Modeling TCP performance with proxy and ARQ

INTRODUCTION The convenience of wireless communications has led to increasing use of wireless networks for civilian and critical applications. With the advent of Internet technology and the increasing popularity of wireless data devices, the wireless industry is evolv- ing its core networks toward IP-based networks. It will be necessary to integrate the wireless networks and the existing wired networks into the Internet. TCP has been the predominant transport protocol used in the wired …     

大带宽延迟网络的FAST TCP启动性能研究

研究显示,FASTTCP在高速长延迟网络中的性能优于其他传输控制协议。通过分析和提升FASTTCP在大带宽延迟网络中的瞬时行为。为FASTTCP提出了一个新的慢启动机制,仿真显示FASTTCP连接的响应性、吞吐率和公平性显著提高。     

TCP/IP协议簇安全隐患分析及改进

在分析TCP/IP协议簇现存的安全隐患的基础上,重点讨论了TCP/IP协议簇改进及发展,提出了基于TCP/IP安全框架的Intranet安全体系结构模型。     

基于NS2的TCP Vegas算法的仿真与研究

提出了TCP Vegas算法的控制机制,探究了影响其性能的主要因素,使用仿真软件NS2模拟了TCPVegas在各种因素影响下的性能情况。仿真结果表明,TCP Vegas与TCP Reno相比,在吞吐量和频带利用率方面有明显的优势。     

The impact of computer-mediated and traditional academic task presentation on the performance and behaviour of children with ADHD

This project aimed to examine whether the use of computers could have a positive impact on the performance of academic tasks and their behaviour whilst completing them of children with ADHD. This small exploratory study therefore investigated the impact of the use of a laptop computer, with and without stimulating animations and features incorporated into task presentation, on Key Stage 2 level science tasks. The effects of these different forms of computer presentation were examined in relation to performance on more traditionally presented, pen and paper, tasks. The results of this study revealed that, in contrast to typically developing children, participants with ADHD produced the greatest number of accurate responses on the more basic computerised tasks (presented as simple Microsoft Word documents) and exhibited significantly more on-task activity on animated computerised tasks. In summary, computerised presentation significantly improved the accuracy of responses and the on-task focus of participants with ADHD. These early findings are encouraging and may have wide reaching practical implications in terms of the design and implementation of educational software aimed at promoting improvements for children with ADHD in terms of both their academic performance and, critically, appropriate on-task focus and behaviour in the classroom.     

基于Android的Socket（TCP／IP）在LED灯光控制系统中的应用

采用Socket的通信方法,根据TCP／IP通信协议进行数据传输,基于Android操作系统平台,通过Zigbee无线通信与自组网技术,设计了以Android操作系统为平台的客户端应用程序,实现了通过无线wifi网络与Windows系统的电脑服务器之间进行通信,解决了如何利用基于Android系统的手持终端对Zigbee无线网络中的LED灯光进行远程调控的问题,提出并实现了一种新的LED灯的智能控制方案．     

变时滞大系统的振动性理论及应用

本文将纯量时滞泛函微分方程解的振动性理论推广到时滞大系统;通过引进V函数,获得了线性及非线性变时滞大系统振动的充分条件。     

基于时延无线MIMO信道的仿真与实现

本文通过对目前提出的无线MIMO信道进行总结,详细分析了MIMO信道的空时模型。为了对MIMO无线通信技术进行有效的研究与评估,在基于3GPP中的TR25.996协议的基础上,根据接收信号的平均到达角、扩展角和收发两端天线的拓扑结构,创建了一个基于时延的无线MIMO信道仿真方法。通过对时延无线MIMO模型的仿真,验证了基于时延无线MIMO信道特性。     

Experimental study on semi-open heat pipes and its applications

Semi-open heat pipes were studied experimentally in this work. A new kind of semi-open heat pipe with fluid swirl backflow was developed on the basis of the traditional semi-open heat pipe. Heat transfer characteristics during operation and start-up of closed heat pipe traditional semi-open heat pipe and swirl flow semi-open heat pipe were investigated. The swirl orifice's backflow effect on enhancing the working limitation was obtained. Heat exchangers or waste heat boilers made of swirl flow semi-open heat pipes and semi-open heat pipes have been successfully used in high or variable gas temperature engineering applications.     

民营企业融资的局限与渠道拓展--浙江省台州市路桥区融资的调查分析

民营企业在经历了原始积累和快速发展阶段后，正处于第二次飞跃阶段。民营企业涉足的领域不断扩大，资本及技术含量大为提高，对融资及金融服务在规模和方式上均有了更高的要求。本文主要通过对台州市路桥区民营企业融资情况的调查和分析，探讨民营企业在融资渠道、融资方式等方面所面临的问题。     

Academic delay of gratification and children's study time allocation as a function of proximity to consequential academic goals

Students (N = 302) in Chinese elementary schools were assessed regarding their academic delay of gratification (ADOG) and reported the time they devoted to non-school study and playtime during an extended interval prior to taking a high-stakes final exam. Students high compared those low in ADOG were more likely to spend time studying and less time playing several weeks prior to the exam. Growth curve analyses verified, however, that this difference diminished as a function of the temporal proximity to the exam, and that the group differences were non-existent just before the exam. Associations between ADOG and students' academic motivation and use of learning strategies replicated those obtained previously with adults in the USA. Results contribute to the general literatures on volition, homework and the dynamics of conflicting goals and action tendencies.     

