岳麓书院藏秦简《数书》中的土地面积计算

岳麓书院藏秦简<数书>里有计算矩形、箕形、圆形三种平面图形土地面积的算题,涉及大广术、启从(纵)术、里田术、少广术、圆面积割补术等计算方法,其中大多数算题亦见于<九章算术>和张家山汉简<算数书>,也有些算题仅见于书院秦简.这些关于面积的算题反映了秦代土地面积计算的水平.     

引导学生学通学活物理通量概念

物理学中的"通量"概念非常重要,根据通量的基本定义展开讨论"电通亮"、"磁通量"、"光通量"及"水流速疏通量"等概念,从而引导学生如何形成基本概念,学会实学,领悟真知;如何理解概念,学会融会贯通,扩展知识;如何更新知识,学会创新思维,自我升华.     

“双循环”格局下脱贫攻坚与乡村振兴有效衔接的进路研究

实现脱贫攻坚与乡村振兴有效衔接,应准确把握“双循环”新发展格局“空间重构基础上要素组合优化和区域高质量发展”的战略要义。从减贫规律认知升华、行为外嵌转向发展自觉、资源配置优化与延续效应发挥三个层面分析脱贫攻坚与乡村振兴有效衔接行为的内在逻辑,厘清“双循环”新发展格局建设对于脱贫攻坚与乡村振兴有效衔接工作的机遇与挑战。提出应着力做好发展规划统筹、体制政策健全完善、产业转型升级、相对贫困治理、全域生态宜居环境创建、新时代文明实践中心高质量建设、乡村治理体系与治理能力现代化协同推进、城乡融合发展等领域工作,推进脱贫攻坚与乡村振兴有效衔接工作及其与“双循环”新发展格局建设的良性互动。     

中国粮食增产的主要因素贡献分解与实证估算

已有测算中国粮食增产要素贡献率的方法存在虚增或低估某要素贡献率的缺陷,文章通过改进粮食增产贡献率测算方法实证估计了2003—2016年期间单产、播种面积和结构调整对中国粮食增产的贡献。结果表明,中国粮食实现“十二连增”的巨大成就主要是单产增长贡献,年均贡献率50%以上,播种面积和作物内部结构调整也是不可忽视的重要力量,年均贡献率分别为30%与10%以上。然而,未来中国粮食增产依靠播种面积扩大和结构调整的空间变窄,需要探索新的增产路径。     

Mixture inverse Gaussian for unobserved heterogeneity in the autoregressive conditional duration model

In this paper, we assume that the duration of a process has two different intrinsic components or phases which are independent. The first is the time it takes for a trade to be initiated in the market (for example, the time during which agents obtain knowledge about the market in which they are operating and accumulate information, which is coherent with Brownian motion) and the second is the subsequent time required for the trade to develop into a complete duration. Of course, if the first time is zero then the trade is initiated immediately and no initial knowledge is required. If we assume a specific compound Bernoulli distribution for the first time and an inverse Gaussian distribution for the second, the resulting convolution model has a mixture of an inverse Gaussian distribution with its reciprocal, which allows us to specify and test the unobserved heterogeneity in the autoregressive conditional duration (ACD) model.

Our proposals make it possible not only to capture various density shapes of the durations but also easily to accommodate the behaviour of the tail of the distribution and the non monotonic hazard function. The proposed model is easy to fit and characterizes the behaviour of the conditional durations reasonably well in terms of statistical criteria based on point and density forecasts.     

Bayesian sample‐size determination methods considering both worthwhileness and unpromisingness for exploratory two‐arm randomized clinical trials with binary endpoints

A randomized exploratory clinical trial comparing an experimental treatment with a control treatment on a binary endpoint is often conducted to make a go or no‐go decision. Such an exploratory trial needs to have an adequate sample size such that it will provide convincing evidence that the experimental treatment is either worthwhile or unpromising relative to the control treatment. In this paper, we propose three new sample‐size determination methods for an exploratory trial, which utilize the posterior probabilities calculated from predefined efficacy and inefficacy criteria leading to a declaration of the worthwhileness or unpromisingness of the experimental treatment. Simulation studies, including numerical investigation, showed that all three methods could declare the experimental treatment as worthwhile or unpromising with a high probability when the true response probability of the experimental treatment group is higher or lower, respectively, than that of the control treatment group.     

企业财务危机预警双基点距离比值法

本文介绍了国内外主要企业财务危机预警模型,对模型的空间几何意义进行解释。提出了企业财务危机预警双基点距离比值模型,该模型采用非线性方法对危机企业与非危机企业的财务指标集合进行分割。用112例样本实证,预警识别率达到92.8%。     

基于可变参数优化的相关证据合成方法研究

总结了相关证据合成的理论方法,分析了已有合成方法的不足,对相关证据的相关焦元 的分布情况进行了分析,提出一种面向问题的基于可变参数的相关证据的合成方法. 方法只对 相关焦元的基本可信数进行修正,克服了对相关证据所有焦元进行修正的弱点,使修正的对象 更加合理,修正系数可用基于学习的寻优方法得到. 在相关证据的相关焦元的基本可信数未知 的情况下也可进行相关证据的合成. 计算结果表明该方法对合成的结果有明显的改进     

Improved communality estimation in factor analysis

The symmetric treatment of an asymmetric approach to factor analysis is shown to provide accurate communality estimates. In comparison with existing estimates including upper and lower bounds, the present approach is shown to be superior. In one example with known communalities, the present approach perfectly captures those communalities. In two empirical examples, it is shown to produce better communality estimates than any existing method.     

Estimating the probability of obtaining nonfeasible parameter estimates of the generalized pareto distribution

In this paper we consider the problem of estimating the parameters of the generalized Pareto distribution. Both the method of moments and probability-weighted moments do not guarantee that their respective estimates will be consistent with the observed data. We present simple programs to predict the probability of obtaining such nonfeasible estimates. Our estimation techniques are based on results from intensive simulations and the successful modelling of the lower tail of the distribution of the upper bound of the support. More simulations are performed to validate the new procedure.