Experience with approximate reliability-based optimization methods II: an exhaust system problem

Traditional reliability-based design optimization (RBDO) requires a double-loop iteration process. The inner optimization loop is to find the reliability and the outer is the regular optimization loop to optimize the RBDO problem with reliability objectives or constraints. It is known that the computation can be prohibitive when the associated function evaluation is expensive. This situation is even worse when a large number of reliability constraints are present. As a result, many approximate RBDO methods, which convert the double loop to a single loop, have been developed. In this research, an engineering problem with a large number of constraints (144) is designed to test RBDO methods based on the first-order reliability method (FORM), including single- and double-loop methods. In addition to the number of constraints, this problem possesses many local minimums. Some original authors of the RBDO methods are also asked to solve the same problem. The results and the efficiencies for different methods are published and discussed.     

Connected sensor cover: self-organization of sensor networks for efficient query execution

Spatial query execution is an essential functionality of a sensor network, where a query gathers sensor data within a specific geographic region. Redundancy within a sensor network can be exploited to reduce the communication cost incurred in execution of such queries. Any reduction in communication cost would result in an efficient use of the battery energy, which is very limited in sensors. One approach to reduce the communication cost of a query is to self-organize the network, in response to a query, into a topology that involves only a small subset of the sensors sufficient to process the query. The query is then executed using only the sensors in the constructed topology. The self-organization technique is beneficial for queries that run sufficiently long to amortize the communication cost incurred in self-organization. In this paper, we design and analyze algorithms for suchself-organization of a sensor network to reduce energy consumption. In particular, we develop the notion of a connected sensor cover and design a centralized approximation algorithm that constructs a topology involving a near-optimal connected sensor cover. We prove that the size of the constructed topology is within an O(logn) factor of the optimal size, where n is the network size. We develop a distributed self-organization version of the approximation algorithm, and propose several optimizations to reduce the communication overhead of the algorithm. We also design another distributed algorithm based on node priorities that has a further lower communication overhead, but does not provide any guarantee on the size of the connected sensor cover constructed. Finally, we evaluate the distributed algorithms using simulations and show that our approaches results in significant communication cost reductions.     

某超高层建筑TMD风振控制分析

某超高层建筑总高度492m，风致振动将控制结构的荷载和舒适度。为减小风振响应，提高结构舒适度，拟在第90层设置两个相同调频质量阻尼器。将该超高层建筑简化为14质点多自由度体系，利用高频天平实验结果，在时域内计算了结构在受控与不受控情况下的风振响应，分析了调频质量阻尼器的控制效果，给出了设计方案。     

膜结构风荷载和风致响应研究进展

膜结构是近年来在大跨度空间结构中广泛采用的结构形式。由于膜材料柔软、质轻的特点，膜结构对风的作用却十分敏感，风荷载是该类结构设计中的主要控制荷载，在响应分析中必须考虑气动弹性效应，但至今仍没有行之有效的分析方法。从风洞试验研究、响应分析方法和数值模拟等方面详细评述了膜结构风致振动的研究进展，并给出了今后研究的建议。     

Preparation of CeO2 Buffer Layer on Cube Textured Nickel Substrate by Reactive Sputtering

Preparation of CeO_2 Buffer Layer on Cube Textured Nickel Substrate by Reactive Sputtering     

QoS驱动的Web Services方案相关合成

现有的Web Services合成算法较少关注Services的多标准,且较少考虑方案相关的思想.即使有算法考虑到上述问题,但为了体现方案相关,把全部的方案进行穷举后再进行对比,因此工作量繁杂.将QoS方法引入Web Services合成,对方法进行改进,从而在QoS的计算中体现方案相关.通过向量表示Services的代价,然后相应地改进迪捷斯特拉算法,逐步更新代价向量并计算QoS值进行路径选择.实验证明,该算法能在较好的时间复杂度内得到用户满意的合成方案, 在用户给定输出数量较大时,优势更为明显.     

WAP网关中安全层的设计与实现

Internet技术和无线网络技术的快速发展使它们已经成为迈向信息社会的两个重要标志。如何结合两者的技术优势,不受信息源和用户访问位置的限制,以统一的标准向用户提供无处不在的信息服务,正成为网络界和电信业界共同关注的一个焦点问题。而WAP协议正是为此而应运而生。文章介绍了笔者和北京Si-Tech公司共同开发的WAP网关框架和模块结构,并重点讨论了WTLS的特点和实现内容,最后描述了所实现的WTLS层的处理机制和数据结构。     

基于神经计算机并行运算的连续语音识别

人工神经网络具有强大的模式分类能力,除此之外还有一个优点即其大量的并行神经计算能力,使得以低廉的硬件开销来实现高速并行运算成为可能,这在实时模式识别中是非常重要的。文章介绍了以预言神一号小型神经计算机的并行神经运算为核心的连续语音的实时识别的算法,实验表明该算法有很高的实时性和较好的识别率。     

基于QoS的多路视频回放

由于PC的速度有限,当视频回放的路数较多时,可能无法同时满足所有路的回放CPU资源要求,这时就需要进行合理的资源分配和调度。在多路回放中,每一路视频流可能对应于一种不同的网络带宽和传输质量,用户对每一路的回放质量、速度要求也会有差别。该文根据用户服务质量(QoS)要求,利用多缓冲区和调度算法对多路视频回放给出了一种优化解决方案。实验运行表明,该文算法的性能优于现有商用多路视频播放器。     

基于组件的信息系统安全等级划分方法

为了在信息系统的安全评估工作中更好地应用《计算机信息系统安全保护等级划分准则》,该文在研究该准则与《信息技术安全技术信息技术安全性评估准则》的基础上,提出了一种基于安全组件进行安全等级划分的方法,并以前者第二等级为例给出了完整的安全描述和划分实例。