Measuring benefits from spatially-explicit surface water quality improvements: The roles of distance,scope, scale,and size

Programs to improve water quality do not improve all water bodies equally. Evaluation of the benefits of such programs must account for where improvements occur and the relative magnitude of improvements that occur in different places. This study uses a choice experiment survey to explore how the value to a household of a surface water quality improvement varies as a function of (i) the distance between the household and the affected streams and rivers, (ii) the degree to which the quality of the water has been improved, (iii) how many stream and river miles have been improved, and (iv) the sizes of the affected streams and rivers. Results show evidence that value declines with distance in an approximately linear way, weak evidence that large rivers are worth more than small rivers, and no evidence that willingness-to-pay is nonlinear in either the degree of water quality improvement or the number of stream miles improved. These results indicate that it may be defensible in applied work to value small, spatially-explicit water quality improvement projects independently and then sum over projects.     

航班计划优化研究概述

从航班计划优化的不同时间阶段分析,可以将航班计划优化分为航班计划静态编排优化、基于航班延误预测的航班计划动态反馈优化和基于机场协同决策(A-CDM)的航班计划动态调整角度三类;进而从航班时刻、机型指派、航班频率等编制环节分析了航班计划静态编排优化;随后利用延误波及预测与数据挖掘预测的优化方法分析了基于航班延误预测的航班计划动态反馈优化的相关研究。最后,根据航班计划优化复杂性分析,给出了航班计划优化的发展趋势和未来研究方向。     

突发公共事件对电影行业影响的量化研究

人工收集和整理2012—2018年在中国市场上映的首轮院线电影信息数据，构建电影需求的嵌套logit回归模型，以新冠肺炎疫情为准自然实验，来量化突发公共事件对电影行业复产复工的影响。结果显示：第一，关于上映时间选择，在恢复营业后，如果所有因为疫情尚未上映的电影选择顺延上映能有效避免过度竞争的局面。第二，关于上映节奏控制，控制好未定档电影的上映节奏，保持适当的竞争能促进经济效益提升。其中，从11月份开始以每周两部的频率上映未定档电影的经济效益最佳。第三，关于上映方式选择，与线下播放相比，疫情期间选择线上播放能及时收回成本并有利于经济收益最大化的实现。研究结论为电影行业制定复产复工策略提供依据，为未来应对突发公共卫生事件提供参考。     

Panel LM unit root tests with level and trend shifts

This paper considers a Lagrange multiplier (LM) based panel unit root test that allows for heterogeneous structural breaks in both the intercepts and slopes of a series. We note that many popular time series variables are likely to exhibit changing means and/or trends over time. Given that the usual tests will depend on the nuisance parameters indicating the locations of the trend breaks, we adopt a transformation procedure that makes our new panel unit root tests invariant to the nuisance parameters. To illustrate the importance of the power gain provided by our test, we examine the convergence hypothesis using relative ratios of per capita health care expenditures in 20 OECD countries. Our results provide evidence that the convergence hypothesis is supported.     

民航地空通信自适应抗干扰系统设计与性能分析

在复杂电磁环境下，由于民航地空通信大频偏的要求，滤波器无法滤除波道内的干扰。针对此问题，提出了一种自适应抗干扰系统设计方法。对于落在波道内且与地空通信信号有效频带不重叠的干扰，首先对通信信号进行载波频率估计，然后使用自适应滤波方法进行干扰抑制；对于落在波道内且与地空通信信号有效频带重叠的恒包络干扰，首先重构载波信号，消除对恒包络信号估计的影响，然后根据恒包络信号的特性重构干扰信号并进行干扰分离。实验结果表明，该系统设计方法在不改变民航地空通信架构的前提下，抗有效频带外干扰的能力最大可以提升23.8 dB，抗恒包络干扰的能力最大可以提升39.4 dB，从而可以大幅提高航空飞行安全水平。     

采用航迹特征的智能机型识别

针对空战目标识别中机型自动识别比较困难的问题，提出了采用航迹特征的智能目标识别方法。利用卷积神经网络（Convolutional Neural Network，CNN）分层学习特征的能力，训练CNN算法模型自动地从航迹数据中学习有用的特征并分类。利用沿海实地采集的15个类别的飞机航迹数据，经一系列数据预处理后作为智能识别算法的训练和测试数据，在验证实验中描述了算法网络的相关配置,对比了CNN与其他分类器的识别结果。实验结果表明，CNN具有很好的识别性能。     

社保基金持股与企业盈余质量:A股上市公司的证据

本文利用中国A股上市公司2006-2015年的数据,研究社保基金持股对上市公司盈余质量的影响。我们用上市公司财务重述作为测度盈余质量的指标,发现社保基金持股能够显著降低企业发布财务重述的概率,这表明社保基金对上市公司盈余质量的提高具有促进作用。并且,社保基金的这一治理作用在国有企业、内部治理水平较差以及市场化程度较低地区的上市公司中更加显著。通过双重差分模型和安慰剂检验等方法弱化了内生性问题之后,以上结论依然成立,说明社保基金持股和盈余质量提升之间存在因果关系,我们称之为社保基金的公司治理作用。进一步研究发现,社保基金可以通过抑制控股股东资金占用、增加机构调研次数等途径提升被持股公司的盈余质量。本文有助于认识和评估社保基金持股对于上市公司的监督与治理作用。     

一种机载三维音频技术的快速计算方法

针对机载三维音频应用的实时性需求，提出了一种基于单耳相对头相关传递函数和改进型混响模型的机载三维音频快速实现方法，在较传统实现方式性能无明显下降的情况下降低了80%的计算量。对提出的算法在F-16战斗机模拟强噪声环境下进行相关主观试听实验，同时在某型飞机音频系统中实验验证。实验结果表明,所提方法在实时处理3路三维音频时，三维音频方位分辨精度在5°以内，可满足实际机载平台使用需求。     

‘Whatever it takes’ and the role of Eurozone news

This letter shows that the ‘Whatever it takes’ speech by ECB President Draghi on 26 July 2012 and the ensuing installation of the Outright Monetary Transactions’ framework are associated with a reduction in the domestic and cross-border effect of Eurozone news on absolute yield changes in Eurozone sovereign debt. These results are consistent with the popular view that these actions helped to avoid a collapse of the Eurozone.     

Distribution of residual autocorrelations for multiplicative seasonal ARMA models with uncorrelated but nonindependent error terms

In this paper, we consider portmanteau tests for testing the adequacy of multiplicative seasonal autoregressive moving‐average models under the assumption that the errors are uncorrelated but not necessarily independent. We relax the standard independence assumption on the error terms in order to extend the range of applications of the seasonal autoregressive moving‐average models. We study the asymptotic distributions of residual and normalized residual empirical autocovariances and autocorrelations under weak assumptions on noise. We establish the asymptotic behavior of the proposed statistics. A set of Monte Carlo experiments and an application to monthly mean total sunspot number are presented.