Step by step: tenant accounts of securing and maintaining quality housing with a housing choice voucher

Previous research on renters’ experiences in the Housing Choice Voucher (HCV) program is robust, but much of it has been conducted in the context of mobility interventions providing added resources. In contrast, this study focuses on HCV renters’ experiences searching for housing without the support of a mobility intervention. In semistructured interviews, 34 HCV renters describe their housing search processes and outcomes. We find that renters struggle to secure housing in their preferred neighborhoods due to limited information and financial costs such as application fees and security deposits. Discussion focuses on practice and policy reforms that might support greater housing choice.     

Estimating mixtures of normal distributions via empirical characteristic function

This paper uses the empirical characteristic function (ECF) procedure to estimate the parameters of mixtures of normal distributions. Since the characteristic function is uniformly bounded, the procedure gives estimates that are numerically stable. It is shown that, using Monte Carlo simulation, the finite sample properties of th ECF estimator are very good, even in the case where the popular maximum likelihood estimator fails to exist. An empirical application is illustrated using the monthl excess return of the Nyse value-weighted index.     

What You Know or Who You Know? Occupation-specific work experience and job matching through social networks

While work experience is generally seen as an indicator of human capital, it may also reflect the accumulation of social capital. This study examines how work experience facilitates informal access to employment—that is, being matched with a new employer through an informal search or informal recruitment through the non-search process (without engaging in a job search). Results from fixed effects regression on panel data from the NLSY show that experience is related to informal entry into new jobs, though in a very specific way. The odds of being informally recruited into a new job improve as work experience in related occupations rises, but this relationship holds only among men. These findings highlight the social benefits of occupation-specific work experience that accrue to men but not to women, suggesting an alternative explanation for the gender disparity in wage returns to experience.     

考虑信息搜索的环境污染群体性事件最优决策模型

坚决打好污染防治攻坚战是建设全面小康社会三大任务之一,环境污染群体性事件影响社会稳定和生态文明建设。在当今信息渠道多元化的自媒体时代下,群众能够通过信息搜索行为为决策获取信息。本文考虑了群众信息搜索行为,构建周边居民信息搜索的环境污染群体性事件最优决策模型,分析了不同条件下均衡策略选择,以及在各种地方政府补贴水平和暗箱操作程度下,周边居民的收益变化情况和策略选择差异。结果表明：当政府的暗箱操作程度较低时,群众的最优化策略为信息搜索后“污染轻微”则“抗议”,否则群众的最优化策略为直接抗议。当群众对项目污染程度为严重的先验概率较低且政府的暗箱操作程度比较高时,群众将选择不抗议策略。当周边居民的识别能力较差,群众将会选择策略信息搜索后“污染轻微”则“不抗议”,当暗箱操作程度足够大时,群众将会选择策略直接抗议。随着地方政府提供补贴水平的增加,群众的抗议强度减弱。了解群众的最优决策,有利于政府对环境群体性事件进行防范和应对,维护社会稳定。     

越轨与规训：网络人肉搜索的道德失范及镜鉴研究

网络技术革新与社会变迁息息相关。然而,伴随网络技术的飞速发展,众多由网络引发的社会弊病日渐凸显, 其中网络人肉搜索俨然是网络入侵现实生活的代表性产物。网络人肉搜索现象是伴随现代网络技术发展到一定时期 而出现的代表性网络社会现象。作为一种网络搜索工具,网络人肉搜索有着显见的优缺点：在强化社会舆论监督的同 时,衍生出肆意侵犯他人隐私、道德观念“去传统化”、道德发展“内卷化”等道德失范问题。为了避免恶意网络人肉搜 索带来的诸多社会越轨行为,需要从完善法律法规、贯彻道德自律准则、优化技术工具等维度来对网络世界进行正确 的规训,从而涤净网络公共空间,使互联网成为推动我国经济结构转型的关键驱动力。     

