基于Akaike信息论准则的无人机OFDM信道估计算法

文章通过对无人机通信信道的分析,指出其稀疏信道特征,使用普通算法对此信道进行信道估计会引入高阶矩阵运算,为加快收敛速度、降低实现难度,文中提出了一种利用GAIC(generalized Akaike information criterion)准则和RPC(phase-rotated Chu sequences)训练序列的OFDM航空信道LS(least square)估计方法,该方法利用GAIC准则确定信道MA(moving average)模型的阶次及抽头位置,为减小信道估计的运算复杂度,引入RPC序列作为训练序列,既满足了LS(least square)估计,又大大减化了计算复杂度.文章针对具体应用给出文中算法的性能仿真结果,证明了此算法可避免高阶矩阵运算,节约了大量权值可忽略抽头所引入的资源占用和计算量,且显著减小估计误差,可更好跟踪快变的稀疏信道.     

RPCI：面向互联网的RPC框架

RPC是互联网后端分布式系统的核心组件,能够降低互联网应用开发、运维成本,提高可用性和可扩展性,但是目前流行的RPC框架不能完全满足互联网应用需求。分析了互联网应用环境下RPC系统的需求,并针对需求提出了面向互联网的RPC系统RPCI。RPCI采用三层架构,将长连接服务器独立出来,以支持无状态应用服务器设计和灵活的请求路由策略,使得系统扩容、升级、运维更加容易。基于thrift实现了RPCI,优化了性能,实验结果表明,RPCI性能优秀,相比常用开源软件thrift性能提升50％以上。     

Fatigue Properties of RPC under Cyclic Loads of Single-stage and Multi-level Amplitude

Fatigue properties of Reactive Powder Concrete (RPC) under axial compression of single-stage and multi-level amplitude in cycles were studied. The tests reveal the fatigue life, the strain and residual life of the RPC samples. Through the analysis of the test results under cyclic loads of single amplitude, the S-N curve of RPC and the evolution rule of macro-damage of RPC were presented, which can be divided into latency stage, stable development stage and instability development stage according to the evol...     

Packaging performance comparison for distribution and export of papaya fruit

This paper presents the development and testing procedures for new packaging systems for papaya fruit. Papaya is a nutritious tropical fruit, consumed both in its fresh form and as a processed product worldwide. Thailand is a major exporter of fresh and processed papayas from Asia. Major quality indices for papayas include colour, size, firmness and freedom from defects and decay. A high percentage of post‐harvest losses of papaya fruits have been reported as exports have increased. Mechanical damage is one of the major causes of the quality loss of papaya fruits, therefore, proper packaging is demanded for better protection. In addition, other criteria are important to meet consumer acceptance. New packaging systems for papayas were compared with the existing systems currently used for local markets. The packaging systems were evaluated in terms of physical protection, heat transfer characteristics for rapid cooling and maintaining optimum temperature and relative humidity during post‐harvest, quality maintenance, and marketing issues. Two cushioning systems, foam nets and paper‐based wrap materials, were also compared. Actual shipment and vibration tests were performed and the effect on quality was determined. The new packaging systems tested showed better protective performance and improved quality parameters, as compared to existing systems. Minimized mechanical injuries resulted in a decreased susceptibility to decay and bruising. Paper‐based cushions showed similar protection to plastic foam nets materials but offered a better ripening response for papayas. The data were compared to seek an optimum packaging system for papayas based on the various criteria. Copyright © 2005 John Wiley & Sons, Ltd.     

掺粉煤灰和矿渣粉的活性粉末混凝土梁受力性能试验研究

根据棱柱体试件的受压试验结果,得到了常温养护下活性粉末混凝土(RPC)的优选配合比和基于该配合比的受压应力-应变曲线上升段方程。根据5根钢筋RPC梁受弯性能试验,获得了这类梁纯弯区段在各级荷载作用下受压边缘压应变及应变沿梁高的分布、开裂荷载和极限荷载、各级荷载作用下的变形及裂缝分布与开展,由试验数据可知,相同条件下这类梁的变形及裂缝宽度均比普通钢筋混凝土梁稍大。通过假定用于受弯承载力计算的RPC受压应力-应变曲线关系下降段为直线,结合试验数据分析,获得与极限压应变相对应的RPC压应力的大小,从而得到RPC应力-应变全曲线方程。基于RPC的受压应力-应变全曲线方程建立了RPC梁正截面承载力计算方法。同时基于试验结果给出了在使用荷载作用下这类梁刚度和裂缝的计算方法。     

硅灰和石英粉对活性粉末混凝土抗压强度贡献的分析

运用火山灰效应数值分析方法定量分析了硅灰和石英粉两种主要组分对RPC抗压强度贡献率、强度贡献数值以及两种组分的强度贡献指数。     

ARGO-YBJ实验的环境监测

ARGO-YBJ实验的中心区域(5000M2)已于2006年6月底完成安装调试并投入试运行.相应的环境监测系统Detector ControI system(DCS)也开始工作,持续不断地记录下实验厅内外的温度、厅内的气压、RPC漏电流等参数.通过对这些参数数据的分析,可以清楚地了解探测器的工作状况,以维持整个阵列长期稳定运行,同时为理解实验数据和物理分析工作提供参考.     

基于RPC的通用数据库性能测试工具构架

以常见数据库测试基准为对象,以实际测试工作为基础,总结分析在数据库性能测试工作中所需的测试程序的构架需求。借助远程过程调用机制,设计并实现一种满足可控、互通、分布、高效和灵活需求的数据库性能测试系统通用构架,该构架兼顾用户界面的交互,引入异步通信机制增强整个系统的可用性。     

CLOS的分布实现技术

ＣＬＯＳ系统是一个嵌入ＣｏｍｍｏｎＬｉｓｐ的面向对象标准语言，本文结合我们提出的类划分方法，通过引入同步或异步通信协议和ＲＰＣ并发控制，详细介绍了一个新的分布ＣＬＯＳ系统ＰａｒＣＬＯＳ。测试结果表明：若结点较均匀，运行效率大于８０％。     

移动Agent系统综述

移动Ａｇｅｎｔ系统是一种崭新的分布式计算和网络通讯的模式,介绍了移动Ａｇｅｎｔ的概念和移动Ａｇｅｎｔ系统与其它相关技术的比较,强调了移动Ａｇｅｎｔ系统所必须解决的几个关键问题,同时分析了现有的几个实际的移动Ａｇｅｎｔ系统,对移动Ａｇｅｎｔ系统的应用进行了展望。