基于数字图像处理技术的再生混凝土数值模拟

为了研究骨料形态对再生混凝土材料力学性能的影响,基于势能原理的基面力元法,利用图像处理技术和MATLAB软件,建立了再生混凝土真实骨料细观模型。应用FORTRAN分析软件对再生混凝土试件进行单轴拉伸试验的数值模拟,研究了真实骨料细观模型再生混凝土宏观应力-应变曲线变化规律和试件的破坏形态。结果显示,真实骨料模型得到的宏观应力-应变曲线和试验曲线吻合度较高,骨料形状对试件的破坏形态影响较小。模型可真实地模拟再生混凝土在单轴拉伸作用下的损伤破坏过程,准确地反映试件的实际骨料形态。     

基于新知识生产函数的青海高新技术企业创新驱动力研究

基于新经济增长模型,通过岭回归实证检验,分析了青海省高新技术企业创新产出的影响因素。实证结果显示企业内部研发投入和人力资本对创新产出有积极作用,集聚知识溢出水平对创新产出的贡献较大,政府支持力度对创新产出的作用不稳定。最后,结合高新技术企业调研现状和实证结果提出了高新技术企业提高创新产出的对策建议。     

CHILD CARE PRICES AND MATERNAL EMPLOYMENT: A META‐ANALYSIS

The literature estimates for labor force participation elasticity with regard to child care prices are extensive and varying. While some estimates imply substantial gains from child care subsidies, others find insignificant effects. To determine the causes of the variance, this paper reviews and analyzes the elasticity sizes using estimates from 36 peer‐reviewed articles and working papers in the literature. We start by reviewing the theoretical and empirical aspects related to participation elasticity with regard to child care costs, paying special attention to sample characteristics, methodological aspects, and macro level factors. We conclude by providing a meta‐regression using control variables based on our review of the literature to explain some of the differences between the estimates. As research builds on and improves the methods and assumptions in prior works, elasticity estimates have become smaller over time. This decline might also be partially explained by changes in labor market characteristics. In countries with high rates of part‐time work and very high or very low rates of female labor force participation, we find elasticity rates to be smaller.     

资本回报率、人力资本投资与收入不平等——基于Galor-Zeira模型的扩展

资本回报率下降对人力资本投资、收入不平等程度有较大影响。本文将可变资本回报率加入Galor-Zeira模型,理论推导发现:收入不平等陷阱并非不可逾越的障碍。当技能劳动力工资高于受教育固定成本时,随着资本回报率下降,接受教育的遗赠临界水平将降低,更多家庭将发现投资人力资本是有利的,稳态的技能劳动力比例将提高。在当前资本回报率下降的大背景下,提高技能劳动力工资、降低受教育成本、对教育贷款实施财政减免优惠、为农村中等教育支出减负和提升农村教育质量、倡导节俭和重视遗赠的文化氛围在长期都有助于提高技能劳动力比重以及缓和收入不平等。     

Cooperative conversion and communalization: Closely observed interactions between the material and the mental

Various authors, including Elinor Ostrom, have shown that the legal form of a cooperative has many of the characteristics of a Common. Here we focus on cooperative conversion, through which conventional enterprises become labor‐managed firms (LMFs), viewing it dynamically as a communalization process. These processes are addressed in the light of a field survey carried out in France, looking at six firms involved in cooperative conversion. The changes entailed are two‐dimensional, both material and mental. This is visible, for example, when finding the capital to mount an LMF: members of the workforce must draw on their own funds; they must also believe in the project. Through our empirical observations we highlight the obstacles in the way of forming an LMF. In particular participants must undertake a work of negotiation hinging on stakes marked by the two, largely inseparable dimensions. Ultimately we query the ethic brought into play in the collective action of constituting a Common. Specifically, individuals must contribute to a collective action underpinned by principles of self‐governance, or commoning, the rock on which the Common rests. A key finding of our study is to demonstrate that a Common can only be successfully created if the constituent processes are consistent with the overall goal. In other words the manner in which we travel is inseparable from our final destination; otherwise we shall surely lose our way.     

Human resource management practices and voluntary turnover: a study of internal workforce and external labor market contingencies

We tested relationships between employee quit rates and two bundles of human resource (HR) practices that reflect the different interests of the two parties involved in the employment relationship. To understand the boundary conditions for these effects, we examined an external contingency proposed to influence the exchange-based effects of HR practices on subsequent quit rates – the local industry-specific unemployment rate – and an internal contingency proposed to shape employees’ conceptualization of their exchange relationship – their employment status (i.e. full-time, part-time and temporary employment). Analyses of lagged data from over 200 Canadian establishments show that inducement HR practices (e.g. extensive benefits) and performance expectation HR practices (e.g. performance-based bonuses) had different effects on quit rates, and the former effect was moderated by unemployment rate. The effects of HR practices on quit rates did not differ between FT and PT employees, but a different pattern of main and interactive effects was found among temporary workers. These findings suggest that employees’ exchange-based decisions to leave may be less affected by the number of hours they expect to work each week, and more by the number of weeks they expect to work.     

延迟退休年龄下隔代抚育与劳动参与的抉择*——基于工资收入随机性假定的研究

隔代抚育会对延迟退休年龄政策在促进劳动力供给上产生挤出效应。为了对此进行验证，本文在工资收入随机性的假定及延迟退休5年的情景下，模拟了面临孙辈照护需求的女性临近退休者提前退休所产生的福利变化。进一步，本文采用CHIP和CHARLS的微观调查数据，对不同群组的收入增长率和收入风险进行了估计，继而分析了当面临孙辈照护需求时这些收入特征对退休决策者制度退休和退休后劳动参与抉择产生的影响。总体上，在延迟退休年龄政策下，隔代抚育将对女性劳动力供给产生挤出效应。当面临孙辈照护需求时，女性临近退休者的制度退休抉择主要受自身收入增长率和收入风险的影响，收入增长率越低，或收入风险越高，她们提前退休的意愿就越强烈；制度退休后的劳动参与则更多地受子女收入增长率的影响，子女收入增长率越高，劳动参与的概率越低。     

现阶段我国农村剩余劳动力转移途径分析

随着农业生产率的提高，农村劳动力的隐性失业问题也日益显露出来，并逐渐成为限制中国经济整体发展的重要因素。本文对农村剩余劳动力转移的传统途径所面临的新问题做细致分析，同时提出以三化(城镇化、工业化、知识化)互动、整体推进的方式来解决农村剩余劳动力问题的新途径，并提出确保三化互动得以实施的若干相应对策。     

Resistance to Trade Liberalization in Unionized Sector

This paper studies the lobbying against trade liberalization by both a firm and a union in the same industry. We find that the relationship between their political activities depends on the effect of political activity by one on the marginal effectiveness of political activity by the other. We also show that, when they are strongly risk-averse and their political activities are strategic complements, trade liberalization is likely to be successful if business is brisk, the foreign firm's production cost is high or the number of union members is small. However, when they are not strongly risk-averse, these results hold reversely.     

我国劳动力流动的动态和预期经济效应分析

劳动力流动是市场机制发挥配置资源作用的表现。从静态分析看,劳动力流动调剂了供需双方缺口,提高了整个社会福利水平。从动态角度看,我国的中心城市和经济先发展地区具有吸引资金、技术和知识资本的优越条件,决定着劳动力流动方向,而且因累积循环作用,引起回波效应大于扩散效