劳动力转移对城乡居民收入差距的非线性影响研究

借鉴已有相关研究成果,将劳动力转移、农业技术水平与城乡居民收入差距联系起来思考,可以具体地考察劳动力转移对城乡居民收入差距的影响.文章以农业技术水平作为门槛变量,选取2009—2019年中国31个省份的面板数据,利用泰尔指数测定城乡收入差距,以劳动力转移作为核心解释变量构建面板门槛模型,实证得出劳动力转移对城乡居民收入差距的非线性影响.研究发现:劳动力转移可以缩小城乡居民收入差距,且该影响具有单一门槛效应.在农业技术水平较低时,劳动力转移对城乡居民收入差距收敛效应较小;当农业技术水平越过门槛值达到较高水平后,劳动力转移对缩小城乡居民收入差距的效果几乎增加了一倍.此后,通过替换解释变量泰尔指数为城乡人均可支配收入比、替换核心解释变量农业技术水平为农业生产效率重新建立面板门槛模型,发现上述结论仍然成立,其检验结果具有较强的稳健性.文章将农业技术进步、劳动力转移、城乡居民收入差距这三个重要变量纳入同一模型框架中,在加深劳动力流动影响城乡居民收入差距这一视角的研究的同时,对缩小城乡居民收入差距政策的制定提供了重要的参考意义.     

概念迁移视阈下基于语料库的非英语专业学习者动名词搭配错误研究

文章拟从概念迁移视角研究大学英语写作中的动-名词搭配错误，研究采用语料库定量与定性相结合的分析方法。语料取材于中国学习者英语语料库（CLEC），包括大学英语低年级学习者（St3）和高年级学习者（St4）两个子语料库。利用检索工具Ant Conc3.58检索中国学习者作文中的动-名词搭配错误，从而对大学生英语写作中的动-名词搭配错误进行描述与分类，进而分析造成大学生英语写作动-名词搭配误用的潜在原因，并对现有大学英语教学做出反思。     

Accurate computation of single and product moments of order statistics under progressive censoring

An accurate procedure is proposed to calculate approximate moments of progressive order statistics in the context of statistical inference for lifetime models. The study analyses the performance of power series expansion to approximate the moments for location and scale distributions with high precision and smaller deviations with respect to the exact values. A comparative analysis between exact and approximate methods is shown using some tables and figures. The different approximations are applied in two situations. First, we consider the problem of computing the large sample variance–covariance matrix of maximum likelihood estimators. We also use the approximations to obtain progressively censored sampling plans for log-normal distributed data. These problems illustrate that the presented procedure is highly useful to compute the moments with precision for numerous censoring patterns and, in many cases, is the only valid method because the exact calculation may not be applicable.     

“省直管县”改革能否提升县级财力水平?

将“省直管县”财政体制改革作为拟自然实验，基于全国县级面板数据，利用可有效校正选择偏差问题的 PSM-DID 方法构造“反事实”状态，估计改革对县级财力水平的平均处理效应。结果显示: 改革增加了人均本级财政收入，却减少了人均转移支付水平，且下降幅度较大，致使人均财政总收入减少，表明“省直管县”改革不但无法提升，甚至会在一定程度上恶化县级财政状况。东、中部地区的平均处理效应与全国类似，上述结论具有比较好的稳健性。此外，还进行了影响机制检验，地级市与县、县与县之间的财政竞争以及省对各市、县的协调机制会在一定程度上影响财政体制改革的效果。     

A Bayesian Analysis of Abundance,Trend, and Population Viability for Harbor Seals in Iliamna Lake,Alaska

Harbor seals in Iliamna Lake, Alaska, are a small, isolated population, and one of only two freshwater populations of harbor seals in the world, yet little is known about their abundance or risk for extinction. Bayesian hierarchical models were used to estimate abundance and trend of this population. Observational models were developed from aerial survey and harvest data, and they included effects for time of year and time of day on survey counts. Underlying models of abundance and trend were based on a Leslie matrix model that used prior information on vital rates from the literature. We developed three scenarios for variability in the priors and used them as part of a sensitivity analysis. The models were fitted using Markov chain Monte Carlo methods. The population production rate implied by the vital rate estimates was about 5% per year, very similar to the average annual harvest rate. After a period of growth in the 1980s, the population appears to be relatively stable at around 400 individuals. A population viability analysis assessing the risk of quasi‐extinction, defined as any reduction to 50 animals or below in the next 100 years, ranged from 1% to 3%, depending on the prior scenario. Although this is moderately low risk, it does not include genetic or catastrophic environmental events, which may have occurred to the population in the past, so our results should be applied cautiously.     

Restricted minimax estimation in semiparametric linear models

Abstract

In this article we develop the minimax estimation approach of general linear models to the semiparametric linear models when the parameters are simultaneously constrained by an ellipsoid and linear restrictions. Combining sample information and prior constraints the minimax estimator is obtained and compared with partially least square estimator by theoretical and simulation methods.     

湖北省乡镇企业1978—2002年发展概况、问题及对策研究

1978～2002年,湖北省乡镇企业在企业单位数量、对经济增长贡献及转移农村剩余劳动力等方面对该省经济产生了重要的推动作用。然而,随着市场经济体制的深入发展和不断完善,乡镇企业发展也遇到了前所未有的困难。本文在深入分析当前乡镇企业所面临的问题基础上,提出了乡镇企业未来发展的战略对策。     

复亚半正定矩阵

给出了复亚半正定矩阵的概念，研究了它的基本性质及行列式理论，将Hermite阵的Schur定理，华罗庚定理，Minkowski不等式，凸性不等式，Ostrowski-Taussky不等式推广到了较广泛的复矩阵类，扩大了Minkowski不等式的指数范围，削弱了华罗庚不等式的条件。     

关于第二类级联构造Bent序列的讨论(英文)

考虑用 4个长为 2 n - 2 的Bent序列或线性序列级联构造Bent序列的问题 ,给出了第二类线性基Bent序列的类型以及级联序列为第二类Bent基Bent序列的一个充分条件 .     

论上市公司国有股减持对我国公司法的挑战

围绕上市公司国有股减持人们提出了许多方案。这些方案的实施对我国公司法上的小股东利益保护、公司治理及发起人股份转让限制制度提出了严峻挑战。我国公司法必须从建立系统的小股东利益保护法律制度、包括约束内部人控制和公司机关更迭衔接制度在内的公司治理制度和放宽发起人股份转让限制条件三个方面予以完善,才能应对挑战和保障国有股减持的顺利进行。