TY - CONF TI - PLIF imaging of naphthalene-ablation products in a Mach 5 turbulent boundary layer AU - Lochman, B.J. AU - Murphree, Z.R. AU - Narayanaswamy, V. AU - Clemens, N.T. AB - A new technique is currently under development that uses planar laser-induced fluorescence (PLIF) imaging of sublimated naphthalene to image the transport of ablation products in a hypersonic boundary layer. The primary motivation for this work is to understand scalar transport in hypersonic boundary layers and to develop a database for validation of computational models. The naphthalene is molded into a rectangular insert that is mounted flush with the floor of a Mach 5 wind tunnel. The distribution of naphthalene in the boundary layer is imaged by using PLIF, where the laser excitation is at 266 nm and the fluorescence is collected in the range of 320 to 380 nm. To investigate the use of naphthalene PLIF as a quantitative diagnostic technique, a series of experiments is conducted to determine the linearity of the fluorescence signal with laser fluence, as well as the temperature and pressure dependencies of the signal. The naphthalene fluorescence at 297 K is determined to be linear for laser fluence that is less than about 200 J/m 2 . The temperature dependence of the naphthalene fluorescence signal is found at atmospheric pressure over the temperature range of 297K to 525K. A monotonic increase in the fluorescence is observed with increasing temperature. Naphthalene fluorescence lifetime measurements were also made in pure-air and nitrogen environments at 300 K over the range 3.3 kPa to 101.3 kPa. The results in air show the expected Stern-Volmer behavior with decreasing lifetimes at increasing pressure, whereas nitrogen exhibits the opposite trend. Preliminary PLIF images of the sublimated naphthalene are acquired in a Mach 5 turbulent boundary layer. Relatively low signal-to-noise-ratio images were obtained at a stagnation temperature of 345 K, but much higher quality images were obtained at a stagnation temperature of 375 K. Our results indicate that PLIF of sublimating naphthalene may be an effective tool for studying scalar transport in hypersonic flows. C2 - 2010/// C3 - 27th AIAA Aerodynamic Measurement Technology and Ground Testing Conference 2010 DA - 2010/// DO - 10.2514/6.2010-4346 VL - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877723148&partnerID=MN8TOARS ER - TY - CONF TI - Investigation of a pulsed-plasma jet for shock / boundary layer control AU - Narayanaswamy, V. AU - Clemens, N.T. AU - Raja, L.L. C2 - 2010/// C3 - 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition DA - 2010/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78649810322&partnerID=MN8TOARS ER - TY - JOUR TI - Characterization of a high-frequency pulsed-plasma jet actuator for supersonic flow control AU - Narayanaswamy, V. AU - Raja, L.L. AU - Clemens, N.T. T2 - AIAA Journal AB - thepulsed-plasmajet,thejetisinjectednormallyintoaMach3crossflowandthepenetrationdistanceismeasuredby using schlieren imaging. These measurements show that the jet penetrates 1.5 boundary-layer thicknesses into the crossflow andthe jet-to-crossflowmomentum fluxratioisestimated to be0.6.Aseries of experiments wasconducted to determine the characteristics of the pulsed-plasma jet issuing into stagnant air at a pressure of 35 torr. These resultsshowthattypicaljetvelocitiesofabout250 m=scanbeinducedwithdischargeenergiesofabout30mJperjet. Furthermore, the maximum pulsing frequency was found to be about 5 kHz, because above this frequency the jet beginstomisfire.Themisfiringappearstobeduetothe finitetimeittakesforthecavitytoberechargedwithambient air between discharge pulses. The velocity at the exit of the jet is found to be primarily dependent on the discharge current and independent of other discharge parameters such as cavity volume and orifice diameter. Temperature measurementsaremadeusingopticalemissionspectroscopyandrevealthepresenceofconsiderablenonequilibrium between rotational and vibrational modes. The gas heating efficiency was found to be 10% and this parameter is shown to have a direct effect on the plasma jet velocity. These results indicate that the pulsed-plasma jet creates a sufficiently strong flow perturbation that holds great promise as a supersonic flow actuator. DA - 2010/// PY - 2010/// DO - 10.2514/1.41352 VL - 48 IS - 2 SP - 297-305 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-76949095393&partnerID=MN8TOARS ER - TY - CONF TI - Novel PCM and jet impingement based cooling scheme for high density transient heat loads AU - Parida, P.R. AU - Ekkad, S.V. AU - Ngo, K. AB - Breakthroughs in the recent cutting-edge technologies have become increasingly dependent on the ability to safely dissipate large amount of heat from small areas. Improvements in cooling techniques are therefore required to avoid unacceptable temperature rise and at the same time maintain high efficiency. Jet impingement is one such cooling scheme which has been widely used to dissipate transient and steady concentrated heat loads. With constantly increasing transient cooling needs, conventional pin-fin cooling and conventional jet impingement cooling are not meeting the requirements. Considerable improvements are therefore required to meet such stringent requirements without any significant changes in the cooling system. A combined cooling scheme based on jet impingement and phase change materials (PCMs) is presented as one such alternative to existing cooling systems. A high heat storage capability of PCMs in combination with a high heat transfer rates from impingement cooling can help overcome the existing heat distribution and transient cooling problems in high heat flux dissipating devices. Preliminary conjugate CFD simulations show promising results. Additionally, experimental validation of the simulation predictions has also been performed. A reasonably good agreement was found between the predictions and experiments. C2 - 2010/// C3 - 2010 14th International Heat Transfer Conference, IHTC 14 DA - 2010/// DO - 10.1115/IHTC14-22841 VL - 7 SP - 443-450 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860511271&partnerID=MN8TOARS ER - TY - CONF TI - Study of flow and convective heat transfer in a simulated scaled up low emission annular combustor AU - Sedalor, T. AU - Patil, S. AU - Ekkad, S. AU - Tafti, D. AU - Kim, Y. AU - Moon, H.-K. AU - Srinivasan, R. AB - Modern Dry Low Emissions (DLE) combustors are characterized by highly swirling and expanding flows that makes the convective heat load on the gas side difficult to predict and estimate. A coupled experimental-numerical study of swirling flow inside a DLE annular combustor model is presented. A simulated scaled up annular combustor shell was designed with a generic fuel nozzle model to create the swirl in the flow. The experiment was simulated with a cold flow and heated combustor walls in a low speed wind tunnel. An infrared camera was used to obtain the temperature distribution along the liner wall. The experiment was conducted at various Reynolds numbers to investigate the effect on the convective heat transfer peak locations. A CFD study performed using FLUENT was used to get a better understanding of high swirl flow field and its effect on the heat transfer on liner walls. Results show that the heat transfer distributions in the annulus have slightly different characteristics for the concave and convex walls. Results also show a much slower drop in heat transfer coefficient enhancement with increasing Reynolds number compared to can combustor liner walls. C2 - 2010/// C3 - Proceedings of the ASME Turbo Expo DA - 2010/// DO - 10.1115/GT2010-22986 VL - 4 SP - 787-794 M1 - PARTS A AND B UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-82055165249&partnerID=MN8TOARS ER - TY - CONF TI - Innovative liquid cooling configurations for high heat flux applications AU - Parida, P.R. AU - Ekkad, S.V. AU - Ngo, K. AB - Breakthroughs in the recent cutting-edge technologies have become increasingly dependent on the ability to safely dissipate large amount of heat from small areas. Improvements in cooling techniques are therefore required to avoid unacceptable temperature rise and at the same time maintain a high efficiency. Jet impingement is one such cooling scheme which has been widely used to dissipate transient and steady concentrated heat loads. But with constantly increasing cooling needs, conventional jet impingement cooling is no longer a viable option. Considerable improvements are therefore required to meets such stringent requirements. A combination of swirl-impingement-fin generating geometry is one such alternative. Even without a fin, an overall enhancement of 150% - 200% in the maximum heat transfer coefficient has been recorded both experimentally and computationally due to impingement and associated swirl. Moreover, the presence of fins further increases the cooling area. The present scheme is therefore expected to overcome the existing heat distribution and cooling problems in high heat flux dissipating devices. C2 - 2010/// C3 - 2010 12th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, ITherm 2010 DA - 2010/// DO - 10.1109/ITHERM.2010.5501356 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77955200574&partnerID=MN8TOARS ER - TY - CONF TI - Experimental and numerical investigations of a transonic, high turning turbine cascade with a divergent endwall AU - Abraham, S. AU - Panchal, K. AU - Xue, S. AU - Ekkad, S.V. AU - Ng, W. AU - Brown, B.J. AU - Malandra, A. AB - The paper presents detailed measurements of midspan total pressure loss, secondary flow field, static pressure measurements on airfoil surface at midspan, near hub and near the end walls in a transonic turbine airfoil cascade. Numerous low-speed experimental studies have been carried out to investigate the performance of turbine cascades. Profile and secondary loss correlations have been developed and improved over the years to include the induced incidence and leading edge geometry and to reflect recent trends in turbine design. All of the above investigations have resulted in better understanding of flow field in turbine passages. However, there is still insufficient data on the performance of turbine blades with high turning angles operating at varying incidences angles at transonic Mach numbers. In the present study, measurements were made at +10, 0 and −10 degree incidence angles for a high turning turbine airfoil with 127 degree turning. The exit Mach numbers were varied within a range from 0.6 to 1.1. Additionally, the exit span is increased relative to the inlet span resulting in one end wall diverging from inlet to exit at 13 degree angle. This was done in order to obtain a ratio of inlet Mach number to exit Mach number which is representative to that encountered in real engine and simulates the blade and near end wall loading that is seen in an engine. 3D viscous compressible CFD analysis was carried out in order to compare the results with experimentally obtained values and to further investigate the design and off-design flow characteristics of the airfoil under study. All aerodynamic measurements were compared with CFD analysis and a reasonably good match was observed. C2 - 2010/// C3 - American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM DA - 2010/// DO - 10.1115/FEDSM-ICNMM2010-30393 VL - 1 SP - 569-576 M1 - PARTS A, B AND C UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-80054982232&partnerID=MN8TOARS ER - TY - CONF TI - A transient infrared technique for measuring surface and endwall heat transfer in a transonic turbine cascade AU - Reagle, C. AU - Newman, A. AU - Xue, S. AU - Ng, W. AU - Ekkad, S. AU - Moon, H.K. AU - Zhang, L. AB - This paper describes a method for obtaining surface and endwall heat transfer in an uncooled transonic cascade facility using infrared thermography measurements. Midspan heat transfer coefficient results are first presented for an engine representative first stage nozzle guide vane at exit Mach number of 0.77, Reynolds number of 1.05×106 and freestream turbulence intensity of 16%. The results obtained from infrared thermography are compared with previously published results using thin film gauges in the same facility on the same geometry. There is generally good agreement between the two measurement techniques in both trend and overall level of heat transfer coefficient over the vane surface. Stanton number contours are then presented for a blade endwall at exit Mach number of 0.88, Reynolds number of 1.70×106 and freestream turbulence intensity of 8%. Infrared thermography results are qualitatively compared with results from a published work obtained with liquid crystals at similar flow conditions. Results are qualitatively in agreement. C2 - 2010/// C3 - Proceedings of the ASME Turbo Expo DA - 2010/// DO - 10.1115/GT2010-22975 VL - 4 SP - 405-411 M1 - PARTS A AND B UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-82055194137&partnerID=MN8TOARS ER - TY - CONF TI - Human Injury Evaluation on Production 125cc. Scooter under Side Slip Impact AU - Fong, Rey-Yie AU - Cheng, Jung-Ho C2 - 2010/// C3 - Abaqus Taiwan Users’ Conference DA - 2010/// ER - TY - CONF TI - 95' Planning Yacht Deck Structure Arrangement and Parameter Optimization AU - Lin, Yu-Chieh AU - Fong, Rey-Yie C2 - 2010/// C3 - Abaqus Taiwan Users’ Conference DA - 2010/// ER - TY - CONF TI - Thermo-mechanical modeling of RF MEMS devices AU - Rezvanian, O. AU - Zikry, M.A. AB - Time-dependent thermoelectromechanical behavior of metal contacts in microelectromechanical system (MEMS) devices and packaging is studied. The analysis relates the electrical constriction resistance to contact temperature and contact surface evolution over time, using a microcontact asperity creep model for metal microcontacts under continual applied or residual stresses. The effects of contact temperature on constriction resistance are investigated. This work provides guidance toward the rational design of microcontacts with enhanced reliabilities by better defining variables that control the electrical resistance at such microcontcats. C2 - 2010/// C3 - 2010 3rd International Conference on Thermal Issues in Emerging Technologies, Theory and Applications - Proceedings, ThETA3 2010 DA - 2010/// DO - 10.1109/THETA.2010.5766380 SP - 63-67 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79957982395&partnerID=MN8TOARS ER - TY - CONF TI - The effects of precipitates and Mn-bearing particles on the high strain-rate compression of high strength aluminum AU - Elkhodary, K. AU - Lee, W. AU - Cheeseman, B. AU - Sun, L. AU - Brenner, D. AU - Zikry, M. C2 - 2010/// C3 - Materials Research Society Symposium Proceedings DA - 2010/// VL - 1225 SP - 19-23 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952052398&partnerID=MN8TOARS ER - TY - CONF TI - High-speed full-spectrum interrogation of fiber Bragg gratings for composite impact sensing AU - Chadderdon, S. AU - Vella, T. AU - Selfridge, R. AU - Schultz, S. AU - Webb, S. AU - Park, C. AU - Peters, K. AU - Zikry, M. AB - This paper presents a means for the high repetition rate interrogation of fiber Bragg gratings (FBG's). The new system highlights a method that allows a tradeoff between the full spectrum capture rate and the wavelength range and/or the spectral resolution of the technique. Rapid capture of the entire reflection spectrum at high interrogation rates shows important features that are missed when using methods that merely track changes in the peak location of the spectrum. The essential feature of the new system is that it incorporates a MEMs tunable filter driven by a variable frequency openloop sinusoidal source. The paper demonstrates the new system on a laminated composite system under impact loading. C2 - 2010/// C3 - Proceedings of SPIE - The International Society for Optical Engineering DA - 2010/// DO - 10.1117/12.847662 VL - 7648 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77953516554&partnerID=MN8TOARS ER - TY - CONF TI - Modeling Particle Loading in Fibrous Filter Media AU - Hosseini, S.A. AU - Tafreshi, H.V. T2 - American Filtration and Separation Society C2 - 2010/3/22/ C3 - American Filtration and Separation Society CY - San Antonio, Texas DA - 2010/3/22/ PY - 2010/3/22/ ER - TY - CONF TI - Modeling Particle Filtration in 3-D Electrospun Nanofibrous Filters AU - Hosseini, S.A. AU - Tafreshi, H.V. T2 - American Filtration and Separation Society C2 - 2010/3/22/ C3 - American Filtration and Separation Society CY - San Antonio, Texas DA - 2010/3/22/ PY - 2010/3/22/ ER - TY - CONF TI - Modeling Radiative Heat Transfer in Fibrous Insulation Media AU - Tahir, M.A. AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - NETInc, Innovative Nonwovens Conference C2 - 2010/11/10/ CY - Raleigh, North Carolina DA - 2010/11/10/ PY - 2010/11/10/ ER - TY - CONF TI - Modeling Filtration Efficiency of Electrospun Nanofibrous Filters AU - Hosseini, S.A. AU - Tafreshi, H.V. T2 - Nanofibers for the 3rd Millennium C2 - 2010/8/30/ CY - Raleigh, North Carolina DA - 2010/8/30/ PY - 2010/8/30/ ER - TY - JOUR TI - Modeling the role of microstructural parameters in radiative heat transfer through disordered fibrous media AU - Tahir, M.A. AU - Tafreshi, H. Vahedi AU - Hosseini, S.A. AU - Pourdeyhimi, B. T2 - International Journal of Heat and Mass Transfer AB - Understanding the influence of microstructural parameters on the rate of heat transfer through a disordered fibrous medium is important for the design and development of heat insulation materials. In this work, by generating virtual 3-D geometries that resemble the internal microstructure of fibrous insulation materials, we simulated the influence of diameter, orientation, and emissivity of the fibers, as well as the media’s porosity and thickness on the radiative heat transmittance. Our simulations are based on a Monte Carlo ray tracing algorithm that we have developed for studying radiative heat flow in 3-D disordered media. The media were assumed to be made up of cylindrical opaque fibers with specular surface. The advantage of our modeling approach is that it does not require any empirical input values, and can directly be used to isolate and study the role of individual microstructural parameters of the media. The major limitation of the model is that it is accurate as long as the fibers can be considered large relative to the wavelength of the incoming rays. Our results indicate that heat flux through a fibrous medium decreases by increasing the packing fraction of the fibers when the thickness and fiber diameter are kept constant. Increasing the fibers’ absorptivity (or emissivity) was observed to decrease the radiation transmittance through the media. Our simulations also revealed that for constant porosity and thickness, the heat flux transmitted across the medium can be reduced by using finer fibers. The steady state temperature profiles across the thicknesses of media with different properties were obtained and found to be independent of the fibers’ emissivity. DA - 2010/10// PY - 2010/10// DO - 10.1016/j.ijheatmasstransfer.2010.06.030 VL - 53 IS - 21-22 SP - 4629-4637 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2010.06.030 DB - Crossref KW - Ray tracing KW - Fibrous media KW - Insulation materials KW - Radiation modeling ER - TY - JOUR TI - Modeling particle filtration in disordered 2-D domains: A comparison with cell models AU - Hosseini, S.A. AU - Tafreshi, H. Vahedi T2 - Separation and Purification Technology AB - In this work, Stokes equations are numerically solved in a series of 2-D geometries comprised of randomly distributed fibers, using the Fluent CFD code. Particle collection due to interception and Brownian diffusion has been incorporated in the CFD calculations by developing two C++ subroutines that run in the Fluent environment. We have also modified the Discrete Phase Model of the Fluent code to correctly predict the effect of Brownian motion on a particle trajectory, and to obtain nanoparticle collection efficiency of a filter medium via the Lagrangian method. Our simulations are aimed at studying aerosol filtration in disordered 2-D fibrous media, and their results are compared with the predictions of existing cell-model-type (ordered 2-D models) semi-analytical correlations, as well as our previous simulation data obtained from 3-D simulations. Our results revealed that disordered 2-D fiber arrangements can be utilized to predict the performance of fibrous filters with reasonable accuracy and CPU time. Collection efficiencies obtained from our 2-D models seem to be marginally lower than those of 3-D simulations, for nanoparticles, and slightly higher, for larger particles. Pressure drop predictions of disordered 2-D media are found to be lower than that of ordered 2-D models, but higher than that of 3-D fibrous models. The latter is found to be in very good agreement with experiment. We have also studied the impact of aerodynamic slip on the collection efficiency of our filter media, and concluded that aerodynamic slip improves the collection efficiency of a filter medium, especially for larger particles. DA - 2010/8/17/ PY - 2010/8/17/ DO - 10.1016/j.seppur.2010.06.001 VL - 74 IS - 2 SP - 160-169 J2 - Separation and Purification Technology LA - en OP - SN - 1383-5866 UR - http://dx.doi.org/10.1016/j.seppur.2010.06.001 DB - Crossref KW - Aerosol filtration KW - Disordered fibrous media KW - CFD simulation KW - Particle tracking ER - TY - JOUR TI - 3-D simulation of particle filtration in electrospun nanofibrous filters AU - Hosseini, S.A. AU - Tafreshi, H. Vahedi T2 - Powder Technology AB - Virtual 3-D geometries resembling the internal microstructure of electrospun fibrous materials are generated in this work to simulate the pressure drop and collection efficiency of nanofibrous media when challenged with aerosol particles in the size range of 25 to 1000 nm. In particular, we solved the air flow field in the void space between the fibers in a series of 3-D fibrous geometries with a fiber diameter in the range of 100 to 1000 nm and a Solid Volume Fraction (SVF) in the range of 2.5 to 7.5%, using the Fluent CFD code, and simulated the flow of large and fine particles through these media using Lagrangian and Eulerian methods, respectively. Particle collection due to interception and Brownian diffusion, as well as the slip effect at the surface of nanofibers, has been incorporated in the CFD calculations by developing customized C++ subroutines that run in the Fluent environment. Particle collection efficiency and pressure drop of the above fibrous media are calculated and compared with analytical/empirical results from the literature. The numerical simulations presented here are believed to be the most complete and realistic filter modeling published to date. Our simulation technique, unlike previous studies based on oversimplified 2-D geometries, does not need any empirical correction factors, and can be used to directly simulate pressure drop and efficiency of any fibrous media. DA - 2010/7// PY - 2010/7// DO - 10.1016/j.powtec.2010.03.020 VL - 201 IS - 2 SP - 153-160 J2 - Powder Technology LA - en OP - SN - 0032-5910 UR - http://dx.doi.org/10.1016/j.powtec.2010.03.020 DB - Crossref KW - CFD simulation KW - Slip velocity KW - Fibrous media KW - Particle interception KW - Particle diffusion ER - TY - JOUR TI - Modeling fluid spread in thin fibrous sheets: Effects of fiber orientation AU - Ashari, A. AU - Bucher, T.M. AU - Tafreshi, H. Vahedi AU - Tahir, M.A. AU - Rahman, M.S.A. T2 - International Journal of Heat and Mass Transfer AB - In this paper, a dual-scale model is developed to simulate the radial spreading of liquids in thin fibrous sheets. Using 3-D microscale simulations, the required constitutive equations, capillary pressure and relative permeability, have been determined at each saturation level and used in a macroscale model developed based on the Richards’ equation of two-phase flow in porous media. The dual-scale approach allowed us to include the partially-saturated region of a porous medium in calculations. Simulating different fibrous sheets with identical parameters but different in-plane fiber orientations, it is revealed that the rate of fluid spread increases with increasing the in-plane alignment of the fibers. Our simulations are discussed with respect to existing studies in the literature. DA - 2010/4// PY - 2010/4// DO - 10.1016/j.ijheatmasstransfer.2010.01.015 VL - 53 IS - 9-10 SP - 1750-1758 J2 - International Journal of Heat and Mass Transfer LA - en OP - SN - 0017-9310 UR - http://dx.doi.org/10.1016/j.ijheatmasstransfer.2010.01.015 DB - Crossref KW - Fibrous porous media KW - Two-phase flows KW - Anisotropic permeability KW - Fiber orientation KW - Absorbency KW - CFD simulation ER - TY - JOUR TI - Modeling permeability of 3-D nanofiber media in slip flow regime AU - Hosseini, S.A. AU - Tafreshi, H. Vahedi T2 - Chemical Engineering Science AB - Over the last few decades, numerous analytical and/or numerical expressions have been developed for predicting the permeability of a fibrous medium. These expressions, however, are not accurate in predicting the permeability of media made up of nanofibers. This is because the previous expressions were mostly developed for coarse fibers, where using the so-called no-slip velocity boundary condition at the fiber surface is quite justified. Removing the no-slip velocity restriction in this work, we study the effect of slip flow on the permeability of fibrous materials made up of nanofibers. This has been accomplished by generating a large series of 3-D virtual geometries that resemble the microstructure of a nanofiber (e.g., electrospun) material. Stokes flow equations are solved numerically in the void space between the nanofibers, with the slip flow boundary condition developed based on the Maxwell first order model. The influence of fiber diameter and solid volume fraction (SVF) on the media's permeability is studied, and used to establish a correction factor for the existing permeability expressions when used for nanofiber media. DA - 2010/3// PY - 2010/3// DO - 10.1016/j.ces.2009.12.002 VL - 65 IS - 6 SP - 2249-2254 J2 - Chemical Engineering Science LA - en OP - SN - 0009-2509 UR - http://dx.doi.org/10.1016/j.ces.2009.12.002 DB - Crossref KW - Transport phenomena KW - Nanofibers KW - Porous media KW - Slip flow KW - CFD simulation KW - Filtration ER - TY - JOUR TI - Influence of fiber orientation distribution on performance of aerosol filtration media AU - Fotovati, S. AU - Vahedi Tafreshi, H. AU - Pourdeyhimi, B. T2 - Chemical Engineering Science AB - This work is conducted to better our understanding of the influence of fibers’ in-plane and through-plane orientations on pressure drop and collection efficiency of fibrous media. The Stokes flow equations are numerically solved in virtual, 3-D, fibrous geometries with varying in-plane and/or through-plane orientations. Pressure drop and aerosol collection efficiency characteristics of such media are calculated and compared with available studies from the literature. Our results indicate that pressure drop and submicron particle capture efficiency of common fibrous filters with a fiber diameter of about 10 μm are independent of the in-plane orientation of the fibers, but decrease with increasing the fibers’ through-plane orientation. More interestingly, it was found that filters with higher through-plane fiber orientations have a higher figure of merit if challenged with nanoparticles. The figure of merit of these media, however, decreases as the particle size increases, reversing the effect of fibers’ through-plane orientation. It was also shown that when the diameter of the particles is comparable to that of the fibers, collection efficiency increases with decreasing the fibers’ in-plane orientation, while the pressure drop remains almost unchanged. This indicates that decreasing the fibers’ in-plane orientation increased the figure of merit of media made of nanofibers. DA - 2010/// PY - 2010/// DO - 10.1016/j.ces.2010.06.032 VL - 65 IS - 18 SP - 5285-5293 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77955432242&partnerID=MN8TOARS KW - Aerosol KW - Filtration KW - Porous media KW - Fibrous materials KW - 3-D Modeling KW - Fiber orientation ER - TY - CONF TI - Effect of fiber orientation distribution on filter performance AU - Fotovati, S. AU - Vahedi Tafreshi, H. AU - Pourdeyhimi, B. C2 - 2010/// C3 - American Filtration and Separations Society Annual National Conference and Exposition 2010 DA - 2010/// VL - 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84883817446&partnerID=MN8TOARS ER - TY - CONF TI - Capture efficiency and pressure drop of bimodal filter media AU - Fotovati, S. AU - Vahedi Tafreshi, H. AU - Pourdeyhimi, B. C2 - 2010/// C3 - American Filtration and Separations Society Annual National Conference and Exposition 2010 DA - 2010/// VL - 2 SP - 710-718 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84883771850&partnerID=MN8TOARS ER - TY - JOUR TI - A semi-analytical model for simulating fluid transport in multi-layered fibrous sheets made up of solid and porous fibers AU - Ashari, A. AU - Bucher, T.M. AU - Vahedi Tafreshi, H. T2 - Computational Materials Science AB - Direct simulation of fluid transport in fibrous media consisting of swelling (i.e., fluid-absorbing) and non-swelling (i.e., solid) fibers is a challenge. In this work, we have developed a semi-analytical modeling approach that can be used to predict the fluid absorption and release characteristics of multi-layered composite fabrics made up of swelling and non-swelling fibrous sheets. The simulations presented here are based on a numerical solution of Richards’ equation. Two different fibrous sheets composed of non-swelling (PET) and swelling (Rayon) fibers with different Solid Volume Fractions (SVFs) and thicknesses were arbitrarily chosen in this study for demonstration purposes. The sheets’ capillary pressure and relative permeability are obtained via a combination of numerical simulations and experiment. In particular, the capillary pressure expression for non-swelling media is obtained from the analytical expressions that we previously developed via 3-D microscale simulations, while the capillary pressure for swelling media is obtained via height rise experiments. The relative permeability expressions for both swelling and non-swelling media are obtained from the analytical expressions previously developed via 3-D microscale simulations, which are also in agreement with experimental correlations from the literature. On the macroscale, simulation results are reported for fluid transport in bi-layered composite fabrics, and comparison is made between the performances of these fabrics in terms of the order in which the layers are stacked on top of one another. A higher rate of absorption was observed when the layer in contact with the fluid is that comprised of swelling fibers. A similar study was conducted for motion-induced fluid release from the composite fabrics when partially-saturated with a fluid. It was shown that less fluid release is expected when the swelling sheet is placed in contact with the surface. DA - 2010/// PY - 2010/// DO - 10.1016/j.commatsci.2010.08.030 VL - 50 IS - 2 SP - 378-390 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78449255008&partnerID=MN8TOARS KW - Capillary pressure KW - Relative permeability KW - Richards' equation KW - Swelling fibers KW - Fluid absorption KW - Fluid release ER - TY - JOUR TI - Analytical expressions for predicting capture efficiency of bimodal fibrous filters AU - Fotovati, S. AU - Vahedi Tafreshi, H. AU - Ashari, A. AU - Hosseini, S.A. AU - Pourdeyhimi, B. T2 - Journal of Aerosol Science AB - In this work, a series of numerical simulations are formulated for studying the performance (collection efficiency and pressure drop) of filter media with bimodal diameter distributions. While there are numerous analytical expressions available for predicting performance of filters made up of fibers with a unimodal fiber diameter distribution, there are practically no simple relations for bimodal filters. In this paper, we report on the influence of the fiber diameter dissimilarity and the number (mass) fraction of each component on the performance of a bimodal filter. Our simulation results are utilized to establish a unimodal equivalent diameter for the bimodal media, thereby taking advantage of the existing expressions of unimodal filters for capture efficiency prediction. Our results indicate that the cube root relation of Tafreshi, Rahman, Jaganathan, Wang, and Pourdeyhimi (2009) offers the closest predictions for the range of particle diameters, coarse fiber number (mass) fractions, fiber diameter ratios, and solid volume fractions (SVF) considered in this