Variable selection for spatial Poisson point processes via a regularization method

It is often of interest to use regression analysis to study the relationship between occurrence of events in space and spatially-indexed covariates. One model for such regression analysis is the Poisson point process. Here, we develop a method to perform the selection of covariates and the estimation of model parameters simultaneously for this model via a regularization method. We assess the finite-sample properties of our method with a simulation study. In addition, we propose a variant of our method that allows the selection of covariates at multiple pixel resolutions. For illustration, we consider the locations of a tree species, Beilschmiedia pendula, in a study plot at Barro Colorado Island in central Panama. We find that Beilschmiedia pendula occurs in greater abundance at locations with higher elevation and steeper slope. Also, we identify three species to which Beilschmiedia pendula tends to be attracted, two species by which it appears to be repelled, and a species with no apparent relationship.     

Who wins from an FTA induced revival of world trade?

The last decade has been characterized by a slowdown in globalization, referred to by some as "slowbalisation" and “deglobalization”. The COVID-19 pandemic has reinforced this impression. To overcome the deadlock in the Doha round negotiations at WTO the major players in world trade are negotiating or have already implemented several free trade agreements (FTAs) as a second-best solution. We analyze within a common framework nine mega FTAs, some of them are already in effect, others will be enacted soon. Overall, not the big players in world trade, the EU and the United States win by a simultaneous implementation of the nine FTAs. Japan would be the winner because it participates in four combinations (overlaps) of FTAs: EU-Japan, USA-Japan, CPTPP and RCEP. The United States hardly gain from further globalization. Similarly, the EU27 cannot profit much from further globalization.     

资产价格泡沫何时发生崩溃？——基于LPPL模型的在中国金融市场上的有效性检验

本研究基于对数周期幂律模型LPPL（Log Periodic Power Law Model），针对金融时间序列将一维价格波动翻译成反映市场泡沫微观结构的多维变量。通过对多维变量的动态监测，把握市场中泡沫的演变并预测泡沫破裂的临界点，从而有效降低或防范金融资产泡沫破裂所导致的风险。为检验LPPL模型在中国金融市场中的适用性，本文分别使用上证综指、四个期货连续合约以及两支个股检验模型效果。实证结果表明当金融资产价格序列呈现超指数加速震荡上升或下降时，该模型能获得稳定的估计效果，有效预测泡沫破裂临界时点。     

统计模型的“不确定性”问题:与倾向值方法

量化社会学研究往往基于特定的统计模型展开。近十几年来日益流行的倾向值方法也不例外，其在实施过程中需要同时拟合估计倾向值得分的“倾向值模型”与估计因果关系的“结果模型”。然而，无论是其模型形式还是系数估计，统计模型本身都具有不可忽视的“不确定性”问题。本研究在倾向值分析方法的框架下，系统梳理和阐释了模型形式不确定性与模型系数不确定性的内涵及其处理方法。通过分析“蒙特卡洛模拟”数据与经验调查数据，本文展示了在使用倾向值方法进行因果估计的过程中，研究者如何通过“贝叶斯平均法”进行多个备选倾向值模型的选择，以及如何通过联合估计解决倾向值模型与估计模型中的系数不确定性问题。本文的研究也表明，在考虑倾向值估计过程的不确定性之后，结果模型中对于因果关系的估计呈现更小的置信区间和更高的统计效率。     

Modeling the Dependence of Conditional Correlations on Market Volatility

Several models have been developed to capture the dynamics of the conditional correlations between time series of financial returns and several studies have shown that the market volatility is a major determinant of the correlations. We extend some models to include explicitly the dependence of the correlations on the market volatility. The models differ by the way—linear or nonlinear, direct or indirect—in which the volatility influences the correlations. Using a wide set of models with two measures of market volatility on two datasets, we find that for some models, the empirical results support to some extent the statistical significance and the economic significance of the volatility effect on the correlations, but the presence of the volatility effect does not improve the forecasting performance of the extended models. Supplementary materials for this article are available online.     

以边境口岸辐射城镇化:西南边境地区发展模式研究

边境地区因地制宜地推进城镇化,具有"富民、兴边、强国、睦邻"的重大现实意义。迅速兴起的互市贸易、口岸经济、跨境经济表明,以边境口岸辐射城镇化可以促使生产要素整合和人口转移,形成人口规模聚集,培育互市型、口岸型和跨境经济合作型城镇,呈现三个层次的沿边发展模式体系。西南边境地区应当挖掘各自的优势,促进各种要素的合理流动和高效聚集,形成优势互补,从而推进西南边境地区的综合发展。     

优势视角下司法社会工作实践模式探析

在分析问题模式与优势模式两者差异的基础上,提出了衡量优势视角下司法社会工作的六大实践标准;以及优势视角模式对司法社会工作的贡献及存在的不足;最终对优势视角下我国司法社会工作实践提出了相关建议与对策。     

我国养老机构护工培训模式的类型

养老机构护工素质是制约我国养老业发展的一个极其重要的因素。而护工培训体系的不完善则又制约了护工素质的提高。本文基于中部地区养老机构护工培训工作的调查,把目前我国护工培训体系划分为四个模式类型,它们分别是政府培训模式、市场培训模式、社会培训模式和混合培训模式,这些模式分别适应于不同的外部环境。     

我国家庭结构的变迁对农村养老模式的影响

传统的大家庭是家庭养老的基石,可是转型时期的中国家庭发生了裂变:传统家庭结构分化,家庭规模趋向小型,联合大家庭解体,核心家庭占主体。这些变化使得传统的家庭养老模式受到挑战,尤其在承载了中国约75%的老年人口的农村,如何有效缓解由农村家庭结构变迁对传统家庭养老保障带来的冲击,显得尤为重要。     

第二语言学习者产出性词汇发展的理论模式

研究外语课堂环境下产出性词汇的发展,旨在评估课堂教学对学习者产出性知识发展的影响,并在此基础上来制定词汇大纲将更符合实际情况,同时对词汇习得的心理机制有更全面的认识.除了对词汇教学以启示外,还将激发更多相关研究:无论是充实解释性的理论,还是从事实证性研究,以进一步确定影响二语词汇能力发展的内外因素.