TY - JOUR
TI - Influence of crossflow-induced swirl and impingement on heat transfer in an internal coolant passage of a turbine airfoil
AU - Ekkad, S.V.
AU - Pamula, G.
AU - Acharya, S.
T2 - Journal of Heat Transfer
AB - Detailed heat transfer distributions are presented inside a two-pass coolant channel with crossflow-induced swirl and impingement. The impingement and passage crossflow are generated from one coolant passage to the adjoining coolant passage through a series of straight or angled holes along the dividing wall. The holes provide for the flow turning from one passage to another typically achieved in a conventional design by a 180-deg U-bend. The holes direct the flow laterally from one passage to another and generate different secondary flow patterns in the second pass. These secondary flows produce impingement and swirl and lead to higher heat transfer enhancement. Three different lateral hole configurations are tested for three Reynolds numbers (Re=10,000, 25,000, 50,000). The configurations were varied by angle of delivery and location on the divider wall. A transient liquid crystal technique is used to measure the detailed heat transfer coefficient distributions inside the passages. Results with the new crossflow feed system are compared with the results from the traditional 180-deg turn passage. Results show that the crossflow feed configurations produce significantly higher Nusselt numbers on the second pass walls without affecting the first pass heat transfer levels. The heat transfer enhancement is as high as seven to eight times greater than obtained in the second pass for a channel with a 180-deg turn. The increased measured pressure drop (rise in friction factor) caused by flow through the crossflow holes are compensated by the significant heat transfer enhancement obtained by the new configuration. [S0022-1481(00)03103-0]
DA - 2000///
PY - 2000///
DO - 10.1115/1.1289020
VL - 122
IS - 3
SP - 587-597
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0034251863&partnerID=MN8TOARS
ER -
TY - JOUR
TI - Impingement heat transfer measurements under an array of inclined jets
AU - Ekkad, S.
AU - Huang, Y.
AU - Han, J.-C.
T2 - Journal of thermophysics and heat transfer
AB - References 1Marotta, E. E., and Fletcher, L. S., “Thermal Contact Conductance of Selected Polymeric Materials,” Journal of Thermophysics and Heat Transfer, Vol. 10, No. 2, 1996, pp. 334–342. 2Mikic, B. B., “Thermal Contact Conductance; Theoretical Considerations,” International Journal of Heat and Mass Transfer, Vol. 17, 1974, pp. 205–214. 3Cooper, M., Mikic, B. B., and Yovanovich, M. M., “Thermal Contact Conductance,” International Journal of Heat and Mass Transfer, Vol. 12, 1969, pp. 279–300. 4Parihar, S. K., and Wright, N. T., “Thermal Contact Resistance at Elastomer toMetal Interfaces,” InternationalCommunicationsinHeat andMass Transfer, Vol. 24, No. 8, 1997, pp. 1083–1092. 5Makushkin, A. P., “Study of Stress-Strain of Polymer Layer During Spherical Indenter Penetration,” Trenie I Iznos, Vol. 5, No. 5, 1984, pp. 823–832. 6Greenwood, J. A., and Williamson, J. B. P., “Contact of Nominally Flat Surfaces,” Proceeding of the Royal Society of London, Series A: Mathematical and Physical Sciences, Vol. A295, 1966, pp. 300–319.
DA - 2000///
PY - 2000///
DO - 10.2514/2.6524
VL - 14
IS - 2
SP - 286-288
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0033734436&partnerID=MN8TOARS
ER -
TY - JOUR
TI - Detailed heat transfer measurements inside straight and tapered two-pass channels with rib turbulators
AU - Ekkad, S.V.
AU - Pamula, G.
AU - Shantiniketanam, M.
T2 - Experimental Thermal and Fluid Science
AB - Most of the studies on gas turbine blade internal channels have focused on constant cross-sectional areas from entrance to turn. Gas turbine blades are typically tapered from hub to tip to reduce thermal loading. These channels exist inside high-performance turbine blades for providing effective cooling to the blade external surface, which is exposed to high-temperature gas flow. Heat transfer measurements are presented for both the straight and tapered square channels including the turn region with and without rib turbulators. The straight channels will have a uniform square cross-section area of 5.08×5.08cm2. For the tapered channels, the square cross-sectional area reduces from entrance into the first pass (5.08×5.08cm2) to the 180° turn (2.54×2.54cm2) and then expands from turn to exit in the second pass (5.08×5.08cm2). The heat transfer results for tapered channels are compared with results for straight channels. Results show that heat transfer in tapered smooth channels is enhanced significantly due to flow acceleration in the first pass, a combination of taper and turn and flow deceleration in the second pass. Overall, the tapered channels significantly produce higher heat transfer enhancements compared to the Dittus–Boelter correlation for fully developed flow especially in the after-turn region. Based on the results from this study, the heat transfer inside tapered channels in the after-turn region cannot be predicted by calculating local Reynolds numbers and using straight channel heat transfer correlations. However, the first pass Nusselt number enhancement distributions are similar for both straight and tapered channels when normalized using the local Nusselt number based on local Reynolds number. The difference in the after-turn region between the straight and tapered channels is reduced with the addition of rib turbulators.
DA - 2000///
PY - 2000///
DO - 10.1016/S0894-1777(00)00022-4
VL - 22
IS - 3-4
SP - 155-163
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0034280281&partnerID=MN8TOARS
ER -
TY - JOUR
TI - A transient liquid crystal thermography technique for gas turbine heat transfer measurements
AU - Ekkad, S.V.
AU - Han, J.-C.
T2 - Measurement Science and Technology
AB - This paper presents in detail the transient liquid crystal technique for convective heat transfer measurements. A historical perspective on the active development of liquid crystal techniques for convective heat transfer measurement is also presented. The experimental technique involves using a thermochromic liquid crystal coating on the test surface. The colour change time of the coating at every pixel location on the heat transfer surface during a transient test is measured using an image processing system. The heat transfer coefficients are calculated from the measured time responses of these thermochromic coatings. This technique has been used for turbine blade internal coolant passage heat transfer measurements as well as turbine blade film cooling heat transfer measurements. Results can be obtained on complex geometry surfaces if visually accessible. Some heat transfer results for experiments with jet impingement, internal cooling channels with ribs, flow over simulated TBC spallation, flat plate film cooling, cylindrical leading edge and turbine blade film cooling are presented for demonstration.
DA - 2000///
PY - 2000///
DO - 10.1088/0957-0233/11/7/312
VL - 11
IS - 7
SP - 957-968
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0034235042&partnerID=MN8TOARS
ER -
TY - CONF
TI - Influence of cross-flow induced swirl and impingement on heat transfer in a two-pass channel connected by two rows of holes
AU - Pamula, G.
AU - Ekkad, S.V.
AU - Acharya, S.
AB - Detailed heat transfer distributions are presented inside a two-pass coolant square channel connected by two rows of holes on the divider walls. The enhanced cooling is achieved by a combination of impingement and crossflow-induced swirl. Three configurations are examined where the cross flow is generated from one coolant passage to the adjoining coolant passage through a series of straight and angled holes and a two-dimensional slot placed along the dividing wall. The holes/slots deliver the flow from one passage to another typically achieved in a conventional design by a 180° U-bend. Heat transfer distributions will be presented on the sidewalls of the passages. A transient liquid crystal technique is applied to measure the detailed heat transfer coefficient distributions inside the passages. Results for the three hole supply cases are compared with the results from the traditional 180° turn passage for three channel flow Reynolds numbers ranging between 10000 and 50000. Results show that the new feed system, from first pass to second pass using crossflow injection holes, produce significantly higher Nusselt numbers on the second pass walls. The heat transfer enhancement in the second pass of these channels are as high as 2–3 times greater than that obtained in the second pass for a channel with a 180° turn. Results are also compared with channels that have only one row of discharge holes.
C2 - 2000///
C3 - Proceedings of the ASME Turbo Expo
DA - 2000///
DO - 10.1115/2000-GT-0235
VL - 3
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84955163751&partnerID=MN8TOARS
ER -
TY - CONF
TI - Film cooling on a flat surface with a single row of cylindrical angled holes: Effect of discrete tabs
AU - Ekkad, S.V.
AU - Nasir, H.
AU - Acharya, S.
C2 - 2000///
C3 - American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD
DA - 2000///
VL - 366
SP - 3-12
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0347705413&partnerID=MN8TOARS
ER -
TY - JOUR
TI - Film cooling measurements on cylindrical models with simulated thermal barrier coating spallation
AU - Ekkad, S.V.
AU - Han, J.C.
T2 - Journal of thermophysics and heat transfer
AB - Detailed heat transfer coefficient and film effectiveness distributions are presented on a cylindrical leading-edge model with simulated thermal barrier coating spallation using a transient liquid crystal technique. Tests were performed in a low-speed wind tunnel on a cylindrical model in a crossflow with two rows of injection holes. Mainstream Reynolds number based on the cylinder diameter was 1.009 x 10 5 . The two rows of injection holes were ±15 deg from stagnation. The film holes were spaced four hole diameters apart and were angled 30 and 90 deg to the surface in the spanwise and streamwise directions, respectively. The simulated spallation cavities were rectangular in shape and had rounded edges. The simulated spallation was placed at two locations, 20-40 deg (S3) and 35-55 deg (S4), respectively. The cylinder surface was coated with thermochromic liquid crystals, and a transient test was run to obtain the heat transfer coefficients and film effectiveness. The effect of coolant blowing ratio was studied for blowing ratios of 0.4 and 0.8. Results show that the Nusselt numbers increase and film effectiveness values decrease with an increasing blowing ratio
DA - 2000///
PY - 2000///
DO - 10.2514/2.6531
VL - 14
IS - 2
SP - 194-200
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0033742951&partnerID=MN8TOARS
ER -
TY - CONF
TI - Microstructurally induced ductile deformation mechanisms and grain-boundary effects in polycrystalline aggregates
AU - Ashmawi, W.M.
AU - Zikry, M.A.
C2 - 2000///
C3 - Materials Research Society Symposium - Proceedings
DA - 2000///
VL - 578
SP - 339-344
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0033697993&partnerID=MN8TOARS
ER -
TY - CONF
TI - Control of failure evolution in 3D cellular woven composite systems
AU - Baucom, J.N.
AU - Zikry, M.A.
AU - Qiu, Y.
AB - Abstract This investigation examines the role of porosity in the perforation resistance of 3-D woven fiber reinforced epoxy panels under impact by rigid projectiles at velocities of 100 to 200 m/s. Incident and residual velocities are measured to determine the energy absorption by the target. To compare samples of different areal density, the energy is normalized by the target areal density. The sample responses segregate by porosity, and the more highly porous samples absorb a greater amount of specific energy. The reason for this is unclear but may be due to the deflection of matrix cracks by pores or due to the greater flexibility of the fibers to absorb energy through tensile straining. Although porosity is generally an undesirable property in textile composites, the induction of porosity may result in reduced panel weight without degradation of ballistic performance, a clear advantage for weight minimization.
C2 - 2000///
C3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
DA - 2000///
DO - 10.1115/IMECE2000-2155
VL - 2000-G
SP - 59-65
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0242537027&partnerID=MN8TOARS
ER -
TY - CONF
TI - Simulation of Supersonic Cluster Beams for the Deposition of Nanostructured Films I
AU - Tafreshi, H.V.
AU - Benedek, G.
AU - Piseri, P.
AU - Barborini, E.
AU - Milani, P.
T2 - Nozzle Design Study, Conference on High Performance Parallel Computing (CAPI 2000)
C2 - 2000/9/21/
C3 - Nozzle Design Study, Conference on High Performance Parallel Computing (CAPI 2000)
CY - Milan, Italy
DA - 2000/9/21/
PY - 2000/9/21/
ER -
TY - CONF
TI - Simulation of Supersonic Cluster Beams for the Deposition of Nanostructured Films
AU - Tafreshi, H.V.
AU - Benedek, G.
AU - Milani, P.
