Global planning of accelerated degradation tests based on exponential dispersion degradation models

The accelerated degradation test (ADT) is an efficient tool for assessing the lifetime information of highly reliable products. However, conducting an ADT is very expensive. Therefore, how to conduct a cost-constrained ADT plan is a great challenging issue for reliability analysts. By taking the experimental cost into consideration, this paper proposes a semi-analytical procedure to determine the total sample size, testing stress levels, the measurement frequencies, and the number of measurements (within a degradation path) globally under a class of exponential dispersion degradation models. The proposed method is also extended to determine the global planning of a three-level compromise plan. The advantage of the proposed method not only provides better design insights for conducting an ADT plan, but also provides an efficient algorithm to obtain a cost-constrained ADT plan, compared with conventional optimal plans by grid search algorithms.     

Ethnic groups,political exclusion and domestic terrorism

This study examines whether the exclusion of ethnic groups from political power is an important contributing factor to domestic terrorism. To empirically test this question, we employ a negative binomial regression estimation on 130 countries during the period from 1981 to 2005. We find that countries in which certain ethnic populations are excluded from political power are significantly more likely to experience domestic terrorist attacks and to suffer from terrorist casualties; furthermore, ethnic group political exclusion is a more consistent and substantive predictor of domestic terrorist activity than general political repression or economic discrimination.     

Algorithm to solve a chance‐constrained network capacity design problem with stochastic demands and finite support

We consider the problem of determining the capacity to assign to each arc in a given network, subject to uncertainty in the supply and/or demand of each node. This design problem underlies many real‐world applications, such as the design of power transmission and telecommunications networks. We first consider the case where a set of supply/demand scenarios are provided, and we must determine the minimum‐cost set of arc capacities such that a feasible flow exists for each scenario. We briefly review existing theoretical approaches to solving this problem and explore implementation strategies to reduce run times. With this as a foundation, our primary focus is on a chance‐constrained version of the problem in which α% of the scenarios must be feasible under the chosen capacity, where α is a user‐defined parameter and the specific scenarios to be satisfied are not predetermined. We describe an algorithm which utilizes a separation routine for identifying violated cut‐sets which can solve the problem to optimality, and we present computational results. We also present a novel greedy algorithm, our primary contribution, which can be used to solve for a high quality heuristic solution. We present computational analysis to evaluate the performance of our proposed approaches. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 236–246, 2016     

Strategic obfuscation of production capacities

Recent supply‐chain models that study competition among capacity‐constrained producers omit the possibility of producers strategically setting wholesale prices to create uncertainty with regards to (i.e., to obfuscate) their production capacities. To shed some light on this possibility, we study strategic obfuscation in a supply‐chain model comprised of two competing producers and a retailer, where one of the producers faces a privately‐known capacity constraint. We show that capacity obfuscation can strictly increase the obfuscating producer's profit, therefore, presenting a clear incentive for such practices. Moreover, we identify conditions under which both producers' profits increase. In effect, obfuscation enables producers to tacitly collude and charge higher wholesale prices by moderating competition between producers. The retailer, in contrast, suffers a loss in profit, raises retail prices, while overall channel profits decrease. We show that the extent of capacity obfuscation is limited by its cost and by a strategic retailer's incentive to facilitate a deterrence. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 244–267, 2014     

均匀面积映射及其在均匀纹理映射中的应用

为形成一个具有更小拉伸的网格参数化映射,在三角形网格面片面积均匀分布的情况下,采用分两步走的均匀面积映射法。通过均质化参数域里的三角形面积,用均匀或不均匀方式有效地降低了采样稀疏问题的影响,避免了传统方法中矩阵奇异值的计算。对三角形网格,先进行均值协调参数化,然后通过一个凸组合让参数域更加均匀,得到一个拉伸较低、面积更加均匀的三角形分布,从而可以更好地取样且适合于纹理映射。通过实验和对比,可以证明在均匀纹理映射方面,均匀面积映射法比保角映射法和等积投影映射法都有明显的提高。     

A self‐adapting genetic algorithm for project scheduling under resource constraints

This papers deals with the classical resource‐constrained project scheduling problem (RCPSP). There, the activities of a project have to be scheduled subject to precedence and resource constraints. The objective is to minimize the makespan of the project. We propose a new heuristic called self‐adapting genetic algorithm to solve the RCPSP. The heuristic employs the well‐known activity list representation and considers two different decoding procedures. An additional gene in the representation determines which of the two decoding procedures is actually used to compute a schedule for an individual. This allows the genetic algorithm to adapt itself to the problem instance actually solved. That is, the genetic algorithm learns which of the alternative decoding procedures is the more successful one for this instance. In other words, not only the solution for the problem, but also the algorithm itself is subject to genetic optimization. Computational experiments show that the mechanism of self‐adaptation is capable to exploit the benefits of both decoding procedures. Moreover, the tests show that the proposed heuristic is among the best ones currently available for the RCPSP. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 433–448, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10029     

Partial input to output impacts in DEA: Production considerations and resource sharing among business subunits

Data envelopment analysis (DEA) is a methodology for evaluating the relative efficiencies of peer decision‐making units (DMUs), in a multiple input/output setting. Although it is generally assumed that all outputs are impacted by all inputs, there are many situations where this may not be the case. This article extends the conventional DEA methodology to allow for the measurement of technical efficiency in situations where only partial input‐to‐output impacts exist. The new methodology involves viewing the DMU as a business unit, consisting of a set of mutually exclusive subunits, each of which can be treated in the conventional DEA sense. A further consideration involves the imposition of constraints in the form of assurance regions (AR) on pairs of multipliers. These AR constraints often arise at the level of the subunit, and as a result, there can be multiple and often inconsistent AR constraints on any given variable pair. We present a methodology for resolving such inconsistencies. To demonstrate the overall methodology, we apply it to the problem of evaluating the efficiencies of a set of steel fabrication plants. © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013     

试论价层轨道的杂化——兼论杂化轨道理论与价层电子对互斥理论的统一

在分子结构理论中,杂化轨道理论在多原子分子的空间构型被实验确定后,能够根据一定的假设给出合理的解释;价层电子对互斥理论主要用于预测分子或离子的空间构型,但其假设有些生硬、推理不够严密,对VP与电子对空间构型之间关系的推导比较繁琐,不易理解,也不能很好地解释一些多原子分子(如PF5、IF7等分子)中存在键长不等的现象。两种理论在各自的领域都取得了很大的成功,也各有其不足之处,一直未能统一。价层轨道杂化理论正是在综合了这两种理论的优点之后得到的。该理论在假设较少———即假设中心原子的价层轨道在成键时都要发生杂化,该假设与实验事实完全相符———的前提下,利用立体几何学原理对多原子分子的空间构型进行了非常简洁的推导,其结果不仅可全部继承前两种理论的成功之处,而且还能解释多原子分子中出现的键长不同、存在异构体等现象,这是其独到之处,也是其创新之处。     

画法几何模型在计算机辅助图测、图解及图显中的应用

本文用画法几何的模型,以计算机为辅助工具,进行图测、图解和图显。试行结果既快速准确,又形象直观。使数据的计算过程及计算结果可视化,便于检查结果、修改参数及调试程序。     

有限元网格自动生成的Delaunay算法

介绍一种有限元网格自动生成算法,算法对点的位置没有任何限制,增加新点时,可在原有网格基础上生成新的符合Delaunay性质的三角形有限元网格．