work. Our study revealed that the figure of merit (FOM) of bimodal filters increases with increasing fiber diameter ratios for Brownian particles (dp<100 nm), and decreases when challenged with larger particles. It has also been shown that when increasing the ratio of coarse fibers to fine fibers, FOM increases for Brownian particles, and decreases for larger particles. DA - 2010/// PY - 2010/// DO - 10.1016/j.jaerosci.2010.01.002 VL - 41 IS - 3 SP - 295-305 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77049092273&partnerID=MN8TOARS KW - Bimodal filter media KW - Aerosol filtration KW - Slip flow KW - Interception modeling KW - CFD simulation ER - TY - JOUR TI - Piezoelectric accelerometers for ultrahigh temperature application AU - Zhang, Shujun AU - Jiang, Xiaoning AU - Lapsley, Michael AU - Moses, Paul AU - Shrout, Thomas R. T2 - Applied Physics Letters AB - High temperature sensors are of major importance to aerospace and energy related industries. In this letter, a high temperature monolithic compression-mode piezoelectric accelerometer was fabricated using YCa4O(BO3)3 (YCOB) single crystals. The performance of the sensor was tested as function of temperature up to 1000 °C and over a frequency range of 100–600 Hz. The accelerometer prototype was found to possess sensitivity of 2.4±0.4 pC/g, across the measured temperature and frequency range, indicating a low temperature coefficient. Furthermore, the sensor exhibited good stability over an extended dwell time at 900 °C, demonstrating that YCOB piezoelectric accelerometers are promising candidates for high temperature sensing applications. DA - 2010/1/4/ PY - 2010/1/4/ DO - 10.1063/1.3290251 VL - 96 IS - 1 SP - 013506 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3290251 DB - Crossref KW - accelerometers KW - calcium compounds KW - high-temperature techniques KW - piezoelectric devices KW - yttrium compounds ER - TY - JOUR TI - In situ stabilized carbon nanofiber (CNF) reinforced epoxy nanocomposites AU - Zhu, Jiahua AU - Wei, Suying AU - Ryu, Jongeun AU - Budhathoki, Mahesh AU - Liang, Gang AU - Guo, Zhanhu T2 - Journal of Materials Chemistry AB - Carbon nanofibers (CNFs) suspended epoxy resin nanocomposites and the corresponding polymer nanocomposites are fabricated. The surface of CNFs is introduced a functional amine terminated groups via silanization, which in situ react with epoxy monomers. This in situ reaction favors the CNFs dispersion and improves the interfacial interaction between CNFs and monomers. Effects of particle loading, surface treatment and operating temperatures of rheological tests on the complex viscosity, storage modulus and loss modulus are systematically studied. Unique rheological phenomena “a decreased viscosity with a better dispersion” are observed and explained in terms of the improved filler dispersion quality. Meanwhile, significant increase in the tensile property and storage modulus is observed and related to the better dispersion and the introduced strong interfacial interaction as revealed by SEM imaging. Finally, electrical conductivity is investigated and an unusual deficiency of surface treatment to improve the electrical conductivity is explained by an insulating coating layer. DA - 2010/// PY - 2010/// DO - 10.1039/c0jm00063a VL - 20 IS - 23 SP - 4937-4948 SN - 0959-9428 1364-5501 UR - http://dx.doi.org/10.1039/c0jm00063a ER - TY - JOUR TI - Inkjet printed electronics using copper nanoparticle ink AU - Kang, Jin Sung AU - Kim, Hak Sung AU - Ryu, Jongeun AU - Hahn, H. Thomas AU - Jang, Seonhee AU - Joung, Jae Woo T2 - Journal of Materials Science: Materials in Electronics AB - Inkjet printing of electrode using copper nanoparticle ink is presented. Electrode was printed on a flexible glass epoxy composite substrate using drop on demand piezoelectric dispenser and was sintered at 200 °C of low temperature in N2 gas condition. The printed electrodes were made with various widths and thickness. In order to control the thickness of the printed electrode, number of printing was varied. Resistivity of printed electrode was calculated from the cross-sectional area measured by a profilometer and resistance measured by a digital multimeter. Surface morphology of electrode was analyzed using scanning electron microscope (SEM) and atomic force microscope (AFM). From the study, it was found that 10 times printed electrode has the most stable grain structure and low resistivity of 36.7 nΩ m. DA - 2010/1/8/ PY - 2010/1/8/ DO - 10.1007/s10854-009-0049-3 VL - 21 IS - 11 SP - 1213–1220 SN - 0957-4522 1573-482X UR - http://dx.doi.org/10.1007/s10854-009-0049-3 ER - TY - CONF TI - Noise Enhanced Performance of Coupled Oscillators: Entropy Studies AU - Telly, Saliou AU - Perkins, Edmon AU - Shrestha, Dibesh AU - Balachandran, Balakumar T2 - 13th Conference on Nonlinear Vibrations, Dynamics, and Multi-body Systems C2 - 2010/// CY - Blacksburg, VA DA - 2010/// PY - 2010/// ER - TY - CONF TI - A Contactless Polymer Derived Ceramic Temperature Sensing System for Turbine Applications AU - Liu, J. AU - Li, J. AU - Grummel, B. AU - Xu, C. AU - Shen, J. T2 - Annual Technical Symposium C2 - 2010/// CY - Florida Center for Advanced AeroPropulsion DA - 2010/// PY - 2010/// ER - TY - JOUR TI - A Parallel Discontinuous Galerkin Code for Compressible Fluid Flows on Unstructured Grids AU - Ali, A. AU - Luo, H. AU - Syed, K.S. AU - Ishaq, M. T2 - Journal of Engineering and Applied Sciences DA - 2010/// PY - 2010/// VL - 29 IS - 1 SP - 57–75 ER - TY - CONF TI - Automated Sensitivity-Based Optimization for Control and Identification AU - Vermillion, Chris C2 - 2010/// C3 - 2010 Workshop on Identification for Automotive Systems DA - 2010/// ER - TY - CHAP TI - Control of Nonholonomic and Underactuated Systems AU - Lynch, Kevin AU - Bloch, Anthony AU - Drakunov, Sergey AU - Reyhanoglu, Mahmut AU - Zenkov, Dmitry T2 - The Control Systems Handbook, Second Edition PY - 2010/12/8/ DO - 10.1201/b10384-49 SP - 42-1-42-36 OP - PB - CRC Press SN - 9781420073645 9781420073652 UR - http://dx.doi.org/10.1201/b10384-49 DB - Crossref ER - TY - JOUR TI - Investigation of moisture-induced delamination failure in a semiconductor package via multi-scale mechanics AU - Kim, Hak-Sung AU - Huh, Jeehyang AU - Ryu, Jongeun T2 - Journal of Physics D: Applied Physics AB - In this work, moisture-induced interfacial delamination in a semiconductor package was investigated by experiment and multi-scale numerical analysis. The interfacial adhesion strength between a silicon wafer and an epoxy adhesive layer was characterized by a die-shear test with respect to moisture concentration and temperature. Molecular dynamics simulation was performed to study the effect of moisture and temperature on the interfacial adhesion energy and strength at the Si/epoxy adhesive interface. Based on the molecular dynamics predicted interfacial adhesion strength, a numerical stress analysis was performed considering hygro-swelling stress and the thermo-mechanical stress during a solder reflow process to predict the moisture-induced delamination failure of the semiconductor package. The multi-scale simulation result was compared with the actual reliability test result. From this study, it was concluded that the proposed multi-scale simulation technique can be used successfully for the prediction of moisture-induced package failure. DA - 2010/12/22/ PY - 2010/12/22/ DO - 10.1088/0022-3727/44/3/034007 VL - 44 IS - 3 SP - 034007 J2 - J. Phys. D: Appl. Phys. OP - SN - 0022-3727 1361-6463 UR - http://dx.doi.org/10.1088/0022-3727/44/3/034007 DB - Crossref ER - TY - JOUR TI - Thermal boundary layers over a shrinking sheet: An analytical solution AU - Fang, T. AU - Zhang, J. T2 - Acta Mechanica DA - 2010/// PY - 2010/// DO - 10.1007/s00707-009-0183-2 VL - 209 IS - 3-4 SP - 325-343 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-72849146251&partnerID=MN8TOARS ER - TY - CONF TI - Waste heat powered adsorption system to provide air conditioning for heavy-duty vehicles AU - Zhong, Y. AU - Wert, K.L. AU - Fang, T. C2 - 2010/// C3 - ASHRAE Transactions DA - 2010/// VL - 116 SP - 300-309 M1 - PART 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952635208&partnerID=MN8TOARS ER - TY - JOUR TI - Flow of a weakly conducting fluid in a channel filled with a porous medium AU - Pantokratoras, A. AU - Fang, T. T2 - Transport in Porous Media DA - 2010/// PY - 2010/// DO - 10.1007/s11242-009-9470-6 VL - 83 IS - 3 SP - 667-676 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77953872760&partnerID=MN8TOARS KW - Porous medium KW - Couette flow KW - Poiseuille flow KW - Lorentz force KW - Analytical solution ER - TY - JOUR TI - Effects of injection pressure on low-sooting combustion in an optical hsdi diesel engine using a narrow angle injector AU - Fang, T. AU - Lee, C.-F. AU - Coverdill, R. AU - White, R. T2 - SAE Technical Papers DA - 2010/// PY - 2010/// DO - 10.4271/2010-01-0339 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877184323&partnerID=MN8TOARS ER - TY - JOUR TI - Optimal design of a vibration-based energy harvester using magnetostrictive material (MsM) AU - Hu, J AU - Xu, F AU - Huang, A Q AU - Yuan, F G T2 - Smart Materials and Structures AB - In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) was designed and tested to enable the powering of a wireless sensor. In particular, the conversion efficiency, converting from magnetic to electric energy, is approximately modeled from the magnetic field induced by the beam vibration. A number of factors that affect the output power such as the number of MsM layers, coil design and load matching are analyzed and explored in the design optimization. From the measurements, the open-circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the second natural frequency 324 Hz. The AC output power is 970  µW, giving a power density of 279 µW cm − 3. The attempt to use electrical reactive components (either inductors or capacitors) to resonate the system at any frequency has also been analyzed and tested experimentally. The results showed that this approach is not feasible to optimize the power. Since the MsM device has low output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device is implemented using a discontinuous conduction mode (DCM) buck-boost converter. The DC output power after the voltage quadrupler reaches 705  µW and the corresponding power density is 202 µW cm − 3. The output power delivered to a lithium rechargeable battery is around 630  µW, independent of the load resistance. DA - 2010/12/23/ PY - 2010/12/23/ DO - 10.1088/0964-1726/20/1/015021 VL - 20 IS - 1 SP - 015021 J2 - Smart Mater. Struct. OP - SN - 0964-1726 1361-665X UR - http://dx.doi.org/10.1088/0964-1726/20/1/015021 DB - Crossref ER - TY - JOUR TI - Corrigendum to ‘Forced Convection with Slip-Flow in a Channel Occupied by a Hyperporous Medium Saturated by a Rarefied Gas’, Transport in Porous Media, 64, 161–170, 2006, and ‘Thermally Developing Forced Convection in a Porous Medium Occupied by a Rarefied Gas: Parallel Plate Channel or Circular Tube with Walls at Constant Heat Flux’, Transport in Porous Media, 76, 345–362, 2009 AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - Transport in Porous Media DA - 2010/9/17/ PY - 2010/9/17/ DO - 10.1007/s11242-010-9654-0 VL - 85 IS - 2 SP - 657-658 J2 - Transp Porous Med LA - en OP - SN - 0169-3913 1573-1634 UR - http://dx.doi.org/10.1007/s11242-010-9654-0 DB - Crossref ER - TY - JOUR TI - Mechanical modeling of a wrinkled fingertip immersed in water AU - Yin, Jie AU - Gerling, Gregory J. AU - Chen, Xi T2 - Acta Biomaterialia AB - Fingertips often wrinkle after extended exposure to water. The underlying mechanics issues, in particular the critical parameters governing the wrinkled morphology, are studied by using both finite element simulation and analytical modeling. The wrinkling behaviors, characterized by the wrinkle-to-wrinkle distance (wavelength), wrinkle depth (amplitude) and critical wrinkling stress/strain, are investigated as the geometry and material parameters of the fingertip are varied. A simple reduced model is employed to understand the effect of finger curvature and skin thickness, whereas a more refined full anatomical model provides the basis for analyzing the effect of a multilayered skin structure. The simulation results demonstrate that the stiffness of the stratum corneum and the dermal layer in the skin has a large effect on the wrinkling behavior, which agrees well with the analytical predictions. From the uncovered mechanical principles, potential ways for effectively slowing down and suppressing skin wrinkles are proposed; among them, increasing the modulus of the dermal layer in the skin appears to be the most effective. DA - 2010/4// PY - 2010/4// DO - 10.1016/j.actbio.2009.10.025 VL - 6 IS - 4 SP - 1487-1496 J2 - Acta Biomaterialia LA - en OP - SN - 1742-7061 UR - http://dx.doi.org/10.1016/j.actbio.2009.10.025 DB - Crossref KW - Skin wrinkles KW - Surface topography KW - Modeling KW - Finite element analysis ER - TY - JOUR TI - Buckling patterns of thin films on curved compliant substrates with applications to morphogenesis and three-dimensional micro-fabrication AU - Chen, Xi AU - Yin, Jie T2 - Soft Matter AB - Self-assembled buckling patterns of thin films on compliant substrates have been subjected to extensive studies and shown great promise in micro-fabrication. However, most previous studies were limited to planar substrates, and the study of buckling of films on curved substrates has not received sufficient attention. With the constraining effect from various types of substrate curvature, numerous new types of buckling morphologies may emerge which not only enable true three-dimensional (3D) fabrication of microstructures and microdevices, but also have important implications for the morphogenesis of quite a few natural and biological systems. We review the scientific aspects of elastic buckling of thin films on several representative curved substrates, emphasizing the critical effect of substrate curvature, its interaction with other material/system parameters, ways to control the buckles based on mechanical and physical principles, and bridge them with prospective applications in biology, biomedical engineering, and small-scale fabrication. DA - 2010/// PY - 2010/// DO - 10.1039/c0sm00401d VL - 6 IS - 22 SP - 5667 J2 - Soft Matter LA - en OP - SN - 1744-683X 1744-6848 UR - http://dx.doi.org/10.1039/c0sm00401d DB - Crossref ER - TY - JOUR TI - Conductive Polypyrrole/Tungsten Oxide Metacomposites with Negative Permittivity AU - Zhu, Jiahua AU - Wei, Suying AU - Zhang, Lei AU - Mao, Yuanbing AU - Ryu, Jongeun AU - Mavinakuli, Pallavi AU - Karki, Amar B. AU - Young, David P. AU - Guo, Zhanhu T2 - The Journal of Physical Chemistry C AB - Polypyrrole (PPy) nanocomposites reinforced with tungsten oxide (WO3) nanoparticles (NPs) and nanorods (NRs) are fabricated by a surface-initiated polymerization method. The electrical conductivity is observed to depend strongly on the particle loadings, molar ratio of oxidant to pyrrole monomer, and the filler morphology. The electron transportation in the nanocomposites follows a quasi-three-dimensional variable range hopping (VRH) conduction mechanism as evidenced by the temperature-dependent conductivity function. Unique negative permittivity is observed in both pure PPy and its nanocomposites, and the switching frequency (frequency where the real permittivity switches from negative to positive) can be tuned by changing the particle loading, ratio of oxidant to pyrrole monomer, and the filler morphology. The extent of charge carrier localization calculated from the VRH mechanism is well-correlated to the dielectric properties of the nanocomposites. WO3 NRs are observed to be more efficient in improving the electrical conductivity, dielectric permittivity, and thermal stability of the resulting nanocomposites as compared to those with WO3 NPs. The microstructures of pure PPy and its nanocomposites are observed by scanning electron microscopy and transmission electron microscopy. Powder X-ray diffraction analysis demonstrates the crystalline structure of WO3 nanostructures, as well as their corresponding nanocomposites. Thermogravimetric analysis reveals a significantly enhanced thermal stability with the addition of nanofillers. DA - 2010/9/10/ PY - 2010/9/10/ DO - 10.1021/jp1062463 VL - 114 IS - 39 SP - 16335-16342 J2 - J. Phys. Chem. C LA - en OP - SN - 1932-7447 1932-7455 UR - http://dx.doi.org/10.1021/jp1062463 DB - Crossref ER - TY - JOUR TI - Magnetic Epoxy Resin Nanocomposites Reinforced with Core−Shell Structured Fe@FeO Nanoparticles: Fabrication and Property Analysis AU - Zhu, Jiahua AU - Wei, Suying AU - Ryu, Jongeun AU - Sun, Luyi AU - Luo, Zhiping AU - Guo, Zhanhu T2 - ACS Applied Materials & Interfaces AB - Epoxy resin nanocomposites reinforced with various loadings of core−shell structured nanoparticles (Fe@FeO) are prepared using a surface wetting method. Nanoparticle loading effect on the viscosity of epoxy monomers is well-correlated to Cross’ rheological model. Dynamic mechanical analysis (DMA) results reveal that the glass transition temperature is increased by 10 °C with the addition of nanoparticles, which is surprisingly independent of the particle loadings. The saturation magnetization (Ms) of the 20 wt % Fe@FeO/epoxy nanocomposites is 17.03 emu/g, which is about 15.8% of that of the pure nanoparticles. Meanwhile, the coercivity increases from 62.33 to 202.13 Oe after the nanoparticles are dispersed in the epoxy matrix. The electrical conductivity percolation is found to be around 5−10 wt %, where the resistance of the nanocomposites sharply decreases by 6 orders of magnitude. Thermal stability and tensile properties of the pristine epoxy and nanocomposites are also investigated in this work. DA - 2010/7// PY - 2010/7// DO - 10.1021/am100361h VL - 2 IS - 7 SP - 2100-2107 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/am100361h DB - Crossref KW - polymer-matrix composites KW - magnetic properties KW - rheology KW - nanoparticles KW - electrical properties KW - mechanical properties ER - TY - JOUR TI - Carbon Nanotube Mat as Mediator-Less Glucose Sensor Electrode AU - Ryu, Jongeun AU - Kim, Hansang AU - Lee, Sangeui AU - Hahn, H. Thomas AU - Lashmore, David T2 - Journal of Nanoscience and Nanotechnology AB - In this paper, the direct electron transfer of glucose oxidase (GOx) on carbon nanotube (CNT) mat electrode is demonstrated. Because of the electrical conductivity and mechanical strength of CNT mat, it can be used as an electrode as well as a catalyst support. Therefore, the preparation process for the CNT mat based sensor electrode is simpler than that of the conventional CNT dispersed sensor electrodes. GOx was covalently immobilized on the oxidized CNT mat, which is connected to a wire by using silver paste and epoxy glue. Attenuated Total Reflectance Fourier Transform-Infrared (ATR-FTIR) result shows transmittance peaks at 1637 cm(-1) and 1525 cm(-1) which are corresponding to the band I and II of amide. Cyclic voltammetric shows a pair of well-defined redox peaks with the average formal potential of -0.425 V (vs. Ag/AgCl reference electrode) in the phosphate buffered saline solution (1 x PBS, pH 7.4). Calculated electron transfer rate constant and the surface density of GOx were 1.71 s(-1) and (3.27 +/- 0.20) x 10(-13) mol/cm2, respectively. Cyclic voltammograms of GOx-CNT mat in glucose solution show that the immobilized GOx retains its catalytic activity to glucose. The amperometric sensor response showed a linear dependence on the glucose concentration in the range of 0.2 mM to 2.18 mM with a detection sensitivity of 4.05 microA mM(-1) cm(-2). The Michaelis-Menten constant of the immobilized GOx was calculated to be 2.18 mM. DA - 2010/2/1/ PY - 2010/2/1/ DO - 10.1166/jnn.2010.1892 VL - 10 IS - 2 SP - 941-947 J2 - J. Nanosci. Nanotech. LA - en OP - SN - 1533-4880 UR - http://dx.doi.org/10.1166/jnn.2010.1892 DB - Crossref KW - Glucose Sensor KW - Glucose Oxidase KW - Direct Electron Transfer KW - Carbon Nanotube Mat KW - Amperometry KW - Mediator-Less ER - TY - JOUR TI - Intense pulsed light induced platinum–gold alloy formation on carbon nanotubes for non-enzymatic glucose detection AU - Ryu, Jongeun AU - Kim, Kyunghyun AU - Kim, Hak-Sung AU - Hahn, H. Thomas AU - Lashmore, David T2 - Biosensors and Bioelectronics AB - We demonstrated a novel method for the formation of alloy nano-islands on carbon nanotube (CNT). The two metal layers (Pt, Au) were sputtered on CNTs and the intense pulsed light (IPL) was irradiated on the metal layers. The absorbed light provides enough energy for the diffusion mixing between Pt and Au, forming Pt-Au alloy phase. While the alloy is being formed by the IPL irradiation, the metal layers are broken into nano-islands on CNT due to the surface energy minimization between the metal layers and CNT. The surface characterizations of the Pt-Au/CNT were performed with X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectroscopy. Different compositions of alloy nanoparticles were obtained by adjusting the deposition thicknesses of Pt and Au on CNT. Pt50Au50/CNT electrode showed the highest glucose oxidation current peak among Pt, Pt70Au30, Pt50Au50, Pt30Au70, and Au/CNT electrodes while the electroactive surface areas of them are kept to be similar (average surface area=7.00 cm2, coefficient of variation=0.06). The amperometric response of Pt50Au50/CNT electrode to the glucose concentrations showed a wide linear range up to 24.44 mM with a high detection sensitivity of 10.71 μA mM(-1) cm(-2). Reproducibility and long-term stability of the Pt-Au/CNT electrode were also proven in the experiments. DA - 2010/10/15/ PY - 2010/10/15/ DO - 10.1016/j.bios.2010.07.021 VL - 26 IS - 2 SP - 602-607 J2 - Biosensors and Bioelectronics LA - en OP - SN - 0956-5663 UR - http://dx.doi.org/10.1016/j.bios.2010.07.021 DB - Crossref KW - Glucose sensor KW - Intense pulsed light KW - Carbon nanotubes KW - Photothermal dewetting KW - Nanoparticle KW - Platinum alloy ER - TY - JOUR TI - Carbon nanotubes with platinum nano-islands as glucose biofuel cell electrodes AU - Ryu, Jongeun AU - Kim, Hak-Sung AU - Hahn, H. Thomas AU - Lashmore, David T2 - Biosensors and Bioelectronics AB - A novel method using intense pulsed light (IPL) for the metal nano-island formation on carbon nanotube (CNT) was introduced. The IPL-induced photothermal dewetting process improved platinum (Pt) catalyst utilization by transforming nano-islands from Pt film on CNT and increasing the surface area for the subsequent sputtering. The irradiation of high intensity of light on the Pt film causes surface-energy-driven diffusion of Pt atoms and forms the array of nano-islands on CNT. The thickness of Pt film can change the size of nano-islands. Cyclic voltammetry showed a dramatically improved glucose oxidation at the IPL morphology modified Pt-CNT electrode compared to the Pt sputtered CNT electrode without IPL irradiation. The power densities of glucose/air biofuel cell based on the morphology modified Pt-CNT electrode and the as-sputtered Pt-CNT electrode were 0.768 microW/cm(2) and 0.178 microW/cm(2), respectively. The biofuel cell based on morphology modified Pt-CNT electrode showed highly stable output in long-term performance. The power density dropped 14.1% in 30 days. Efforts are underway to improve the interface transfer to achieve higher potential and current output. DA - 2010/3// PY - 2010/3// DO - 10.1016/j.bios.2009.11.019 VL - 25 IS - 7 SP - 1603-1608 J2 - Biosensors and Bioelectronics LA - en OP - SN - 0956-5663 UR - http://dx.doi.org/10.1016/j.bios.2009.11.019 DB - Crossref KW - Glucose KW - Biofuel cell KW - Intense pulsed light KW - Carbon nanotubes KW - Photothermal dewetting ER - TY - CHAP TI - A BGK-Based Discontinuous Galerkin Method for the Navier-Stokes Equations on Arbitrary Grids AU - Luo, Hong AU - Luo, Luqing AU - Xu, Kun T2 - Computational Fluid Dynamics Review 2010 PY - 2010/7// DO - 10.1142/9789814313377_0006 SP - 103-122 OP - PB - WORLD SCIENTIFIC SN - 9789814313360 9789814313377 UR - http://dx.doi.org/10.1142/9789814313377_0006 DB - Crossref ER - TY - CONF TI - A comparative analysis of electronic pedal algorithms using a driver-in-the-loop simulator and system identification of driver behavior AU - Boris, Ryan AU - Vermillion, Chris AU - Butts, Ken T2 - 2010 American Control Conference (ACC 2010) AB - In modern automobiles, the driver's accelerator pedal position is fed to an electronic control unit, which has traditionally interpreted this pedal input as desired throttle angle but can interpret the pedal position in other ways as well. In this paper, we consider three interpretations of pedal position, namely desired throttle angle, desired net engine torque, and desired wheel torque. We design separate controllers for each pedal interpretation. For each controller, we evaluate drivers' abilities to simultaneously track a speed setpoint and keep high frequency vehicle acceleration to a minimum, relying on classical control theory to come up with preliminary hypotheses and a driver-in-the-loop simulator for determining which hypotheses hold. We also perform parametric system identification for each of the subjects used in this study, for each of the controllers, to assess any differences in driver behavior across the different controllers. We have concluded, for the vehicle platform studied here, the engine torque control provides comparable performance to direct throttle control, with improved drivability, whereas both throttle and engine torque control yield performance that is far superior to wheel torque control. C2 - 2010/6// C3 - Proceedings of the 2010 American Control Conference DA - 2010/6// DO - 10.1109/acc.2010.5531117 PB - IEEE SN - 9781424474271 9781424474264 9781424474257 UR - http://dx.doi.org/10.1109/acc.2010.5531117 DB - Crossref ER - TY - CONF TI - Model predictive engine torque control with real-time driver-in-the-loop simulation results AU - Vermillion, Chris AU - Butts, K AU - Reidy, Kevin T2 - 2010 American Control Conference (ACC 2010) AB - This paper presents the design and simulation results for a novel off-idle engine torque control strategy that uses online model predictive control (MPC) to simultaneously manage drivability, emissions, and fuel economy, while delivering desired engine torque. In order to achieve a tractable optimization, a modular control approach is used, wherein MPC is used to manipulate desired air/fuel ratio, engine air charge, spark advance, and variable valve timing, whereas lower level controllers are designed using conventional design techniques to deliver these desired values. The performance of the proposed control strategy is exhibited through simulation results on two test cases, including a driver-in-the-loop simulator. Results show that the model predictive torque control strategy yields a significant overall improvement in terms of a combined drivability, emissions, and fuel economy metric. C2 - 2010/6// C3 - Proceedings of the 2010 American Control Conference DA - 2010/6// DO - 10.1109/acc.2010.5531241 PB - IEEE SN - 9781424474271 9781424474264 9781424474257 UR - http://dx.doi.org/10.1109/acc.2010.5531241 DB - Crossref ER - TY - JOUR TI - Experimental Investigation of Cooling Performance of Metal-Based Microchannels AU - Parida, Pritish R. AU - Mei, Fanghua AU - Jiang, Jing AU - Meng, Wen Jin AU - Ekkad, Srinath V. T2 - Heat Transfer Engineering AB - Metal-based microchannel heat exchangers (MHEs) are of current interest due to the combination of high heat transfer performance and improved mechanical integrity. Efficient methods for fabrication and assembly of functional metal-based MHEs are essential to ensure the economic viability of such devices. Al- and Cu-based high-aspect-ratio microscale structures (HARMS) have been fabricated through molding replication using metallic mold inserts. Such metallic HARMS were assembled through eutectic bonding to form Al- and Cu-based MHEs, on which heat transfer tests were conducted to determine the overall cooling rate and time constants. Electrically heated Cu blocks were placed outside the MHEs and provided a constant flux, and water flowing within the microchannels acted as the coolant. Experimental results show a great influence of the type of metal, flow rate, and the surrounding conditions on the overall cooling performance of the MHEs. DA - 2010/5// PY - 2010/5// DO - 10.1080/01457630903409654 VL - 31 IS - 6 SP - 485-494 J2 - Heat Transfer Engineering LA - en OP - SN - 0145-7632 1521-0537 UR - http://dx.doi.org/10.1080/01457630903409654 DB - Crossref ER - TY - JOUR TI - Selected Papers From the 19th National & 8th ISHMT-ASME Heat and Mass Transfer Conference AU - Revankar, Shripad T. AU - Ekkad, Srinath V. T2 - Heat Transfer Engineering AB - We are glad to present this special issue of Heat Transfer Engineering with a selection of papers presented at the 19th National & 8th ISHMT-ASME Heat and Mass Transfer Conference, held January 3–5, 2008. The conference was jointly sponsored by the Indian Society of Heat and Mass Transfer (ISHMT) and the American Society of Mechanical Engineers (ASME) and was held at the Jawaharlal Nehru Technological University (JNTU), College of Engineering Kukatpally in Hyderabad, India. DA - 2010/5// PY - 2010/5// DO - 10.1080/01457630903408268 VL - 31 IS - 6 SP - 431-432 J2 - Heat Transfer Engineering LA - en OP - SN - 0145-7632 1521-0537 UR - http://dx.doi.org/10.1080/01457630903408268 DB - Crossref ER - TY - JOUR TI - Acoustic Sizing of an Ultrasound Contrast Agent AU - Maresca, David AU - Emmer, Marcia AU - van Neer, Paul L.M.J. AU - Vos, Hendrik J. AU - Versluis, Michel AU - Muller, Marie AU - de Jong, Nico AU - van der Steen, Antonius F.W. T2 - Ultrasound in Medicine & Biology AB - Because the properties of ultrasound contrast agent populations after administration to patients are largely unknown, methods able to study them noninvasively are required. In this study, we acoustically performed a size distribution measurement of the ultrasound contrast agent Definity(®). Single lipid-shelled microbubbles were insonified at 25 MHz, which is considerably higher than their resonance frequency, so that their acoustic responses depended on their geometrical cross sections only. We calculated the size of each microbubble from their measured backscattered pressures. The acoustic size measurements were compared with optical reference size measurements to test their accuracy. Our acoustic sizing method was applied to 88 individual Definity(®) bubbles to derive a size distribution of this agent. The size distribution obtained acoustically showed a mean diameter (2.5 μm) and a standard deviation (0.9 μm) in agreement within 8% with the optical reference measurement. At 25 MHz, this method can be applied to bubble sizes larger than 1.2 μm in diameter. It was observed that similar sized bubbles can give different responses (up to a factor 1.5), probably because of shell differences. These limitations should be taken into account when implementing the method in vivo. This acoustic sizing method has potential for estimating the size distribution of an ultrasound contrast agent noninvasively. DA - 2010/10// PY - 2010/10// DO - 10.1016/j.ultrasmedbio.2010.06.014 VL - 36 IS - 10 SP - 1713-1721 J2 - Ultrasound in Medicine & Biology LA - en OP - SN - 0301-5629 UR - http://dx.doi.org/10.1016/j.ultrasmedbio.2010.06.014 DB - Crossref KW - Acoustic bubble sizing KW - Ultrasound contrast agent KW - Definity (R) KW - Single bubbles KW - High frequency KW - Size distribution ER - TY - JOUR TI - High-efficiency broadband solar cell architectures based on arrays of volumetrically distributed narrowband photovoltaic fibers AU - O’Connor, Brendan AU - Nothern, Denis AU - Pipe, Kevin P. AU - Shtein, Max T2 - Optics Express AB - We propose a novel solar cell architecture consisting of multiple fiber-based photovoltaic (PV) cells. Each PV fiber element is designed to maximize the power conversion efficiency within a narrow band of the incident solar spectrum, while reflecting other spectral components through the use of optical microcavity effects and distributed Bragg reflector (DBR) coatings. Combining PV fibers with complementary absorption and reflection characteristics into volume-filling arrays enables spectrally tuned modules having an effective dispersion element intrinsic to the architecture, resulting in high external quantum efficiency over the incident spectrum. While this new reflective tandem architecture is not limited to one particular material system, here we apply the concept to organic PV (OPV) cells that use a metal-organic-metal-dielectric layer structure, and calculate the expected performance of such arrays. Using realistic material properties