低碳环境下的车辆路径问题及禁忌搜索算法研究

基于节能减排的新视角,本文研究了低碳环境下由第三方提供运输服务的车辆路径问题,在安排车辆路径时,同时考虑了能耗、碳排放和租车费用,而这些费用不仅与距离有关,也与客户点的需求量和车辆速度有关。提出了考虑车辆运量和速度的能耗计算方法,建立了非满载运输方式下的低碳路径模型——LCRP。设计了基于路径划分的禁忌搜索算法RS-TS对问题进行求解,该算法引入了一种新颖的路径编码与解码算法WSS,采用了三种邻域搜索方法。通过基准测试实例验证了算法能有效地找到满意解,并揭示了距离、能耗、行驶时间等参数之间的关系,实验分析表明采用低碳路径安排更加经济环保且选择中低的交通速度更有利于节约能耗和降低碳排放。     

Inference in segmented line regression: a simulation study

A segmented line regression model has been used to describe changes in cancer incidence and mortality trends [Kim, H.-J., Fay, M.P., Feuer, E.J. and Midthune, D.N., 2000, Permutation tests for joinpoint regression with applications to cancer rates. Statistics in Medicine, 19, 335–351. Kim, H.-J., Fay, M.P., Yu, B., Barrett., M.J. and Feuer, E.J., 2004, Comparability of segmented line regression models. Biometrics, 60, 1005–1014.]. The least squares fit can be obtained by using either the grid search method proposed by Lerman [Lerman, P.M., 1980, Fitting segmented regression models by grid search. Applied Statistics, 29, 77–84.] which is implemented in Joinpoint 3.0 available at http://srab.cancer.gov/joinpoint/index.html, or by using the continuous fitting algorithm proposed by Hudson [Hudson, D.J., 1966, Fitting segmented curves whose join points have to be estimated. Journal of the American Statistical Association, 61, 1097–1129.] which will be implemented in the next version of Joinpoint software. Following the least squares fitting of the model, inference on the parameters can be pursued by using the asymptotic results of Hinkley [Hinkley, D.V., 1971, Inference in two-phase regression. Journal of the American Statistical Association, 66, 736–743.] and Feder [Feder, P.I., 1975a, On asymptotic distribution theory in segmented regression Problems-Identified Case. The Annals of Statistics, 3, 49–83.] Feder [Feder, P.I., 1975b, The log likelihood ratio in segmented regression. The Annals of Statistics, 3, 84–97.] Via simulations, this paper empirically examines small sample behavior of these asymptotic results, studies how the two fitting methods, the grid search and the Hudson's algorithm affect these inferential procedures, and also assesses the robustness of the asymptotic inferential procedures.     

The Effect of Expected Income on Individual Migration Decisions

This paper develops a tractable econometric model of optimal migration, focusing on expected income as the main economic influence on migration. The model improves on previous work in two respects: it covers optimal sequences of location decisions (rather than a single once‐for‐all choice) and it allows for many alternative location choices. The model is estimated using panel data from the National Longitudinal Survey of Youth on white males with a high‐school education. Our main conclusion is that interstate migration decisions are influenced to a substantial extent by income prospects. The results suggest that the link between income and migration decisions is driven both by geographic differences in mean wages and by a tendency to move in search of a better locational match when the income realization in the current location is unfavorable.     

基于网格的数字图书馆分布式资源存储模型分析

基于网格的资源存储采用存储虚拟化、简化存储管理等模式,具有高可用性、可管理性、可扩充性和高安全性等优势。能全面有效地解决数字图书馆的资源存储问题。同时,为了构建数字图书馆分布式资源网格存储应用模型,提出了存储空间管理、元数据目录服务、副本管理、备份管理等功能模块设计。     

基于HyperMesh的活塞网格划分策略研究

网格划分作为有限元数值模拟分析的一个重要环节,它直接影响着后续数值计算求解时间及分析结果的精确性。活塞作为多特征的复杂结构体,其网格划分具有很大的难度。借助于HyperMesh软件强大的CAE建模、网格划分及可视化功能,针对同一活塞几何模型的网格划分和质量检查,对比不同网格条件下模态分析过程和结果的差异,进而阐明了得到高质量活塞网格的处理对策和技巧,为同类型结构的网格划分和最优化分析提供参考。