Therefore, the current study provides a qualitative and quantitative data to better understand C-rate dependent phenomenon of LiFePO4 battery cells. C2 - 2013/// C3 - ASME International Mechanical Engineering Congress and Exposition Proceeding CY - San Diego, CA DA - 2013/// DO - 10.1115/imece2013-63013 VL - IMECE2013-63013 ER - TY - CONF TI - A biomechanical study of directional mechanical properties of porcine skin tissues AU - Huang, H.-Y. S. AU - Huang, S. AU - Gettys, T. A. AU - Harrysson, O. C2 - 2013/// C3 - ASME 2013 International Mechanical Engineering Congress & Exposition DA - 2013/// ER - TY - JOUR TI - The effects of microstructural defects on hot spot formation in cyclotrimethylenetrinitramine-polychlorotrifluoroethylene energetic aggregates AU - LaBarbera, D. A. AU - Zikry, M. A. T2 - JOURNAL OF APPLIED PHYSICS AB - Shock initiation due to hot spot formation has been investigated in energetic aggregates subjected to dynamic thermo-mechanical loading conditions. A dislocation-density based crystalline plasticity and specialized finite-element formulations were used to predict hot spot formation due to dynamic thermo-mechanical loading conditions in cyclotrimethylenetrinitramine-polymer energetic aggregates. The effects of grain boundary misorientations, porosity, grain morphology, dislocation densities, and crystal-binder interactions were coupled with adiabatic plasticity heating, thermal decomposition, and dissipated heat to analyze hot spot formation. The predictions indicate that hot spot formation occurs when temperatures become unbounded in localized regions between voids. The time to hot spot formation decreases with increases in dynamic pressure loads, which is consistent with experimental results. DA - 2013/6/28/ PY - 2013/6/28/ DO - 10.1063/1.4811684 VL - 113 IS - 24 SP - SN - 0021-8979 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84879877008&partnerID=MN8TOARS ER - TY - JOUR TI - The Effect of Vertical Throughflow on the Onset of Convection Induced by Internal Heating in a Layered Porous Medium AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - TRANSPORT IN POROUS MEDIA DA - 2013/10// PY - 2013/10// DO - 10.1007/s11242-013-0207-1 VL - 100 IS - 1 SP - 101-114 SN - 0169-3913 KW - Throughflow KW - Heterogeneity KW - Instability KW - Horizontal layers KW - Internal heating ER - TY - JOUR TI - The Effect of Pulsating Deformation on the Onset of Convection in a Porous Medium AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2013/7// PY - 2013/7// DO - 10.1007/s11242-013-0168-4 VL - 98 IS - 3 SP - 713-724 SN - 0169-3913 KW - Deforming porous medium KW - Thermal instability KW - Pulsating permeability ER - TY - JOUR TI - The Effect of Heterogeneity on the Onset of Double-Diffusive Convection Induced by Internal Heating in a Porous Medium: A Layered Model AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2013/10// PY - 2013/10// DO - 10.1007/s11242-013-0206-2 VL - 100 IS - 1 SP - 83-99 SN - 0169-3913 KW - Heterogeneity KW - Instability KW - Horizontal layers KW - Internal heating KW - Double diffusion ER - TY - JOUR TI - Spray characteristics of a swirl atomiser in trigger sprayers using water-ethanol mixtures AU - Yao, Shanshan AU - Fang, Tiegang T2 - CANADIAN JOURNAL OF CHEMICAL ENGINEERING AB - Abstract Pressure swirl atomisers are widely used in both industry and daily life. It is critical to understand the spray transient behaviour for better design of these systems. This paper presents an experimental study of conical liquid sheets breakup from a swirl atomiser nozzle in trigger sprayers. Spray and atomisation characteristics were measured and analysed. Water–ethanol mixtures were used to simulate different fluids on the breakup and atomisation quality of the spray development process with a wide range of surface tension while maintaining relatively small changes in fluid viscosity and density. The spray images were taken by a high speed digital camera and post‐processed to analyse the global spray structure, spray cone angle, and breakup length. The droplet size and its distribution were measured using a laser diffraction technique. It was observed that the surface waves grow rapidly on the cone‐shaped liquid sheets and breakup into liquid ligaments and droplets during the initial stage of fluid dispensing. Then the spray transitions into the developed stage. Near the end of the dispensing process, the liquid cone collapses with poor atomisation (large droplets) due to momentum loss. The comparison between different fluids showed that the spray cone angle and liquid breakup length decreased with the increase of ethanol percentage ratio. The percentiles parameters, Sauter mean diameter (SMD) and particle size distribution were measured and compared for different locations. High surface tension fluids produce larger droplets than lower surface tension fluids, which have the same trend as the percentiles parameters and SMD. Results also show that droplet size and its distribution depend on the location of the measurement. Generally speaking, smaller droplet size is found for a location away from the nozzle axis in the vertical direction. In the horizontal direction, larger droplet sizes are found for a location closer to the nozzle exit. © 2013 Canadian Society for Chemical Engineering DA - 2013/7// PY - 2013/7// DO - 10.1002/cjce.21821 VL - 91 IS - 7 SP - 1312-1324 SN - 0008-4034 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84878717947&partnerID=MN8TOARS KW - swirl atomiser KW - trigger sprayer KW - spray atomisation KW - droplet size distribution KW - visualisation ER - TY - JOUR TI - Single-component poly(epsilon-caprolactone) composites AU - Gurarslan, Alper AU - Shen, Jialong AU - Tonelli, Alan E. T2 - POLYMER AB - Abstract Non-covalently bonded crystalline inclusion compounds (ICs) have been formed by threading host cyclic starches, α-cyclodextrins (α-CDs), onto guest poly(e-caprolactone) (PCL) chains and by co-crystallization of guest PCL and host urea (U). PCLs were coalesced from both ICs by appropriate removal of the α-CD and U hosts. When added at low concentrations, PCL coalesced from its α-CD–IC served as an effective self-nucleating agent for the bulk crystallization of as-received PCL from the melt. Film sandwiches consisting of two layers of as-received (asr) (control), and one layer each of asr and self-nucleated (nuc) (composite) PCLs were produced by melt pressing. A composite sandwich consisting of a film of neat PCL coalesced from its U–IC (c-PCL) and a film of asr-PCL was also melt pressed. DSC showed that both composite films maintain their characteristic structures and properties even after melt-pressing them together. Both single component film sandwiches exhibited strong interfaces and better mechanical properties than the asr-PCL/asr-PCL control composite sandwiches. These results are similar to those previously obtained on similarly prepared nylon-6 (N-6) sandwich composites made with asr- and nuc-N-6 films with the same levels of crystallinity. However, while the elongation at break was greatly reduced in the asr-N-6/nuc-N-6 composite, asr-/asr-, asr-/c-, and asr-/nuc-, PCL/PCL-composites all showed similarly large elongations at break. The above room temperature and well below room temperature glass-transition temperatures of N-6 and PCL are likely the cause of their widely different elongations at break. DA - 2013/10/4/ PY - 2013/10/4/ DO - 10.1016/j.polymer.2013.08.017 VL - 54 IS - 21 SP - 5747-5753 SN - 1873-2291 KW - Cyclodextrin KW - Single polymer composite KW - Poly(epsilon-caprolactone) ER - TY - JOUR TI - Quantification of parameter uncertainty for robust control of shape memory alloy bending actuators AU - Crews, John H. AU - McMahan, Jerry A. AU - Smith, Ralph C. AU - Hannen, Jennifer C. T2 - SMART MATERIALS AND STRUCTURES AB - In this paper, we employ Bayesian parameter estimation techniques to derive gains for robust control of smart materials. Specifically, we demonstrate the feasibility of utilizing parameter uncertainty estimation provided by Markov chain Monte Carlo (MCMC) methods to determine controller gains for a shape memory alloy bending actuator. We treat the parameters in the equations governing the actuator's temperature dynamics as uncertain and use the MCMC method to construct the probability densities for these parameters. The densities are then used to derive parameter bounds for robust control algorithms. For illustrative purposes, we construct a sliding mode controller based on the homogenized energy model and experimentally compare its performance to a proportional-integral controller. While sliding mode control is used here, the techniques described in this paper provide a useful starting point for many robust control algorithms. DA - 2013/11// PY - 2013/11// DO - 10.1088/0964-1726/22/11/115021 VL - 22 IS - 11 SP - SN - 1361-665X ER - TY - JOUR TI - Product sampling during transient continuous countercurrent hydrolysis of canola oil and development of a kinetic model AU - Wang, Wei-Cheng AU - Natelson, Robert H. AU - Stikeleather, Larry F. AU - Roberts, William L. T2 - COMPUTERS & CHEMICAL ENGINEERING AB - A chemical kinetic model has been developed for the transient stage of the continuous countercurrent hydrolysis of triglycerides to free fatty acids and glycerol. Departure functions and group contribution methods were applied to determine the equilibrium constants of the four reversible reactions in the kinetic model. Continuous countercurrent hydrolysis of canola oil in subcritical water was conducted experimentally in a lab-scale reactor over a range of temperatures and the concentrations of all neutral components were quantified. Several of the rate constants in the model were obtained by modeling this experimental data, with the remaining determined from calculated equilibrium constants. Some reactions not included in the present, or previous, hydrolysis modeling efforts were identified from glycerolysis kinetic studies and may explain the slight discrepancy between model and experiment. The rate constants determined in this paper indicate that diglycerides in the feedstock accelerate the transition from “emulsive hydrolysis” to “rapid hydrolysis”. DA - 2013/11/11/ PY - 2013/11/11/ DO - 10.1016/j.compchemeng.2013.06.003 VL - 58 SP - 144-155 SN - 1873-4375 KW - Hydrolysis KW - Triglycerides KW - Diglycerides KW - Free fatty acids ER - TY - JOUR TI - Optimization of Forced Convection Heat Transfer in a Composite Porous Medium Channel AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2013/9// PY - 2013/9// DO - 10.1007/s11242-013-0189-z VL - 99 IS - 2 SP - 349-357 SN - 1573-1634 KW - Forced convection KW - Porous medium KW - Channel KW - Optimization ER - TY - JOUR TI - Onset of Convection with Internal Heating in a Weakly Heterogeneous Porous Medium AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2013/7// PY - 2013/7// DO - 10.1007/s11242-013-0158-6 VL - 98 IS - 3 SP - 543-552 SN - 1573-1634 KW - Thermal instability KW - Heterogeneity KW - Porous medium ER - TY - JOUR TI - Onset of Convection with Internal Heating in a Porous Medium Saturated by a Nanofluid AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2013/8// PY - 2013/8// DO - 10.1007/s11242-013-0174-6 VL - 99 IS - 1 SP - 73-83 SN - 1573-1634 KW - Thermal instability KW - Nanofluid KW - Porous medium ER - TY - JOUR TI - Mass Recalibration of FT-ICR Mass Spectrometry Imaging Data Using the Average Frequency Shift of Ambient Ions AU - Barry, Jeremy A. AU - Robichaud, Guillaume AU - Muddiman, David C. T2 - JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY AB - Achieving and maintaining high mass measurement accuracy (MMA) throughout a mass spectrometry imaging (MSI) experiment is vital to the identification of the observed ions. However, when using FTMS instruments, fluctuations in the total ion abundance at each pixel due to inherent biological variation in the tissue section can introduce space charge effects that systematically shift the observed mass. Herein we apply a recalibration based on the observed cyclotron frequency shift of ions found in the ambient laboratory environment, polydimethylcyclosiloxanes (PDMS). This calibration method is capable of achieving part per billion (ppb) mass accuracy with relatively high precision for an infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) MSI dataset. Comparisons with previously published mass calibration approaches are also presented. DA - 2013/7// PY - 2013/7// DO - 10.1007/s13361-013-0659-0 VL - 24 IS - 7 SP - 1137-1145 SN - 1879-1123 KW - Mass spectrometry imaging KW - FT-ICR MS KW - Mass calibration KW - MALDESI KW - MMA ER - TY - JOUR TI - Investigation on the effect of aperture sizes and receiver positions in coupled rooms AU - Xiang, Ning AU - Escolano, Jose AU - Navarro, Juan M. AU - Jing, Yun T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA AB - Some recent concert hall designs have incorporated coupled reverberation chambers to the main hall that have stimulated a range of research activities in architectural acoustics. The coupling apertures between two or more coupled-volume systems are of central importance for sound propagation and sound energy decays throughout the coupled-volume systems. In addition, positions of sound sources and receivers relative to the aperture also have a profound influence on the sound energy distributions and decays. This work investigates the effect of aperture size on the behavior of coupled-volume systems using both acoustic scale-models and diffusion equation models. In these physical and numerical models, the sound source and receiver positions relative to the aperture are also investigated. Through systematic comparisons between results achieved from both physical scale models and numerical models, this work reveals valid ranges and limitations of the diffusion equation model for room-acoustic modeling. DA - 2013/6// PY - 2013/6// DO - 10.1121/1.4802740 VL - 133 IS - 6 SP - 3975-3985 SN - 0001-4966 ER - TY - JOUR TI - Influence of Subsurface Hybrid Material Growth on the Mechanical Properties of Atomic Layer Deposited Thin Films on Polymers AU - Sun, Yujie AU - Padbury, Richard P. AU - Akyildiz, Halil I. AU - Goertz, Matthew P. AU - Palmer, Jeremy A. AU - Jur, Jesse S. T2 - CHEMICAL VAPOR DEPOSITION AB - Abstract The mechanical properties of atomic layer deposition (ALD) coatings play a key role in their long‐term use as encapsulation barriers for organic‐based, flexible, electronic devices. Nano‐indentation characteristics and flexure testing of nanometer‐scale alumina on polyamide 6 (PA6) films are investigated to determine the influence of a sub‐surface hybrid layer formed during the ALD process. This hybrid layer is observed to affect the mechanical performance of the thin films, in particular at lower processing temperatures. This work has important consequences on how ALD materials need to be applied and evaluated on polymers for application as encapsulation barrier layers. DA - 2013/6// PY - 2013/6// DO - 10.1002/cvde.201207042 VL - 19 IS - 4-6 SP - 134-141 SN - 1521-3862 KW - ALD nucleation KW - Flexibility KW - Hybrid layer KW - Mechanical properties KW - PA6 ER - TY - JOUR TI - Induced wetting of polytetrafluoroethylene by atomic layer deposition for application of aqueous-based nanoparticle inks AU - Halbur, Jonathan C. AU - Padbury, Richard P. AU - Jur, Jesse S. T2 - MATERIALS LETTERS AB - Atomic layer deposition of aluminum oxide is shown to control the surface energy and wetting properties of polytetrafluoroethylene (PTFE) films and membranes. Independent of deposition temperature, gradual and abrupt wetting transitions were observed for PTFE films and membranes, respectively. To assess the enhanced compatibility of treated PTFE substrates with nanoparticle inks, drop casting and inkjet printing of silver nanoparticle solutions are performed and analyzed by optical microscopy and time of flight secondary ion mass spectroscopy. Untreated PTFE substrates showed poor compatibility with the nanoparticle inks, drying in a coffee ring pattern, whereas aluminum oxide treated PTFE substrates exhibited uniform silver nanoparticle distribution after drying. DA - 2013/6/15/ PY - 2013/6/15/ DO - 10.1016/j.matlet.2013.03.063 VL - 101 SP - 25-28 SN - 1873-4979 KW - PTFE KW - Atomic layer deposition KW - Nanoparticle compatibility KW - Surface energy KW - Wetting KW - Al2O3 ER - TY - JOUR TI - Improving mechanical and electrical properties of oriented polymer-free multi-walled carbon nanotube paper by spraying while winding AU - Liu, Wei AU - Zhao, Haibo AU - Yong, Zhenzhong AU - Xu, Geng AU - Wang, Xin AU - Xu, Fujun AU - Hui, David AU - Qiu, Yiping T2 - COMPOSITES PART B-ENGINEERING AB - In this study, a new method is introduced for fabricating carbon nanotube (CNT) paper, in which the solvent is sprayed on the CNT sheet while it is wound on a rotating mandrel. As the solvent evaporated, the capillary force pulls CNT closer together, resulting in a CNT paper with a high degree of alignment and a high packing density. Three batches of multi-walled CNTs with different wall thicknesses, tube diameters and lengths are utilized for synthesizing highly oriented CNT papers. It is found that CNTs with smallest diameter of 8 nm form strongest CNT paper with a tensile strength of 563 MPa and a tensile modulus of 15 GPa, while that made with CNTs of 10 nm diameter shows the highest electrical conductivity of 5.5 × 104 S/m. DA - 2013/10// PY - 2013/10// DO - 10.1016/j.compositesb.2013.05.043 VL - 53 SP - 342-346 SN - 1879-1069 KW - Nano-structures KW - Preform KW - Mechanical Properties KW - Electrical Properties ER - TY - JOUR TI - Forced Convection Past a Rotating Sphere: Modeling Oxygen Transport to a Pond Snail Embryo AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - Helisoma trivolvis pond snail embryos are known for their rotation, which is induced by beating of cilia at the embryo's surface. A common hypothesis links this behavior to enhancing oxygen transfer to the embryo's surface. In this paper, this hypothesis is quantified, and the effect of the rotation on the supply of oxygen to an embryo, which is approximately spherical in shape, is studied. To the best of our knowledge, this is the first research presenting a quantitative study on the effect of an embryo's rotation on facilitating gaseous exchange between the embryo and the environment. DA - 2013/12// PY - 2013/12// DO - 10.1115/1.4024871 VL - 135 IS - 12 SP - SN - 1528-8943 KW - oxygen transfer enhancement KW - rotating embryos KW - flow induced by a rotating sphere ER - TY - JOUR TI - Flexoelectric sensing using a multilayered barium strontium titanate structure AU - Kwon, S. R. AU - Huang, W. B. AU - Zhang, S. J. AU - Yuan, F. G. AU - Jiang, X. N. T2 - SMART MATERIALS AND STRUCTURES AB - The flexoelectric effect has been recently explored for its promise in electromechanical sensing. However, the relatively low flexoelectric coefficients of ferroelectrics inhibit the potential to develop flexoelectric sensing devices. In this paper, a multilayered structure using flexoelectric barium strontium titanate (Ba0.65Sr0.35TiO3 or BST) ceramic was fabricated in an attempt to enhance the effective flexoelectric coefficients using its inherent scale effect, and hence to improve the flexoelectric sensitivity. The performances of piezoelectric and flexoelectric cantilevers with the same dimensions and under the same conditions were compared. Owing to the flexoelectric scaling effect, under the same force input, the BST flexoelectric structure generated a higher charge output than its piezoelectric P(VDF-TrFE) and PMN-30PT counterparts when its thickness was less than 73.1 μm and 1.43 μm, respectively. Also, amplification of the charge output using the multilayered structure was then experimentally verified. The prototyped structure consisted of three layers of 350 μm-thick BST plates with a parallel electric connection. The charge output was approximately 287% of that obtained using a single-layer structure with the same total thickness of the multilayered structure under the same end deflection input, which suggests high sensitivity sensing can be achieved using multilayer flexoelectric structures. DA - 2013/11// PY - 2013/11// DO - 10.1088/0964-1726/22/11/115017 VL - 22 IS - 11 SP - SN - 1361-665X ER - TY - JOUR TI - Deep Saline Fluids in Geologic Basins: The Possible Role of the Soret Effect AU - Nield, D. A. AU - Kuznetsov, A. V. AU - Simmons, Craig T. T2 - TRANSPORT IN POROUS MEDIA DA - 2013/9// PY - 2013/9// DO - 10.1007/s11242-013-0186-2 VL - 99 IS - 2 SP - 297-305 SN - 0169-3913 KW - Soret effect KW - Geoscientific studies KW - Salinity ER - TY - JOUR TI - Conceptual Design of Ocean Compressed Air Energy Storage System AU - Lim, Saniel D. AU - Mazzoleni, Andre P. AU - Park, Joong-kyoo AU - Ro, Paul I. AU - Quinlan, Brendan T2 - MARINE TECHNOLOGY SOCIETY JOURNAL AB - Abstract In this paper, an ocean compressed air energy storage (OCAES) system is introduced as a utility-scale energy storage option for electricity generated by wind, ocean currents, tides, and waves off the coast of North Carolina. Geographically, a location from 40 to 70 km off the coast of Cape Hatteras is shown to be a good location for an OCAES system. Building upon existing compressed air energy storage (CAES) system designs, a conceptual design of an OCAES system with thermal energy storage (TES) is presented. A simple thermodynamic analysis is presented for an adiabatic CAES system which shows that the overall efficiency is 66%. In addition, finite element simulations are presented, which show the flow induced loads that will be experienced by OCAES air containers on the ocean floor. We discuss the fact that the combination of the buoyancy force and flow-induced lift forces (due to ocean currents) generates a periodic loading on the storage container and seabed, and how this presents engineering challenges related to the development of methods for reliably resisting these loads for decades in a corrosive environment. We also present a system, based on hydrolysis, which can be used for storing energy (in the form of oxygen and hydrogen gas) in containers on the ocean floor. DA - 2013/// PY - 2013/// DO - 10.4031/mtsj.47.2.5 VL - 47 IS - 2 SP - 70-81 SN - 1948-1209 KW - energy storage KW - CAES KW - compressed air energy storage KW - adiabatic CAES ER - TY - JOUR TI - Announcing the 2012 Measurement Science and Technology Outstanding Paper Awards AU - Foss, John AU - Dewhurst, Richard AU - Yacoot, Andrew AU - Regtien, Paul AU - Peters, Kara T2 - MEASUREMENT SCIENCE AND TECHNOLOGY AB - Since 1991, Measurement Science and Technology has awarded a Best Paper prize. The Editorial Board of this journal believes that such a prize is an opportunity to thank authors for submitting their work, and serves as an integral part of the on-going quality review of the journal. The current breadth of topical areas that are covered by MST has made it advisable to expand the recognition of excellent publications. Hence, since 2005 the Editorial Board have presented 'Outstanding Paper Awards'. This year awards were presented in the areas of 'Measurement Science' and 'Fluid Mechanics'. Although the categories mirror subject sections in the journal, the Editorial Board consider articles from all categories in the selection process. 