for organic absorbers, transport layers, metallic electrodes, and DBR coatings, 17% power conversion efficiency can be reached. DA - 2010/8/26/ PY - 2010/8/26/ DO - 10.1364/oe.18.00a432 VL - 18 IS - S3 SP - A432 J2 - Opt. Express LA - en OP - SN - 1094-4087 UR - http://dx.doi.org/10.1364/oe.18.00a432 DB - Crossref ER - TY - JOUR TI - Correlations between Mechanical and Electrical Properties of Polythiophenes AU - O’Connor, Brendan AU - Chan, Edwin P. AU - Chan, Calvin AU - Conrad, Brad R. AU - Richter, Lee J. AU - Kline, R. Joseph AU - Heeney, Martin AU - McCulloch, Iain AU - Soles, Christopher L. AU - DeLongchamp, Dean M. T2 - ACS Nano AB - The elastic moduli of polythiophenes, regioregular poly(3-hexylthiophene) (P3HT) and poly-(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (pBTTT), are compared to their field effect mobility showing a proportional trend. The elastic moduli of the films are measured using a buckling-based metrology, and the mobility is determined from the electrical characteristics of bottom contact thin film transistors. Moreover, the crack onset strain of pBTTT films is shown to be less than 2.5%, whereas that of P3HT is greater than 150%. These results show that increased long-range order in polythiophene semiconductors, which is generally thought to be essential for improved charge mobility, can also stiffen and enbrittle the film. This work highlights the critical role of quantitative mechanical property measurements in guiding the development of flexible organic semiconductors. DA - 2010/11/16/ PY - 2010/11/16/ DO - 10.1021/nn1018768 VL - 4 IS - 12 SP - 7538-7544 J2 - ACS Nano LA - en OP - SN - 1936-0851 1936-086X UR - http://dx.doi.org/10.1021/nn1018768 DB - Crossref KW - organic electronics KW - P3HT KW - pBTTT KW - flexible electronics KW - elastic modulus ER - TY - JOUR TI - Micellar Morphology in Sulfonated Pentablock Copolymer Solutions AU - Choi, Jae-Hong AU - Kota, Arun AU - Winey, Karen I. T2 - Industrial & Engineering Chemistry Research AB - The morphology of solutions of poly[t-butyl styrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene-b-t-butyl styrene] (tBS-HI-SS-HI-tBS) pentablock copolymers with a range of sulfonation levels was studied by small-angle X-ray scattering and transmission electron microscopy. For dilute pentablock copolymer solutions, TEM confirms the spherical micellar morphology. Small-angle X-ray scattering results and their interpretation using the Kinning−Thomas model reveal that sulfonated pentablock copolymer solutions with all levels of sulfonation exhibit spherical micellar morphologies with a core of SS and a corona of solvated HI-tBS. Both the radius of the micelle core and the closest approach distance between cores increase with sulfonation level, while the number density of micelles decreases. The calculated fraction of micelles per unit volume shows an increase and then a plateau with sulfonation level. The manipulation of micelle size dramatically impacts the processability. DA - 2010/12// PY - 2010/12// DO - 10.1021/ie1002476 VL - 49 IS - 23 SP - 12093-12097 J2 - Ind. Eng. Chem. Res. LA - en OP - SN - 0888-5885 1520-5045 UR - http://dx.doi.org/10.1021/ie1002476 DB - Crossref ER - TY - JOUR TI - Nanomechanical characterization of dispersion and its effects in nano-enhanced polymers and polymer composites AU - Gershon, Alan L. AU - Cole, Daniel P. AU - Kota, Arun K. AU - Bruck, Hugh A. T2 - Journal of Materials Science DA - 2010/6/22/ PY - 2010/6/22/ DO - 10.1007/s10853-010-4597-y VL - 45 IS - 23 SP - 6353-6364 J2 - J Mater Sci LA - en OP - SN - 0022-2461 1573-4803 UR - http://dx.doi.org/10.1007/s10853-010-4597-y DB - Crossref ER - TY - JOUR TI - Atomic scale studies of spall behavior in nanocrystalline Cu AU - Dongare, Avinash M. AU - Rajendran, Arunachalam M. AU - LaMattina, Bruce AU - Zikry, Mohammed A. AU - Brenner, Donald W. T2 - Journal of Applied Physics AB - The micromechanisms related to ductile failure during dynamic loading of nanocrystalline Cu are investigated in a series of large-scale molecular dynamics simulations. Void nucleation, growth, and coalescence is studied for a nanocrystalline Cu system with an average grain size of 6 nm under conditions of impact of a shock piston with velocities of 250, 500, 750, and 1000 m/s and compared to that observed in single crystal copper. Higher impact velocities result in higher strain rates and higher values of spall strengths for the metal as well as nucleation of larger number of voids in smaller times. For the same impact velocity, the spall strength of the nanocrystalline metal, however, is lower than that for single crystal copper. The results obtained for void nucleation and growth in nanocrystalline Cu for various impact velocities and for single crystal copper [001] suggests two distinct stages of evolution of voids. The first stage (I) corresponds to the fast nucleation of voids followed by the second stage (II) attributed to growth and coalescence of voids. The first stage is found to be dependent on the microstructure of the system as well as the shock pressure/strain rate, whereas, the second stage of void growth is independent of the strain rate and microstructure of the system and dependent only on the number of voids nucleated. DA - 2010/12// PY - 2010/12// DO - 10.1063/1.3517827 VL - 108 IS - 11 SP - 113518 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.3517827 DB - Crossref ER - TY - CONF TI - Ultra-high Resolution Optics for EUV and Soft X-ray Inelastic Scattering AU - Voronov, D. L. AU - Cambie, R. AU - Ahn, M. AU - Anderson, E. H. AU - Chang, C. H. AU - Gullikson, E. M. AU - Heilmann, R. K. AU - Salmassi, F. AU - Schattenburg, M. L. AU - Yashchuk, V. V. AU - Padmore, H. A. AU - Garrett, R. AU - Gentle, I. AU - Nugent, K. AU - Wilkins, S. T2 - SRI 2009, 10TH INTERNATIONAL CONFERENCE ON RADIATION INSTRUMENTATION AB - We describe a revolutionary new approach to high spectral resolution soft x‐ray optics. Conventionally in the soft x‐ray energy range, high spectral resolution is obtained by use of a relatively low line density grating operated in 1st order with small slits. This severely limits throughput. This limitation can be removed by use of a grating either in very high order, or with very high line density, if one can maintain high diffraction efficiency. We have developed a new technology for achieving both of these goals which should allow high throughput spectroscopy, at resolving powers of up to 106 at 1 keV. Such optics should provide a revolutionary advance for high resolution lifetime free spectroscopy, such as RIXS, and for pulse compression of chirped beams. We report recent developmental fabrication and characterization of a prototype grating optimized for 14.2 nm EUV light. The prototype grating with a 200 nm period of the blazed grating substrate coated with 20 Mo/Si bilayers with a period of 7.1 nm demonstrates good dispersion in the third order (effective groove density of 15,000 lines per mm) with a diffraction efficiency of more than 33%. C2 - 2010/// C3 - DA - 2010/// DO - 10.1063/1.3463360 PB - AIP UR - http://dx.doi.org/10.1063/1.3463360 DB - Crossref KW - blazed gratings KW - multilayer EUV KW - soft x-rays KW - lithography KW - anisotropic etch ER - TY - JOUR TI - High-efficiency 5000 lines/mm multilayer-coated blazed grating for extreme ultraviolet wavelengths AU - Voronov, Dmitriy L. AU - Ahn, Minseung AU - Anderson, Erik H. AU - Cambie, Rossana AU - Chang, Chih-Hao AU - Gullikson, Eric M. AU - Heilmann, Ralf K. AU - Salmassi, Farhad AU - Schattenburg, Mark L. AU - Warwick, Tony AU - Yashchuk, Valeriy V. AU - Zipp, Lucas AU - Padmore, Howard A. T2 - Optics Letters AB - Volume x-ray gratings consisting of a multilayer coating deposited on a blazed substrate can diffract with very high efficiency, even in high orders if diffraction conditions in-plane (grating) and out-of-plane (Bragg multilayer) are met simultaneously. This remarkable property, however, depends critically on the ability to create a structure with near atomic perfection. In this Letter we report on a method to produce these structures. We report measurements that show, for a 5000l/mm grating diffracting in the third order, a diffraction efficiency of 37.6% at a wavelength of 13.6nm. This work now shows a direct route to achieving high diffraction efficiency in high order at wavelengths throughout the soft x-ray energy range. DA - 2010/7/29/ PY - 2010/7/29/ DO - 10.1364/ol.35.002615 VL - 35 IS - 15 SP - 2615 J2 - Opt. Lett. LA - en OP - SN - 0146-9592 1539-4794 UR - http://dx.doi.org/10.1364/ol.35.002615 DB - Crossref ER - TY - JOUR TI - Design and optimization of broadband wide-angle antireflection structures for binary diffractive optics AU - Chang, Chih-Hao AU - Waller, Laura AU - Barbastathis, George T2 - Optics Letters AB - We propose a class of antireflecting structures that can effectively suppress reflections for binary diffractive optics. In this structure, multiple periodic thin films with gradually varying refractive indices are used to shift all reflected diffraction to the transmitted orders. The structure is optimized to operate over broad bands and wide angles using rigorous coupled-wave analysis and genetic algorithms. We validated the structure numerically using finite-difference time-domain methods. The proposed structure may lead to more efficient diffractive devices for applications in thin-film photovoltaic, waveguide coupler, and holographic optical elements. DA - 2010/3/18/ PY - 2010/3/18/ DO - 10.1364/ol.35.000907 VL - 35 IS - 7 SP - 907 J2 - Opt. Lett. LA - en OP - SN - 0146-9592 1539-4794 UR - http://dx.doi.org/10.1364/ol.35.000907 DB - Crossref ER - TY - JOUR TI - Assembling nanoparticle catalysts with nanospheres for periodic carbon nanotube structure growth AU - Chang, Chih-Hao AU - In, Hyun Jin AU - Takahashi, Satoshi AU - Deterre, Martin AU - Choi, Hyungryul Johnny AU - Gotrik, Kevin W AU - Barbastathis, George T2 - Nanotechnology AB - We have developed a novel method to grow carbon nanotubes in a periodic structure using a simple one-step self-assembly process. In this approach, monodispersed nanospheres are utilized to assemble smaller nanoparticle catalysts into an ordered periodic pattern. Using this process, we have grown carbon nanotube bundles into a honeycomb structure. The proposed method eliminates the need for lithography and material deposition, greatly reducing the fabrication complexity and cost. DA - 2010/12/9/ PY - 2010/12/9/ DO - 10.1088/0957-4484/22/3/035301 VL - 22 IS - 3 SP - 035301 J2 - Nanotechnology OP - SN - 0957-4484 1361-6528 UR - http://dx.doi.org/10.1088/0957-4484/22/3/035301 DB - Crossref ER - TY - JOUR TI - Ultrafast thermoreflectance techniques for measuring thermal conductivity and interface thermal conductance of thin films T2 - Journal of Applied Physics AB - The thermal conductivity of thin films and interface thermal conductance of dissimilar materials play a critical role in the functionality and the reliability of micro/nanomaterials and devices. The ultrafast laser-based thermoreflectance techniques, including the time-domain thermoreflectance (TDTR) and the frequency-domain thermoreflectance (FDTR) techniques are excellent approaches for the challenging measurements of interface thermal conductance of dissimilar materials. Both TDTR and FDTR signals on a trilayer structure which consists of a thin film metal transducer, a target thin film, and a substrate are studied by a thermal conduction model. The sensitivity of TDTR signals to the thermal conductivity of thin films is analyzed to show that the modulation frequency needs to be selected carefully for a high precision TDTR measurement. However, such a frequency selection, which is closely related to the unknown thermal properties and consequently hard to make before TDTR measurement, can be avoided in FDTR measurement. We also found out that in FDTR method, the heat transport in a trilayer structure could be divided into three regimes, and the thermal conductivity of thin films and interface thermal conductance can be obtained subsequently by fitting the data in different frequency range of one FDTR measurement, based on the regime map. Both TDTR and FDTR measurements are then conducted along with the analysis to obtain the thermal conductivity of SiO2 thin films and interface thermal conductance between SiO2 and Si. FDTR measurement results agree well with the TDTR measurements, but promises to be a much easier implementation than TDTR measurements. DA - 2010/11// PY - 2010/11// DO - 10.1063/1.3504213 UR - http://dx.doi.org/10.1063/1.3504213 ER - TY - JOUR TI - Tuning the thermal conductivity of polymers with mechanical strains T2 - Physical Review B AB - The low thermal conductivity of polymers limits their heat spreading capability, which is one of the major technical barriers for the polymer-based products, especially electronics, such as organic light emitting diodes. It is highly desirable to enhance the thermal conductivity of polymer materials including polymer composites. Mechanical stretching could align polymer chains which are intrinsically low-dimensional material that could have very high thermal conductivity and thus enhancing the thermal conductivity of polymers. In this work, the all-atom model molecular-dynamics simulation is conducted to investigate the tuning of polymer thermal conductivity using mechanical strains. The simulation results show that the thermal conductivity of polymers increases with the increasing strain and the enhancement is larger when the polymer is stretched slower. Molecular weight also affects the thermal conductivity under the same stretching condition. More importantly, the thermal-conductivity enhancement could be exponentially fitted with the orientational order parameter which describes the chain conformation change. This study could guide the development of advanced reconfigurable and tunable thermal management technologies. DA - 2010/5/28/ PY - 2010/5/28/ DO - 10.1103/physrevb.81.174122 UR - http://dx.doi.org/10.1103/physrevb.81.174122 ER - TY - JOUR TI - Heat transfer enhancement by filling metal porous medium in central area of tubes T2 - Journal of the Energy Institute AB - Given that the fluid within the tubes of some industrial heat exchangers is under a state of fully developed laminar flow with a constant Nu number, increasing the surface area for heat transfer will significantly increase the flow resistance. In this paper, we filled metal porous medium with high thermal conductivity, high porosity and high filling radius in the central area of fully developed laminar flow within the tube, and established corresponding numerical models for fluid flow and heat transfer. Numerical simulation results indicate that after filling the tube with metal porous medium, the temperature profiles within the porous medium area are very uniform, and the temperature difference between the tube wall and the fluid decreases significantly which correspondingly results in a notable increase of Nu number; meanwhile, the characteristic of flow field redistribution occurs within the enhanced tube, but the total flow resistance composed of the Darcy resistance and inertial resistance of the porous medium area and the shear stress caused by velocity gradient and fluid viscosity of the non-porous medium area near the wall increase; correspondingly, the performance evaluation criteria (PEC) value is thus applied to evaluate the effect of the heat tranfer enhancement method. For a tube of 9 mm in radius, the PEC values are all above 1 when the filling radius of the metal porous medium is larger than 7 mm. DA - 2010/3/1/ PY - 2010/3/1/ DO - 10.1179/014426010x12592427711911 UR - http://dx.doi.org/10.1179/014426010x12592427711911 KW - Heat transfer enhancement KW - Porous medium KW - Performance evaluation criteria ER - TY - CONF TI - The LES-ODT model for turbulent premixed flames AU - Echekki, T. AU - Park, J. C2 - 2010/// C3 - 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition DA - 2010/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78649864613&partnerID=MN8TOARS ER - TY - CONF TI - SiCN ceramic fibers with aligned carbon nanotubes AU - Sarkar, S. AU - Zou, J. AU - Xu, C. AU - An, L. AU - Zhai, L. C2 - 2010/// C3 - International SAMPE Symposium and Exhibition (Proceedings) DA - 2010/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78649483096&partnerID=MN8TOARS ER - TY - CONF TI - Robust estimation of a maneuvering target from multiple unmanned air vehicles' measurements AU - Allen, R. AU - Lin, K.-C. AU - Xu, C. AB - When multiple UAVs collaborate to track a maneuvering target, their position measurement sensors are sometimes corrupted by noise biases (e.g. sensor drifting). In this case, the zero-mean noise assumption of the Kalman filter is therefore violated and the desired optimal estimate will not be guaranteed. In this paper, an H-infinity filter is utilized to estimate the position of the maneuvering target to compensate for non-zero-mean noise. Furthermore, the constrained H-infinity filter is shown to be superior to the Kalman filter. C2 - 2010/// C3 - 2010 International Symposium on Collaborative Technologies and Systems, CTS 2010 DA - 2010/// DO - 10.1109/CTS.2010.5478465 SP - 537-545 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77954470508&partnerID=MN8TOARS ER - TY - JOUR TI - Polymer-derived ceramic composite fibers with aligned pristine multiwalled carbon nanotubes AU - Sarkar, S. AU - Zou, J. AU - Liu, J. AU - Xu, C. AU - An, L. AU - Zhai, L. T2 - ACS Applied Materials and Interfaces AB - Polymer-derived ceramic fibers with aligned multiwalled carbon nanotubes (MWCNTs) are fabricated through the electrospinning of polyaluminasilazane solutions with well-dispersed MWCNTs followed by pyrolysis. Poly(3-hexylthiophene)-b-poly (poly (ethylene glycol) methyl ether acrylate) (P3HT-b-PPEGA), a conjugated block copolymer compatible with polyaluminasilazane, is used to functionalize MWCNT surfaces with PPEGA, providing a noninvasive approach to disperse carbon nanotubes in polyaluminasilazane chloroform solutions. The electrospinning of the MWCNT/polyaluminasilazane solutions generates polymer fibers with aligned MWCNTs where MWCNTs are oriented along the electrospun jet by a sink flow. The subsequent pyrolysis of the obtained composite fibers produces ceramic fibers with aligned MWCNTs. The study of the effect of polymer and CNT concentration on the fiber structures shows that the fiber size increases with the increment of polymer concentration, whereas higher CNT content in the polymer solutions leads to thinner fibers attributable to the increased conductivity. Both the SEM and TEM characterization of the polymer and ceramic fibers demonstrates the uniform orientation of CNTs along the fibers, suggesting excellent dispersion of CNTs and efficient CNT alignment via the electrospinning. The electrical conductivity of a ceramic fibers with 1.2% aligned MWCNTs is measured to be 1.58 × 10−6 S/cm, which is more than 500 times higher than that of bulk ceramic (3.43 × 10−9 S/cm). Such an approach provides a versatile method to disperse CNTs in preceramic polymer solutions and offers a new approach to integrate aligned CNTs in ceramics. DA - 2010/// PY - 2010/// DO - 10.1021/am1000085 VL - 2 IS - 4 SP - 1150-1156 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77953716483&partnerID=MN8TOARS KW - align KW - carbon nanotubes KW - polymer-derived ceramic KW - electrospun fibers ER - TY - JOUR TI - Non-premixed acoustically perturbed swirling flame dynamics AU - Idahosa, U. AU - Saha, A. AU - Xu, C. AU - Basu, S. T2 - Combustion and Flame AB - An investigation into the response of non-premixed swirling flames to acoustic perturbations at various frequencies (fp = 0–315 Hz) and swirl intensities (S = 0.09 and 0.34) is carried out. Perturbations are generated using a loudspeaker at the base of an atmospheric co-flow burner with resulting velocity oscillation amplitudes |u′/Uavg| in the 0.03–0.30 range. The dependence of flame dynamics on the relative richness of the flame is investigated by studying various constant fuel flow rate flame configurations. Flame heat release rate is quantitatively measured using a photomultiplier with a 430 nm bandpass filter for observing CH∗ chemiluminescence which is simultaneously imaged with a phase-locked CCD camera. The flame response is observed to exhibit a low-pass filter characteristic with minimal flame response beyond pulsing frequencies of 200 Hz. Flames at lower fuel flow rates are observed to remain attached to the central fuel pipe at all acoustic pulsing frequencies. PIV imaging of the associated isothermal fields show the amplification in flame aspect ratio is caused by the narrowing of the inner recirculation zone (IRZ). Good correlation is observed between the estimated flame surface area and the heat release rate signature at higher swirl intensity flame configurations. A flame response index analogous to the Rayleigh criterion in non-forced flames is used to assess the potential for a strong flame response at specific perturbation configurations and is found to be a good predictor of highly responsive modes. Phase conditioned analysis of the flame dynamics yield additional criteria in highly responsive modes to include the effective amplitude of velocity oscillations induced by the acoustic pulsing. In addition, highly responsive modes were characterized by velocity to heat release rate phase differences in the ±π/2 range. A final observed characteristic in highly responsive flames is a Strouhal number between 1 and 3.5 based on the burner co-flow annulus diameter (St = fpUavg/dm). Finally, wavelet analyses of heat release rate perturbations indicate highly responsive modes are characterized by sustained low frequency oscillations which accompany the high amplitude velocity perturbations at these modes. Higher intensity low frequency heat release rate oscillations are observed for lean flame/low pulsing frequency conditions. DA - 2010/// PY - 2010/// DO - 10.1016/j.combustflame.2010.05.008 VL - 157 IS - 9 SP - 1800-1814 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77954386686&partnerID=MN8TOARS KW - Swirl stabilized flames KW - Non-premixed flames KW - Rayleigh criterion KW - Forced flame response KW - Wavelet analysis KW - Acoustic flame perturbation ER - TY - CONF TI - Micro-machinable polymer-derived ceramic sensors for high-temperature applications AU - Liu, Jian AU - Xu, Chengying AU - An, Linan T2 - SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring A2 - Tomizuka, Masayoshi AB - Micro-sensors are highly desired for on-line temperature/pressure monitoring in turbine engines to improve their efficiency and reduce pollution. The biggest challenge for developing this type of sensors is that the sensors have to sustain at extreme environments in turbine engine environments, such as high-temperatures (>800 °C), fluctuated pressure and oxidation/corrosion surroundings. In this paper, we describe a class of sensors made of polymer-derived ceramics (PDCs) for such applications. PDCs have the following advantages over conventional ceramics, making them particularly suitable for these applications: (i) micromachining capability, (ii) tunable electric properties, and (iii) hightemperature capability. Here, we will discuss the materials and their properties in terms of their applications for hightemperature micro-sensors, and microfabrication technologies. In addition, we will also discuss the design of a heat-flux sensor based on polymer-derived ceramics. C2 - 2010/3/25/ C3 - Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2010 DA - 2010/3/25/ DO - 10.1117/12.848529 VL - 7647 PB - SPIE UR - http://dx.doi.org/10.1117/12.848529 DB - Crossref KW - polymer-derived ceramics KW - high temperature micro-sensor KW - micro-machining ER - TY - JOUR TI - Making bulk ceramics from polymeric precursors AU - Jiang, T. AU - Hill, A. AU - Fei, W. AU - Wei, Y. AU - Tellam, M. AU - Xu, C. AU - An, L. T2 - Journal of the American Ceramic Society AB - In this paper, we report a simple technique for making bulk Si‐based ceramics from polymeric precursor. In this technique, a porous polymer preform with high porosity is used as a template. The preform is thermally decomposed before the precursor during pyrolysis to form interconnected pores for releasing gaseous species resulting from pyrolysis of precursors to avoid the formation of cracks within resultant ceramics. The thermal decomposition behavior of both template and precursor is studied for determining the proper pyrolysis procedure. The microstructure, porosity, and mechanical strength of the ceramics obtained are characterized. DA - 2010/// PY - 2010/// DO - 10.1111/j.1551-2916.2010.04069.x VL - 93 IS - 10 SP - 3017-3019 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78649544025&partnerID=MN8TOARS ER - TY - CONF TI - Machinability study of SiC nano-particles reinforced Magnesium nanocomposites during micro-milling processes AU - Li, J. AU - Liu, J. AU - Xu, C. AB - This paper experimentally investigates the machinability of Magnesium Metal Matrix Composites (Mg-MMCs) with high volume fractions of SiC nano-particles. Samples of Mg-MMCs with 5 Vol.%, 10 Vol.% and 15 Vol.% reinforcements of SiC nano-particles were studied and compared with pure Magnesium. Different feedrates and spindle speeds were chosen as varied cutting parameters. Cutting forces, surface morphology and roughness were measured to understand the machinability of the four different materials during the micro-milling process. Based on the experimental results, it is observed that the cutting force increases with the increase of the spindle speed, the feedrate and/or the volume fraction. A drastic increasing rate is observed when the nano-particles’ volume fraction is increased from 5 to 10 Vol.%. The effect of the volume fraction is also studied in frequency domain, combined with the effect of the spindle speed and feedrate. More detailed theoretical analysis will be further studied to better understand the effect of the volume fraction on the machined surface quality and machining productivity. C2 - 2010/// C3 - ASME 2010 International Manufacturing Science and Engineering Conference, MSEC 2010 DA - 2010/// DO - 10.1115/MSEC2010-34294 VL - 2 SP - 391-398 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-82455186163&partnerID=MN8TOARS ER - TY - JOUR TI - Fabrication of Si3N4/SiC nanocomposites toughened by in-situ formed low-dimensional nanostructures AU - Yang, W. AU - Gao, F. AU - Xu, C. AU - Wei, G. AU - An, L. T2 - Solid State Sciences AB - We report the fabrication of Si3N4/SiC nano/nano-composite reinforced by single-crystal low-dimensional nanostructures via spark plasma sintering of nanocomposite powders containing in-situ formed Si3N4 nanowires/nanobelts. The fabricated nanocomposite is analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and selective area electron diffraction. The results show that the in-situ formed Si3N4 nanowires/nanobelts are uniformly distributed within the matrix. Such a nanocomposite could exhibit improved mechanical properties, due to the superior mechanical properties and uniform distribution of the nano-reinforcements. DA - 2010/// PY - 2010/// DO - 10.1016/j.solidstatesciences.2010.07.013 VL - 12 IS - 9 SP - 1692-1695 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77956056271&partnerID=MN8TOARS KW - Ceramics KW - Silicon carbide KW - Silicon nitride ER - TY - JOUR TI - Fabrication of AA6061/Al<inf>2</inf>O<inf>3</inf>nano ceramic particle reinforced composite coating by using friction stir processing AU - Yang, M. AU - Xu, C. AU - Wu, C. AU - Lin, K.-C. AU - Chao, Y.J. AU - An, L. T2 - Journal of Materials Science DA - 2010/// PY - 2010/// DO - 10.1007/s10853-010-4525-1 VL - 45 IS - 16 SP - 4431-4438 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77955471177&partnerID=MN8TOARS ER - TY - CONF TI - Experimental setup for multi-sensor fusion and data correlation analysis during CNC steel turning process AU - Joslin, A. AU - Hernandez, M. AU - Deane, E. AU - Collins, S. AU - Xu, C. AU - Wilson, D.F. AB - This paper discusses a preliminary setup for an ongoing research project with goals of off-line modeling and optimization for a CNC turning process of AISI 4137 steel alloy; followed by online monitoring, optimization, and control of the machining process. A full factorial Design Of Experiment (DOE) of three machining parameter factors was created in Minitab™ and Analysis of Variance was performed, in order to determine which parameters influenced the machining process the most. Accelerometers, acoustic emission sensors and force sensors have given researchers insights into the relationships between mechanical vibration and tool condition during the turning process. Similarly, correlations have been recognized between electrical power consumption, machining forces, tool temperature, and tool condition. While monitoring the machining process with sophisticated force and acceleration sensors is effective, implementation in a large scale factory environment may not be an economical solution to online monitoring and control. Finding an ideal combination of sensors capable of monitoring significant factors that affect the CNC steel turning process will allow process optimization and reduce the cost of machining. C2 - 2010/// C3 - ASME 2010 International Manufacturing Science and Engineering Conference, MSEC 2010 DA - 2010/// DO - 10.1115/MSEC2010-34308 VL - 1 SP - 461-467 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-82455174828&partnerID=MN8TOARS ER - TY - CONF TI - Acoustic perturbation effects on the fluid dynamics and swirling flame response in a non-premixed co-flow burner AU - Idahosa, U. AU - Saha, A. AU - Khatami, N. AU - Xu, C. AU - Basu, S. AB - An investigation into the response of non-premixed swirling flames to acoustic perturbations at various frequencies (fp = 0–315 Hz) and swirl intensities (S = 0.09 and 0.34) is carried out. Perturbations are generated using a loudspeaker at the base of an atmospheric co-flow burner with resulting velocity oscillation amplitudes |u′/Uavg| in the 0.03–0.30 range. The dependence of flame dynamics on the relative richness of the flame is investigated by studying various constant fuel flow rate flame configurations. Flame heat release is quantitatively measured and simultaneously imaged using a photomultiplier (PMT) and a phase-locked CCD camera. Both of which are fitted with 430nm bandpass filters for observing CH*chemiluminescence. The flame response is observed to exhibit a low-pass filter characteristic with minimal flame response beyond pulsing frequencies of 200Hz. Flames at lower fuel flow rates are observed to remain attached to the central fuel pipe at all acoustic pulsing frequencies. PIV imaging of the associated isothermal fields show the amplification in flame aspect ratio is caused by the narrowing of the inner recirculation zone (IRZ). The Rayleigh criterion (R) is used to assess the potential for instability of specific perturbation configurations and is found to be a good predictor of unstable modes. Phase conditioned analysis of the flame dynamics yield additional criteria in highly responsive modes to include the effective amplitude of velocity oscillations induced by the acoustic pulsing. Highly amplified responses were observed in pulsed flame configurations with Strouhal numbers (St = fpUavg/dm) in the 1–3.5 range. Heat release to velocity perturbation time delays on the order of the acoustic pulsing period also characterized the highly responsive flames. Finally, wavelet analyses of heat release perturbations indicate sustained low frequency oscillations that become more prominent for low acoustic pulsing frequencies in lean flame configurations. C2 - 2010/// C3 - Proceedings of the ASME Turbo Expo DA - 2010/// DO - 10.1115/GT2010-23735 VL - 2 SP - 1309-1321 M1 - PARTS A AND B UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-82055207375&partnerID=MN8TOARS ER - TY - JOUR TI - Online Tool Deflection Compensation in End Milling of Curved Workpiece AU - Tang, Y. AU - Xu, C. T2 - International Journal of Electronics, Computing and Engineering Education DA - 2010/// PY - 2010/// VL - 1 IS - 1 SP - 23–28 ER - TY - SOUND TI - Experimental Setup for Multi-sensor Fusion and Data Correlation Analysis during CNC Steel Turning Process AU - Joslin, A. AU - Hernandez, M. AU - Collins, S. AU - Giesecke, D. AU - Ji, Y. AU - Xu, C. DA - 2010/// PY - 2010/// ER - TY - SOUND TI - Carbon Nanofiber Reinforced Polymer Derived Ceramic Nanocomposites AU - Shao, G. AU - Xu, C. AU - An, L. DA - 2010/// PY - 2010/// ER - TY - CONF TI - Enhancing student engagement in engineering statics with online tools AU - Howard, A. K. T. AB - Engineering Statics at North Carolina