青云QingCloud正式推出Redis缓存集群服务

正北京2014年12月19日电/--国内领先的基础云服务商青云Qing Cloud日前宣布,基于Redis的缓存集群服务现已正式推出。Qing Cloud此次推出的Redis高性能缓存集群包含多个缓存节点,支持一主一从和一主多从的架构,并提供可持久化和自动备份服务,确保用户数据的快速读写和高可用性。Redis是一款基于内存的Key-Value数据库。与传统数据库相比,Redis的优势在于它将数据存储在内存中,读写性能得以巨大提升,适合那些频繁读写、并对速度要求较高的业务场景。鉴     

一种高效的Redis Cluster的分布式缓存系统

为了满足大型互联网应用对高并发访问、快速响应、动态扩展、易维护性等需求,本文基于Redis 4.0设计并实现了一种Redis Cluster分布式缓存系统,集成了可视化开源工具CacheCloud对该系统进行实时监控和高效管理,基于官方Redis-Bechmark进行了QPS性能测试,并与Codis分布式缓存系统进行了对比.实验结果表明Redis Cluster各功能高效运作,性能优越,在并发访问数10 000以上时响应时间明显优于Codis.     

Redis在计费系统中的应用研究

随着互联网的不断发展,电信运营商的数据业务量出现的爆发式的增长,话单量越来越大、按内容计费的业务越来越多,用户与系统的交互不断增强,访问集中,造成数据库负载过大,影响系统的的处理性能和响应时间;缓存技术就是解决此问题的一种方案,缓存技术以其简单的设计、高效的存储性能得到了越来越广泛的应用。本文主要介绍Redis的特性以及在计费系统中的应用。     

基于ASP.NET在线测试系统的设计与实现

介绍了基于ASP.NET在线测试系统的设计方案.该方案采用分层结构模型,并在数据库访问模块设计中,运用Abstract Factory设计模式解决模块通用性和扩展性.提出XML Web服务和客户端脚本相结合的方法设计B/S模式下定时器.针对在线测试对性能要求高的特点,采用OPEN XML技术、连接池、数据缓存、页面缓存等技术对系统性能进行优化.实验表明系统运行稳定、可供大量用户同时在线测试,并能实时处理数据.     

Redis在高速缓存系统中的应用

随着互联网的发展,各种类型的应用层出不穷,网站访问量越来越大、内容越来越多,用户与系统的交互不断增强,访问集中,造成数据库负载过大,网站显示延迟等影响.缓存技术就是解决此问题的一种方案,缓存技术以其简单的设计、高效的存储性能得到了越来越广泛的应用,而内存数据库则是一种优秀的缓存解决方案.主要介绍Redis的特性以及在系统中的应用.     

Redis缓存技术在自动气象站资料调用中的优化应用

为了提高气象自动站资料的检索查询效率,采用基于内存Key-Value结构的Redis数据库技术,通过搭建Redis数据库集群,把数据缓存在内存中并实现主从复制,提出一种适合气象自动站数据特性的数据存储结构模型,使得高频次访问的气象自动站数据能够直接从内存中读取,有效地减少数据查询响应的时间.本文分析了逐小时自动气象站观测资料的调用情况和到报时间特性,并基于Redis分别从业务库、索引库和时间库对逐小时自动站资料进行存储设计和具体实现,最后通过实验比对,得出采用Redis缓存逐小时自动气象站观测资料的检索效率比直接访问CIMISS检索效率高,该方法也可以应用到其它资料的检索调用业务场景中,具有较好的推广应用价值.     

基于集群架构的公共自行车数据可视化系统

针对公共自行车数据可视化系统的性能问题,提出了一种整合Web服务器集群、数据库集群以及缓存框架服务器的集群架构,设计并实现了基于该架构的公共自行车数据可视化系统。系统使用Nginx搭建反向代理服务器,使用Redis搭建缓存服务器。设计的系统还集成了Session一致性策略、前端性能优化等技术。针对公共自行车普通用户和管理者分别设计了移动端应用(APP)和Web可视化页面。测试结果表明:设计的系统满足了用户对公共自行车可视化系统功能和性能的要求。     

Codis分布式缓存架构在电力系统中的应用研究

Redis因具备快速响应、数据安全等特点,常被选作系统缓存工具.由于受到单节点性能约束,传统电力系统中通常会选择Redis集群架构.但是在Redis集群实际部署过程中,往往呈现出扩展性差、维护困难等缺陷.为此,提出一种基于Codis的分布式缓存架构方案,以对传统电力系统中的Redis集群进行优化.通过电力系统中业务存储能力、数据检索效率、性能优良检测等多角度,对搭建的Codis分布式缓存架构进行理论研究与应用测试,证明了该方案在数据存储、信息检索、部署运维等方面具有一定优势.     

基于Linux的健康云平台服务优化

移动互联网和健康大数据正在引发医疗健康管理产业发生颠覆性变革,各级厂商着力构建形成一套基于“互联网+物联网+医疗服务”技术的以O2O商业模式为主的云端健康管理系统平台.“中科慧康”云健康平台主要为健康机构以及用户提供健康管理的平台.本文从平台架构设计和系统优化入手,从负载均衡,分布式缓存,数据库优化,socket转发服务器等方面设计了良好的云平台以支撑业务发展.实验结果表明,该系统架构可以满足百万级别的数据转发和用户访问,应用实践表明了该方案的可行性.     

基于混合策略的低成本云存储方案

为了保证云存储系统数据的高可用性、降低数据存储成本和带宽成本、缩短数据对象的访问时间,提出一种称为缓存大小自适应确定(CAROM)的新方案。CAROM结合传统的基于缓存策略的方法和纠错码方法来提高云文件系统的弹性和效率。另外,为了在缓存大小及其效益间实现平衡,提出一种基于总体成本凸函数特性的自适应方法来实现缓存大小的自适应选择。在基于现实世界文件系统数据的性能评估中,CAROM方案的存储成本和带宽成本分别比复制策略和纠错码策略下降60%和43%,同时访问延时与复制策略相当。结果表明,CAROM方案在支持当前云文件系统语义一致性的同时,兼具带宽成本低、存储成本低和访问成本低等特性。     

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).