TY - JOUR TI - Simulating cavitation and hydraulic flip inside hydroentangling nozzles T2 - Textile Research Journal DA - 2004/// PY - 2004/// UR - https://publons.com/wos-op/publon/65200209/ ER - TY - CONF TI - Effects of tip gap film injection from plain and squealer blade tips AU - Nasir, H. AU - Ekkad, S.V. AU - Bunker, R.S. AU - Prakash, C. AB - The present study investigates the effect of orthogonal tip gap film injection from a plain and squealer tip of a HPT first stage rotor blade. The pressure ratio (inlet total pressure to exit static pressure) for the cascade used was 1.2, and the experiments were run in a blow-down test rig with a four-blade stationary linear cascade. The Reynolds number based on cascade exit velocity and axial chord length was 8.61×105 and the inlet and exit Mach numbers were 0.16 and 0.55, respectively. Five holes are located along the camber line of the blade tip. A transient infrared technique was used to measure the local heat transfer coefficient and film effectiveness from a single transient test. All measurements were made for three blowing ratios of 1.0, 1.5, and 2.0. For all the cases, a small tip gap-to-blade span ratio of 0.5% was used. The squealer depth-to-blade span ratio of 4.16% was used for the squealer. Results show that the film injection has some effect for plain tips but has no effect or negligible effect for squealer tips. C2 - 2004/// C3 - Proceedings of the ASME Turbo Expo 2004 DA - 2004/// DO - 10.1115/gt2004-53455 VL - 3 SP - 419-427 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-10244221127&partnerID=MN8TOARS ER - TY - JOUR TI - Effect of squealer geometry on tip flow and heat transfer for a turbine blade in a low speed cascade AU - Saxena, V. AU - Ekkad, S.V. T2 - Journal of Heat Transfer AB - Abstract A detailed investigation on the effect of squealer geometries on the blade tip leakage flow and associated heat transfer is presented for a scaled up high pressure turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip profile of a first stage rotor blade is used to fabricate the two-dimensional blade. The wind tunnel accommodates an 116° turn for the blade cascade. The mainstream Reynolds number based on the axial chord length based on cascade exit velocity is 4.83×105. An upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates a free-stream turbulence of 4.8%. The center blade has a tip clearance gap of 1.56% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. Results show that the presence of the squealer alters the tip gap flow field significantly and produces lower overall heat transfer coefficients. The effects of different squealer arrangements are basically to study the effect of squealer rim placement on tip leakage flow and associated heat transfer. Detailed heat transfer measurements are obtained using a steady state liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0–0.4. Results show that suction side squealers may be favorable in terms of overall reduction in heat transfer coefficients over the tip surface. However, the presence of a full squealer is most beneficial in terms of reducing overall heat load on the tip surface. There is reasonable effect of wake induced periodicity on tip heat transfer. DA - 2004/// PY - 2004/// DO - 10.1115/1.1777580 VL - 126 IS - 4 SP - 546-553 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-7244247150&partnerID=MN8TOARS ER - TY - CONF TI - Heat transfer study of a novel low-crossflow design for jet impingement AU - Hebert, R. AU - Ekkad, S.V. AU - Khanna, V. AU - Abreu, M. AU - Moon, H.-K. AB - Impingement heat transfer is significantly affected by initial cross-flow or by the presence of cross-flow from upstream spent jets. In this study, a zero cross-flow design is presented. The zero-crossflow design creates spacing between hole arrays to allow for spent flow to be directed away from impinging jets. Three configurations with different impingement holes placements are studied and compared with pure impingement with spent crossflow cases for the same jet Reynolds number. Three jet Reynolds numbers are studied for Rej = 10000, 20000, and 30000. Detailed heat transfer distributions are obtained using the transient liquid crystal technique. The zero-cross flow design clearly shows minimal degradation of impingement heat transfer due to crossflow compared to conventional design with lower mass flow rate requirement and lesser number of overall impingement holes due to the reduced cross-flow effect on the impingement region. C2 - 2004/// C3 - American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD DA - 2004/// DO - 10.1115/IMECE2004-60468 VL - 375 SP - 583-588 M1 - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-20344408308&partnerID=MN8TOARS ER - TY - JOUR TI - Effect of tip gap and squealer geometry on detailed heat transfer measurements over a high pressure turbine rotor blade tip AU - Nasir, H. AU - Ekkad, S.V. AU - Kontrovitz, D.M. AU - Bunker, R.S. AU - Prakash, C. T2 - Journal of Turbomachinery AB - The present study explores the effects of gap height and tip geometry on heat transfer distribution over the tip surface of a HPT first-stage rotor blade. The pressure ratio (inlet total pressure to exit static pressure for the cascade) used was 1.2, and the experiments were run in a blow-down test rig with a four-blade linear cascade. A transient liquid crystal technique was used to obtain the tip heat transfer distributions. Pressure measurements were made on the blade surface and on the shroud for different tip geometries and tip gaps to characterize the leakage flow and understand the heat transfer distributions. Two different tip gap-to-blade span ratios of 1% and 2.6% are investigated for a plane tip, and a deep squealer with depth-to-blade span ratio of 0.0416. For a shallow squealer with depth-to-blade span ratio of 0.0104, only 1% gap-to-span ratio is considered. The presence of the squealer alters the tip gap flow field significantly and produces lower overall heat transfer coefficients. The effects of different partial squealer arrangements are also investigated for the shallow squealer depth. These simulate partial burning off of the squealer in real turbine blades. Results show that some partial burning of squealers may be beneficial in terms of overall reduction in heat transfer coefficients over the tip surface. DA - 2004/// PY - 2004/// DO - 10.1115/1.1731416 VL - 126 IS - 2 SP - 221-228 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-7644220874&partnerID=MN8TOARS ER - TY - CONF TI - Effect of jet pulsation and duty cycle on film cooling from a single jet on a leading edge model AU - Ekkad, S.V. AU - Ou, S. AU - Rivir, R.B. AB - The effect of jet pulsation and duty cycle on film effectiveness and heat transfer was investigated on a film hole located on the circular leading edge of a blunt body. A transient infrared technique was used to measure both heat transfer coefficients and film effectiveness from a single test. Detailed Frossling number and film effectiveness distributions were obtained for all flow conditions. Jet pulsing frequencies of 5 Hz, 10 Hz, and 20 Hz have been studied. The effect of duty cycle created by the valve opening and closing times was also set at different levels of 10%, 25%, 50%, and 75% of designated 100% fully open condition for different blowing ratios from 0.25 to 2.0. The combination of pulse frequency and duty cycle was investigated for different blowing ratios on a single leading edge hole located at 22-deg from geometric leading edge. Results indicate that higher effectiveness and lower heat transfer coefficients are obtained at the reduced blowing ratios which result from reduced duty cycles. The effect of varying the pulsing frequency from 5 Hertz to 20 Hertz is not discernable beyond the level of experimental uncertainty. Effective blowing ratio due to lowering of the duty cycle at a given blowing ratio seems to plays a more important role in combination with pulsing which provides improved cooling effectiveness at lower heat transfer coefficients. C2 - 2004/// C3 - American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD DA - 2004/// DO - 10.1115/IMECE2004-60466 VL - 375 SP - 575-582 M1 - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-20344398461&partnerID=MN8TOARS ER - TY - JOUR TI - Effect of blade tip geometry on tip flow and heat transfer for a blade in a low-speed cascade AU - Saxena, V. AU - Nasir, H. AU - Ekkad, S.V. T2 - Journal of Turbomachinery AB - A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer of a scaled up HPT turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the two-dimensional blade. The wind tunnel accommodates an 116 deg turn for the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83×105. The upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates the required freestream turbulence of 4.8%. The center blade has a tip clearance gap of 1.5625% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. The effect of crosswise trip strips to reduce leakage flow and associated heat transfer is investigated with strips placed along the leakage flow direction, against the leakage flow and along the chord. Cylindrical pin fins and pitch variation of strips over the tip surface are also investigated. Detailed heat transfer measurements are obtained using a steady-state HSI-based liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0. to 0.2, and to 0.4. Results show that the trip strips placed against the leakage flow produce the lowest heat transfer on the tips compared to all the other cases with a reduction between 10–15% compared to the plain tip. Results also show that the pitch of the strips has a small effect on the overall reduction. Cylindrical pins fins and strips along the leakage flow direction do not decrease the heat transfer coefficients and in some cases enhance the heat transfer coefficients by as much as 20%. DA - 2004/// PY - 2004/// DO - 10.1115/1.1643385 VL - 126 IS - 1 SP - 130-138 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1942425037&partnerID=MN8TOARS ER - TY - CONF TI - Combination of impingement and trip strips for combustor liner backside cooling AU - Hebert, R. AU - Ekkad, S.V. AU - Khanna, V. AB - Effective cooling of modern low NOx combustor liners is achieved through combinations of impingement and other heat transfer enhancement methods. In the present study, a combination of impingement and trip strips is studied to determine the optimum location of trip strips with respect to impingement jet arrays. Heat transfer with pure impingement has degradation downstream due to increased cross-flow effects. To counter the cross-flow induced heat transfer degradation, a combination technique wherein impingement is combined with ribs placed in between impingement rows or downstream of the impingement array is studied. Three configurations with increased rib placements and reduced impingement holes are studied and compared with pure impingement cases for the same jet Reynolds number. Three jet Reynolds numbers are studied for Rej = 10000, 20000, and 30000. Detailed heat transfer distributions are obtained using the transient liquid crystal technique. Results show that the presence of ribs increases jet impingement heat transfer on the surface with lower mass flows. The effectiveness of the combination ribs and impingement can provide higher heat transfer with reduced cooling air requirements. C2 - 2004/// C3 - Proceedings of the ASME Heat Transfer/Fluids Engineering Summer Conference 2004, HT/FED 2004 DA - 2004/// DO - 10.1115/ht-fed2004-56536 VL - 3 SP - 179-185 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-21544472888&partnerID=MN8TOARS ER - TY - CONF TI - A transient infrared thermography method for simultaneous film cooling effectiveness and heat transfer coefficient measurements from a single test AU - Ekkad, S.V. AU - Ou, S. AU - Rivir, R.B. AB - In film cooling situations, there is a need to determine both local adiabatic wall temperature and heat transfer coefficient to fully assess the local heat flux into the surface. Typical film cooling situations are termed three temperature problems where the complex interaction between the jets and mainstream dictates the surface temperature. The coolant temperature is much cooler than the mainstream resulting in a mixed temperature in the film region downstream of injection. An infrared thermography technique using a transient surface temperature acquisition is described which determines both the heat transfer coefficient and film effectiveness (non-dimensional adiabatic wall temperature) from a single test. Hot mainstream and cooler air injected through discrete holes are imposed suddenly on an ambient temperature surface and the wall temperature response is captured using infrared thermography. The wall temperature and the known mainstream and coolant temperatures are used to determine the two unknowns (heat transfer coefficient and film effectiveness) at every point on the test surface. The advantage of this technique over existing techniques is the ability to obtain the information using a single transient test. Transient liquid crystal techniques have been one of the standard techniques for determining h and η for turbine film cooling for several years. Liquid crystal techniques do not account for non uniform initial model temperatures while the transient IR technique measures the entire initial model distribution. The transient liquid crystal technique is very sensitive to the angle of illumination and view while the IR technique is not. The IR technique is more robust in being able to take measurements over a wider temperature range which improves the accuracy of h and η. The IR requires less intensive calibration than liquid crystal techniques. Results are presented for film cooling downstream of a single hole on a turbine blade leading edge model. C2 - 2004/// C3 - Proceedings of the ASME Turbo Expo 2004 DA - 2004/// DO - 10.1115/gt2004-54236 VL - 3 SP - 999-1005 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-10244229755&partnerID=MN8TOARS ER - TY - JOUR TI - A transient infrared thermography method for simultaneous film cooling effectiveness and heat transfer coefficient measurements from a single test AU - Ekkad, S.V. AU - Ou, S. AU - Rivir, R.B. T2 - Journal of Turbomachinery AB - In film cooling situations, there is a need to determine both local adiabatic wall temperature and heat transfer coefficient to fully assess the local heat flux into the surface. Typical film cooling situations are termed three temperature problems where the complex interaction between the jets and mainstream dictates the surface temperature. The coolant temperature is much cooler than the mainstream resulting in a mixed temperature in the film region downstream of injection. An infrared thermography technique using a transient surface temperature acquisition is described which determines both the heat transfer coefficient and film effectiveness (nondimensional adiabatic wall temperature) from a single test. Hot mainstream and cooler air injected through discrete holes are imposed suddenly on an ambient temperature surface and the wall temperature response is captured using infrared thermography. The wall temperature and the known mainstream and coolant temperatures are used to determine the two unknowns (the heat transfer coefficient and film effectiveness) at every point on the test surface. The advantage of this technique over existing techniques is the ability to obtain the information using a single transient test. Transient liquid crystal techniques have been one of the standard techniques for determining h and η for turbine film cooling for several years. Liquid crystal techniques do not account for nonuniform initial model temperatures while the transient IR technique measures the entire initial model distribution. The transient liquid crystal technique is very sensitive to the angle of illumination and view while the IR technique is not. The IR technique is more robust in being able to take measurements over a wider temperature range which improves the accuracy of h and η. The IR requires less intensive calibration than liquid crystal techniques. Results are presented for film cooling downstream of a single hole on a turbine blade leading edge model. DA - 2004/// PY - 2004/// DO - 10.1115/1.1791283 VL - 126 IS - 4 SP - 597-603 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-14744294190&partnerID=MN8TOARS ER - TY - CONF TI - Failure modes and grain-boundary effects in polycrystalline materials AU - Zikry, M.A. AU - Ashmawi, W.M. C2 - 2004/// C3 - Materials Research Society Symposium - Proceedings DA - 2004/// DO - 10.1557/proc-819-n1.3 VL - 819 SP - 21-26 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-5544263626&partnerID=MN8TOARS ER - TY - CONF TI - Failure identification methodology for woven composites incorporating sensor degradation AU - Pearson, J. AU - Prabhugoud, M. AU - Zikry, M. AU - Peters, K. AB - The long-term goal of this project is the development of embedded, optimally distributed, multi-scale sensing methodologies that can be integrated into material systems for failure identification in structural systems. The coupling of sensor data fusion with a three-dimensional predictive framework will provide insight and understanding of events that are difficult, if not impossible, in any experimental study, such as subsurface damage and crack nucleation in structural systems. The current work presents an experimental study of the survivability and degradation behavior of an optical fiber Bragg grating sensor, surface mounted on a woven fiber composite material system during multiple low velocity impacts. The results reveal that as sensor degradation occurs, additional coupling phenomena other than Bragg reflection are observed in the grating sensor. From these additional modes, information on the sensor/host bond and fiber degradation is obtained. C2 - 2004/// C3 - American Society of Mechanical Engineers, Materials Division (Publication) MD DA - 2004/// DO - 10.1115/IMECE2004-61802 VL - 99 SP - 31-40 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-19644380376&partnerID=MN8TOARS ER - TY - JOUR TI - Erratum: Evolution of failure mechanisms in 2D and 3D woven composite systems under quasi-static perforation (Journal of Composite Materials, 37, 18, (1651-1674) DOI: 10.1177/0021998304042170) AU - Baucom, J.N. AU - Zikry, M.A. T2 - Journal of Composite Materials DA - 2004/// PY - 2004/// DO - 10.1177/0021998304042170 VL - 38 IS - 6 SP - 535 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1842474470&partnerID=MN8TOARS