TY - JOUR TI - Role of baffles on flow fields inside wet-lay mixing tanks and their potential influence on fiber dispersion T2 - Textile Research Journal DA - 2003/// PY - 2003/// UR - https://publons.com/wos-op/publon/65200206/ ER - TY - JOUR TI - Dimple Enhanced Heat Transfer in High Aspect Ratio Channels AU - Ekkad, S.V. AU - Nasir, H. T2 - Journal of Enhanced Heat Transfer AB - Detailed heat transfer measurements are presented for a rectangular channel with dimples on one wall. Dimpled surfaces provide high heat transfer enhancement comparable to ribbed surfaces with reduced overall pressure drop. The heat transfer coefficients were measured using a transient liquid crystal technique. The effect of the channel flow Reynolds number was investigated for a wide range from 10,000 to 65,000. The channel is a 25.4 mm ґ 101.6 mm (1" ґ 4") rectangular cross-section with dimples on one of the 101.6 mm walls. Heat transfer enhancement around three times that of a smooth channel was achieved for all flow conditions. The overall pressure drop through the dimpled section of the passage was also measured. The resulting thermal performance of the dimpled surfaces is significantly higher than that of channels with protruding ribs. DA - 2003/// PY - 2003/// DO - 10.1615/JEnhHeatTransf.v10.i4.40 VL - 10 IS - 4 SP - 395-405 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1542708321&partnerID=MN8TOARS ER - TY - JOUR TI - Improved film cooling from cylindrical angled holes with triangular tabs: Effect of tab orientations AU - Nasir, H. AU - Acharya, S. AU - Ekkad, S. T2 - International Journal of Heat and Fluid Flow AB - The effect of discrete delta (or triangular)-shaped tabs with different orientations on the film cooling performance from a row of cylindrical holes is investigated. The holes are inclined at 35° along the streamwise direction and the tabs are located along the upstream edge of the holes. Three tab orientations are investigated: (1) tabs placed parallel to the film cooled surface covering a part of the hole; (2) tabs oriented downward at −45°; and (3) tabs oriented upwards at 45°. Measurements were carried out in a low-speed wind tunnel using the transient liquid crystal technique. The mainstream velocity and free-stream turbulence intensity in the low-speed wind tunnel are 9 m/s and 7% respectively and the mainstream Reynolds number based on hole diameter is around 7100. Three blowing ratios of 0.56, 1.13, and 1.7 are tested. Results show that the tabs oriented downwards provide the highest effectiveness at a blowing ratio of 0.56 while the tabs oriented horizontally provides the highest film effectiveness at blowing ratios of 1.13 and 1.7. The higher effectiveness with the tabs is due to the generation of secondary eddies counter-rotating with respect to the kidney pair; these eddies reduce jet penetration and thus increase film-cooling effectiveness. The horizontally oriented tabs produce higher discharge coefficients (lower pressure drop) over the entire range of blowing ratios. DA - 2003/// PY - 2003/// DO - 10.1016/S0142-727X(03)00082-1 VL - 24 IS - 5 SP - 657-668 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0042284896&partnerID=MN8TOARS ER - TY - CONF TI - Impingement heat transfer under linearly stretched arrays of holes AU - Gao, L. AU - Ekkad, S.V. AU - Bunker, R.S. AB - Impingement heat transfer for linearly stretched arrays of holes is investigated. In real engine configurations, impingement arrays are not always square with evenly spaced holes both in streamwise and spanwise direction. They are primarily directed to hot spot locations thus producing nonsquare arrays. In this study, the spacing between the holes increases in both the streamwise and spanwise direction simulating the stretching of the hole arrays downstream. Two different arrays are investigated with the first array having uniform diameter holes through the array placed in a stretched format. The second array has holes placed in the same locations with increasing diameter along the streamwise direction. The measured heat transfer coefficients for these arrays are then predicted using existing impingement heat transfer correlations based on regular evenly spaced arrays. Results show that the published correlations over-predict the effect of cross-flow. Also, the correlation was extrapolated for this study due to lack of information for extremely strong cross-flow effects. All measurements were obtained using the transient liquid crystal technique. C2 - 2003/// C3 - American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI DA - 2003/// DO - 10.1115/GT2003-38178 VL - 5 A SP - 91-100 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0347596456&partnerID=MN8TOARS ER - TY - CONF TI - Effect of tip gap and squealer geometry on measured heat transfer over a HPT rotor blade tip AU - Nasir, H. AU - Ekkad, S.V. AU - Kontrovitz, D.M. AU - Bunker, R.S. AU - Prakash, C. AB - The present study explores the effects of gap height and tip geometry on heat transfer distribution over the tip surface of a HPT first stage rotor blade. The pressure ratio (inlet total pressure to exit static pressure for the cascade) used was 1.2, and the experiments were run in a blow-down test rig with a four-blade linear cascade. A transient liquid crystal technique was used to obtain the tip heat transfer distributions. Pressure measurements were made on the blade surface and on the shroud for different tip geometries and tip gaps to characterize the leakage flow and understand the heat transfer distributions. Two different tip gap-to-blade span ratio of 1% and 2.6% are investigated for a plane tip and a deep squealer with depth-to-blade span ratio of 0.0416. For a shallow squealer with depth-to-blade span ratio of 0.0104, only 1% gap-to-span ratio is considered. The presence of the squealer alters the tip gap flow field significantly and produces lower overall heat transfer coefficients. The effects of different partial squealer arrangements are also investigated for the shallow squealer depth. These simulate partial burning off of the squealer in real turbine blades. Results show that in some cases, partial burning of squealers along the pressure surface may be beneficial in terms of overall reduction in heat transfer coefficients over the tip surface compared to the plain tip. C2 - 2003/// C3 - American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD DA - 2003/// DO - 10.1115/IMECE2003-41294 VL - 374 SP - 11-21 M1 - 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1842534972&partnerID=MN8TOARS ER - TY - CONF TI - Effect of blade tip geometry on tip flow and heat transfer for a blade in a low speed cascade AU - Saxena, V. AU - Nasir, H. AU - Ekkad, S.V. AB - A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer of a scaled up HPT turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the 2-D blade. The wind tunnel accommodates an 116° turn for the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83 × 105. The upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates the required free-stream turbulence of 4.8%. The center blade has a tip clearance gap of 1.5625% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. The effect of crosswise trip strips to reduce leakage flow and associated heat transfer is investigated with strips placed along the leakage flow direction, against the leakage flow and along the chord. Cylindrical pin fins and pitch variation of strips over the tip surface are also investigated. Detailed heat transfer measurements are obtained using a steady state HSI-based liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0. to 0.2, and to 0.4. Results show that the trip strips placed against the leakage flow produce the lowest heat transfer on the tips compared to all the other cases with a reduction between 10–15% compared to the plain tip. Results also show that the pitch of the strips has a small effect on the overall reduction. Cylindrical pins fins and strips along the leakage flow direction do not decrease the heat transfer coefficients and in some cases enhance the heat transfer coefficients by as much as 20%. C2 - 2003/// C3 - American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI DA - 2003/// DO - 10.1115/GT2003-38176 VL - 5 A SP - 81-90 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0346335565&partnerID=MN8TOARS ER - TY - JOUR TI - Flat surface film cooling from cylindrical holes with discrete tabs AU - Nasir, H. AU - Ekkad, S.V. AU - Acharya, S. T2 - Journal of Thermophysics and Heat Transfer AB - The effect of discrete delta-shaped tabs on film cooling performance from a row of cylindrical angled holes is investigated. The holes are inclined at 35 deg along the streamwise direction. Four tab locations are investigated: 1) tabs placed along the upstream edge of the hole covering 33% of the hole, 2) tabs placed along the upstream edge covering 11% of the hole, 3) tabs placed along the downstream edge of the hole, and 4) tabs placed along the lateral edges of the hole. They are compared to the baseline case without tabs. Measurements were carried out in a low-speed wind tunnel using the transient liquid crystal technique. The mainstream velocity and freestream turbulence intensity in the low-speed wind tunnel are 8.5 m/s and 6%, respectively, and the Reynolds number based on hole diameter is 6375. Three blowing ratios of 0.56, 1.13, and 1.7 are tested DA - 2003/// PY - 2003/// DO - 10.2514/2.6786 VL - 17 IS - 3 SP - 304-312 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0042767685&partnerID=MN8TOARS ER - TY - CONF TI - A material model for multi-scale analysis of textile composites AU - Bahei-El-Din, Y.A. AU - Rajendran, A.M. AU - Zikry, M.A. C2 - 2003/// C3 - Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference DA - 2003/// DO - 10.2514/6.2003-1476 VL - 1 SP - 685-690 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0042012928&partnerID=MN8TOARS ER - TY - JOUR TI - A case study of prototyping methods and design for manufacture: electrostatic window blinds AU - Kiefer, S. AU - Silverberg, Larry M. AU - Gonzalez, M. T2 - Journal of Engineering Design AB - This paper presents a case study of the design development of a new product, electrostatically actuated window blinds. The text presents a description of each stage in the prototype development followed by a discussion of different prototyping methods and design for manufacture and assembly issues. Results from electromechanical and thermal analyses of the product itself are also included. This case study determined that, for this product development, the most efficient, cost-effective prototyping solution was simple plastic injection moulding. It also concluded that following good design for manufacture and assembly practices during prototype construction will save time and money when transitioning to a production design. DA - 2003/// PY - 2003/// DO - 10.1080/0954482021000050820 VL - 15 IS - 1 SP - 91–106 ER - TY - CONF TI - The Role of Nozzle Design in Characteristics of the Hydroentangling Waterjets AU - Tafreshi, H.V. AU - Begenir, A. AU - Pourdeyhimi, B. T2 - 16th Annual Conference on Liquid Atomization and Spray Systems (ILASS Americas) C2 - 2003/5/18/ C3 - 16th Annual Conference on Liquid Atomization and Spray Systems (ILASS Americas) CY - Monterey, California DA - 2003/5/18/ PY - 2003/5/18/ ER - TY - CONF TI - The Role of Nozzle Design in Characteristics of the Hydroentangling Waterjets: Experimental Study AU - Begenir, A. AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - International Nonwovens Technical Conference (INTC 2003) C2 - 2003/9/15/ C3 - International Nonwovens Technical Conference (INTC 2003) CY - Baltimore, Maryland DA - 2003/9/15/ PY - 2003/9/15/ ER - TY - CONF TI - A Study on Cavitation inside Hydroentangling Nozzles AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - International Nonwovens Technical Conference (INTC 2003) C2 - 2003/9/15/ C3 - International Nonwovens Technical Conference (INTC 2003) CY - Baltimore, Maryland DA - 2003/9/15/ PY - 2003/9/15/ ER - TY - CONF TI - Gas-particle decoupling by nozzle-induced aerodynamic effects AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - American Filtration and Separation Society C2 - 2003/6/17/ C3 - American Filtration and Separation Society CY - Reno, Nevada DA - 2003/6/17/ PY - 2003/6/17/ ER - TY - JOUR TI - The structure of negatively curved spongy carbon AU - Benedek, G. AU - Vahedi-Tafreshi, H. AU - Barborini, E. AU - Piseri, P. AU - Milani, P. AU - Ducati, C. AU - Robertson, J. T2 - Diamond and Related Materials AB - This work reports on the production and characterization of a novel form of nanostructured carbon consisting of three-dimensional, fully connected sp2 networks. This form of carbon is characterized by interconnected thin layers forming a spongy structure with meso- and macroporosity. The spongy carbon is produced by a pulsed microplasma cluster source in the presence of a metal–organic catalyst and it can be deposited as a film by supersonic cluster beam deposition (SCBD). Unlike fullerenes, nanotubes and graphite, which consist of zero-, one- or two-dimensional covalent objects held together by van der Waals’ forces, this novel structure consists of a robust, multiply connected graphene sheet which is fully covalent in three dimensions. Theoretical analysis indicates that such carbon sponges apparently grow as minimal surfaces and have the long-sought topological structure of random schwarzites. DA - 2003/// PY - 2003/// DO - 10.1016/S0925-9635(03)00082-7 VL - 12 IS - 3-7 SP - 768-773 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0038184103&partnerID=MN8TOARS ER - TY - JOUR TI - Simulating the flow dynamics in hydroentangling nozzles: Effect of cone angle and nozzle aspect ratio AU - Vahedi Tafreshi, H. AU - Pourdeyhimi, B. T2 - Textile Research Journal DA - 2003/// PY - 2003/// VL - 73 IS - 8 SP - 700-704 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0042731538&partnerID=MN8TOARS ER - TY - JOUR TI - Role of baffles on flow fields inside wet-lay mixing tanks and their pontential influence on fiber dispersion AU - Vahedi Tafreshi, H. AU - Pourdeyhimi, B. T2 - Textile Research Journal DA - 2003/// PY - 2003/// VL - 73 IS - 7 SP - 575-582 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0041339609&partnerID=MN8TOARS ER - TY - JOUR TI - Design of a fastener clinching process using FEM AU - Wenning, Patrick H. AU - Ngaile, Gracious AU - Altan, Taylan T2 - Transaction of the North American Manufacturing Research Institution of SME DA - 2003/// PY - 2003/// VL - 31 SP - 17–24 ER - TY - CONF TI - Design and Analysis of Press and Shrink Fit Joints AU - Morrisey, P. AU - Eischen, J.W. AU - Dow, T.A. C2 - 2003/10// C3 - Proceedings of the American Society for Precision Engineering Conference DA - 2003/10// ER - TY - CONF TI - Discontinuous feedback control of a 3 link planar PPR underactuated manipulator AU - Mahindrakar, A.D. AU - Banavar, R.N. AU - Reyhanoglu, M. T2 - 40th Conference on Decision and Control AB - In this paper we consider the synthesis of a point-to-point control law for a three degrees of freedom planar PPR underactuated manipulator moving in a horizontal plane. We apply a discontinuous feedback controller construction derived for a special class of underactuated systems. By using a coordinate transformation, we transform the system into chained form which makes it suitable for the application of the discontinuous control law. Simulation results are presented that demonstrate the effectiveness of the controller. C2 - 2003/7/10/ C3 - Proceedings of the 40th IEEE Conference on Decision and Control (Cat. No.01CH37228) CY - Orlando, FL DA - 2003/7/10/ PY - 2001/12/4/ DO - 10.1109/cdc.2001.980626 PB - IEEE SN - 0780370619 UR - http://dx.doi.org/10.1109/cdc.2001.980626 ER - TY - CONF TI - Feedback control of an underactuated system with two unactuated degrees of freedom AU - Reyhanoglu, M. T2 - 40th Conference on Decision and Control AB - Studies the problem of controlling a planar rigid body containing a sliding block, which represents an underactuated mechanical system with two unactuated degrees of freedom. The main result of the paper is the construction of a point-to-point discontinuous feedback controller for the system by utilizing the nonlinear coupling between the directly actuated degrees of freedom and the unactuated degrees of freedom. C2 - 2003/7/10/ C3 - Proceedings of the 40th IEEE Conference on Decision and Control (Cat. No.01CH37228) CY - Orlando, FL DA - 2003/7/10/ PY - 2001/12/4/ DO - 10.1109/cdc.2001.980838 PB - IEEE SN - 0780370619 UR - http://dx.doi.org/10.1109/cdc.2001.980838 ER - TY - JOUR TI - Applied Linear Optimal Control: Examples and Algorithms AU - Bryson,, AE, Author AU - Reyhanoglu,, M, Reviewer T2 - Applied Mechanics Reviews AB - Preface 1. Static estimation 2. Random processes 3. Dynamic estimation - filters 4. Dynamic estimation - smoothers 5. LQ SFB follower-controllors 6. LQG follower-controllers 7. Smoothers for controlled plants 8. Time-invariant filters 9. Time-invariant LQ SFB follower-controllers 10. Time-invariant LQG follower-controllers 11. Worst case controllers 12. Robust TI LQG controllers Appendices References Index. DA - 2003/7/1/ PY - 2003/7/1/ DO - 10.1115/1.1579457 VL - 56 IS - 4 SP - B55-B56 LA - en OP - SN - 0003-6900 2379-0407 UR - http://dx.doi.org/10.1115/1.1579457 DB - Crossref ER - TY - JOUR TI - New relationships for temperature sensitivity of radiation AU - Fang, T. T2 - International Communications in Heat and Mass Transfer AB - In this work, the temperature sensitivity of radiation is extended to a certain wavelength interval and is also classified into two categories including the Temperature Sensitivity of Radiators (TSR) and the Temperature Sensitivity of Radiation Detectors (TSRD). Both the exact relationships and the approximated theories are presented. It is found that for a gray-body radiator with temperature-independent emissivity, the TSR