基于动态备份的容错网格任务调度*

提出了一种基于自适应备份的网格容错任务调度算法:最高百分之k备份算法.该算法对任务的安全需求和资源的信任等级进行匹配,在系统安全等级较低并且网络和主机可能失效的网格环境中进行容错任务调度.调度时,该算法根据整个网格系统的安全状况,对具有最高安全需求的百分之k的任务进行动态备份,任务备份数根据系统安全状况自适应变化,并对失败的任务重新调度.仿真结果表明,该算法可以有效提高不安全网格环境下的任务调度成功率,具有很好的容错性和可扩展性,优于固定备份数的网格任务调度算法.     

基于多处理机的混合实时任务容错调度

提出了一种混合实时任务容错调度算法．该算法采用Rate Monotonic(RM)算法完成周期任务的静态调度；采用预订处理机时间方法和Earlier Deadline First(EDF)算法动态调度非周期任务；采用主／副版本备份技术确保系统的容错能力．通过充分利用周期任务的剩余处理机时间调度非周期任务和主动备份与被动备份相结合的方法有效地减少了处理机数．仿真结果证明了算法的有效性．     

云环境下周期和非周期混合实时任务双容错调度算法

云环境中的处理机故障已成为云计算不可忽视的问题,容错成为设计和发展云计算系统的关键需求。针对一些容错调度算法在任务调度过程中调度效率低下以及任务类型单一的问题,提出一种处理机和任务主副版本分组的容错调度方法;并给出了副版本可重叠执行的判定方法,以及任务最坏响应时间的计算公式。通过实验和分析表明,和以前算法相比,将处理机分成两组分别执行任务主版本和任务副版本,减少了任务调度所需进行可调度测试的时间,增加了副版本重叠执行的机会,减少了所需的处理机个数,对提高系统处理机的利用率和容错调度的效率具有重要的意义。     

安全和自适应备份的网格任务调度

现有的跨自治域网格任务调度算法均使用固定数目的任务备份来提高任务调度的成功率和容错性,无法适应网格环境动态性的特点.提出了三种基于自适应备份数并考虑网格安全因素的任务调度算法,分别为简单自适应备份算法、最高百分之K备份算法和懒惰备份算法.自适应备份算法根据整个网格系统的安全状况,自适应调整需备份的任务及任务备份数,并对失败的任务重新调度.仿真结果表明,基于自适应备份的网格任务调度算法可以有效提高不安全网格环境下的任务调度成功率,具有很好的容错性和可扩展性,优于固定备份数的任务调度算法.     

基于异构分布式系统的实时容错调度算法

目前文献中研究的实时容错调度算法都是基于同构分布式系统，系统中的所有处理机完全相同。该文首先建立了一个基于异构分布式系统实时容错调度模型，异构分布式系统中的各个处理机均不相同。基于该异构分布式系统模型，该文引入了可靠性代价（reliability cost）概念，并提出两种静态实时容错调度算法（RTFTNO和RTFTRC）用于调度周期性实时容错任务。算法RTFTRC在调度任务时，尽量使系统的可靠性代价最小；而算法RTFTNO在调度实时任务时，没有考虑系统的可靠性代价。该文详细讨论了两种调度算法的性能。性能模拟实验分别比较了两个算法的可靠性代价，超时比率和可调度性；并研究了任务的计算时间与可靠性代价的关系以及调度长度阈值与最小处理机个数的关系。实验结果表明，算法RTFTRC的性能优于算法RTFTNO。     

混合型实时容错调度算法的设计和性能分析

以往文献中研究的实时容错调度算法都只能调度单一的具有容错需求的任务.该文建立了一个混合型实时容错调度模型,提出一种静态实时容错调度算法.该算法能同时调度具有容错需求的实时任务和无容错需求的实时任务.该文还提出了一个求解最小处理机个数的算法,用于对静态实时容错调度算法的性能进行模拟分析.为了提高静态调度算法的调度性能,提出了一种动态调度算法.最后,通过模拟实验分析了静态和动态调度算法的性能.实验表明,调度算法的性能与实时任务的个数、任务的计算时间、周期和处理机个数等系统参数相关.     

异构分布式系统中实时周期任务的容错调度算法

提出一个基于抢占性实时周期任务的可靠性调度模型,该模型与现有可靠性模型相比充分考虑了单处理机故障容错情况下的系统可靠性,因而更加接近现实和精确.在此基础上,提出一个基于异构分布式系统的实时容错调度算法IRDFTAHS,IRDFTAHS算法以提高系统的可靠性为目标来进行任务的分配,从而在不增加硬件代价的前提条件下通过调度增加了系统的可靠性.该算法同时支持主动和被动两种方式的副版本,使得容错调度算法具有更大的灵活性.最后,通过仿真实验对IRDFTAHS和现有的调度算法在几个方面进行比较.实验结果表明,IRDFTAHS算法的综合性能优于现有算法.     

三模容错多处理器动态实时调度算法

实时系统现在面临着越来越迫切的容错要求。目前流行的主副备份方式对于任务集有着特殊要求,要求时间限能够允许主副备份串行地执行,并且系统需要提供相应的硬件来检测处理器错误,因此限制了容错的应用范围。本文提出基于三模冗余比较的实时容错算法,采用了副本重载技术和主副本串并行混合调度策略。分析和实验结果表明,该算法具
有更好的适应性。     

基于延迟主动副版本的分布式实时容错调度算法

主/副版本备份技术是分布式系统常用的实时容错调度方法,然而传统的主动方式副版本即使在无处理机故障时也需要在备份处理机上完全运行,增加了处理机消耗.提出一种基于固定优先级调度算法的延迟主动副版本(deferred active backup-copy)备份技术,该技术通过尽量向后调度主动方式的副版本,并在主版本成功执行时终止副版本的执行来减少备份的冗余度.在此基础上,提出一种基于该技术的以最小化处理机数目为优化目标的启发式任务分配算法--基于延迟主动副版本的最佳适应算法DABCBF(deferred active backup-copy based best-fit algorithm).DABCBF在保证系统的实时性和容错能力的前提条件下,通过尽量减少主版本的最坏响应时间来最大程度地减少冗余,以节省处理机.最后通过仿真实验,证明了算法的可行性和有效性.     

容错实时任务调度的DSPN建模与分析

复杂系统的形式化描述对新系统的设计以及现有系统的改进与评价都具有十分重要的作用;针对处理机系统容错实时混合任务调度,提出采用确定与随机Petri网进行建模与性能分析;首先,根据任务执行的优先级、周期性、容错性和实时性,将任务分为四类;然后,采用DSPN对任务调度执行过程,不同优先级任务抢占式调度,处理机故障及故障恢复过程进行建模,由此构成处理机系统容错实时任务调度过程的DSPN模型;最后,仿真实验结果表明,在负载相同情况下,处理机利用率基本相同,且具有容错的实时任务调度算法可以有效地降低任务错失率;容错实时任务调度DSPN模型可以为复杂任务调度系统的Petri网建模与分析奠定了基础,并为实际工程应用提供了理论指导。     

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.