External debt,growth and investment for developing countries: some evidence for the debt overhang hypothesis

Portuguese Economic Journal - We investigate the effect of total, public, and private external debt stocks on the growth rate and also on total, government, and private investment by using data for...     

Optimal model averaging forecasting in high-dimensional survival analysis

This article considers ultrahigh-dimensional forecasting problems with survival response variables. We propose a two-step model averaging procedure for improving the forecasting accuracy of the true conditional mean of a survival response variable. The first step is to construct a class of candidate models, each with low-dimensional covariates. For this, a feature screening procedure is developed to separate the active and inactive predictors through a marginal Buckley–James index, and to group covariates with a similar index size together to form regression models with survival response variables. The proposed screening method can select active predictors under covariate-dependent censoring, and enjoys sure screening consistency under mild regularity conditions. The second step is to find the optimal model weights for averaging by adapting a delete-one cross-validation criterion, without the standard constraint that the weights sum to one. The theoretical results show that the delete-one cross-validation criterion achieves the lowest possible forecasting loss asymptotically. Numerical studies demonstrate the superior performance of the proposed variable screening and model averaging procedures over existing methods.     

基于演化博弈的新型上下级行为期望研究

为了探究如何建立共赢的新型上下级行为,文章将演化博弈应用于二者之间复杂行为的交互作用研究中,构建双方的动态演化博弈模型;计算博弈双方在不同行为选择下的收益,并进行了稳定性分析;然后运用MATLAB对双方的行为演化路径进行了仿真模拟.结果表明:该系统的演化方向与系统的初始条件有关;不同的初始条件下,能得到四个演化稳定点;最后,对三种含有不服从行为策略的组合提出了对策建议.     

数据变革、数据理论与数据治理: 一个简要述评

本文阐述和探究了数字时代下的数据变革趋势及国家支持政策、数据经济理论和数据治理的基本问题.首先,促进数据要素的运用与发展已经成为全球共识.其次,基于不同假定和市场情境,学术界对搜集与使用用户数据问题的理论研究在数据共享的效率影响方面得出了不同结论:当消费者是否理性、是否拥有信息优势的假定不同时,数据优势是否会被滥用、数据共享是否会提升效率的研究结论完全相反;在数据技术、数据交易、数据支付等不同市场情境中,会出现多种福利结果,如效率提升、市场失灵、服务提供者可能滥用数据信息优势等.最后,学术界对于数据治理方面的研究主要围绕数据产权的界定与分配、数据集中及数据(和算法)伦理责任等三个方面展开.数据产权界定和分配主要依据数据分类分级原则对初始数据进行判定;数据集中主要从可触达性或可及性而非产权角度、从数据产业价值链条的角度来审视;数据(和算法)伦理责任包括可解释、可问责、透明、正义与中立等方面的义务.本文的探究和梳理有助于深化对数据的认识和治理.     

试析我国中小企业绩效管理存在的问题及对策

我国的经济发展主要是由国企和中小企业带动,而绩效管理则是维持企业正常运转的重要组成部分。我国是人口大国,也是发展中国家,所以我国中小企业都如雨后春笋般发展迅速,但是目前的中小企业的绩效管理还存在一些问题,亟待解决。     

稻鳅共生种养模式试验研究

[目的]稻鳅共生是典型的稻田综合利用模式,符合生态农业发展方向。通过对稻鳅共生生态系统的生理生态学机制开展试验研究,为进一步推广稻鳅共生种养模式提供科学依据。[方法]采用田间试验方法,以水稻单作为对照,研究了不同泥鳅养殖密度下的稻鳅共生对水稻农艺性状、土壤理化性质、水稻产量构成的影响,并对稻鳅共生种养模式进行了经济效益分析。[结果]与对照处理相比,水稻长势在株高、有效分蘖率、根长等方面有一定提高。养殖田水稻株高增高了3%,有效分蘖率提高了8%~11%,根长提高了8.8%~31.3%。在土壤理化性质方面,与对照相比,土壤容重降低了7.1%~21.2%,孔隙度增加了4.1%~14.7%。实验前后养殖田内土壤有机质增加了3.5%~26.5%,对照田降低了2.5%~5.8%。土壤肥力(氮、磷、钾)减少,但减少幅度小于对照处理。稻鳅共生种养模式下水稻产量提高了5%~25%,同时稻田增收泥鳅1 725~3 375kg/hm2,净收入为1.836 0万~2.307 0万元/hm2,经济效益提高了3.65~4.84倍。稻鳅共生种养模式中泥鳅的养殖密度为30万尾/hm2时稻田的生态效益和经济效益最佳。[结论]稻鳅共生有效改善了土壤理化性质,促进了水稻的生长,提高了稻田产量和产值。     

