TY - CONF TI - Simulations of dimensional effects in solid oxide fuel cells AU - Mahmud Hasan, A.B. AU - Ekkad, S.V. AU - Mensah, P. AB - Two dimensional simulation models for a solid oxide fuel cell (SOFC) including gas channels have been studied using the commercial software FEMLAB which has a multi-physics approach. The models include full coupling between the mass balances at the anode and cathode, the balance of the ionic current carried by the oxide ion, and a balance of electronic current with an assumption of isothermal conditions. Three cross-section areas of 1cm × 1cm, 3cm × 3cm, and 5 cm × 5cm were chosen to study the dimensional effect. An additional 1cm × 1cm channel with rectangular protrusions was also studied to investigate geometry effects. Simulation results show expected result of increases in fuel cell properties like convective flux, electric potential with increasing cell flow area. The smaller fuel cell surface is altered by adding rectangular protrusions to increase surface area. The presence of rectangular protrusions also show increased current density production compared to a wall without protrusions. It is expected that the proposed simulations can be used to significantly help the design and operation of a SOFC in practical applications. C2 - 2005/// C3 - Proceedings of the ASME Summer Heat Transfer Conference DA - 2005/// DO - 10.1115/HT2005-72394 VL - 4 SP - 11-16 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-29644447790&partnerID=MN8TOARS ER - TY - CONF TI - Film cooling measurements for novel hole configurations AU - Lu, Y. AU - Fauchcaux, D. AU - Ekkad, S.V. AB - Film cooling performance for a row of cylindrical holes can be. The effect of the slot exit area and shape is investigated. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on free-stream velocity and film hole diameter of 7150 at three different coolant-to-mainstream blowing ratios of 0.5, 1.0, and 1.5. Two designs with a crescent shaped exit and a slot exit are considered. The results show that the crescent shaped exits provide significantly higher film cooling effectiveness than the cylindrical hole exit at all blowing ratios. The converging slot exit provides similar effectiveness as the crescent for higher blowing ratios. However, the crescent shape also enhances heat transfer coefficients significantly. Overall effectiveness for both crescent and converging slot exits are clearly superior to the standard cylindrical hole. C2 - 2005/// C3 - Proceedings of the ASME Summer Heat Transfer Conference DA - 2005/// DO - 10.1115/HT2005-72396 VL - 3 SP - 59-66 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-29644435324&partnerID=MN8TOARS ER - TY - CONF TI - The effects of feeding configurations to water flooding and general performance of a proton exchange membrane fuel cell AU - Mahmud Hasan, A.B. AU - Guo, S.M. AU - Ekkad, S.V. AB - The performance of a Proton Exchange Membrane Fuel Cell (PEMFC) using different feeding configurations has been studied. Three bipolar plates, namely serpentine, straight channel and interdigitated designs, were arranged in different combinations for the PEMFC anode and cathode sides. Nine combinations in total were tested under different flow rates, working temperatures and loadings. The cell voltage versus current density and the cell power density versus current density curves were obtained. After operating the PEMFC under high current densities, the cell was split and the water flooding in the feeding channels was visually inspected. Experimental results showed that for different feeding configurations, interdigitated bipolar plate in anode side and serpentine bipolar plate in cathode side had the best performance in terms of cell voltage-current density curve, power density output rate, percentage of flooded area in the feeding channels, the pattern of flooding and the fuel utilization rate. C2 - 2005/// C3 - American Society of Mechanical Engineers, Advanced Energy Systems Division (Publication) AES DA - 2005/// DO - 10.1115/IMECE2005-81268 VL - 45 SP - 429-435 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-33645068600&partnerID=MN8TOARS ER - TY - JOUR TI - Impingement heat transfer, part II: Effect of streamwise pressure gradient AU - Hebert, R. AU - Ekkad, S.V. AU - Gao, L. AU - Bunker, R.S. T2 - Journal of Thermophysics and Heat Transfer AB - This is Part II of a two-part paper on jet-impingement heat transfer. The effect of streamwise pressure gradient on jet-impingement heat transfer is investigated. In realistic configurations, impingement arrays do not always impinge in channels that have parallel walls. Converging channels create positive pressure gradient, and diverging channels create adverse pressure gradient. In this study, the effect of nonparallel walls on jet-impingement heat transfer is investigated. Firstly for impingement arrays with jet-to-jet streamwise and spanwise spacing of fourhole diameters and eight-hole diameters and then for the linearly stretched arrays discussed in Part I. Two jet Reynolds numbers are studied for all cases for Re =6 × × 10 3 , and 10 3 . Also, the jet height-to-diameter ratio is increased from 1 to 5 to generate the adverse pressure gradient and decreased from 5 to 1 to generate the positive pressure gradient. Results show that the effect of streamwise pressure gradient alters the flow distribution causing significant variations in heat-transfer distributions. Accelerating flow causes streamwise jet stretching, whereas decelerating flow causes spanwise jet stretching. The results for converging and diverging channels are compared with results for parallel plate channels with different spacing to compare the effect of the streamwise pressure gradient. DA - 2005/// PY - 2005/// DO - 10.2514/1.8588 VL - 19 IS - 1 SP - 66-71 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-12744263177&partnerID=MN8TOARS ER - TY - JOUR TI - Impingement heat transfer, part I: Linearly stretched arrays of holes AU - Gao, L. AU - Ekkad, S.V. AU - Bunker, R.S. T2 - Journal of Thermophysics and Heat Transfer AB - This is Part I of a two-part paper to study new configurations for impingement heat transfer. In Part I, linearly stretched arrays of holes are investigated, and in Part II the effect of pressure gradient on jet-impingement heat transfer is studied. Impingement holes in real engines 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 and the second array having increasing diameter holes. Three jet Reynolds numbers between 2 x 10 3 and 10 3 are studied for three different jet height-to-diameter ratios between 1 and 5. The measured heat-transfer coefficients for these arrays are then predicted using existing impingement heat-transfer correlations based on regular evenly spaced arrays DA - 2005/// PY - 2005/// DO - 10.2514/1.8551 VL - 19 IS - 1 SP - 57-65 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-12744263181&partnerID=MN8TOARS ER - TY - CONF TI - Film cooling from a row of holes embedded in transverse slots AU - Lu, Y. AU - Nasir, H. AU - Ekkad, S.V. AB - Film cooling performance for a row of cylindrical holes can be enhanced by embedding the row in transverse slots. The geometry of the transverse slot greatly affects the cooling performance downstream of injection. The effect of the slot exit area and edge shape is investigated. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on free-stream velocity and film hole diameter of 7150 at three different coolant-to-mainstream blowing ratios of 0.5, 1.0, and 1.5. The results show that the film cooling holes provide higher film effectiveness when embedded in a slot. However, in some geometries when the slot begins at the upstream edge of the hole, the film effectiveness diminishes. The heat transfer coefficient enhancement due to the embedding is not significantly higher compared to the typical unembedded cylindrical hole. The overall heat flux ratio comparing film cooling with embedded holes to unembedded holes shows that the full slot and downstream slot spacing after the hole exit produce the highest heat flux reduction. The holes-in-slot geometry is certainly very promising. C2 - 2005/// C3 - Proceedings of the ASME Turbo Expo DA - 2005/// DO - 10.1115/GT2005-68598 VL - 3 PART A SP - 585-592 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-27744550896&partnerID=MN8TOARS ER - TY - CONF TI - CFD for jet impingement heat transfer with single jets and arrays AU - Ibrahim, M.B. AU - Kochuparambil, B.J. AU - Ekkad, S.V. AU - Simon, T.W. AB - CFD experiments were conducted for heat transfer with jet impingement over solid surfaces. The parameters include: 1) Jet Reynolds number from 3,000 to 23,000, 2) Jet-to-target-plate spacing (z/d), from 2 to 14 (single jet), d is jet diameter, 3) Target plate shape: 3a) flat, 3b) concave, 3c) convex, (single jet), 4) One row of seven jets impinging on a flat surface, the channel has one end closed (at 24d away from the most upstream jet axis), 5) Three rows of seven jets each in-line arrangement impinging on a flat surface, the channel has one end closed (at 24d away from the most upstream jet axis). Four CFD models (utilizing FLUENT commercial code) have been considered: 1) laminar flow (no turbulent transport), and turbulent flow with turbulence modeling by 2) the standard k–ε model, 3) the k–ω model, and 4) the v2–f model. The predictions of Nu number for each case were compared with experimental data available from the literature. It is shown that the v2–f model gives the best overall performance, though the k–ω model gives good predictions for most of the flow, with the exception of near the stagnation zone for some cases. The models are in much better agreement (with the data) as z/d grows and at larger radial locations from the jet axis, as expected. For multiple jets in one row (z/d = 2), again the v2–f showed the best overall agreement with the experimental data. The k–ω model is not as good while k–ε clearly overpredicts the Nusselt numbers. For multiple jets in three inline rows (z/d = 5), all the three models were in overall agreement with the experimental data. However, k–ε and k–ω exhibit an important phenomenon, reported by the experiments: a decrease of the stagnation Nu from the upstream jet to the downstream ones. The v2–f model did not reproduce this feature. C2 - 2005/// C3 - Proceedings of the ASME Turbo Expo DA - 2005/// DO - 10.1115/GT2005-68341 VL - 3 PART A SP - 359-373 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-27744594135&partnerID=MN8TOARS ER - TY - CONF TI - Effect of tip and pressure side coolant injection on heat transfer distributions for a plane and recessed tip AU - Nasir, H. AU - Ekkad, S.V. AU - Bunker, R.S. AB - The present study investigates the effects of coolant injection on adiabatic film effectiveness and heat transfer coefficients from a plane and recessed tip of a HPT first stage rotor blade. Three cases where coolant is injected from (a) five orthogonal holes located along the camber line, (b) seven angled holes located near the blade tip along the pressure side and (c) combination cases when coolant is injected from both tip and pressure side holes were studied. The pressure ratio (inlet total pressure to exit static pressure for the cascade) across the blade row was 1.2, and the experiments were run in a blow-down test rig with a four-blade linear cascade. The Reynolds number based on cascade exit velocity and axial chord length was 8.61×105 and the inlet and exit Mach number were 0.16 and 0.55, respectively. A transient infrared (IR) technique was used to measure adiabatic film effectiveness and heat transfer coefficient simultaneously for three blowing ratios of 1.0, 2.0, and 3.0. For all the cases, gap-to-blade span ratio of 1% was used. The depth-to-blade span ratio of 0.0416 was used for the recessed tip. Pressure measurements on the shroud were also taken to characterize the leakage flow and understand the heat transfer distributions. For tip injection, when blowing ratio increases from 1.0 to 2.0, film effectiveness increases for both plane and recessed tip. At blowing ratio 3.0, lift off is observed for both cases. In case of pressure side coolant injection and for plane tip, lift off is observed at blowing ratio 2.0 and reattachments of jets are observed at blowing ratio 3.0. But, almost no effectiveness is observed for squealer tip at all blowing ratios with pressure side injection. For combination case, very high effectiveness is observed at blowing ratio 3.0 for both plane and recessed blade tip. It appears that for this high blowing ratio, coolant jets from the tip hit the shroud first and then reattach back on to the blade tip. For tip injection, as blowing ratio increases heat transfer coefficient decreases for both plane and recessed tip. In case of pressure side coolant injection and for plane tip, film injection reduced heat transfer coefficient along the pressure side. Minimal effect is observed for recessed tip at all blowing ratios. For combination case, very high heat transfer coefficient is observed at blowing ratio 3.0 for both plane and recessed blade tip. It appears that for this high blowing ratio, coolant jets from the tip hit the shroud first and then reattach back on to the blade tip. C2 - 2005/// C3 - Proceedings of the ASME Turbo Expo DA - 2005/// DO - 10.1115/GT2005-68595 VL - 3 PART A SP - 573-584 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-27744449608&partnerID=MN8TOARS ER - TY - CONF TI - Radiation and cladding modes as independent measurements of Bragg grating sensor integrity AU - Prabhugoud, M. AU - Pearson, J. AU - Peters, K. AU - Zikry, M. AB - This article presents the use of Bragg reflection and cladding mode measurements to independently measure axial strain and the integrity of a Bragg grating sensor. While the Bragg reflection is known to be sensitive to applied strain, the cladding modes are shown to be sensitive to expected damage within the sensor such as microcracking and debonding from the host structure. This phenomenon allows the intelligent self-testing of the Bragg grating sensor without additional instrumentation and permits the separate identification of sensor failure from the failure of the host structure. The growth of cladding modes during degradation of a Bragg grating is experimentally demonstrated in controlled tension tests with different fiber-host interface conditions. C2 - 2005/// C3 - Proceedings of SPIE - The International Society for Optical Engineering DA - 2005/// DO - 10.1117/12.597782 VL - 5758 SP - 440-450 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-25144473506&partnerID=MN8TOARS ER - TY - CONF TI - Failure and damage identification in woven composites with fiber Bragg grating sensors AU - Pearson, J. AU - Prabhugoud, M. AU - Zikry, M. AU - Peters, K. AU - Sitar, M. AU - Davis, L. AB - In this study, measurements from low-impact velocity experiments and embedded and surface mounted optical fiber Bragg grating (FBG) sensors were used to obtain detailed information pertaining to damage progression in two-dimensional laminate woven composites. The woven composites were subjected to multiple strikes at 2m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces. The FBG sensors were embedded and surface mounted at different critical locations near penetration-induced damaged regions. These FBG sensors were used to obtain initial residual strains and axial and transverse strains that correspond to matrix cracking and delamination. The transmission and the reflection spectra were continuously monitored throughout the loading cycles. They were used, in combination with the peak contact forces, to delineate repeatable sensor responses corresponding to material failure. From the FBG spectra, fiber and matrix damage were separated by an analysis based on signal intensity, the presence of cladding modes, and the behavior of individual Bragg peaks as a function of evolving and repeated impact loads. This provided an independent feedback on the integrity of the Bragg gratings. A comparison by number of strikes and dissipated energies corresponding to material perforation indicates that embedding these sensors did not affect the integrity of the woven systems and that these measurements can provide accurate failure strains. C2 - 2005/// C3 - Proceedings of SPIE - The International Society for Optical Engineering DA - 2005/// DO - 10.1117/12.599771 VL - 5765 SP - 540-551 M1 - PART 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-25144476656&partnerID=MN8TOARS ER - TY - JOUR TI - Theme issue on modeling of metal forming processes AU - Badr, H. AU - M.Arif, A.F. AU - Sheikh, A.K. AU - Shuaib, A.N. AU - Khan, Z. AU - Khan, A.S. AU - Tseng, A.A. AU - Zikry, M.A. T2 - Arabian Journal for Science and Engineering DA - 2005/// PY - 2005/// VL - 30 IS - 1 C UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-32544458475&partnerID=MN8TOARS ER - TY - CONF TI - Modeling of nanoindentation and microstructural ductile behavior in metallic material systems AU - Ma, J.B. AU - Ashmawi, W. AU - Zikry, M.A. AU - Schall, D. AU - Brenner, D.W. C2 - 2005/// C3 - Materials Research Society Symposium Proceedings DA - 2005/// VL - 841 SP - 317-322 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-23844433619&partnerID=MN8TOARS ER - TY - CONF TI - Damage progression identification in woven composites with fiber bragg grating sensors AU - Pearson, J. AU - Prabhugoud, M. AU - Zikry, M. AU - Peters, K. AB - In this study, measurements from low-impact velocity experiments including embedded and surface mounted optical fiber Bragg grating (FBG) sensors were used to obtain detailed information pertaining to damage progression in two-dimensional laminate woven composites. The woven composites were subjected to multiple strikes at 2m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces. The FBG sensors were embedded and surface mounted at different critical locations near penetration-induced damaged regions. These FBG sensors were used to obtain initial residual strains and axial and transverse strains that correspond to matrix cracking and delamination. The transmission and reflection spectra were continuously monitored throughout the loading cycles. They were used, in combination with the peak contact forces, to delineate repeatable sensor responses corresponding to material failure. From the FBG spectra, fiber and matrix damage were separated by an analysis based on signal intensity, the presence of cladding modes, and the behavior of individual Bragg peaks as a function of evolving and repeated impact loads. This provided an independent feedback on the integrity of the Bragg gratings. A comparison by number of impact strikes and dissipated energies corresponding to material perforation indicates that embedding these sensors did not affect the integrity of the woven systems