Ed
E. de Klerk
info
Please Note
<p>This page displays the records of the person named above and is not linked to a unique person identifier. This record may need to be merged to a profile.</p>
3 records found
1
This thesis addresses synchromodal planning at operational level from the perspective of a logistics service provider. The existing infrastructure and the transportation activities are studied and modeled as an optimization problem with simultaneous vehicle routing and container-to-mode assignment. A special characteristic of this problem is the uncertain data. In other words, it is assumed that the release times of the containers belong to an uncertainty interval, and no further statistical information is available. The problem is then classified according to an extensive framework previously developed within the project. An extensive body of literature is reviewed to identify current modeling approaches and their theoretical and practical limitations. This literature study shows that, although discrete time models have been intensively investigated, there are few studies which propose continuous modeling of time. The container routing problem is modeled as a mixed integer program with explicit time variables and lateness penalties. A robust formulation is then proposed to eliminate the uncertain parameters from the objective function and constraints. By solving the new model exactly, with the aid of an optimization solver, robust solutions are obtained corresponding to transportation plans which remain feasible for any realization of the release times within the pre-specified uncertainty interval. In order to introduce some flexibility in the transportation plan, the continuous time variables are modeled as affine functions of the uncertain parameters. The resulting two-stage decision model is tested for a small-sized instance in both situations, with high and low lateness penalties. The computational results show that the adjustable robust model yields on the one hand, route-dependent adjusted solutions for the case of penalized lateness, and on the other hand, a direct improvement of the objective function for the case of tolerated lateness. The results suggest that the adjustable robust optimization framework has sufficient potential to model the synchromodal container routing problem. This thesis concludes with addressing some of the limitations of the proposed model and indicating concrete approaches for countering them.
...
This thesis addresses synchromodal planning at operational level from the perspective of a logistics service provider. The existing infrastructure and the transportation activities are studied and modeled as an optimization problem with simultaneous vehicle routing and container-to-mode assignment. A special characteristic of this problem is the uncertain data. In other words, it is assumed that the release times of the containers belong to an uncertainty interval, and no further statistical information is available. The problem is then classified according to an extensive framework previously developed within the project. An extensive body of literature is reviewed to identify current modeling approaches and their theoretical and practical limitations. This literature study shows that, although discrete time models have been intensively investigated, there are few studies which propose continuous modeling of time. The container routing problem is modeled as a mixed integer program with explicit time variables and lateness penalties. A robust formulation is then proposed to eliminate the uncertain parameters from the objective function and constraints. By solving the new model exactly, with the aid of an optimization solver, robust solutions are obtained corresponding to transportation plans which remain feasible for any realization of the release times within the pre-specified uncertainty interval. In order to introduce some flexibility in the transportation plan, the continuous time variables are modeled as affine functions of the uncertain parameters. The resulting two-stage decision model is tested for a small-sized instance in both situations, with high and low lateness penalties. The computational results show that the adjustable robust model yields on the one hand, route-dependent adjusted solutions for the case of penalized lateness, and on the other hand, a direct improvement of the objective function for the case of tolerated lateness. The results suggest that the adjustable robust optimization framework has sufficient potential to model the synchromodal container routing problem. This thesis concludes with addressing some of the limitations of the proposed model and indicating concrete approaches for countering them.
In this dissertation we look at the seriation problem and the applications of this problem. Given a set of items, we try to find an ordering based on the similarity between the items. We start by explaining the mathematical theory behind the seriation problem. Then we describe a couple of different methods that can be used to find a solution for the problem. After that, we apply these methods to various different datasets. The results of these tests will be analysed.
Solving a seriation problem can be an alternative way to already existing methods when finding a ranking of items for a given dataset. The goal is to find out if is also a viable method to use in practice. ...
Solving a seriation problem can be an alternative way to already existing methods when finding a ranking of items for a given dataset. The goal is to find out if is also a viable method to use in practice. ...
In this dissertation we look at the seriation problem and the applications of this problem. Given a set of items, we try to find an ordering based on the similarity between the items. We start by explaining the mathematical theory behind the seriation problem. Then we describe a couple of different methods that can be used to find a solution for the problem. After that, we apply these methods to various different datasets. The results of these tests will be analysed.
Solving a seriation problem can be an alternative way to already existing methods when finding a ranking of items for a given dataset. The goal is to find out if is also a viable method to use in practice.
Solving a seriation problem can be an alternative way to already existing methods when finding a ranking of items for a given dataset. The goal is to find out if is also a viable method to use in practice.
Omdat het veelgebruikte QWERTY-toetsenbord voor een mobiele telefoon, waarop veelal met één vinger getypt wordt, geen optimale typtijd genereert, wordt gezocht naar een nieuwe toetsenbordindeling. Om dit Toetsenbord Layout Probleem op te lossen, worden in de eerste plaats twee nieuwe toetsenroosters gecreëerd, namelijk een met hexagonale toetsen en een met rechthoekige toetsen. Met behulp van WhatsApp gesprekken en de nieuw gevormde toetsenroosters worden twee matrices gemaakt, die gebruikt worden om een kwadratisch toewijzingsprobleem (QAP) op te stellen. Vervolgens wordt met behulp van de eigenvalue bound, Gilmore-Lawler bound en reduced Gilmore-Lawler bound ondergrenzen bepaald voor dit probleem. Ook wordt de gemiddelde waarde van alle mogelijke oplossingen bepaald met de mean objective value. Hierna wordt met twee heuristieken geprobeerd voor beide toetsenrooster een optimale toetsindeling te vinden, namelijk met local search en simulated annealing. Uiteindelijk worden met simulated annealing de twee best gevonden toetsenbordindelingen gevonden. Met de hexagonale layout blijkt iets sneller te kunnen worden getypt dan met de rechthoekige layout, maar voor beide geldt dat ze maximaal 14 procent verbeterd zouden kunnen worden, kijkend naar de onderzochte ondergrenzen.
...
Omdat het veelgebruikte QWERTY-toetsenbord voor een mobiele telefoon, waarop veelal met één vinger getypt wordt, geen optimale typtijd genereert, wordt gezocht naar een nieuwe toetsenbordindeling. Om dit Toetsenbord Layout Probleem op te lossen, worden in de eerste plaats twee nieuwe toetsenroosters gecreëerd, namelijk een met hexagonale toetsen en een met rechthoekige toetsen. Met behulp van WhatsApp gesprekken en de nieuw gevormde toetsenroosters worden twee matrices gemaakt, die gebruikt worden om een kwadratisch toewijzingsprobleem (QAP) op te stellen. Vervolgens wordt met behulp van de eigenvalue bound, Gilmore-Lawler bound en reduced Gilmore-Lawler bound ondergrenzen bepaald voor dit probleem. Ook wordt de gemiddelde waarde van alle mogelijke oplossingen bepaald met de mean objective value. Hierna wordt met twee heuristieken geprobeerd voor beide toetsenrooster een optimale toetsindeling te vinden, namelijk met local search en simulated annealing. Uiteindelijk worden met simulated annealing de twee best gevonden toetsenbordindelingen gevonden. Met de hexagonale layout blijkt iets sneller te kunnen worden getypt dan met de rechthoekige layout, maar voor beide geldt dat ze maximaal 14 procent verbeterd zouden kunnen worden, kijkend naar de onderzochte ondergrenzen.