雷电流数学模型分析

雷电流模型是自然雷电流的数学表达。通过雷电流数学模型可以得到建筑物防雷研究所关心的参量,它是建筑物雷电防护的基础。雷电流频谱分析对确定适合的雷电防护措施,消除或减弱雷电对建筑物弱电系统的破坏作用具有重要意义。选取双指数函数模型和霍德勒函数模型进行对比仿真分析和频谱分析,研究结果表明:霍德勒函数模型与BERGER等人的观测测量结果是一致的;雷电流所含频率丰富,且集中在低频部分。     

车辆综合电子系统光纤通道统一网络体系结构研究

在分析新型车辆综合电子系统体系结构特征的基础上,采用光纤通道（Fibre Channel,FC）技术,引入功能区和统一网络的概念,提出一种新型车辆综合电子系统FC统一网络体系结构。在此基础上,设计了一种新型车辆综合电子系统FC统一网络拓扑结构初步方案,该方案能够实现系统性能和成本的有效统一,为新型车辆综合电子系统体系结构设计提供了有益参考。     

一类二次微分系统在三次多项式扰动下的极限环估计

计算了一类二次Hamilton微分系统的一阶Mel’nikov函数,通过此方法对该系统在三次多项式扰动下分岔的极限环个数进行了估计。     

一种新的小波收缩统一阈值函数

提出一种新的小波收缩统一阈值函数,并证明了新阈值函数具有收敛性,通过调节可变参数的取值可以改变新阈值函数的趋向,为图像阈值去噪的自适应处理提供了可能.此外,给出了新阈值函数的期望、方差与风险的关系式.仿真结果表明新阈值函数不仅能有效去除噪声,而且比两种经典的阈值函数有更高的灵活性,可以获得更高的信噪比和更好的视觉效果.     

基于数据压缩的LSP参数高效量化算法

文中为解决超长帧编码系统中联合帧数过多导致LSP参数量化性能下降这个问题,将多项式拟合引入超长帧编码系统中,利用多项式拟合压缩LSP参数矩阵,以降低量化时实际联合的帧数。再用分裂矩阵量化器进行量化。仿真结果表明,在120 bps的参数量化速率下,此算法的量化性能优于矩阵量化算法(MQ),平均谱失真比MQ算法降低了0.0719 dB,平均分段信噪比提高了0.1971 dB。     

Approximation results for min‐max path cover problems in vehicle routing

This article studies a min‐max path cover problem, which is to determine a set of paths for k capacitated vehicles to service all the customers in a given weighted graph so that the largest path cost is minimized. The problem has wide applications in vehicle routing, especially when the minimization of the latest service completion time is a critical performance measure. We have analyzed four typical variants of this problem, where the vehicles have either unlimited or limited capacities, and they start from either a given depot or any depot of a given depot set. We have developed approximation algorithms for these four variants, which achieve approximation ratios of max{3 ‐ 2/k,2}, 5, max{5 ‐ 2/k,4}, and 7, respectively. We have also analyzed the approximation hardness of these variants by showing that, unless P = NP , it is impossible for them to achieve approximation ratios less than 4/3, 3/2, 3/2, and 2, respectively. We have further extended the techniques and results developed for this problem to other min‐max vehicle routing problems.© 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

“过渡衔接词语”在大学英语短文写作中的作用

短文写作是大学英语四级考试的一个重要组成部分 ,短文写作的成功与否将直接影响到是否通过四级。本文将从三个方面归纳、分析三段式短文中常用的过渡衔接词语在英语短文写作中的“闪光”点作用。旨在帮助学生认识过渡衔接词语的重要性 ,从而提高写作水平     

MADM中不同属性的规范化研究

不同属性值的规范化是多属性决策问题中的重要过程.提出了一种属性值作为点到优区间和劣区间的距离的定义,依据该定义得到了属性值规范化新方法,并通过实例证明了新规范化方法的有效性.     

双枝模糊评判在舰炮性能评估中的应用*

针对舰炮武器性能指标,运用双枝模糊决策方法对舰炮武器性能进行综合评估.该方法提出了新的论域[-1,1],使评估更能符合人的思维逻辑,能够客观的对舰炮性能进行评估,通过对多中舰炮的具体参数指标进评估,得出各种舰炮的性能优劣的排序,具体的数学模型仿真表明,对舰炮武器性能的评估是行之有效的.     

On efficient algorithms for finding efficient salvo policies

We consider the salvo policy problem, in which there are k moments, called salvos, at which we can fire multiple missiles simultaneously at an incoming object. Each salvo is characterized by a probability p_i: the hit probability of a single missile. After each salvo, we can assess whether the incoming object is still active. If it is, we fire the missiles assigned to the next salvo. In the salvo policy problem, the goal is to assign at most n missiles to salvos in order to minimize the expected number of missiles used. We consider three problem versions. In Gould's version, we have to assign all n missiles to salvos. In the Big Bomb version, a cost of B is incurred when all salvo's are unsuccessful. Finally, we consider the Quota version in which the kill probability should exceed some quota Q. We discuss the computational complexity and the approximability of these problem versions. In particular, we show that Gould's version and the Big Bomb version admit pseudopolynomial time exact algorithms and fully polynomial time approximation schemes. We also present an iterative approximation algorithm for the Quota version, and show that a related problem is NP-complete.