and that these measurements can provide accurate failure strains. C2 - 2005/// C3 - American Society of Mechanical Engineers, Materials Division (Publication) MD DA - 2005/// DO - 10.1115/IMECE2005-80487 VL - 100 MD SP - 49-57 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-33645654612&partnerID=MN8TOARS ER - TY - CONF TI - A Study on Hydroentangling Waterjets AU - Anantharamaiah, N. AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - International Nonwoven Technical Conference (INTC 2005) C2 - 2005/9/19/ C3 - International Nonwoven Technical Conference (INTC 2005) CY - St. Louis, Missouri DA - 2005/9/19/ PY - 2005/9/19/ ER - TY - CONF TI - Water Flow Simulation in Nonwovens Made of Hydrophilic and Non-hydrophilic Fibers AU - Tafreshi, H.V. AU - Maze, B. AU - Pourdeyhimi, B. T2 - Belt-wide Cotton Conference C2 - 2005/1/6/ C3 - Belt-wide Cotton Conference CY - New Orleans, Louisiana DA - 2005/1/6/ PY - 2005/1/6/ ER - TY - ER - TY - CHAP TI - Near-Net shape forging and new development AU - Ngaile, Gracious AU - Shirgaokar, Manas T2 - Cold and Hot Forging: Fundamentals and Applications A2 - Altan, Taylan A2 - Ngaile, Gracious A2 - Shen, Gangshu PY - 2005/// DO - 10.31399/asm.tb.chffa.t51040319 PB - ASM International SN - 9781627083003 ER - TY - CHAP TI - Process Modeling in Impression-Die Forging Using Finite-Element Analysis AU - Ngaile, Gracious AU - Shirgaokar, Manas AU - Shen, Gangshu T2 - Cold and Hot Forging: Fundamentals and Applications A2 - Altan, Taylan A2 - Ngaile, Gracious A2 - Shen, Gangshu PY - 2005/// DO - 10.31399/asm.tb.chffa.t51040193 PB - ASM International SN - 9781627083003 ER - TY - CHAP TI - Friction and Lubrication AU - Ngaile, Gracious AU - Gariety, Mark T2 - Cold and Hot Forging: Fundamentals and Applications A2 - Altan, Taylan A2 - Ngaile, Gracious A2 - Shen, Gangshu PY - 2005/// DO - 10.31399/asm.tb.chffa.t51040067 PB - ASM International SN - 9781627083003 ER - TY - CHAP TI - Plastic Deformation: Complex state of stress and flow rules AU - Ngaile, Gracious T2 - Cold and Hot Forging: Fundamentals and Applications A2 - Altan, Taylan A2 - Ngaile, Gracious A2 - Shen, Gangshu PY - 2005/// DO - 10.31399/asm.tb.chffa.t51040051 PB - ASM International SN - 9781627083003 ER - TY - CHAP TI - Plastic Deformation: Strain and Strain Rate AU - Ngaile, Gracious AU - Shirgaokar, Manas T2 - Cold and Hot Forging: Fundamentals and Applications A2 - Altan, Taylan A2 - Ngaile, Gracious A2 - Shen, Gangshu PY - 2005/// DO - 10.31399/asm.tb.chffa.t51040017 PB - ASM International SN - 9781627083003 ER - TY - BOOK TI - Cold and Hot Metal Forging: Fundamentals and Applications AU - Altan, Taylan AU - Ngaile, Gracious AU - Shen, Ganshu DA - 2005/// PY - 2005/// PB - ASM International SN - 978-0-87170-805 ER - TY - JOUR TI - Performance of single-crystal Pb(Mg1∕3Nb2∕3)-32%PbTiO3 stacked actuators with application to adaptive structures AU - Woody, Shane C. AU - Smith, Stuart T. AU - Jiang, Xiaoning AU - Rehrig, Paul W. T2 - Review of Scientific Instruments AB - This article presents the performance of ultra-high-strain single-crystal piezoelectric stacked actuators using the composition Pb(Mg1∕3Nb2∕3)-32%PbTiO3 (PMN-32%PT)for adaptive structures (in particular for space-based applications). Generally, dimensionally adaptive or smart structures often utilize piezoelectric actuators [in particular lead zirconate titanate (PZT) elements] to provide high-frequency response motion. However, most commercial stacks are limited in range (often &lt;0.1% strain) and the motion is further reduced at low or cryogenic temperatures for satellite-based and many other applications. Comparatively, single-crystal actuators such as the ultra-high-strain PMN-32%PT provide greater than a factor of 4 displacement, factor of 2 strain energy density, and cryogenic displacements are comparable to room-temperature conditions for PZT actuators. Nonetheless, there are some technological and fundamental limitations, such as plate thickness, which is generally greater than 0.5mm, low elastic modulus, and low strain at each end of the stacks. Three stack configurations with 3, 5, and 40 active layers are tested and discussed. This report discusses each configuration type as a function of lost motion, obtainable strain rates, preload designs, applied stiffness, stress gradients, electric fields, and bandwidth performances. The results obtained in this study aim to show performance and discuss the relative merits and limitations of using this actuator material for adaptive structures. A case study is presented for a high bandwidth steering mirror using ultra-high-strain single crystals. Closed loop control results from the platform’s response are briefly discussed. DA - 2005/7// PY - 2005/7// DO - 10.1063/1.1984974 VL - 76 IS - 7 SP - 075112 J2 - Review of Scientific Instruments LA - en OP - SN - 0034-6748 1089-7623 UR - http://dx.doi.org/10.1063/1.1984974 DB - Crossref ER - TY - JOUR TI - Strong, high-frequency, ac electric-field-induced rhombohedra-tetragonal phase transition in Pb(Mg1∕3Nb2∕3)O3–PbTiO3 single crystal AU - Zhan, Chun AU - Wu, Juntao AU - Yin, Shizhuo AU - Jiang, Xiaoning T2 - Journal of Applied Physics AB - Dielectric properties of Pb(Mg1∕3Nb2∕3)O3–PbTiO3 single crystals grown by a modified Bridgman method are investigated under strong, high-frequency (&gt;100kHz) ac field. It is found that there is a phase transition due to the applied ac field, which may be due to the following reasons: (1) strong ac field periodically moves domains at fast speed that heats up the crystal due to the friction of domain change; and (2) phase transition happens because of the increase of the temperature. Compared with conventional heating techniques, ac field-induced phase transition is a quicker and more effective way. In addition, it is also found that continuous ac excitation can make the phase transition easier that may be due to the deaging effect caused by continuous ac excitation. Experimental results confirm the increase of d33 and the change of transmittance under strong ac field, which further verifies that phase transition indeed happens. DA - 2005/4// PY - 2005/4// DO - 10.1063/1.1881794 VL - 97 IS - 7 SP - 074107 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.1881794 DB - Crossref ER - TY - JOUR TI - A small, linear, piezoelectric ultrasonic cryomotor AU - Dong, Shuxiang AU - Yan, Li AU - Wang, Naigang AU - Viehland, Dwight AU - Jiang, Xiaoning AU - Rehrig, Paul AU - Hackenberger, Wes T2 - Applied Physics Letters AB - A small, linear-type, piezoelectric ultrasonic cryomotor has been developed for precision positioning at extremely low temperatures (⩾−200°C)⁠. This cryomotor consists of a pair of Pb(Mg1∕3Nb2∕3)O3−PbTiO3 single crystal stacks, which are piezoelectrically excited into the rotating third-bending mode of the cryomotor stator’s center, which in turn drives a contacted slider into linear motion via frictional forces. The performance characteristics achieved by the cryomotor are: (i) a maximum linear speed of >50mm∕s⁠; (ii) a stroke of >10mm⁠; (iii) a driving force of >0.2N⁠; (iv) a response time of ∼29ms⁠; and (v) a step resolution of ∼20nm⁠. DA - 2005/1/31/ PY - 2005/1/31/ DO - 10.1063/1.1855424 VL - 86 IS - 5 SP - 053501 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.1855424 DB - Crossref ER - TY - BOOK TI - Spaceflight mechanics 2004 : proceedings of the 14th AAS/AIAA Space flight mechanics meeting held 8-12 February 2004, Maui, Hawaii AU - Coffey, S.L. AU - Mazzoleni, A.P. AU - Luu, K.K. AU - Glover, R.A. T2 - Advances in the astronautical sciences DA - 2005/3// PY - 2005/3// SP - 3318 M1 - 119 PB - Univelt for the American Astronautical Society SN - 9780877035152 ER - TY - JOUR TI - Controllability and Point-to-Point Control of 3-DOF Planar Horizontal Underactuated Manipulators AU - Mahindrakar, A.D. AU - Banavar, R.N. AU - Reyhanoglu, M. T2 - International Journal of Control AB - This paper presents the controllability properties of an underactuated 3R manipulator and the application of a discontinuous point-to-point control law for a three-degree-of-freedom (DOF) PPR manipulator. In the first half we present a controllability analysis at various actuator configurations of the manipulator. A novel contribution is that we use a single co-ordinate system to analyse the controllability at all the three possible configurations. In the second half we present a discontinuous feedback control law for point-to-point control of a 3 DOF PPR underactuated manipulator moving in a horizontal plane. Simulation results are presented that demonstrate the effectiveness of the controller. DA - 2005/1// PY - 2005/1// DO - 10.1080/00207170412331317422 VL - 78 IS - 1 SP - 1–13 ER - TY - JOUR TI - Selective edge removal for unstructured grids with Cartesian cores AU - Löhner, Rainald AU - Luo, Hong AU - Baum, Joseph D. T2 - Journal of Computational Physics AB - Several rules for redistributing geometric edge-coefficient obtained for grids of linear elements derived from the subdivision of rectangles, cubes or prisms are presented. By redistributing the geometric edge-coefficient, no work is carried out on approximately half of all the edges of such grids. The redistribution rule for triangles obtained from rectangles is generalized to arbitrary situations in 3-D, and implemented in a typical 3-D edge-based flow solver. The results indicate that without degradation of accuracy, CPU requirements can be cut considerably for typical large-scale grids. This allows a seamless integration of unstructured grids near boundaries with efficient Cartesian grids in the core regions of the domain. DA - 2005/6// PY - 2005/6// DO - 10.1016/j.jcp.2004.11.034 VL - 206 IS - 1 SP - 208-226 J2 - Journal of Computational Physics LA - en OP - SN - 0021-9991 UR - http://dx.doi.org/10.1016/j.jcp.2004.11.034 DB - Crossref KW - CFD KW - FEM KW - Cartesian grids KW - edge-based solvers ER - TY - JOUR TI - Exact solutions of incompressible Couette flow with porous walls for slightly rarefied gases AU - Fang, Tiegang AU - Lee, Chia-fon F. T2 - Heat and Mass Transfer DA - 2005/9/14/ PY - 2005/9/14/ DO - 10.1007/s00231-005-0009-2 VL - 42 IS - 3 SP - 255-262 J2 - Heat Mass Transfer LA - en OP - SN - 0947-7411 1432-1181 UR - http://dx.doi.org/10.1007/s00231-005-0009-2 DB - Crossref KW - transient Couette flow KW - exact solution KW - slightly rarefied gas KW - porous channel KW - micro-channel KW - slip flow KW - heat transfer KW - incompressible flow ER - TY - JOUR TI - Low temperature combustion within a small bore high speed direct injection (HSDI) diesel engine AU - Fang, T. AU - Coverdill, R.E. AU - Lee, C.-F.F. AU - White, R.A. T2 - SAE Technical Papers DA - 2005/// PY - 2005/// DO - 10.4271/2005-01-0919 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877219266&partnerID=MN8TOARS ER - TY - JOUR TI - Liquid and vapor fuel distributions within a High Speed Direct Injection (HSDI) diesel engine operating in HCCI and conventional combustion modes AU - Fang, T. AU - Coverdill, R.E. AU - Lee, C.-F.F. AU - White, R.A. T2 - SAE Technical Papers DA - 2005/// PY - 2005/// DO - 10.4271/2005-01-3838 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877425830&partnerID=MN8TOARS ER - TY - JOUR TI - An electromechanical material testing system for in situ electron microscopy and applications AU - Zhu, Y. AU - Espinosa, H. D. T2 - Proceedings of the National Academy of Sciences AB - We report the development of a material testing system for in situ electron microscopy (EM) mechanical testing of nanostructures. The testing system consists of an actuator and a load sensor fabricated by means of surface micromachining. This previously undescribed nanoscale material testing system makes possible continuous observation of the specimen deformation and failure with subnanometer resolution, while simultaneously measuring the applied load electronically with nanonewton resolution. This achievement was made possible by the integration of electromechanical and thermomechanical components based on microelectromechanical system technology. The system capabilities are demonstrated by the in situ EM testing of free-standing polysilicon films, metallic nanowires, and carbon nanotubes. In particular, a previously undescribed real-time instrumented in situ transmission EM observation of carbon nanotubes failure under tensile load is presented here. DA - 2005/9/29/ PY - 2005/9/29/ DO - 10.1073/pnas.0506544102 VL - 102 IS - 41 SP - 14503-14508 J2 - Proceedings of the National Academy of Sciences LA - en OP - SN - 0027-8424 1091-6490 UR - http://dx.doi.org/10.1073/pnas.0506544102 DB - Crossref KW - carbon nanotube KW - microelectromechanical system KW - nanomechanics KW - nanowires ER - TY - JOUR TI - Epitaxially influenced boundary layer model for size effect in thin metallic films AU - Bažant, Zdeněk P. AU - Guo, Zaoyang AU - Espinosa, Horacio D. AU - Zhu, Yong AU - Peng, Bei T2 - Journal of Applied Physics AB - It is shown that the size effect recently observed by Espinosa et al., [J. Mech. Phys. Solids51, 47 (2003)] in pure tension tests on free thin metallic films can be explained by the existence of a boundary layer of fixed thickness, located at the surface of the film that was attached onto the substrate during deposition. The boundary layer is influenced by the epitaxial effects of crystal growth on the dislocation density and texture (manifested by prevalent crystal plane orientations). This influence is assumed to cause significantly elevated yield strength. Furthermore, the observed gradual postpeak softening, along with its size independence, which is observed in short film strips subjected to pure tension, is explained by slip localization, originating at notch-like defects, and by damage, which can propagate in a stable manner when the film strip under pure tension is sufficiently thin and short. For general applications, the present epitaxially influenced boundary layer model may be combined with the classical strain-gradient plasticity proposed by Gao et al., [J. Mech. Phys. Solids 47, 1239 (1999)], and it is shown that this combination is necessary to fit the test data on both pure tension and bending of thin films by one and the same theory. To deal with films having different crystal grain sizes, the Hall–Petch relation for the yield strength dependence on the grain size needs to be incorporated into the combined theory. For very thin films, in which a flattened grain fills the whole film thickness, the Hall–Petch relation needs a cutoff, and the asymptotic increase of yield strength with diminishing film thickness is then described by the extension of Nix’s model of misfit dislocations by Zhang and Zhou [J. Adv. Mater. 38, 51 (2002)]. The final result is a proposal of a general theory for strength, size effect, hardening, and softening of thin metallic films. DA - 2005/4// PY - 2005/4// DO - 10.1063/1.1861150 VL - 97 IS - 7 SP - 073506 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.1861150 DB - Crossref ER - TY - JOUR TI - A microelectromechanical load sensor for in situ electron and x-ray microscopy tensile testing of nanostructures AU - Zhu, Yong AU - Moldovan, N. AU - Espinosa, Horacio D. T2 - Applied Physics Letters AB - We report on the performance of a microelectromechanical system (MEMS) designed for the in situ electron and x-ray microscopy tensile testing of nanostructures, e.g., carbon nanotubes and nanowires. The device consists of an actuator and a load sensor with a gap in between, across which nanostructures can be placed, nanowelded, and mechanically tested. The load sensor is based on differential capacitance measurements, from which its displacement history is recorded. By determining the sensor stiffness, the load history during the testing is obtained. We calibrated the device and examined its resolution in the context of various applications of interest. The device is the first true MEMS in which the load is electronically measured. It is designed to be placed in scanning and transmission electron microscopes and on x-ray synchrotron stages. DA - 2005/1/3/ PY - 2005/1/3/ DO - 10.1063/1.1844594 VL - 86 IS - 1 SP - 013506 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.1844594 DB - Crossref ER - TY - JOUR TI - A Model of the Upper Extremity for Simulating Musculoskeletal Surgery and Analyzing Neuromuscular Control AU - Holzbaur, Katherine R. S. AU - Murray, Wendy M. AU - Delp, Scott L. T2 - Annals of Biomedical Engineering DA - 2005/6// PY - 2005/6// DO - 10.1007/S10439-005-3320-7 VL - 33 IS - 6 SP - 829-840 J2 - Ann Biomed Eng LA - en OP - SN - 0090-6964 1573-9686 UR - http://dx.doi.org/10.1007/S10439-005-3320-7 DB - Crossref KW - computer simulation KW - upper limb KW - muscle KW - shoulder KW - elbow KW - wrist ER - TY - CHAP TI - Birefringence and Transverse Strain Sensitivity in Bragg Grating Sensors AU - Prabhugoud, Mohanraj AU - Peters, Kara T2 - Sensing Issues in Civil Structural Health Monitoring PY - 2005/11/14/ DO - 10.1007/1-4020-3661-2_43 SP - 433-442 OP - PB - Springer-Verlag SN - 1402036604 UR - http://dx.doi.org/10.1007/1-4020-3661-2_43 DB - Crossref KW - fiber Bragg grating KW - birefringence KW - finite element method ER - TY - JOUR TI - Comparison of three ultrasonic axial transmission methods for bone assessment AU - Muller, M. AU - Moilanen, P. AU - Bossy, E. AU - Nicholson, P. AU - Kilappa, V. AU - Timonen, J. AU - Talmant, M. AU - Cheng, S. AU - Laugier, P. T2 - Ultrasound in Medicine & Biology AB - This study compared three approaches to bone assessment using ultrasonic axial transmission. In 41 fresh human radii, velocity of the first arriving signal was measured with a commercial device (Sunlight Omnisense) operating at 1.25 MHz, a prototype based on 1-MHz bidirectional axial transmission and a low-frequency (200 kHz) prototype, also measuring the velocity of a slower wave. Cortical and trabecular bone mineral density, cortical thickness and cross-sectional area were determined by peripheral quantitative computed tomography. Significant but modest correlation between velocities reflects differences in the nature of the propagating waves and methodological differences. Of the higher frequency devices, bidirectional measurements provided stronger correlations with bone properties than did conventional measurements. High-frequency devices were less sensitive to cortical thickness than was the low-frequency device, because higher frequency waves interrogate thinner cortical layers. The results suggest that different axial transmission approaches reflect different bone properties. Therefore, a multifrequency technique might be useful in probing different bone properties. DA - 2005/5// PY - 2005/5// DO - 10.1016/j.ultrasmedbio.2005.02.001 VL - 31 IS - 5 SP - 633-642 J2 - Ultrasound in Medicine & Biology LA - en OP - SN - 0301-5629 UR - http://dx.doi.org/10.1016/j.ultrasmedbio.2005.02.001 