State University is taught to both distance-education and on-campus sections simultaneously. Statics has been remodeled to include online and in-class tools to encourage all students to stay actively engaged with the material. Seven online tools which have been incorporated into the redesigned course are presented and discussed: review modules, reading introductions and quizzes, class notes with video example problems, recorded lectures, skills quizzes, synchronous office hours and asynchronous message boards, and clickers. Results indicate students come to class consistently, are more likely to complete readings, and appreciate the just-in-time online resources. One faculty member can now supervise larger numbers of students and homework grading has been cut in half. C2 - 2010/// C3 - ASME 2010 International Mechanical Engineering Congress & Exposition DA - 2010/// DO - 10.1115/imece2010-38363 ER - TY - CONF TI - Development of a changeable airfoil optimization model for use in the multidisciplinary design of unmanned aerial vehicles AU - Ferguson, S. AU - Tilstra, A. H. AU - Seepersad, C. C. AU - Wood, K. L. AB - Complex systems need to perform in a variety of functional states and under varying operating conditions. Therefore, it is important to manage the different values of design variables associated with the operating states for each subsystem. The research presented in this paper uses multidisciplinary optimization (MDO) and changeable systems methods together in the design of a reconfigurable Unmanned Aerial Vehicle (UAV). MDO is a useful approach for designing a system that is composed of distinct disciplinary subsystems by managing the design variable coupling between the subsystem and system level optimization problems. Changeable design research addresses how changes in the physical configuration of products and systems can better meet distinct needs of different operating states. As a step towards the development of a realistic reconfigurable UAV optimization problem, this paper focuses on the performance advantage of using a changeable airfoil subsystem. Design principles from transformational design methods are used to develop concepts that determine how the design variables are allowed to change in the mathematical optimization problem. The performance of two changeable airfoil concepts is compared to a fixed airfoil design over two different missions that are defined by a sequence of mission segments. Determining the configurations of the static and changeable airfoils is accomplished using a genetic algorithm. Results from this study show that aircraft with changeable airfoils attain increased performance, and that the manner by which the system transforms is significant. For this reason, the changeable airfoil optimization developed in this paper is ready to be integrated into a complete MDO problem for the design of a reconfigurable UAV. C2 - 2010/// C3 - Proceedings of the ASME international design engineering technical conferences and computers and information in engineering conference, vol 5, pts a and b - 35th design automation conference DA - 2010/// DO - 10.1115/detc2009-87482 SP - 57-68 ER - TY - CONF TI - Deformation of precipitate platelets in high strength aluminum alloys under high strain-rate compression AU - Elkhodary, K. AU - Lee, W. AU - Cheeseman, B. AU - Sun, L.P. AU - Brenner, D.W. AU - Zikry, M.A. C2 - 2010/// C3 - TMS Annual Meeting DA - 2010/// VL - 2 SP - 47-52 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952596072&partnerID=MN8TOARS ER - TY - CONF TI - Towards self-sensing of deap actuators: Capacitive sensing experimental analysis AU - York, A. AU - Seelecke, S. AB - Dielectric Electro-Active Polymers (DEAP’s) have become attractive material for various actuation and sensing applications such as light weight and energy efficient valve and pumping systems. The materials ability to act as both and actuator and a sensor enable DEAP actuators to have “self-sensing” capabilities. This advancement provides low cost actuator systems that do not require external sensors for feedback control. This paper explores the capacitive sensing capabilities of a DEAP actuator under loading conditions typical for pumping and valve applications. The capacitive sensing capabilities of the actuator are tested using a method similar to that used by Jung et al. [1] which uses the DEAP actuator as a variable capacitor in a high pass filter circuit. This sensing circuit produces a direct voltage output when the actuator is displaced. The sensing response of this system is experimentally investigated under mechanical loading. The sensor is shown to have an effective sensitivity of .041 (V/Vexc) / mm. In addition, the initial results of a dual sensing and actuating system are presented. C2 - 2010/// C3 - Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, 2010, vol. 1 DA - 2010/// DO - 10.1115/smasis2010-3847 SP - 307-314 ER - TY - CONF TI - Practical implementation of resistance feedback measurement for position control of a flexible smart inhaler nozzle AU - Furst, S. J. AU - Hangekar, R. AU - Seelecke, S. AB - Many “smart materials” have the capacity to be used simultaneously as both an actuator and sensor. For example, SMA actuator wires can be heated by Joule heating to induce contraction; at the same time, the resistance across the SMA wire can be measured to give the user some indication of the strain in the wire. This multi-functional capability enables the design of applications requiring extremely light-weight and streamlined embedded sensors and actuators. One such “smart structure” application is the flexible nozzle used in the Smart Inhaler system under development at North Carolina State University. The Smart Inhaler allows a doctor to control the locations within the pulmonary system that are medicated by controlling the location at which medication is injected into an inhaled airflow. This can reduce the amount of healthy tissue that is exposed to potentially toxic medications, such as those used to treat lung cancer. However, the practical challenge of injecting medication into a flow without disturbing the flow requires a highly controllable yet non-obstructive nozzle. This paper presents a scheme that correlates the resistance measurement across an SMA actuator wire to the wire strain and the resulting deformation of the flexible nozzle. The relationship between resistance and nozzle deformation is nonlinear and hysteretic; however, the repeatability of the relationship allows the user to calibrate the feedback measurement. This enables the wire to be used as both position sensor and positioning actuator. The results represent the first experiments that exploit the multi-functional capabilities of SMA wires in the context of a practical embedded sensor and actuator application. C2 - 2010/// C3 - Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, 2010, vol 2 DA - 2010/// DO - 10.1115/smasis2010-3840 SP - 205-213 ER - TY - CONF TI - Electro-mechanical analysis of a deap actuator coupled to a negative-rate bias spring mechanism AU - Hodgins, M. AU - York, A. AU - Seelecke, S. AB - This paper presents the design and analysis of a Negative-rate Bias Spring (NBS) paired with a Dielectric Electro-Active Polymer (DEAP). A NBS is a bi-stable mechanism with a negative slope region between its two stable configurations. The objective of this work is to demonstrate the increased stroke output of a DEAP actuator when biased by such a bistable mechanism. Possible devices that could use this actuation technology are lightweight, miniature pumps and valves. First, the NBS is mechanically tested and its bi-stable behavior is observed along with the negative slope region between the stable configurations. Then the NBS is coupled with a circular DEAP actuator (to provide the bias force) and is experimentally tested under a variety of loading conditions with a focus on the force and stroke capabilities. The stroke output of the device was approximately 1mm for a range of electrical loading rates (0.1Hz, 1Hz, and 10Hz). The measured force and stroke are then correlated to the force vs. displacement data observed during the mechanical characterization experiments. Additionally, the force vs. displacement behavior of the NBS-DEAP is analytically modeled and showed good comparison with the results. C2 - 2010/// C3 - Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, 2010, vol. 1 DA - 2010/// DO - 10.1115/smasis2010-3849 SP - 315-322 ER - TY - CONF TI - Development of a 6-channel power controller for simultaneous actuation and resistance measurement of SMA wires AU - Hangekar, R. AU - Furst, S. AU - Seelecke, S. AB - The use of ‘multifunctional’ Shape Memory Alloy wires as embedded actuators and sensors has been proposed for numerous novel applications. The SMA wires are actuated as a result of the Joule heating induced by passing electric current through it. The resistance of the SMA wire can simultaneously be measured during its actuation enabling it to be used as sensor data that relates to the strain and temperature of the wire. In order to control actuation stroke from the SMA wire, the Joule heating (electric power supplied to the SMA wire) of the wire needs to be controlled. Therefore, a 6-channel power controller device has been developed that simultaneously controls the power supplied to six different SMA wires and measures the resistance of these wires during excitation. This paper continues from the previously presented concept of a multi-channel power controller implementation. The focus of this paper is to discuss the operation, calibration methods and optimization techniques to improve the performance and robustness of the device and to eliminate the issues in multi-channel implementation. Further, this device is implemented in a test setup to study the position control of SMA wire using resistance feedback. Results of these tests can be utilized in practical applications involving SMA wires as embedded actuators and sensors, such as Smart Inhaler system being developed at North Carolina State University. C2 - 2010/// C3 - Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, 2010, vol 2 DA - 2010/// DO - 10.1115/smasis2010-3846 SP - 461-470 ER - TY - CONF TI - Analysis of fiber Bragg grating spectral features for in-situ assessment of sandwich composites AU - Hackney, D. AU - Webb, S. AU - Peters, Kara AB - In this paper we summarize recent advances derived from full-spectral interrogation of FBG sensors for structural health monitoring and damage identification in composites. Previous work has correlated signals from FBG reflected spectra to stress concentrations near crack tips, curing conditions during processing of composite laminates and the progression of delamination due to multiple low-velocity impacts in woven composite laminates. In this paper we investigate the information gained from FBG sensors embedded at the facesheet-core interface in foam-core sandwich composites subjected to low-velocity impact loading. We also discuss recent advances in interrogation systems for these sensors which will permit dynamic evaluation of these parameters. These results demonstrate the richness of information that can be obtained from full-spectral interrogation of FBG sensors in a complex, multiple stress component environment. C2 - 2010/// C3 - Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, 2010, vol 2 DA - 2010/// DO - 10.1115/smasis2010-3886 SP - 813–820 ER - TY - BOOK TI - Turbulent combustion modeling: Advances, new trends and perspectives A3 - Echekki, T. DA - 2010/// PY - 2010/// PB - Berlin: Springer Verlag SN - 9789400704114 ER - TY - JOUR TI - The onset of nanofluid bioconvection in a suspension containing both nanoparticles and gyrotactic microorganisms AU - Kuznetsov, A. V. T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - The purpose of this paper is to study the onset of bioconvection in a horizontal layer filled with a nanofluid that also contains gyrotactic microorganisms. The idea is to use microorganisms to induce or enhance convection in a nanofluid. A linear instability analysis is used to solve this problem. A Galerkin method is utilized to obtain an analytical solution for the critical Rayleigh number for the non-oscillatory situation. As in the case of a regular nanofluid (without the microorganisms), the presence of nanoparticles can either reduce or increase the value of the critical Rayleigh number, depending on whether the basic nanoparticle distribution is top-heavy or bottom-heavy. In contrast, the effect of gyrotactic microorganisms is always destabilizing. DA - 2010/12// PY - 2010/12// DO - 10.1016/j.icheatmasstransfer.2010.08.015 VL - 37 IS - 10 SP - 1421-1425 SN - 1879-0178 KW - Nanofluid bioconvection KW - Gyrotactic microorganisms KW - Brownian motion KW - Thermophoresis KW - Natural convection KW - Horizontal layer ER - TY - JOUR TI - The Onset of Double-Diffusive Nanofluid Convection in a Layer of a Saturated Porous Medium AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - TRANSPORT IN POROUS MEDIA DA - 2010/12// PY - 2010/12// DO - 10.1007/s11242-010-9600-1 VL - 85 IS - 3 SP - 941-951 SN - 0169-3913 KW - Nanofluid convection KW - Porous media KW - Brownian motion KW - Thermophoresis KW - Natural convection KW - Horizontal layer ER - TY - JOUR TI - The Onset of Convection in a Heterogeneous Porous Medium with Transient Temperature Profile AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - TRANSPORT IN POROUS MEDIA DA - 2010/12// PY - 2010/12// DO - 10.1007/s11242-010-9586-8 VL - 85 IS - 3 SP - 691-702 SN - 1573-1634 KW - Permeability heterogeneity KW - Transient heating KW - Thermal instability KW - Horizontal layer ER - TY - JOUR TI - Deformation and failure of single-packets in martensitic steels AU - Hatem, T.M. AU - Zikry, M.A. T2 - Computers, Materials and Continua DA - 2010/// PY - 2010/// VL - 17 IS - 2 SP - 127-147 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78349278902&partnerID=MN8TOARS ER - TY - JOUR TI - Bending Properties of Al-Steel and Steel-Steel Composite Metal Foams AU - Brown, Judith A. AU - Vendra, Lakshmi J. AU - Rabiei, Afsaneh T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE DA - 2010/11// PY - 2010/11// DO - 10.1007/s11661-010-0343-y VL - 41A IS - 11 SP - 2784-2793 SN - 1543-1940 ER - TY - JOUR TI - Autonomous Soaring: The Montague Cross-Country Challenge AU - Edwards, Daniel J. AU - Silverberg, Larry M. T2 - JOURNAL OF AIRCRAFT AB - A novel method was developed for locating and allowing gliders to stay in thermals (convective updrafts). The method was applied to a 5 kg, glider, called ALOFT (autonomous locator of thermals), that was entered in the 2008 Montague Cross-Country Challenge held on 13-15 June 2008 in Montague, California. In this competition, remote-controlled gliders in the 5 kg class competed on the basis of speed and distance. ALOFT was the first known autonomously soaring aircraft to enter a soaring competition and its entry provided a valuable comparison between the effectiveness of manual soaring and autonomous soaring. ALOFT placed third in the competition in overall points, outperforming manually-flown aircraft in its ability to center and use updrafts, especially at higher altitudes and in the presence of wind, to fly more optimal airspeeds, and to fly directly between turn points. The results confirm that autonomous soaring is a bona fide engineering subdiscipline, which is expected to be of interest to engineers, who might find that this has some utility in the aviation industry. DA - 2010/// PY - 2010/// DO - 10.2514/1.c000287 VL - 47 IS - 5 SP - 1763-1769 SN - 1533-3868 ER - TY - JOUR TI - An intermetallic Fe-Zr catalyst used for growing long carbon nanotube arrays AU - Zhao, Haibo AU - Bradford, Philip D. AU - Wang, Xin AU - Liu, Wei AU - Luo, Tzy Jiun Mark AU - Jia, Quanxi AU - Zhu, Yuntian AU - Yuan, Fuh-Gwo T2 - MATERIALS LETTERS AB - Metallic nanoparticles containing single and binary components have been known for their catalytic properties to grow carbon nanotube (CNT) arrays. In this paper, an intermetallic catalyst consisting of iron and zirconium was used to grow millimeter long, well aligned arrays. The Fe–Zr catalysts enabled the growth of 1.7 mm-long carbon nanotube arrays in 45 min. A comparison with pure iron catalyst indicated that adding Zr to iron can stabilize the Fe catalyst at the CNT growth temperature and moderate its reactivity. SEM images showed the different growth behaviors for Fe–Zr and Fe catalysts. The long, uniform CNT arrays grown here have potential applications in many advanced composites. DA - 2010/9/30/ PY - 2010/9/30/ DO - 10.1016/j.matlet.2010.05.045 VL - 64 IS - 18 SP - 1947-1950 SN - 1873-4979 KW - Carbon nanotube KW - Chemical vapor deposition KW - Fe-Zr ER - TY - JOUR TI - Recent developments and the future of bone mimicking: materials for use in biomedical implants AU - Rabiei, Afsaneh T2 - EXPERT REVIEW OF MEDICAL DEVICES AB - Keywords:: cobalt–chromium alloyscomposite metal foamimplantable materialsmodulus of elasticitystainless steelstiffnessstress shieldingtitanium alloys DA - 2010/11// PY - 2010/11// DO - 10.1586/erd.10.51 VL - 7 IS - 6 SP - 727-729 SN - 1743-4440 KW - cobalt-chromium alloys KW - composite metal foam KW - implantable materials KW - modulus of elasticity KW - stainless steel KW - stiffness KW - stress shielding KW - titanium alloys ER - TY - JOUR TI - Modeling piezoelectric actuators with Hysteretic Recurrent Neural Networks AU - Lien, J. P. AU - York, Alexander AU - Fang, Tiegang AU - Buckner, Gregory D. T2 - SENSORS AND ACTUATORS A-PHYSICAL AB - This paper describes the application of Hysteretic Recurrent Neural Networks (HRNNs) to the modeling of polycrystalline piezoelectric actuators. Because piezoelectric materials exhibit voltage/strain relationships that are hysteretic and rate-dependent, the HRNN is composed of neurons with activation functions that incorporate these characteristics. Individual neurons are shown to agree with existing models of ideal single-crystal piezoelectric behavior. The combination of many such neurons into a network allows prediction of the heterogeneous behavior of polycrystalline materials. This model is shown to approximate the strain and polarization of an unloaded commercial stack actuator at multiple loading rates. A comparison is made to a recurrent Radial Basis Function Network model, and the HRNN is demonstrated to more accurately generalize across data sets. The model is further shown to execute on a PC platform at rates over 100 Hz, fast enough to support its application to real-time control. DA - 2010/10// PY - 2010/10// DO - 10.1016/j.sna.2010.08.013 VL - 163 IS - 2 SP - 516-525 SN - 0924-4247 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78049473465&partnerID=MN8TOARS KW - Piezoelectric KW - Ferroelectric KW - Neural Network KW - Hysteresis KW - Actuator ER - TY - JOUR TI - Flame synthesis of hybrid nanowires with carbon shells and tungsten-oxide cores AU - Merchan-Merchan, Wilson AU - Saveliev, Alexei V. AU - Jimenez, Walmy Cuello AU - Salkar, Gautam T2 - CARBON AB - We report the flame synthesis of hybrid nanowires composed of tungsten-oxide cores covered with uniform carbon shells. The synthesis is performed using 1-mm diameter tungsten probes inserted in an opposed-flow methane oxy-flame. The unique thermal and chemical composition of the generated flame tends to convert pure (99.9%) bulk tungsten into 1-D structures of unique morphology. The physical characteristics of the nanowires grown on the 1-mm diameter tungsten probe include lengths of up to 50 μm and diameters ranging from 20 to 50 nm. A two step hybrid nanowire synthesis mechanism is proposed. The initial step forms tungsten-oxide nanorods in the oxygen-rich flame region. The second step involves rapid formation of carbon shells from hydrocarbons transferred from the carbon-rich zone of the flame during the probe removal. DA - 2010/12// PY - 2010/12// DO - 10.1016/j.carbon.2010.08.028 VL - 48 IS - 15 SP - 4510-4518 SN - 1873-3891 ER - TY - JOUR TI - Transient infrared thermography for damage evaluation in aerospace composites AU - Pawar, S. AU - Peters, K. T2 - NONDESTRUCTIVE CHARACTERIZATION FOR COMPOSITE MATERIALS, AEROSPACE ENGINEERING, CIVIL INFRASTRUCTURE, AND HOMELAND SECURITY 2010 AB - In this paper we investigate the performance of defect detection using long duration transient thermography for woven composite laminates subjected to low-velocity impacts. Two types of defects are studied: inclusions represented by foam tabs inserted into the laminate during fabrication and barely visible impact damage due to low-velocity impacts. These defects represent the expected damage states that are necessary for inspection during the service life of a woven composite aircraft component. The long duration transient thermography is demonstrated to successfully detect the embedded inclusions, with a dimension to depth ratio detection capability of approximately 3. It is also demonstrated that the detection of low velocity impact damage with the transient thermography is less successful due to uneven emissivity of the surface. Therefore, processing of the image using a self referencing algorithm is performed which improves the damage detection clarity. DA - 2010/// PY - 2010/// DO - 10.1117/12.847789 VL - 7649 SP - SN - 0277-786X KW - barely visible impact damage KW - infrared thermography KW - composite laminate ER - TY - JOUR TI - The Role of Embedded Sensors in Damage Assessment of Composite Laminates AU - Park, Chun AU - Peters, Kara AU - Zikry, Mohammed T2 - SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS 2010 AB - Various densities of optical fibers are embedded into a total of eighty woven, graphite fiber-epoxy composite laminates, for which the response to low velocity impacts are evaluated. The goal of this work is to determine the role of hostsensor interaction on the lifetime of the host material system. The woven composites are subjected to multiple impacts at 14.5 J until perforation of the specimen. We obtain the energy dissipated by the laminate and the maximum contact force between the impactor laminate for each strike. From these experimental data we calculate the statistical distribution of the total energy dissipated at failure as a function of embedded optical fiber density. The total dissipated energy, a measure of the specimen lifetime, decreased with increasing embedded optical fiber density, however remained constant after a threshold density was reached. The total maximum contact force per specimen, a measure of the specimen stiffness, continued to decrease with the number of embedded optical fibers. DA - 2010/// PY - 2010/// DO - 10.1117/12.847634 VL - 7648 SP - SN - 0277-786X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77953489216&partnerID=MN8TOARS KW - Woven composite KW - embedded optical fiber sensor network KW - low velocity impact ER - TY - JOUR TI - Self-repairing polymer optical fiber sensor AU - Song, Young J. AU - Peters, Kara J. T2 - SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS 2010 AB - This article presents experimental demonstrations of a self-writing waveguide in a photopolymerizable resin system. The waveguide will be embedded in a structure and serve as a self-repairing strain sensor. The sensor would fabricate via lightwaves in the ultraviolet (UV) wavelength range and operate as a sensor in the infrared (IR) wavelength range. Optimized self-written waveguides are obtained by varying the input UV laser power and testing the repeatability of the waveguide fabrication between two optical fibers. An IR laser output is then transmitted between two MM fibers during the fabrication process to quantify the response of the self-repaired optical sensor by measuring the transmitted IR power. The IR power is successfully transmitted through a self-written waveguide; however problems with optical fiber alignment and bending of the waveguide can induce loss of IR transmission. DA - 2010/// PY - 2010/// DO - 10.1117/12.847631 VL - 7648 SP - SN - 1996-756X KW - Self-writing KW - polymer waveguides KW - optical fiber sensor ER - TY - CONF TI - Mechanical behavior of a bi-stable negative-rate bias spring system AU - Hodgins, M. AU - Seelecke, S. C2 - 2010/// C3 - Behavior and mechanics of multifunctional materials and composites 2010 DA - 2010/// VL - 7644 ER - TY - JOUR TI - Impact induced damage assessment in composite laminates through embedded fiber Bragg gratings AU - Webb, S. AU - Peters, K. AU - Zikry, M. A. AU - Vella, T. AU - Chadderdon, S. AU - Selfridge, R. AU - Schultz, S. T2 - SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS 2010 AB - In this study we evaluate the measurements of fiber Bragg sensor spectra from a sensor embedded in a composite laminate subjected to multiple low velocity impacts. The full-spectral response of the sensor is interrogated in reflection at 100 kHz during the impact events. The measurement of the time dependent spectra features are compared with previous results obtained at a 534 Hz interrogation rate. With the increased interrogation rate, we can observe a smooth transition in the full-spectra response of the sensor between strikes and the presence of peak-splitting due to transverse compression from the beginning of the laminate lifetime. Finally, at the 100 kHz acquisition rate, it is possible to determine the maximum wavelength and accurately determine the duration of the impact event for all of the strikes. DA - 2010/// PY - 2010/// DO - 10.1117/12.847543 VL - 7648 SP - SN - 1996-756X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77953525959&partnerID=MN8TOARS KW - fiber Bragg grating sensor KW - full-spectral interrogation KW - impact testing KW - composite laminate KW - damage identification ER - TY - JOUR TI - Fabrication and Characterization of High Frequency Phased Arrays for NDE Imaging AU - Jiang, Xiaoning AU - Snook, Kevin AU - Liu, Ruibin AU - Geng, Xuecang AU - Hackenberger, Wesley S. T2 - NONDESTRUCTIVE CHARACTERIZATION FOR COMPOSITE MATERIALS, AEROSPACE ENGINEERING, CIVIL INFRASTRUCTURE, AND HOMELAND SECURITY 2010 AB - PMN-PT single crystal 1-3 composite high frequency phased arrays with center frequency of 35 MHz were fabricated and characterized for silicon carbide (SiC) NDE imaging applications. The 35 MHz 64-element array was successfully prototyped using PMN-PT single crystal and PC-MUT technology. The broad bandwidth > 90% and high sensitivity (echo amplitude > 500 mV from the impulse response with 0 gain) was observed with reasonably high uniformity. These high frequency phased arrays are promising for ceramic NDE imaging. DA - 2010/// PY - 2010/// DO - 10.1117/12.847624 VL - 7649 SP - SN - 1996-756X KW - single crystal piezoelectrics KW - high frequency ultrasound KW - NDE KW - NDT KW - PC-MUT KW - phased array ER - TY - JOUR TI - Embedded fiber Bragg sensors for damage identification in sandwich composites after impact AU - Hackney, Drew A. AU - Peters, Kara J. T2 - SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS 2010 AB - The use and viability of fiber Bragg grating sensors in sandwich composite structures for the purpose of structural health monitoring under low velocity impact. Initially, a group of twelve specimens were tested to characterize the impact response of sandwich composite structures. Each specimen test consisted of repeated impacts at a constant impact energy to measure and observe damage progression. Once this was completed, a single optical fiber with a fiber Bragg grating was embedded in the structure between the core and the faceplate to and measured using a laser. The shift and deformation of the reflected spectrum from the fiber Bragg grating sensor resulting from each strike was analyzed and the corresponding strain was measured. The peak wavelength shift measurements did not have a strong correlation to the accumulation of damage in the sandwich laminate. However, the spectral distortion did evolve throughout the initial accumulation of damage in the laminate. Further analysis of the spectrum is needed to correlate the spectral response to the damage modes. DA - 2010/// PY - 2010/// DO - 10.1117/12.848351 VL - 7648 SP - SN - 1996-756X KW - Fiber Bragg Grating KW - Sandwich Composite KW - Low Velocity Impact KW - Non-Destructive Evaluation KW - Structural Health Monitoring ER - TY - JOUR TI - Development, Assembly, and Validation of an SMA-Actuated 2-Joint Nozzle and 6-Channel Power Supply for Use in a Smart Inhaler System AU - Furst, Stephen J. AU - Hangekar, Rohan AU - Seelecke, Stefan T2 - ACTIVE AND PASSIVE SMART STRUCTURES AND INTEGRATED SYSTEMS 2010, PTS 1 AND 2 AB - The Smart Inhaler design concept recently developed at NC State University has the potential to target the delivery of inhaled aerosol medication to specified locations within the lung system. This targeted delivery could help patients with pulmonary ailments by reducing the exposure of healthy lung tissue to potentially harmful medications. However, controlled delivery can only be accomplished if medication is injected at a precise location in an inhaled stream of properly conditioned laminar flow. In particular, the medication must be injected into the inhaled flow using a small nozzle that can be positioned without disturbing the flow. This paper outlines the procedure used to assemble and control a key component of the smart inhaler: a shape memory alloy (SMA) based dual-joint flexible nozzle that exploits the sensing and actuating capabilities of thermally activated SMA wires. A novel 6-channel power-supply is used to control input power and measure the resistance across the SMA. Since a practical fabrication process may result in SMA wires with different contact resistances, the power supply employs an initialization procedure to self-calibrate and provide normalized power distribution 6 SMA wires simultaneously. Furthermore, a robust control scheme is used to ensure that a constant current is provided to the wires. In validation tests, a LabVIEW-based video positioning system was used to measure the deflection of the nozzle tip and joint rotation. Results show that the carefully controlled assembly of a stream-lined nozzle can produce a practical smart structure, and joint rotation is predictable and repeatable when power input is also controlled. Future work will assess the use of the SMA-resistance measurement as position feedback and PID position control power as a measurement of the convective cooling that results from the moving airflow. DA - 2010/// PY - 2010/// DO - 10.1117/12.853399 VL - 7643 SP - SN - 0277-786X ER - TY - JOUR TI - A new family of unsteady boundary layers over a stretching surface AU - Fang, Tiegang AU - Zhang, Ji AU - Yao, Shanshan T2 - APPLIED MATHEMATICS AND COMPUTATION AB - In this paper, a new family of unsteady boundary layers over a stretching flat surface was proposed and studied. This new class of unsteady boundary layers involves the flows over a constant speed stretching surface from a slot, and the slot is moving at a certain speed. Depending on the slot moving parameter, the flow can be treated as a stretching sheet problem or a shrinking sheet problem. Both the momentum and thermal boundary layers were studied. Under special conditions, the solutions reduce to the unsteady Rayleigh problem and the steady Sakiadis stretching sheet problem. Solutions only exist for a certain range of the slot moving parameter, α. Two solutions are found for −53.55° < α < −45°. There are also two solution branches for the thermal boundary layers at any given Prandtl number in this range. Compared with the upper solution branch, the lower solution branch leads to simultaneous reduction in wall drag and heat transfer rate. The results also show that the motion of the slot greatly affects the wall drag and heat transfer characteristics near the wall and the temperature and velocity distributions in the fluids. DA - 2010/12/15/ PY - 2010/12/15/ DO - 10.1016/j.amc.2010.09.031 VL - 217 IS - 8 SP - 3747-3755 SN - 1873-5649 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650034159&partnerID=MN8TOARS KW - Similarity solution KW - Unsteady boundary layer KW - Stretching surface KW - Shrinking surface ER - TY - JOUR TI - Viscous Flow with Second-Order Slip Velocity over a Stretching Sheet AU - Fang, Tiegang AU - Aziz, Abdul T2 - ZEITSCHRIFT FUR NATURFORSCHUNG SECTION A-A JOURNAL OF PHYSICAL SCIENCES AB - In this paper, viscous flow with a second-order slip condition over a permeable stretching surface is solved analytically. The current work differs from the previous studies in the application of a new second-order slip velocity model. The closed form solution reported is an exact solution of the full governing Navier-Stokes equations. The effects of slip and mass transfer parameters are