T2 - National Conference on Physics of Matter (INFMeeting)
C2 - 2000/6/9/
C3 - National Conference on Physics of Matter (INFMeeting)
CY - Genoa, Italy
DA - 2000/6/9/
PY - 2000/6/9/
ER -
TY - JOUR
TI - Evaluation Method of Tribological Conditions in Net Shape Cold Forging of Products with Concave-Convex Profiles
AU - Saiki, Hiroyuki
AU - Marumo, Yasuo
AU - Ruan, Liqun
AU - Ngaile, Gracious
T2 - Japanese Technology of plasticity
DA - 2000/10//
PY - 2000/10//
VL - 41
IS - 477
SP - 1036–1040
ER -
TY - CONF
TI - Bending Deflections Due to Scribe-Induced Residual Stress
AU - Austin, B.
AU - Love, B.
AU - Dow, T.
AU - Eischen, J.W.
AU - Scattergood, R.
T2 - American Society for Precision Engineering Conference
C2 - 2000///
C3 - Proceedings of the American Society for Precision Engineering Conference
CY - Scottsdale, AZ
DA - 2000///
PY - 2000///
ER -
TY - CONF
TI - Optimal Pickup Locations for Fabric Handling
AU - Lankalapalli, S.
AU - Eischen, J.W.
T2 - ASME 2000 International Mechanical Engineering Congress and Exposition
C2 - 2000/11//
C3 - Mechanics in biology : presented at the 2000 ASME International Mechanical Engineering Congress and Exposition, November 5-10, 2000, Orlando, Florida
CY - Orlando, Florida
DA - 2000/11//
PY - 2000/11/5/
PB - American Society of Mechanical Engineers
SN - 9780791819173
ER -
TY - CHAP
TI - Collision Detection in Cloth Modeling
AU - Bigliani, R.
AU - Eischen, J.W.
T2 - Cloth Modeling and Animation
A2 - Peters, A.K.
PY - 2000///
ER -
TY - CHAP
TI - Continuum Versus Particle Representations
AU - Eischen, J.W.
AU - Bigliani, R.
T2 - Cloth modeling and animation
A2 - House, D.
A2 - Breen, D.E.
PY - 2000///
PB - A.K. Peters
SN - 9781568810904 9781439863947 9780429065095
ER -
TY - CONF
TI - Control Problems for Planar Maneuvers of a Spacecraft with Fuel Slosh
AU - Reyhanoglu, M.
AU - Cho, S.
AU - McClamroch, N.H.
T2 - International Conference on Nonlinear Problems in Aviation
C2 - 2000///
C3 - Proceedings of the International Conference on Nonlinear Problems in Aviation
CY - Daytona Beach, FL
DA - 2000///
PY - 2000///
SP - 579–584
ER -
TY - JOUR
TI - Discontinuous feedback control of a special class of underactuated mechanical systems
AU - Reyhanoglu, Mahmut
AU - Cho, Sangbum
AU - Harris McClamroch, N.
T2 - International Journal of Robust and Nonlinear Control
AB - We study a control problem for a special class of underactuated mechanical systems, namely for mechanical systems with several directly actuated degrees of freedom and a single unactuated degree of freedom that must be controlled through the system coupling. Specific assumptions are introduced that define this class, which includes many important models of mechanical system examples. The main result of the paper is the construction of a discontinuous nonlinear feedback controller for which the closed loop equilibrium at the origin is made ‘globally attractive’. The control construction approach is introduced in detail, and a proof of attractiveness is presented. The results are applied to control of the planar motion of a rigid body with a single unactuated internal degree of freedom. Copyright © 2000 John Wiley & Sons, Ltd.
DA - 2000/4/15/
PY - 2000/4/15/
DO - 10.1002/(sici)1099-1239(20000415)10:4<265::aid-rnc470>3.0.co;2-n
VL - 10
IS - 4
SP - 265-281
J2 - Int. J. Robust Nonlinear Control
LA - en
OP -
SN - 1049-8923 1099-1239
UR - http://dx.doi.org/10.1002/(sici)1099-1239(20000415)10:4<265::aid-rnc470>3.0.co;2-n
DB - Crossref
ER -
TY - CONF
TI - Dynamics of multibody vehicles and their formulation as nonlinear control systems
AU - Cho, Sangbum
AU - McClamroch, N.H.
AU - Reyhanoglu, M.
T2 - 2000 American Control Conference (ACC 2000)
AB - We develop equations of motion for multibody vehicles that can be used for nonlinear system analysis and control design. A multibody vehicle consists of a base body that can undergo general motion in three dimensions, as well as a finite number of body interconnections that can deform relative to the base body and hence define the shape of the multibody. A Lagrangian development leads to equations of motion that are expressed in terms of the locked inertia and the mechanical connection. We show that the equations of motion can be written in terms of the base body translational and angular momentum (or equivalently the base body translational and angular velocities) and generalized coordinates for the shape. The coupling between the base body translational and rotational dynamics and the shape dynamics is made clear in this formulation. We define several fundamental categories of underactuated control problems, based on specific control actuation assumptions.
C2 - 2000///
C3 - Proceedings of the 2000 American Control Conference. ACC (IEEE Cat. No.00CH36334)
CY - Chicago, IL
DA - 2000///
PY - 2000/6/28/
DO - 10.1109/acc.2000.876955
PB - IEEE
SN - 0780355199
UR - http://dx.doi.org/10.1109/acc.2000.876955
ER -
TY - JOUR
TI - Visualization of preflame and combustion reactions in engine cylinders
AU - Jansons, M.
AU - Lin, S.
AU - Fang, T.
AU - Rhee, K.T.
T2 - SAE Technical Papers
DA - 2000///
PY - 2000///
DO - 10.4271/2000-01-1800
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877485919&partnerID=MN8TOARS
ER -
TY - CONF
TI - Feedback control of a space vehicle with unactuated fuel slosh dynamics
AU - Cho, Sangbum
AU - McClamroch, M.
AU - Reyhanoglu, Mahmut
T2 - AIAA Guidance, Navigation, and Control Conference and Exhibit
AB - We develop a mathematical model that describes the accelerating flight of a spacecraft in a fixed plane. The spacecraft is represented as a rigid body and fuel slosh dynamics are included using a common pendulum model. The control inputs are defined by a transverse body fixed force and a pitching moment about the center of mass of the spacecraft; the slosh dynamics are assumed to be unactuated. The model is placed in the form of a nonlinear control system that allows for the study of planar vehicle maneuvers. We develop a nonlinear feedback controller that stabilizes a relative equilibrium corresponding to suppression of the transverse, pitch, and slosh dynamics. This controller is a significant extension of what has been done previously, since it simultaneousl y controls both the rigid vehicle motion and the fuel slosh dynamics.
C2 - 2000/8/14/
C3 - AIAA Guidance, Navigation, and Control Conference and Exhibit
DA - 2000/8/14/
DO - 10.2514/6.2000-4046
PB - American Institute of Aeronautics and Astronautics
SN - 9781624103018
UR - http://dx.doi.org/10.2514/6.2000-4046
DB - Crossref
ER -
TY - JOUR
TI - Heat generation during the fatigue of a cellular Al alloy
AU - Rabiei, A.
AU - Hutchinson, J. W.
AU - Evans, A. G.
T2 - Metallurgical and Materials Transactions A
AB - The heat generation from a notch during the compression-compression fatigue of a cellular Al alloy has been measured and compared with a model. The measurements indicate that heat is generated because of hysteresis occurring in narrow cyclic plastic zones outside the notch. This process continues until the notch closes. At closure, a brief period of heat generation arises because of friction along the notch faces. A plasticity model based on the Dugdale zone is shown to provide a reasonably accurate characterization of the heat generated, with the proviso that an “ineffective” zone be transposed onto the notch tip. It is found that the temperatures generated are too small to cause fatigue by thermal softening. A fatigue mechanism based on either geometric softening of the cells or crack growth in the cell walls is implied.
DA - 2000/4//
PY - 2000/4//
DO - 10.1007/s11661-000-0108-0
VL - 31
IS - 4
SP - 1129-1136
J2 - Metall and Mat Trans A
LA - en
OP -
SN - 1073-5623 1543-1940
UR - http://dx.doi.org/10.1007/s11661-000-0108-0
DB - Crossref
ER -
TY - JOUR
TI - A study on fracture behavior of particle reinforced metal matrix composites by using acoustic emission source characterization
AU - Rabiei, A.
AU - Enoki, M.
AU - Kishi, T.
T2 - Materials Science and Engineering: A
AB - Abstract A one directional acoustic emission (AE) source characterization has been used during a three point bending fracture toughness test on 6061 aluminum matrix composites with Al2O3 particle reinforcements of 5 and 10 μm sizes, in order to evaluate the dynamic process of micro-fracture in these materials. Different acoustic emission sources are characterized and, as a result, two types of AE events are distinguished. It is observed that at very low strain levels void nucleation is the main source for acoustic emission. At higher levels, the micro pop-in of primary voids and their eventual coalescence results in a different type of acoustic emission. In fine particle reinforced materials, when the amplitude of AE events in void nucleation at fine particles is not high enough to be detected, the main source of AE events is only the void coalescence. By increasing the particle size, the number of detectable events during void nucleation is increased.
DA - 2000/11//
PY - 2000/11//
DO - 10.1016/s0921-5093(00)01218-1
VL - 293
IS - 1-2
SP - 81-87
J2 - Materials Science and Engineering: A
LA - en
OP -
SN - 0921-5093
UR - http://dx.doi.org/10.1016/s0921-5093(00)01218-1
DB - Crossref
KW - acoustic emission
KW - metal matrix composites
KW - Green's function
KW - void nucleation
KW - coalescence
ER -
TY - JOUR
TI - Failure mechanisms associated with the thermally grown oxide in plasma-sprayed thermal barrier coatings
AU - Rabiei, A
T2 - Acta Materialia
AB - The microstructure and durability of a thermal barrier coating (TBC) produced by the thermal spray method have been characterized. Upon exposure, the bond coat chemistry and microstructure change by inter-diffusion with the substrate and upon thickening of the thermally grown oxide (TGO). A wedge impression test, in conjunction with observations by scanning electron microscopy, has been used to probe the failure mechanisms. At short exposure times, when the TGO thickness is less than about 5 μm, the growth of the TGO does not affect the crack patterns in the TBC and delaminations induced by wedge impression propagate within the TBC about 30 μm from the interface. An amorphous phase at the splat interfaces promotes this failure mode. As the thickness of TGO increases during exposure, cracks form in the TBC around imperfections at the interface. Moreover, induced delaminations develop a trajectory close to the interface, propagating not only through the TBC but also within the TGO and along the interfaces. A scaling result based on the misfit around imperfections caused by TGO growth has been used to rationalize the critical TGO thickness when the TBC fails.
DA - 2000/9//
PY - 2000/9//
DO - 10.1016/s1359-6454(00)00171-3
VL - 48
IS - 15
SP - 3963-3976
OP -
SN - 1359-6454
UR - http://dx.doi.org/10.1016/s1359-6454(00)00171-3
DB - Crossref
KW - coating
KW - plasma spray
KW - thermally activated process
KW - scanning electron microscopy
KW - fracture toughness
ER -
TY - JOUR
TI - Soot formation effects of oxygen concentration in the oxidizer stream of laminar coannular nonpremixed methane/air flames
AU - Lee, KO
AU - Megaridis, CM
AU - Zelepouga, S
AU - Saveliev, AV
AU - Kennedy, LA
AU - Charon, O
AU - Ammouri, F
T2 - COMBUSTION AND FLAME
AB - This experimental investigation analyzes the soot formation effects of oxygen concentration in the oxidizer stream (O2 + N2) ventilating laminar jet nonpremixed methane flames. The base flame incorporates air as the oxidizer; two additional flames, with respective oxygen concentrations of 50% and 100% in the ventilating coflow, are also examined. The microstructure of soot collected from selected flame locations is determined combining thermophoretic sampling and transmission electron microscopy. A laser-light extinction technique is employed along with tomographic inversion to measure the soot volume fraction distributions within the three flames. The results indicate that soot surface growth and oxidation rates in the methane/50% oxygen flame are higher compared to the respective rates in the methane/air base flame. The rate of soot inception becomes stronger with increasing oxygen content in the oxidizer stream. Soot yields diminish with increasing oxygen concentration, as do luminous flame spatial dimensions. Soot aggregate data on the soot annulus suggest a higher degree of agglomeration under oxygen-enriched conditions. Finally, the fractal dimensions of selected soot aggregate samples are measured to be 1.64 (methane/air flame) and 1.65 (methane/50% oxygen flame), being similar to previously published values for carbonaceous soot.