DB - Crossref KW - cortical bone KW - ultrasound axial transmission KW - in vitro KW - bone properties ER - TY - JOUR TI - A moving-wall boundary layer flow of a slightly rarefied gas free stream over a moving flat plate AU - Fang, Tiegang AU - Lee, Chia-fon F. T2 - Applied Mathematics Letters AB - In the current work, the boundary layer flow of a slightly rarefied gas free stream over a moving flat plate is presented and solved numerically. The first-order slip boundary condition is adopted in the derivation. The dimensionless velocity and shear stress profiles are plotted and discussed. A theoretical derivation of the estimated solution domain is developed, which will give a very close estimation to the exact solution domain obtained numerically. The influences of velocity slip at the wall on the velocity and shear stress are also addressed. DA - 2005/5// PY - 2005/5// DO - 10.1016/j.aml.2004.08.006 VL - 18 IS - 5 SP - 487-495 J2 - Applied Mathematics Letters LA - en OP - SN - 0893-9659 UR - http://dx.doi.org/10.1016/j.aml.2004.08.006 DB - Crossref KW - moving flat plate KW - Blasius equation KW - slightly rarefied gas ER - TY - JOUR TI - Doppler writing and linewidth control for scanning beam interference lithography AU - Montoya, Juan C. AU - Chang, Chih-Hao AU - Heilmann, Ralf K. AU - Schattenburg, Mark L. T2 - Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures AB - Scanning beam interference lithography (SBIL) is a technique which is used to create large-area periodic patterns with high phase accuracy. This is accomplished by combining interference lithography and an X-Y scanning stage. We previously reported parallel scan mode in which the stage scans in a direction parallel to the interference fringes. Here we present a method called Doppler scanning. In this mode, the stage is scanned perpendicular to the interference fringes. In order to obtain high-contrast latent gratings in the exposed photoresist, several parameters must be controlled. These parameters include vibration, fringe period error, time delay (for Doppler writing), dose, beam overlap, and polarization. In this article we present results of how the time delay, fringe period error, and exposure dose effect the contrast and linewidth of our latent grating images. Furthermore, SBIL has a unique ability to read gratings in a metrology mode configuration. This article also describes how Doppler metrology mode allows us to measure the time delay of our system. DA - 2005/// PY - 2005/// DO - 10.1116/1.2127938 VL - 23 IS - 6 SP - 2640 J2 - J. Vac. Sci. Technol. B LA - en OP - SN - 0734-211X UR - http://dx.doi.org/10.1116/1.2127938 DB - Crossref ER - TY - JOUR TI - Design of a multilevel fuzzy controller for nonlinear systems and stability analysis AU - Xu, C. AU - Shin, Y.C. T2 - IEEE Transactions on Fuzzy Systems AB - In this paper, a multilevel fuzzy control (MLFC) system is developed and implemented to deal with the real-world nonlinear plants with intrinsic uncertainties and time-varying parameters. The proposed fuzzy control strategy has a hierarchical structure with an adaptation mechanism embedded in the lower level to tune the output membership functions (MFs) of the first layer fuzzy controller and can be used to control a system with an input-output monotonic relationship or a piecewise monotonic relationship. The stability of the closed-loop system under the proposed MLFC is theoretically proven. Simulations are carried out by applying the proposed multilevel fuzzy control (MLFC) to a uncertain nonlinear plants, and it is shown that much better system performances are achieved compared with conventional fuzzy logic controllers (FLC), even in presence of disturbance and noise. DA - 2005/// PY - 2005/// DO - 10.1109/TFUZZ.2005.859308 VL - 13 IS - 6 SP - 761-778 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-30344443968&partnerID=MN8TOARS ER - TY - JOUR TI - High-Reynolds number viscous flow computations using an unstructured-grid method AU - Luo, H AU - Baum, JD AU - Lohner, R T2 - JOURNAL OF AIRCRAFT AB - An unstructured grid method is presented to compute three-dimensional compressible turbulent flows for complex geometries. The Navier-Stokes equations, along with the one-equation turbulence model of Spalart-Allmaras are solved by the use of a parallel, matrix-free implicit method on unstructured tetrahedral grids. The developed method has been used to predict drags in the transonic regime for both DLR-F4 and DLR-F6 configurations to assess the accuracy and efficiency of the method DA - 2005/// PY - 2005/// DO - 10.2514/1.7575 VL - 42 IS - 2 SP - 483-492 SN - 0021-8669 ER - TY - JOUR TI - Extension of Harten-Lax-van Leer scheme for flows at all speeds AU - Luo, H AU - Baum, JD AU - Lohner, R T2 - AIAA JOURNAL AB - The Harten, Lax, and van Leer with contact restoration (HLLC) scheme has been modified and extended in conjunction with time-derivative preconditioning to compute flow problems at all speeds. It is found that a simple modification of signal velocities in the HLLC scheme based on the eigenvalues of the preconditioned system is only needed to reduce excessive numerical diffusion at the low Mach number. The modified scheme has been implemented and used to compute a variety of flow problems in both two and three dimensions on unstructured grids. Numerical results obtained indicate that the modified HLLC scheme is accurate, robust, and efficient for flow calculations across the Mach-number range. ISTORICALLY, numerical algorithms for the solution of the Euler and Navier‐Stokes equations are classified as either pressure-based or density-based solution methods. The pressurebased methods, originally developed and well suited for incompressible flows, are typically based on the pressure correction techniques. They usually use a staggered grid and solve the governing equations in a segregated manner. The density-based methods, originally developed and robust for compressible flows, use time-arching procedures to solve the hyperbolic system of governing equations in a coupled manner. In general, density-based methods are not suitable for efficiently solving low Mach number or incompressible flow problems, because of large ratio of acoustic and convective timescales at the low-speed flow regimes. To alleviate this stiffness and associated convergence problems, time-derivative preconditioning techniques have been developed and used successfully for solving low-Machnumber and incompressible flows by many investigators, including Chorin, 1 Choi and Merkle, 2 Turkel, 3 Weiss and Smith, 4 and Dailey and Pletcher, 5 among others. Such methods seek to modify the time component of the governing equations so that the convergence can be made independent of Mach number. This is accomplished by altering the acoustic speeds of the system so that all eigenvalues become of the same order, and thus condition number remains bounded independent of the Mach number of the flows. Over the last two decades characteristic-based upwind methods have established themselves as the methods of choice for prescribing the numerical fluxes for compressible Euler equations. When these upwind methods are used to compute the numerical fluxes for the preconditioned Euler equations, solution accuracy at low speeds can be compromised, unless the numerical flux formulation is modified to take into account the eigensystem of the precondi DA - 2005/6// PY - 2005/6// DO - 10.2514/1.7567 VL - 43 IS - 6 SP - 1160-1166 SN - 1533-385X ER - TY - JOUR TI - Initiation of pulsed corona discharge under supercritical conditions AU - Lock, EH AU - Saveliev, AV AU - Kennedy, LA T2 - IEEE TRANSACTIONS ON PLASMA SCIENCE AB - Supercritical carbon dioxide is a medium with unique properties and variety of applications in modern green chemistry. The generation of pulsed corona discharge in supercritical CO/sub 2/ is studied experimentally for point-to-plane and wire-to-plane geometries. The low breakdown voltages recorded near the critical point are attributed to peculiarities of electron kinetics in a medium characterized by high spatial inhomogeneity and enhanced cluster formation. DA - 2005/4// PY - 2005/4// DO - 10.1109/tps.2005.845302 VL - 33 IS - 2 SP - 850-853 SN - 1939-9375 KW - breakdown KW - corona KW - discharge KW - supercritical ER - TY - JOUR TI - Energy extraction from a porous media reciprocal flow burner with embedded heat exchangers AU - Contarin, F AU - Barcellos, WM AU - Saveliev, AV AU - Kennedy, LA T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - Superadiabatic combustion in porous media allows a stable burning of ultralean methane/air mixtures, far below flammability limits. The intrinsic heat regeneration process of the porous matrix and the low degree of thermal nonequilibrium between the gas and the solid phases maintain temperatures of less than 1600 K resulting in extremely low levels of CO and NOx production. Due to the transient nature of this phenomenon, a method to confine the combustion into a practical burner has been engineered. The Reciprocal Flow Burner (RFB) is an effective and simple system to achieve this result by arranging the reaction zone to travel back and forth along the length of the burner. This ultimately results in a relatively uniform temperature profile over the central zone of the reactor. Embedding heat exchangers into the ends of the bed makes it an appealing alternative for high-efficiency, low-emission heat generation. In the present work, experimental results are presented and compared to an earlier numerical model to provide a better understanding of heat extraction from a RFB. DA - 2005/2// PY - 2005/2// DO - 10.1115/1.1844539 VL - 127 IS - 2 SP - 123-130 SN - 1528-8943 KW - filtration combustion KW - porous combustion KW - heat exchanger KW - process heater ER - TY - JOUR TI - Fullerene formation in atmospheric pressure opposed flow oxy-flames AU - Silvestrini, M AU - Merchan-Merchan, W AU - Richter, H AU - Saveliev, A AU - Kennedy, LA T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - Samples of condensable material from opposed flow diffusion flames of methane and acetylene and oxygen enriched air at atmospheric pressure were collected and analyzed by high-pressure liquid chromatography to determine the fullerene yield. High resolution transmission electron microscopy studies revealed the presence of fullerenes and well-defined carbon layers with various degrees of curvature. Results show that fullerene formation strongly increases with the acetylene content in the fuel. Increasing strain rate positively affects the fullerene content in the condensable material; higher strain rate flames favor fullerenes over soot, indicating lower fullerene consumption by soot due to lower soot concentration. If the oxygen content in the oxidizing oxygen/nitrogen mixture is increased, fullerene concentration increases due to the higher temperatures and higher precursor concentration. Similar relative variations of fullerene concentrations with flame conditions are predicted by the numerical model. However, the absolute concentrations of fullerenes are, in general, underpredicted by 4 orders of magnitude. This result can be partially attributed to uncertainties in the rate coefficients for H-abstraction and C2H2-addition. This discrepancy also suggests that other important fullerene formation pathways are to be included in the numerical model. DA - 2005/// PY - 2005/// DO - 10.1016/j.proci.2004.08.238 VL - 30 SP - 2545-2552 SN - 1873-2704 KW - fullerenes KW - nanotubes KW - soot KW - fullerenic carbon KW - combustion synthesis ER - TY - BOOK TI - Basic experiments in PID control for engineers DA - 2005/// PY - 2005/// PB - Boston : Pearson/Custom Publishing SN - 053697571X ER - TY - PAT TI - Polar coordinate-based profilometer and methods AU - Sohn, A. AU - Garrard, K. P. AU - Dow, T. A. C2 - 2005/// DA - 2005/// PY - 2005/// ER - TY - JOUR TI - Transient wave propagation of isotropic plates using a higher-order plate theory AU - Yang, S AU - Yuan, FG T2 - INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES AB - Transient wave propagation of isotropic thin plates using a higher-order plate theory is presented in this paper. The aim of this investigation is to assess the applicability of the higher-order plate theory in describing wave behavior of isotropic plates at higher frequencies. Both extensional and flexural waves are considered. A complete discussion of dispersion of isotropic plates is first investigated. All the wave modes and wave behavior for each mode in the low and high-frequency ranges are provided in detail. Using the dispersion relation and integral transforms, exact integral solutions for an isotropic plate subjected to pure impulse load and a number of wave excitations based on the higher-order theory are obtained and asymptotic solutions which highlight the physics of waves are also presented. The axisymmetric three-dimensional analytical solutions of linear wave equations are also presented for comparison. Results show that the higher-order theory can predict the wave behavior closely with exact linear wave solutions at higher frequencies. DA - 2005/7// PY - 2005/7// DO - 10.1016/j.ijsolstr.2004.12.014 VL - 42 IS - 14 SP - 4115-4153 SN - 1879-2146 KW - transient wave propagation KW - higher-order plate theory KW - three-dimensional elasticity KW - dispersion relation KW - Green's function KW - structural health monitoring ER - TY - JOUR TI - Thrust force, torque, and tool wear in drilling the bulk metallic glass AU - Bakkal, M AU - Shih, AJ AU - McSpadden, SB AU - Scattergood, RO T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE AB - The thrust force, torque, and tool wear in drilling of Zr-based bulk metallic glass (BMG) material are investigated. Drilling the BMG at high speed generates the chip light emission, high tool temperature, and severe tool wear. At low spindle speed, the BMG work-material builds up at the major and margin cutting edges and may break the drill. A range of feasible spindle speed and feed rate for the efficient drilling of BMG without the detrimental chip light emission and cutting edge work-material build-up has been identified in this study. Under the same drilling condition, the WC-Co tool generally requires less thrust force and about the same torque than the high-speed steel tool. The progressive wear of the major and margin cutting edges for BMG drilling is examined. Severe drill wear is associated with the bright BMG chip light emission. Without chip light emission, the drill wear is visible but not severe. This study concluded that precision holes in BMG could be generated with proper selection of tooling and process parameters. DA - 2005/6// PY - 2005/6// DO - 10.1016/j.ijmachtools.2004.11.005 VL - 45 IS - 7-8 SP - 863-872 SN - 1879-2170 KW - bulk metallic glass KW - drilling KW - drilling force and torque KW - drill wear ER - TY - JOUR TI - The onset of bioconvection in a suspension of negatively geotactic microorganisms with high-frequency vertical vibration AU - Kuznetsov, A T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - The effect of vertical vibration on the stability of a dilute suspension of negatively geotactic microorganisms in a fluid layer of finite depth is investigated. For the case of high-frequency vibration, solutions of governing equations are decomposed into two components: one which varies slowly with time and a second which varies rapidly with time. An averaging method is utilized to derive the equations describing the mean flow. Linear stability analysis is used to investigate stability of the obtained averaged equations. DA - 2005/10// PY - 2005/10// DO - 10.1016/j.icheatmasstransfer.2005.05.004 VL - 32 IS - 9 SP - 1119-1127 SN - 1879-0178 KW - vertical vibration KW - negatively geotactic microorganisms KW - stability KW - averaging method ER - TY - JOUR TI - Relative polycyclic aromatic hydrocarbon concentrations in unsteady counterflow diffusion flames AU - Xiao, J AU - Austin, E AU - Roberts, WL T2 - COMBUSTION SCIENCE AND TECHNOLOGY AB - ABSTRACT Qualitative measurements of polycyclic aromatic hydrocarbon (PAH) concentrations made in counterflow diffusion flames subjected to both steady and oscillating strain rates are presented. Planar laser-induced fluorescences was used to make spatially and temporally resolved measurements of the relative concentrations of PAH. The measurements for each PAH size class were made as a function of strain rate, forcing frequency, and fuel type. The peak laser-induced fluorescence spectra from PAHs is known to be a function of the number of benzene rings that make up the particular PAH. It was found that, with increasing strain rate, the intensity of PAH fluorescence decreases dramatically, though unequally, among the three size classes measured. With an unsteady strain rate, the PAH intensity oscillates in phase for frequencies below 50 Hz. When nondimensionalized relative concentration is plotted, it is shown that the smaller PAHs continue to respond to the instantaneous strain rate at a higher frequency than larger PAHs. DA - 2005/4// PY - 2005/4// DO - 10.1080/00102200590917239 VL - 177 IS - 4 SP - 691-713 SN - 1563-521X KW - PAH KW - unsteady diffusion flames KW - PLIF ER - TY - JOUR TI - Porous medium model for investigating transient heat and moisture transport in firefighter protective clothing under high-intensity thermal exposure AU - Chitrphiromsri, P. AU - Kuznetsov, A. V. T2 - Journal of Porous Media AB - The aim of this study is to understand the performance of firefighter protective clothing in preventing thermal injury of skin that may result from exposure to high-intensity thermal radiation. A mathematical model is developed to study transient heat and moisture transport through multilayer fabric assemblies. The model accounts for changes in thermophysical and transport properties of the fabric due to the presence of moisture. Numerical simulations are performed to study heat and moisture transport in wet fabrics that are subjected to intensive flash fire exposure. The numerical solutions are further analyzed to provide a detailed physical understanding of the transport processes. Moisture in the fabric tends to vaporize starting from the outside surface of the fabric to the inside surface of the fabric during heating, and then part of it recondenses in the interior of the fabric during the cooldown. It is observed that the temperature distribution in the fabric layers and the total heat flux to the skin are significantly influenced by the amount and distribution of the moisture in the protective clothing. DA - 2005/// PY - 2005/// DO - 10.1615/jpormedia.v8.i5.80 VL - 8 IS - 5 SP - 511-528 ER - TY - JOUR TI - Measurements of laminar burning velocity and Markstein number using high-speed chemiluminescence imaging