农业生产风险管理策略的研究

农业生产经营风险管理所涉及的风险因素很多,主要有:(1)单产变化;(2)价格变化;(3)新技术或新知识变化;(4)农业投入水平变化;(5)政府政策变化;(6)法律变化;(7)消费者偏好变化,等等。通过权衡风险和收益,采用适宜的管理策略来规避风险,提高收益,形成了一系列非确定性关系下的风险决策方法。联系河北省20世纪90年代以来农业生产的实际情况,探讨了各种主要的规避或减少农业生产风险的方法和策略,如利用偏相关系数最小的方法选择稳定的生产项目;采用多种经营以分散风险的组合策略;提高农业生产经营灵活性的诸多措施;利用二次规划以建立风险最小而又能保证一定收入水平的最优规划方法等。     

基于投入产出视角的政府公共投资效率研究

长期以来,中国一直非常注重利用政府公共投资的扩张来实现区域经济持续稳定增长的目标,但近年来城镇化中的公共品供给不足与过剩并存\地方经济运行质量与政府投融资平台风险累积等一系列矛盾和投资低效率问题已经成为极大影响中国城镇化进程的重要因素。基于投入产出的分析视角,采用面板随机系数模型,对1995—2011年东、中、西部政府公共投资的投入产出效率进行横向和纵向比较.结果表明:中国不同地区政府公共投资的效率改进都不太理想,政府支出并没有显著提高单个要素产出效率或全要素生产率;中国政府公共投资整体规模和区域分配上仍存在较为严重的问题。     

Averaging Lorenz curves

A large number of functional forms has been suggested in the literature for estimating Lorenz curves that describe the relationship between income and population shares. The traditional way of overcoming functional-form uncertainty when estimating a Lorenz curve is to choose the function that best fits the data in some sense. In this paper we describe an alternative approach for accommodating functional-form uncertainty, namely, how to use Bayesian model averaging to average the alternative functional forms. In this averaging process, the different Lorenz curves are weighted by their posterior probabilities of being correct. Unlike a strategy of picking the best-fitting function, Bayesian model averaging gives posterior standard deviations that reflect the functional-form uncertainty. Building on our earlier work (Chotikapanich and Griffiths, 2002), we construct likelihood functions using the Dirichlet distribution and estimate a number of Lorenz functions for Australian income units. Prior information is formulated in terms of the Gini coefficient and the income shares of the poorest 10% and poorest 90% of the population. Posterior density functions for these quantities are derived for each Lorenz function and are averaged over all the Lorenz functions.     

中等职业教育财政投入现状分析与对策研究——以河北省为例

文章通过发放调查问卷,归纳、整理“十二五”期间的财务会计报表对河北省中等职业教育财政投入状况进行了分析,揭示了存在的主要问题,提出了改进中等职业教育财政投入机制的对策和建议。     

Exact average coverage probabilities and confidence coefficients of confidence intervals for discrete distributions

For a confidence interval (L(X),U(X)) of a parameter θ in one-parameter discrete distributions, the coverage probability is a variable function of θ. The confidence coefficient is the infimum of the coverage probabilities, inf  _θ P _θ (θ∈(L(X),U(X))). Since we do not know which point in the parameter space the infimum coverage probability occurs at, the exact confidence coefficients are unknown. Beside confidence coefficients, evaluation of a confidence intervals can be based on the average coverage probability. Usually, the exact average probability is also unknown and it was approximated by taking the mean of the coverage probabilities at some randomly chosen points in the parameter space. In this article, methodologies for computing the exact average coverage probabilities as well as the exact confidence coefficients of confidence intervals for one-parameter discrete distributions are proposed. With these methodologies, both exact values can be derived.     

贫困测量中恩格尔系数的失效及分析

 恩格尔系数在我国的适用性问题是学术界重要议题之一。本文利用对哈尔滨市和沈阳市贫困人口的调查数据,分析了恩格尔系数在我国城市贫困测量中失效的问题及原因。研究者尝试对恩格尔系数的分子、分母进行了重新界定和适当的修正,研究检验表明,从宏观测量和微观测量两个方面,修正恩格尔系数都能更准确的反映我国城市贫困家庭的真实生活水平。     

变数额标准为人员标准——农村低保标准确定的范式转换

中国扶贫和发展的情况表明,要解决农村全部贫困人员的温饱问题必须建立农村低保制度。受扶贫和城市低保对像确认的影响,我国实行农村低保试点的地区多采取数额标准作为确定农村低保对象的主要确认方法。鉴于数额标准在确定农村低保对象中的种种缺陷和弊端,文章在分析农村低保意义的基础上论证了变数额标准为人员标准在农村低保对象确认中的意义、作用、应注意的问题和确认的方法。     

应用同伦正则化算法反演二维溶质运移模型中的弥散系数

利用同伦正则化算法探讨了二维对流弥散方程的依赖空间变量的弥散系数反演问题.讨论了初始迭代值、数值微分步长、以及收敛精度对算法实现的影响.数值模拟表明,同伦正则化算法对于此类参数反演问题是一种有效的方法.     

Synthetic double sampling s chart

This study proposes a synthetic double sampling s chart that integrates the double sampling (DS) s chart and the conforming run length chart. An optimization procedure is proposed to compute the optimal parameters of the synthetic DS s chart. The performance of the synthetic DS s chart is compared with other existing control charts for monitoring process standard deviation. The results show that the synthetic DS s chart is more effective for detecting increases in the process standard deviation for a wide range of shifts. An example is provided to illustrate the operation procedure of the synthetic DS s chart.     

Approximate confidence intervals for the weighted kappa coefficient of a binary diagnostic test subject to a case–control design

Case–control design to assess the accuracy of a binary diagnostic test (BDT) is very frequent in clinical practice. This design consists of applying the diagnostic test to all of the individuals in a sample of those who have the disease and in another sample of those who do not have the disease. The sensitivity of the diagnostic test is estimated from the case sample and the specificity is estimated from the control sample. Another parameter which is used to assess the performance of a BDT is the weighted kappa coefficient. The weighted kappa coefficient depends on the sensitivity and specificity of the diagnostic test, on the disease prevalence and on the weighting index. In this article, confidence intervals are studied for the weighted kappa coefficient subject to a case–control design and a method is proposed to calculate the sample sizes to estimate this parameter. The results obtained were applied to a real example.