Smoothing fertility trends in agricultural field experiments

Fertility trend within blocks and local variations are the major obstacles to estimate cultivar contrasts in agricultural field trials. This paper examines methods of smoothing fertility trends in field trials using the P-spline. We begin by smoothing trend within block and for each block, and proceeds to demonstrate how it can be extended to smooth trends in trials with two-dimensional setting. We propose simultaneous modelling of trends and local variation. We use Papadakis [J.S. Papadakis, Comparison de differentes methds d'expermentation phytotechnique, Rev. Argen. Agronom. 7 (1940), pp. 297–362.] and kriged covariate to model local variation. We emphasize on the benefit of using P-spline to compromise between parametric and non-parametric approaches. Data sets from wheat and barley trials, designed as randomized complete block design and row-column, are analyzed. We set out a simple strategy of choosing between additive model and two-dimensional setting. We explore different estimation methods and offer some generalizations. The results show importance of the P-spline in modelling trend and the need to choose between additive and two-dimensional settings.     

论宪法视野下的国土空间用途管制制度

国土空间用途管制作为国土空间治理的重要手段,对于推进空间治理体系和治理能力现代化,在更高层次上构建人与自然和谐共生的关系具有十分重要的作用。国土空间用途管制制度是整个生态文明制度体系中不可或缺的重要组成部分,但目前国土空间用途管制的制度依据主要表现为政策性文件,缺乏权威、统一和专门的法律规定,与依法治国时代背景下在法治轨道上推进生态文明建设的客观要求不相适应,需要加快构建国土空间用途管制法律制度,为国土空间用途管制提供法治保障。本文以此问题为导向,把国土空间用途管制制度置于宪法视野中加以审视,主要通过历史梳理和文本分析,厘清国土空间用途管制的科学内涵,探究其合宪性基础和宪法许可界限。本文认为,我国与国土空间用途管制相关的宪法规范经历了以土地和其他自然资源所有权确权为主的萌芽阶段、以各自然要素分散管制为主的发展阶段,以及全域全要素统筹管制的确立阶段。如今,国土空间用途管制因应了生态环境保护和生态文明建设的国家任务、保障国土空间资源开发利用秩序、实现国土空间治理体系和治理能力现代化等要求,从而得以在现行宪法中找寻到其获得宪法许可的合宪性基础。与此同时,现行宪法又为国土空间用途管制设定了许可...     

劳动力价格上涨、粮食生产机械化及其产出效应

农业机械化是实现现代农业和保障粮食安全的重要基础。基于2001-2020年中国省级面板数据,实证分析劳动力价格对粮食生产机械化的影响以及粮食生产机械化的产出效应,并考察该影响及效应在耕种收各环节上的差异性。研究结果表明：劳动力价格上涨显著正向影响粮食生产综合机械化水平、机耕水平及机收水平;农机总动力对粮食产出具有显著的空间溢出效应;大中型农机动力及大中型农机机耕、机播及机收动力均对粮食产量具有显著的直接影响和空间溢出效应,且其空间溢出效应均大于直接效应。研究建议加快突破粮食生产的薄弱环节,促进农业社会化服务发展,推动农机资源在省际间合理流动与科学调配,加强小农生产与现代农业的衔接,加速实现粮食生产全程机械化与农业农村现代化。     

房地产金融风险演化特征及其影响因素——基于动态空间杜宾模型

房地产金融风险是系统性金融风险的重要组成部分,防范房地产金融风险是落实中国金融安全战略的关键。基于2011—2020年中国31个省份面板数据,描述了房地产金融风险的时空演化特征,并通过构建动态空间杜宾模型探究房地产金融风险的溢出机制及其影响因素。研究发现:(1)中国房地产金融风险呈现波动上升的时序演化特征,且省际差异逐渐缩小;全局存在明显的空间依赖性,局部空间格局以高—高集聚和低—低集聚为主;(2)房地产金融风险在时间、空间和时空维度上分别表现出雪球效应、溢出效应和警示效应;(3)地方政府债务风险对房地产金融风险存在正向直接影响和负向空间溢出效应,而信贷扩张对其存在正向直接影响和正向空间溢出效应。因此,应统筹省际政策联动,加强地方政府债务管理,监控房地产信贷规模,以防范房地产金融风险。     