DA - 2000/4//
PY - 2000/4//
DO - 10.1016/s0010-2180(99)00131-5
VL - 121
IS - 1-2
SP - 323-333
SN - 0010-2180
ER -
TY - JOUR
TI - Relative effect of acetylene and PAHs addition on soot formation in laminar diffusion flames of methane with oxygen and oxygen-enriched air
AU - Zelepouga, SA
AU - Saveliev, AV
AU - Kennedy, LA
AU - Fridman, AA
T2 - COMBUSTION AND FLAME
AB - Abstract The influence of the addition of acetylene and polycyclic aromatic hydrocarbons (PAHs) on soot formation was studied experimentally for nonpremixed, axisymmetric, coflowing flames of methane with oxygen and oxygen-enriched air. Four reference flames, containing 21, 35, 50, and 100% of oxygen in the oxidizer stream, were seeded with calibrated levels of acetylene, acenaphthene (C12H10), phenanthrene (C14H10), and pyrene (C16H10). It was found that all additives studied enhance soot formation in the reference flames, with the integral soot content increasing linearly with the additive concentration. The increases in the flames’ soot volume fractions induced by the addition of PAH compounds were significantly larger relative to the increase due to acetylene addition. The effect of PAH addition on soot growth became substantially stronger with oxygen enrichment of the oxidizer stream. Conversely the relative increase in soot concentration in the flames seeded with acetylene was nearly the same regardless of oxygen content in the oxidizer stream. Estimated additive-to-soot conversion ratios show high degrees of PAHs transformation to soot for all flames studied. The additive-to-soot conversion ratio for pyrene was found to be nearly 2 and remains practically constant with increase of oxygen content. Comparatively, the additive-to-soot conversion ratio for acetylene was close to 0.3 for methane/air flame and decreased with oxygen enrichment. These results suggest that conversion of PAHs to soot is controlled by a relatively fast kinetic mechanism. The conversion rate of acetylene is much slower and may involve a number of stages, including rate-limiting stage of PAHs formation.
DA - 2000/7//
PY - 2000/7//
DO - 10.1016/s0010-2180(00)00104-8
VL - 122
IS - 1-2
SP - 76-89
SN - 0010-2180
ER -
TY - JOUR
TI - Chemical structures of methane-air filtration combustion waves for fuel-lean and fuel-rich conditions
AU - Kennedy, LA
AU - Bingue, JP
AU - Saveliev, AV
AU - Fridman, AA
AU - Foutko, SI
T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE
AB - Chemical structures of filtration combustion waves in an inert porous media were analyzed comparatively for lean and rich methane-air mixtures. Temperature, velocity, and chemical products of the combustion waves were studied experimentally in the range of equivalence ratios from 0.2 to 2.5. Downstream (superadiabatic) wave propagation was observed for ultralean ( ≤0.45) and ultrarich ( ≥1.7) mixtures. Upstream (underadiabatic) propagation corresponds to the range of equivalence ratios from 0.45 to 1.7. It was found that with the equal heat content, rich mixtures have essentially higher combustion temperatures than corresponding lean mixtures. The products of partial methane oxidation (H2, CO, and C2 hydrocarbons) are dominant for ultrarich superadiabatic combustion where up to 60% of methane is converted to CO and H2. A numerical model, based on a two-temperature approximation and detailed combustion chemistry, is developed to analyze species profiles and the combustion mechanism of the filtration waves. The model predictions for combustion temperatures and chemical products are in good agreement with experimental data. Kinetic simulation revealed the complex chemical structure of the ultrarich superadiabatic waves. It is shown that this wave is composed of an exothermic “partial oxidation” reaction zone followed by an endothermic “steam reforming” zone.
DA - 2000///
PY - 2000///
DO - 10.1016/s0082-0784(00)80359-8
VL - 28
SP - 1431-1438
SN - 1873-2704
ER -
TY - JOUR
TI - The law of large numbers for fuzzy numbers with unbounded supports
AU - Hong, DH
AU - Ro, PI
T2 - FUZZY SETS AND SYSTEMS
AB - We study laws of large numbers for mutually T-related fuzzy numbers with unbounded supports where T is an Archimedean t-norm and generalize earlier result of Badard.
DA - 2000/12/1/
PY - 2000/12/1/
DO - 10.1016/S0165-0114(98)00188-2
VL - 116
IS - 2
SP - 269-274
SN - 0165-0114
KW - fuzzy numbers
KW - t-norm
KW - law of large numbers
ER -
TY - JOUR
TI - Partially premixed combustion in lifted turbulent jets
AU - Lyons, KM
AU - Watson, KA
T2 - COMBUSTION SCIENCE AND TECHNOLOGY
AB - This article reports observations of structures consistent with triple flame reaction zones in the stabilization region of turbulent nonpremixed jet flames. Previous studies of laminar mixing layers and nonpremixed jets show Hi brachial structures, however reports of triple flame structures in turbulent flowfields are sparse, The asymmetric coflow, which facilitates visualizing the luminous flame structure, is described and the observed double and triple flame structures are discussed. Flame luminosity data is presented and the relevance to CH planar laser-induced fluorescence (PLIF) studies of leading edge flame structures is discussed. Furthermore, connection is drawn to select theoretical studies of triple flames and partially premixed combustion.
DA - 2000///
PY - 2000///
DO - 10.1080/00102200008947298
VL - 156
SP - 97-105
SN - 0010-2202
KW - flame stabilization
KW - triple flame
KW - jet flame
KW - partially premixed combustion
ER -
TY - JOUR
TI - Numerical simulation of a three-dimensional flame/shock wave interaction
AU - Roy, CJ
AU - Edwards, , JR
T2 - AIAA JOURNAL
AB - A three-dimensional Navier-Stokes solver for chemically reacting flows is used to study the structure of a supersonic hydrogen-air flame stabilized in a Mach 2.4 rectangular cross-section wind tunnel. The numerical model uses a 9-species, 21-reaction hydrogen oxidation mechanism and employs Menter's hybrid κ-ω/κ-e turbulence model. An assumed probability density function is used to account for the effects of turbulent temperature fluctuations on the ensemble-averaged chemical reaction rates. Results are presented for a configuration studied at the University of Michigan in which the effects of wedge-generated shock waves on flame stability were determined. Computed pitot and static pressure profiles are compared with experimental measurements, and axial density gradient contour plots are compared with experimental schlieren photographs. The highly three-dimensional structure of the flame is described in detail, and stabilization mechanisms are discussed
DA - 2000/5//
PY - 2000/5//
DO - 10.2514/2.1035
VL - 38
IS - 5
SP - 745-754
SN - 0001-1452
ER -
TY - JOUR
TI - Simultaneous particle-imaging velocimetry and OH planar laser-induced fluorescence measurements in an unsteady counterflow propane/air diffusion flame
AU - Welle, EJ
AU - Roberts, WL
AU - Decroix, ME
AU - Carter, CD
AU - Donbar, JM
T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE
AB - To study the transient response of a diffusion flame to an unsteady flowfied, quatitative measurements of velocity, using particle-imaging velocimetry, and OH measurements, using planar laser-induced fluorescence, were made simultaneously in an oscillating conterflow diffusion flame. These non-intrusive measurements were performed to spatially and tempoerally resolved flowrield and flame characteristics as a function of initial strain rate and forcing frequency. For the forcing frequencies considered in this study, the strain rate fluctuations were found to lag the velocity fluctuations, but the phase difference decresed with increasing forcing frequency. At lower forcing frequencies, the width of the OH field responded quasi-steadily, but as the forcing frequency increased, the OH field showed transient effects. The dilatation velocity, defined as the difference between the minimum velocity in the preheat zone and the maximum velocity in the reaction zone, was used as a flame temperature indicator. The dilatation velocity revealed that the phase difference between the velocity and the temperature increased with increasing forcing frequency, confirming the existence of a diffusion limited response. The resuls presented here help to illuminate the interconnecting relationships between the chemistry, fluid dynamics, and reactant transport times.
DA - 2000///
PY - 2000///
DO - 10.1016/s0082-0784(00)80609-8
VL - 28
SP - 2021-2027
SN - 1873-2704
ER -
TY - JOUR
TI - Turbulent three-dimensional air flow and trace gas distribution in an inhalation test chamber
AU - Longest, PW
AU - Kleinstreuer, C
AU - Kinsey, JS
T2 - JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
AB - Steady incompressible turbulent air flow and transient carbon monoxide transport in an empty Rochester-style human exposure chamber have been numerically simulated and compared with experimental data sets. The system consisted of an inlet duct with a continuous carbon monoxide point source, 45- and 90-degree bends, a round diffuser, a round-to-square transition, a rectangular diffuser, the test chamber, a perforated floor, and again transition pieces from the chamber to an outlet duct. Such a configuration induced highly nonuniform vortical flow patterns in the chamber test area where a pollutant concentration is required to be constant at breathing level for safe and accurate inhalation studies. Presented are validated momentum and mass transfer results for this large-scale system with the main goals of determining the development of tracer gas (CO) distributions in the chamber and analyzing the contributions to CO-mixing. Numerical simulations were conducted employing a k-ε model and the latest available RNG k-ε model for air and CO-mixing. Both models predict similar velocity fields and are in good agreement with measured steady and transient CO-concentrations. It was found that secondary flows in the inlet section and strong vortical flow in the chamber with perforated flooring contributed to effective mixing of the trace gas at breathing levels. Specifically, in the height range of 1.4 m<h<2.0 m above the chamber floor, predicted CO-concentrations rapidly reached a near constant value which agrees well with experimental results. This work can be extended to analyze trace gas mixing as well as aerosol dispersion in occupied test chambers with or without flow redirection devices installed in the upstream section. A complementary application is particle transport and deposition in clean rooms of the electronic, pharmaceutical, and health care industries. [S0098-2202(00)01702-8]
DA - 2000/6//
PY - 2000/6//
DO - 10.1115/1.483270
VL - 122
IS - 2
SP - 403-411
SN - 0098-2202
ER -
TY - JOUR
TI - An experimental investigation of the creping process in low-density paper manufacturing
AU - Ramasubramanian, MK
AU - Shmagin, DL
T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME
AB - In this paper, a unique apparatus for the laboratory simulation and analysis of the creping process is described. The device consists of a fluid-heated micro-yankee dryer, 25.4 cm (10 inches) in diameter, and 8.25 cm (3.25 inches) wide, and a creping blade engaging system mounted on a three-component piezoelectric load cell. Mechatronics design principles were followed to design the device so that discrete paper samples can be creped at speeds over 250 meters/minute. The device has been used to study the effect of various manufacturing process parameters such as the creping adhesive type, concentration (application rate), creping geometry (creping angle), machine speed, and moisture content in the sheet at the time of creping, and their influence on sheet structure and creping forces. A mechanistic description of the creping process is also presented. [S1087-1357(00)02102-X]
DA - 2000/8//
PY - 2000/8//
DO - 10.1115/1.1285908
VL - 122
IS - 3
SP - 576-581
SN - 1087-1357
ER -
TY - JOUR
TI - r-Refinement grid adaptation algorithms and issues
AU - McRae, DS
T2 - COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
AB - Issues concerning r-refinement adaptation are discussed in terms of the research underway at North Carolina State University. A brief justification for adaptation is offered and adaptation criteria are stated. The NCSU adaptation algorithms DSAGA and SIERRA are described and results obtained with these algorithms are used to illustrate the adaptation issues. Grid quality, truncation errors added and reduced by adaptation, and current research areas are discussed. Qualitative analysis of grids produced by the adaptive algorithms reveals that conventional standards of grid quality are violated frequently in regions where solution improvement due to adaptation is evident. Alignment of the grid with solution features is shown to be a more appropriate indication of mesh improvement than cell shape. Benefits and weaknesses of r-refinement adaptation are summarized and areas for further research are noted.
