Comparisons of Three Approaches for Discrete Conditional Models

This article describes three methods for computing a discrete joint density from full conditional densities. They are the Gibbs sampler, a hybrid method, and an interaction-based method. The hybrid method uses the iterative proportional fitting algorithm, and it is derived from the mixed parameterization of a contingency table. The interaction-based approach is derived from the canonical parameters, while the Gibbs sampler can be regarded as based on the mean parameters. In short, different approaches are motivated by different parameterizations. The setting of a bivariate conditionally specified distribution is used as the premise for comparing the numerical accuracy of the three methods. Detailed comparisons of marginal distributions, odds ratios and expected values are reported. We give theoretical justifications as to why the hybrid method produces better approximation than the Gibbs sampler. Generalizations to more than two variables are discussed. In practice, Gibbs sampler has certain advantages: it is conceptually easy to understand and there are many software tools available. Nevertheless, the hybrid method and the interaction-based method are accurate and simple alternatives when the Gibbs sampler results in a slowly mixing chain and requires substantial simulation efforts.     

A New Inference Framework for Dependency Networks

Dependency networks (DNs) have been receiving more attention recently because their structures and parameters can be easily learned from data. The full conditional distributions (FCDs) are known conditions of DNs. Gibbs sampling is currently the most popular inference method on DNs. However, sampling methods converge slowly and it can be hard to diagnose their convergence. In this article, we introduce a set of linear equations to describe the relations between joint probability distributions (JPDs) and FCDs. These equations provide a novel perspective to understand reasoning on DNs. Based on these linear equations, we develop both exact and approximate algorithms for inference on DNs. Experiments show that the proposed approximate algorithms can produce effective results by maintaining low computational complexity.     

中国流动人口通婚圈研究——基于流动人口动态监测数据的实证分析

改革开放以来,随着人口迁移流动的发展,人们的社会交际圈子迅速扩大,大规模的人口迁移流动对社会以及流动人口自身都产生了多方面的影响,其中对其婚恋行为的影响是一个值得研究的重要领域,但目前学界和政府对此关心仍然不够。文章使用2013年国家卫计委流动人口动态监测数据,运用二元Logistic回归分析方法对流动人口通婚圈研究发现：除流动人口的年龄、性别、户口和受教育程度等基本特征外,迁移流动行为也与通婚圈扩展具有显著的相关性。在流入地的居留时间、迁移流动地域范围和相对结婚时间都与跨省通婚有关,地理通婚圈扩展是社会良性发展的标志,但也不能忽视通婚圈扩展所带来的一些新问题和挑战。     

贫困落后地区积累贫困的经济运行机制分析

贫困落后地区的经济运行是以劳动力长边最大限度地替代资本 (技术 )短边 ,超强度地开发土地资源维系的。生态环境的不断恶化 ,迫使这些地区投入更多的劳动力 ,从而形成了长边扩展难以遏止的恶性循环。扶贫战略与区域经济增长战略不仅在战略实施时所处的发展阶段不同 ,而且实施战略的目标及资源配置流向也不同 ,不能以集中投资的工业化战略来代替扶贫战略。可将国家的各种转移支付和政策性贷款集中投资于社会基础设施建设上 ,提供贫困成员改善生产基础条件和环境条件所需的资金、技术方面的支援 ,加强贫困地区的基础教育。扶贫战略是一项长期的战略 ,它不是一场运动 ,更不是创造“政绩”工程     

论“首都经济圈”建设

"首都经济圈"战略是"十二五"时期国家区域发展总体战略的重要组成部分。本文借鉴东京都市圈、巴黎都市圈等国际知名"首都圈"发展战略,分析"首都经济圈"建设对于北京和周边区域及我国发展的战略意义,明确"首都经济圈"范围界定的原则、具体范围、圈层划分及各个城市的职能分工,提出打造"首都经济圈"应以保障首都功能实现、提升区域创新能力为核心和统领,抓住四大战略重点,即明确经济圈的核心功能、创新区域合作的体制机制、推动基础设施一体化建设、强化生态环境建设和绿色发展。     

白银生产与拉丁美洲的依附性现代化——以安第斯地区为例

白银生产是殖民地美洲最重要的经济活动之一,对整个地区的经济、社会和政治生活都起着重要的主导作用."白银经济圈"的形成和发展,不仅对拉丁美洲内部殖民地经济造成了重要影响,而且是不平等世界分工形成的一个重要条件.文章以安第斯白银产区为例,分析白银生产对拉丁美洲社会经济发展造成的严重后果,探讨拉美后来依附性发展的早期症结所在.白银生产和安第斯地区社会经济的变化发展过程,突出反映了拉丁美洲沦为欠发达地区的过程.白银生产是拉美依附性现代化形成的重要根源之一.     

试析美国《同心圆》年刊诗歌的创作风格

美国当代诗歌、散文年刊<同心圆>(Full Circle)刊载了美国、中国、巴西、肯尼亚等国学者和诗人的作品.充满了民主、博爱的进步思想,而且形成了一种独特的审美创作风格:从于心,秀于笔,追求仁与美的统一境界;以当代生活为素材,体现时代精神的律动;采取日常生活的语言,创造透明清新的风格.     

An iterative procedure for robust circle fitting

The problem of fitting circles and circular arcs to observed points arises in many areas of science. However, the fitting results by using most geometric and algebraic methods are not usually acceptable in the presence of outliers. An iterative procedure for robust circle fitting is proposed. During the iteration, Taubin's method is employed to obtain the center and radius. And then the geometric distances from the data points to the circle are computed, with which outliers are identified and removed. Numerical examples demonstrate that the proposed iterative procedure can alleviate the corrupted effect of outliers on the circle parameter estimates.     

圆文化性别色彩辨析

圆文化是中国传统文化的一个重要内容。从文化人类学的角度进行考察,圆与女性之间存在着一种神秘的文化联系。作为一个社会性属概念,圆是女性的空间象征符号,是远古时期大母神"子宫崇拜"的结果。圆文化浓厚的性别文化色彩直接影响了中国哲学上的圆道观以及圆美意识,且渗透在了传统文化的各个层面。     

民间组织在破解农民“种植怪圈”中的作用——以山东大白菜种植为例

农民不按照市场需求及规律决定种植选择,看到别人种植什么也跟着种植什么,在下一个收获季节增产却不增收,出现“种植怪圈”。导致“种植怪圈”的原因很多,最主要的是农民缺乏准确及时的信息引导,盲目种植,从而造成市场大起大落。政府应该加强宏观调控,做好生产形势调研和市场预测分析,及时发布指导意见,引导农民合理安排种植,减少农业生产的盲目性,确保市场均衡供应,但面对市场,政府的作用和力量是有限的,需要民间组织等社会力量共同参与。政府鼓励、引导和规范民间组织扩大农业服务领域和范围,把产前、产中和产后三个环节有机连接起来,提高农业组织化程度,增强农产品市场竞争力,规避农业经营风险,促进农民增收,共同引领农民走出“种植怪圈”。