法庭语音比对中话者自身变化性建模方法研究

针对法庭说话人识别中待鉴定人员语音样本不足的问题,提出了一种新的对说话人自身变化性建模的替代性方法以及相应的方差控制算法。使用同条件下的参考数据库构建识别系统的多个相同说话人得分模型,代替检验需要的多个非同期的带检验人员语音样本比较时的得分模型,以获得能反映说话人自身变化性的统计模型。基于目前最新的法庭证据评估的似然比证据强度评估体系,使用MFCC（Mel Frequency Cepstral Coefficients）和GFCC（Gammatone Frequency Cepstral Coefficients）特征对该方法的有效性进行了验证,并对上述特征进行了特征级和决策级融合。实验结果表明：该方法在纯净语音环境和噪声环境下都具有很高的识别率和稳定性,并且特征级融合能进一步提高识别系统的性能。     

一种基于共振峰恢复和Ｍellin变换的非特定人语音特征提取方法

针对非特定人语音识别中的声道长度归一化问题,首先研究一种能够去牛基音激励的,基于自相关估计的共振峰（Ｆormart) 频谱恢复方法,说明了不同说话人发同一元音时的频谱互为尺度化的关系,以及它们与同一说话人发不同元音时频谱的差别,然后结合具有尺度不变性的Ｍellin变换,提出了一种适用于非特定人的语音特征提取方法,在实难中,对从非特定人收集的２０个汉语元音,分别提取了其ＦＦＴ倒谱,Ｍel倒谱,ＦＦＴ－Ｍellin倒谱及本文Ｆormant-Mellin倒谱,并用一种很直观的Ｆ－roato分辨率准则进行了性能评价,结果表明,无论是对纯净的,还是对带附加白噪声的发音样本,本文由共振峰恢复和Ｍellin变换相结合得到的语音特征都具有较高的分辨率。     

基于MFCC和BP神经网络的说话人识别研究

介绍了语音的美尔倒谱特征及提取算法,并提取语音段的美尔倒谱特征,建立BP神经网络,用Matlab进行仿真识别,表明能较好的实现连续语音的说话人识别。     

一种基于正弦激励的线性预测模型的语音转换方法

在正弦激励模型的线性预测(LP)残差转换的基础上,提出了一种改进语音特征转换性能的语音转换方法.基于线性预测分析和综合的构架,该方法一方面通过谱包络估计声码器提取源说话人的线性预测编码(LPC)倒谱包络,并使用双线性变换函数实现倒谱包络的转换;另一方面由谐波正弦模型对线性预测残差信号建模和分解,采用基音频率变换将源说话人的残差信号转换为近似目标说话人的残差信号.最后由修正后的残差信号激励时变滤波器得到转换语音,滤波器参数通过转换得到的LPC倒谱包络实时更新.实验结果表明,该方法在主观和客观测试中都具有良好的结果,能有效地转换说话人声音特征,获得高相似度的转换语音.     

基于加权Mel倒谱系数的说话人识别

说话人识别中的首要问题是从语音信号中提取能唯一表现说话人个性特征的有效而稳定可靠的特征参数.把感知加权技术应用到Mel倒谱分析中,通过对基于心理声学模型计算得到的信号掩蔽比插值获得权重函数,并将权重函数应用到Mel倒谱分析中获得加权Mel倒谱系数(WMCEP),以此为特征进行说话人识别.实验结果表明,WMCEP比MFCC和Mel倒谱系数(MCEP)能更好地逼近说话人的谱包络,在噪声环境下的鲁棒性更好,因此其识别性能要优于MFCC和MCEP.     

复杂环境下的说话人识别

支持向量机是统计学习理论的一个重要学习方法,它是专门针对小样本的;N维Mel倒谱系数和能较好的表征说话人特征。该文使用支持向量机和Mel倒谱特征和建立了一个文本无关的说话人识别系统,并且该系统不受说话人情绪影响。实验表明该系统对说话人识别有很强的适应性。     

基于语音结构化模型的数字语音识别

提出一种新的基于语音结构化模型的语音识别方法,并应用于非特定人数字语音识别.每一个数字语音计算倒谱特征之后提取语音中存在的对说话人差异具有不变性的结构化特征——全局声学结构(acoustical universal structure,AUS),并建立结构化模型,识别时提取测试语音的全局声学结构,然后与各数字语音的结构化模型进行匹配.测试了少量语料训练下的识别性能并与传统HMM (hidden Markov model)方法进行比较,结果表明该方法可以取得优于HMM的性能,语音结构化模型可以有效消除说话人之间的差异.     

基于发声机理与人耳感知特性的说话人识别

Mel频率倒谱系数（MFCC）与线性预测倒谱系数（LPCC）融合算法只能反映语音静态特征,且LPCC对语音低频局部特征描述不足。为此,提出将希尔伯特黄变换（HHT）倒谱系数与相对光谱一感知线性预测倒谱系数（RASTA—PLPCC）融合,得到一种既反映发声机理又体现人耳感知特性的说话人识别算法。HHT倒谱系数体现发声机理,能反映语音动态特性,并更好地描述信号低频局部特征,可改进LPCC的不足。PLPCC体现人耳感知特性,识别性能强于MFCC,用3种融合算法对两者进行融合,将融合特征用于高斯混合模型进行说话人识别。仿真实验结果表明,该融合算法较已有的MFCC与LPCC融合算法识别率提高了8．0％。     

基于基频的情感语音聚类的说话人识别方法

针对存在情感差异性语音情况下说话人识别系统性能急剧下降以及缺乏充足情感语音训练说话人模型的问题,提出一种基于基频的情感语音聚类的说话人识别方法,能有效利用系统可获取的少量情感语音.该方法通过对男女说话人设定不同的基频阈值,根据阈值,对倒谱特征进行聚类,为每个说话人建立不同基频区间的模型.在特征匹配时,选用最大似然度的基频区间模型的得分作为该说话人的得分.在中文情感语音库上的测试结果表明,与传统的基于中性训练语音的高斯混合模型说话人识别方法和结构化训练方法相比,该方法具有更高的识别率.     

基于HHT倒谱系数的说话人识别算法

针对LPCC只反应语音静态特征且不能突出其低频局部特征问题,提出一种以HHT倒谱系数为特征的说话人识别算法,HHT的经验模态分解使语音的低频局部特征得到更好的描述,Hilbert变换能够刻画语音动态特性,改进了LPCC的不足。用经验模态分解将语音分解为一系列固有模态函数分量并做Hilbert变换求得Hilbert边际谱,计算总边际谱的对数功率谱并做DCT得13维倒谱系数,将此特征送入高斯混合模型进行说话人识别。仿真实验结果表明,基于HHT倒谱系数的说话人识别算法,相较LPCC识别率提高了12.59%,但特征提取时间增加了19.27 s。     

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).