ER - TY - CONF TI - Demonstration of failure identification methodology incorporating sensor degradation AU - Prabhugoud, M. AU - Pearson, J. AU - Peters, K. AU - Zikry, M. AB - The long-term goal of this project is the development of embedded, optimally distributed, multi-scale sensing methodologies that can be integrated into material systems for failure identification in structural systems. The coupling of sensor data fusion with a three-dimensional predictive framework will provide insight and understanding of events that are difficult, if not impossible, in any experimental study, such as subsurface damage and crack nucleation in structural systems. The current work presents an experimental study of the survivability and degradation behavior of an optical fiber Bragg grating sensor, surface mounted on a woven fiber composite material system during multiple low velocity impacts. The results reveal that as sensor degradation occurs, additional coupling phenomena other than Bragg reflection are observed in the grating sensor. From these additional modes, information on the sensor/host bond and fiber degradation is obtained. C2 - 2004/// C3 - Proceedings of SPIE - The International Society for Optical Engineering DA - 2004/// DO - 10.1117/12.540093 VL - 5391 SP - 107-116 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-10044277158&partnerID=MN8TOARS ER - TY - CONF TI - In-plane and Through-plane Liquid Flow Simulation in Nonwoven Glass Fiber Mats AU - Tafreshi, H.V. AU - Maze, B. AU - Pourdeyhimi, B. T2 - International Nonwovens Technical Conference (INTC 2004) C2 - 2004/9/20/ C3 - International Nonwovens Technical Conference (INTC 2004) CY - Toronto, Ontario, Canada DA - 2004/9/20/ PY - 2004/9/20/ ER - TY - CONF TI - A Study on Hydroentangling Impact Force AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - International Nonwovens Technical Conference (INTC 2004) C2 - 2004/9/20/ C3 - International Nonwovens Technical Conference (INTC 2004) CY - Toronto, Ontario, Canada DA - 2004/9/20/ PY - 2004/9/20/ ER - TY - CONF TI - Modeling Particle Filtration by Glass Fiber Filters AU - Tafreshi, H.V. AU - Maze, B. AU - Pourdeyhimi, B. T2 - Fiber Society Spring Symposium C2 - 2004/6/17/ C3 - The Fiber Society Spring Symposium CY - St. Louis, Missouri DA - 2004/6/17/ PY - 2004/6/17/ ER - TY - CONF TI - Modeling Submicron Particle Filtration by Virtual Glass Fiber Mats AU - Tafreshi, H.V. AU - Maze, B. AU - Pourdeyhimi, B. T2 - Advances in Filtration & Separations Media C2 - 2004/11/14/ C3 - Advances in Filtration & Separations Media CY - Baltimore, Maryland DA - 2004/11/14/ PY - 2004/11/14/ ER - TY - MGZN TI - Cavitation and Hydraulic Flip AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - Fluent News DA - 2004/// PY - 2004/// VL - 13 SP - 38 M1 - 1 ER - TY - JOUR TI - Simulating cavitation and hydraulic flip inside hydroentangling nozzles AU - Vahedi Tafreshi, H. AU - Pourdeyhimi, B. T2 - Textile Research Journal DA - 2004/// PY - 2004/// VL - 74 IS - 4 SP - 359-364 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0345722190&partnerID=MN8TOARS ER - TY - CONF TI - Optimal Pick-up Locations for Transport and Handling of Limp Materials AU - Eischen, J.W. AU - Lankalapalli, S. T2 - Eighth Pan American Congress of Applied Mechanics C2 - 2004/1// C3 - Proceedings of the Eighth Pan American Congress of Applied Mechanics CY - Havana, Cuba DA - 2004/1// PY - 2004/1/5/ ER - TY - CONF TI - Maneuvering control problems for a spacecraft with unactuated fuel slosh dynamics AU - Reyhanoglu, M. T2 - 2003 IEEE Conference on Control Applications, 2003. CCA 2003. AB - This paper studies maneuvering control problems for a spacecraft with fuel slosh in a zero gravity environment. The spacecraft is represented as a rigid body and fuel slosh dynamics are included using a single vibrating mass model. Both pendulum and mass-spring analogies are considered. The control inputs are defined by a thrust along the spacecraft's longitudinal axis, a transverse body fixed force and a pitching moment about the center of mass of the spacecraft. The control objective is to suppress the slosh mode, as well as the transverse and pitch dynamics, while the spacecraft accelerates in axial direction. A nonlinear feedback controller is developed to achieve this objective. C2 - 2004/3/2/ C3 - Proceedings of 2003 IEEE Conference on Control Applications, 2003. CCA 2003. CY - Istanbul, Turkey DA - 2004/3/2/ PY - 2003/6/25/ DO - 10.1109/cca.2003.1223522 PB - IEEE SN - 078037729X UR - http://dx.doi.org/10.1109/cca.2003.1223522 ER - TY - CONF TI - The design, fabrication, and characterization of millimeter scale motors for miniature direct drive robots AU - Palmer, J.A. AU - Mulling, J.F. AU - Dessent, B. AU - Grant, E. AU - Eischen, J.W. AU - Gruverman, A. AU - Kingon, A.I. AU - Franzon, P.D. T2 - IEEE International Conference on Robotics and Automation, 2004. Proceedings. ICRA '04. 2004 AB - This paper reports on research into miniature, direct drive, high force/torque motors to support insect-sized mobile robotic platforms. The primary focus is on scalable motors based on piezoelectric transducers. The contributions of this work include: (1) the design, analysis, and characterization of a miniature mode conversion rotary ultrasonic motor based on a piezoelectric stack transducer; this produced a static torque density of 0.37 Nm/kg, (2) a millimeter scale linear piezometer, constructed with a parallel arrangement of annular stressed unimorph piezoelectric transducers and passive latches, exhibited 0.23 N of blocked force, and (3) simulation data is presented that compares these motor concepts to commercial systems in the context of scalability. Results suggest that smaller versions of the rotary ultrasonic motor would possess a static torque density seven times that of a commercial 3-mm electromagnetic system. This technology shows promise for driving the platform. C2 - 2004/// C3 - IEEE International Conference on Robotics and Automation, 2004. Proceedings. ICRA '04. 2004 DA - 2004/// DO - 10.1109/robot.2004.1302454 PB - IEEE SN - 0780382323 UR - http://dx.doi.org/10.1109/robot.2004.1302454 DB - Crossref KW - piezoelectric KW - scale KW - ultrasonic motor ER - TY - JOUR TI - The hydromagnetic flow over an oscillating flat plate with arbitrary periodic oscillation AU - Fang, Tiegang T2 - Mechanics Research Communications AB - Abstract In this paper, the hydromagnetic flow over a flat plate with arbitrary periodic oscillation is solved exactly. The solution is also applicable for common incompressible viscous flow over a flat plate with arbitrary oscillation. It is found that the penetration of hydromagnetic flow will decrease with increasing non-dimensional magnetic parameter M. The transient part will die away after a certain time for a specific M. The solution will collapse into the steady-state case after a long time. However, for non-hydromagnetic flow, there will be no steady-state solution if the coefficient of the zero-frequency component is not zero. DA - 2004/1// PY - 2004/1// DO - 10.1016/S0093-6413(03)00084-3 VL - 31 IS - 1 SP - 129-135 J2 - Mechanics Research Communications LA - en OP - SN - 0093-6413 UR - http://dx.doi.org/10.1016/S0093-6413(03)00084-3 DB - Crossref KW - hydromagnetic flow KW - unsteady solution KW - stokes' second problem KW - transient solution KW - steady-state solution ER - TY - JOUR TI - Similarity Solutions for Heat Conduction in a Semi-Infinite Medium with Power Law Thermal Conductivity AU - Fang, Tiegang T2 - International Communications in Heat and Mass Transfer AB - Similarity transformation technique is applied to a general 1-D heat conduction problem for a semi-infinite media with arbitrary temperature dependent thermal conductivity. The general similarity equation is derived. The attention is paid to a commonly used power law thermal conductivity assumption. The similarity equation is simplified and solved for power law thermal conductivity. The temperature distribution and wall heat fluxes for both wall heating problem and wall cooling problem are solved and discussed for arbitrary power indices DA - 2004/5// PY - 2004/5// DO - 10.1016/S0735-1933(04)00029-6 VL - 31 IS - 4 SP - 477–485 SN - 0735-1933 UR - http://dx.doi.org/10.1016/S0735-1933(04)00029-6 ER - TY - JOUR TI - Unsteady solution of viscous fluid flow in an infinite cylinder with a variable body force AU - Fang, Tiegang T2 - Physics of Fluids AB - In this Brief Communication, the unsteady viscous flow with a variable body force in an infinite cylinder is solved exactly. The solution describes the transient velocity profiles and pressure gradients, which can be used in the application of sedimentation of spherical particles in viscous fluid. The current solution is compared with the previously solved problem between two infinite parallel plates. It is found that, for a similar body force, the central-line velocity of the cylinder will be greater than that of the two-infinite-plate case. But the slip velocity at the wall of cylinder will be smaller than that of the flow between two infinite plates. The transient pressure gradients are also different, resulting in a smaller value for the cylindrical case with a similar body force. DA - 2004/1// PY - 2004/1// DO - 10.1063/1.1628689 VL - 16 IS - 1 SP - 200-203 J2 - Physics of Fluids LA - en OP - SN - 1070-6631 1089-7666 UR - http://dx.doi.org/10.1063/1.1628689 DB - Crossref ER - TY - JOUR TI - Soot diagnostics using laser-induced incandescence within an optically accessible HSDI diesel engine AU - Mathews, W.S. AU - Fang, T. AU - Coverdill, R.E. AU - Lee, C.-F.F. AU - White, R.A. T2 - SAE Technical Papers DA - 2004/// PY - 2004/// DO - 10.4271/2004-01-1412 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877213195&partnerID=MN8TOARS ER - TY - JOUR TI - Influences of fluid property variation on the boundary layers of a stretching surface AU - Fang, T. T2 - Acta Mechanica DA - 2004/7/26/ PY - 2004/7/26/ DO - 10.1007/s00707-004-0125-y VL - 171 IS - 1-2 SP - 105-118 SN - 0001-5970 1619-6937 UR - http://dx.doi.org/10.1007/s00707-004-0125-y ER - TY - JOUR TI - Further Discussion on the Incompressible Pressure—Driven Flow in a Channel with Porous Walls AU - Fang, Tiegang T2 - International Communications in Heat and Mass Transfer AB - The unsteady velocity profiles for a pressure-driven Poiseuille flow in a channel with porous walls under mass transfer is analyzed and solved exactly. The steady state temperature distribution with viscous dissipation is also derived and solved exactly. The influences of mass transfer on transient velocity and state steady temperature profiles are presented and discussed. The wall heat transfer characteristics are also analyzed DA - 2004/5// PY - 2004/5// DO - 10.1016/S0735-1933(04)00030-2 VL - 31 IS - 4 SP - 487–500 SN - 0735-1933 UR - http://dx.doi.org/10.1016/S0735-1933(04)00030-2 ER - TY - JOUR TI - A note on the incompressible couette flow with porous walls AU - Fang, Tiegang T2 - International Communications in Heat and Mass Transfer AB - Analytical solutions play important roles in the understanding of fluid dynamics and heat transfer related problems. Some analytical solutions for incompressible steady/unsteady 2-D problems have been obtained in literature, but only a few of those are found under heat transfer conditions (which brings more complexities into the problem). This paper is focused on the analytical solutions to the basic problem of incompressible unsteady 2-D laminar flows with heat transfer. By using the traveling wave method, fluid dynamic governing equations are developed based on classical Navier–Stokes equations and can be reduced to ordinary differential equations, which provide reliable explanations to the 2-D fluid flows. In this study, a set of analytical solutions to incompressible unsteady 2-D laminar flows with heat transfer are obtained. The results show that both the velocity field and the temperature field take an exponential function form, or a polynomial function form, when traveling wave kind solution is assumed and compared in such fluid flow systems. In addition to heat transfer problem, the effects of boundary input parameters and their categorization and generalization of field forming or field evolutions are also obtained in this study. The current results are also compared with the results of Cai et al. (R. X. Cai, N. Zhang. International Journal of Heat and Mass Transfer, 2002, 45: 2623-2627) and others using different methods. It is found that the current method can cover the results and will also extend the fluid dynamic model into a much wider parameter ranges (and flow situations). DA - 2004/1// PY - 2004/1// DO - 10.1016/S0735-1933(03)00199-4 VL - 31 IS - 1 SP - 31-41 J2 - International Communications in Heat and Mass Transfer LA - en OP - SN - 0735-1933 UR - http://dx.doi.org/10.1016/S0735-1933(03)00199-4 DB - Crossref ER - TY - JOUR TI - Evolution of failure mechanisms in 2D and 3D woven composite systems under quasi-static perforation (vol 37, pg 1651, 2003) AU - Baucom, J. N. AU - Zikry, Mohammed T2 - Journal of Composite Materials AB - The effects of reinforcement geometry, in 2D and 3D woven fabric-reinforced composites, on the progression of damage and perforation failure at quasi-static loading rates (10-80 mm/s) are investigated. The broad classes of glass-fiber-reinforced systems that were examined include 2D plain-woven laminates, 3D orthogonally woven monolithic systems, and 3D orthogonally woven laminates. The experimental results indicate that the 3D laminates consistently had greater damage tolerance than the 2D laminates and the 3D monolithic composites. The enhanced damage tolerance of the 3D systems is due to unique energy absorption mechanisms, which involve the crimped portion of z-tows. DA - 2004/// PY - 2004/// DO - 10.1177/0021998303035178 VL - 38 IS - 6 SP - 535 KW - quasi-static puncture KW - GFRP KW - 3D orthogonal weave KW - damage progression ER - TY - JOUR TI - Effect of temperature on capacitive RF MEMS switch performance—a coupled-field analysis AU - Zhu, Yong AU - Espinosa, Horacio D T2 - Journal of Micromechanics and Microengineering AB - Three-dimensional multiphysics finite element analysis (FEA) was performed to investigate the reliability of RF MEMS switches at various operational temperatures. The investigated MEMS capacitive switch consists of a freestanding metal membrane actuated by a bottom electrode coated by a dielectric film. Coupled-field simulations between thermal, structural and electrostatic domains were performed. The simulations show that temperature significantly changes both the membrane stress state and out-of-plane geometry. In particular, the membrane buckles when temperature increase, from room temperature, takes place. The buckling temperature, i.e. the upper bound to the operational temperature, is a function of manufacturing residual stress state, membrane initial out-of-plane profile and a mismatch in materials coefficient of thermal expansion. The analysis also shows that temperature reduction, from room temperature to −40 °C, causes an increase in pull-in voltage to values that could compromise the switch reliability as a result of charge build-up in the dielectric layer. Our analyses illustrate that by proper designing of the membrane out-of-plane profile, it is possible to keep the pull-in voltage, at all operational temperatures, within allowable values. This design feature of RF MEMS switches offers an effective way to achieve reliable pull-in voltages in applications where large temperature variations are expected such as in satellites and airplane condition monitoring based on wireless communication. DA - 2004/6/22/ PY - 2004/6/22/ DO - 10.1088/0960-1317/14/8/021 VL - 14 IS - 8 SP - 1270-1279 J2 - J. Micromech. Microeng. OP - SN - 0960-1317 1361-6439 UR - http://dx.doi.org/10.1088/0960-1317/14/8/021 DB - Crossref ER - TY - JOUR TI - Reliability of capacitive RF MEMS switches at high and low temperatures AU - Zhu, Yong AU - Espinosa, Horacio D. T2 - International Journal of RF and Microwave Computer-Aided Engineering AB - Some applications of RF MEMS switches, such as aircraft condition monitoring and distributed satellite communication, present a unique challenge for device design and reliability. This article examines these switches when operational temperatures in the range −60°C to 100°C are envisioned. The basic operation of a capacitive MEMS switch is described and two tools for examining device reliability, modeling, and on-chip experimentation, are discussed in the case of capacitive MEMS switches. 1D, 2D, and 3D models are presented with emphasis on 3D coupled-field finite-element analysis, including temperature effects. Results and findings from the 3D simulations are reported. In particular, the advantages of employing corrugated membranes in the design of RF MEMS switches are assessed. Their performance in terms of reliability as a function of temperature is quantified. The effects of corrugation on the geometric parameters are discussed in the context of device-design optimization. In order to assess reliability experimentally, the M-test and the membrane deflection experiment (MDE) are reviewed due to their on-chip characteristic and simplicity. Ways in which these experimental/computational methodologies can be combined for identifying material properties and device performance is also highlighted. