保证公平的最大化OFDMA系统容量策略

针对正交频分多址系统中容量与公平之间的矛盾,提出在子载波分配中兼顾公平、在功率分配中保证公平度门限的最大化系统容量策略.该策略首先将现有子载波方法与匈牙利算法结合,在优先最大化系统容量的基础上兼顾公平;然后利用基于公平度门限的人工蜂群功率分配算法,在优先保证公平度门限的基础上最大化系统容量.实验结果表明:该策略的子载波分配方法能够最大化系统容量并兼顾用户的公平,可实现系统容量和用户公平度的同时提升;该策略的人工蜂群功率分配方法具有较好的稳健性和全局寻优能力,即使在用户数较大时也能够实现所要求的公平度门限并最大化系统容量.研究结果验证了所提出策略的有效性.     

拥挤度驱动的总体布线层分配算法

针对多层布线问题，提出以拥挤度为驱动目标，完成布线资源的合理分配，同时达到布线层资源占用少和通孔数少等优化目标的层分配算法．首先采用启发式方法获得初始分配方案，然后通过模拟退火技术优化分配结果，最后采用试探策略优化层资源占用．工业实验数据表明，该算法能够实现线网层合理分配，获得满足拥挤度的优化解．     

基于用户云服务集群的资源动态调度研究

用户购买云服务器设施来搭建用户服务器集群,并将业务迁移到云服务器上后,很大程度上没有充分利用购买的计算资源。而随着业务量访问增加,传统的用户集群往往会通过增加服务节点来应对此情况,此时又需购买额外的云服务设施。论文基于传统用户的集群系统,使用改进的TOPSIS（逼近理想解排序法）算法结合集群监控信息来动态调度集群中节点上的应用。实验表明,该方案可以充分发挥用户购买的云服务器设施的计算资源,利用用户私有闲置资源来应对业务的突发访问,合理的调度用户服务器集群之间的业务应用分配,提高用户集群资源利用率的同时也保证了应用服务质量,节约了用户成本。     

异构云计算体系结构及其多资源联合公平分配策略

资源分配策略是当前云计算研究领域中的一个重要研究热点,异构云计算体系结构下的复杂应用问题研究中,最基本的问题在于如何将总体有限的资源分配给多个租户或应用,以达到效率或收效最大化.但是,在经典的资源分配问题中,任务或者用户往往是“贪婪”的;因此,在总体资源有限的前提下,资源分配的公平性就显得尤为重要.为了满足不同的任务需求,达到多种资源分配的公平性,设计了一个虚拟化的异构云计算体系结构,提出了该体系结构下基于占优资源的多资源联合公平分配算法(maximizing multi-resource fairness based on dominant resource,MDRF),并且证明了算法的帕累托等相关属性;给出了占优资源熵(dominant resource entropy,DRE)和占优资源权重(dominant resource weight,DRW)的定义,占优资源熵更加精确地刻画了用户资源请求与任务所调度到的服务器资源之间的适应程度,使系统的自适应能力更强同时提高了资源利用率.占优资源权重保障了用户优先获取资源的优先次序,协同所采用保障公平性的Max-Min Fairness策略,使资源的分配更加有序.实验表明,我们的策略有更高的系统资源利用率,并且使需求与供给更加匹配,进而使用户的占优资源获取更多,提高了服务质量.     

云环境下基于偏好的资源公平分配策略

资源分配策略是云计算领域的一个重要研究热点,其主要目标是同时考虑云用户和云提供商双方的利益,有效满足系统用户和任务的公平性,同时尽可能达到系统资源的充分利用。考虑到云环境中的用户需求各异,每个用户的任务请求数量不同,各个任务的资源需求也不同,设计了一种基于偏好的公平分配策略FABP,并给出了用户优先级和任务优先级的定义。实验分析表明,该算法不仅能缩短平均任务调度时间,而且还可以保证任务调度过程中用户和任务的公平性,实现综合资源利用率的最大化。     

