P2P系统中降低错误相关性的方法

目前许多P2P网络存储系统都采用了m／n容错机制来提高系统的可用性和可靠性,但是在实际应用中,服务器之间发生相关错误会导致这种容错机制具有低容错率．针对这种问题,描述了一种在P2P系统中寻找低错误相关的服务器节点集合的方法,m／n容错机制可以通过使用此集合中的服务器节点来提高其容错率,从而使得系统具有高可用性和可靠性,并对此方法进行了实验分析,验证了方法实用有效．     

Test Time Minimization for Hybrid BIST of Core-Based Systems

This paper presents a solution to the test time minimization problem for core-based systems. We assume a hybrid BIST approach, where a test set is assembled, for each core, from pseudorandom test patterns that are generated online, and deterministic test patterns that are generated off-line and stored in the system. In this paper we propose an iterative algorithm to find the optimal combination of pseudorandom and deterministic test sets of the whole system, consisting of multiple cores, under given memory constraints, so that the total test time is minimized. Our approach employs a fast estimation methodology in order to avoid exhaustive search and to speed-up the calculation process. Experimental results have shown the efficiency of the algorithm to find near optimal solutions.     

远距离射频识别系统及其应用简论

RFID(Radio Frequency Identification)采用无线射频实现可移动存储设备与计算机或PLC之间的数据交换。一个典型的RFID系统包括载码体(即数据存储器),与载码体通讯的天线,以及处理天线与PC(或PLC)之间通信的控制器(天线与控制器一体时,我们称之为只读器或读写器)。射频识别技术被广泛应用于工业自动化、商业自动化、交通运输控制管理、防伪等众多领域,甚至军事用途。     

WCDMA中RF优化及路测数据分析方法

WCDMA网络是目前在用的主流网络,WCDMA的网络优化对用户和运营商有重要作用。RF优化是WCDMA网络优化的主要部分之一。RF优化主要结合路测数据进行。因此,本文通过对RF优化流程及路测数据分析方法的分析,提出路测的主要的KPI指标,并对弱覆盖、导频污染、邻区漏配和切换问题等常见的网络优化问题进行分析。     

WCDMA中RF优化及路测数据分析方法

WCDMA网络是目前在用的主流网络,WCDMA的网络优化对用户和运营商有重要作用。RF优化是WCDMA网络优化的主要部分之一。RF优化主要结合路测数据进行。因此,本文通过对RF优化流程及路测数据分析方法的分析,提出路测的主要的KPI指标,并对弱覆盖、导频污染、邻区漏配和切换问题等常见的网络优化问题进行分析。     

民机全动飞行模拟器鉴定测试软件开发

为按照新鉴定标准鉴定飞行模拟器性能, 提交鉴定测试报告, 对飞行模拟器鉴定测试软件的开发进行研究; 首先介绍了飞行模拟器性能鉴定测试标准; 其次介绍了软件系统结构、软件的总体设计和主要模块详细设计; 最后通过某型飞行模拟器某测试标准数据验证了软件功能基本实现, 能达到实际使用要求.     

小波变换在单片机信号去噪中的应用

在单片机系统工作环境中存在着各种噪声干扰,尽管已采取了一些抗干扰措施,但不可避免会有噪声进入系统。该文根据单片机系统中的信号特点,基于小波变换自动变焦功能,提出用小波变换对含噪信号进行去噪。基于小波变换的去噪是在对含噪信号进行分解的过程中,通过门限方法抽取有用信号的小波系数,然后重建而得以实现。仿真结果表明了在单片机控制系统中利用小波变换进行信号去噪的可行性和有效性。     

基于时效量化的Web服务评价模型

现有的服务评价方法缺乏时效性,而应用于其他系统的时效量化方法难以体现服务评价时效在衰退上的差异特征。由此,建立了基于时效量化的Web服务评价模型。模型以评价时效的遗忘特征为切入点,分析评价时效与人类记忆的关系,揭示评价时效遗忘速率的更新规律,构建符合时效衰退差异的时效量化方法。同时,根据量化结果,优化评价窗口长度,从而解决人工设定窗口长度的不合理性。实验表明,模型在满足时效衰退差异性的基础上,确保了较低的评价误差和计算代价,并合理拟合用户评价,具有一定理论研究和实际应用价值。     

Decreasing Computational Time of Urban Cellular Automata Through Model Portability

This paper investigates how portability of a model between different computer operating systems can lead to increased efficiency in code execution. The portability problem is not a trivial one, as many geographic models are designed to be run inside a set environment (Unix, Solaris, Linux, and Windows), and are further limited by hardware constraints. The SLEUTH urban growth model [K.C Clarke, S. Hoppen, and L. Gaydos. “A self-modifying cellular automaton model of historical urbanization in the San Francisco Bay area”, Environment and Planning B, 24:247–261, 1997.] was implemented under three different operating systems (Solaris, Linux, and Windows). Results suggest that the model's performance is optimized by porting it from its original environment (Unix/Solaris) to Linux or Windows where faster processors are available. While the results show optimization of model performance, there are some suggestions of computational bottlenecks that may eventually limit the increased performance of the model. Regardless, the research demonstrates that the portability of a model can lead to not only to a decrease in computation time, but may increase the viability in practical applications and attract a wider user base.     

