4 种计数型Bloom Filter 的性能分析与比较

对3 种已有的计数型Bloom filter——Na?ve Counting Bloom Filter(NCBF),Space-Code Bloom Filter (SCBF)和d-left Counting Bloom Filter(dlCBF)——的查询错误概率进行了分析,得出了NCBF 的计数器防溢出条件 以及SCBF 和dlCBF 的参数最优设置准则.提出了一种衡量计数型Bloom filter 性能的指标:负载适应性.针对dlCBF 负载适应性差的问题,对dlCBF 进行了改进,提出了一种计数型Bloom filter:Binary Shrinking d-left Counting Bloom Filter(BSdlCBF).通过仿真实验,以计数误差、空间复杂度以及负载适应性为性能指标,对上述4 种CBF 进行了比较. 实验结果表明,BSdlCBF 具有最低的空间复杂度、最小的计数误差以及最佳的负载适应性. BSdlCBF 赢得上述性能 优势的代价在于其计算复杂度比其他3 种计数型Bloom filter 略高.     

4 种计数型Bloom Filter 的性能分析与比较

对3种已有的计数型Bloom filter--Na(I)ve Counting Bloom Filter(NCBF),Space-Code Bloom Filter (SCBF)和d-left Counting Bloom Filter(dlCBF)--的查询错误概率进行了分析,得出了NCBF的计数器防溢出条件以及SCBF和dlCBF的参数最优设置准则.提出了一种衡量计数型Bloom filter性能的指标:负载适应性.针对dlCBF负载适应性差的问题,对dlCBF进行了改进,提出了一种计数型Bloom filter:Binary Shrinking d-left Counting Bloom Filter(BSdlCBF).通过仿真实验,以计数误差、空间复杂度以及负载适应性为性能指标,对上述4种CBF进行了比较.实验结果表明,BSdlCBF具有最低的空间复杂度、最小的计数误差以及最佳的负载适应性. BSdlCBF赢得上述性能优势的代价在于其计算复杂度比其他3种计数型Bloom filter略高.     

d-Left CBF技术在P2P中的研究

分析了Bloom Filter技术在时下流行的P2P分布式系统中的应用,着重介绍基于Bloom Filter的d-Left Counting Bloom Filtr(CBF)技术,d-left CBF利用d-lef thashing的方法存储fingerprint,将hash value分为两部分,分别用于存储随机地址和fingerprint,从而提高工作效率,并支持节点动态删除操作,应用于节点异常活跃的P2P系统中.     

分片计数布隆过滤器及其在Hbase二级索引的应用

针对Hadoop Database(Hbase)仅支持主索引结构,即通过主键和主键的range来检索数据的问题,提出利用Counting Bloom Filter的新变体建立二级索引来支持非主键数据的检索.分析了已有的Counting Bloom Filter(CBF)技术,针对CBF溢出概率高的问题,提出一种新的Split Counting Bloom Filter(SCBF)技术,SCBF将标准CBF分成多个相互独立的区域,由这多个区域共同存储元素的fingerprint.实验结果表明,与标准CBF相比,SCBF降低了溢出概率,充分提高了过滤器的性能,可以很好地用来建立Hbase二级索引.     

ODBF:基于操作型衰落Bloom Filter的P2P网络弱状态路由算法

在P2P网络中,基于衰落Bloom Filter的弱状态路由算法试图将每条查询消息沿着成员资格信息量最强的方向传递,并最终以较低的传输代价和传输时延确保较高的查准率.研究发现衰落Bloom Filter在传递过程中存在严重的多径叠加和噪音问题,这直接导致查询消息以很高的概率沿着错误的方向传播,甚至会退化为泛洪路由算法.为解决这一挑战性难题,文中提出了基于操作型衰落Bloom Filter的弱状态路由算法ODBF(Operative Deca-ying Bloom Filter).ODBF通过分别保存对象的衰落Bloom Filter及源节点等信息,使得ODBF能够有效解决基于衰落Bloom Filter的路由信息在P2P网络中的多径叠加和信息回流问题,有效抑制噪音的影响,进而使得基于弱状态的路由能够以很高的概率沿着正确方向进行.     