DA - 2000///
PY - 2000///
DO - 10.1016/S0045-7825(99)00372-2
VL - 189
IS - 4
SP - 1161-1182
SN - 0045-7825
ER -
TY - JOUR
TI - Using computer spreadsheets for water flow and biofilter sizing in recirculating aquaculture production systems
AU - Losordo, TM
AU - Hobbs, AO
T2 - AQUACULTURAL ENGINEERING
AB - North Carolina State University has been active in the development, evaluation and demonstration of recirculating aquaculture technology since 1989. In the process, numerous engineering and economic spreadsheets (worksheets) have been developed to assist in the design and analysis of these systems. The spreadsheet described in this paper is based on a set of mass balance equations developed and described by Losordo and Westers (Vol. 27, 1994 pp. 9–60) to estimate the carrying capacity and required flow rates of recirculating aquaculture production systems. This spreadsheet can be used to estimate the recycle flowrate that is required to maintain user specified water quality conditions for a given feed input rate and water treatment system configuration. These water quality conditions include suspended solids, total ammonia-nitrogen, and dissolved oxygen concentration. The spreadsheet also provides an estimate of the new water required by the system to maintain a user specified nitrate-nitrogen concentration. In addition, the spreadsheet provides an estimate of the required biofilter volume and cross-sectional (top) surface area for the given biofilter shape, depth and specific surface area of the biofilter media. The mass balance equations used in this spreadsheet are based upon waste metabolites generated and oxygen consumed by daily inputs of feed into a system.
DA - 2000/9//
PY - 2000/9//
DO - 10.1016/S0144-8609(00)00048-0
VL - 23
IS - 1-3
SP - 95-102
SN - 0144-8609
KW - recirculating system
KW - spreadsheet model
KW - systems design
ER -
TY - JOUR
TI - Simulation of coupled turbulent flow and heat transfer in the wedge-shaped pool of a twin-roll strip casting process
AU - Kim, WS
AU - Kim, DS
AU - Kuznetsov, AV
T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
AB - The proper choice of nozzle in a twin-roll strip casting process is important to obtain the stabilization of the molten steel and free surface and a stable temperature distribution in a wedge-shaped pool. In this study, a numerical investigation of the coupled turbulent flow and heat transfer in a twin-roll strip casting process was performed for two patterns of melt-feed through a nozzle. In addition, the patterns for the removal of superheat for different gap thicknesses were analyzed using a local Nusselt number along the roll surface. The flow turbulence was examined using the low-Reynolds-number k–ε turbulence model of Launder and Sharma. The results show that the use of a submerged nozzle may have a beneficial impact on the stabilization of the free-surface zone. The increased gap thickness yields an increased local Nusselt number in the downstream section of the wedge-shaped pool where the cross-sectional flow area is reduced.
DA - 2000/10//
PY - 2000/10//
DO - 10.1016/S0017-9310(00)00013-2
VL - 43
IS - 20
SP - 3811-3822
SN - 0017-9310
ER -
TY - JOUR
TI - High strain-rate shear-strain localization in f.c.c. crystalline materials: a perturbation analysis
AU - Zikry, MA
AU - Pothier, MR
AU - Baucom, JN
T2 - INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
AB - Abstract A new perturbation formulation has been developed that is based on a rate-dependent crystalline plasticity constitutive formulation to investigate planar high strain-rate instabilities and shear-strain localization in face-centered cubic (f.c.c.) crystalline materials. This new formulation can account for strain-rate sensitivity values that range from rate-independent to highly rate-dependent values. Hence, accurate and detailed predictions of material instabilities and shear-strain localization can be obtained for high strain-rate deformations of crystalline materials that are rate-sensitive, such as f.c.c. materials. Critical instability parameters are obtained for deformation modes that account for the effects of strain-rate history, inertia, strain-hardening, wave number, and thermal and geometrical softening for applied strain-rates that range from 100 to 5000 s−1. Post-instability behavior and localization modes are monitored by tracking the rate of growth of stability parameters beyond the initial instability point. Results from these perturbation analyses are in good agreement with rate-independent limiting cases and high strain-rate experimental observations. The present study underscores the importance of characterizing material instabilities and shear-strain localization in terms of the competing softening and hardening mechanisms of the lattice structure.
DA - 2000/10//
PY - 2000/10//
DO - 10.1016/S0020-7683(99)00266-8
VL - 37
IS - 43
SP - 6177-6202
SN - 0020-7683
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0345852386&partnerID=MN8TOARS
KW - shear strain localization
KW - high strain-rate
KW - f.c.c. crystalline materials
KW - perturbation analyses
KW - material failure and instability
ER -
TY - JOUR
TI - Determination and representation of the stress coefficient terms by path-independent integrals in anisotropic cracked solids
AU - Yang, S
AU - Yuan, FG
T2 - INTERNATIONAL JOURNAL OF FRACTURE
DA - 2000/2//
PY - 2000/2//
DO - 10.1023/A:1007639126484
VL - 101
IS - 4
SP - 291-319
SN - 0376-9429
KW - anisotropic materials
KW - crack-tip fields
KW - stress intensity factor
KW - energy release rate
KW - T-stress
KW - stress coefficient terms
KW - J-integral
KW - Betti's reciprocal theorem
ER -
TY - JOUR
TI - Anti-windup controller design using linear parameter-varying control methods
AU - Wu, F
AU - Grigoriadis, KM
AU - Packard, A
T2 - INTERNATIONAL JOURNAL OF CONTROL
AB - In this paper, we seek to provide a systematic anti-windup control synthesis approach for systems with actuator saturation within a linear parameter-varying (LPV) design framework. The closed-loop induced L2 gain control problem is considered. Different from conventional two-step anti-windup design approaches, the proposed scheme directly utilizes saturation indicator parameters to schedule accordingly the parameter-varying controller. Hence, the synthesis conditions are formulated in terms of linear matrix inequalities (LMIs) that can be solved very efficiently. The resulting gain-scheduled controller is non-linear in general and would lead to graceful performance degradation in the presence of actuator saturation non-linearities and linear performance recovery. An aircraft longitudinal dynamics control problem with two input saturation non-linearities is used to demonstrate the effectiveness of the proposed LPV anti-windup scheme.
DA - 2000/8//
PY - 2000/8//
DO - 10.1080/002071700414211
VL - 73
IS - 12
SP - 1104-1114
SN - 1366-5820
ER -
TY - JOUR
TI - Transient flow field effects on soot volume fraction in diffusion flames
AU - Decroix, ME
AU - Roberts, WL
T2 - COMBUSTION SCIENCE AND TECHNOLOGY
AB - Abstract Quantitative measurements of soot concentration made in an oscillating propane-air counterflow diffusion flame are presented. The non-intrusive laser induced incandescence (LII) technique was used to make spatially and temporally resolved measurements of soot volume fraction in these transient flames as a function of initial steady strain rate, forcing frequency, and forcing amplitude of the strain rate fluctuation. The results of this study show that the soot formation process becomes insensitive to fluctuations in strain rate at high initial strain rates. At low initial strain rates, however, the maximum soot concentration is drastically reduced with high frequency, high amplitude fluctuations compared to the corresponding steady strain soot volume fraction. Low frequency oscillations are found to always increase the maximum soot concentration, by up to a factor of six for some conditions. These measurements provide important insight into the response of the chemistry control1ing the soot formation process in flamelets subject to unsteady rates of strain.
DA - 2000///
PY - 2000///
DO - 10.1080/00102200008935801
VL - 160
SP - 165-189
SN - 0010-2202
ER -
TY - JOUR
TI - Reduced-order modelling and parameter estimation for a quarter-car suspension system
AU - Kim, C
AU - Ro, PI
T2 - PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING
AB - This paper presents a new approach to obtaining an accurate simple model for complex mechanical systems. The methodology is applied to a quarter-car suspension system with complex linkage structures. Firstly, a multi-body dynamic model which includes kinematic characteristics is developed. Using a linearization technique, a 32-state linear model for a quarter-car system is obtained. Secondly, model reduction techniques are applied to find a reasonable reduced-order model. The result of the model reduction shows the validity of the two-mass model given that the parameters are correctly identified. The paper presents both an analytical and an experimental way of identifying the parameters of the two-mass system based on the reduced-order model. The identified parameters are shown to vary significantly from component data typically used for the two-mass system depending on kinematic structures of the suspension system. The modelling procedures outlined in this paper provide a precise and efficient way of designing active suspension systems that minimizes a necessary tuning process.
DA - 2000///
PY - 2000///
DO - 10.1243/0954407001527907
VL - 214
IS - D8
SP - 851-864
SN - 2041-2991
KW - reduced-order model
KW - quarter-car suspension
KW - identification
KW - equivalent parameters
ER -
TY - JOUR
TI - Least-square curve and surface localization for shape conformance checking.
AU - Qu, J.
AU - Sarma, R.
T2 - Journal of Manufacturing Systems
DA - 2000///
PY - 2000///
VL - 19
IS - 5
SP - 297-304
ER -
TY - JOUR
TI - Extinction of laminar counterflow diffusion flames of CH4 and C3H8 fuels with inert jet impingement
AU - Chen, RH
AU - Lattimer, C
AU - Roberts, WL
T2 - COMBUSTION SCIENCE AND TECHNOLOGY
AB - Experimental results of N2-diluted counterflow diffusion flames of CH4 and C3H18 vs, air with local extinction are reponed. The local extinction was caused by inert jet impingement on flames at selected locations either from the fuel or oxidizer side of the reaction zone. This was done to simulate how local extinction affects flame extinction over a larger flame area. The results are: (1) Local extinction of both CH4 and C3H8 flames occurs at a lower strain rate when the inert jet impingement originates from the airside. (2) The global extinction strain rate for CH4 flames is insensitive to the location and number (one vs. three) of local extinction sites. (3) For C3H8 flames, one single inert jet impinging from the airside along the centerline is more effective in causing global extinction than three inert jets impinging at regions away from the centerline. This suggests that flame extinction over a larger area may depend on strategically selected smaller local extinction sites. Furthermore, since similar results of (3) are not observed in this study for CH4 flames, fuel chemistry may also play a role in the effectiveness of local extinction transitioning to global extinction. Differences between flame stabilization mechanisms with and without local extinction are discussed and the implications for turbulent diffusion flames are outlined.
DA - 2000///
PY - 2000///
DO - 10.1080/00102200008935798
VL - 160
SP - 103-118
SN - 1563-521X
KW - counterflow diffusion flame
KW - flame stabilization
KW - extinction
KW - local extinction
KW - impingement
ER -
TY - JOUR
TI - Dopant transport during semiconductor crystal growth in space with a steady magnetic field
AU - Hockenhull, T. E.
AU - Ma, N.
