Finding an anti-risk path between two nodes in undirected graphs

Given a weighted graph G=(V,E) with a source s and a destination t, a traveler has to go from s to t. However, some of the edges may be blocked at certain times, and the traveler only observes that upon reaching an adjacent site of the blocked edge. Let ℘={P _G (s,t)} be the set of all paths from s to t. The risk of a path is defined as the longest travel under the assumption that any edge of the path may be blocked. The paper will propose the Anti-risk Path Problem of finding a path P _G (s,t) in ℘ such that it has minimum risk. We will show that this problem can be solved in O(mn+n ²log n) time suppose that at most one edge may be blocked, where n and m denote the number of vertices and edges in G, respectively. This research is supported by NSF of China under Grants 70525004, 60736027, 70121001 and Postdoctoral Science Foundation of China under Grant 20060401003.     

Improving the Numerical Performance of Static and Dynamic Aggregate Discrete Choice Random Coefficients Demand Estimation

The widely used estimator of Berry, Levinsohn, and Pakes (1995) produces estimates of consumer preferences from a discrete‐choice demand model with random coefficients, market‐level demand shocks, and endogenous prices. We derive numerical theory results characterizing the properties of the nested fixed point algorithm used to evaluate the objective function of BLP's estimator. We discuss problems with typical implementations, including cases that can lead to incorrect parameter estimates. As a solution, we recast estimation as a mathematical program with equilibrium constraints, which can be faster and which avoids the numerical issues associated with nested inner loops. The advantages are even more pronounced for forward‐looking demand models where the Bellman equation must also be solved repeatedly. Several Monte Carlo and real‐data experiments support our numerical concerns about the nested fixed point approach and the advantages of constrained optimization. For static BLP, the constrained optimization approach can be as much as ten to forty times faster for large‐dimensional problems with many markets.     

略谈“故宫学”研究的层次

"故宫学"作为一门新的、有形的学问和学科,其研究存在是由基础向尖端逐步推进的三个层次:一为专业史研究层次,内分专业通史研究和专业断代史研究二小层次,这是"故宫学"研究的基础层次。二为文物文献研究层次,注重学术史的梳理和档案史的清理,属于就文物说文物和就文献说文献,这是"故宫学"研究的主要层次。三为综合比较研究层次,强调不同时期和不同种类,属于就文物比文献和就文献较文物,这是"故宫学"研究的最高层次。     

论契诃夫对知识分子的文化批判与文化救赎

在19、20世纪之交,原本一直扮演着启蒙者角色的俄国知识分子,非但没有为发展资本主义制造舆论,培育出健康的资产阶级文化,促进俄国由传统社会向现代社会转型,反而使自身被发展中的资本主义社会抛进了尴尬境地.契诃夫面对知识分子的这种失职,在作品中展开了文化批判,指出知识分子已被庸俗生活腐蚀、陷入意识形态的痴迷和信仰匮乏的焦虑之中,被信仰危机所困扰.这一批判消解了百余年来俄国知识分子作为社会精英的神话.契诃夫认为:知识分子只有积极参与“小事论”社会运动,重新建构新的文化理想,才能实现自我救赎.     

提升河北省文化旅游产业核心竞争力的思考

新兴文化旅游业是河北省发展绿色经济,实现"绿色崛起"的重要途径。梳理了河北省内各地区文化旅游资源,在分析文化旅游产业发展的基础上,提出提升河北省文化旅游业竞争力要关注旅游者消费理念和方式的转变,有针对性地开拓市场;以现代营销理念宣传特色文化旅游品牌,建立消费者对旅游品牌的忠诚度;实施差异化战略,统筹发展,加强各行业和地区的联动;利用现代信息技术打造立体化旅游渠道,开发"情境旅游";发挥旅游地高校文化传播力和影响力的措施。     

钢 混凝土双面组合箱梁日照温度场研究

自然环境中的钢 混凝土双面组合箱梁受到日照作用影响,在梁体内部会产生温度应力。对某地的日气温变化及日照辐射量进行计算;利用有限元软件ANSYS进行仿真分析,计算双面组合箱梁截面在日照条件下的温度分布,对比分析正负弯矩区截面温度分布的异同,得到组合梁表面日温度变化规律;选取温差最大时的数值结果进行分析,用多项式拟合沿梁截面高度温度梯度分布。     

政治关联、企业绩效与企业行为的研究综述

自Krueger开创性地指出企业家花费时间和金钱与政府官员建立关系能给企业带来利益以来,企业与政治之间的关系一直是经济学家关注的热点问题之一。本文梳理了近年来关于政治关联(political connections)与企业价值之间的主要理论和实证文献。在实证文献综述中,从政治关联对企业价值与企业行为影响的这两个维度出发,按照文献的发展脉络和逻辑关系,阐述了这些文献的概念定义、度量方法、样本选择及主要结论。最后进行了总结并提出进一步研究的展望。     

重新思考群己权界:帕累托自由不可能性定理考辩

阿马蒂亚·森所证明的帕累托自由不可能性定理证明:两个似乎是不证自明的原则——最小自由原则和帕累托原则——之间是会存在冲突的。这一定理所蕴含的是一个元问题:确定自由边界的理据是什么?消解森定理中的悖论,需要形成某种合理的偏好。偏好的合理性、自由和权利边界是在历史过程中动态形成的,在不同的社会历史阶段是动态调整的。理解森定理,对于分析当下中国面对的种种权利冲突具有重要的现实意义。     

The relationship between Civil Unions and fertility in France: Preliminary evidence

This paper explores the relationship between fertility and the introduction of new laws regulating cohabitation, in a context of low fertility and high out of wedlock childbearing. We show that in France, while fertility and marriage rates moved closely together before 1999, since the introduction (in 1999) of the “Pacte Civil de Solidarité” (PACS)—a cohabitation contract less binding than marriage—this relationship is much weaker. Surprisingly, legal unions (defined as marriage plus PACS) and fertility continue to move together after this date. We provide evidence of the relationship between the introduction of PACS and fertility, utilizing the regional variation in the number of PACS per woman (PACS intensity) and the differences in fertility before and after 1999. We show that French Departments with high PACS intensity did not show a different trend in fertility before 1999 than those with low PACS intensity (excluding Metropolitan Paris). However, they did experience an increase in their fertility levels after the introduction of PACS. This suggests the need to collect better and more detailed data, in order to assess whether the recent increases in French fertility can be partially explained by the availability of PACS.