二维离散余弦变换的一种新的快速算法

介绍了二维离散余弦变换的一种新的快速算法,对于N×N DCT(N=2~m),只需用N个一维DCT和若干加法运算,与常规的行—列法相比,所需的乘法运算量减少了一半,也比其它快速算法的乘法运算量要少,而加法运算量基本上是相同的。     

基于GS正交算法的信号检测方法

基于ＧＳ（Ｇｒａｍ－Ｓｃｈｍｉｄｔ）正文算法，推导出一个正交基范数阈值，据此阈值可在ＧＳ正交化过程中判定出信号矢量空间的维数，从面实现对信号源个数的检测。在此基础上，利用所获得的正交基构造一个信号矢量空间，并在此空间中定义了一个搜索画数来实现对信号方位的估计。这种方法的优点在于算法简单，运算量小，且特别适于大阵列的测向。计算机模拟结果也显示了本方法的良好检测效果。     

修正FTF算法用于高速数传快衰落信道自适应均衡的研究

短波高速数传是当前通信领域研究的一个重要方面,克服这类信道快衰落时变特性给数传带来的障碍是研究的中心课题.近些年提出和探讨的最小平方自适应均衡新技术,人们认为是解决这一问题的有效途径,普遍为人关注.本文对作者已提出的计算复杂度低、稳定性良好的修正 FTF 自适应均衡算法作了进一步研究.考查了其硬件实现方面的问题并模拟分析了均衡性能,初值选取,最佳级数和启动时训练与否的影响等,得出了许多有益的结论.这些分析与讨论对于硬件实现是十分必要的.     

自动化立体仓库中货位实时分配优化问题研究

本文研究了单元货格式自动化立体仓库中的货位实时分配问题。该问题可分为两方面：为入库分配空货位和为出库选择货位。在考虑了堆垛机的加减速对其运行速度的影响后,以堆垛机将要进行的所有操作的行程时间之和作为优化目标,通过调整堆垛机的后续操作的行程时间在总行程时间中的权重,依次构建了三个优化目标函数。然后利用结合了模拟退火方法的遗传算法对其进行了求解,并利用了多种技术提高算法的效率。最后利用仿真技术,通过改变仿真时系统中的货物类型总数、堆垛机的停留策略和装载能力,对该算法在不同情况下的效果进行了验证。仿真结果表明在不同情况下,该算法都可不同程度地减少堆垛机的平均行程时间。     

A latent Markov model for detecting patterns of criminal activity

Summary.  The paper investigates the problem of determining patterns of criminal behaviour from official criminal histories, concentrating on the variety and type of offending convictions. The analysis is carried out on the basis of a multivariate latent Markov model which allows for discrete covariates affecting the initial and the transition probabilities of the latent process. We also show some simplifications which reduce the number of parameters substantially; we include a Rasch-like parameterization of the conditional distribution of the response variables given the latent process and a constraint of partial homogeneity of the latent Markov chain. For the maximum likelihood estimation of the model we outline an EM algorithm based on recursions known in the hidden Markov literature, which make the estimation feasible also when the number of time occasions is large. Through this model, we analyse the conviction histories of a cohort of offenders who were born in England and Wales in 1953. The final model identifies five latent classes and specifies common transition probabilities for males and females between 5-year age periods, but with different initial probabilities.     

Generalized likelihood ratio tests for the structure of semiparametric additive models

Semiparametric additive models (SAMs) are very useful in multivariate nonparametric regression. In this paper, the authors study nonparametric testing problems for the nonparametric components of SAMs. Using the backfitting algorithm and the local polynomial smoothing technique, they extend to SAMs the generalized likelihood ratio tests of Fan &Jiang (2005). The authors show that the proposed tests possess the Wilks‐type property and that they can detect alternatives nearing the null hypothesis with a rate arbitrarily close to root‐n while error distributions are unspecified. They report simulations which demonstrate the Wilks phenomenon and the powers of their tests. They illustrate the performance of their approach by simulation and using the Boston housing data set.     

Publication bias and meta-analysis for 2×2 tables: an average Markov chain Monte Carlo EM algorithm

Summary. A major difficulty in meta-analysis is publication bias . Studies with positive outcomes are more likely to be published than studies reporting negative or inconclusive results. Correcting for this bias is not possible without making untestable assumptions. In this paper, a sensitivity analysis is discussed for the meta-analysis of 2×2 tables using exact conditional distributions. A Markov chain Monte Carlo EM algorithm is used to calculate maximum likelihood estimates. A rule for increasing the accuracy of estimation and automating the choice of the number of iterations is suggested.     

Semi-parametric estimation of disequilibrium models

This paper presents an easy-to-compute semi-parametric (SP) method to estimate a simple disequilibrium model proposed by Fair and Jaffee (1972). The proposed approach is based on a non-parametric interpretation of the EM (Expectation and Maximization) principle (Dempster et al; 1977) and the least squares method. The simple disequilibrium model includes the demand equation, the supply equation, and the condition that only the minimum of quantity demanded and quantity supplied is observed. The method used here allows one to consistently estimate the disequilibrium model without fully specifying the distribution of error terms in both demand and supply equations. Our Monte Carlo study suggests that the proposedestimator is better than the normal maximum likelihood estimator under asymmetric error distributions. and comparable to the nlaximunl likelihood estimator under synirnetric error distributions in finite samples. Aggregate U.S. labor market data from Quandt and Rosen (1988) is used to illustrate the procedure.     

Mixture separation for mixed-mode data

One possible approach to cluster analysis is the mixture maximum likelihood method, in which the data to be clustered are assumed to come from a finite mixture of populations. The method has been well developed, and much used, for the case of multivariate normal populations. Practical applications, however, often involve mixtures of categorical and continuous variables. Everitt (1988) and Everitt and Merette (1990) recently extended the normal model to deal with such data by incorporating the use of thresholds for the categorical variables. The computations involved in this model are so extensive, however, that it is only feasible for data containing very few categorical variables. In the present paper we consider an alternative model, known as the homogeneous Conditional Gaussian model in graphical modelling and as the location model in discriminant analysis. We extend this model to the finite mixture situation, obtain maximum likelihood estimates for the population parameters, and show that computation is feasible for an arbitrary number of variables. Some data sets are clustered by this method, and a small simulation study demonstrates characteristics of its performance.     

采用CORDIC算法的自适应抗干扰处理

自适应阵列处理技术因为能够大大提高电子系统的抗干扰能力、可靠性、分辨能力等重要指标而得到越来越广泛的应用。但其实时处理由于算法的巨大运算量而难以实现。ＣＯＲＤＩＣ算法具有将多种复杂函数的计算转变为统一的简单的移位加法操作，并适于ＶＬＳＩ硬件实现的特点，为人们设计既面向自适应抗干扰算法结构，又面向算法基本运算的ＶＬＳＩ专用阵列处理机来完成实时自适应抗干扰处理任务提供了新的途径。本文介绍ＣＯＲＤＩＣ算法的基本原理，并研究了ＱＲ分解最小二乘算法基于ＣＯＲＤＩＣ算法芯片的实现。