一种面向数据流模型的流计数算法

在研究数据流过程中,基于现有的概要数据结构Bloom Filter,给出改进的K Bloom Filter结构,从理论上对假阳性误判进行分析,得出两者具有相同的在误判率f0下表示集合规模的上限n0,因此,K Bloom Filter的误判率在可控范围内。提出基于K Bloom Filter的流计数算法,与基于Bloom Filter的流计数算法相比,在相同的空间复杂度O(m)和插入操作时间复杂度O(k)情况下,该算法降低了统计结果的误差。     

基于衰落Bloom Filter 的P2P 网络弱状态路由算法

在P2P网络中,基于衰落Bloom Filter的弱状态路由算法试图将每条查询消息沿着成员资格信息量最强的方向传递,并最终以较低的传输代价和传输时延确保较高的查准率.衰落Bloom Filter在传递过程中存在严重的多径叠加和噪音问题,这直接导致查询消息会以很高的概率沿着错误的方向传播,甚至会退化为泛洪路由算法.为了解决这一挑战性难题,提出了DWalker这种基于衰落Bloom Filter的高效弱状态路由算法.DWalker基于有向随机网络,采用指数衰落Bloom Filter来发布和传播每个节点共享资源的信息,且其最大传播距离小于网络中任意两点之间距离的期望值,从而有效抑制了衰落Bloom Filter在传播过程中的多径叠加问题.DWalker采用多个Bloom Filter而不是单个Bloom Filter来表达一项路由条目,在单个Bloom Filter的错误发生概率达到设计上限时,可按需动态增加新的Bloom Filter,以将更多资源对象信息纳入到当前路由条目中.DWalker仅根据当前节点的各项路由条目中值为1的比特位所占的最大比例,以及查询消息在正确转发方向对应的路由条目中对应比特位中值为1的个数的临界值,就能使进入目标对象传播范围内的查询消息以较高的概率辨认出正确的路由方向.理论分析和实验结果表明,DWalker能够以较低的查询消息代价、较小的路由条目存储开销以及较短的查询时延,使绝大多数查询消息沿正确方向转发,从而获得较高的查准率.     

基于动态附加布隆过滤器的RFID数据冗余处理算法

针对RFID设备在读取标签信息时产生的高度冗余会造成实时传输压力、存储空间浪费和上层应用分析结果不可靠等问题,提出一种动态附加布隆过滤器算法(Dynamic-Additional Bloom Filter,DATRBF)来清除RFID冗余数据.首先结合RFID动态数据流特点,利用时间和阅读器因素的影响设计了基础布隆过滤器(Time-Reader Bloom Filter,TRBF),然后根据定时间区间内数据量变化动态决定是否调整或附加额外的TRBF,通过附加TRBF从而扩充数组的方式将误判率控制在阈值内,最后结合两个过滤器对数据是否冗余进行综合判断.实验证明,在过滤RFID实时动态数据流中的冗余数据时,DATRBF算法相比传统布隆过滤器(Bloom Filter,BF)和时空布隆过滤器(Temporal-Spatial Bloom Filter,TSBF)有明显的优势,在数据量随机波动时DATRBF的误判率平均约为TSBF的49％,且DATRBF算法能够在数据量持续上升时保持平稳的低误判率.     

基于DCBF的流抽样测量算法

为了提高系统的处理效率,减少系统的测量误差,提出了一种基于动态计数型布鲁姆过滤器（Dynamic Counting Bloom Filter,DCBF）的流抽样测量算法。该算法使用基于报文级别的抽样,并通过DCBF进行流查找和统计,且在CBF计数器溢出时动态增加新的CBF。经理论分析和实验表明,该算法不仅提高了系统的运行效率,减少了存储空间的消耗,同时具有准确性和可扩展性,能很好地适用于高速链路的流量测量中。     

数据流中频繁项近似挖掘算法

提出新的数据结构ESBF(Extensible and Scalable Bloom Filter)-可扩展的Bloom Filter.并提出基于ESBF的数据流中频繁项近似挖掘算法,该算法在保证较高精度的同时,实现比同类算法具有更好的时间效率且在一般情况下具更好的空间效率,并证明只需ln(-M/lnρ)·e/ε·1/(ε·M)个计数器就能保证满足用户规定的误差ε及可信度ρ要求.     

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.