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Vehicle Routing with Time Windows  Finding optimal solutions efficiently
, 1999
"... This paper presents two ideas for using structural information for solving the Vehicle Routing Problem with Time Windows (VRPTW). The VRPTW is a generalization of the well known capacity constrained Vehicle Routing Problem (VRP). In the VRP a fleet of vehicles based at a central depot must service a ..."
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This paper presents two ideas for using structural information for solving the Vehicle Routing Problem with Time Windows (VRPTW). The VRPTW is a generalization of the well known capacity constrained Vehicle Routing Problem (VRP). In the VRP a fleet of vehicles based at a central depot must service a set of customers. In the VRPTW all customers have a time window. Service of a customer must begin within the interval given by the time window. The objective is to minimize some aspect of operating costs (for example total distance traveled, number of vehicles needed or a combination of parameters).
A Tabu Search Approach to the Strategic Airlift Problem, in second review with the
 Journal of. Military Operations Research
, 2006
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Adaptive tools in virtual environments  Independent component analysis for multimedia
, 2002
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Informatics and Mathematical Modelling
, 2002
"... Adaptive tools in virtual environments Independent component analysis for multimedia ..."
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Adaptive tools in virtual environments Independent component analysis for multimedia
This document was prepared with L ATEX and printed by Jespersen Offset. Preface
, 1999
"... Ph.D. degree in engineering. The thesis deals with different aspects of mathematical modelling of systems ..."
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Ph.D. degree in engineering. The thesis deals with different aspects of mathematical modelling of systems
Printed by IMM, DTU
, 2001
"... This thesis is submitted in partial fulfilment of the requirements for the Ph.D. degree at the Technical University of Denmark (DTU). The project took place as an industrial research Ph.D. project administered by the Danish Academy of Technical Sciences (ATV) and financially supported by the Danish ..."
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This thesis is submitted in partial fulfilment of the requirements for the Ph.D. degree at the Technical University of Denmark (DTU). The project took place as an industrial research Ph.D. project administered by the Danish Academy of Technical Sciences (ATV) and financially supported by the Danish Agency for Trade and Industry in the period August 1st 1997 – August 31st 2001 during which there was a total of 10.5 months leave. It was carried out with the following partners: MathTech Aps, Informatics and Mathematical Modelling (IMM) at DTU, and
TimeDependent HazardousNetwork Design Problem
, 2015
"... We extend the hazmat network design problem to account for the timedependent road closure as a policy tool in order to reduce hazmat transport risk by altering carriers ’ departure times and route choices. We formulate the dynamic network design problem using an alternativebased model with each al ..."
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We extend the hazmat network design problem to account for the timedependent road closure as a policy tool in order to reduce hazmat transport risk by altering carriers ’ departure times and route choices. We formulate the dynamic network design problem using an alternativebased model with each alternative representing a simultaneous path and departure time choice. A column generationbased heuristic that uses two subproblems is proposed to generate alternatives to be included in the model. Numerical experiments confirm the efficiency of the heuristic. The proposed framework can be used to identify alternative regulatory schemes by varying the regulator’s intervention level. Each scheme corresponds to a certain tradeoff between the transport risk and economic viability. To illustrate the insights that can be obtained through the use of our methodology, we present a case study based on a transportation network from Sioux Falls, South Dakota.
A Column Generation Approach for the Periodic Vehicle Routing Problem with Time Windows
, 2009
"... We present a column generation approach for obtaining strong lower bounds to the periodic vehicle routing problem with time windows (PVRPTW) where customers must be served several times during a planning period. For this a setcovering model is introduced whose linear programming relaxation is solve ..."
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We present a column generation approach for obtaining strong lower bounds to the periodic vehicle routing problem with time windows (PVRPTW) where customers must be served several times during a planning period. For this a setcovering model is introduced whose linear programming relaxation is solved. The pricing subproblem, responsible for generating new columns, is an elementary shortest path problem with resource constraints. The latter is solved by a label correcting dynamic programming algorithm for which we introduce appropriate label resources, extension functions, and dominance rules. Different settings for this algorithm are suggested and applied in combination to tune its behavior. We further propose a greedy randomized adaptive search procedure (GRASP) to solve the pricing subproblem. Experimental results on test instances differing in size, time windows and period length indicate strong lower bounds for many instances and the advantage of applying the metaheuristic in combination with the dynamic programming algorithm to save computation time on larger instances.
BOUNDING PROCEDURES ON BIDIRECTIONAL LABELING ALGORITHM OF
, 2011
"... I hereby declare that all information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work. ..."
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I hereby declare that all information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work.