AU - Marley, SK AU - Roberts, WL T2 - COMBUSTION AND FLAME DA - 2005/6// PY - 2005/6// DO - 10.1016/j.combustflame.2005.02.011 VL - 141 IS - 4 SP - 473-477 SN - 1556-2921 ER - TY - JOUR TI - Low-velocity impact damage progression in woven E-glass composite systems AU - Baucom, JN AU - Zikry, MA T2 - COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING AB - The objective of this experimental study is to obtain a detailed understanding of the effects of reinforcement geometry on damage progression in woven composite panels under repeated drop-weight impact loading conditions. The composite systems included a 2D plain-woven laminate, a 3D orthogonally woven monolith, and a biaxially reinforced warp-knit. The radial spread of damage was smallest for the 2D laminates and largest for the 3D woven composites. The 3D composites had the greatest resistance to penetration and dissipated more total energy than the other systems. This is due to unique energy absorption mechanisms, which involve the crimped portion of z-tows in the 3D composites, and implies that failure can be controlled by manipulation of the properties of the z-tows. The 3D systems provide both an inherent capability to dissipate energy over a larger area and a greater perforation strength than other systems with comparable areal densities and fiber-volume-fractions. DA - 2005/// PY - 2005/// DO - 10.1016/j.compositesa.2004.07.008 VL - 36 IS - 5 SP - 658-664 SN - 1878-5840 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-13844315208&partnerID=MN8TOARS KW - 3-Dimensional reinforcement KW - impact behaviour KW - fragmentation KW - damage tolerance ER - TY - JOUR TI - Light emission, chip morphology, and burr formation in drilling the bulk metallic glass AU - Bakkal, M AU - Shih, AJ AU - McSpadden, SB AU - Liu, CT AU - Scattergood, RO T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE AB - The chip light emission, chip morphology, burr formation and machined surface in drilling of Zr-based bulk metallic glass (BMG) material are investigated. This study demonstrates that the work- and tool-material as well as the feed rate and spindle speed, two drilling process parameters, all affect the onset of chip light emission. Slow feed rate and high spindle speed increase the specific cutting energy and promote the exothermic oxidation and light emission of the chip. Six types of chip morphology, powder, short ribbon, long ribbon, long spiral, long ribbon tangled, and fan, are observed in BMG drilling. The long ribbon tangled chip morphology is unique for BMG material. On the machined surface under quick stop condition, the fracture topography unique to metallic glass with tributary, void, and vein patterns is observed. Different burr formations are observed: the roll-over shape in the entry and the crown shape in the exit edge. The size of burr in the exit edge is typically larger than that in the entrance edge. High feed rate helps to reduce the size of burr in both entrance and exit edges. This study concludes that the WC–Co tool-material, due to its high thermal conductivity and hardness, performs better in drilling BMG than the high speed steel tool. DA - 2005/6// PY - 2005/6// DO - 10.1016/j.ijmachtools.2004.11.004 VL - 45 IS - 7-8 SP - 741-752 SN - 1879-2170 KW - bulk metallic glass KW - drilling KW - light emission KW - chip morphology KW - burr formation ER - TY - JOUR TI - Investigation of laminar flow in a helical pipe filled with a fluid saturated porous medium AU - Cheng, L AU - Kuznetsov, AV T2 - EUROPEAN JOURNAL OF MECHANICS B-FLUIDS AB - Laminar flow in a helical pipe filled with a fluid saturated porous medium is investigated numerically. The analysis is based on a full momentum equation for the flow in porous media that accounts for the Brinkman and Forchheimer extensions of the Darcy law as well as for the flow inertia. Accounting for the flow inertia is shown to be important for predicting secondary flow in a helical pipe. The effects of the Darcy number, the Forchheimer coefficient as well as the curvature and torsion of the helical pipe on the axial flow velocity and secondary flow are investigated numerically. DA - 2005/// PY - 2005/// DO - 10.1016/j.euromechflu.2004.08.002 VL - 24 IS - 3 SP - 338-352 SN - 1873-7390 KW - helical pipe KW - porous medium KW - laminar flow KW - orthogonal helical coordinates ER - TY - JOUR TI - Heat transfer in a laminar flow in a helical pipe filled with a fluid saturated porous medium AU - Cheng, LP AU - Kuznetsov, AV T2 - INTERNATIONAL JOURNAL OF THERMAL SCIENCES AB - This paper presents the first attempt to investigate numerically heat transfer in a helical pipe filled with a fluid saturated porous medium; the analysis is based on the full momentum equation for porous media that accounts for the Brinkman and Forchheimer extensions of the Darcy law as well as for the flow inertia. Numerical computations are performed in an orthogonal helical coordinate system. The effects of the Darcy number, the Forchheimer coefficient as well as the Dean and Germano numbers on the axial flow velocity, secondary flow, temperature distribution, and the Nusselt number are investigated. DA - 2005/8// PY - 2005/8// DO - 10.1016/j.ijthermalsci.2004.12.009 VL - 44 IS - 8 SP - 787-798 SN - 1778-4166 KW - heat transfer KW - helical pipe KW - porous medium KW - laminar flow KW - orthogonal helical coordinates ER - TY - JOUR TI - Encapsulation and polymerization of acetylene molecules inside a carbon nanotube AU - Kim, G. AU - Kim, Y. AU - Ihm, J. T2 - Chemical Physics Letters DA - 2005/// PY - 2005/// VL - 416 IS - 06-Apr SP - 279-282 ER - TY - JOUR TI - Effect of fouling on stability of bioconvection of gyrotactic microorganisms in a porous medium AU - Kuznetsov, AV AU - Avramenko, AA T2 - JOURNAL OF POROUS MEDIA AB - The main objective of this article is to investigate the effect of fouling on the stability of a uniform suspension of gyrotactic motile microorganisms in a fluid-saturated porous medium. Fouling occurs because of the deposition of microorganisms on a porous matrix. This deposition decreases porosity and permeability of the porous medium. Stability analysis carried out in this article reveals that there is a critical porosity of the porous medium. If the porous medium utilized for this process has a smaller porosity than critical, the uniform suspension of gyrotactic microorganisms is stable and bioconvection does not develop. If the porous medium has larger porosity than critical, the uniform suspension is unstable and bioconvection develops. In this article, a combination of analytical and numerical methods is utilized to solve this problem. First, a linear stability analysis is carried out analytically. Then, at the final stage of the research, numerical methods are utilized to compute the critical Darcy number. DA - 2005/// PY - 2005/// DO - 10.1615/JPorMedia.v8.i1.40 VL - 8 IS - 1 SP - 45-53 SN - 1934-0508 ER - TY - JOUR TI - Autonomous coordination of aircraft formations using direct and nearest-neighbor approaches AU - Silverberg, L AU - Levedahl, BA T2 - JOURNAL OF AIRCRAFT AB - Two approaches are developed for autonomous coordination of aircraft formations. The development of the approaches relies on past work in the areas of distributed control (modal, robust, optimal, and decentralized). The formation coordination problem is divided into a tracking problem (changing the formation) and a regulation problem (maintaining the formation). How to separate the spatial parts of the tracking problem from the temporal parts is demonstrated. With respect to the regulation problem, it is shown that the goal of the regulation problem is to dampen uniformly the motion of the aircraft. It is pointed out that for fuel-optimality the closed-loop damping factors of the aircraft need to be less than π/2. Two types of decentralized coordination are examined: direct coordination (using inertial measurements) and nearest-neighbor coordination (using relative measurements). A perturbation analysis is developed for the efficient calculation of control gains that minimize power and uniformly dampen motion. A numerical example illustrates robust formation changes from nine-aircraft (3 × × 3) grids to V-type formations. Why the performance of direct coordination is generally better than the performance of nearestneighbor coordination and why implementing direct coordination is simpler than implementing nearest-neighbor coordination are explained. However, nearest-neighbor coordination can be used in collision avoidance, and so it must still be considered as a viable option. DA - 2005/// PY - 2005/// DO - 10.2514/1.6868 VL - 42 IS - 2 SP - 469-477 SN - 1533-3868 ER - TY - JOUR TI - Low Reynolds number turbulent lifted flames in high co-flow AU - Terry, SD AU - Lyons, KM T2 - COMBUSTION SCIENCE AND TECHNOLOGY AB - ABSTRACT This study presents the results of experiments designed to investigate flame lift-off behavior to nozzle velocity, co-flow velocity, fuel-type, and nozzle size for low Reynolds Number turbulent flows (in and near the hysteresis regime). Local excess jet velocities are computed using jet relations from Tieszen et al. The results show that the local excess jet velocity remains linear with respect to nozzle velocity through most of the hysteresis regime, even though flame lift-off height is not linear. This suggests a non-linear relation not captured by Kalghatgi (Citation1984) for lift-off in the near field and hysteresis regime. Local excess jet velocities at the reattachment point were also computed for flames that are lifted more than three nozzle diameters above the burner. The results show that there is a minimum excess jet velocity for which a flame can stabilize. This minimum velocity is inversely proportional to the laminar burning velocity of the fuel squared. A new relation for lift-off height at the reattachment point for flames in the hysteresis region is derived and compared to experimental data. Keywords: lifted flamespartial premixingflame stabilityflame propagation This research was partially supported by the U.S. Army Research Office (Contract W911NF-05-1-0045), Dr. David Mann, Monitor. DA - 2005/11// PY - 2005/11// DO - 10.1080/00102200500240489 VL - 177 IS - 11 SP - 2091-2112 SN - 1563-521X KW - lifted flames KW - partial premixing KW - flame stability KW - flame propagation ER - TY - JOUR TI - Inverse design of adaptive airfoils with aircraft performance considerations AU - Jepson, J. K. AU - Gopalarathnam, A. T2 - Journal of Aircraft DA - 2005/// PY - 2005/// VL - 42 IS - 6 SP - 1622-1630 ER - TY - JOUR TI - Effects of preferential and differential diffusion on the mutual annihilation of two premixed hydrogen-air flames AU - Ranganath, B AU - Echekki, T T2 - COMBUSTION THEORY AND MODELLING AB - The unsteady process of upstream head-on quenching of two laminar premixed hydrogen–air flames at different equivalence ratios in one dimension is investigated numerically in the presence of preferential and differential diffusion effects. Important chemical and transport characteristics of the mutual annihilation process are studied during the two primary stages of upstream mutual annihilation, preheat layers' and reaction layers' interactions. Because of the diffusive mobility of the fuel, hydrogen, relative to heat and the oxidizer, preferential and differential diffusion effects result in a shift in the equivalence ratio in the reaction zone to leaner conditions. This shift, in turn, affects the subsequent reaction layers' interactions through qualitative and quantitative changes in the rates of reactants' consumption and radicals' production. Another consequence of this shift is the presence of excess and ‘unburnt’ fuel or oxidizer at the end of the mutual annihilation process. The process of mutual annihilation occurs over time scales that are significantly shorter than characteristic residence times associated with flames. DA - 2005/11// PY - 2005/11// DO - 10.1080/13647830500294006 VL - 9 IS - 4 SP - 659-672 SN - 1741-3559 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-27844561696&partnerID=MN8TOARS KW - premixed laminar flames KW - laminar flame quenching KW - computation and theory ER - TY - JOUR TI - Computational models for simulating multicomponent aerosol evaporation in the upper respiratory airways AU - Longest, PW AU - Kleinstreuer, C T2 - AEROSOL SCIENCE AND TECHNOLOGY AB - An effective model for predicting multicomponent aerosol evaporation in the upper respiratory system that is capable of estimating the vaporization of individual components is needed for accurate dosimetry and toxicology analyses. In this study, the performance of evaporation models for multicomponent droplets over a range of volatilities is evaluated based on comparisons to available experimental results for conditions similar to aerosols in the upper respiratory tract. Models considered include a semiempirical correlation approach as well as resolved-volume computational simulations of single and multicomponent aerosol evaporations to test the effects of variable gas-phase properties, surface blowing velocity, and internal droplet temperature gradients. Of the parameters assessed, concentration-dependent gas-phase specific heat had the largest effect on evaporation and should be taken into consideration for respiratory aerosols that contain high volatility species, such as n-heptane, at significant concentrations. For heavier droplet components or conditions below body temperatures, semiempirical estimates were shown to be appropriate for respiratory aerosol conditions. In order to reduce the number of equations and properties required for complex mixtures, a resolved-volume evaporation model was used to identify a twelve-component surrogate representation of potentially toxic JP-8 fuel based on comparisons to experimentally reported droplet evaporation data. Due to the relatively slow evaporation rate of JP-8 aerosols, results indicate that a semiempirical evaporation model in conjunction with the identified surrogate mixture provide a computationally efficient method for computing droplet evaporation that can track individual toxic markers. However, semiempirical methodologies are in need of further development to effectively compute the evaporation of other higher volatility aerosols for which variable gas-phase specific heat does play a significant role. DA - 2005/2// PY - 2005/2// DO - 10.1080/027868290908786 VL - 39 IS - 2 SP - 124-138 SN - 0278-6826 ER - TY - JOUR TI - Analysis of surface roughness effects on heat transfer in micro-conduits AU - Koo, J AU - Kleinstreuer, C T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - Modern heat rejection systems, such as micro-heat sinks, are attractive because of their potential for high performance at small size and low weight. However, the impact of microscale effects on heat transfer have to be considered and quantitatively analyzed in order to gain physical insight and accurate Nusselt number data. The relative surface roughness (SR) was selected as a key microscale parameter, represented by a porous medium layer (PML) model. Assuming steady laminar fully developed liquid flow in microchannels and microtubes, the SR effects in terms of PML thermal conductivity ratio and Darcy number on the dimemsionless temperature profile and Nusselt number were analyzed. In summary, the PML characteristics, especially the SR-number and conductivity ratio km/kf, greatly affect the heat transfer performance where the Nusselt number can be either higher or lower than the conventional value. The PML influence is less pronounced in microtubes than in parallel-plate microchannels. DA - 2005/6// PY - 2005/6// DO - 10.1016/j.ijheatmasstransfer.2005.01.024 VL - 48 IS - 13 SP - 2625-2634 SN - 1879-2189 KW - thermal flow KW - microchannels KW - microtubes KW - computational analyses microscale parameters dimensionless temperature profiles KW - Nusselt numbers ER - TY - JOUR TI - Acoustic damping rate measurements in binary mixtures of atomic species via transient-grating spectroscopy AU - Li, YY AU - Roberts, WL AU - Brown, MS AU - Gord, , JR T2 - EXPERIMENTS IN FLUIDS DA - 2005/10// PY - 2005/10// DO - 10.1007/s00348-005-1012-6 VL - 39 IS - 4 SP - 687-693 SN - 1432-1114 KW - transient-grating spectroscopy KW - acoustic dissipation KW - optical diagnostics KW - laser-induced thermal acoustics ER - TY - JOUR TI - Transpermanent magnetics using alternating uniform linear stacks AU - Silverberg, L AU - Duval, L T2 - JOURNAL OF MECHANICAL DESIGN AB - Abstract In this paper we apply recent developments in transpermanent magnetics to the problem of ultra-low-power valve control. Whereas the traditional approach to ultra-low-power valve control is based on latching mechanisms that turn off valves during inactive periods, in this paper we describe an approach that eliminates the need for latching mechanisms. Instead of latching mechanisms, the principles of transpermanent magnetics are employed to switch the states of permanent magnets; the use of permanent magnets instead of electromagnets eliminates power loads during inactive periods, thereby reducing power consumption to ultralow levels. The permanent magnets in a transpermanent magnet valve are configured in a stack. The relationships between the strength and number of permanent magnets in the stack and the stroke and resolution of the valve are developed. In this paper we show that the alternating uniform linear stack is well suited for digital process valves having a small number of states. Then in the paper we report on the design and testing of a laboratory prototype valve that uses an alternating uniform linear stack. The prototype valve had five states yielding a range of flow rates between 0 and 1.58m∕s with a resolution of 0.3m∕s. In this paper we find that transpermanent valves represent a promising valve technology for digital process valves. DA - 2005/7// PY - 2005/7// DO - 10.1115/1.1897743 VL - 127 IS - 4 SP - 679-687 SN - 1050-0472 ER - TY - JOUR TI - Size effect of nanoparticles in chemical mechanical polishing - A transient model AU - Zeng, TF AU - Sun, T T2 - IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING AB - When a workpiece to be polished is placed on the carrier of a polishing machine, it is pressed down to the polishing pad. Large abrasives make contact between the pad and the workpiece before the smaller ones. The larger abrasives are pressed into the pad and indented into the workpiece. These particles are the active abrasives and participate in material removal. The abrasives with a size less than the gap between the pad and the workpiece move freely in the valleys/voids of the pad and are inactive. As the gap decreases during the polishing process, smaller abrasives trapped between the pad and the workpiece become active in polishing. Thus, the