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 317–328, 2004. DA - 2004/// PY - 2004/// DO - 10.1002/mmce.20015 VL - 14 IS - 4 SP - 317-328 J2 - Int J RF and Microwave Comp Aid Eng LA - en OP - SN - 1096-4290 1099-047X UR - http://dx.doi.org/10.1002/mmce.20015 DB - Crossref KW - MEMS KW - RF switch KW - reliability KW - mechanical testing KW - MEMS modeling KW - coupled analysis ER - TY - JOUR TI - Fabrication of Particle-Reinforced Polymers with Continuous Gradient Architectures Using Twin Screw Extrusion Process AU - Gallant, Frederick M. AU - Bruck, Hugh A. AU - Kota, Arun K. T2 - Journal of Composite Materials AB - The operation of the twin screw extrusion (TSE) process under transient conditions is investigated for the manufacture of particle-reinforced polymers with continuous gradient architectures. Mixing models of the residence time distribution (RTD) and residence volume distribution (RVD) are used to characterize the TSE process. By convolving the mixing models with the transient input conditions, a new convolution process model has been developed to predict the gradient architectures that evolve within the extrudate. In situ optical contrast measurements and a posteriori measurements of optical contrast, density, and solids loading are used to verify the convolution process model for a step change in the input conditions. DA - 2004/11// PY - 2004/11// DO - 10.1177/0021998304048414 VL - 38 IS - 21 SP - 1873-1893 J2 - Journal of Composite Materials LA - en OP - SN - 0021-9983 1530-793X UR - http://dx.doi.org/10.1177/0021998304048414 DB - Crossref KW - residence time distribution KW - residence volume distribution KW - functionally graded materials KW - gradient architecture KW - polymer composites KW - convolution process model ER - TY - JOUR TI - High-rate flame synthesis of vertically aligned carbon nanotubes using electric field control AU - Merchan-Merchan, Wilson AU - Saveliev, Alexei V. AU - Kennedy, Lawrence A. T2 - Carbon AB - The electric field controlled synthesis of carbon nanomaterials on a Ni-based catalytic support positioned at the fuel side of the opposed flow oxy-flame is studied experimentally. Carbon nanomaterials formed on the probe surface are comparatively analyzed for two characteristic operational modes: a grounded probe mode and a floating probe mode. In a grounded mode a number of various carbon nanostructures are formed depending on the probe location in flame. Observed nanoforms include multi-walled carbon nanotubes (MWNTs), MWNT bundles, helically coiled tubular nanofibers, and ribbon-like coiled nanofibers with rectangular cross-section. The presence of various carbon nanoforms is attributed to the space variation of flame parameters, namely flame temperature and concentration of chemical species. It is found that the presence of an electric potential (floating mode operation) provides the ability to control the nanostructure morphology and synthesis rate. A thick layer (35–40 μm) of vertically aligned carbon nanotubes (VACNTs) is found to be formed on the probe surface in the floating potential mode. This layer is characterized by high uniformity and narrow distribution of nanotube diameters. Overall, the electric field control method demonstrates stabilization of the structure in a wide flame region while growth rate remains dependent on flame location. DA - 2004/// PY - 2004/// DO - 10.1016/j.carbon.2003.12.086 VL - 42 IS - 3 SP - 599-608 J2 - Carbon LA - en OP - SN - 0008-6223 UR - http://dx.doi.org/10.1016/j.carbon.2003.12.086 DB - Crossref KW - carbon nanotubes KW - catalyst support KW - scanning electron microscopy ER - TY - JOUR TI - Vaporizing Microdroplet Inhalation, Transport, and Deposition in a Human Upper Airway Model AU - Zhang, Zhe AU - Kleinstreuer, Clement AU - Kim, Chong S. AU - Cheng, Yung S. T2 - Aerosol Science and Technology AB - Evaluation of injuries from inhalation exposure to toxic fuel requires detailed knowledge of inhaled aerosol transport and deposition in human airways. Focusing on highly toxic, easily volatized JP-8 fuel droplets, the three-dimensional airflow, temperature distributions, and fluid-particle thermodynamics, i.e., droplet motion as well as evaporation, are simulated and analyzed for laminar as well as locally turbulent flow conditions. Specifically, using a commercial finite-volume software with user-supplied programs as a solver, the Euler-Lagrange approach for the fluid-particle thermodynamics is employed with: (1) a low Reynolds number k-ω model for laminar-to-turbulent airflow, and (2) a stochastic model for random fluctuations in the droplet trajectories with droplet evaporation. Presently, the respiratory system consists of two major segments of a simplified human cast replica, i.e., a representative oral airway from mouth to trachea (Generation 0) and a symmetric four-generation upper bronchial tree model (G0 to G3). Experimentally validated computational fluid-particle thermodynamics results show that evaporation of JP-8 fuel droplets is greatly affecting deposition in the human airway. Specifically, droplet deposition fractions due to vaporization decrease with increasing ambient temperatures and decreasing inspiratory flow rates. It is also demonstrated that assuming idealized velocity profiles and particle distributions in or after the trachea may greatly overpredict particle deposition efficiencies in the upper bronchial tree. DA - 2004/1// PY - 2004/1// DO - 10.1080/02786820300985 VL - 38 IS - 1 SP - 36-49 J2 - Aerosol Science and Technology LA - en OP - SN - 0278-6826 1521-7388 UR - http://dx.doi.org/10.1080/02786820490247597 DB - Crossref ER - TY - JOUR TI - INVESTIGATION OF HYSTERESIS IN ACOUSTICALLY DRIVEN CHANNEL FLOW AT ULTRASONIC FREQUENCY AU - Wan, Qun AU - Kuznetsov, A. V. T2 - Numerical Heat Transfer, Part A: Applications AB - ABSTRACT The purpose of this article is to investigate the hysteresis phenomenon in the acoustic streaming flow in a channel. The channel is bounded by one stationary beam and one beam vibrating in a standing wave form. According to Wan and Kuznetsov [1-2 Q. Wan and A. V. Kuznetsov , Streaming in a Channel Bounded by an Ultrasonically Oscillating Beam and Its Cooling Efficiency , Numer. Heat Transfer A , vol. 45 , pp. 21 – 47 , 2004 . Q. Wan and A. V. Kuznetsov , Theoretical Analysis of Oscillating and Streaming Fields between Two Parallel Beams and Numerical Investigation of the Cooling Efficiency , ASME Summer Heat Transfer Conf. , Las Vegas , NV , ASME Paper HT2003-40367 , 2003 . ], the acoustic streaming within the channel is driven by the slip velocity at the edge of the acoustic boundary layer near the vibrating beam. The streaming flow exhibits two different types of flow patterns at small and large channel widths. In this article, a transition between these two flow patterns and the corresponding jump in the Nusselt number as the channel width changes is investigated. As a result of extensive numerical investigations, a hysteretic region is discovered. When the channel width falls into the hysteresis region, the flow pattern and the heat transfer efficiency depends on whether the channel width is increasing or decreasing. Outside the hysteresis region, such dependence does not exist. DA - 2004/12/20/ PY - 2004/12/20/ DO - 10.1080/10407780590885873 VL - 47 IS - 2 SP - 137-146 J2 - Numerical Heat Transfer, Part A: Applications LA - en OP - SN - 1040-7782 1521-0634 UR - http://dx.doi.org/10.1080/10407780590885873 DB - Crossref ER - TY - JOUR TI - Laminar forced convection in curved channel with vortex structures AU - Avramenko, A. A. AU - Kobzar, S. G. AU - Shevchuk, I. V. AU - Kuznetsov, A. V. AU - Basok, B. I. T2 - Journal of Thermal Science DA - 2004/5// PY - 2004/5// DO - 10.1007/s11630-004-0023-6 VL - 13 IS - 2 SP - 143-150 J2 - J. of Therm. Sci. LA - en OP - SN - 1003-2169 1993-033X UR - http://dx.doi.org/10.1007/s11630-004-0023-6 DB - Crossref KW - heat transfer KW - Dean vortexes KW - curvilinear channel KW - quadrature ER - TY - JOUR TI - High fidelity blazed grating replication using nanoimprint lithography AU - Chang, Chih-Hao AU - Montoya, J. C. AU - Akilian, M. AU - Lapsa, A. AU - Heilmann, R. K. AU - Schattenburg, M. L. AU - Li, M. AU - Flanagan, K. A. AU - Rasmussen, A. P. AU - Seely, J. F. AU - Laming, J. M. AU - Kjornrattanawanich, B. AU - Goray, L. I. T2 - Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures AB - We report progress in using nanoimprint lithography to fabricate high fidelity blazed diffraction gratings. Anisotropically etched silicon gratings with 200nm period and 7.5° blaze angle were successfully replicated onto 100mm diameter wafers with subnanometer roughness and excellent profile conformity. Out-of-plane distortion induced by residual stress from polymer films was also analyzed and found to be extremely low. The replicated blazed gratings were tested and demonstrated high x-ray diffraction efficiencies. This process was developed for fabricating blazed diffraction gratings for the NASA Constellation-X x-ray telescope. DA - 2004/// PY - 2004/// DO - 10.1116/1.1809614 VL - 22 IS - 6 SP - 3260 J2 - J. Vac. Sci. Technol. B LA - en OP - SN - 0734-211X UR - http://dx.doi.org/10.1116/1.1809614 DB - Crossref ER - TY - JOUR TI - Numerical investigation of buoyancy effects on triple flame stability AU - Echekki, T. AU - Chen, J.-Y. AU - Hegde, U. T2 - Combustion Science and Technology DA - 2004/// PY - 2004/// VL - 176 IS - 3 SP - 381-407 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1542316705&partnerID=MN8TOARS ER - TY - JOUR TI - On the computation of multi-material flows using ALE formulation AU - Luo, H AU - Baum, JD AU - Lohner, R T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - Computation of compressible multi-fluid flows with a general equation of state using interface tracking and moving grid approach is discussed in this paper. The AUSM+, HLLC, and Godunov methods are presented and implemented in the context of arbitrary Lagrangian–Eulerian formulation for solving the unsteady compressible Euler equations. The developed methods are fully conservative, and used to compute a variety of multi-component flow problems, where the equations of state can be drastically different and stiff. Numerical results indicate that both ALE HLLC and Godunov schemes demonstrate their simplicity and robustness for solving such multi-phase flow problems, and yet ALE AUSM+ scheme exhibits strong oscillations around material interfaces even using a first order monotone scheme and therefore is not suitable for this class of problems. DA - 2004/2/10/ PY - 2004/2/10/ DO - 10.1016/j.jcp.2003.09.026 VL - 194 IS - 1 SP - 304-328 SN - 0021-9991 ER - TY - JOUR TI - Optimizing tube hydroforming using process simulation and experimental verification AU - Aue-u-lan, Y. AU - Ngaile, G. AU - Altan, T. T2 - Journal of Materials Processing Technology AB - The success of a tube hydroforming (THF) process is highly dependent on the loading paths (axial feed versus pressure) used. Finite element (FE)-based simulation was used to determine optimum loading paths for hydroforming of structural parts with different tubular materials. Experimental and simulation results have demonstrated that FE-based loading paths can significantly reduce trial and error, enhance productivity and expand the THF capability in forming complex parts. The test results also demonstrated that the reliability of the FE-based loading paths is highly dependent on the accuracy of the material properties of the blank, interface friction, and how close the properties of the welding zone are to the base material of the tubular blank. DA - 2004/// PY - 2004/// DO - 10.1016/S0924-0136(03)00854-9 VL - 146 SP - 137-143 KW - tube hydroforming KW - FEM KW - simulation ER - TY - JOUR TI - Optimization of mechanical crimping to assemble tubular components AU - Shirgaokar, M. AU - Cho, H. AU - Ngaile, G. AU - Altan, T. AU - Yu, J.-H. AU - Balconi, J. AU - Rentfrow, R. AU - Worrell, W. J. T2 - Journal of Materials Processing Technology AB - The crimping process is used often in the assembly of tubular components. In this study, with the aid of the finite-element method (FEM), the mechanical crimping operation was evaluated and optimized for a specific application. The effect of various process variables, such as the geometry, alignment and stroke of the crimper and the friction at the crimper–tube interface were investigated. Thus, it was possible to optimize the process so that the effect of springback could be reduced and the assembly quality, as indicated by the pullout force, could be improved. The crimping process of a single-grooved rod with a tube was evaluated as a case study. Based on the FE simulations, it was possible to determine the optimum alignment and the optimum design for two types of crimper geometries. DA - 2004/// PY - 2004/// DO - 10.1016/S0924-0136(03)00842-2 VL - 146 SP - 35-43 KW - assembly KW - crimping KW - pullout test KW - FEM ER - TY - JOUR TI - Optimization of blank dimensions to reduce springback in the flexforming process AU - Palaniswamy, H. AU - Ngaile, G. AU - Altan, T. T2 - Journal of Materials Processing Technology AB - In sheet metal forming operations, springback of the part during unloading largely determines whether the part conforms to the design dimensions and tolerances. Finite element simulations were performed in order to study the interrelationship of the blank dimensions and interface conditions on the springback for an axisymmetric conical part manufactured by flexforming. Sensitivity analysis done using the finite element method (FEM) demonstrated that the magnitude of springback and the overall dimensional quality are highly influenced by the initial dimensions of the blank. A conventional optimization method combined with FEM was used to obtain optimum blank dimensions that can reduce springback. DA - 2004/// PY - 2004/// DO - 10.1016/S0924-0136(03)00841-0 VL - 146 SP - 28-34 KW - finite element KW - flexforming KW - springback KW - optimization ER - TY - JOUR TI - Lubrication in tube hydroforming (THF). Part II: Performance evaluation of lubricants using LDH test and pear-shaped tube expansion test AU - Ngaile, G. AU - Jaeger, S. AU - Altan, T. T2 - Journal of Materials Processing Technology AB - Two model tests to evaluate lubricant performance under realistic tribological conditions occurring in the transition and expansion zones of a tube hydroforming (THF) process are presented. The model test for the transition zone is based on the limiting dome height (LDH) test principle. For the expansion zone, a pear-shaped tube expansion test (PET) developed by the authors is employed. Four lubricants were tested and ranked based on (a) dome wall thinning behavior (for LDH), (b) tube wall thinning, tube protrusion height (PH), tube bursting pressure (for PET), and (c) surface topography. Friction coefficients for the lubricants were estimated by matching the experimental and FE results. DA - 2004/// PY - 2004/// DO - 10.1016/S0924-0136(03)00851-3 VL - 146 SP - 116-123 KW - limiting dome-height KW - pear-shaped tube expansion test KW - tube hydroforming process ER - TY - JOUR TI - Lubrication in tube hydroforming (THF). Part I: Lubrication mechanisms and development of model tests to evaluate lubricants and die coatings in the transition and expansion zones AU - Ngaile, G. AU - Jaeger, S. AU - Altan, T. T2 - Journal of Materials Processing Technology AB - The lubrication mechanisms that occur at the tool–workpiece interface for the transition and expansion zones are discussed. Suitable lubrication systems for the transition and expansion zones are reviewed based on the mechanics of deformation and material flow at the interface. Details of two model tests for evaluating the performance of tube hydroforming (THF) lubricants and die coatings are given. The optimization of die geometries for the model tests is based on sensitivity analysis through the finite element method together with experimental verification. The details of these tests are given and their development is discussed. DA - 2004/// PY - 2004/// DO - 10.1016/S0924-0136(03)00850-1 VL - 146 SP - 108-115 KW - tube hydroforming KW - lubrication KW - finite element method ER - TY - JOUR TI - Hydraulic crimping: Application to the assembly of tubular components AU - Shirgaokar, M. AU - Ngaile, G. AU - Altan, T. AU - Yu, J.-H. AU - Balconi, J. AU - Rentfrow, R. AU - Worrell, W. J. T2 - Journal of Materials Processing Technology AB - The crimping process using a polyurethane tool and hydraulic pressure can be used in the assembly of tubular components. This crimping operation was evaluated with the aid of the finite element method (FEM) and its application to the assembly of tubular components was investigated. The goal was to enhance the performance of the assembly by determining the optimum process and geometrical parameters, such as the material properties of the tube, the interference between the inserted rod and the tube and the rod–tube interface friction. FE simulations were used to evaluate the crimping operation under various process conditions. The crimping process of a double grooved rod/bullet with a tubular casing was evaluated as a case study. It was possible to determine the effect of manufacturing tolerances and misalignment between the rod and the casing on the quality of the final assembly in terms of the pullout force. DA - 2004/// PY - 2004/// DO - 10.1016/S0924-0136(03)00843-4 VL - 146 SP - 44-51 KW - assembly KW - crimping KW - pullout test KW - FEM ER - TY - JOUR TI - Finite element simulation of magnesium alloy sheet forming at elevated temperatures AU - Palaniswamy, H. AU - Ngaile, G. AU - Altan, T. T2 - Journal of Materials Processing Technology AB - The use of lightweight magnesium (Mg) alloy offers significant potential to improve automotive fuel efficiency. However, the application of formed magnesium alloy components in auto-body structures is restricted due to this material’s low formability at room temperature and lack of knowledge for processing magnesium alloys at elevated temperature. In this study, non-isothermal finite element (FE) simulation has been conducted for forming round cups and rectangular pans from Mg alloy AZ31B sheet at elevated temperatures. The results were compared with experiments, conducted at the Technical University, Hanover. Simulation and experiments predicted increase in limiting draw ratio (LDR) with increase in temperature. Maximum LDR was obtained at the forming temperature of 200 °C. FE simulation results agreed well with experimental observations. DA - 2004/// PY - 2004/// DO - 10.1016/S0924-0136(03)00844-6 VL - 146 SP - 52-60 KW - finite element KW - magnesium KW - warm sheet forming ER - TY - JOUR TI - Determination of flow stress for sheet metal forming using the viscous pressure bulge (VPB) test AU - Gutscher, G. AU - Wu, H.-C. AU - Ngaile, G. AU - Altan, T. T2 - Journal of Materials Processing Technology AB - In sheet metal forming operations the mechanical properties of the sheet material (i.e. flow stress or stress–strain curve) greatly influence metal flow and product quality. Therefore, accurate determination of the flow stress is of paramount importance in process simulation via finite element method (FEM). In this paper the use of the viscous pressure bulge (VPB) test for determination of flow stress under biaxial state of stress is discussed. With the VPB test, larger strains, which are relevant for stamping operations, can be achieved compared to the standard tensile test used to-date. In this study, FEM simulations and experiments have been performed in order to study the interrelationship of the geometric and material variables such as dome wall thinning, dome radius, dome height, strain hardening index, material strength coefficient, and anisotropy. From the study a robust method to determine the flow stress under biaxial deformation conditions using a viscous material as pressure medium has been developed. DA - 2004/// PY - 2004/// DO - 10.1016/S0924-0136(03)00838-0 VL - 146 SP - 1-7 KW - sheet metal forming KW - formability KW - flow stress KW - FEM ER - TY - BOOK TI - Cold and hot forging: Fundamentals and applications DA - 2004/// PY - 2004/// PB - Materials Park, Ohio: ASM International SN - 0871708051 ER - TY - CONF TI - A shaft design aid for integrating basic elements of introductory machine design AU - Tollner, E. W. AU - Huang, H.