数字经济巩固拓展脱贫攻坚成果与 乡村振兴有效衔接 ———基于非线性空间效应研究

基于 2011—2018 年中国省级面板数据,构建不同空间权重矩阵,采用空间杜宾模型检验数字 经济对脱贫攻坚成果与乡村振兴有效衔接的空间溢出效应。 研究结果表明:(1)数字经济对巩固拓展脱 贫攻坚成果与乡村振兴有效衔接具有助推作用,同时具有明显的空间溢出效应。 从整体层面以及地区层 面看,在地理距离权重与空间邻接权重下,数字经济对临近地区均具有为正向空间溢出效应即扩散效应。 (2)数字经济对脱贫攻坚成果与乡村振兴有效衔接的空间溢出效应具有地区异质性,呈现东中西依次递 增趋势,在落后的西部地区数字经济红利能够实现效用最大化。 (3)数字经济对脱贫攻坚成果与乡村振 兴有效衔接存在空间非线性,即空间溢出效应存在双门槛,随着数字经济逐步跨越门槛值,对本地区的直 接效应呈现倒“U”趋势,溢出效应呈现“U”形。     

中国省际经济差距来源分析

在利用索洛模型对中国省区1985—2009年经济增长进行分解的基础上,结合空间标准差指标并采用基于VAR模型的脉冲响应函数分析了中国省际经济差距状况及来源。研究发现:总的来看,中国省区劳均产出与要素投入均呈现空间σ趋异倾向,而全要素生产率则在呈现空间σ收敛后趋于稳定。进一步利用VAR模型及脉冲响应函数分析发现,在较长时期内,要素投入总体上扩大了中国省际经济差距,而全要素生产率则有助于缩小省际经济差距,这主要是由要素投入的经济拉动滞后效应和技术的扩散效应所致。     

The discretely observed immigration-death process: Likelihood inference and spatiotemporal applications

ABSTRACT

We consider a stochastic process, the homogeneous spatial immigration-death (HSID) process, which is a spatial birth-death process with as building blocks (i) an immigration-death (ID) process (a continuous-time Markov chain) and (ii) a probability distribution assigning iid spatial locations to all events. For the ID process, we derive the likelihood function, reduce the likelihood estimation problem to one dimension, and prove consistency and asymptotic normality for the maximum likelihood estimators (MLEs) under a discrete sampling scheme. We additionally prove consistency for the MLEs of HSID processes. In connection to the growth-interaction process, which has a HSID process as basis, we also fit HSID processes to Scots pine data.     

The practice of mining gegstatistics in 1980

The scope of the term “Mining Geostatistics” is defined in the context of a brief historical review of the topic. Assumptions andtools adapted from probability theory are applied first to linear estimation problems leading to the iging” estimator and then shown capable of extension to non- ationary and non-linear situa­tions, in which conditional simulation, conditional distributions and “disjunctive Kriging” become applicable. Directions for further research work are indicated regarding variogram identification and modelling of random functions where stationarity or linearity may not hold. The brief review suggests that the mutual benefits of practice and theory will continue to develop.     

On the Prediction of the Subpopulation Total Based on Spatially Correlated Longitudinal Data

In a special case of the general linear mixed model, one random component obeys a spatial autoregressive process and another a temporal autoregressive process. The population and any affiliations to subpopulations may change in time. The empirical best linear unbiased predictor is derived and may be used even if the sample size in the subpopulation is null in the period of interest. The mean squared error and its estimator are expressed. The accuracy of the predictor and the bias of the mean squared error estimator are addressed through simulations.     

我国出生性别比空间特征与影响因素分析

本文利用空间统计学方法对五普和六普出生性别比的时空演变与影响因素进行了分析。结果发现：十年中我国出生性别比的空间集聚特征更加明显;计生政策、公共卫生水平、经济因素对性别偏好的影响显著,城镇化水平的影响不显著,教育、公共服务水平对性别比的影响有待深入研究。