一种应用约束优化理论的TOA定位算法

移动通信、声源探测等领域的应用要求通过分布在不同位置的信号接收站得到的TOA测量值实现对辐射信号源进行定位。针对这个问题,提出了一种应用约束优化理论的基于TOA的定位算法,将由定位方程得到的加权线性最小二乘函数作为目标函数,并选择未知矢量元素之间的关系作为约束条件。仿真实验中将该方法与两步加权最小二乘等方法和CRLB进行比较的结果表明,约束优化理论的应用有效提高了定位精度。     

一种改进的三边定位算法

针对基于加权最小二乘(WLS)的三边定位算法在线性化过程中损失定位信息的问题,提出了一种改进的三边定位算法。该算法利用WLS算法粗略估计未知节点的坐标,并利用损失的定位信息构建定位模型,通过求解该定位模型实现精确定位。仿真结果表明,与基于WLS的三边定位算法相比,该算法有效提高了定位精度,且巷道长宽比越大,定位性能越好。     

基于残差加权的三维DV-Hop改进WSN定位算法

针对无线传感网诸多具体应用中需要节点位置信息的实际需求,提出一种基于残差加权的三维DV-Hop改进定位算法的解决方案。该方案通过引入残差函数将提高定位精度的问题转化为等式约束条件下残差最小化的求解问题,采用最小二乘准则对待定节点与锚节点的最小跳数进行平均加权处理,并利用二次规划法将其最终转化为无约束条件下最小化的问题。经理论分析得出了三维DV-Hop改进定位算法的模型,实现待定节点的坐标估计并提高了定位精度。仿真结果表明,在相同通信半径、不同锚节点比例的情况下,改进三维DV-Hop定位算法的性能得到了明显提高。     

基于时间反演的到达时间定位

针对传统算法在室内超宽带（UWB）到达时间（TOA）定位系统里很难准确搜寻出第一条直射路径,从而导致定位精度不高的问题,提出了基于时间反演（TR）的TOA室内UWB定位算法。首先,利用TR处理的空时聚焦特性确定第一条直射路径,从而估计这条路径的TOA;其次,通过加权最小二乘（WLS）定位算法对不同的估计分量赋予相应的权值以提高定位精度。仿真结果表明,相较传统TOA定位,所提方案在低信噪比条件下的均方根误差（RMSE）减小了28.6%,可见该方案有效提升了系统定位精度。     

联合TDOA-AOA无线传感器网络半定规划定位算法研究

在无线传感器网络定位中,TDOA和AOA联合定位可有效利用多种位置信息提高定位精度.由于传统联合加权最小二乘(WLS)的目标函数非线性,在应用于无线传感器网络定位时,会产生多个局部最优解.因此,针对该问题本文将约束加权最小二乘问题转化为二次约束二次规划问题,之后通过引入半定松弛(SDR)方法将联合定位问题转换为低复杂度的半定规划问题(SDP),进而寻找全局最优解.并且针对实际应用中参考节点带误差的情形分析和推导了定位算法.与已有算法相比,提出的算法在参考节点无误差和有误差时都有更高的精度.此外,提出的SDP算法还能够实现只有两个参考节点下的目标定位.     

基于准最小二乘法的光伏阵列模型鲁棒参数估计方法

光伏阵列的模型参数估计在光伏发电系统的仿真、输出功率预测、最大功率点跟踪等方面有重要意义。当测量数据中只含随机误差时,以加权最小二乘（WLS）为优化函数的参数估计方法有较好的辩识效果。但是当测量数据中含有显著误差时,WLS参数辩识的效果较差。为解决此问题,本文提出了一种以准加权最小二乘法（QWLS）为优化函数的参数估计方法来减小显著误差的影响,采用了赤池信息量准则(AIC)设计QWLS最优参数,将该方法应用于光伏阵列中构造模型鲁棒参数估计问题。最后将WLS和QWLS分别结合序列二次规划（SQP）算法,进行光伏阵列模型的参数估计仿真与实验测试。测试结果显示QWLS参数估计结果更准确,验证了准最小二乘法的鲁棒性与有效性。     

线性最小二乘法的RSSI定位精确计算方法

基于接收信号强度指示(RSSI)定位模型,提出了一种目标节点位置的精确计算方法。将RSSI定位问题所描述的非线性优化函数转化为线性最小二乘法估计问题,将定位结果直接用代数解表示。分别提出了目标节点信号发射强度已知和未知下的非约束线性最小二乘(ULLS)定位方法。同时对非约束线性最小二乘法下的参数进一步优化,提出了约束线性最小二乘法以提高定位精度。仿真验证了该定位计算方法的有效性,测试了不同信号强度噪声对定位误差的影响。结果同时表明,约束线性最小二乘法比非约束线性最小二乘法的定位误差更小,非常接近于定位结果的克拉美罗下界值(CRLB)。     

基于动态T检验的修正最小二乘BFGS定位算法

针对传统基于接收信号强度指示RSSI(Received Signal Strength Indicator)的最小二乘定位算法精度有限的问题,从降低信号噪声影响出发,提出一种基于动态T检验的修正最小二乘-BFGS定位算法。在测距阶段,将T检验法动态应用于RSSI值筛选,以消除较大测量误差影响,提高测距精度;定位阶段,先基于平均测算距离对传统的最小二乘法进行修正,提升初步定位精度0.3~2米;在此基础上,以信号强度误差最小为目标优化函数,基于BFGS算法对修正最小二乘法计算的初值进行迭代求精,以进一步提高定位精度。仿真实验表明,该算法有效提升了定位精度,在100 m×100 m范围内可比传统最小二乘定位误差降低4~11米。     

基于改进支持向量回归算法的移动机器人定位

为了提高移动机器人定位精度,提出了一种基于正交编码器和陀螺仪的轮式移动机器人定位系统,建立机器人的定位模型和运动学模型。研究了支持向量回归（SVR）算法,为获得更好的鲁棒性,对目标函数误差平方进行加权,分析不同参数优化算法对支持向量机回归准确率的影响。以自制的移动机器人为实验平台,将改进的算法与最小二乘支持向量回归（LSSVR）算法、加权最小二乘支持向量回归（WLSSVR）算法进行比较,对比了用改进算法时机器人在木地板场地与瓷砖场地的定位误差情况,并对正交编码器+陀螺仪定位系统与双码盘定位系统、单码盘+陀螺仪定位系统进行比较。实验结果表明,改进的算法使机器人的定位精度明显高于对比算法,并且所提出的定位系统定位效果较好。     

WSNs中基于RSS的协作式节点定位算法

针对现有的测距技术准确性易受环境噪声影响的特点,在多维标度(MDS)分析法的基础上,结合加权最小二乘(WLS)法,加以改进,提出一种基于接收信号强度(RSS)的协作式定位算法-WLS-MDS.仿真实验结果表明:与MDS以及线性最小二乘(LLS)定位算法相比,所提算法在环境噪声干扰严重以及锚节点数目受限的极端条件下,仍然能够达到较为理想的定位精度,更加适合应用于实际的大规模无线传感器网络(WSNs).     

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).