A multidirectional shear rheometer for polymer melts

A parallel plate shear rheometer for polymer melts was built for superposed shear tests in two orthogonal directions. To examine its performance, a standard test was developed, including a change of the shear direction by angles between 0° and 180°. The results were analyzed to obtain preliminary information on the multidirectional shear behavior of a low-density polyethylene melt. The measured orthogonal components of the shear force were added and then split again into components of the original and of the changed shear direction. It was found, within the range of error, that these components depend only on time and on the shear rate, but not on the angle by which the shear direction is changed. The total shear rate was 0.56 s^–1.Dedicated to Prof. Dr. Joachim Meissner on the occasion of his 60th birthday.     

考虑行车状态的一维元胞自动机交通流模型

在Nagel Schrekenberg单车道元胞自动机交通流模型（简称NS模型）的基础上，考虑车辆之间的相对运动薛郁等提出了一种改进的单车道元胞自动机交通流模型（简称改进的NS模型）.通过两种情况列出了改进的NS模型存在不尽周严的地方，随之在新模型中引入了行车状态 变量和反馈规则，从而控制车辆出现倒车和刹车过急等现象.通过计算机对新模型进行模拟 ，发现减速概率和车流密度对车流状态的演化影响很大，当减速概率高（如道路条件差）时 ，即使车流密度低，车流也会出现局部堵塞状态；而当减速概率一定时，随着车流密度增加 ，车流的运动相与堵塞相发生了全局性的交替出现，此时类似于波的波峰和波谷的传播.与 改进的NS模型相比较，新模型模拟的车流量较高，说明新模型减少了车流的总体停滞状态. 关键词： 交通流 元胞自动机 行车状态 反馈规则     

Gravitational-wave research with resonant antennas

Summary A brief historical survey of the GW experiments is presented. In particular, the experiments with resonant detectors are illustrated and the problems arising when comparing data of different detectors for the search of coincidences are discussed. The experimental results so far obtained are shown, among them the correlation during the SN1987A with various GW and neutrino detectors. Finally a warning for the long times needed to improve the sensitivity of the GW detectors is given and the improvements expected with spherical resonant detectors are mentioned.     

基于有限元仿真的东风11型救援小车支撑块结构优化

对东风11型救援小车支撑件进行了有限元分析．通过有限元计算。详细分析了有效应力分布情况；找出了应力集中较大的区域．并分析了其主要原因；观察了应力值最大区域并提出了改善应力集中的方法和措施。从而达到了结构优化的目的．     

Optimizing the periodic pick-up of raw materials for a manufacturer of auto parts

We describe a solution procedure for a special case of the periodic vehicle routing problem (PVRP). Operation managers at an auto parts manufacturer in the north of Spain described the optimization problem to the authors. The manufacturer must pick up parts (raw material) from geographically dispersed locations. The parts are picked up periodically at scheduled times. The problem consists of assigning a pickup schedule to each of its supplier’s locations and also establishing daily routes in order to minimize total transportation costs. The time horizon under consideration may be as long as 90 days. The resulting PVRP is such that the critical decision is the assignment of locations to schedules, because once this is done, the daily routing of vehicles is relatively straightforward. Through extensive computational experiments, we show that the metaheuristic procedure described in this paper is capable of finding high-quality solutions within a reasonable amount of computer time. Our main contribution is the development of a procedure that is more effective at handling PVRP instances with long planning horizons when compared to those proposed in the literature.     

An application of Special Ordered Sets to a periodic milk collection problem

We present an OR-based approach to support a milk collection problem in a special branch of dairy industry. The annual growth of the sector and the continuous imbalance between milk supply and demand, has urged the sector to look for a different approach to their daily milk collection problem. Specific details of the problem environment (i.e., the continuous production on supply level and the delivery conditions on demand level) gave rise to choose for a short- to medium-term planning approach. The proposed decision support system has to be considered as an efficient tool for generating stable milk collection plans which in turn also serves as an effective starting point for the vehicle routing problem. From a computational point of view it turned out that the application of Special Ordered Sets type 1 (SOS1) was very useful. Although it appears from literature that the computational advantage of SOS1 is restricted to supplementary model conditions, this study shows that these conditions are not necessarily needed.     

Semi-empirical likelihood ratio confidence intervals for the difference of two sample means

We all know that we can use the likelihood ratio statistic to test hypotheses and construct confidence intervals in full parametric models. Recently, Owen (1988,Biometrika,75, 237–249; 1990,Ann. Statist.,18, 90–120) has introduced the empirical likelihood method in nonparametric models. In this paper, we combine these two likelihoods together and use the likelihood ratio to construct confidence intervals in a semiparametric problem, in which one model is parametric, and the other is nonparametric. A version of Wilks's theorem is developed.     

集货送货一体化的物流配送车辆路线问题的标号算法

本文结合实际情况,对具有时间窗约束的集货送货一体化的车辆路线问题进行了研究,针对该问题的特点,采用修正的多属性标号算法对该问题进行求解,并通过C 编程语言实现了该算法,最后用一个示例表明本文的算法是有效的.     

Evaluating alternative system configurations using simulation: A nonparametric approach

The real utility of simulation lies in comparing different alternatives that might represent competing system designs. Conventional statistical techniques are not directly applicable to the analysis of simulation output data in the evaluation of competing alternatives since the usual assumptions of normality and common variance are difficult to justify in simulation experiments. This paper revisits a known nonparametric test whose application has recently become feasible due to considerable increases in computing power:randomization tests assess the significance of the observed value of the test statistic by evaluating different permutations of the data. The procedure only requires invariance of the data under all permutations.     

车辆路径问题的混合优化算法

讨论了一类车辆路径调度问题(VRP)及其数学模型，并且分析了以遗传算法求解该类问题时的染色体表示和有关遗传操作，然后结合2-opt局部优化算法提出了GA with2-opt算法来求解VRP问题，试验结果说明了该算法的有效性和可行性。