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961.
Experimental determination of the velocity distribution in the deformation zone is of significant importance to investigate the metal flow in both conventional and asymmetrical rolling processes. In this paper, a scanning laser Doppler velocimetry (LDV) system, designed for measuring the velocity distributions in the deformation zone in plate rolling is reported. The LDV used for the rolling process is briefly described and then the scanning mechanism based on beam displacement by a rotating transparent plate is introduced. The relationship among the scanning distance, the beam-cross angle of the LDV system and the rotating angle of the plate is established. The scanning LDV was first tested with a rotating disk and then applied in the rolling process. The test results have demonstrated the feasibility of the scanning LDV. 相似文献
962.
Jingqi Guan Ying Yang Bo Liu Yuanyuan Ma Xiaofang Yu Jing Liu Qiubin Kan 《Reaction Kinetics and Catalysis Letters》2008,95(2):313-320
MoV0.3Te0.17 and MoV0.3Te0.17Nb0.12 catalysts were prepared by a hydrothermal synthesis route and tested for the oxidation of isobutane and isobutene. Characterization
results showed that the structure and property of Mo-V-Te-based catalysts are relatively different depending on the presence
of the Nb element. Catalytic tests showed that the selectivity of methacrolein can comparatively be improved by the addition
of Nb into the MoV0.3Te0.17 catalyst for the selective oxidation of isobutane. 相似文献
963.
This paper presents an integral vorticity method for solving three‐dimensional Navier–Stokes equations. A finite volume scheme is implemented to solve the vorticity transport equation, which is discretized on a structured hexahedral mesh. A vortex sheet algorithm is used to enforce the no‐slip boundary condition through a vorticity flux at the boundary. The Biot–Savart integral is evaluated to compute the velocity field, in conjunction with a fast algorithm based on multipole expansion. This method is applied to the simulation of uniform flow past a sphere. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
964.
Rinaldo M. Colombo Massimiliano D. Rosini 《Mathematical Methods in the Applied Sciences》2005,28(13):1553-1567
We present a model for the flow of pedestrians that describes features typical of this flow, such as the fall due to panic in the outflow of people through a door. The mathematical techniques essentially depend on the use of non‐classical shocks in scalar conservation laws. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
965.
SOME INEQUALITIES ABOUT DUAL MIXED VOLUMES OF STAR BODIES 总被引:1,自引:0,他引:1
The authors establish some inequalities about the dual mixed volumes of star bodies in R^n. These inequalities are the analogue in the Brunn-Minkowski theory of the inequalities of Marcus-Lopes and Bergstrom about symmetric functions of positive reals. 相似文献
966.
This work deals with a free boundary identification problem in a steady viscoplastic flow. We provide a novel identification model based on a non-linear optimization. The fluid motion is governed by the incompressible Norton–Hoff model coupled with the heat equation. The viscosity of the fluid is modeled by the non-linear Arrhenius law. Our point of view is to treat the problem as a shape sensitivity of a cost functional formulated on the free boundary and governed by the normal component of the velocity of the flow. We analyze the mathematical statement of the forward problem. The equations related to the free boundary are simplified. Various properties of this optimization are proved. Since the state of Norton–Hoff model is not regular enough we introduce a parameter penalization. The shape gradient of the considered cost functional is given in the strong sense up to the parameter of penalization. We supply the expression of the shape gradient in a weak sense. 相似文献
967.
The effect of the nonparallelism of the boundary layer flow over a flat plate on its stability characteristics has been investigated
by several authors, and it was claimed that the results of the theoretical calculations are already in good agreement with
the experimental observations. However, this is not true. In this paper, this problem is reinvestigated, using two different
methods. It is found that within the framework of linear theory, the theoretical results are in fact not in good agreement
with the experimental observations. To settle this problem, nonlinear effect must be taken into consideration.
Projects Supported by the Science Fund of the Chinese Academy of Sciences 相似文献
968.
This paper describes the formulation of a nonlinear mixed integer programming model for a large-scale product development
and distribution problem and the design and computational implementation of a special purpose algorithm to solve the model.
The results described demonstrate that integrating the art of modeling with the sciences of solution methodology and computer
implementation provides a powerful approach for attacking difficult problems. The efforts described here were successful because
they capitalized on the wealth of existing modeling technology and algorithm technology, the availability of efficient and
reliable optimization, matrix generation and graphics software, and the speed of large-scale computer hardware. The model
permitted the combined use of decomposition, general linear programming and network optimization within a branch and bound
algorithm to overcome mathematical complexity. The computer system reliably found solutions with considerably better objective
function values 30 to 50 times faster than had been achieved using general purpose optimization software alone. Throughout
twenty months of daily use, the system was credited with providing insights and suggesting strategies that led to very large
dollar savings.
This research was supported in part by the Office of Naval Research Contract N00014-78-C-0222, by the Center for Business
Decision Analysis*, by the University of Texas at Austin, and by the David Bruton, Jr., Centennial Chair in Business Decision
Support Systems. Reproduction in whole or in part is permitted for any purpose of the U.S. Government.
Center for Business Decision Analysis, Graduate School of Business — GSB 3.126, University of Texas, Austin, Texas 78712,
USA. 相似文献
969.
970.
D. Gabai 《Commentarii Mathematici Helvetici》2000,75(1):109-124
A -injective closed surface in an orientable 3-manifold with a tangentially smooth, transversely C
0 taut foliation can be homotoped to an immersed surface which is either transverse to the foliation except at isolated saddle
tangencies or mapped into a leaf.
Received: November 11, 1997 相似文献