Non‐dominated Time‐Window Policies in City Distribution

Urban freight contributes significantly to pollution, noise disturbance, traffic congestion, and safety problems in city centers. In many cities, local governments have introduced policy measures, in particular time‐access restrictions, to alleviate these problems. However, setting time windows is very challenging due to the conflicting interests and objectives of the stakeholders involved. In this article, we examine whether it is possible to develop time‐window policies that enhance environmental sustainability and distribution efficiencies, while meeting the objectives of the municipalities. We develop a framework for balancing retailer (costs), municipality (satisfaction), and environmental (emissions) objectives, using data envelopment analysis, under different urban time‐window policies. The approach is illustrated by a case study of three Dutch retail organizations, with a large number of stores affected by such time windows. On the basis of an evaluation of 99 different time‐window policies, our results show that harmonizing time windows between neighboring cities leads to the best overall performance. The currently used time‐window policy appears to perform reasonably well, but can be improved on all dimensions . However, harmonizing time‐window policies may be difficult to realize in practice.     

Third-grade retention and reading achievement in Texas: A nine year panel study

The academic performance of over 38,000 Texas students who failed the state’s 1994 reading test was examined through their sophomore year in high school. Propensity score matching resulted in strata with retained and promoted students of comparable observed characteristics. Reading scores were analyzed using a two-level hierarchical linear model. Same grade comparisons show that third graders failing the state-mandated reading test who repeated the grade consistently outperformed in later grades the socially promoted children who also failed the third grade test. Additional analyses indicate that alternative explanations for the findings such as omitted variables, regression to the mean, differential panel attrition and cohort effects are not supported. The results are consistent with findings from other recent studies which suggest that grade retention in third grade may help increase student achievement.     

浅析大数据背景下网络营销服务模式的革新

"大数据"技术具有着极高的科技价值和经济价值,基于大数据的网络营销已经成为企业智慧营销的重要手段。本文先从商务和技术两个角度分析了大数据技术的内涵,然后分析了大数据技术在网络营销领域的应用,最后提出企业在应用大数据技术过程中应该注意的问题,以期促进大数据技术在网络营销领域的应用和发展。     

从《史记·五帝本纪》看司马迁的学术研究方法

《五帝本纪》作为《史记》开篇之作,被誉为“中华正史第一本纪”,历来受到学界广泛的关注和高度评价.《史记·五帝本纪》体现出司马迁的“实录”精神和学术研究方法,主要体现为资料收集的广博性、田野调查的广泛性、甄别选材的严谨性、研究思考的深入性等方面.司马迁的“实录”精神和学术研究方法不仅是对历史事实的秉笔直书,更是严谨求实的科学研究方法的体现,对于当今学术研究仍具有深刻的启示作用.     

中国林业科技进步贡献率的要素分解及测算研究——基于2002—2011年31个省(市、自治区)的统计数据

中国林业经济增长受到传统资本、劳动和林地面积等投入要素的影响之外,林业科技进步因素的作用越来越重要。将广义林业科技进步细分为狭义林业科技进步,采用中国31个省(市、自治区)林业相关面板统计数据,运用扩展的C-D生产函数结合索洛余值法,测算中国狭义林业科技进步贡献率。研究结果表明:2003—2011年连续9年,狭义林业科技进步、林业固定资产投资、林业从业人员、林地面积、林业人力资本累积效应及林业产业结构变动因素对中国林业经济增长的平均贡献率分别为15.34%、61.47%、2.79%、10.77%、9.14%、0.49%。基于上述分析,提出进一步提升中国林业科技贡献率的具体对策建议。     

数据挖掘中属性项压缩的统计方法研究

文章试图将统计思想与(Rough)粗糙集理论相结合,针对事务性数据库属性项压缩问题提出了一些行之有效的方法,即基于重要性的属性压缩、基于相依性的属性压缩、属性项的广义线形分析及压缩、基于多重相关性的属性项压缩,以此达到数据库压缩之目的。     