寒冷地区冬季双层光伏外窗热电性能实验研究

为研究不同运行模式下双层光伏外窗在寒冷地区冬季的热电性能,通过比较分析封闭式双层光伏窗、内循环式双层光伏窗及送风式双层光伏窗的有效得热量、传热系数及光伏发电量,阐明不同运行模式对光伏外窗热电性能的影响。实验结果表明,办公建筑双层光伏窗采用送风式与封闭式相结合的运行模式,不仅可以增加建筑日间的室内有效得热量,减少新风预热负荷,同时还能有效减少建筑夜间的热量损失,进而减少建筑的热负荷,更有利于建筑节能。     

TC18钛合金钻削加工性能与响应面优化试验

为优化TC18钛合金钻削加工参数、提高钻削表面质量,对TC18钛合金进行单因素钻削加工试验,分析加工过程中所产生的轴向力与各钻削参数的影响规律。使用响应面法(response surface methodology,RSM)得出轴向力线性回归预测模型,并进行方差分析和显著性检验;以获得较优加工表面质量的同时有更高的加工效率为参评指标进行参数优化,得到最优参数组合,并对最优参数组合进行试验验证。结果表明:步进量对所产生的轴向力无显著影响,而主轴转速与进给速度对轴向力影响较大;所得轴向力模型较为可靠,试验验证最优参数组合实际值与预测值相对误差满足工程允许范围。     

Modelling impact of dredging and dumping in ebb-flood channel systems

For a channel-shoal system in a funnel-shaped basin the impact of dredging and dumping is investigated using a complex process-based model. First, the residual flow and sediment transport circulations are analysed for the channel-shoal pattern, which has emerged after a long-term model simulation. Results are compared to the Western Scheldt estuary, which forms the inspiration for this study. Subsequently, different dredge and dump scenarios are modelled, according to a conceptual model, in which ebb-and flood-channels and enclosed shoals form morphodynamic units (cells) with their own sediment circulation. Model results show that dumping sediment in a channel further reduces the channel depth and induces erosion in the opposite channel, which enhances tilting of the cross-section of the cell and eventually can lead to the degeneration of a multiple channel system into a single channel. The impact of different dredging and dumping cases agrees with results from a stability analysis. This means that this type of model applied to a realistic geometry can potentially be used for better prediction of the impact of human interventions.     

石家庄市居住空间分异模型及发展趋势初探

城市居住空间的地域分异是城市社会分化最直接的体现。在介绍我国城市社会空间结构理论的基础上,调查获取了石家庄市125个居住小区的数据,构建了石家庄市居住空间分异模型。把石家庄市居住区划分为富有阶层分布区、富裕阶层分布区、一般阶层分布区和低收入阶层分布区四个等级。通过研究认为,石家庄市已经开始出现空间居住分异现象,但目前还处于初级阶段。最后,对石家庄市未来居住空间分异的趋势进行了预测。     

多级斜板式斜板的角度对水沙分离影响的实验研究

为了研究多级斜板式水沙分离装置中斜板安装角度的变动对装置的水沙分离效果所产生的影响,对同一流量、不同含沙浓度进行了水沙分离实验。结果表明:流量控制在0.9m3/h左右、含沙浓度在15kg/m3之内时,溢流泥沙颗粒D50随泥沙浓度增大而逐渐减小,装置的分离率就高;当斜板的角度α为45°、β为60°时,装置的水沙分离效果最佳,分离率最高。     

无线传感器网络跨层通信协议综述与分析

设计基于跨层机制的通信协议,以达到优化网络性能、有效分配网络资源的目的,是无线传感器网络研究中的一项关键技术.对现有的基于跨层设计的网络通信协议进行综述和分析,并以跨层通信协议设计的目的性为着眼点,对跨层通信协议划分为3类：提高互操作性和增强网络适应性为目的的跨层设计,提高某些性能标准为目的的跨层设计和无分层模型设计.该分类方式有助于网络设计人员进行更具有针对性和实用性跨层设计.     

基于Profibus-DP的变频控制实验系统的研制与应用

介绍了Profibus-DP通信协议,阐述了变频器和PLC的通信原理、参数设置和编程过程,并在此基础上研制出了由变频器、S7-300PLC组成的基于Profibus-DP的变频控制实验系统。介绍了实验系统的硬件组成、结构、系统功能及软件实现,简述了实验系统在实验教学中的应用、优点及实用价值。     

掺杂锂渣和再生粗骨料大偏压长柱力学性能试验研究

对9根不同锂渣掺量、不同再生粗骨料替代率下的掺杂锂渣和再生粗骨料的大偏压长柱进行加载试验,研究其受压力学性能。结果表明:试件的破坏形态、竖向位移、混凝土应变、中部钢筋应变与普通钢筋混凝土相似;平截面假定适用于试件;400MPa级钢筋在大偏压长柱中的加载过程中能够很好地发挥其作用,通过现行规范计算出的承载力具有较大安全储备,但要精确计算承载力,还需对规范公式进行相应的调整。