discussed. DA - 2010/12// PY - 2010/12// DO - 10.1515/zna-2010-1212 VL - 65 IS - 12 SP - 1087-1092 SN - 1865-7109 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78649829745&partnerID=MN8TOARS KW - Similarity Solution KW - Stretching Surface KW - Navier-Stokes Equations KW - Analytical Solution KW - Exact Solution KW - Slip Flow ER - TY - JOUR TI - The Effects of Embedded Optical Fiber Density on the Impact Response and Lifetime of Laminated Composites AU - Park, Chun AU - Peters, Kara AU - Zikry, Mohammed T2 - JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES AB - Graphite fiber/epoxy, two-dimensional woven composite laminates were fabricated with various densities of embedded optical fibers at the midplane. The specimens were subjected to multiple low-velocity impacts until failure, as the energy dissipated by the laminate and the maximum contact force were measured for each impact event. Cumulative probability distributions were calculated for each embedded optical fiber density, from which probability distribution functions in terms of embedded optical fiber density were extrapolated. At low fiber densities, the total energy dissipated by the specimen and the total maximum contact force over the lifetime of the specimen decreased rapidly with increasing optical fiber density. After a threshold embedded optical fiber density, the optical fibers dominated the failure mode of the laminate and the laminate lifetime, and the overall stiffness was not affected by the embedded optical fiber density. The obtained probability distribution functions could be applied for future optimization of embedded sensor placement for smart composite structures. DA - 2010/12// PY - 2010/12// DO - 10.1177/1045389x10390250 VL - 21 IS - 18 SP - 1819-1829 SN - 1530-8138 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650907528&partnerID=MN8TOARS KW - composite laminates KW - embedded sensors KW - structural health monitoring ER - TY - JOUR TI - Slip Magnetohydrodynamic Viscous Flow over a Permeable Shrinking Sheet AU - Tie-Gang, Fang AU - Ji, Zhang AU - Shan-Shan, Yao T2 - CHINESE PHYSICS LETTERS AB - The magnetohydrodynamic (MHD) flow under slip conditions over a shrinking sheet is solved analytically. The solution is given in a closed form equation and is an exact solution of the full governing Navier-Stokes equations. Interesting solution behavior is observed with multiple solution branches for certain parameter domain. The effects of the mass transfer, slip, and magnetic parameters are discussed. DA - 2010/12// PY - 2010/12// DO - 10.1088/0256-307x/27/12/124702 VL - 27 IS - 12 SP - SN - 0256-307X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78651086198&partnerID=MN8TOARS ER - TY - JOUR TI - FLOW ADJACENT TO A FLAT PLATE IN A DARCY-BRINKMAN POROUS MEDIUM OSCILLATING WITH ARBITRARY PERIODIC OSCILLATION AU - Pantokratoras, Asterios AU - Fang, Tiegang T2 - JOURNAL OF POROUS MEDIA AB - In this note, an exact solution is presented for the flow produced by a plate oscillating with arbitrary periodic oscillation in a porous medium. The velocity field is composed of a steady state part and a transient part. It is found that the flow depends on the permeability parameter. The velocity profiles and the wave penetration depth are damped in the transverse direction due to the existence of the porous medium. The influence of the porous medium on the oscillation increases with the increase of the permeability parameter. DA - 2010/// PY - 2010/// DO - 10.1615/jpormedia.v13.i8.70 VL - 13 IS - 8 SP - 759-763 SN - 1091-028X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77958600460&partnerID=MN8TOARS KW - oscillating plate KW - porous medium KW - Stokes' problem ER - TY - JOUR TI - Efficiency of electrostatic air moving devices AU - June, Michael S. AU - Kribs, James AU - Lyons, Kevin M. T2 - JOURNAL OF ELECTROSTATICS AB - An ion-driven gas flow is characterized by the breakdown of a gas into ions in the presence of a high electric potential. Ions flow due to the potential gradient. Mass transfer motivates bulk airflow. In the current study, an ionic air moving device was constructed using needles as ion sources, and a ring as collector. Airflow and efficiency were evaluated at various ring widths and with various numbers of ionization sites. Efficiency was seen to increase with ring width if airflow and distance was held constant and also increased with the number of ionization sites when airflow was held constant. DA - 2010/10// PY - 2010/10// DO - 10.1016/j.elstat.2010.06.001 VL - 68 IS - 5 SP - 419-423 SN - 0304-3886 KW - Ion-driven gas flow KW - Air moving device KW - Efficiency KW - P-Q curve KW - Flow bench KW - Corona discharge ER - TY - JOUR TI - Capillary-pressure driven adhesion of rigid-planar surfaces AU - Ward, T. T2 - Journal of Colloid and Interface Science DA - 2010/// PY - 2010/// VL - 354 IS - 2 SP - 816-824 ER - TY - JOUR TI - A novel approach to fabricate high volume fraction nanocomposites with long aligned carbon nanotubes AU - Bradford, Philip D. AU - Wang, Xin AU - Zhao, Haibo AU - Maria, Jon-Paul AU - Jia, Quanxi AU - Zhu, Y. T. T2 - COMPOSITES SCIENCE AND TECHNOLOGY AB - Conventional micro-fiber-reinforced composites provide insight into critical structural features needed for obtaining maximum composite strength and stiffness: the reinforcements should be long, well aligned in a unidirectional orientation, and should have a high reinforcement volume fraction. It has long been a challenge for researchers to process CNT composites with such structural features. Here we report a method to quickly produce macroscopic CNT composites with a high volume fraction of millimeter long, well aligned CNTs. Specifically, we use the novel method, shear pressing, to process tall, vertically aligned CNT arrays into dense aligned CNT preforms, which are subsequently processed into composites. Alignment was confirmed through SEM analysis while a CNT volume fraction in the composites was calculated to be 27%, based on thermogravimetric analysis data. Tensile testing of the preforms and composites showed promising mechanical properties with tensile strengths reaching 400 MPa. DA - 2010/11/15/ PY - 2010/11/15/ DO - 10.1016/j.compscitech.2010.07.020 VL - 70 IS - 13 SP - 1980-1985 SN - 1879-1050 KW - Carbon nanotubes KW - Nanocomposites KW - Polymer-matrix composites (PMCs) KW - Electrical properties KW - Mechanical properties ER - TY - JOUR TI - Uncertainty Reduction of Damage Growth Properties Using Structural Health Monitoring AU - Coppe, Alexandra AU - Haftka, Raphael T. AU - Kim, Nam H. AU - Yuan, Fuh-Gwo T2 - JOURNAL OF AIRCRAFT AB - Structural health monitoring provides sensor data that can monitor fatigue-induced damage in service. This information may in turn be used to improve the characterization of material properties that govern damage growth for the structure beingmonitored. These properties are oftenwidely distributed amongnominally identicalmaterials because of differences in manufacturing processes and due to aging effects. Improved accuracy in damage growth characteristics would allowmore accurate prediction of the remaining useful life of the structural component. In this paper, a probabilistic approach using Bayesian inference is employed to progressively reduce the uncertainty in structure-specific damage growth parameters in spite of noise and bias in sensor measurements. Starting from an initial wide distribution of damage growth parameters that are obtained from coupon tests, the distribution is progressively narrowed using damage growth data between consecutivemeasurements. Detailed discussions on how to construct the likelihood function under the given noise of sensor data and how to update the distribution are presented. The approach is applied to simulated damage growth in fuselage panels due to cycles of pressurization. It is shown that the proposed method rapidly converges to the accurate damage growth parameters when the initial damage size is relatively large: e.g., 20 mm. Fairly accurate damage growth parameters are obtained even with measurement errors of 5mm. Using the identified damage growth parameters, it is shown that the 95% conservative remaining useful life converges to the true remaining useful life from the conservative side. The proposed approach may have the potential of turning aircraft into flying fatigue laboratories. DA - 2010/// PY - 2010/// DO - 10.2514/1.c000279 VL - 47 IS - 6 SP - 2030-2038 SN - 1533-3868 ER - TY - JOUR TI - The onset of convection in a horizontal nanofluid layer of finite depth AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - EUROPEAN JOURNAL OF MECHANICS B-FLUIDS AB - This paper presents a linear stability analysis for the onset of natural convection in a horizontal nanofluid layer. The employed model incorporates the effects of Brownian motion and thermophoresis. Both monotonic and oscillatory convection for free–free, rigid–rigid, and rigid–free boundaries are investigated. The oscillatory instability is possible when nanoparticles concentrate near the bottom of the layer, so that the density gradient caused by such a bottom-heavy nanoparticle distribution competes with the density variation caused by heating from the bottom. It is established that the instability is almost purely a phenomenon due to buoyancy coupled with the conservation of nanoparticles. It is independent of the contributions of Brownian motion and thermophoresis to the thermal energy equation. Rather, the Brownian motion and thermophoresis enter to produce their effects directly into the equation expressing the conservation of nanoparticles so that the temperature and the particle density are coupled in a particular way, and that results in the thermal and concentration buoyancy effects being coupled in the same way. DA - 2010/// PY - 2010/// DO - 10.1016/j.euromechflu.2010.02.003 VL - 29 IS - 3 SP - 217-223 SN - 1873-7390 KW - Nanofluid KW - Brownian motion KW - Thermophoresis KW - Natural convection KW - Horizontal layer ER - TY - JOUR TI - The Onset of Convection in a Layer of Cellular Porous Material: Effect of Temperature-Dependent Conductivity Arising From Radiative Transfer AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - The onset of convection in a horizontal layer of a cellular porous material heated from below is investigated. The problem is formulated as a combined conductive-convective-radiative problem in which radiative heat transfer is treated as a diffusion process. The problem is relevant to cellular foams formed from plastics, ceramics, and metals. It is shown that the variation of conductivity with temperature above that of the cold boundary leads to an increase in the critical Rayleigh number (based on the conductivity of the fluid at that boundary temperature) and an increase in the critical wave number. On the other hand, the critical Rayleigh number based on the conductivity at the mean temperature decreases with increase in the thermal variation parameter if the radiative contribution to the effective conductivity is sufficiently large compared with the nonradiative component. DA - 2010/7// PY - 2010/7// DO - 10.1115/1.4001125 VL - 132 IS - 7 SP - SN - 0022-1481 KW - cellular porous medium KW - radiative heat transfer KW - temperature-dependent conductivity KW - onset of convection KW - Horton-Rogers-Lapwood problem ER - TY - JOUR TI - Preform design for forging and extrusion processes based on geometrical resemblance AU - Yang, C. AU - Ngaile, G. T2 - PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART B-JOURNAL OF ENGINEERING MANUFACTURE AB - Preform design in multi-stage forging processes is critical to ensure the production of defect-free parts. Moreover, owing to the geometry and material-flow complexities in forging processes, finding the optimal preform shapes could be difficult and time consuming. This paper proposes an efficient preform design methodology based on geometrical resemblance, which requires several finite element analysis simulation iterations to obtain a good preform shape. The initial and subsequent simulations are carried out by constructing a slightly larger part that geometrically resembles the desired part. Initial finite element analysis simulation of the larger part is performed with a reasonably guessed preform shape, whose forming defects or flash formation would be corrected in subsequent steps. Then a series of intermediate parts of similar shape and between the largest part and the desired part in size are constructed. The undeformed shape corresponding to an intermediate part can be obtained by backwards tracing of material flow from the simulation results of the larger part. This undeformed shape is then taken as the preform shape of the intermediate part. The procedure is repeated until the intermediate part is geometrically close to the desired part, which leads to the preform shape. In order to verify this preform-design methodology, several case studies on forging and extrusion processes have been carried out. The methodology has been shown to be computationally efficient, requiring as few as three finite element iterations to obtain a good preform shape. DA - 2010/// PY - 2010/// DO - 10.1243/09544054jem1799 VL - 224 IS - B9 SP - 1409-1423 SN - 2041-2975 KW - preform design KW - forging KW - finite element simulation ER - TY - JOUR TI - MODELING TRAFFIC JAMS IN SLOW AXONAL TRANSPORT AU - Kuznetsov, A. V. AU - Avramenko, A. A. AU - Blinov, D. G. T2 - JOURNAL OF MECHANICS IN MEDICINE AND BIOLOGY AB - The purpose of this paper is to develop a model capable of simulating traffic jams in slow axonal transport. Slowing of slow axonal transport is an early sign of some neurodegenerative diseases. Axonal swellings observed near the end stage of such diseases may be an indication of traffic jams developing in axons that cause the slowing down of slow axonal transport. Traffic jams may result from misregulation of microtubule-associated proteins caused by an imbalance in intracellular signaling or by mutations of these proteins. This misregulation leads to a decay of microtubule tracks in axons, effectively reducing the number of "railway tracks" available for molecular-motor-assisted transport of intracellular organelles. In this paper, the decay of microtubule tracks is modeled by a reduction of the number density of microtubules in the central part of the axon. Simulation results indicate that the model predicts the build-up of the bell-shaped concentration wave, as the wave approaches the bottleneck (blockage) region. This increase in concentration will likely plug the bottleneck region resulting in a traffic jam that would hinder the slow axonal transport. DA - 2010/9// PY - 2010/9// DO - 10.1142/s0219519410003502 VL - 10 IS - 3 SP - 445-465 SN - 1793-6810 KW - Molecular motors KW - motor-assisted transport KW - neurons KW - axons KW - slow axonal transport KW - traffic jams ER - TY - JOUR TI - Hybrid Grid Generation Method for Complex Geometries AU - Luo, Hong AU - Spiegel, Seth AU - Loehner, Rainald T2 - AIAA JOURNAL AB - A hybrid mesh generation method is described to discretize complex geometries. The idea behind this hybrid method is to combine the orthogonality and directionality of a structured grid, the efficiency and simplicity of a Cartesian grid, and the flexibility and ease of an unstructured grid in an attempt to develop an automatic, robust, and fast hybrid mesh generation method for configurations of engineering interest. A semistructured quadrilateral grid is first generated on the wetted surfaces. A background Cartesian grid, covering the domain of interest, is then constructed using a Quadtree-based Cartesian Method. Those Cartesian cells overlapping with the semistructured grids or locating outside of computational domain are then removed using an Alternating Digital Tree method. Finally, an unstructured grid generation method is used to generate unstructured triangular cells to fill all empty regions in the domain as a result of the trimming process. The automatic placement of sources at the geometrical irregularities is developed to render these regions isotropic, thus effectively overcoming the difficulty of generating highly stretched good-quality elements in these regions. The self-dividing of the exposed semistructured elements with high aspect ratio and the adaptation of the background mesh using the cell size information from the exposed semistructured elements for generating Cartesian cells are introduced to improve the quality of unstructured triangular elements and guarantee the success of the unstructured grid generation in the void regions. The developed hybrid grid generation method is used to generate a hybrid grid for a number of test cases, demonstrating its ability and robustness to mesh complex configurations. DA - 2010/11// PY - 2010/11// DO - 10.2514/1.j050491 VL - 48 IS - 11 SP - 2639-2647 SN - 0001-1452 ER - TY - JOUR TI - Effect of the degree of polar mismatching on traffic jam formation in fast axonal transport AU - Kuznetsov, A. V. T2 - COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING AB - This paper simulates an axon with a region of reversed microtubule (MT) polarity, and investigates how the degree of polar mismatching in this region affects the formation of organelle traps in the axon. The model is based on modified Smith-Simmons equations governing molecular-motor-assisted transport in neurons. It is established that the structure that develops as a result of a region with disoriented MTs consists of two organelle traps, the trap to the left of this region accumulates plus-end-oriented organelles and the trap to the right of this region accumulates minus-end-oriented organelles. The presence of such a structure is shown to inhibit the transport of organelles down the axon. The degree by which the transport of organelles is inhibited depends on the degree of polar mismatching of MTs in the region between MT traps. Four cases with a different degree of polar mismatching are investigated. DA - 2010/// PY - 2010/// DO - 10.1080/10255840903505154 VL - 13 IS - 6 SP - 711-722 SN - 1476-8259 KW - molecular motors KW - motor-assisted transport KW - neurons KW - axons and dendrites KW - intracellular organelles KW - vesicle traps ER - TY - JOUR TI - Effect of strong heterogeneity on the onset of convection in a porous medium: Importance of spatial dimensionality and geologic controls AU - Simmons, Craig T. AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - WATER RESOURCES RESEARCH AB - The effect of strong heterogeneity on the onset of convection induced by a vertical density gradient in a saturated heterogeneous porous medium governed by Darcy's law is investigated. A computer package has been developed to study the applicability of an average Rayleigh number as a criterion for the onset of convection in strongly heterogeneous geologic media. The heterogeneous geologic media have been described using random spatial functions for the permeability field which are lognormally distributed and spatially correlated. Both isotropic and anisotropic correlation lengths within the geologic structure are considered. This paper presents the first 3D theoretical treatment of the conditions for the onset of convection (Rayleigh stability criteria) in strongly heterogeneous porous media. We elucidate the critical role that spatial dimensionality (2D versus 3D flow) plays in controlling convection processes and stability criteria. Our results quantitatively demonstrate for the first time that spatial dimensionality is a dominant control on the onset of convection in a strongly heterogeneous geologic medium. Unbounded Rayleigh number behavior is observed in 3D. This leads to the important new conclusion that a Rayleigh number (based on mean quantities) is unlikely to be a valid predictor for the onset of convection in 3D strongly heterogeneous porous media. Furthermore, we systematically and quantitatively demonstrate that the onset of convection in a heterogeneous geologic medium is highly sensitive to changes in the standard deviation of the lognormal permeability field, moderately sensitive to changes in the level of correlation length, and relatively insensitive to the anisotropy of correlation length. DA - 2010/9/30/ PY - 2010/9/30/ DO - 10.1029/2009wr008606 VL - 46 SP - SN - 0043-1397 ER - TY - JOUR TI - Effect of Local Thermal Non-equilibrium on the Onset of Convection in a Porous Medium Layer Saturated by a Nanofluid AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - TRANSPORT IN POROUS MEDIA DA - 2010/6// PY - 2010/6// DO - 10.1007/s11242-009-9452-8 VL - 83 IS - 2 SP - 425-436 SN - 0169-3913 KW - Local thermal non-equilibrium KW - Nanofluid KW - Porous medium KW - Instability KW - Natural convection ER - TY - JOUR TI - Drop production and tip-streaming phenomenon in a microfluidic flow-focusing device via an interfacial chemical reaction AU - Ward, T. AU - Faivre, M. AU - Stone, H. A. T2 - Langmuir DA - 2010/// PY - 2010/// VL - 26 IS - 12 SP - 9233-9239 ER - TY - JOUR TI - Diamond tool wear when machining Al6061 and 1215 steel AU - Lane, B. M. AU - Shi, M. AU - Dow, T. A. AU - Scattergood, R. T2 - WEAR AB - Different rates of wear of diamond tools depend on the physical and chemical nature of the workpiece material. Wear mechanisms for diamond tools can be either abrasive or chemical in nature, or a combination thereof. Differentiating the affects of these wear mechanisms can be accomplished by measuring the wear geometry of the cutting edge as a function of cutting distance. Orthogonal cutting experiments using 6061 aluminum and 1215 steel were conducted to illustrate abrasive and abrasive plus chemical wear, respectively. Wear of the diamond tool was measured using the electron beam induced deposition method. This method provides nanometer resolution images of the tool edge (edge radius and wear land) that can be used to calculate volumetric wear loss and wear rates. A method for determining the Archard wear coefficient for diamond turning based on measured wear and cutting forces is also introduced. Comparisons are made between the tool wear resulting from the two materials, and hypotheses related to the wear mechanism are presented. DA - 2010/5/12/ PY - 2010/5/12/ DO - 10.1016/j.wear.2010.02.019 VL - 268 IS - 11-12 SP - 1434-1441 SN - 0043-1648 KW - Diamond tool wear KW - Flank wear KW - Edge radius KW - Wear land KW - Electron beam induced deposition ER - TY - JOUR TI - Comparison of active transport in neuronal axons and dendrites AU - Kuznetsov, A. V. T2 - MATHEMATICAL BIOSCIENCES AB - This paper presents a theoretical study, based on modified Smith–Simmons equations, that compares transport of intracellular organelles in two different neurite outgrowths, dendrites and axons. It is demonstrated that the difference in microtubule polarity orientations in dendrites and axons has significant implications on motor-assisted transport in these neurite outgrowths. The developed approach presents a qualitative theoretical basis for understanding important questions such as why axons exhibit almost an unlimited grows potential in vitro while dendrites remain relatively short. It is shown that the difference in a microtubule polarity arrangement between axons and dendrites may be a regulatory mechanism for limiting dendritic growth. Other biological implications of the developed theory as well as other possible reasons for the difference in microtubule structure between axons and dendrites are discussed. DA - 2010/12// PY - 2010/12// DO - 10.1016/j.mbs.2010.10.003 VL - 228 IS - 2 SP - 195-202 SN - 0025-5564 KW - Mathematical modeling KW - Molecular motors KW - Fast axonal transport KW - Neurons KW - Axons and dendrites KW - Intracellular organelles ER - TY - JOUR TI - A computational fluid dynamics modeling and experimental study of the mixing process for dispersion of synthetic fibers in wet-lay forming AU - Ramasubramanian, M. K. AU - Shiffler, D. A. AU - Jayachandran, A. T2 - TAPPI Journal DA - 2010/// PY - 2010/// VL - 9 IS - 3 SP - 6-13 ER - TY - JOUR TI - Robust parameter-dependent fault-tolerant control for actuator and sensor faults AU - Cai, Xuejing AU - Wu, Fen T2 - INTERNATIONAL JOURNAL OF CONTROL AB - In this article, we study a robust fault-tolerant control (FTC) problem for linear systems subject to time-varying actuator and sensor faults. The faults under consideration are loss of effectiveness in actuators and sensors. Based on the estimated faults from a fault detection and isolation scheme, robust parameter-dependent FTC will be designed to stabilise the faulty system under all possible fault scenarios. The synthesis condition of such an FTC control law will be formulated in terms of linear matrix inequalities (LMIs) and can be solved efficiently by semi-definite programming. The proposed FTC approach will be demonstrated on a simple faulty system with different fault levels and fault estimation error bounds. DA - 2010/// PY - 2010/// DO - 10.1080/00207179.2010.481024 VL - 83 IS - 7 SP - 1475-1484 SN - 1366-5820 KW - fault-tolerant control KW - actuator and sensor faults KW - gain-scheduling control KW - L-2 gain optimisation KW - LMI ER - TY - JOUR TI - Nanofluid convective heat transfer in a parallel-disk system AU - Feng, Yu AU - Kleinstreuer, Clement T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - Inherently low thermal conductivities of basic fluids form a primary limitation in high-performance cooling which is an essential requirement for numerous thermal systems and micro-devices. Nanofluids, i.e., dilute suspensions of, say, metal-oxide nanoparticles in a liquid, are a new type of coolants with better heat transfer performances than their pure base fluids alone. Using a new, experimentally validated model for the thermal conductivity of nanofluids, numerical simulations have been executed for alumina-water nanofluid flow with heat transfer between parallel disks. The results indicate that, indeed, nanofluids are promising new coolants when compared to pure water. Specifically, smoother mixture flow fields and temperature distributions can be achieved. More importantly, given a realistic thermal load, the Nusselt number increases with higher nanoparticle volume fraction, smaller nanoparticle diameter, reduced disk-spacing, and, of course, larger inlet Reynolds number, expressed in a novel form as Nu = Nu(Re and Br). Fully-developed flow can be assumed after a critical radial distance, expressed in a correlation Rcrit = fct(Re), has been reached and hence analytic solutions provide good approximations. Nanofluids reduce the system’s total entropy generation rate while hardly increasing the required pumping power for any given Rein. Specifically, minimization of total entropy generation allows for operational and geometric system-optimization in terms of Sgen = fct (Re and δ). DA - 2010/10// PY - 2010/10// DO - 10.1016/j.ijheatmasstransfer.2010.06.031 VL - 53 IS - 21-22 SP - 4619-4628 SN - 1879-2189 KW - Nanofluid KW - Convective heat transfer KW - Impinging-jet KW - Parallel disk KW - Entropy generation KW - Wall temperature control ER - TY - JOUR TI - Comparison Between Numerically Simulated and Experimentally Measured Flowfield Quantities Behind a Pulsejet AU - Geng, Tao AU - Zheng, Fei AU - Kuznetsov, Andrey V. AU - Roberts, William L. AU - Paxson, Daniel E. T2 - FLOW TURBULENCE AND COMBUSTION AB - Pulsed combustion is receiving renewed interest as a potential route to higher performance in air breathing propulsion and ground based power generation systems. Pulsejets offer a simple experimental device with which to study unsteady combustion phenomena and validate simulations. Previous computational fluid dynamics (CFD) simulations focused primarily on pulsejet combustion and exhaust processes. This paper describes a new inlet sub-model which simulates the fluidic and mechanical operation of a valved pulsejet head. The governing equations for this sub-model are described. Sub-model validation is provided through comparisons of simulated and experimentally measured reed valve motion, and time averaged inlet mass flow rate. The updated pulsejet simulation, with the inlet sub-model implemented, is validated through comparison with experimentally measured combustion chamber pressure, inlet mass flow rate, operational frequency, and thrust. Additionally, the simulated pulsejet exhaust flowfield, which is dominated by a starting vortex ring, is compared with particle imaging velocimetry (PIV) measurements on the bases of velocity, vorticity, and vortex location. The results show good agreement between simulated and experimental data. The inlet sub-model is shown to be critical for the successful modeling of pulsejet operation. This sub-model correctly predicts both the inlet mass flow rate and its phase relationship with the combustion chamber pressure. As a result, the predicted pulsejet thrust agrees very well with experimental data. DA - 2010/6// PY - 2010/6// DO - 10.1007/s10494-010-9247-6 VL - 84 IS - 4 SP - 653-667 SN - 1573-1987 KW - Pulsejet KW - Valve model KW - Exhaust flow field KW - Vortex location KW - Turbulence ER - TY - JOUR TI - Bio-thermal convection caused by combined effects of swimming of oxytactic bacteria and inclined temperature gradient in a shallow fluid layer AU - Avramenko, A. A. AU - Kuznetsov, A. V. T2 - INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW AB - Purpose The aim of this paper is to investigate the onset of bio‐thermal convection in a shallow fluid layer; the convection is thus driven by the combined effect of swimming of oxytactic microorganisms and inclined temperature gradient. Design/methodology/approach Linear stability analysis of the basic state is performed; the numerical problem is solved using the collocation method. Findings The most interesting outcome of this analysis is the correlation between three Rayleigh numbers, two traditional, “thermal” Rayleigh numbers, which are associated with the vertical and horizontal temperature gradients in the fluid layer, and the bioconvection Rayleigh number, which is associated with the density variation induced by the upswimming of microorganisms. Research limitations/implications Further research should address the application of weakly nonlinear analysis to this problem. Practical implications The increase of the horizontal thermal Rayleigh number stabilizes the basic flow. The effect of increasing the horizontal thermal Rayleigh number is to distort the basic temperature profile away from the linear one. The increase of the Schmidt number stabilizes the basic flow. The increase of the Prandtl number first causes the bioconvection Rayleigh number to decrease and then to increase. Originality/value To the best of the authors’ knowledge, this is the first research dealing with the effect of inclined temperature gradient on the stability of bioconvection. DA - 2010/// PY - 2010/// DO - 10.1108/09615531011016939 VL - 20 IS - 2 SP - 157-173 SN - 1758-6585 KW - Convection KW - Temperature distribution KW - Thermal stability KW - Fluids KW - Microbiology ER - TY - JOUR TI - Viscous flow over a shrinking sheet with an arbitrary surface velocity AU - Fang, Tiegang AU - Zhong, Yongfang T2 - COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION AB - In this paper, an analytical solution in a closed form for the boundary layer flow over a shrinking sheet is presented when arbitrary velocity distributions are applied on the shrinking sheet. The solutions with seven typical velocity profiles are derived based on a general closed form expression. Such flow is usually not self-similar and the solution can only be implemented when the mass transfer at the wall is prescribed and determined by the moving velocity of the wall. The characteristics of the flows with the typical velocity distributions are discussed and compared with previous similarity solutions. The flow is observed to have quite different behavior from that of the self-similar flow reported in the literature and the results demonstrate distinctive momentum and energy transport characteristics. Some plots of the stream functions are also illustrated to show the difference in flow field between the shrinking sheet and the stretching sheet. An integral approach to solve boundary layer flow over a shrinking or stretching sheet with uncoupled arbitrary surface velocity and wall mass transfer velocity is outlined and the effectiveness of this approach is discussed. DA - 2010/12// PY - 2010/12// DO - 10.1016/j.cnsns.2010.01.034 VL - 15 IS - 12 SP - 3768-3776 SN - 1878-7274 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952744808&partnerID=MN8TOARS KW - Similarity solution KW - Stretching surface KW - Shrinking sheet KW - Navier-Stokes equations KW - Analytical solution ER - TY - JOUR TI - The regime diagram for premixed flame kernel-vortex