基于VAR模型的沪深股市基金指数的实证分析

以沪深股市基金指数为研究对象,通过向量自回归(VAR)模型、协整分析、向量误差修正模型(VECM)以及方差分解来检验两者之间的内在关系。结果表明,上证基金指数和深证基金指数对信息的反应不是非常一致,它们相互影响,且存在着长期均衡关系,上证基金指数引导着深证基金指数,深证基金指数在一定程度上反过来影响着上证基金指数。     

有源电力滤波器中空间矢量脉宽调制模块的仿真研究

介绍了空间矢量脉宽调制(SVPWM)的基本原理,提出了在Matlab/Simulink环境下用S函数实现空间矢量脉宽调制模块的方法,描述了仿真模型的设计过程和编程要点,并将其应用到有源电力滤波器的仿真系统中。给出了仿真结果,为基于SVPWM的有源电力滤波器的研究打下了基础。     

基于SVPWM的无速度传感器矢量控制的研究

通过介绍空间电压矢量脉宽调制(SVPWM)控制策略在无速度传感器矢量控制系统中的实现,在此基础上给出了基于DSP的全数字化调速系统,并分别建立了改进的电压型转子磁链观测模型和PI自适应速度估算模型。实验结果表明:所采用的控制方法正确可行,控制系统具有良好的性能。     

Re-examining the effects of adding relevance information in a relevance feedback environment

This paper presents an investigation about how to automatically formulate effective queries using full or partial relevance information (i.e., the terms that are in relevant documents) in the context of relevance feedback (RF). The effects of adding relevance information in the RF environment are studied via controlled experiments. The conditions of these controlled experiments are formalized into a set of assumptions that form the framework of our study. This framework is called idealized relevance feedback (IRF) framework. In our IRF settings, we confirm the previous findings of relevance feedback studies. In addition, our experiments show that better retrieval effectiveness can be obtained when (i) we normalize the term weights by their ranks, (ii) we select weighted terms in the top K retrieved documents, (iii) we include terms in the initial title queries, and (iv) we use the best query sizes for each topic instead of the average best query size where they produce at most five percentage points improvement in the mean average precision (MAP) value. We have also achieved a new level of retrieval effectiveness which is about 55–60% MAP instead of 40+% in the previous findings. This new level of retrieval effectiveness was found to be similar to a level using a TREC ad hoc test collection that is about double the number of documents in the TREC-3 test collection used in previous works.     

Enhancing web page classification through image-block importance analysis

We present a term weighting approach for improving web page classification, based on the assumption that the images of a web page are those elements which mainly attract the attention of the user. This assumption implies that the text contained in the visual block in which an image is located, called image-block, should contain significant information about the page contents. In this paper we propose a new metric, called the Inverse Term Importance Metric, aimed at assigning higher weights to important terms contained into important image-blocks identified by performing a visual layout analysis. We propose different methods to estimate the visual image-blocks importance, to smooth the term weight according to the importance of the blocks in which the term is located. The traditional TFxIDF model is modified accordingly and used in the classification task. The effectiveness of this new metric and the proposed block evaluation methods have been validated using different classification algorithms.     

New predictive control algorithms based on Least Squares Support Vector Machines

INTRODUCTION Model predictive control (MPC), based on pre-dictive model and receding horizon optimization, has become an attractive feedback control strategy, be-cause it has found successful applications, especially in the process industry. For this kind of control strategy, the predictive model is a crucial component because the essence of MPC is to optimize the fore-cast of process behavior (Rawlings, 2000), and the forecast is accomplished with the predictive model. If the controll…     

基于DSP的感应电动机矢量控制系统的设计

本文从矢量控制原理入手详细介绍了基于DSP的感应电动机矢量控制系统的软硬件组成及设计方案。系统采用数字信号处理器TMS320F240使硬件结构大为简化,可实现感应电动机的单片控制。实验结果证实了该方案设计是可行有效的,易于工程实现。     

镜对称及矢势的简单推导

对于某些电流分布与磁场分布,本文应用镜对称操作原理及Ｓｔｏｋｅｓ定理简单推导其矢势Ａ→。     

浅析贝叶斯分类方法在手机垃圾短信过滤系统中的应用

论述了贝叶斯分类方法在手机垃圾短信过滤系统中的应用,利用该方法对短信内容进行分类识别,从而实现对垃圾短信的有效过滤,最后对贝叶斯分类模型进行了结果分析与评估,证明该分类模型具有一定的现实可行性和可扩展性。     

线性变换的幂零性

幂零的线性变换是一类较为特殊的线性变换.本文介绍了幂零的线性变换一些性质、线性变换的幂零性与矩阵的幂零性关系以及幂零矩阵的一个应用.