Logical Time in Distributed Software Systems

This paper presents a survey of implementation of logical time in asynchronous distributed systems. We provide an argument that justifies the use of logical time as a mechanism for detecting causal relationships between events. Further, we formally introduce the notion of a logical time system (a logical clock) and proceed to discuss the properties of the scalar, vector, and matrix clocks. Finally, we consider the modifications of the vector clock that reduce the average communication overhead while retaining the property of isomorphism.     

基于规则的专家系统时间估计研究

在一些复杂控制系统中,专家系统作为一个决策控制器,满足整个系统的性能需要,因此研究专家系统的推理时间是必要的.专家系统的推理时间与其推理模式、知识库结构等因素有关.针对知识库结构,探讨了基于规则的专家系统的推理时间问题,利用时间齐次马尔可夫链为专家系统知识库建模,并给出了相应的时间估计模型.     

Empirical Test Observations in Client-Server Systems

Formal statistical analysis of defect databases for two commercial client-server products for disparate applications - C-language parsing and geophysical modeling - tests the hypothesis that defects in the graphical client mask more important underlying defects in the computational server. It also quantifies the benefit of continued testing after delivery in terms of reduced software defect densities apparent to end users.     

Development of VHDL‐AMS neuro‐fuzzy behavioral models for RF/microwave passive components

The new generation of System‐on‐Chip (SoC) incorporates digital, analogue, RF/microwave and mixed‐signal components. Such circuits impose to reconsider the traditional design methods. Mixed‐signal designers need novel design methodologies which will have to include accurate behavioral libraries of devices and processes into hierarchical design flows. Thus, this paper describes a behavioral modeling approach which generates neuro‐fuzzy‐based models for RF/microwave devices. The models, so obtained, can be easily integrated into a VHDL‐AMS simulator. This modeling approach is applied to a microwave tunable phase shifter and it is illustrated by the development of a VHDL‐AMS model library for RF/microwave applications. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Scalability versus Execution Time in Scalable Systems

Parallel programming is elusive. The relative performance of different parallel implementations varies with machine architecture, system and problem size. How to compare different implementations over a wide range of machine architectures and problem sizes has not been well addressed due to its difficulty. Scalability has been proposed in recent years to reveal scaling properties of parallel algorithms and machines. In this paper, the relation between scalability and execution time is carefully studied. The concepts of crossing point analysis and range comparison are introduced. Crossing point analysis finds slow/fast performance crossing points of parallel algorithms and machines. Range comparison compares performance over a wide range of ensemble and problem size via scalability and crossing point analysis. Three algorithms from scientific computing are implemented on an Intel Paragon and an IBM SP2 parallel computer. Experimental and theoretical results show how the combination of scalability, crossing point analysis, and range comparison provides a practical solution for scalable performance evaluation and prediction. While our testings are conducted on homogeneous parallel computers, the proposed methodology applies to heterogeneous and network computing as well.     

工作流系统中的时间管理

介绍了工作流系统中时间管理的范畴。从工作流系统中时间约束的建模、时间约束的执行和运行后的数据分析三个方面全面概述时间管理的研究内容,为在实践中构建具有时间约束的工作流系统奠定了理论基础。     

工作流系统时间管理

时间管理是工作流管理软件系统的关键部分,也是工作流技术实施复杂企业应用的严重局限.开展时间管理研究,对于增强工作流管理软件系统的柔性、确保工作流计划的高效执行和提高企业的竞争力具有重要意义.时间管理的关键在于时间信息的有效建模.首先介绍了工作流管理系统的时间问题.其次,综述了时间建模与分析的研究现状,包括时间约束的建模、时序一致性验证与时间违反的处理.最后,基于对现有研究方法的分析与评价,指出了工作流系统时间管理的发展方向.时间管理的支持对于开发灵活性和实用性的工作流管理系统具有重要的指导意义.     

基于ATEasy的通用射频测试系统研究与实现

针对引进现代电子装备及系统中射频模块故障频发的问题,为实现对引进电子装备及系统射频模块的自动测试及故障诊断,达到降低外送维修成本、缩短维修周期、提高维修效率等目的,研制通用射频测试系统;通用射频测试系统硬件基于GPIB及VXI总线技术集成精密测试仪器仪表实现,利用VXI矩阵开关构建模块串并回路,设计系统通用接口适配器,提出自动测试射频模块工作电流及电压的电路设计;软件架构及测试程序采用美国GEOTest公司的ATEasy8.0;目前基于ATEasy集成开发环境开发射频模块测试程序,已实现20余种射频模块的自动测试及故障诊断;经验证,测试结果有效;该系统为引进现代电子装备及系统射频模块的测试开辟新的途径,提供新的支持.