Probability inequalities via negative dependence for random variables conditioned on order statistics

Distributions are studied which arise by considering independent and identically distributed random variables conditioned on events involving order statistics. It is shown that these distributions are negatively dependent in a very strong sense. Furthermore, bounds are found on the distribution functions. The conditioning events considered occur naturally in reliability theory as the time to system failure for k-out-of-n systems. An application to systems formed with “second-hand” components is given.     

A heuristic method for facility planning in telecommunications networks with multiple alternate routes

Given point-to-point demand forecasts of transmission facilities for services such as voice or data transmission in each period of a finite planning horizon, a decision has to be made as to which types of transmission facilities—together with the amounts of transmission circuits—are to be installed, if any, on each link of the telecommunications network, in each period of the planning horizon. The availability of alternative transmission systems with significantly different costs and circuit capacities necessitates the determination of a minimum (discounted) cost facility installation scheme. This combinatoric choice problem is complicated by the availability of switching equipments enabling the transmission of some of the traffic through intermediary points. This possibility of alternately routing the traffic or the facility requirements of certain point pairs further complicates the problem while creating the opportunity to benefit from economies of scale. We present here a heuristic method for finding a good solution for the general problem; namely, we consider multiple transmission systems and multiple alternate routes. Numerical examples are given and computational experience is reported.     

Can Limited Intervention Work? Lessons from Britain’s Success Story in Sierra Leone

ABSTRACT

Following frustrating campaigns in Iraq and Afghanistan, Western interventions are becoming more limited, with troops being deployed for short bursts and residual peace-building tasks being left to others. Although this approach limits exposure for the intervening government, it struggles to achieve meaningful political change. Examining the comparatively successful British intervention in Sierra Leone (2000–02), this article identifies the conditions for effectiveness in these campaigns. It challenges the historiography of the case by framing armed confrontations and raids as enablers of politics rather than ends in themselves; indeed, in both the conduct and study of intervention, politics must reign supreme.     

DS/FH信号跟踪的频率相位修正技术

直序/跳频(direct sequence/frequency hopping, DS/FH)扩频信号的跟踪受到多普勒效应和电离层效应的严重影响,使其难以应用于卫星导航的抗干扰领域。为了解决该问题,提出将递归最小二乘滤波修正的方法应用在DS/FH信号跟踪上。将处于不同通道中心频率的多普勒频率估计转化到DS/FH信号的整体中心频率进行并滤波,在频率捷变时对载波数控振荡器进行修正。根据对频率跳变前后载波相位和码相位突变的观察,实时估计电离层的电子密度,在频率捷变时修正载波相位和码相位。仿真实验证明,所提方法能够有效地消除DS/FH信号跟踪中的频率相位不连续问题,其跟踪精度与直序扩频信号度基本是相同量级。     

An extensible modeling framework for dynamic reassignment and rerouting in cooperative airborne operations

Unmanned aerial vehicles (UAVs), increasingly vital to the success of military operations, operate in a complex and dynamic environment, sometimes in concert with manned aircraft. We present an extensible modeling framework for the solution to the dynamic resource management (DRM) problem, where airborne resources must be reassigned to time‐sensitive tasks in response to changes in battlespace conditions. The DRM problem is characterized by diverse tasks with time windows, heterogeneous resources with fuel‐ and payload‐capacity limitations, and multiple competing objectives. We propose an integer linear programing formulation for this problem, where mathematical feasibility is guaranteed. Although motivated by airborne military operations, the proposed general modeling framework is applicable to a wide array of settings, such as disaster relief operations. Additionally, land‐ or water‐based operations may be modeled within this framework, as well as any combination of manned and unmanned vehicles. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

噪声调频信号发生器的研究与设计

为满足现代电子干扰对噪声调频信号源低功耗、快速和灵活可控的要求,采用基于Wallace算法的一种直接快速生成算法,提出了一种运算量小、速度快和全数字结构的可配置噪声调频信号发生器系统设计方案。系统利用正态分布的可加性直接生成高斯白噪声随机变量,采用数字频率合成(DDS)技术完成调频功能,通过内置串行接口配置发生器参数和输出系统运行状态信息。同时,提供了基于FPGA的系统实现方案,其生成信号波形具有严格的相干性和可控性,且对外界环境不敏感。     

m序列在电视指令制导中的应用

针对某电视指令制导系统的无线电指令编码加密进行了分析和研究,介绍了一种基于171序列编码加密方案.该方案根据m序列的特点采用双层密钥,大大扩大了密钥空间,限制了密码分析者攻击时的累加性,提高了通讯的安全性.     

稳态条件高斯推理在电磁态势估计中的应用

根据电磁态势估计原理,建立含连续结点和离散结点的混合贝叶斯网络模型,对一级融合的输出数据进行二级处理,估计干扰前后单架飞机对单个保护目标的威胁的变化情况。针对传统的连接树推理算法的不足,提出稳态条件高斯推理算法。新算法不仅能实现数值稳定性,还能根据高斯混合模型精确计算查询结点的边缘概率密度。仿真实验表明,稳态条件高斯推理是解决电磁态势估计问题的一种有效方法,且威胁估计的精度高。     

地空导弹武器装备RMS论证参数体系研究

通过对地空导弹武器装备RMS(可靠性、维修性、保障性)参数存在的问题进行分析,提出了RMS参数的选取原则,并建立了地空导弹武器装备RMS参数体系,为装备可靠性、维修性、保障性论证奠定了基础,该体系的建立有助于提高武器装备战备完好性、任务成功性,减低使用维修人员和保障资源费用。