2012 Award Winners—Measurement Science Physical characterization and performance evaluation of an x-ray micro-computed tomography system for dimensional metrology applications J Hiller1, M Maisl2 and L M Reindl3 1 Department of Mechanical Engineering, Technical University of Denmark (DTU), Produktionstorvet, Building 425, 2800 Kgs Lyngby, Denmark 2 Development Center for X-Ray Technology (EZRT), Fraunhofer Institute for Non-Destructive Testing (IZFP), Campus E3 1, 66123 Saarbrucken, Germany 3 Laboratory for Electrical Instrumentation, Institute for Microsystem Technology (IMTEK), University of Freiburg, Georges-Kohler-Allee 103, 79110 Freiburg, Germany This year's award goes to another paper [1] dealing with micro-measurements, using a scientific measurement technique that is both old and traditional. However, it is the advent of modern technology with computational techniques that have offered new insights into the capability of the measurement method. The paper describes an x-ray computed tomography (CT) system. Such systems are increasingly used in production engineering, where non-destructive measurements of the internal geometries of workpieces can be made with high information density. CT offers important alternatives to tactile or optical measurement systems which sometimes cannot reach internal features. The subject discussed is very important for measurement science. It is concerned with the many factors that affect precision and accuracy in CT metrology. These include issues in the scanning and reconstruction process, the image processing, and the 3D data evaluation. They all influence the dimensional measurement properties of the system as a whole. Therefore, as the authors point out, it is important to know what leads to, and what are the consequences of, such things as experimental geometrical misalignment of the scanner system, or image unsharpness (blurring), or noise or image artefacts. This paper is therefore directed at the implementation of a modern CT system, identifying what is important with implementation of the technique, and what are the likely sources of systematic and random error. After a useful introduction, the paper carefully describes a 3D micro-CT system developed at the Fraunhofer Institute for Non-Destructive Testing in Saarbrucken, Germany, to carry out dimensional measurements on small plastic and metal parts. Considerable emphasis is placed on the characterization of the x-ray tube, with discussion about the effective focal spot size and focus drift. Likewise, there is a detailed account of the flat-panel detector, before examining the contrast and noise transfer properties in the measuring volume. These features are important for achieving short term accuracy, whilst a later section discusses temperature measurements that affect long term accuracy. As a consequence, the image sharpness, noise or image artefacts, are evaluated. In a simple example, the length measurement property of the scanner for a given set of scanning parameters was obtained by using a calibrated ball-bar with a reference length of 8.7678 mm. Two different approaches for systematic error compensation were applied. They obtained an expanded measurement uncertainty of 6.9 µm down to 1.0 µm, which confirms the excellent dimensional measurement that can be achieved with a micro-CT scanner. The paper concludes with a useful summary of their characterization and performance studies. It also sets down possible future research activities in CT metrology. In particular, it identifies the need for development of CT scanning planning strategies to reduce measurement uncertainties in general and to minimize user influence in particular. This paper is excellent in its presentation and scientific description. Issues have been clearly described, and the paper should help establish x-ray micro-computed CT as a fully accepted measuring system in manufacturing engineering. Its contents were supported by 66 references. This helps to put the contribution into context with contributions from previous research papers. The nomination for this paper was supported by seven panel members, higher than any other paper, and it was rated as excellent during the refereeing process. 2012 Award Winners—Fluid Mechanics Polynomial element velocimetry (PEV): a technique for continuous in-plane velocity and velocity gradient measurements for low Reynolds number flows C R Samarage1,2, J Carberry2, G J Sheard2 and A Fouras1,2 1 Laboratory for Dynamic Imaging, Monash University, Melbourne, VIC 3800, Australia 2 Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC 3800, Australia The technique proposed in this article [2] is highly relevant to the wide community of experimentalists that make use of particle image velocimetry. The authors have addressed the issue of how to accurately measure the velocity field and the velocity gradient distribution. The method proposed is elegant and innovative in that it introduces polynomial base functions to represent the spatially varying velocity field within an 'element'. The working principle is clearly described and illustrated. It is noted that the authors have taken a modest position by limiting their conclusions to the case of low Reynolds number flows. It is expected that further developments of this work could lead to successful applications at higher Reynolds numbers and turbulent flows. For the cases analyzed in this work, the authors have achieved a significant improvement in describing the velocity and the vorticity in proximity of the wall. Lastly, the authors have discussed with an open attitude the possible shortcomings of the method. They have indicated the points that will deserve attention when further research efforts are dedicated to the topic. Given the above considerations, the MST outstanding paper selection committee for measurements in fluids, chaired by Professor John Foss, has nominated this article for the MST 2012 outstanding paper award. The chairmen would like to thank the authors for choosing to publish their work in Measurement Science and Technology, and hope that other researchers enjoy reading these works and feel encouraged to submit their own best work to the journal. References [1] Hiller J, Maisl M and Reindl L M 2012 Physical characterization and performance evaluation of an x-ray micro-computed tomography system for dimensional metrology applications Meas. Sci. Technol. 23 085404 (18pp) [2] Samarage C R, Carberry J, Sheard G J and Fouras A 2012 Polynomial element velocimetry (PEV): a technique for continuous in-plane velocity and velocity gradient measurements for low Reynolds number flows Meas. Sci. Technol. 23 105304 (16pp) DA - 2013/7// PY - 2013/7// DO - 10.1088/0957-0233/24/7/070101 VL - 24 IS - 7 SP - SN - 1361-6501 ER - TY - JOUR TI - An analytical solution describing the propagation of positive injury signals in an axon: effect of dynein velocity distribution AU - Kuznetsov, A. V. T2 - COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING AB - A model describing the propagation of positive injury signals from the lesion site in an axon towards the neuron soma is described. It is assumed that these signals are driven by dynein molecular motors. An analytical solution that accounts for the probability density function (pdf) of a dynein velocity distribution is obtained. Two examples of pdf of dynein velocity distributions that follow from the results published in Ross et al. (2006, Processive bidirectional motion of dynein–dynactin complexes in vitro. Nat Cell Biol. 8:562–570) and Deinhardt et al. (2006, Rab5 and Rab7 control endocytic sorting along the axonal retrograde transport pathway. Neuron 52:293–305) are considered. The effect of dynein velocity distribution on the rate of spreading of the signal wave is discussed. It is demonstrated that the obtained solution can be applied to the problem of how neurons measure the distance between the lesion site and the neuron soma. DA - 2013/7/1/ PY - 2013/7/1/ DO - 10.1080/10255842.2011.632376 VL - 16 IS - 7 SP - 699-706 SN - 1025-5842 KW - neuronal injury KW - positive injury signals KW - motor-dependent signals KW - dynein motors KW - retrograde axonal transport ER - TY - JOUR TI - A sensor for the direct measurement of curvature based on flexoelectricity AU - Yan, Xiang AU - Huang, Wenbin AU - Kwon, Seol Ryung AU - Yang, Shaorui AU - Jiang, Xiaoning AU - Yuan, Fuh-Gwo T2 - SMART MATERIALS AND STRUCTURES AB - A direct curvature sensing measurement based on the flexoelectricity of Ba0.64Sr0.36TiO3 (BST) material through electromechanical coupling is proposed and developed in this paper. The curvature sensing was demonstrated in four point bending tests of a beam with bonded BST curvature sensors under different applied loads with low time-harmonic frequencies from 0.5 to 3 Hz. A shear lag concept which describes the efficiency of the loading transfer from the epoxy bonding layer was taken into account in extracting the actual curvature from the sensor measurement. A finite element analysis has been performed to estimate the curvature transfer efficiency and the bonding layer thickness is found to be a critical parameter in determining the curvature transfer. Experimental results showed a good linearity of charge output dependence on curvature inputs in a limited frequency range and showed a curvature sensitivity of 30.78 pC m, in comparison with 32.48 pC m from theoretical predictions. Using the measured curvature, the bending stiffness of the beam was then obtained from the experimentally obtained moment–curvature curve. This work demonstrated that the flexoelectric BST sensor provides a direct curvature measurement instead of using a traditional strain gage sensor through interpolation, and thus offers an important avenue for on-line and in situ structural health monitoring. DA - 2013/8// PY - 2013/8// DO - 10.1088/0964-1726/22/8/085016 VL - 22 IS - 8 SP - SN - 1361-665X ER - TY - JOUR TI - Three-Dimensional Nanolithography Using Light Scattering from Colloidal Particles AU - Zhang, Xu A. AU - Elek, Jonathan AU - Chang, Chih-Hao T2 - ACS NANO AB - The interaction between light and colloidal elements can result in a wealth of interesting near-field optical patterns. By examining the optical and colloidal properties, the intensity distribution can be tailored and harnessed for three-dimensional nanolithography. Here, we examine the use of light scattering from colloidal particles to fabricate complex hollow nanostructures. In this approach, a single colloidal sphere is illuminated to create a scattering pattern, which is captured by a photoresist in close proximity. No external optical elements are required, and the colloidal elements alone provide the modulation of the optical intensity pattern. The fabricated nanostructures can be designed to have multiple shells, confined volumes, and single top openings, resembling "nano-volcanoes." The geometry of such structures is dependent on the scattered light distribution and can be accurately modeled by examining the light-particle interaction. The hollow nanostructures can be used to trap nanomaterial, and we demonstrate their ability to trap 50 nm silica nanoparticles. These well-defined surface hollow structures can be further functionalized for applications in controlled drug delivery and biotrapping. Colloidal elements with different geometries and material compositions can also be incorporated to examine other light-colloid interactions. DA - 2013/7// PY - 2013/7// DO - 10.1021/nn402637a VL - 7 IS - 7 SP - 6212-6218 SN - 1936-086X KW - nanolithography KW - three-dimensional nanostructures KW - colloids KW - self-assembly KW - light scattering ER - TY - JOUR TI - The Cheng-Minkowycz problem for natural convective boundary layer flow in a porous medium saturated by a nanofluid: A revised model AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - The classical Cheng–Minkowycz problem considers natural convection past a vertical plate in a fluid-saturated porous medium. In our previous work we extended the Cheng–Minkowycz problem to the case when a porous medium is saturated by a nanofluid. We utilized Buongiorno’s nanofluid model that includes the effects of Brownian motion and thermophoresis. The major limitation of our previous model was active control of nanoparticle volume fraction at the boundary. Here we revisited our previous model and extended it to the case when the nanofluid particle fraction on the boundary is passively rather than actively controlled. This makes the model physically more realistic than our previous model as well as models employed by other authors simulating nanofluid flow in porous media. DA - 2013/10// PY - 2013/10// DO - 10.1016/j.ijheatmasstransfer.2013.06.054 VL - 65 SP - 682-685 SN - 0017-9310 KW - Nanofluid KW - Porous medium KW - Brownian motion KW - Thermophoresis KW - Boundary layer KW - Vertical plate ER - TY - JOUR TI - Study on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O-3-0.3 PbTiO3 single crystal with nano-patterned composite electrode AU - Chang, Wei-Yi AU - Huang, Wenbin AU - Bagal, Abhijeet AU - Chang, Chih-Hao AU - Tian, Jian AU - Han, Pengdi AU - Jiang, Xiaoning T2 - JOURNAL OF APPLIED PHYSICS AB - Effect of nano-patterned composite electrode and backswitching poling technique on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 was studied in this paper. Composite electrode consists of Mn nano-patterns with pitch size of 200 nm, and a blanket layer of Ti/Au was fabricated using a nanolithography based lift-off process, heat treatment, and metal film sputtering. Composite electrode and backswitching poling resulted in 27% increase of d33 and 25% increase of dielectric constant, and we believe that this is attributed to regularly defined nano-domains and irreversible rhombohedral to monoclinic phase transition in crystal. The results indicate that nano-patterned composite electrode and backswitching poling has a great potential in domain engineering of relaxor single crystals for advanced devices. DA - 2013/9/21/ PY - 2013/9/21/ DO - 10.1063/1.4821517 VL - 114 IS - 11 SP - SN - 1089-7550 ER - TY - JOUR TI - Protein transport in the connecting cilium of a photoreceptor cell: Modeling the effects of bidirectional protein transitions between the diffusion-driven and motor-driven kinetic states AU - Kuznetsov, A. V. T2 - COMPUTERS IN BIOLOGY AND MEDICINE AB - Physics of protein transport through the connecting cilium (CC) of a photoreceptor cell is a long-standing question in cellular biology. There is evidence implicating both molecular motor-driven and diffusion-driven modes of intracellular transport. Based on available experimental clues, this paper develops a new model for intraflagellar transport (IFT) of proteins synthesized in the inner segment and transported through the CC to the outer segment of a photoreceptor cell. The model accounts for the competition between two modes of protein transport: molecular motor-driven transport and diffusion. The obtained solutions made it possible to calculate how the number of protein molecules transported through the CC at a given time depends on their diffusivity. Modeling results were compared with published experimental estimates, and conclusions about possible contributions of diffusion to IFT were made. DA - 2013/7/1/ PY - 2013/7/1/ DO - 10.1016/j.compbiomed.2013.03.009 VL - 43 IS - 6 SP - 758-764 SN - 1879-0534 KW - Photoreceptor cilium KW - Intraflagellar transport KW - Anterograde motors KW - Soluble proteins KW - Mathematical modeling ER - TY - JOUR TI - Physics and model of strengthening by parallel stacking faults AU - Jian, W. W. AU - Cheng, G. M. AU - Xu, W. Z. AU - Koch, C. C. AU - Wang, Q. D. AU - Zhu, Y. T. AU - Mathaudhu, S. N. T2 - APPLIED PHYSICS LETTERS AB - We have recently reported that parallel stacking faults (SFs) can tremendously increase the strength of a magnesium alloy. The strengthening is found to increase linearly with the reciprocal of the mean SF spacing, d. In this study we analyze dislocation interactions with SFs, and then propose a physics-based model to explain the observed relationship between yield strength and SFs spacing. Similar to the empirical Hall-Petch relationship for grain size, it is expected that this strengthening mechanism will hold true for a variety of materials engineered with parallel spaced stacking faults over a wide range of fault spacing. DA - 2013/9/23/ PY - 2013/9/23/ DO - 10.1063/1.4822323 VL - 103 IS - 13 SP - SN - 0003-6951 ER - TY - JOUR TI - Noncontact Manipulation of Light Objects Based on Parameter Modulations of Acoustic Pressure Nodes AU - Park, Joong-kyoo AU - Ro, Paul I. T2 - JOURNAL OF VIBRATION AND ACOUSTICS-TRANSACTIONS OF THE ASME AB - An investigation of noncontact manipulation techniques based on acoustic levitation was undertaken in air. The standing wave acoustic levitation (SWAL) was observed when standing waves trap small objects at pressure nodes. In this paper, two ultrasonic bolt-clamped Langevin type transducers (BLTs) generating traveling waves by modulating parameters of the two traveling waves were used to manipulate a trapped object. Frequency, amplitude, and phase modulations of the two actuators were exploited. From simulation and experiments, the phase modulation was prominent among other methods due to its long range and smooth operation. It is also found that angles between two actuators affect the trajectory of the trapped object during the parameter modulations. Sinusoidal and elliptic paths of the object were observed experimentally through a combination of parameters at certain tilt angles. DA - 2013/6// PY - 2013/6// DO - 10.1115/1.4023816 VL - 135 IS - 3 SP - SN - 1528-8927 KW - standing wave acoustic levitation KW - noncontact manipulation KW - parameter modulations KW - acoustic radiation pressure KW - ultrasound ER - TY - JOUR TI - Lung Deposition Analyses of Inhaled Toxic Aerosols in Conventional and Less Harmful Cigarette Smoke: A Review AU - Kleinstreuer, Clement AU - Feng, Yu T2 - INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH AB - Inhaled toxic aerosols of conventional cigarette smoke may impact not only the health of smokers, but also those exposed to second-stream smoke, especially children. Thus, less harmful cigarettes (LHCs), also called potential reduced exposure products (PREPs), or modified risk tobacco products (MRTP) have been designed by tobacco manufacturers to focus on the reduction of the concentration of carcinogenic components and toxicants in tobacco. However, some studies have pointed out that the new cigarette products may be actually more harmful than the conventional ones due to variations in puffing or post-puffing behavior, different physical and chemical characteristics of inhaled toxic aerosols, and longer exposure conditions. In order to understand the toxicological impact of tobacco smoke, it is essential for scientists, engineers and manufacturers to develop experiments, clinical investigations, and predictive numerical models for tracking the intake and deposition of toxicants of both LHCs and conventional cigarettes. Furthermore, to link inhaled toxicants to lung and other diseases, it is necessary to determine the physical mechanisms and parameters that have significant impacts on droplet/vapor transport and deposition. Complex mechanisms include droplet coagulation, hygroscopic growth, condensation and evaporation, vapor formation and changes in composition. Of interest are also different puffing behavior, smoke inlet conditions, subject geometries, and mass transfer of deposited material into systemic regions. This review article is intended to serve as an overview of contributions mainly published between 2009 and 2013, focusing on the potential health risks of toxicants in cigarette smoke, progress made in different approaches of impact analyses for inhaled toxic aerosols, as well as challenges and future directions. DA - 2013/9// PY - 2013/9// DO - 10.3390/ijerph10094454 VL - 10 IS - 9 SP - 4454-4485 SN - 1660-4601 KW - conventional or less harmful cigarettes KW - aerosol toxicology KW - cigarette smoke droplet KW - vapor deposition KW - second-hand smoke KW - impact analysis KW - computational fluid-particle dynamics ER - TY - CONF TI - Indirect intelligent sliding mode control using hysteretic recurrent neural networks with application to a shape memory alloy actuated beam AU - Hannen, J. C. AU - Buckner, G. D. AB - This paper presents the development of an indirect intelligent sliding mode controller (IISMC) for shape memory alloy (SMA) actuators. The controller manipulates applied voltage, enabling temperature control in one or more SMA tendons, which are offset to produce bending in a flexible beam tip. Hysteresis compensation is achieved using a hysteretic recurrent neural network (HRNN), which maps the nonlinear, hysteretic relationships between SMA temperatures and bending angle. Incorporating this HRNN into a variable structure control architecture provides robustness to model uncertainties and parameter variations. Single input, single output and multivariable implementations of this control strategy are presented. Controller performance is evaluated using a flexible beam deflected by single and antagonistic SMA tendons. Experimental results demonstrate precise tracking of a variety of reference trajectories for both configurations, with superior performance compared to an optimized PI controller for each system. Additionally, the IISMC demonstrates robustness to parameter variations and disturbances. C2 - 2013/// C3 - Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, vol 1 DA - 2013/// DO - 10.1115/smasis2012-7930 SP - 295-303 ER - TY - JOUR TI - Focusing guided waves using surface bonded elastic metamaterials AU - Yan, Xiang AU - Zhu, Rui AU - Huang, Guoliang AU - Yuan, Fuh-Gwo T2 - APPLIED PHYSICS LETTERS AB - Bonding a two-dimensional planar array of small lead discs on an aluminum plate with silicone rubber is shown numerically to focus low-frequency flexural guided waves. The “effective mass density profile” of this type of elastic metamaterials (EMMs), perpendicular to wave propagation direction, is carefully tailored and designed, which allows rays of flexural A0 mode Lamb waves to bend in succession and then focus through a 7 × 9 planar array. Numerical simulations show that Lamb waves can be focused beyond EMMs region with amplified displacement and yet largely retained narrow banded waveform, which may have potential application in structural health monitoring. DA - 2013/9/16/ PY - 2013/9/16/ DO - 10.1063/1.4821258 VL - 103 IS - 12 SP - SN - 1077-3118 ER - TY - JOUR TI - Energy harvesting using a PZT ceramic multilayer stack AU - Xu, Tian-Bing AU - Siochi, Emilie J. AU - Kang, Jin Ho AU - Zuo, Lei AU - Zhou, Wanlu AU - Tang, Xiudong AU - Jiang, Xiaoning T2 - SMART MATERIALS AND STRUCTURES AB - In this paper, the interdisciplinary energy harvesting issues on piezoelectric energy harvesting were investigated using a '33' mode (mechanical stress and/or electric field are in parallel to the polarization direction) lead zirconate titanate multilayer piezoelectric stack (PZT-Stack). Key energy harvesting characteristics including the generated electrical energy/power in the PZT-Stack, the mechanical to electrical energy conversion efficiency, the power delivered from the PZT-Stack to a resistive load, the electrical charge/energy transferred from the PZT-Stack to a super-capacitor were systematically addressed. Theoretical models for power generation and delivery to a resistive load were proposed and experimentally affirmed. In a quasi-static regime, 70% generated electrical powers were delivered to matched resistive loads. A 35% mechanical to electrical energy conversion efficiency, which is more than 4 times higher than other reports, for the PZT-Stack had been obtained. The generated electrical power and power density were significantly