process of chemical-mechanical polishing is dynamic, while all previous modeling is static. This paper establishes a dynamic model for the abrasives. The modeling considers the transient motion of the workpiece/particle/pad in the vertical direction and the change of the roughness of the workpiece. A study of the transient motion shows an increasing number of active particles and a changing polishing rate in the first 2 min. It also demonstrates that the viscoelastic properties of the pad and the workpiece surface roughness are important factors in determining the polishing rate. This paper also shows that when the average particle size is smaller than an optimum size, the polishing rate increases with increasing particle size for the same particle density or same wt% abrasives. Yet, if the average particle size is larger than the optimum size, the polishing rate decreases with increasing particle size. DA - 2005/11// PY - 2005/11// DO - 10.1109/TSM.2005.858508 VL - 18 IS - 4 SP - 655-663 SN - 1558-2345 KW - chemical-mechanical polishing (CMP) KW - material removal mechanism KW - model KW - workpiece roughness ER - TY - JOUR TI - Processing TiPdNi base thin-film shape memory alloys using ion beam assisted deposition AU - Baldwin, E AU - Thomas, B AU - Lee, JW AU - Rabiei, A T2 - SURFACE & COATINGS TECHNOLOGY AB - A new generation of thin-film shape memory alloys (SMA) has been developed with less than 2 μm thickness for MEMS microactuator applications. In this study, thin-film TiPdNi SMA was processed using ion beam assisted deposition (IBAD) with and without in situ heat treatment. As-deposited films were found to be amorphous. Postdeposition annealing lead to bulk diffusion of palladium to the substrate interface and silicon into the bulk film, creating a porous cross section. Various forms of tensile failures were observed including decohesion and delamination as a result of postdeposition annealing. Effect of heating and cooling rates was studied as well as in situ heat treatment during deposition. Deposition using the IBAD technique with in situ heat treatment was successful in producing fully martensitic films 1.5 μm thick and with reduced grain size and film defects, compared to the other sputter deposited films and IBAD deposited followed by postdeposition heat treatment. The effects of various processing parameters, and heat treatment conditions, on film properties have been studied. DA - 2005/12/21/ PY - 2005/12/21/ DO - 10.1016/j.surfcoat.2004.08.172 VL - 200 IS - 7 SP - 2571-2579 SN - 0257-8972 KW - shape memory alloy KW - ion beam assisted deposition KW - thin film KW - TiPdNi KW - heat treatment ER - TY - JOUR TI - Numerical simulation of wall shear stress and particle-based hemodynamic parameters in pre-cuffed and streamlined end-to-side anastomoses AU - Longest, PW AU - Kleinstreuer, C AU - Deanda, A T2 - ANNALS OF BIOMEDICAL ENGINEERING DA - 2005/12// PY - 2005/12// DO - 10.1007/s10439-005-7784-2 VL - 33 IS - 12 SP - 1752-1766 SN - 1573-9686 KW - particle hemodynamics KW - hemodynamic wall parameters KW - near-wall residence time KW - femoropopliteal bypass KW - end-to-side anastomosis KW - intimal hyperplasia KW - pre-cuffed grafts KW - streamlined grafts ER - TY - JOUR TI - Ideal aerodynamics of ground effect and formation flight AU - King, RM AU - Gopalarathnam, A T2 - JOURNAL OF AIRCRAFT AB - The theoretical induced-drag benefits are presented for ideally loaded wings flying in formation and ground effect. An optimum-downwash approach using a vortex-lattice implementation was used to study formations of wings loaded optimally for minimum induced drag with roll trim. An exact approach was also developed to examine the drag of elliptically loaded wings in formation. The exact approach allows for decomposition of the benefits by considering the mutual-interference contributions from different pairs of wings in a formation DA - 2005/// PY - 2005/// DO - 10.2514/1.10942 VL - 42 IS - 5 SP - 1188-1199 SN - 1533-3868 ER - TY - JOUR TI - Free convection in a liquid-encapsulated molten semiconductor in a vertical magnetic field AU - Yang, M AU - Ma, N T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - This paper treats the free 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 vertical magnetic field. The magnetic field provides an electromagnetic (EM) damping of the molten semiconductor which is an excellent electrical conductor but has no direct effect on the motion of the liquid encapsulant. The competition between the two free convections determines the direction of the velocity of the interface. DA - 2005/9// PY - 2005/9// DO - 10.1016/j.ijheatmasstransfer.2005.04.019 VL - 48 IS - 19-20 SP - 4010-4018 SN - 1879-2189 ER - TY - JOUR TI - Experimental study applying a migration technique in structural health monitoring AU - Lin, X AU - Yuan, FG T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - This article presents the experimental results of adopting a geophysical migration technique to interpret the ultrasonic flexural wave signals for the purpose of realizing quantitative damage identification in structures. In this study, a homogeneous isotropic plate is examined with a surface-mounted linear array of piezoelectric ceramic (PZT) disk. The piezoelectric disks function as actuators to excite flexural waves and also as sensors to receive the waves scattered from the structural damage in the plate. A prestack reverse-time migration technique, which is an advanced technique in geophysics to reverse the reflection wavefield and to image the Earth’s interior, is then used to back-propagate the scattering waves and to image damage in the plate. The configuration of the experimental setup is presented and its capability of accurately generating and receiving flexural waves is validated by comparing the collected signals with an analytical solution of transient response of a narrowband signal in a piezoelectric sensor/actuator integrated plate using Mindlin plate theory. Finally, the migration results from the scattering waves of an artificial damage are presented. It is shown that the existence of the damage is correctly revealed through migration process in the experiment as it has been shown using synthetic data. DA - 2005/12// PY - 2005/12// DO - 10.1177/1475921705057973 VL - 4 IS - 4 SP - 341-353 SN - 1741-3168 KW - damage identification KW - prestack migration KW - flexural wave KW - Mindlin plate theory KW - dispersion relation KW - group velocity KW - piezoelectric ceramic disk ER - TY - JOUR TI - Computational analysis of biomechanical contributors to endovascular graft failure AU - Li, Z AU - Kleinstreuer, C AU - Farber, M T2 - BIOMECHANICS AND MODELING IN MECHANOBIOLOGY DA - 2005/12// PY - 2005/12// DO - 10.1007/s10237-005-0003-0 VL - 4 IS - 4 SP - 221-234 SN - 1617-7940 ER - TY - JOUR TI - Automated knot tying for fixation in minimally invasive, robot-assisted cardiac surgery AU - Kuniholm, JF AU - Buckner, GD AU - Nifong, W AU - Orrico, M T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME AB - Cardiovascular disease (CVD) is perhaps the most significant worldwide health issue. While open-heart surgery remains the predominant treatment, significant advancements have been made in minimally invasive surgery (MIS) and minimally invasive robot-assisted (MIRA) surgery. MIRA techniques offer many advantages over open-heart procedures and have extended the capabilities of MIS. However, these benefits come at the cost of increased operating times due to time spent tying knots. The additional bypass time limits patient access and is the most significant barrier to the adoption of MIRA techniques. This research seeks to overcome this barrier by designing a device for MIRA cardiac procedures that automates the knotting of sutures. If this task can be automated while ensuring the delivery of high-quality knots, great progress can be made in transforming the field. MIRA cardiac procedures can move from novel procedures performed by a select group of surgeons on a limited pool of patients to a viable alternative available to the majority of patients with CVD. In this research we propose a design for a self-contained device that delivers a locking knot. Results suggest that consistent knots can be delivered at a time savings of 12.5% and 26.4% over manual knots for trained and untrained users of a surgical robot, respectively. DA - 2005/11// PY - 2005/11// DO - 10.1115/1.2055307 VL - 127 IS - 6 SP - 1001-1008 SN - 1528-8951 ER - TY - JOUR TI - Atomistic simulations of J-integral in 2D graphene nanosystems AU - Jin, Y AU - Yuan, FG T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AB - The J-integral is investigated in discrete atomic systems using molecular mechanics simulations. A method of calculating J-integral in specified atomic domains is developed. Two cases, a semiinfinite crack in an infinite domain under the remote K-field deformation and a finite crack length in a finite geometry under the tensile and shear deformation prescribed on the boundary, are studied in the two-dimensional graphene sheets and the values of J-integral are obtained under small-strain deformation. The comparison with energy release rates in Mode I and Mode II based on continuum theory of linear elastic fracture mechanics show good agreements. Meanwhile, the nonlinear strain and stress relation of a 2D graphene sheet is evaluated and is fitted with a power law curve. With necessary modifications on the Tersoff-Brenner potential, the critical values of J-integral of 2D graphene systems, which denoted as Jc, are eventually obtained. The results are then compared with those from the relevant references. DA - 2005/12// PY - 2005/12// DO - 10.1166/jnn.2005.414 VL - 5 IS - 12 SP - 2099-2107 SN - 1533-4880 KW - atomistic simulation KW - J-integral KW - molecular mechanics KW - fracture toughness KW - nano KW - global energy method KW - local force method ER - TY - JOUR TI - A rate-dependent two-dimensional free energy model for ferroelectric single crystals AU - Seelecke, S AU - Kim, SJ AU - Ball, BL AU - Smith, RC T2 - CONTINUUM MECHANICS AND THERMODYNAMICS AB - The one-dimensional free energy model for ferroelectric materials developed by Smith et al. [29–31] is generalized to two dimensions. The two-dimensional free energy potential proposed in this paper consists of four energy wells that correspond to four variants of the material. The wells are separated by four saddle points, representing the barriers for 90°-switching processes, and a local maximum, across which 180°-switching processes take place. The free energy potential is combined with evolution equations for the variant fractions based on the theory of thermally activated processes. The model is compared to recent measurements on BaTiO3 single crystals by Burcsu et al. [8], and predicitions are made concerning the response to the application of in-plane multi-axial electric fields at various frequencies and loading directions. The kinetics of the 90°- and 180°-switching processes are discussed in detail. DA - 2005/12// PY - 2005/12// DO - 10.1007/s00161-005-0207-7 VL - 17 IS - 4 SP - 337-350 SN - 1432-0959 KW - ferroelectric materials KW - 2-D free energy model KW - hysteresis KW - rate-dependent effects ER - TY - JOUR TI - Sliding mode observation and control for semiactive vehicle suspensions AU - Dixit, RK AU - Buckner, GD T2 - VEHICLE SYSTEM DYNAMICS AB - This paper investigates the application of robust, nonlinear observation and control strategies, namely sliding mode observation and control (SMOC), to semiactive vehicle suspensions using a model reference approach. The vehicle suspension models include realistic nonlinearities in the spring and magnetorheological (MR) damper elements, and the nonlinear reference models incorporate skyhook damping. Since full state measurement is difficult to achieve in practice, a sliding mode observer (SMO) that requires only suspension deflection as a measured input is developed. The performance and robustness of sliding mode control (SMC), SMO, and SMOC are demonstrated through comprehensive computer simulations and compared to popular alternatives. The results of these simulations reveal the benefits of sliding mode observation and control for improved ride quality, and should be directly transferable to commercial semiactive vehicle suspension implementations. DA - 2005/2// PY - 2005/2// DO - 10.1080/00423110412331290455 VL - 43 IS - 2 SP - 83-105 SN - 1744-5159 ER - TY - JOUR TI - Linear parameter-varying antiwindup compensation for enhanced flight control performance AU - Lu, B AU - Wu, F AU - Kim, SW T2 - JOURNAL OF GUIDANCE CONTROL AND DYNAMICS AB - Actuator saturation is one of the major issues of flight control in the high angle-of-attack region. This paper presents a saturation control scheme for linear parameter varyjing (LPV) systems from an antiwindup control perspective. The proposed control approach is advantageous from the implementation standpoint because it can be thought of as an augmented control algorithm to the existing control system. Moreover, the synthesis condition for an antiwindup compensator is formulated as a linear matrix inequality (LMI) optimization problem and can be solved efficiently. We have applied te LPV antiwindup controller to an F-16 longitudinal autopilot control system design and compared it with the thrust vectoring control scheme. The nonlinear simulations show that an LPV antiwindup controller improves flight quality and offers advantages over thrust vectoring in a high angle-of-attack region. DA - 2005/// PY - 2005/// DO - 10.2514/1.4952 VL - 28 IS - 3 SP - 494-505 SN - 1533-3884 ER - TY - JOUR TI - Application of accelerometer data to Mars Odyssey aerobraking and atmospheric modeling AU - Tolson, RH AU - Dwyer, AM AU - Hanna, JL AU - Keating, GM AU - George, BE AU - Escalera, PE AU - Werner, MR T2 - JOURNAL OF SPACECRAFT AND ROCKETS AB - Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields. DA - 2005/// PY - 2005/// DO - 10.2514/1.15173 VL - 42 IS - 3 SP - 435-443 SN - 1533-6794 ER - TY - JOUR TI - Actuation and control strategies for miniature robotic surgical systems AU - Stevens, J. M. AU - Buckner, G. D. T2 - Journal of Dynamic Systems, Measurement, and Control AB - During the past 20years, tremendous advancements have been made in the fields of minimally invasive surgery (MIS) and minimally invasive, robotically assisted (MIRA) cardiac surgery. Benefits from MIS include reduced pain and trauma, reduced risks of post-operative complications, shorter recovery times, and more aesthetically pleasing results. MIRA approaches have extended the capabilities of MIS by introducing three-dimensional vision, eliminating hand tremors, and enabling the precise articulation of smaller instruments. These advancements come with their own drawbacks, however. Robotic systems used in MIRA cardiac procedures are large, costly, and do not offer the miniaturized articulation necessary to facilitate tremendous advancements in MIS. This paper demonstrates that miniature actuation can overcome some of the limitations of current robotic systems by providing accurate, repeatable control of a small end effector. A 10× model of a two link surgical manipulator is developed, using antagonistic shape memory alloy wires as actuators, to simulate motions of a surgical end-effector. Artificial neural networks are used in conjunction with real-time visual feedback to “learn” the inverse system dynamics and control the manipulator endpoint trajectory. Experimental results are presented for indirect, on-line learning and control. Manipulator tip trajectories are shown to be accurate and repeatable to within 0.5mm. These results confirm that SMAs can be effective actuators for miniature surgical robotic systems, and that intelligent control can be used to accurately control the trajectory of these systems. DA - 2005/// PY - 2005/// DO - 10.1115/1.2098892 VL - 127 IS - 4 SP - 537-549 ER - TY - JOUR TI - A six-step asymmetric synthesis of (+)-hyperaspine AU - Comins, DL AU - Sahn, JJ T2 - ORGANIC LETTERS AB - ADVERTISEMENT RETURN TO ISSUEPREVLetterNEXTA Six-Step Asymmetric Synthesis of (+)-HyperaspineDaniel L. Comins and James J. SahnView Author Information Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204 Cite this: Org. Lett. 2005, 7, 23, 5227–5228Publication Date (Web):October 21, 2005Publication History Received26 August 2005Published online21 October 2005Published inissue 1 November 2005https://doi.org/10.1021/ol052068vCopyright © 2005 American Chemical SocietyRequest reuse permissionsArticle Views1383Altmetric-Citations44LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (39 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Alcohols,Enantioselective synthesis,Ketones,Redox reactions Get e-Alerts DA - 2005/11/10/ PY - 2005/11/10/ DO - 10.1021/ol052068v VL - 7 IS - 23 SP - 5227-5228 SN - 1523-7052 ER - TY - JOUR TI - Vertical gradient freezing using submerged heater growth with rotation and with weak magnetic and electric fields AU - Holmes, A. M. AU - Wang, X. AU - Ma, N. AU - Bliss, D. F. AU - Iseler, G. W. T2 - International Journal of Heat and Fluid Flow DA - 2005/// PY - 2005/// VL - 26 IS - 5 SP - 792-800 ER - TY - JOUR TI - The onset of bioconvection in a suspension of gyrotactic microorganisms in a fluid layer of finite depth heated from below AU - Kuznetsov, AV T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - The aim of this paper is to investigate the effect of heating from below on the stability of a suspension of motile gyrotactic microorganisms in a fluid layer of finite depth. This problem is relevant to a number of geophysical applications, such as investigation of the dynamics of some species of thermophiles (heat-loving microorganisms) living in hot springs. It is established that heating from below makes the system more unstable and helps the development of bioconvection. By performing a linear stability analysis, a correlation for the critical bioconvection Rayleigh number is obtained. DA - 2005/4// PY - 2005/4// DO - 10.1016/j.icheatmasstransfer.2004.10.021 VL - 32 IS - 5 SP - 574-582 SN - 1879-0178 KW - thermo-bioconvection KW - motile microorganisms KW - gyrotaxis KW - stability KW - heating from below ER - TY - JOUR TI - Settling of bidispersed small solid particles in a dilute suspension containing gyrotactic micro-organisms AU - Geng, P AU - Kuznetsov, AV T2 - INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE AB - The motivation of this research is to investigate the feasibility of utilizing bioconvection for enhancing mixing in a suspension of small solid particles. This may be important in micro-fluidic applications relevant to biotechnology and medicine, such as analyses of DNA or drugs, screening of patients, and combinatorial synthesis. Traditionally, the mixing of fluids in micro-volumes