集群网络评测模型的新探索

传统集群网络(cluster area network,简称cLAN)的评测模型主要考虑了延迟、带宽、路由、拥塞、网络拓扑结构等因素.但这些因素是否足以描述实际应用程序在集群上的通信行为,或者对其在集群系统上的性能给出一个很好的预测呢?当对NAS Parallel Benchmark(2.4版本)在集群系统深腾1800(DeepComp 1800)上进行大量测试时发现,集群网络的通信性能可以被一种特殊的通信模式(LU模式)所严重影响.更深入的研究表明,这个影响LU模式的因素是独立于前面所述的如延迟、带宽、路由、拥塞、网络拓扑结构等因素的.因此有必要对集群网络的评测模型重新进行审视,并增加一个新的性能评测因子以反映这个新发现的现象.从研究结果来看,这个重新审视也将对集群系统上的并行算法设计以及实际大规模科学计算的应用程序性能的优化提供一些新的思路.

工作群体有效性评价及群体工作设计

This thesis study the problem of work group effectiveness and group job design according to extensive literature investigation and the analysis of realistic background. The whole research consists of four parts: (1) The evaluation of work group effectiveness, the aim is to search to criteria that can describe and analysis work group, and explore the cognitive dimensions of effectiveness of Chinese subjects; (2) The study on the relationship between group job characteristic and effectiveness, the aim is to find the general correlation between work group characteristic and effectiveness, and try to search the most important core variable; (3) The study on the preference for the way of group work; (4) The study of the relationship between group composition and group effectiveness, try to examine how different approaches of personnel selection influence work results. The results indicate: (1) The evaluation of group effectiveness mainly consists of two dimensions: performance and the employee's attitude and feelings toward the group, so we can use these two dimensions and corresponding criteria as the standard of effectiveness evaluation. (2) According to the analysis of related literature, we can determine work group characteristic from five aspects: job design, the interdependence among members, group composition, organizational background, group process. (3) Experimental study find that different group job characteristics have different relationship models with effectiveness criteria. Job design, the interdependence among group members, group composition have significant correlation relationships with two kinds of effectiveness criteria; organizational background mainly has relationships with satisfaction criteria; group process mainly has relationships with performance criteria. (4) The choice for people to select the way of group work has the consistency, that is people prefer to "Self--managed work groups"; but different groups have the difference, the main group dimension is the difference between group members and group leaders. (5) Work groups which were composed accordingly to interpersonal attraction have higher levels of communication, coordination, group cohesion and job satisfaction than ability--based groups based. But the performance evaluation under these two conditions has no difference. The thesis analysis and discuss the research results, also point out several questions that needed to be explored further and the possible research directions in the future. This study has some reference value in group--level performance appraisal and reward design, the content and method of group--level job design, and personnel selection of group, etc.

卫星激光通信Ⅱ地面检测和验证技术

星间激光通信终端的主要技术指标和运行性能必须事先在地面实验室条件下进行模拟检验, 因此在研制卫星激光通信终端的同时必须发展相应的系统性检测和验证平台, 主要包括激光通信性能检验、光跟瞄性能检验和光束质量检验。本文综述了卫星激光通信终端检验技术的国外进展, 介绍了我们全物理模拟的地面检测验证思路和方法。

Optoelectronic quotient-selected modified signed-digit division

A novel optoelectronic quotient-selected modified signed-digit division technique is proposed. This division method generates one quotient digit per iteration involving only one shift operation, one quotient selection operation and one addition/subtraction operation. The quotient digit can be selected by observing three most significant digits of the partial remainder independent of the divisor. Two algorithms based on truth-table look-up and binary logic operations are derived. For optoelectronic implementation, an efficient shared content-addressable memory based architecture as well as compact logic array processor based architecture with an electron-trapping device is proposed. Performance evaluation of the proposed optoelectronic quotient-selected division shows that it is faster than the previously reported convergence division approach. Finally, proof-of-principle experimental results are presented to verify the effectiveness of the proposed technique. (C) 2001 Society of Photo-Optical Instrumentation Engineers.

空间激光通信中的分集接收与分集均衡技术

全面对采用空间分集技术和时域Rake接收机分集的带限空间光通信系统的原理进行了模拟和分析，首次在空间激光通信领域提出了综合了分集接收和均衡技术的联合信道均衡器方法，通过计算机仿真分析，研究了不同空间分集方法在非相关空间光开关键控信号下的误比特率，在不同符号间干扰条件下采用rake接收时的误比特率，以及在不同信噪比和不同信道数时采用联合分集均衡的误码率。研究的结果确认联合分集均衡方法能够明显的提高空间光通信系统的性能。

