Thesis (Ph. D.)--Lehigh University, 2005. / Includes vita. Includes bibliographical references (leaves 184-192).

Techn. University, Diss., 2003--Berlin.

Thesis (Ph. D.)--Washington State University, August 2007. / Includes bibliographical references (p. 103-105).

Techn. University, Diss., 2004--Darmstadt.

Thesis (M.S.)--Washington State University, May 2007. / Includes bibliographical references (p. 39-42).

Στόχος της παρούσας εργασίας, είναι η σχεδίαση και η υλοποίηση ενός προγράμματος, το οποίο θα υπολογίζει την βέλτιστη διαδρομή μεταξύ δύο σημείων στην πόλη της Πάτρας, το οποία συνδέονται με αστική συγκοινωνία. Στα πλαίσια της εργασίας αυτής, συγκεντρώθηκαν τα δεδομένα που αφορούν τις διαδρομές των λεωφορείων, τα δρομολόγια και οι χρόνοι μετάβασης. Στη συνέχεια, τα δεδομένα αυτά κωδικοποιήθηκαν κατάλληλα και δημιουργήθηκε πρόγραμμα το οποίο θα τα χρησιμοποιεί για να υπολογίζει την βέλτιστη δρομολόγηση μεταξύ δύο σημείων που θα επιλέγει ο χρήστης. Το πρόγραμμα παρέχεται και ως ανεξάρτητη εκτελέσιμη εφαρμογή αλλά και ως υπηρεσία web, με δυνατότητα εγκατάστασης στον web server του εργαστηρίου. / The main purpose of this Diploma Thesis is the development of a computer program, that is going to estimate the best route between two city points in the city of Patras. These two places are accessible by Patras public transportation system. For this project, we gathered all the appropriate data that are related with the bus routes, the routes, and the time between subsequent bus stop. Furthermore, these data were encoded in such a way, that they are accessible by our program, which calculates the best route between two points chosen by a user. This program was developed as an independent executable application but also as a web service, with the ability to be uploaded in the laboratory’s web server.

The advance of internet applications, such as video streaming, big data and cloud computing, is reshaping the telecommunication and internet industries. Bandwidth demands in datacentres have been boosted by these emerging data-hungry internet applications. Regarding inter- and intra-datacentre communications, fine-grained data need to be exchanged across a large shared memory space. Large-scale high-speed optical switches tend to use a rearrangeably non-blocking architecture as this limits the number of switching elements required. However, this comes at the expense of requiring more sophisticated route selection within the switch and also some forms of time-slotted protocols. The looping algorithm is the classical routing algorithm to set up paths in rearrangeably non-blocking switches. It was born in the electronic switch era, where all links in the switches are equal. It is, therefore, not able to accommodate loss difference between optical paths due to the different length of waveguides and distinct numbers of crossings, and bends, leading to sub-optimal performance. We, therefore, propose an advanced path-selection algorithm based on the looping algorithm that minimises the path-dependent loss. It explores all possible set-ups for a given connection assignment and selects the optimal one. It guarantees that no individual path would have a sufficiently substantial loss, therefore, improve the overall performance of the switch. The performance of the proposed algorithm has been assessed by modelling switches using the VPI simulator. An 8×8 Clos-tree switch demonstrates a 2.7dB decrease in loss and 1.9dB improvement in IPDR with 1.5 dB penalty for the worst case. An 8×8 dilated Beneš shows more than 4 dB loss reduction for the lossiest path and 1.4 dB IPDR improvement for 1 dB power penalty. The improved algorithm can be run once for each switch design and store its output in a compact lookup table, enabling rapid switch reconfiguration. Microelectromechanical systems (MEMS) based optical switches have been fabricated with over 1,000 ports which meet the port count requirements in data centre networks. However, the reconfiguration speed of the MEMS switches is limited to the millisecond to microsecond timescale, which is not sufficient for packet switching in datacentres. Opto-electronic devices, such as Mach-Zehnder Interferometers (MZIs) and semiconductor optical amplifiers (SOAs) with nanosecond response time show the potential to fulfil the requirements of packet switching. However, the scalability of MZI switches is inherently limited by insertion loss and accumulated crosstalk, while the scalability of SOA switches is restricted by accumulated noise and distortion. We, therefore, have proposed a dilated Beneš hybrid MZI-SOA design, where MZIs are implemented as 1×2 or 2×1 low-loss switching elements, minimising crosstalk by using a single input, and where short SOAs are included as gain or absorption units, offering either loss compensation or crosstalk suppression though adding only minimal noise and distortion. A 4×4 device has been fabricated and exhibits a mere 1.3dB loss, an extinction ratio of 47dB, and more than 13dB IPDR for a 0.5dB power penalty. When operating with 10 Gb/s per port, 6pJ/bit energy consumption is demonstrated, delivering 20% reduced energy consumption compared with SOA-based switches. The tolerance of the current control accuracy of this switch is very broad. Within a 5 mA bias current range, the power penalty can be maintained below 0.2 dB for 8 dB IPDR and 12 mA for 10 dB IPDR with a penalty less 0.5 dB. The excellent crosstalk and power penalty performance demonstrated by this chip enable the scalability of this hybrid approach. The performance of 16×16 port dilated Beneš hybrid switch is experimentally assessed by cascading 4×4 switch chips, demonstrating an IPDR of 15 dB at a 1 dB penalty with a 0.6 dB power penalty floor. In terms of switches with port count larger than 16×16, the power penalty performance has been analysed with physical layer simulations fitted with state-of-the-art data. We assess the feasibility of three potential topologies, with different architectural optimisations: dilated Beneš, Beneš and Clos-Beneš. Quantitative analysis for switches with up to 2048 ports is presented, achieving a 1.15dB penalty for a BER of 10-3, compatible with soft-decision forward error correction.