higher than those from a similar weight and size cantilever-type piezoelectric harvester in both resonance and off-resonance modes. In addition, our study indicated that the capacitance and piezoelectric coefficient of the PZT-Stack were strongly dependent on the dynamic stress. DA - 2013/6// PY - 2013/6// DO - 10.1088/0964-1726/22/6/065015 VL - 22 IS - 6 SP - SN - 1361-665X ER - TY - JOUR TI - Effects of Ambient Temperature and Oxygen Concentration on Diesel Spray Combustion Using a Single-Nozzle Injector in a Constant Volume Combustion Chamber AU - Jing, Wei AU - Roberts, William L. AU - Fang, Tiegang T2 - COMBUSTION SCIENCE AND TECHNOLOGY AB - This work investigates the effects of ambient conditions on diesel spray combustion in an optically accessible, constant volume chamber using a single-nozzle fuel injector. The ambient O2 concentration was varied between five discrete values from 10% to 21% and three different ambient temperatures (800 K, 1000 K, and 1200 K). These conditions simulate different exhaust gas recirculation (EGR) levels and ambient temperatures in diesel engines. Both conventional diesel combustion and low temperature combustion (LTC) modes were observed under these conditions. A transient analysis and a quasi-steady state analysis are employed in this article. The transient analysis focuses on the flame development from beginning to the end, illustrating how the flame structure changes during this process; the quasi-steady state analysis focuses on the stable flame structure. The transient analysis was conducted using high-speed imaging of both OH* chemiluminescence and natural luminosity (NL). In addition, three different images were acquired using an ICCD camera, corresponding to OH* chemiluminescence, narrow-band flame emission at 430 nm (Band A) and at 470 nm (Band B), and were used to investigate the quasi-steady state combustion process. From the transient analysis, it was found that the NL signal becomes stronger and confined to narrow regions when the temperature and O2 concentration increase during the development of flame. The OH* intensity is much lower for the 10% ambient O2 and 800 K conditions compared to the higher temperatures and O2 levels. This implies the occurrence of LTC under these conditions. Results from the quasi-steady combustion stage indicate that high-temperature reactions effectively oxidize the soot in the downstream locations where only OH* signal is observed. In addition, an area was calculated for each spectral region, and results show that the area of Band A and Band B emissions in these images is larger than the area of OH* emissions at the lower O2 concentrations while the area of OH* emission is larger than the area of Band A and Band B emissions at higher O2 concentrations, for a given ambient temperature. Moreover, the mixture stoichiometry was analyzed using a reformulated definition of excess air ratio for diluted combustion, and this shows that more mixing is required to achieve complete combustion for low ambient oxygen concentration conditions where longer and wider flames are observed. This observation is also verified by the flame length estimated from the NL images. DA - 2013/9/2/ PY - 2013/9/2/ DO - 10.1080/00102202.2013.798315 VL - 185 IS - 9 SP - 1378-1399 SN - 0010-2202 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84882388541&partnerID=MN8TOARS KW - Diesel engine KW - Excess air ratio KW - Low-temperature combustion KW - Natural luminosity KW - OH* chemiluminescence KW - Spray combustion ER - TY - JOUR TI - Dislocations with edge components in nanocrystalline bcc Mo AU - Cheng, G. M. AU - Xu, W. Z. AU - Jian, W. W. AU - Yuan, H. AU - Tsai, M. H. AU - Zhu, Y. T. AU - Zhang, Y. F. AU - Millett, P. C. T2 - Journal of Materials Research DA - 2013/// PY - 2013/// DO - 10.1557/jmr.2012.403 VL - 28 IS - 13 SP - 1820-1826 ER - TY - CONF TI - Development of robust control algorithms for shape memory alloy bending actuators AU - Crews, J. H. AU - Smith, R. C. AU - Hannen, J. C. AB - In this paper, we present a systematic approach to developing robust control algorithms for a single-tendon shape memory alloy (SMA) bending actuator. Parameter estimation and uncertainty quantification are accomplished using Bayesian techniques. Specifically, we utilize Markov Chain Monte Carlo (MCMC) methods to estimate parameter uncertainty. The Bayesian parameter estimation results are used to construct a sliding mode control (SMC) algorithm where the bounds on uncertainty are used to guarantee controller robustness. The sliding mode controller utilizes the homogenized energy model (HEM) for SMA. The inverse HEM compensates for hysteresis and converts a reference bending angle to a reference temperature. Temperature in the SMA actuator is estimated using an observer, and the sliding mode controller ensures that the observer temperature tracks the reference temperature. The SMC is augmented with proportional-integral (PI) control on the bending angle error. C2 - 2013/// C3 - Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, vol 1 DA - 2013/// DO - 10.1115/smasis2012-7989 SP - 391-400 ER - TY - JOUR TI - Design, Fabrication, and Characterization of a Single-Aperture 1.5-MHz/3-MHz Dual-Frequency HIFU Transducer AU - Ma, Jianguo AU - Guo, Sijia AU - Wu, Di AU - Geng, Xuecang AU - Jiang, Xiaoning T2 - IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL AB - High-intensity focused ultrasound (HIFU) treatment efficiency is critical in maximizing the hyperthermia and reducing the surgery time. In this paper, a single-aperture, 1.5 MHz/3 MHz dual-frequency HIFU transducer was designed, fabricated, and characterized for tissue ablation enhancement. Double PZT-2 layers were configured in serial and dual-frequency ultrasound waves can be concurrently generated by exciting one of the PZT-2 layers. Impulse responses from the prototype showed that the wave amplitudes at 1.5 and 3 MHz were about the same, and both are more than 12 dB larger than those of higher orders of harmonics. Tissue ablation tests demonstrated that higher temperature rise can be achieved with dual-frequency ultrasound than with single-frequency ablation at the same acoustic power. DA - 2013/7// PY - 2013/7// DO - 10.1109/tuffc.2013.2724 VL - 60 IS - 7 SP - 1519-1529 SN - 1525-8955 ER - TY - JOUR TI - DROP: the durable reconnaissance and observation platform AU - Parness, A. AU - McKenzie, C. T2 - Industrial Robot-an International Journal DA - 2013/// PY - 2013/// VL - 40 IS - 3 SP - 218-223 ER - TY - JOUR TI - A review of entropy generation in nanofluid flow AU - Mahian, Omid AU - Kianifar, Ali AU - Kleinstreuer, Clement AU - Al-Nimr, Moh'd A. AU - Pop, Ioan AU - Sahin, Ahmet Z. AU - Wongwises, Somchai T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - The development and use of nanofluids, i.e., dilute suspensions of nanoparticles in liquids, have found a wide range of applications in consumer products, nanomedicine, energy conversion, and microsystem cooling. Of special interest is the use of nanofluid flow for enhanced convection heat transfer to achieve rapid cooling of high heat-flux devices. However, for proper optimization of such thermal engineering systems in terms of design and operation, not only the heat transfer has to be maximized but the entropy generation has to be minimized as well. In this paper, theoretical and computational contributions on entropy generation due to flow and heat transfer of nanofluids in different geometries and flow regimes are reviewed. First, a variety of models used to calculate the thermophysical properties of nanofluids are presented. Then, the effects of thermal nanofluid flow on the rate of entropy generation for different applications are discussed. Finally, some suggestions for future work are presented. The aim of this review paper is to motivate the researchers to pay more attention to the entropy generation analysis of heat and fluid flow of nanofluids to improve the system performance. DA - 2013/10// PY - 2013/10// DO - 10.1016/j.ijheatmasstransfer.2013.06.010 VL - 65 SP - 514-532 SN - 1879-2189 KW - Nanofluid flow KW - Thermophysical property KW - Entropy generation ER - TY - JOUR TI - A novel Kalman filter based approach for multiscale reacting flow simulations AU - Srivastava, Shubham AU - Echekki, Tarek T2 - COMPUTERS & FLUIDS AB - A multi-scale approach for coupling a coarse-grained (CG) deterministic solution for a reacting flow with a fine-grained (FG) stochastic solution is proposed. The model includes a CG solution for the mass density and momentum and a FG solution for the temperature. A model for the turbulent transport in the FG solution is implemented using the linear-eddy model (LEM), which combines a deterministic implementation for reaction, diffusion and large-scale transport with a stochastic implementation for fine-scale transport. A common variable is obtained from these solutions based on a CG density field defined from continuity on the coarse scales and the spatial filtering of the density derived from the state equation in the FG solution. Kalman filtering is used to combine these two solutions. The resulting CG density is both smooth and steered by heat release from the FG solution. The algorithm is demonstrated on a 1D model combining continuity and the Burgers’ equation for the CG solution and the temperature equation with heat release for the FG solution. The results establish the feasibility of Kalman filtering in coupling deterministic CG solutions and stochastic FG solutions in reacting flow applications. DA - 2013/7/20/ PY - 2013/7/20/ DO - 10.1016/j.compfluid.2013.04.008 VL - 81 SP - 1-9 SN - 1879-0747 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877832954&partnerID=MN8TOARS KW - Turbulent reacting flows KW - Kalman filtering KW - Large-eddy simulation ER - TY - JOUR TI - Transcranial ultrasound imaging with speed of sound-based phase correction: a numerical study AU - Wang, Tianren AU - Jing, Yun T2 - PHYSICS IN MEDICINE AND BIOLOGY AB - This paper presents a numerical study for ultrasound transcranial imaging. To correct for the phase aberration from the skull, two critical steps are needed prior to brain imaging. In the first step, the skull shape and speed of sound are acquired by either CT scans or ultrasound scans. In the ultrasound scan approach, phased array and double focusing technique are utilized, which are able to estimate the thickness of the skull with a maximum error of around 10% and the average speed of sound in the skull is underestimated by less than 2%. In the second step, the fast marching method is used to compute the phase delay based on the known skull shape and sound speed from the first step, and the computation can be completed in seconds for 2D problems. The computed phase delays are then used in combination with the conventional delay-and-sum algorithm for generating B-mode images. Images of wire phantoms with CT or ultrasound scan-based phase correction are shown to have much less artifact than the ones without correction. Errors of deducing speed of sound from CT scans are also discussed regarding its effect on the transcranial ultrasound images. Assuming the speed of sound grows linearly with the density, this study shows that, the CT-based phase correction approach can provide clear images of wire phantoms even if the speed of sound is overestimated by 400 m s−1, or the linear coefficient is overestimated by 40%. While in this study, ultrasound scan-based phase correction performs almost equally well with the CT-based approach, potential problems are identified and discussed. DA - 2013/10/7/ PY - 2013/10/7/ DO - 10.1088/0031-9155/58/19/6663 VL - 58 IS - 19 SP - 6663-6681 SN - 1361-6560 ER - TY - JOUR TI - Tissue characterization using an acoustic wave tactile sensor array AU - Kim, Kyungrim AU - Jiang, Xiaoning T2 - HEALTH MONITORING OF STRUCTURAL AND BIOLOGICAL SYSTEMS 2013 AB - Tactile perception of different types of tissue is important in order for surgeons to perform procedures correctly and safely. This is especially true in minimally invasive surgery (MIS) where the surgeon must be able to locate the target tissue without a direct line of sight or direct finger touch. In this study, tissue characterization using an acoustic wave tactile sensor array was investigated. This type of tactile sensor array can detect the acoustic impedance change of target materials. Abnormal tissues can have different Young’s moduli and shear moduli caused by composition change compared to those of healthy tissues. This also leads to a difference in acoustic impedance which can be detected using our sensor array. The array was fabricated using a face-shear mode PMN-PT piezoelectric resonator which is highly sensitive to acoustic impedance load. Gelatin and water mixtures with weight concentration of 5 wt % - 30 wt % were prepared as tissue phantoms. The shear modulus of each phantom was measured using bulk face-shear mode crystal resonators, and it was found that shear modulus change from 120 kPa to 430 kPa resulted on 30 % electrical impedance shift from the resonator. Imaging display of elastic properties of prepared phantoms was also tested using the fabricated sensor array. The proposed tissue characterization technique is promising for the development of effective surgical procedures in minimally invasive surgery. DA - 2013/// PY - 2013/// DO - 10.1117/12.2009518 VL - 8695 SP - SN - 1996-756X KW - acoustic wave KW - tactile sensor KW - tissue characterization KW - face-shear mode resonator ER - TY - JOUR TI - Through-the-thickness identification of impact damage in composite laminates through pulsed phase thermography AU - Pawar, Sachin S. AU - Peters, Kara T2 - MEASUREMENT SCIENCE AND TECHNOLOGY AB - In this paper we demonstrate through-the-thickness imaging of barely visible impact damage in a two-dimensional woven, carbon fiber epoxy laminate using pulsed phase thermography (PPT). Specifically we calibrate the defect depth with blind frequency for the particular material system using a specimen with simulated defects in the form of polymer foam inclusions. The calibrated depth versus blind frequency relation is then applied to specimens with barely visible impact damage due to low-velocity impacts. The polymer foam reproduces the irregular boundaries and thin nature of the delaminations, but does not reproduce through-the-thickness variations. The extent of delamination at different depths was reconstructed as a function of depth for varying levels of impact energy. The extent of damage imaged using PPT corresponded well with visual observations and microscopy images. DA - 2013/11// PY - 2013/11// DO - 10.1088/0957-0233/24/11/115601 VL - 24 IS - 11 SP - SN - 1361-6501 KW - pulsed phase thermography KW - composites KW - low-velocity impact KW - barely visible impact damage ER - TY - JOUR TI - The onset of bio-thermal convection induced by a combined effect of gyrotactic and oxytactic microorganisms AU - Kuznetsov, A. V. T2 - INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW AB - Purpose The purpose of this paper is to investigate the stability of a suspension containing both gyrotactic and oxytactic microorganisms for the case when the suspension occupies a horizontal layer of finite depth. The lower boundary of the layer is assumed rigid while at the upper boundary both situations of rigid and stress‐free boundary conditions are considered. Design/methodology/approach Linear instability analysis is utilized, and the obtained eigenvalue problem is solved analytically using a one‐term Galerkin method. Findings The obtained eigenvalue equation relates three Rayleigh numbers, the traditional thermal Rayleigh number and two bioconvection Rayleigh numbers, for gyrotactic and oxytactic microorganisms. Research limitations/implications Only the case of non‐oscillatory instability (which always occurs when heating from the bottom is considered) is analyzed. Further experimental research is needed to elucidate possible interaction between gyrotactic and oxytactic microorganisms. The developed theory is applicable only for dilute suspensions. Originality/value This paper extends the traditional theory of bio‐thermal convection to the case when the suspension contains two types of motile microorganisms exhibiting different behaviors. DA - 2013/// PY - 2013/// DO - 10.1108/hff-09-2011-0178 VL - 23 IS - 6 SP - 979-1000 SN - 1758-6585 KW - Thermobioconvection KW - Gyrotactic and oxytactic microorganisms KW - Natural convection KW - Onset of instability KW - Horizontal layer KW - Convection KW - Micro-organisms ER - TY - JOUR TI - Temperature Rise in Tissue Ablation Using Multi-Frequency Ultrasound AU - Guo, Sijia AU - Jing, Yun AU - Jiang, Xiaoning T2 - IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL AB - High-intensity focused ultrasound (HIFU) is becoming an increasingly important noninvasive surgical tool, despite the challenges in temperature rise control and unwanted heating problems. In this study, experiments and simulations on tissue ablation effectiveness were performed using multi-frequency HIFU with frequency differences of more than 500 kHz (center frequencies are 950 kHz, 1.5 MHz, and 3.3 MHz). In the experiments, the temperature was recorded as chicken breast tissue was heated by single-frequency, dual-frequency, and tri-frequency HIFU configurations at controlled acoustic power and exposure time. 5% to 10% temperature rise differences were observed between single- and multi-frequency modes, indicating that multi-frequency HIFU is more effective at producing faster temperature rises. Cavitation detection tests were conducted to compare the cavitation pressure fields between single- and multi-frequency ultrasound. Moreover, simulations on single-frequency and multi-frequency acoustic fields as well as bio-heating-induced temperature fields were performed. With the comparison between experimental and simulation results, we believe that the more effective tissue ablation using multi-frequency ultrasound is likely attributed to the enhanced cavitation, a promising result for HIFU applications. DA - 2013/8// PY - 2013/8// DO - 10.1109/tuffc.2013.2751 VL - 60 IS - 8 SP - 1699-1707 SN - 1525-8955 ER - TY - JOUR TI - Robust Switched Filtering for Time-Varying Polytopic Uncertain Systems AU - Duan, Chang AU - Wu, Fen T2 - JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME AB - This paper studies the problem of designing robust switched filters for time-varying polytopic uncertain systems. The synthesis conditions for a set of filters under a min-switching rule are derived to guarantee globally asymptotical stability with optimized robust H∞ performance. Specifically, the conditions are expressed as bilinear matrix inequalities (BMIs) and can be solved by linear matrix inequality (LMI) optimization techniques. The proposed approach utilizes a piecewise quadratic Lyapunov function to reduce the conservativeness of robust filtering methods based on single Lyapunov function, thus better H∞ performance can be achieved. Both continuous and discrete-time robust filter designs are considered. To simplify filter implementation, a method to remove redundancy in min-switching filter members is also introduced. The advantages of the proposed robust switching filters are illustrated by several examples. DA - 2013/11// PY - 2013/11// DO - 10.1115/1.4025027 VL - 135 IS - 6 SP - SN - 1528-9028 KW - polytopic uncertain systems KW - robust switching state estimation KW - min-switching logic KW - robust H-infinity performance ER - TY - JOUR TI - Reduced-Order Aerodynamic Modeling of Flapping Wing Energy Harvesting at Low Reynolds Number AU - Bryant, Matthew AU - Gomez, Juan Carlos AU - Garcia, Ephrahim T2 - AIAA JOURNAL AB - Energy harvesting from flowing fluids using flapping wings and fluttering aeroelastic structures has recently gained significant research attention as a possible alternative to traditional rotary turbines, especially at and below the centimeter scale. One promising approach uses an aeroelastic flutter instability to drive limit cycle oscillations of a flexible piezoelectric energy harvesting structure. Such a system is well suited to miniaturization and could be used to create self-powered wireless sensors wherever ambient flows are available. In this paper, we examine modeling of the aerodynamic forces, power extraction, and efficiency of such a flapping wing energy harvester at a low Reynolds number on the order of 1000. Two modeling approaches are considered: a quasi-steady method generalized from existing models of insect flight and a modified model that includes terms to account for the effects of dynamic stall. These two modeling approaches are applied to predicting the instantaneous aerodynamic force histories of an oscillating airfoil as well as parametric studies of the energy extraction efficiency. The modified model is shown to provide better agreement with computational fluid dynamics simulations of a flapping energy harvester. DA - 2013/12// PY - 2013/12// DO - 10.2514/1.j052364 VL - 51 IS - 12 SP - 2771-2782 SN - 1533-385X ER - TY - JOUR TI - Processing and evaluation of bioactive coatings on polymeric implants AU - Rabiei, Afsaneh AU - Sandukas, Stefan T2 - JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A AB - Polyetheretherketone (PEEK) is a high‐performance polymer with advantages over metallic biomaterials for application in spinal implants. In this study, hydroxyapatite (HA) coatings were deposited onto PEEK substrates using radio‐frequency magnetron sputtering for the purpose of improving bioactivity. An intermediate coating layer of yttria‐stabilized zirconia (YSZ) was first deposited onto the PEEK substrates to provide heat shielding during subsequent post‐deposition heat treatment to prevent degradation of PEEK substrates and coating/substrate interface. Plasma activation of the PEEK substrate surfaces before deposition resulted in a significant increase in coating adhesion strength. Post‐deposition heat treatments of microwave and hydrothermal annealing were studied with the goal of forming crystalline HA without the use of high temperatures required in conventional annealing. Microstructural and compositional analyses by scanning electron microscopy (SEM) and X‐ray diffraction revealed that the YSZ layer exhibited a crystalline structure as‐deposited, with columnar grains oriented along the growth direction, whereas the HA layer was shown to be amorphous as‐deposited. After microwave annealing, the HA coating exhibited a columnar crystalline microstructure, similar to that of the underlying YSZ crystalline layer; XRD analysis confirmed a crystalline HA phase in the coating. It is suggested that the existence of the crystalline YSZ layer aids in the formation of the HA layer upon heating, possibly lowering the activation energy for crystallization by providing nucleation sites for HA grain formation. Cell culture tests showed a significant increase in initial cell attachment and growth on the microwave‐annealed coatings, compared with uncoated PEEK and amorphous HA surfaces. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 2621–2629, 2013. DA - 2013/9// PY - 2013/9// DO - 10.1002/jbm.a.34557 VL - 101 IS - 9 SP - 2621-2629 SN - 1552-4965 KW - hydroxyapatite coating KW - PEEK KW - osteoblast response KW - magnetron sputtering KW - spinal fusion cage ER - TY - JOUR TI - Nonlinear gain-scheduling output-feedback control for polynomial nonlinear systems subject to actuator saturation AU - Wu, Fen AU - Hays, Scott T2 - INTERNATIONAL JOURNAL OF CONTROL AB - This paper investigates nonlinear gain-scheduling control approaches for a class of polynomial nonlinear systems, containing an output-dependent vector field with input saturation. Using the polytopic differential inclusion and norm-bounded differential inclusion (NDI) of saturation and dead-zone functions, the nonlinear plants are transformed into systems with measurable parameters. For the polytopic differential inclusion description, a quasi-linear parameter varying (quasi-LPV) output-feedback controller will be sought for saturation control. On the other hand, the NDI model leads to a nonlinear fractional transformation (NFT) output-feedback controller for saturated nonlinear systems. The quasi-LPV and NFT output-feedback control synthesis conditions are derived in the forms of output-dependent matrix inequalities. They can be reformulated as sum-of-squares (SOS) optimisations and solved efficiently using SOS programming. The proposed nonlinear gain-scheduling saturation control approaches will be demonstrated using the Van der Pol equation. DA - 2013/9/1/ PY - 2013/9/1/ DO - 10.1080/00207179.2013.792001 VL - 86 IS - 9 SP - 1607-1619 SN - 1366-5820 KW - actuator saturation KW - gain-scheduling control KW - output feedback KW - polynomial nonlinear systems KW - SOS programming ER - TY - JOUR TI - Nanostructure fabrication on germanium and silicon by nanocoining imprint technique AU - Zdanowicz, Erik AU - Dow, Thomas A. AU - Scattergood, Ronald O. AU - Youssef, Khaled T2 - PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY AB - Germanium (Ge) and silicon (Si) material response to indentation with a nanostructured die is investigated. A diamond die attached to a high speed actuator previously used to create large arrays of nanofeatures on metallic surfaces was used to create nanofeatures on Ge and Si samples. The pressure induced transformation of Ge and Si from a diamond cubic brittle phase to a more ductile beta-tin metallic phase due to the nanofeatures on the die was investigated. Results using the dynamic nanocoining method showed chip-like deformation around the individual nanofeatures indicative of the beta-tin phase transformation at the nanofeature level. Micro-Raman measurements confirmed the metallic transition from evidence including metastable and amorphous phases after indentation. Indents created using a common linear indentation method exhibited similar behavior. The Si nanofeature deformation was compared to electroless (EL) nickel and the deformation differed as dictated by the mechanism of material flow. Although not observed in Si, fracture occurred in some Ge indents at higher loads as a result of the lower fracture toughness compared to Si. DA - 2013/10// PY - 2013/10// DO - 10.1016/j.precisioneng.2013.05.004 VL - 37 IS - 4 SP - 871-879 SN - 1873-2372 KW - Nanocoining KW - Phase transformation KW - Nanostructured KW - Diamond die KW - Silicon KW - Germanium ER - TY - JOUR TI - In-situ atomic-scale observation of irradiation-induced void formation AU - Xu, Weizong AU - Zhang, Yongfeng AU - Cheng, Guangming AU - Jian, Weiwei AU - Millett, Paul C. AU - Koch, Carl C. AU - Mathaudhu, Suveen N. AU - Zhu, Yuntian T2 - NATURE COMMUNICATIONS AB - The formation of voids in an irradiated material significantly degrades its physical and mechanical properties. Void nucleation and growth involve discrete atomic-scale processes that, unfortunately, are not yet well understood due to the lack of direct experimental examination. Here we report an in-situ atomic-scale observation of the nucleation and growth of voids in hexagonal close-packed magnesium under electron irradiation. The voids are found to first grow into a plate-like shape, followed by a gradual transition to a nearly equiaxial geometry. Using atomistic simulations, we show that the initial growth in length is controlled by slow nucleation kinetics of vacancy layers on basal facets and anisotropic vacancy diffusivity. The subsequent thickness growth is driven by thermodynamics to reduce surface energy. These experiments represent unprecedented resolution and characterization of void nucleation and growth under irradiation, and might help with understanding the irradiation damage of other hexagonal close-packed materials. The irradiation of crystalline materials is known to create various types of lattice defects, which can degrade mechanical performance. Here, Xu et al. observe the in-situnucleation and growth of atomic-scale voids in magnesium during electron irradiation. DA - 2013/8// PY - 2013/8// DO - 10.1038/ncomms3288 VL - 4 SP - SN - 2041-1723 ER - TY - JOUR TI - Focusing flexural Lamb waves by designing elastic metamaterials bonded on a plate AU - Yan, X. AU - Zhu, R. AU - Huang, G. L. AU - Yuan, F. G. T2 - HEALTH MONITORING OF STRUCTURAL AND BIOLOGICAL SYSTEMS 2013 AB - In this paper, a method to focus flexural Lamb waves to a local area by mounting elastic metamaterials (EMMs) on the surface of the plate is proposed. The EMM consists of silicon rubber and lead connected in series bonded vertically on an aluminum plate. A simplified effective mass-“spring”-mass model is used to study the EMM plate. The frequency-dependent effective mass density of the EMM plate is determined with the aid of the numerically based effective medium method. By making use of the low locally resonant frequency of the EMM plate, the EMM plate is carefully designed with different dimensions to attain high effective mass densities. The effective mass density can be assumed to dominate the change of wave velocity and propagation direction in the EMM plate. An effective mass density profile is then employed along the transverse direction of wave propagation to achieve focusing. Finally, numerical simulation with finite element method (FEM) is utilized to investigate the focusing phenomenon of the A0 mode Lamb waves at 30 kHz and the out-of-plane displacement response beyond the EMM region. Numerical simulation results have shown that focusing the low frequency A0 mode Lamb waves using EMMs is feasible. The focusing may have potential applications in structural health monitoring by manipulating Lamb waves through controlling and focusing Lamb waves to any arbitrary location of the plate with amplified displacement and yet largely retained five-peaked toneburst waveform. DA - 2013/// PY - 2013/// DO - 10.1117/12.2009506 VL - 8695 SP - SN - 1996-756X KW - Focusing KW - Lamb waves KW - elastic metamaterials KW - structural health monitoring ER - TY - CONF TI - Feedback design for saturated polynomial nonlinear systems via higher order Lyapunov functions AU - Yang, S. W. AU - Wu, F. AB - In this work, we develop a new control design approach to deal with saturated polynomial nonlinear systems by using higher order Lyapunov functions. By combining power transformation with Sum-of-Squares (SOS) techniques, we can augment the systems with more state variables representing higher order combinations of the original ones. Then, the search of higher order Lyapunov functions for original systems can be recast to the design of quadratic Lyapunov functions for augmented systems. By computing for higher order Lyapunov functions using norm-bounded differential inclusion (NDI) LMI conditions, the flexible representations of augmented systems can help us to achieve better performance than quadratic based method. Two examples illustrate the improvements to enlarge the region of attraction and to improve the ℋ∞ performance for nonlinear systems subjected to saturation nonlinearity, respectively.© 2012 ASME C2 - 2013/// C3 - Proceedings of the ASME 5th Annual Dynamic Systems and Control Division Conference and JSME 11th Motion and Vibration Conference, DSCC 2012, vol 2 DA - 2013/// DO - 10.1115/dscc2012-movic2012-8644 SP - 645-652 ER - TY - JOUR TI - Electrothermomechanical Modeling and Analyses of Carbon Nanotube Polymer Composites AU - Xu, S. AU - Rezvanian, O. AU - Zikry, M. A. T2 - JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME AB - A new finite element (FE) modeling method has been developed to investigate how the electrical-mechanical-thermal behavior of carbon nanotube (CNT)–reinforced polymer composites is affected by electron tunneling distances, volume fraction, and physically realistic tube aspect ratios. A representative CNT polymer composite conductive path was chosen from a percolation analysis to establish the three-dimensional (3D) computational finite-element (FE) approach. A specialized Maxwell FE formulation with a Fermi-based tunneling resistance was then used to obtain current density evolution for different CNT/polymer dispersions and tunneling distances. Analyses based on thermoelectrical and electrothermomechanical FE approaches were used to understand how CNT-epoxy composites behave under electrothermomechanical loading conditions. DA - 2013/4// PY - 2013/4// DO - 10.1115/1.4023912 VL - 135 IS - 2 SP - SN - 1528-8889 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84888342251&partnerID=MN8TOARS KW - carbon nanotube KW - percolation KW - tunneling resistance KW - electrical conductivity ER - TY - JOUR TI - Design, fabrication and test of a small aperture, dual frequency ultrasound transducer AU - Ma, Jianguo AU - Wang, Zhuochen AU - Jiang, Xiaoning T2 - HEALTH MONITORING OF STRUCTURAL AND BIOLOGICAL SYSTEMS 2013 AB - High resolution ultrasound medical imaging requires high frequency transducers, which usually are known with decreased penetration depth because of high loss in two-way-loop at high frequencies. To obtain high resolution imaging at large depth, a dual frequency transducer was designed for contrast imaging. Specifically, a 35 MHz receiving transducer with aperture of 0.6 mm x 0.6 mm was integrated into a 6.5 MHz transmitting transducer with aperture of 0.6 mm x 3 mm. High pressure ultrasound at low frequency was generated by the transducer to excited microbubbles in tissue. High frequency component of the nonlinear response from microbubbles were received by the 35 MHz transducer for high resolution imaging at a relatively large depth. The prototyped transducer showed the ability of transmitting about 2 MPa pressure at 6.5 MHz, under an input of 5-cycle burst at 250 Vpp, which is high enough to generate nonlinear oscillation of microbubbles. The pulse-echo test showed that the -6 dB bandwidth of the 35 MHz transducer is 34.4% and the loop sensitivity is -38.3 dB. The small aperture, dual frequency ultrasound transducers developed in this paper are promising for high resolution ultrasound medical imaging. DA - 2013/// PY - 2013/// DO - 10.1117/12.2009716 VL - 8695 SP - SN - 1996-756X KW - ultrasound transducer KW - dual frequency KW - contrast imaging KW - small aperture ER - TY - JOUR TI - Charge Transport in Highly Face-On Poly(3-hexylthiophene) Films AU - Gargi, Deepak AU - Kline, R. Joseph AU - DeLongchamp, Dean M. AU - Fischer, Daniel A. AU - Toney, Michael F. AU - Brendan T. O'Connor, T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - We report that the π-stacking direction in poly(3-hexylthiophene) (P3HT) films can be made to orient strongly out-of plane by uniaxially straining films in orthogonal directions, providing a valuable opportunity to evaluate charge transport in a very unusual microstructure for this material. The structure of the films was characterized using UV–visible spectroscopy, X-ray diffraction, and near-edge X-ray absorption fine structure spectroscopy, showing that unstrained films have a weakly edge-on stacking character with a large orientation distribution, whereas films strained biaxially by 100% in orthogonal directions have highly face-on stacking. In the biaxially strained films the face-on packing occurs while the P3HT long axis orientation is found to be only weakly anisotropic in-plane. Charge transport is characterized in an organic thin-film transistor (OTFT) configuration, showing that the saturated field effect mobility in the biaxially strained films is greater than that for unstrained films for channel lengths ≤10 μm. The mobilities are found to have different channel-length dependence, attributed primarily to differences in the field-dependent charge-transport behavior, resulting in the mobility being comparable for channel lengths of 20 μm. The results suggest that edge-on packing is not a prerequisite for relatively high-field-effect mobility in P3HT-based OTFTs. DA - 2013/8/29/ PY - 2013/8/29/ DO - 10.1021/jp4050644 VL - 117 IS - 34 SP - 17421-17428 SN - 1932-7447 ER - TY - JOUR TI - An exact solution of transient equations describing slow axonal transport AU - Kuznetsov, A. V. T2 - COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING AB - An exact analytical solution of equations describing slow axonal transport of cytoskeletal elements (CEs) injected in an axon is presented. The equations modelling slow axonal transport are based on the stop-and-go hypothesis. The simplest model implementing this hypothesis postulates that CEs switch between pausing and running kinetic states, and that the probabilities of CE transition between these two states are described by first-order rate constants. It is assumed that initially CEs are injected such that they form a uniform pulse of a given width. All injected CEs are initially attributed to the pausing state. It is shown that within 30 s kinetic processes redistribute CEs between pausing and running states; after that the process occurs under quasi-equilibrium conditions. The parameter accessible to experiments is the total concentration of CEs (pausing plus running). As the initial rectangular-shaped pulse moves, it changes its shape to become a bell-shaped wave that spreads out as it propagates. The wave's amplitude is decreasing during the wave's propagation. It is also shown that the system forgets its initial condition, meaning that if one starts with pulses of different widths, after sometime they converge to the same bell-shaped wave. DA - 2013/11/1/ PY - 2013/11/1/ DO - 10.1080/10255842.2012.662679 VL - 16 IS - 11 SP - 1232-1239 SN - 1476-8259 KW - slow axonal transport KW - stop-and-go hypothesis KW - neurons KW - molecular motors KW - exact solution ER - TY - JOUR TI - A vibration energy harvester using diamagnetic levitation AU - Palagummi, S. AU - Yuan, F. G. T2 - ACTIVE AND PASSIVE SMART STRUCTURES AND INTEGRATED SYSTEMS 2013 AB - In this paper a novel electromagnetic vibration type energy harvester which uses a diamagnetic levitation system is conceptualized, designed, fabricated, and tested. The harvester uses two diamagnetic plates made of pyrolytic graphite between which a cylindrical magnet levitates passively. Two archimedean spiral coils are placed in grooves which are engraved in the pyrolytic graphite plates, used to convert the mechanical energy into electrical energy efficiently. The geometric configurations of coils are selected based on the field distribution of the magnet to enhance the efficiency of the harvester. A thorough theoretical analysis is done to compare with the experiment results. At an input power of 103.45 μW and at a frequency of 2.7 Hz, the harvester generated a power of 0.744 μW at an efficiency of 0.72 %. Both theoretical and experimental results show that this new energy harvesting system is efficient and can capture low frequency broadband spectra. DA - 2013/// PY - 2013/// DO - 10.1117/12.2009657 VL - 8688 SP - SN - 1996-756X KW - Energy harvesting KW - diamagnetic KW - levitation KW - nonlinear KW - self-power ER - TY - JOUR TI - The Effect of Strong Heterogeneity on the Onset of Convection Induced by Internal Heating in a Porous Medium: A Layered Model AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - TRANSPORT IN POROUS MEDIA DA - 2013/8// PY - 2013/8// DO - 10.1007/s11242-013-0175-5 VL - 99 IS - 1 SP - 85-100 SN - 0169-3913 KW - Heterogeneity KW - Instability KW - Horizontal layers KW - Internal heating ER - TY - JOUR TI - Nondestructive inspection of CFRP adhesively bonded joints using embedded FBG sensors AU - Webb, S. AU - Shin, P. AU - Peters, K. AU - Selfridge, R. AU - Schultz, S. T2 - FIBER OPTIC SENSORS AND APPLICATIONS X AB - One challenging need for inspection capabilities is in adhesively bonded joints between composite components, a common location of premature failure in aerospace structures. In this work we demonstrate that dynamic, full spectral scanning of FBG sensors embedded in the adhesive bond can identify changes in bond quality through the measurement of non-linear dynamics of the joint. Eighteen lap joint specimens were fabricated with varying manufacturing quality. Ten samples also included fiber Bragg grating (FBG) sensors embedded in the adhesive bond for real-time inspection during a simulated flight condition of these single-lap joints. Prior to testing, pulse phase thermography imaging of the pristine specimens revealed defects such as air bubbles, adhesive thickness variations, and weak bonding surface between the laminate and adhesive. The lap joint specimens were then subjected to fatigue loading, with regular interrogation of the FBG sensors at selected load cycle intervals. The FBG data was collected during vibration loading of the lap joint to represent an in-flight environment. Changes in the lap joint dynamic response, including the transition to non-linear responses, were measured from both the full-spectral and peak wavelength FBG data. These changes were correlated to initial manufacturing defects and the progression of fatigue-induced damage independently measured with pulse phase imaging and visual inspections of the failure surfaces. DA - 2013/// PY - 2013/// DO - 10.1117/12.2018443 VL - 8722 SP - SN - 1996-756X KW - fiber Bragg grating sensors KW - composite lap joint KW - full spectral interrogation KW - pulsed phase thermography ER - TY - JOUR TI - Hybrid imaging of damage progress in composites through thermal imaging and embedded sensing AU - Pawar, S. AU - Peters, K. T2 - SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS INTEGRATION 2013 AB - In this paper, we investigate the fusion of imaging data from pulsed phase thermography (PPT) with local temperature data obtained from embedded fiber Bragg grating (FBG) sensors for non-destructive evaluation of composite structures. We use the square pulse heating applied for the PPT imaging as the input thermal wave for both the imaging and sensing processes. In addition, the role of the local microstructure surrounding the FBG on the measured wavelength shift as a function of temperature is derived analytically. Fusing the FBG wavelength response with the PPT data at the corresponding pixel and depth is shown to provide a unique characterization of the local material condition. DA - 2013/// PY - 2013/// DO - 10.1117/12.2010016 VL - 8693 SP - SN - 1996-756X KW - fiber Bragg grating sensors KW - composite monitoring KW - infrared thermography ER - TY - JOUR TI - Fast damage imaging using the time-reversal technique in the frequency-wavenumber domain AU - Zhu, R. AU - Huang, G. L. AU - Yuan, F. G. T2 - SMART MATERIALS AND STRUCTURES AB - The time-reversal technique has been successfully used in structural health monitoring (SHM) for quantitative imaging of damage. However, the technique is very time-consuming when it is implemented in the time domain. In this paper, we study the technique in the frequency‐wavenumber (f‐k) domain for fast real-time imaging of multiple damage sites in plates using scattered flexural plate waves. Based on Mindlin plate theory, the time reversibility of dispersive flexural waves in an isotropic plate is theoretically investigated in the f‐k domain. A fast damage imaging technique is developed by using the cross-correlation between the back-propagated scattered wavefield and the incident wavefield in the frequency domain. Numerical simulations demonstrate that the proposed technique cannot only localize multiple damage sites but also potentially identify their sizes. Moreover, the time-reversal technique in the f‐k domain is about two orders of magnitude faster than the method in the time domain. Finally, experimental testing of an on-line SHM system with a sparse piezoelectric sensor array is conducted for fast multiple damage identification using the proposed technique. (Some figures may appear in colour only in the online journal) DA - 2013/7// PY - 2013/7// DO - 10.1088/0964-1726/22/7/075028 VL - 22 IS - 7 SP - SN - 0964-1726 ER - TY - JOUR TI - Fabrication of subwavelength periodic nanostructures using liquid immersion Lloyd's mirror interference lithography AU - Bagal, Abhijeet AU - Chang, Chih-Hao T2 - OPTICS LETTERS AB - We have developed a liquid immersion Lloyd’s mirror interference lithography system to fabricate subwavelength periodic nanostructures. In this approach, we construct the Lloyd’s mirror interferometer within a liquid medium to increase the ambient index. The light wavelength is scaled by the refractive index of the immersion fluid, reducing the minimum interference pattern period and increasing the spatial resolution. The all-liquid system ensures continuous fluid contact with the sample without an external mechanism, allows rapid adjustment of pattern period with subwavelength resolution, and retains the passive vibration-correction capability of Lloyd’s mirror interferometers. Using this approach, we have successfully fabricated a grating structure with 112 nm period using a laser with 325 nm wavelength, attaining a numerical aperture of 1.45. The proposed immersion strategy can be adapted to improve pattern resolution of more complex interference lithography systems. DA - 2013/7/15/ PY - 2013/7/15/ DO - 10.1364/ol.38.002531 VL - 38 IS - 14 SP - 2531-2534 SN - 0146-9592 ER - TY - JOUR TI - Effects of ambient oxygen concentration on biodiesel and diesel spray combustion under simulated engine conditions AU - Zhang, Ji AU - Jing, Wei AU - Roberts, William L. AU - Fang, Tiegang T2 - ENERGY AB - This study investigates the effect of ambient oxygen concentration on biodiesel and diesel spray combustion under simulated compression-ignition engine conditions in a constant-volume chamber. The apparent heat release rate (AHRR) is calculated based on the measured pressure. High-speed imaging of OH* chemiluminescence and natural luminosity (NL) is employed to visualize the combustion process. Temporally and spatially resolved NL and OH* contour plots are obtained. The result indicates that AHRR depends monotonically on the ambient oxygen concentration for both fuels. A lower oxygen concentration yields a slower AHRR increase rate, a lower peak AHRR value, but a higher AHRR value during the burn-out stage when compared with higher ambient oxygen concentration conditions. OH* chemiluminescence and NL contours indicate that biodiesel may experience a longer premixed-combustion duration. The 18% ambient O2 condition works better for biodiesel than diesel in reducing soot luminosity. With 12% O2, diesel combustion is significantly degraded. However, both fuels experience low temperature combustion at 10% O2. These results may imply that biodiesel is able to achieve the desired lower soot production under a moderate oxygen level with higher combustion efficiency, while diesel needs to be burned under very low ambient oxygen concentration for low soot production. DA - 2013/8/1/ PY - 2013/8/1/ DO - 10.1016/j.energy.2013.05.063 VL - 57 SP - 722-732 SN - 1873-6785 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84880702414&partnerID=MN8TOARS KW - Biodiesel KW - Diesel KW - Spray combustion KW - Constant-volume chamber KW - Chemiluminescence KW - Luminosity ER - TY - JOUR TI - Design of a curvature sensor using a flexoelectric material AU - Yan, X. AU - Huang, W. B. AU - Kwon, S. R. AU - Yang, S. R. AU - Jiang, X. N. AU - Yuan, F. G. T2 - SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2013 AB - A curvature sensor based on flexoelectricity using Ba0.64Sr0.36TiO3 (BST) material is proposed and developed in this paper. The working principle of the sensor is based on the flexoelectricity, exhibiting coupling between mechanical strain gradient and electric polarization. A BST curvature sensor is lab prepared using a conventional solid state processing method. The curvature sensing is demonstrated in four point bending tests of the beam under harmonic loads. BST sensors are attached on both side surfaces of an aluminum beam, located symmetrically with respect to its neutral axis. Analyses have shown that the epoxy bonding layer plays a critical role for curvature transfer. Consequently a shear lag effect is taken into account for extracting actual curvature from the sensor measurement. Experimental results demonstrated good linearity from the charge outputs under the frequencies tests and showed a sensor sensitivity of 30.78pC•m in comparison with 32.48pC•m from theoretical prediction. The BST sensor provides a direct curvature measure instead of using traditional strain gage through interpolation and may offer an optional avenue for on-line and in-situ structural health monitoring. DA - 2013/// PY - 2013/// DO - 10.1117/12.2009941 VL - 8692 SP - SN - 1996-756X KW - Curvature sensor KW - BST flexoelectric material KW - strain gradient KW - structural health monitoring ER - TY - JOUR TI - Computational Analysis of Non-Spherical Particle Transport and Deposition in Shear Flow With Application to Lung Aerosol Dynamics-A Review AU - Kleinstreuer, Clement AU - Feng, Yu T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME AB - All naturally occurring and most man-made solid particles are nonspherical. Examples include air-pollutants in the nano- to micro-meter range as well as blood constituents, drug particles, and industrial fluid-particle streams. Focusing on the modeling and simulation of inhaled aerosols, theories for both spherical and nonspherical particles are reviewed to analyze the contrasting transport and deposition phenomena of spheres and equivalent spheres versus ellipsoids and fibers. DA - 2013/2// PY - 2013/2// DO - 10.1115/1.4023236 VL - 135 IS - 2 SP - SN - 1528-8951 KW - lung-aerosol dynamics KW - nonspherical particles KW - particle transport and deposition ER - TY - JOUR TI - Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber Bragg grating sensors AU - Webb, S. AU - Shin, P. AU - Peters, K. AU - Zikry, M. A. AU - Chadderdon, S. AU - Stan, N. AU - Selfridge, R. AU - Schultz, S. T2 - SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS INTEGRATION 2013 AB - In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor embedded at the adhesive layer of a single composite lap joint subjected to harmonic excitation after fatigue loading. After a fully-reversed cyclic fatigue loading is applied to the composite lap joint, the full spectral response of the sensor is interrogated in reflection at 100 kHz during two states: with and without an added harmonic excitation. The dynamic response of the FBG sensor indicates strong nonlinearities as damage progresses. The short-time Fourier transform (STFT) is computed for the extracted peak wavelength information to reveal time-dependent frequencies and amplitudes of the dynamic FBG sensor response. Pulse-phase thermography indicates a progression in defect size at the adhesive layer that strongly suggests non-uniform loading of the FBG sensor. DA - 2013/// PY - 2013/// DO - 10.1117/12.2010018 VL - 8693 SP - SN - 1996-756X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84878407243&partnerID=MN8TOARS KW - fiber Bragg grating sensors KW - composite lap joint KW - full spectral interrogation KW - vibration monitoring ER - TY - JOUR TI - Analysis of non-spherical particle transport in complex internal shear flows AU - Feng, Y. AU - Kleinstreuer, C. T2 - PHYSICS OF FLUIDS AB - Focusing on ellipsoidal particles of different aspect ratios, the motion characteristics, including critical angle and stable vs. unstable rotational periods, are computationally analyzed in developing and fully developed tubular flows. As an application of particle transport and deposition, the one-way coupled Euler-Lagrange method enhanced by Euler's rotation equations is then employed to simulate laminar-turbulent flow in a subject-specific lung-airway model. First, to gain some basic insight into the dynamics of non-spherical particles, tubular flow is considered where the trajectories of ellipsoidal fibers with randomly initialized incidence angles were released at different inlet-plane positions, computed and visualized. Local and overall particle deposition results are compared between spheres, ellipsoidal fibers, and sphere-equivalent particles for which a revised Stokes diameter was developed. Concerning non-spherical particle transport and deposition in a subject-specific respiratory system, the validated computer simulation model provides realistic and accurate particle-deposition results. Specifically, slender non-spherical particles (i.e., those with higher aspect ratios) are potentially more harmful than thicker ones due to their ability to penetrate into deeper lung regions when somewhat aligned with the major flow field. Furthermore, non-spherical particle deposition is enhanced as the breathing rate increases. DA - 2013/9// PY - 2013/9// DO - 10.1063/1.4821812 VL - 25 IS - 9 SP - SN - 1089-7666 ER - TY - JOUR TI - A single crystal lead magnesium niobate-lead titanate multilayer-stacked cryogenic flextensional actuator AU - Xu, Tian-Bing AU - Tolliver, Laura AU - Jiang, Xiaoning AU - Su, Ji T2 - APPLIED PHYSICS LETTERS AB - A “33” mode single crystal lead magnesium niobate-lead titanate flextensional actuator with large displacement, high load capability, and broad bandwidth was designed, prototyped, and evaluated at temperatures ranging from room temperature to cryogenic temperatures. Measuring 27.4 × 10 × 13.6 mm (height) overall and weighing 9.2 g, the actuator generates a 96.5 μm displacement in the Z-direction at 170 Vrms. The level of displacement remained constant under compressive loads up to 5 kg force. The actuator maintains 66% of its room temperature displacement at −196 °C. The measured displacements matched well with those modeled using ANSYS finite element analysis. DA - 2013/1/28/ PY - 2013/1/28/ DO - 10.1063/1.4790142 VL - 102 IS - 4 SP - SN - 0003-6951 ER - TY - JOUR TI - A reconstructed discontinuous Galerkin method based on a Hierarchical WENO reconstruction for compressible flows on tetrahedral grids AU - Luo, Hong AU - Xia, Yidong AU - Spiegel, Seth AU - Nourgaliev, Robert AU - Jiang, Zonglin T2 - Journal of Computational Physics AB - A reconstructed discontinuous Galerkin (RDG) method based on a hierarchical WENO reconstruction, termed HWENO (P1P2) in this paper, designed not only to enhance the accuracy of discontinuous Galerkin methods but also to ensure the nonlinear stability of the RDG method, is presented for solving the compressible Euler equations on tetrahedral grids. In this HWENO (P1P2) method, a quadratic polynomial solution (P2) is first reconstructed using a Hermite WENO reconstruction from the underlying linear polynomial (P1) discontinuous Galerkin solution to ensure the linear stability of the RDG method and to improve the efficiency of the underlying DG method. By taking advantage of handily available and yet invaluable information, namely the derivatives in the DG formulation, the stencils used in the 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 developed HWENO (P1P2) method is used to compute a variety of flow problems on tetrahedral meshes to demonstrate its accuracy, robustness, and non-oscillatory property. The numerical experiments indicate that the HWENO (P1P2) method is able to capture shock waves within one cell without any spurious oscillations, and achieve the designed third-order of accuracy: one order accuracy higher than the underlying DG method. DA - 2013/3// PY - 2013/3// DO - 10.1016/j.jcp.2012.11.026 VL - 236 SP - 477-492 J2 - Journal of Computational Physics LA - en OP - SN - 0021-9991 UR - http://dx.doi.org/10.1016/j.jcp.2012.11.026 DB - Crossref KW - Discontinuous Galerkin method KW - WENO reconstruction KW - Unstructured grids ER - TY - JOUR TI - Thermo-chemical wear model and worn tool shapes for single-crystal diamond tools cutting steel AU - Lane, B. M. AU - Dow, T. A. AU - Scattergood, R. T2 - WEAR AB - An Arrhenius-type thermochemical wear model proposed by past researchers is evaluated for predicting diamond tool wear when machining low carbon steel. Tool temperature values are determined using finite element modeling. These temperatures are related to tool wear measured after diamond turning tests on a low carbon steel workpiece to determine constants in the Arrhenius-type model. Measured tool wear shows a transition in worn tool shape from low speed (1 mm/s) to high speed (4 m/s) machining tests. Model results show a minimum value of wear per cutting distance occurs at a cutting speed of 2.5 m/s. The model also gives an activation energy between 25.0 kJ/mol and 29.3 kJ/mol. In addition, this model is used to explain experimental results obtained by others researching chemical wear of diamond. DA - 2013/3/15/ PY - 2013/3/15/ DO - 10.1016/j.wear.2013.02.012 VL - 300 IS - 1-2 SP - 216-224 SN - 1873-2577 KW - Diamond tool KW - Electron microscopy KW - Diffusion KW - FEM ER - TY - JOUR TI - Submicron particle filtration in monolith filters - A modeling and experimental study AU - Wu, Mengbai AU - Jasper, Warren J. AU - Kuznetsov, Andrey V. AU - Johnson, Nathan AU - Rasipurarn, Srinivasan C. T2 - JOURNAL OF AEROSOL SCIENCE AB - With over a million micron-sized channels per square centimeter arranged in a regular pattern on a thin film, monolith filters have significant potential for submicron aerosol particle filtration, even though the filtration process with this class of filters has not been well studied. In order to better understand the capture mechanisms and the main factors that affect the capture efficiency, so as to build predictive numerical models and to improve the design of monolith filters, the filtration process in monolith filters was investigated both experimentally and numerically. Using an electrostatic particle classifier (EPC) and a condensation particle counter (CPC), the experimental platform measured the capture efficiency of salt particles with diameters ranging from 50–300 nm on two monolith filter samples. Based on the filtration process and the repeating geometric structure, a single unit model was proposed. The drag force, electrostatic force, and Brownian motion are considered as the major forces affecting particle motion. Published theories underestimated the capture efficiency compared to the experimental results. The Brownian motion model and the capture criterion were then empirically modified to gain better agreement with the experiment. DA - 2013/3// PY - 2013/3// DO - 10.1016/j.jaerosci.2012.09.002 VL - 57 SP - 96-113 SN - 1879-1964 KW - Monolith filter KW - Submicron particles KW - Aerosol filtration KW - Slip flow KW - Quality factor ER - TY - JOUR TI - Phacoemulsification and +14 diopter intraocular lens placement in a Saddlebred foal AU - Harrington, Jay T. AU - McMullen, Richard J., Jr. AU - Clode, Alison B. AU - Gilger, Brian C. T2 - VETERINARY OPHTHALMOLOGY AB - Abstract A 2‐month‐old, 110‐kg Saddlebred filly presented for evaluation of bilateral cataracts. A hypermature cataract in the left eye (OS) and an incipient nuclear cataract in the right eye (OD) were diagnosed. Electroretinography and ocular ultrasound revealed no contraindications for surgical removal of the cataractous lens OS. Phacoemulsification and implantation of a +14 diopter (D) intraocular lens (IOL) OS were performed at 4 months of age without complication, with the exception of a partial iridectomy performed on a small iris section that prolapsed through the corneal incision. Complete ophthalmic examinations, including ocular ultrasound and streak retinoscopy, were performed 1, 2, 6 weeks, 4 months, 1, and 2 years postoperatively. Diffuse corneal edema and a superficial corneal ulcer developed OS during the early postoperative period and resolved without complication. Dyscoria was identified owing to anterior synechia of the dorsomedial iris at the incision site. Two years after surgery, menace response, palpebral reflex, dazzle reflex, and pupillary light reflexes were present in both eyes (OU). The IOL remained centrally positioned within the capsule, with mild anterior tilting of the superior portion of the IOL and mild fibrosis of the lens capsule. The postoperative net refractive error was +0.31 D OS. Based on this report, a +14 D IOL may be the appropriate choice following lens extraction in a foal to achieve refraction near emmetropia at maturity. To our knowledge, this is the first report of phacoemulsification and IOL implantation in a foal with long‐term follow‐up. DA - 2013/3// PY - 2013/3// DO - 10.1111/j.1463-5224.2012.01032.x VL - 16 IS - 2 SP - 140-148 SN - 1463-5224 KW - cataract KW - equine phacoemulsification KW - foal KW - intraocular lens KW - ocular ultrasound KW - retinoscopy ER - TY - JOUR TI - Multifunctional and Durable Nanofiber-Fabric-Layered Composite for Protective Application AU - Shi, Quan AU - Vitchuli, Narendiran AU - Nowak, Joshua AU - Jiang, Shan AU - Caldwell, Jane M. AU - Breidt, Frederick AU - Bourham, Mohamed AU - Zhang, Xiangwu AU - McCord, Marian T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - A multifunctional and durable nanofiber-fabric-layered composite (NFLC) material was prepared by depositing electrospun Ag/PAN hybrid nanofibers onto a Nylon/cotton 50: 50 fabric substrate. The NFLCs showed excellent aerosol barrier efficiency and good air/moisture permeability. In addition, they showed excellent antibacterial efficiency by completely inhibiting the growth of both Gram-negative E. coli and Gram-positive S. aureus. The interfacial adhesion between the nanofiber layer and fabric substrate was significantly improved by atmospheric plasma pretreatment of the substrate. The resultant NFLCs showed excellent resistance to peeling, twisting, and flexing forces. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 DA - 2013/4/15/ PY - 2013/4/15/ DO - 10.1002/app.38465 VL - 128 IS - 2 SP - 1219-1226 SN - 1097-4628 KW - nanostructured polymers KW - textiles KW - biomedical applications ER - TY - JOUR TI - Full-Spectral Interrogation of Fiber Bragg Grating Sensors Exposed to Steady-State Vibration AU - Webb, S. AU - Peters, K. AU - Zikry, M. A. AU - Chadderdon, S. AU - Nikola, S. AU - Selfridge, R. AU - Schultz, S. T2 - EXPERIMENTAL MECHANICS DA - 2013/4// PY - 2013/4// DO - 10.1007/s11340-012-9661-x VL - 53 IS - 4 SP - 513-530 SN - 1741-2765 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84874796178&partnerID=MN8TOARS KW - Fiber Bragg grating sensors KW - Non-uniform strain KW - Full spectral interrogation KW - Vibration monitoring ER - TY - JOUR TI - Effect of various parameters on properties of composite steel foams under variety of loading rates AU - Rabiei, Afsaneh AU - Garcia-Avila, Matias T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Steel–steel composite metal foams (CMF) are manufactured using steel hollow spheres (with variety of different sphere sizes, surface roughness and carbon content) embedded in a stainless steel matrix through powder metallurgy technique and are investigated experimentally under compression loading with variety of loading rates. The microstructural and mechanical properties of the material were studied using optical and scanning electron microscopy, energy dispersive spectroscopy, quasi-static, and dynamic compressive loading up to 26 m/s. It is observed that the yield and plateau strength as well as the energy absorption capabilities of the composite foams are increased with increasing loading rate and by decreasing sphere sizes. Such mechanical properties improved by additional carbon content in the sphere wall at strains below 17% while the effect of density, resulted from porosity content, showed an improvement on the densification strain and plateau strengths at higher than 17% strain. The effect of spheres surface roughness and carbon content on mechanical properties of CMF seemed to be minimal compared to other parameters. As a result, the features controlling the life time and performance of composite metal foams under static and dynamic loading have been categorized into two main groups. The first group that controls the yield and plateau strength of the foam at lower strain levels includes bonding strength between the spheres and matrix which is a function of the sphere surface roughness and the gradient chemical composition between the spheres and matrix. The second group that controls the relative density, densification strain and plateau strength at higher strain levels belongs to the sphere diameter and the porosity content in both spheres and matrix. Moreover, increasing the loading rate improves the yield strength of all CMF samples. DA - 2013/3/1/ PY - 2013/3/1/ DO - 10.1016/j.msea.2012.11.108 VL - 564 SP - 539-547 SN - 0921-5093 KW - Composite metal foam KW - Dynamic loading KW - Quasi-static loading KW - Hollow spheres KW - Powder metallurgy ER - TY - JOUR TI - Effect of diluents on soot precursor formation and temperature in ethylene laminar diffusion flames AU - Kailasanathan, Ranjith Kumar Abhinavam AU - Yelverton, Tiffany L. B. AU - Fang, Tiegang AU - Roberts, William L. T2 - COMBUSTION AND FLAME AB - Soot precursor species concentrations and flame temperature were measured in a diluted laminar co-flow jet diffusion flame at pressures up to eight atmospheres while varying diluent type. The objective of this study was to gain a better understanding of soot production and oxidation mechanisms, which could potentially lead to a reduction in soot emissions from practical combustion devices. Gaseous samples were extracted from the centerline of an ethylene–air laminar diffusion flame, which was diluted individually with four diluents (argon, helium, nitrogen, and carbon dioxide) to manipulate flame temperature and transport properties. The diluted fuel and co-flow exit velocities (top-hat profiles) were matched at all pressures to minimize shear-layer effects, and the mass fluxes were fixed over the pressure range to maintain constant Reynolds number. The flame temperature was measured using a fine gauge R-type thermocouple at pressures up to four atmospheres. Centerline concentration profiles of major non-fuel hydrocarbons collected via extractive sampling with a quartz microprobe and quantification using GC/MS + FID are reported within. The measured hydrocarbon species concentrations are vary dramatically with pressure and diluent, with the helium and carbon dioxide diluted flames yielding the largest and smallest concentrations of soot precursors, respectively. In the case of C2H2 and C6H6, two key soot precursors, helium diluted flames had concentrations more than three times higher compared with the carbon dioxide diluted flame. The peak flame temperature vary with diluents tested, as expected, with carbon dioxide diluted flame being the coolest, with a peak temperature of 1760 K at 1 atm, and the helium diluted flame being the hottest, with a peak temperature of 2140 K. At four atmospheres, the helium diluted flame increased to 2240 K, but the CO2 flame temperature increased more, decreasing the difference to approximately 250 K. DA - 2013/3// PY - 2013/3// DO - 10.1016/j.combustflame.2012.11.004 VL - 160 IS - 3 SP - 656-670 SN - 1556-2921 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84872855275&partnerID=MN8TOARS KW - Elevated pressure KW - Laminar diffusion flame KW - Diluent KW - Species concentration KW - Soot KW - Temperature ER - TY - JOUR TI - Diode laser endoscopic cyclophotocoagulation in the normal equine eye AU - Harrington, Jay T. AU - McMullen, Richard J., Jr. AU - Cullen, John M. AU - Campbell, Nigel B. AU - Gilger, Brian C. T2 - VETERINARY OPHTHALMOLOGY AB - Abstract Objective To determine the clinical and histologic effects of diode endoscopic cyclophotocoagulation (ECP) in the phakic equine eye. Animals studied Phase I: 10 equine cadaver eyes. Phase II: four normal adult horses. Procedures Phase I: ECP probe angle of reach (AR) was determined. Multiple ECP energy levels: 0.75, 0.90, 1.05, 1.20, 1.35, 1.50 J, and the resulting visible and histologic ciliary process changes were evaluated. Phase II: Ocular quadrants were treated with ECP at 0.90, 1.14, 1.38 J, and a control. The contralateral eye underwent a sham operation. Tissue changes (clinical and histologic) were evaluated. Results Phase I: Mean combined AR was 162 ± 29 degrees. Mean visible tissue scores: 2.60 ± 0.58 (0.75 J) to 5.04 ± 0.30 (1.50 J) from possible total of 6. Tissue ‘popping’ was observed at 1.50 J. Histologic ciliary tissue damage was present at all settings. Phase II: Mean visible tissue scores: 2.90 ± 0.48 (0.90 J), 3.61 ± 0.57 (1.14 J), and 4.52 ± 0.56 (1.38 J). Tissue ‘popping’ was observed at 1.38 J. Histologic ciliary tissue damage was present at all settings. Clinical effects included acute inflammation, intraocular pressure reduction, cataract formation, corneal edema, corneal ulceration, and postoperative ocular hypertension. Conclusions Diode ECP between 0.90 and 1.14 J is a potential treatment option for glaucoma in horses based on visible tissue effects and target ciliary epithelium damage. Iatrogenic cataract development may limit the use of an anterior chamber approach in phakic horses. Supported in part by an ACVO VAF grant. DA - 2013/3// PY - 2013/3// DO - 10.1111/j.1463-5224.2012.01035.x VL - 16 IS - 2 SP - 97-110 SN - 1463-5224 KW - diode laser KW - endoscopic cyclophotocoagulation KW - equine KW - glaucoma KW - histopathology ER - TY - JOUR TI - Analytical modelling of retrograde transport of nerve growth factors in an axon: a transient problem AU - Kuznetsov, A. V. T2 - COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING AB - The purpose of this paper was to develop an analytical solution describing retrograde transport of nerve growth factors (NGFs) from a target tissue to the neuron soma. The obtained solution is applied to describe two situations: (1) when all dynein motors are moving at a constant velocity and (2) when the dynein velocity distribution is described by a probability density function. The dynamics of NGF concentrations and fluxes is investigated. It is established that the magnitude of the diffusion flux forms a wave localised in space and propagating towards the neuron soma; the magnitude of this wave decreases as the wave propagates downstream. The dynein-driven flux of NGFs is demonstrated to be the main component in the NGF flux, which is shown to be strongly correlated with the NGF concentration. DA - 2013/1/1/ PY - 2013/1/1/ DO - 10.1080/10255842.2011.607445 VL - 16 IS - 1 SP - 95-102 SN - 1025-5842 KW - nerve growth factors KW - neurotrophins KW - dynein motors KW - retrograde axonal transport ER - TY - JOUR TI - A novel principal component analysis-based acceleration scheme for LES-ODT: An a priori study AU - Mirgolbabaei, Hessam AU - Echekki, Tarek T2 - COMBUSTION AND FLAME AB - A parameterization of the composition space based on principal component analysis (PCA) is proposed to represent the transport equations with the one-dimensional turbulence (ODT) solutions of a hybrid large-eddy