interactions-Revisited AU - Vasudeo, Nikhil AU - Echekki, Tarek AU - Day, Marcus S. AU - Bell, John B. T2 - PHYSICS OF FLUIDS AB - Regimes of flame kernel-vortex (KV) interactions are investigated numerically using a detailed mechanism for hydrogen chemistry. The parametric simulations explore a wide range of conditions that are representative of conditions encountered at various degrees of turbulence intensity. The results show that KV interactions can be classified into five different regimes, which include (1) the laminar kernel regime, (2) the wrinkled kernel regime, (3) the breakthrough regime, (4) the global extinction regime, and (5) the regeneration after global extinction (RGE) regime. With the exception of the last regime, the transition from one regime to another in the order listed corresponds to increasing the vortex size and strength. Operation at the RGE regime reveals interesting dynamics of the flame front that results in reignition or mending of combustion regimes after most of the original kernel has extinguished due to intense straining. Two different types of combustion zones are observed, which correspond to a flamelet structure as well as to more diffuse structures of merged flame segments. A revised regime diagram of the KV interactions is proposed that includes the broader range of KV interactions and incorporates the new RGE regime. DA - 2010/4// PY - 2010/4// DO - 10.1063/1.3372167 VL - 22 IS - 4 SP - SN - 1089-7666 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77953334145&partnerID=MN8TOARS KW - chemically reactive flow KW - combustion KW - flames KW - flow simulation KW - turbulence KW - vortices ER - TY - JOUR TI - Tension-compression asymmetry in nanocrystalline Cu: High strain rate vs. quasi-static deformation AU - Dongare, Avinash M. AU - Rajendran, Arunachalam M. AU - LaMattina, Bruce AU - Zikry, Mohammed A. AU - Brenner, Donald W. T2 - COMPUTATIONAL MATERIALS SCIENCE AB - Large-scale molecular dynamics (MD) simulations are used to understand the yield behavior of nanocrystalline Ni and Cu with grain sizes ⩽10 nm at high strain rates. The calculated flow stress values at a strain rate of 109 s−1 suggest an asymmetry in the strength values in tension and compression with the nanocrystalline metal being stronger in compression than in tension. This tension–compression strength asymmetry is observed to decrease with a decrease in grain size of the nanocrystalline metal up to a grain size of 4 nm, after which, a further decrease in grain size results in an increase in the strength asymmetry. The effect of strain rate on the yield behavior of nanocrystalline metals as obtained from MD simulations is discussed and compared with that reported in the literature obtained by molecular statics simulations for quasi-static loading conditions. DA - 2010/8// PY - 2010/8// DO - 10.1016/j.commatsci.2010.05.004 VL - 49 IS - 2 SP - 260-265 SN - 1879-0801 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77955425342&partnerID=MN8TOARS KW - Molecular dynamics KW - Nanocrystalline metals KW - Tension-compression asymmetry KW - Plastic deformation ER - TY - JOUR TI - Robust fault detection and isolation for parameter-dependent LFT systems AU - Cai, Xuejing AU - Wu, Fen T2 - INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL AB - Abstract In this paper, we consider robust fault detection and isolation (FDI) problems for faulty linear systems with linear fractional transformation (LFT) parameter dependency and propose an observer‐based solution by using multiobjective optimization techniques. To simplify the design process, a general faulty LFT system will be constructed from the standard LFT description by converting actuator/system component faults into sensor faults first. Then a bank of parameter‐dependent FDI filters will be designed to identify each fault. Each FDI filter will generate a residual signal to track an individual fault with minimum error and to suppress the effects of disturbances, time‐varying parameters and other fault signals. The design of LFT parameter‐dependent FDI filters, as a multiobjective optimization problem, will be formulated in terms of linear matrix inequalities (LMIs) and can be solved efficiently. A numerical example is used to demonstrate the proposed fault detection and isolation approach for LFT systems with different parametric structures. Copyright © 2009 John Wiley & Sons, Ltd. DA - 2010/5/10/ PY - 2010/5/10/ DO - 10.1002/rnc.1468 VL - 20 IS - 7 SP - 764-776 SN - 1099-1239 KW - fault detection and isolation KW - LFT systems KW - actuator and sensor faults KW - multiobjective optimization KW - LMI ER - TY - JOUR TI - Novel flame-gradient method for synthesis of metal-oxide channels, nanowires and nanorods AU - Merchan-Merchan, Wilson AU - Saveliev, Alexei V. AU - Cuello-Jimenez, Walmy T2 - JOURNAL OF EXPERIMENTAL NANOSCIENCE AB - The formation of 1D and 3D transition metal oxide (TMO) nano- and micron-size structures on molybdenum, iron and tungsten probes inserted in a counter-flow flame is studied experimentally. The unique thermal profile and chemical composition of the generated flame tends to convert almost pure bulk (99.9%) transition metal materials into 1D and 3D architectures. The synthesised Mo-, Fe- and W-oxide structures exhibit unique morphological characteristics. The application of Mo probes results in the formation of micron-size hollow and solid Mo-oxide channels. The formation of solid iron oxide nanorods is observed on iron probes. The use of W probes results in the synthesis of 1D solid carbon/metal oxide nanowires. This study confirms the existence of a common generic mechanism controlling the growth of the structures on the high-temperature probes. Metal oxide/hydroxides are formed on the probe surface exposed to the high-temperature oxidative environment. These oxides/hydroxides are further evaporated and transported by the gas flow to the low-temperature side where they are reduced to other oxide forms and deposited in the form of 1D or 3D TMO materials. This study reveals that a preferential growth at the edges of the MoO2 whisker tips leads to the development of hollow structures. DA - 2010/// PY - 2010/// DO - 10.1080/17458080903464108 VL - 5 IS - 3 SP - 199-212 SN - 1745-8099 KW - transition metal oxides KW - nanostructures KW - combustion synthesis KW - electron microscopy ER - TY - JOUR TI - Modeling organelle transport in branching dendrites with a variable cross-sectional area AU - Kuznetsov, A. V. T2 - Journal of Biological Physics AB - The purpose of this paper is to develop a method for calculating organelle transport in dendrites with a non-uniform cross-sectional area that depends on the distance from the neuron soma. The model is based on modified Smith-Simmons equations governing molecular motor-assisted organelle transport. The developed method is then applied to simulating organelle transport in branching dendrites with two particular microtubule (MT) orientations reported from experiments. It is found that the rate of organelle transport toward a dendrite's growth cone heavily depends on the MT orientation, and since there is experimental evidence that the MT orientation in a particular region of a dendrite may depend on the dendrite's developmental stage, the obtained results suggest that a rearrangement of the MT structure may depend on the amount of organelles needed at the growth cone. DA - 2010/// PY - 2010/// DO - 10.1007/s10867-010-9191-7 VL - 36 IS - 4 SP - 385-403 ER - TY - JOUR TI - Modeling of particle trajectories in an electrostatically charged channel AU - Wu, Mengbai AU - Kuznetsov, Andrey V. AU - Jasper, Warren J. T2 - PHYSICS OF FLUIDS AB - Modeling and analyses of filtration efficiency in electrostatically charged monolith filters are important for evaluating and designing this class of filters. Unlike traditional fibrous filters which comprise external flow around a fiber, monolith filters are modeled as internal flow through small channels. Analogous to single fiber theory for external flows, single channel theory is used to analyze basic fluid mechanics in monolith filters and predict filtration efficiencies. The model incorporates three forces: hydrodynamic forces, electrostatic forces, and Brownian motion. Fluid velocity within the channels is calculated by using an analytical solution for circular channel flow, within which the slip boundary condition is considered because of small length scales. This velocity field is then used to evaluate the drag force on the particle according to Stokes’s law. For this model, a one-way coupling between the fluid flow and the particle motion is assumed due to the fact that the relaxation time for the particles simulated in this paper is very small compared to the time the particles spend in the channel. The electrostatic field is computed assuming a uniform charge distribution on the inner surface of a cylindrical channel of finite length. Using a Monte Carlo simulation, particles are randomly injected into a single channel to determine the filtration efficiency. DA - 2010/4// PY - 2010/4// DO - 10.1063/1.3369004 VL - 22 IS - 4 SP - SN - 1070-6631 KW - Brownian motion KW - channel flow KW - drag KW - electric field effects KW - filtration KW - flow simulation KW - hydrodynamics KW - Monte Carlo methods KW - slip flow KW - two-phase flow ER - TY - JOUR TI - Influence of aspect ratio on the dynamics of a freely moving circular disk AU - Shenoy, A. R. AU - Kleinstreuer, C. T2 - JOURNAL OF FLUID MECHANICS AB - The influence of aspect ratio (χ = diameter/thickness) on the vortex shedding behaviour of fixed, and freely moving, circular disk has been investigated numerically. The aspect ratio significantly changes the structure of the vortices shed from the disk, thus altering the fluid induced forces. Disks of χ = 2 and 4 were selected, and by choosing Re = 240 periodic behaviour was observed for both the ‘fixed’ and ‘freely’ moving disks. First, the vortex structures shed from a ‘fixed’ circular disk of χ = 2 and 4 were computed for Re = 240. This was followed by a computation of their trajectories falling ‘freely’ under the action of gravity at Re = 240. For the ‘fixed’ disk of χ = 2, periodic shedding of one-sided hairpin-shaped vortex loops was observed. The flow field had a spatial planar symmetry and the vortices were shed from the same location, resulting in an asymmetric lateral force on the disk. The Strouhal number ( St ), calculated using the fluctuation in the axial velocity in the far-wake, was 0.122. This vortex shedding behaviour is referred to as the ‘single-sided’ vortex shedding mode. For the ‘fixed’ disk of χ = 4, periodic shedding of hairpin-shaped vortex loops was observed from the diametrically opposite location of the disk. The flow field had a spatial planar symmetry, and also a spatio-temporal one, with respect to a plane orthogonal to the spatial symmetry plane. The shed vortices induced a symmetric lateral force on the disk with a zero mean. The computed Strouhal number, was equal 0.122, same as that for χ = 2. This vortex shedding behaviour is referred as the ‘double-sided’ vortex shedding mode. For the ‘freely falling’ disk of χ = 2, an oscillatory motion was observed in a plane with a 83° phase lag between the lateral and angular velocity. The Strouhal number ( St b ), calculated using the oscillation frequency of the ‘freely’ falling disk was equal to 0.116, which is comparable to the St of the fixed disk. For a ‘freely falling’ disk of χ = 4, oscillatory motion was observed in a plane with a 21° phase lag between the lateral and angular velocity. The Strouhal number ( St b ) was equal to 0.171, which differs from the St observed in the wake of the fixed disk. DA - 2010/6/25/ PY - 2010/6/25/ DO - 10.1017/s0022112010000418 VL - 653 SP - 463-487 SN - 0022-1120 ER - TY - JOUR TI - Effect of vesicle traps on traffic jam formation in fast axonal transport AU - Kuznetsov, A. V. T2 - MATHEMATICAL BIOSCIENCES AB - The purpose of this paper is to develop a model for simulation of the formation of organelle traps in fast axonal transport. Such traps may form in the regions of microtubule polar mismatching. Depending on the orientation of microtubules pointing toward the trap region, these traps can accumulate either plus-end or minus-end oriented vesicles. The model predicts that the maximum concentrations of organelles occur at the boundaries of the trap regions; the overall concentration of organelles in the axon with traps is greatly increased compared to that in a healthy axon, which is expected to contribute to mechanical damages of the axon. The organelle traps induce hindrance to organelle transport down the axon; the total organelle flux down the axon with traps is found to be significantly reduced compared to that in a healthy axon. DA - 2010/8// PY - 2010/8// DO - 10.1016/j.mbs.2010.05.003 VL - 226 IS - 2 SP - 147-155 SN - 0025-5564 KW - Molecular motors KW - Neurons KW - Axons and dendrites KW - Intracellular organelles KW - Vesicle traps KW - Traffic jams ER - TY - JOUR TI - Diamond tool wear measurement by electron-beam-induced deposition AU - Shi, M. AU - Lane, B. AU - Mooney, C. B. AU - Dow, T. A. AU - Scattergood, R. O. T2 - PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY AB - Quantitative characterization of a diamond tool profile is critical to reveal tool wear mechanisms. An electron-beam-induced deposition (EBID) method reported previously is further developed and improved to measure diamond tool profiles using a field emission scanning electron microscope (SEM). The edge radius and wear land length for new and worn diamond tools were derived from analysis of the EBID-SEM images. Experimental results are presented to show that the methodology is an effective means to characterize diamond tool wear. DA - 2010/10// PY - 2010/10// DO - 10.1016/j.precisioneng.2010.03.009 VL - 34 IS - 4 SP - 718-721 SN - 1873-2372 KW - Diamond turning KW - Diamond tool wear KW - EBID KW - Edge radius KW - Wear land ER - TY - JOUR TI - A GPGPU Compiler for Memory Optimization and Parallelism Management AU - Yang, Yi AU - Xiang, Ping AU - Kong, Jingfei AU - Zhou, Huiyang T2 - ACM SIGPLAN NOTICES AB - This paper presents a novel optimizing compiler for general purpose computation on graphics processing units (GPGPU). It addresses two major challenges of developing high performance GPGPU programs: effective utilization of GPU memory hierarchy and judicious management of parallelism. The input to our compiler is a naïve GPU kernel function, which is functionally correct but without any consideration for performance optimization. The compiler analyzes the code, identifies its memory access patterns, and generates both the optimized kernel and the kernel invocation parameters. Our optimization process includes vectorization and memory coalescing for memory bandwidth enhancement, tiling and unrolling for data reuse and parallelism management, and thread block remapping or address-offset insertion for partition-camping elimination. The experiments on a set of scientific and media processing algorithms show that our optimized code achieves very high performance, either superior or very close to the highly fine-tuned library, NVIDIA CUBLAS 2.2, and up to 128 times speedups over the naive versions. Another distinguishing feature of our compiler is the understandability of the optimized code, which is useful for performance analysis and algorithm refinement. DA - 2010/6// PY - 2010/6// DO - 10.1145/1809028.1806606 VL - 45 IS - 6 SP - 86-97 SN - 0362-1340 KW - Performance KW - Experimentation KW - Languages KW - GPGPU KW - Compiler ER - TY - JOUR TI - Performance of North American Bioreactor Landfills. II: Chemical and Biological Characteristics AU - Barlaz, Morton A. AU - Bareither, Christopher A. AU - Hossain, Azam AU - Saquing, Jovita AU - Mezzari, Isabella AU - Benson, Craig H. AU - Tolaymat, Thabet M. AU - Yazdani, Ramin T2 - JOURNAL OF ENVIRONMENTAL ENGINEERING AB - The objective of this research was to examine the performance of five North American bioreactor landfills. This paper represents the second of a two-part series and addresses biological and chemical aspects of bioreactor performance including gas production and management, and leachate chemistry. The data support accelerated methane generation at several landfills (k=0.08–0.21 1/year) relative to the AP-42 default decay rate (k=0.04 1/year). While the data indicate that gas collection increases at bioreactor landfills, a general relationship between decay rate and moisture added or wet weight water content could not be identified. There was no indication that gas collection increases appreciably when the water content reaches 40%. Most of the leachates at the landfills in this study were commingled from cells operating as a bioreactor and conventionally. Nevertheless, trends in pH and BOD:COD in the bioreactor leachates were consistent with the impacts of enhanced biological activity. Ammonia concentrations also increased over time but remained below levels reported to be inhibitory. For both heavy metals and speciated organic chemicals, there was no indication that bioreactor landfill leachate is significantly different from leachate generated at conventional landfills. DA - 2010/8// PY - 2010/8// DO - 10.1061/(asce)ee.1943-7870.0000220 VL - 136 IS - 8 SP - 839-853 SN - 1943-7870 KW - Landfills KW - Bioreactor KW - Solid waste KW - Leachate quality KW - Methane ER - TY - JOUR TI - Lateral field excitation properties of langasite single crystal AU - Ma, T. F. AU - Zhang, C. AU - Feng, G. P. AU - Jiang, X. N. T2 - Chinese Physics. B, (Beijing, China) AB - In this work, bulk acoustic wave propagation properties of langasite single crystal excited by lateral electric field have been investigated. Three important crystal cuts have been identified for different operational modes of lateral field excitation (LFE) on langasite substrate, namely the (yxl)65° (pure-LFE mode), (yxl)45° (quasi-LFE mode), and (yxl)0° (pseudo-LFE mode). Devices on langasite substrate with the above cuts were fabricated and tested, and the experimental results agree well with the theoretical analysis. It is found that a pure thickness shear mode exists in the (yxl)65° langasite LFE device with the bare side facing liquid, and no spurious mode is found due to its moderately large piezoelectric coupling factor. In addition, (yxl)0° langasite LFE device is also found suitable for liquid phase sensing applications. DA - 2010/// PY - 2010/// DO - 10.1088/1674-1056/19/8/087701 VL - 19 IS - 8 ER - TY - JOUR TI - Large-Eddy/Reynolds-Averaged Navier-Stokes Simulations of Sonic Injection into Mach 2 Crossflow AU - Boles, John A. AU - Edwards, Jack R. AU - Baurle, Robert A. T2 - AIAA JOURNAL AB - Computational predictions of transverse injection of air, helium, and ethylene into a Mach 1.98 crossflow of air are presented. A hybrid large-eddy simulation/Reynolds-averaged Navier―Stokes turbulence model is used. A blending function, dependent on modeled turbulence variables, is used to shift the turbulence closure from the Menter t-ω model near solid surfaces to a Smagorinsky subgrid model in the outer part of the incoming boundary layer and in the jet mixing zone. The results show reasonably good agreement with time-averaged Mie-scattering images of the plume structure for both helium and air injection and with experimental surface pressure distributions, even though the penetration of the jet into the crossflow is slightly overpredicted. Predictions of ethylene mole fraction at several transverse stations within the plume are in good agreement with time-averaged Raman-scattering mole-fraction data. The model results are used to examine the validity of the commonly used assumption of the constant turbulent Schmidt number in the intense mixing zone downstream of the injection location. The assumption of a constant turbulent Schmidt is shown to be inadequate for jet mixing dominated by large-scale entrainment. DA - 2010/7// PY - 2010/7// DO - 10.2514/1.j050066 VL - 48 IS - 7 SP - 1444-1456 SN - 1533-385X ER - TY - JOUR TI - Impact source identification in finite isotropic plates using a time-reversal method: theoretical study AU - Chen, Chunlin AU - Yuan, Fuh-Gwo T2 - SMART MATERIALS AND STRUCTURES AB - This paper aims to identify impact sources on plate-like structures based on the synthetic time-reversal (T-R) concept using an array of sensors. The impact source characteristics, namely, impact location and impact loading time history, are reconstructed using the invariance of time-reversal concept, reciprocal theory, and signal processing algorithms. Numerical verification for two finite isotropic plates under low and high velocity impacts is performed to demonstrate the versatility of the synthetic T-R method for impact source identification. The results show that the impact location and time history of the impact force with various shapes and frequency bands can be readily obtained with only four sensors distributed around the impact location. The effects of time duration and the inaccuracy in the estimated impact location on the accuracy of the time history of the impact force using the T-R method are investigated. Since the T-R technique retraces all the multi-paths of reflected waves from the geometrical boundaries back to the impact location, it is well suited for quantifying the impact characteristics for complex structures. In addition, this method is robust against noise and it is suggested that a small number of sensors is sufficient to quantify the impact source characteristics through simple computation; thus it holds promise for the development of passive structural health monitoring (SHM) systems for impact monitoring in near real-time. DA - 2010/10// PY - 2010/10// DO - 10.1088/0964-1726/19/10/105028 VL - 19 IS - 10 SP - SN - 1361-665X ER - TY - JOUR TI - Full-spectrum interrogation of fiber Bragg gratings at 100 kHz for detection of impact loading AU - Vella, T. AU - Chadderdon, S. AU - Selfridge, R. AU - Schultz, S. AU - Webb, S. AU - Park, C. AU - Peters, K. AU - Zikry, M. T2 - MEASUREMENT SCIENCE AND TECHNOLOGY AB - This paper explains key innovations that allow monitoring of detailed spectral features of an FBG in response to impact loading. The new system demonstrates capture of FBG spectral data at rates of 100 kHz. Rapid capture of the entire reflection spectrum at such high reading rates shows important features that are missed when using systems that merely track changes in the peak location of the spectrum. The update rate of 100 kHz allows resolution of features that occur on transient time scales as short as 10 µs. This paper gives a detailed description of the unique features of the apparatus and processes used to capture the data at such a rapid rate. Furthermore, we demonstrate this interrogation scheme on a composite laminate system during impact. DA - 2010/9// PY - 2010/9// DO - 10.1088/0957-0233/21/9/094009 VL - 21 IS - 9 SP - SN - 1361-6501 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77958167493&partnerID=MN8TOARS KW - high-speed FBG interrogation systems KW - fiber Bragg gratings KW - impact damage assessment KW - structural health monitoring ER - TY - JOUR TI - Forced convection in a channel partly occupied by a bidisperse porous medium: Asymmetric case AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - This paper presents an analytic investigation of forced convection in parallel-plate channel partly occupied by a bidisperse porous medium and partly by a fluid clear of solid material, the distribution being asymmetrical. The walls of the channel are subject to an uniform heat flux; the flow is assumed to be hydrodynamically and thermally fully developed. The layer of a bidisperse porous medium is attached to one of the channel walls; it is modeled utilizing a two-velocity two-temperature formulation using Darcy’s law. The Beavers–Joseph boundary condition is employed at the bidisperse porous medium/clear fluid interface. The dependences of the Nusselt number on a conductivity ratio, a velocity ratio, a volume fraction, internal heat exchange parameter, and the position of the porous-fluid interface are investigated. Both cases of symmetric and asymmetric heating are investigated, which is specified by the asymmetry heating parameter introduced here. For the case of asymmetric heating, a singular behavior of the Nusselt number is found and explained. DA - 2010/11// PY - 2010/11// DO - 10.1016/j.ijheatmasstransfer.2010.07.046 VL - 53 IS - 23-24 SP - 5167-5175 SN - 0017-9310 KW - Bidispersed porous medium KW - Forced convection KW - Channel KW - Porous medium-fluid interface ER - TY - JOUR TI - Flow of a Weakly Conducting Fluid in a Channel Filled with a Darcy-Brinkman-Forchheimer Porous Medium AU - Zhao, B. Q. AU - Pantokratoras, A. AU - Fang, T. G. AU - Liao, S. J. T2 - TRANSPORT IN POROUS MEDIA DA - 2010/10// PY - 2010/10// DO - 10.1007/s11242-010-9550-7 VL - 85 IS - 1 SP - 131-142 SN - 1573-1634 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77956873895&partnerID=MN8TOARS KW - Porous medium KW - Couette flow KW - Poiseuille flow KW - Lorentz force KW - Analytical solution KW - HAM ER - TY - JOUR TI - Flight Test of Stable Automated Cruise Flap for an Adaptive Wing Aircraft AU - Cox, Craig AU - Gopalarathnam, Ashok AU - Hall, Charles E., Jr. T2 - Journal of Aircraft AB - 0p-optimization function was effective in producing pressure differentials that would have reduced drag. The effectivenessoftheC 0 p-maintenancefunctioncouldnotbedeterminedbecauseoflargesample-to-samplevariations in measured C 0 p values. It remains unknown whether this high-frequency content actually represented rapidly varying pressures on the airfoil surface or if it was the result of noise in the measurement system. DA - 2010/7// PY - 2010/7// DO - 10.2514/1.46789 VL - 47 IS - 4 SP - 1178-1188 J2 - Journal of Aircraft LA - en OP - SN - 0021-8669 1533-3868 UR - http://dx.doi.org/10.2514/1.46789 DB - Crossref ER - TY - JOUR TI - FORCED CONVECTION WITH PHASE-LAGGED OSCILLATORY COUNTERFLOW IN A SATURATED POROUS CHANNEL AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - JOURNAL OF POROUS MEDIA AB - An analytical solution is obtained for forced convection in a parallel plate channel occupied by a layered saturated porous medium with counterflow produced by pressure gradients oscillating in time about a zero mean. The case of asymmetrical constant heat-flux boundary conditions is considered, and the Brinkman model is employed for the porous medium. Expressions for the velocity, temperature distribution, and Nusselt number are obtained. It is found that oscillation about a zero mean does not cause the Nusselt number to oscillate, but in general its value is dependent on the frequency of oscillation, the variation becoming significant at large values of the frequency. DA - 2010/// PY - 2010/// DO - 10.1615/jpormedia.v13.i7.20 VL - 13 IS - 7 SP - 601-611 SN - 1934-0508 KW - forced convection KW - counterflow KW - oscillatory flow KW - porous medium KW - channel ER - TY - JOUR TI - Combustion synthesis of carbon nanotubes and related nanostructures AU - Merchan-Merchan, Wilson AU - Saveliev, Alexei V. AU - Kennedy, Lawrence AU - Jimenez, Walmy Cuello T2 - PROGRESS IN ENERGY AND COMBUSTION SCIENCE AB - Recently flames have emerged as a viable alternative method for the synthesis of carbon nanotubes and related nanostructures. The flame volume provides a carbon-rich chemically reactive environment capable of generating nanostructures during short residence times in a continuous single-step process. Various flame configurations, fuel types, and catalytic materials have been employed in an attempt to achieve controlled growth of multi-walled and single-walled carbon nanotubes as well as other carbon nanostructures such as nanofibers, carbon micro-trees, and whiskers. Premixed and non-premixed flames in co-flow and counterflow geometries were examined using low atmospheric and elevated pressures, various hydrocarbon fuels, oxygen enrichment, and dilution with inert gases were employed as well. Catalytic materials in the form of solid untreated supports, solid supports with pre-fabricated catalytic sites, and also in the form of aerosol have demonstrated high activity and selectivity in the growth of various nanostructures. The ability to synthesize and control carbon nanotube orientation, length, diameter, uniformity, purity, and internal morphology is essential for the fabrication of nanomechanical and electrical devices. An understanding of the growth mechanism and development of control methods such as the electric field, particle loading, and nanotemplates is critically important to address these issues. Today, flames are envisioned as the alternative technique for the synthesis of SWNTs in tons/year production scale leading to the development of related technologies such as purification and separation methods. DA - 2010/12// PY - 2010/12// DO - 10.1016/j.pecs.2010.02.005 VL - 36 IS - 6 SP - 696-727 SN - 0360-1285 KW - Combustion synthesis KW - Carbon nanotubes KW - Carbon nanofibers KW - Growth mechanisms KW - Electric field KW - Nanotemplates ER - TY - JOUR TI - An electrothermal microactuator with Z-shaped beams AU - Guan, Changhong AU - Zhu, Yong T2 - JOURNAL OF MICROMECHANICS AND MICROENGINEERING AB - This paper introduces a Z-shaped thermal microactuator for in-plane motion, which could be complementary to the well-established comb drives and V-shaped thermal actuators. The Z-shaped actuators share many features in common with the V-shaped ones, but offer certain advantages such as smaller feature size and larger displacement. They also offer a large range of stiffness and output force that is between those of the V-shaped actuators and comb drives. In particular, they can achieve smaller stiffness without buckling, which renders them as simultaneous load sensors. The Z-shaped actuator was modeled analytically and verified by multiphysics finite element analysis. Among all the design parameters, the beam width and the length of the central beam were identified as the major ones in tuning the device displacement, stiffness, stability and output force. Experimental measurements of three arrays of Z-shaped thermal actuators agreed well with the finite element analysis. In addition, the quasi-static and dynamic performances of individual Z-shaped thermal actuators were measured. The average temperature in the device structure was estimated from the electric resistivity at each actuation voltage. The bandwidth of the Z-shaped thermal actuators can be increased for devices with a substrate underneath. DA - 2010/8// PY - 2010/8// DO - 10.1088/0960-1317/20/8/085014 VL - 20 IS - 8 SP - SN - 0960-1317 ER - TY - JOUR TI - A reconstructed discontinuous Galerkin method for the compressible Navier-Stokes equations on arbitrary grids AU - Luo, Hong AU - Luo, Luqing AU - Nourgaliev, Robert AU - Mousseau, Vincent A. AU - Dinh, Nam T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - A reconstruction-based discontinuous Galerkin (RDG) method is presented for the solution of the compressible Navier–Stokes equations on arbitrary grids. The RDG method, originally developed for the compressible Euler equations, is extended to discretize viscous and heat fluxes in the Navier–Stokes equations using a so-called inter-cell reconstruction, where a smooth solution is locally reconstructed using a least-squares method from the underlying discontinuous DG solution. Similar to the recovery-based DG (rDG) methods, this reconstructed DG method eliminates the introduction of ad hoc penalty or coupling terms commonly found in traditional DG methods. Unlike rDG methods, this RDG method does not need to judiciously choose a proper form of a recovered polynomial, thus is simple, flexible, and robust, and can be used on arbitrary grids. The developed RDG method is used to compute a variety of flow problems on arbitrary meshes to demonstrate its accuracy, efficiency, robustness, and versatility. The numerical results indicate that this RDG method is able to deliver the same accuracy as the well-known Bassi–Rebay II scheme, at a half of its computing costs for the discretization of the viscous fluxes in the Navier–Stokes equations, clearly demonstrating its superior performance over the existing DG methods for solving the compressible Navier–Stokes equations. DA - 2010/9/20/ PY - 2010/9/20/ DO - 10.1016/j.jcp.2010.05.033 VL - 229 IS - 19 SP - 6961-6978 SN - 1090-2716 KW - Reconstruction schemes KW - Discontinuous Galerkin methods KW - Compressible Navier-Stokes equations ER - TY - JOUR TI - cox regression in nested case-control studies with auxiliary covariates AU - Pantokratoras, A. AU - Fang, T. G. T2 - Transport in Porous Media DA - 2010/// PY - 2010/// VL - 83 IS - 3 SP - 667-676 ER - TY - JOUR TI - The central oblique collision efficiency of spherical nanoparticles in the brownian coagulation AU - Wang, Y. M. AU - Lin, J. Z. AU - Feng, Y. T2 - Modern Physics Letters. B, Condensed Matter Physics, Statistical Physics, Applied Physics DA - 2010/// PY - 2010/// VL - 24 IS - 14 SP - 1523-1531 ER - TY - JOUR TI - The Effect of Strong Heterogeneity on the Onset of Convection in a Porous Medium: 2D/3D Localization and Spatially Correlated Random Permeability Fields AU - Nield, D. A. AU - Kuznetsov, A. V. AU - Simmons, Craig T. T2 - TRANSPORT IN POROUS MEDIA DA - 2010/7// PY - 2010/7// DO - 10.1007/s11242-009-9455-5 VL - 83 IS - 3 SP - 465-477 SN - 1573-1634 KW - Heterogeneity KW - Stability KW - Natural convection KW - Computer package ER - TY - JOUR TI - Mott transition in Ga-doped MgxZn1-xO: A direct observation AU - Wei, Wei AU - Nori, Sudhakar AU - Jin, Chunming AU - Narayan, Jagdish AU - Narayan, Roger J. AU - Ponarin, Dmtri AU - Smirnov, Alex T2 - MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS AB - This paper reports the direct evidence for Mott transition in Ga-doped MgxZn1−xO thin films. Highly transparent Ga-doped MgxZn1−xO thin films were grown on c-plane sapphire substrates using pulsed laser deposition. 