Optimization Model and Algorithm for Crew Management During Airline Irregular Operations

Airline irregular operations have long been a realm where human experience and judgement are the most important tools to utilize. Crew management during irregular operations is usually the bottleneck of the whole system-recovering process due to complicated crew schedules and restrictive crew legalities as well as the size and scope of the hub-and-spoke networks adopted by major carriers. A system-wide multi-commodity integer network flow model and a heuristic search algorithm for the above purpose are presented and discussed in this paper. The computational experiences show that the algorithm is efficient enough to solve problems of realistic size and also has the flexibility to accommodate practical business requirements.     

Compliance Versus Risk in Assessing Occupational Exposures

Assessments of occupational exposures to chemicals are generally based upon the practice of compliance testing in which the probability of compliance is related to the exceedance [γ, the likelihood that any measurement would exceed an occupational exposure limit (OEL)] and the number of measurements obtained. On the other hand, workers’ chronic health risks generally depend upon cumulative lifetime exposures which are not directly related to the probability of compliance. In this paper we define the probability of “overexposure” (θ) as the likelihood that individual risk (a function of cumulative exposure) exceeds the risk inherent in the OEL (a function of the OEL and duration of exposure). We regard θ as a relevant measure of individual risk for chemicals, such as carcinogens, which produce chronic effects after long-term exposures but not necessarily for acutely-toxic substances which can produce effects relatively quickly. We apply a random-effects model to data from 179 groups of workers, exposed to a variety of chemical agents, and obtain parameter estimates for the group mean exposure and the within- and between-worker components of variance. These estimates are then combined with OELs to generate estimates of γ and θ. We show that compliance testing can significantly underestimate the health risk when sample sizes are small. That is, there can be large probabilities of compliance with typical sample sizes, despite the fact that large proportions of the working population have individual risks greater than the risk inherent in the OEL. We demonstrate further that, because the relationship between θ and γ depends upon the within- and between-worker components of variance, it cannot be assumed a priori that exceedance is a conservative surrogate for overexposure. Thus, we conclude that assessment practices which focus upon either compliance or exceedance are problematic and recommend that employers evaluate exposures relative to the probabilities of overexposure.     

所有制、行业效率与转型经济下的中国企业生存

 在转型经济条件下我国企业生存具有独特的特点。本文对湖南省1998-2007年新成立的54159家国有和私营工业企业数据样本进行了研究。结果表明,即使在行业层面,效率仍对企业生存产生了显著的正向影响,我国私营企业生存状况受效率影响作用较大,国有企业受效率影响较小,随着经济转型的深入,效率在改善中国企业生存方面的作用越来越大,而目前我国国有企业的生存还并未受经济转型时期的影响。     

批发和零售业在ISIC4.0和NACE2.0中的分类比较研究及启示

 ISIC是世界上对经济活动进行分类的最成熟、最权威、最有影响力的国际标准,而NACE派生于国际标准产业分类体系,是派生型产业分类体系的典型代表。深入了解最新版ISIC4.0和NACE2.0的批发和零售业分类的差别,对我国国民经济行业分类的批发和零售业依据ISIC4.0进行修改和调整具有重要的借鉴价值,同时对正确收集、处理和测算批发和零售业的经济指标以及国际间数据比较至关重要。故本文对上述两大产业分类体系进行比较研究,揭示批发和零售业在上述产业体系中的差别,提出我国国民经济行业分类体系的批发和零售业分类的改进建议。     

我国参加国际比较项目（ICP）的演变历程

 自1993年以来,我国先后5次以不同形式开展国际比较项目（ICP）调查活动,更深入、更广泛地融入到国际统计体系之中。每次调查的基准期、调查范围、比较对象、比较方法、组织方式各不相同,比较结果也各不相同。我国参加ICP的演变历程见证了政府统计发展和能力提高的过程。     

通货膨胀预期视角下的货币政策对资产价格反应问题的研究

通过纳入通胀预期,本文研究了我国货币政策对资产价格（房价和股价）反应的方式、非对称性和急缓程度,结果表明：（1）通胀预期在货币政策分别对房价和股价的反应中起到明显不同的作用;（2）货币政策“关注”房价而“盯住”股价,即货币政策“间接地”根据通胀预期调整对房价的反应,但通常并未考虑通胀预期就“直接” 调整对股价的反应;（3）货币政策在整个样本期内均对房价作出正向反应,且随通胀预期的不断攀升反应逐渐增强,但对股价却采取所谓“调牛不调熊”的非对称反应,且随股价涨幅的增加反应逐渐增强;（4）这两种非对称反应均是逐渐(平滑)调整的。最后,本文还从政策层面上讨论了货币政策对资产价格反应的持续性问题。     

A simple procedure for the selection of significant effects

Summary.  Given a large number of test statistics, a small proportion of which represent departures from the relevant null hypothesis, a simple rule is given for choosing those statistics that are indicative of departure. It is based on fitting by moments a mixture model to the set of test statistics and then deriving an estimated likelihood ratio. Simulation suggests that the procedure has good properties when the departure from an overall null hypothesis is not too small.     

Maximum Likelihood Estimations and EM Algorithms with Length-biased Data

Length-biased sampling has been well recognized in economics, industrial reliability, etiology applications, epidemiological, genetic and cancer screening studies. Length-biased right-censored data have a unique data structure different from traditional survival data. The nonparametric and semiparametric estimations and inference methods for traditional survival data are not directly applicable for length-biased right-censored data. We propose new expectation-maximization algorithms for estimations based on full likelihoods involving infinite dimensional parameters under three settings for length-biased data: estimating nonparametric distribution function, estimating nonparametric hazard function under an increasing failure rate constraint, and jointly estimating baseline hazards function and the covariate coefficients under the Cox proportional hazards model. Extensive empirical simulation studies show that the maximum likelihood estimators perform well with moderate sample sizes and lead to more efficient estimators compared to the estimating equation approaches. The proposed estimates are also more robust to various right-censoring mechanisms. We prove the strong consistency properties of the estimators, and establish the asymptotic normality of the semi-parametric maximum likelihood estimators under the Cox model using modern empirical processes theory. We apply the proposed methods to a prevalent cohort medical study. Supplemental materials are available online.     

西安市经济投资效能的势分析

以西安市1995—2008年的数据为基础,对西安市经济现状进行分析,并采用定量和定性研究相结合的方法,运用势分析模型对生产函数进行扩展,力求客观而准确地计算出经济增长要素即劳动力资本、固定资产投资、能源消费量、产业结构变动等的势效系数,进而分析各要素发挥的效能及全部要素投入的综合效能,预测各要素未来的发展趋势,探究提高各投入指标要素投资效能的方法及改变经济增长方式的思路和对策,提升西安市的可持续发展能力。