Perfect simulation of conditionally specified models

We discuss how the ideas of producing perfect simulations based on coupling from the past for finite state space models naturally extend to multivariate distributions with infinite or uncountable state spaces such as auto-gamma, auto-Poisson and autonegative binomial models, using Gibbs sampling in combination with sandwiching methods originally introduced for perfect simulation of point processes.     

度约束欧氏Steiner最小树问题及其求解

在欧氏Steiner最小树的基础上，对每个正则点加上了度约束限制，提出了度约束欧氏Steiner最小树问题，分析了该问题的特性，给出了该问题的模拟退火和蚂蚁算法求解过程，并使用Delphi语言编程，在Windows XP平台上运行通过．通过大量算例的计算结果验证了该问题的实用性及算法的有效性．     

混合威布尔分布参数估计的L-M算法

混合威布尔分布模型常用来分析具有多种失效模式的机械系统或零部件的可靠性寿命数据,为提高混合威布尔分布未知参数估计的精度,利用非线性最小二乘理论,建立了小子样条件下两重混合威布尔分布参数优化估计模型,将L-M算法用于优化求解。以概率图参数估计法的结果作为迭代初始值,提高了迭代求解的速度。计算实例表明利用该方法估计混合威布尔分布参数是可行的,而且能够获得较精确的结果。     

混合遗传算法在矩形板材下料问题上的应用研究

根据基本遗传算法在解决板材下料优化中存在的问题,提出了将局部搜索算法和遗传算法相结合,取各自的优点来更好地解决矩形板材下料优化问题.     

基于数据挖掘的入侵检测系统研究

文章基于数据挖掘技术,针对当前入侵检测系统的不足,把数据挖掘技术应用到入侵检测系统中,并给出系统模型,论证了这种模型的理论价值和现实可行性.     

A three-state disease model with interval-censored data: Estimation and applications to AIDS and cancer

In presence of interval-censored data, we propose a general three-state disease model with covariates. Such data can arise, for example, in epidemiologic studies of infectious disease where both the times of infection and disease onset are not directly observed, or in cancer studies where the time of disease metastasis is known up to a specified interval. The proposed model allows the distributions of the transition times between states to depend on covariates and the time in the previous state. An estimation procedure for the underlying distributions and the model coefficients is suggested with the EM algorithm. The EMS algorithm (Smoothed EM algorithm) is also considered to obtain smooth estimates of the distributions. The proposed method is illustrated with data from an AIDS study and a study of patients with malignant melanoma.     

求解QoS组播路由问题的改进蚂蚁算法

蚂蚁算法是一种相对较新的启发式方法，通过模拟蚂蚁的觅食行为，提出了求解QoS组播路由问题的改进蚂蚁算法。仿真实验表明，该算法能以较高速度收敛，有效地解决QoS组播路由问题。     

搜索引擎安全性的思考

搜索引擎的安全性问题是网络安全问题的一种。本文首先分析了搜索引擎所产生的安全性漏洞并针对这些漏洞提出了技术对策。随后,文章着重探讨了搜索引擎安全性引发的网络安全对道德建设的挑战及其应对措施。     

INCOMPLETE DATA IN GENERALIZED LINEAR MODELS WITH CONTINUOUS COVARIATES

This paper proposes a method for estimating the parameters in a generalized linear model with missing covariates. The missing covariates are assumed to come from a continuous distribution, and are assumed to be missing at random. In particular, Gaussian quadrature methods are used on the E-step of the EM algorithm, leading to an approximate EM algorithm. The parameters are then estimated using the weighted EM procedure given in Ibrahim (1990). This approximate EM procedure leads to approximate maximum likelihood estimates, whose standard errors and asymptotic properties are given. The proposed procedure is illustrated on a data set.     

Conditioning of Marked Point Processes within a Bayesian Framework

Shale units with low permeability create barriers to fluid flow in a sandstone reservoir. A spatial stochastic model for the location of shale units in a reservoir is defined. The model is based on a marked point process formulation, where the marks are parameterized by random functions for the shape of a shale unit. This extends the traditional formulation in the sense that conditioning on the actual observations of the shale units is allowed in an arbitrary number of wells penetrating the reservoir. The marked point process for the shale units includes spatial interaction of units and allows a random number of units to be present. The model is defined in a Bayesian setting with prior pdfs assigned to size–shape parameters of shale units. The observations of shales in wells are associated with a likelihood function. The posterior pdf of the marked point process can only partially be developed analytically; the final solution must be determined by sampling using the Metropolis–Hastings algorithm. An example is presented, demonstrating the consequences of increasing the number of wells in which observations are made.