一种稀疏度自适应的稀疏傅里叶变换算法

稀疏快速傅里叶变换需要信号以傅氏域的稀疏度为先验信息,但稀疏度通常是未知的,在一定程度上限制了算法的应用。为此,提出一种新的稀疏傅里叶变换算法。在下采样域进行能量检测,得到稀疏度的初始值,通过增大下采样维度提高稀疏度估计的准确性,从而近似估计稀疏度,设定阈值剔除冗余信息从而得到较好效果。实验结果表明,当信号长度大于219或稀疏度小于900时,该算法性能优于西方快速傅里叶变换,且具有较强的鲁棒性。     

一种快速线性时频变换方法

信号的频率含量在很多应用中是非常重要的,很多算法在这方面进行了研究。普通的S变换可以同时提供时间和频率信息,但需要的计算要求较高。本文介绍了一种线性时频变换方法,包括傅里叶变换（FT）、短时傅里叶变换（STFT）和S变换（ST）。它是一种离散的,可逆的,无冗余的变换算法,具有快速傅里叶变换（FFT）相同的计算复杂度。经过合理的调试和仿真,该方法有效地对非平稳信号频谱进行采样和加窗过滤,得到连续S变换频谱,说明在信号分析中具有可行性和适用性。     

基于VC＋＋的多路离散信号频谱分析系统

从快速傅里叶变换(FFT)的原理出发,利用VisualC 实现了"多路离散信号频谱分析系统"的研制与开发.该系统实现了快速傅里叶变换,多通道时域波形,幅值谱,互功率谱的绘制与显示.每通道1024点的离散信号来自于历史数据,以文本文件保存,文件的首行包含诸如采样点数、采样通道、采样周期等采样信息,自第二行起保存信号数据.频谱分析过程中,首先读取文本文件的数据,再时其进行分析与处理.     

基于稀疏傅里叶变换的低采样率宽带频谱感知

针对传统频谱感知方法应用于宽带频谱感知时存在采样率过高的现象,提出一种基于稀疏傅里叶变换的采用奈奎斯特采样进行宽带信号频谱感知的方法。该算法在频谱分布稀疏时具有极低的误判率,并在频谱占用率增加时,提出了改进的算法,最后利用MATLAB仿真验证了稀疏傅里叶变换用于宽带频谱感知方案的可行性。相比传统方法,本文的频谱感知方案需要的采样率仅为奈奎斯特采样率的20%。     

基于全相位频谱校正的TMBOC信号的捕获

针对使用传统部分匹配滤波器（PMF）结合快速傅里叶变换（FFT）无法精确捕获时分复用二进制偏移载波（TMBOC）调制信号的问题,提出一种基于全相位频谱校正的捕获方法。首先通过PMF过程对接收信号进行部分相关运算,再使用全相位快速傅里叶变换（apFFT）算法对多普勒效应进行补偿,最后结合全相位频谱校正技术对功率谱进行校正。仿真结果表明,在同一条件下,该算法比PMF-FFT加窗算法检测概率提高了3 dB左右,并有效缩短了捕获时间。该算法可比PMF-FFT加窗算法更精确捕获TMBOC信号。     

基于小波降噪的稀疏傅里叶变换时延估计

稀疏傅里叶变换时延估计具有较低的运算时间复杂度,但在低信噪比时无法准确估计出时延.针对稀疏傅里叶变换时延估计在噪声干扰下时延估计精度下降的缺点,提出了基于小波降噪的稀疏傅里叶变换时延估计算法.算法利用小波降噪方法处理接收到的信号,再对降噪后的信号进行稀疏傅里叶变换广义相关,通过检测相关函数的谱峰得到估算的时延值.实验仿真以及对实测数据的验证均表明,在低信噪比条件下,基于小波降噪的稀疏傅里叶变换时延估计算法在保证数据高处理速度的同时,具有较好的抗噪性以及较高的时延估值精确度.     

一种基于FFT计算离散小波变换的方法

将小波变换和快速傅里叶变换（FFT）方法相结合,分析研究了用快速傅里叶变换计算离散小波变换的方法,总结变换结果和滤波器长度之间的移位关系,并提出通过把输入信号信号循环移位,实现完全重构的方法。这种方法计算的时间复杂度和快速傅里叶变换相当。     

基于稀疏快速傅里叶变换的信号压缩处理

随着数据采集能力和采样频率的不断提高,采用传统的奈奎斯特采样定理会获得海量的数据,这给信号的存储和传递带来了极大挑战。提出基于稀疏快速傅里叶变换的信号压缩方法,利用信号在频域的稀疏性,压缩信号所需的存储空间,在保证拥有足够小的误码率的前提下,以高概率重构原始信号。     

一种三维快速傅里叶变换并行算法

三维快速傅里叶变换在物理计算领域中被广泛地使用.传统并行算法所使用的面划分和块划分方法并不适合稀疏三维向量的傅里叶变换.提出了一种新三维快速傅里叶变换的并行算法,针对稀疏三维向量的傅里叶变换,新算法通过重新调整x,Y,z三个方向的计算顺序,能最大限度地减少计算量以及进程间的通信量,从而减少计算时间,提高并行加速比.详尽的理论分析以及多个高性能计算平台上的实验结果证明:在对稀疏三维向量作傅里叶变换时,新算法优于传统算法.     

基于噪声倒谱阈值频谱估计的语音活动检测

针对低方差频谱估计的语音活动检测(VAD)中Welch频谱估计方法计算量大的问题,提出利用倒谱阈值方法估计VAD中的噪声功率谱.该方法在静音时期为噪声的倒谱设置阈值,利用快速傅里叶变换计算频谱,再更新VAD中的判决阈值.算法复杂度分析与仿真结果表明,该方法的检测性能与Welch方法相当,计算量降低约18%,同时降低整个...     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

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。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

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.