一种基于密度聚类的小生境差分进化算法

针对基本差分进化算法早熟收敛的缺陷,提出了一种基于密度聚类的小生境差分进化算法。该算法基于DE/rand/2/bin变异方式全局搜索能力强、鲁棒性好和DE/best/2/bin变异方式局部搜索能力强、收敛速度快的特点,首先初始化一个没有子种群的全局种群,再在全局种群中采用DE/rand/2/bin进行迭代搜索,并对其中的个体进行聚类,当聚类簇中的个体数目达到规定的最小规模时形成一个小生境子种群,然后在各子种群中采用改进的DE/best/2/bin进行迭代搜索并重新进行聚类,从而提高进化过程中种群的多样性,增强算法跳出局部最优的能力。仿真实验表明,该方法能显著提高算法的收敛速度和全局搜索能力,有效避免早熟收敛。     

基于多尺度并行免疫克隆优化聚类算法

针对无监督分类问题,提出一种多尺度并行免疫克隆优化聚类算法.算法中,进化在多个子群之间并行进行,不同子群的抗体根据子群适应度采用不同变异尺度.进化初期,利用大尺度变异子群实现全局最优解空间的快速定位,同时变异尺度随着适应值的提升逐渐降低;进化后期,利用小尺度变异子群完成局部解空间的精确搜索.将新算法与其他聚类算法进行比较,所得结果表明新算法具有较好的聚类性能和鲁棒性.     

基于随机扩散搜索的协同差分进化算法

针对差分进化算法存在的收敛速度慢、稳健性差等问题,借鉴多种群并行机制和随机搜索策略,提出一种基于随机扩散搜索的协同差分进化算法。引入反向混沌搜索的初始化机制,利用随机扩散搜索策略将种群分为成功和失败2个子群并进行改进,对改进的成功和失败子群分别采用不同的差分策略,克服单一差分策略的缺陷,同时定期使子群的部分最好与最差个体实现一对一的信息交流,从而达到协同进化的目的。仿真结果证明,与粒子群优化算法及差分进化算法相比,该算法具有较好的收敛速度和寻优能力。     

基于多变异个体的多目标差分进化改进算法

针对多目标差分进化算法在高维函数下收敛速度慢和易早熟的问题,提出一种基于多变异个体的多目标差分进化改进算法。通过在多目标差分进化算法的个体变异及交叉操作中,引入多个变异个体,使得在高维多目标函数情况下,多目标差分进化算法种群可以更好地保持多样性,减少种群陷入局部最优解的可能性,从而提高该算法在高维多目标优化问题环境下,最优值解的搜索速度及全局最优值解的查找能力。实验结果表明,在高维多目标环境下,与标准多目标差分进化算法相比,该算法可以更快速地找到多个目标函数组的非劣最优值解集。     

双种群差分进化规划算法

标准差分进化算法（SDE）具有算法简单,控制参数少,易于实现等优点。但在难优化问题中,算法存在收敛速度较慢和容易早熟等缺陷。为克服此缺点,提出一种改进算法--双种群差分进化规划算法（BGDEP）。该算法将种群划分为两个子群独立进化,分别采用DE/rand/1/bin和DE/best/2/bin版本生成变异个体。每隔δt（取5~10）代,将两个子群合并为一个种群,再应用混沌重组算子将之划分为两个子群,以实现子群间的信息交流。在双种群协同差分进化的同时,应用非均匀变异算子对其最优个体执行进化规划操作,使得算法具有较快的收敛速度和较强的全局寻优能力。为测试BGDEP的性能,给出了4个30维benchmark函数优化问题的对比数值实验。结果表明,BGDEP的求解精度、收敛速度、鲁棒性等性能优于SDE、双种群差分进化（BGDE）和非均匀变异进化规划（NUMEP）等4种算法。     

基于共轭梯度法的反馈差分进化混合算法及其在弹簧设计中的应用

分析了差分进化算法多种变异方式的特点以及每种变异方式所适应的搜索状态,建立了一条能够让种群根据自身的搜索环境来动态选择变异方式的反馈回路,使个体能够自学习、自调节地高效搜索。在每一代的最优个体邻域内,采用共轭梯度法确定最佳的共轭搜索方向,向量能够在最优解邻域内进行细致的局部搜索。根据混合算法的子代更新形式,从理论上证明了种群能够以概率1的方式收敛到全局最优解。与其它进化算法的对比实验结果表明,本文的差分进化算法有效提高了benchmark函数的最优值精度,加快了收敛速度。在弹簧设计问题中,利用改进的差分进化混合算法得到了较好的结构参数。     

基于两阶段变异交叉策略的差分进化算法

针对差分进化算法存在的收敛速度慢、稳健性差等问题,借鉴多种变异优化策略,提出一种基于两阶段不同变异交叉策略的差分进化算法。引入反向混沌搜索的初始化方法,将初始种群分为较好和较差2个子种群,两阶段依次对上一阶段改进的较好和较差2个子种群采用不同的差分进化策略,并定期将较好和较差2个子种群重新按适应值排列组合进入下一阶段,以提高种群的质量,同时克服单一差分策略的缺陷。函数仿真结果表明,与其他差分进化算法相比,该算法的收敛速度和寻优精度均得到明显改善。     

基于双种群的小生境差分进化算法

将非线性方程组的求解问题转化为函数优化问题,当方程组有多个解时,它的适应值函数就是具有多个最优解的多峰函数.为此,提出了基于双种群的小生境差分进化算法.在该算法中,进化在两个不同的子群间并行进行,通过使用不同的变异策略,实现种群在解空间具有尽可能分散的探索能力的同时在局部具有尽可能细致的搜索能力.通过子群重组实现子群间的信息交换,然后引入小生境淘汰机制.对典型测试函数的优化结果表明,该算法能找到全部解,而且精度好.     

融合改进差分进化思想的K-调和均值聚类

针对K-调和均值聚类算法易陷入局部最优的缺点,提出了一种基于改进差分进化的K-调和均值聚类算法。该算法通过引入基于Logistic变尺度混沌搜索和指数递增交叉概率算子的差分进化算法来增强全局寻优能力。实验结果表明,该算法能够较好地克服K-调和均值算法的缺点,在保证收敛速度的同时增强了算法的全局搜索能力。     

基于多代种群进化信息改进的差分进化算法研究

差分进化算法是进化算法中一种性能较为优良的全局数值优化算法,已在人工智能、信号处理等方面取得广泛应用,但当前研究往往仅考虑进化过程中某一代种群的分布信息,而忽略进化过程中多代种群累积的分布信息,造成信息利用不充分。借助自适应协方差矩阵进化策略的思想,充分利用进化过程中累积的种群分布信息,同时,由于自适应协方差矩阵存在收敛早熟、易陷入局部最优的缺点,先后对变异和交叉操作进行相应改进,以平衡算法的全局搜索能力和局部搜索能力。首先,根据种群中个体适应度值进行排序,由余弦函数改进的概率模型计算个体参与变异操作的概率,基向量和差分向量中末端向量根据概率值降序选择,差分向量中起始向量升序选择,从而提高种群的搜索范围;然后,对协方差矩阵进行特征分解,并在由特征向量构建的坐标系中执行交叉操作,该种方式生成的实验向量更接近全局最优解。针对上述改进操作,采用IEEE CEC2014作为评估函数,实验结果表明,相比现有的差分进化改进算法,本改进算法的实验性能提升更为明显。     

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).