Spatiotemporal Modeling of Asian Citrus Canker Risks: Implications for Insurance and Indemnification Fund Models

Asiatic citrus canker is a disease that poses a significant hazard to commercial citrus production. This article examines spatiotemporal models of the risks of citrus canker transmission. Models evaluate risks and are used to price annual contracts, which would pay producers a prespecified indemnity in the event that their grove is found to be infected with canker. Implications for risk management policy are discussed.     

Food Aid, Food Prices, and Producer Disincentives in Ethiopia

Although the short-term aims of food aid are well conceived, strong concerns have been voiced regarding the long-term impacts of such aid on incentives for agricultural producers in recipient countries. This article examines the statistical link between food aid shipments and food prices in Ethiopia over the period 1996–2006. Monthly data from three markets and three commodities are used to estimate a system of seemingly unrelated regression models for food prices. Results indicate that previous year food aid shipments reduce prices in all producer and consumer markets. These effects, however, appear to be limited to the set of internationally traded commodities that are domestically marketed. A recursive regression procedure is used to identify the food aid threshold at which a negative aid effect emerges. Food aid shipments that constitute less than 10% of domestic production appear to be benign, but shipments above this level show signs of being disruptive to local markets. We use a simple policy simulation to argue that production-sensitive targeting, e.g., conditioning food aid on local food production, would help to circumvent disincentive effects.     

Poverty, Risk Aversion, and Path Dependence in Low-Income Countries: Experimental Evidence from Ethiopia

In most low-income countries, rural households depend on mixed rain-fed agriculture/livestock production, which is very risky. Due to numerous market failures, there are few ways to shift risks to third parties. The literature has focused on what determines the responses of households in such environments. Of special concern are path dependencies in which households experiencing failure are prone to further failure and potential poverty traps. This paper estimates levels and determinants of risk aversion in the highlands of Ethiopia. We find high risk aversion and evidence that constraints have important impacts on risk-averting behavior with perhaps significant implications for long-term poverty. The results also suggest the possibility of path dependence and offer insights into links between risk aversion and poverty traps.     

The Procompetitive Effect of Demand-Enhancing Check-Off Programs

This article explores demand-enhancing check-off programs and how such programs may influence both private programs as well as industry market structure. Under duopoly, a firm may increase its sales through privately funding product quality improvements. However, such endogenous sunk costs may also be used to exclude a rival. Industry-funded check-off programs affect firms' strategies and can be procompetitive. The rationale lies not only in how the check-off enhancement is perceived by consumers but also in the way the check-off's crowding-out effect reduces the ability of a firm to use its private expenditures to bar a rival's market access.     

On Crop Biodiversity, Risk Exposure, and Food Security in the Highlands of Ethiopia

This paper investigates the effects of crop genetic diversity on farm productivity and production risk in the highlands of Ethiopia. Using a moment-based approach, the analysis uses a stochastic production function capturing mean, variance, and skewness effects. Welfare implications of diversity are evaluated using a certainty equivalent, measured as expected income minus a risk premium (reflecting the cost of risk). We find that the effect of diversity on skewness dominates its effect on variance, meaning that diversity reduces the cost of risk. The analysis also shows that the beneficial effects of diversity become of greater value in degraded land.     

土壤污染防治法背景下的城乡绿地系统建设：趋势与对策

《中华人民共和国土壤污染防治法》的颁布标志着中国将形成完善的土壤污染防治法律体系,建立从污染土壤调查、修复、风险防控、监测到场地再利用,从环境标准到规划管理的全方位制度。生态文明制度建设的宏观背景,再加上中国土壤污染严重、规模大、修复难、成本高、周期长等特征,将导致大量污染场地转变为绿地或生态用地,最终对绿地系统的数量与规模、布局与功能、规划与管理、环境质量标准等多个维度产生实质性影响。分析这一趋势,对其影响提出预判,最终提出对策建议。     

汇水系统绿地雨洪调蓄研究——以武汉港西汇水系统为例

绿地有一定的雨洪调蓄功能,雨洪状况下,如何在汇水系统尺度利用和保护绿地亟待研究。选取95处位于武汉港西汇水系统的地块,调研地块性质,利用ArcGIS提取不透水比例及平均坡度,并进行SWMM水文模型演算。通过实验性模拟结果的对比,得出汇水系统的绿地雨洪调蓄效率(λ＝0.13m3/m2)、汇水系统(g＝36%)和各类用地(g＝18%～47%)基于雨水调蓄理念下的最低绿地率,使汇水系统水文状况达到海绵城市建设标准。讨论了不同重现期下汇水系统的绿地雨洪调蓄效能,旨在完善绿地雨洪调蓄的研究方法、指标体系及利用与保护策略,为相关研究与实践提供借鉴。     

基于RBF和PSO的双喉道气动矢量喷管优化设计

本文探索了一种能多变量综合优化的方法,即对喷管进行参数化设计后,用均匀试验设计(UED)将试验样本均匀散布在设计区间内,求出各性能参数后,利用径向基神经网络(RBF)对试验样本进行拟合,再用粒子群算法(PSO)对训练好的神经网络进行寻优,找出了更好的双喉道气动矢量喷管设计参数组合。数值模拟结果显示,优化后的双喉道气动矢量喷管的矢量角有了明显提高。试验表明这种优化方法具有很好的优化能力,可以用来对喷管几何外形进行参数优化。      

碳债券的估值及敏感性分析

论文以2014年5月13日中广核电附加碳收益中期票据的成功发行为背景,在假设核证碳减排量(CER)服从几何分形过程的情况下,结合分形过程的蒙特卡洛模拟,研究了中期碳债券的设计和估值问题,并分析了不同的期权条款设计带来的风险差异。研究认为相对较复杂的强路径依赖型亚式浮息碳债券,在碳现货价格波动性较大的情况下,简单的欧式浮息碳债券是更好的设计选择。     

公司治理、大股东资金占用与盈余质量

论文从大股东资金占用行为的影响因素与行为后果两个角度出发,研究公司治理机制与大股东资金占用行为的关系以及大股东资金占用行为与盈余质量的相关关系。研究结果发现：第一大股东控制程度越高,其占用上市公司资金的可能性越大并且这种现象在国有控股上市公司中更为严重,公司治理综合水平对大股东资金占用程度起到了有效的抑制作用,大股东这种资金占用行为对企业盈余质量具有显著的影响。