甘肃省土地利用结构动态演变及其驱动力分析

在GIS技术支持下,以甘肃省1997--2006年土地利用变更调查数据及相关经济社会统计数据为基础,借助系统论中的信息熵原理,揭示了甘肃省用地结构动态演变特征,阐述了影响土地利用结构动态演变的主要自然、政策等驱动力,最后利用主成分分析方法,对该区用地结构动态演变的经济社会主要驱动因子进行了分析与探讨。     

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.     

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。     

关于异地城市化的思考

异地城市化已经成为我国城市化进程的重要组成部分,但这一领域的研究相对较为薄弱.从我国异地城市化的形成发展入手,对异地城市化的特点、形成原因进行了剖析,同时研究了异地城市化对我国经济、社会发展和城市化进程的积极作用和负面影响,也揭示了异地城市化过程中所存在的问题与障碍,最后指出了异地城市化的必要性,同时也提出了一些促进我国异地城市化进一步协调发展的建议与对策.     

需求侧、供给侧视角下中国经济增长动力转换实证研究

为找出中国经济持续高速增长背后的驱动因素,了解增长动力的演变规律,本文基于投入产出模型,从最终需求的角度解析消费、投资和出口对经济拉动作用的动态变化;同时运用DEA方法,从要素供给角度分析中国各地区劳动、资本和TFP对经济增长的贡献,结合需求侧和供给侧的双重角度,探讨经济增长的动力转换特征和问题。结果表明,中国经济增长的需求动力来源由前期的消费转变为出口后,近年来又转变为投资,而资本要素一直是中国各省市增长的主要要素驱动力。中国的经济增长正处在投资主导阶段,经济快速增长的背后伴随着效率下降等问题。     

Establishing the validity of cycle path capacity assumptions in the Highway Capacity Manual

Cycle mode share increase is widely desired, but highway design practitioners lack the numerical tools to deliver infrastructure, instead relying on design standards and intuition, with little literature basis. As a case in point, the US Highway Capacity Manual (which is well used internationally) has developed levels of service for cycle infrastructure that are, at their core, based on an assumption of noninteraction between multiple cyclists. This paper uses a modified implementation of the Social Force Model to test the validity of this assumption. Necessary changes such as the consideration of acceleration characteristics and minimum maintainable speed are included. The resulting model produces valid outcomes in keeping with established traffic flow properties, reflecting three-phase traffic flow theory and the ability for the stochastic elements in traffic flow to cause flow breakdown. The developed simulation indicates that there is a fundamental difference in outcome if cyclists are assumed to have a fixed speed versus one they can change given their surroundings. This difference in outcomes is found to exist within the range of literature design flow capacities for bicycle infrastructure and also yields emergent outcomes that align closely with those known behaviors of highway vehicles, which intuitively transfer to cyclists. These findings reinforce the standing need for large-scale empirical studies to determine the basic numerical and behavioral parameters for cyclists, upon which all design ultimately rests.     

余能原理基面力元法在桁架弹塑性分析中的应用

基面力元法(BFEM)是一种新型的有限单元法,是以"基面力"来描述一点的应力状态。为了编制适用于桁架弹塑性分析的MATLAB基面力元程序,以余能原理基面力元法为基础,将基面力元法的平面4节点的实体单元模型向桁架单元进行退化,列出了退化桁架单元的柔度矩阵、单元轴力和节点位移的具体表达式,并对其控制方程进行了必要的处理。根据退化的桁架单元模型,采用增量法的思想和线性强化弹塑性模型,以三杆超静定桁架和复杂静定桁架为算例进行了计算。将计算结果与大型有限元分析软件ABAQUS的T2D2计算结果进行了对比分析,发现所用方法与ABAQUS的计算结果高度吻合,进一步验证了基面力理论的正确性和程序的适用性。     

试论我国劳动力转移对农村经济发展影响

“三农”问题是当前的重中之重,提高农民收入的主要方法之一是将大量滞留在农村富余劳动力有效转移。农业劳动力转移,可以降低农业生产总成本,增加农民收入,发展农村经济,也在一定程度上提高了劳动力自身的素质。但由于我国目前法律制度的不完善,社会保障体系不健全,导致农村劳动力转移过程中出现许多阻碍经济发展和社会不公平现象。解决这些问题,对促进农村经济发展,构建社会主义和谐社会具有重要意义。     

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。     

加快构建和完善黑龙江省县域经济市场化

加快构建和完善县域经济市场化提高农业竞争力,要取消各种带有排他性、歧视性和垄断性的政策,消除市场上的种种关卡、壁垒.要稳定和完善以家庭联产承包责任制为基础统分结合的双层经营体制.按市场需求组织生产,要和本县的资源条件相结合,发挥资源优势,杷市场导向和发挥资源优势结合起来.加快发展第三产业.要充分发挥我省城市(镇)的中心作用,实行城乡一体化发展.应扩大农业方面的对外经济技术交流,鼓励兴办"三资"农业企业和农产品加工企业.要建立起健全有效、分工明确的市场监督管理体系,就必须加强和改善我省县域市场经济的宏观调控.进一步认真做好县级政府职能的转变,从主要是管理企业的微观经济活动转换到主要是对县域经济的宏观调控上来.