is the same as TSRD for an ideal thermal radiation detector. However, there exists difference between an ideal quantum detector and an ideal thermal detector. This extension makes the defined quantity easier to be used in a lot of applications such as the design of industrial furnace and radiation detectors. DA - 2003/// PY - 2003/// DO - 10.1016/S0735-1933(03)00028-9 VL - 30 IS - 2 SP - 173-184 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0037353679&partnerID=MN8TOARS ER - TY - JOUR TI - Further study on a moving-wall boundary-layer problem with mass transfer AU - Fang, T. T2 - Acta Mechanica DA - 2003/// PY - 2003/// DO - 10.1007/s00707-002-0979-9 VL - 163 IS - 3-4 SP - 183-188 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0042973084&partnerID=MN8TOARS ER - TY - JOUR TI - Similarity solutions for a moving-flat plate thermal boundary layer AU - Fang, T. T2 - Acta Mechanica DA - 2003/// PY - 2003/// DO - 10.1007/s00707-003-0004-y VL - 163 IS - 3-4 SP - 161-172 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0041470273&partnerID=MN8TOARS ER - TY - JOUR TI - General discussion on displacement law of radiation AU - Fang, T. T2 - International Communications in Heat and Mass Transfer AB - The Wien's displacement law is generalized to the situations for a certain wavelength interval and non-blackbody radiator. The theory results in a closed form equation. The emissivity distribution can have great influences on the displacement law. The estimated temperature for given wavelengths may largely differ from those based on the Wien's displacement law and extended displacement law for blackbody radiation DA - 2003/// PY - 2003/// DO - 10.1016/S0735-1933(03)00111-8 VL - 30 IS - 5 SP - 737-743 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0043068111&partnerID=MN8TOARS ER - TY - JOUR TI - A new approximation method to evaluate thermal contrast AU - Fang, T. T2 - Infrared Physics and Technology AB - A new approximate approach is developed to evaluate the thermal contrast detected by a thermal detector or a quantum detector for a focal plane radiation-detecting instrument. Simple formulas for the detected thermal contrast are obtained. Two terms are included in the thermal contrast. The first term is based on the derivative of emissivity with respect to temperature. The second term is based on the temperature-dependent emissivity. The results can give a more straightforward relationship of these two terms than the previous methods. It is more useful in practical applications than the previous results. The relative error between the current approximation and the previous method is also assessed. It is found that the error will be less than 1% when λT<3000 μm K. Based on the new results, the influences of the two terms are investigated regarding some aspects including lower limit wavelength, wavelength interval of the detector and type of detectors. Although the computed examples are in infrared spectra and room temperature, the analysis and results can be applied to other wavelength and temperature, too. Application to internal combustion engines is also investigated. DA - 2003/// PY - 2003/// DO - 10.1016/S1350-4495(02)00210-4 VL - 44 IS - 3 SP - 191-198 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0037882110&partnerID=MN8TOARS KW - radiometry KW - emissivity KW - infrared KW - thermal contrast KW - thermal detector KW - quantum detector ER - TY - JOUR TI - Further discussion on the optimun temperature of efficiency of production for blackbody radiation AU - Fang, T. T2 - International Communications in Heat and Mass Transfer AB - In this paper, the exact equation governing the optimum temperature of efficiency of blackbody radiation production for a certain wavelength interval is obtained. The new formula is compared with the previous result, and it is found that, under certain condition, the new equation will collapse into the previous theory. The dependence of optimum temperature and the error between the two formulas on lower limit wavelength and bandwidth are also discussed. DA - 2003/// PY - 2003/// DO - 10.1016/S0735-1933(03)00006-X VL - 30 IS - 1 SP - 47-52 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0037257325&partnerID=MN8TOARS ER - TY - JOUR TI - Mechatronic control of distributed noise and vibration: A Lyapunov approach AU - Reyhanoglu, Mahmut T2 - Automatica AB - Compliant actuators are essential for ensuring safety in physical human-robot interaction. A compact-sized series elastic actuator (SEA), a type of compliant actuators, was developed to guarantee high force control fidelity and low output impedance in our previous work. This study is focused on the control design of a compliant robot arm driven by the developed SEA. The control problem is formulated into a singularly perturbed form which contains a slow rigid robot dynamics and a fast SEA dynamics. To achieve high-precision tracking without serious control chattering, a second-order sliding mode control (SMC) law is proposed such that the equilibrium point of the closed-loop rigid robot dynamics has semiglobal exponential stability. A derivative-type control law is employed such that the equilibrium point of the closed-loop SEA dynamics has global exponential stability. As the SMC law developed is continuous so that the rigid robot dynamics is continuously differentiable, the singular perturbation theory is applicable to establish semiglobal practical exponential stability of the entire system. This study provides the first application of continuous SMC to robots driven by compliant actuators. Experimental results have verified a high-accuracy and high-resolution tracking performance of the robot control system. DA - 2003/9// PY - 2003/9// DO - 10.1016/s0005-1098(03)00145-6 VL - 39 IS - 9 SP - 1664-1666 J2 - Automatica LA - en OP - SN - 0005-1098 UR - http://dx.doi.org/10.1016/s0005-1098(03)00145-6 DB - Crossref ER - TY - JOUR TI - Computation of Compressible Flows using a Two-equation Turbulence Model on Unstructured Grids AU - Luo, Hong AU - Baum, Joseph D. AU - Löhner, Rainald T2 - International Journal of Computational Fluid Dynamics AB - This paper presents a numerical method for solving compressible turbulent flows using a k - l turbulence model on unstructured meshes. The flow equations and turbulence equations are solved in a loosely coupled manner. The flow equations are advanced in time using a multi-stage Runge-Kutta time stepping scheme, while the turbulence equations are advanced using a multi-stage point-implicit scheme. The positivity of turbulence variables is achieved using a simple change of dependent variables. The developed method is used to compute a variety of turbulent flow problems. The results obtained are in good agreement with theoretical and experimental data, indicating that the present method provides a viable and robust algorithm for computing turbulent flows on unstructured meshes. Keywords: k -ε Turbulence ModelPositivity Of Turbulence VariablesUnstructured Grids DA - 2003/1// PY - 2003/1// DO - 10.1080/1061856021000034337 VL - 17 IS - 1 SP - 87-93 J2 - International Journal of Computational Fluid Dynamics LA - en OP - SN - 1061-8562 1029-0257 UR - http://dx.doi.org/10.1080/1061856021000034337 DB - Crossref KW - k-epsilon turbulence model KW - positivity of turbulence variables KW - unstructured grids ER - TY - JOUR TI - OPTIMIZATION OF PIN-FIN HEAT SINKS USING ANISOTROPIC LOCAL THERMAL NONEQUILIBRIUM POROUS MODEL IN A JET IMPINGING CHANNEL AU - Kim, Seo Young AU - Kuznetsov, Andrey V. T2 - Numerical Heat Transfer, Part A: Applications AB - Abstract A numerical study has been carried out to optimize the thermal performance of a pin-fin heat sink. A pin-fin heat sink, which is placed horizontally in a channel, is modeled as a hydraulically and thermally anisotropic porous medium. A uniform heat flux is prescribed at the bottom of the heat sink. Cool air is supplied from the top opening of the channel and exhausts to the channel outlet. Comprehensive numerical solutions are derived from the governing Navier-Stokes and energy equations using the Brinkman-Forchheimer extended Darcy model and the local thermal nonequilibrium (LTNE) porous model for the region occupied by the heat sink. Results from this study indicate that the anisotropy in permeability and solid-phase effective thermal conductivity changes substantially with the variation of porosity. Optimum porosity for maximum heat dissipation depends on the pin-fin thickness, the pin-fin height, and the Reynolds number. A correlation for predicting the optimum porosity for a pin-fin heat sink is proposed. Generally, in the case of thin pin-fins the heat sink should be designed to have a high porosity, while in the case of thick pin-fins the heat sink should be designed to have a relatively low porosity. DA - 2003/12// PY - 2003/12// DO - 10.1080/716100528 VL - 44 IS - 8 SP - 771-787 J2 - Numerical Heat Transfer, Part A: Applications LA - en OP - SN - 1040-7782 1521-0634 UR - http://dx.doi.org/10.1080/716100528 DB - Crossref ER - TY - JOUR TI - On scalar dissipation and partially premixed flame propagation AU - Watson, K.A. AU - Lyons, K.M. AU - Donbar, J.M. AU - Carter, C.D. T2 - Combustion Science and Technology AB - Measurements of the scalar dissipation rate in the region immediately upstream of a lifted jet flame are presented. The scalar dissipation is determined in this isothermal region from a planar measurement of a two-dimensional conserved scalar (jet fluid) using laser Rayleigh scattering. Fields of the scalar dissipation rate are presented in addition to tabulated values for three different liftoff heights ( Re d =4800, 6400, and 8300). Scalar dissipation rates do not reach levels thought to cause extinction of the leading edge based on comparison with extinction data for counterflow diffusion flames. Additionally, results are presented on the axial flame propagation velocities relative to the jet flow. The data indicate that over the three flow conditions, the flame velocity relative to the flow is approximately constant during the case of a quasi-stationary lifted flame. In light of these findings, it is suggested that concepts involving partially premixed flame propagation, rather than those of critical scalar dissipation rate, are central to modern lifted flame stabilization models. DA - 2003/4// PY - 2003/4// DO - 10.1080/00102200302393 VL - 175 IS - 4 SP - 649-664 J2 - Combustion Science and Technology LA - en OP - SN - 0010-2202 1563-521X UR - http://dx.doi.org/10.1080/00102200302393 DB - Crossref KW - lifted flame KW - flame stabilization KW - laser diagnostics KW - partially premixed combustion ER - TY - JOUR TI - Fabrication of sawtooth diffraction gratings using nanoimprint lithography AU - Chang, Chih-Hao AU - Heilmann, R. K. AU - Fleming, R. C. AU - Carter, J. AU - Murphy, E. AU - Schattenburg, M. L. AU - Bailey, T. C. AU - Ekerdt, J. G. AU - Frankel, R. D. AU - Voisin, R. T2 - Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures AB - We report a process which integrates interference lithography, nanoimprint lithography, and anisotropic etching to fabricate replicated diffraction gratings with sawtooth profiles. This new process greatly reduces grating fabrication time and cost, while preserving the groove shape and smoothness. Relief gratings with 400 nm period inverted triangular profiles and 200 nm period gratings with 7° blaze angle were replicated from silicon masters with surface roughness of less than 1 nm. This process was developed for fabricating the off-plane blazed diffraction gratings for the NASA Constellation-X x-ray telescope. DA - 2003/// PY - 2003/// DO - 10.1116/1.1627814 VL - 21 IS - 6 SP - 2755 J2 - J. Vac. Sci. Technol. B LA - en OP - SN - 0734-211X UR - http://dx.doi.org/10.1116/1.1627814 DB - Crossref ER - TY - JOUR TI - Nanometer-level repeatable metrology using the Nanoruler AU - Konkola, Paul T. AU - Chen, Carl G. AU - Heilmann, Ralf K. AU - Joo, Chulmin AU - Montoya, Juan C. AU - Chang, Chih-Hao AU - Schattenburg, Mark L. T2 - Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures AB - We report on the measurement of the fringe-to-substrate phase error in our Nanoruler system. This system utilizes scanning beam interference lithography to pattern and measure large-area, nanometer-accuracy gratings that are appropriate for semiconductor and integrated opto-electronic metrology. We present the Nanonruler’s metrology system that is based on digital frequency synthesizers, acousto-optics, and heterodyne phase sensing. It is used to assess the fringe-to-substrate placement stability and the accuracy of the feedback signals. The metrology system can perform measurements in real time, on the fly, and at arbitrary locations on the substrate. Experimental measurements are presented that demonstrate the nanometer-level repeatability of the system. Dominant error sources are highlighted. DA - 2003/// PY - 2003/// DO - 10.1116/1.1610003 VL - 21 IS - 6 SP - 3097 J2 - J. Vac. Sci. Technol. B LA - en OP - SN - 0734-211X UR - http://dx.doi.org/10.1116/1.1610003 DB - Crossref ER - TY - JOUR TI - Unstructured Navier-Stokes grid generation at comers and ridges AU - Sharov, D AU - Luo, H AU - Baum, JD AU - Lohner, R T2 - INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS AB - Abstract Problems related to automatic generation of highly stretched unstructured grids suitable for 3‐D Reynolds‐averaged Navier–Stokes computations are addressed. Special attention is given to treatment of such geometrical irregularities as convex and concave ridges as well as corners where the ridges meet. The existing unstructured grid generation approaches may fail or produce poor quality meshes in such geometrical regions. The proposed solution is based on special meshing of non‐slip body surfaces resulting in smooth and robust volume meshing and high overall quality of generated grids. Several examples demonstrate the efficiency of the method for complex 3‐D geometries. Copyright © 2003 John Wiley Sons, Ltd. DA - 2003/10/30/ PY - 2003/10/30/ DO - 10.1002/fld.615 VL - 43 IS - 6-7 SP - 717-728 SN - 1097-0363 KW - grid generation KW - unstructured grids KW - CFD KW - FEM ER - TY - JOUR TI - Carbon nanostructures in opposed-flow methane oxy-flames AU - Merchan-Merchan, W AU - Saveliev, AV AU - Kennedy, LA T2 - COMBUSTION SCIENCE AND TECHNOLOGY AB - Carbon nanostructures formed in the opposed-flow flames of methane- and oxygen-enriched air are studied experimentally using thermophoretic sampling technique and high-resolution transmission electron microscopy (TEM). Reconstructed evolution of soot particles along the burner centerline shows the existence of two characteristic layers. The narrow layer of polydisperse precursor particles is located on the oxidizer side of the stagnation plane. The precursor particles undergo carbonization and agglomeration as they are driven to the stagnation plane forming the layer of mature soot aggregates on the fuel side of the precursor layer. High-resolution TEM imaging performed on precursors and mature soot particles reveals the presence of highly organized carbon nanostructures formed inside the tarlike amorphous condensate by carbonization process. Two characteristic structures are observed. They resemble shapes of carbon onions and carbon nanopolyhedral particles. Multiwalled carbon nanotubes (MWNTs) appeared to be present in the collected samples along with other carbon particulates. TEM imaging reveals incidence of isolated MWNTs, MWNT clusters, and clusters of MWNT with soot and nanopolyhedral particles. The nanotube growth by elongation of partially carbonized nanopolyhedral particles is considered as a possible mechanism of noncatalytic MWNT formation. DA - 2003/12// PY - 2003/12// DO - 10.1080/714923286 VL - 175 IS - 12 SP - 2217-2236 SN - 1563-521X KW - soot formation KW - soot microstructure KW - thermophoretic sampling KW - carbon nanotube ER - TY - JOUR TI - Metal catalyzed synthesis of carbon nanostructures in an opposed flow methane oxygen flame AU - Saveliev, AV AU - Merchan-Merchan, W AU - Kennedy, LA T2 - COMBUSTION AND FLAME AB - Results of an experimental study on metal-catalyzed synthesis of carbon tubular nanostructures in opposed flow flame are reported. The catalytic support made of Ni-alloy was positioned at the fuel side of the opposed flow flame formed by fuel (96%CH4+4%C2H2) and oxidizer (50%O2+50%N2) streams. The electron microscopy studies reveal the presence of highly organized carbonaceous structures with the configurations showing strong dependence on the flame location. Several typical structures were detected. These include: multiwalled nanotubes (MWNT), MWNT bundles, irregular high-density carbon nanofibers, long (up to 0.2 mm) uniform-diameter (∼100 nm) nanofibers, helical regularly coiled tubular nanofibers, and ribbon-like coiled nanofibers with rectangular cross section. Transmission electron microscopy (TEM) studies performed on long nanofibers revealed the presence of highly organized multiple (∼100) graphene layers. These layers are parallel to the nanofiber axis resembling the structure of MWNT. The TEM studies of coiled nanofibers show internal tubular structure and the presence of regular carbon lattice. The well-aligned bundles of nanotubes were examined by TEM showing tight packing of MWNTs with varying inner and outer diameters. The diversity of formed nanomaterials is attributed to the strong variation of flame properties along the flame axis including temperature, hydrocarbon and radical pool. This provides strong selectivity for formation of different nanoforms even without adjustment of catalyst properties. DA - 2003/10// PY - 2003/10// DO - 10.1016/s0010-2180(03)00142-1 VL - 135 IS - 1-2 SP - 27-33 SN - 0010-2180 KW - carbon nanotubes KW - combustion synthesis KW - nano processing ER - TY - JOUR TI - A reciprocal flow filtration combustor with embedded heat exchangers: numerical study AU - Contarin, F AU - Saveliev, AV AU - Fridman, AA