QoS-aware replica placement for data intensive applications

In recent years, with the rapid development of data intensive applications, data replication has become an enabling technology for the data grid to improve data availability, and reduce file transfer time and bandwidth consumption. The placement of replicas has been proven to be the most difficult problem that must be solved to realize the process of data replication. This paper addresses the quality of service （QoS） aware replica placement problem in data grid, and proposes a dynamic programming based replica placement algorithm that not only has a QoS requirement guarantee, but also can minimize the overall replication cost, including storage cost and communication cost. By simulation, experiments show that the replica placement algorithm outperforms an existing popular replica placement technique in data grid.     

Method for replica creation in data grids based on complex networks

In order to reduce makespan and storage consumption in data grids,a node selection model for replica creation is proposed.The model is based on the degree distribution of complex networks.We define two candidate replica nodes: a degree-based candidate pool and a frequency-based candidate pool,through which a degree-based candidate pool is defined m consideration of onsidering the access frequency,a candidate pool-based frequency is also defined.The data replica is copied to the node with the minimum local cost in the two pools.Further,this paper presents and proves a replica creation theorem.A dynamic multi-replicas creation algorithm(DMRC)is also provided.Simulation results show that the proposed method may simultaneously reduce makespan and data used in space storage consumption.     

用户兴趣感知的内容副本优化放置算法

提出了用户兴趣感知的内容副本优化放置算法。该算法首先基于聚类算法从用户访问日志提取各用户的群体内容兴趣主题,依据其所辖用户的个体兴趣度加权得其群体兴趣度,并对其进行实时更新;然后在非线性优化模型下,以最小化平均响应时间为目标,优先放置群体兴趣度较大的副本,以实现被放置副本与用户内容兴趣主题的最大匹配。在平均响应时间、请求响应匹配度、负载均衡和邻近副本利用率等方面,与1-Greedy-Insert等算法进行对比,仿真结果显示各性能指标平均提升了约30%,验证了算法的有效性。     

云存储系统中数据副本服务的可靠性保障研究

以数据节点与网络链路的可靠性因素分析为基础,提出了云存储系统的数据副本服务可靠性模型。根据访问可靠性与数据副本数量、用户访问量之间的关系,设计数据服务可靠性、副本生成时机、存储节点选择的确定方法,实现了副本分布、删除算法,并在云存储系统ERS-Cloud上进行一系列实验,结果表明该方法能够有效保障数据服务的可靠性,进一步降低副本的冗余存储数量。     

电镜冷冻复型技术在非生物材料研究中的应用

本文叙述冷冻复型方法在透射电镜样品制备中的应用。这一方法不仅在生物医学领域得到广泛应用，而且在化学、石油等非生物领域也是一项不可缺少的实验技术。对生物样品而言，可较好地保存细胞的天然形态结构；对非生物样品而言，也能反映其真实结构；另外，实验周期短是这一方法的突出特点。本文根据作者多年来的工作经验，就如何获得质量较好的复型膜以及实验过程中存在的一些问题和所作的改进作一介绍：如排除陶瓷材料器皿对膜的损伤和破坏；解决表面张力小的液体样品高出样品杯平面的问题；以及掌握复型膜的喷涂技术、塑料薄膜样品的复型膜剥离技巧等。     

数据网格中一种填空式副本分配算法

在数据网格应用中,数据会由于性能和可用性等原因进行复制.如何使数据复本合理分布以降低通信开销是数据网格系统需要解决的重要问题.本文针对一种简化的数据网格环境,考虑存储资源代理对数据的访问频率和代理间的网络性能,提出一种填空式数据副本分配算法(CDRDA).通过该算法得到的数据副本分配,构成多级虚拟存储架构.数据副本根据被存储资源代理访问的频率分布在访问开销小的节点上,从而使系统的整体访问效率达到近似最优.     

