对象存储系统中一种高效的分层对象布局算法

在对象存储系统中,如何有效地在对象存储设备上分布对象是其面临的重大挑战.需要一个能够常数时间内定位对象,同时能公平地分布对象以及自适应存储规模变化的对象布局算法.目前大部分布局算法只能适应单层模式,少数的多层模式对设备配置有严格的要求,而且无法在常数时间内定位对象,自适应性较差.提出了一种新的分层对象布局算法,首先使用最大最小聚类算法将设备集合进行分类,支持灵活的设备配置.然后使用提出的EFAH Hashing算法在集群间和集群内分布对象.理论和实验证明,新的分层对象布局算法可以在常数时间内定位对象,从而减轻元数据服务器的计算量.同时可以在设备之间较公平地分布对象,达到I/O负载均衡的目的.而且在设备集合变化时,迁移较少的对象数以满足对象再次分布的公平性.     

大规模网络存储系统的数据布局算法研究

可扩展和可靠的数据管理是实现大规模网络存储系统的关键技术,需要一个能够自适应存储规模变化、公平、冗余、高可用的数据布局算法。本文根据不同的设计目标以及存储环境的同构和异构特性,分析了四类布局算法:同构的布局算法、非冗余的异构布局算法、冗余的异构布局算法和高可用的布局算法。对现有布局算法存在的问题进行了讨论,并指出了未来的研究方向。     

云环境下一种兼顾成本与存储空间的副本策略

传统的副本布局大多假定数据是独立的、不需要任何管理成本,但并未考虑副本开销以及中间数据的生成对副本布局的影响。为此,给出一种兼顾成本与存储空间的两阶段高效数据副本生成与存储策略,在数据副本初始布局阶段,基于遗传算法通过比较数据传输开销与存储开销,尽可能地将数据放置在数据中心。在数据中心利用数据生成关系,通过比较数据存储开销与生成开销,并基于Dijkstra最短路径算法确定最小数据开销的数据存储与生成策略。实验结果表明,成本感知的两阶段副本存储与生成策略在确保数据可靠性访问的同时,可以有效减少数据开销与数据存储空间,从而提升云存储系统性能。     

大规模网络存储系统中面向可靠性的数据布局算法

如何有效地在大规模的网络存储系统中存放数据是一个具有挑战性的问题.深入研究如何在满足存储的公平、冗余和自适应性的情况下,基于存储设备不同的可靠性能,充分考虑存储数据的重要性进行数据布局.用整数规划的形式描述了面向不同可靠性等级的存储设备进行数据布局的优化问题,并说明了这个问题是NP难的.提出了一种块级别的面向可靠性的数据分级布局算法,保证了布局算法的公平、冗余以及自适应性,并分析了数据布局算法的合理性和可行性.     

长寿命星载NAND Flash自适应坏块管理策略

针对长期在轨运行设备的存储可靠性问题,提出了一种自适应坏块管理策略。首先对星载NAND Flash存储系统建立马尔可夫可靠性模型,其次根据使用情况预估设备产生的坏块数量,并设置数据存储空间的大小;然后根据设备实际在轨坏块数量动态调整数据存储空间,在确保一定时间内有稳定的存储空间的基础上保持较高的空间利用率;最后对自适应坏块管理策略进行了仿真分析。结果表明,在某一写入速率下,该自适应坏块管理策略的空间利用率不低于85%。     

基于通用带权分布式哈希表的数据放置算法研究

研究了动态网络环境下基于网络的存储系统的数据放置算法,分析了现有的数据放置算法,提出了通用带权分布式哈希表算法.与相容哈希算法和对数算法定义的评判函数相比,考虑了各个节点的存储空间、数据分发节点与数据存储节点之间的物理距离、网络带宽等的限制.仿真结果表明,该算法能够实现数据的公平分发.     

大规模网络存储系统的数据布局策略研究

如何有效地对数据进行布局是大规模网络存储系统面临的重大挑战,需要公平、冗余、自适应、高可靠以及高可用的数据布局策略.根据大规模网络存储系统体系结构的发展,详细介绍了P2P系统、SAN存储系统以及对象存储系统的数据布局策略,最后总结和比较了各种布局策略的优缺点,并指出基于数据重要性以及访问热度的数据布局策略等是未来可能的研究方向.     

基于分布结构自适应筛选的数据库存储优化设计

通过对数据库的存储结构优化设计,提高数据库的吞吐量。传统方法采用存储节点校验数据适应度分区的数据库存储模型,数据库中存在重复冗余数据,不能自适应滤除,导致数据存储开销较大。提出了一种基于分布结构自适应筛选的数据库存储优化模型,首先进行数据库的存储机制和分布式数据结构分析,采用相空间重构方法进行存储空间的结构分布重组,采用分布结构自适应筛选方法对提取的数据信息流进行重复冗余数据滤波处理,改善数据在数据库存储空间中的结构分布,实现数据库存储优化。仿真结果表明,采用改进的方法进行数据库构建,能提高数据库存储吞吐量,降低数据存储开销,提高数据库的访问和调度性能,展示较好的应用价值。     

机组状态监测系统自适应实时数据库的研究

针对炼厂催化裂化装置，构建了能量回收机组状态监测与故障诊断系统，通过对在线采集数据管理方案的研究，提出了一种新型的自适应实时数据库的结构和算法。该数据库中入库算法的核心是根据机组的当前状态决定实时数据的入库级别，最终实现“不漏取有价值数据，不收录无价值数据”的目标，以保证不泄露设备运行周期内所有有价值的数据点，并在有限的数据库存储空间中保存尽可能多的监测数据，同时最大限度地提高数据库的检索效率，实现了数据库的自适应存储与管理。同时，用C语言对数据包结构进行了描述，并给出了数据选择性入库的程序框图。     

大规模存储中的一个有效的数据放置算法

存大规模存储中,经常面临组件的增加和失败。为了提高可用性和可管理性,研究和比较了不同的数据定位机制,设计了一个离散的、自适应的算法。这个算法保证任何一个特定的数据对象的副本不会被放置在同一个存储节点上。并且根据存储节点的能力公平地分布数据对象到存储节点上。当新的存储节点加入系统或已存在的节点退出系统时,需重新分布的数据对象被尽可能地减少。算法中没有集中控制点,保证了系统的可扩展性。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.