T2 - Magnetohydrodynamics
CN - [Not currently held by TRLN member libraries]
DA - 2000///
PY - 2000///
VL - 36
IS - 3
SP - 289-296
ER -
TY - JOUR
TI - Simultaneous Rayleigh imaging and CH-PLIF measurements in a lifted jet diffusion flame
AU - Watson, KA
AU - Lyons, KM
AU - Donbar, JM
AU - Carter, CD
T2 - COMBUSTION AND FLAME
AB - Simultaneous Rayleigh scattering and CH planar laser-induced fluorescence (PLIF) measurements near the stabilization region of a lifted methane–air diffusion flame are presented. The goals of this investigation are to establish flow patterns responsible for complete breaks in the CH profile that indicate local flame extinction and evaluate the stabilization mechanisms over a range of flow conditions. Considerable attention has been given to vortex–flame interactions as a primary extinction mechanism of turbulent diffusion flames. The existence of holes in the flame zone is thought to result from the radial penetration of the flame by vortices from the internal fuel jet. In this investigation, Rayleigh scattering is used as a qualitative indication of gas temperature, thereby providing valuable information about the fluid near regions of local extinction, as indicated by well-defined breaks in the CH layer. The extent of premixedness in the region upstream from the CH structure is also assessed from the Rayleigh signal level. Furthermore, the roles of premixedness in flame stabilization, the nature of the leading edge, and lift-off height oscillation are discussed.
DA - 2000/10//
PY - 2000/10//
DO - 10.1016/S0010-2180(00)00133-4
VL - 123
IS - 1-2
SP - 252-265
SN - 0010-2180
ER -
TY - JOUR
TI - Numerical simulation of the effect of thermal dispersion on forced convection in a circular duct partly filled with a Brinkman-Forchheimer porous medium
AU - Kuznetsov, AV
AU - Xiong, M
T2 - INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW
AB - A numerical simulation of the fully developed forced convection in a circular duct partly filled with a fluid saturated porous medium is presented. The Brinkman‐Forchheimer‐extended Darcy equation is used to describe the fluid flow in the porous region. The energy equation for the porous region accounts for the effect of thermal dispersion. The dependence of the Nusselt number on a number of parameters, such as the Reynolds number, the Darcy number, the Forchheimer coefficient, as well as the thickness of the porous region is investigated. The numerical results obtained in this research are in agreement with published experimental data.
DA - 2000///
PY - 2000///
DO - 10.1108/09615530010338169
VL - 10
IS - 5-6
SP - 488-501
SN - 1758-6585
KW - numerical simulation
KW - porous media
KW - thermal dispersion
ER -
TY - JOUR
TI - Feasibility of contact and non-contact approaches to material handling using traveling waves and transition characteristics
AU - Ro, P. I.
AU - Loh, B.G.
T2 - IEEE Transactions on Industrial Electronics
DA - 2000///
PY - 2000///
VL - 47
IS - 6
SP - 1134-1135
ER -
TY - PCOMM
TI - Changing the propagation direction of flexural ultrasonic progressive waves by modulating excitation frequency
AU - Loh, BG
AU - Ro, PI
DA - 2000/11/16/
PY - 2000/11/16/
DO - 10.1006/jsvi.2000.3013
SP - 171-178
ER -
TY - JOUR
TI - Rheological effects on pulsatile hemodynamics in a stenosed tube
AU - Buchanan, , JR
AU - Kleinstreuer, C
AU - Comer, JK
T2 - COMPUTERS & FLUIDS
AB - Transient laminar axisymmetric flow through a tube with a smooth local area reduction of 75% is considered. Using an experimentally validated control volume method, the influence of three rheology models (i.e., Newtonian, power law and Quemada) are investigated. Three Womersley numbers (Wo=r0ω/ν1/2:=4.0, 7.5 and 12.5) are compared for a sinusoidal input pulse which varies between 0 and 400 with a mean Reynolds number of 200. The primary application is pulsatile flow in axisymmetric stenosed artery segments. Results show that for the highest Womersley number considered here, a second co-rotating vortex is formed distal to the primary vortex. Also, the shear-thinning rheological models have a secondary effect on the flow field that primarily appears in terms of subtle changes to the hemodynamic wall parameters (i.e., the time-averaged wall shear stress, spatial wall shear stress gradient, and oscillatory shear index). The non-Newtonian models affect the entrainment of fluid-like particles in the post-stenotic region measurably. The particle residence time (PRT), defined as the ratio of transient to steady residence times, is found to be less than or equal to unity for the majority of fluid elements for all rheologies and Womersley numbers considered. The highest fraction of PRT < 1 is found at moderate Womersley numbers. Pathological fluid elements, where PRT > 10, is found to increase with increasing Wo and is decreased by the non-Newtonian formulations. This is due to a low-shear high-viscosity band that impedes the progress of fluid particles into the near wall region.
DA - 2000/7//
PY - 2000/7//
DO - 10.1016/S0045-7930(99)00019-5
VL - 29
IS - 6
SP - 695-724
SN - 0045-7930
KW - stenosis
KW - transient flow
KW - non-Newtonian fluids
KW - particle residence times
KW - hemodynamic wall parameter
ER -
TY - JOUR
TI - Reduced order modeling and parameter estimation for quarter car suspension system
AU - Ro, P. I.
T2 - Journal of Automobile Engineering
AB - This paper presents a new approach to obtaining an accurate simple model for complex mechanical systems. The methodology is applied to a quarter-car suspension system with complex linkage structures. Firstly, a multi-body dynamic model which includes kinematic characteristics is developed. Using a linearization technique, a 32-state linear model for a quarter-car system is obtained. Secondly, model reduction techniques are applied to find a reasonable reduced-order model. The result of the model reduction shows the validity of the two-mass model given that the parameters are correctly identified. The paper presents both an analytical and an experimental way of identifying the parameters of the two-mass system based on the reduced-order model. The identified parameters are shown to vary significantly from component data typically used for the two-mass system depending on kinematic structures of the suspension system. The modelling procedures outlined in this paper provide a precise and efficient way of designing active suspension systems that minimizes a necessary tuning process.
DA - 2000///
PY - 2000///
DO - 10.1177/095440700021400804
VL - 214
IS - D
SP - 851-864
ER -
TY - JOUR
TI - Investigation of the effect of transverse thermal dispersion on forced convection in porous media
AU - Kuznetsov, AV
T2 - ACTA MECHANICA
DA - 2000///
PY - 2000///
DO - 10.1007/BF01453643
VL - 145
IS - 1-4
SP - 35-43
SN - 1619-6937
ER -
TY - JOUR
TI - Hemodynamics analyses of arterial expansions with implications to thrombosis and restenosis
AU - Hyun, S
AU - Kleinstreuer, C
AU - Archie, JP
T2 - MEDICAL ENGINEERING & PHYSICS
AB - It is assumed that critical hemodynamic factors play an important role in the onset, localization and degree of post-operative complications, for example, thrombosis and restenosis. Of special interest are sudden expansion flows, which may occur in straight artery segments such as the common carotid after endarterectomy or end-to-end anastomoses. Sudden expansion geometries are possible origins of early post-operative emboli and significant myointimal hyperplasia resulting in early or late complications. Transient laminar axisymmetric and fully three-dimensional blood flows were simulated employing a validated finite volume code in conjunction with a Runge–Kutta particle tracking technique. Disturbed flow indicators, which may predict the onset of thrombosis and/or restenosis, were identified and employed to evaluate 90°-step and smooth expansion geometries. Smooth expansion geometries have weaker disturbed flow features than step expansion geometries. Specifically, the regions near the expansion wall and the reattachment point are susceptible to both atherosclerotic lesion and thrombi formations as indicated by non-uniform hemodynamic indicators such as near-zero wall shear stress and elevated wall shear stress gradients as well as blood particle accumulation and deposition. A new parameter, the wall shear stress angle deviation (WSSAD) has been introduced, which indicates areas of abnormal endothelial cell morphology and particle wall deposition. In turn, regions of low wall shear stress and high wall shear stress gradients are recognized as susceptible sites for arterial diseases. Thus, it is interesting to note that high WSSAD surface areas cover low wall shear stress, high wall shear stress gradient locations as well as high wall particle deposition. A gradual change in step expansion geometry provides better results in terms of WSSAD values and hence potentially reducing atherosclerosis as well as thrombi formation.
DA - 2000/1//
PY - 2000/1//
DO - 10.1016/S1350-4533(00)00006-0
VL - 22
IS - 1
SP - 13-27
SN - 1350-4533
KW - computational hemodynamics simulations
KW - transient particle-hemodynamics
KW - sudden and smooth expansions
KW - arterial disease indicators
KW - thrombosis
KW - restenosis
ER -
TY - JOUR
TI - Analysis of axisymmetrically-loaded filament wound composite cylindrical shells
AU - Yuan, FG
AU - Yang, W
AU - Kim, H
T2 - COMPOSITE STRUCTURES
AB - Exact elasticity solutions for laminated composite cylindrical shells under axisymmetric loading are presented. The material of the shell is assumed to be cylindrically anisotropic. Based on the three-dimensional anisotropic elasticity, three coupled governing partial differential equations in terms of displacements are developed. The general expressions for the stresses and displacements by using the Frobenius method in the radial coordinate are discussed. The closed form solutions based on Flügge thin shell theory are also derived for comparison purposes. Detailed stress and displacement distributions for long laminated shells with layups [90/0/45/−45]s and [45/−45]s under periodic band loads are investigated.
DA - 2000/10//
PY - 2000/10//
DO - 10.1016/S0263-8223(00)00061-1
VL - 50
IS - 2
SP - 115-130
SN - 1879-1085
KW - elasticity solutions
KW - laminated composite cylindrical shells
KW - axisymmetric loading
ER -
TY - JOUR
TI - The significance of effective modulus theory (homogenization) in composite laminate mechanics
AU - Pagano, NJ
AU - Yuan, FG
T2 - COMPOSITES SCIENCE AND TECHNOLOGY
AB - In this work, we consider the issues regarding the homogenization of fiber-reinforced layers in a laminate in the presence of macroscopic (ply-level) stress gradients. This is accomplished by considering a series of (free edge) boundary value problems similar to those treated by Pagano and Rybicki in 1974. Despite our inability to provide such a homogenization theory, if one truly exists, we can devise approaches to predict the fiber/matrix interfacial stresses in an arbitrary cell by applying certain displacements and/or tractions on the cell boundaries. These boundary conditions are those derived by representing each layer in the laminate by conventional effective modulus theory. It is shown that these approximations can lead to reasonably accurate interfacial stresses and offer great promise as a means of solving practical laminate problems reinforced by fibers of moderate diameter.
DA - 2000///
PY - 2000///
DO - 10.1016/S0266-3538(00)00042-7
VL - 60
IS - 12-13
SP - 2471-2488
SN - 0266-3538
KW - micromechanics
KW - homogenization
KW - effective module
KW - laminates
ER -
TY - JOUR
TI - Microstructure organization in para-aramid fibers
AU - Davis, H
AU - Singletary, J
AU - Srinivasarao, M
AU - Knoff, W
AU - Ramasubramanian, MK
T2 - TEXTILE RESEARCH JOURNAL
AB - The existence of "lateral birefringence," i.e., the difference between the refractive index for light polarized parallel to the fiber radius and light polarized perpendicular to the radius in the cross-sectional plane, combined with the existence of electron diffraction contrast "bands" in longitudinal fiber sections has led to work appearing to indicate that para-aramid fibers, in particular poly(para-phenylene terephthalamide), have an almost crystallographically perfect orthotropic structure in which the hydrogen bonds are all parallel to fiber radii. Optical path difference profiles, calculated based on the proposed orthotropic structure, are in reasonable qualitative agreement with interference microscope data. Quantitatively, however, the orthotropic structure is only partially developed based on published values of the principle refractive indices. Furthermore, the degree to which this structure is developed varies with distance from the fiber axis in some fibers' types.