-Y. S. C2 - 2004/// C3 - American Society for Engineering Education Annual Conference & Exposition, Salt Lake City, Utah DA - 2004/// SP - 66 ER - TY - JOUR TI - A new thermal conductivity model for nanofluids AU - Koo, J AU - Kleinstreuer, C T2 - JOURNAL OF NANOPARTICLE RESEARCH DA - 2004/12// PY - 2004/12// DO - 10.1007/s11051-004-3170-5 VL - 6 IS - 6 SP - 577-588 SN - 1572-896X KW - nanofluids KW - effective thermal conductivity KW - apparent thermal conductivity KW - Brownian motion KW - interparticle potential KW - modeling and simulation ER - TY - JOUR TI - Numerical modeling of a falling bioconvection plume in a porous medium AU - Becker, SM AU - Kuznetsov, AV AU - Avramenko, AA T2 - FLUID DYNAMICS RESEARCH AB - This paper considers a bioconvection plume in a fluid saturated porous medium. Bioconvection plumes may arise as a result of an unstable density stratification caused by up-swimming microorganisms. This unstable density stratification occurs when the microorganisms, heavier than water, accumulate in the upper regions of the fluid. The plume transports cells and oxygen from the upper fluid region to the lower fluid regions. This paper finds a numerical solution for the steady-state plume in a porous medium by utilizing an implicit finite difference method. The effects of varying pertinent parameters are investigated. A similarity solution of the plume is also obtained for comparison purposes. DA - 2004/11// PY - 2004/11// DO - 10.1016/j.fluiddyn.2004.07.003 VL - 35 IS - 5 SP - 323-339 SN - 1873-7005 KW - bioconvection KW - oxytactic bacteria KW - plume KW - porous media ER - TY - JOUR TI - Manipulation of nanoparticles in supersonic beams for the production of nanostructured materials AU - Piseri, P AU - Tafreshi, HV AU - Milani, P T2 - CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE AB - Production and manipulation of nanoparticles in the gas phase is of primary importance for the synthesis of nanostructured materials and for the development of industrial processes based on nanotechnology. In this review we will present and discuss the approach based on the use of aerodynamic focusing methods coupled to supersonic expansions to obtain high intensity cluster beams with a control on nanoparticle mass and spatial distribution. The implication of this techniques for the synthesis of nanostructured materials will be also presented. DA - 2004/// PY - 2004/// DO - 10.1016/j.cossms.2004.08.002 VL - 8 IS - 3-4 SP - 195-202 SN - 1879-0348 KW - nanoparticles KW - supersonic beams KW - aerodynamic focusing KW - nanostructured materials ER - TY - JOUR TI - Effects of leading edge entrainment on the double flame structure in lifted ethanol spray flames AU - Marley, S. K. AU - Welle, E. J. AU - Lyons, K. M. AU - Roberts, W. L. T2 - Experimental Thermal and Fluid Science DA - 2004/// PY - 2004/// DO - 10.1016/j.ecpthermflusci.2004.01.009 VL - 29 IS - 1 SP - 23-31 ER - TY - JOUR TI - Computational analysis of an independent ramjet stream in a combined cycle engine AU - Bond, RB AU - Edwards, , JR T2 - AIAA JOURNAL AB - A new concept for the low-speed propulsion mode in rocket-based combined cycle engines has been developed as part of the NASA GTX program. This concept, called the independent ramjet stream (IRS) cycle, is a variation of the traditional ejector ramjet (ER) design and involves the injection of hydrogen fuel directly into the airstream, where it is ignited by the rocket plume. The advantage of the IRS design is that it allows for a single large rocket instead of several smaller rockets, and its required combustor length is smaller than that of a traditional ER design. Both of these features make the IRS design lighter. Experiments and computational fluid dynamics are currently being used to evaluate the feasibility of the new design. In this work, a Navier‐Stokes code valid for general reactive flows is applied to the model engine under cold-flow, ER, and IRS cycle operation. Pressure distributions corresponding to cold-flow and ER operation are compared with experimental data. The engine response under IRS cycle operation is examined for different reaction models and grid sizes. The solutions exhibit a high sensitivity to both grid resolution and reaction mechanism but do indicate that thermal throat ramjet operation is possible through the injection and burning of additional fuel into the airstream. DA - 2004/11// PY - 2004/11// DO - 10.2514/1.4465 VL - 42 IS - 11 SP - 2276-2283 SN - 1533-385X ER - TY - JOUR TI - An analytical finite element technique for predicting thrust force and torque in drilling AU - Strenkowski, JS AU - Hsieh, CC AU - Shih, A T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE AB - An analytical finite element technique was developed for predicting the thrust force and torque in drilling with twist drills. The approach was based on representing the cutting forces along the cutting lips as a series of oblique sections. Similarly, cutting in the chisel region was treated as orthogonal cutting with different cutting speeds depending on the radial location. For each section, an Eulerian finite element model was used to simulate the cutting forces. The section forces were combined to determine the overall thrust force and drilling torque. Good agreement between the predicted and measured forces and torques was found in orthogonal and oblique cutting and in drilling tests. The drilling tests were performed on AISI 1020 for several drill diameters, spindle speeds, and feed rates. An extension of the technique for predicting drill temperatures has also been described. DA - 2004/10// PY - 2004/10// DO - 10.1016/j.ijmachtools.2004.01.005 VL - 44 IS - 12-13 SP - 1413-1421 SN - 1879-2170 KW - finite element modeling KW - drilling KW - drilling thrust force and torque ER - TY - JOUR TI - Interacting effects of uniform flow, plane shear, and near-wall proximity on the heat and mass transfer of respiratory aerosols AU - Longest, PW AU - Kleinstreuer, C T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - Individual and interacting effects of uniform flow, plane shear, and near-wall proximity on spherical droplet heat and mass transfer have been assessed for low Reynolds number conditions beyond the creeping flow regime. Validated resolved volume simulations were used to compute heat and mass transfer surface gradients of two-dimensional axisymmetric droplets and three-dimensional spherical droplets near planar wall boundaries for conditions consistent with inhalable aerosols (5 ⩽ d ⩽ 300 μm) in the upper respiratory tract. Results indicate that planar shear significantly impacts droplet heat and mass transfer for shear-based Reynolds numbers greater than 1, which occur for near-wall respiratory aerosols with diameters in excess of 50 μm. Wall proximity is shown to significantly enhance heat and mass transfer due to conduction and diffusion at separation distances less than five particle diameters and for small Reynolds numbers. For the Reynolds number conditions of interest, significant non-linear effects arise due to the concurrent interaction of uniform flow and shear such that linear superposition of Sherwood or Nusselt number terms is not allowable. Based on the validated numeric simulations, multivariable Sherwood and Nusselt number correlations are provided to account for individual flow characteristics and concurrent non-linear interactions of uniform flow, planar shear, and near-wall proximity. These heat and mass transfer correlations can be applied to effectively compute condensation and evaporation rates of potentially toxic or therapeutic aerosols in the upper respiratory tract, where non-uniform flow and wall proximity are expected to significantly affect droplet transport, deposition, and vapor formation. DA - 2004/10// PY - 2004/10// DO - 10.1016/j.ijheatmasstransfer.2004.05.029 VL - 47 IS - 22 SP - 4745-4759 SN - 1879-2189 KW - droplet heat and mass transfer KW - respiratory aerosols KW - near-wall droplet evaporation KW - droplet Nusselt and Sherwood number correlations ER - TY - JOUR TI - Tool force and deflection compensation for small milling tools AU - Dow, TA AU - Miller, EL AU - Garrard, K T2 - PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY AB - A technique to compensate for deflection of small milling tools (diameter<1 mm) has been demonstrated. This open-loop technique involves predicting the cutting and thrust forces, applying these forces to the tool, calculating the shape error due to tool deflection and creating a new tool path to eliminate this error. The tool force model has evolved from a decade of research to predict the forces in diamond turning. This model was modified to include the effects of tool rotation in milling as well as the changes in contact area and force direction using a ball end mill to create a free form surface. Experimental measurements were made to corroborate the components of the tool forces in the cutting and thrust directions. The force model was then combined with tool stiffness to calculate the deflection of the tool as a function of the depth of cut, the up-feed per revolution and the geometry of the part. Two experiments were used to demonstrate the effectiveness of this error compensation technique—a slot and a large circular groove. Each experiment reduced the error due to tool deflection by an order of magnitude from 20–50 μm to 2–5 μm. DA - 2004/1// PY - 2004/1// DO - 10.1016/S0141-6359(03)00072-2 VL - 28 IS - 1 SP - 31-45 SN - 1873-2372 KW - milling KW - machining forces KW - tool deflection KW - tool stiffness KW - error compensation ER - TY - JOUR TI - Structural health monitoring and damage detection using an intelligent parameter varying (IPV) technique AU - Saadat, S AU - Noori, MN AU - Buckner, GD AU - Furukawa, TD AU - Suzuki, Y T2 - INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS AB - Most structural health monitoring and damage detection strategies utilize dynamic response information to identify the existence, location, and magnitude of damage. Traditional model-based techniques seek to identify parametric changes in a linear dynamic model, while non-model-based techniques focus on changes in the temporal and frequency characteristics of the system response. Because restoring forces in base-excited structures can exhibit highly non-linear characteristics, non-linear model-based approaches may be better suited for reliable health monitoring and damage detection. This paper presents the application of a novel intelligent parameter varying (IPV) modeling and system identification technique, developed by the authors, to detect damage in base-excited structures. This IPV technique overcomes specific limitations of traditional model-based and non-model-based approaches, as demonstrated through comparative simulations with wavelet analysis methods. These simulations confirm the effectiveness of the IPV technique, and show that performance is not compromised by the introduction of realistic structural non-linearities and ground excitation characteristics. DA - 2004/12// PY - 2004/12// DO - 10.1016/j.ijnonlinmec.2004.03.001 VL - 39 IS - 10 SP - 1687-1697 SN - 1878-5638 KW - system identification KW - artificial neural networks KW - hysteresis KW - non-linear systems KW - damage detection KW - structural health monitoring KW - wavelet analysis ER - TY - JOUR TI - Strong magnetic field asymptotic model for binary alloyed semiconductor crystal growth AU - Wang, X AU - Ma, N T2 - JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER AB - We present an asymptotic model for the unsteady species transport during bulk growth of alloyed semiconductor crystals with a transverse magnetic field. During growth of alloyed semiconductors such as germanium-silicon (GeSi), 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 melt motion and the distribution of species for a crystal grown in a strong transverse magnetic field DA - 2004/// PY - 2004/// DO - 10.2514/1.11905 VL - 18 IS - 4 SP - 476-480 SN - 1533-6808 ER - TY - JOUR TI - Numerical modeling of turbulent flow in a composite porous/fluid duct utilizing a two-layer k-epsilon model to account for interface roughness AU - Kuznetsov, A T2 - INTERNATIONAL JOURNAL OF THERMAL SCIENCES AB - This paper is aimed at investigating the effect of roughness of the porous/fluid interface on turbulent convection heat transfer in composite porous/fluid ducts. It is expected that in many cases the effect of interface roughness on convection may be more significant than the effect of possible flow turbulization in the porous region. The analysis of appropriate dimensionless parameters shows that in many practical situations even if the flow in the clear fluid region is turbulent, the flow in the porous region remains laminar. The problem is thus reduced to matching the turbulent flow solution in the clear fluid region with the laminar flow solution in the porous region at the rough interface. It is shown that roughness of the porous/fluid interface significantly impacts turbulent flow in the clear fluid region as well as overall heat transfer in the duct. DA - 2004/11// PY - 2004/11// DO - 10.1016/j.ijthermalsci.2004.02.011 VL - 43 IS - 11 SP - 1047-1056 SN - 1778-4166 ER - TY - JOUR TI - Modeling the thermal protective performance of heat resistant garments in flash fire exposures AU - Song, GW AU - Barker, RL AU - Hamouda, H AU - Kuznetsov, AV AU - Chitrphiromsri, P AU - Grimes, RV T2 - TEXTILE RESEARCH JOURNAL AB - This research developes a numerical model to predict skin burn injury resulting from heat transfer through a protective garment worn by an instrumented manikin exposed to laboratory-controlled flash fire exposures. This model incorporates characteristics of the simulated flash fire generated in the chamber and the heat-induced changes in fabric thermophysical properties. The model also accounts for clothing air layers between the garment and the manikin. The model is validated using an instrumented manikin fire test system. Results from the numerical model help contribute to a better understanding of the heat transfer process in protective garments exposed to intense flash fires, and to establishing systematic methods for engineering materials and garments to produce optimum thermal protective performance. DA - 2004/12// PY - 2004/12// DO - 10.1177/004051750407401201 VL - 74 IS - 12 SP - 1033-1040 SN - 0040-5175 ER - TY - JOUR TI - Kinematics and wear of tool blades for scrap tire shredding AU - Shih, AJ AU - McCall, RC T2 - MACHINING SCIENCE AND TECHNOLOGY AB - Abstract The wear of tool blades for cost-effective scrap tire shredding is investigated. Rotary disk cutters are widely used for cutting scrap tires into small pieces. The hard, wear-resistant tool blades mounted on the periphery of disk cutters maintain a narrow gap between blades and generate the cutting action. The kinematics of the relative motion of two adjacent disk cutters is derived to model the overlap region on blades during cutting. The model predictions match well with the actual shapes of the worn regions on used tool blades. The wear of tool blades made of AISI D2 and CRU-WEAR (CW) tool steels for scrap tire shredding is evaluated. A coordinate measurement machine was used to measure the tool wear. The wear on the blade surface is not uniform. Regions with high wear rate are explained using the kinematics analysis. The CW blades show a lower wear rate, about half of that of D2 blades, and a potential choice for cost savings. DA - 2004/3// PY - 2004/3// DO - 10.1081/MST-200028728 VL - 8 IS - 2 SP - 193-210 SN - 1091-0344 KW - scrap tire processing KW - kinematics KW - tool wear ER - TY - JOUR TI - Interaction of transverse heterogeneity and thermal development of forced convection in a porous medium AU - Nield, DA AU - Kuznetsov, AV T2 - TRANSPORT IN POROUS MEDIA DA - 2004/10// PY - 2004/10// DO - 10.1023/B:TIPM.0000032701.17429.97 VL - 57 IS - 1 SP - 103-111 SN - 1573-1634 KW - transverse heterogeneity KW - thermal development KW - forced convection KW - Graetz problem ER - TY - JOUR TI - Hybrid large-eddy/Reynolds-averaged Navier-Stokes simulations of shock-separated flows AU - Fan, CC AU - Xiao, XD AU - Edwards, , JR AU - Hassan, HA 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 - 2004/// PY - 2004/// DO - 10.2514/1.3735 VL - 41 IS - 6 SP - 897-906 SN - 1533-6794 ER - TY - JOUR TI - Extended anti-windup control schemes for LTI and LFT systems with actuator saturations AU - Wu, Fen AU - Soto, Marco T2 - International Journal of Robust and Nonlinear Control AB - Abstract In this paper, the popular anti‐windup control scheme will be extended in two important directions. The first scenario is the control of LTI systems subject to actuators with both magnitude and rate constraints. The second case of extension is LFT systems with input saturations. Based on the extended Circle criterion, we will develop convex anti‐windup control synthesis conditions in the form of LMIs for each class of systems. The explicit anti‐windup controller formula are also provided to facilitate compensator construction. The effectiveness of proposed anti‐windup control schemes will be demonstrated using a flight control example. Copyright © 2004 John Wiley & Sons, Ltd. DA - 2004/10// PY - 2004/10// DO - 10.1002/rnc.943 VL - 14 IS - 15 SP - 1255-1281 J2 - Int. J. Robust Nonlinear Control LA - en OP - SN - 1049-8923 1099-1239 UR - http://dx.doi.org/10.1002/rnc.943 DB - Crossref KW - input magnitude and rate saturations KW - anti-windup compensation KW - stability and performance KW - linear matrix inequality (LMI) KW - controller construction ER - TY - JOUR TI - Efficient computation of micro-particle dynamics including wall effects AU - Longest, PW AU - Kleinstreuer, C AU - Buchanan, , JR T2 - COMPUTERS & FLUIDS AB - This study describes an effective method for one-way coupled Eulerian–Lagrangian simulations of spherical micro-size particles, including particle–wall interactions and the quantification