0.1 at.%, 0.5 at.% and 1 at.% Ga-doped Mg0.1Zn0.9O films were selected for resistivity measurements in the temperature range from 250 K to 40 mK. The 0.1 at.% Ga-doped Mg0.1Zn0.9O thin film showed typical insulator-like behavior and the 1 at.% Ga-doped Mg0.1Zn0.9O thin film showed typical metal-like behavior. The 0.5 at.% Ga-doped Mg0.1Zn0.9O film showed increasing resistivity with decreasing temperature; resistivity was saturated with a value of 1.15 × 10−2 Ω cm at 40 mK, which is characteristic of the metal–insulator transition region. Temperature-dependent conductivity σ(T) in the low temperature range revealed that the electron-electron scattering is the dominant dephasing mechanism. The inelastic scattering time is found to vary as T−3/2. DA - 2010/7/25/ PY - 2010/7/25/ DO - 10.1016/j.mseb.2010.03.078 VL - 171 IS - 1-3 SP - 90-92 SN - 1873-4944 KW - Mott transition KW - Magnesium zinc oxide KW - Gallium doping KW - Thin film KW - Pulsed laser deposition ER - TY - JOUR TI - Leading-edge flame fluctuations in lifted turbulent flames AU - Moore, N. J. AU - Lyons, K. M. T2 - Combustion Science and Technology AB - Abstract Studies are presented that examine the fluctuations in liftoff height of lifted methane flames in the presence of air coflow. At a certain jet exit velocity, a flame will lift from the burner exit and stabilize at some downstream position. The partially-premixed flame front of the lifted flame oscillates in the axial direction, with the fluctuations becoming greater in flames stabilized further downstream. These fluctuations are also observed in flames where blowout is imminent. This work investigates the role of fuel velocity and air co-flow on flame fluctuations in both stable and unstable regimes. The results of video imaging of a lifted methane-air diffusion flame are presented and discussed. Images are used to ascertain the changes in the reaction zone that influence these fluctuations and relate the movement to blowout. Keywords: BlowoutCoflowCombustionFlame stabilityMethane ACKNOWLEDGEMENTS The research reported in this paper has been supported by the U.S. Army Research Office (Contracts W911NF0510045 and W911NF0810142). DA - 2010/// PY - 2010/// DO - 10.1080/00102200903355017 VL - 182 IS - 7 SP - 777-793 ER - TY - JOUR TI - Inherent instability investigation for low speed laser welding of aluminum using a single-mode fiber laser AU - Paleocrassas, A. G. AU - Tu, J. F. T2 - JOURNAL OF MATERIALS PROCESSING TECHNOLOGY AB - The causes of instability are investigated for low speed welding of aluminum from 10 mm/s down to 1 mm/s using a 300 W single-mode fiber laser. Results show that the welding is stable until the speed drops below a certain threshold (∼1 mm/s) at which there was a significant change in the process mechanism, causing shallow, inefficient welds with many defects. A power distribution model and several tests are used to examine different types of power losses at low speeds. It is then hypothesized that, at low speeds, the CW laser beam mainly irradiates at the molten pool, which absorbs a large portion of the beam energy near the surface. The majority of this absorbed energy subsequently is either lost via evaporation or transferred into the bulk material via convection and conduction without being used for melting the solid at the welding front. A laser pulsing scheme was used to test the above hypothesis. It was found that, through proper control of the duty cycle and frequency to prevent overheating of the molten pool, a high aspect ratio weld shape can be restored at low speeds, thus, confirming the hypothesis. In addition, the 1 mm/s low speed threshold is found to be related to the initial molten pool propagation speed, which is found to be approximately 1.4 mm/s. Although this paper does not propose a solution to restore process stability, the understanding of the instability origin will be helpful in the search of such a solution to overcome the process instability for slow speed welding of aluminum. DA - 2010/7/1/ PY - 2010/7/1/ DO - 10.1016/j.jmatprotec.2010.04.002 VL - 210 IS - 10 SP - 1411-1418 SN - 0924-0136 KW - Instability KW - Keyhole KW - Melting front KW - Laser welding KW - Porosity KW - Fiber laser KW - Crack repair KW - Heat-treatable aluminum alloy ER - TY - JOUR TI - Global and Local Fiber Optic Sensors for Health Monitoring of Civil Engineering Infrastructure Retrofit with FRP Materials AU - Jiang, Guoliang AU - Dawood, Mina AU - Peters, Kara AU - Rizkalla, Sami T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - Fiber-reinforced polymer (FRP) materials are currently used for strengthening civil engineering structures and bridges. The effectiveness of the strengthening system is highly dependent on the bond characteristics of the FRP material to the external surface of the structure. This article presents the application of two types of fiber optic sensors, which can be embedded in FRP materials to monitor the global and local behavior of the strengthened structure, respectively. The global sensor is designed to evaluate the overall condition of a structure based on the measured elongation of the FRP layer along the entire span of the structure. The success of this low-cost global sensor has been demonstrated using a full-scale prestressed concrete bridge girder that was loaded up to failure. The test results indicate that this type of sensor can be used to identify major changes in the overall behavior of the structure such as cracking of prestressed members or yielding of the internal reinforcement. The second sensor component consists of fiber Bragg grating sensors. The sensors were used to monitor the behavior of steel double-lap shear specimens tested under tensile loading up to failure. The measurements were used to identify abnormal structural behaviors such as epoxy cracking and/or FRP debonding. The test results compared well to the numerical values obtained from a three dimensional shear-lag model that was previously developed to predict the sensor response. DA - 2010/7// PY - 2010/7// DO - 10.1177/1475921709352989 VL - 9 IS - 4 SP - 309-322 SN - 1741-3168 KW - global and local fiber optic sensors KW - health monitoring KW - strengthening civil engineering infrastructure KW - prestressed concrete KW - structural steel KW - fiber optic ribbons KW - fiber Bragg gratings ER - TY - JOUR TI - Experimental characterization of the hysteretic and rate-dependent electromechanical behavior of dielectric electro-active polymer actuators AU - York, A. AU - Dunn, J. AU - Seelecke, S. T2 - SMART MATERIALS & STRUCTURES AB - Dielectric electro-active polymers (DEAPs) can achieve substantial deformation (>300% strain) while sustaining, compared to their ionic counterparts, large forces. This makes them attractive for various actuation and sensing applications such as in light weight and energy efficient valve and pumping systems. Many applications operate DEAP actuators at higher frequencies where rate-dependent effects influence their performance. This motivates the seeking of dynamic characterization of these actuators beyond the quasi-static regime. This paper provides a systematic experimental investigation of the quasi-static and dynamic electromechanical properties of a DEAP actuator. In order to completely characterize the fully coupled behavior, force versus displacement measurements at various constant voltages and force versus voltage measurements at various fixed displacements are conducted. The experiments are conducted with a particular focus on the hysteretic and rate-dependent material behavior. These experiments provide insight into the electrical dynamics and viscoelastic relaxation inherent in DEAP actuators. This study is intended to provide information, including high frequency performance analysis, useful to anyone designing dynamic actuator systems using DEAPs. DA - 2010/9// PY - 2010/9// DO - 10.1088/0964-1726/19/9/094014 VL - 19 IS - 9 SP - SN - 0964-1726 ER - TY - JOUR TI - Equations describing molecular-motor-assisted transport in dendrites with a non-uniform cross-sectional area AU - Kuznetsov, A. V. T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - The purpose of this paper is to develop new transport equations describing transport of intracellular organelles by a combined effect of diffusion and molecular-motor-driven transport in dendrites of neuron cells that have a non-uniform cross-sectional area which depends on the distance from the neuron soma. The obtained equations are solved numerically for two types of microtubule (MT) orientations that are experimentally found in dendrites. In one type of dendrites, which is found in cultured rat hippocampal neurons, MTs have a mixed polarity orientation while in the second type, which is found in Drosophila neurons, MTs have the minus-end-out polarity orientation. Simulations show important differences in organelle transport in these two types of dendrites. The conclusion is that the MT orientation has a profound effect on the total rate of organelle transfer toward the growth cone of a dendrite and consequently determines its growth potential and its growth rate. DA - 2010/8// PY - 2010/8// DO - 10.1016/j.icheatmasstransfer.2010.05.020 VL - 37 IS - 7 SP - 725-730 SN - 1879-0178 KW - Molecular motors KW - Motor-assisted transport KW - Neurons KW - Dendrites KW - Intracellular organelles ER - TY - JOUR TI - Effect of diffusion on slowing the velocity of a bell-shaped wave in slow axonal transport AU - Kuznetsov, A. V. AU - Avramenko, A. A. AU - Blinov, D. G. T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - This paper models transport of organelles by slow axonal transport utilizing the stop-and-go hypothesis, which postulates that in slow axonal transport the motion of organelles does not occur continuously; instead, organelles move along microtubules (MTs) alternating between short periods of rapid movement, short on-track pauses, and prolonged off-track pauses, when they temporarily disengage from MTs. The model considers six kinetic states of organelles: anterogradely moving state, retrogradely moving state, anterogradely pausing state, retrogradely pausing state, off-track anterograde state, and off-track retrograde state. The paper extends the existing model of slow axonal transport by accounting for the diffusivity of off-track organelles and investigates how the diffusivity of these organelles affects the amplitude, velocity, and rate of change of the variance of the bell-shaped wave which describes the probability density function (PDF) corresponding to the ratio of the chance of finding an organelle within an infinitesimal interval in the axon to the length of this interval. The velocity of this wave characterizes the average effective velocity (calculated including pauses) of an organelle in slow axonal transport while the rate of change of the variance characterizes the rate of spread of the initial packet of organelles transported in the axon. The goal of this research is not only to develop a more accurate transport model, but also to understand fundamentally the effects of diffusion on slow axonal transport. It is demonstrated that diffusion decreases the amplitude of the wave and increases the rate of its spread but does not affect wave's velocity. DA - 2010/8// PY - 2010/8// DO - 10.1016/j.icheatmasstransfer.2010.05.010 VL - 37 IS - 7 SP - 770-774 SN - 0735-1933 KW - Molecular motors KW - Motor-assisted transport KW - Neurons KW - Axons KW - Slow axonal transport KW - Stop-and-go hypothesis ER - TY - JOUR TI - Dynamic shear-strain localization and inclusion effects in lath martensitic steels subjected to high pressure loads AU - Hatem, T. M. AU - Zikry, M. A. T2 - JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS AB - A three-dimensional multiple-slip dislocation-density based crystalline formulation, specialized finite-element formulations, and specialized Voronoi tessellations adapted to martensitic orientations, were used to investigate shear–strain localization, and dislocation-density evolution in martensitic microstructures under dynamic compressive loading conditions. The formulation is based on accounting for variant morphologies and orientations, secondary-phase structures, and initial dislocations-densities that are uniquely inherent to martensitic microstructures. The effects of strain rate and inclusions on the evolution of shear–strain localization were investigated. The analysis indicates that variant morphology and orientations have a direct consequence on dislocation-density accumulation and inelastic localization in martensitic microstructures, and that lath directions, orientations, and arrangements are critical characteristics of high-strength martensitic dynamic behavior. It is shown that tensile hydrostatic pressure due to the unloading of the plastic waves at the free boundary and extensive shear–strain accumulation occurs at certain triple junctions. Furthermore, plastic shear-slip accumulation between inclusions and the surrounding martensitic matrix results in shear–strain localization and increases in the tensile hydrostatic pressure at critical locations, such as trip junctions. DA - 2010/8// PY - 2010/8// DO - 10.1016/j.jmps.2010.04.009 VL - 58 IS - 8 SP - 1057-1072 SN - 1873-4782 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-80052492778&partnerID=MN8TOARS KW - Lath martensite KW - Dislocation-densities KW - Dynamic loading KW - Crystalline plasticity KW - Shear-strain localization ER - TY - JOUR TI - Dynamic Modeling of a Wind-Driven Tumbleweed Rover Including Atmospheric Effects AU - Hartl, Alexandre E. AU - Mazzoleni, Andre P. T2 - JOURNAL OF SPACECRAFT AND ROCKETS AB - Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields. DA - 2010/// PY - 2010/// DO - 10.2514/1.45174 VL - 47 IS - 3 SP - 493-502 SN - 0022-4650 ER - TY - JOUR TI - Defect-mediated room temperature ferromagnetism in zinc oxide AU - Mal, Siddhartha AU - Narayan, J. AU - Nori, Sudhakar AU - Prater, J. T. AU - Kumar, D. T2 - SOLID STATE COMMUNICATIONS AB - We have introduced systematic changes in the electrical, magnetic and optical properties of undoped ZnO films through irradiation with an UV Excimer laser. Increases in the electrical conductivity and magnetic moment have been controlled precisely with the number of laser pulses, without altering the Wurtzite crystal structure and n-type semiconducting characteristics of the films. The laser induced ferromagnetism and concomitant conductivity enhancement can be reversed through subsequent thermal annealing. Hence, we have successfully demonstrated reversible switching of RTFM in undoped ZnO by employing oxygen annealing (off) and laser irradiation (on). We discuss these findings in terms of defects and defect complexes created by pulsed laser irradiation. DA - 2010/9// PY - 2010/9// DO - 10.1016/j.ssc.2010.06.030 VL - 150 IS - 35-36 SP - 1660-1664 SN - 0038-1098 KW - Magnetic semiconductor KW - Thin films KW - Laser irradiation KW - Oxygen and zinc vacancies ER - TY - JOUR TI - Carbon nanotube yarn strain sensors AU - Zhao, Haibo AU - Zhang, Yingying AU - Bradford, Philip D. AU - Zhou, Qian AU - Jia, Quanxi AU - Yuan, Fuh-Gwo AU - Zhu, Yuntian T2 - NANOTECHNOLOGY AB - Carbon nanotube (CNT) based sensors are often fabricated by dispersing CNTs into different types of polymer. In this paper, a prototype carbon nanotube (CNT) yarn strain sensor with excellent repeatability and stability for in situ structural health monitoring was developed. The CNT yarn was spun directly from CNT arrays, and its electrical resistance increased linearly with tensile strain, making it an ideal strain sensor. It showed consistent piezoresistive behavior under repetitive straining and unloading, and good resistance stability at temperatures ranging from 77 to 373 K. The sensors can be easily embedded into composite structures with minimal invasiveness and weight penalty. We have also demonstrated their ability to monitor crack initiation and propagation. DA - 2010/7/30/ PY - 2010/7/30/ DO - 10.1088/0957-4484/21/30/305502 VL - 21 IS - 30 SP - SN - 1361-6528 ER - TY - JOUR TI - Adaptive and active materials: Selected papers from the ASME 2009 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS 09) (Oxnard, CA, USA, 21-23 September 2009) AU - Lynch, C. AU - Brei, D. AU - Chaplya, P. AU - Ounaies, Z. AU - Kamlah, M. AU - Seelecke, S. AU - Lucato, S. D. E. AU - Weiland, L. T2 - Smart Materials & Structures DA - 2010/// PY - 2010/// VL - 19 IS - 9 ER - TY - JOUR TI - Viscous flow over a shrinking sheet with a second order slip flow model AU - Fang, Tiegang AU - Yao, Shanshan AU - Zhang, Ji AU - Aziz, Abdul T2 - COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION AB - In this paper, viscous flow over a shrinking sheet is solved analytically using a newly proposed second order slip flow model. The closed solution is an exact solution of the full governing Navier–Stokes equations. The solution has two branches in a certain range of the parameters. The effects of the two slip parameters and the mass suction parameter on the velocity distribution are presented graphically and discussed. For certain combinations of the slip parameters, the wall drag force can decrease with the increase of mass suction. These results clearly show that the second order slip flow model is necessary to predict the flow characteristics accurately. DA - 2010/7// PY - 2010/7// DO - 10.1016/j.cnsns.2009.07.017 VL - 15 IS - 7 SP - 1831-1842 SN - 1878-7274 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-74449090532&partnerID=MN8TOARS KW - Similarity solution KW - Stretching surface KW - Shrinking sheet KW - Navier-Stokes equations KW - Analytical solution KW - Exact solution KW - Slip flow ER - TY - JOUR TI - The Cheng-Minkowycz problem for cellular porous materials: Effect of temperature-dependent conductivity arising from radiative transfer AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - Abstract The Cheng–Minkowycz problem involving natural convection boundary layer flow adjacent to a vertical wall in a saturated cellular porous medium subject to Darcy’s law is investigated. The problem is formulated as a combined conductive–convective–radiative problem in which radiative heat transfer is treated as a diffusion process. The problem is relevant to cellular foams formed from plastics, ceramics, and metals. The situation in which radiative conductivity is modeled utilizing the Stefan–Boltzmann law is investigated. If the temperature variation parameter, Tr, is equal to zero, the classical Cheng–Minkowycz solution is recovered. For a non-zero value of Tr the results show that the reduced Rayleigh number is a decreasing function of Tr. DA - 2010/6// PY - 2010/6// DO - 10.1016/j.ijheatmasstransfer.2010.02.042 VL - 53 IS - 13-14 SP - 2676-2679 SN - 0017-9310 KW - Cheng-Minkowycz problem KW - Cellular porous medium KW - Radiative heat transfer KW - Temperature-dependent conductivity KW - Boundary layer ER - TY - JOUR TI - Natural convective boundary-layer flow of a nanofluid past a vertical plate AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - INTERNATIONAL JOURNAL OF THERMAL SCIENCES AB - The natural convective boundary-layer flow of a nanofluid past a vertical plate is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. A similarity solution is presented. This solution depends on a Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. For various values of Pr and Le, the variation of the reduced Nusselt number with Nr, Nb and Nt is expressed by correlation formulas. It was found that the reduced Nusselt number is a decreasing function of each of Nr, Nb and Nt. DA - 2010/2// PY - 2010/2// DO - 10.1016/j.ijthermalsci.2009.07.015 VL - 49 IS - 2 SP - 243-247 SN - 1778-4166 KW - Nanofluid KW - Brownian motion KW - Thermophoresis KW - Natural convection KW - Boundary layer KW - Vertical plate ER - TY - JOUR TI - Modeling the effect of a microtubule swirl on fast axonal transport AU - Kuznetsov, A. V. AU - Avramenko, A. A. AU - Blinov, D. G. T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - Many neurodegenerative diseases, such as Alzheimer's disease, are linked to swellings occurring in the long arms of neurons. Many scientists believe that these swellings result from traffic jams caused by the failure of the intracellular machinery responsible for fast axonal transport; such traffic jam can plug an axon and prevent the sufficient amount of organelles to be delivered toward the synapse of the axon. One possible mechanistic explanation of the formation of traffic jams in axons induced by overexpression of tau protein is based on the hypothesis that the traffic jam is caused not by the failure of molecular motors to transport organelles along individual microtubules but rather by the disruption of the microtubule system in an axon, by the formation of a swirl of disoriented microtubules at a certain location in the axon. This paper develops a model for investigating the effect of a microtubule swirl, as well as the effect of reversing polarity of a microtubule segment in the swirl region, on fast axonal transport. DA - 2010/3// PY - 2010/3// DO - 10.1016/j.icheatmasstransfer.2009.11.005 VL - 37 IS - 3 SP - 234-238 SN - 1879-0178 KW - Molecular motors KW - Motor-assisted transport KW - Neurons KW - Axons and dendrites KW - Intracellular organelles KW - Traffic jams ER - TY - JOUR TI - Functionally graded hydroxyapatite coatings doped with antibacterial components AU - Bai, Xiao AU - More, Karren AU - Rouleau, Christopher M. AU - Rabiei, Afsaneh T2 - ACTA BIOMATERIALIA AB - A series of functionally graded hydroxyapatite (FGHA) coatings incorporated with various percentages of silver were deposited on titanium substrates using ion beam-assisted deposition. The analysis of the coating's cross-section using transmission electron microscopy (TEM) and scanning transmission electron microscopy equipped with energy dispersive X-ray spectroscopy has shown a decreased crystallinity as well as a distribution of nanoscale (10-50nm) silver particles from the coating/substrate interface to top surface. Both X-ray diffraction and fast Fourier transforms on high-resolution TEM images revealed the presence of hydroxyapatite within the coatings. The amount of Ag (wt.%) on the outer surface of the FGHA, as determined from X-ray photoelectron spectroscopy, ranged from 1.09 to 6.59, which was about half of the average Ag wt.% incorporated in the entire coating. Average adhesion strengths evaluated by pull-off tests were in the range of 83+/-6 to 88+/-3MPa, which is comparable to 85MPa for FGHA without silver. Further optical observations of failed areas illustrated that the dominant failure mechanism was epoxy failure, and FGHA coating delamination was not observed. DA - 2010/6// PY - 2010/6// DO - 10.1016/j.actbio.2009.12.002 VL - 6 IS - 6 SP - 2264-2273 SN - 1878-7568 KW - Ion beam processing KW - Hydroxyapatite coating KW - Adhesion strength KW - Antimicrobial ER - TY - JOUR TI - Forced convection in cellular porous materials: Effect of temperature-dependent conductivity arising from radiative transfer AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - Forced convection in a channel occupied by a saturated cellular porous medium is investigated. The problem is formulated as a combined conductive–convective–radiative problem in which radiative heat transfer is treated as a diffusion process. The problem is relevant to cellular foams formed from plastics, ceramics and metals. Special cases in which radiative conductivity is modeled as a power function of temperature as well as the Stefan-Boltzmann case are investigated. Analytical and numerical solutions are obtained; Darcy and clear fluid limits are also studied. DA - 2010/6// PY - 2010/6// DO - 10.1016/j.ijheatmasstransfer.2010.02.041 VL - 53 IS - 13-14 SP - 2680-2684 SN - 1879-2189 KW - Cellular porous medium KW - Radiative heat transfer KW - Temperature-dependent conductivity ER - TY - JOUR TI - Effect of three treatment protocols on acute ocular hypertension after phacoemulsification and aspiration of cataracts in dogs AU - Crasta, Manuela AU - Clode, Alison B. AU - McMullen, Richard J., Jr. AU - Pate, Diana O. AU - Gilger, Brian C. T2 - VETERINARY OPHTHALMOLOGY AB - Objective To compare the effect of topical latanoprost, intracameral carbachol, or no adjunctive medical therapy on the development of acute postoperative hypertension (POH) and inflammation after routine phacoemulsification and aspiration (PA) of cataracts in dogs. Design Retrospective study. Procedures Dogs received either one drop of topical 0.005% latanoprost (21 dogs, 39 eyes), an intracameral injection of 0.3 mL of 0.01% carbachol (15 dogs, 30 eyes), or no adjunctive therapy (46 dogs, 90 eyes) immediately following PA of cataract(s). Intraocular pressure (IOP) was measured in all dogs 2 and 4 h after surgery. IOP was measured and aqueous flare assessed at 8am the day after surgery. Results Carbachol-treated dogs had significantly higher mean IOP (33.2 ± SD 20.8 mmHg) 2 h after surgery than dogs receiving no adjunctive therapy (22.0 ± SD 14.1 mmHg) (P = 0.049). There were no significant differences in IOP among groups at any other time point. There were no significant differences in number of POH episodes between dogs treated with carbachol (47%), latanoprost (29%), or dogs that received no adjunctive therapy (33%). There were no significant differences in mean aqueous flare grade between eyes treated with latanoprost (1.7 ± SD 0.4) or carbachol (1.4 ± SD 0.6), and eyes that received no adjunctive therapy (1.7 ± SD 0.4). Conclusions Topical 0.005% latanoprost or intracameral injection of 0.3 mL of 0.01% carbachol after PA in dogs did not reduce POH or increase intraocular inflammation compared to dogs not receiving adjunctive therapy after PA of cataracts. DA - 2010/1// PY - 2010/1// DO - 10.1111/j.1463-5224.2009.00748.x VL - 13 IS - 1 SP - 14-19 SN - 1463-5224 KW - carbachol KW - cataract KW - dogs KW - IOP KW - latanoprost KW - phacoemulsification ER - TY - JOUR TI - Effect of the width of regions with severed microtubules on transport of organelles down the axon AU - Kuznetsov, A. V. T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - This paper investigates the effects of structural changes in the microtubule system on traffic jam formation in fast axonal transport and on inhibiting transport of organelles down the axon. Understanding this process is important for understanding the underlying reasons for many neurodegenerative diseases, such as Alzheimer's disease. In particular, the effect of the width of regions with severed microtubules (also called organelle traps) on the amount of organelles delivered to the synapse of the axon is investigated. Three cases with a different degree of microtubule polar mismatching in the microtubule swirl region are investigated. It is demonstrated that in all three cases increasing the width of organelle trap regions significantly decreases the flux of organelles down the axon compared to that in a healthy axon, in which case organelle traps are absent. DA - 2010/5// PY - 2010/5// DO - 10.1016/j.icheatmasstransfer.2009.12.008 VL - 37 IS - 5 SP - 443-448 SN - 0735-1933 KW - Molecular motors KW - Motor-assisted transport KW - Fast axonal transport KW - Neurons KW - Axons and dendrites KW - Intracellular organelles KW - Vesicle traps KW - Traffic jams ER - TY - JOUR TI - Assessment of damage in composite laminates through dynamic, full-spectral interrogation of fiber Bragg grating sensors AU - Propst, A. AU - Peters, K. AU - Zikry, M. A. AU - Schultz, S. AU - Kunzler, W. AU - Zhu, Z. AU - Wirthlin, M. AU - Selfridge, R. T2 - SMART MATERIALS AND STRUCTURES AB - In this study, we demonstrate the full-spectral interrogation of a fiber Bragg grating (FBG) sensor at 535 Hz. The sensor is embedded in a woven, graphite fiber–epoxy composite laminate subjected to multiple low-velocity impacts. The measurement of unique, time dependent spectral features from the FBG sensor permits classification of the laminate lifetime into five regimes. These damage regimes compare well with previous analysis of the same material system using combined global and local FBG sensor information. Observed transient spectral features include peak splitting, wide spectral broadening and a strong single peak at the end of the impact event. Such features could not be measured through peak wavelength interrogation of the FBG sensor. Cross-correlation of the measured spectra with the original embedded FBG spectrum permitted rapid visualization of average strains and the presence of transverse compressive strain on the optical fiber, but smeared out the details of the spectral profile. DA - 2010/1// PY - 2010/1// DO - 10.1088/0964-1726/19/1/015016 VL - 19 IS - 1 SP - SN - 0964-1726 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-74849118513&partnerID=MN8TOARS ER - TY - JOUR TI - Alternative solutions for longitudinal fins of rectangular, trapezoidal, and concave parabolic profiles AU - Aziz, A. AU - Fang, Tiegang T2 - Energy Conversion and Management AB - The traditional thermal analysis of fins is based on the assumption of specified thermal boundary conditions at the base and tip of the fin. For situations when the fin base is in contact with a fluid experiencing condensation and the fin is required to remove the energy released by the fluid, the base is subjected to two boundary conditions: a fixed temperature and a fixed heat flux. This paper develops solutions for the temperature distribution in the fins under these conditions. Solutions are provided for rectangular, trapezoidal, and concave parabolic (finite tip thickness). Results illustrating the relationship between the dimensionless heat flux, the fin parameter, and dimensionless tip temperature are provided for all three geometries. The case of convective fin tip is also considered and lead to a relationship between the dimensionless heat flux, the fin parameter, and the Biot number at the tip. The results presented here provide tools that not only complement the traditional analyses but are believed to have more direct relevance for the fin designers. DA - 2010/// PY - 2010/// DO - 10.1016/j.enconman.2010.03.012 VL - 51 IS - 11 SP - 2188-2194 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77953915774&partnerID=MN8TOARS ER - TY - JOUR TI - A Linear Mapping Technique for Dispersion Removal of Lamb Waves AU - Liu, L. AU - Yuan, F. G. T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - A robust signal processing technique using linear mapping for removing dispersion of Lamb waves is presented in this article. Based on the assumption that the dispersion relation characteristic can be adequately approximated by a finite polynomial in the region close to the high wave energy intensity, the dispersion effect begins to reveal in the second-order term of the polynomial. The linear mapping performed in the finite usable frequency domain is to transform the original in priori known dispersion relation into the linear dispersion relation, i.e., truncated the polynomial up to the linear term which is nondispersive. The linear mapping technique does not require the propagation-path lengths and can be applied to the signals consisting of multiple arrivals with the same wave mode or dispersion characteristic. Synthetic and experimental data for isotropic plates with finite in-plane dimensions excited by the fundamental flexural wave mode are shown to demonstrate the robustness of the proposed dispersion removal technique. DA - 2010/1// PY - 2010/1// DO - 10.1177/1475921709341012 