AU - Kennedy, LA T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - A reciprocal flow filtration combustor with embedded heat exchangers is numerically studied. In this system the combustion of methane and air mixture is stabilized in a transient porous media combustor by periodical switching the direction of the flow. Two heat exchangers are placed in the terminal sections of the porous matrix, constraining the reaction in the central insulated zone. The predicted temperature profile inside the reactor has a typical trapezoidal shape. The central plateau temperature ranges between 1300 and 1600 K as the equivalence ratio varies from 0.15 to 0.7 and the filtration velocity from 15 to 45 cm/s. The efficiency spans the range of 50–80% being higher for higher equivalence ratios and filtration velocities. DA - 2003/3// PY - 2003/3// DO - 10.1016/s0017-9310(02)00371-x VL - 46 IS - 6 SP - 949-961 SN - 1879-2189 ER - TY - JOUR TI - Simultaneous determination of flow stress and interface friction by finite element based inverse analysis technique AU - Cho, H AU - Ngaile, G T2 - CIRP ANNALS-MANUFACTURING TECHNOLOGY AB - A finite element based Inverse analysis technique has been developed to determine the flow stress and friction at the tool/workplace interface simultaneously from one set of material tests. The Inverse problem is aimed at minimizing the error between experimental data and predictions made by rigid-plastic finite element simulations. The ring compression test and the modified limiting dome height test (sheet blank with a hole at center stretched with a hemispherical punch) were selected for evaluating the method for bulk forming and for sheet forming, respectively. The determined flow stress data were compared with corresponding data obtained Independently using the well-lubricated cylinder compression test and hydraulic bulge test. Results show that the method discussed In the study is efficient and accurate. DA - 2003/// PY - 2003/// DO - 10.1016/s0007-8506(07)60570-8 VL - 52 IS - 1 SP - 221-224 KW - finite element method (FEM) KW - material KW - inverse analysis ER - TY - CONF TI - Finite Element Implementation of a Structural Constitutive Model for Planar Collagenous Tissues AU - Sun, W. AU - Huang, Hsiao-Ying Shadow AU - Argento, M.S. AU - Sacks, M. S. C2 - 2003/// C3 - Proceedings of the Second MIT Conference on Computational Solid and Fluid Mechanics CY - Cambridge, MA DA - 2003/// SP - 210 PB - Amsterdam: Elsevier Science, SN - 0080440487 ER - TY - JOUR TI - Computational thermodynamics analysis of vaporizing fuel droplets in the human upper airways AU - Zhang, Z AU - Kleinstreuer, C T2 - JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING AB - The detailed knowledge of air flow structures as well as particle transport and deposition in the human lung for typical inhalation flow rates is an important precursor for dosimetry-and-health-effect studies of toxic particles as well as for targeted drug delivery of therapeutic aerosols. Focusing on highly toxic JP-8 fuel aerosols, 3-D airflow and fluid-particle thermodynamics in a human upper airway model starting from mouth to Generation G3 (G0 is the trachea) are simulated using a user-enhanced and experimentally validated finite-volume code. The temperature distributions and their effects on airflow structures, fuel vapor deposition and droplet motion/evaporation are discussed. The computational results show that the thermal effect on vapor deposition is minor, but it may greatly affect droplet deposition in human airways. DA - 2003/11// PY - 2003/11// DO - 10.1299/jsmeb.46.563 VL - 46 IS - 4 SP - 563-571 SN - 1340-8054 KW - liquid aerosol transport and deposition KW - JP-8 fuel KW - human airways KW - heat and mass transfer ER - TY - JOUR TI - Boundary-layer analysis of forced convection with a plate and porous substrate AU - Nield, DA AU - Kuznetsov, AV T2 - ACTA MECHANICA DA - 2003/12// PY - 2003/12// DO - 10.1007/s00707-003-0050-5 VL - 166 IS - 1-4 SP - 141-148 SN - 1619-6937 ER - TY - JOUR TI - Evolution of failure mechanisms in 2D and 3D woven composite systems under quasi-static perforation AU - Baucom, JN AU - Zikry, MA T2 - JOURNAL OF COMPOSITE MATERIALS AB - The effects of reinforcement geometry, in 2D and 3D woven fabric-reinforced composites, on the progression of damage and perforation failure at quasi-static loading rates (10-80 mm/s) are investigated. The broad classes of glass-fiber-reinforced systems that were examined include 2D plain-woven laminates, 3D orthogonally woven monolithic systems, and 3D orthogonally woven laminates. The experimental results indicate that the 3D laminates consistently had greater damage tolerance than the 2D laminates and the 3D monolithic composites. The enhanced damage tolerance of the 3D systems is due to unique energy absorption mechanisms, which involve the crimped portion of z-tows. DA - 2003/// PY - 2003/// DO - 10.1177/0021998303035178 VL - 37 IS - 18 SP - 1651-1674 SN - 1530-793X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0042793491&partnerID=MN8TOARS KW - quasi-static puncture KW - GFRP KW - 3D orthogonal weave KW - damage progression ER - TY - JOUR TI - Efficient simulation of Bragg grating sensors for implementation to damage identification in composites AU - Prabhugoud, M AU - Peters, K T2 - SMART MATERIALS AND STRUCTURES AB - A computationally efficient method is proposed to interpret optical fiber sensor data collected from Bragg grating sensors embedded in composites. The method divides the composite into remote field and critical field regions with respect to any developed damage. These regions are defined via non-uniformities in the sensor response. The remote field response is treated via an optimal shear-lag theory first presented by Mendels and Nairn. This formulation provides a rapid solution of the average fiber axial stress at the location of each sensor. The critical field region is modeled via a finite element sensor model including the effects of multi-axis loading on the sensor and an optical loss due to local fiber curvature. The response of the Bragg grating sensor to the effects of axial, bending and shear loading are simulated for inclusion in the model. The bending loss response as a function of fiber curvature is experimentally measured. The application of this method is demonstrated through a numerical example, simulating the response of sensors embedded in a lamina to the presence of a transverse crack. DA - 2003/12// PY - 2003/12// DO - 10.1088/0964-1726/12/6/008 VL - 12 IS - 6 SP - 914-924 SN - 1361-665X ER - TY - JOUR TI - Piezoelectric resonating structures for microelectronic cooling AU - Wu, T. AU - Ro, P. I. AU - Kingon, A. I. AU - Mulling, J. F. T2 - Smart Materials & Structures AB - The design of piezoelectric resonating structures was investigated for generating acoustic streaming which may be used for cooling microelectronic components. The vibration characteristics of different piezoelectric structures were simulated by the finite element method and validated with analytical approaches. Considering the product of resonance frequency and dynamic tip deflection as a performance merit, the effects of length and location of the actuators as well as the boundary conditions were analyzed for four different piezoelectric resonator designs. Results show that there exist optimal length and location of actuators on the passive structures. DA - 2003/// PY - 2003/// DO - 10.1088/0964-1726/12/2/304 VL - 12 IS - 2 SP - 181-187 ER - TY - JOUR TI - Low-Reynolds-number turbulent flows in locally constricted conduits: A comparison study AU - Zhang, Z AU - Kleinstreuer, C T2 - AIAA JOURNAL AB - In numerous internal flow systems the velocity field can undergo all flow regimes, that is, from laminar, via transitional, to fully turbulent. Considering two test conduits with local constrictions, four turbulence models, with an emphasis on low-Reynolds-number (LRN) turbulence models, were compared and evaluated. The objective was to identify a readily available LRN turbulence model with which incompressible laminar-to-turbulent velocity and pressure fields in complex three-dimensional conduits can be directly computed. The comparison study revealed that the renormalization group (RNG) κ-e and Menter κ-ω models amplify the flow instabilities after tubular constrictions and hence fail to capture the laminar flow behavior at low Reynolds numbers DA - 2003/5// PY - 2003/5// DO - 10.2514/2.2044 VL - 41 IS - 5 SP - 831-840 SN - 0001-1452 ER - TY - JOUR TI - Inflow boundary conditions for hybrid large eddy/Reynolds averaged Navier-Stokes simulations AU - Xiao, XD AU - Edwards, , JR AU - Hassan, HA AU - Baurle, RA T2 - AIAA JOURNAL AB - Inflow boundary conditions are developed for hybrid large-eddy simulation (LES)/Reynolds-averaged Navier-Stokes approaches. They are based on an extension of the rescaling-reintroducing method developed for LES to a hybrid scheme. A blending function is used to shift the turbulence closure from a κ-ζ model near the wall to a κ-Δ subgrid-scale model away from the wall. The approach was tested for a flat plate and then applied to the study of a 25-deg compression-expansion ramp for a Mach number of 2.88 and a Reynolds number of 3.24 × 10 7 /m. In general, improvements over the κ-ζ model were noted in the recovery region. The significance of this work is that it provides a way for LES methods to address flows at a high Reynolds number DA - 2003/8// PY - 2003/8// DO - 10.2514/2.2130 VL - 41 IS - 8 SP - 1481-1489 SN - 0001-1452 ER - TY - JOUR TI - Effects of gross heterogeneity and anisotropy in forced convection in a porous medium: Layered medium analysis AU - Nield, D. A. AU - Kuznetsov, A. V. T2 - Journal of Porous Media AB - The effects of gross heterogeneity and anisotropy, associated with horizontal fissures in a porous medium filling a parallel-plate channel, on forced convection are studied. An approximate analysis, based on a piecewise-constant (layered) distribution of permeability across the channel, is used to model the experiments performed by Paek et al. (1999) on foam material with drilled-out tubes. The analysis leads to estimates of the Nusselt number, Nu. Drilling out the tubes leads to a reduction in the value of Nu but an even greater reduction in the friction factor, f, so that the net result is an increase in the value of Nu/f, i.e., for a given driving pressure gradient the heat transfer is increased. DA - 2003/// PY - 2003/// DO - 10.1615/jpormedia.v6.i1.30 VL - 6 IS - 1 SP - 51-57 ER - TY - JOUR TI - A free energy model for hysteresis in ferroelectric materials AU - Smith, RC AU - Seelecke, S AU - Ounaies, Z AU - Smith, J T2 - JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES AB - This paper provides a theory for quantifying the hysteresis and constitutive nonlinearities inherent to piezoceramic compounds through a combination of free energy analysis and stochastic homogenization techniques. In the first step of the model development, Helmholtz and Gibbs free energy relations are constructed at the lattice or domain level to quantify the relation between the field and polarization in homogeneous, single crystal compounds which exhibit uniform effective fields. The effects of material nonhomogeneities, polycrystallinity, and variable effective fields are subsequently incorporated through the assumption that certain physical parameters, including the local coercive and effective fields, are randomly distributed and hence manifestations of stochastic density functions associated with the material. Stochastic homogenization in this manner provides low-order macroscopic models with effective parameters that can be correlated with physical properties of the data. This facilitates the identification of parameters for model construction, model updating to accommodate changing operating conditions, and control design utilizing model-based inverse compensators. Attributes of the model, including the guaranteed closure of biased minor loops in quasistatic drive regimes, are illustrated through examples. DA - 2003/11// PY - 2003/11// DO - 10.1177/1045389X03038841 VL - 14 IS - 11 SP - 719-739 SN - 1045-389X KW - hysteresis model KW - ferroelectric materials KW - piezoceramic compounds ER - TY - JOUR TI - Three-dimensional stress analyses in composite laminates with an elastically pinned hole AU - Yang, B AU - Pan, E AU - Yuan, FG T2 - INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES AB - We present a three-dimensional (3-D) stress analysis for composite laminates with an elastically pinned circular hole. The effects of friction, bearing force and bypass loading on the stress redistribution are studied in detail. The numerical approach is based on a multilayer boundary element method (MLBEM), a non-traditional BEM particularly designed for anisotropic composite laminates, coupled with the traditional BEM for the pin filling the hole. The unique characteristic of the MLBEM is that the fundamental solution employs Green’s functions that satisfy the interfacial continuity conditions and top- and bottom-surface traction-free and symmetry conditions. This fundamental solution allows us to design a BE scheme without involving discretization on the interfaces and surfaces unless the laminates are imposed by different boundary conditions. Consequently, in this case of pinned joint, only the hole surface among the composite boundary and interfaces needs to be discretized. A Coulomb-type friction law is used to simulate the frictional contact interaction between the composite and pin. To solve the frictional contact problem, an iterative scheme of successive over-relaxation has been proposed where the contact location and frictional contact condition are determined at the same time in the iteration solution. By applying the MLBEM, stress analyses are performed for a laminate plate with the stacking sequence (0/∓45/90)s. The issues of engineering interests, such as the loading-sequence and cycling dependencies of stress state due to the presence of friction, are addressed. The solutions, shown by complicated contact maps and stress states around the hole, suggested that a 3-D approach to pinned composite joints is necessary for the interpretation of the underlying physics. DA - 2003/4// PY - 2003/4// DO - 10.1016/S0020-7683(02)00523-1 VL - 40 IS - 8 SP - 2017-2035 SN - 0020-7683 KW - three-dimensional stress analysis KW - composite laminates KW - bolted joint KW - bearing and bypass loading KW - frictional contact KW - boundary element method ER - TY - JOUR TI - Investigation of turbulence effects on forced convection in a composite porous/fluid duct: Constant wall flux and constant wall temperature cases AU - Kuznetsov, A AU - Cheng, L AU - Xiong, M T2 - HEAT AND MASS TRANSFER DA - 2003/7// PY - 2003/7// DO - 10.1007/S00231-002-0377-9 VL - 39 IS - 7 SP - 613-623 SN - 1432-1181 ER - TY - JOUR TI - Halide acid pretreatments of photocatalysts for oxidation of aromatic air contaminants: rate enhancement, rate inhibition, and a thermodynamic rationale AU - Lewandowski, M AU - Ollis, DF T2 - JOURNAL OF CATALYSIS AB - The effects of chlorine radical generation during the photocatalytic oxidation of aromatic contaminants in air can be significant. Previous studies have shown that cofeeding chlorinated olefins (TCE, PCE) may increase the removal of branched aromatics (toluene, xylenes), presumably by initiating chlorine radical chain reactions. Hydrochloric acid catalyst pretreatments produce a similar enhancement of aromatic conversions. However, both approaches were ineffective for rate enhancement toward benzene, while hydrobromic and hydriodic acid pretreatments diminished the photocatalytic oxidation of both benzene and toluene. The present study broadens this halide acid inquiry to include hydrofluoric acid catalyst pretreatments and to examine halide acid influences on the removal of m-xylene as well. Only HCl pretreatments enhanced activity, and only for the branched aromatics (toluene and m-xylene). These results appear consistent with a thermodynamic analysis proposed here, which indicates that (1) fluorine radical generation is not energetically feasible under the conditions considered, (2) bromine and iodine radical generation is energetically feasible, but the radicals are insufficiently reactive to initiate the degradation of aromatics, and (3) chlorine radicals are predicted to be sufficiently energetic to abstract hydrogen from the methyl groups of branched aromatics, but not from the more strongly bound hydrogen atoms on the aromatic ring. These calculations are all in accord with our experimental results for the photocatalytic oxidation aromatics. The consistency of these thermodynamic arguments is also further support for the presumed halide radical pathway for rate enhancement. DA - 2003/7/1/ PY - 2003/7/1/ DO - 10.1016/S0021-9517(03)00030-7 VL - 217 IS - 1 SP - 38-46 SN - 0021-9517 KW - photocatalysis KW - photocatalyst KW - TiO2 KW - aromatics KW - benzene KW - toluene KW - xylene KW - rate enhancement KW - pretreatment KW - chlorine KW - halides KW - radicals ER - TY - JOUR TI - Computational analysis of effects of external carotid artery flow and occlusion on adverse carotid bifurcation hemodynamics AU - Hyun, S AU - Kleinstreuer, C AU - Archie, JP T2 - JOURNAL OF VASCULAR SURGERY AB - This is a computational analysis of the effects of external carotid artery (ECA) flow, waveform, and occlusion geometry on two hemodynamic wall parameters associated with intimal hyperplasia and atherosclerosis. Transient three-dimensional fluid mechanics analysis was applied to a standard carotid artery bifurcation. Mean internal carotid artery (ICA) flow was maintained at 236 mL/min with a normal waveform. ECA flow was increased from zero to 151 mL/min (64% of ICA flow) with both a normal biphasic waveform and a damped waveform. Geometry of five ECA occlusions was studied: distal, proximal stump, smooth, smooth without carotid sinus, and