基于门限的无线传感器网络密钥管理方案

由于无线传感器网络在能量消耗、内存开销和计算能力等方面的局限性,传统的网络密钥管理方法已不适用。为此提出了一种适用于无线传感器网络的密钥预分配方法——基于（t,n）-门限方案,给出了密钥分配方法,并从方案的连通性、安全性等方面进行了有效的分析,结果表明该算法在这些方面有一定的优势。     

A model to design recreational boat mooring fields

This article develops a mathematical model and heuristic algorithm to design recreational boating mooring fields. The boating industry is important to the Florida economy, and boat storage is becoming a concern among those in the industry. The mooring field design problem is formulated to maximize the total number of boat feet moored in the mooring field. In the model, we allow two adjacent moorings to overlap, which introduces a risk that under certain conditions the boats on these moorings could contact each other. We identify the conditions when contact is possible and quantify the probability of contact. The mooring field design problem is formulated as a nonlinear mixed‐integer programming problem. To solve the problem, we decompose it into two separate models, a mooring radii assignment model and a mooring layout model, which are solved sequentially. The first is solved via exhaustive enumeration and the second via a depth‐first search algorithm. Two actual mooring fields are evaluated, and in both cases our model leads to better layouts than ones experts developed manually. The mooring field design model rationalizes the mooring field design and shows that in one case by increasing the risk from 0 to 1%, the mooring efficiency increases from 74.8% to 96.2%. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009     

Dynamic signatures and their use in comparing the reliability of new and used systems

The signature of a system with independent and identically distributed (i.i.d.) component lifetimes is a vector whose ith element is the probability that the ith component failure is fatal to the system. System signatures have been found to be quite useful tools in the study and comparison of engineered systems. In this article, the theory of system signatures is extended to versions of signatures applicable in dynamic reliability settings. It is shown that, when a working used system is inspected at time t and it is noted that precisely k failures have occurred, the vector s [0,1]^n‐k whose jth element is the probability that the (k + j)th component failure is fatal to the system, for j = 1,2,2026;,n ‐ k, is a distribution‐free measure of the design of the residual system. Next, known representation and preservation theorems for system signatures are generalized to dynamic versions. Two additional applications of dynamic signatures are studied in detail. The well‐known “new better than used” (NBU) property of aging systems is extended to a uniform (UNBU) version, which compares systems when new and when used, conditional on the known number of failures. Sufficient conditions are given for a system to have the UNBU property. The application of dynamic signatures to the engineering practice of “burn‐in” is also treated. Specifically, we consider the comparison of new systems with working used systems burned‐in to a given ordered component failure time. In a reliability economics framework, we illustrate how one might compare a new system to one successfully burned‐in to the kth component failure, and we identify circumstances in which burn‐in is inferior (or is superior) to the fielding of a new system. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009     

RTW在某型直升机飞控系统半物理仿真中的应用

开发高性能可靠的飞控计算机是直升机研制的重要一步.在试飞之前,需要对飞控系统进行全面的仿真测试.基于Simulink的RTW工具箱和嵌入式VxWorks操作系统,提出一种进行飞控系统半物理仿真的方案.详细说明了仿真平台的组成、RTW的配置方法和生成实时仿真代码的过程.仿真时应用了RTW的外部模式,说明了其原理和具体配置方法.深入分析了RTW生成的目标文件中直升机模型信号量和参数的存取方式,并提出了一种可行的办法.最后给出仿真结果并验证了该方案的可行性,此方案已经应用于进一步的试飞工作中.     

一种基于滑模变结构观测器的故障检测方法

提出一种基于滑模变结构观测器的残差生成及故障检测方法.利用滑模变结构所具有的对未知输入扰动的不变性,移除外界扰动对残差的影响,使残差只对故障信号敏感,从而提高故障检测的准确性,较好地解决基于状态估计的故障检测方法中检测鲁棒性与灵敏度之间的矛盾.仿真验证结果表明了该故障检测方法有较高的检测鲁棒性,同时对小幅值故障较为灵敏.     

分层分布式分群监控体系下的网格资源发现机制

网格中资源发现机制是把资源提供者和资源请求者联系起来的重要环节.在分析分层分布式分群监控体系结构和现有资源发现机制的基础上,提出将集中式目录服务、资源路由表和移动代理三种机制相结合的网格资源发现机制.实验验证该机制在小范围内查找具有性能高效的特点,而在大范围内查找减少了资源发现代理的分发数量,降低了系统消息的负载,进而降低了网络资源的占用.     

基于变结构控制的自动驾驶仪设计

自动驾驶仪作为导弹制导控制系统的主要组成部分,是确保导弹在制导飞行中具有良好的稳定性和可控性的关键.而变结构控制以其在一定条件下对干扰和参数变化具有完全自适应的突出优点,在自动驾驶仪中已经有了深入的研究和实际的应用.简要概述了自动驾驶仪的设计难点、变结构在驾驶仪设计中的应用进展,然后针对战术导弹滚转通道设计了两种不同结构的变结构驾驶仪,并进行了仿真、分析比较.     

人员交通类场所人员荷载研究

对人员交通类场所的特点进行了分析,将人员交通类场所归纳为简单通道、复杂通道、候机（车）厅、进出港厅等组件。针对简单通道和进出港厅,采用“人员流量法”和“人员密度法”两种方法计算人员荷载;针对复杂通道,采用空间上分解为流线、时间上分解为阶段的方法计算人员荷载;针对候机（车）厅,按照设计容量确定人员荷载。并给出了一个包括国家铁路、地铁的综合交通枢纽换乘层人员荷载计算的典型案例。     

嵌入式浏览器中SSL的设计与实现

针对嵌入式浏览器信息传输的安全性问题和嵌入式软件的特点,介绍了SSL协议,提出了一种在嵌入式浏览器中实现对SSL协议支持的方法.通过分析影响SSL协议客户端性能的因素,对SSL的实现过程进行了适当的优化,使用会话恢复机制、只对服务器进行验证的简单握手模式、减少TCP调用次数和优化对批量数据加密算法等方法,实现了嵌入式浏览器对SSL协议的支持;并介绍了方法在嵌入式浏览器JARI_Browser中的实现过程.实际的应用验证了该方法的可行性和正确性.     

关于改进综合英语课程教学的思考

本文从英语专业的培养目标入手,分析了英语专业综合英语课程教学中存在的问题,通过对如何改进该课程教学的探讨,提出了在教学中重视培养学生的综合能力、学习策略及创新能力,英语专业人才培养才能更好地为社会需求服务。