DA - 2000/11//
PY - 2000/11//
DO - 10.1177/004051750007001102
VL - 70
IS - 11
SP - 945-950
SN - 0040-5175
ER -
TY - JOUR
TI - Fluid flow and heat transfer analysis of Couette flow in a composite duct
AU - Kuznetsov, AV
T2 - ACTA MECHANICA
DA - 2000///
PY - 2000///
DO - 10.1007/BF01182508
VL - 140
IS - 3-4
SP - 163-170
SN - 0001-5970
ER -
TY - JOUR
TI - Asymptotic crack-tip fields in an anisotropic plate subjected to bending, twisting moments and transverse shear loads
AU - Yuan, FG
AU - Yang, S
T2 - COMPOSITES SCIENCE AND TECHNOLOGY
AB - Asymptotic crack-tip fields, including the effect of transverse shear deformation, in an anisotropic plate under bending, twisting moments and transverse shear loads are presented. By utilizing the Hellinger–Reissner variational principle, the equilibrium equations and generalized strain/stress relations for anisotropic Reissner plate theory are obtained. Assuming the displacement and stress resultant are in a separation-of-variable form, it is found that, for the first two order terms of the asymptotic solution, the equations governing crack-tip fields of anisotropic plate bending are analogous to those governing plane stress and anti-plane deformation of anisotropic elasticity. Thus the Stroh formalism can be used to characterize the crack-tip fields of the anisotropic plate up to the second-order term and the energy release rate can be expressed in a very compact form in terms of stress intensity factors and the Barnett–Lothe tensor L. The first three order terms of the crack-tip displacement and stress fields including the “T-stresses” in bending and transverse shear are presented. The displacement and stress fields near crack tips in isotropic plates up to the second order are also provided. The energy release rate expression for orthotropic and isotropic plates is also derived. The solutions of anisotropic plates by a combination of in-plane and bending loads is also investigated. The expression of the path-independent integral, J, in terms of the generalized stress and strain is derived which is useful to calculate the value of stress intensity factors. Finally, on the basis of the asymptotic solutions, methods of determining stress intensity factors and T-stresses are proposed.
DA - 2000///
PY - 2000///
DO - 10.1016/S0266-3538(00)00043-9
VL - 60
IS - 12-13
SP - 2489-2502
SN - 1879-1050
ER -
TY - JOUR
TI - A unified loading parameter for creep-crack growth
AU - Wang, WX
AU - Yuan, FG
AU - Takao, Y
T2 - PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
AB - This paper presents a unified loading parameter JT for creep–crack growth. The parameter JT is a path–independent integral and is derived through an energy analysis based on an assumption that a small creep deformation dominant region exists around the crack tip. The relationship between JT and existing path–independent or path–dependent integrals for special creep–crack growth problems is examined. Existing path–independent or path–dependent integrals for special cases of short or long time are included in JT. The present path–independent integral JT is not limited to any specified constitutive relations except for a small region close to the crack tip, and then it is valid for general creep materials. Energy analysis shows that JT possesses a definite physical meaning and can be used as a loading parameter to characterize the crack growth in time–dependent materials, such as metal under various high–temperature environments and other rate–sensitive materials. In fact, the JT is a kind of J–type integral for creep materials and it also has an intimate relation with existing C(t) and C* integrals. An experimental procedure for evaluating JTas well as C* is discussed.
DA - 2000/1/8/
PY - 2000/1/8/
DO - 10.1098/rspa.2000.0512
VL - 456
IS - 1993
SP - 163-183
SN - 1471-2946
KW - creep-crack growth
KW - time-dependent fracture
KW - unified loading parameter
KW - path-independent integral
KW - experimental method
ER -
TY - JOUR
TI - Three-dimensional Green's functions in anisotropic piezoelectric bimaterials
AU - Pan, E
AU - Yuan, FG
T2 - INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
AB - In this paper, a recently proposed method by E. Pan and F.G. Yuan (Int. J. Solids Struct., 2000) for the calculation of the elastic bimaterial Green’s functions is extended to the analysis of three-dimensional Green’s functions for anisotropic piezoelectric bimaterials. The method is based on the Stroh formalism and two-dimensional Fourier transforms in combination with Mindlin’s superposition method. We first derive Green’s functions in exact form in the Fourier transform domain. When inverting the Fourier transform, a polar coordinate transform is introduced so that the radial integral from 0 to +∞ can be carried out exactly. Therefore, the bimaterial Green’s functions in the physical domain are derived as a sum of a full-space Green’s function and a complementary part. While the full-space Green’s function is in an explicit form, as derived recently by E. Pan and F. Tonon (Int. J. Solids Struct., 37 (2000): 943–958), the complementary part is expressed in terms of simple regular line integrals over [0, 2π] that are suitable for standard numerical integration. Furthermore, the present bimaterial Green’s functions can be reduced to the special cases such as half-space, surface, interfacial, and full-space Green’s functions. Uncoupled solutions for the purely elastic and purely electric case can also be simply obtained by setting the piezoelectric coefficients equal to zero. Numerical examples for Green’s functions are given for both half-space and bimaterial cases with transversely isotropic and anisotropic material properties to verify the applicability of the technique. Certain interesting features associated with these Green’s functions are observed and discussed, as related to the selected material properties.
DA - 2000/11//
PY - 2000/11//
DO - 10.1016/S0020-7225(00)00017-3
VL - 38
IS - 17
SP - 1939-1960
SN - 0020-7225
ER -
TY - BOOK
TI - The best hikes of Pisgah National Forest
AU - Goldsmith, C. F
AU - Hamrick, H.
AU - Shannon, E.G.
AU - Hamrick, H. J.
CN - GV199.42.N66 G64 2000
DA - 2000///
PY - 2000///
PB - Winston-Salem, NC: J.F. Blair Publisher
SN - 0895871904
ER -
TY - JOUR
TI - Robust friction compensation for submicrometer positioning and tracking for a ball-screw-driven slide system
AU - Ro, PI
AU - Shim, W
AU - Jeong, S
T2 - PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY
AB - Ball-screw-driven slide systems are largely used in industry for motion control applications. Their performance using standard proportional-integral-derivative (PID) control algorithm is unsatisfactory in submicrometer motion control because of nonlinear friction effects. In this article, controllers based on a bristle-type nonlinear contact model are developed and implemented for submicrometer motion. For submicrometer positioning, a proportional-derivative (PD) control scheme with a nonlinear friction estimate algorithm is developed, and its performance is compared with that of a PID controller. For tracking, a disturbance observer was added to reject external disturbances and to improve robustness. The experimental results indicate that the proposed controller has consistent performance in positioning with under 1.5% of steady-state error in the submicrometer range. For tracking performance, the proposed controller shows good and robust tracking with respect to parameter variation.
DA - 2000/4//
PY - 2000/4//
DO - 10.1016/S0141-6359(00)00030-1
VL - 24
IS - 2
SP - 160-173
SN - 1873-2372
KW - friction compensation
KW - submicrometer
KW - disturbance observer
KW - ball-screw
ER -
TY - JOUR
TI - Low-diffusion flux-splitting methods for real fluid flows with phase transitions
AU - Edwards, J. R.
AU - Franklin, R. K.
AU - Liou, M. S.
T2 - AIAA Journal
AB - Methods for extending the AUSM+ low-diffusion flux-splitting scheme toward the calculation of real fluid flows at all speeds are presented. The single-phase behavior of the fluid is defined by the Sanchez-Lacombe equation of state, a lattice-fluid description. Liquid-vapor phase transitions are modeled through a homogeneous equilibrium approach. Time-derivative preconditioning is utilized to allow effective integration of the equation system at all flow speeds and all states of compressibility. Modifications to the preconditioned variant of AUSM+ necessary to preserve solution accuracy under such conditions are presented in detail. One-dimensional results are presented for the faucet problem, a classic test case for multifluid algorithms, as well as for liquid octane flow through a converging-diverging nozzle. Two-dimensional calculations are presented for water flow over a hemisphere/cylinder geometry and liquid carbon dioxide flow through a capillary nozzle
DA - 2000///
PY - 2000///
DO - 10.2514/2.1145
VL - 38
IS - 9
SP - 1624-1633
ER -
TY - JOUR
TI - Effects of grain boundaries and dislocation density evolution on large strain deformation modes in fcc crystalline materials
AU - Ashmawi, WM
AU - Zikry, MA
T2 - JOURNAL OF COMPUTER-AIDED MATERIALS DESIGN
DA - 2000///
PY - 2000///
DO - 10.1023/A:1008717428264
VL - 7
IS - 1
SP - 55-62
SN - 0928-1045
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0033876739&partnerID=MN8TOARS
KW - dislocation densities
KW - failure
KW - grain-boundaries
KW - multiple-slip crystal plasticity
KW - pile-ups
ER -
TY - JOUR
TI - Computer simulation and geometric design of endarterectomized carotid artery bifurcations
AU - Hyun, S
AU - Kleinstreuer, C
AU - Archie, JP
T2 - CRITICAL REVIEWS IN BIOMEDICAL ENGINEERING
AB - The main goal of this computational study is to establish surgical guidelines for optimal geometries of carotid endarterectomy reconstructions that may measurably reduce postoperative complications, that is, thrombosis, stroke, and/or restenosis. The underlying hypotheses are that nonuniform hemodynamics, or "disturbed flows," are linked to arterial diseases and consequently that minimization of "disturbed flow" indicators leads to geometric bifurcation designs that lower postoperative complication rates. Considering transient 3-D laminar blood flow in partially occluded, in-plane, rigid-wall carotid artery bifurcations, the results presented include time-averaged indicators of "disturbed flow", such as the wall shear stress, spatial wall shear stress gradient, and wall shear stress angle deviation. In addition, trajectories and deposition patterns of critical blood particles (i.e., monocytes) are shown and evaluated. Within given physiological constraints, the vessel geometry was then changed in order to reduce the magnitudes of key indicators associated with thrombosis (i.e., blood clot formation) or restenosis (e.g., renewed atherosclerosis and/or hyperplasia). The quantitative results and knowledge base generated will be crucial for future clinical trials.
DA - 2000///
PY - 2000///
DO - 10.1615/critrevbiomedeng.v28.i12.100
VL - 28
IS - 1-2
SP - 53-59
SN - 0278-940X
KW - branching blood vessels
KW - arterial diseases
KW - particle-hemodynamics
KW - numerical analysis
ER -
TY - JOUR
TI - Computational analyses and design improvements of graft-to-vein anastomoses
AU - Longest, PW
AU - Kleinstreuer, C
AU - Andreotti, PJ
T2 - CRITICAL REVIEWS IN BIOMEDICAL ENGINEERING
AB - For hemodialysis patients, arteriovenous grafts are omnipresent. Unfortunately, a large percentage of such grafts fail within the first year after surgery because of occlusive lesions mainly at the venous anastomotic site. It is textbook knowledge that critical values of certain hemodynamic parameters, such as low (oscillatory) wall shear stresses, large sustained wall shear stress gradients, significant changes in wall shear stress angles, excessive radial pressure gradients, etc., play significant roles in the onset and/or development of vascular diseases. The idea is to geometrically design graft-to-vein configurations such that aggravating flow patterns are reduced, and hence stenotic developments are minimized. Focusing on a new blood rheological model in conjunction with three graft-to-vein anastomotic configurations, that is, a base case, the Bard-IMPRA VenafloTM graft, and a new graft-end design, the corresponding transient laminar 3-D hemodynamics are numerically simulated and compared. The design criterion for the best performance of these junction geometries is the most significant reduction in locally disturbed flow as expressed by equally weighted indicator functions for the onset and progression of stenotic developments. As a result of this comparison study, quantitative recommendations for arteriovenous loop graft designs toward increased patency rates are provided. The resulting improved graft design will be scrutinized in clinical trials.
DA - 2000///
PY - 2000///
DO - 10.1615/critrevbiomedeng.v28.i12.240
VL - 28
IS - 1-2
SP - 141-147
SN - 0278-940X
KW - hemodialysis
KW - graft failure
KW - hemodynamic simulations
KW - geometric designs
ER -
TY - JOUR
TI - Three-dimensional Green's functions in anisotropic bimaterials
AU - Pan, E.
AU - Yuan, F. G.