面向MANET环境的动态自适应副本放置算法研究

移动自组网环境给数据复制技术带来了新的挑战。本文提出了一种分布式动态自适应副本放置算法,算法以数据访问的通信开销作为目标函数,每个副本节点从其邻居节点收集读写请求的局部信息,动态地调整副本放置方案以适应访问请求和网络拓扑的变化。本文还提出了基于稳定邻居的副本放置算法以减小由于节点移动给副本放置带来的振荡。模拟实验表明,在移动自组网环境中,本文提出的算法有效地减少了数据访问的通信开销,提高了数据访问的效率。     

具负载平衡之IPTV影音串流系统

影音媒体具高带宽及实时特性,因此影音串流系统的服务质量的提升端赖影音服务器的有效管理。在此提出一套Video replication及Access request distribution的算法,藉由将热门影音分散到各影音服务器以及影音存取的分散,以达到各影音服务器系统负载平衡的效果。在此比较了3个不同的算法的负载平衡的状况,经实例验证,提出的算法确能达到影音服务器负载平衡的效果,承载更多的系统服务要求。该系统构建在Smart-i TV的IPTV系统台,并讨论了实作的相关技术。     

Design of replica bit line control circuit to optimize power for SRAM

A design of a replica bit line control circuit to optimize power for SRAM is proposed. The proposed design overcomes the limitations of the traditional replica bit line control circuit, which cannot shut off the word line in time. In the novel design, the delay of word line enable and disable paths are balanced. Thus, the word line can be opened and shut off in time. Moreover, the chip select signal is decomposed, which prevents feedback oscillations caused by the replica bit line and the replica word line. As a result, the switch power caused by unnecessary discharging of the bit line is reduced. A 2-kb SRAM is fully custom designed in an SMIC 65-nm CMOS process. The traditional replica bit line control circuit and the new replica bit line control circuit are used in the designed SRAM, and their performances are compared with each other. The experimental results show that at a supply voltage of 1.2 V, the switch power consumption of the memory array can be reduced by 53.7%.     

基于存储联盟的双层动态副本创建策略—SADDRES

针对面向企业的数据网格应用,给出了平民数据网f格DGHB的概念,并提出了针对DGHB网格的一种基于存储联盟的双层动态副本创建策略—SADDRES.通过在数据网格模拟工具OptorSim中的模拟,分析、比较了SADDRES策略与基于缓存的副本创建策略、基于经济模型的副本创建策略等多种策略的性能.实验结果表明,SADDRES策略在面向企业的数据网格应用中具有更好的系统性能.     

Fabrication of various curved relief structures through concave surface forming and soft replica molding

In this case, our groups presented various optical structures through the presented method, involving concave surface forming and soft replica molding. The method of concave surface forming is mainly for the fabrication of concave surface. The method of soft replica molding is mainly for the fabrication of replica. Concave and convex relief structures, including circular curved relief structures, convex relief structures with platform structures on the top, refractive beam-shaping elements, these structures with dual curvatures and asymmetric structures, can be easily made through the presented method, respectively. All processes of manufacture are in several simple steps without multistep optical lithography and complex masks.     

Impact of node distance on selfish replica allocation in a mobile ad-hoc network

Many data replication techniques have been proposed to minimize performance degradation caused by network partitioning in a mobile ad-hoc network. Most of them assume that all mobile nodes collaborate fully in terms of sharing their memory space. However, in reality, some nodes may selfishly decide to only cooperate partially, or not at all, with other nodes. Recently, a new approach to selfish replica allocation has been proposed to handle node selfishness. However, there is still much room for improvement. We empirically observe that the previous selfish replica allocation strategy suffers from long query delay and poor data accessibility, because it utilizes only non-selfish nodes that may be faraway nodes. In this paper, we propose a novel replica allocation strategy in the presence of selfish nodes, that takes into account both selfish behavior and node distance. Moreover, through a novel node leveling technique, we utilize the memory space of all connected nodes, including selfish nodes. The conducted simulations demonstrate that the proposed strategy outperforms existing replica allocation techniques in terms of data accessibility, query delay, and communication cost.     

Distance control strategy for deploying content replica servers in an edge cloud

To reduce fetching cost from a remote source,it is natural to cache information near the users who may access the information later.However,with development of 5 G ultra-dense cellular networks andmobile edge computing(MEC),a reasonable selection among edge servers for content delivery becomes a problem when the mobile edge obtaining sufficient replica servers.In order to minimize the total cost accounting for both caching and fetching process,we study the optimal resource allocation for the content replica servers’ deployment.We decompose the total cost as the superposition of cost in several coverages.Particularly,we consider the criterion for determining the coverage of a replica server and formulate the coverage as a tradeoff between caching cost and fetching cost.According to the criterion,a coverage isolation(CI) algorithm is proposed to solve the deployment problem.The numerical results show that the proposed CI algorithm can reduce the cost and obtain a higher tolerance for different centrality indices.     

