Browsing by Subject "CO2 emissions"
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Item Open Access Accommodating new flights into an existing airline flight schedule(Elsevier, 2019) Şafak, Özge; Atamtürk, A.; Aktürk, M. SelimWe present two novel approaches to alter a flight network for introducing new flights while maximizing airline’s profit. A key feature of the first approach is to adjust the aircraft cruise speed to compensate for the block times of the new flights, trading off flying time and fuel burn. In the second approach, we introduce aircraft swapping as an additional mechanism to provide a greater flexibility in reducing the incremental fuel cost and adjusting the capacity. The nonlinear fuel-burn function and the binary aircraft swap and assignment decisions complicate the optimization problem significantly. We propose strong mixed-integer conic quadratic formulations to overcome the computational difficulties. The reformulations enable solving instances with 300 flights from a major U.S. airline optimally within reasonable compute times.Item Open Access Environment Kuznets curve for CO2 emissions: a cointegration analysis for China(Elsevier Ltd, 2009) Jalil, A.; Mahmud, S. F.This study examines the long-run relationship between carbon emissions and energy consumption, income and foreign trade in the case of China by employing time series data of 1975-2005. In particular the study aims at testing whether environmental Kuznets curve (EKC) relationship between CO2 emissions and per capita real GDP holds in the long run or not. Auto regressive distributed lag (ARDL) methodology is employed for empirical analysis. A quadratic relationship between income and CO2 emission has been found for the sample period, supporting EKC relationship. The results of Granger causality tests indicate one way causality runs through economic growth to CO2 emissions. The results of this study also indicate that the carbon emissions are mainly determined by income and energy consumption in the long run. Trade has a positive but statistically insignificant impact on CO2 emissions. © 2009 Elsevier Ltd. All rights reserved.Item Open Access The green location-routing problem(Elsevier, 2019) Dükkancı, Okan; Kara, Bahar Y.; Bektaş, TolgaThis paper introduces the Green Location-Routing Problem (GLRP), a combination of the classical Location-Routing Problem (LRP) and the Pollution-Routing Problem (PRP). The GLRP consists of (i) locating depots on a subset of a discrete set of points, from where vehicles of limited capacity will be dispatched to serve a number of customers with service requirements, (ii) routing the vehicles by determining the order of customers served by each vehicle and (iii) setting the speed on each leg of the journey such that customers are served within their respective time windows. The objective of the GLRP is to minimize a cost function comprising the fixed cost of operating depots, as well as the costs of the fuel and CO2 emissions. The amount of fuel consumption and emissions is measured by a widely used comprehensive modal emission model. The paper presents a mixed integer programming formulation and a set of preprocessing rules and valid inequalities to strengthen the formulation. Two solution approaches; an integer programming based algorithm and an iterated local search algorithm are also presented. Computational analyses are carried out using adaptations of literature instances to the GLRP in order to analyze the effects of a number parameters on location and routing decisions in terms of cost, fuel consumption and emission. The performance of the heuristic algorithms are also evaluated.Item Open Access The green network design problem(Elsevier, 2019) Dükkancı, Okan; Bektaş, T.; Kara, Bahar Y.; Faulin, J.; Grassman, S. E.; Juan, A. A.; Hirsch, P.Logistics activities are at the heart of world trade, but they also have unintended consequences on the environment due to the use of land, energy, and other types of natural resources. The significant energy usage by the more traditional means of transportation results in emissions, one of the most prominent of all negative externalities, that in turn causes air pollution affecting human health. One way to reduce such externalities is the (re-)design of the overall network on which logistics activities take place, giving rise to green network design problems, where the minimization of emissions is an integral and explicit part of the objective. The aim of this chapter is to present an overview and a classification of green network design problems arising at different levels of decision making, from operational to strategic, and will present definitions, optimization models, and practical applications for some of the key problems in this category.