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排序方式: 共有1561条查询结果,搜索用时 15 毫秒
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This article examines non-farm employment in the context of Chinese rural institutional change, based on evidence from discrete-time logistic models for event history analysis using the Life History and Social Change survey. We find the transition to non-farm sector rose rapidly during the Great Leap Forward and market reform, while the Cultural Revolution saw it reach the lowest ebb. While male advantage prevailed exclusively during the Cultural Revolution and early marketization, education possessed a stable positive effect in all historical periods. Although the returns to different kinds of political capital vary along with institutional dynamics, intergenerational reproduction was greatly reduced after the Cultural Revolution.  相似文献   
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蒋勇  魏蓉 《科技和产业》2023,23(15):86-91
装配式建筑供应链的运作存在很多不确定性。为提高供应链管理效率,促进建筑业的发展,运用供应链运作参考(SCOR)模型对装配式建筑供应链脆弱因子进行识别,将装配式供应链系统划分为6个子系统;通过系统动力学(SD)模型对供应链脆弱性进行仿真。结果表明,装配制造流程是脆弱性最大的子系统,整个供应链的脆弱性随着建筑项目的推进而增大。  相似文献   
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Processing export plays a significant role in international trade. In this paper, focusing on firm-level dynamics, we show that firms learn from their processing export experience to improve their subsequent ordinary export outcomes. Using transaction-level trade data and firm-level production data, we show that firms’ ordinary export performance, at both extensive and intensive margins, is enhanced by their own processing experience. Firms also export products with improved quality after engaging in processing exports of similar products. Furthermore, we investigate potential channels through which firms learn from processing experience. We find that firms potentially learn from processing experience to enhance production efficiency, to better understand how to improve product appeal to cater to specific markets, and to gain better and easier access to inputs. Moreover, we find that exporters benefit more from processing experience for larger markets with fiercer competition. Similarly, stronger learning effects are also observed when processing experience is associated with products that embody less diffused knowledge and are more differentiated. Also, firms learn more from processing experience when they are more actively engaged in processing imports. Lastly, we verify the economic significance and quantify the importance of these potential channels.  相似文献   
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姜瑞海  张晨  肖炜 《科技和产业》2021,21(11):243-248
为解决常规钻井水力学公式对偏心流场计算结果与实际有所差别的问题,揭示大位移井偏心环空水力行为规律,基于fluent软件对幂律钻井液偏心环空紊流流动进行了数值模拟研究,分析偏心度、稠度系数、流性指数、屈服值、钻杆与钻头组合对流动规律的影响.结果表明,随偏心度、稠度系数、流性指数、屈服值、钻杆与钻头尺寸比例的增大,环空中宽间隙处的流速、压力逐渐增大,而窄间隙处的流速、压力逐渐减小.  相似文献   
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碳达峰和碳中和的提出对城市群发展提出新的要求,城市群高速发展与环境问题间的矛盾日益加剧,绿色低碳发展路径亟待研究.以京津冀城市群为研究对象,在梳理城市群发展影响因素的基础上,分析城市群循环系统构成中要素间的关联关系,并通过量化模型,搭建基于系统动力学的城市群绿色低碳发展系统;重点从经济、能源、环境和城市聚合4个角度构建仿真系统,建立要素间量化函数,设定基本场景,以2010—2019年数据为基础,对系统进行仿真运行.算例结果表明,构建的仿真系统通过了检验,拟合程度较好;通过设计不同场景,验证相关参数变化时对系统运行的影响程度,发现综合场景对未来系统运行效益最佳,兼顾了经济发展与碳减排问题,能够促进城市向群绿色低碳发展.  相似文献   
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In this paper we propose a macro-dynamic age-structured set-up for the analysis of epidemics/economic dynamics in continuous time.The resulting optimal control problem is reformulated in an infinite dimensional Hilbert space framework where we perform the basic steps of dynamic programming approach.Our main result is a verification theorem which allows to guess the feedback form of optimal strategies. This will be a departure point to discuss the behavior of the models of the family we introduce and their policy implications.  相似文献   
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This paper derives a closed-form solution of the AK endogenous growth model with logarithmic preferences and anticipated future consumption which enters additively into effective consumption. We get an explicit representation of the time paths of the economic variables in level by resorting to Gaussian Hypergeometric functions. We compare the model with anticipated future consumption to the model with habit formation. The maximum utility attainable in the model with anticipation is shown to be higher than the one attainable in the model with habits. Using the derived explicit expressions, we perform some comparative-dynamics and -statics analyses with respect to relevant parameters. Numerical simulations complement the theoretical results. Thus, this work provides further support to the usefulness of especial functions in the study of economic dynamics.  相似文献   
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We analyze the implications of transboundary pollution externalities on environmental policymaking in a spatial setting, in which pollution diffuses across the global spatial economy independently of the specific location in which it is originally generated. This framework gives rise to a simple regional optimal pollution control problem allowing us to compare the global and local solutions in which, respectively, the transboundary externality is and is not taken into account in the determination of the optimal policy by individual local policymakers. We show that it is not obvious that transboundary externalities are a source of inefficiency per se since this is strictly related to the spatial features of the initial distribution of pollution. If the initial pollution distribution is spatially homogeneous then the local and global solutions will coincide and thus no efficiency loss will arise from transboundary externalities, but if it is spatially heterogeneous the local solution will be suboptimal and thus a global approach to environmental problems will be needed to achieve efficiency. From a normative perspective, in this latter (and most realistic) case we also quantify the amount of policy intervention needed at local level in order to achieve the globally desirable goal of pollution eradication in the long run. Our conclusions hold true in a number of different settings, including situations in which the spatial domain is either bounded or unbounded, and situations in which macroeconomic–environmental feedback effects are taken into account.  相似文献   
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