A flexible flowshop problem with total flow time minimization

In this study, we consider total flow time problem in a flexible flowshop environment. We develop a branch and bound algorithm to find the optimal schedule. The efficiency of the algorithm is enhanced by upper and lower bounds and a dominance criterion. Computational experience reveals that the algorithm solves moderate sized problems in reasonable solution times.     

Noether环的几点注记

本文利用特征模给出了Ｎｏｅｔｈｅｒ环的一些充分必要条件，并由此讨论了Ｎｏｅｔｈｅｒ环上的内射模与平坦模的一些性质     

凝聚环和IF环

本文利用特征模，Ｎ０－内射维数对凝聚环给出了一些新的刻划．得到了凝聚环与ＩＦ环的一些有意义的性质．推广了引文［１］中的两个主要定理之一的定理２的结论．     

非光滑优化的二阶必要条件

1 引言 对无约束最优化问题,其必要条件要求在局部极小点x处沿任何方向的梯度为零,曲率为正。而对约束最优化问题,首先它的局部极小点必须是可行点,其次不仅要求验证局部 极小点的某个邻域内的二阶项(曲率),而且也要认识到约束曲率也起相当重要的作用。现实中存在这样的问题,在x点处G正定,而它不是局部极小点。因此必须考虑约束最优化问题的二阶必要性条件。 本文研究了非线性规划的二阶必要性条件,其约束函数的一阶导数为方向Lipschitz连续。 2 方向Lipschitz连续函数的性质 定义2.1 设f是R~n上的一个广义实值函数,f在x∈R~n处有限,称f在x处是方向Lipschitz连续的,如果至少存在一点y∈R~n使得 其中( 定义2.2 设f如定义2.1,定义f在R~n处的次导数集如下 其中 本文多次引用f↑(x;y),因此我们首先介绍f↑(x;y)的3个基本性质:     

清江水布垭水电站地下厂房岩体质量评价及反馈设计研究

考虑地下水 ,地应力及结构面产状和岩溶、剪切带发育的特点修正 ,确定了水布垭水电站地下工程洞室工程岩体质量 ,进行了地下工程的 RMR分类研究 ,讨论了与水布垭地下工程反馈设计及信息法施工的有关问题。     

碾压混凝土坝渗流场与应力场耦合模型研究

针对碾压混凝土坝存在众多施工层面问题,提出了确定影响层厚度以及相应物理力学参数的方法;在此基础上,探讨并建立了碾压混凝土坝渗流场与应力场两场耦合模型,研制了相应的三维有限元程序．研究表明,结合试验和理论分析确定的碾压混凝土坝层面影响层的厚度、弹性模量和泊松比等参数更切合实际;提出的碾压混凝土坝渗流场与应力场两场耦合模型,能较好地体现两场耦合作用,开发的三维有限元模型能较充分反映碾压混凝土坝施工层面的特性．通过研究,为分析施工层面对碾压混凝土坝变化性态影响,以及了解大坝的应力和渗流的相互作用提供了科学依据．     

Sensitivity analysis of truss structures and its application to the fully stressed design

Based upon the theorems of structural variations this paper derives a set of expressions for calculating partial derivatives of internal forces, stresses and joint displacements with respect to bar areas for truss structures. Compared with the known formulas for finding the gradients of structural behaviours the calculation effort with the proposed expressions in this paper is usually smaller because the additional virtual loadings needed are relatively fewer. It is of practical significance to various optimization methods in which the calculation of gradients of behaviours is widely used. Moreover, applying the derived formulas to the fully stressed design (FSD), we obtain an improved iterative method for FSD. The numerical examples show that the new method considerably reduces the reanalysis number required to converge to an FSD in comparison with the simple stress ratio method.     

STUDY ON COUPLING MODEL OF SEEPAGE-FIELD AND STRESS-FIELD FOR ROLLED CONTROL CONCRETE DAM

IntroductionRCCDisbuiltwithconcreterolledandcompactedlayeruponlayer.Therefore,thereisonehorizontalconstructioninterfacebetweentwoconterminouslayers.Iftheconterminouslayersarenotcementedclosely ,theconstructioninterfaceswillbecomeweakpartsofRCCDthatinfluencethestrengthandstabilityofRCCD .Ontheotherhand ,theanti_seepageabilityofconstructioninterfacesisthedeterminantofanti_seepagecharacteristicsofthewholeRCCD .Whenadamisconstructedandfilledbywater,seepage_fieldcomesintobeinginthedambody ,w…     

基于CCD成像的分光计演示实验设计与应用

分光计在大学物理实验中用来测三棱镜的顶角、折射率以及光波波长或者光栅常数等物理量,掌握和使用分光计是一个重要的实验技能,由于调节内容较多,快速调出反射镜两个面反射的十字像一直是分光计实验中的难点.本文就此设计了基于CCD成像的系统使反射的十字像能够成像在电脑显示器上,扩大视野,便于调整,在给学生讲解演示中效果好.     

Asymptotic Upper Bounds for Ramsey Functions

 We show that for any graph G with N vertices and average degree d, if the average degree of any neighborhood induced subgraph is at most a, then the independence number of G is at least Nf _{a +1}(d), where f _{a +1}(d)=∫₀ ¹(((1−t)^{1/( a +1)})/(a+1+(d−a−1)t))dt. Based on this result, we prove that for any fixed k and l, there holds r(K _k + _l ,K _n )≤ (l+o(1))n ^k /(logn) ^{k −1}. In particular, r(K _k , K _n )≤(1+o(1))n ^{k −1}/(log n) ^{k −2}. Received: May 11, 1998 Final version received: March 24, 1999