Improving Convergence of the HastingsMetropolis Algorithm with an Adaptive Proposal

The HastingsMetropolis algorithm is a general MCMC method for sampling from a density known up to a constant. Geometric convergence of this algorithm has been proved under conditions relative to the instrumental (or proposal) distribution. We present an inhomogeneous HastingsMetropolis algorithm for which the proposal density approximates the target density, as the number of iterations increases. The proposal density at the n th step is a non-parametric estimate of the density of the algorithm, and uses an increasing number of i.i.d. copies of the Markov chain. The resulting algorithm converges (in n ) geometrically faster than a HastingsMetropolis algorithm with any fixed proposal distribution. The case of a strictly positive density with compact support is presented first, then an extension to more general densities is given. We conclude by proposing a practical way of implementation for the algorithm, and illustrate it over simulated examples.     

两相交流伺服电机动态性能的研究

对于两相交流电机的速度伺服系统,分析在幅值控制时系统的机械特性与调节特性,提出了影响两相交流伺服电机动态性能的因素是系统的机械时间常数及增益系数的变化。为了防止因机械时间常数及增益系数的变化而引起的动态特性变差,采用一种简易跟随模型参考自适应控制方法,通过模型与自适应机构的调节作用,改善两相交流伺服电机系统的动态特性和控制精度。计算机仿真结果表明,电机的动态持性良好。     

CAS理论与高校德育

文章在简要介绍复杂适应系统 (CAS)理论的基础上 ,认为CAS理论对高校德育工作具有方法论意义 ;在CAS理论视野中 ,高校德育工作应该遵循如下五个基本原则 :主体原则、活力原则、整体涌现性原则、目的性原则和冲突化原则。     

关于藏族语文之现代化研究

影响藏族地区社会发展的原因是多方面的 ,其中藏汉双语教育和藏族语言文字能否实现现代化是重要的因素之一。我国藏文信息技术具有全方位、多次层处理藏文自然科学和社会科学的能力。     

语篇理解过程及其心理机制

从认知心理学、心理语言学角度讨论了语篇理解的过程及其心理机制。首先从命题、推断、局部与整体连贯三个层次上讨论了语篇理解的认知过程 ;然后从认知构件、认知理解模式对认知结构的模拟以及语篇处理过程中的资源限制三个维度论述了语篇理解的心理机制。文章最后指出 ,语篇理解研究的进一步深化取决于研究方法的改进和研究领域的拓展     

无锡市肉制品企业现状分析及发展对策研究

通过实地企业的调研及分析 ,阐述发展肉禽类加工的意义 ,探讨了无锡市肉禽类加工的现状 ,指出了肉禽类加工存在的主要问题 ,在此基础上 ,提出了无锡市肉禽类加工发展的对策。     

A Comparison of Partially Adaptive and Reweighted Least Squares Estimation

The small sample performance of least median of squares, reweighted least squares, least squares, least absolute deviations, and three partially adaptive estimators are compared using Monte Carlo simulations. Two data problems are addressed in the paper: (1) data generated from non-normal error distributions and (2) contaminated data. Breakdown plots are used to investigate the sensitivity of partially adaptive estimators to data contamination relative to RLS. One partially adaptive estimator performs especially well when the errors are skewed, while another partially adaptive estimator and RLS perform particularly well when the errors are extremely leptokur-totic. In comparison with RLS, partially adaptive estimators are only moderately effective in resisting data contamination; however, they outperform least squares and least absolute deviation estimators.     

Random variate transformations in the Gibbs sampler: issues of efficiency and convergence

In the non-conjugate Gibbs sampler, the required sampling from the full conditional densities needs the adoption of black-box sampling methods. Recent suggestions include rejection sampling, adaptive rejection sampling, generalized ratio of uniforms, and the Griddy-Gibbs sampler. This paper describes a general idea based on variate transformations which can be tailored in all the above methods and increase the Gibbs sampler efficiency. Moreover, a simple technique to assess convergence is suggested and illustrative examples are presented.     

以信息加工观点看待学习策略

学习策略是学习心理学研究的热点之一,许多学者对学习策略有不同的定义。信息加工的学习理论已成为研究学习心理学的主流。作者通过对学习策略的定义、认知策略的含义、元认知的内涵以及三者之间的关系的论述,试图以学习的信息加工观点来探讨学习策略的实质。     

一种改进的图像模糊增强法

基于医学图像对比度差以致正常组织和病态组织难以区分,本文在讨论了Pal.King模糊增强的基础上,对模糊算法进行了改进,改进后的模糊算法效果明显,能增强图像细微细节,提高图像的对比度,改善图像视觉效果,提高诊断的准确性。