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101.
A globally convergent algorithm for transportation continuous network design problem 总被引:2,自引:0,他引:2
The continuous network design problem (CNDP) is characterized by a bilevel programming model, in which the upper level problem
is generally to minimize the total system cost under limited expenditure, while at the lower level the network users make
choices with regard to route conditions following the user equilibrium principle. In this paper, the bilevel programming model
for CNDP is transformed into a single level convex programming problem by virtue of an optimal-value function tool and the
relationship between System Optimum (SO) and User Equilibrium (UE). By exploring the inherent nature of the CNDP, the optimal-value
function for the lower level user equilibrium problem is proved to be continuously differentiable and its derivative in link
capacity enhancement can be obtained efficiently by implementing user equilibrium assignment subroutine. However, the reaction
(or response) function between the upper and lower level problem is implicit and its gradient is difficult to obtain. Although,
here we approximately express the gradient with the difference concept at each iteration, based on the method of successive
averages (MSA), we propose a globally convergent algorithm to solve the single level convex programming problem. Comparing
with widely used heuristic algorithms, such as sensitivity analysis based (SAB) method, the proposed algorithm needs not strong
hypothesis conditions and complex computation for the inverse matrix. Finally, a numerical example is presented to compare
the proposed method with some existing algorithms. 相似文献
102.
Computer modelling of hot pressing is provided. Kinetics are described for compaction during hot pressing in a rigid die, and the change in density distribution, irreversible solid phase strain accumulation, and equivalent stresses are studied by means of the finite element method. Shrinkage during the preparation of complex-shaped articles by hot pressing pure Al2O3 powder in a graphite die without a protective atmosphere and the physicomechanical properties of the finished article are studied. Calculated and experimental results agree satisfactorily. 相似文献
103.
三参量速度分析的迭代算法 总被引:3,自引:3,他引:0
徐常练 《石油地球物理勘探》1993,28(5):614-622
采用预求倾角法进行三参量速度分析时,首先要确定地下界面的倾向和倾角。若没有准确速度,就求不准倾向和倾角,因此无法一次求得准确的结果。若采用迭代算法,则可以使三参量逐渐向精确值逼近。在地层倾角小于45^0的情况下,迭代是收敛的。在有噪音的情况下,噪音会使叠加道集上同相轴的时间发生变化,从而影响倾向的确定,因此在迭代的每一步,都必须估算倾向。理论实际资料的试算表明,采用迭代方法求取地下界面参数是切实可 相似文献
104.
垂直定向液晶光阀及光电特性的研究 总被引:2,自引:0,他引:2
系统地讨论了排列相畸变模式液晶光阀结构,原理和制作,结合实际测试对其等效电路和电学匹配进行了分析,详细讨论了它的光电特性及相互关系,实测的液晶垂直排列方式工作的液晶光阀性能指标为,分辨率大于50lp/mm,白光输入灵敏度为6.77μW/cm^2,响应时间为200ms/300ms,白光输出对比度为200:1。 相似文献
105.
冷弯型钢纵向变形的理论分析及计算 总被引:5,自引:0,他引:5
对冷弯型钢的纵向变形过程进行了力学分析,得到了变形微分方程,求得了转动角的理论公式,并对其变形形状进行了分析计算。 相似文献
106.
Abstract. Large sample properties of the least‐squares and weighted least‐squares estimates of the autoregressive parameter of the explosive random‐coefficient AR(1) process are discussed. It is shown that, contrary to the standard AR(1) case, the least‐squares estimator is inconsistent whereas the weighted least‐squares estimator is consistent and asymptotically normal even when the error process is not necessarily Gaussian. Conditional asymptotics on the event that a certain limiting random variable is non‐zero is also discussed. 相似文献
107.
From the principle of of the Domain Decomposition Method (DDM), we analyse the 2nd-order linear elliptic partial differential problems and link the Separated-Layers Algorithm (SLA) with DDM. The mathematical properties of SLA and numerical example are presented to obtain satisfactory computation results. For general linear differential ones, also are the structure of SLA and its characteristics discussed. 相似文献
108.
应用Gleeble-1500热模拟实验机进行等温压缩试验,研究了变形工艺参数对34CrMoV结构钢动态再结晶行为的影响.结果表明,其流变应力随变形温度升高而降低,随应变速率提高而增大;随着应变速率的降低,应变量的增加和变形温度的升高,动态再结晶速度加快且奥氏体晶粒得到细化. 相似文献
109.
The evolution of surface defects during shape rolling of high‐speed steel billets is studied using longitudinal surface defects prepared by machining and welding. The reduction of the defects during rolling in a production mill is compared to the total area reduction of the billets. Samples are collected after pass 4, 6, 8, 14, 19 and the final pass, 28, representing the finished 5.5mm wire. By inspecting the cross sections, the rotation of the billets from pass to pass is evaluated. Results from FE simulations on solid billets are compared to the experimental results. Generally, simulations predict less reduction than observed experimentally. In most cases cracks reduce most effectively followed by carbon steel welds and stainless steel welds. 相似文献
110.
Ivan Cimrák 《Archives of Computational Methods in Engineering》2007,15(3):277-309
The Landau-Lifshitz (LL)equation of micromagnetism governs rich variety of the evolution of magnetization patterns in ferromagnetic
media. This is due to the complexity of physical quantities appearing in the LL equation. This complexity causes also an interesting
mathematical properties of the LL equation: nonlocal character for some quantities,nonconvex side-constraints, strongly nonlinear
terms. These effects influence also the numerical approximations. In this work, recent developments on the approximation of
weak solutions, together with the overview of well-known methods for strong solutions,are addressed.
Author is supported by the Fund for Scientific Research - Flanders FWO (Belgium). 相似文献