T2 - International Journal of Solids and Structures
AB - In this paper, three-dimensional Green’s functions for anisotropic bimaterials are studied based on Stroh formalism and two-dimensional Fourier transforms. Although the Green’s functions can be expressed exactly in the Fourier transform domain, it is difficult to obtain the explicit expressions of the Green’s functions in the physical domain due to the general anisotropy of the material and a geometry plane involved. Utilizing Fourier inverse transform in the polar coordinate and combining with Mindlin’s superposition method, the physical-domain bimaterial Green’s functions are derived as a sum of a full-space Green’s function and a complementary part. While the full-space Green’s function is in an explicit form, the complementary part is expressed in terms of simple regular line-integrals over [0, 2π] that are suitable for standard numerical integration. Furthermore, the present bimaterial Green’s functions can be reduced to the special cases such as half-space, surface, interfacial, and full-space Green’s functions. Numerical examples are given for both half-space and bimaterial cases with isotropic, transversely isotropic, and anisotropic material properties to verify the applicability of the technique. For the half-space case with isotropic or transversely isotropic material properties, the Green’s function solutions are in excellent agreement with the existing analytical solutions. For anisotropic half-space and bimaterial cases, numerical results show the strong dependence of the Green’s functions on the material properties.
DA - 2000///
PY - 2000///
DO - 10.1016/S0020-7683(99)00216-4
VL - 37
IS - 38
SP - 5329-5351
ER -
TY - JOUR
TI - Forced convection in a Couette flow in a composite duct: An analysis of thermal dispersion and non-Darcian effects
AU - Xiong, M.
AU - Kuznetsov, A. V.
T2 - Journal of Porous Media
DA - 2000///
PY - 2000///
DO - 10.1615/jpormedia.v3.i3.60
VL - 3
IS - 3
SP - 245-255
ER -
TY - JOUR
TI - Estimation of the boundary heat flux in grinding via the conjugate gradient method
AU - Carvalho, RN
AU - Orlande, HRB
AU - Ozisik, MN
T2 - HEAT TRANSFER ENGINEERING
AB - The unknown boundary surface heat flux in workpieces during grinding is estimated by the application of inverse heat transfer analysis. The conjugate gradient method of function estimation is used for the minimization procedure. Simulated temperature measurements are used in the inverse analysis for typical practical cases, in order to show that results more accurate than those available in the literature are obtained with the present solution approach. Actual experimental data are also used in the computations to estimate the surface heat flux.
DA - 2000///
PY - 2000///
DO - 10.1080/01457630050144523
VL - 21
IS - 4
SP - 71-82
SN - 1521-0537
ER -
TY - JOUR
TI - Development of a robotic bridge maintenance system
AU - Lorenc, SJ
AU - Handlon, BE
AU - Bernold, LE
T2 - AUTOMATION IN CONSTRUCTION
AB - This paper will expand on the Robotic Bridge Maintenance System (RBMS) developed by the Construction Automation and Robotics Laboratory (CARL) at North Carolina State University (NCSU). The system consists of a 4-dof robot, designed and built at NCSU, mounted on the end of a truck-mounted peeper crane. Additionally, a containment system is mounted in front of the robot to contain the toxic waste created by the removal of the lead-based paint from the bridge beams and trusses.
DA - 2000/5//
PY - 2000/5//
DO - 10.1016/S0926-5805(99)00040-0
VL - 9
IS - 3
SP - 251-258
SN - 0926-5805
KW - robotic bridge maintenance system
KW - teleoperated
KW - construction applications
ER -
TY - JOUR
TI - Boundary element analysis of three-dimensional cracks in anisotropic solids
AU - Pan, E
AU - Yuan, FG
T2 - INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING
AB - This paper presents a boundary element analysis of linear elastic fracture mechanics in three-dimensional cracks of anisotropic solids. The method is a single-domain based, thus it can model the solids with multiple interacting cracks or damage. In addition, the method can apply the fracture analysis in both bounded and unbounded anisotropic media and the stress intensity factors (SIFs) can be deduced directly from the boundary element solutions. The present boundary element formulation is based on a pair of boundary integral equations, namely, the displacement and traction boundary integral equations. While the former is collocated exclusively on the uncracked boundary, the latter is discretized only on one side of the crack surface. The displacement and/or traction are used as unknown variables on the uncracked boundary and the relative crack opening displacement (COD) (i.e. displacement discontinuity, or dislocation) is treated as a unknown quantity on the crack surface. This formulation possesses the advantages of both the traditional displacement boundary element method (BEM) and the displacement discontinuity (or dislocation) method, and thus eliminates the deficiency associated with the BEMs in modelling fracture behaviour of the solids. Special crack-front elements are introduced to capture the crack-tip behaviour. Numerical examples of stress intensity factors (SIFs) calculation are given for transversely isotropic orthotropic and anisotropic solids. For a penny-shaped or a square-shaped crack located in the plane of isotropy, the SIFs obtained with the present formulation are in very good agreement with existing closed-form solutions and numerical results. For the crack not aligned with the plane of isotropy or in an anisotropic solid under remote pure tension, mixed mode fracture behavior occurs due to the material anisotropy and SIFs strongly depend on material anisotropy. Copyright © 2000 John Wiley & Sons, Ltd.
DA - 2000/5/20/
PY - 2000/5/20/
DO - 10.1002/(SICI)1097-0207(20000520)48:2<211::AID-NME875>3.0.CO;2-A
VL - 48
IS - 2
SP - 211-237
SN - 0029-5981
KW - boundary element method
KW - fracture mechanics
KW - stress intensity factor
KW - crack opening displacement
KW - dislocations
ER -
TY - JOUR
TI - An object transport system using flexural ultrasonic progressive waves generated by two-mode excitation
AU - Loh, BG
AU - Ro, PI
T2 - IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL
AB - An object transport system using low amplitude and high frequency progressive waves generated by two-mode excitation is presented. A theoretical model for the system was developed using normal mode expansion and the modal participation factor. To identify the factors that affect the transport speed, the changes with the mass of objects on the beam, the input power, the phase difference, and the excitation frequency were experimentally investigated. With a power input of 40 W, a transport speed of 10 cm/s was obtained for an object weighing 30 g. The tests indicate that, not only the phase difference but also the excitation frequency, were the dominant factors in determining the transport speed and direction. Specifically, when the excitation frequency was chosen to be at the exact midpoint of the two modes, the object stopped moving. A slight change of frequency in either direction resulted in change of object transport direction. For actual factory application, a simple stop-go and tracking control using the General Purpose Interface Bus (GPIB) were implemented.
DA - 2000/7//
PY - 2000/7//
DO - 10.1109/58.852083
VL - 47
IS - 4
SP - 994-999
SN - 0885-3010
ER -
TY - JOUR
TI - An experimental investigation of rotary diamond truing and dressing of vitreous bond wheels for ceramic grinding
AU - Shih, AJ
T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE
AB - Experiments of rotary diamond truing and dressing of vitreous bond grinding wheels were conducted to investigate the effects of feed, speed ratio, and overlap ratio on cylindrical grinding of zirconia. The applications of ceramic engine components with complex and precise form and the lack of technology for precision truing of diamond grinding wheels have driven the need to study the use of vitreous bond CBN and SiC wheels for form grinding of ceramics. Truing and grinding forces and the roundness and surface finish of ground zirconia parts were measured. By varying truing process parameters, a wide range of surface finish and roundness could be achieved. Experimental results showed that wheels trued at speed ratio below −1.0 could grind parts with fine surface finish and good roundness. The analysis of truing and grinding results showed the trend of increasing grinding force at higher specific truing energy and better surface finish at higher grinding force. The lack of speed control of the direct–drive, variable–speed truing spindle was observed and its effect on the reverse of direction of truing force at positive speed ratios was studied.
DA - 2000/9//
PY - 2000/9//
DO - 10.1016/S0890-6955(00)00022-5
VL - 40
IS - 12
SP - 1755-1774
SN - 0890-6955
KW - ceramic gridding
KW - truing
KW - dressing
ER -
TY - JOUR
TI - High speed and high material removal rate grinding of ceramics using the vitreous bond CBN wheel
AU - Shih, AJ
AU - McSpadden, SB
AU - Morris, TO
AU - Grant, MB
AU - Yonushonis, TM
T2 - MACHINING SCIENCE AND TECHNOLOGY
AB - Abstract High-speed (up to 127 m/s) and high material removal rate grinding experiments were conducted using a vitreous bond cubic boron nitride (CBN) wheel to investigate the effects of material removal rate, wheel speed, dwell time and truing speed ratio on cylindrical grinding of silicon nitride and zirconia. Experimental results show that operating the grinding wheel at a high surface speed can reduce grinding forces, enable high material removal rates, and achieve a higher grinding ratio (G-ratio). The material removal rate was increased to 9.6 and 7.6 mm3/s/mm for zirconia and silicon nitride, respectively, to explore the advantage of using high wheel speeds for cost-effective, high-material-removal-rate grinding of ceramics. Models for specific grinding force vs. the specific material removal rate and G-ratio vs. grinding wheel surface speed were developed based on the experimental results. Overall, this study showed that high grinding wheel surface speed is beneficial to the grinding of ceramics.
DA - 2000///
PY - 2000///
DO - 10.1080/10940340008945699
VL - 4
IS - 1
SP - 43-58
SN - 1532-2483
ER -
TY - JOUR
TI - Development of O(Nm(2)) preconditioned multigrid solvers for Euler and Navier-Stokes equations
AU - Edwards, , JR
AU - Thomas, JL
T2 - AIAA JOURNAL
DA - 2000/4//
PY - 2000/4//
DO - 10.2514/2.1018
VL - 38
IS - 4
SP - 717-720
SN - 0001-1452
ER -
TY - JOUR
TI - Wavelet-based approach for structural damage detection
AU - Hou, Z.
AU - Noori, M.
AU - St. Amand, R.
T2 - Journal of Engineering Mechanics
AB - A wavelet-based approach is proposed for structural damage detection and health monitoring. Characteristics of representative vibration signals under the wavelet transformation are examined. The methodology is then applied to simulation data generated from a simple structural model subjected to a harmonic excitation. The model consists of multiple breakable springs, some of which may suffer irreversible damage when the response exceeds a threshold value or the number of cycles of motion is accumulated beyond their fatigue life. In cases of either abrupt or accumulative damages, occurrence of damage and the moment when it occurs can be clearly determined in the details of the wavelet decomposition of these data. Similar results are observed for the real acceleration data of the seismic response recorded on the roof of a building during the 1971 San Fernando earthquake. Effects of noise intensity and damage severity are investigated and presented by a detectability map. Results show the great promise of the wavelet approach for damage detection and structural health monitoring.
DA - 2000///
PY - 2000///
DO - 10.1061/(ASCE)0733-9399(2000)126:7(677)
VL - 126
IS - 7
SP - 677-683
ER -
TY - JOUR
TI - The design and operational characteristics of the CP&L/EPRI fish barn: a demonstration of recirculating aquaculture technology
AU - Losordo, TM
AU - Hobbs, AO
AU - DeLong, DP
T2 - AQUACULTURAL ENGINEERING
AB - The Carolina Power & Light Company, in conjunction with the Electric Power Research Institute of Palo Alto, California has developed a commercial fish production demonstration utilizing water reuse technology developed at the North Carolina State University Fish Barn. The fish production system is housed in a 39.6 m long by 9.75 m wide barn structure located on the campus of North Carolina State University in Raleigh, NC. Fish production activities began in the spring of 1998. The facility is designed to produce 45 tonnes of fish annually, with the first crop being tilapia. The project is being operated as a public demonstration of this technology, with biological, engineering and economic data being collected by research and extension personnel at North Carolina State University. This paper outlines the design of the recirculating system technology used to recycle water through the main fish production tanks.
