聚硅氧烷先驱体转化制备2D Cf/Si-O-C材料

以二维碳纤维布和廉价的聚硅氧烷为原料,采用先驱体转化工艺制备2D Cf/Si-O-C材料,对其力学性能进行了考察,并与以聚碳硅烷为先驱体制备的2D Cf/SiC材料在价格和性能方面进行了对比。实验表明,2D Cf/Si-O-C材料力学性能较2D Cf/SiC材料有所下降,但成本大大降低。2D Cf/Si-O-C材料弯曲强度达到157.9 MPa,断裂韧性达到8.4MPa.m1/2,剪切强度达到23.4MPa,并且在1400℃下能较好保持材料的力学性能。     

Emergency transshipment in decentralized dealer networks: When to send and accept transshipment requests

While there has been significant previous literature on inventory transshipment, most research has focused on the dealers' demand filling decision (when to fill transshipment requests from other dealers), ignoring the requesting decision (when to send transshipment requests to other dealers). In this paper we develop optimal inventory transshipment policies that incorporate both types of decisions. We consider a decentralized system in which the dealers are independent of the manufacturer and of each other. We first study a network consisting of a very large number of dealers. We prove that the optimal inventory and transshipment decisions for an individual dealer are controlled by threshold rationing and requesting levels. Then, in order to study the impact of transshipment among independent dealers in a smaller dealer network, we consider a decentralized two‐dealer network and use a game theoretic approach to characterize the equilibrium inventory strategies of the individual dealers. An extensive numerical study highlights the impact of the requesting decision on the dealers' equilibrium behavior in a decentralized setting. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

互耦影响存在时修正MUSIC算法的DOA估计

首先用矩量法精确分析了考虑互耦影响时天线阵元的电流分布,给出了计算电流的解析式,并仿真计算了单元直线阵的电流分布。然后以等效网络法为基础研究互耦影响存在时修正MUSIC算法的DOA估计性能,仿真实验表明在互耦影响存在时MUSIC算法失效,而修正MUSIC算法仍然具有良好的DOA估计性能。     

利用数形结合方法求解几类代数问题

数学研究的对象是现实世界的数量关系(数)和空间形式(形)。“数”和“形”常按照一定的条件相互转化。数形结合思想是数学的重要的思想方法之一,并蕴于数学基础知识和基本技能之中,在数学解题中应用十分广泛。其实质是将抽象的数学语言与直观图形结合起来,发挥“数”与“形”两种信息的转化及其优势互补与整合,使逻辑思维与形象思维完美统一起来。对于培养学生的创新意识和创造思维具有积极的促进作用。     

再议数学解题中的化归方法

本文通过一些例题阐述了化归方法在解决数学问题时应遵循的五个原则,对师范院校的学生学习数学教法有一定的参考价值。     

TOPSIS法用于区域防空重点保卫目标排序计算

区域防空作战中优化选择重点保卫目标,集中部署优势防空兵力,才能确保重点目标不受或少受损失.分析了影响保卫目标重要性的主要因素,采取德尔菲法获得指标值,采用层次分析法得到指标权重,利用逼近理想解的排序法对保卫目标的重要性进行了定量分析.最后通过算例对算法的正确性和实用性进行了验证.     

爆炸复合接头剪切强度测试方法研究

参照正交各向异性层压复合板层间剪切强度的测试方法,提出了用于测试爆炸复合接头复合界面剪切强度的3种方法;并建立三维有限元模型,分别对3种测试方法进行模拟;最后分别对3种方法进行了测试试验.结果表明,3种试验方法均能有效测试爆炸复合接头的剪切强度,其中对称试件双切口拉伸法最适合实际应用.     

集合线对对数周期偶极子天线的影响

主要研究了对数周期偶极子天线.基于Pocklington积分方程和全域基函数,采用矩量法结合网络理论建立了天线算法模型;使用该模型计算了在天线阵和集合线共同作用下天线的辐射方向图,得出了集合线在不同频段上对天线辐射性能的影响,并通过截短延长线长度改善了天线低频段的辐射特性,增强了天线轴向方向性.     

基于接触的捞雷具夹紧爪接触面形状优化

介绍了在捞雷具夹紧爪设计过程中引入的基于接触的有限元形状优化设计方法.传统的机械设计方法仅考虑了零件的几何尺寸,而对其形状的设计却考虑不够,导致设计结果不理想.文中将基于接触的有限元形状优化方法应用于传统的机械设计过程.对捞雷具夹紧爪建立基于有限元分析的优化设计模型,使夹紧爪既能满足打捞鱼雷的要求,又得到了优化的形状.结构的特性与受力状况均得到改善.     

Property distribution and configurations of sovereign states: A rational economic model

A nation's wealth is both an object of conquest to covetous aggressors and a resource to its owners for self defense. To maintain autonomy every country must mount a defense which either makes its capture (1) more expensive than any aggressor can afford, or (2) more expensive than it is worth to aggressors. Whether this condition can be satisfied for all countries simultaneously depends as shown in this paper on relative efficacy of military offense versus defense, the aggregate of wealth among nations and its distribution, and the benefits a conqueror may obtain from conquest, including the duration of these benefits. The paper shows how these factors fit together to determine the sustainability and stability of the international distribution of property as embodied in the configuration of sovereign states.