Comparison of the RF MEMS switches with dielectric layers on the bridge’s lower surface and on the transmission line

Previously, we proposed that the dielectric layer of RF MEMS switch can be fabricated either on the transmission line, as traditional switches, or on the lower surface of the bridge. This paper presents a detailed comparison of the RF MEMS switches with different positions of dielectric layer. Through theoretically analyzing the physical model of fringing capacitance, it is revealed that different positions of dielectric layer can result in different switch capacitances. Therefore, the change of d...     

软件实现主备倒换的设计

提出了一种软件实现通信系统主备倒换的改进机制,并且适用于多模软基站通信系统。一方面,数据同步和链路切换不再同时进行,数据同步放在了预倒换阶段,从而大大缩短了主备倒换时间;另一方面,备倒主(备状态切换为主状态)先于主倒备进行,即不允许出现软件双备的情况,保证系统在任何情况下都有可用的主控板。并且该机制适用于未来基站的发展趋势——多模软基站通信系统,针对于正常倒换和异常倒换两类情况,通过倒换条件判断,预倒换、备倒主、主倒备的顺序完成主备倒换来实现主备之间的快速可靠切换。并且该机制对倒换失败的情况做了恰当的处理。     

交换机冗余链路引起的网络拥塞问题

网络中,冗余链路可以保障网络的高可用性,但它也会引起数据帧在网路中不停地兜圈,导致广播风暴、MAC地址表不稳定、重复帧等,从而引起网络拥塞。该文结合模拟实验探讨了交换机的工作原理及数据转发流程,及如何避免数据帧的兜圈引起网络拥塞,为网络设备的高可用性配置提供了实践指导。     

无线传感器网络多汇聚节点动态路径切换机制

为了解决在具有多个汇聚节点的传感器网络中由于节点能耗不均匀而产生一些节点能量提前耗尽的问题,提出一种节点动态路径切换机制.该机制利用梯度传输协议计算出每一个节点至各汇聚节点的成本字段,选出距离各节点最近和次近的汇聚节点并进行分群.节点在信息传输时将依据上游节点电力层级进行对比,动态选取较高电力层级的上游节点作为其下一跳节点,建立到最近或次近汇聚节点的传输路径.实验结果表明,采用该机制可以在不同来源产生环境下达到延长整个网络存活时间的效果.     

Maximum likelihood analysis of algorithms and data structures

We present a new approach for an average-case analysis of algorithms and data structures that supports a non-uniform distribution of the inputs and is based on the maximum likelihood training of stochastic grammars. The approach is exemplified by an analysis of the expected size of binary tries as well as by three sorting algorithms and it is compared to the known results that were obtained by traditional techniques. Investigating traditional settings like the random permutation model, we rediscover well-known results formerly derived by pure analytic methods; changing to biased data yields original results. All but one step of our analysis can be automated on top of a computer-algebra system. Thus our new approach can reduce the effort required for an average-case analysis, allowing for the consideration of realistic input distributions with unknown distribution functions at the same time. As a by-product, our approach yields an easy way to generate random combinatorial objects according to various probability distributions.     

飞行器姿态控制系统中的一种计算机仿真研究

针对飞行器姿态控制系统的参数时变性和不确定性干扰等特点,本文给出了一种基于Ackermann规则的滑模变结构控制器,并在设计滑模面时,引入积分项来消除干扰等因素给系统带来的稳态误差;为消除抖动,在控制器中引入模糊系统来实现去抖;同时设计灰色补偿控制项来抵消不确定项对系统造成的不利影响。最后进行了计算机数字仿真,结果表明本文所设计的控制器具有很好的效果。     

形式背景的交约简

从拓扑的角度研究形式背景的属性约简问题。对于非决策形式背景,提出基于集合交集的属性约简的新的定义,并得出了交协调集的判定定理,证明了交协调集与概念格协调集是等价的;最后,讨论了带有决策的形式背景的属性约简问题。     

高速脉冲信号源的设计与实现

高速脉冲信号源是数据采集系统的重要组成部分,常用于系统的自检与测试中.根据实际要求,提出了高速运放调理和高速电子开关两种方案.分别对高速运放、信号幅值调理、驱动电路和高速电子开关的选择进行了研究,给出了具体的硬件电路设计.并结合相关理论,分析了信号在传输过程中出现的反射现象,提出了符合要求的解决方案.此高速脉冲信号源已成功应用于某采集设备的自检和测试中,效果良好.     

A comprehensive solution for application‐level adaptation

Driven by the emergence of mobile and pervasive computing there is a growing demand for context‐aware software systems that can dynamically adapt to their run‐time environment. We present the results of project MADAM that has delivered a comprehensive solution for the development and operation of context‐aware, self‐adaptive applications. The main contributions of MADAM are (a) a sophisticated middleware that supports the dynamic adaptation of component‐based applications, and (b) an innovative model‐driven development methodology that is based on abstract adaptation models and corresponding model‐to‐code transformations. MADAM has demonstrated the viability of a general, integrated approach to application‐level adaptation. We discuss our experiences with two real‐world case studies that were built using the MADAM approach. Copyright © 2008 John Wiley & Sons, Ltd.