在数据仓库中如何有效地实现数据立方体的计算

有效的实现数据立方体的计算是提高数据仓库查询效率的有力方法。在设计方体时要对方体维护成本和查询响应时间这两个因素加以考虑，从而产生了方体的部分物化和全物化两种方法。通过对数据仓库中如何有效的进行数据立方体计算的讨论，提出了实现数据立方体部分物化和全物化的算法。     

应用数字波导网格法模拟室内声场及其MATLAB实现

在介绍数字波导网格法基本原理的基础上，采用MATLAB语言对一刚性矩形房间和一矩形教室的声场进行模拟计算，最后对应用数字波导阿格法进行了一些讨论。     

基于MSPH方法模拟激光对树脂基复合材料的辐照效应

树脂基复合材料在激光辐照下通常会发生复杂的物理化学变化,可能涉及材料热分解、烧蚀、汽化和比较复杂的界面问题。鉴于无网格粒子法在处理大变形、网格畸变和材料烧蚀等问题时有优势,利用改进的光滑粒子方法对激光辐照下复合材料树脂基热解时的三维温度场模型进行数值求解。将数值模拟结果与实验结果进行对比,考察了改进的光滑粒子方法对所考虑问题的适用性。结果表明:改进的光滑粒子方法适合于模拟激光对树脂基复合材料的辐照效应,在激光与物质相互作用领域,该方法也是值得关注的一种数值方法。     

一种基于虚拟工作空间的有状态网格服务副本复制方法

 网格副本复制技术只能对无状态的数据、文件资源等进行复制,而不能对网格服务这种包含软硬件需求、有状态的服务形式进行复制.为解决网格服务的访问瓶颈、负载均衡等问题,本文提出一种基于虚拟工作空间的有状态网格服务副本复制方法Ragsres.Ragsres利用虚拟工作空间良好的执行分离属性和对执行环境可定制化的特性,实现对网格服务运行所需的软硬件环境的搭建和复制;根据虚拟机监控快照技术的数据转换原理,完成网格服务内存状态的复制;采用web服务的有状态资源模拟技术,实现有状态资源的状态复制.     

美欧发布数据战略对我国的启示

近期,美欧相继出台数据战略,描述未来的数据发展愿景。两部数据战略中的一系列措施和行动将助力美欧扩大其优势,也对我国有一定的借鉴意义。对美欧数据战略举措进行了研究,在数据基础、数据开放、数据人才培育、个人数据利用等方面加快布局,提升我国大数据和数字经济的发展能力。     

Using Hash Tree for Delegation Revocation in Grids

Grid security infrastructure （GSI） provides the security in grids by using proxy certificates to delegate the work of authentication. At present, revocation proxy certificate has two kinds of methods, one is using certificate revocation list （CRL） and the other is giving the certificate a short period of validity. However, when a lot of certifications are revoked, CRL will be the burden in the system. If the certificate has a short period of validity, entities should be often updating the certificate. In this paper, we propose a scheme for proxy certificate revocation using hash tree. Our scheme only needs hash value comparisons to achieve the purpose of certificate revocation. Previous two methods have to wait the expiration of the certificate. Therefore, our scheme is more flexible than previous methods.     

基于行过扫数据降低大面阵CCD图像噪声算法研究

针对全帧转移大面阵电荷耦合器件(CCD)多帧图像数据随时间漂移的现象和测试电路引入的噪声,导致无法准确评估CCD器件的参数,文章提出一种基于行过扫数据校正算法。行有效像元数据与对应行垂直过扫数据同时输出,通过有效像元数据减去垂直过扫数据均值,对图像数据漂移的现象进行抑制。测试电路中模拟模块与数字模块同时作用于单行有效像元数据与垂直过扫数据,通过有效像元数据减去垂直过扫数据均值,消除测试电路引入的噪声。实验结果表明,经过该算法校正后的器件读出噪声减小了20%,暗场差值图像中超过15 e^-和25 e^-的比例减小了25%。该算法适用于大面阵CCD器件,可校正测试系统引入的测试误差,提高全帧转移大面阵CCD器件测试效率。