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991.
992.
实用下料优化问题模型建立及解法 总被引:2,自引:1,他引:1
“下料问题(cuttingstockproblem)”是把相同形状的一些原材料分割加工成若干个不同规格大小的零件的问题,此类问题在工程技术和工业生产中有着重要和广泛的应用.本文首先以材料最省为原则建立模型,采用分层基因算法模型求解出模型的解,若此结果不符合时间限制条件,则通过以客户时间需求为第一目标的分组抽样模型处理后,再借助分层基因算法给出该模型的最优解. 相似文献
993.
P. S. Koval'chuk N. P. Podchasov V. V. Kholopova 《International Applied Mechanics》2003,39(3):312-317
Consideration is given to a nonlinear problem on the nonstationary deformation of cylindrical shells filled with a perfect incompressible liquid and subjected to radial pulse loading distributed along a part of the lateral surface 相似文献
994.
This work presents the parametric study on the far-field sound pressure radiated from an infinite fluid-filled/semi-submerged cylindrical shell excited by a radial point load. Here, the exterior fluid is non-viscous, isotropic and irrotational coaxial flow. The formula of the radial velocity of the shell in wave-number domain is developed by using the wave-number domain approach (WDA). Then, the analytic expressions are derived for the far-field sound pressure radiating from the shell by using the same method presented in Salaün [Journal of the Acoustical Society of America 90 (1991) 2173]. The influences of parameters such as fluid velocity, structural damping, position of the force, and structural thickness on the far-field sound pressure are investigated. The sound pressure is shown to be very different from the one in the case of a fluid-filled/full-submerged cylindrical shell. Furthermore, it is shown that the pressure and the resonance frequency would increase with the fluid velocity increasing for downstream propagation. The reverse is true for upstream propagation. Moreover, the far-field sound pressure is related to the position and frequency of the excited force. In addition, the influences of structural damping and thickness are shown to be very important. 相似文献
995.
A Taylor series augmentation of a weak statement (a ‘Taylor weak statement’ or ‘Taylor-Galerkin’ method) is used to systematically reduce the dispersion error in a finite element approximation of the one-dimensional transient advection equation. A frequency analysis is applied to determine the phase velocity of semi-implicit linear, quadratic and cubic basis one-dimensional finite element methods and of several comparative finite difference/finite volume algorithms. The finite element methods analysed include both Galerkin and Taylor weak statements. The frequency analysis is used to obtain an improved linear basis Taylor weak statement finite element algorithm. Solutions are reported for verification problems in one and two dimensions and are compared with finite volume solutions. The improved finite element algorithms have sufficient phase accuracy to achieve highly accurate linear transient solutions with little or no artificial diffusion. 相似文献
996.
997.
In the present paper, a comparative study of numerical solutions for Newtonian fluids based on the lattice‐Boltzmann method (LBM) and the classical finite volume method (FVM) is presented for the laminar flow through a 4:1 planar contraction at a Reynolds number of value one, Re=1. In this study, the stress field for LBM is directly obtained from the distribution function. The calculations of the stress based on the FVM‐data use the evaluations of velocity gradients with finite differences. The stress field for both LBM and FVM is expressed in the present study in terms of the shear stress and the first normal stress difference. The lateral and axial profiles of the velocity, the shear stress and the first normal stress difference for both methods are investigated. It is shown that the LBM results for the velocity and the stresses are in excellent agreement with the FVM results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
998.
S. Z. Adzhiev V. V. Vedenyapin 《Computational Mathematics and Mathematical Physics》2007,47(6):998-1006
The Boltzmann equation for a mixture of particles with different masses is modeled using symmetric discrete velocity models
that involve energy interchange between the species of the mixture. The computational complexity of this problem is investigated.
New discrete models are presented.
Published in Zhurnal Vychislitel’noi Matematiki i Matematicheskoi Fiziki, 2007, Vol. 47, No. 6, pp. 1045–1054. 相似文献
999.
BALUJA Shipra 《中国化学》2006,24(10):1327-1331
From experimental data of density,viscosity and ultrasonic velocity,the various acoustical properties,such asspecific impedance(Z),isentropic compressibility(к_s),Rao's molar sound function(R_m),the van der Waals con-stant(b),molar compressibility(W),intermolecular free length(L_f),relaxation strength(r),internal pressure(π),free volume(V_f),solvation number(S_n)etc.,were calculated for three Schiff bases in 1,4-dioxane and dimethylfor-mamide(DMF)at 318.15 K.The results are interpreted in terms of molecular interactions occurring in the solu-tions. 相似文献
1000.