simulation (LES) and ODT scheme. The 1D ODT solutions are embedded in the 3D LES domain and solve for thermo-chemical scalars; while, the LES governing equations solve for the flow. An a priori validation of the proposed approach is implemented based on stand-alone ODT solutions of the Sandia Flame F, which is characterized by different regimes of combustion starting with pilot stabilization, to extinction and reignition and self-stabilized combustion. The PCA analysis is carried out with a full set of the thermo-chemical scalars’ vector as well as a subset of this vector. The subset is made up primarily of major species and temperature. The results show that the different regimes are reproduced using only three principal components for the thermo-chemical scalars based on the full and a subset of the thermo-chemical scalars’ vector. Reproduction of the source term of the principal components represents a challenge, because of the inherent non-linearity of reaction rates’ expressions. It is found that using the subset of the thermo-chemical scalars’ vector both minor species and the first three principal components source terms are reasonably well predicted. DA - 2013/5// PY - 2013/5// DO - 10.1016/j.combustflame.2013.01.007 VL - 160 IS - 5 SP - 898-908 SN - 1556-2921 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875091614&partnerID=MN8TOARS KW - Turbulent flames KW - The one-dimensional turbulence model KW - Principal component analysis ER - TY - JOUR TI - A compartmental model of neuropeptide circulation and capture between the axon soma and nerve terminals AU - Kuznetsov, I. A. AU - Kuznetsov, A. V. T2 - INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING AB - SUMMARY This paper is motivated by a recent experimental research by Levitan and colleagues (Wong MY, Zhou C, Shakiryanova D, Lloyd TE, Deitcher DL, Levitan ES. Neuropeptide delivery to synapses by long‐range vesicle circulation and sporadic capture. Cell 2012; 148 (5): 1029–1038), which discovered and explained the circulation of dense core vesicles (DCVs) between the neuron soma and nerve terminals. We developed a compartmental mechanistic model to simulate this circulation. The model includes five compartments, the axonal compartment and four en passant boutons, which are small axonal varicosities that are present in many axon terminals. By postulating expressions for DCV fluxes between the compartments and for the rates of DCV capture in the boutons and utilizing conservation of DCVs, ODEs modeling concentrations in each of the compartments were developed. The equations were then solved numerically. The obtained results provide insight into how DCV circulation develops, what the circulation is at steady state, and how it may be affected by defects in retrograde transport. Copyright © 2013 John Wiley & Sons, Ltd. DA - 2013/5// PY - 2013/5// DO - 10.1002/cnm.2542 VL - 29 IS - 5 SP - 574-585 SN - 2040-7939 KW - neurons KW - axonal transport KW - neuropeptide transport KW - dense core vesicles KW - mathematical modeling ER - TY - JOUR TI - The viability and limitations of percolation theory in modeling the electrical behavior of carbon nanotube-polymer composites AU - Xu, S. AU - Rezvanian, O. AU - Peters, K. AU - Zikry, M. A. T2 - NANOTECHNOLOGY AB - A new modeling method has been proposed to investigate how the electrical conductivity of carbon nanotube (CNT) reinforced polymer composites are affected by tunneling distance, volume fraction, and tube aspect ratios. A search algorithm and an electrical junction identification method was developed with a percolation approach to determine conductive paths for three-dimensional (3D) carbon nanotube arrangements and to account for electron tunneling effects. The predicted results are used to understand the limitations of percolation theory and experimental measurements and observations, and why percolation theory breaks down for specific CNT arrangements. DA - 2013/4/19/ PY - 2013/4/19/ DO - 10.1088/0957-4484/24/15/155706 VL - 24 IS - 15 SP - SN - 1361-6528 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875677113&partnerID=MN8TOARS ER - TY - JOUR TI - Temperature control in thermal microactuators with applications to in-situ nanomechanical testing AU - Qin, Qingquan AU - Zhu, Yong T2 - APPLIED PHYSICS LETTERS AB - Thermal microactuators are used in many micro/nano-technologies. To circumvent undesired heating of the end effector, heat sink beams are co-fabricated with the thermal actuator and connected to the substrate. This paper reports a combined experimental and modeling study on the effect of such heat sink beams. Temperature distribution is measured and simulated using Raman scattering and multiphysics finite element method, respectively. Our results show that heat sink beams are effective in controlling the temperature of the thermal actuator. Insights on how to achieve both low temperature and large actuator displacement for in-situ mechanical testing of nanoscale specimens are provided. DA - 2013/1/7/ PY - 2013/1/7/ DO - 10.1063/1.4773359 VL - 102 IS - 1 SP - SN - 1077-3118 ER - TY - JOUR TI - Switching fault-tolerant control of a flexible air-breathing hypersonic vehicle AU - Wu, Fen AU - Cai, Xuejing T2 - PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART I-JOURNAL OF SYSTEMS AND CONTROL ENGINEERING AB - In this paper, we will apply a switching fault-tolerant control approach to an air-breathing hypersonic vehicle subject to time-varying actuator and sensor faults. The faults under consideration include loss of effectiveness of the actuators and sensors. Possible fault scenarios are categorized into different fault cases based on the fault type and its location. For each case, a parameter-dependent (or constant gain) fault-tolerant control controller is designed to stabilize the faulty system with an optimal controlled performance. The synthesis condition of each local fault-tolerant control law is formulated in terms of linear matrix inequalities. To achieve both local optimal performance and switching stability, Youla parameterization of each individual local fault-tolerant control controller is performed and the result is applied to the closed-loop system. The quadratic stability of a fast switching closed-loop system is guaranteed by a common Lyapunov function. Simulation results based on the non-linear flexible hypersonic vehicle model and fault-tolerant linear-parameter-varying controllers are presented and the reults of these studies demonstrate the effectiveness of the proposed switching fault-tolerant control approach for application to a hypersonic vehicle. DA - 2013/1// PY - 2013/1// DO - 10.1177/0959651812453914 VL - 227 IS - I1 SP - 24-38 SN - 2041-3041 KW - Fault-tolerant control KW - hypersonic vehicle KW - actuator and sensor faults KW - switching and gain-scheduling control KW - Youla parametrization KW - L-2-gain optimization KW - linear matrix inequality ER - TY - JOUR TI - Stress relaxation in carbon nanotube-based fibers for load-bearing applications AU - Zu, Mei AU - Li, Qingwen AU - Zhu, Yuntian AU - Zhu, Yong AU - Wang, Guojian AU - Byun, Joon-Hyung AU - Chou, Tsu-Wei T2 - CARBON AB - Carbon nanotube (CNT) based continuous fiber, a CNT assembly that could retain the superb properties of individual CNTs on a macroscopic scale, has emerged as a promising candidate for reinforcement in multifunctional composites. While existing research has extensively examined their short-term mechanical properties based upon quasi-static measurements, the long-term durability of CNT fibers has been largely neglected. Here we report time-dependent behavior of CNT fibers, with a particular focus on tensile stress relaxation. Both the pure CNT fiber and the CNT/epoxy composite fiber exhibited significant stress decay during the relaxation process, and this time-dependent behavior became more significant at a higher initial strain level, a lower strain rate and a greater gauge length. The present approach signifies a fundamental difference in the load-bearing characteristics between CNT fibers and traditional advanced fibers, which has major implications for the long-term durability of CNT fibers in load-bearing multifunctional applications. DA - 2013/2// PY - 2013/2// DO - 10.1016/j.carbon.2012.09.036 VL - 52 SP - 347-355 SN - 0008-6223 ER - TY - JOUR TI - On preheating and dilution effects in non-premixed jet flame stabilization AU - Lamige, Sylvain AU - Min, Jiesheng AU - Galizzi, Cedric AU - Andre, Frederic AU - Baillot, Francoise AU - Escudie, Dany AU - Lyons, Kevin M. T2 - COMBUSTION AND FLAME AB - The impact of preheating and dilution on methane/air non-premixed flame stability are studied experimentally. Six preheating levels are considered for initial reactant temperature between 295 K and 850 K in a round jet configuration. Four diluent gases are added on the air-side, either CO2, N2, Ar or a (CO2 + Ar) mixture having the same molar heat capacity as N2. For undiluted flames, jet transition velocities between attached and lifted states are investigated depending on initial reactant temperature. The hysteresis zone defined by these stability limits is shifted towards higher jet velocities with preheating. Whereas jet and coflow temperatures were identical in similar previous experiments, the present work allows examination of the thermal effects from either fuel or oxidizer streams. Flame stability is described based on the propagative aspects of the flame leading-edge, by analogy with the temperature dependency of the laminar burning velocity of a stoichiometric mixture. Results show that the jet temperature has a major influence on the lifting of an attached flame, whereas the coflow temperature remains important for the reattachment of a lifted flame. In addition, flame stability experiments have been performed at high levels of both preheating and dilution. Stability maps of critical dilution ratios at lifting have been obtained with preheating. It appears that the ability of a diluent to break flame stability keeps the same relative order as at ambient temperature. It is even enhanced with preheating because higher temperature widens the gap between diluent molar heat capacities Cp. The Cp approach is however not sufficient to interpret the temperature dependency of the relative influence of the different dilution effects. Furthermore, the role played by the jet flow regime on attached flame stability in dilution-induced lifting experiments is highlighted when dilution is coupled with preheating. DA - 2013/6// PY - 2013/6// DO - 10.1016/j.combustflame.2013.01.026 VL - 160 IS - 6 SP - 1102-1111 SN - 1556-2921 KW - Non-premixed combustion KW - Flame stability KW - Stability limits KW - Hysteresis KW - Preheating KW - Dilution ER - TY - JOUR TI - Modeling of Flow Through a Sandwiched Monolith Filter AU - Gangadharan, S. AU - Sanghavi, R. S. AU - Kuznetsov, A. V. AU - Jasper, W. J. T2 - PARTICULATE SCIENCE AND TECHNOLOGY AB - The flow field and filtration efficiency was modeled and analyzed for a novel monolith filter, comprised of a series of layers of microchannels. In our simulations, we considered two scenarios: the fluid flowing tangentially across the filter face (cross flow) and fluid flowing normal to the filter face (normal flow). The aim of this article is to study the effect of having two or more layers of filters in series on particle capture efficiency. This will help in understanding the mechanisms of particle capture and provide inputs for studying particle segregation or selective filtration using monolith filters. The influences of particle size, number of filter layers and pressure drop on particle capture efficiency were also investigated. DA - 2013/5/1/ PY - 2013/5/1/ DO - 10.1080/02726351.2012.715614 VL - 31 IS - 3 SP - 226-233 SN - 0272-6351 KW - Multi-stage filtration KW - numerical modeling KW - particle size segregation ER - TY - JOUR TI - Microstructurally induced fracture nucleation and propagation in martensitic steels AU - Shanthraj, P. AU - Zikry, M. A. T2 - JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS AB - A dislocation-density grain boundary (GB) interaction scheme that is representative of dislocation-density transmission and blockage within GBs is developed and incorporated into a dislocation-density based multiple-slip crystalline plasticity framework for a detailed analysis of fracture nucleation and growth in martensitic steels. This formulation accounts for variant morphologies and orientation relationships (ORs) that are uniquely inherent to lath martensitic microstructures. Specialized finite-element (FE) methodologies using overlapping elements to represent evolving failure surfaces and microstructurally-based failure criteria for cleavage are then used to investigate the effects of martensitic variant distributions and ORs on the dominant dislocation-density mechanisms for the localization of plastic strains, and the initiation and propagation of fracture surfaces in martensitic microstructures subjected to quasi-static and dynamic strain-rates. The results indicate that the local dislocation-density behavior at the variant boundaries and the interiors influence dominant failure initiation and growth. A dislocation-density GB interaction, which is based on dislocation-density accumulation and transmission at variant boundaries, is developed and used to predict stress build-up or relaxation, and together with the orientation of the cleavage planes in relation to the lath morphology, intergranular and transgranular fracture modes can be determined. DA - 2013/4// PY - 2013/4// DO - 10.1016/j.jmps.2012.11.006 VL - 61 IS - 4 SP - 1091-1105 SN - 0022-5096 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84874657104&partnerID=MN8TOARS KW - Dislocation-density KW - Grain boundary KW - Crystal plasticity KW - Failure ER - TY - JOUR TI - Fabrication of Functional Nanowire Devices on Unconventional Substrates Using Strain-Release Assembly AU - Durham, John W., III AU - Zhu, Yong T2 - ACS APPLIED MATERIALS & INTERFACES AB - We report three representative nanowire (NW) devices for applications in stretchable electronics, strain sensing, and optical sensing. Fabrication of such devices is based on a recently developed strain-release assembly method. NWs are first aligned transversely on an elastomeric substrate using the strain-release assembly. Constant resistance is achieved in silicon (Si) NW devices stretched up to ∼40% of axial strain, highlighting a new concept of transverse buckling. Combining the NW assembly with transfer printing extends suitable device substrates beyond elastomers to other unconventional materials (e.g., flexible and transparent materials). Following this combined process, flexible SiNW strain sensors are fabricated on plastics capable of sensing up to 1.6% bending strain and gauge factors >1000; flexible zinc oxide NW ultraviolet sensors are demonstrated with quick recovery (∼2 s) and excellent repeatability on plastics. Our results show promise for the strain-release assembly as a simple and cost-effective process to fabricate NW devices on unconventional substrates. DA - 2013/1/23/ PY - 2013/1/23/ DO - 10.1021/am302384z VL - 5 IS - 2 SP - 256-261 SN - 1944-8244 KW - nanowire KW - assembly KW - transfer printing KW - flexible electronics KW - strain sensor KW - UV sensor KW - stretchable electronics ER - TY - JOUR TI - Experimental and Computational Investigation of Low-Impact Velocity and Quasi-Static Failure of PMMA AU - Pearson, J. D. AU - LaBarbera, D. AU - Prabhugoud, M. AU - Peters, K. AU - Zikry, M. A. T2 - EXPERIMENTAL MECHANICS DA - 2013/1// PY - 2013/1// DO - 10.1007/s11340-012-9650-0 VL - 53 IS - 1 SP - 53-66 SN - 1741-2765 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84872276475&partnerID=MN8TOARS KW - Fiber-optic Bragg sensor KW - Local strains KW - Low-velocity impact KW - Quasi-static KW - PMMA ER - TY - JOUR TI - Enhanced Performance of Electrothermal Plasma Sources as Fusion Pellet Injection Drivers and Space Based Mini-Thrusters via Extension of a Flattop Discharge Current AU - Winfrey, A. Leigh AU - Abd Al-Halim, Mohamed A. AU - Saveliev, Alexei V. AU - Gilligan, John G. AU - Bourham, Mohamed A. T2 - JOURNAL OF FUSION ENERGY DA - 2013/6// PY - 2013/6// DO - 10.1007/s10894-012-9578-5 VL - 32 IS - 3 SP - 371-377 SN - 0164-0313 KW - Electrothermal plasma sources KW - Fusion pellet acceleration KW - Ablative capillaries ER - TY - JOUR TI - Crude glycerol combustion: Particulate, acrolein, and other volatile organic emissions AU - Steinmetz, Scott A. AU - Herrington, Jason S. AU - Winterrowd, Christopher K. AU - Roberts, William L. AU - Wendt, Jost O. L. AU - Linak, William P. T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - Crude glycerol is an abundant by-product of biodiesel production. As volumes of this potential waste grow, there is increasing interest in developing new value added uses. One possible use, as a boiler fuel for process heating, offers added advantages of energy integration and fossil fuel substitution. However, challenges to the use of crude glycerol as a boiler fuel include its low energy density, high viscosity, and high autoignition temperature. We have previously shown that a refractory-lined, high swirl burner can overcome challenges related to flame ignition and stability. However, critical issues related to ash behavior and the possible formation of acrolein remained. The work presented here indicates that the presence of dissolved catalysts used during the esterification and transesterification processes results in extremely large amounts of inorganic species in the crude glycerol. For the fuels examined here, the result is a submicron fly ash comprised primarily of sodium carbonates, phosphates, and sulfates. These particles report to a well-developed accumulation mode (0.3–0.7 μm diameter), indicating extensive ash vaporization and particle formation via nucleation, condensation, and coagulation. Particle mass emissions were between 2 and 4 g/m3. These results indicate that glycerol containing soluble catalyst is not suitable as a boiler fuel. Fortunately, process improvements are currently addressing this issue. Additionally, acrolein is of concern due to its toxicity, and is known to be formed from the low temperature thermal decomposition of glycerol. Currently, there is no known reliable method for measuring acrolein in sources. Acrolein and emissions of other volatile organic compounds were characterized through the use of a SUMMA canister-based sampling method followed by GC–MS analysis designed for ambient measurements. Results indicate crude glycerol combustion produces relatively small amounts of acrolein (∼15 ppbv) and other volatile organic compounds, with emissions comparable to those from natural gas combustion. DA - 2013/// PY - 2013/// DO - 10.1016/j.proci.2012.07.050 VL - 34 SP - 2749-2757 SN - 1873-2704 KW - Glycerol combustion KW - Emission characterization KW - Bio-fuels KW - Acrolein measurements KW - Waste fuels ER - TY - JOUR TI - Cellular growth algorithms for shape design of truss structures AU - Tschida, Colin E. AU - Silverberg, Larry M. T2 - COMPUTERS & STRUCTURES AB - This paper introduces a novel approach to truss structure shape design, drawing inspiration from biological processes, that treats each joint or member of a truss as a cell and the entire truss as a multicellular organism. The approach mimics plant tropisms in which, through cellular growth, cells change their size and shape in response to scripted gene commands. Examples illustrate the effectiveness of the approach; it is shown to produce arching and double-arching of pinned-pinned trusses, bulging of cantilever trusses and a plant-like tropic response. DA - 2013/1// PY - 2013/1// DO - 10.1016/j.compstruc.2012.10.006 VL - 116 SP - 1-6 SN - 1879-2243 KW - Truss KW - Design KW - Bio-inspired KW - Optimization KW - Evolutionary algorithms ER - TY - JOUR TI - A note on modeling high speed flow in a bidisperse porous medium AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - Transport in Porous Media DA - 2013/// PY - 2013/// DO - 10.1007/s11242-012-0102-1 VL - 96 IS - 3 SP - 495-499 ER - TY - JOUR TI - The Onset of Convection in a Layered Porous Medium with Vertical Throughflow AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2013/6// PY - 2013/6// DO - 10.1007/s11242-013-0148-8 VL - 98 IS - 2 SP - 363-376 SN - 0169-3913 KW - Heterogeneity KW - Throughflow KW - Thermal instability KW - Horizontal layers ER - TY - JOUR TI - Significant hardening due to the formation of a sigma phase matrix in a high entropy alloy AU - Tsai, Ming-Hung AU - Yuan, Hao AU - Cheng, Guangming AU - Xu, Weizong AU - Jian, Weiwei W. AU - Chuang, Ming-Hao AU - Juan, Chien-Chang AU - Yeh, An-Chou AU - Lin, Su-Jien AU - Zhu, Yuntian T2 - INTERMETALLICS AB - The hardening in Al0.3CrFe1.5MnNi0.5 high-entropy alloy not only nearly triples the hardness of the alloy, but also shows a quick hardening response and the absence of overaging. However, the crystal structure, morphology, and composition of the hardening phase have not yet been confirmed. Here, such information regarding the hardening phase is investigated. It was found that the hardening phase is a Cr–Mn–Fe ternary sigma phase. Unlike in conventional engineering alloys, the sigma phase is not precipitated from the matrix, instead, the whole BCC matrix transforms to sigma phase almost without changing its composition. Therefore, the hardening phenomenon is not a precipitation hardening reaction as suggested before. DA - 2013/2// PY - 2013/2// DO - 10.1016/j.intermet.2012.09.022 VL - 33 SP - 81-86 SN - 1879-0216 KW - Age-hardening KW - Precipitates KW - Electron microscopy, transmission ER - TY - JOUR TI - Shin: Generalized Trust Propagation with Limited Evidence AU - Hang, Chung-Wei AU - Zhang, Zhe AU - Singh, Munindar P. T2 - COMPUTER AB - Shin incorporates a probabilistic method for revising trust estimates in trustees, yielding higher prediction accuracy than traditional approaches that base trust exclusively on a series of referrals culminating with the trustee. DA - 2013/3// PY - 2013/3// DO - 10.1109/mc.2012.116 VL - 46 IS - 3 SP - 78-85 SN - 1558-0814 ER - TY - JOUR TI - Self-healing sandwich structures incorporating an interfacial layer with vascular network AU - Chen, Chunlin AU - Peters, Kara AU - Li, Yulong T2 - SMART MATERIALS AND STRUCTURES AB - A self-healing capability specifically targeted for sandwich composite laminates based on interfacial layers with built-in vascular networks is presented. The self-healing occurs at the facesheet–core interface through an additional interfacial layer to seal facesheet cracks and rebond facesheet–core regions. The efficacy of introducing the self-healing system at the facesheet–core interface is evaluated through four-point bend and edgewise compression testing of representative foam core sandwich composite specimens with impact induced damage. The self-healing interfacial layer partially restored the specific initial stiffness, doubling the residual initial stiffness as compared to the control specimen after the impact event. The restoration of the ultimate specific skin strength was less successful. The results also highlight the critical challenge in self-healing of sandwich composites, which is to rebond facesheets which have separated from the core material. DA - 2013/2// PY - 2013/2// DO - 10.1088/0964-1726/22/2/025031 VL - 22 IS - 2 SP - SN - 0964-1726 ER - TY - JOUR TI - Sakiadis flow with nonlinear Rosseland thermal radiation AU - Pantokratoras, Asterios AU - Fang, Tiegang T2 - PHYSICA SCRIPTA AB - In a recent paper by Cortell (2008 