optimal reconstruction. Two time-averaged and area-averaged hemodynamic wall parameters were computed from the velocity and wall shear stress (WSS) solutions, ie, wall shear stress angle gradient (WSSAG) and oscillatory shear index (OSI). Both local and area-averaged hemodynamic wall parameters were computed for the distal common carotid artery (CCA) and the proximal ICA. When ECA flow with a normal waveform is increased from zero to 151 mL/min, area-averaged WSS values increase in the CCA, from 3.0 to 4.4 dynes/cm2 (46%), and in the ICA, from 16.5 to 17.1 dynes/cm2 (4%); minimum local WSS values in the carotid sinus remain less than 1 dyne/cm2; maximum local values of WSSAG and OSI are observed in the carotid sinus and increase from 3.5 to 9.1 radian/cm (160%) and 0.23 to 0.46 (100%), respectively; CCA plus ICA area-averaged WSSAG increases by 52%, and OSI increases by 144%; and damping of the ECA waveform has little effect on local or area-averaged WSSAG but reduces OSI to 68%. When the ECA is occluded, the minimum local WSS in the carotid sinus is less than 1 dyne/cm2. However, if the carotid sinus is removed or the CCA-ICA geometry hemodynamically optimized, the minimum WSS is approximately 4 dynes/cm2. Similarly, eliminating the carotid sinus markedly reduces local maximum WSSAG, from 3.0-3.5 radian/cm to 0.3 radian/cm, and reduces local maximum OSI from 0.22-0.49 to 0.04. Area-averaged WSSAG and OSI over the CCA and ICA are reduced by approximately 50% with elimination of the carotid sinus. The degree of adverse carotid bifurcation hemodynamics as measured with WSSAG and OSI is directly proportional to ECA flow. The marked difference in normal ICA and ECA flow waveforms does not contribute to adverse wall hemodynamics. Location of an ECA occlusion (distal, proximal, stump, smooth) does not affect adverse carotid hemodynamics; however, marked improvement is obtained with elimination of the carotid sinus. DA - 2003/6// PY - 2003/6// DO - 10.1016/S0741-5214(02)75326-3 VL - 37 IS - 6 SP - 1248-1254 SN - 0741-5214 ER - TY - JOUR TI - A computational mechanics model for the brim forming process in paperboard container manufacturing AU - Ramasubramanian, MK AU - Muthuraman, K T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME AB - The manufacturing process of brim forming in paperboard containers consists of taking a thin paperboard shell and forming a brim to provide additional stiffness to the structure. A paper cup is an example of such a structure manufactured at rates exceeding 300 units per minute. A realistic model for the manufacturing process is not available and the effects of process and material parameters are not well understood. In this study, a finite element model of this highly nonlinear problem is presented. The model takes into account the material orthotropy and nonlinear elastic-plastic behavior, die paperboard contact interaction during loading and unloading, and friction between the metal die and paperboard, die geometry, and environmental conditions. Model predictions of the force-displacement curve agree well with the experimentally observed results. DA - 2003/8// PY - 2003/8// DO - 10.1115/1.1580527 VL - 125 IS - 3 SP - 476-483 SN - 1087-1357 ER - TY - JOUR TI - Vertical gradient freezing of doped gallium-antimonide semiconductor crystals using submerged heater growth and electromagnetic stirring AU - Ma, N AU - Bliss, DF AU - Iseler, GW T2 - JOURNAL OF CRYSTAL GROWTH AB - An investigation of the melt growth of uniformly doped gallium–antimonide (GaSb) semiconductor crystals as well as other III–V alloy crystals with uniform composition are underway at the US Air Force Research Laboratory at Hanscom Air Force Base by the vertical gradient freeze (VGF) method utilizing a submerged heater. Stirring can be induced in the GaSb melt just above the crystal growth interface by applying a small radial electric current in the liquid together with an axial magnetic field. The transport of any dopant and/or alloy component by the stirring can promote better melt homogeneity and allow for more rapid growth rates before the onset of constitutional supercooling. This paper presents a numerical model for the unsteady transport of a dopant during the VGF process by submerged heater growth with a steady axial magnetic field and a steady radial electric current. As the strength of the electromagnetic (EM) stirring increases, the convective dopant transport increases, the dopant transport in the melt reaches a steady state at an earlier time during growth, and the top of the crystal which has solidified after a steady state has been achieved exhibits axial dopant homogeneity. For crystal growth with stronger EM stirring, the crystal exhibits less radial segregation and the axially homogeneous section of the crystal is longer. Dopant distributions in the crystal and in the melt at several different stages during growth are presented. DA - 2003/11// PY - 2003/11// DO - 10.1016/S0022-0248(03)01575-6 VL - 259 IS - 1-2 SP - 26-35 SN - 0022-0248 KW - fluid flows KW - magnetic fields KW - mass transfer KW - segregation KW - gradient freeze technique KW - growth from melt KW - antimonides KW - semiconducting III-V materials ER - TY - JOUR TI - Synthesis and excited-state photodynamics of a perylene-monoimide-oxochlorin dyad. A light-harvesting array AU - Muthukumaran, K AU - Loewe, RS AU - Kirmaier, C AU - Hindin, E AU - Schwartz, JK AU - Sazanovich, , IV AU - Diers, , JR AU - Bocian, DF AU - Holten, D AU - Lindsey, JS T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - A perylene-oxochlorin dyad has been prepared and characterized for potential use as a new light-harvesting motif. The dyad (PMI−ZnO) consists of a perylene-monoimide dye (PMI) joined at the 5-position of a zinc oxochlorin (ZnO) via a diphenylethyne linker. The dyad and its subunits have been studied in both polar and nonpolar media using static and time-resolved optical spectroscopy and electrochemical techniques. Energy flows very rapidly from both unrelaxed (vibrationally, conformationally, or electronically) and relaxed forms of the excited perylene (PMI*) to the ground-state oxochlorin with an effective time constant of ∼4 ps and an efficiency of 99% in both toluene and benzonitrile. Subsequently, there is little or no quenching of the excited oxochlorin (ZnO*) in either solvent. These findings are consistent with the expectation that all charge-separated states such as PMI- ZnO+ lie energetically above both PMI* and ZnO* in both polar and nonpolar media. Furthermore, light absorption by the perylene and oxochlorin occurs in complementary regions, giving broad spectral coverage. Thus, the new perylene-oxochlorin dyad is an excellent light-harvesting unit that can be incorporated into more elaborate architectures for use in solar-energy and molecular-photonics applications. DA - 2003/4/17/ PY - 2003/4/17/ DO - 10.1021/jp026941a VL - 107 IS - 15 SP - 3431-3442 SN - 1520-6106 ER - TY - JOUR TI - Phonon heat conduction in micro- and nano-core-shell structures with cylindrical and spherical geometries AU - Zeng, TF AU - Liu, W T2 - JOURNAL OF APPLIED PHYSICS AB - This study examines the definition of temperatures at interfaces and within thin films when the phonons are in nonequilibrium, and provides a general solution for the temperature distribution within the micro- and nanocylindrical and spherical shells. By applying the Boltzmann transport equation and the established methods of thermal radiation heat transfer, analytical solutions for the temperature distribution and equivalent thermal conductivity are obtained for micro- and nanocylindrical and spherical shells. The study shows that significant drops in temperature occur at the interfaces of micro- and nanocylindrical and spherical shells. For cylindrical shells, the effective thermal conductivity is determined by both the film thickness and the diameter of the inner cylinder. For spherical shells, the effective conductivity is mainly determined by the size of the inner sphere. DA - 2003/4/1/ PY - 2003/4/1/ DO - 10.1063/1.1556566 VL - 93 IS - 7 SP - 4163-4168 SN - 0021-8979 ER - TY - JOUR TI - On scalar dissipation and partially premixed flame propagation AU - Watson, K. A. AU - Lyons, K. M. AU - Donbar, J. M. AU - Carter, C. D. T2 - Combustion Science and Technology DA - 2003/// PY - 2003/// DO - 10.1080/00102200390196386 VL - 175 IS - 4 SP - 649-664 ER - TY - JOUR TI - Numerical simulation of wall shear stress conditions and platelet localization in realistic end-to-side arterial anastomoses AU - Longest, PW AU - Kleinstreuer, C T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME AB - Research studies over the last three decades have established that hemodynamic interactions with the vascular surface as well as surgical injury are inciting mechanisms capable of eliciting distal anastomotic intimal hyperplasia (IH) and ultimate bypass graft failure. While abnormal wall shear stress (WSS) conditions have been widely shown to affect vascular biology and arterial wall self-regulation, the near-wall localization of critical blood particles by convection and diffusion may also play a significant role in IH development. It is hypothesized that locations of elevated platelet interactions with reactive or activated vascular surfaces, due to injury or endothelial dysfunction, are highly susceptible to IH initialization and progression. In an effort to assess the potential role of platelet-wall interactions, experimentally validated particle-hemodynamic simulations have been conducted for two commonly implemented end-to-side anastomotic configurations, with and without proximal outflow. Specifically, sites of significant particle interactions with the vascular surface have been identified by a novel near-wall residence time (NWRT) model for platelets, which includes shear stress-based factors for platelet activation as well as endothelial cell expression of thrombogenic and anti-thrombogenic compounds. Results indicate that the composite NWRT model for platelet-wall interactions effectively captures a reported shift in significant IH formation from the arterial floor of a relatively high-angle (30 deg) graft with no proximal outflow to the graft hood of a low-angle graft (10 deg) with 20% proximal outflow. In contrast, other WSS-based hemodynamic parameters did not identify the observed system-dependent shift in IH formation. However, large variations in WSS-vector magnitude and direction, as encapsulated by the WSS-gradient and WSS-angle-gradient parameters, were consistently observed along the IH-prone suture-line region. Of the multiple hemodynamic factors capable of eliciting a hyperplastic response at the cellular level, results of this study indicate the potential significance of platelet-wall interactions coinciding with regions of low WSS in the development of IH. DA - 2003/10// PY - 2003/10// DO - 10.1115/1.1613298 VL - 125 IS - 5 SP - 671-681 SN - 1528-8951 ER - TY - JOUR TI - Numerical analysis of the basketball shot AU - Silverberg, L AU - Tran, C AU - Adcock, K T2 - JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME AB - This paper numerically analyzes the dynamics of the basketball shot. The focus of the paper is on the development of a general formulation for the dynamics of the shot beginning when the ball leaves the shooter’s hand and ending when the shot is made or missed. The numerical analysis developed in this paper can be used to conduct a parametric study of the dynamics of the basketball shot, which in turn, can be used to improve individual shooting and team strategy. The individual skill level of the shooter enters the formulation through the statistical accuracy of the release. The paper then shows how to determine the shooter’s probability of making a given shot. DA - 2003/12// PY - 2003/12// DO - 10.1115/1.1636193 VL - 125 IS - 4 SP - 531-540 SN - 1528-9028 ER - TY - JOUR TI - Nonequilibrium electron and phonon transport and energy conversion in heterostructures AU - Zeng, TF AU - Chen, G T2 - MICROELECTRONICS JOURNAL AB - We establish a unified model dealing with the transport of electrons and phonons in double heterojunction structures with the coexistence of three nonequilibrium processes: (1) nonequilibrium among electrons, (2) nonequilibrium among phonons, and (3) nonequilibrium between electrons and phonons. Using this model, we investigate the energy conversion efficiency based on concurrent thermoelectric and thermionic effects on electrons and size effects on electrons and phonons. It is found that heterostructures can have an equivalent figure of merit higher than the corresponding bulk materials. DA - 2003/3// PY - 2003/3// DO - 10.1016/S0026-2692(02)00189-1 VL - 34 IS - 3 SP - 201-206 SN - 0026-2692 KW - heterostructures KW - quasi-equilibrium KW - Boltzmann transport equations ER - TY - JOUR TI - Micro-stress prediction in composite laminates with high stress gradients AU - Hutapea, P AU - Yuan, FG AU - Pagano, NJ T2 - INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES AB - The objective of this research is to develop a macroscopic theory, which can provide the connection between macro-mechanics and micro-mechanics in characterizing the micro-stress of composite laminates in regions of high macroscopic stress gradients. The micro-polar theory, a class of higher-order elasticity theory, of composite laminate mechanics is implemented in a well-known Pipes–Pagano free edge boundary problem. The micro-polar homogenization method to determine the micro-polar anisotropic effective elastic moduli is presented. A displacement-based finite element method based on micro-polar theory in anisotropic solids is developed in analyzing composite laminates. The effects of fiber volume fraction and cell size on the normal stress along the artificial interface resulting from ply homogenization of the composite laminate are also investigated. The stress response based on micro-polar theory is compared with those deduced from the micro-mechanics and classical elasticity theory. Special attention of the investigation focuses on the stress fields near the free edge where the high macro-stress gradient occurs. The normal stresses along the artificial interface and especially, the micro-stress along the fiber/matrix interface on the critical cell near the free edge where the high macro-stress gradient detected are the focus of this investigation. These micro-stresses are expected to dominate the failure initiation process in composite laminate. A micro-stress recovery scheme based on micro-polar analysis for the prediction of interface micro-stresses in the critical cell near the free edge is found to be in very good agreement with “exact” micro-stress solutions. It is demonstrated that the micro-polar theory is able to capture the micro-stress accurately from the homogenized solutions. DA - 2003/5// PY - 2003/5// DO - 10.1016/S0020-7683(03)00018-0 VL - 40 IS - 9 SP - 2215-2248 SN - 0020-7683 KW - laminates KW - stress KW - micro-polar ER - TY - JOUR TI - Impact-induced deformation fields in 2D and 3D woven composites AU - Bahei-El-Din, YA AU - Zikry, MA T2 - COMPOSITES SCIENCE AND TECHNOLOGY AB - The deformation fields and kinematics of woven composite material systems, due to impact loads, were analyzed and characterized for various structural and load parameters. Target plates comprising of woven composites with 3D and 2D preforms were considered. Kinetic energies in the range of 18–39,000 J, due to projectile velocities in the range of 2–1000 m/s, were investigated. The impact problem model accounts for geometrical details of the flat target plates and the hemispherical projectile. Contact solutions at dissimilar surfaces were modeled with gap elements, and the solution of the nonlinear dynamic problem was obtained by the finite element method. In the present study, we investigated wave propagation effects, and how their spatial and temporal distribution is related to the evolution of multi-dimensional elastic fields and potential damage modes. Unit cells representative of the 2D and 3D woven composites were used to obtain estimates of the overall elastic moduli. It was found that the compression wave induced by impact reflected several times between the free surfaces of the target plate before fiber failure initiated, and that this was one of the major mechanisms leading to penetration. At low velocity impact, the deformations were similar to quasi-static bending deformation modes, and failure is predicted to be due to fiber breakage at the backside of the target plate. At higher impact velocities, wave propagation effects are more significant and lead to penetration at the impact face. For all material systems, localized shear damage in 3D woven systems and extensive shear delamination in 2D woven systems preceded complete penetration. DA - 2003/5// PY - 2003/5// DO - 10.1016/S0266-3538(03)00021-6 VL - 63 IS - 7 SP - 923-942 SN - 0266-3538 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0037403705&partnerID=MN8TOARS KW - textile composites KW - impact behavior KW - microstructure KW - finite element analysis ER - TY - JOUR TI - Effects of temperature-dependent viscosity in forced convection in a porous medium: Layered-medium analysis AU - Nield, DA AU - Kuznetsov, AV T2 - JOURNAL OF POROUS MEDIA DA - 2003/// PY - 2003/// DO - 10.1615/JPorMedia.v6.i3.60 VL - 6 IS - 3 SP - 213-222 SN - 1934-0508 ER - TY - JOUR TI - Effects of heterogeneity in forced convection in a porous medium: Parallel-plate channel, Brinkman model AU - Nield, DA AU - Kuznetsov, AV T2 - JOURNAL OF POROUS MEDIA AB - The effects of variation (in the transverse direction, in layers) of permeability and thermal conductivity, on fully developed forced convection in a parallel-plate channel filled with a saturated porous medium, is investigated analytically on the basis of a Brinkman model, for the case of isoflux boundaries and a two-step variation. The results demonstrate that the effect of permeability