has been limited to diffusion. Due to the microscopic size of the organisms involved in bioconvection, bioconvective flows are a prospective and novel alternative for micro-fluidic mixing. This paper considers a bidispersed suspension of small solid particles that have different densities and settling velocities in a fluid that contains motile gyrotactic micro-organisms. The particles are assumed to be sufficiently small so that their Brownian diffusion is not negligible. It is found that the number density distribution of solid particles of one type impacts that of particles of the other type as well as that of micro-organisms. DA - 2005/7// PY - 2005/7// DO - 10.1016/j.ijengsci.2005.03.002 VL - 43 IS - 11-12 SP - 992-1010 SN - 1879-2197 KW - bioconvection KW - small particles KW - sedimentation KW - motile micro-organisms ER - TY - JOUR TI - Nanoscopic modeling of fracture of 2D graphene systems AU - Jin, Y AU - Yuan, FG T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AB - Macroscopic fracture parameters are investigated on 2D graphene systems containing atomic-scale cracks. In the discrete atomistic simulations the interatomic forces are described by the Tersoff-Brenner potential. Two methods to calculate the elastic energy release rates in atomic systems, the global energy method and the local force method, are developed. The values of energy release rates of several graphene systems in symmetric (mode I) and antisymmetric (mode II) small deformation are obtained from atomistic simulations and then compared with the results obtained through homogenized material properties based on linear elastic fracture mechanics. The results show good agreement between discrete atomistic and continuum mechanics modeling for fracture. Meanwhile, atomic stress fields in front of crack tips are investigated through molecular mechanics simulation by applying remote K-field deformation. The atomic stress distributions match very well with those of linear elastic solutions. These establish connections of fracture parameters between microscopic and macroscopic description of fracture in covalently bonded solids. DA - 2005/4// PY - 2005/4// DO - 10.1166/jnn.2005.071 VL - 5 IS - 4 SP - 601-608 SN - 1533-4880 KW - atomistic simulation KW - molecular mechanics KW - fracture KW - nano KW - energy release rate KW - stress intensity factor ER - TY - JOUR TI - Magnetic servo levitation by sliding-mode control of nonaffine systems with algebraic input invertibility AU - Gutierrez, HM AU - Ro, PI T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - Magnetic Servo Levitation (MSL) is an important actuation principle with potential applications ranging from ultrahigh-precision positioning to high-speed rail systems. This paper describes a nonlinear controller design technique for MSL that has inherent robustness to both parametric uncertainties and unmodeled dynamics. Most of the currently available literature on sliding mode considers nonlinear systems that are linear (affine) in the input action. The proposed technique allows designing sliding-mode controllers for the family of nonaffine problems that have an input nonlinearity algebraically invertible with respect to the available control action. This differs from the standard approach of input feedback linearization, and is based on a modified sliding condition that can be used to synthesize a switching control law. An equivalent control term can also be included, substantially enhancing the performance of the controller. Experimental results show that the proposed technique can achieve excellent tracking at high speeds in a fast-tool servo system actuated by MSL. DA - 2005/10// PY - 2005/10// DO - 10.1109/TIE.2005.855651 VL - 52 IS - 5 SP - 1449-1455 SN - 1557-9948 KW - equivalent control KW - fast-tool servo system KW - input feedback linearization KW - magnetic servo levitation KW - nonaffine nonlinear systems KW - sliding-mode control ER - TY - JOUR TI - Linear instability analysis of a suspension of oxytactic bacteria in superimposed fluid and porous layers AU - Avramenko, AA AU - Kuznetsov, AV T2 - TRANSPORT IN POROUS MEDIA DA - 2005/11// PY - 2005/11// DO - 10.1007/s11242-004-7462-0 VL - 61 IS - 2 SP - 157-175 SN - 1573-1634 KW - superimposed porous and fluid layers KW - bioconvection KW - oxytactic bacteria KW - motile microorganisms ER - TY - JOUR TI - Investigation of stability of a laminar flow in a parallel-plate channel filled with a fluid saturated porous medium AU - Avramenko, AA AU - Kuznetsov, AV AU - Basok, BI AU - Blinov, DG T2 - PHYSICS OF FLUIDS AB - Instability of a laminar flow in a parallel-plate channel filled with a fluid saturated porous medium is investigated on the basis of a modified Orr-Sommerfeld equation. This equation takes into account three drag terms: the Darcy term that describes friction between the fluid and the porous matrix, the Forchheimer quadratic drag term that describes a form drag due to the solid obstacles, and the Brinkman term, which is a viscous term similar to the Laplacian term in the Navier-Stokes equations. Numerical analysis is carried out using the collocation method. The dependence of the critical Reynolds number on porosity and permeability of the porous medium is analyzed numerically. DA - 2005/9// PY - 2005/9// DO - 10.1063/1.2041607 VL - 17 IS - 9 SP - SN - 1089-7666 ER - TY - JOUR TI - Blasting and erosion wear of wood using sodium bicarbonate and plastic media AU - Lemaster, R. L. AU - Shih, A. J. AU - Yu, Z. T2 - Forest Products Journal DA - 2005/// PY - 2005/// VL - 55 IS - 5 SP - 59-64 ER - TY - JOUR TI - A numerical investigation of dopant segregation by modified vertical gradient freezing with moderate magnetic and weak electric fields AU - Wang, X. AU - Ma, N. AU - Bliss, D. F. AU - Iseler, G. W. T2 - International Journal of Engineering Science DA - 2005/// PY - 2005/// VL - 43 IS - 12-Nov SP - 908-924 ER - TY - JOUR TI - A computational study of natural convection in a liquid-encapsulated molten semiconductor with a horizontal magnetic field AU - Yang, M. AU - Ma, N. T2 - International Journal of Heat and Fluid Flow DA - 2005/// PY - 2005/// VL - 26 IS - 5 SP - 810-816 ER - TY - JOUR TI - Optical sensor for noncontact measurement of lignin content in high-speed moving paper surfaces AU - Ramasubramanian, MK AU - Venditti, RA AU - Ammineni, C AU - Mallapragada, V T2 - IEEE SENSORS JOURNAL AB - An optical sensor for real-time measurement of lignin content in moving paper sheets is described in this paper. The sensor is useful for high-speed automated sorting of papers according to lignin content in a mixed-waste stream for efficient recycling. The sensor measures lignin fluorescence when excited in the visible region. Results indicate that when paper surfaces are excited with a laser source (532 nm), the lignin fluorescence spectrum shows a peak near 650 nm. Measurement of this peak intensity from paper samples is a measure of lignin content and correlates linearly with the standard chemical method for lignin determination (Klasson lignin content). Newsprint samples, typically containing high lignin, produce high intensity, while ledger printing and writing grades with low lignin content produce low-fluorescence intensity. The proposed sensor configuration is discussed and results from a systematic study of variables, namely, text printed on surface, homogeneous dyed in color, printed color patches, paper thickness, sensor configuration parameters such as excitation source intensity, and distance from sample surface are reported. In dynamic tests on a simulated conveyor operating at realistic speeds, the sensor is able to reliably measure fluorescence intensities on unprinted samples without ambiguity and identify high and low lignin-containing samples. DA - 2005/10// PY - 2005/10// DO - 10.1109/JSEN.2005.851007 VL - 5 IS - 5 SP - 1132-1139 SN - 1558-1748 KW - fluorescence KW - lignin KW - optical sensor KW - paper KW - recycling KW - sorting ER - TY - JOUR TI - Investigation of the onset of thermo-bioconvection in a suspension of oxytactic microorganisms in a shallow fluid layer heated from below AU - Kuznetsov, AV T2 - THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS DA - 2005/10// PY - 2005/10// DO - 10.1007/s00162-005-0167-3 VL - 19 IS - 4 SP - 287-299 SN - 1432-2250 KW - thermo-bioconvection KW - oxytactic microorganisms KW - stability KW - bioconvection Rayleigh number ER - TY - JOUR TI - Incorporation of aircraft performance considerations in inverse airfoil design AU - Jepson, JK AU - Gopalarathnam, A T2 - JOURNAL OF AIRCRAFT AB - Although significant advances have been made in inverse airfoil design methodology, the tailoring of an airfoil to maximize one or more aircraft performance parameters still involves cycling between airfoil design and aircraft performance computations. A design formulation is presented that incorporates aircraft performance considerations in the inverse design of low-speed laminar-flow airfoils for piston engine driven propeller-powered airplanes. Two aircraft performance parameters are considered: level-flight maximum speed and maximum range. It is shown that the lift coefficient for the lower and upper corners of the airfoil low-drag range can be appropriately adjusted to tailor the airfoil for these two aircraft performance parameters. The design problem is posed as a part of a multidimensional Newton iteration in an existing conformal-mapping based inverse design code, PROFOIL. This formulation automatically adjusts the lift coefficients for the corners of the low-drag range as required for the airfoil‐aircraft matching. The design formulation also has the capability to handle a constraint on the stall speed by automatically adjusting the wing area to account for changes to the airfoil maximum lift coefficient. Two examples are presented to illustrate the process for a general aviation aircraft, and the results are validated by comparison with results from postdesign aircraft performance computations. Nomenclature A R= wing aspect ratio b = wing span C D = aircraft or wing drag coefficient based on Sw Cd = airfoil drag coefficient based on chord CL = aircraft or wing lift coefficient based on Sw Cl = airfoil lift coefficient based on chord DA - 2005/// PY - 2005/// DO - 10.2514/1.5373 VL - 42 IS - 1 SP - 199-207 SN - 1533-3868 ER - TY - JOUR TI - Damage identification in a composite plate using prestack reverse-time migration technique AU - Wang, L AU - Yuan, FG T2 - STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL AB - Migration technique, which is normally used in geophysical prospecting, is proposed to locate and image multiple delamination damages in a laminated composite plate. In this simulation study, an active diagnostic system with a linear array of actuators/sensors is used to excite/receive the lowest mode of flexural waves in the laminate. The wavefield scattered from the damages and sensor array data are synthesized using a two-dimensional explicit finite difference scheme to model wave propagation in the laminate based on the Mindlin plate theory. A prestack reverse-time migration technique is then adopted to interpret the synthetic sensor array data and to visualize the damages. The phase and group velocities of flexural waves in the composite plate are derived from the dispersion relations, and subsequently an excitation-time imaging condition specifically for migration of waves in the plate is introduced based on ray tracing and group velocity. Then the prestack reverse-time migration is performed using the same finite difference scheme to back-propagate the scattered energy to the damages. During the migration process, the laminate is imaged in terms of velocity of the transverse deformation. The locations and dimensions of the damages can be visually displayed. Simulated results demonstrate that multiple delamination damages can be successfully identified and the resulting image correlates well with the target damages. DA - 2005/9// PY - 2005/9// DO - 10.1177/1475921705055233 VL - 4 IS - 3 SP - 195-211 SN - 1741-3168 KW - damage identification KW - prestack migration KW - flexural wave KW - Mindlin plate theory KW - dispersion relation KW - group/phase velocity KW - composite laminate ER - TY - JOUR TI - A study on processing of a composite metal foam via casting AU - Rabiei, A AU - AT O'Neill, T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The research sited in this paper involves the development of a new closed cell composite metal foam using gravity casting techniques. The foam is comprised of steel hollow spheres packed into a random dense arrangement, with the interstitial space between spheres infiltrated with a casting aluminum alloy. The measured density of the material is 2.4 g/cm3, with a relative density of 41.5%. The composite foam developed in this study displayed superior compressive strength and energy absorption capacity. The compressive strength averaged 67 MPa over a region of 10–50% strain, densification began at approximately 50% strain, and the energy absorption at 50% strain is 30 MJ/m3. Scanning electron microscopy (SEM)–energy dispersive X-ray spectroscopy (EDX) compositional analysis affirmed the presence of expected phases in the hollow spheres and aluminum matrix. This novel material has promising applications in the aerospace, automotive, and biomedical industries. DA - 2005/9/15/ PY - 2005/9/15/ DO - 10.1016/j.msea.2005.05.089 VL - 404 IS - 1-2 SP - 159-164 SN - 0921-5093 KW - closed cell foam KW - hollow spheres KW - casting KW - energy absorption KW - composite metal foam ER - TY - JOUR TI - On flame holes and local extinction in lifted-jet diffusion flames AU - Lyons, KM AU - Watson, KA AU - Carter, CD AU - Donbar, JM T2 - COMBUSTION AND FLAME AB - This work examines the dynamics of confined bluff body flames in the process of lean blowoff (LBO) using simultaneous stereo-PIV (particle image velocimetry), OH PLIF (planar laser induced fluorescence) and formaldehyde (CH2O) PLIF. Flames at high density ratios blow off in at least two distinct stages: stage 1, where intermittent extinction occurs along the flame front, but the flame and flow remain qualitatively similar to stable conditions, and stage 2, where there is permanent downstream flame extinction and large-scale changes in dynamic flow characteristics. This paper particularly focuses on stage 2 processes, with the goal of understanding what ultimately leads to irrecoverable flame blowoff. A test facility was developed with the flexibility to achieve two goals: (1) approach LBO by keeping the parameters that influence its hydrodynamic stability approximately constant, particularly flow velocity (ubulk) and gas expansion ratio (σ), and (2) compare near-LBO dynamics under conditions where, well away from blowoff, the flame is globally stable (high σ case) and globally unstable (low σ case, where the Bénard-Von Karman, BVK, instability of the flow is present). The latter case was of particular interest as most prior detailed diagnostic studies of LBO have been performed at high σ, BVK-suppressed conditions. We find that the transient blowoff process remains largely unchanged in the high and low σ cases, apparently due to the fact that the BVK instability reappears in either case under conditions very close to LBO. In all cases, blowoff is preceded by permanent downstream extinction that moves progressively closer to the bluff body as LBO is approached. We also find that near-LBO dynamics are intrinsically three dimensional, due to both secondary instabilities of the shear layer and large out-of-plane motions believed to be due to confinement effects associated with bluff body-wall interactions. These three-dimensional structures often manifest themselves as burning reactant fingers which are caught in the backflow of the recirculation zone; under very near LBO conditions they impinge on the back of the bluff body and extinguish as well. At the very edge of blowoff, the recirculation zone is no longer composed of hot products and is unable to autoignite the oncoming reactant flow, leading to global extinction. The characteristic time associated with this feedback between downstream extinction and wake structure alteration that leads to blowoff is about two orders of magnitude larger than the characteristic flow time, D/ubulk. We also discuss several implications of these results on computations of LBO - in particular, LBO's intrinsically three-dimensionality and the need for many flow through times to capture it. DA - 2005/8// PY - 2005/8// DO - 10.1016/j.combustflame.2005.04.006 VL - 142 IS - 3 SP - 308-313 SN - 0010-2180 ER - TY - JOUR TI - Fluid-structure interaction effects on sac-blood pressure and wall stress in a stented aneurysm AU - Li, Z AU - Kleinstreuer, C T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME AB - Abstract An aneurysm is a local artery ballooning greater than 50% of its nominal diameter with a risk of sudden rupture. Minimally invasive repair can be achieved by inserting surgically a stent-graft, called an endovascular graft (EVG), which is either straight tubular, curved tubular, or bifurcating. However, post-procedural complications may arise because of elevated stagnant blood pressure in the cavity, i.e., the sac formed by the EVG and the weakened aneurysm wall. In order to investigate the underlying mechanisms leading to elevated sac-pressures and hence to potentially dangerous wall stress levels and aneurysm rupture, a transient 3-D stented abdominal aortic aneurysm model and a coupled fluid-structure interaction solver were employed. Simulation results indicate that, even without the presence of endoleaks (blood flowing into the cavity), elevated sac pressure can occur due to complex fluid-structure interactions between the luminal blood flow, EVG wall, intra-sac stagnant blood, including an intra-luminal thrombus, and the aneurysm wall. Nevertheless, the impact of sac-blood volume changes due to leakage on the sac pressure and aneurysm wall stress was analyzed as well. While blood flow conditions, EVG and aneurysm geometries as well as wall mechanical properties play important roles in both sac pressure and wall stress generation, it is always the maximum wall stress that is one of the most critical parameters in aneurysm rupture prediction. All simulation results are in agreement with experimental data and clinical observations. DA - 2005/8// PY - 2005/8// DO - 10.1115/1.1934040 VL - 127 IS - 4 SP - 662-671 SN - 1528-8951 KW - stented aneurysm KW - computational fluid-structure interaction simulations KW - abdominal aortic aneurysm KW - sac pressure KW - wall stress ER - TY - JOUR TI - Computational analysis of the feasibility of a micro-pulsejet AU - Wan, Q AU - Roberts, WL AU - Kuznetsov, AV T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - This paper investigates