Chin. Phys. Lett. 25 1340–2) the effect of radiation on the classical Sakiadis flow along a moving plate in a calm fluid was considered. The results in that paper have been produced using a linearized Rosseland approximation, which is valid only for small temperature differences between the plate and the ambient fluid. In the present work, we extend the above work to a nonlinear Rosseland approximation, which is valid for both small and large temperature differences. DA - 2013/1// PY - 2013/1// DO - 10.1088/0031-8949/87/01/015703 VL - 87 IS - 1 SP - SN - 1402-4896 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84872068683&partnerID=MN8TOARS ER - TY - JOUR TI - Quantification of the effectiveness of various adhesives in holding an SMA actuator wire during joule heating AU - Furst, S. J. AU - Bumgarner, D. AU - Seelecke, S. T2 - Journal of Adhesion DA - 2013/// PY - 2013/// VL - 89 IS - 4 SP - 301-322 ER - TY - JOUR TI - Numerical investigation of axonal cargo rerouting in a dendrite: A three kinetic state model AU - Kuznetsov, A. V. T2 - INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING AB - The purpose of this paper is to develop a three-kinetic state model to investigate axonal cargo rerouting in a dendrite. It is assumed that axonal cargos are transported by kinesin motors; they can enter dendrites riding on plus-end-out microtubules (MTs). If this happens, cargos are rerouted by dissociating from these MTs and associating with minus-end-out MTs. The same kinesin motors then move axonal cargos out of the dendrite. The model predicts how far axonal cargos can penetrate into the dendrite, concentrations of various populations of axonal cargos, and cargo fluxes. DA - 2013/3// PY - 2013/3// DO - 10.1002/cnm.2521 VL - 29 IS - 3 SP - 428-443 SN - 2040-7947 KW - neurons KW - intracellular transport KW - axons and dendrites KW - axonal cargo KW - cargo targeting ER - TY - JOUR TI - Morphology, structure and composition of precipitates in Al0.3CoCrCu0.5FeNi high-entropy alloy AU - Tsai, Ming-Hung AU - Yuan, Hao AU - Cheng, Guangming AU - Xu, Weizong AU - Tsai, Kun-Yo AU - Tsai, Che-Wei AU - Jian, Weiwei W. AU - Juan, Chien-Chang AU - Shen, Wan-Jui AU - Chuang, Ming-Hao AU - Yeh, Jien-Wei AU - Zhu, Yuntian T. T2 - INTERMETALLICS AB - High-entropy alloy is a new class of metallic materials with great potential for many applications. However, their microstructural characteristics, particularly those of precipitates, remain poorly understood. This has hindered the establishment of structure-property relationship in these alloys. Here, we report the morphology, crystal structure and composition of the precipitates in the Al0.3CoCrCu0.5FeNi high-entropy alloy. Two types of precipitates were identified, namely the plate-like and the spherical precipitates. Their formation sequence and mechanism during the cooling process are discussed based on thermodynamics. DA - 2013/1// PY - 2013/1// DO - 10.1016/j.intermet.2012.07.036 VL - 32 SP - 329-336 SN - 1879-0216 KW - Precipitates KW - Microstructure KW - Widmanstatten morphology KW - Electron microscopy KW - transmission ER - TY - JOUR TI - Low-temperature evaporative glass scoring using a single-mode ytterbium fiber laser AU - Tu, J. F. AU - Riley, P. E. B. T2 - OPTICS AND LASERS IN ENGINEERING AB - Glass cutting is increasingly important in industry to cut glass into various sizes for high definition televisions, cell phones, laptops, and tablet computers. A conventional mechanical cutter is usually used to score the glass before a bending force is applied to separate the glass along the scoring mark. This paper presents a laser glass scoring technique aimed at replacing the mechanical cutter to reduce cracks. This scoring technique, denoted as the Low-temperature Evaporative Glass Scoring process (LEGS), is different because laser energy is not directly absorbed by the glass. To achieve the proposed laser scoring, a laser beam is focused through the glass onto a metal substrate. The metal substrate absorbs the laser energy to generate a metal vapor to etch the glass, forming a scoring mark. The feasibility of this glass scoring technique is demonstrated using a continuous-wave fiber laser, at a low power of 60 W, and a 7075-T6 Aluminum alloy plate as the metal substrate. When the laser beam scans across the substrate, the laser energy creates a quasi-static aluminum molten pool, covered by an aluminum vapor at a temperature about 3000 K. At an optimal setting of 51 μm gap distance, 60 W laser power, and 6 mm/s scoring speed, a uniform scoring mark of 37 μm width and 120 μm depth was successfully generated on a piece of soda-lime glass without visible micro-cracks. The paper also discussed the uncertainties and their remedies involved in the LEGS process. To facilitate the process design, a model for predicting the aluminum vapor temperature was developed. This model accounted for the laser focus, reflection, absorption and transmission, laser energy distribution, and the aluminum melting and vaporization processes. Finally, this model was validated by comparing the actual melt depth of the aluminum substrate with the one predicted by the model. DA - 2013/6// PY - 2013/6// DO - 10.1016/j.optlaseng.2013.01.005 VL - 51 IS - 6 SP - 696-706 SN - 1873-0302 KW - Laser glass cutting KW - Glass scribing KW - Glass scoring KW - Evaporative scoring KW - Fiber laser ER - TY - JOUR TI - Infrared Matrix-Assisted Laser Desorption Electrospray Ionization (IR-MALDESI) Imaging Source Coupled to a FT-ICR Mass Spectrometer AU - Robichaud, Guillaume AU - Barry, Jeremy A. AU - Garrard, Kenneth P. AU - Muddiman, David C. T2 - JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY AB - Mass spectrometry imaging (MSI) allows for the direct monitoring of the abundance and spatial distribution of chemical compounds over the surface of a tissue sample. This technology has opened the field of mass spectrometry to numerous innovative applications over the past 15 years. First used with SIMS and MALDI MS that operate under vacuum, interest has grown for mass spectrometry ionization sources that allow for effective imaging but where the analysis can be performed at ambient pressure with minimal or no sample preparation. We introduce here a versatile source for MALDESI imaging analysis coupled to a hybrid LTQ-FT-ICR mass spectrometer. The imaging source offers single shot or multi-shot capability per pixel with full control over the laser repetition rate and mass spectrometer scanning cycle. Scanning rates can be as fast as 1 pixel/second and a spatial resolution of 45 μm was achieved with oversampling. DA - 2013/1// PY - 2013/1// DO - 10.1007/s13361-012-0505-9 VL - 24 IS - 1 SP - 92-100 SN - 1044-0305 KW - FTMS KW - Mass spectrometry imaging KW - Infrared laser KW - MALDESI KW - Atmospheric pressure ER - TY - JOUR TI - Electro-mechanical modeling of the piezoresistive response of carbon nanotube polymer composites AU - Xu, S. AU - Rezvanian, O. AU - Zikry, M. A. T2 - SMART MATERIALS AND STRUCTURES AB - A coupled electro-mechanical FE approach was developed to investigate the piezoresistive response of carbon nanotube polymer composites. Gauge factors (GFs) and resistance variations of CNT–polymer composite systems were obtained by coupling Maxwell equations to mechanical loads and deformations through initial piezoresistive coefficients of the CNTs, the epoxy, and the tunnel regions, for different arrangements, percolated paths, tunnel distances, and tensile, compressive, and bending loading conditions. A scaling relation between GFs and applied strains was obtained to understand how variations in loading conditions and CNT arrangements affect sensing capabilities and piezoresistive carbon nanotube polymer composite behavior. These variations in GFs were then used to understand how the coupled strains, stresses and current densities vary for aligned and percolated paths for the different loading conditions, CNT arrangements, and tunnel distances. For the percolated path under tensile loading conditions, elastic strains as high as 16% and electrical conductivities that were four orders in magnitude greater than the initial matrix conductivity were obtained. Results for the three loading conditions clearly demonstrate that electrical conductivity and sensing capabilities can be optimized as a function of percolation paths, tunneling distance, orientation, and loading conditions for piezoresistive applications with large elastic strains and conductivities. DA - 2013/5// PY - 2013/5// DO - 10.1088/0964-1726/22/5/055032 VL - 22 IS - 5 SP - SN - 1361-665X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876921770&partnerID=MN8TOARS ER - TY - JOUR TI - Correlating Stiffness, Ductility, and Morphology of Polymer:Fullerene Films for Solar Cell Applications AU - Awartani, Omar AU - Lemanski, Bethany I. AU - Ro, Hyun Wook AU - Richter, Lee J. AU - DeLongchamp, Dean M. AU - Brendan T. O'Connor, T2 - ADVANCED ENERGY MATERIALS AB - Abstract The development of flexible and physically robust organic solar cells requires detailed knowledge of the mechanical behavior of the heterogeneous material stack. However, in these devices there has been limited research on the mechanical properties of the active organic layer. Here, two critical mechanical properties, stiffness and ductility, of a widely studied organic solar cell active layer, a blend film composed of poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl C61‐butyric acid methyl ester (PCBM) are reported. Processing conditions are varied to produce films with differing morphology and correlations are developed between the film morphology, mechanical properties and photovoltaic device performance. The morphology is characterized by fitting the absorption of the P3HT:PCBM films to a weakly interacting H‐aggregate model. The elastic modulus is determined using a buckling metrology approach and the crack onset strain is determined by observing the film under tensile strain using optical microscopy. Both the elastic modulus and crack onset strain are found to vary significantly with processing conditions. Processing methods that result in improved device performance are shown to decrease both the compliance and ductility of the film. DA - 2013/3// PY - 2013/3// DO - 10.1002/aenm.201200595 VL - 3 IS - 3 SP - 399-406 SN - 1614-6840 KW - bulk heterojunction morphology KW - flexible electronics KW - mechanical properties KW - organic electronics KW - solar cells ER - TY - JOUR TI - Closed-form analytical solutions of flow and heat transfer for an unsteady rear stagnation-point flow AU - Fang, Tiegang AU - Jing, Wei T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - In this paper, flow and heat transfer characteristics of an unsteady rear stagnation-point flow over a moving wall with transpiration are studied. The flow solution is an exact solution to the unsteady Navier–Stokes equations. By ignoring the viscous dissipation terms, analytical solutions of the boundary layer energy equation are obtained for the cases with a constant wall temperature and a prescribed time-dependent wall heat flux. The effects of the controlling parameters on the solution domain, the velocity distribution and the temperature distribution in the fluids are analyzed. With certain given values of the controlling parameters, two solution branches are found for both the flow and the heat transfer problems. These closed-form solutions are rare and can be used as a benchmark problem for numerical code validation. DA - 2013/7// PY - 2013/7// DO - 10.1016/j.ijheatmasstransfer.2013.02.049 VL - 62 IS - 1 SP - 55-62 SN - 0017-9310 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875443267&partnerID=MN8TOARS KW - Similarity equation KW - Unsteady rear stagnation-point flow KW - Moving wall KW - Navier-Stokes equations KW - Analytical solution KW - Heat transfer ER - TY - JOUR TI - Atmospheric plasma application to improve adhesion of electrospun nanofibers onto protective fabric AU - Vitchuli, Narendiran AU - Shi, Quan AU - Nowak, Joshua AU - Nawalakhe, Rupesh AU - Sieber, Michael AU - Bourham, Mohamed AU - Zhang, Xiangwu AU - McCord, Marian T2 - JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY AB - Nylon 6 electrospun nanofibers were deposited on plasma-pretreated woven fabric substrates with the objective of improving adhesion between them. The prepared samples were evaluated for adhesion strength and durability of nanofiber mats by carrying out peel strength, flex resistance, and abrasion resistance tests. The test results showed significant improvement in the adhesion of nanofiber mats on woven fabric substrates due to atmospheric plasma pretreatment. The samples also exhibited good flex and abrasion resistance characteristics. X-ray photoelectron spectroscopy and water contact angle analyses indicate that plasma pretreatment introduces radicals, increases the oxygen content on the substrate surface, and leads to formation of active chemical sites that may be responsible for enhanced cross-linking between the substrate fabric and the electrospun nanofibers, which in turn increases the adhesion properties. The work demonstrates that the plasma treatment of the substrate fabric prior to deposition of electrospun nanofiber mats is a promising method to prepare durable functional materials. DA - 2013/4/1/ PY - 2013/4/1/ DO - 10.1080/01694243.2012.727164 VL - 27 IS - 8 SP - 924-938 SN - 0169-4243 KW - adhesion KW - atmospheric pressure plasma KW - cross-linking KW - dielectric barrier discharge KW - electrospinning KW - water contact angle ER - TY - JOUR TI - Antireflection effects at nanostructured material interfaces and the suppression of thin-film interference AU - Yang, Qiaoyin AU - Zhang, Xu A. AU - Bagal, Abhijeet AU - Guo, Wei AU - Chang, Chih-Hao T2 - NANOTECHNOLOGY AB - Thin-film interference is a well-known effect, and it is commonly observed in the colored appearance of many natural phenomena. Caused by the interference of light reflected from the interfaces of thin material layers, such interference effects can lead to wavelength and angle-selective behavior in thin-film devices. In this work, we describe the use of interfacial nanostructures to eliminate interference effects in thin films. Using the same principle inspired by moth-eye structures, this approach creates an effective medium where the index is gradually varying between the neighboring materials. We present the fabrication process for such nanostructures at a polymer-silicon interface, and experimentally demonstrate its effectiveness in suppressing thin-film interference. The principle demonstrated in this work can lead to enhanced efficiency and reduce wavelength/angle sensitivity in multilayer optoelectronic devices. DA - 2013/6/14/ PY - 2013/6/14/ DO - 10.1088/0957-4484/24/23/235202 VL - 24 IS - 23 SP - SN - 1361-6528 ER - TY - JOUR TI - A magnetically levitated vibration energy harvester AU - Wang, X. Y. AU - Palagummi, S. AU - Liu, L. AU - Yuan, F. G. T2 - SMART MATERIALS AND STRUCTURES AB - In this paper a novel electromagnetic vibration type energy harvester that uses a diamagnetic levitation system is conceptualized, designed, fabricated, and tested. The harvester uses two diamagnetic plates made of pyrolytic graphite between which a cylindrical magnet levitates passively. Two thick cylindrical coils, placed in grooves which are engraved in the pyrolytic graphite plates, are used to convert the mechanical energy into electrical energy efficiently. The geometric configurations of the coils are selected based on the field distribution of the magnet to enhance the efficiency of the harvester. A thorough theoretical analysis is carried out to compare with experimental results. At an input power of 103.45 μW and at a frequency of 2.7 Hz, the harvester generated a power of 0.74 μW with a system efficiency of 0.72%. Both theoretical and experimental results show that this new energy harvesting system can capture low frequency broadband spectra. DA - 2013/5// PY - 2013/5// DO - 10.1088/0964-1726/22/5/055016 VL - 22 IS - 5 SP - SN - 0964-1726 ER - TY - JOUR TI - The effects of microstructure and morphology on fracture nucleation and propagation in martensitic steel alloys AU - Shanthraj, P. AU - Zikry, M. A. T2 - MECHANICS OF MATERIALS AB - A dislocation-density based multiple-slip crystalline plasticity framework, which accounts for variant morphologies and orientation relationships (ORs) that are uniquely inherent to lath martensitic microstructures, and a dislocation-density grain boundary (GB) interaction scheme, which is based on dislocation-density transmission and blockage at variant boundaries, is developed and used to predict stress accumulation or relaxation at the variant interfaces. A microstructural failure criterion, which is based on resolving these stresses on martensitic cleavage planes, and specialized finite-element (FE) methodologies using overlapping elements to represent evolving fracture surfaces are used for a detailed analysis of fracture nucleation and intergranular and transgranular crack growth in martensitic steels. The effects of block and packet boundaries are investigated, and the results indicate that the orientation of the cleavage planes in relation to the slip planes and the lath morphology are the dominant factors that characterize specific failure modes. The block and packet sizes along the lath long direction are the key microstructural features the affect toughening mechanisms, such as crack arrest and deflection, and these mechanisms can be used to control the nucleation and propagation of different failure modes. DA - 2013/3// PY - 2013/3// DO - 10.1016/j.mechmat.2012.11.010 VL - 58 SP - 110-122 SN - 1872-7743 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84872336398&partnerID=MN8TOARS KW - Dislocation density KW - Grain boundary KW - Lath martensite KW - Failure KW - Cleavage planes ER - TY - JOUR TI - Soot temperature and KL factor for biodiesel and diesel spray combustion in a constant volume combustion chamber AU - Zhang, Ji AU - Jing, Wei AU - Roberts, William L. AU - Fang, Tiegang T2 - APPLIED ENERGY AB - This paper presents measurements of the soot temperature and KL factor for biodiesel and diesel combustion in a constant volume chamber using a two-color technique. This technique uses a high-speed camera coupled with two narrowband filters (550 nm and 650 nm, 10 nm FWHM). After calibration, statistical analysis shows that the uncertainty of the two-color temperature is less than 5%, while it is about 50% for the KL factor. This technique is then applied to the spray combustion of biodiesel and diesel fuels under an ambient oxygen concentration of 21% and ambient temperatures of 800, 1000 and 1200 K. The heat release result shows higher energy utilization efficiency for biodiesel compared to diesel under all conditions; meanwhile, diesel shows a higher pressure increase due to its higher heating value. Biodiesel yields a lower temperature inside the flame area, a longer soot lift-off length, and a smaller soot area compared to diesel. Both the KL factor and the total soot with biodiesel are lower than with diesel throughout the entire combustion process, and this difference becomes larger as the ambient temperature decreases. Biodiesel shows approximately 50–100 K lower temperatures than diesel at the quasi-steady stage for 1000 and 1200 K ambient temperature, while diesel shows a lower temperature than biodiesel at 800 K ambient. This result may raise the question of how important the flame temperature is in explaining the higher NOx emissions often observed during biodiesel combustion. Other factors may also play an important role in controlling NOx emissions. Both biodiesel and diesel temperature measurements show a monotonic dependence on the ambient temperature. However, the ambient temperature appears to have a more significant effect on the soot formation and oxidation in diesel combustion, while biodiesel combustion soot characteristics shows relative insensitivity to the ambient temperature. DA - 2013/7// PY - 2013/7// DO - 10.1016/j.apenergy.2013.02.023 VL - 107 SP - 52-65 SN - 1872-9118 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875117595&partnerID=MN8TOARS KW - Biodiesel KW - Diesel KW - Spray combustion KW - Two-color thermometry KW - Constant volume chamber ER - TY - CONF TI - Mechanics of Diffusion-Induced Fractures in Lithium-ion Battery Materials AU - ChiuHuang, Cheng-Kai AU - Stamps, Michael A. AU - Huang, Hsiao-Ying Shadow C2 - 2013/// C3 - Materials Research Soaciety 2013 Spring Meeting CY - San Francisco, CA DA - 2013/// VL - 1541 SP - 1541-F04-04 ER - TY - JOUR TI - MSiReader: An Open-Source Interface to View and Analyze High Resolving Power MS Imaging Files on Matlab Platform AU - Robichaud, Guillaume AU - Garrard, Kenneth P. AU - Barry, Jeremy A. AU - Muddiman, David C. T2 - JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY AB - During the past decade, the field of mass spectrometry imaging (MSI) has greatly evolved, to a point where it has now been fully integrated by most vendors as an optional or dedicated platform that can be purchased with their instruments. However, the technology is not mature and multiple research groups in both academia and industry are still very actively studying the fundamentals of imaging techniques, adapting the technology to new ionization sources, and developing new applications. As a result, there important varieties of data file formats used to store mass spectrometry imaging data and, concurrent to the development of MSi, collaborative efforts have been undertaken to introduce common imaging data file formats. However, few free software packages to read and analyze files of these different formats are readily available. We introduce here MSiReader, a free open source application to read and analyze high resolution MSI data from the most common MSi data formats. The application is built on the Matlab platform (Mathworks, Natick, MA, USA) and includes a large selection of data analysis tools and features. People who are unfamiliar with the Matlab language will have little difficult navigating the user-friendly interface, and users with Matlab programming experience can adapt and customize MSiReader for their own needs. DA - 2013/5// PY - 2013/5// DO - 10.1007/s13361-013-0607-z VL - 24 IS - 5 SP - 718-721 SN - 1879-1123 KW - Mass spectrometry imaging KW - Software KW - High mass resolving power KW - FT-ICR-MS KW - Open-source ER - TY - JOUR TI - Ion-irradiation-induced ferromagnetism in undoped ZnO thin films AU - Mal, Siddhartha AU - Nori, Sudhakar AU - Narayan, J. AU - Prater, J. T. AU - Avasthi, D. K. T2 - ACTA MATERIALIA AB - We have introduced defects in ZnO epitaxial thin films by swift heavy 107Ag9+ ion irradiation and investigated systematically their magnetic, electrical and optical properties. Oxygen annealed ZnO films are epitaxial single crystals that exhibit no long-range magnetic order. However, in this paper it is shown that room-temperature ferromagnetism (RTFM) can be introduced in a controlled manner in these films using ion irradiation and that the magnetization increases with ion dose. This qualitatively agrees with earlier studies which showed that RTFM could be induced in ZnO films through either vacuum thermal annealing or pulsed laser annealing below energy densities that lead to melting. Raman studies of the ion irradiated samples revealed dramatic changes in the vibration modes that correlated with increases in the carrier concentration, indicative of lattice disorder and defect creation. We compare these results with those observed in laser irradiated