高分1号冬小麦解译面积核算方法研究

[目的]以高分1号(GF-1)融合2m卫星遥感影像为基础数据源,结合土地利用现状数据、高分多源遥感影像和地面样方等数据,对冬小麦分类提取中存在的面积误差问题进行研究和分析。[方法]文章以河南省永城市为研究区,在冬小麦提取结果聚类处理基础上,基于线性地物缓冲区数据,采用GIS空间运算实现线性地物面积扣除,接着分析了样方数据和土地利用现状数据再扣除零星地物面积比例上的差异,并采用样方零星地物平均扣除系数对全市各乡镇耕地与非耕地中冬小麦提取面积进行了相关统计和误差分析。[结果]永城市冬小麦最终解译面积11. 29万hm~2,其中线性地物和零星地物扣除面积分别为6 613. 08hm~2和3 875. 22hm~2,占研究区冬小麦解译面积的5. 86%和3. 32%,与统计上报数据相比,其处理前后误差由14. 12%降低至4. 41%,有效地提高冬小麦提取面积精度。[结论]误差来源分析与修正对冬小麦解译面积核算精度具有重要影响,该研究为县级区域尺度下冬小麦面积提取核算提供了思路和借鉴。     

Supply chain finance: A three-party decision model with suppliers' guarantees for retailers

Under the premise that financing constraints frequently occur in the supply chain, this paper investigates the financing model of the supplier providing guarantee for the retailer under symmetric and asymmetric information. The optimal solutions of the retailer, the supplier, and the bank are studied by using the Stackelberg game. Results show that increasing the supplier's guarantee proportion can effectively improve the bank's reasonable margin rate and increase the supplier's profit. Under the condition of asymmetric information, the bank can increase the probability of credit loan in the supply chain by reducing the cost of spot check and setting up a reasonable fine limit.     

Modeling green vehicle adoption: An integrated approach for policy evaluation

This article employs an integrated discrete-continuous car ownership model to jointly forecast households’ future preferences on vehicle type, quantity and use, and to estimate greenhouse gas (GHG) emissions. The model system is estimated on a dataset collected from a web-based stated preference survey conducted in Maryland in 2014. The data contain vehicle purchase decisions and sociodemographic information of 456 households who were requested to state their future preferences over a 9-year period (2014–2022). In each time period, a respondent is faced to four alternatives that include the current vehicle, a new gasoline vehicle, a new hybrid electric vehicle, and a new battery electric vehicle. Intertemporal choices between conventional and “green” vehicles such as hybrid and electric cars capture dynamics in vehicle purchase decisions. Short run and medium-long run situations were predicted and compared based on the first 4-year data and the entire 9-year data of the dynamic panel. Vehicle GHG emissions were calculated correspondingly. We find the introduction of “green” vehicles makes a positive impact on car ownership and use, especially in a medium-long run. Two “green” taxation policies, gasoline tax and ownership tax, were proposed and their impact on vehicle use and emission reductions was evaluated. Results indicate that: (a) gasoline tax is a more effective way to reduce vehicle miles traveled and GHG emissions and (b) gasoline tax makes a higher impact on car use and emission reductions in the medium-long run, while ownership tax makes a higher impact in the short run.     

公私合作模式下绿色社区项目利益相关者共同治理研究

在绿色社区全寿命周期内存在多元化的利益相关者主体,它们之间的目标和利益即存在统一方面也表现出冲突方面,特别是在社区运营管理阶段。为了体现绿色社区全寿命周期的绿色、生态、低碳理念,就需要建立起与之适应的各利益相关者共同参与的绿色社区的社区共同运营管理模式。公私合作模式(PPP)的功能不仅体现在其卓越的融资表现上,公私合作的内涵更是符合社区各参与人进行共同治理的理论要求。本文将对公私合作模式下绿色社区项目的各利益相关者进行分析,构建绿色社区利益相关者共同运营管理机制。