the feasibility of a 2-cm micro-pulsejet by numerically simulating the inviscid gas dynamic phenomena within the exhaust tube and comparing them with those for a pulsejet on the order of 50 cm in length. After initial combustion, the pressure wave propagates towards the exit and reflects back as a rarefaction wave, which generates a minimum pressure in the combustion chamber. This low pressure must be sufficient to open the reed valves to allow fresh reactants to enter. It is shown that for both large and micro-pulsejets, the minimum pressure is low enough. The characteristic operating frequency is found to be approximately inversely proportional to the pulsejet length. Estimation of the boundary layer thickness in the pulsejet shows that viscosity plays a very significant role in the micro-pulsejet and cannot be neglected. DA - 2005/1// PY - 2005/1// DO - 10.1016/j.icheatmasstransfer.2004.05.020 VL - 32 IS - 1-2 SP - 19-26 SN - 1879-0178 KW - pulsejet KW - micro-size engine KW - pulse combustion KW - numerical modeling ER - TY - JOUR TI - Adaptive system identification applied to the biomechanical response of the human trunk during sudden loading AU - Lawrence, BM AU - Mirka, GA AU - Buckner, GD T2 - JOURNAL OF BIOMECHANICS AB - Epidemiological evidence indicates that sudden loading of the torso is a risk factor for low back injury. Accurately quantifying the time-varying loading of the spine during sudden loading events and how these loading profiles are affected by workplace factors such as fatigue, expectation, and training can potentially lead to intervention strategies that can reduce these risks. Electromyographic and trunk motion data were collected from six male participants who performed a series of sudden loading trials with varying levels of expectation (no preview, 300-ms audible preview), fatigue (no fatiguing exertion preceding sudden load, short duration/high intensity fatiguing exertion preceding sudden load), and training (untrained, trained). These data were used as inputs to an adaptive system identification model wherein time-varying lower back stiffness, torque, work, and impulse magnitudes were calculated. Results indicated that expectation significantly increased peak and average stiffness by 70% and 113%, respectively, and significantly decreased peak torque, work, and impulse magnitudes by 36%, 50%, and 45%, respectively. Training significantly decreased peak torque and work by 25% and 34%, respectively. The results also showed a significant interaction between expectation and training wherein training had a positive effect during the trials with preview but no effect during the trials with no preview (increased peak stiffness by 17% and decreased impulse magnitude by 43%). DA - 2005/12// PY - 2005/12// DO - 10.1016/j.jbiomech.2004.09.038 VL - 38 IS - 12 SP - 2472-2479 SN - 1873-2380 KW - sudden loading KW - fatigue KW - training KW - lumbar KW - injury KW - modeling ER - TY - JOUR TI - The interaction of bioconvection caused by gyrotactic micro-organisms and settling of small solid particles AU - Kuznetsov, A. V. AU - Geng, P. T2 - International Journal of Numerical Methods for Heat & Fluid Flow DA - 2005/// PY - 2005/// DO - 10.1108/0961550510590597 VL - 15 IS - 4 SP - 328-347 ER - TY - JOUR TI - Structural, microstructural, and electrical properties of gold films and Schottky contacts on remote plasma-cleaned, n-type ZnO{0001} surfaces AU - Coppa, BJ AU - Fulton, CC AU - Kiesel, SM AU - Davis, RF AU - Pandarinath, C AU - Burnette, JE AU - Nemanich, RJ AU - Smith, DJ T2 - JOURNAL OF APPLIED PHYSICS AB - Current–voltage measurements of Au contacts deposited on ex situ cleaned, n-type ZnO(0001) [(0001¯)] surfaces showed reverse bias leakage current densities of ∼0.01(∼0.1)A∕cm2 at 4.6 (3.75) V reverse bias and ideality factors &gt;2 (both surfaces) before sharp, permanent breakdown (soft breakdown). This behavior was due primarily to the presence of (1.6–2.0)±0.1[(0.7–2.6)±0.1] monolayers (ML) of hydroxide, which forms an electron accumulation layer and increases the surface conductivity. In situ remote plasma cleaning of the (0001) [(0001¯)] surfaces using a 20vol%O2∕80vol%He mixture for the optimized temperatures, times, and pressure of 550±20°C(525±20°C), 60 (30) min, and 0.050 Torr reduced the thickness of the hydroxide layer to ∼0.4±0.1ML and completely eliminated all detectable hydrocarbon contamination. Subsequent cooling of both surfaces in the plasma ambient resulted in the chemisorption of oxygen and a change from 0.2 eV of downward band bending for samples cooled in vacuum to 0.3 eV of upward band bending indicative of the formation of a depletion layer of lower surface conductivity. Cooling in either ambient produced stoichiometric ZnO{0001} surfaces having an ordered crystallography as well as a step-and-terrace microstructure on the (0001¯) surface; the (0001) surface was without distinctive features. Sequentially deposited, unpatterned Au films, and presumably the rectifying gold contacts, initially grew on both surfaces cooled in the plasma ambient via the formation of islands that subsequently coalesced, as indicated by calculations from x-ray photoelectron spectroscopy data and confirmed by transmission electron microscopy. Calculations from the current–voltage data of the best contacts revealed barrier heights on the (0001) [(0001¯)] surfaces of 0.71±0.05(0.60±0.05)eV, a saturation current density of (4±0.5)×10−6A∕cm2(2.0±0.5×10−4A∕cm2), a lower value of n=1.17±0.05(1.03±0.05), a significantly lower leakage current density of ∼1.0×10−4A∕cm2(∼91×10−9A∕cm2) at 8.5 (7.0) V reverse bias prior to sharp, permanent breakdown (soft breakdown). All measured barrier heights were lower than the predicted Schottky–Mott value of 1.0 eV, indicating that the interface structure and the associated interface states affect the Schottky barrier. However, the constancy in the full width at half maximum of the core levels for Zn 2p(1.9±0.1eV) and O 1s(1.5±0.1eV), before and after sequential in situ Au depositions, indicated an abrupt, unreacted Au∕ZnO(0001) interface. Transmission electron microscopy confirmed the abruptness of an epitaxial interface. Annealing the contacts on the (0001) surface to 80±5 and 150±5°C resulted in decreases in the ideality factors to 1.12±0.05 and 1.09±0.05 and increases in saturation current density to 9.05 and 4.34μA∕cm2, the barrier height to 0.82±0.5 and 0.79±0.5eV, and in the leakage current densities to ∼2×10−3A∕cm2 at 6 V and ∼20×10−3A∕cm2 at 7 V, respectively. DA - 2005/5/15/ PY - 2005/5/15/ DO - 10.1063/1.1898436 VL - 97 IS - 10 SP - SN - 1089-7550 ER - TY - JOUR TI - SOS-based solution approach to polynomial LPV system analysis and synthesis problems AU - Wu, F AU - Prajna, S T2 - INTERNATIONAL JOURNAL OF CONTROL AB - Abstract Based on sum-of-squares (SOS) decomposition, we propose a new solution approach for polynomial linear parameter-varying (LPV) system analysis and control synthesis problems. Instead of solving matrix variables over positive cone, the SOS approach tries to find a suitable decomposition to verify the positiveness of given polynomials. The complexity of the SOS-based numerical method is polynomial of the problem size, and is computationally attractive. This approach also leads to more accurate solutions to LPV systems than most existing relaxation methods. Several examples have been used to demonstrate benefits of the SOS-based solution approach. DA - 2005/5/20/ PY - 2005/5/20/ DO - 10.1080/00207170500114865 VL - 78 IS - 8 SP - 600-611 SN - 1366-5820 ER - TY - JOUR TI - Measurements of the soot volume field in laminar diffusion flames at elevated pressures AU - McCrain, LL AU - Roberts, WL T2 - COMBUSTION AND FLAME AB - Soot volume fraction (fv) is measured quantitatively in a laminar diffusion flame, with either methane or ethylene as fuel, at elevated pressures up to 2.5 MPa in order to gain a better understanding of the effects of pressure on the soot formation process. Soot continues to be of interest because it is a sensitive indicator of the interactions between combustion chemistry and fluid mechanics and known to be detrimental to human health. To examine the effects of increased pressure on soot production, laser-induced incandescence (LII) is used to obtain the desired spatially resolved measurements of fv as the pressure is incrementally increased to 2.5 MPa. The effects of pressure on the physical characteristics of the flame are also observed. Using a laser light extinction technique, the path-integrated soot volume fraction scales with pressure as p1.0 and p1.2 for the methane–air and ethylene–air flames, respectively, at 65% of the flame height. From the LII images, it is observed that the soot layer radius decreases with increasing pressure, scaling as approximately p−0.5 at 65% of the flame height, for both methane and ethylene flames. The local peak fv is found to scale with pressure as p1.2 for methane and p1.7 for ethylene flames, which is different than the path-integrated soot pressure dependence. The location of peak soot is observed to move from the edges toward the tip of the flame as the pressure is increased for both fuels. DA - 2005/1// PY - 2005/1// DO - 10.1016/j.combustflame.2004.10.005 VL - 140 IS - 1-2 SP - 60-69 SN - 1556-2921 KW - soot volume fraction KW - high-pressure flames KW - laser induced incandescence ER - TY - JOUR TI - Heat transfer performance of a cooling system using vibrating piezoelectric beams AU - Wu, T AU - Ro, PI T2 - JOURNAL OF MICROMECHANICS AND MICROENGINEERING AB - A prototype of a miniature cooling system for microelectronics using vibrating piezoelectric beam was proposed and constructed. The flow patterns and cooling effects of the system were investigated experimentally. The vibration characteristics of the piezoelectric beam were simulated by the finite element method. Cooling effects were measured in terms of the temperature drop of the heat source above the vibrating beam. The electric field applied on the piezoelectric beam and the gap between heat source and actuator were adjusted to find the best cooling result. A temperature drop of 25.9 °C from 92 °C can be observed for the heat source when operating at a certain condition, which indicates the feasibility of using the present miniature cooling system in small devices. The heat transfer performance of the cooling system was analyzed as well. The results show that the enhancement of heat transfer between the heat source and the beam can be up to 210% with the acoustic streaming generated by the beam vibration in the present experimental studies. The enhanced heat transfer can be attributed to the generation of vortical streaming by the vibrating beam which was also captured in the flow visualization experiments. DA - 2005/1// PY - 2005/1// DO - 10.1088/0960-1317/15/1/030 VL - 15 IS - 1 SP - 213-220 SN - 1361-6439 ER - TY - JOUR TI - Forced convective cooling via acoustic streaming in a narrow channel established by a vibrating piezoelectric bimorph AU - Wan, Q AU - Wu, T AU - Chastain, J AU - Roberts, WL AU - Kuznetsov, AV AU - Ro, PI T2 - FLOW TURBULENCE AND COMBUSTION AB - Forced convection in a narrow channel is investigated both numerically and experimentally. The flow field is established through the mechanism of acoustic streaming. This is accomplished by high frequency vibration of one of the channel walls, which is composed of a piezoelectric bimorph. In the numerical computations, the Navier-Stokes equations are decomposed into the acoustic equations and the streaming equations by the perturbation method. The acoustic field is first numerically obtained, which provides the driving force for the streaming field. The streaming field and the associated temperature field are then obtained numerically. Heat losses from a heat source are measured to determine the efficiency of this as a cooling method. The air-flow patterns in the channel between the heat source and the bimorph actuator are visualized using the particle tracking velocimetry. The visualization clearly shows that vortical streaming (acoustic streaming) can be induced by bimorph vibration, which enhances heat transfer between the heat source and the surrounding air. The temperature decreases obtained computationally and experimentally are in good agreement. DA - 2005/3// PY - 2005/3// DO - 10.1007/s10494-005-4132-4 VL - 74 IS - 2 SP - 195-206 SN - 1573-1987 KW - acoustic streaming KW - forced convection KW - cooling enhancement KW - vibrating surface ER - TY - JOUR TI - Forced convection in a composite parallel plate channel: modeling the effect of interface roughness and turbulence utilizing a kappa-epsilon model AU - Zhu, J AU - Kuznetsov, AV T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - In this paper, a composite parallel plate channel whose central part is occupied by a clear fluid and whose peripheral part is occupied by a fluid-saturated porous medium is considered. The modeling is based on the assumption that the flow in the clear fluid region is turbulent while in the porous region the flow remains laminar. The turbulent and laminar flow solutions are matched at the porous/fluid interface, which is assumed rough. Two different models are utilized for calculating turbulent viscosity in the clear fluid region, the algebraic Cebeci–Smith model and a k–ε model. Numerical results obtained utilizing both models are compared and analyzed in detail. DA - 2005/1// PY - 2005/1// DO - 10.1016/j.icheatmasstransfer.2004.05.019 VL - 32 IS - 1-2 SP - 10-18 SN - 1879-0178 KW - turbulence KW - porous media KW - kappa-epsilon model KW - rough interface ER - TY - JOUR TI - Semiconductor crystal growth by modified vertical gradient freezing with electromagnetic stirring AU - Wang, XH AU - Ma, N AU - Bliss, DF AU - Iseler, GW T2 - JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER AB - This paper presents a numerical model for the unsteady transport of a dopant during the VGF process by submerge d heater growth with a steady axial magnetic field and a steady radial electric current. Electromagnetic (EM) stirring can be induced in the gallium antimonide melt just above the crystal growth interface by applying a small radial electric current in the melt together with an axial magnetic field. The application of EM stirring provides a significant convective dopant transport in the melt so that the crystal solidifies with relatively good radial homogeneity. Dopant distributions in the crystal and in th e melt at several different stages during growth are presented. DA - 2005/// PY - 2005/// DO - 10.2514/1.10279 VL - 19 IS - 1 SP - 95-100 SN - 1533-6808 ER - TY - JOUR TI - A borehole temperature during drilling in a fractured rock formation AU - Fomin, S AU - Hashida, T AU - Chugunov, V AU - Kuznestov, AV T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - Drilling in brittle crystalline rocks is often accompanied by a fluid loss through the finite number of the major fractures intercepting the borehole. These fractures affect the flow regime and temperature distributions in the borehole and rock formation. In this study, the problem of borehole temperature variation during drilling of the fractured rock is analyzed analytically by applying the approximate generalized integral-balance method. The model accounts for different flow regimes in the borehole, for different drilling velocities, for different locations of the major fractures intersecting the borehole, and for the thermal history of the borehole exploitation, which may include a finite number of circulation and shut-in periods. Normally the temperature fields in the well and surrounding rocks are calculated numerically by the finite difference and finite element methods or analytically, utilizing the Laplace-transform method. The formulae obtained by the Laplace-transform method are usually complex and require tedious numerical evaluations. Moreover, in the previous research the heat interactions of circulating fluid with the rock formation were treated assuming constant bore-face temperatures. In the present study the temperature field in the formation disturbed by the heat flow from the borehole is modeled by the heat conduction equation. The thermal interaction of the circulating fluid with the formation is approximated by utilizing the Newton law of cooling at the bore-face. The discrete sinks of fluid on the bore-face model the fluid loss in the borehole through the fractures. The heat conduction problem in the rock is solved analytically by the heat balance integral method. It can be proved theoretically that the approximate solution found by this method is accurate enough to model thermal interactions between the borehole fluid and the surrounding rocks. Due to its simplicity and accuracy, the derived solution is convenient for the geophysical practitioners and can be readily used, for instance, for predicting the equilibrium formation temperatures. DA - 2005/1// PY - 2005/1// DO - 10.1016/j.ijheatmasstransfer.2004.07.042 VL - 48 IS - 2 SP - 385-394 SN - 1879-2189 KW - fluid loss KW - borehole KW - temperature KW - heat flux KW - bore-face KW - fluid circulation KW - integral-balance method ER - TY - JOUR TI - Thermally developing forced convection in a channel occupied by a porous medium saturated by a non-Newtonian fluid AU - Nield, DA AU - Kuznetsov, A T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - The classical 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 constant temperature, for the case of a non-Newtonian fluid of power-law type. A Brinkman-Forchheimer model is used for the momentum equation. The analysis for the case of small modified Darcy number leads to expressions for the local Nusselt number and average Nusselt number as functions of the dimensionless longitudinal coordinate, the power-law index, a modified Darcy number, and a modified Reynolds-Forchheimer number (with the last three parameters being involved via a boundary-layer thickness). DA - 2005/3// PY - 2005/3// DO - 10.1016/j.ijheatmasstransfer.2004.09.040 VL - 48 IS - 6 SP - 1214-1218 SN - 1879-2189 ER - TY - JOUR TI - Evaluation of stamping lubricants at various temperature levels using the ironing test AU - Chandrasekharan, S AU - Palaniswamy, H AU - Jain, N AU - Ngaile, G AU - Altan, T T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE AB - Lubricants are employed in stamping operations in order to (a) improve the material flow into the die cavity, (b) reduce wear and galling in the die and (c) obtain good surface finish of the part. Process conditions such as high temperatures and pressures could cause the lubricant to fail, thus resulting in galling or tearing of the part, damage to the tooling, and lost production. Therefore, selection of an appropriate lubricant based on the process conditions is important in the stamping industry. Several