and vacuum annealed samples, and then discuss these findings in the context of defects and defect complexes created during the high-energy heavy ion irradiation process. We propose a unified mechanism to explain RTFM and n-type conductivity enhancements during irradiation, and laser and vacuum annealing. DA - 2013/5// PY - 2013/5// DO - 10.1016/j.actamat.2012.09.071 VL - 61 IS - 8 SP - 2763-2768 SN - 1359-6454 KW - Zinc oxide KW - Thin films KW - Pulsed laser deposition KW - Magnetic semiconductors KW - Raman spectra ER - TY - JOUR TI - Finite element analysis of the piezoelectric stacked-HYBATS transducer AU - Tolliver, Laura AU - Xu, Tian-Bing AU - Jiang, Xiaoning T2 - SMART MATERIALS AND STRUCTURES AB - Finite element modeling (FEM) of a piezoelectric multilayer-stacked hybrid actuation/transduction system (stacked-HYBATS) is investigated in this paper using ANSYS software. This transducer consists of two positive strain components operating in d33 mode and one negative strain component operating in d31 mode to generate large displacements. FEM results are compared with experimental and analytical results to provide insight into the actuation mechanisms, verify the device's three displacement components, and estimate its blocking force. FEM calculations found the effective piezoelectric coefficient to be exceptional, about 3.11 × 106 pm V−1 at resonance. Stacked-HYBATS was quantitatively compared to commercially available flextensional actuators using finite element analysis. It was found that under the same electric field the yielded displacement of a stacked-HYBATS is about 200% and 15% larger than that of a same-sized d31 and d33 flextensional actuator, respectively. These findings suggest that stacked-HYBATS is promising for precision positioning, vibration control, and acoustic applications. DA - 2013/3// PY - 2013/3// DO - 10.1088/0964-1726/22/3/035015 VL - 22 IS - 3 SP - SN - 1361-665X ER - TY - JOUR TI - Experimental verification of transient nonlinear acoustical holography AU - Jing, Yun AU - Cannata, Jonathan AU - Wang, Tianren T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA AB - This paper presents an experimental study on nonlinear transient acoustical holography. The validity and effectiveness of a recently proposed nonlinear transient acoustical holography algorithm is evaluated in the presence of noise. The acoustic field measured on a post-focal plane of a high-intensity focused transducer is backward projected to reconstruct the pressure distributions on the focal and a pre-focal plane, which are shown to be in good agreement with the measurement. In contrast, the conventional linear holography produces erroneous results in this case where the nonlinearity involved is strong. Forward acoustic field projection was also carried out to further verify the algorithm. DA - 2013/5// PY - 2013/5// DO - 10.1121/1.4796120 VL - 133 IS - 5 SP - 2533-2540 SN - 1520-8524 ER - TY - JOUR TI - Experimental and numerical studies on vertical properties of a new multi-dimensional earthquake isolation and mitigation device AU - Xu, Zhaodong AU - Lu, Liheng AU - Shi, Benqiang AU - Yuan, Fuhgwo T2 - SHOCK AND VIBRATION AB - When designing critical structures such as long-span structures and high-rise buildings, earthquake excitation in the vertical direction, in addition to the horizontal direction, should also be taken into consideration. Study on new devices that can mitigate and isolate multi-dimensional (including both horizontal and vertical) earthquake actions has a remarkable significance. A new kind of multi-dimensional earthquake isolation and mitigation device was recently developed, and experimental study on vertical performances of the device under different excitation frequencies and amplitudes has been carried out in this paper. The characteristics of the vertical properties including the initial stiffness, the energy dissipation stiffness, the energy dissipation per cycle and the vertical damping ratio changing with excitation frequency and amplitude were studied, and the formulas describing the characteristics were proposed. It can be concluded that the initial stiffness and the energy dissipation stiffness increase slightly with increasing frequency, while the energy dissipation per cycle and the damping ratio decrease slightly with increasing frequency, the initial stiffness, the energy dissipation stiffness and the damping ratio will decrease slightly with increasing excitation amplitudes, and the proposed formulas can describe the vertical properties of the multi-dimensional earthquake isolation and mitigation device changing with excitation frequency and amplitude. DA - 2013/// PY - 2013/// DO - 10.1155/2013/325387 VL - 20 IS - 3 SP - 401-410 SN - 1875-9203 KW - Multi-dimensional KW - earthquake isolation and mitigation device KW - energy dissipation KW - viscoelastic KW - vertical properties KW - dynamic responses ER - TY - JOUR TI - Environmental implications of iron fuel borne catalysts and their effects on diesel particulate formation and composition AU - Nash, David G. AU - Swanson, Nicholas B. AU - Preston, William T. AU - Yelverton, Tiffany L. B. AU - Roberts, William L. AU - Wendt, Jost O. L. AU - Linak, William P. T2 - JOURNAL OF AEROSOL SCIENCE AB - Metal fuel borne catalysts (FBCs) can be used with diesel fuels to effectively reduce engine out particle mass emissions. Internationally, metal FBCs are used for both on-road and off-road applications, although current regulations in the U.S. restrict their on-road use. Although metal FBCs are intended to be used with specialized diesel particulate filters (DPFs) where they are effectively trapped to oxidize additional soot and regenerate the filter, they are sometimes used without DPFs, and, under these conditions, contribute to ambient air emissions and potential health effects. This paper explores potential environmental and health aspects of FBC in diesel fuels, when burned in diesel engines without DPF's. However, rather than examine data from a range of diesel engines, the work focuses on the impact of systematic changes in the fuel composition on emissions from a single, small prototype diesel generator. Experiments using ferrocene as a diesel fuel additive, with varying fuel Fe concentrations from 0 to 200 ppm, indicate ∼30–40% decreases in particle mass, total particle volume, and black carbon emissions, and increases (approaching a factor of 5) in particle number concentrations associated with 10–30 nm Fe particles liberated during soot oxidation. Fe concentrations in overall particle emissions increase from 0.1% to 7.5% as the Fe catalyst is increased from 0 to 200 ppm. The Fe is emitted primarily in the elemental form. While polycyclic aromatic hydrocarbons (PAHs) are reduced with increasing Fe, emissions of alkanes and organic acids show no clear trend. These experimental results can be interpreted in the light of a mechanism whereby the Fe acts to oxidize soot-related PAH species, but does not affect organic compounds associated with unburned fuel and lubrication oil that avoid flame processes. Calculations performed to predict the evolution of the particle size distribution (PSD) associated with the emitted particles suggest that once diluted to simulate behavior along a highway, the Fe-rich nuclei mode is likely to persist for some time. This has health effect implications related to potential exposures associated with these particles. DA - 2013/4// PY - 2013/4// DO - 10.1016/j.jaerosci.2013.01.001 VL - 58 SP - 50-61 SN - 1879-1964 KW - Metal fuel borne catalysts KW - Diesel particle emissions KW - Ferrocene KW - Particle size and composition KW - Soot oxidation ER - TY - JOUR TI - Dynamics of a dissipative, inelastic gravitational billiard AU - Hartl, Alexandre E. AU - Miller, Bruce N. AU - Mazzoleni, Andre P. T2 - PHYSICAL REVIEW E AB - The seminal physical model for investigating formulations of nonlinear dynamics is the billiard. This article expands on our previously published work concerning a real-world billiard. Here we provide a detailed mathematical model for describing the motion of a realistic billiard for arbitrary boundaries, where we include rotational effects and additional forms of energy dissipation. Simulations of the model are applied to parabolic, wedge, and hyperbolic billiards that are driven sinusoidally. The simulations demonstrate that the parabola has stable, periodic motion, while the wedge and hyperbola (at high driving frequencies) appear chaotic. The hyperbola, at low driving frequencies, behaves similarly to the parabola, i.e., has regular motion. Direct comparisons are made between the model's predictions and previously published experimental data. The representation of the coefficient of restitution employed in the model resulted in approximate agreement with the experimental data for all boundary shapes investigated. We show how the coefficient of restitution varies under different model assumptions. It is shown that the data can be successfully modeled with a simple set of parameters. DA - 2013/3/1/ PY - 2013/3/1/ DO - 10.1103/physreve.87.032901 VL - 87 IS - 3 SP - SN - 1550-2376 ER - TY - JOUR TI - Development of time-reversal method for impact source identification on plate structures AU - Chen, Chunlin AU - Li, Yulong AU - Yuan, Fuh-Gwo T2 - SHOCK AND VIBRATION AB - This paper presents a detailed study on the impact source identification of a plate structure using time-reversal (T-R) method. Prior to impact monitoring, the plate is calibrated (or characterized) by transfer functions at discrete locations on the plate surface. Both impact location and impact loading time-history are identified using T-R technique and associated signal processing algorithms. Numerical verification for finite-size isotropic plates under low velocity impacts is performed to demonstrate the versatility of T-R method for impact source identification. The tradeoff between accuracy of the impact location detection and calibration spacing is studied in detail. In particular, the effect of plate thickness on calibration spacing has been examined. A number of parameters selected for determining the impact location, approximated transfer functions and steps taken for reconstructing the impact loading time-history are also examined. Two types of noise with various intensities contaminated in strain response and/or transfer functions are investigated for demonstrating the stability and reliability of the T-R method. The results show that T-R method is robust against noise in impact location detection and force reconstruction in circumventing the inherent ill-conditioned inverse problem. Only transfer functions are needed to be calibrated and four sensors are requested in T-R method for impact identification. DA - 2013/// PY - 2013/// DO - 10.1155/2013/312169 VL - 20 IS - 3 SP - 561-573 SN - 1875-9203 KW - Impact location detection KW - impact force reconstruction KW - time-reversal method KW - calibration spacing KW - noise effect ER - TY - JOUR TI - A note on the variation of nanofluid viscosity with temperature AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - Abstract The variation with temperature of the effective viscosity of a nanofluid, together with the effect of particle size on this quantity, is discussed. The analysis of available experimental correlations suggests that the effect of the particle size is approximately independent of the temperature, and increases the viscosity by an amount that decreases with the increase of size. Physically, we expect that this happens because increased size means fewer particles per unit volume, which results in decreased interference with the rate at which fluid molecules reorganise themselves in groups. DA - 2013/2// PY - 2013/2// DO - 10.1016/j.icheatmasstransfer.2012.11.001 VL - 41 SP - 17-18 SN - 0735-1933 KW - Nanofluid KW - Viscosity variation with temperature ER - TY - JOUR TI - Diamagnetic levitation for nonlinear vibration energy harvesting: Theoretical modeling and analysis AU - Liu, Lei AU - Yuan, F. G. T2 - JOURNAL OF SOUND AND VIBRATION AB - This paper provides theoretical modeling and analysis of applying diamagnetic levitation for nonlinear vibration energy harvesting in detail by first identifying potential merits as well as limitations. Based on a magnetic dipole model, analytical analysis is conducted by providing simplified analytical expressions of restoring forces and electromagnetic damping which are then transformed into a hardening spring model and results in a Duffing equation with strong nonlinearity. In addition, constraints on physical geometry are discussed and derived in the view of practical energy harvester design. More importantly, the derivation and discussion extended to multi-well potential suggest that diamagnetic levitation may enable designing an energy harvester that subject to cross-well chaos with a compact volume and wideband responses. Without mechanical damping in any form, diamagnetic levitation may be considered as a promising mechanism for developing vibration energy harvesters with great performance, and the paper provides a technology push on the possibility. DA - 2013/1/21/ PY - 2013/1/21/ DO - 10.1016/j.jsv.2012.08.004 VL - 332 IS - 2 SP - 455-464 SN - 1095-8568 ER - TY - JOUR TI - Spray and atomization of diesel fuel and its alternatives from a single-hole injector using a common rail fuel injection system AU - Chen, P.-C. AU - Wang, W.-C. AU - Roberts, W.L. AU - Fang, Tiegang T2 - Fuel AB - Fuel spray and atomization characteristics play an important role in the performance of internal combustion engines. As the reserves of petroleum fuel are expected to be depleted within a few decades, finding alternative fuels that are economically viable and sustainable to replace the petroleum fuel has attracted much research attention. In this work, the spray and atomization characteristics were investigated for commercial No. 2 diesel fuel, biodiesel (FAME) derived from waste cooking oil (B100), 20% biodiesel blended diesel fuel (B20), renewable diesel fuel produced in house, and civil aircraft jet fuel (Jet-A). Droplet diameters and particle size distributions were measured by a laser diffraction particle analyzing system and the spray tip penetrations and cone angles were acquired using a high speed imaging technique. All experiments were conducted by employing a common-rail high-pressure fuel injection system with a single-hole nozzle under room temperature and pressure. The experimental results showed that biodiesel and jet fuel had different features compared with diesel. Longer spray tip penetration and larger droplet diameters were observed for B100. The smaller droplet size of the Jet-A were believed to be caused by its relatively lower viscosity and surface tension. B20 showed similar characteristics to diesel but with slightly larger droplet sizes and shorter tip penetration. Renewable diesel fuel showed closer droplet size and spray penetration to Jet-A with both smaller than diesel. As a result, optimizing the trade-off between spray volume and droplet size for different fuels remains a great challenge. However, high-pressure injection helps to optimize the trade-off of spray volume and droplet sizes. Furthermore, it was observed that the smallest droplets were within a region near the injector nozzle tip and grew larger along the axial and radial direction. The variation of droplet diameters became smaller with increasing injection pressure. DA - 2013/// PY - 2013/// DO - 10.1016/j.fuel.2012.08.013 VL - 103 SP - 850-861 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870517496&partnerID=MN8TOARS ER - TY - JOUR TI - Simultaneous LII and PIV measurements in the soot formation region of turbulent non-premixed jet flames AU - Narayanaswamy, V. AU - Clemens, N. T. T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - An experimental study was performed to investigate the soot–turbulence interaction in the soot-formation region of turbulent non-premixed co-flowing ethylene/N2 jet flames. Simultaneous velocity and soot volume-fraction (fv) fields were obtained using two-component particle image velocimetry and laser-induced incandescence, respectively. Measurements were made for jet exit Reynolds numbers between 8500 and 12,300, and the measurement location was 10 jet diameters downstream, near the beginning of the yellow luminous region where soot is first formed. In agreement with previous studies, the peak mean fv in the production region is inversely related to the bulk strain rate. The simultaneous data show that soot is formed to the inside of the stoichiometric surface (inferred from stoichiometric velocity), but the formation region moves outside to regions of lower velocity and strain rate as the bulk strain rate is increased. Soot structures form in low strain rate regions, but their upstream edge is seen to become stretched out and aligned at a preferred angle (near 45 degrees) owing to alignment with the instantaneous principal extensive strain rate. Statistical analysis shows that the soot exists, on average, in fluid with axial velocity of about 3 m/s and strain rate of 700 s−1, regardless of the jet exit velocity. The radial profiles of the covariance between fv and radial velocity are consistent with a model where the soot is formed at a preferred radial location (near the reaction zone) and then is transported by turbulent fluctuations to regions of lower fv. DA - 2013/// PY - 2013/// DO - 10.1016/j.proci.2012.06.018 VL - 34 IS - 1 SP - 1455-1463 SN - 1873-2704 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877691505&partnerID=MN8TOARS KW - Soot-turbulence interaction KW - Soot transport KW - Turbulent flames KW - LII KW - PIV ER - TY - JOUR TI - NOx emissions from high swirl turbulent spray flames with highly oxygenated fuels AU - Bohon, Myles D. AU - Roberts, William L. T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - Combustion of fuels with fuel bound oxygen is of interest from both a practical and a fundamental viewpoint. While a great deal of work has been done studying the effect of oxygenated additives in diesel and gasoline engines, much less has been done examining combustion characteristics of fuels with extremely high mass fractions of fuel bound oxygen. This work presents an initial investigation into the very low NOx emissions resulting from the combustion of a model, high oxygen mass fraction fuel. Glycerol was chosen as a model fuel with a fuel bound oxygen mass fraction of 52%, and was compared with emissions measured from diesel combustion at similar conditions in a high swirl turbulent spray flame. This work has shown that high fuel bound oxygen mass fractions allow for combustion at low global equivalence ratios with comparable exhaust gas temperatures due to the significantly lower concentrations of diluting nitrogen. Despite similar exhaust gas temperatures, NOx emissions from glycerol combustion were up to an order of magnitude lower than those measured using diesel fuel. This is shown to be a result not of specific burner geometry, but rather is influenced by the presence of higher oxygen and lower nitrogen concentrations at the flame front inhibiting NOx production. DA - 2013/// PY - 2013/// DO - 10.1016/j.proci.2012.07.064 VL - 34 SP - 1705-1712 SN - 1873-2704 KW - NOx KW - Oxygenated fuel KW - Glycerol combustion KW - Emission characterization ER - TY - JOUR TI - Hydrocarbon species concentrations in nitrogen diluted ethylene-air laminar jet diffusion flames at elevated pressures AU - Kailasanathan, Ranjith Kumar Abhinavam AU - Book, Emily K. AU - Fang, Tiegang AU - Roberts, William L. T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - Hydrocarbon species concentrations are measured in a laminar jet diffusion flame at elevated pressures with the objective of better understanding soot production and oxidation mechanisms, which will ultimately lead to a reduction in soot emissions from practical combustion hardware. Samples were extracted from the centerline of an ethylene flame diluted with nitrogen. The diluted fuel and co-axial air top-hat exit velocities were matched and the mass fluxes were held constant at all pressures. This paper reports centerline concentration profiles of major non-fuel hydrocarbons and 5 different PAH species measured via extractive sampling with a quartz microprobe and quantification using GC/MS + FID. The peak concentration of acetylene decreased with increase in pressure, suggesting rapid conversion to heavier compounds, whereas the concentrations of the other major heavier non-fuel hydrocarbons increase with an increase in pressure. The measured peak species concentration as a function of pressure is seen to closely follow a power law function, Pn, where n varies from less than zero for acetylene, propane and diacetylene to greater than unity for the larger PAH species. DA - 2013/// PY - 2013/// DO - 10.1016/j.proci.2012.06.148 VL - 34 IS - 1 SP - 1035-1043 SN - 1873-2704 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877712376&partnerID=MN8TOARS KW - Laminar flames KW - High pressure KW - Extractive sampling KW - Non-fuel hydrocarbons KW - Soot formation ER - TY - JOUR TI - Aromatization of n-octane over Pd/C catalysts AU - Yin, Mengchen AU - Natelson, Robert H. AU - Campos, Andrew A. AU - Kolar, Praveen AU - Roberts, William L. T2 - FUEL AB - Abstract Gas-phase aromatization of n-octane was investigated using Pd/C catalyst. The objectives were to: (1) determine the effects of temperature (400–600 °C), weight hourly space velocity (WHSV) (0.8–∞), and hydrogen to hydrocarbon molar ratio (MR) (0–6) on conversion, selectivity, and yield (2) compare the activity of Pd/C with Pt/C and Pt/KL catalysts and (3) test the suitability of Pd/C for aromatization of different alkanes including n-hexane, n-heptane, and n-octane. Pd/C exhibited the best aromatization performance, including 54.4% conversion and 31.5% aromatics yield at 500 °C, WHSV = 2 h−1, and a MR of 2. The Pd/C catalyst had higher selectivity towards the preferred aromatics including ethylbenzene and xylenes, whereas Pt/KL had higher selectivity towards benzene and toluene. The results were somewhat consistent with adsorbed n-octane cyclization proceeding mainly through the six-membered ring closure mechanism. In addition, Pd/C was also capable of catalyzing aromatization of n-hexane and n-heptane. DA - 2013/1// PY - 2013/1// DO - 10.1016/j.fuel.2012.06.095 VL - 103 SP - 408-413 SN - 1873-7153 KW - Aromatization KW - Dehydrocyclization KW - Catalyst KW - Pd/C KW - Alkanes ER - TY - JOUR TI - Modeling transport of a pulse of radiolabeled organelles in a Drosophila unipolar motor neuron AU - Kuznetsov, A. V. T2 - JOURNAL OF BIOLOGICAL PHYSICS AB - Based on published experimental evidence, this paper develops a model for the transport of a pulse of radiolabeled organelles in a unipolar Drosophila motor neuron. In particular, since published data indicate that no microtubules (MTs) travel from the primary neurite into the dendrite, it is investigated how organelles are transported into the dendrite. Analytical solutions describing concentrations of kinesin- and dynein-driven organelles in the primary neurite, axon, and dendrite are obtained. The effects of increasing the width of the pulse and increasing the rate of organelle transition rate from the kinesin-driven to the dynein-driven state are investigated. DA - 2013/1// PY - 2013/1// DO - 10.1007/s10867-012-9292-6 VL - 39 IS - 1 SP - 145-158 SN - 1573-0689 KW - Unipolar neurons KW - Branch point KW - Intracellular transport KW - Axonal and dendritic cargos KW - Mathematical modeling ER -