网络监控系统的仿真分析与规划设计

为了实现一卫星地面站的网络监控系统的扩容,提高网络监控系统性能,文中利用OPNET对此监控系统进行了一系列的仿真分析,首先确认系统有进一步扩展的能力,然后设计扩展方案,并进一步的仿真分析验证扩容方案的可行性.在仿真过程中,将此系统的业务进行模型抽象,作为一种新的标准应用添加到应用层.这样既满足了系统精确建模的需求又简化了自定义应用(custom application)中繁琐的参数配置.在扩容方案可行性的验证过程中,通过规划设计子观测站系统的拓扑结构、定义其支持的业务,对扩展方案进行了详细的仿真分析,结果表明设计方案可以满足系统的要求.     

CANopen现场总线设备通信协议测试系统

在分析CANopen协议结构和特点的基础上,介绍了CANopen现场总线设备通信协议测试系统,该系统是以解决CANopen设备的协议一致性问题以及简化网络组态为目标而开发的.通过该项设计使系统可以检测CANopen设备的通信参数,并测试出CANopen设备所应用的协议是否与标准的CANopen协议一致.另外,该系统也能对CANopen设备进行默认参数配置或自定义参数配置,从而简化了网络组态,并为设备间的正常通信提供基础.     

基于NS2的无线网络仿真和自定义协议添加

文章讨论了如何使用NS2进行无线网络的仿真,包括配置无线节点、建立网络拓扑、设置节点运动方式、在节点上设置数据流。此外还讨论了针对具体应用需求,向NS2中添加自定义协议的方法和步骤,并以停止—等待协议为例,说明了添加的具体过程。     

基于Web的异常数据检测系统设计与实现

针对大数据处理中数据来源复杂,且在清洗过程中存在较多相似的问题,开发了一款异常数据检测系统。系统使用流行的Python编程语言和轻量级的Flask Web框架,能够简化数据处理工作中的重复流程,极大减轻数据分析的工作量,提高工作效率,利用系统内置的异常检测算法和用户上传的自定义算法完成对数据中异常的检测工作。     

基于Opnet的TCP拥塞控制仿真

文章介绍了功能强大的网络仿真软件Opnet,分析了其仿真特点和功能,重点讨论了如何使用Opnet进行网络建模。结合TCP拥塞控制的实例,介绍了基于Opnet的TCP拥塞控制仿真的建模方法、业务应用配置以及各种网络参数的配置,并分析了各种网络环境参数对网络性能和仿真结果的影响。     

基于用户自定义指标的多变量控制系统性能评估技术

大量的计算以及对一般关联矩阵先验知识的需求导致用户自定义指标在实际工业应用中存在诸多不便,鉴于此,为了减少对过程模型信息的需求,避免估计一般关联矩阵,研究了如何简化用户自定义指标的计算,并提出了两种改进的用户自定义指标的计算方法.该方法仅需过程常规数据和对过程输入/输出时延或关联矩阵阶次的估计便可完成指标的计算.最后通过仿真验证了两种方法的优越性和有效性.     

基于仿真的物料平衡系统测评

为了更好地测评石化企业生产执行系统(MES)软件的物料平衡模块数据校正功能,提出了一种基于仿真的数据校正结果的测评方法。该方法通过搭建仿真模型产生全厂物流过程的真值,并应用动态数据驱动方法进行模型参数的修正,即通过向仿真真值添加测量误差生成误差可配置的测量值,模拟现场真实的测量网络;应用物料平衡系统及其内嵌数据协调算法对测量值进行数据校正得到校正值,将校正值分别与仿真真值、测量值进行对比,定量评估数据协调算法的性能。相对于仅比较校正值和测量值的原评定方法,该方法能更加精确、全面地测评数据校正算法的效果,并在某石化企业的案例中得到验证。     