benchmark tests emulating stamping operations have been developed and are used to evaluate the performance of candidate lubricants. The major drawback of most of these tests is their inability to emulate high contact pressures and sliding velocities, which are crucial parameters for lubricity, especially in the case of high-speed progressive or transfer die operations involving ironing. Moreover, most of these tests are conducted at room temperature, while in reality; the process temperature can reach as high as 200 °C. The ironing tribotest developed at the Engineering Research Center for Net Shape Manufacturing (ERC/NSM) induces high contact pressures and temperatures, thus emulating the conditions in a production environment. Application of the test to screen candidate lubricants for stamping operations involving the ironing process is discussed in this paper. DA - 2005/4// PY - 2005/4// DO - 10.1016/j.ijmachtools.2004.09.014 VL - 45 IS - 4-5 SP - 379-388 SN - 1879-2170 KW - ironing KW - lubrication KW - tribotest ER - TY - JOUR TI - A new wall stress equation for aneurysm-rupture prediction AU - Li, Z AU - Kleinstreuer, C T2 - ANNALS OF BIOMEDICAL ENGINEERING DA - 2005/2// PY - 2005/2// DO - 10.1007/s10439-005-8979-2 VL - 33 IS - 2 SP - 209-213 SN - 1573-9686 KW - Laplace structure equation KW - abdominal aortic aneurysm KW - semi-empirical wall stress equation KW - AAA-rupture prediction ER - TY - JOUR TI - Growth of binary alloyed semiconductor crystals by the vertical Bridgman-Stockbarger process with a strong magnetic field AU - LaPointe, SJ AU - Ma, N AU - Mueller, DW T2 - JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME AB - This paper presents a model for the unsteady species transport for the growth of alloyed semiconductor crystals during the vertical Bridgman-Stockbarger process with a steady axial magnetic field. During growth of alloyed semiconductors such as germanium-silicon (GeSi) and mercury-cadmium-telluride (HgCdTe), the solute’s concentration is not small, so that density differences in the melt are very large. These compositional variations drive compositionally driven buoyant convection, or solutal convection, in addition to thermally driven buoyant convection. These buoyant convections drive convective transport, which produces nonuniformities in the concentration in both the melt and the crystal. This transient model predicts the distribution of species in the entire crystal grown in a steady axial magnetic field. The present study presents results of concentration in the crystal and in the melt at several different stages during crystal growth. DA - 2005/5// PY - 2005/5// DO - 10.1115/1.1899169 VL - 127 IS - 3 SP - 523-528 SN - 1528-901X ER - TY - JOUR TI - A two-velocity two-temperature model for a bi-dispersed porous medium: Forced convection in a channel AU - Nield, DA AU - Kuznetsov, AV T2 - TRANSPORT IN POROUS MEDIA DA - 2005/6// PY - 2005/6// DO - 10.1007/s11242-004-1685-y VL - 59 IS - 3 SP - 325-339 SN - 0169-3913 KW - bi-dispersed medium KW - two-velocity KW - two-temperature KW - forced convection KW - channel ER - TY - JOUR TI - Modeling heat and moisture transport in firefighter protective clothing during flash fire exposure AU - Chitrphiromsri, P AU - Kuznetsov, A T2 - HEAT AND MASS TRANSFER DA - 2005/1// PY - 2005/1// DO - 10.1007/s00231-004-0504-x VL - 41 IS - 3 SP - 206-215 SN - 1432-1181 ER - TY - JOUR TI - Fuel Lewis number effects in unsteady Burke-Schumann hydrogen flames AU - Chaos, M AU - Chen, RH AU - Welle, EJ AU - Roberts, WL T2 - COMBUSTION SCIENCE AND TECHNOLOGY AB - ABSTRACT Flame response (as determined by temperature and flame thickness) to unsteady hydrodynamics has been measured in acoustically pulsed Burke–Schumann hydrogen flames at two different oscillation frequencies and amplitudes. The effect of fuel Lewis number (Le F) on flame dynamics is isolated by investigating steady and unsteady 40% H2/60% He (Le F > 1) and 40% H2/60% Ar (Le F < 1) flames. For a given flame with Le F < 1, local temperature was found to increase with stretch imparted on the reaction zone by the unsteady flow, whereas the opposite trend was observed for the Le F > 1 flame. Unsteadiness might qualitatively alter the effect of the fuel Lewis number. Notably, for Le F < 1 flames under oscillations of sufficiently high frequency and amplitude, the temperature at the flame tip is higher than that in the shoulder regions, and is different from the temperature field of both steady and low-frequency oscillation flames. This suggests that the effect of unsteady flame stretch may overwhelm that of the flame curvature for sufficiently high unsteadiness. DA - 2005/1// PY - 2005/1// DO - 10.1080/00102200590883660 VL - 177 IS - 1 SP - 75-+ SN - 1563-521X KW - unsteadiness KW - Lewis number KW - stretch KW - curvature KW - pulsation KW - diffusion flame ER - TY - CONF TI - Semiconductor crystal growth by modified vertical gradient freezing with electromagnetic stirring AU - Wang, X.-H. AU - Ma, N. AU - Bliss, D. F. AU - Iseler, G. W. C2 - 2005/// C3 - AIAA 43rd Aerospace Sciences Meeting and Exhibit, Reno, NV, Jan. 2005 DA - 2005/// VL - 2005-0916 M1 - 2005 Jan. ER - TY - JOUR TI - Thermal development of forced convection in a channel or duct partly occupied by a porous medium AU - Nield, DA AU - Kuznetsov, AV T2 - JOURNAL OF POROUS MEDIA DA - 2005/// PY - 2005/// DO - 10.1615/JPorMedia.v8.i6.70 VL - 8 IS - 6 SP - 627-638 SN - 1091-028X ER - TY - JOUR TI - Liquid-encapsulated Czochralski growth of doped gallium-antimonide semiconductor crystals using a strong steady magnetic field AU - Yang, M. AU - Ma, N. Bliss AU - D. F., AU - Morton, J. L. T2 - Magnetohydrodynamics DA - 2005/// PY - 2005/// VL - 41 IS - 1 SP - 73-86 ER - TY - JOUR TI - Thermo-bioconvection in a suspension of oxytactic bacteria AU - Kuznetsov, AV T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - This paper studies thermo-bioconvection, a macroscopic convective motion induced in a fluid layer by the combined effect of density stratification caused by the upswimming of oxytactic microorganisms and heating from below. Both agencies affecting the density are destabilizing; therefore, monotonic instability is expected. Oscillatory instability may be possible in the case of cooling from below. DA - 2005/8// PY - 2005/8// DO - 10.1016/j.icheatmasstransfer.2004.11.005 VL - 32 IS - 8 SP - 991-999 SN - 1879-0178 KW - thermo-bioconvection KW - motile microorganisms KW - oxytaxis KW - stability KW - heating from below ER - TY - JOUR TI - SOS-based solution approach to polynomial LPV system analysis and synthesis problems AU - Wu, F. AU - Prajna, S. T2 - International Journal of Control DA - 2005/// PY - 2005/// DO - 10.1080/002071270500114865 VL - 78 IS - 8 SP - 600-611 ER - TY - JOUR TI - Numerical model for Bridgman-Stockbarger crystal growth with a magnetic field AU - Wang, XH AU - Ma, N T2 - JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER AB - This paper presents a model for the unsteady species transport for the growth of doped semiconductor crystals during the vertical Bridgman‐Stockbarger process with a steady axial magnetic field. This dilute species transport depends on the convective and diffusive species transport of the dopant. This convective species transport is driven by buoyant convection in the melt, which produces compositional nonuniformities in both the melt and the crystal. This transient model predicts the distribution of species in the entire crystal grown in a steady axial magnetic field. The present study presents results of concentration in the crystal and in the melt at several different stages during crystal growth. I. Introduction D URING crystal growth without a magnetic field or with a weak magnetic field, turbulent or oscillatory melt motions can produce undesirable spatial oscillations of the concentration, or microsegregation, in the crystal. 1 Turbulent or oscillatory melt motions lead to fluctuations in the heat transfer across the growth interface from the melt to the crystal. Because the local rate of crystallization depends on the balance between the local heat fluxes in the melt and the crystal, fluctuations in the heat flux from the melt create fluctuations in the local growth rate, which create microsegregation. A moderate magnetic field can be used to create a body force that provides an electromagnetic (EM) damping of the melt motion can to eliminate oscillations in the melt motion and thus in the concentration of the crystal. Unfortunately, the elimination of mixing and a moderate or strong EM damping of the residual melt motion can lead to a large variation of the crystal’s composition in the direction perpendicular to the growth direction (radial macrosegregation). On the other hand, if the magnetic field strength is so strong that the melt motion is reduced sufficiently so that it has no effect on the composition in the crystal, then this diffusion-controlled species transport can produce a radially and axially uniform composition in the crystal grown. 2 To achieve diffusion-controlled species trans� DA - 2005/// PY - 2005/// DO - 10.2514/1.13307 VL - 19 IS - 3 SP - 406-412 SN - 1533-6808 ER - TY - JOUR TI - Laminar nanofluid flow in microheat-sinks AU - Koo, J. M. AU - Kleinstreuer, C. T2 - International Journal of Heat and Mass Transfer DA - 2005/// PY - 2005/// DO - 10.1016/j.ijheattransfer.2005.01.029 VL - 48 IS - 13 SP - 2652-2661 ER - TY - JOUR TI - System identification of base-isolated building using seismic response data AU - Furukawa, T. AU - Ito, M. AU - Izawa, K. AU - Noori, M. N. T2 - Journal of Engineering Mechanics AB - Due to the complex nature of the excitation, and the inherent dynamics characteristics of restoring force of the base isolation systems, the response of base-isolated structures subject to strong earthquakes often experiences excursion into the inelastic range. Therefore, in designing base-isolated structures, the nonlinear hysteretic restoring force model of the base isolation system is frequently used to predict structural response and to evaluate structural safety. In this paper, the prediction error method system identification technique is used in conjunction with nonlinear state-space models for identification of a base-isolated structure. Using a variety of nonlinear restoring force models and bidirectional recorded seismic responses, several identification runs are conducted to evaluate the accuracy of the selected models. Several nonlinear restoring force models are utilized for the base-isolation system, including a multiple shear spring (MSS) model. Among all models used, results indicate that the trilinear hysteretic MSS model closely matches the actual hysteretic restoring force profile and time histories obtained directly from the observed data. DA - 2005/// PY - 2005/// DO - 10.1061/(ASCE)0733-9399(2005)131:3(268) VL - 131 IS - 3 SP - 268-275 ER - TY - JOUR TI - Mathematical modelling of two-phase non-Newtonian flow in a helical pipe AU - Cheng, L AU - Kuznetsov, AV AU - Sandeep, KP T2 - INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS AB - Governing equations for a two-phase 3D helical pipe flow of a non-Newtonian fluid with large particles are derived in an orthogonal helical coordinate system. The Lagrangian approach is utilized to model solid particle trajectories. The interaction between solid particles and the fluid that carries them is accounted for by a source term in the momentum equation for the fluid. The force-coupling method (FCM), developed by M.R. Maxey and his group, is adopted; in this method the momentum source term is no longer a Dirac delta function but is spread on a numerical mesh by using a finite-sized envelop with a spherical Gaussian distribution. The influence of inter-particle and particle–wall collisions is also taken into account. Copyright © 2005 John Wiley & Sons, Ltd. DA - 2005/6/30/ PY - 2005/6/30/ DO - 10.1002/fld.950 VL - 48 IS - 6 SP - 649-670 SN - 1097-0363 KW - non-Newtonian fluid KW - two-phase flow KW - helical pipe KW - orthogonal helical coordinates KW - force-coupling method ER - TY - JOUR TI - Investigation of hysteresis in acoustically driven channel flow at ultrasonic frequency AU - Wan, Q AU - Kuznetsov, AV T2 - NUMERICAL HEAT TRANSFER PART A-APPLICATIONS DA - 2005/1/15/ PY - 2005/1/15/ DO - 10.1080/1047780590885873 VL - 47 IS - 2 SP - 137-146 SN - 1521-0634 ER - TY - JOUR TI - Distributed parameter-dependent modeling and control of flexible structures AU - Wu, F AU - Yildizoglu, SE T2 - JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME AB - In this paper, distributed parameter-dependent modeling and control approaches are proposed for flexible structures. The distributed model is motivated from distributed control design, which is advantageous in reducing control implementation cost and increasing control system reliability. This modeling approach mainly relies on a central finite difference scheme to capture the distributed nature of the flexible system. Based on the proposed distributed model, a sufficient synthesis condition for the design of a distributed output-feedback controller is presented using induced L2 norm as the performance criterion. The controller synthesis condition is formulated as linear matrix inequalities, which are convex optimization problems and can be solved efficiently using interior-point algorithms. The distributed controller inherits the same structure as the plant, which results in a localized control architecture and a simple implementation scheme. These modeling and control approaches are demonstrated on a non-uniform cantilever beam problem through simulation studies. DA - 2005/6// PY - 2005/6// DO - 10.1115/1.1898240 VL - 127 IS - 2 SP - 230-239 SN - 1528-9028 ER - TY - JOUR TI - Comparison of micro- and nano-size particle depositions in a human upper airway model AU - Zhang, Z AU - Kleinstreuer, C AU - Donohue, JF AU - Kim, CS T2 - JOURNAL OF AEROSOL SCIENCE AB - Simulation results of microparticle and nanoparticle deposition patterns, local concentrations, and segmental averages are contrasted for a human upper airway model starting from the mouth to planar airway generation G3 under different inspiratory flow conditions. Specifically, using a commercial finite-volume software with user-supplied programs as a solver, the Euler–Euler (nanoparticles) or the Euler–Lagrange (microparticles) approach was employed with a low-Reynolds-number k–ω model for laminar-to-turbulent airflow and submodels for particle-phase randomization. The results show that depositions of both micro- and nano-size particles vary measurably in the human upper airways; however, the deposition distributions are much more uniform for nanoparticles. The maximum deposition enhancement factor, which is defined as the ratio of local to average deposition concentrations, ranges from about 40 to 2400 for microparticles and about 2 to 11 for nanoparticles with inspiratory flow rates in the range of 15⩽Qin⩽60 l/min. In addition, some airway bifurcations in generations G0 to G3 subjected to high inlet flow rates (say, Qin=60l/min) may receive only very small amounts of large micro-size particles (say, with aerodynamic diameter dae⩾10μm) due to largely preferred upstream deposition. It has been hypothesized that, uniformly deposited nanoparticles of similar concentrations may have greater toxicity effects when compared to microparticles of the same material. DA - 2005/2// PY - 2005/2// DO - 10.1016/j.jaerosci.2004.08.006 VL - 36 IS - 2 SP - 211-233 SN - 1879-1964 KW - microparticle deposition KW - nanoparticle deposition KW - human upper airways KW - computational fluid-particle dynamics ER - TY - JOUR TI - Blood flow and structure interactions in a stented abdominal aortic aneurysm model AU - Li, ZH AU - Kleinstreuer, C T2 - MEDICAL ENGINEERING & PHYSICS AB - Since the introduction of endovascular techniques in the early 1990s for the treatment of abdominal aortic aneurysms (AAAs), the insertion of an endovascular graft (EVG) into the affected artery segment has been greatly successful for a certain group of AAA patients and is continuously evolving. However, although minimally invasive endovascular aneurysm repair (EVAR) is very attractive, post-operative complications may occur. Typically, they are the result of excessive fluid–structure interaction dynamics, possibly leading to EVG migration. Considering a 3D stented AAA, a coupled fluid flow and solid mechanics solver was employed to simulate and analyze the interactive dynamics, i.e., pulsatile blood flow in the EVG lumen, pressure levels in the stagnant blood filling the AAA cavity, as well as stresses and displacements in the EVG and AAA walls. The validated numerical results show that a securely placed EVG shields the diseased AAA wall from the pulsatile blood pressure and hence keeps the maximum wall stress 20 times below the wall stress value in the non-stented AAA. The sac pressure is reduced significantly but remains non-zero and transient, caused by the complex fluid–structure interactions between luminal blood flow, EVG wall, stagnant sac blood, and aneurysm wall. The time-varying drag force on the EVG exerted by physiological blood flow is unavoidable, where for patients with severe hypertension the risk of EVG migration is very high. DA - 2005/6// PY - 2005/6// DO - 10.1016/j.medengphy.2004.12.003 VL - 27 IS - 5 SP - 369-382 SN - 1873-4030 KW - fluid-structure interaction KW - stented abdominal aortic aneurysm KW - endovascular graft KW - sac pressure KW - wall stress KW - drag force KW - EVG migration ER - TY - JOUR TI - A sensor for measurement of friction coefficient on moving flexible surfaces AU - Ramasubramanian, MK AU - Jackson, SD T2 - IEEE SENSORS JOURNAL AB - Measurement of coefficient of friction between surfaces is of interest in numerous engineering applications. Although laboratory tests of material samples in tribological systems are used to measure the friction coefficient, on-line friction measurement on newly manufactured surfaces, or between two interacting surfaces of interest, is nonexistent. In this paper, we describe a new sensor, called the tribosensor, that accomplishes real-time friction coefficient measurement between materials, where one of the two materials in the tribological pair is being processed or manufactured at high speeds, such as in paper, plastics, aluminum, and other flexible materials. This paper discusses the operating principle of the sensor, design configuration, and performance characterization. Comparison with traditional off-line laboratory measurements is also presented. DA - 2005/10// PY - 2005/10// DO - 10.1109/JSEN.2005.845205 VL - 5 IS - 5 SP - 844-849 SN - 1558-1748 KW - coefficient of friction (COF) KW - flexible materials KW - friction KW - manufacturing KW - real-time sensor KW - tribology ER -