基于RS编码及网格编码调制的光PPM通信纠错技术

分析了RS（Reed-Solomon）纠错码和网格编码调制（Trellis Coded Modulation，TCM）技术在光脉冲位置调制通信中的应用．在此基础上，提出了以RS码作为外码，以网格编码调制技术作为内码，用于光脉冲位置调制通信的新编码方案，能以几乎不减少通信速率的优势，提高传统RS码系统在时变带限光信道中的通信性能．模拟研究了在不同空间光信道条件下，传统RS码的符号正确传输率和误码率，并对网格编码调制的编码增益、RS码与网格编码调制级联时的编码增益进行了仿真研究，证实了本方案的有效性．

LBO晶体上1064，532nm倍频增透膜的镀制及性能分析

用电子束蒸发沉积方法在X切LBO（X-LBO）晶体上镀制了两种不同膜系结构的1064和532nm倍频增透膜，其中一种膜系结构为基底／ZrO2／Y2O3／A12O3／SiO2／空气，另一种为基底／0．5Al2O3／ZrO2／Y2O3／A12O3／SiO2／空气，两种膜系结构的主要差别在于有无氧化铝过渡层。测量了薄膜的反射率光谱曲线，发现两种增透膜在1064和532nm处的反射率均小于0．5％，实际镀制结果与理论设计曲线的差异主要是由材料折射率的变化引起的。且对样品在空气环境中进行了温度为473K的退火处理，

Rate-equation-based circuit model of high-speed semiconductor lasers

Based oil rare equations of semiconductor laser, a symbolically-defined model for optical transmission system performance evaluation and network characterization in both time- and frequency domains is presented. The steady-state and small-signal characteristics, such as current-photon density curve, current-voltage curve, and input impedance, call be predicted from this model. Two important dynamic characteristics, second-order harmonic distortion and two-tone third-order intermodulation products, are evaluated under different driving conditions. Experiments show that the simulated results agree well with the published data. (c) 2007 Wiley Periodicals, Inc.

曙光5000A天体大规模数值模拟软件性能测试

在国产百万亿次超级计算机曙光5000A上进行了天体大规模数值模拟软件的性能和可扩展测试实验,详细介绍了软件中的测试程序以及测试环境和过程,并对测试结果进行了分析.对于80×80×50的网格规模,采用每节点4进程测试了16～128个处理器核,每节点8进程、16进程分别测试了16～512个处理器核,相对加速比最终分别达到5.33、10.48和12.57,并行效率分别达到66.66%、32.58%和32.29%.对于160×160×100的网格规模,测试了每节点16进程的64～8192个核的性能,最大相对加速比为12.46,并行效率为9.73%.测试结果表明,曙光5000A具有良好的性能,测试结果对软件下一步的优化研究具有重要的指导意义.

国产万亿次机群系统NPB性能测试分析

对3个国产万亿次机群系统进行了NPB性能测试分析,重点研究大规模并行处理时(处理器数目达到上千个)的性能特点和趋势.分析了不同的处理器、互连网络等系统配置对NPB性能的影响,发现NPB的8个程序在3个万亿次机器上的性能特点和表现并不一致,表明国产高性能机群在设计上正在逐渐走出同质化的趋势,向多样化发展.进一步分析表明,目前NPB程序的可扩展性可以达到几百个处理器,但尚不能达到上千个处理器,NPB程序能发挥出的系统峰值的百分比仍然徘徊在10%左右,机群系统的并行可扩展性和应用程序对机器运算潜能的利用还需要进一步提高.对于处理器数目达到上千个的万亿次机群系统来说,对集合通信和细粒度通信能力的支持亟需提高.

两种线程池的实现和性能评价

线程池被广泛地应用在中间件如Web应用服务器、事务监控器等的实现中。实现线程池的方法主要有半同步/半异步(Half-Sync/Half-Asyn)模式和领导者/跟随者(Leader/Follower)模式。实现了这两种线程池,从理论上分析了它们的性能,并进行了性能实验。实验数据表明Leader/Follower模式具有较高的性能优势。

VCSTalk:基于DEA的开源软件开发人员效率评价工具

介绍了VCSTalk的具体设计和实现架构,并展示了它用于评价若干开源软件项目中的开发人员效率的一个具体实例.

Approximate analytical optical transfer function for a wavefront-coded imaging system with two-dimensional rectangularly separable phase masks

Wavefront coding can be used to extend the depth of field of incoherent imaging systems and is a powerful system-level technique. In order to assess the performance of a wavefront-coded imaging system, defocused optical transfer function (OTF) is the metric frequently used. Unfortunately, to the best of our knowledge, among all types of phase masks, it is usually difficult to obtain the analytical OTF except the cubic one. Although numerical computation seems good enough for performance evaluation, the approximate analytical OTF is still indispensable because it can reflect the relationship between mask parameters and system frequency response in a clearer way. Thus, a method is proposed to derive the approximate analytical OTF for two-dimensional rectangularly separable phase masks. The analytical results are well consistent with the direct numerical computations, but the proposed method can be accepted only from engineering point of view and needs rigorous proof in future. (c) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3485759]