基于物元模型-AHP的电子战无人机作战效能评估

针对电子战无人机作战效能评估问题,建立了电子战无人机作战效能评估指标体系通用框架,提出了基于物元模型-AHP的评估方法,并建立了数学评估模型,以某次复杂电磁环境下电子战无人机联合进攻演练任务为背景,给出了评估模型的仿真算例,结果表明,该方法在电子战无人机作战效能评估中是可行和有效的。     

Fast handoff with reducing waste rate approach for wireless resources management in UMTS mobile networks

3G Wideband CDMA systems adopt the Orthogonal Variable Spreading Factor code tree as the channelization codes management for achieving high data rate transmission in personal multimedia communications. It assigns a single channelization code for each accepted connection. Nevertheless, it wastes the system capacity when the required rate is not powers of two of the basic rate. One good solution is to assign multiple codes for each accepted connection but it causes two inevitable drawbacks: long handoff delay and new call setup delay due to high complexity of processing with multiple channelization codes, and high cost of using more number of rake combiners. Especially, long handoff delay may result in more call dropping probability and higher Grade of Service, which will degrade significantly the utilization and revenue of the 3G cellular systems. Therefore, we propose herein an adaptive efficient codes determination algorithm based on the Markov Decision Process analysis approach to reduce the waste rate and reassignments significantly while providing fast handoff. Numerical results demonstrate that the proposed approach yields several advantages, including the lowest GOS, the least waste rate, and the least number of reassignments. Meanwhile, the optimal number of rake combiners is also analyzed in this paper. This research was supported in part by the National Science Council of Taiwan, ROC, under contract NSC-93-2213-E-324-018.     

On the effects of the packet size distribution on the packet loss process

Real-time multimedia applications have to use forward error correction (FEC) anderror concealment techniques to cope with losses in today’s best-effort Internet. The efficiency of these solutions is known however to depend on the correlation between losses in the media stream. In this paper we investigate how the packet size distribution affects the packet loss process, that is, the distribution of the number of lost packets in a block, the related FEC performance and the average loss run length. We present mathematical models for the loss process of the MMPP+M/D/1/K and the MMPP+M/M/1/K queues; we validate the models via simulations, and compare the results to simulation results with an MPEG-4 coded video trace. We conclude that the deterministic packet size distribution (PSD) not only results in lower stationary loss probability than the exponential one, but also gives a less correlated loss process, both at a particular average link load and at a particular stationary loss probability as seen by the media stream.Our results show that for applications that can only measure the packet loss probability, the effects of the PSD on FEC performance are higher in access networks, where a single multimedia stream might affect the multiplexing behavior. Our results show that the effects of the PSD on FEC performance are higher in access networks, where a single multimedia stream might affect the multiplexing behavior and thus can improve the queuing performance by decreasing the variance of its PSD.     

基于1 μ m 600 V BCD工艺的高压栅驱动电路

基于低压BCD工艺,与华润上华合作开发了1μm 600 V BCD工艺平台,可以集成600V高压LDMOS和高压结终端.基于此工艺平台,设计了一种高压半桥栅驱动电路.该电路具有独立的低端和高端输入通道,内置长达1 μs的死区时间,防止高低端同时导通.采用双脉冲电平位移结构完成15～615V的电平位移,同时集成过流和欠压等保护功能.高端采用新型的电平位移结构,版图面积减小12％.测试结果表明,高端浮置电平可以加到750V,高低端输出上升时间为50 ns,延迟匹配为150 ns,输出峰值电流大于2A,电路响应快,可靠性高.     

基于MPI的进程拓扑感知映射研究

本文首先介绍了获取应用程序通信拓扑和物理拓扑的方法,结合进程间通信量和通信频次定义了进程间亲和度,并针对具有分层网络、NUMA效应的硬件系统,设计了相应的进程映射算法.该算法根据进程间的亲和度对进程集合进行划分,在划分过程中构造出和物理拓扑树同构的树状结构,随后在两棵同构树的对应节点上做映射来解决应用程序进程到物理节点、处理核心的映射问题.在一个多核集群系统上的实验表明,使用本文提出的进程映射方法可以有效提高并行应用程序的通信效率,显著减少程序的总体执行时间.     

A process-tolerant out-of-band blocker rejection technique for SAW-less receivers

In this paper, an active filtering technique is presented which is capable of filtering the out-of-band blockers in wireless receivers. The concept is based on the feedforward cancellation technique where a blocker replica is subtracted at the output of the low-noise amplifier (LNA). In contrast to the previously reported feedforward cancellation methods, exact gain and phase matching are easily obtained in the proposed architecture to produce a highly selective narrowband frequency response at the output of the LNA with wide rejection bandwidth. For the proof of concept, the system is implemented in a 65 nm CMOS technology. It occupies a total area of 0.8 mm² and the current consumption is 24 mA from a 1.2 V supply. The system post-layout simulations showed a blocker rejection of more than 33 dB for blocker signals 100 MHz away from the desired signal when the feedforward path is activated. The noise figure (NF) of the entire system is 3.8 dB that degrades to 5.8 dB when the feedforward path is activated.     

基于过程反馈的课堂教学改革研究

针对当前教学中存在的问题,提出基于过程管理的课堂教学改革方法.以Java Web课程为例,就教学内容、教学模式、考核方法等方面对基于过程管理的课堂教学改革如何实行进行了详细的说明.实践表明基于过程管理的教学能大大的提高学生学习的积极性,提高了教学效果,适应当前应用型培养人才的需求,具有推广和参考价值.     

基于半马尔科夫决策过程的视频传输拥塞控制算法

针对传输控制协议(TCP, transmission control protocol)的拥塞控制算法未能满足视频传输质量要求的问题,提出了一种基于半马尔科夫决策过程的视频传输拥塞控制算法。首先, 为克服目前基于峰值信噪比的视频质量评估方法实时性低的缺点,设计了一种可在线运行的无参考视频质量评估方法。其次,根据接收端视频质量的反馈,采用半马尔科夫决策过程对拥塞控制进行建模,并通过求解此模型得到拥塞控制参数的调整策略。仿真实验结果表明,与目前典型的拥塞控制算法相比,该算法不但具备更好的TCP友好性,而且有效地提高了解码后视频序列的主观和客观质量。     

电子组装中PCBA清洗技术

清洗对于电子产品可靠性有着非常重要的影响,针对印制电路组件污染物进行了系统阐述,并对不同的清洗技术和工艺进行了总结归纳,讨论了影响清洗效果的各个因素及其检验规范,为实际生产起到了指导性作用。