Hadoop平台公平调度算法研究与优化

Hadoop Map Reduce框架的公平调度算法以统一的固定配置文件管理计算节点上计算槽的数量,这不能保障集群负载均衡,亦不能满足不同用户的资源需求。针对公平调度算法配置方式的不足,提出一种动态反馈的调度算法。该算法结合公平调度算法预先分配的特性,能够对计算节点上的计算槽进行动态调整。实验结果表明,基于动态反馈的改进算法有效地提高了集群的执行效率。     

云环境下公平性优化的资源分配方法

针对云数据中心资源分配不均、效率不高、资源错位等问题,为了满足不同用户的需求,达到多种资源分配的公平性,实现资源的高效利用,提出了全局优势资源公平（GDRF）分配算法。GDRF算法采用多轮分配方式,即先通过用户已分配资源量确定分配资格,每轮再通过全局优势资源共享比和全局优势资源权重来确定具体的分配用户,分配过程充分考虑了资源的匹配情况,采用了max-min fairness思想的渐进填充方式,并且将多资源分配公平性统一度量模型运用到了算法中。实验基于一个Google集群数据模型与基于占优资源的多资源联合公平分配算法作了比较。实验结果表明,GDRF算法分配的虚拟机总量提高了12%,资源总利用率提高了0.5个百分点,公平评估值提高了约15%,并且该算法的资源组合分配的适应度较高,使得用户需求和供给更匹配。     

数据密集作业在GPU集群上的调度算法研究

数据密集型作业包含大量的任务,使用GPU设备来提高任务的性能是目前的主要手段.但是,在解决数据密集型作业之间的GPU资源公平共享以及降低任务所需数据在网络间的传输代价方面,现有的研究方法没有综合考虑资源公平与数据传输代价的矛盾.分析了GPU集群资源调度的特点,提出了一种基于最小代价最大任务数的GPU集群资源调度算法,解决了GPU资源的公平分配与数据传输代价较高的矛盾.将调度过程分为两个阶段：第1阶段为各个作业按照数据传输代价给出自己的最优方案;第2阶段为资源分配器合并各个作业的方案,按照公平性给出全局的最优方案.首先,给出了GPU集群资源调度框架的总体结构,各个作业给出自己的最优方案,资源分配进行全局优化;第二,给出了网络带宽估计策略以及计算任务的数据传输代价的方法;第三,给出了基于GPU数量的资源公平分配的基本算法;第四,提出了最小代价最大任务数的资源调度算法,描述了资源非抢夺、抢夺以及不考虑资源公平策略的实现策略;最后,设计了6种数据密集型计算作业,对所提出的算法进行了实验.通过实验验证,最小代价最大任务数的资源调度算法对于资源公平性能够达到90%左右,同时亦能保证作业并行运行时间最小.     

基于效用最优化的多路径网络资源公平分配

网络资源最优分配除了要提高资源的利用率外,还应该实现面向服务、以用户为中心的资源分配目标,从而达到网络资源的公平分配,最大程度的满足用户的满意度.为了实现上述分配目标,文中考虑了多路径网络的资源公平分配问题,将多路径网络效用最大化模型分解为3个独立的子问题,而每个子问题其实对应于互联网体系结构的一层,并阐述了各个子问题的经济学含义.分析了用户所支付的价格和路径所收取的价格之间的关系,并提出了一类流量控制算法,通过该算法可以得到网络资源的最优公平分配.同时,考虑了算法在实际网络中的具体实现,并提出了基于窗口的流量控制机制.     

认知无线Mesh网络联合多路径路由和信道分配策略

从路径交叉的角度为认知无线Mesh网络提出一种新的联合多路径路由和信道分配策略,该策略结合按需路由的基本流程,同时根据所选路径情况设置交叉节点的中继功能,以主用户曾经占用每个信道的最少次数作为衡量标准来选择信道,并给出了一种解决信道冲突的方案。仿真结果表明,所提策略与基于链接、基于干扰的策略相比,能够显著改善平均吞吐量和时延等网络参数性能。     

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。     

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.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).