variation is that an above-average permeability near the walls leads to an increase in Nusselt number, and this is explained in terms of variation in the curvature of the temperature profile. This effect of permeability variation becomes less important as the Darcy number increases. The effect of conductivity variation is more complex; there are two opposing effects and the Nusselt number is not always a monotonic function of the conductivity variation. This effect of conductivity variation retains its importance as the Darcy number increases. DA - 2003/// PY - 2003/// DO - 10.1615/JPorMedia.v6.i4.40 VL - 6 IS - 4 SP - 257-266 SN - 1934-0508 ER - TY - JOUR TI - Effect of non-uniformity of source vibration amplitude on the sound field wave number, attenuation coefficient and Reynolds stress for the acoustic streaming AU - Wan, Q AU - Kuznetsov, AV T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - The aim of this paper is to analytically solve the sound field generated by a standing wave induced in a vibrating beam. This case is different from a plane wave which is the traditional way of inducing acoustic streaming. The analytical solution shows that the amplitude non-uniformity can be represented by a non-uniformity coefficient y, which characterizes the ratio of the wave number or the attenuation coefficient to their values for the classical plane wave case. The non-uniformity coefficient γ is also obtained by resolving the acoustic field utilizing full numerical solution. Numerical and analytical results are in a good agreement. The Reynolds stress generated by a beam vibrating at one of its modes is also calculated. The maximum values of the Reynolds stress are achieved at the anti-node coordinates and small negative minimum values of the Reynolds stress are observed at the node coordinates. An interesting four-vortex-per-wavelength structure is predicted for such sound field. DA - 2003/1// PY - 2003/1// DO - 10.1016/S0735-1933(03)00004-6 VL - 30 IS - 1 SP - 27-36 SN - 1879-0178 ER - TY - JOUR TI - Development of an engineering approach to computations of turbulent flows in composite porous/fluid domains AU - Kuznetsov, AV AU - Xiong, M T2 - INTERNATIONAL JOURNAL OF THERMAL SCIENCES AB - The purpose of this paper is to develop an engineering approach to computations of turbulent flows in composite domains partly occupied by a clear fluid and partly by a fluid saturated porous medium. Previous research concerning turbulent flows in porous media indicates that the effect of porous media is to dampen turbulence. Therefore, in porous/fluid domains the penetration depth of turbulent eddies into the porous region is expected to be small. The authors suggest assuming that the flow over the whole porous region remains laminar and matching turbulent flow solution in the clear fluid region with the laminar flow solution in the turbulent flow region. Although the flow in the porous region is assumed to be laminar, linear Darcy or Brinkman–Darcy models cannot be utilized to describe momentum transport in the porous region because of large filtration velocity. The momentum transport model in the porous layer utilized in this research is based on the Brinkman–Forchheimer-extended Darcy equation, which allows the accounting for deviation from linearity and also allows a smooth matching of the filtration velocity at the porous/fluid interface. Because of the large filtration velocity in the porous region, the energy equation in the porous region also accounts for the thermal dispersion effects. DA - 2003/10// PY - 2003/10// DO - 10.1016/S1290-0729(03)00063-2 VL - 42 IS - 10 SP - 913-919 SN - 1290-0729 ER - TY - JOUR TI - Bioconvection of negatively geotactic microorganisms in a porous medium: the effect of cell deposition and declogging AU - Kuznetsov, AV AU - Jiang, N T2 - INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW AB - Mechanisms of deposition and declogging are considered while formulating a new continuum model for bioconvection in a dilute suspension of motile, negatively geotactic microorganisms in a porous medium. According to research in 1988, bioconvection is the name given to pattern‐forming convective motions set up in suspensions of swimming microorganisms. “Negative geotaxis” means that the microorganisms tend to swim against the gravitational force. This paper is motivated by experimental research by Kessler who investigated the effect of porous media on the development of convection instability in algal suspensions. In the model suggested in this paper, the decrease of permeability due to cell adsorption by the porous medium is considered and the influence of this permeability decrease on the development of bioconvection is studied. The existence and stability of a two‐dimensional plume in a rectangular enclosure with stress‐free sidewalls is investigated. Governing equations include the Darcy law as well as the microorganism conservation equations. A conservative finite‐difference scheme is utilized to solve these equations numerically. The analysis of the proposed model reveals that the major factors affecting the development of bioconvection are the initial permeability of the porous medium and the rate of cell deposition. For small permeability, the resistance to the fluid flow is too large, and bioconvection does not develop. If the rate of cell deposition is too large, the number of suspended cells quickly becomes too small because of cell capturing by the porous medium. For this reason, the critical density difference in the top fluid layer cannot be reached, and bioconvection does not develop. DA - 2003/// PY - 2003/// DO - 10.1108/09615530310464535 VL - 13 IS - 2-3 SP - 341-364 SN - 1758-6585 KW - convection KW - porous media KW - instability ER - TY - JOUR TI - A similarity solution for a falling plume in bioconvection of oxytactic bacteria in a porous medium AU - Kuznetsov, AV AU - Avramenko, AA AU - Geng, P T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - In this paper, a numerical investigation on mixed bioconvection flow of silver(Ag)-magnesium oxide(MgO)-water hybrid nanofluid in a trapezoidal porous cavity under the effect of inclined periodic magnetic field is carried out. Brinkman–Forchheimer-extended Darcy model for the porous medium is adopted. Galerkin weighted residual finite element method is implemented to simulate the governing steady dimensionless equations. The resulting discrete nonlinear algebraic systems are treated using the adaptive Newton's method. The fluid flow, heat and mass transfer behavior are examined in variation of parameters as Hartmann number (Ha = 0−100), angle of periodic magnetic field (θ = 0∘−90∘), period of periodic magnetic field (Λ = 0.1−1), bioconvection Rayleigh number (Rb = 10−100), Richardson number (Ri = 0.1−5), Lewis number (Le = 1−10) and Peclet number (Pe = 0.1−1). The rise in Hartmann number has a weakening effect on both transfer of heat and mass. When θ = 0∘, convective heat and mass transfer is the smallest at Λ = 1 where the most reduction in the average Nusselt and Sherwood numbers is 9.14% and 6.98% as Λ is raised from 0.1 to 1, respectively, and occurs at Ha = 100. The significant decrement in the average Nusselt number is 42.57% at Ha = 75 and in the Sherwood number is 10.4% at Ha = 50 when θ is changed from 0∘ to 90∘. DA - 2003/1// PY - 2003/1// DO - 10.1016/S0735-1933(03)00005-8 VL - 30 IS - 1 SP - 37-46 SN - 0735-1933 ER - TY - JOUR TI - Transient grating spectroscopy with delayed thermalization in non-combusting CO/air mixtures AU - Li, YY AU - Roberts, WL AU - Brown, MS AU - Herring, GC T2 - OPTICS COMMUNICATIONS AB - Transient grating spectroscopy is used to observe slowly forming thermal gratings in a mixture (non-combusting CO/air at ⩽0.7 MPa) of two gases that are individually transparent. Thermalization in the mixture implies a photochemical process at 532 nm that populates the metastable singlet level 1Δg in O2 through collision-assisted absorption in O2 pairs. The laser intensity dependence of this process is measured. DA - 2003/10/15/ PY - 2003/10/15/ DO - 10.1016/j.optcom.2003.08.036 VL - 226 IS - 1-6 SP - 255-258 SN - 0030-4018 KW - transient grating spectroscopy KW - TGS KW - active oxygen KW - singlet O-2((1)Delta(g)) ER - TY - JOUR TI - Three-dimensional Green's functions for composite laminates AU - Yuan, FG AU - Yang, S AU - Yang, B T2 - INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES AB - The three-dimensional Green’s functions due to a point force in composite laminates are solved by using generalized Stroh formalism and two-dimensional Fourier transforms. Each layer of the composite is generally anisotropic and linearly elastic. The interfaces between different layers are parallel to the top and bottom surfaces of the composite and are perfectly bonded. The Green’s functions of point forces applied at the free surface, interface, and in the interior of a layer are derived in the Fourier transformed domain respectively. The surfaces are imposed by a proportional spring-type boundary condition. The spring-type condition may be reduced to traction-free, displacement-fixed, and mirror-symmetric conditions. Numerical examples are given to demonstrate the validity and elegance of the present formulation of three-dimensional point-force Green’s functions for composite laminates. DA - 2003/1// PY - 2003/1// DO - 10.1016/S0020-7683(02)00545-0 VL - 40 IS - 2 SP - 331-342 SN - 1879-2146 KW - anisotropic elasticity KW - Green's function KW - three dimensions KW - composite laminates KW - Stroh formalism KW - Fourier transforms ER - TY - JOUR TI - Thermally developing forced convection in a porous medium: parallel plate channel with walls at uniform temperature, with axial conduction and viscous dissipation effects AU - Nield, DA AU - Kuznetsov, AV AU - Xiong, M T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - A modified Graetz methodology is applied to investigate the thermal development of forced convection in a parallel plate channel filled by a saturated porous medium, with walls held at uniform temperature, and with the effects of axial conduction and viscous dissipation included. The Brinkman model is employed. The analysis leads to expressions for the local Nusselt number, as a function of the dimensionless longitudinal coordinate and other parameters (Darcy number, Péclet number, Brinkman number). DA - 2003/2// PY - 2003/2// DO - 10.1016/S0017-9310(02)00327-7 VL - 46 IS - 4 SP - 643-651 SN - 0017-9310 ER - TY - JOUR TI - Thermally developing forced convection in a porous medium: Parallel-plate channel or circular tube with walls at constant heat flux AU - Nield, DA AU - Kuznetsov, AV AU - Xiong, M T2 - JOURNAL OF POROUS MEDIA AB - An adaptation of the classical Graetz methodology is applied to investigate the thermal development of forced convection in a parallel-plate channel or a circular tube filled by a saturated porous medium, with walls held at constant heat flux. The Brinkman model is employed. The analysis leads to expressions for the local Nusselt number and average Nusselt number, as functions of the dimensionless longitudinal coordinate and the Darcy number. DA - 2003/// PY - 2003/// DO - 10.1615/JPorMedia.v6.i3.50 VL - 6 IS - 3 SP - 203-212 SN - 1091-028X ER - TY - JOUR TI - The effects of nozzle geometry on waterjet breakup at high Reynolds numbers AU - Tafreshi, HV AU - Pourdeyhimi, B T2 - EXPERIMENTS IN FLUIDS DA - 2003/10// PY - 2003/10// DO - 10.1007/s00348-003-0685-y VL - 35 IS - 4 SP - 364-371 SN - 0723-4864 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0345329521&partnerID=MN8TOARS ER - TY - JOUR TI - Stability and convergence of a hybrid adaptive feedforward observer AU - Tran, CM AU - Southward, SC T2 - JOURNAL OF GUIDANCE CONTROL AND DYNAMICS DA - 2003/// PY - 2003/// DO - 10.2514/2.5036 VL - 26 IS - 1 SP - 189-192 SN - 0731-5090 ER - TY - JOUR TI - Single void morphological and grain-boundary effects on overall failure in FCC polycrystalline systems AU - Ashmawi, WM AU - Zikry, MA T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - An investigation of how dislocation-density interactions, such as impedance, transmission, and absorption, with grain-boundaries (GBs) affect and control void growth and porosity evolution in F.C.C. aggregates has been conducted. A multiple-slip rate-dependent crystalline constitutive formulation that is coupled to the evolution of mobile and immobile dislocation-densities, a new internal porosity formulation for microvoid nucleation and growth, and specialized computational schemes have been developed to understand and quantify the interrelated effects of GB orientation, mobile and immobile dislocation-density evolution, and dislocation-density transmission and blockage on microvoid nucleation and growth. The effects of GB structure and orientation on ductile failure have been accounted for by the development of GB interfacial kinematic conditions that account for dislocation-density interactions with GBs, such as full and partial transmission, impedance, blockage, and absorption. Pile-ups and transmission regions are identified and monitored as the deformation and failure evolves. It is shown that mobile dislocation-density saturation, void size and shape, and dislocation-density interactions within the grains and the GBs are the interrelated triggering mechanisms that lead to porosity nucleation, growth, and localization. DA - 2003/2/25/ PY - 2003/2/25/ DO - 10.1016/s0921-5093(02)00325-8 VL - 343 IS - 1-2 SP - 126-142 SN - 1873-4936 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0037465014&partnerID=MN8TOARS KW - void morphology KW - microvoid nucleation and growth KW - porosity KW - grain-boundary KW - dislocation-density interactions KW - pile-ups KW - ductile failure ER - TY - JOUR TI - Simulating the flow dynamics in hydroentangling nozzles: Effect of cone angle and nozzle aspect ratio AU - Tafreshi, HV AU - Pourdeyhimi, B T2 - TEXTILE RESEARCH JOURNAL AB - Flow behavior in various nozzle shapes from the hydroentangling cone-capillary family is modeled in this paper. The work studies the effects of cone angle and nozzle aspect ratio (the ratio of the capillary section to its diameter) on water-jet formation. In particular, two sets of nozzles are considered. The first set consists of nozzles that have an aspect ratio of one and cone angles of 19, 15, 11, 7, and 3°, respectively. The nozzles in the second set have their inlet and outlet diameters fixed, but their aspect ratios vary from 1 to 6. The results from a two-phase axisymmetric steady-state model of turbulent nozzle flow reveal that decreasing the cone angle or increasing the nozzle aspect ratio does not affect the hydroentangling water-jet characteristics. The computational scheme is validated by comparing part of the results with the available experimental data in the literature. DA - 2003/8// PY - 2003/8// DO - 10.1177/004051750307300807 VL - 73 IS - 8 SP - 700-704 SN - 0040-5175 UR - https://publons.com/wos-op/publon/65200207/ ER - TY - JOUR TI - Optimum downwash behind wings in formation flight AU - Frazier, JW AU - Gopalarathnam, A T2 - JOURNAL OF AIRCRAFT AB - other hand, the scaling parameter M1® is more suitable (Fig. 2b). The upstream in uence appears to be a quadratic function of M1®, and the correlation of the downstream in uence and M1® is also reasonablygood.The extentof the interactionregionshowsa similar trend as the upstream and downstream in uences. A good collapse of the data with M1® can be seen. The peakpressuredownstreamof thecornercanbeused to characterize the strength of the upstreamcompressionprocesses. In Fig. 3 it can be seen that the peak pressure downstream of the concave corner can also be scaled with M1®. Stronger compression is associatedwith increasingfreestreamMach number and concave-corner angle. Note that the peak pressure at M1®D 12:30 increases up to 42% of dynamic pressure. DA - 2003/// PY - 2003/// DO - 10.2514/2.3162 VL - 40 IS - 4 SP - 799-803 SN - 0021-8669 ER - TY - JOUR TI - Natural convection in a liquid-encapsulated molten semiconductor with a steady magnetic field AU - Kuniholm, JF AU - Ma, N T2 - INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW AB - This paper treats the buoyant convection in a layer of boron oxide, called a liquid encapsulant, which lies above a layer of a molten compound semiconductor (melt) between cold and hot vertical walls in a rectangular container with a steady horizontal magnetic field B. The magnetic field provides an electromagnetic damping of the molten semiconductor which is an excellent electrical conductor but has no direct effect on the motion of the liquid encapsulant. The temperature gradient drives counter-clockwise circulations in both the melt and encapsulant. These circulations alone would lead to positive and negative values of the horizontal velocity in the encapsulant and melt, respectively, near the interface. The competition between the two buoyant convections determines the direction of the horizontal velocity of the interface. DA - 2003/2// PY - 2003/2// DO - 10.1016/S0142-727X(02)00205-9 VL - 24 IS - 1 SP - 130-136 SN - 0142-727X ER - TY - JOUR TI - Effects of the heating process and body dimensions on the estimation of the thermal conductivity components of orthotropic solids AU - Mejias, MM AU - Orlande, HRB AU - Ozisik, MN T2 - INVERSE PROBLEMS IN ENGINEERING AB - In this article, we design the experiment for estimating the thermal conductivity components of an orthotropic medium, with respect to the solid dimensions and to the magnitude of the fluxes that are used to heat the solid. The D-optimum approach is used in the experimental design. By using a transformation that maps the heat conduction equation for an orthotropic medium into the heat conduction equation for an isotropic medium, we show that thermal conductivity components with identical relative accuracies can be estimated by appropriately selecting the experimental variables under picture. The