K-median问题贪心近似算法的分析与实验

讨论K-median问题的贪心近似算法及其在实际计算中的表现。提出一个解K-median问题的贪心算法,证明该算法的近似度为O(ln(n/k)),通过实验证明该贪心算法在实际应用当中可以取得较好的效果,大约有90%的客户能被距离其最近、次近和第三近的设备服务。     

λ-连通分割和最优区域分并分割算法

本文提出适用于多维灰度图象的λ-连通分割算法,其计算时间为0(m|∑_m|);这里m为空间∑_m的维数.我们对λ-连通分割作了误差分析,并利用长度k-局部受限的概念,证明当图象在∑_m中的连通量不大于(1/2)|∑_m|时,k必须大于O(m-1)ln n)且几乎不需要超过O((m+1)ln n). 我们改进了经典的区域分并(四叉树)分割方法,得到其时间复杂性为O(|∑_m|·log_2|∑_m|)的算法,并从理论和应用两方面对这两种方法作了比较.     

双层无线传感网络的3连通近似算法

主要研究双层无线传感网络模型,即数据信息流只能在传感器和中继器或中继器和中继器之间传输,而不能在传感器之间传输。近似算法基于两个子问题：k圆盘覆盖问题和单层传感网络的k连通问题,而后在部分中继器周围设置“等六边形”结构的中继器点,最终达到整个网络的3-连通水平。该算法的最终性能比为8α+β,其中α为k圆盘覆盖近似算法的性能比,β为单层传感网络的k连通近似算法的性能比。     

无人值守传感器网络的低通信成本存储算法

针对无人值守传感器网络的数据存储问题, 提出了一种低通信成本的分布式数据存储算法。算法采用步数为cn的定向随机游走机制, 将网络中的k个源数据包按照一定的接收概率分散存储到了网络中所有的n个节点, 在每个节点形成了一个存储数据包。实验表明, 基于该算法的存储过程完成之后, 即使有部分传感器节点损坏, sink节点只要随机收集到k+ε（ε≥10）个存储数据包, 就能成功计算出原来的k个源数据包。与具有代表性的基于LT码方法相比, 该算法在节约sink节点访问成本的同时, 也将网络的通信时间复杂度从O(n　ln　n)降到了O(n), 具有良好的应用潜质。     

个体单体型问题参数化算法研究

个体单体型问题指如何利用个体DNA测序片断数据,根据不同的优化准则确定该个体单体型的计算问题.因为技术上的限制,DNA测序实验中能直接测定的片断长度是有限的,一个片断所覆盖的最大SNP位点数k1通常小于10;出于时间和金钱的考虑,覆盖一个SNP位点的最大片断数k2也不是很大,通常约为10左右;与要测定的单体型SNP位点总数,n及所测序的DNA片断总数m相比,k1和k2均很小.在此基础上,文中对个体单体型问题最少SNP位点删除MSR和最少片段删除MFR模型进行了参数化,提出了时间复杂度分别为O(nk1k2+mlogm+mk1)和O(mk22+mlogm+nk2)求解无空隙MSR和MFR的精确算法.和Bafna等提出的时间复杂度为O(mn2)和O(m2n+m2)的精确算法相比,文中的算法效率提高了很多,具有较高的实用价值.     

一般设施定位问题计算复杂度和近似算法研究

设施定位问题即UFL问题是NP-hard的组合优化问题,是聚类问题领域的热点问题之一,在数据挖掘和分类识别方面有着重要应用.多年来其近似算法研究一直是计算机科学工作者关注的焦点,然而现有研究结果大多关于Metric空间,一般距离空间中该问题结果始终未见.针对最大连接费用至多是最小连接费用ω＞1倍的一般距离空间中设施定位问题,简称一般设施定位问题,借助集合覆盖问题,利用问题归约方法证明其不存在近似性能比小于1.243 0.316ln(ω-1)的多项式时间近似算法,除非NPDTIME(nO(log log n));设计了一般设施定位问题的局部搜索算法,证明算法近似性能比是(1 ω)/α,ω＞1,1≤α≤2.仿真实验表明,一般设施定位问题局部搜索算法的求解质量极高;通过实验进一步研究了该算法并给出了改进方法.     

一种构建最优二叉查找树的贪心算法

分析最优二叉查找树与哈夫曼树的异同,提出解决最优二叉查找树问题的贪心算法,证明算法的正确性,并用C++程序设计语言编码实现。该算法时间复杂度为O(n2),空间复杂度为O(n),实现了空间复杂度阶的突破。实验结果表明:所提出的贪心算法的效率明显优于动态规划算法。     

基于积极集策略的最小闭包球问题算法研究

首先,基于每次迭代计算距离当前球心最远的两个点,提出一种求解n维空间中m个点的最小闭包球问题的(1+ε)-近似算法.对于ε∈(0,1),建立了该算法的核心集大小和计算复杂度,分别为O(1/ε)和O(mn/ε).然后,给出一种积极集策略,每次迭代计算距离当前球心最远的N个点.将该策略结合到提出的算法中,得到一个基于积极集策略的算法.最后,实验结果表明基于积极集策略的算法能够快速、有效地求解m》n的大规模数据集的近似最小闭包球.     

测试集问题的集合覆盖贪心算法的深入近似

测试集问题是一个有着广泛应用的NP难问题.集合覆盖贪心算法是测试集问题的一个常用近似算法,其由集合覆盖问题得到的近似比21nn+1能否改进是一个公开的问题.集合覆盖贪心算法的推广被用来求解生物信息学中出现的冗余测试集问题.通过分析条目对被区分次数的分布情况,用去随机方法证明了集合覆盖贪心算法对测试集问题的近似比可以为1.51nn+0.5lnlnn+2,从而缩小了这种算法近似比分析的间隙.另外,给出了集合覆盖贪心算法对冗余度为n-1的加权冗余测试集问题的近似比的紧密下界(2-o(1))lnn-Θ 1).     

图(k,m)最优划分的近似算法

本文提出了无向图(k,m)最优划分的一个近似算法,证明了这是一个产生近似最优解的多项式时间算法。在最坏情况下,该算法的性能保证为一个参数k所界定,这里k是与问题输入尺寸无关的。     

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.