一个新的基于通信竞争的任务调度算法

任务调度是并行处理的一个非常关键的方面。目前的调度算法大多假定处理器完全互连、可以并行接收数据,而没有考虑实际应用中通信链路的竞争及延迟,进而导致调度算法在具体应用中效率较低。论文研究异构计算环境下具有依赖关系任务的边调度问题,结合传统任务调度问题中的有效策略,提出一种新的调度算法,该算法通过串行化通信边使通信竞争集成化。实验结果表明,与各种经典调度方案相比,该算法显著地改善了精确性和效率。     

基于直接后继节点完成时间的异构调度算法

分布式环境下的异构计算系统（HCS）是大数据时代进行数据密集型计算不可或缺的,一个有效的任务调度算法可以提高整个异构计算系统的效率。在对异构环境下的任务调度进行有向无环图（DAG）建模的基础上,提出基于直接后继节点完成时间的异构调度算法（HSFT）。在计算开销和通信开销差异度较大的异构环境中,考虑两者之间的平衡,采用更为合理的以计算均值与标准方差的乘积和通信权值与任务节点出度的比值作为优先权值计算方法,并在考虑最快完成时间（EFT）的基础上,将直接后继节点完成时间（SFT）用于处理器分配策略。实验结果表明,HSFT在不增加算法时间复杂度的情况下,比HEFT、SDBATS、PEFT等算法有更短的调度长度（makespan）、更优的调度长度比和效率。     

网格计算中一种改进的启发式任务调度算法

网格计算技术是20世纪90年代出现的新兴研究领域.网格系统由异构的资源组成.网格计算中,一个好的任务调度算法不但要考虑所有任务的makespan,使其值尽量小,同样要考虑到整个系统机器间的负载平衡问题.对异构计算环境下的元任务调度算法进行了分析,针对Min-min算法可能引发的负载不平衡问题,结合网格计算环境的特点,提出了一种适用于网格计算环境中的任务调度算法.     

异构计算系统的独立任务调度启发式算法

有效的任务调度是异构计算系统获取高性能的关键因素之一，由于任务调度问题是NP-困难的，为了获取尽可能好的解．文献中存在许多启发式调度算法。针对异构计算系统的独立任务调度问题，在分析现有启发式调度算法的优缺点的基础上．综合考虑负载平衡和使尽可能多的任务调度到具有较小处理时间的机器上，提出一种新的调度算法．命名为最佳最小完成时间（BMCT）调度算法，与文献中其它算法进行比较表明，它能产生更好的调度结果。     

异构环境下降低慢任务抖动的调度算法——DPST

为解决在异构计算环境中现有的云计算负载均衡算法存在的慢任务频繁抖动的问题,提出了一种能减低慢任务调度抖动概率的算法--DPST算法。首先通过定义一种异构计算节点中异构任务的能力度量,对执行异构任务的节点处理能力进行了归一化;然后通过引入节点能力预判机制,降低慢任务无效调度的次数;并且利用慢任务和慢节点双队列机制,提高了调度效率。实验结果表明,DPST相对于Hadoop平台在异构环境下任务调度的抖动次数下降了40%以上。由于有效降低了任务调度的抖动次数,在异构环境中DPST算法能明显地缩短任务的平均响应时间并提高系统的吞吐量。     

一种改进的启发式网格任务调度算法

网格任务调度算法是影响网格成功与否的关键技术之一。网格计算中,一个好的任务调度算法不但要考虑所有任务的makespan,使其值尽量小,同样要考虑到整个系统机器间的负载平衡问题。文章对异构计算环境下的元任务调度算法进行了分析,针对Min-min算法可能引发的负载不平衡问题,结合网格计算环境的特点,提出了一种适用于网格计算环境中的任务调度算法。     

异构计算环境下基于优先队列划分的调度算法

人工智能的飞速发展对高性能计算提出了更高的要求,异构计算环境下任务调度问题一直是高性能计算中的关键问题.本文提出一种基于优先队列划分的调度算法(PQDSA),该算法根据DAG(有向无循环图)任务集的入口节点数量确定优先队列数,通过任务的通信开销和计算开销划分任务队列,进而将关键节点任务分配给合适的队列,以产生效果较佳的任务调度队列,从而提高任务间的并行性,降低任务集的完工时间.与此同时,进一步基于插入策略将任务调度到处理器上,使任务调度更加高效地执行.PQDSA算法可以减少任务间的时间消耗,提高处理器的调度效率.通过与两个经典算法的性能对比,实验结果表明本文提出的PQDSA算法在任务完工时间和调度效率方面都要明显优于对比的算法.     

一种基于任务复制调度算法研究

分布式计算系统中任务调度是NP完全问题，调度算法可以分为任务复制和无任务复制两类．本文在简述了传统TDS算法的缺陷后，提出了一种改进的TDS任务调度算法-MTDS,该算法基于异构计算系统的特点，采用动态DAG图，尽可能的提前每个任务的执行时间，缩短所有任务完成的执行时间；并且避免出现在某一个执行序列中由于某一任务执行时间过长，而影响整个程序的执行时间．     

一种全局较优的静态任务调度算法

针对现有任务调度算法优先级选取过于单一所产生局部较优调度结果的问题,从全局较优出发,提出一种先分层后分支决定优先级的静态任务调度算法—HGCOTS算法。该算法考虑了任务间较大的通信开销和冗余任务对异构CMP任务调度效率的影响,通过综合区间插入和任务复制技术最大限度地降低了任务间的通信开销,对冗余任务进行删除,明显提高了任务调度效率。使用随机生成图进行模拟实验,与其他算法相比,新算法具有更小的调度长度。     

设备网格中的任务调度算法

基于设备网格环境中仪器设备的利用率和提交任务的QoS需求来考虑,结合任务调度算法Min-min,提出了一种设备网格中的Qos-Balance任务调度算法.该算法既保证了负载均衡性和又可满足提交任务的QoS需求.实验结果表明,该算法是一种可行的设备网格任务调度算法.最后介绍了算法实验的结果分析.     

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。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

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.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.