Nonparametric empirical Bayes for the Dirichlet process mixture model

The Dirichlet process prior allows flexible nonparametric mixture modeling. The number of mixture components is not specified in advance and can grow as new data arrive. However, analyses based on the Dirichlet process prior are sensitive to the choice of the parameters, including an infinite-dimensional distributional parameter G ₀. Most previous applications have either fixed G ₀ as a member of a parametric family or treated G ₀ in a Bayesian fashion, using parametric prior specifications. In contrast, we have developed an adaptive nonparametric method for constructing smooth estimates of G ₀. We combine this method with a technique for estimating α, the other Dirichlet process parameter, that is inspired by an existing characterization of its maximum-likelihood estimator. Together, these estimation procedures yield a flexible empirical Bayes treatment of Dirichlet process mixtures. Such a treatment is useful in situations where smooth point estimates of G ₀ are of intrinsic interest, or where the structure of G ₀ cannot be conveniently modeled with the usual parametric prior families. Analysis of simulated and real-world datasets illustrates the robustness of this approach.     

Gamma failure‐time mixture models: yet another way to establish efficacy

Using a Yamaguchi‐type generalized gamma failure‐time mixture model, we analyse the data from a study of autologous and allogeneic bone marrow transplantation in the treatment of high‐risk refractory acute lymphoblastic leukaemia, focusing on the time to recurrence of disease. We develop maximum likelihood techniques for the joint estimation of the surviving fractions and the survivor functions. This includes an approximation to the derivative of the survivor function with respect to the shape parameter. We obtain the maximum likelihood estimates of the model parameters. We also compute the variance‐covariance matrix of the parameter estimators. The extended family of generalized gamma failure‐time mixture models is flexible enough to include many commonly used failure‐time distributions as special cases. Yet these models are not used in practice because of computational difficulties. We claim that we have overcome this problem. The proposed approximation to the derivative of the survivor function with respect to the shape parameter can be used in any statistical package. We also address the issue of lack of identifiability. We point out that there can be a substantial advantage to using the gamma failure‐time mixture models over nonparametric methods. Copyright © 2003 John Wiley & Sons, Ltd.     

城商行经营效率及其影响因素实证分析——基于53家城商行面板数据的随机前沿模型

根据2009—2011年国内53家城商行相应数据可构建计算城商行经营效率的随机前沿模型。样本城商行总资产占当年城商行总资产的比重达到了70%,样本商行分布于国内29个省、市、自治区、直辖市,由此可得出影响城商行经营效率的影响因素。实证研究结果发现:2009—2011年间,随着跨区域经营的大力推进、引进战略投资者、公司治理机制改革的深入以及资产质量控制的提升,国内城商行经营效率呈现出明显的改进趋势,第一大股东非国有股、引进战略投资者、跨区域经营、降低不良贷款率、降低第一大股东的持股比例等均对城商行的经营绩效产生显著的积极影响。     

基于贝叶斯面板平滑转换模型的房价阈值效应研究

针对经济变量之间普遍存在的非线性关系,导致线性模型拟合失效的问题,构建面板数据平滑转换模型,刻画变量之间关系的非对称性。采用贝叶斯方法进行模型的参数估计,避免非线性最小二乘算法难以收敛,参数估计不确定。通过分析模型结构,选择参数先验分布,设计相应的Metropolis-Hasting-Gibbs混合抽样算法,据此估计模型参数;在此基础上,利用省域面板数据分析房价阈值效应问题。研究结果表明:参数的动态迭代轨迹收敛,MH-Gibbs混合抽样算法能够准确地估计模型各参数,解决了非线性最小二乘无法收敛的问题,证明了贝叶斯面板数据平滑转换模型的有效性;同时也验证了房价波动的阈值效应以及房价与城市化、城乡收入差距之间的非线性关系。