小波变换的语音去噪方法

提出一种改进的语音去噪处理方法：二次小波分解全局阈值法。该方法不同于传统阈值滤波方法,首先对语音信号的高频部分进行二次分解,然后应用阈值滤波的方法对信号进行去噪处理。该方法在MATLAB上进行了模拟实验,实验结果表明该方法提高了信噪比,去除了大部分噪声,相当完整地保留了有效信号能量,很好地解决噪声对语音信号干扰的问题。     

最大类间方差法在寻北仪信号降噪中的应用

在分析了陀螺噪声信号的特点以及现有去除陀螺噪声方法的基础上,将最大类间方差法应用到陀螺寻北仪输出信号的滤波处理中,从而有效地减小了信号中的高频噪声,提高了信噪比,抑制了陀螺仪的漂移.介绍了该方法的原理与实现过程,并结合陀螺寻北仪的实地振动实验,对陀螺寻北仪的实测数据进行了分析研究,证明了使用该方法对陀螺寻北仪输出信号进行滤波处理的可行性和有效性.     

心电图中滤除基线漂移的研究

介绍了一种利用中值滤波器来滤除信号中基线漂移的方法。由于中值滤波器是一种非线性信号处理方法,具有计算简单,处理速度快的特点,从而能在有效抑制基线漂移噪声的情况下,提高整体的运算速度。采用MIT-BIH数据库中的心电数据对该方法进行检验,结果显示该方法能很好地滤除ECG中的基线漂移噪声,同时将该方法与常用的两种方法进行实时性比较,实验结果表明该方法在确保信号不失真的情况下,提高了系统的运算速度。     

基于Transformer的汽轮机滚动轴承早期微弱故障检测方法研究

为了应对滚动轴承早期微弱故障的挑战本文提出了一种新的方法。该方法首先采用PCA（主成分分析）对振动信号进行特征筛选，以降低数据维度，有效地简化了振动数据的结构，增强了特征的表达力。接着，使用CEEMDAN（完全自适应噪声集合经验模态分解）算法来分解被背景噪声干扰的微弱故障振动信号，它通过在经验模态分解（EMD）的基础上引入自适应噪声，增强了对微弱特征的识别能力，有够效地分离出趋势和噪声数据，显著提高了故障诊断的准确性。最后，引入Transformer模型，进一步优化了特征的提取和表征，实现对长序列数据的高效处理，用于微弱故障特征的提取和表征。这一综合方法具有降维、噪声抑制和长序列处理等多重优势，有望在滚动轴承故障检测中取得显著成果。     

改进CEEMDAN-小波包阈值降噪在旋转机械轴承中的应用

针对旋转机械滚动轴承振动加速度信号在采集过程中存在大量噪声导致振动信号表征不明显的问题，提出了一种在对自适应噪声完备集合经验模态分解(CEEMDAN)进行改进的基础上与小波包阈值降噪联合的一种数据去噪方法。首先，通过计算分解后得到的各分量的均方根和互相关系数对与原始信号相关性较大的分量进行提取；然后，分别计算提取后每个分量对应的阈值进行小波包阈值降噪处理；最后，将处理后的信号与分量中不存在噪声的分量进行叠加，即为降噪后的信号。经过对比实验验证，改进CEEMDAN-小波包阈值降噪方法的信噪比最大提高6.41,均方根误差降低0.12,证明了本方法的有效性。     

一种新的未知雷达辐射源聚类分选方法

未知雷达信号的分选一直是雷达对抗情报处理中的难题。因此,提出了一种新的基于数据势场聚类的未知雷达信号分选方法。该方法无需预先指定分类数,利用信号参数之间的关联性自动进行聚类,以此达到分选的效果。同时方法适宜于处理大量数据,对噪声影响不敏感,无需先验知识支撑。最后,通过计算机仿真验证了该方法的可行性和有效性。     

基于EMD阈值算法的脉冲涡流信号消噪

针对脉冲涡流信号夹杂着较多的高频噪声,提出了一种新的经验模态分解阈值消噪算法。首先将信号分解为多个本征模态函数（Intrinsic Mode Function,IMF）,对信噪比低的高频IMF进行减小噪声能量处理后得到重组信号;再对重组信号进行EMD分解后根据白噪声统计特性对IMF筛选,对噪声含量多的IMF进行小波阈值消噪;最后将处理过的IMF与噪声含量少的IMF重构得到消噪后的信号。实验仿真的结果和数据表明,该方法可以减少失真,获得更高的信噪比,能够较好地消除噪声的干扰恢复出原始的信号。     

一种基于模糊逻辑的数字信号滤波方法

提出了一种用模糊逻辑推理对数字信号进行滤波的方法.根据带有噪声信号的特性,通过比较该信号与其前、后几个信号的差异,再运用模糊逻辑推理规则,就可以判断出该信号是否带有噪声,并对其进行处理.通过实验说明:该方法可以滤除信号中带有的脉冲噪声和同分布噪声,方法简单,结果满意.     

基于三维曲波变换的弱信号恢复方法研究

传统的弱信号恢复方法在强噪声背景下具有较大的局限性,有用的信息往往淹没在强噪声背景下不易被识别。针对这个难点,提出一种基于三维曲波变换的弱信号恢复的方法。该方法将三维曲波变换和自适应滤波器相融合,从而提高数据中弱信号的能量,使得弱信号更易于被恢复。为了验证该方法的有效性,对楔形模型与实际三维数据进行处理。实验结果表明,恢复后的数据信噪比提高了2 dB到3 dB,频带也被拓宽了150 Hz,弱信号得到较好的恢复。     

火箭飞行实时测量数据的小波滤波快速算法

为充分实现火箭飞行实时测量数据的实时处理功能，结合弹道处理的实际，给出了一种基于小波方法的实时信号所包含噪声的在线快速识别算法，该算法原理简捷，易实现，计算复杂度较低，其时间复杂性为O(1)；分析了用于火箭飞行测量数据消噪的小波及其闽值的选取原则，通过对雷达跟踪测量数据的实际分析和处理，就数据是否处于火箭在级间分离段提出了不同的处理方法，实践证明无论是滤波后信号的残留噪声还是消耗的时间上小波方法都优于α-β-γ滤波，且实现了数据的实时处理功能，充分满足了实时性要求。     

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).