我国电子商务发展的制约因素及应对策略

电子商务正取得日新月异的发展 ,以网络化、知识管理、全球化为主要特征的新经济已成为不可逆转的趋势。在分析了制约我国电子商务发展的各因素后 ,我们应从加强网络基础设施建设 ,完善电子商务的法律环境及物流配送系统等方面 ,为我国电子商务的发展创造良好的宏观环境 ;与此同时 ,通过转变企业观念 ,构建企业自身网络基础设施 ,促进企业积极参与电子商务     

On the Convergence of the Monte Carlo Maximum Likelihood Method for Latent Variable Models

While much used in practice, latent variable models raise challenging estimation problems due to the intractability of their likelihood. Monte Carlo maximum likelihood (MCML), as proposed by Geyer & Thompson (1992 ), is a simulation-based approach to maximum likelihood approximation applicable to general latent variable models. MCML can be described as an importance sampling method in which the likelihood ratio is approximated by Monte Carlo averages of importance ratios simulated from the complete data model corresponding to an arbitrary value of the unknown parameter. This paper studies the asymptotic (in the number of observations) performance of the MCML method in the case of latent variable models with independent observations. This is in contrast with previous works on the same topic which only considered conditional convergence to the maximum likelihood estimator, for a fixed set of observations. A first important result is that when is fixed, the MCML method can only be consistent if the number of simulations grows exponentially fast with the number of observations. If on the other hand, is obtained from a consistent sequence of estimates of the unknown parameter, then the requirements on the number of simulations are shown to be much weaker.     

Statistical and Combinatorial Aspects of Comparative Genomics*

Abstract. This document presents a survey of the statistical and combinatorial aspects of four areas of comparative genomics: gene order based measures of evolutionary distances between species, construction of phylogenetic trees, detection of horizontal transfer of genes, and detection of ancient whole genome duplications.     

左思风力之成因初探

西晋诗人左思的诗风在西晋文坛上独树一帜，称之为“左思风力”，前人对此有较多地论述，然而就诗风形成的原因却缺乏深入地探究。本文试图从社会时代背景、家庭因素、性格特征三个方面对此加以分析，旨在能够更好地把握左思其人及其诗风。     

The analysis of incomplete data using stochastic covariates

In the development of many diseases there are often associated random variables which continuously reflect the progress of a subject towards the final expression of the disease (failure). At any given time these processes, which we call stochastic covariates, may provide information about the current hazard and the remaining time to failure. Likewise, in situations when the specific times of key prior events are not known, such as the time of onset of an occult tumour or the time of infection with HIV-1, it may be possible to identify a stochastic covariate which reveals, indirectly, when the event of interest occurred. The analysis of carcinogenicity trials which involve occult tumours is usually based on the time of death or sacrifice and an indicator of tumour presence for each animal in the experiment. However, the size of an occult tumour observed at the endpoint represents data concerning tumour development which may convey additional information concerning both the tumour incidence rate and the rate of death to which tumour-bearing animals are subject. We develop a stochastic model for tumour growth and suggest different ways in which the effect of this growth on the hazard of failure might be modelled. Using a combined model for tumour growth and additive competing risks of death, we show that if this tumour size information is used, assumptions concerning tumour lethality, the context of observation or multiple sacrifice times are no longer necessary in order to estimate the tumour incidence rate. Parametric estimation based on the method of maximum likelihood is outlined and is applied to simulated data from the combined model. The results of this limited study confirm that use of the stochastic covariate tumour size results in more precise estimation of the incidence rate for occult tumours.     

文艺复兴与天主教

资产阶级的新文化运动文艺复兴与封建主义意识形态的主要代表天主教之间 ,由于社会现实的巨大变化和诸多的文化因素 ,不仅有对立和抗争 ,而且有传承乃至合作 ,不仅有变异而且有遗传 ,不仅有本质差别 ,而且有血脉相连     

Breaking the intergenerational transmission of child abuse: Beyond the mother-child relationship

Studies comparing abusive and non-abusive parents who were abused as children are reviewed to determine protective factors that may lead to a break in the transmission pattern. Non-abusers have several factors in common. For instance: they have extensive emotional and social support from significant others. they are aware of what happened to them as children and are openly angry about their abuse. and many of them received (psycho)therapy as adolescents or young adults. Discovering protective factors by which some parents overcome a family pattern of abuse is valuable in guiding both prevention and intervention efforts. A brief discussion of the influence of methodological variations of different studies on reported transmission rates precedes the review. Furthermore. attention is given to the underrepresentation of (abusive) fathers in theory as well as in research on child abuse. The effects of undervaluation of gender differences are discussed in terms of their importance in the occurrence and (breaks in the) transmission of child abuse.     

影响分析化学实验结果因素的探讨

本文探讨了影响分析化学实验结果的因素，指出溶液的酸度、试剂的浓度，用量、加入顺序和溶剂等都对分析实验的结果产生影响，并分析了其原因。     

丹东民营经济发展实证分析

本文从丹东民营经济现状出发,在深入实际调查研究基础上,对相关数据进行筛选、分类、加工、整理,系统分析丹东民营经济的运行过程,从中找出丹东民营经济发展中存在的问题及形成原因。同时,通过对丹东地区经济发展的内外环境变化趋势的预测,并结合地方社会、经济、文化等方面的实际,制定丹东民营经济在今后一段时间内的发展目标,提出具有较强针对性和可操作性的对策建议,以期使丹东民营经济再上一个新的台阶。     

浅析影响大学生英语自主学习能力的因素

本文对影响大学生英语自主学习能力的相关因素加以分析。