of near-wall stasis at possibly elevated concentrations. The focus is on particle-hemodynamics simulations where particle suspensions are composed of critical blood cells, such as monocytes, and the carrier fluid is non-Newtonian. Issues regarding adaptive time-step integration of the particle motion equation, relevant point-force model terms, and adaptation of surface-induced particle forces to arbitrary three-dimensional geometries are outlined. By comparison to available experimental trajectories, it is shown that fluid-element pathlines may be used to simulate non-interacting blood particles removed from wall boundaries under dilute transient conditions. However, when particle–wall interactions are significant, an extended form of the particle trajectory equation is required which includes terms for Stokes drag, near-wall drag modifications, or lubrication forces, pressure gradients, and near-wall particle lift. Still, additional physical and/or biochemical wall forces in the nano-meter range cannot be readily calculated; hence the near-wall residence time (NWRT) model indicating the probability of blood particle deposition is presented. The theory is applied to a virtual model of a femoral bypass end-to-side anastomosis, where profiles of the Lagrangian-based NWRT parameter are illustrated and convergence is verified. In order to effectively compute the large number of particle trajectories required to resolve regions of particle stasis, the proposed particle tracking algorithm stores all transient velocity field solution data on a shared memory architecture (SGI Origin 2400) and computes particle trajectories using an adaptive parallel approach. Compared to commercially available particle tracking packages, the algorithm presented is capable of reducing computational time by an order of magnitude for typical transient one-way coupled blood particle simulations in complex cyclical flow domains. DA - 2004/5// PY - 2004/5// DO - 10.1016/j.compfluid.2003.06.002 VL - 33 IS - 4 SP - 577-601 SN - 0045-7930 ER - TY - JOUR TI - Effect of the interface roughness on turbulent convective heat transfer in a composite porous/fluid duct AU - Kuznetsov, AV AU - Becker, SM T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - Flow over a finite porous medium is investigated using different interfacial conditions. In such configuration, a macroscopic interface is identified between the two media. In the first model, no diffusion-flux is considered when treating the statistical energy balance at the interface. The second approach assumes that diffusion fluxes of turbulent kinetic energy on both sides of the interface are unequal. Comparing these two models, this paper presents numerical solutions for such hybrid medium, considering here a channel partially filled with a porous layer through which fluid flows in turbulent regime. One unique set of transport equations is applied to both regions. Effects of Reynolds number, porosity, permeability and jump coefficient on mean and turbulence fields are investigated. Results indicate that depending on the value of the stress jump parameter, substantially dissimilar fields for the turbulence energy are obtained. Negative values for the stress jump parameter give results closer to experimental data for the turbulent kinetic energy at the interface. DA - 2004/1// PY - 2004/1// DO - 10.1016/s0735-1933(03)00197-0 VL - 31 IS - 1 SP - 11-20 SN - 0735-1933 ER - TY - JOUR TI - Effect of small particles on the stability of bioconvection in a suspension of gyrotactic microorganisms in a layer of finite depth AU - Kuznetsov, AV AU - Avramenko, AA T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - An analysis of the bioconvective slump point flow of nanofluid is addressed. The studied nanofluid, which contains gyrotactic microorganisms, was investigated in a porous medium on a nonlinear tensile plate in which it was placed. The scaling group transformation approach converted the analyzed PDEs to ODEs. ODEs obtained are solved using the numerical method (rkf-45) and AGM, and the results are compared with DTM and RKF methods. The accuracy of the obtained answers is remarkable compared to the mentioned methods. An increase in the density of motile microorganism distribution caused by the increment in values of bioconvection Peclet number is desired. In addition, a rapid increase in heat transfer rate and mass transfer rate happens when there is an increase in the thermophoresis parameter, heat source parameter, chemical reaction parameter, and Brownian motion parameter in a sequence. In this study, we investigated the SPF of bioconvective nanofluids containing GM. It is observed that the flow velocity increases as Da−1 decreases. As Rb increases, bioconvection increases. These studies may be used for biotechnological applications, such as the design of bioconjugates or the increase of mass transfer in microfluidics. DA - 2004/1// PY - 2004/1// DO - 10.1016/s0735-1933(03)00196-9 VL - 31 IS - 1 SP - 1-10 SN - 0735-1933 ER - TY - JOUR TI - Combined effects of rotating magnetic field and rotating system on the thermocapillary instability in the floating zone crystal growth process AU - Ma, N AU - Walker, JS AU - Witkowski, LM T2 - JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME AB - This paper presents a linear stability analysis for the thermocapillary convection in a liquid bridge bounded by two planar liquid-solid interfaces at the same temperature and by a cylindrical free surface with an axisymmetric heat input. The two solid boundaries are rotated at the same angular velocity in one azimuthal direction, and a rotating magnetic field is applied in the opposite azimuthal direction. The critical values of the Reynolds number for the thermocapillary convection and the critical-mode frequencies are presented as functions of the magnetic Taylor number for the rotating magnetic field and of the Reynolds number for the angular velocity of the solid boundaries. DA - 2004/4// PY - 2004/4// DO - 10.1115/1.1666883 VL - 126 IS - 2 SP - 230-235 SN - 1528-8943 KW - crystal growth KW - heat transfer KW - magnetohydrodynamics KW - stability KW - thermocapillary ER - TY - JOUR TI - Blending functions in hybrid large-eddy/Reynolds-averaged Navier-Stokes simulations AU - Xiao, X AU - Edwards, , JR AU - Hassan, HA T2 - AIAA JOURNAL AB - Several blending functions for use in hybrid large-eddy simulation (LES)/Reynolds-averaged Navier-Stokes (RANS) simulations of shock-separated flows are tested. The blending functions shift the turbulence closure from a k-ζ turbulence model near solid surfaces to a k − ∆ subgrid closure away from the wall. Three distinct forms for the blending function are developed: one that depends on the ratio of the von Karman length scale and the Taylor microscale, another that depends on the ratio of the RANS eddy viscosity to the subgrid eddy viscosity, and a third which replaces the von Karman length scale in the first form with the distance to the nearest wall. Comparisons are made for two cases: Mach 2.79 flow over a 20-deg compression corner and Mach 2.88 flow over a 25-deg compression/expansion corner. boundary conditions for all calculations employ the rescaling/reintroducing procedure developed by Xiao et al. (Xiao, X., Edwards, J. R., Hassan, H. A., and Baurle, R. A., Inflow Boundary Conditions for Hybrid Large Eddy/Reynolds Averaged Navier-Stokes Simulations, AIAA Journal ,V ol. 41, No. 8, 2003, pp. 1481-1489) for hybrid LES/RANS simulations of wall-bounded flows. In general, the blending function based on the von Karman length scale gives the best results when compared with measured data. The skin friction predictions show the highest sensitivity to the various blending functions. DA - 2004/12// PY - 2004/12// DO - 10.2514/1.2094 VL - 42 IS - 12 SP - 2508-2515 SN - 0001-1452 ER - TY - JOUR TI - Three-dimensional numerical simulation of a circulating fluidized bed reactor for multi-pollutant control AU - Mao, DM AU - Edwards, , JR AU - Kuznetsov, AV AU - Srivastava, RK T2 - CHEMICAL ENGINEERING SCIENCE AB - Circulating fluidized bed adsorber (CFBA) technology is regarded as a potentially effective method for simultaneously controlling emissions of sulfur dioxide, fine particulate matter, and trace heavy metals, such as mercury vapor. In order to analyze CFBA systems in detail, a gas mixture/solids mixture model based on the three-dimensional Navier–Stokes equations is developed for particle flow, agglomeration, physical and chemical adsorption in a circulating fluidized bed. The solids mixture consists of two solids, one with components of CaO and CaSO4, and the other being an activated carbon. The gas mixture is composed of fine particulate matter (PM), sulfur dioxide, mercury vapor, oxygen and inert gas. Source terms representing fine particulate matter agglomeration onto sorbent particles, sulfur dioxide removal through chemical adsorption onto calcined lime, and mercury vapor removal through physical adsorption onto activated carbon are formulated and included into the model. The governing equations are solved using high-resolution upwind-differencing methods, combined with a time-derivative preconditioning method for efficient time-integration. Numerical simulations of bench-scale operation of a prototype CFBA reactor for multi-pollutant control are described. DA - 2004/10// PY - 2004/10// DO - 10.1016/j.ces.2004.06.004 VL - 59 IS - 20 SP - 4279-4289 SN - 0009-2509 KW - modelling KW - simulation KW - fluidization KW - adsorption KW - coagulation KW - multiphase flow ER - TY - JOUR TI - The design and characterization of a novel piezoelectric transducer-based linear motor AU - Palmer, JA AU - Dessent, B AU - Mulling, JF AU - Usher, T AU - Grant, E AU - Eischen, JW AU - Kingon, AI AU - Franzon, PD T2 - IEEE-ASME TRANSACTIONS ON MECHATRONICS AB - Before microminiature robots can be realized, new direct drive micromotor systems must be developed. In this research, a linear motor system for a miniature jumping robot was desired. However, current systems must display better force/torque characteristics than is currently available. This paper deals with the design, construction, and testing, of a macro-scale, unidirectional, direct drive linear piezomotor that operates like an inchworm. It uses a parallel arrangement of unimorph piezoelectric transducers, in conjunction with passive mechanical latches, to perform work on a coil spring. Experimental results showed that the linear piezomotor achieved a maximum no-load velocity of 161 mm/s, and a blocked force of 14 N, at a drive signal frequency of 100 Hz. Thereafter, back slip in the latch assembly restricted the forward motion. Based on the results obtained with the macro-level linear piezomotor, it is concluded that smaller direct drive piezomotor designs based on unimorph piezoelectric transducers are achievable. System scalability will be addressed in a future publication. DA - 2004/6// PY - 2004/6// DO - 10.1109/TMECH.2004.828647 VL - 9 IS - 2 SP - 392-398 SN - 1941-014X KW - direct drive motors KW - linear piezomotor KW - passive latches KW - piezoelectric transducers ER - TY - JOUR TI - Stability of a suspension of gyrotactic microorganisms in superimposed fluid and porous layers AU - Avramenko, AA AU - Kuznetsov, AV T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - The aim of this paper is to investigate the stability of a suspension of motile gyrotactic microorganisms in a system that consists of superimposed fluid and porous layers. This is relevant to many biological applications, such as growing motile microorganisms in Petri dishes. By performing a linear stability analysis a correlation for the critical Rayleigh number is obtained. DA - 2004/11// PY - 2004/11// DO - 10.1016/j.icheatmasstransfer.2004.08.003 VL - 31 IS - 8 SP - 1057-1066 SN - 0735-1933 ER - TY - JOUR TI - Particle-hemodynamics simulations and design options for surgical reconstruction of diseased carotid artery bifurcations AU - Hyun, S AU - Kleinstreuer, C AU - Longest, PW AU - Chen, C T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME AB - Based on the hypothesis that aggravating hemodynamic factors play a key role in the onset of arterial diseases, the methodology of “virtual prototyping” of branching blood vessels was applied to diseased external carotid artery (ECA) segments. The goals were to understand the underlying particle-hemodynamics and to provide various geometric design options for improved surgical reconstruction based on the minimization of critical hemodynamic wall parameters (HWPs). First, a representative carotid artery bifurcation (CAB) and then CABs with stenosed ECAs, i.e., a distally occluded ECA and an ECA stump, were analyzed based on transient three-dimensional blood flow solutions, employing a user-enhanced commercial finite volume code. Specifically, the HWPs, i.e., oscillatory shear index, wall shear stress angle gradient, near-wall residence time of monocytes, and near-wall helicity angle difference were evaluated to compare the merits of each design option, including a reconstructed near-optimal junction which generates the lowest HWP-values. The results provide physical insight to the biofluid dynamics of branching blood vessels and guide vascular surgeons as well as stent manufacturers towards interventions leading to high sustained patency rates. DA - 2004/4// PY - 2004/4// DO - 10.1115/1.1688777 VL - 126 IS - 2 SP - 188-195 SN - 1528-8951 ER - TY - JOUR TI - On convexified robust control synthesis AU - Wu, F AU - Bei, L T2 - AUTOMATICA AB - In this paper, we study a convexified robust control problem and its relation to gain-scheduling control. It reveals that the robust control synthesis condition becomes convex under a special plant structure. Moreover, for this class of robust control problems, the gain-scheduling control approach from scaled small-gain theorem will not provide any performance improvement over convexified robust controllers. Based on this observation, a convexified robust control synthesis framework with stringent performance and computational efficacy is proposed. DA - 2004/6// PY - 2004/6// DO - 10.1016/j.automatica.2004.01.010 VL - 40 IS - 6 SP - 1003-1010 SN - 1873-2836 KW - robust control KW - gain-scheduling control KW - convexity KW - scaled H infinity optimization KW - linear matrix inequality ER - TY - JOUR TI - Modified transfer matrix formulation for Bragg grating strain sensors AU - Prabhugoud, M AU - Peters, K T2 - JOURNAL OF LIGHTWAVE TECHNOLOGY AB - This paper presents a formulation for the application of the transfer matrix method to Bragg grating strain sensors. A modified T-matrix representation is detailed for the sensor problem based on an effective period derived from the coupling coefficients. This modified T-matrix formulation is shown to converge to the coupled-mode equations solution for a large number of grating segments, even in the presence of significant strain gradients. Several numerical examples are presented to demonstrate the importance of inclusion of the strain gradient in the calculation. In addition, the current formulation is validated by application to previously published experimental data. DA - 2004/10// PY - 2004/10// DO - 10.1109/JLT.2004.833281 VL - 22 IS - 10 SP - 2302-2309 SN - 1558-2213 KW - detector KW - gratings KW - strain KW - transfer function matrices ER - TY - JOUR TI - Forced convection in a helical pipe filled with a saturated porous medium AU - Nield, DA AU - Kuznetsov, AV T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - An analysis is made of laminar forced convection in a helical pipe of circular cross-section and filled by a porous medium saturated with a fluid, for the case when the curvature and torsion of the pipe are both small. The Darcy model is employed, and boundaries with either uniform flux or uniform temperature are considered. It is found that curvature induces a secondary flow at first order in the parameter ε = κa, where κ is the curvature and a is the radius of the pipe. On the other hand, the Nusselt number is unchanged to first order in ε but is increased at second order, for either set of thermal boundary conditions. The effect of torsion on the velocity appears at second order, but torsion does not affect the Nusselt number at second order. DA - 2004/11// PY - 2004/11// DO - 10.1016/j.ijheatmasstransfer.2004.07.015 VL - 47 IS - 24 SP - 5175-5180 SN - 1879-2189 ER - TY - JOUR TI - Forced convection in a bi-disperse porous medium channel: a conjugate problem AU - Nield, DA AU - Kuznetsov, AV T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - Forced convection in a plane channel filled with a saturated bi-disperse porous medium, coupled with conduction in plane slabs bounding the channel, is investigated analytically on the basis of a two-velocity, two-temperature model. It is found that the effect of the finite thermal resistance due to the slabs is to reduce both the heat transfer to the porous medium and the degree of local thermal non-equilibrium. An increase in value of the Péclet number leads to a decrease in the rate of exponential decay in the downstream direction but does not affect the value of a suitably defined Nusselt number. The dependence of Nusselt number on Biot number associated with the boundary slabs, the interphase heat exchange parameter, the interphase thermal conductivity ratio, the interphase effective permeability ratio, and the macroscopic void fraction, is investigated. DA - 2004/11// PY - 2004/11// DO - 10.1016/j.ijheatmasstransfer.2004.07.018 VL - 47 IS - 24 SP - 5375-5380 SN - 1879-2189 ER - TY - JOUR TI - Fixed abrasive diamond wire saw slicing of single-crystal silicon carbide wafers AU - Hardin, CW AU - Qu, J AU - Shih, AJ T2 - MATERIALS AND MANUFACTURING PROCESSES AB - Abstract This article investigates the slicing of single-crystal silicon carbide (SiC) with a fixed abrasive diamond wire. A spool-to-spool rocking motion diamond wire saw machine using a 0.22 mm nominal diameter diamond wire with 20 µm average size diamond grit was used. The effect of wire downfeed speed on wafer surface roughness and subsurface damage was first investigated. The surface marks generated by loose diamond grit and stagnation of the wire during the change of the wire-cutting direction were studied. The use of scanning acoustic microscopy (SAcM) as a nondestructive evaluation method to identify the subsurface damage was explored. Effects of using a new diamond wire on cutting forces and surface roughness were also investigated. Scanning electron microscopy has been used to examine the machined surfaces and