无线Mesh网络中的多约束QoS路由算法

无线Mesh网络中多媒体数据的实时传输应用日益广泛,这些应用对网络的带宽、时延和抖动有着较高要求,需要无线Mesh网络提供一定的QoS保障机制.QoS路由是实现QoS保障的关键环节.在路由协议AODV的基础上,提出了一种具有多个QoS参数约束的路由算法(MQ-AODV),通过改进路由选择函数及扩展路由维护机制,为多媒体传输应用业务提供QoS保障.在路由发现的过程中,MQ-AODV引入了一个归一化的路由选择函数,简化了多约束路由算法中的NP-complete问题.在路由维护方面,提出了一种路由预先修复机制,在数据流传输过程中保障路径质量.仿真结果表明,MQ-AODV算法比AODV更好地减少了数据流传输的延迟和丢包,有效提高了网络的吞吐量.     

基于NS2的BACnet网络DoS攻击仿真研究

BACnet是楼控网络领域唯一的ISO标准;NS2是目前广泛使用的一种面向对象的基于离散事件驱动的网络仿展ぞ?随着BACnet网络与IP网络的集成,使得BACnet网络面临更多与传统IP网络相同的安全威胁.文中利用NS2仿真软件对BACnet网络的安全威胁进行研究,首先阐述了BACnet网络层协议数据单元(NPDU)的结构,给出了在NS2中添加一个简化的BACnet分组头、路由表和代理的详细过程和代码;在此基础上通过一个BACnet网络层DoS攻击及其防范策略的仿真实验,验证了这些代码的正确性,仿真结果真实有效,从而论证了使用NS2对BACnet网络安全问题进行仿真研究的可行性和有效性.     

基于Struts框架构建网络管理系统

探讨了基于Struts框架开发多子应用模块的网络管理系统的一种新方法。系统从功能上划分为多个子应用模块,每个子应用模块都采用了多层次的体系结构,联合使用业务代理和DAO模式,通过Struts框架内置的SwitchAction类和XML配置文件进行模块之间的切换和信息传递。简化了应用的并行开发过程,缩短了开发周期,实现了用户界面表示、应用业务逻辑和数据访问逻辑的分离,使系统具有良好的稳定性罐壮性和可扩展性。     

上海电子口岸海关税费EDI支付系统中的设计标准

通关电子化、技术标准化是电子口岸建设的核心技术,国内的标准设计必须与国际标准接轨.以海关税费EDI支付系统为背景,重点介绍报文标准的设计和国际标准的应用.     

Improving performance and energy efficiency of embedded processors via post-fabrication instruction set customization

Encapsulating critical computation subgraphs as application-specific instruction set extensions is an effective technique to enhance the performance and energy efficiency of embedded processors. However, the addition of custom functional units to the base processor is required to support the execution of custom instructions. Although automated tools have been developed to reduce the long design time needed to produce a new extensible processor for each application, short time-to-market, significant non-recurring engineering and design costs are issues. To address these concerns, we introduce an adaptive extensible processor in which custom instructions are generated and added after chip-fabrication. To support this feature, custom functional units (CFUs) are replaced by a reconfigurable functional unit (RFU). The proposed RFU is based on a matrix of functional units which is multi-cycle with the capability of conditional execution. To generate more effective custom instructions, they are extended over basic blocks and hence, multiple-exits custom instruction and intuition behind it are introduced. Conditional execution capability has been added to the RFU to support the multi-exit feature of custom instructions. Because the proposed RFU has limitations on hardware resources (i.e., connections and processing elements), an integrated mapping-temporal partitioning framework is proposed to guarantee that the generated custom instructions can be mapped on the RFU (mappable custom instructions). Experimental results show that multi-exit custom instructions enhance the performance and energy efficiency by an average of 32% and 3% compared to custom instructions limited to one basic block, respectively. A maximum speedup of 4.9, compared to a single-issue embedded processor, and an average speedup of 1.9 was achieved on MiBench benchmark suite. The maximum and average energy saving are 56% and 22%, respectively. These performance and energy efficiency are obtained at the cost of 30% area overhead.     

