Endüstri Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/279

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End date: 2019Publisher: search.filters.publisher.Taylor & Francis Ltd

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  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Inference in Multivariate Linear Regression Models With Elliptically Distributed Errors
    (Taylor & Francis Ltd, 2014) Yazici, Mehmet; Islam, M. Qamarul; Yildirim, Fetih
    In this study we investigate the problem of estimation and testing of hypotheses in multivariate linear regression models when the errors involved are assumed to be non-normally distributed. We consider the class of heavy-tailed distributions for this purpose. Although our method is applicable for any distribution in this class, we take the multivariate t-distribution for illustration. This distribution has applications in many fields of applied research such as Economics, Business, and Finance. For estimation purpose, we use the modified maximum likelihood method in order to get the so-called modified maximum likelihood estimates that are obtained in a closed form. We show that these estimates are substantially more efficient than least-square estimates. They are also found to be robust to reasonable deviations from the assumed distribution and also many data anomalies such as the presence of outliers in the sample, etc. We further provide test statistics for testing the relevant hypothesis regarding the regression coefficients.
  • Article
    Citation - WoS: 20
    Citation - Scopus: 23
    Freight Transportation Using High-Speed Train Systems
    (Taylor & Francis Ltd, 2016) Ozcan, M. Keskin; Ertem, M. A.; Keskin Özcan, M.
    This study investigates the use of high-speed trains (HSTs) for transporting freight, such as small cargo and mail. A HST scheduling model is constructed to observe the effects of including freight in a passenger-only system. The proposed mathematical model is tested with an experimental study using the Turkish State Railways high-speed rail network and train sets. Freight transportation is analyzed in two cases, namely, adding separate freight trains to the system and using passenger trains for freight transportation. It can be concluded that dividing the sequences of cities into two allows for the completion of train services earlier in the day, and using the same train for transporting both passengers and freight provides more time saving in the system.