基于作业过程的园林绿化项目资源清单模型

结合生产要素六元理论，对园林绿化项目资源进行界定；以作业过程为信息关联节点，通过施工工序分解和资源特征匹配，构造园林绿化项目的“产出-作业”分配关系描述矩阵和“作业-资源”消耗关系描述矩阵。XX科技园林绿化企业的应用结果表明，项目资源清单模型解决了目前园林绿化企业资源信息分离使用的现状，是企业快速构建项目资源计划表、项目施工方案以及快速估算项目成本等的基础数据信息。     

基于成本优化的制造业生产物流装配线排序问题分析

为了降低制造业的生产成本，提高收益，在分析生产物流配线闲置和超载成本的基础上，采用粒子群算法对其进行优化，并利用模糊自适应改进惯性权值，通过实证研究表明该方法实用，可操作性强，可以有效降低制造业生产物流成本，具有广泛的应用价值。     

Money,random matching and endogenous growth: A quantitative analysis

In this study, we develop a search-and-matching monetary growth model to analyze the effects of inflation on economic growth and social welfare by introducing endogenous economic growth via capital externality into a two-sector search-and-matching model. We find that the channel through which inflation affects economic growth in the search-and-matching model is different from the traditional cash-in-advance model. To facilitate the calibration, we obtain an empirical estimate of the effects of inflation on economic growth using panel regressions. In the simulation analysis, we quantitatively evaluate the welfare effect of inflation in the search-and-matching endogenous growth model and compare it to a search-and-matching exogenous growth model. We find that the welfare effect of inflation is nonlinear in the endogenous growth model whereas it is linear in the exogenous growth model. Furthermore, we find that the welfare cost of inflation under endogenous growth is up to four times as large as the welfare cost of inflation under exogenous growth.     

Numerical Maximisation of Likelihood: A Neglected Alternative to EM?

There is by now a long tradition of using the EM algorithm to find maximum‐likelihood estimates (MLEs) when the data are incomplete in any of a wide range of ways, even when the observed‐data likelihood can easily be evaluated and numerical maximisation of that likelihood is available as a conceptually simple route to the MLEs. It is rare in the literature to see numerical maximisation employed if EM is possible. But with excellent general‐purpose numerical optimisers now available free, there is no longer any reason, as a matter of course, to avoid direct numerical maximisation of likelihood. In this tutorial, I present seven examples of models in which numerical maximisation of likelihood appears to have some advantages over the use of EM as a route to MLEs. The mathematical and coding effort is minimal, as there is no need to derive and code the E and M steps, only a likelihood evaluator. In all the examples, the unconstrained optimiser nlm available in R is used, and transformations are used to impose constraints on parameters. I suggest therefore that the following question be asked of proposed new applications of EM: Can the MLEs be found more simply and directly by using a general‐purpose numerical optimiser?     

区域产业发展视角的农业综合开发影响评估——基于对蔬菜产业的干预效应分析

【目的】通过定量方法准确评估农业综合开发对区域优势产业发展的影响有重要意义。【方法】从农业综合开发对蔬菜产业的项目干预效应入手,以县级为单位,将当年农业综合开发项目扶持内容包括蔬菜产业的县级单位划分为干预组,其他为控制组。采用可以有效解决样品选择偏差的倾向得分匹配方法,通过引入协变量、平衡检验、匹配等步骤,在控制组中找到与干预组成员单位特征相似的成员,构建反事实研究框架。【结果】结果得出,项目干预组比控制组区域的蔬菜播种面积占比高出1~3个百分点,说明农业综合开发项目对蔬菜产业的扶持对蔬菜播种面积的扩大有促进作用,利于蔬菜产业壮大。通过协变量影响力分析得出,地区的蔬菜生产优势是最重要的影响因素,从侧面证明了农业综合开发项目的扶持方向紧跟区域优势的政策宗旨。【结论】可见,通过有方向性的农业综合开发项目实施扶持特定产业对促进区域优势产业发展和实现农业结构优化是有效的。     