剪纸在传统节日中的去与留

光阴如梭,时光如箭,多姿多彩的节日礼俗像万花筒一样装点着现代人的生活。当我们沉浸在节日的欢声笑语中,欣赏着各种节日中的特种景象时,可曾想过为我们节日气氛增光添彩的各种风俗活动的由来?以蔚县剪纸为例,分析其出现和发展的现实状况。     

基于VB的定制软件开发与应用

由于用户水平及其特殊的业务流程要求不同,特别是对一些微小企业,通用管理软件已经不能完全适应管理的需求。理清基于VB环境的定制软件系统的层次结构,定制软件的设计开发工作,主要集中在应用层中的定制模块的开发,并成功地应用于多个管理系统的开发工作。     

基于产品感性定制模型的顾客协同设计系统

为使产品定制模型更加适合缺少相关领域专业知识的大众消费者,建立了基于感性工学的产品感性定制模型.引入配件感性性能指数、产品感性性能矩阵对产品感性性能进行量化.使用层次分析法实现了求解与顾客对产品感性性能需求对应的产品工程配置的方法.并应用产品感性定制模型,构建了基于Web和虚拟现实技术的顾客协同设计系统.     

基于COM的CAE应用开发平台

根据CAE发展趋势，提出新一代的开放式CAE仿真开发平台，采用Web的三层架构，基于COM组件技术，用户可以在此基础上定制专业产品仿真工具。     

New Graphics Controller for Electrostatic Plotting

Recent developments in electrostatic plotting techonology-specifically in areas related to the plotter's speed, density, and color-forced processing requirements for graphics controllers beyond what is possible with traditional approaches. New market segments in the VLSI field, which were opened by the introduction of color, created more demanding applications, exceeding 10 million graphic elements per single E-size drawing. Conventional technology and architecture cannot generate the performance requirements within the given cost constraints. The new RPM (Raster Processing Machine) controller is based on a unique modular pipeline architecture, VLSI implementation of rasterizing routines, and parallel processing for performance and bottleneck by passing. For simple plots a single board processor based on the Motorola 68000 provides conversion from random graphic elements to the raster form required. As plot complexity increases, a special bipolar processor with a writable control store is added. For applications covering large graphic constructs with special texture (often needed for color generation), two custom chips on a dedicated VLSI board are added to the system. Multiplicity of processors and buses is possible for additional throughput. The controller's performance, along with the analysis of potential constraints, is also described.     

An architecture framework for an adaptive extensible processor

To improve the performance of embedded processors, an effective technique is collapsing critical computation subgraphs as application-specific instruction set extensions and executing them on custom functional units. The problem with this approach is the immense cost and the long times required to design a new processor for each application. As a solution to this issue, we propose an adaptive extensible processor in which custom instructions (CIs) are generated and added after chip-fabrication. To support this feature, custom functional units are replaced by a reconfigurable matrix of functional units (FUs). A systematic quantitative approach is used for determining the appropriate structure of the reconfigurable functional unit (RFU). We also introduce an integrated framework for generating mappable CIs on the RFU. Using this architecture, performance is improved by up to 1.33, with an average improvement of 1.16, compared to a 4-issue in-order RISC processor. By partitioning the configuration memory, detecting similar/subset CIs and merging small CIs, the size of the configuration memory is reduced by 40%.     

Supporting accessible hypermedia in web-based educational systems: defining an accessibility application profile for learning resources

The design and development of web-based educational systems for people with special abilities have recently attracted the attention of the research community. However, although a number of systems that claim to meet accessibility needs and preferences are proposed, most of them are typically supported by hypermedia and multimedia educational content that is specially designed for the user targeted group. Such approaches prevent their user groups (both learners and their tutors) from accessing other available resources. Therefore, it is important to be able to built generic e-learning systems that would allow the reuse of existing learning resources in different accessibility demanding applications. To this end, in this article we propose a methodology for defining an accessibility application profile that captures the accessibility properties of learning objects in a standard form and we examine its application to the IEEE Learning Object Metadata (LOM) standard.