信号调节器与传感器的匹配研究

工程测量技术人员在工程项目中常常遇到不知如何在众多的信号调理器中挑选一台适合与传感器配接的仪器的问题。据此,以磁电式传感器、压电加速度计和力平衡式加速度计3种常见类型的传感器为例,结合具体型号的产品,介绍与传感器配接的信号调理器的选择方法以及应注意的问题。     

财权和事权相匹配关系研究

在政府间财政关系中,财权和事权的匹配是主要的财政关系之一,明确财权和事权的划分,保证财权和事权相匹配是我国财税改革的关键。然而,当前政府间财权和事权划分不明确,导致了财权上移、事权下放等问题,没有达到真正意义上的匹配。文中在此回顾各方意见,总结政府间财权与事权的理论依据和存在的问题,并对现阶段的改革对政府间财权事权关系的影响做了简要评述。     

Memory recall errors in retrospective surveys: A reverse record check study

This paper reports on a study to compare self-reports during an interview with staff who attended a University health centre in Turkey, with the records of visits to the same health centre over the previous 12 months. Design of the study reflects the effects of importance of the event, duration since the event, frequency of the occurrence of the event, measurement scale of the event, and bounded and unbounded recalling. In order to assess the extent of recall error, responses to retrospective questions on health centre visits are compared with administrative records. Statistical models are proposed for short and long term human memory recall error effects on responses.     

Waiting time probabilities in the M/G/1 + M queue

We consider an M/G/1 queueing system where the customers may leave the queue if their services do not commence before an exponentially distributed random time. The (conditional) offered waiting time distribution is approximated by a gamma distribution via matching the first and second moments of the actual waiting time. A simulation study is conducted to assess the accuracy of the approximation and it reveals that the approximation performs satisfactorily under general conditions on service time distributions.     

THE ESTIMATED EFFECT OF CATHOLIC SCHOOLING ON EDUCATIONAL OUTCOMES USING PROPENSITY SCORE MATCHING

This paper examines the effect of attending a Catholic high school on educational outcomes. The statistical analysis is based on data obtained from the US National Educational Longitudinal Study. Using propensity score matching methods to control for selection bias, we find that Catholic schooling improves maths test scores, with stronger effects for males than for females, but appears to have little effect (if any) on reading scores. Catholic schooling also raises high school graduation rates and substantially increases the likelihood of enrolment in a 4‐year college. Use of the difference‐in‐difference method suggests that the effect of Catholic schooling on changes in maths scores is more muted, though still statistically significant.     

“倒挂型”土地利用总体规划的耕地保护效果评价

研究目的:揭示"倒挂型"土地利用总体规划与耕地保护效果之间的关系,以期为国土空间规划的编制提供参考。研究方法:倾向值匹配法。研究结果:(1)耕地"倒挂型"规划对耕地面积净变化的影响具有统计显著性,2006—2008年,耕保指标"倒挂型"规划使耕地面积净变化量平均减少2.270万hm2;(2)2010—2016年,耕保指标"倒挂型"规划使耕地面积净变化量平均减少0.496万hm2;(3)建设用地"倒挂型"规划对耕地面积净变化量并无显著影响。研究结论:在省级政府耕地保护责任目标考核的制度环境下,耕地"倒挂型"规划对地方政府形成一定压力,促使各级政府采取措施加以应对,从而使得"倒挂型"规划在一定程度上降低了耕地净减少量。     

基于PSM-DID模型的政策对试点企业经营绩效的影响评价研究——以供应链创新与应用试点政策为例

近年来,我国政府积极推进供应链领域政策的制定与发布,如何更好地评估既有政策带来的绩效成为政府进一步完善供应链相关政策的关键。本文选取商务部“供应链创新与应用试点”政策(商建函[2018]142号)作为研究对象,并构建双重差分倾向得分匹配(PSM-DID)模型,将试点企业经营绩效中的盈利能力指标ROA作为被解释变量,利用Stata15.0对2015~2019年5年间覆盖3494家样本企业的面板数据,共15278个样本进行处理计算,以此对该政策实施对试点企业经营绩效的影响效果进行评价。结果表明:2018年开始实施的供应链创新与应用试点政策,对试点企业的经营绩效ROA有着显著的正向促进作用。此外,企业规模、企业的资产负债率、托宾Q值和企业固定资产投资比率都对ROA有显著影响。其中企业规模和托宾Q值对ROA有正向影响,资产负债率和固定资产投资比率对ROA有负向影响。     

普及互联网使用有助于缩小农村内部收入差距吗？——来自CLDS村级数据的经验证据

由于互联网具有普惠性和亲贫性,个体使用互联网对其收入增长的促进作用在群体上表现为互联网使用普及的平均收入增长效应和收入差距缩小效应。采用“中国劳动力动态调查”（CLDS）2014年、2016年、2018年三期的数据,分析互联网使用普及对农村社区（村庄）平均家庭收入和家庭收入差距的影响,结果显示：村庄内使用互联网家庭的占比提高不仅能显著提升平均家庭收入水平,而且会显著降低家庭收入基尼系数,验证了互联网的普惠性和亲贫性;当普及程度小于0.4时互联网使用对家庭收入差距的影响不显著（具有随着互联网使用率提高由正转负的趋势）,当普及程度大于0.4后互联网使用对家庭收入差距具有显著的负向影响;互联网使用普及可以通过促进服务业发展、提升劳动力技能等群体改善效应缩小农村内部收入差距。因此,应当加快网络基础设施建设,推进互联网使用在农村地区的普及,着重提高弱势群体对互联网使用的可及性,推动互联网与农村应用场景的深度耦合,充分发挥互联网的普惠性和亲贫性功效,有效促进农村居民的收入水平提升和收入差距缩小。     

无源超高频抗金属标签天线设计方法综述

射频识别（RFID）技术的不断发展,对标签天线提出了更高的要求。普通标签天线直接应用于金属表面时,由于受到金属边界的影响,其性能会出现一定程度的下降。详细介绍了4种无源超高频抗金属标签天线的设计方法,包括调整天线与金属面的间距、采用吸波材料、引入高阻抗表面基板、采用平面倒F天线（PIFA）或微带天线结构,并分析了每种方法的优缺点及其对标签天线的阻抗匹配、带宽、尺寸、识别距离以及成本等方面的影响。微带贴片天线不仅具有低剖面、高方向性等优点,而且含有金属接地板,常用作抗金属标签天线的设计原型。在抗金属标签天线的设计与实际应用中,研究者可针对具体要求灵活运用这些设计方法。     

The Productivity Effects of Worker Mobility Between Heterogeneous Firms

We analyze the effect of worker inflows on establishments’ productivity, using German data. Previous studies for other countries have found positive effects of hiring workers from superior (more productive or higher paying) firms. Ranking establishments by their median wage, we find that inflows from inferior establishments seem to increase hiring establishments’ productivity. Further empirical analyses suggest our findings are due to a positive selection of such inflows from their sending establishments. These workers might have to find a better job match in order to advance their careers, an interpretation supported by the finding that the effect is driven by workers with short tenure at their previous employer. Our findings reflect the increasingly assortative pattern of worker mobility in Germany found in a related strand of literature.