高能量下的硬球散射截面

本文采用分波法 ,讨论了在极高能量下 ,半径为 R的硬球的散射问题 ,其结果是散射截面趋于 2πR2 。     

A Generalized View on Continuum Regression

ABSTRACT. We generalize the relationship between continuum regression (Stone & Brooks, 1990) and ridge regression, by showing that any optimization principle will yield a regressor proportional to a ridge regressor, provided only that the principle implies maximizing a function of the regressor's sample correlation coefficient and its sample variance. This relationship shows that continuum regression as defined via ridge regression ("least squares ridge regression") is a more generally valid methodology than previously realized, and also opens up for alternative choices of its second and subsequent factors.     

有限时域内部分缺货的变质品生产-定价策略研究

研究有限时域内对变质产品同时安排生产计划和制定定价策略的问题。有限时域被划分成同等长度的多个周期,产品以固定的生产率间歇生产,并以固定的速率发生变质。需求同时依赖于时间和产品价格,在每个周期内都允许缺货且短缺量部分延迟订购。目的是要寻求一个使有限时域内系统的平均利润最大化的生产计划和定价策略。在算例中,分别讨论了需求随时间增大和减小两种不同的需求模式,采用Box复合算法,通过数值计算求得相应的最优生产计划和定价策略。分析表明：对于成长期或销售季初的产品,系统应采用“小批量多批次”的生产方式;而对于衰退期或销售季末的产品,应采用“大批量小批次”的生产方式。此外,不同类型的产品在不同需求模式下的定价策略有所不同：对于有限时域较短或变质率较高的产品,处于衰退期或销售季末的定价要低于成长期或销售季初的定价;相反,对于有限时域相对较长或变质率较低的产品,在衰退期或销售季末的最优定价要高于在成长期或销售季初的定价。     

The heterogeneous impact of insurance on health care demand among young adults: a panel data analysis*

Success of the recently implemented Affordable Care Act hinges on previously uninsured young adults enrolling in coverage. How will increased coverage, in turn, affect health care utilization? This paper applies variable coefficient panel models to estimate the impact of insurance on health care utilization among young adults. The econometric setup, which accommodates nonlinear usage measures, attempts to address the potential endogeneity of insurance status. The main finding is that, for approximately one-fifth of young adults, insurance does not substantially alter health care consumption. On the other hand, another one-fifth of young adults have large moral hazard effects. Among that group, insurance increases the probability of having a routine checkup by 71–120%, relative to mean probabilities, and insurance increases the number of curative-based doctor office visits by 67–181%, relative to the mean number of visits.     

Bayesian inference for a partially observed birth–death process using data on proportions

Stochastic kinetic models are often used to describe complex biological processes. Typically these models are analytically intractable and have unknown parameters which need to be estimated from observed data. Ideally we would have measurements on all interacting chemical species in the process, observed continuously in time. However, in practice, measurements are taken only at a relatively few time‐points. In some situations, only very limited observation of the process is available, for example settings in which experimenters can only observe noisy observations on the proportion of cells that are alive. This makes the inference task even more problematic. We consider a range of data‐poor scenarios and investigate the performance of various computationally intensive Bayesian algorithms in determining the posterior distribution using data on proportions from a simple birth‐death process.     

Analytical expression for the integrated squared density partial derivative of a multivariate normal mixture distribution

This paper describes the derivation of the analytical expression for the integrated squared density partial derivative (ISDPD) in a multivariate normal mixture model. The analytical expression of the ISDPD is derived for arbitrary dimensions with partial derivative orders up to four. Although the value of the ISDPD can be obtained by using the common numerical integration via mathematical software (such as Maple, Mathematica, Matlab, etc), it suffers from the limitation of computation time when the dimension or the number of mixture components of the considered multivariate normal mixture model are large. Moreover, numerical comparison indicates the benefits of speed offered by our proposed analytical expression are far superior to the numerical integration performed by Maple. With this analytical expression, the ISDPD can apace be calculated with no assistance of numerical integration.     

论网络语言中谐音的运用

网络语言是网络时代出现的一种新型语篇类型,是语言的一种功能变体,其标志性语体特征是变异性和个性化.而许多网络词语和语句正是运用了谐音的手段,使网络语言呈现出其特有的魅力.最后,文章对网络语言的发展和规范化问题进行了探讨.     

广义Gamma分布簇广义线性混合模型的构建

 本文在广义Gamma分布簇基础上引入异质性来构建广义线性混合模型。本文构建的广义Gamma分布簇广义线性混合模型在广义线性混合模型的框架下分析,通过参数重整技术把广义Gamma分布簇变量的建模问题与指数分布簇变量的建模问题联系起来,模型推断可以方便地利用广义线性混合模型和广义线性模型的研究成果,同时也可以方便地推广到其他模型。三参数广义Gamma分布可以收缩到两参数的Gamma分布、Weibull分布或指数分布,能降低模型误设的风险,还能便利地分析误差结构。     

基于PSO-PLS的组合预测方法在GDP预测中的应用

GDP预测是经济预测中一个非常重要的问题,随着经济的发展,对其预测精度的要求也越来越高.在考虑样本权重的基础上,提出一种微粒群算法与部分最小二乘回归方法相结合的组合预测方法,即采用微粒群方法对样本最优权重进行求解,在所得样本权重系数的基础上,用部分最小二乘回归方法确定组合预测的权重系数.将该方法用于中国GDP预测取得了较好的结果,与其他几种传统方法相比,预测精度有一定程度的提高,说明算法的有效性和可行性.