Analysis of Travel Times and CO2 Emissions in Time‐Dependent Vehicle Routing

Due to the growing concern over environmental issues, regardless of whether companies are going to voluntarily incorporate green policies in practice, or will be forced to do so in the context of new legislation, change is foreseen in the future of transportation management. Assigning and scheduling vehicles to service a pre‐determined set of clients is a common distribution problem. Accounting for time‐dependent travel times between customers, we present a model that considers travel time, fuel, and CO₂ emissions costs. Specifically, we propose a framework for modeling CO₂ emissions in a time‐dependent vehicle routing context. The model is solved via a tabu search procedure. As the amount of CO₂ emissions is correlated with vehicle speed, our model considers limiting vehicle speed as part of the optimization. The emissions per kilometer as a function of speed are minimized at a unique speed. However, we show that in a time‐dependent environment this speed is sub‐optimal in terms of total emissions. This occurs if vehicles are able to avoid running into congestion periods where they incur high emissions. Clearly, considering this trade‐off in the vehicle routing problem has great practical potential. In the same line, we construct bounds on the total amount of emissions to be saved by making use of the standard VRP solutions. As fuel consumption is correlated with CO₂ emissions, we show that reducing emissions leads to reducing costs. For a number of experimental settings, we show that limiting vehicle speeds is desired from a total cost perspective. This namely stems from the trade‐off between fuel and travel time costs.     

Functional Differencing

In nonlinear panel data models, the incidental parameter problem remains a challenge to econometricians. Available solutions are often based on ingenious, model‐specific methods. In this paper, we propose a systematic approach to construct moment restrictions on common parameters that are free from the individual fixed effects. This is done by an orthogonal projection that differences out the unknown distribution function of individual effects. Our method applies generally in likelihood models with continuous dependent variables where a condition of non‐surjectivity holds. The resulting method‐of‐moments estimators are root‐N consistent (for fixed T) and asymptotically normal, under regularity conditions that we spell out. Several examples and a small‐scale simulation exercise complete the paper.     

关于人文-社会科学成果的评估标准

人文-社会科学的成果评估,只应以论著本身作为评估对象,课题来源的级别、核心刊物与否、是否获奖、是否被媒体报道,均不直接与学术研究相关,不能作为评估的依据。应改革目前高等学校和社会科学研究单位中较为普遍存在的将量化管理简单地用于对学术研究的考察与成果的评估上。     

应届高校毕业生就业心理问题的个性化干预措施临床研究

据教育部公布的数据显示,2021届高校毕业生总规模高达909万人,同比增加35万.毕业生数量的激增,导致"就业难"问题更为突出.高校毕业生作为一个特殊群体,就业面临很大困难和不确定性.这些影响因素,易导致高校毕业生产生焦虑、抑郁等不良情绪,因此针对主要影响因素进行个性化干预对改善其就业心理问题,促进心理和生理健康具有重要意义.通过分析影响应届高校毕业生不良的就业心理的因素,提出针对性干预措施,评估其效果,为提高普通高校毕业生身心健康水平提供更多参考.     

教育扩招促进了代际流动?

本文基于中国综合社会调查的数据,以改革开放后参加工作的群体为研究对象,实证分析了中国高等教育扩招对代际流动的影响。研究发现,没有充足证据证明教育扩招促进了代际流动。一方面,尽管教育在扩张前后始终是决定个人社会经济地位高低的最重要因素,但教育扩招没有显著改善教育机会不均等问题,从而也无法减弱家庭背景以教育为中介对子女初职社会经济地位的间接影响,带来代际流动的改善。另一方面,教育扩招的结构化效应不显著,大学毕业生面临的劳动力市场并非完全遵循绩效原则,因此,即便教育扩招提高了他们在社会总人口中的相对比例,也无法带来社会整体代际流动的改善。因此,发挥教育扩招促进代际流动的功能,不仅要强调教育机会的分配公平问题,同时也要努力完善劳动力市场建设,促进就业机会均等。     

