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排序方式: 共有1402条查询结果,搜索用时 203 毫秒
251.
After a Birkhoff system is restricted by constraints, the determining equations, the Lie symmetries, the structure equation and the form of conserved quantities corresponding to the Lie symmetries will change. Some Lie symmetries will disappear and under certain conditions some Lie symmetries will still remain present. The condition under which Lie symmetries and conserved quantities of the system will remain is given. 相似文献
252.
本研究了带线性等式的约束条件的有限总体中的最优预测问题,给出了条件可预测变量和条件最优线性无偏测的定义,得到了条件可预测变量的所有条件最优线性无偏预测,并证明了它在几乎处处意义下的唯一性。 相似文献
253.
具有动应力和动位移约束的离散变量结构形状优化设计方法 总被引:4,自引:0,他引:4
讨论了动应力、动位移约束下离散变量状优化设计问题。首先用拟静力算法,将结构惯性力极值作为静载荷施加到结构上,求得结构的动位移和动内力,然后将考虑动应力约束和动作移约束的离散变量结构优化设计问题化为静应力和静位移约束的优化问题。在求解过程中,将单元内力作了一阶近似,并将多约束问题转化为单约束问题,然后利用两类变量统一考虑的离散变量结构形状优化设计的综合算法进行求解。 相似文献
254.
In Australia, cane transport is the largest unit cost in the manufacturing of raw sugar, making up around 35% of the total manufacturing costs. Producing efficient schedules for the cane railways can result in significant cost savings. This paper presents a study using Constraint Logic Programming (CLP) to solve the cane transport scheduling problem. Tailored heuristic labelling order and constraints strategies are proposed and encouraging results of application to several test problems and one real-life case are presented. The preliminary results demonstrate that CLP can be used as an effective tool for solving the cane transport scheduling problem, with a potential decrease in development costs of the scheduling system. It can also be used as an efficient tool for rescheduling tasks which the existing cane transport scheduling system cannot perform well. 相似文献
255.
IntroductionThedynamicequationsofmotionofmultibodysystemswithconstraintsarethefollowingdifferential/algebraicequations,i.e.,E... 相似文献
256.
N.H. Scott 《Journal of Elasticity》2000,58(3):269-275
A new modulus of elasticity is defined to be the ratio of an equibiaxial stress to the relative area change in the planes
in which the stress acts. This area modulus of elasticity is intermediate in properties between Young's modulus and the bulk
modulus. Expressions for the area modulus are computed in isotropic elasticity. A simple, convenient expression for the compliance
tensor of transverse isotropy is found in terms of, amongst others, the longitudinal (axial) area modulus and this leads to
a new, concise condition for positive definiteness of the compliance tensor. The limits of incompressibility, inextensibility
and constant area are briefly considered.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
257.
We derive a Weierstrass-type formula for conformal Lagrangian immersions in Euclidean 4-space, and show that the data satisfies
an equation similar to Dirac equation with complex potential. Alternatively this representation has a simple formulation using
quaternions. We apply it to the Hamiltonian stationary case and construct all possible tori, thus obtaining a first approach
to a moduli space in terms of a simple algebraic-geometric problem on the plane. We also classify Hamiltonian stationary Klein
bottles and show they self-intersect.
Received: January 25, 2000. 相似文献
258.
Summary. We derive a hierarchy of models for gas-liquid two-phase flows in the limit of infinite density ratio, when the liquid is
assumed to be incompressible. The starting model is a system of nonconservative conservation laws with relaxation. At first
order in the density ratio, we get a simplified system with viscosity, while at the limit we obtain a system of two conservation
laws, the system of pressureless gases with constraint and undetermined pressure. Formal properties of this constraint model
are provided, and sticky blocks solutions are introduced. We propose numerical methods for this last model, and the results
are compared with the two previous models.
Received April 20, 2000; accepted September 12, 2000 %%Online publication November 15, 2000 Communicated by Gérard
Iooss 相似文献
259.
A branch-and-bound algorithm for the resource-constrained project scheduling problem 总被引:7,自引:0,他引:7
We describe a time-oriented branch-and-bound algorithm for the resource-constrained project scheduling problem which explores
the set of active schedules by enumerating possible activity start times. The algorithm uses constraint-propagation techniques
that exploit the temporal and resource constraints of the problem in order to reduce the search space. Computational experiments
with large, systematically generated benchmark test sets, ranging in size from thirty to one hundred and twenty activities
per problem instance, show that the algorithm scales well and is competitive with other exact solution approaches. The computational
results show that the most difficult problems occur when scarce resource supply and the structure of the resource demand cause
a problem to be highly disjunctive. 相似文献
260.
给出了在动应力、动位移和动稳定约束下离散变量结构布局优化设计问题的数学模型,用“拟静力”算法,将具有动应力约束、动位移约束和动稳定约束的离散变量结构布局优化设计问题化为静应力、静位移和静稳定约束的优化问题,然后利用两级优化算法求解该模型.优化过程由两级组成,拓扑级优化和形状级优化.在每一级,都使用了综合算法,并且在搜索过程中都根据两类设计变量的相对差商值进行搜索.对包含稳定约束和不包含稳定约束的优化结果做了比较,结果显示稳定性约束对优化结果产生较大的影响. 相似文献