Levenberg-Marquardt method is applied for the solution of the present parameter estimation problem by using simulated temperature measurements. DA - 2003/2// PY - 2003/2// DO - 10.1080/1068276031000105686 VL - 11 IS - 1 SP - 75-89 SN - 1068-2767 KW - orthotropic solid KW - thermal conductivity components KW - experimental design KW - Levenberg-Marquardt method ER - TY - JOUR TI - Design of low Reynolds number airfoils with trips AU - Gopalarathnam, A AU - Broughton, BA AU - McGranahan, BD AU - Selig, MS T2 - JOURNAL OF AIRCRAFT AB - A design philosophy for low Reynolds number airfoils that judiciously combines the tailoring of the airfoil pressure distribution using a transition ramp with the use of boundary-layer trips is presented. Three airfoils with systematic changes to the shape of the transition ramp have been designed to study the effect of trips on the airfoil performance. The airfoils were wind-tunnel tested with various trip locations and at Reynolds numbers of 100,000 and 300,000 to assess the effectiveness of the design philosophy. The results show that the design philosophy was successfullyusedin integratinga boundary-layertrip from theoutsetin theairfoildesignprocess.FortheReynolds numbers and the range of airfoil shapes considered, however, airfoils designed with trips do not hold any clear advantage over airfoils designed for good performance in the clean condition. DA - 2003/// PY - 2003/// DO - 10.2514/2.3157 VL - 40 IS - 4 SP - 768-775 SN - 1533-3868 ER - TY - JOUR TI - Analysis of transient-rating signals for reacting-flow applications AU - Brown, MS AU - Li, YY AU - Roberts, WL AU - Gord, , JR T2 - APPLIED OPTICS AB - Single-shot transient-grating measurements for thermometry in pressurized reacting flows are examined in the context of rapid digital signal processing. Simple approaches are discussed for temperature determination and rejection of unwanted signals in real-time measurement applications. Examples of temperature data in pressurized postflame gases are presented in the form of probability-density functions (PDFs). Three contributions to the PDF half-widths are discussed. Analysis of phase-matching requirements indicates that beam steering as a result of density fluctuations affects the signal amplitude but not the grating period. Therefore, such stochastic beam deviations have little effect on the derived temperatures. Mode noise on the cw probe beam as well as linear light scattering are found to be insignificant in the frequency range of the observed transient-grating acoustic signature. Use of a single-mode laser for the pump beams is shown to enhance the signal intensity. DA - 2003/1/20/ PY - 2003/1/20/ DO - 10.1364/AO.42.000566 VL - 42 IS - 3 SP - 566-578 SN - 2155-3165 ER - TY - JOUR TI - Analysis of stability of bioconvection of motile oxytactic bacteria in a horizontal fluid saturated porous layer AU - Kuznetsov, AV AU - Avramenko, AA T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - Stability of a suspension of motile oxytactic microorganisms in a shallow layer filled with a fluid saturated porous medium is investigated. Because the layer is shallow, oxygen concentration is larger than the minimum concentration required for the bacteria to be active and the bacteria are actively swimming in the direction of maximum oxygen gradient in every location within the layer. Linear stability analysis results in the determination of the critical value of the product of Raleigh and Darcy numbers DA - 2003/7// PY - 2003/7// DO - 10.1016/S0735-1933(03)00097-6 VL - 30 IS - 5 SP - 593-602 SN - 0735-1933 ER - TY - JOUR TI - Analysis of progressive fiber debonding in elastic laminates AU - Bahei-El-Din, YA AU - Botrous, AG T2 - INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES AB - The evolution of fiber debonding, and sliding, in fibrous laminates is modeled by a coupled micro/macro-mechanical analysis scheme. The laminates under consideration have a symmetric layup, and are subjected to mechanical loads. The individual plies are elastic, have a unidirectional reinforcement, and can suffer local damage at the fiber/matrix interface when the resolved normal and shear stresses exceed their ultimate magnitudes. The local fields in the plies are assumed to be periodic, and are approximated by the finite element method for overall loads and local resolved stresses that are in excess of the interface strength. Local effects in the individual plies are scaled up to the laminate analysis through stress transformation factors, which are a function of the elastic properties of the plies and their stacking configuration. The proposed analysis was implemented for a periodic array model of the laminas, and for in-plane loading of the laminate. The model predictions for a unidirectional steel/epoxy system subjected to transverse loading compare remarkably well with experimental measurements. This result, and several other examples given for axial and off-axis loading of SiC/CAS laminates, illustrate the model capabilities in predicting the overall strains in the presence of simultaneous, progressive debonding in the individual plies. DA - 2003/12// PY - 2003/12// DO - 10.1016/S0020-7683(03)00353-6 VL - 40 IS - 25 SP - 7035-7053 SN - 1879-2146 KW - laminate mechanics KW - micromechanics KW - debonding KW - analytical modeling KW - finite element analysis ER - TY - JOUR TI - Turbulence filter and POD analysis for velocity fields in lifted CH4-air diffusion flames AU - Kodal, A AU - Watson, KA AU - Roberts, WL AU - Lyons, KM T2 - FLOW TURBULENCE AND COMBUSTION DA - 2003/// PY - 2003/// DO - 10.1023/B:APPL.0000004914.21646.c4 VL - 70 IS - 1-4 SP - 21-41 SN - 1386-6184 KW - lifted flame KW - POD KW - turbulent KW - turbulence filter ER - TY - JOUR TI - The response of a propane-air counter-flow diffusion flame subjected to a transient flow field AU - Welle, EJ AU - Roberts, WL AU - Carter, CD AU - Donbar, JM T2 - COMBUSTION AND FLAME AB - OH planar laser-induced fluorescence (PLIF) and particle image velocimetry have been used to study the frequency response of laminar C3H8-air counterflow diffusion flames to assess the adequacy of the steady-flamelet models. Particle image velocimetry was used to determine the flame strain rate, while OH PLIF was used both to measure temperature at the flame front, using the two-line PLIF technique, and the reaction-zone width. Both measurements demonstrate that the frequency response of flames subjected to a time-varying flow field is diffusion-limited. At the 30-Hz and 50-Hz forcing frequencies, the maximum reaction-zone temperature and width were found to respond quasi-steadily. However, at higher forcing frequencies-i.e., 100 and 200 Hz-transient behavior is evident from the phase relationship between the imposed sinusoidal strain rate and the resulting peak temperature and reaction-zone width. The measured values of the OH-field widths were well fit by an offset sine function. In all cases when the oscillation amplitude is normalized by the cycle mean strain rate and plotted against the non-dimensional flow field frequency, the results collapse onto a single line having a steep negative slope. DA - 2003/11// PY - 2003/11// DO - 10.1016/S0010-2180(03)00167-6 VL - 135 IS - 3 SP - 285-297 SN - 0010-2180 KW - unsteady flame KW - diffusion flame KW - transient flame KW - PLIF KW - PIV KW - stokes parameter ER - TY - JOUR TI - Targeted drug aerosol deposition analysis for a four-generation lung airway model with hemispherical tumors AU - Kleinstreuer, C AU - Zhang, Z T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME AB - One important research area of broad interest is the development of highly efficient drug delivery systems for desired site deposition and uptake. For example, controlled drug aerosol release and targeting to specific regions of the lung is a novel way to combat lung diseases, diabetes, virus infections, cancers, etc. Determination of feasible air-particle streams is a prerequisite for the development of such delivery devices, say, smart inhalers. The concept of "controlled particle release and targeting" is introduced and results are discussed for a representative model of bronchial lung airways afflicted with hemispherical tumors of different sizes and locations. It is shown that under normal particle inlet conditions a particle mass fraction of only up to 11% may deposit on the surface of a specific tumor with critical radius r/R approximately 1.25, while a controlled particle release achieves deposition fractions of 35 to 92% for a realistic combination of inlet Stokes and Reynolds numbers, depending mainly on tumor size. Furthermore, with the controlled release and targeting approach nearby healthy tissue is hardly impacted by the typically aggressive drug aerosols. Assuming laminar, quasi-steady, three-dimensional air flow and spherical non-interacting micron-particles in sequentially bifurcating rigid airways, the results were obtained using a validated commercial finite-volume code with user-enhanced programs on a high-end engineering workstation. The new concept is generic and hence should be applicable to other regions of the respiratory system as well. DA - 2003/4// PY - 2003/4// DO - 10.1115/1.1543548 VL - 125 IS - 2 SP - 197-206 SN - 1528-8951 ER - TY - JOUR TI - Size scales for accurate homogenization in the presence of severe stress gradients AU - Yuan, F. G. AU - Pagano, N. J. T2 - Mechanics of Advanced Materials and Structures DA - 2003/// PY - 2003/// DO - 10.1080/15376490390231836 VL - 10 IS - 4 SP - 353-365 ER - TY - JOUR TI - Numerical study of the efficiency of acoustic streaming for enhancing heat transfer between two parallel beams AU - Wan, Q AU - Kuznetsov, AV T2 - FLOW TURBULENCE AND COMBUSTION DA - 2003/// PY - 2003/// DO - 10.1023/B:APPL.0000004916.01838.63 VL - 70 IS - 1-4 SP - 89-114 SN - 1386-6184 KW - acoustic streaming KW - forced convection KW - heat transfer enhancement ER - TY - JOUR TI - Nanoindentation characterization of surface layers of electrical discharge machined WC-Co AU - Qu, J AU - Riester, L AU - Shih, AJ AU - Scattergood, RO AU - Lara-Curzio, E AU - Watkins, TR T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - This study applies nanoindentation and other analysis techniques to investigate the influence of wire electrical discharge machining (EDM) process on the structure and properties of machined surface layers of WC–Co composites. Multiple indents were conducted on the cross-section of the surface recast layer, sub-surface heat-affected zone, and bulk material. The energy disperse X-ray spectrometry and X-ray diffraction were used to analyze the material compositions in the heat-affected zone and recast layer and to study the electrical spark eroded surface. The indents were inspected by scanning electron microscopy to distinguish between regular and irregular indents in these three regions. Irregular indents were caused by the porosity, soft matrix material, separation of grain boundaries, and thermal cracks caused by EDM process. The hardness and modulus of elasticity obtained from regular indents in bulk material and heat-affected zone were comparable to those of WC. It was found that the recast layer had lower hardness and modulus of elasticity than the bulk material and heat-affected zone. DA - 2003/3/15/ PY - 2003/3/15/ DO - 10.1016/s0921-5093(02)00395-7 VL - 344 IS - 1-2 SP - 125-131 SN - 0921-5093 KW - nanoindentation KW - mechanical properties KW - metal matrix ceramic composites KW - electrical discharge machining ER - TY - JOUR TI - Mechanical properties of polyphenylene-sulfide (PPS) bonded NdFe-B permanent magnets AU - Garrell, MG AU - Ma, BM AU - Shih, AJ AU - Lara-Curzio, E AU - Scattergood, RO T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Mechanical properties, namely tensile and flexural strengths and elastic modulus, of polyphenylene-sulfide (PPS) bonded Nd–Fe–B magnets have been studied from −40 to 180 °C. The ultimate tensile strength (Sut) of PPS bonded magnets decreases with increasing temperature. The tensile strength of PPS bonded Nd–Fe–B magnets was reduced significantly above 100 °C. At 180 °C, the PPS bonded magnets still exhibit a Sut of 16–18 MPa. For bonded magnets with about 60% volume fraction of Nd–Fe–B powder, the PPS bonded magnet shows about twice the tensile strength and half the ultimate strain compared to that of Nylon bonded magnet. At room temperature, the flexural strength is, in general, comparable to the tensile strength. Dynamic elastic modulus measured using the impact resonance method was in good agreement with the elastic modulus obtained from tensile tests. Scanning Electron Microscopy analyses of the fractured surfaces revealed two distinct failure mechanisms. Debonding along the Nd–Fe–B particle and PPS interface is the main cause for failures at 100 and 180 °C. The fracture of Nd–Fe–B particle was observed on the fracture surface of specimens tested at −40 and 23 °C. DA - 2003/10/25/ PY - 2003/10/25/ DO - 10.1016/s0921-5093(03)00400-3 VL - 359 IS - 1-2 SP - 375-383 SN - 0921-5093 KW - polyphenylene-sulfide bonded magnets KW - tensile strength KW - flexural strength KW - elastic modulus ER - TY - JOUR TI - H(infinity) and L(2)-to-L(infinity) gain control of linear parameter-varying systems with parameter-varying delays AU - Tan, K AU - Grigoriadis, KM AU - Wu, F T2 - IEE PROCEEDINGS-CONTROL THEORY AND APPLICATIONS AB - The analysis and state-feedback synthesis problems for linear parameter-varying systems with parameter-varying time delays are addressed. It is assumed that the state-space data and the time delays are dependent on parameters that are measurable in real-time and vary in a compact set with bounded variation rates. We explore the stability, L2 gain performance and L2 - to- L∞ gain performance for these systems using parameter-dependent Lyapunov functionals. In addition, the design of parameter-dependent state-feedback controllers that guarantee stability and desired induced norm performance are examined. Both analysis and synthesis conditions are formulated in terms of linear matrix inequalities that can be solved via efficient interior-point algorithms. DA - 2003/9// PY - 2003/9// DO - 10.1049/ip-cta:20030708 VL - 150 IS - 5 SP - 509-517 SN - 1350-2379 ER - TY - JOUR TI - Distributed control for interconnected linear parameter dependent systems AU - Wu, F T2 - IEE PROCEEDINGS-CONTROL THEORY AND APPLICATIONS AB - Stability analysis and performance control problems for a class of interconnected parameter-dependent systems with linear fractional parameter dependency are considered. The time and spatially varying parameters are assumed measurable in real-time for controller use. The distributed controller inherits the spatial structure of the plant, which is implementable through parallel computation. The stability of the interconnected parameter-dependent systems is established using a distributed Lyapunov function. Moreover, the synthesis condition of distributed parameter-dependent control gain is formulated as a convex optimisation in the form of a linear matrix inequality. An explicit distributed controller formula is also provided by exploiting the connection between the continuous and the discrete interconnected system descriptions. DA - 2003/9// PY - 2003/9// DO - 10.1049/ip-cta:20030706 VL - 150 IS - 5 SP - 518-527 SN - 1350-2379 ER - TY - JOUR TI - Cost-effective grinding of zirconia using the dense vitreous bond silicon carbide wheel AU - Shih, AJ AU - Scattergood, RO AU - Curry, AC AU - Yonushonis, TM AU - Gust, DJ AU - Grant, MB AU - McSpadden, SB AU - Watkins, TR T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME AB - Results of grinding zirconia using wheels with fine grain size SiC and dense vitreous bond are presented. Wheel wear results demonstrated that this type of SiC wheel could grind fully and partially stabilized zirconia (PSZ) very effectively. X-ray diffraction was used to analyze the percentage of monoclinic phase in the PSZ base material, ground surface, and debris. As expected, due to the stress- and temperature-induced phase transformation during grinding, the percentage of monoclinic phase on the ground surface was increased relative to the base material. However, X-ray diffraction showed no monoclinic phase in the PSZ debris. This suggests that, during grinding, the low thermal conductivity of zirconia and SiC, compared to that of diamond, facilitates heat retention in the chip and softens the work-material. This makes the efficient grinding of PSZ possible. Grinding temperature measurement results supported this hypothesis. DA - 2003/5// PY - 2003/5// DO - 10.1115/1.1559167 VL - 125 IS - 2 SP - 297-303 SN - 1087-1357 ER - TY - JOUR TI - Thermodynamic modeling and simulation of cavitating nozzle flow AU - Vortmann, C AU - Schnerr, GH AU - Seelecke, S T2 - INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW AB - Numerical simulations of cavitating flows are frequently performed by applying simple law of state-cavitation models. Here, the phase transition criterion is usually defined by assuming that cavitation occurs, if the pressure drops below the equilibrium vapor pressure. Since this simple modeling should be improved, an advanced method is developed, which takes phase non-equilibrium effects into account. The inclusion of non-equilibrium effects is important for future simulations of high-speed flows in very small-scale injector nozzles. Related to the van der Waals theory, the new approach is based on postulating Gibbs free energy for the phase mixture. This leads to a rate equation for quality. The two-phase flow is treated numerically by combining the rate equation with a volume-of-fluid algorithm. Unsteady calculations of cavitating flow in a converging–diverging passage and in a channel with a triangular obstacle show cyclically developing cavitation zones. The capability of this model to predict typical effects of cavitation, e.g. the formation of a re-entrant jet, is