On the Properties of the SAVE Directions

In quadratic discriminant analysis, the use of SAVE (Cook and Weisberg, 1991 Cook, R.D., Weisberg, S. (1991). Discussion of Li (1991). J. Amer. Statist. Assoc. 86:328–32.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]; Pardoe et al., 2007 Pardoe, I., Yin, X., Cook, R. (2007). Graphical tools for quadratic discriminant analysis. Technometrics 49:172–183.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) is often recommended for dimension-reduction purposes. However, the associated directions tend to over-emphasize the differences of the groups in dispersion, ignoring at the same time those in location. This behavior makes often the plots of the corresponding canonical coordinates difficult to interpret. In this article, the properties of SAVE are investigated and related to those of the SIR and SIRII components. Applications with real data are presented. Comparisons with previous work in this area are also discussed.     

Behavioral finance in corporate governance: economics and ethics of the devil’s advocate

The Common Law, parliamentary democracy, and academia all institutionalize dissent to check undue obedience to authority; and corporate governance reformers advocate the same in boardrooms. Many corporate governance disasters could be averted if directors asked hard questions, demanded clear answers, and blew whistles. Work by Milgram suggests humans have an innate predisposition to obey authority. This excessive subservience of agent to principal, here dubbed a “type II agency problem”, explains directors’ eerie submission. Rational explanations are reviewed, but behavioral explanations appear more complete. Experimental work shows this predisposition disrupted by dissenting peers, conflicting authorities, and distant authorities. Thus, independent directors, chairs, and committees excluding CEOs might induce greater rationality and more considered ethics in corporate governance. Empirical evidence of this is scant—perhaps reflecting problems identifying genuinely independent directors.

The bandpass problem: combinatorial optimization and library of problems

A combinatorial optimization problem, called the Bandpass Problem, is introduced. Given a rectangular matrix A of binary elements {0,1} and a positive integer B called the Bandpass Number, a set of B consecutive non-zero elements in any column is called a Bandpass. No two bandpasses in the same column can have common rows. The Bandpass problem consists of finding an optimal permutation of rows of the matrix, which produces the maximum total number of bandpasses having the same given bandpass number in all columns. This combinatorial problem arises in considering the optimal packing of information flows on different wavelengths into groups to obtain the highest available cost reduction in design and operating the optical communication networks using wavelength division multiplexing technology. Integer programming models of two versions of the bandpass problems are developed. For a matrix A with three or more columns the Bandpass problem is proved to be NP-hard. For matrices with two or one column a polynomial algorithm solving the problem to optimality is presented. For the general case fast performing heuristic polynomial algorithms are presented, which provide near optimal solutions, acceptable for applications. High quality of the generated heuristic solutions has been confirmed in the extensive computational experiments. As an NP-hard combinatorial optimization problem with important applications the Bandpass problem offers a challenge for researchers to develop efficient computational solution methods. To encourage the further research a Library of Bandpass Problems has been developed. The Library is open to public and consists of 90 problems of different sizes (numbers of rows, columns and density of non-zero elements of matrix A and bandpass number B), half of them with known optimal solutions and the second half, without.     

浅析农民增收的关键

农业 、农 村、农民 问题 引 起广 泛的 关 注,农民 增收 更成 为 社会 焦 点。 政府 为解 决 “三 农”问 题 ,提 高农 民收 入 采取 了一 系列措 施 ,给农 民 带来 了很 大 的实 惠。但 要从 根 本上 消除 农民 的 贫困 状 态,还 得 依靠 农业 自 身的 发展 。农业 产 业化 经营 ,它 通过 专业化 生 产、可有 效 降低 生产 成本 ;它通 过 一体 化经 营 、最 大程 度 地减 少了 农 民利 益的 损 失;它 通过 构筑 社 会化 服务 体 系,保障 农民收 入 持续 稳定 增长 ;因 而 适合 市场 的 要求 ,代 表先 进农 业 的方 向 ,而成 为 解决 农民 增 收问 题的 关 键     

中小企业面临的问题及对策研究

中小企业是我国国民经济发展的重要组成部分,发展中小企业是国家经济建设不可回避的问题与任务。本文对目前中小企业所面临的问题进行了分析,并从完善政府行政工作、企业战略决策和体制改革等方面提出了几点建议。