分子距边矢量结合神经网络法预测二(口恶)(口英)类化合物PCDFs的logKow值

采用以基团间距离、边数为基准的分子距边矢量作为二口恶口英类化合物多氯代二苯并呋喃(PCDFs)的分子结构描述符,结合反向传播人工神经网络方法建立了PCDFs的正辛醇/水分配系数(logKow)与分子结构描述符之间的定量关系模型.结果表明,所采用的结构描述符对于分子结构具有很好的区分能力,所建立的模型对于校验样本的预测精度较高.利用所得模型,对文献尚未报道logKow实验值的其他所有85种PCDFs给出了预测值.     

分子距边矢量结合神经网络法预测二E Ying类化合物PCDFs的logKOW值

采用以基团间距离、边数为基准的分子距边矢量作为二EYing类化合物多氯代二苯并呋喃（PCDFs)的分子结构描述符，结合反向传播人工神经网络方法建立了PCDFs的正辛醇／水分配系数（logKow)与分子结构描述符之间的定量关系模型。结果表明，所采用的结构描述符对于分子结构具有很好的区分能力，所建立的模型对于校验样本的预测精度较高。利用所得模型，对文献尚未报道logKow实验值的其他所有85种PCDFs给出了预测值。     

单苯环氯取代指数法预测二噁类化合物PCDDs的正辛醇/水分配系数

采用单苯环氯取代指数作为氯代二苯并二口恶口英类化合物 (PCDDs)的分子结构描述符 ,通过正向逐步线性回归方法建立了PCDDs的logKow与分子结构描述符之间的定量关系模型。与文献报道的MOD模型相比 ,该模型不仅具有显著的相关性 (n =43,Radj=0 898,SE =0 195 ,在α =0 0 5时 ,F =2 0 45 5 ,p =0 0 0 0 0 ) ,而且对于分子结构具有更好的区分能力。利用建立的模型 ,对没有logKow文献值的其他 33种PCDDs化合物给出了预测值     

应用AM1量化参数预测多氯代二苯并呋喃的logKow

采用G98W程序包中的AM1方法对135个多氯代二苯并呋喃(PCDFs)分子和二苯并呋喃进行了优化计算，作业命令为#p Am1 op tfreq scf(eonver=9)，以计算所得的分子轨道能量、碳原子电荷作为PCDFs分子结构描述符，运用多元线性回归技术建立了PCDFs的logKow与分子轨道能量、碳原子电荷的四元线性方程，相关系数为0．9306，标准偏差为0．1849，经修正的，Jackknife法检验该模型的稳健性好，并对未有实验数据的85个PCDIr’s的logKow进行预测。     

单苯环氯取代指数法预测二EYing类化合物PCDDs的正辛醇／水分配系数

采用单苯环氯取代指数作为氯代二苯并二EYing类化合物（PCDDs）的分子结构描述符,通过正向逐步线性回归方法建立了PCDDs的logKow与分子结构描述符之间的定量关系模型。与文献报道的MOD模型相比,该模型不仅具有显著的相关性（n=43,Radj=0.898,SE=0.195,在α＝0．05时,F＝20．455,p=0.0000),而且对于分子结构具有更好的分区能力。利用建立的模型,对没有logKow文献值的其他33种PCDDs化合物给出了预测值。     

多氯代二苯并呋喃光解半衰期的拓扑研究

多氯代二苯并呋喃(PCDFs)是环境持久性污染物,光化学降解是其主要降解途径.计算了PCDFs的原子特征值δi,利用分子图形技术获得连接性修饰指数mXL,以该指数作为分子结构描述符,采用最小二乘法用逐步多元线性回归分析48种PCDFs的光解半衰期,建立了2个能预测吸附到云杉针叶表面和飞灰表面的PCDFs光解半衰期的定量结构-性质关系模型,估算的平均误差分别为0.047和0.062.采用留一法检验模型稳健性,得预测模型,预测另外一些PCDFs分子的光解半衰期,预测值和实验值几乎一致.这些模型能解释PCDFs光解半衰期的递变规律,而且稳定性较好,预测能力较强.     

对多氯代二苯并二噁(口英)的定量结构-气相色谱保留行为关系研究

采用分子电性距离矢量（MEDV）描述子表征多氯代二苯并二噁[口英]（PCDDs）,结合基于预测的变量选择和建模方法（VSMP）,从MEDV中挑选出1-2个描述子,对不同固定相下PCDDs的气相色谱保留值建立定量线性模型。结果表明MEDV分子描述子对分子结构具有很好的分辨能力,利用VSMP方法挑选的MEDV描述子很好表达了描述子与气相色谱保留值之间的相关关系,所建立的模型相关系数（R）均大于0．98,留一法交互检验的相关系数（q）均大于0．97;并均匀挑选2／3有实验数据的异构体作为训练集,余下的1／3作为检验集,进行了变量挑选、建模,结果表明,挑选的变量与用全部已知样本建模时一致,最后对没有实验值的异构体进行了预测。     

对多氯代二苯并二噁的定量结构-气相色谱保留行为关系研究

采用分子电性距离矢量(MEDV)描述子表征多氯代二苯并二(口惡)(口英)(PCDDs),结合基于预测的变量选择和建模方法(VSMP),从MEDV中挑选出1-2个描述子,对不同固定相下PCDDs的气相色谱保留值建立定量线性模型。结果表明MEDV分子描述子对分子结构具有很好的分辨能力。利用VSMP方法挑选的MEDV描述子很好表达了描述子与气相色谱保留值之间的相关关系,所建立的模型相关系数(R)均大于0.98,留一法交互检验的相关系数(q)均大于0.97;并均匀挑选2/3有实验数据的异构体作为训练集,余下的1/3作为检验集,进行了变量挑选、建模,结果表明,挑选的变量与用全部已知样本建模时一致,最后对没有实验值的异构体进行了预测。     

多氯代二苯并呋喃定量结构性质关系的研究

基于定量结构-性质相关(QSPR)研究多氯代二苯并呋喃化合物的性质具有重要意义。采用分子电性距离矢量(MEDV)表征135个多氯代二苯并呋喃化合物(PCDFs)的分子结构,运用多元线性回归(MLR)技术,同时采用逐步回归结合统计检测筛选模型变量,建立PCDFs的气相色谱保留指数(RI)、正辛醇/水分配系数(LogK_(ow))、基于2种色谱条件下的2组气相色谱保留时间与MEDV的QSPR模型,模型的线性相关系数均在0.8971～0.9963之间。继用留一法和外部样本检验模型稳定性能。结果:所建QSPR模型的稳定性和预测能力良好。     

有机过氧化物自加速分解温度的QSPR研究

基于定量构效关系(QSPR)原理,对有机过氧化物的自加速分解温度(SADT)与其分子结构间的内在联系进行了研究。应用CODESSA软件计算46种有机过氧化物的分子描述符。采用最佳多元线性回归(B-MLR)法对描述符进行筛选获得7个特征描述符,并同时建立线性回归模型。将7个特征描述符作为输入参数,采用支持向量机(SVM)法建立非线性模型。随后对模型进行验证,结果表明,B-MLR模型和SVM模型均具有良好的拟合能力、稳定性和预测能力,且SVM模型的性能(R_(train)~2=0.958,R_(test)~2=0.862)优于B-MLR模型(R_(train)~2=0.930,R_(test)~2=0.844)。通过对特征描述符的分析发现了影响SADT的主要结构因素。采用Williams图分析了模型的应用域,结果表明所有样本均在模型的应用域范围内。本文所建立的B-MLR模型和SVM模型可应用于有机过氧化物SADT的预测。     

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).