studied. Simulation of cavitating flow in the channel with a triangular obstacle is compared with the experiment and with numerical investigations of other authors. DA - 2003/10// PY - 2003/10// DO - 10.1016/S0142-727X(03)00003-1 VL - 24 IS - 5 SP - 774-783 SN - 0142-727X KW - cavitation KW - two-phase flow KW - equation-of-state KW - van der Waals KW - Landau KW - CFD KW - volume-of-fluid KW - injection nozzles ER - TY - JOUR TI - Thermally developing forced convection in a porous medium: Circular duct with walls at constant temperature, with longitudinal conduction and viscous dissipation effects AU - Kuznetsov, AV AU - Xiong, M AU - Nield, DA T2 - TRANSPORT IN POROUS MEDIA DA - 2003/12// PY - 2003/12// DO - 10.1023/A:1025060524816 VL - 53 IS - 3 SP - 331-345 SN - 0169-3913 KW - forced convection KW - thermal development KW - viscous dissipation KW - channel KW - duct ER - TY - JOUR TI - Species heat and mass transfer in a human upper airway model AU - Zhang, Z AU - Kleinstreuer, C T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - Steady 3-D airflow and scalar transport of ultrafine particles, dp<0.1 μm, and fuel vapors within the human upper airways are simulated and analyzed for laminar as well as locally turbulent flow conditions. Presently, our respiratory system consists of two major segments of a simplified human cast replica, i.e., a representative oral airway from mouth to trachea (Generation 0) and a symmetric four-generation upper bronchial tree model (G0–G3). The simulation has been validated with experimental data in terms of ultrafine particle deposition efficiencies. The present computational results show the following: (1) At low breathing rates (Qin≈15 l/min), ambient temperature variations (ΔTmax=47 °C) influence the local velocity fields and vapor concentrations; however, the total and segmental deposition fractions of fuel vapor in the upper airway are essentially unaffected. (2) The inlet flow rate has a significant effect on vapor deposition, i.e., the higher the flow rate the lower the deposition fraction. (3) The convective heat transfer coefficient averaged over an individual bifurcation unit can be correlated as Nu=0.568(RePr)0.495 (600 < Re < 6000). (4) Two new Sherwood number correlations capture the convective mass transfer for the oral airway and individual bifurcations. The methodology outlined and physical insight provided can be also applied to other intake configurations, such as engine ports and inlets to air-breathing propulsion systems. DA - 2003/12// PY - 2003/12// DO - 10.1016/S0017-9310(03)00358-2 VL - 46 IS - 25 SP - 4755-4768 SN - 1879-2189 ER - TY - JOUR TI - Particle-hemodynamics modeling of the distal end-to-side femoral bypass: effects of graft caliber and graft-end cut AU - Longest, PW AU - Kleinstreuer, C T2 - MEDICAL ENGINEERING & PHYSICS AB - Late-stage occlusions of peripheral synthetic bypass grafts are frequently due to intimal hyperplasia and/or thrombosis at the distal anastomosis, resulting in unacceptably high failure rates. It has been widely established that hemodynamic and blood particle interactions with the vascular surface as well as surgical injury and compliance mismatch are inciting mechanisms capable of eliciting various cellular level responses associated with distal anastomotic intimal hyperplasia (IH) formation. Primary geometric factors influencing anastomotic hemodynamics include the graft-to-artery diameter ratio and graft-hood shape, which are determined by the graft caliber and initial graft-end cut selected by the vascular surgeon. In this study, the particle-hemodynamic effects of graft-end cuts (straight, curved, and S-shaped) and graft-to-artery diameter ratios (2:1 vs. 1.5:1) have been numerically assessed in four common unexpanded anastomotic configurations with respect to vortical flow patterns, wall shear stress based parameters, and platelet interactions with the vascular surface. Sites of significant platelet–wall interactions have been identified by a novel near-wall residence time (NWRT) model, which includes shear stress based factors for platelet activation and endothelial cell expression of anti-thrombogenic compounds. Of the configurations evaluated, straight and curved graft-end cuts with a graft-to-artery diameter ratio of 1.5:1 were found to reduce the particle-hemodynamic potential for IH development at locations critical to flow delivery. Nevertheless, the potential for significant IH occurrence via platelet and/or endothelial response pathways was highly evident in all conventional anastomoses considered, such that a decisively superior configuration was not determined. These results illustrate the need for alternative anastomotic designs with the intent of reducing critical hemodynamic wall parameters and mitigating regions of significant particle–wall interactions. DA - 2003/12// PY - 2003/12// DO - 10.1016/S1350-4533(03)00124-3 VL - 25 IS - 10 SP - 843-858 SN - 1873-4030 KW - particle-hemodynamics KW - hemodynamic wall parameters KW - near-wall residence time KW - femoropopliteal bypass KW - end-to-side anastomosis KW - intimal hyperplasia ER - TY - JOUR TI - Particle hemodynamics analysis of Miller cuff arterial anastomosis AU - Longest, PW AU - Kleinstreuer, C AU - Archie, JP T2 - JOURNAL OF VASCULAR SURGERY AB - Studies of animal and human below-knee anastomoses with Miller cuffs indicate that improved graft patency results from redistribution of intimal hyperplasia away from areas critical to flow delivery, such as the arterial toe. We hypothesize that particle hemodynamic conditions are a biophysical mechanism potentially responsible for the clinically observed shift in intimal hyperplasia localization associated with better patency of the Miller configuration.Computational fluid dynamics analysis of vortical flow patterns, wall shear stress fields, and potential for platelet interaction with the vascular surface was performed for realistic three-dimensional conventional and Miller cuff distal end-to-side anastomoses. Sites of significant platelet-wall interaction, including elevated near-wall particle concentrations and stasis, were identified with a validated near-wall residence time model, which includes shear stress-based factors for particle activation and surface reactivity.Particle hemodynamics largely coincide with the observed redistribution of intimal hyperplasia away from the critical arterial toe region. Detrimental changes in wall shear stress vector magnitude and direction are significantly reduced along the arterial suture line of the Miller cuff, largely as a result of increased anastomotic area available for flow redirection. However, because of strong particle-wall interaction, resulting high near-wall residence time contours indicate significant intimal hyperplasia along the graft-vein suture line and in the vicinity of the arterial heel.While a number of interacting mechanical, biophysical, and technical factors may be responsible for improved Miller cuff patency, our results imply that particle hemodynamics conditions engendered by Miller cuff geometry provide a mechanism that may account for redistribution of intimal hyperplasia. In particular, it appears that a focal region of significant particle-wall interaction at the arterial toe is substantially reduced with the Miller cuff configuration. DA - 2003/12// PY - 2003/12// DO - 10.1016/S0741-5214(03)00950-9 VL - 38 IS - 6 SP - 1353-1362 SN - 0741-5214 ER - TY - JOUR TI - Optimization of pin-fin heat sinks using anisotropic local thermal nonequilibrium porous model in a jet impinging channel AU - Kim, S. Y. AU - Kuznetsov, A. V. T2 - Numerical Heat Transfer. Part A, Applications DA - 2003/// PY - 2003/// DO - 10.1080/10407780390229675 VL - 44 IS - 8 SP - 771-787 ER - TY - JOUR TI - Optimal pick-up locations for transport and handling of limp materials - Part II: Two-dimensional parts AU - Lankalapalli, S AU - Eischen, JW T2 - TEXTILE RESEARCH JOURNAL AB - Pick-up locations are obtained on two-dimensional limp parts that minimize a measure of deformation (strain energy). The parts are modeled as shells undergoing arbitrarily large deformations and rotations by a geometrically exact nonlinear shell finite element formulation. The strain energy is computed from the finite element solution for deforma tion, and the optimal locations are obtained by solving a bound constrained optimization problem. Results are given for various two-dimensional shapes. DA - 2003/10// PY - 2003/10// DO - 10.1177/004051750307301004 VL - 73 IS - 10 SP - 867-874 SN - 0040-5175 ER - TY - JOUR TI - Optimal pick-up locations for transport and handling of limp materials - Part I: One-dimensional strips AU - Lankalapalli, S AU - Eischen, JW T2 - TEXTILE RESEARCH JOURNAL AB - Pick-up locations are obtained on strips of limp material that minimize a measure of deformation (strain energy). The strips are modeled as continuous beams subjected to a uniformly distributed load using small and large deflection beam theories. Pick-up locations correspond to n support locations of the continuous beam. Strain energy is computed from a finite element solution, and optimal locations are obtained by solving unconstrained and bound constrained optimization problems. Results are in terms of a nondimensional number that characterizes the flexibility of the beam and are applicable to a wide range of limp materials. Some results for fabric strips are also presented. DA - 2003/9// PY - 2003/9// DO - 10.1177/004051750307300907 VL - 73 IS - 9 SP - 787-796 SN - 1746-7748 ER - TY - JOUR TI - Liquid flow in microchannels: experimental observations and computational analyses of microfluidics effects AU - Koo, JM AU - Kleinstreuer, C T2 - JOURNAL OF MICROMECHANICS AND MICROENGINEERING AB - Experimental observations of liquid microchannel flows are reviewed and results of computer experiments concerning channel entrance, wall slip, non-Newtonian fluid, surface roughness, viscous dissipation and turbulence effects on the friction factor are discussed. The experimental findings are classified into three groups. Group I emphasizes 'flow instabilities' and group II points out 'viscosity changes' as the causes of deviations from the conventional flow theory for macrochannels. Group III caters to studies that did not detect any measurable differences between micro- and macroscale fluid flow behaviors. Based on numerical friction factor analyses, the entrance effect should be taken into account for any microfluidic system. It is a function of channel length, aspect ratio and the Reynolds number. Non-Newtonian fluid flow effects are expected to be important for polymeric liquids and particle suspension flows. The wall slip effect is negligible for liquid flows in microconduits. Significant surface roughness effects are a function of the Darcy number, the Reynolds number and cross-sectional configurations. For relatively low Reynolds numbers, Re < 2000, onset to turbulence has to be considered important because of possible geometric non-uniformities, e.g., a contraction and/or bend at the inlet to the microchannel. Channel-size effect on viscous dissipation turns out to be important for conduits with Dh < 100 µm. DA - 2003/9// PY - 2003/9// DO - 10.1088/0960-1317/13/5/307 VL - 13 IS - 5 SP - 568-579 SN - 1361-6439 ER - TY - JOUR TI - Hybrid simulation approach for cavity flows: Blending, algorithm, and boundary treatment issues AU - Baurle, RA AU - Tam, CJ AU - Edwards, , JR AU - Hassan, HA T2 - AIAA JOURNAL AB - The maturation of high-performance computer architectures and computational algorithms has prompted the development of a new generation of models that attempt to combine the robustness and efficiency offered by the Reynolds averaged Navier-Stokes equations with the higher level of modeling offered by the equations developed for large eddy simulation. The application of a new hybrid approach is discussed, where the transition between these equation sets is controlled by a blending function that depends on local turbulent flow properties, as well as the local mesh spacing. The utilization of local turbulence properties provides added control in specifying the regions of the flow intended for each equation set, removing much of the burden from the grid-generation process. Moreover, the model framework allows for the combination of existing closure model equations, avoiding the difficulty of formulating a single set of closure coefficients that perform well in both Reynolds averaged and large eddy simulation modes. Simple modifications to common second-order accurate Reynolds averaged Navier-Stokes algorithms are proposed to enhance the capturing of large eddy motions DA - 2003/8// PY - 2003/8// DO - 10.2514/2.2129 VL - 41 IS - 8 SP - 1463-1480 SN - 0001-1452 ER - TY - JOUR TI - Hemodynamics simulation and identification of susceptible sites of atherosclerotic lesion formation in a model abdominal aorta AU - Buchanan, , JR AU - Kleinstreuer, C AU - Hyun, S AU - Truskey, GA T2 - JOURNAL OF BIOMECHANICS AB - Employing the rabbit's abdominal aorta as a suitable atherosclerotic model, transient three-dimensional blood flow simulations and monocyte deposition patterns were used to evaluate the following hypotheses: (i) simulation of monocyte transport through a model of the rabbit abdominal aorta yields cell deposition patterns similar to those seen in vivo, and (ii) those deposition patterns are correlated with hemodynamic wall parameters related to atherosclerosis. The deposition pattern traces a helical shape down the aorta with local elevation in monocyte adhesion around vessel branches. The cell deposition pattern was altered by an exercise waveform with fewer cells attaching in the upper abdominal aorta but more attaching around the renal orifices. Monocyte deposition was correlated with the wall shear stress gradient and the wall shear stress angle gradient. The wall stress gradient, the wall shear stress angle gradient and the normalized monocyte deposition fraction were correlated with the distribution of monocytes along the abdominal aorta and monocyte deposition is correlated with the measured distribution of monocytes around the major abdominal branches in the cholesterol-fed rabbit. These results suggest that the transport and deposition pattern of monocytes to arterial endothelium plays a significant role in the localization of lesions. DA - 2003/8// PY - 2003/8// DO - 10.1016/S0021-9290(03)00088-5 VL - 36 IS - 8 SP - 1185-1196 SN - 1873-2380 KW - computational blood flow simulation KW - rabbit aorta KW - atherosclerotic model KW - hemodynamic wall parameters KW - monocyte deposition KW - experimental data comparisons ER - TY - JOUR TI - Goniometric characteristics of optical fibres for temperature measurement in diesel engine exhaust filters AU - Boothe, BJ AU - Shih, AJ AU - Kong, N AU - Roberts, WL T2 - MEASUREMENT SCIENCE AND TECHNOLOGY AB - The accurate in situ, non-contact measurement of the temperature distribution within diesel after-treatment filters requires the employment of optical fibres with special tip geometry. The goniometric characteristics of optical fibres with flat, 45° angled and bent and polished tips are studied such that the specific radiation acceptance region can be determined. One 2 mm diameter fused silica and two 0.425 mm diameter sapphire optical fibres are examined. Detailed discussion of the relative intensity profiles observed for these fibres is presented. Of the three fibres evaluated, the 45° angled tip geometry provides the most precise response for measuring radiation emitted from the internal filter walls. Exploiting the characteristics of total internal reflection, the 45° angled tip fibre accepts the maximum quantity of incident radiation at an angle perpendicular to the optical axis. DA - 2003/5// PY - 2003/5// DO - 10.1088/0957-0233/14/5/305 VL - 14 IS - 5 SP - 563-572 SN - 1361-6501 KW - goniometric characteristics KW - optical fibre KW - angled tip KW - effective numerical aperture ER - TY - JOUR TI - Evolution of mechatronics into a graduate degree program in the United States: The NC State University master of science program with mechatronics concentration AU - Ramasubramanian, M. K. AU - Noori, M. N. AU - Lee, G. K. T2 - International Journal of Engineering Education DA - 2003/// PY - 2003/// VL - 19 IS - 4 SP - 519-524 ER - TY - JOUR TI - Evolution of failure mechanisms in 2D and 3D woven composite systems under quasi-static perforation AU - Baucom, J. N. AU - Zikry, Mohammed T2 - Journal of Composite Materials DA - 2003/// PY - 2003/// DO - 10.1177/002199803035178 VL - 37 IS - 18 SP - 1651–1674 ER - TY - JOUR TI - Direct numerical simulation of autoignition in non-homogeneous hydrogen-air mixtures AU - Echekki, T AU - Chen, JH T2 - COMBUSTION AND FLAME AB - The autoignition of spatially non-homogeneous hydrogen-air mixtures in 2-D random turbulence and mixture fraction fields is studied using the Direct Numerical Simulation (DNS) approach coupled with detailed kinetics. The coupling between chemistry and the unsteady scalar dissipation rate field is investigated over a wide range of different autoignition scenarios. The simulations show that autoignition is initiated at discrete spatially localized sites, referred to as kernels, by radical build-up in high-temperature, fuel-lean mixtures, and at relatively low dissipation rates. Detailed analysis of the dominant chemistry and the relative roles of reaction and diffusion is implemented by tracking the evolution of four representative kernels that characterize the range of ignition behaviors observed in the simulation. This evolution yields different autoignition delay scenarios as well as extinction at the different sites based on the local dissipation rates and their temporal histories. Where significant autoignition delay and extinction are observed, a shift in the relative roles of dominant reactions that contribute to radical production and consumption during this induction phase is observed. This