Motivated by collaborative recycling efforts for non-profit agencies, we study a variant of the periodic location routing problem, in which one decides the set of open depots from the customer set, the capacity of open depots, and the visit frequency to nodes, in an effort to design networks for collaborative pickup activities. We formulate this problem, highlighting the challenges introduced by these decisions. We examine the relative dfficulty introduced with each decision through exact solutions and a heuristic approach which can incorporate extensions of model constraints and solve larger instances. The work is motivated by a project with a network of hunger relief agencies (e.g., food pantries, soup kitchens and shelters) focusing on collaborative approaches to address their cardboard recycling challenges collectively. We present a case study based on data from the network. In this novel setting, we evaluate collaboration in terms of participation levels and cost impact. These insights can be generalized to other networks of organizations that may consider pooling resources.

In this paper we present and analyze the application of an Ant System to the Vehicle Routing Problem with Backhauls and Time Windows (VRPBTW). At the core of the algorithm we use an Insertion procedure to construct solutions. We provide results on the learning and runtime behavior of the algorithm as well as a comparison with a custom made heuristic for the problem. / Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"

L'efficacité du transport des marchandises en ville est un sujet complexe préoccupant les autorités locales depuis de nombreuses années. Les enjeux sont immenses, une meilleure organisation du trafic devant permettre d'augmenter la sécurité, réduire les nuisances, minimiser les coûts. La Logistique Urbaine vise à concevoir des systèmes de distribution des marchandises en ville permettant d'acheminer les flux dans les meilleures conditions à la fois pour la communauté et les transporteurs. Cette thèse se deroule dans le cadre du projet ANR MODUM qui propose un système basé sur un anneau de Centres de Distribution Urbains (CDU) situés autour d'une ville. La première partie étudie ce système d'un point de vue stratégique et tactique. Le Multicommodity-Ring Location Routing Problem aborde les décisions concernants l'installation et la connexion en anneau des CDU en simplifiant les détails plus tactiques. Trois méthodes ont été developpées et testées sur un jeu d'instances exhaustif se révélant très efficaces. The Multicommodity-Ring Vehicle Routing Problem est le problème dérivé que l'on obtient quand l'anneau est fixé. Une approche de type Branch&Price est proposée pour ce problème. La deuxième partie porte sur le Vehicle Routing Problem with Intermediate Replenishment Facilities, un problème plus tactique qui se produit dans un système logistique lorsque les véhicules peuvent se recharger auprès des points de remplissage et effectuer plusieurs tournées lors d'une même journée. Plusieurs algorithmes exacts ont été developpés et testés. Les résultats obtenus sur des jeux d'instances tirés de la littérature sont prometteurs. / Urban freight transport is a matter of increasing concern in the economic, commercial, social and environmental operations of our cities, due to the constantly increasing growth and urbanization of the civilization. An improved managem ent of the traffic related to the freight transport can have a positive impact in many respects : security, congestion of the road network, noise and air pollution, costs. City Logistics studies the dynamic management of urban freight transport in order to deliver distribution systems solutions that may be suitable for both the community and freight carriers. This thesis originates from the ANR Project MODUM, which proposes a freight distribution system based on a ring of Urban Distribution Centers (UDCs) located in the outskirts of a city. In the first part, this system is studied from both a strategic and a tactical point of view. The Multicommodity-Ring Location Routing Problem (MRLRP) considers long-term decisions, i.e. the installation of the UDCs and the ring connection, without disregarding more tactical aspects. The MRLRP has been tackled by three solution methods, which proved effective on a large set of test instances. In the second part of the thesis, the Vehicle Routing Problem with Intermediate Replenishment Facilities (VRPIRF) is studied. The VRPIRF is a more tactical problem that arises in City Logistics each time both the multi-trip and the multi-depot features, i.e. the possibility for a vehicle to be reloaded at one of a set of facilities, are present. Several exact algorithms, namely two of type Branch&Cut and two of type Branch& Price, have been developed for this problem. computational experiments on benchmark instances taken from the literature have been conducted to assess their performance, leading to very promising results.