The design and analysis of unequal error protection fountain coding for multiple source networks over binary erasure channels

A novel network model of multiple source fountain coding is developed and a novel class of generic multiple source fountain codes with unequal error protection(UEP)property is proposed.The And–Or tree analysis technique is generalized to analyze the asymptotic performance of the proposed codes and a joint optimization method employing both linear and nonlinear programs is developed to optimize the degree distributions.Furthermore,we propose three basic methods to achieve UEP property and the performance of each method is discussed.We employ these analytical results and optimization method to design and discuss several UEP codes with two and four sources for different application scenarios.Simulation results verify that the proposed codes can be applied to the networks with any number of sources and can provide strong UEP property in various ways based on the proposed three basic methods.     

VMStore: Distributed storage system for multiple virtual machines

Desktop virtualization is a very hot concept in both industry and academic communities. Since virtualized desktop system is based on multiple virtual machines (VM), it is necessary to design a distributed storage system to manage the VM images. In this paper, we design a distributed storage system, VMStore, by taking into account three important characteristics: high performance VM snapshot, booting optimization from multiple images and redundancy removal of images data. We adopt a direct index structure of...     

基于网格监控系统的动态监控间隔的研究

网格环境是由很多元素构成的高度复杂的分布式计算环境。对于网格来说,监控其中每个计算节点的状态是至关重要的。然而频繁地监控资源的状态信息会增加系统的负担。本文提出一种动态调整监控间隔的方法, 来降低监控服务所需的花费,并利用动态监控间隔来准确地获取监控事件,最后通过在网格环境下进行实验,对该方法做出客观的评价。     

稀土Ce中间合金对A356铝合金组织的影响

主要研究了不同Ce中间合金对A356铝合金的细化变质的效果,结果表明:Al-10Ce和Al-4Ti-4Ce-B中间合金对A356合金具有较好的细化变质效果,Al-5Sr-5Ce中间合金对A356的细化变质效果不够理想,而Al-10Sr中间合金的添加对Al-4Ti-4Ce-B中间合金的细化变质具有促进作用。本文还进行了Ce对A356合金细化变质机理的探讨。     

AC 800F控制器在宣钢七号高炉自动化系统中的应用

宣钢7#高炉是一座450M^3中型高炉，年产生铁约55万多吨。本文介绍的就是宣钢7#高炉的自动控制系统，该自动化系统采用ABB公司的Industrial IT工业集散过程控制系统（DCS）。该系统控制稳定、可靠、故障率低。将先进控制思想、现代通讯技术和自动化技术的最新发展集于一身。     

计算机绘图与技术图样表达式（续一）

发明一种技术图样表达式.它用英文字母表示图形种类和尺寸要素,并用算术符号等字符表示图形和尺寸相互间的关系.用技术图样表达式可同时表示出图样的形状、大小、定位和公差、粗糙度等技术数据.图样表达式可作技术制图的尺寸标注,使图样大为简化;作计算机传输的信息,使计算机制图更为简易.     

某车载式可升降微波塔的抗风分析

本文以某车载式可升降微波塔架为工程背景,分别运用拟静力法和计算流体动力学方法(CFD)计算该微波塔架的风荷载,利用SAP2000工程软件建立了该微波塔架的三维空间有限元模型,分析了静力风荷载作用下结构的位移响应和部分构件的内力响应,并对该种车载式结构提出了合理的改进意见。     

Filtration of fine particles in atmospheric aerosol with electrospinning nanofibers and its size distribution

In this study,the size distribution of atmospheric aerosol in Beijing was monitored by the scanning mobility particle sizer spectrometer and the optical particle sizer.The size of particles in atmospheric aerosol was primarily distributed in the range of less than 1 m.It showed different changes with the mass concentrations of particulate matters with an aerodynamic diameter of 2.5 m(PM2.5)for different sizes of fine particles.The amount of ultrafine particles(less than about 60 nm)decreased while the larger ones(60 nm)increased along with the mass concentration of PM2.5 in atmospheric aerosol.This was because of the formation of the secondary atmospheric aerosol.The polylactic acid(PLA)nanofibers were prepared for filtering the aerosol by electrospinning.PLA nanofiber mats were used as the middle layer to design the composite filter membranes.Atmospheric aerosol was used as dust source in the filtration test.The results showed that the filtration efficiency of the composite filter media increased along with the thickness of nanofiber mats,which was controlled by the collection time during electrospinning.Filtration efficiency can be improved obviously by compositing with a thin layer of nanofibers.     

新型接地电阻测试系统研究

介绍接地电阻测试的基本原理,设计了符合IEC61010标准的由工业PC控制的接地电阻测试系统。系统由程控电源、测试回路、信号采样、调理电路和数据采集接口卡等部分组成。实验数据表明系统工作稳定,数据重复精度高。