农村婚姻挤压的类型及其生成机制

婚姻挤压是指由于适婚男女性别比失衡导致其中一种性别的人口无法找到配偶的现象。我国农村婚姻挤压主要挤压的是适婚男性农民,它包括宏观层面的性别挤压、中观层面的梯度挤压和微观层面的竞争挤压等机制。其中,性别挤压机制挤压的主要是农村中的适婚男性,而农村适婚女性较少被挤压;梯度挤压机制挤压的是作为婚姻市场低洼地带的自然和经济条件落后地区的适婚男性农民,而作为婚姻市场优势地带的自然和经济条件相对较好地区的适婚男性农民被挤压得较少;竞争挤压机制挤压的主要是在婚姻市场低洼地带内部的婚姻市场竞争中无法支付高额婚姻成本的适婚男性,而该地区家庭条件相对较好的适婚男性被挤压的程度相对较低。农村适婚性别比失衡的社会后果最终由处于婚姻市场低洼地带的底层家庭的适婚男性承担,他们最容易成为农村找不到配偶的“光棍”。     

Conditional Monte Carlo Gradient Estimation in Economic Design of Control Limits

The economic approach to determining the optimal control limits of control charts requires estimating the gradient of the expected cost function. Simulation is a very general methodology for estimating the expected costs, but for estimating the gradient, straightforward finite difference estimators can be inefficient. We demonstrate an alternative approach based on smoothed perturbation analysis (SPA), also known as conditional Monte Carlo. Numerical results and consequent design insights are obtained in determining the optimal control limits for exponentially weighted moving average and Bayes charts. The results indicate that the SPA gradient estimators can be significantly more efficient than finite difference estimators, and that a simulation approach using these estimators provides a viable alternative to other numerical solution techniques for the economic design problem.     

非线性检验及预测在污水处理厂评价中的应用

为了避免污水处理厂规模盲目扩大造成的投资效率低下的现象发生,科学地预测合理的用水量必不可少。基于用水量的实际历史数据,利用BDS检验、Box-Pierce检验和Box-Ljung检验以及非线性检验,如代替数据检验Surrogate date test、Hinich双谱检验、White人工神经网络检验来选择时间序列重构预测模型。根据实际用水量情况,比较各种不同重构模型预测误差,包括线性AR模型以及随机森林、随机梯度Boosting、支持向量、人工神经网络和自适应样条等。结果表明,有着非线性关系的人工神经网络误差最小,符合检验结果。     

兰州—西宁城市区域人口密度梯度变化及内在机理研究

基于SNEF的多中心区域密度函数揭示兰州—西宁城市区域的人口密度梯度变化,进而探讨人口集聚与扩散的趋势,并建立多元回归方程来解释中心城市人口密度梯度变化的内在机理。区域密度函数的估计结果显示,兰州—西宁城市区域存在的兰州市、西宁市与临夏市三个人口高密度中心表现出不同的密度梯度变化特点,也反映出不同的人口集聚与扩散趋势。兰州市与西宁市呈现出密度梯度上升,人口向中心城市集聚的趋势;而临夏市密度梯度下降,表现出人口向外扩散的趋势。通过岭回归建立回归方程的估计结果显示,密度梯度变化主要受城市规模、第二产业从业人员比例、交通可达性等因素的显著影响,第一从业人员比例、第三产业从业人员比例以及生态环境质量对于密度梯度变化的影响不显著。     

企业技术创新能力相关因素重要性排序分析

评价企业的技术创新能力是认识与把握技术创新活动的本质与规律、系统总结创新经验的主要手段。它对于正确制定技术创新战略 ,提高企业技术创新水平 ,减小创新不确定性具有重要意义。本文首先构建了技术创新能力评价指标体系 ,在此基础上用层次分析法和模糊集合论等理论对评价指标进行权重分析 ,并对影响企业技术创新能力的相关因素进行重要性排序。     

Building adaptive estimating equations when inverse of covariance estimation is difficult

Summary. To construct an optimal estimating function by weighting a set of score functions, we must either know or estimate consistently the covariance matrix for the individual scores. In problems with high dimensional correlated data the estimated covariance matrix could be unreliable. The smallest eigenvalues of the covariance matrix will be the most important for weighting the estimating equations, but in high dimensions these will be poorly determined. Generalized estimating equations introduced the idea of a working correlation to minimize such problems. However, it can be difficult to specify the working correlation model correctly. We develop an adaptive estimating equation method which requires no working correlation assumptions. This methodology relies on finding a reliable approximation to the inverse of the variance matrix in the quasi-likelihood equations. We apply a multivariate generalization of the conjugate gradient method to find estimating equations that preserve the information well at fixed low dimensions. This approach is particularly useful when the estimator of the covariance matrix is singular or close to singular, or impossible to invert owing to its large size.     

关于“一类非光滑数学规划Kuhn-Tucker条件充分性”的注记

本文把关于仅含不等式约束的非光滑数学规划的一种最优性充要条件推广为含有等式约束的情况。     

Invexity: an updated survey and new results for nonsmooth functions

The purpose of this paper is to introduce two recent developments in optimization theory which have the potential for significant impact when applied to the many optimization problems in mathematical statistics. The needs of optimization theory have served as the catalyst for the introduction and recent development of two important concepts: invexity and generalized differentiability. The former is a significant generalization of the simple yet powerful concept of convexity, while the latter extends the differentiabe calculus to functions that are not differentiabe in any traditional two-sided sense. For the most part these concepts have been developed independently in the literature. In this paper we provide an updated review of many of the results concerning smooth invex functions and merge the two concepts by introducing invexity for nonsmooth functions. For both real-valued and vector-valued nonsmooth functions we present recent results on optimality conditions, duality, and converse duality. No previous knowledge of invexity or nonsmooth analysis is assumed; a self-contained section on generalized differentiability for Lipschitz functions is included.     

Kernel estimation of regression function gradient

Abstract

This paper is focused on kernel estimation of the gradient of a multivariate regression function. Despite the importance of this topic, the progress in this area is rather slow. Our aim is to construct a gradient estimator using the idea of local linear estimator for a regression function. The quality of this estimator is expressed in terms of the Mean Integrated Square Error. We focus on a choice of bandwidth matrix. Further, we present some data-driven methods for its choice and develop a new approach. The performance of presented methods is illustrated using a simulation study and real data example.     

水中有限长功能梯度材料圆柱壳声辐射研究

研究了径向简谐集中力激励下的水中功能梯度复合材料有限长圆柱壳的振动和声辐射问题。从有限长功能梯度材料振动方程出发，利用模态叠加法，推导出了圆柱壳在径向集中力激励下，平面振动平均振速和声辐射效率表达式。通过数值仿真计算了不同梯度指数下圆柱壳的平均振速、辐射功率和辐射效率。为功能梯度材料圆柱壳声辐射的研究提供了一种有效方法。