北京市农村集体建设用地规划管理研究

通过分析北京农村集体建设用地规划管理现状,明确农村集体建设用地规划管理工作中存在的问题以及根源,提出符合北京实际的农村集体建设用地规划管理体系建议,为进行社会主义新农村建设构建良好的制度框架,保障新一轮北京城市总体规划在部区的有效实施.     

An efficient budget allocation policy for decentralisation of responsibility for site decontamination projects

Selection and execution of site decontamination projects is often best left to local authorities, in accordance with the subsidiarity principle, even though the budget for such projects is made available through a central authority. In this paper we suggest a practical budget allocation policy which a central authority can employ to allocate budgets to local authorities, while still optimising the central authority's environmental objective function. The procedure is fully consistent with the principle of decentralisation of responsibility for selection and execution of projects, and requires a minimum information exchange between local and central levels. Despite the information asymmetry between local and central levels, incentive compatibility problems can be (partially) prevented by choosing an appropriate evaluation mechanism. At the same time, the procedure is computationally effective and efficient, and can guarantee a fair budget allocation, making it easy to implement and politically acceptable.     

Take a risk: Preferring prevention over control of biological invaders

Scientists have argued that invasive species can be managed most cost effectively with greater investments in prevention. Further, under ideas like the precautionary principle it is reasonable to expect that a cautious manager would use more prevention relative to control because it keeps more invaders out. Yet, this is not typically done. In many cases, private and public resources are invested primarily to control existing invaders rather than to prevent new invasions. Managers frequently wait until after invaders have arrived and then scramble to limit the damages. We believe these paradoxical decisions can be understood by recognizing the link between typical human preferences for risk bearing and the technology of risk reduction. We demonstrate quantitatively how managers perceived to be cautious or averse to risk tend to shy away from prevention relative to control. This counterintuitive result arises because control is a safer choice than prevention because its productivity is relatively less risky: it works to remove existing invaders from the system. In contrast, the productivity of prevention is more uncertain because prevention only reduces the chance of invasion, it does not eliminate it, and invasion may not occur even in the absence of prevention. Managers' averse to risk will inherently avoid as much uncertainty as possible, whether the source of uncertainty regards ecological outcomes or economic productivity. Implications for environmental decision making are clear. In invasive species management, if managers act as though they are risk averse, their caution can backfire when it leads to more control rather than prevention. The social consequences of this choice are a greater probability of future invasions and lower social welfare. Our results suggest that social welfare is highest when managers were willing to “take a risk” with prevention.     

软件限时开发方法的研究与应用

限时开发是快速应用开发的最佳实践之一。文章介绍了限时开发的基本概念和优点以及适用的项目范围,通过一个进销存软件的开发实例说明如何成功地应用限时开发方法。     

逆向物流再造网络成本优化的相关机会目标规划模型研究

逆向物流凭借着其重大的经济社会价值，成为了企业物流战略的重要组成部分。本文简要介绍了逆向物流的经济价值和特点，划分了逆向物流产品构成，重点研究了逆向物流再造网络的结构和特点，并运用相关机会规划理论建立了逆向物流再造网络的成本优化模型。     

Spatial agglomeration and endogenous growth

This paper constructs a dynamic general equilibrium model with spatial interactions in which a human capital externality is the centripetal force towards agglomeration. The resource cost of transportation is, on the other hand, the main centrifugal force, preventing a city from growing unboundedly. A central feature of our analysis is the dynamic interaction between (perpetual) economic growth and (bounded) city growth. We examine the socially optimal and the decentralized growth rates as well as city sizes. In the decentralized environment, individuals under-invest, whereas cities are under-populated. We show how public policies may enable a decentralized city to attain the socially optimal allocation.     

城市流通系统:研究现状与一个综合性框架

现代流通产业的发展演变过程是伴随着现代城市的产生与发展过程进行的,现代城市是现代流通产业的载体,而城市则因为流通产业的发展而发展、壮大.因而,流通问题与城市问题是密不可分的.目前城市流通问题的研究集中在商业地理学领域,而传统流通理论则游离于该领域之外,这种游离造成了该领域研究的一些问题.本文在比较全面地回顾和评述了国内外学者对城市流通问题研究现状的基础上提出了一个综合性的研究框架,以期为城市流通问题的研究提供新的视角.     

中国城市中的三种贫困类型

我们课题组在 1 999年进行了一次覆盖六省市的住户调查。本文利用这次调查数据对中国城市贫困的性质和特点进行了考察。通过综合考虑收入标准和消费标准 ,我们把中国城镇贫困分为三种类型 ,即持久性贫困、暂时性性贫困和选择性贫困。在贫困人口中 ,有一大部分是属于选择性贫困 ,即他们的收入高于贫困线而消费低于贫困线。我们对贫困户的消费函数进行了估计 ,其结果显示以下几个因素对贫困状况产生重要的影响 :修匀收入的效应 ;人们防备外部环境不确定性的心理 ;人们为将来投资而进行储蓄的行为 ;家庭对子女教育和医疗服务的特别需要。我们还对三种贫困类型进行了比较分析 ,从中发现预测的金融资产和预测的收入 ,以及教育和医疗的特殊需要都对不同类型的贫困户的消费行为起到重要的影响作用     

基于时间约束的多源多品种随机配送系统模型

在基于时间竞争的随机需求环境下,配送系统设计除了使系统总费用的期望值最小外,还要考虑系统稳定性和服务水平等方面的要求。在说明了建模的假设条件后,建立了考虑随机需求和时间约束的多源配送系统随机模型。通过等价变换,将随机模型转化为确定性等价问题,从而方便了问题的求解。     

Theory and practice of monetary policy

Summary. We consider an optimally managed renewable resource with stochastic non-concave growth function. We characterize the conditions under which the optimal policy leads to global extinction, global conservation and the existence of a safe standard of conservation. Our conditions are specified in terms of the economic and ecological primitives of the model: the biological growth function, the welfare function, the distribution of shocks and the discount rate. Our results indicate that, unlike deterministic models, extinction and conservation in stochastic models are not determined by a simple comparison of the growth rate and the discount rate; the welfare function plays an important role.Received: 20 October 2004, Revised: 28 February 2005, JEL Classification Numbers: D90, O11, O41, Q32.Santanu Roy: Correspondence toResearch on this paper was completed when the second author visited Cornell University in July, 2003. We thank the Center for Analytic Economics and the Department of Economics at Cornell University for making this research visit possible. The current version has gained considerably from the comments made by an anonymous referee.