wire wear. This study demonstrated the feasibility of fixed abrasive diamond wire cutting of SiC wafers and the usage of a SAcM to examine the subsurface damage. DA - 2004/// PY - 2004/// DO - 10.1081/AMP-120029960 VL - 19 IS - 2 SP - 355-367 SN - 1532-2475 KW - diamond wire KW - wire saw KW - wafer slicing KW - silicon carbide KW - scanning acoustic microscopy ER - TY - JOUR TI - Clustering effects on discontinuous gold film NanoCells AU - Seminario, JM AU - Ma, YF AU - Agapito, LA AU - Yan, LM AU - Araujo, RA AU - Bingi, S AU - Vadlamani, NS AU - Chagarlamudi, K AU - Sudarshan, TS AU - Myrick, ML AU - Colavita, PE AU - Franzon, PD AU - Nackashi, DP AU - Cheng, L AU - Yao, YX AU - Tour, JM T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AB - Reproducible negative differential resistance (NDR)-like switching behavior is observed in NanoCells. This behavior is attributed to the formation of filaments and clusters between the discontinuous gold films. Control experiments are performed by self-assembly of insulating molecules between the gold islands and conducting molecules on these islands. Additional control experiments are performed by removing the filaments and clusters between islands using a piranha bath. The results are consistent with theoretical predictions and extend the domain of molecular electronics based in organic molecules to include nanosized clusters as active units. This facilitates a scenario where synthetically accessible organic molecules, with defined characteristics, can be adjusted by metallic nanoclusters as an in situ fine-tuning element, able to compensate for the lack of addressing in the nanosize regime. DA - 2004/9// PY - 2004/9// DO - 10.1166/jnn.2004.104 VL - 4 IS - 7 SP - 907-917 SN - 1533-4899 KW - negative differential resistance KW - NanoCell KW - clustering KW - filamentary formation KW - discontinuous gold film KW - interlinking molecule KW - self-assembling KW - ab initio KW - molecular dynamics KW - density functional theory KW - nanotechnology KW - molecular electronics KW - nanoelectronics ER - TY - JOUR TI - A stochastic model for localized disturbances and its applications AU - Hou, ZK AU - Hera, A AU - Noori, M T2 - PROBABILISTIC ENGINEERING MECHANICS AB - A stochastic model for local disturbances, particularly for a temporal harmonic with random modulations in amplitude and/or phase, is proposed in this paper. Results for the second moment responses of a linear single-degree-of-freedom system to this type of stochastic loading demonstrate a significant change in response characteristics due to a small uncertainty. A local phenomenon may last much longer and resonance may be smeared to a broad range. Integrated with wavelet transform, the proposed approach may be used to model a random process with non-stationary frequency content. Especially, it can be effectively used for Monte Carlo simulation to generate large size of samples that have similar characteristics in time and frequency domains as a pre-selected mother sample has. The technique has a great potential for the case where uncertainty study is warranted but the available samples are limited. DA - 2004/7// PY - 2004/7// DO - 10.1016/j.probengmech.2004.02.004 VL - 19 IS - 3 SP - 211-218 SN - 0266-8920 KW - random vibration KW - stochastic modeling KW - random process KW - wavelet analysis KW - Monte Carlo simulation KW - earthquake engineering KW - structural dynamics ER - TY - JOUR TI - Investigation of the acoustic streaming in a rectangular cavity induced by the vibration of its lid AU - Wan, Q AU - Kuznetsov, AV T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - In this paper, the Network Simulation Method (NSM) is used to model an unsteady, viscous, flow problem: the heated lid-driven filled with nanofluid and in the presence of a pulsating flow. Through this method is analyzed the influence of the amplitude, wave number and oscillation frequency of sinusoidal velocity waves at the lid on the convection performance of the cavity. It is stated that this method is simple and efficient for solving unsteady, viscous, Navier–Stokes equations, through the design and resolution of an electrical circuit network whose equations are formally equivalent to the ones of the fluid flow problem. Results show that, for the case of Pr = 3.93, Re = 50, Ri = 11.82, sinusoidal velocity waves at the lid increase the time-averaged Nusselt number in the cavity with respect to the non-pulsating case up to a 16%. This is due to enhancement of the transport phenomena induced by the pulsating flow. DA - 2004/5// PY - 2004/5// DO - 10.1016/S0735-1933(04)00028-4 VL - 31 IS - 4 SP - 467-476 SN - 0735-1933 ER - TY - JOUR TI - End milling of elastomers - Fixture design and tool effectiveness for material removal AU - Shih, AJ AU - Lewis, MA AU - Strenkowski, JS T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME AB - This paper describes the machining of elastomers using sharp, woodworking tools and the machining of cryogenically cooled elastomers. Due to the lack of information on tool selection for elastomer machining, a set of thirteen tools that cover different sizes and tool geometries and materials was used in this study. Fixture design was found to be critical in machining of elastomers because of its relatively low elastic modulus. The cutting force created during machining can generate significant deformations in the elastomer workpiece. The finite element technique is used to analyze the structural stiffness of the elastomer workpiece under different geometric configurations. The effective stiffness is defined to quantify and compare the stiffness of elastomer workpiece machined by different tool sizes. The cleanliness of the groove machined by end milling is investigated. Use of some down-cut end-milling tools effectively removed the elastomer material at room temperature and generated a clean groove. The tool configuration and part fixturing are identified as the two most important variables that affect the cleanliness of machined grooves. Cooling the elastomer workpiece by solid carbon dioxide (dry ice) to about −78.6°C improved the machined surface finish. DA - 2004/2// PY - 2004/2// DO - 10.1115/1.1616951 VL - 126 IS - 1 SP - 115-123 SN - 1528-8935 ER - TY - JOUR TI - Diffusion profiles of high dosage Cr and V ions implanted into silicon AU - Zhang, P AU - Stevie, F AU - Vanfleet, R AU - Neelakantan, R AU - Klimov, M AU - Zhou, D AU - Chow, L T2 - JOURNAL OF APPLIED PHYSICS AB - The depth profiles of high dosage Cr+52 and V+51 ions implanted in (100) crystalline silicon after thermal anneal at temperatures between 300 °C and 1000 °C are studied by secondary ion mass spectrometry and cross-sectional transmission electron microscopy. At dosages of 1×1015 ions/cm2 and above, the surface layer of silicon substrate is amorphorized. During the subsequent thermal annealing, the depth profiles of the implanted ions are strongly coupled with the solid phase epitaxial growth of amorphous silicon. Silicide precipitate formation is important to understand the differences between Cr and V diffusion. After anneal of the 1×1015 ions/cm2 implanted samples at 900 °C and 1000 °C, most of the Cr has left the silicon, but only 10% of the V has escaped. The 1×1014 ions/cm2 Cr-implanted sample shows Cr ions exist only near the surface after 1000 °C anneal. The V-implanted sample, on the other hand, only shows a narrowing of the V profile after 1000 °C anneal. DA - 2004/7/15/ PY - 2004/7/15/ DO - 10.1063/1.1756221 VL - 96 IS - 2 SP - 1053-1058 SN - 1089-7550 ER - TY - JOUR TI - Chip morphology and forces in end milling of elastomers AU - Shih, AJ AU - Luo, J AU - Lewis, MA AU - Strenkowski, JS T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME AB - This paper describes chip morphology and forces in end milling of elastomers. A classification system that identifies elastomer chips based on their size and morphology is described. Optical pictures and Scanning Electron Microscopy (SEM) micrographs were used to examine and classify chips. A four-step examination procedure is developed to specify seven types of chips. Serrated chip formation with apparent adiabatic shear bands was observed for one end milling condition. The low thermal conductivity of elastomer is a possible cause for the observed shear band formation. Another type of serrated chip was found with surface wavy marks due to vibration of the workpiece. End milling force components were also recorded and analyzed. It was found that end milling of solid carbon dioxide cooled elastomers generated higher forces than the room temperature workpiece. A correlation of the maximum uncut chip thickness on averaged peak cutting force components is identified for different spindle speeds. This has indicated the potential for modeling elastomer machining processes. DA - 2004/2// PY - 2004/2// DO - 10.1115/1.1633276 VL - 126 IS - 1 SP - 124-130 SN - 1528-8935 ER - TY - JOUR TI - Robust control of high speed end milling with unknown process parameter and CNC delay AU - Tu, J. F. AU - Corless, M. AU - Jeppsson, J. T2 - Journal of Aerospace Engineering AB - Lack of complete knowledge of process characteristics, particularly uncertainties associated with milling processes and spindle behavior, severely limits the reliability of high speed spindles to support high speed machining. Attempts to regulate high speed milling processes based on sensing spindle power and controlling feed rate to prevent spindle stalls have not been successful, mainly due to the fact that power is often not the limiting factor. Instead, problems such as chatter, cutter and/or part deflection, milling forces, and its effects on the rapid wear of the taper of the tool holder and the spindle bearings can easily lead to scrapped parts and/or spindle breakdowns unless extreme care is taken. This paper addresses the stability analysis and design of a novel, robust, nonlinear milling controller implemented at Boeing Co. This controller is aimed at driving an end mill at the highest possible feedrate without damaging the cutter and the spindle. The successful implementation of this controller at Boeing has significantly reduced spindle failures in their extremely demanding high speed machining production lines. DA - 2004/// PY - 2004/// DO - 10.1061/(asce)0893-1321(2004)17:1(1) VL - 17 IS - 1 SP - 09- ER - TY - JOUR TI - Production and metrology of cylindrical inertial confinement fusion targets with sinusoidal perturbations AU - Balkey, MM AU - Day, RD AU - Batha, SH AU - Elliot, NE AU - Pierce, T AU - Sandoval, DL T2 - FUSION SCIENCE AND TECHNOLOGY AB - Shock waves generated during inertial confinement fusion implosions propagate toward the center of the capsule encountering interfaces between materials with different densities, such as between the ablator and the DT fuel. These interactions are hydrodynamically unstable and the resulting instability causes mixing of the materials at the interface, which is predicted to have detrimental effects on fusion burn. In this experiment, the growth of a single-mode perturbation machined into a radiographically opaque marker layer, driven by a strong shock, is measured during a cylindrically symmetric implosion. These measurements are used to validate simulations and theories of the complex hydrodynamics. Since any perturbation on the marker layer surface will lead to instability growth, precise knowledge of the initial conditions is critical. The targets used in this experiment have up to a 3.0-μm-amplitude, mode 28 (θ = 98 μm) sinusoidal perturbation machined into a 438-μm-outerradius aluminum band with a nominal thickness of 8 μm. The perturbations were machined using a fast-tool servo [B. JARED and T. A. DOW, Precision Engineering Center Annual Report, North Carolina State University, Raleigh NC, p. 123 (1996)] and were metrologized using a linear variable differential transformer [FRANK J. OLIVER, Practical Instrumentation Tranducers, p. 42-45, Hayden Book Company (1971)]. In this paper, the importance of metrology is discussed and is shown to be critical to the interpretation of experimental results. DA - 2004/3// PY - 2004/3// DO - 10.13182/FST04-A435 VL - 45 IS - 2 SP - 107-112 SN - 1943-7641 ER - TY - JOUR TI - Effect of turbulence on forced convection in a composite tube partly filled with a porous medium AU - Kuznetsov, AV T2 - JOURNAL OF POROUS MEDIA DA - 2004/// PY - 2004/// DO - 10.1615/JPorMedia.v7.i1.60 VL - 7 IS - 1 SP - 59-64 SN - 1934-0508 ER - TY - JOUR TI - Modeling of residual stresses for thermally strained GaN/Al2O3 heterostructures AU - Ashmawi, WM AU - Zikry, MA AU - Wang, K AU - Reeber, RR T2 - JOURNAL OF CRYSTAL GROWTH AB - A finite element model and a specialized constitutive formulation were used to predict the evolving interfacial thermal mismatch stresses and strains in gallium nitride/alumina epitaxial layered systems. The constitutive formulation was based on having the coefficients of thermal expansion vary as a function of temperature for both material systems, which were assumed to be transversely isotropic. Different layer configurations were investigated, and it is shown that layer geometry is controlled by the evolution of induced thermal mismatch properties and residual stresses. DA - 2004/6/1/ PY - 2004/6/1/ DO - 10.1016/j.jcrysgro.2004.02.105 VL - 266 IS - 4 SP - 415-422 SN - 1873-5002 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-2442603520&partnerID=MN8TOARS KW - Einstein model KW - finite element KW - stresses KW - thermal mismatch KW - epitaxial growth KW - alumina KW - gallium nitride KW - transversely-isotropic materials ER - TY - JOUR TI - Macrosegregation during alloyed semiconductor crystal growth in strong axial and transverse magnetic fields AU - Farrell, MV AU - Ma, N T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - Abstract This paper presents a model for the unsteady species transport during bulk growth of alloyed semiconductor crystals with both axial and transverse magnetic fields. 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 produce non-uniformities 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 magnetic field. The present study investigates the effects of magnetic field orientation and strength on the segregation in alloyed semiconductor crystals, and presents results of concentration in the crystal and in the melt at several different times during crystal growth. DA - 2004/7// PY - 2004/7// DO - 10.1016/j.ijheatmasstransfer.2004.02.021 VL - 47 IS - 14-16 SP - 3047-3055 SN - 1879-2189 ER - TY - JOUR TI - Improvement of parameter estimation for non-linear hysteretic systems with slip by a fast Bayesian bootstrap filter AU - Li, SJ AU - Suzuki, Y AU - Noori, M T2 - INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS AB - Modeling and identification of non-linear hysteretic systems are widely encountered in the structural dynamics field, especially for the hysteresis with slip. A model, called SL model, which can describe the pinching of most practical hysteresis loops perfectly was proposed by Baber and Noori (J. Eng. Mech. 111 (1985) 1010). A method of estimating the parameters of SL model on the basis of input–output data based on bootstrap filter was proposed by the writers. Bootstrap filter is a filtering method based on Bayesian state estimation and Monte Carlo method, which has the great advantage of being able to handle any functional non-linearity and system and/or measurement noise of any distribution. The standard bootstrap filter, however, is not time efficient, i.e., it is very time consuming and is not suitable for real-time applications. In this paper, previous work by the writers is extended to do the parameter estimation of SL model by a fast Bayesian bootstrap filtering technique. Simulation results are presented to demonstrate the performance of the algorithm. DA - 2004/11// PY - 2004/11// DO - 10.1016/j.ijnonlinmec.2004.02.005 VL - 39 IS - 9 SP - 1435-1445 SN - 1878-5638 KW - system identification KW - hysteretic system KW - bootstrap filter KW - Bayesian estimation KW - Monte Carlo method ER - TY - JOUR TI - Effect of small solid particles on the development of bioconvection plumes AU - Geng, P AU - Kuznetsov, AV T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - We investigate numerically the impact of small solid particles on the steady-state bioconvection plume caused by up-swimming of motile gyrotactic micro-organisms. Small solid particles that are heavier than water are added into the upper fluid layer when bioconvection has already attained its steady-state. As sedimentation process goes on, solid particles get involved in convection. They impact the fluid flow and cause the transition of the bioconvection plume to a different steady-state DA - 2004/7// PY - 2004/7// DO - 10.1016/S0735-1933(04)00050-8 VL - 31 IS - 5 SP - 629-638 SN - 0735-1933 ER - TY - JOUR TI - Computational evaluation of quiet tunnel hypersonic boundary-layer stability experiments AU - Manning, ML AU - Chokani, N 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 - 2004/// PY - 2004/// DO - 10.2514/1.10698 VL - 41 IS - 3 SP - 406-415 SN - 1533-6794 ER - TY - JOUR TI - Chip formation, cutting forces, and tool wear in turning of Zr-based bulk metallic glass AU - Bakkal, M AU - Shih, AJ AU - Scattergood, RO T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE AB - The chip light emission and morphology, cutting forces, surface roughness, and tool wear in turning of Zr-based bulk metallic glass (BMG) material are investigated. Machining results are compared with those of aluminum 6061-T6 and AISI 304 stainless steel under the same cutting conditions. This study demonstrates that the high cutting speeds and tools with low thermal conductivity and rake angle activate the light emission and chip oxidation in BMG machining. For the BMG chip without light emission, serrated chip formation with adiabatic shear band and void formation is observed. The cutting force analysis further correlates the chip oxidation and specific cutting energy and shows the significant reduction of cutting forces for machining BMG at high cutting speeds. The machined surface of BMG has better surface roughness than that of the other two work materials. Some tool wear features, including the welding of chip to the tool tip and chipping of the polycrystalline cubic boron nitride (PCBN) tool edge, are reported for turning of BMG. This study concludes that BMG can be machined with good surface roughness using conventional cutting tools. DA - 2004/7// PY - 2004/7// DO - 10.1016/j.ijmachtools.2004.02.002 VL - 44 IS - 9 SP - 915-925 SN - 1879-2170 