基于星载极化SAR数据的农作物分类识别进展评述

［目的］农作物播种面积信息不仅可为农情监测和作物估产提供重要的数据保障，还是国家制定粮食政策和经济计划的重要依据。快速、准确地获取农作物播种面积信息能为农业生产管理提供决策支持。极化SAR不受云雨天气的影响，在农作物遥感监测方面具有巨大的应用潜力，有效利用极化SAR数据进行农作物识别研究对促进雷达技术在国家农业遥感监测和农业供给侧结构性改革中发挥更大作用具有重要意义。［方法］以星载极化SAR技术的发展过程为论述主线，从单、双极化SAR数据，单、双极化SAR数据结合光学影像，全极化SAR数据三个发展阶段，对极化SAR数据在农作物分类识别中的研究与应用进行总结，并对比分析不同的识别特征、融合算法以及分类算法的优缺点。［结果］以往研究存在以下不足：当前研究多以识别水稻为主，对于难以识别的旱地作物研究较少；目前对旱地作物识别精度不高，平均识别精度不足85%；缺乏对不同作物散射机制及其随时相变化的研究，导致分类算法机理性不足，普适性较差。［结论］在今后的研究中，旱地作物散射机制的定量确定，如何利用散射机制及其变化来提高旱地作物遥感识别精度和普适性；目前分类算法大都是基于光学影像设计，如何利用SAR特殊的成像方式优化设计适用于极化SAR数据的分类算法，得到更高的分类精度；如何更好的跟光学遥感等多源数据（光学数据、GIS数据等）结合来提高精度，将成为未来极化SAR农作物识别中三个亟需重点解决的问题。     

The German labor market during the Great Recession: Shocks and institutions

This paper analyzes Germany's unusual labor market experience during the Great Recession. We estimate a general equilibrium model with a detailed labor market block for post-unification Germany. This allows us to disentangle the role of institutions (short-time work, government spending rules) and shocks (aggregate, labor market, and policy shocks) and to perform counterfactual exercises. We identify positive labor market performance shocks (likely caused by labor market reforms) as the key driver for the “German labor market miracle” during the Great Recession.     

Does studying abroad enhance employability?

Over 200,000 European students study abroad under the Erasmus programme. It appears that studying abroad may impart skills which are helpful for professional careers after graduation. Approximately, 54% of European students report that participation in the Erasmus exchange programme helped them to obtain a first job; however, interestingly, those from Central and Eastern European countries report it much more often—in 73% of cases. The aim of this paper is to find out whether studying abroad enhances the employability of higher education graduates in Poland. Using the propensity score matching method and data from a nationwide tracer survey of Polish graduates, we find that Polish students who completed at least one semester of their studies abroad do not benefit in terms of a higher employment rate after graduation.     

设立国家级贫困县能提升当地农民收入水平吗——基于2007~2016年中国296个县面板数据的实证研究

中国自1986年实施贫困县制度以来，国家级贫困县的设立是否能够以及在多大程度上提升了当地农民实际收入水平，需要进行系统科学的实证检验。基于双重差分倾向得分匹配法（PSM-DID），利用2007~2016年全国6个省份296个县的面板数据进行实证研究发现，国家级贫困县的设立非但没能有效提升当地农民实际收入水平，反而对其有持续的负效应。进一步研究发现，贫困地区第二、三产业的发展能够有效提高当地农民实际收入水平，然而贫困县政策并未促进当地产业结构的优化；政府通过正向干预农产品价格能有效增加农民实际收入。从研究结论的政策含义讲，立足贫困户推进精准扶贫、通过招商引资带动有效投资，以及优化县域产业结构，对于提升贫困县的农民收入具有重要现实意义。     

Impacts of sustainability certification on farm income: Evidence from small-scale specialty green tea farmers in Vietnam

Sustainability certification for small-scale farms has gained considerable momentum in developing countries. However, evidence on the economic benefits of certification schemes in the context of domestically consumed foods and beverages is scarce. This paper addresses this gap by evaluating the impacts of sustainability standards on the selling prices, sales, costs and net income of small-scale specialty green tea farming in Vietnam. We analyze original survey data on 401 smallholder green tea farmers and employ propensity score matching to mitigate self-selection bias. Our estimates reveal that certified green tea producers are able to obtain a higher average selling price and sales value. In addition, although certification leads to a dramatic increase in the costs of hired labor, net farm income is still significantly improved.