DA - 2000/5//
PY - 2000/5//
DO - 10.1016/S0144-8609(00)00029-7
VL - 22
IS - 1-2
SP - 3-16
SN - 0144-8609
KW - recirculating system
KW - biological filter media
KW - copper-cadmium reduction
ER -
TY - JOUR
TI - The transverse compression of PPTA fibers - Part II - Fiber transverse structure
AU - Singletary, J
AU - Davis, H
AU - Song, Y
AU - Ramasubramanian, MK
AU - Knoff, W
T2 - JOURNAL OF MATERIALS SCIENCE
DA - 2000/2//
PY - 2000/2//
DO - 10.1023/A:1004716108638
VL - 35
IS - 3
SP - 583-592
SN - 1573-4803
ER -
TY - JOUR
TI - The transverse compression of PPTA fibers - Part I - Single fiber transverse compression testing
AU - Singletary, J
AU - Davis, H
AU - Ramasubramanian, MK
AU - Knoff, W
AU - Toney, M
T2 - JOURNAL OF MATERIALS SCIENCE
DA - 2000/2//
PY - 2000/2//
DO - 10.1023/A:1004764024568
VL - 35
IS - 3
SP - 573-581
SN - 0022-2461
ER -
TY - BOOK
TI - Inverse heat transfer: Fundamentals and applications
AU - Ozisik, M. N.
CN - TJ260 .O97 2000
DA - 2000///
PY - 2000///
PB - New York: Taylor & Francis
SN - 156032838X
ER -
TY - JOUR
TI - An adaptive grid algorithm for air-quality modeling
AU - Srivastava, RK
AU - McRae, DS
AU - Odman, MT
T2 - JOURNAL OF COMPUTATIONAL PHYSICS
AB - A new dynamic adaptive grid algorithm has been developed for use in air-quality modeling. This algorithm uses a higher order numerical scheme—the piecewise parabolic method (PPM)—for computing advective solution fields, a weight function capable of promoting grid node clustering by moving grid nodes, and a conservative interpolation equation using PPM for redistributing the solution field after movement of grid nodes. Applications of the algorithm to model problems show that the algorithm provides solutions more accurate than those obtained with static grids. Performance achieved in model problem simulations indicates that the algorithm has the potential to provide accurate air-quality modeling solutions at costs that may be significantly less than those incurred in obtaining equivalent static grid solutions.
DA - 2000/12/10/
PY - 2000/12/10/
DO - 10.1006/jcph.2000.6620
VL - 165
IS - 2
SP - 437-472
SN - 1090-2716
KW - grid adaptation
KW - air-quality modeling
KW - advection
ER -
TY - JOUR
TI - Transition onset prediction for high-speed flow
AU - McDaniel, RD
AU - Nance, RP
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 - 2000///
PY - 2000///
DO - 10.2514/2.3579
VL - 37
IS - 3
SP - 304-309
SN - 0022-4650
ER -
TY - JOUR
TI - Study of high-lift configurations using k-zeta transition/turbulence model
AU - Czerwiec, R
AU - Edwards, , JR
AU - Rumsey, CL
AU - Bertelrud, A
AU - Hassan, HA
T2 - JOURNAL OF AIRCRAFT
AB - The flow over the multi-element McDonnell Douglas configuration is computed using the κ-ζ transition/turbulence model. The model is capable of calculating transition onset as part of the solution at a cost comparable to Navier-Stokes solvers that employ two-equation models. The model is first incorporated into CFL3D and then used to calculate flows for two angles of attack, 8 and 19 deg, at a freestream Mach number of 0.2 and a Reynolds number of 9 x 10 6 . In general, good agreement is indicated for predicting transition onset and velocity profiles over sections of the main airfoil and flap. Most of the differences between computation and experiment are in the prediction of the extent and penetration of the slat wake at the 19-deg angle-of-attack case. Even for this case relative differences were less than 5%
DA - 2000///
PY - 2000///
DO - 10.2514/2.2728
VL - 37
IS - 6
SP - 1008-1016
SN - 0021-8669
ER -
TY - JOUR
TI - Self-tuning PID control using an adaptive network-based fuzzy inference system
AU - Bishr, M
AU - Yang, YG
AU - Lee, G
T2 - INTELLIGENT AUTOMATION AND SOFT COMPUTING
AB - Abstract This paper presents a self-tuning PID control algorithm using an adaptive network-based fuzzy inference structure (ANFIS). In particular, the design of a self-tuning PID learning-based optimum controller is introduced which can be applied to nonlinear as well as linear systems. A recursive adaptation scheme is employed for on-line implementation of the self-tuning PID controller in which an exponential forgetting factor is used to weigh old data and both an error and control rate cost are used in the backwards pass. Results show that the method is a viable approach for tuning the parameters of a PID controller.
DA - 2000///
PY - 2000///
DO - 10.1080/10798587.2000.10642795
VL - 6
IS - 4
SP - 271-280
SN - 1079-8587
KW - self-tuning control
KW - PID controller
KW - fuzzy-inference systems
KW - adaptive neural network
ER -
TY - JOUR
TI - Multicriteria fuzzy decision-making problems based on vague set theory
AU - Hong, DH
AU - Choi, CH
T2 - FUZZY SETS AND SYSTEMS
AB - Chen et al. (Fuzzy Sets and Systems 67 (1994) (163–172)) present some techniques for handling multicriteria fuzzy decision-making problems based on vague set theory. They provide some functions to measure the degree of suitability of each alternative with respect to a set of criteria presented by vague values. However, in some cases, these functions do not give sufficient information about alternatives. In this paper, we provide new functions to measure the degree of accuracy in the grades of membership of each alternative with respect to a set of criteria represented by vague values. The proposed functions give additional information about alternatives. The techniques proposed in this paper can provide more useful way than those of Chen to efficiently help the decision-maker to make his decision.
DA - 2000/8/16/
PY - 2000/8/16/
DO - 10.1016/S0165-0114(98)00271-1
VL - 114
IS - 1
SP - 103-113
SN - 0165-0114
KW - truth-membership function
KW - vague set
KW - fuzzy set
KW - multicriteria fuzzy decision making
ER -
TY - JOUR
TI - Kinked crack in anisotropic bodies
AU - Yang, S
AU - Yuan, FG
T2 - INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
AB - Solutions are presented for a crack kinking out of the crack plane in a generally anisotropic elastic body under two-dimensional deformation. Based on Stroh formalism, a system of singular integral equations governing the kinking crack with small kink length is given in a simple, straightforward form. The explicit expressions of the stress intensity factors, T-stresses, and energy release rates at the kinked crack tip are presented in terms of some nondimensional coefficients together with the stress intensity factors, T-stresses, and the coefficients of the third term acting on the main crack tip prior to crack kinking. The nondimensional coefficients depend on kink angle and material constants, but not on kink length. The energy release rate ratio which may characterize the competition along different crack growth directions is provided. The role of T-stresses and the third-term applied at the main crack field are determined which can be significant in the kinking and the stability of the kinked crack. Based on the energy release rate fracture criterion, the stability condition of the kinked crack is derived. The influences of anisotropy and loading mixity on the implications of crack kinking behavior is also given. The results for monoclinic materials with symmetry plane at x3=0 are derived from general results. Numerical results for the stress intensity factors, T-stresses at the kinked acrack tip and the energy release rate ratio for some special cases are provided. The dimensionless coefficients for crack kinking of orthotropic materials at the right angle to the main crack plane are tabulated.
DA - 2000/11//
PY - 2000/11//
DO - 10.1016/S0020-7683(99)00222-X
VL - 37
IS - 45
SP - 6635-6682
SN - 1879-2146
KW - crack kinking
KW - anisotropic materials
KW - stress intensity factor
KW - energy release rate
KW - T-stress
KW - g-term
KW - fracture criterion
KW - singular integral equations
KW - stability of kinked crack
ER -
TY - JOUR
TI - Effects of heterogeneity in forced convection in a porous medium: parallel plate channel or circular duct
AU - Nield, DA
AU - Kuznetsov, AV
T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
AB - Abstract The effects of variation (in the transverse direction) of permeability and thermal conductivity, on fully developed forced convection in a parallel plate channel or circular duct filled with a saturated porous medium, is investigated analytically on the basis of a Darcy or Dupuit–Forchheimer model. It is shown that the Dupuit–Forchheimer problem reduces to the Darcy problem with a changed permeability variation. The cases of isoflux and isothermal boundaries are treated in turn. The bulk of the results pertain to a two-step variation, but the case of a weak continuous variation is also considered. The results for the parallel plate geometry and for the circular duct geometry are qualitatively similar. The replacement of isoflux boundaries by isothermal boundaries leads to a reduction of Nusselt number but otherwise there is little change in the pattern. The results demonstrate that the effect of permeability variation is that an above average permeability near the walls leads to an increase in Nusselt number, and this is explained in terms of variation in the curvature of the temperature profile. The effect of conductivity variation is more complex; there are two opposing effects and the Nusselt number is not always a monotonic function of the conductivity variation.
DA - 2000/11//
PY - 2000/11//
DO - 10.1016/S0017-9310(00)00025-9
VL - 43
IS - 22
SP - 4119-4134
SN - 1879-2189
ER -
TY - JOUR
TI - Crack-tip fields for matrix cracks between dissimilar elastic and creeping materials
AU - Yuan, F. G.
AU - Yang, S.
T2 - International Journal of Fracture
DA - 2000///
PY - 2000///
DO - 10.1023/A:1007620114187
VL - 103
IS - 4
SP - 327-360
ER -
TY - JOUR
TI - Aerosol transport and deposition in sequentially bifurcating airways
AU - Comer, JK
AU - Kleinstreuer, C
AU - Hyun, S
AU - Kim, CS
T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME
AB - Deposition patterns and efficiencies of a dilute suspension of inhaled particles in three-dimensional double bifurcating airway models for both in-plane and 90 deg out-of-plane configurations have been numerically simulated assuming steady, laminar, constant-property air flow with symmetry about the first bifurcation. Particle diameters of 3, 5, and 7 μm were used in the simulation, while the inlet Stokes and Reynolds numbers varied from 0.037 to 0.23 and 500 to 2000, respectively. Comparisons between these results and experimental data based on the same geometric configuration showed good agreement. The overall trend of the particle deposition efficiency, i.e., an exponential increase with Stokes number, was somewhat similar for all bifurcations. However, the deposition efficiency of the first bifurcation was always larger than that of the second bifurcation, while in general the particle efficiency of the out-of-plane configuration was larger than that of the in-plane configuration. The local deposition patterns consistently showed that the majority of the deposition occurred in the carinal region. The distribution pattern in the first bifurcation for both configurations were symmetric about the carina, which was a direct result of the uniaxial flow at the inlet. The deposition patterns about the second carina showed increased asymmetry due to highly nonuniform flow generated by the first bifurcation and were extremely sensitive to bifurcation orientation. Based on the deposition variations between bifurcation levels and orientations, the use of single bifurcation models was determined to be inadequate to resolve the complex fluid–particle interactions that occur in multigenerational airways. [S0148-0731(00)01102-X]
DA - 2000/4//
PY - 2000/4//
DO - 10.1115/1.429636
VL - 122
IS - 2
SP - 152-158
SN - 1528-8951
ER -
TY - JOUR
TI - Visual generalization in programming by example
AU - St Amant, R
AU - Lieberman, H
AU - Potter, R
AU - Zettlemoyer, L
T2 - COMMUNICATIONS OF THE ACM
AB - article Free AccessProgramming by example: visual generalization in programming by example Authors: Robert St. Amant North Carolina State Univ., Raleigh North Carolina State Univ., RaleighView Profile , Henry Lieberman Massachusetts Institute of Technology, Cambridge Massachusetts Institute of Technology, CambridgeView Profile , Richard Potter Japan Science and Technology Corp., Tokyo, Japan Japan Science and Technology Corp., Tokyo, JapanView Profile , Luke Zettlemoyer North Carolina State Univ., Raleigh North Carolina State Univ., RaleighView Profile Authors Info & Claims Communications of the ACMVolume 43Issue 301 March 2000pp 107–114https://doi.org/10.1145/330534.330549Published:01 March 2000Publication History 27citation1,552DownloadsMetricsTotal Citations27Total Downloads1,552Last 12 Months66Last 6 weeks4 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteView all FormatsPDF
DA - 2000/3//
PY - 2000/3//
DO - 10.1145/330534.330549
VL - 43
IS - 3
SP - 107-114
SN - 0001-0782
ER -