KW - bulk metallic glass KW - machining KW - cutting forces KW - surface roughness KW - tool wear ER - TY - JOUR TI - Thermally developing forced convection in a porous medium: Parallel-plate channel or circular tube with isothermal walls AU - Nield, DA AU - Kuznetsov, AV AU - Xiong, M T2 - JOURNAL OF POROUS MEDIA AB - The classical Graetz methodology is applied to investigate the thermal development of forced convection in a parallel-plate channel or a circular tube filled by a saturated porous medium, with walls held at constant temperature. The Brinkman model is employed. The analysis leads to expressions for the local Nusselt number and average Nusselt number, as functions of the dimensionless longitudinal coordinate and the Darcy number. DA - 2004/// PY - 2004/// DO - 10.1615/JPorMedia.v7.i1.30 VL - 7 IS - 1 SP - 19-27 SN - 1091-028X ER - TY - JOUR TI - The onset of bioconvection in a horizontal porous-medium layer AU - Nield, DA AU - Kuznetsov, AV AU - Avramenko, AA T2 - TRANSPORT IN POROUS MEDIA DA - 2004/3// PY - 2004/3// DO - 10.1023/B:TIPM.0000003662.31212.5b VL - 54 IS - 3 SP - 335-344 SN - 0169-3913 KW - bioconvection KW - convective instability KW - horizontal layer ER - TY - JOUR TI - Nanoparticle transport and deposition in bifurcating tubes with different inlet conditions AU - Shi, H AU - Kleinstreuer, C AU - Zhang, Z AU - Kim, CS T2 - PHYSICS OF FLUIDS AB - Transport and deposition of ultrafine particles in straight, bent and bifurcating tubes are considered for different inlet Reynolds numbers, velocity profiles, and particle sizes, i.e., 1 nm⩽dp⩽150 nm. A commercial finite-volume code with user-supplied programs was validated with analytical correlations and experimental data sets for nanoparticle depositions, considering a straight tube, a tubular 90° bend, and a G3-G5 double bifurcation with both planar and nonplanar configurations. The focus is on the airflow structures as well as nanoparticle deposition patterns and deposition efficiencies, which were analyzed for planar and nonplanar bifurcating lung airway models representing part of the upper bronchial tree. Deposition takes place primarily by Brownian diffusion, and thus deposition efficiencies increase with decreasing nanoparticle size and lower inlet Reynolds numbers. Deposition in the nonplanar configuration differs only slightly from that in the planar configuration. When compared with axisymmetric inlet conditions, the more realistic, skewed inlet velocity and particle profiles generate nearly axisymmetric deposition patterns as well. This work may elucidate basic physical insight of ultrafine particle transport and deposition relevant to environmental, industrial and biomedical studies. DA - 2004/7// PY - 2004/7// DO - 10.1063/1.1724830 VL - 16 IS - 7 SP - 2199-2213 SN - 1089-7666 ER - TY - JOUR TI - Identification of hysteretic systems with slip using bootstrap filter AU - Li, SJ AU - Suzuki, Y AU - Noori, M T2 - MECHANICAL SYSTEMS AND SIGNAL PROCESSING AB - Hysteretic models with slip are frequently used to predict the non-linear behaviour of many structural systems, for example wood buildings and reinforced concrete structures. A model, called SL model, which can describe the pinching of most practical hysteresis loops perfectly was proposed by Baber and Noori. This model is characterised by control parameters that have to be identified from observed experimental data. A method of estimating the parameters of SL model on the basis of input–output data based on Bayesian state estimation and bootstrap filter is suggested in this paper, which has the great advantages of being able to handle any functional non-linearity and system and measurement noise of any distribution. A numerical simulation shows its suitability and effective for the system even in the case of very severe material non-linearity. DA - 2004/7// PY - 2004/7// DO - 10.1016/j.ymssp.2003.08.001 VL - 18 IS - 4 SP - 781-795 SN - 0888-3270 ER - TY - JOUR TI - Anti-windup control design for exponentially unstable LTI systems with actuator saturation AU - Wu, F AU - Lu, B T2 - SYSTEMS & CONTROL LETTERS AB - In this paper, a new saturation control technique in the framework of anti-windup compensation is developed for exponentially unstable linear time-invariant systems subject to input nonlinearities. The proposed control algorithm guarantees regional stability in the existence of input saturation, and provides less conservative performance than most existing anti-windup schemes. Moreover, an explicit form of anti-windup controller with its order no more than the order of the plant is derived. An inverted pendulum example is used to demonstrate the advantages of the newly proposed anti-windup control technique. DA - 2004/7// PY - 2004/7// DO - 10.1016/j.sysconle.2004.02.007 VL - 52 IS - 3-4 SP - 305-322 SN - 1872-7956 KW - input saturation KW - sector-bounded nonlinearity KW - anti-windup compensation KW - linear matrix inequality ER - TY - JOUR TI - Analytical investigation of a falling plume caused by bioconvection of oxytactic bacteria in a fluid saturated porous medium AU - Kuznetsov, A. V. AU - Avramenko, A. A. AU - Geng, P. T2 - International Journal of Engineering Science AB - The objective of this paper is to investigate theoretically a falling bioconvection plume in a deep chamber filled with a fluid saturated porous medium. The plume may be caused by oxytactic bacteria, such as Bacillus subtilis. The plume transports oxygen from the upper boundary layer, which is rich in cells and oxygen, to the lower part of the chamber, which is depleted of both cells and oxygen. A similarity solution of full governing equations (without utilizing the boundary layer approximation) that describe fluid flow as well as oxygen and cell transport in the plume is obtained. The resulting ordinary differential equations are singular when the similarity variable approaches zero; therefore, a series solution of these ordinary differential equations, which is valid for small values of the similarity variable, is obtained. This series solution is used as a starting point for a numerical solution which makes it possible to investigate the plume for the whole range of values of the similarity variable. DA - 2004/// PY - 2004/// DO - 10.1016/j.ijengsci.2003.08.004 VL - 42 IS - 06-May SP - 557-569 ER - TY - JOUR TI - An intelligent parameter varying (IPV) approach for non-linear system identification of base excited structures AU - Saadat, S AU - Buckner, GD AU - Furukawa, T AU - Noori, MN T2 - INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS AB - Health monitoring and damage detection strategies for base-excited structures typically rely on accurate models of the system dynamics. Restoring forces in these structures can exhibit highly non-linear characteristics, thus accurate non-linear system identification is critical. Parametric system identification approaches are commonly used, but require a priori knowledge of restoring force characteristics. Non-parametric approaches do not require this a priori information, but they typically lack direct associations between the model and the system dynamics, providing limited utility for health monitoring and damage detection. In this paper a novel system identification approach, the intelligent parameter varying (IPV) method, is used to identify constitutive non-linearities in structures subject to seismic excitations. IPV overcomes the limitations of traditional parametric and non-parametric approaches, while preserving the unique benefits of each. It uses embedded radial basis function networks to estimate the constitutive characteristics of inelastic and hysteretic restoring forces in a multi-degree-of-freedom structure. Simulation results are compared to those of a traditional parametric approach, the prediction error method. These results demonstrate the effectiveness of IPV in identifying highly non-linear restoring forces, without a priori information, while preserving a direct association with the structural dynamics. DA - 2004/8// PY - 2004/8// DO - 10.1016/S0020-7462(03)00091-X VL - 39 IS - 6 SP - 993-1004 SN - 0020-7462 KW - system identification KW - artifical neural networks KW - hysteresis KW - nonlinear systems KW - health monitoring ER - TY - JOUR TI - Oxidation and crystallization of Zr-based bulk metallic glass due to machining AU - Bakkal, M. AU - Liu, C. T. AU - Watkins, T. R. AU - Scattergood, R. O. AU - Shih, A. J. T2 - Intermetallics DA - 2004/// PY - 2004/// DO - 10.1016/j.internet.2003.09.017 VL - 12 IS - 2 SP - 195-204 ER - TY - JOUR TI - Modeling and sliding-mode control of friction-based object transport using two-mode ultrasonic excitation AU - Panusittikorn, W AU - Lee, MC AU - Ro, PI T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - This paper introduces a magnetic-free object transport system driven by a friction force on an ultrasonic flexural vibrating beam. This driving mechanism offers unique advantages of silent operation and lubricant-free structure. The characteristics are ideal for a transport system in a clean-room environment. However, the friction drive described by Hertzian contact and Coulomb friction theories is highly nonlinear. The transport system needs a sophisticated control design to deliver a load to a precise location. A traditional feedback controller and sliding-mode control were implemented in the presence of sensor noise and hardware limitation. It is experimentally shown that the tracking performance of the proposed control scheme is superior to the traditional control design. DA - 2004/8// PY - 2004/8// DO - 10.1109/TIE.2004.831761 VL - 51 IS - 4 SP - 917-926 SN - 1557-9948 KW - friction KW - sliding-mode control KW - ultrasonic motors KW - vibration ER - TY - JOUR TI - Leading-edge reaction zones in lifted-jet gas and spray flames AU - Marley, SK AU - Lyons, KM AU - Watson, KA T2 - FLOW TURBULENCE AND COMBUSTION DA - 2004/// PY - 2004/// DO - 10.1023/B:APPL.0000014906.91990.4e VL - 72 IS - 1 SP - 29-47 SN - 1573-1987 KW - diffusion flame KW - double flame KW - entrainment KW - leading-edge KW - spray combustion ER - TY - JOUR TI - Dynamic peak amplitude analysis and bonding layer eiiects of piezoelectric bimorph cantilevers AU - Wu, T AU - Ro, PI T2 - SMART MATERIALS AND STRUCTURES AB - An analytical prediction of dynamic performance for piezoelectric bimorph structures was investigated. A damping ratio was assumed and employed to determine dynamic peak amplitudes at resonances by finding the frequency with of the peak amplitude. Finite element simulations were used to validate the proposed improvement strategy. Results show that the peak amplitude determination method is good enough to predict the dynamic performance of piezoelectric bimorphs. The effects of bonding layers were also analysed by both static and dynamic methods. The bonding influence can be minimized by selecting appropriate bonding materials and dimensions of structures. DA - 2004/2// PY - 2004/2// DO - 10.1088/0964-1726/13/1/024 VL - 13 IS - 1 SP - 203-210 SN - 1361-665X ER - TY - JOUR TI - A micromechanical model for damage progression in woven composite systems AU - Bahei-El-Din, YA AU - Rajendran, AM AU - Zikry, MA T2 - INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES AB - Damage progression in woven composites is modeled for multiscale analysis of structures. The proposed model is a representative volume element (RVE) of the woven material, derived from micrographs. In principle, it is applicable to any woven system with periodic fiber placement; however, the focus in this paper is on 3D weaves. The domain and boundary conditions of the RVE are selected such that the model can serve as a repository for predicting the overall behavior under general, multiaxial stress states. The overall response due to applied stress, or strain, and local damage is evaluated by a transformation field analysis (TFA) scheme. Damage mechanisms observed under quasi-static and impact loads are implemented. This includes matrix cracking, frictional sliding and debonding of the fiber bundles, and fiber rupture. The local stress components affected by the active damage modes are removed or reduced by superimposing a transformation stress field on the elastic field caused by the overall loads in the undamaged material. This results in a local stress field that is within the affordable local strength magnitudes, and an overall transformation stress, which modifies the elastic estimate. Implementation of the material model in quasi-static and dynamic finite element procedures is discussed, and examples, which illustrate the model capabilities, are presented. DA - 2004/5// PY - 2004/5// DO - 10.1016/j.ijsolstr.2003.12.006 VL - 41 IS - 9-10 SP - 2307-2330 SN - 1879-2146 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1842484113&partnerID=MN8TOARS KW - woven composites KW - micromechanics KW - damage KW - transformation field analysis ER - TY - JOUR TI - Laminar forced convection in curved channel with vortex structures AU - Avramenko, A. A. AU - Kobzar, S. G. AU - Shevchuk, I. V. AU - Kuznetsov, A. V. AU - Basok, B. I. T2 - International Journal of Turbo & Jet. Engines AB - Theoretical and experimental investigations of heat transfer in flat curvilinear channel have been carried out. Linear and non-linear effects of Dean vortexes on intensity of heat transfer were taken into account. The linear effect, which describe harmonic (sinuous) variation of the heat transfer coefficient near the concave surface of the channel and the non-linear effect causes the general increase of the heat transfer coefficient due to augmentation of heat transfer engendered by the Dean vortexes. For both effects, mathematical relations were obtained in the form of quadratures. These numerical results were modified to the form convenient in engineering calculations. The investigations have shown that both linear and nonlinear components grow up with the Dean number. Nonlinear component \(Q\frac{T}{0}\) increases more abruptly, while the linear one \(Q\frac{T}{1}\) is more conservative. This is a confirmation of stability of vortex structures. DA - 2004/// PY - 2004/// DO - 10.1515/tjj.2004.21.1.19 VL - 21 IS - 1 SP - 19-28 ER - TY - JOUR TI - Effects of viscous dissipation and flow work on forced convection in a channel filled by a saturated porous medium AU - Nield, DA AU - Kuznetsov, AV AU - Xiong, M T2 - TRANSPORT IN POROUS MEDIA DA - 2004/9// PY - 2004/9// DO - 10.1023/B:TIPM.0000026087.77213.c8 VL - 56 IS - 3 SP - 351-367 SN - 0169-3913 KW - viscous dissipation KW - flow work KW - forced convection KW - channel ER - TY - JOUR TI - Vaporizing microdroplet inhalation, transport, and deposition in a human upper airway model AU - Zhang, Z AU - Kleinstreuer, C AU - Kim, CS AU - Cheng, YS T2 - AEROSOL SCIENCE AND TECHNOLOGY AB - Evaluation of injuries from inhalation exposure to toxic fuel requires detailed knowledge of inhaled aerosol transport and deposition in human airways. Focusing on highly toxic, easily volatized JP-8 fuel droplets, the three-dimensional airflow, temperature distributions, and fluid-particle thermodynamics, i.e., droplet motion as well as evaporation, are simulated and analyzed for laminar as well as locally turbulent flow conditions. Specifically, using a commercial finite-volume software with user-supplied programs as a solver, the Euler-Lagrange approach for the fluid-particle thermodynamics is employed with: (1) a low Reynolds number k-ω model for laminar-to-turbulent airflow, and (2) a stochastic model for random fluctuations in the droplet trajectories with droplet evaporation. Presently, the respiratory system consists of two major segments of a simplified human cast replica, i.e., a representative oral airway from mouth to trachea (Generation 0) and a symmetric four-generation upper bronchial tree model (G0 to G3). Experimentally validated computational fluid-particle thermodynamics results show that evaporation of JP-8 fuel droplets is greatly affecting deposition in the human airway. Specifically, droplet deposition fractions due to vaporization decrease with increasing ambient temperatures and decreasing inspiratory flow rates. It is also demonstrated that assuming idealized velocity profiles and particle distributions in or after the trachea may greatly overpredict particle deposition efficiencies in the upper bronchial tree. DA - 2004/1// PY - 2004/1// DO - 10.1080/02786820490247597 VL - 38 IS - 1 SP - 36-49 SN - 1521-7388 ER - TY - JOUR TI - A case study of prototyping methods and design for manufacture: electrostatic window blinds AU - Kiefer, S AU - Silverberg, L AU - Gonzalez, M T2 - JOURNAL OF ENGINEERING DESIGN AB - This paper presents a case study of the design development of a new product, electrostatically actuated window blinds. The text presents a description of each stage in the prototype development followed by a discussion of different prototyping methods and design for manufacture and assembly issues. Results from electromechanical and thermal analyses of the product itself are also included. This case study determined that, for this product development, the most efficient, cost-effective prototyping solution was simple plastic injection moulding. It also concluded that following good design for manufacture and assembly practices during prototype construction will save time and money when transitioning to a production design. DA - 2004/2// PY - 2004/2// DO - 10.1080/0954482021000050820 VL - 15 IS - 1 SP - 91-106 SN - 0954-4828 ER - TY - JOUR TI - Streaming in a channel bounded by an ultrasonically oscillating beam and its cooling efficiency AU - Wan, Q AU - Kuznetsov, AV T2 - NUMERICAL HEAT TRANSFER PART A-APPLICATIONS AB - In this article the oscillating and streaming flow fields in a channel composed of two long parallel beams, one of which is stationary and the other of which oscillates with an ultrasonic frequency in a standing wave form, are investigated. The perturbation technique is utilized under the assumption that the oscillation amplitude is much smaller than the channel width and that the Reynolds number, which is defined by the oscillating frequency and the standing wave number, is much greater than unity. A three-layer structure of both the oscillating and streaming flow fields, which is composed of two very thin boundary layers near the beams and the core region between the boundary layers, is found in the channel. The oscillating velocity fields in all three layers are obtained analytically. The streaming fields within both boundary layers are also obtained analytically based on the oscillating fields. It is found