The Impact of Trade on Intra‐Industry Reallocations and Aggregate Industry Productivity

This paper develops a dynamic industry model with heterogeneous firms to analyze the intra‐industry effects of international trade. The model shows how the exposure to trade will induce only the more productive firms to enter the export market (while some less productive firms continue to produce only for the domestic market) and will simultaneously force the least productive firms to exit. It then shows how further increases in the industry's exposure to trade lead to additional inter‐firm reallocations towards more productive firms. The paper also shows how the aggregate industry productivity growth generated by the reallocations contributes to a welfare gain, thus highlighting a benefit from trade that has not been examined theoretically before. The paper adapts Hopenhayn's (1992a) dynamic industry model to monopolistic competition in a general equilibrium setting. In so doing, the paper provides an extension of Krugman's (1980) trade model that incorporates firm level productivity differences. Firms with different productivity levels coexist in an industry because each firm faces initial uncertainty concerning its productivity before making an irreversible investment to enter the industry. Entry into the export market is also costly, but the firm's decision to export occurs after it gains knowledge of its productivity.     

Noisy Stochastic Games

This paper establishes existence of a stationary Markov perfect equilibrium in general stochastic games with noise—a component of the state that is nonatomically distributed and not directly affected by the previous period's state and actions. Noise may be simply a payoff‐irrelevant public randomization device, delivering known results on the existence of correlated equilibrium as a special case. More generally, noise can take the form of shocks that enter into players' stage payoffs and the transition probability on states. The existence result is applied to a model of industry dynamics and to a model of dynamic electoral competition.     

生猪全产业链安全生产控制模式评价体系构建

根据生猪食品安全的要求,构建了生猪全产业链安全生产控制模式评价系统,并应用系统动力学的原理和方法,建立评价系统指标体系的系统动力学模型。以陕西省杨凌本香农业产业集团的数据为例,应用商用系统动力学软件Vensim PLE进行系统模拟与仿真,对系统进行运行和结果分析。将其导出模拟数据与实际统计数据相比较,结果表明其仿真输出结果与系统的历史数据基本相符,检验了系统的有效性和可靠性。研究发现,只有在生猪生产行业构建全产业链生猪安全生产控制模式,才可有效控制猪肉安全质量;本香农业产业集团生猪全产业链安全生产控制模式是一个高投入、高效率、高回报的生产模式,这一经过长期实践和多年摸索、探讨和总结的经验及结论为生猪生产行业未来发展方向提供了科学的依据。     

二维微槽道内的流动模拟

直接模拟蒙特卡罗方法(DSMC)通过计算机跟踪仿真分子的运动,求解稀薄气体流动规律.选用硬球模型模拟仿真分子间的碰撞,编写DSMC的计算程序,模拟处于滑流和过渡流动领域的二维微槽道内气体流动.结果表明,气体流动在边界附近出现速度滑移和温度跳跃.计算结果和理论值相吻合.     

英语专业本科生口译学习动机衰竭研究——动态系统理论视角下的案例分析

动态系统理论下的二语习得研究认为学习动机处于持续的复杂变化之中。动机衰竭，作为动机的对立面，自然也经历着此消彼长的变化。主流动机衰竭研究倾向于利用横向研究方法考察引起学习者动机衰竭的因素，缺乏动态视角，也忽视了学习者个体差异。基于此，拟从历时性角度出发，采取定性研究方法，利用半结构式访谈考察本科口译课堂中学生学习动机衰竭的变化及影响因素。研究发现：学生的动机衰竭变化特点各异，难以用群体平均值简单概括；而引起动机衰竭的因素有缺乏学习兴趣与目标、学习困难和教学节奏过快。此外，相同教学内容会引起不同学生的动机水平反向变化，即部分学生动机上升，部分学生动机下降。通过研究学习者动机衰竭的个体差异与动态变化，教师能够更全面掌握学生的学习状态，从而对症下药，这有助于拓宽现行动机衰竭研究视角，拓展动态思路。     

谁主认同？转型时期中国女性阶层地位认同的多重建构及其世代变迁

女性的阶层地位认同研究近年来受到广泛关注，但缺乏多重建构视角下基于长期转型背景的世代变迁分析。本文旨在回答两个重要问题：第一，已婚女性的阶层地位认同是否受到婚姻匹配与代际流动的影响，丈夫、父亲与女性自身的客观阶层及其差异如何影响女性的主观地位认同；第二，上述影响模式如何随出生世代发生变化。在使用对角线参照模型分析中国综合社会调查（CGSS）2010—2017年的合并数据后发现：相较于自身的客观阶层，中国已婚女性整体上倾向于以丈夫的客观阶层来建构自身的阶层认同，但越年轻的世代这一倾向越弱；父亲客观阶层的影响则与自身客观阶层的影响并重，甚至随世代变迁略有增强。上述结果体现了中国特色的家庭现代化模式，即已婚女性虽愈少依赖于配偶，但依然与原生家庭保持着紧密连结。     

On two conjectures about perturbations of the stochastic growth rate

The stochastic growth rate describes long-run growth of a population that lives in a fluctuating environment. Perturbation analysis of the stochastic growth rate provides crucial information for population managers, ecologists and evolutionary biologists. This analysis quantifies the response of the stochastic growth rate to changes in demographic parameters. A form of this analysis deals with changes that only occur in some environmental states. Caswell put forth two conjectures about environment-specific perturbations of the stochastic growth rate. The conjectures link the stationary distribution of the stochastic environmental process with the magnitude of some environment-specific perturbations. This note disproves one conjecture and proves the other.     

大空间建筑居留区空调射流与室内羽状气流作用机理研究

在建立非等温射流运动的物理方程时,考虑由室内热源形成的羽状气流对射流运动的热浮升作用力,得到受羽状气流作用的射流运动轨迹表达式.经现场实测验证后,上述理论分析认为,空调射流与羽状气流的相互作用会影响射流轨迹,且在一定程度上改变其运行轨迹.