shift is particularly characterized by an increased role of termination reactions during the intermediate stages of the induction period, which results in extinction in approximately two thirds of the ignition kernels in the computational domain. The fate of the different kernels is associated with: (1) the dissipation of heat that contributes to a slowdown in chemical reactions and a shift in the balance between chain-branching and chain-termination reactions; (2) the dissipation of mass that keeps the radical pool growth in check, and that is promoted by slower reaction rates; and (3) counter to the effects of dissipation of heat and intermediate species, the preferential diffusion of H2 relative to both heat and its diluent, N2, that promotes ignition. Ultimately, the balance between radical production and dissipation determines the success or failure of a given kernel to ignite. A new criterion for unsteady ignition is presented based on the instantaneous balance between radical production and dissipation. A Damköhler number, so defined, must remain above a critical value of unity at all times during the induction period if the kernel is to eventually ignite. Inherent in a multi-step kinetic description of ignition phenomena is the disparate time scales associated with different elementary reactions that, coupled with the characteristic scales of heat and mass dissipation, may yield different dominant chemistries at different stages of the induction process for a given kernel. To capture the strong history effects associated with radical build-up, new ignition progress variables based on key radical species are investigated. DA - 2003/8// PY - 2003/8// DO - 10.1016/S0010-2180(03)00088-9 VL - 134 IS - 3 SP - 169-191 SN - 1556-2921 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0042925437&partnerID=MN8TOARS KW - autoignition KW - hydrogen oxidation KW - DNS KW - turbulent combustion ER - TY - JOUR TI - Development of low-diffusion flux-splitting methods for dense gas-solid flows AU - Mao, DM AU - Edwards, , JR AU - Kuznetsov, AV AU - Srivastava, RK T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - The development of a class of low-diffusion upwinding methods for computing dense gas-solid flows is presented in this work. An artificial compressibility/low-Mach preconditioning strategy is developed for a hyperbolic two-phase flow equation system consisting of separate solids and gas momentum and continuity equations. The eigenvalues of this system are used to devise extensions of the AUSM+ [1] and LDFSS [2] flux-splitting methods that provide high resolution capturing of bubble growth and collapse in gas-solid fluidized beds. Applications to several problems in fluidization are presented. DA - 2003/2/10/ PY - 2003/2/10/ DO - 10.1016/S0021-9991(02)00049-9 VL - 185 IS - 1 SP - 100-119 SN - 1090-2716 KW - upwind discretization KW - time-derivative preconditioning KW - two-phase flow KW - fluidization ER - TY - JOUR TI - Computationally efficient algorithm for frequency-weighted optimal H-infinity model reduction AU - Wu, F. AU - Jaramillo, J. J. T2 - Asian Journal of Control AB - ABSTRACT In this paper, a frequency‐weighted optimal H ∞ model reduction problem for linear time‐invariant (LTI) systems is considered. The objective of this class of model reduction problems is to minimize H ∞ norm of the frequency‐weighted truncation error between a given LTI system and its lower order approximation. A necessary and sufficient solvability condition is derived in terms of LMIs with one extra coupling rank constraint, which generally leads to a non‐convex feasibility problem. Moreover, it has been shown that the reduced‐order model is stable when both stable input and output weights are included, and its state‐space data are given explicitly by the solution of the feasibility problem. An efficient model reduction scheme based on cone complementarity algorithm (CCA) is proposed to solve the non‐convex conditions involving rank constraint. DA - 2003/// PY - 2003/// DO - 10.1111/j.1934-6093.2003.tb00126.x VL - 5 IS - 3 SP - 341-349 ER - TY - JOUR TI - Role of baffles on flow fields inside wet-lay mixing tanks and their potential influence on fiber dispersion AU - Tafreshi, H. V. AU - Pourdeyhimi, B. T2 - Textile Research Journal AB - Dispersion and separation of fiber bundles requires exposing them to a shear stress field to overcome interfiber frictional forces. To this end, fiber-mixing tanks are equipped with baffles to enhance shear and agitation in the water to help disperse the fiber bundles. The time and agitation required to separate and disperse the fibers depends on the fibers being used. It is well known, however. that excessive agitation will give rise to the formation of rope defects in the output because of the high-energy vortices that form behind these baffles. Optimizing the baffle geometry and position is therefore critically important in the wet-lay process. This paper presents some possible ways of eliminating the regions in the water velocity field where strong vortices may be present: in particular, the motivation for this paper is that minimizing vortex formation will lower the probability of rope forma tion. In this regard, we present a series of numerical simulations to model fluid-flow behavior inside wet-lay mixing tanks. A turbulent flow field is obtained by solving the Navier-Stokes equations in a two-dimensional geometry. The turbulent features of the flow are captured using the RNG k-e model. Fibers, modeled as spherical rigid particles with the same volume as the fibers, are introduced into the solution domain and their trajectories are tracked inside the mixing tank. The effects of the baffles and their orientation with respect to flow streamlines are simulated. We report the simulation results for different baffle configurations and show that aligning the baffles with the streamlines and increasing their surface area can eliminate the formation of vortices while still keeping the shear field at a satisfactory level. We hypothesize that eliminating the vortices in the mixing tank reduces the probability of rope formation, but this hypothesis needs to be verified experimentally. DA - 2003/// PY - 2003/// DO - 10.1177/004051750307300703 VL - 73 IS - 7 SP - 575-582 ER - TY - JOUR TI - Relation between near-wall residence times of monocytes and early lesion growth in the rabbit aorto-celiac junction AU - Longest, PW AU - Kleinstreuer, C AU - Truskey, GA AU - Buchanan, , JR T2 - ANNALS OF BIOMEDICAL ENGINEERING DA - 2003/1// PY - 2003/1// DO - 10.1114/1.1531635 VL - 31 IS - 1 SP - 53-64 SN - 0090-6964 KW - atherosclerosis KW - particle hemodynamics KW - hemodynamic wall parameters KW - monocytes KW - adhesion KW - deposition KW - computational fluid dynamics KW - near-wall residence time ER - TY - CONF TI - Macrosegregation during directional solidification of alloyed semiconductor crystals with a transverse magnetic field AU - Dust, J. C. AU - Ma, N. C2 - 2003/// C3 - AIAA Aerospace Sciences Meeting and Exhibit (41st: Reno, NV, 2003). (AIAA paper; no. 2003-1310) DA - 2003/// ER - TY - JOUR TI - Forming shaped/molded structures by integrating meltblowing and robotic technologies AU - Farer, R AU - Seyam, AM AU - Ghosh, TK AU - Batra, SK AU - Grant, E AU - Lee, G T2 - TEXTILE RESEARCH JOURNAL AB - A novel system is described that forms three-dimensional (3D) molded nonwoven structures through proper integration of a laboratory scale meltblown unit with a small die and a six-axis robot. The 3D fiberweb structures can be formed by deposition of fibers from the die of the meltblown unit, which is manipulated by the robot, on any desired 3D mold. The mold rotational and surface speeds can be controlled by an additional external axis. The die is connected by two flexible hoses to the melt extruder of the meltblown unit and a hot air supply system. This system directly sprays fibers onto a 3D mannequin mold to produce structures from polypropylene polymers. With varying degrees of success. several robot manipulation algorithms of fiber deposition on the mold are developed to accurately control the basis weight uniformity the fiberwebs. A rule-based control algorithm using a linear variable differential transducer to map the mold contour results in the greatest fiberweb basis weight uniformity. DA - 2003/1// PY - 2003/1// DO - 10.1177/004051750307300103 VL - 73 IS - 1 SP - 15-21 SN - 0040-5175 ER - TY - JOUR TI - The effect of deposition and declogging on the critical permeability in bioconvection in a porous medium AU - Kuznetsov, AV AU - Avramenko, AA T2 - ACTA MECHANICA DA - 2003/// PY - 2003/// DO - 10.1007/s00707-002-0978-x VL - 160 IS - 1-2 SP - 113-125 SN - 0001-5970 ER - TY - JOUR TI - Method for determination of crack bridging parameters using long optical fiber Bragg grating sensors AU - Studer, M AU - Peters, K AU - Botsis, J T2 - COMPOSITES PART B-ENGINEERING AB - The state of the local fiber–matrix interface highly influences the propagation of cracks in fiber-reinforced composites and thus the stress distribution in any bridging fiber. This paper demonstrates that by embedding a long optical fiber Bragg grating into a reinforcing fiber and using an established model of the grating response to non-uniform stress distributions, one can determine key parameters of a crack bridging model. The grating extending into the epoxy on each side of the crack is subject to a strain function as a result of all micro-mechanical phenomena acting along the fiber. Furthermore, this technique does not require that one knows a priori the exact location of the crack. Two types of central crack specimens with an artificial crack were fabricated and tested, one with a strong interface and one with a weaker interface resulting in frictional sliding. The results demonstrate that this technique is efficient for the measurement of the bridging forces through validation by previous measurements using short Bragg gratings and the deduction of interface parameters. Analysis also shows that the sensitivity of the Bragg grating sensor to the bridging force is sufficient, even for the more realistic case of an initially zero-width crack e.g. grown by fatigue. DA - 2003/// PY - 2003/// DO - 10.1016/S1359-8368(03)00004-0 VL - 34 IS - 4 SP - 347-359 SN - 1879-1069 KW - polymer-matrix composites KW - crack bridging KW - interface KW - optical techniques ER - TY - JOUR TI - Fixed abrasive diamond wire machining - part II: experiment design and results AU - Clark, WI AU - Shih, AJ AU - Lemaster, RL AU - McSpadden, SB T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE AB - Experimental results from fixed abrasive diamond wire machining of wood and foam ceramics are presented. Three types of wood—pine, oak, and fir, and three types of foam ceramic—silicon carbide, zirconia, and zirconia toughened alumina, are tested. The research investigates the life of diamond wire and effects of process parameters on the cutting forces, force ratio, and surface roughness. A scanning electron microscope is used to study the worn diamond wire, machined surfaces, and debris. The diamond wire saw is demonstrated to be very effective in machining foam ceramics. The wire life for cutting wood at slow feed rates is low. The short tool life for dry cutting of wood indicates that more research in new fixed abrasive diamond wire and wire saw machining technologies is necessary. DA - 2003/4// PY - 2003/4// DO - 10.1016/S0890-6955(02)00216-X VL - 43 IS - 5 SP - 533-542 SN - 1879-2170 KW - diamond wire saw KW - wood machining KW - foam ceramics ER - TY - JOUR TI - Fixed abrasive diamond wire machining - part I: process monitoring and wire tension force AU - Clark, WI AU - Shih, AJ AU - Hardin, CW AU - Lemaster, RL AU - McSpadden, SB T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE AB - The process monitoring and mechanics of fixed abrasive diamond wire saw machining are investigated in this study. New techniques to affix diamond particles to a steel wire core have advanced to make this process feasible for the machining of ceramics, wood, and foam materials. Developments in fixed abrasive diamond wire machining are first reviewed. Advantages of using fixed abrasive diamond wire machining are then introduced. The process monitoring and signal processing techniques for measuring the cutting forces, wire speed, down feed rate, and wire bow angle in diamond wire saw machining are developed. The application of a capacitance sensor to measure the wire bow and a procedure to convert the wire bow to vertical cutting force in a rocking motion wire saw machine are developed. The tension force of the wire during cutting is also derived and discussed. DA - 2003/4// PY - 2003/4// DO - 10.1016/S0890-6955(02)00215-8 VL - 43 IS - 5 SP - 523-532 SN - 0890-6955 KW - diamond wire saw KW - wire saw machining KW - process monitoring ER - TY - JOUR TI - Free energy model for hysteresis in magnetostrictive transducers AU - Smith, RC AU - Dapino, MJ AU - Seelecke, S T2 - JOURNAL OF APPLIED PHYSICS AB - This article addresses the development of a free energy model for magnetostrictive transducers operating in hysteretic and nonlinear regimes. Such models are required both for material and system characterization and for model-based control design. The model is constructed in two steps. In the first, Helmholtz and Gibbs free energy relations are constructed for homogeneous materials with constant internal fields. In the second step, the effects of material nonhomogeneities and nonconstant effective fields are incorporated through the construction of appropriate stochastic distributions. Properties of the model are illustrated through comparison and prediction of data collected from a typical Terfenol-D transducer. DA - 2003/1/1/ PY - 2003/1/1/ DO - 10.1063/1.1524312 VL - 93 IS - 1 SP - 458-466 SN - 1089-7550 ER - TY - JOUR TI - Magnetic field effects during liquid-encapsulated Czochralski growth of doped photonic semiconductor crystals AU - Morton, JL AU - Ma, N AU - Bliss, DF AU - Bryant, GG T2 - JOURNAL OF CRYSTAL GROWTH AB - During the liquid-encapsulated Czochralski (LEC) process, a single compound semiconductor crystal such as indium phosphide or gallium antimonide is grown by the solidification of an initially molten semiconductor contained in a crucible. The motion of the electrically conducting molten semiconductor can be controlled with an externally applied magnetic field. This paper presents a model for the unsteady transport of a dopant during the LEC process with a steady axial magnetic field. The convective species transport during growth produces significant segregation in both the melt and the crystal. Dopant distributions in the crystal and in the melt at several different stages during growth are presented. DA - 2003/3// PY - 2003/3// DO - 10.1016/S0022-0248(02)02261-3 VL - 250 IS - 1-2 SP - 174-182 SN - 0022-0248 KW - magnetic fields KW - mass transfer KW - segregation KW - growth from melt KW - liquid encapsulated Czochralski method KW - magnetic field assisted Czochralski method KW - semiconducting III-V compounds ER - TY - JOUR TI - Globally convergent algorithms for nonsmooth nonlinear equations in computational fluid dynamics AU - Coffey, T AU - McMullan, RJ AU - Kelley, CT AU - McRae, DS T2 - JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS AB - In this paper we report on a computational study in which a nonsmooth discretization of the Euler equations for flow in a nozzle is solved with splitting method which is in turn globalized with the method of pseudo-transient continuation. DA - 2003/3/1/ PY - 2003/3/1/ DO - 10.1016/S0377-0427(02)00697-0 VL - 152 IS - 1-2 SP - 69-81 SN - 0377-0427 KW - pseudo-transient continuation KW - nonlinear equations KW - steady-state solutions KW - global convergence KW - splitting methods KW - Euler equations KW - MUSCL approximation ER - TY - JOUR TI - Robust quadratic performance for time-delayed uncertain linear systems AU - Wu, F T2 - INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL AB - Abstract In this paper, the analysis and control synthesis problems were studied for a general class of uncertain linear systems with variable time delay. It is assumed that the structured time‐varying parametric uncertainties enter the system state‐space description in a linear fractional fashion. The generic quadratic performance metric encompasses many types of dynamic system performance measure. In the context of delay‐independent stability, it was shown that the analysis and state‐feedback synthesis problems for such time‐delayed uncertain systems can be formulated equivalently as linear matrix inequality (LMI) optimization problems using the mechanism of full block multipliers. However, the solvability condition to output‐feedback problem was given as bilinear matrix inequality (BMI), which leads to a non‐convex optimization problem. A numerical example is provided to demonstrate the advantages of newly proposed control synthesis condition for time‐delayed uncertain systems over existing approaches. Copyright © 2002 John Wiley & Sons, Ltd. DA - 2003/2// PY - 2003/2// DO - 10.1002/rnc.720 VL - 13 IS - 2 SP - 153-172 SN - 1099-1239 KW - uncertain linear system KW - time delay KW - parametric uncertainty KW - robustness KW - linear matrix inequality ER - TY - JOUR TI - Laminar-to-turbulent fluid-particle flows in a human airway model AU - Kleinstreuer, C AU - Zhang, Z T2 - INTERNATIONAL JOURNAL OF MULTIPHASE FLOW AB - As in many biomedical and industrial applications, gas–solid two-phase flow fields in a curved tube with local area constrictions may be laminar, transitional and/or turbulent depending upon the inlet flow rate and tube geometry. Assuming steady incompressible air flow and non-interacting spherical micron-particles, the laminar-to-turbulent suspension flow problem was solved for a human airway model using a commercial software with user-supplied pre- and post-processing programs. All flow regimes (500