that the streaming velocities approach constant values at the edges of the boundary layers and thus provide slip velocities for the streaming field in the core region. The core-region streaming velocity field is then obtained numerically by solving the Navier–Stokes equations in the stream function–vorticity formulation. Based on the core-region streaming field, which dominates most of the channel, the temperature field is computed for two cases: both beams are kept at constant but different temperatures (case A); and the oscillating beam is kept at a constant temperature while the stationary beam is subjected to a uniform constant heat flux (case B). Cases of different channel widths are computed and a critical width is found. When the channel width is smaller than the critical one, for each half standing wavelength distance along the beams, two symmetric eddies are observed, which occupy almost the whole width of the channel. In this case, the Nusselt number increases with the increase of the channel width. After the critical width, two layers of asymmetric eddies are observed near the oscillating beam and the Nusselt number decreases and approaches unity with further increase of the channel width. The abrupt change of the streaming field and the Nusselt number as the channel width goes through its critical value may be due to a bifurcation caused by instability of the vortex structure in the fluid layer. DA - 2004/1// PY - 2004/1// DO - 10.1080/1040778049026739 VL - 45 IS - 1 SP - 21-47 SN - 1040-7782 ER - TY - JOUR TI - Transpermanent magnetic actuation for spacecraft pointing, shape control, and deployment AU - Silverberg, L AU - Farmer, D 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 - 2004/// PY - 2004/// DO - 10.2514/1.1350 VL - 41 IS - 6 SP - 1051-1055 SN - 1533-6794 ER - TY - JOUR TI - Diamond wire machining of wood AU - Hardin, C. W. AU - Shih, A. J. AU - Lemaster, R. L. T2 - Forest Products Journal DA - 2004/// PY - 2004/// VL - 54 IS - 11 SP - 50-55 ER - TY - JOUR TI - Viscous dissipation effects in microtubes and microchannels AU - Koo, J AU - Kleinstreuer, C T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - The effects of viscous dissipation on the temperature field and ultimately on the friction factor have been investigated using dimensional analysis and experimentally validated computer simulations. Three common working fluids, i.e., water, methanol and iso-propanol, in different conduit geometries were considered. It turns out that for microconduits, viscous dissipation is a strong function of the channel aspect ratio, Reynolds number, Eckert number, Prandtl number and conduit hydraulic diameter. Thus, ignoring viscous dissipation could affect accurate flow simulations and measurements in microconduits. DA - 2004/7// PY - 2004/7// DO - 10.1016/j.ijheatmasstransfer.2004.02.017 VL - 47 IS - 14-16 SP - 3159-3169 SN - 1879-2189 KW - viscous dissipation KW - microchannel KW - microtube KW - computational analyses KW - dimensionless groups KW - temperature distributions KW - friction factor ER - TY - JOUR TI - Switching LPV control designs using multiple parameter-dependent Lyapunov functions AU - Lu, Bei AU - Wu, Fen T2 - Automatica AB - In this paper we study the switching control of linear parameter-varying (LPV) systems using multiple parameter-dependent Lyapunov functions to improve performance and enhance control design flexibility. A family of LPV controllers is designed, each suitable for a specific parameter subregion. They are switched so that the closed-loop system remains stable and its performance is optimized. Two switching logics, hysteresis switching and switching with average dwell time, are examined. The control synthesis conditions for both switching logics are formulated as matrix optimization problems, which are generally non-convex but can be convexified under some simplifying assumptions. The hysteresis switching LPV control scheme is then applied to an active magnetic bearing problem. DA - 2004/11// PY - 2004/11// DO - 10.1016/j.automatica.2004.06.011 VL - 40 IS - 11 SP - 1973-1980 J2 - Automatica LA - en OP - SN - 0005-1098 UR - http://dx.doi.org/10.1016/j.automatica.2004.06.011 DB - Crossref KW - switched linear parameter-varying system KW - multiple parameter-dependent Lyapunov functions KW - switching logics KW - linear matrix inequality KW - non-convexity ER - TY - JOUR TI - Simulating cavitation and hydraulic flip inside hydroentangling nozzles AU - Tafreshi, H. V. AU - Pourdeyhimi, B. T2 - Textile Research Journal AB - Hydroentangling owes its success to the peculiar properties of coherent water jets. For hydroentangling to be feasible at higher pressures, it is extremely important that water jets maintain their collimation for an appreciable distance downstream of the nozzle. How ever, water-jet breakup accelerates at high pressures. Recent studies have shown that cavitation severely affects the integrity of high-pressure water jets. Investigating cavita tion experimentally is not trivial. Computational fluid dynamics simulations offer appro priate tools as a first step. This paper discusses the results of an unsteady-state simulation, which shows the inception and time-evolution of a cavitation cloud inside a hydroentan gling nozzle. Under certain conditions, the cavity cloud extends to the nozzle outlet, resulting in the so-called hydraulic flip. Once hydraulic flip occurs, cavitation suddenly vanishes because the downstream air moves upward into the nozzle and fills the cavity. This air envelops the water flow inside the nozzle, which results in the depletion of cavitation-induced instabilities from the jet surface and elongates the jet breakup length. Moreover, our simulations reveal the approximate time scales of cavity growth through the nozzle. This information is highly relevant for experimental visualization of nozzle cavitation. The discharge and velocity coefficient obtained from the simulation are in a good agreement with published experimental data. DA - 2004/// PY - 2004/// DO - 10.1177/004051750407400413 VL - 74 IS - 4 SP - 359-364 ER - TY - JOUR TI - On the role of microcracks on flow instability in low speed machining of CP titanium AU - Sheikh-Ahmad, JY AU - Quarless, V AU - Bailey, JA T2 - MACHINING SCIENCE AND TECHNOLOGY AB - Abstract Flow instability is observed when machining titanium and its alloys and leads to the localization of plastic deformation into narrow bands. The shear strain at which this localization occurs serves as an important design parameter that measures the workability of a material and its suitability for various applications. In the current investigation, the phenomenon of microcracking during chip formation of grade 2 commercially pure (CP) titanium has been examined as a mechanism that promotes flow instability at low speeds. Based on this study, analytical and descriptive models that have been previously proposed for predicting the onset of flow instability have been revised to account for microcracking. Model predictions were experimentally verified for the orthogonal machining of CP titanium over a wide range of cutting speeds. Additionally, an investigation of plastic deformation across microcracks and localized shear zones was conducted in an effort to better understand strain hardening during chip formation. DA - 2004/11// PY - 2004/11// DO - 10.1081/LMST-200039867 VL - 8 IS - 3 SP - 415-430 SN - 1532-2483 ER - TY - JOUR TI - Numerical investigation of buoyancy effects on triple flame stability AU - Echekki, T T2 - COMBUSTION SCIENCE AND TECHNOLOGY AB - Numerical simulations of laminar two-dimensional triple flames are conducted to investigate the mechanisms of buoyancy-induced instabilities. These simulations are implemented for a selected range of gravity conditions and inlet scalar mixing widths for downward-propagating triple flames (propagating in the same direction as the gravity vector). Increases in the gravity force result in a transition from a stable to an unstable behavior. A linear inviscid stability analysis is performed to explore the mechanisms of instability and to estimate the most amplified frequencies. Unstable triple flame simulations provide detailed flow and scalar information for interrogating the mechanisms of buoyancy-induced instabilities in triple flames. These instabilities are accompanied by baroclinic generation of countervortices consistent with the Kelvin–Helmholtz instabilities. The computed onset of instabilities is accompanied by the advection of the triple flames downstream from their stabilization point. This advection plays a dominant role in the unstable behavior, further illustrating the hydrodynamic, buoyancy-induced nature of these instabilities. The most amplified frequencies from the linear stability analysis are in reasonable agreement with those determined from simulations of unstable triple flames. A parametric study using the linear stability analysis suggests that both the frequencies and amplitudes of disturbances increase with the magnitude of the gravity acceleration constant. Furthermore, the magnitude of amplification is largest just downstream of the two premixed branches. This trend implies the important role of baroclinic vorticity in the onset of instabilities. From the results of unsteady flame simulations, the onset of instability was found to correlate best with the Froude number based on premixed flame thickness and the triple flame propagation speed. DA - 2004/3// PY - 2004/3// DO - 10.1080/00102200490270120 VL - 176 IS - 3 SP - 381-407 SN - 0010-2202 KW - triple flames KW - flame stability KW - partially premixed flames ER - TY - JOUR TI - Multi-scale sensing for damage identification AU - Studer, M AU - Peters, K T2 - SMART MATERIALS AND STRUCTURES AB - Damage identification is important for the lifetime prediction of any structure. In a composite structure, damage can occur at several material scales from micro-cracking to global buckling or delamination. This makes the identification of damage difficult with a single sensing device. In this paper, we propose to monitor a structural volume with an embedded optical fiber sensor network measuring strain, integrated strain, and strain gradients. Two methods are also compared for data fusion of the multi-scale data in order to determine damage parameters. The first calculates strain maps directly from the data; the second method uses a neural network. As an example, an isotropic, homogeneous structural volume with a localized crack is modeled. The results demonstrate that (a) the multi-scale sensing approach improves damage identification and (b) the neural network is a method well adapted for the multi-scale data fusion and significantly improves the damage identification capability. DA - 2004/4// PY - 2004/4// DO - 10.1088/0964-1726/13/2/006 VL - 13 IS - 2 SP - 283-294 SN - 1361-665X ER - TY - JOUR TI - Genetic algorithm for the reconstruction of Bragg grating sensor strain profiles AU - Gill, A AU - Peters, K AU - Studer, M T2 - MEASUREMENT SCIENCE AND TECHNOLOGY AB - This paper presents a genetic algorithm for the interrogation of optical fibre Bragg grating strain sensors. The method encodes the axial strain distribution along the Bragg grating, here represented through the local period distribution, into a gene. To facilitate rapid calculation of the grating reflected intensity spectrum, the transfer-matrix approach is applied. The genetic algorithm inversion method presented requires only intensity information from the sensor and reconstructs non-linear and discontinuous distributions well, including regions with significant gradients. The development of this algorithm will permit the use of Bragg grating sensors for structural damage identification, allowing them to be located in regions where strong strain non-uniformities occur. DA - 2004/9// PY - 2004/9// DO - 10.1088/0957-0233/15/9/027 VL - 15 IS - 9 SP - 1877-1884 SN - 1361-6501 KW - strain distribution KW - optical fibre Bragg grating sensor KW - genetic algorithm KW - damage identification KW - failure analysis ER - TY - JOUR TI - Effect of nozzle geometry on hydroentangling water jets: Experimental observations AU - Begenir, A AU - Tafreshi, HV AU - Pourdeyhimi, B T2 - TEXTILE RESEARCH JOURNAL AB - This paper reports on the role of nozzle geometry on the characteristics of hydroen tangling water jets, specifically the behavior of three different conventional nozzle geometries under pressures below 3500 psi. Profiles of the water jets are digitized with a Nikon Dlx digital camera from which we extract the water-jet breakup lengths and spray angles under different operating conditions. Our preliminary data indicate that the cone-up nozzle produces water jets with considerably shorter intact lengths and slightly larger spray angles and a higher coefficient of discharge compared to the two other geometries considered. We attribute this distinct behavior to friction-induced and cavitation-induced turbulence inside the cone-up nozzles; a constricted water jet is formed by cone-down or cylindrical nozzles. Our results are in excellent agreement with previous experimental and computational data. DA - 2004/2// PY - 2004/2// DO - 10.1177/004051750407400215 VL - 74 IS - 2 SP - 178-184 SN - 1746-7748 ER - TY - JOUR TI - Dynamic and quasi-static failure evolution of 3D woven cellular composite systems AU - Baucom, JN AU - Zikry, MA AU - Qiu, Y T2 - JOURNAL OF REINFORCED PLASTICS AND COMPOSITES AB - The effects of porosity on the impact response and perforation resistance of 3D woven carbon-fiber reinforced epoxy panels under impact by projectiles and under quasi-static three-point bending were experimentally investigated. The 3D cellular composite systems were fabricated by a new method, where porosity can be controlled. The porous samples absorbed a greater amount of specific energy than the nonporous samples. This may be due to the deflection of matrix cracks by the pores and the greater flexibility of the fibers to absorb energy through tensile straining. The quasi-static experiments also indicate that porosity may exhibit strength comparable to nonporous systems. DA - 2004/// PY - 2004/// DO - 10.1177/0731684404032076 VL - 23 IS - 5 SP - 471-481 SN - 0731-6844 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1642443479&partnerID=MN8TOARS KW - carbon fiber KW - cellular matrix composite KW - impact energy absorption KW - perforation KW - porosity ER - TY - JOUR TI - Combustion structures in lifted ethanol spray flames AU - Marley, SK AU - Welle, EJ AU - Lyons, KM T2 - JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME AB - The development of a double flame structure in lifted ethanol spray flames is visualized using OH planar laser-induced fluorescence (PLIF). While the OH images indicate a single reaction zone exists without co-flow, the addition of low-speed co-flow facilitates the formation of a double flame structure that consists of two diverging flame fronts originating at the leading edge of the reaction zone. The outer reaction zone burns steadily in a diffusion mode, and the strained inner flame structure is characterized by both diffusion and partially premixed combustion exhibiting local extinction and re-ignition events. DA - 2004/4// PY - 2004/4// DO - 10.1115/1.1688768 VL - 126 IS - 2 SP - 254-257 SN - 1528-8919 ER - TY - JOUR TI - Airflow structures and nano-particle deposition in a human upper airway model AU - Zhang, Z AU - Kleinstreuer, C T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - Considering a human upper airway model, or equivalently complex internal flow conduits, the transport and deposition of nano-particles in the 1–150 nm diameter range are simulated and analyzed for cyclic and steady flow conditions. Specifically, using a commercial finite-volume software with user-supplied programs as a solver, the Euler–Euler approach for the fluid-particle dynamics is employed with a low-Reynolds-number k–ω model for laminar-to-turbulent airflow and the mass transfer equation for dispersion of nano-particles or vapors. Presently, the upper respiratory system consists of two connected segments of a simplified human cast replica, i.e., the oral airways from the mouth to the trachea (Generation G0) and an upper tracheobronchial tree model of G0–G3. Experimentally validated computational fluid-particle dynamics results show the following: (i) transient effects in the oral airways appear most prominently during the decelerating phase of the inspiratory cycle; (ii) selecting matching flow rates, total deposition fractions of nano-size particles for cyclic inspiratory flow are not significantly different from those for steady flow; (iii) turbulent fluctuations which occur after the throat can persist downstream to at least Generation G3 at medium and high inspiratory flow rates (i.e., Qin⩾30 l/min) due to the enhancement of flow instabilities just upstream of the flow dividers; however, the effects of turbulent fluctuations on nano-particle deposition are quite minor in the human upper airways; (iv) deposition of nano-particles occurs to a relatively greater extent around the carinal ridges when compared to the straight tubular segments in the bronchial airways; (v) deposition distributions of nano-particles vary with airway segment, particle size, and inhalation flow rate, where the local deposition is more uniformly distributed for large-size particles (say, dp=100 nm) than for small-size particles (say, dp=1 nm); (vi) dilute 1 nm particle suspensions behave like certain (fuel) vapors which have the same diffusivities; and (vii) new correlations for particle deposition as a function of a diffusion parameter are most useful for global lung modeling. DA - 2004/7/20/ PY - 2004/7/20/ DO - 10.1016/j.jcp.2003.11.034 VL - 198 IS - 1 SP - 178-210 SN - 1090-2716 KW - inspiratory flow KW - nano-size particle deposition KW - human airways KW - computational fluid-particle dynamics simulation ER - TY - JOUR TI - Machining of a Zr-Ti-Al-Cu-Ni metallic glass AU - Bakkal, M AU - Shih, AJ AU - Scattergood, RO AU - Liu, CT T2 - SCRIPTA MATERIALIA AB - Zr52.5Ti5Cu17.9Ni14.6Al10 metallic glass machining chips were characterized using SEM, X-ray diffraction and nano-indentation. Above a threshold cutting speed, oxidation of the Zr produces high flash temperatures and causes crystallization. The chip morphology was unique and showed the presence of shear bands, void formation and viscous flow. DA - 2004/3// PY - 2004/3// DO - 10.1016/j.scriptamat.2003.11.052 VL - 50 IS - 5 SP - 583-588 SN - 1359-6462 KW - metallic glass KW - machining KW - crystallization ER -