气候变化对农户的经济影响研究——基于南疆红枣主产区农户收入安全视角

气候对农户的影响存在于以农户为中心的两阶段价值链(生产和产后环节)中,农户收入是气候直接影响和农户为规避气候风险调整生产经营行为的结果。基于阿克苏地区2011~2014年316户枣农微观面板数据,在Ricardian模型理论基础上提出气候-两阶段影响模型,运用考虑气候影响的随机系数模型,构建全要素适应性生产函数模型。研究表明:4~8月生长期和9~10月成熟期气温升高对农户增加收入有利,但农户对极端高温的适应能力不足;4~8月主产区降水增加对农户的影响利大于弊,9~10月成熟期降水增加使农户不可避免陷入由气候导致的市场风险;生产阶段气温升高使肥料的产出弹性下降,降水增加使肥料的产出弹性上升,农药的产出弹性下降,气候变化导致农业成本增加,农户适应气候变化的农业调整行为不科学。为保证农户收入安全,农户在生产和产后阶段气候适应能力亟待提高,尤其应充分考虑产后阶段的气候适应性措施。     

Adjusting MV-efficient portfolio frontier bias for skewed and non-mesokurtic returns

This study investigates the bias adjustment for mean–variance efficient portfolio frontiers due to population mean and variance estimation error in Taiwan stock market. Although Siegel and Woodgate (2007; Management Science, 53, 1005–1015) and Kan and Smith (2008; Management Science, 54, 1364–1380) suggested two portfolio frontiers that improved upon the out-of-sample performance of a traditional sample portfolio frontier. However, this study shows that, using the copula function and Gram-Charlier series, the two frontiers are theoretically biased toward the actual frontier unless returns behave normally, and the bias is related to the return skewness and kurtosis. Indeed, the two frontiers are empirically biased to the lower-left side of the actual ones, because the Taiwan stock returns are right-skewed and highly leptokurtic. Thus, this study thus proposes revised portfolio frontiers that are closer to the actual frontier than unrevised ones. This improvement may enhance the estimation accuracy of the capital market line, and hence this study can provide an effective investment reference.     

Evaluating the impact of individual fishing quotas (IFQs) on the technical efficiency and composition of the US Gulf of Mexico red snapper commercial fishing fleet

This study examines the impact of individual fishing quotas (IFQs) on the technical efficiency (TE) and composition of the Gulf of Mexico red snapper commercial fishing fleet. Employing a parametric stochastic distance frontier framework we find that IFQs improved the TE of the vertical line and bottom longline fleets. Our results suggest that the observed TE gains were mainly driven by the retirement of less efficient vessels and, to a lesser extent, by efficiency gains of the remaining vessels. We also document changes in output and input distance elasticities and in returns to scale following the introduction of IFQs. The paper also investigates the impact of regulations and weather on productivity and the effect of crowding on TE. Policy implications stemming from these results are also discussed.     

论刑罚功能与再犯

刑罚的目的是预防犯罪,包括特殊预防与一般预防。但事实证明,现有刑罚已不再容易达到预防犯罪的目的,其功能不能有效发挥,甚至令人担忧。尤其是被法院本着＂宽和精神＂判处拘役、短期有期徒刑的罪犯,再犯现象严重。本文结合某地区再犯刑事案件统计情况进行分析,并提出对刑罚进行修改的建议。     

Efficiency measurement of Chinese airports with flight delays by directional distance function

This paper employs directional distance function to evaluate the technical efficiency of twenty major Chinese airports from 2006 to 2009 within a joint production framework of desirable and undesirable output (i.e. flight delays). The results indicate that the overall average efficiencies of Chinese airports increased over the period of time. The international hub airports are found to operate at higher efficiency level, which indicates that these airports run well in producing more desirable outputs and controlling flight delays. Although the average efficiency score of listed airports is higher than non-listed ones, the difference between the two group is statistically insignificant. A comparison between the results without and with flight delays show that several airports experienced significant changes in their efficiency scores after considering undesirable output.     

网络表情符号分析

本文以网络表情符号为研究对象,对网络表情符号的历史沿革、特点、成因、传播功用以及它的发展趋势进行了分析。     

Public sector transparency and countries’ environmental performance: A nonparametric analysis

Based on the theoretical background of the link between countries’ public sector transparency and environmental policy, our paper provides empirical evidence for a sample of 49 countries for the time period of 1995–2000. Assuming that countries’ environmental performance is a product of their environmental regulations and policies, we utilize a nonparametric estimator for investigating the link with public sector's transparency levels. Specifically, by applying conditional directional distance function models, we incorporate on the measurement of countries’ environmental performance the effect of their public sector transparency levels. In a second stage analysis applying local constant estimators, the results reveal an inverted ‘U’-shape relationship between countries’ public sector transparency levels and their environmental performance.     

基于win8的天气新闻类应用实现

Windows8应用商店开发是微软的一个全新开发技术，本文详细介绍了一款基于win8的天气新闻类应用在开发过程中的设计思路，用到的相关技术：如何使用API，如何提取动态网页中的数据，如何根据动态改变的温度值绘制出正确的温度曲线。应用最终的成功开发表明，设计达到了最初的预期要求，并且对类似应用的开发与研究起了较好的借鉴作用。     

数学思想方法与实变函数教学

本文简要分析了数学思想方法的内涵,分析、概括了实变函数中三个层次的数学思想方法,并讨论了在实变函数教学中加强数学思想方法教育的意义和途径。     

基于Ac1030数据采集卡的光纤参数测量系统

光纤的普及要求对光纤的参数进行有效的检测。OTDR(光时域反射计)的出现,较好地解决了这个问题,方便了光纤的检测和维护。文章首先介绍了OTDR的基本原理,然后简要阐述了数据采集卡AC1030的功能和控制方法,最后重点介绍了软件的设计与实现。