Scheduling multiple divisible loads in homogeneous star systems

In this paper we analyze scheduling multiple divisible loads on a star-connected system of identical processors. It is shown that this problem is computationally hard. Some special cases appear to be particularly difficult, so it is not even known if they belong to the class NP. Exponential algorithms and special cases solvable in polynomial time are presented. M. Drozdowski’s research partially supported by Polish Ministry of Science and Higher Education.     

Optimal structural topologies with transmissible loads

In optimal topological design of structures one obtains the configuration of optimal structures when the design domain, the displacement boundary conditions and the applied loads are specified. In the optimal structure one often notices a marked difference between the main bearing structure and the load transfer zones. The latter are composed of relatively light elements the exact nature of which is not always very distinct. The main purpose of this paper is to allow the main bearing part of the structure to emerge. Moreover the actual location of the load along its line of action is not always a design requirement. In order to include this relaxed condition regarding the loading position the concept of transmissible or sliding forces is introduced in topological design of structures. A transmissible force is a force of given magnitude and direction which can be applied at any point along the line of action of the force. The optimization formulation is similar to standard topological design procedure in addition to the condition of transmissability of the forces. It is shown that this condition reduces to an equal displacement constraint along the line of action of the forces. The method is illustrated by typical structural examples. It is observed that this numerical method produces indeed crisp images of the main structural components, unblurred by the secondary load transfer elements. It is also indicated that many results are often replicas of Prager structures which were previously obtained by analytical methods. Received March 3, 1999     

行车和温度荷载作用下沥青路面的松弛响应分析

目的研究沥青混凝土路面在行车和温度荷载作用下的松弛特性,更好地做到防裂控制工作．方法确定黏弹性材料参数及能够反应温度、沥青混合料黏弹性本构关系,建立典型的路面结构三维有限元模型,模拟面层材料在不同初始变形的应力状态,分析路表弯沉、沥青面层层底和土基顶面的响应．结果沥青路面在荷栽和温度作用下,面层黏弹性材料会使路面应力减小．面层层底和基层层底应力会发生松弛,最后趋于稳定值;在行车载荷作用下弯沉会随着时间的推移发生回弹,最后逐渐趋于稳定．结论松弛是材料本身属性与其他因素无关;应力松弛模量越小,松弛性能越好,低温抗裂性越好．     

Movements with Lateral Constraint

Abstract

The literature on terminal control tasks and continuous tracking tasks suggests a possible model for tasks where the subject must guide a vehicle at his own speed along a course defined by a tolerance band. The model predicts a linear relationship between the average velocity and the width of the tolerance band. Throe experiments are described which simulate vehicle guidance by pencil-and-paper experiments for courses consisting of straight lines and circles. The predictions of the model were confirmed, suggesting that a general measure for the ease of control of a vehicle (or other controlled system) is possible using this technique.     

Base Pressure Measurements under a Scale Model Stockpile

The ability of a granular bulk material to transmit internal shear stress is a fundamental property that is often overlooked or underestimated, yet it is this ability that allows many observed physical phenomena to occur. One such area that continues to be a focus for numerical, theoreticals and experimental researchers is the pressure that a stockpile of granular material places on the supporting surface. While appearing to be a simple problem, the ability of granular materials to transmit shear stress makes this an extremely complex problem. This article presents high-quality data collected under a 2 m high stockpile and full details of the experimental facilities used in the collection of the data.

The work presented is of significant value, having a much greater scale than previous studies (Jotaki & Moriyama, 1979; Lee & Herington, 1971; Smid & Novosad, 1981), and the deliberate inclusion of a central reclaim channel offers insight into stress changes during gravity reclaim and refilling. The results of this work have shown that the so-called 'M' pressure does exist under larger stockpiles both with and without reclaim hoppers; of more significance is the reemergence of the M pressure upon refilling of an emptied stockpile. This clearly illustrates that the M pressure is a robust and natural pressure distribution for a conical stockpile.     

外挂物吊挂的载荷与强度分析

采用MSC Adams软件计算吊挂载荷,再在MSC Patran/Nastran软件中利用Adams所得到的载荷通过有限元分析计算吊挂的强度.     

液化气体船C型独立液货舱载荷分析

通过对3 500 m3液化气C(LPG)运输船单圆筒形液罐的载荷分析,介绍一种简便的利用MSC Patran/Nastran来确定液罐内部载荷以及载荷施加的方法,同时提出两种计算三维状态下液罐内部载荷和施加载荷的方法.     

国际热核聚变实验堆磁体线圈终端盒的设计

线圈终端盒（CTB）是国际热核聚变实验堆超导磁体系统的重要组成部分，其内部组件的漏热常常是整个磁体系统的主要漏热源之一，在很大程度上决定着低温系统的液氦消耗量。本文从降低热负荷的角度对CTB内部冷屏、超导电流传输线、电流引线、阀及冷却管路、外部盒体的设计进行了详细阐述，为最终结构的确定提供了理论依据。     

单层球面网壳的抗震性能分析

网壳结构抗震性能分析是网壳抗震领域研究的重要内容,其进展可大大深化人们对现有结构在地震作用下可能发生破坏的认识,同时也会为进一步的机理研究及抗震设计打下坚实的基础.鉴于以上原因,以抗震问题相对突出的单层球面网壳为研究对象,通过数值方法模拟网壳在强震下的动力响应,对结构抗震性能展开了深入细致的研究.采用了当前国际通用的大型有限元软件ABAQUS,通过变换矢跨比、屋面质量、杆件截面、初始缺陷及地震输入等参数进行了大规模的计算,在对临界荷载、破坏模式等性能指标进行统计分析的基础上得出了矢跨比是网壳抗震性能最重要的影响因素等一系列有意义的结论,加深了现有对网壳结构抗震性能的认识.     

Dynamic impedance of piles in visco-elastic material considering axial loads

The dynamic impedance function of pile in visco-elastie material considering axial loads under lateral dynamic force was analyzed, and the beam dynamic differential equation was used to induce the dynamic impedance function. After analyzing the edge conditions, the dynamic impedance functions were deduced. Contrasted with the result that does not consider axial loads, the axial loads have obvious influence on the dynamic impedance function.And the results show that the dimensionless prarmeter of the dynamic impedance will change from 6 % to 9 % when considering axial loads, and dimensionless prarmeter of the dynamic impedance of the coupling horizontal-sway will increase by 31 %.