VL - 9 IS - 1 SP - 75-86 SN - 1741-3168 KW - wave propagation KW - dispersion removal KW - linear mapping KW - piezoelectric KW - lamb wave ER - TY - JOUR TI - Simulation of Shock/Boundary-Layer Interactions with Bleed Using Immersed-Boundary Methods AU - Ghosh, Santanu AU - Choi, Jung-Il AU - Edwards, Jack R. T2 - JOURNAL OF PROPULSION AND POWER AB - This work utilizes an immersed boundary (IB) method to simulate the effects of arrays of discrete bleed ports in controlling shock wave / turbulent boundary layer inter actions . Both Reynolds averaged Navier -Stokes (RANS) and hybrid large -eddy / Reynolds -averaged Navier -Stokes (LES/RANS) turbulence closures are used with the IB technique. The approach is validated by conducting simulations of Mach 2.5 flow over a perfo rated plate containing 18 individual bleed holes. Predictions of discharge coefficient as a function of bleed plenum pressure are compared with experimental data. Simulations of an impinging oblique shock / boundary layer interaction at Mach 2.45 with an d without active bleed control are also performed. The 68 -hole bleed plate is rendered as an immersed object in the computational domain. Wall pressure predictions show that, in general, the LES/RANS technique under -estimate s the upstream extent of axi al separation that occurs in the absence of bleed. Good agreement with P itot -pressure surveys throughout the interaction region is obtained, however. Active suction completely removes the separation region and induces local disturbances in the wall pres sure distributions that are associated with the expansion of the boundary layer fluid into the bleed port and its subsequ ent re -compression. Predicted Pitot -pressure distributions are in good agreement with experiment for the case with bleed. Swirl stre ngth probability -density distributions are used to estimate the evolution of turbulence length -sca les throughout the interaction, and the effects of bleed on the amplification of Reynolds stresses are highlighted. Finally, simple improvements to engineerin g-level bleed models are proposed based on the computational results. DA - 2010/// PY - 2010/// DO - 10.2514/1.45297 VL - 26 IS - 2 SP - 203-214 SN - 0748-4658 ER - TY - JOUR TI - SMASIS Symposium on Structural Health Monitoring Preface AU - Joshi, Shiv AU - Peters, Kara T2 - JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES DA - 2010/2// PY - 2010/2// DO - 10.1177/1045389x09359109 VL - 21 IS - 3 SP - 223-223 SN - 1045-389X ER - TY - JOUR TI - Radioembolization (yttrium-90 microspheres) for primary and metastatic hepatic malignancies AU - Kennedy, A. S. AU - Salem, R. T2 - Cancer Journal DA - 2010/// PY - 2010/// VL - 16 IS - 2 SP - 163-175 ER - TY - JOUR TI - Peak wavelength interrogation of fiber Bragg grating sensors during impact events AU - Park, Chun AU - Peters, Kara AU - Zikry, Mohammed AU - Haber, Todd AU - Schultz, Stephen AU - Selfridge, Richard T2 - SMART MATERIALS AND STRUCTURES AB - In this paper, we embed fiber Bragg grating (FBG) sensors in graphite fiber–epoxy woven composite laminates to detect evolving damage modes. The peak wavelengths of the FBG sensors are interrogated at 625 and 295 kHz, while the laminates are subjected to 11.0 J low-velocity impact events. It is demonstrated that 295 kHz interrogation is sufficient for accurately collecting the dynamic response of the sensors. The FBG sensors embedded at the laminate midplanes successfully reconstructed the global laminate response to impact. The maximum and full width at half-maximum (FWHM) for the relative strain histories demonstrated the same trends as the maximum and FWHM of the contact force histories measured from the impactor. More noise was present in the strain histories obtained from the FBG sensors than the contact force histories, as the embedded FBGs were sensitive to local perturbations in the stress state. The FBG sensors embedded below the midplane of the laminate were closer to the damage regions and measured complex strain histories. In one case, this strain history revealed the presence of delamination. DA - 2010/4// PY - 2010/4// DO - 10.1088/0964-1726/19/4/045015 VL - 19 IS - 4 SP - SN - 1361-665X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77949894501&partnerID=MN8TOARS ER - TY - JOUR TI - Human-Induced Particle Re-Suspension in a Room AU - Oberoi, Roshan C. AU - Choi, Jung-Il AU - Edwards, Jack R. AU - Rosati, Jacky A. AU - Thornburg, Jonathan AU - Rodes, Charles E. T2 - AEROSOL SCIENCE AND TECHNOLOGY AB - A large-eddy simulation/immersed boundary method for particulate flows in an Eulerian framework is utilized to investigate short-term particle re-suspension due to human motion. The simulations involve a human walking through a room, stopping, and then walking in place, causing particles to be re-suspended from a carpet. The carpet layer is modeled as the porous medium and a classical adhesive force model is applied to model the resistance of the carpet-bound material to hydrodynamic forcing. The effects of parameters such as the foot penetration depth and adhesive force coefficient on mass re-suspended during the foot stamping events are examined. Simulations of particulate re-suspension experiments conducted in a room within a U.S. Environmental Protection Agency test house are also described. The simulations vary the type of human motion (stamping in place versus stamping in place with rotation). The results indicate that significant amounts of particulate material are re-suspended from the carpet layer due to the impingement of the feet during the motion event. The net mass re-suspended for human motion with rotation is two times greater than that for the motion without rotation, while the mass of re-suspended small particles is slightly greater than that of large particles. The re-suspension rates are estimated based on several time scales, and the predicted total particle number concentrations at several locations in the room show good agreement with experimental data. The present CFD model can be utilized to predict particle re-suspension rates as induced by human motion, but further work in modeling the fine-scale details of the re-suspension process is needed. DA - 2010/// PY - 2010/// DO - 10.1080/02786820903530852 VL - 44 IS - 3 SP - 216-229 SN - 1521-7388 ER - TY - JOUR TI - Finite element analysis of barbed sutures in skin and tendon tissues AU - Ingle, N. P. AU - King, M. W. AU - Zikry, M. A. T2 - JOURNAL OF BIOMECHANICS AB - Barbed surgical sutures are a new type of knotless suture that are currently being used clinically in cosmetic and plastic surgery procedures for faster healing and better cosmesis. Clinical studies are also underway to evaluate their performance in other deep tissue applications. However, little is known about their intrinsic mechanical behavior and their interactions with surrounding tissues. The primary objective of the current study was to analyze the mechanical behavior of barbed sutures using a finite element analysis approach. First, the effect of applying a point-pressure load to the tip of the barb and measuring its effect on barb displacement was studied. Second, the effect of an applied displacement to a barb anchored either in skin or tendon material for both the suture and the surrounding tissue. The results indicate that the flexibility of the barb can be increased or decreased by changing the barb geometry. It was concluded that the barb geometry and design need to be modified for use with different types of tissue. For example, in order to achieve the best mechanical anchoring with skin tissue the barb should be more flexible compared to the one designed to work with tendon tissue. The uniqueness of this study is that it is the first to establish a virtual prototyping and designing method for barbed sutures. For example, a new and improved virtual design of barb geometry is proposed and validated. It also provides the first report on how to develop a virtual bench top suture/tissue pullout testing environment. DA - 2010/3/22/ PY - 2010/3/22/ DO - 10.1016/j.jbiomech.2009.11.012 VL - 43 IS - 5 SP - 879-886 SN - 1873-2380 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77549083739&partnerID=MN8TOARS KW - Finite element analysis KW - Suture KW - Barbed KW - Tendon KW - Skin KW - Tissue ER - TY - JOUR TI - A laparoscopic knot-tying device for minimally invasive cardiac surgery☆ AU - Jernigan, Shaphan R. AU - Chanoit, Guillaume AU - Veeramani, Arun AU - Owen, Stephen B. AU - Hilliard, Matthew AU - Cormier, Denis AU - Laffitte, Bryan AU - Buckner, Gregory T2 - European Journal of Cardio-Thoracic Surgery AB - Intracorporeal suturing and knot tying can complicate, prolong or preclude minimally invasive surgical procedures, reducing their advantages over conventional approaches. An automated knot-tying device has been developed to speed suture fixation during minimally invasive cardiac surgery while retaining the desirable characteristics of conventional hand-tied surgeon's knots: holding strength and visual and haptic feedback. A rotating slotted disc (at the instrument's distal end) automates overhand throws, thereby eliminating the need to manually pass one suture end through a loop in the opposing end. The electronic actuation of this disc produces left or right overhand knots as desired by the operator.To evaluate the effectiveness of this technology, seven surgeons with varying laparoscopic experience tied knots within a simulated minimally invasive setting, using both the automated knot-tying tool and conventional laparoscopic tools. Suture types were 2/0 braided and 4/0 monofilament.Mean knot-tying times were 246+/-116 s and 102+/-46 s for conventional and automated methods, respectively, showing an average 56% reduction in time per surgeon (p=0.003, paired t-test). The peak holding strength of each knot (the force required to break the suture or loosen the knot) was measured using tensile-testing equipment. These peak holding strengths were normalised by the ultimate tensile strength of each suture type (57.5 N and 22.1N for 2/0 braided and 4/0 monofilament, respectively). Mean normalised holding strengths for all knots were 68.2% and 71.8% of ultimate tensile strength for conventional and automated methods, respectively (p=0.914, paired t-test).Experimental data reveal that the automated suturing device has great potential for advancing minimally invasive surgery: it significantly reduced knot-tying times while providing equivalent or greater holding strength than conventionally tied knots. DA - 2010/3// PY - 2010/3// DO - 10.1016/j.ejcts.2009.09.024 VL - 37 IS - 3 SP - 626-630 J2 - European Journal of Cardio-Thoracic Surgery LA - en OP - SN - 1010-7940 UR - http://dx.doi.org/10.1016/j.ejcts.2009.09.024 DB - Crossref KW - Automated suturing KW - Knot tying KW - Fixation KW - Minimally invasive surgery ER - TY - JOUR TI - The onset of bio-thermal convection in a suspension of gyrotactic microorganisms in a fluid layer with an inclined temperature gradient AU - Avramenko, A. A. AU - Kuznetsov, A. V. T2 - INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW AB - Purpose The purpose of this paper is to investigate a combined bioconvection and thermal instability problem in a horizontal layer of finite depth with a basic temperature gradient inclined to the vertical. The basic flow, driven by the horizontal component of temperature gradient, is the Hadley circulation, which becomes unstable when the vertical temperature difference and density stratification induced by upswimming of microorganisms that are heavier than water become sufficiently large. Design/methodology/approach Linear stability analysis of the basic state is performed; the numerical problem is solved using the collocation method. Findings The steady‐state solution of this problem is obtained. Linear stability analysis of this steady‐state solution for the case of three‐dimensional disturbances is performed; the numerical problem is solved using the collocation method. The stability problem is governed by three Rayleigh numbers: the bioconvection Rayleigh number and two thermal Rayleigh numbers characterizing temperature gradients in the vertical and horizontal directions, respectively. Research limitations/implications Further research should address the application of weakly non‐linear analysis to this problem. Practical implications The dependence of the critical bioconvection Rayleigh number on the two thermal Rayleigh numbers and other relevant parameters is investigated. Originality/value This paper presents what is believed to be the first research dealing with the effect of inclined temperature gradient on the stability of bioconvection in a suspension of gyrotactic microorganisms. DA - 2010/// PY - 2010/// DO - 10.1108/09615531011008154 VL - 20 IS - 1 SP - 111-129 SN - 1758-6585 KW - Convection KW - Temperature distribution KW - Microorganisms KW - Flow ER - TY - JOUR TI - The effect of local thermal nonequilibrium on the onset of convection in a nanofluid AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - Journal of Heat Transfer AB - The onset of convection in a horizontal layer of a nanofluid is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis, and allows for local thermal nonequilibrium (LTNE) between the particle and fluid phases. The analysis reveals that in some circumstances, the effect of LTNE can be significant, but for a typical dilute nanofluid (with large Lewis number and with small particle-to-fluid heat capacity ratio), the effect is small. DA - 2010/// PY - 2010/// DO - 10.1115/1.4000474 VL - 132 IS - 5 ER - TY - JOUR TI - Simulation of Supersonic Combustion Involving H-2/Air and C2H4/Air AU - Keistler, P. G. AU - Hassan, H. A. T2 - AIAA JOURNAL AB - A turbulence model that calculates the turbulent Prandtl and Schmidt numbers as part of the solution is presented. This model also accounts for compressibility effects, and addresses turbulence/chemistry interaction. Its predictions are compared with two experiments: an axisymmetric case involving mixing, hydrogen combustion, and ethylene combustion; and a three-dimensional ethylene mixing experiment. Fair to good agreement is indicated in the cases where data is available. Chemical mechanisms are found to have an influence on autoignition for hydrogen combustion cases, and on ignition location and flame size for hydrogen/ethylene combustion cases using reduced mechanisms. DA - 2010/1// PY - 2010/1// DO - 10.2514/1.43213 VL - 48 IS - 1 SP - 166-173 SN - 1533-385X ER - TY - JOUR TI - Self-similarity in particle-laden flows at constant volume AU - Grunewald, N. AU - Levy, R. AU - Mata, M. AU - Ward, T. AU - Bertozzi, A. L. T2 - Journal of Engineering Mathematics DA - 2010/// PY - 2010/// VL - 66 IS - 1-3 SP - 53-63 ER - TY - JOUR TI - Numerical Simulations of Effects of Micro Vortex Generators Using Immersed-Boundary Methods AU - Ghosh, Santanu AU - Choi, Jung-Il AU - Edwards, Jack R. T2 - AIAA JOURNAL AB - This work presents an immersed-boundary technique for compressible, turbulent flows and applies the technique to simulate the effects of micro vortex generators in controlling oblique-shock/turbulent boundary-layer interactions. The Reynolds-averaged Navier-Stokes equations, closed using the Menter k-ω turbulence model, are solved in conjunction with the immersed-boundary technique. The approach is validated by comparing solutions obtained using the immersed-boundary technique with solutions obtained on a body-fitted mesh and with experimental laser Doppler anemometry data collected at Cambridge University for Mach 2.5 flow over single micro vortex generators. Simulations of an impinging oblique-shock boundary-layer interaction at Mach 2.5 with and without micro vortex-generator flow control are also performed, considering the development of the flow in the entire wind tunnel. Comparisons are made with experimental laser Doppler anemometry data and surface-pressure measurements from Cambridge University and an analysis of the flow structure is performed. The results show that three dimensional effects initiated by the interaction of the oblique shock with the sidewall boundary layers significantly influence the flow patterns in the actual experiment. The general features of the interactions with and without the micro vortex-generator array are predicted to good accord by the Reynolds-averaged Navier-Stokes/ immersed-boundary model. DA - 2010/1// PY - 2010/1// DO - 10.2514/1.40049 VL - 48 IS - 1 SP - 92-103 SN - 0001-1452 ER - TY - JOUR TI - Mechanical Properties of ZnO Nanowires Under Different Loading Modes AU - Xu, Feng AU - Qin, Qingqun AU - Mishra, Ashish AU - Gu, Yi AU - Zhu, Yong T2 - NANO RESEARCH AB - A systematic experimental and theoretical investigation of the elastic and failure properties of ZnO nanowires (NWs) under different loading modes has been carried out. In situ scanning electron microscopy (SEM) tension and buckling tests on single ZnO NWs along the polar direction [0001] were conducted. Both tensile modulus (from tension) and bending modulus (from buckling) were found to increase as the NW diameter decreased from 80 to 20 nm. The bending modulus increased more rapidly than the tensile modulus, which demonstrates that the elasticity size effects in ZnO NWs are mainly due to surface stiffening. Two models based on continuum mechanics were able to fit the experimental data very well. The tension experiments showed that fracture strain and strength of ZnO NWs increased as the NW diameter decreased. The excellent resilience of ZnO NWs is advantageous for their applications in nanoscale actuation, sensing, and energy conversion. DA - 2010/4// PY - 2010/4// DO - 10.1007/s12274-010-1030-4 VL - 3 IS - 4 SP - 271-280 SN - 1998-0124 KW - ZnO nanowire KW - mechanical property KW - size effect KW - Young's modulus KW - fracture ER - TY - JOUR TI - Hybrid Reynolds-Averaged/Large-Eddy Simulations of a Coaxial Supersonic Freejet Experiment AU - Baurle, R. A. AU - Edwards, J. R. T2 - AIAA JOURNAL AB - Reynolds-averaged and hybrid Reynolds-averaged/large-eddy simulations have been applied to a supersonic coaxial jet flow experiment. The experiment was designed to study compressible mixing flow phenomenon under conditions that are representative of those encountered in scramjet combustors. The experiment used either helium or argon as the inner jet nozzle fluid, and the outer jet nozzle fluid consisted of laboratory air. The inner and outer nozzles were designed and operated to produce nearly pressure-matched Mach 1.8 flow conditions at the jet exit. The purpose of the computational effort was to assess the state of the art for each modeling approach and to use the hybrid Reynolds-averaged/large-eddy simulations to gather insight into the deficiencies of the Reynolds-averaged closure models. The Reynolds-averaged simulations displayed a strong sensitivity to choice of turbulent Schmidt number. The initial value chosen for this parameter resulted in an overprediction of the mixing layer spreading rate for the helium case, but the opposite trend was observed when argon was used as the injectant. A larger turbulent Schmidt number greatly improved the comparison of the results with measurements for the helium simulations, but variations in the Schmidt number did not improve the argon comparisons. The hybrid Reynolds-averaged/largeeddy simulations also overpredicted the mixing layer spreading rate for the helium case, while underpredicting the rate of mixing when argon was used as the injectant. The primary reason conjectured for the discrepancy between the hybrid simulation results and the measurements centered around issues related to the transition from a Reynolds-averaged state to one with resolved turbulent content. Improvements to the inflow conditions were suggested as a remedy to this dilemma. Second-order turbulence statistics were also compared with their modeled Reynolds-averaged counterparts to evaluate the effectiveness of common turbulence closure assumptions. DA - 2010/3// PY - 2010/3// DO - 10.2514/1.43771 VL - 48 IS - 3 SP - 551-571 SN - 0001-1452 ER - TY - JOUR TI - Automated Part Centering With Impulse Actuation AU - Furst, S. J. AU - Dow, T. A. AU - Garrard, K. AU - Sohn, A. T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME AB - Centering a part on a spindle for precision machining is a tedious, time-consuming task. Currently, a skilled operator must measure the run-out of a part using a displacement gauge, then tap the part into place using a plastic or rubber hammer. This paper describes a method to automatically center a part on a vacuum chuck with initial run-out as large as 2.5 mm. The method involves measuring the magnitude and direction of the radial run-out and then actuating the part until the part and spindle centerlines are within 5 μm of each other. The run-out can be measured with either a touch probe mounted to a machine axis or an electronic gauge. The part is tapped into place with a linear actuator driven by a voice coil motor. This paper includes an analysis of run-out measurement uncertainty as well as the design, performance modeling, and testing of the alignment actuator. This actuator was employed for part realignment and successfully positioned a hemispherical part with an initial run-out of 1–2.5 mm to within 5 μm of the spindle centerline. This capability shows that the run-out of a part manually placed on flat vacuum chuck can be automatically corrected. DA - 2010/2// PY - 2010/2// DO - 10.1115/1.4000681 VL - 132 IS - 1 SP - SN - 1528-8935 KW - actuators KW - electric motors KW - hand tools KW - machining KW - plastics ER - TY - JOUR TI - Airflow and Particle Transport in the Human Respiratory System AU - Kleinstreuer, C. AU - Zhang, Z. T2 - ANNUAL REVIEW OF FLUID MECHANICS AB - Airflows in the nasal cavities and oral airways are rather complex, possibly featuring a transition to turbulent jet-like flow, recirculating flow, Dean's flow, vortical flows, large pressure drops, prevailing secondary flows, and merging streams in the case of exhalation. Such complex flows propagate subsequently into the tracheobronchial airways. The underlying assumptions for particle transport and deposition are that the aerosols are spherical, noninteracting, and monodisperse and deposit upon contact with the airway surface. Such dilute particle suspensions are typically modeled with the Euler-Lagrange approach for micron particles and in the Euler-Euler framework for nanoparticles. Micron particles deposit nonuniformly with very high concentrations at some local sites (e.g., carinal ridges of large bronchial airways). In contrast, nanomaterial almost coats the airway surfaces, which has implications of detrimental health effects in the case of inhaled toxic nanoparticles. Geometric airway features, as well as histories of airflow fields and particle distributions, may significantly affect particle deposition. DA - 2010/// PY - 2010/// DO - 10.1146/annurev-fluid-121108-145453 VL - 42 SP - 301-334 SN - 0066-4189 KW - human respiratory air-way models KW - experimental observations and computer simulations KW - laminar/turbulent airflow structures KW - dilute suspensions of nanomaterial KW - solid particles or droplets KW - inhaled/exhaled aerosol transport and deposition ER - TY - JOUR TI - Thermal Instability in a Porous Medium Layer Saturated by a Nanofluid: Brinkman Model AU - Kuznetsov, A. V. AU - Nield, D. A. T2 - TRANSPORT IN POROUS MEDIA DA - 2010/2// PY - 2010/2// DO - 10.1007/s11242-009-9413-2 VL - 81 IS - 3 SP - 409-422 SN - 1573-1634 KW - Thermal instability KW - Nanoparticles KW - Nanofluids KW - Horton-Rogers-Lapwood problem ER - TY - JOUR TI - Reducing Ability and Mechanism for Polyvinylpyrrolidone (PVP) in Silver Nanoparticles Synthesis AU - Wu, Chunwei AU - Mosher, Brian P. AU - Lyons, Kevin AU - Zeng, Taofang T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AB - Recently, it has been found that polyvinylpyrrolidone (PVP), a popular stabilizer in nanoparticles syntheses, possesses reducing ability for Ag+. Previous explanations of the reduction are, however, thought to be plausible. Based on detailed characterizations including UV-Vis, FTIR-ATR and XPS, we uncover the existence of Ag+ -O interaction, and demonstrate that the Ag+ -PVP complex is first formed via the coordination between Ag+ and O in the carbonyl group, which facilitates electron exchange between Ag+ and adjacent N atom on the pyrrolidone ring. The N atoms with lone pair electrons serve as an electron donator, leading reduction of Ag- to form PVP-capped Ag nanoparticles ultimately. DA - 2010/4// PY - 2010/4// DO - 10.1166/jnn.2010.1915 VL - 10 IS - 4 SP - 2342-2347 SN - 1533-4899 KW - Nanoparticles KW - Polyvinylpyrrolidone KW - Reducing ER - TY - JOUR TI - Computer Modeling of Controlled Microsphere Release and Targeting in a Representative Hepatic Artery System AU - Basciano, Christopher A. AU - Kleinstreuer, Clement AU - Kennedy, Andrew S. AU - Dezarn, William A. AU - Childress, Emily T2 - ANNALS OF BIOMEDICAL ENGINEERING DA - 2010/5// PY - 2010/5// DO - 10.1007/s10439-010-9955-z VL - 38 IS - 5 SP - 1862-1879 SN - 1573-9686 KW - Computational fluid-particle dynamics KW - Yttrium-90 particle transport KW - Transient particle-hemodynamics KW - Non-Newtonian fluid KW - Drug-targeting methodology ER - TY - PAT TI - Composite metal foam and methods of preparation thereof AU - Rabiei, A. C2 - 2010/// DA - 2010/// PY - 2010/// ER - TY - JOUR TI - COMPUTER MODELING OF YTTRIUM-90-MICROSPHERE TRANSPORT IN THE HEPATIC ARTERIAL TREE TO IMPROVE CLINICAL OUTCOMES AU - Kennedy, Andrew S. AU - Kleinstreuer, Clement AU - Basciano, Christopher A. AU - Dezarn, William A. T2 - INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS AB - Radioembolization (RE) via yttrium-90 ((90)Y) microspheres is an effective and safe treatment for unresectable liver malignancies. However, no data are available regarding the impact of local blood flow dynamics on (90)Y-microsphere transport and distribution in the human hepatic arterial system.A three-dimensional (3-D) computer model was developed to analyze and simulate blood-microsphere flow dynamics in the hepatic arterial system with tumor. Supplemental geometric and flow data sets from patients undergoing RE were also available to validate the accuracy of the computer simulation model. Specifically, vessel diameters, curvatures, and branching patterns, as well as blood flow velocities/pressures and microsphere characteristics (i.e., diameter and specific gravity), were measured. Three-dimensional computer-aided design software was used to create the vessel geometries. Initial trials, with 10,000 noninteracting microspheres released into the hepatic artery, used resin spheres 32-microm in diameter with a density twice that of blood.Simulations of blood flow subject to different branch-outlet pressures as well as blood-microsphere transport were successfully carried out, allowing testing of two types of microsphere release distributions in the inlet plane of the main hepatic artery. If the inlet distribution of microspheres was uniform (evenly spaced particles), a greater percentage would exit into the vessel branch feeding the tumor. Conversely, a parabolic inlet distribution of microspheres (more particles around the vessel center) showed a high percentage of microspheres exiting the branch vessel leading to the normal liver.Computer simulations of both blood flow patterns and microsphere dynamics have the potential to provide valuable insight on how to optimize (90)Y-microsphere implantation into hepatic tumors while sparing normal tissue. DA - 2010/2/1/ PY - 2010/2/1/ DO - 10.1016/j.ijrobp.2009.06.069 VL - 76 IS - 2 SP - 631-637 SN - 0360-3016 KW - Hepatic artery system KW - Y-90-microspheres KW - Computer modeling KW - Blood flow KW - Particle transport ER - TY - JOUR TI - A novel ultra-light structure for radiation shielding AU - Xu, Siqi AU - Bourham, Mohamed AU - Rabiei, Afsaneh T2 - MATERIALS & DESIGN AB - A new ultra-light structure based on the application of open-cell metal foams has been designed and investigated to determine its ability for attenuation of γ-rays and thermal neutrons. Open-cell metal foam, a unique class of material, has been employed in the structure and is studied in this work where radiation attenuation abilities of foams and foams filled with water and borated water have been compared with bulk Aluminum. The γ-ray attenuation measurements were performed using γ-ray at 0.662, 1.173 and 1.332 MeV photon energies and thermal neutron attenuation measurements were conducted using a polyenergetic thermal neutron beam. The results show that the metallic foam by itself attenuates less γ-ray as compared to bulk material, while the mass attenuation coefficients of foams filled with water is higher than that of bulk metals. The thermal neutron experiment, on the other hand, has shown a dramatic attenuation improvement in foams filled with water and particularly with borated water as compared to bulk metal and foam. DA - 2010/4// PY - 2010/4// DO - 10.1016/j.matdes.2009.11.011 VL - 31 IS - 4 SP - 2140-2146 SN - 1873-4197 ER - TY - JOUR TI - The Effect of Strong Heterogeneity on the Onset of Convection in a Porous Medium: Periodic and Localized Variation AU - Kuznetsov, A. V. AU - Nield, D. A. AU - Simmons, Craig T. T2 - TRANSPORT IN POROUS MEDIA DA - 2010/1// PY - 2010/1// DO - 10.1007/s11242-009-9390-5 VL - 81 IS - 1 SP - 123-139 SN - 1573-1634 KW - Heterogeneity KW - Stability KW - Natural convection KW - Computer package KW - Periodic variation KW - Localized variation ER - TY - JOUR TI - Friction and Shear Strength at the Nanowire-Substrate Interfaces AU - Zhu, Yong AU - Qin, Qingquan AU - Gu, Yi AU - Wang, Zhong Lin T2 - NANOSCALE RESEARCH LETTERS AB - Abstract The friction and shear strength of nanowire (NW)–substrate interfaces critically influences the electrical/mechanical performance and life time of NW-based nanodevices. Yet, very few reports on this subject are available in the literature because of the experimental challenges involved and, more specifically no studies have been reported to investigate the configuration of individual NW tip in contact with a substrate. In this letter, using a new experimental method, we report the friction measurement between a NW tip and a substrate for the first time. The measurement was based on NW buckling in situ inside a scanning electron microscope. The coefficients of friction between silver NW and gold substrate and between ZnO NW and gold substrate were found to be 0.09–0.12 and 0.10–0.15, respectively. The adhesion between a NW and the substrate modified the true contact area, which affected the interfacial shear strength. Continuum mechanics calculation found that interfacial shear strengths between silver NW and gold substrate and between ZnO NW and gold substrate were 134–139 MPa and 78.9–95.3 MPa, respectively. This method can be applied to measure friction parameters of other NW–substrate systems. Our results on interfacial friction and shear strength could have implication on the AFM three-point bending tests used for nanomechanical characterisation. DA - 2010/2// PY - 2010/2// DO - 10.1007/s11671-009-9478-4 VL - 5 IS - 2 SP - 291-295 SN - 1931-7573 KW - Nanowire KW - Interface KW - Friction KW - Shear strength KW - Nanomechanics ER - TY - JOUR TI - Evaluation of modulus of elasticity of composite metal foams by experimental and numerical techniques AU - Vendra, L. AU - Rabiei, A. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The elastic behavior of Al–steel composite metal foams developed by casting technique was characterized by evaluating the modulus of elasticity through compression experiments, constitutive scaling equations and 2D finite element modeling. Experiments showed an elastic modulus of 10–12 GPa for Al–steel composite foams while the scaling laws predicted 3.5 GPa and 30 GPa as the lower and upper bounds of modulus of elasticity respectively. Two-dimensional finite element models of composite foams developed and analyzed assuming perfectly elastic materials, resulted in an elastic modulus of 10 GPa which is in good agreement with the experimental results. DA - 2010/3/25/ PY - 2010/3/25/ DO - 10.1016/j.msea.2009.11.004 VL - 527 IS - 7-8 SP - 1784-1790 SN - 1873-4936 KW - Composite foams KW - Compression KW - Elastic modulus KW - Modeling ER - TY - JOUR TI - Atomic-Scale Study of Plastic-Yield Criterion in Nanocrystalline Cu at High Strain Rates AU - Dongare, A. M. AU - Rajendran, A. M. AU - Lamattina, B. AU - Brenner, D. W. AU - Zikry, M. A. T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE DA - 2010/2// PY - 2010/2// DO - 10.1007/s11661-009-0113-x VL - 41A IS - 2 SP - 523-531 SN - 1073-5623 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77949270731&partnerID=MN8TOARS ER -