多时相极化SAR数据的旱地作物分类研究

[目的]及时、准确地获取旱地作物类型、种植面积及空间分布信息,可为农业生产管理,国家粮食政策提供重要依据。文章主要是对河北省冀州市棉花、玉米、水体和建筑进行分类,比较不同时相及分类方法下RADARSAT-2数据对4种地物的分类精度。[方法](1)计算得到每个时相(2018年7月14日、8月7日、9月24日)全极化RADARSAT-2数据的39个特征;(2)结合随机森林分类器比较不同分解方法(Freeman分解、Yamaguchi分解、MCSM模型和Cloud分解)得到的特征对旱地作物的分类精度影响;(3)分析参与分类的特征数量和时相对分类精度的影响;(4)将多时相多特征相结合,确定研究区内旱地作物的最佳识别方案。[结果]不同分解方法得到的特征越多、分类精度越高;就仅使用单景影像而言,在9月24日(玉米成熟期早期、棉花吐穗期中期)总体分类精度最高;不同分解方法得到的极化特征之间有一定的相关性,同一时相下,增加参与分类的极化特征数量不能有效提高分类精度;使用3个时相上117个极化特征,结合随机森林分类器,可以得到最佳分类精度(总体分类精度达92.89%,Kappa系数为0.885 9)。[结论]结合多时相与多特征相RADARSAT-2数据,能够有效提高复杂种植结构下旱地作物的识别精度,该研究可为旱地作物种植面积的快速提取提供参考。     

Inflation,technological-knowledge bias,and wages

A detailed examination of wage data points to a wage polarization trend vis-à-vis the distribution of qualifications. Theoretically terms, this points to the need for modeling focused on the relevance of the direction of technological knowledge. To this end, we branched production into routine and non-routine tasks. In this way, the results produced positive relationships between the relative supply of skilled workers and the skill premium and between automation and wage polarization.     

河南省经济发展新动能空间极化特征研究

根据对新动能内涵的理解构建河南省经济发展新动能指数，并结合新动能集中度和极化度模型，对河南省经济发展新动能空间极化效应进行分析。研究发现：河南省各地市新动能及其核心要素的集中度存在明显的不均衡现象，且各个地市之间的差距呈现不断扩大的趋势；河南省经济发展新动能空间极化程度呈现逐年上升的态势，表现为郑州对省内其他地市的“持续虹吸”影响。     

Political polarization and international cooperation

We analyze the consequences of political polarization between domestic policymakers for international policy coordination or delegation to a common agency. Coordination is preferred under political polarization if it allows to constrain the policy of policymakers with different policy targets, while delegation allows to determine policies in the future by selecting the appropriate agent. Policymakers have different preferences concerning international coordination and which form it should take. These differences are increasing in political polarization. They agree on delegation if election outcomes are close to being random.     

双通道跟踪接收机的动态极化校相

传统校相方法无法检测双通道单脉冲体制雷达极化失配问题。采用基于静态目标的动态极化校相方法，即在静态条件下，增加一个信标天线正交极化角校相环节，用于完成跟踪接收机和差信道的校相工作。数学模型的构建、仿真计算以及实测结果均表明，采用该方法可以准确识别双通道单脉冲体制雷达双通道极化失配问题，弥补了传统校相方法在检测跟踪接收机和差信道极化失配问题上的缺陷。     

The effect of presidential election outcomes on alcohol drinking

The growing political polarization and the increasing use of social media have been linked to straining social ties worldwide. The 2016 presidential elections in the United States reflected this trend with reports of fear and anxiety among voters. We examine how election results can be linked to episodes of anxiety through the use of alcohol as self-medication. We analyze a daily dataset of household purchases of alcohol in the weeks following presidential elections. We find that, within 30 days from Election Day, a 10 percentage point increase in support for the losing candidate increases alcohol expenditure by 1.1%. The effect is driven by counties with a higher share of supporters of the losing candidate and is robust to controlling more flexibly for omitted variables related to alcohol consumption. The increase in alcohol consumption is present in the 2016 elections and absent in the previous three presidential elections.