Dissertations / Theses on the topic 'Transport optimization'

Nesta tese, nós apresentamos uma compilação de três artigos de otimização aplicados no contexto de transporte urbano de ônibus. O principal objetivo foi estudar e implementar heurísticas com base em Pesquisa Operacional para otimizar problemas de (re)escalonamento de veículos off-line e on-line considerando várias garagens e frota heterogênea. No primeiro artigo, foi proposta uma abordagem heurística para o problema de escalonamento de veículos múltiplas garagens. Acreditamos que as principais contribuições são o método de geração de colunas para grandes instâncias e as técnicas de redução do espaço de estados para acelerar as soluções. No segundo artigo, adicionamos complexidade ao considerar a frota heterogênea, denotada como multiple depot vehicle type scheduling problem (MDVTSP). Embora a importância e a aplicabilidade do MDVTSP, formulações matemáticas e métodos de solução para isso ainda sejam relativamente inexplorados. A principal contribuição desse trabalho foi o método de geração de colunas para o problema com frota heterogênea, já que nenhuma outra proposta na literatura foi identificada no momento pelos autores. Na terceira parte desta tese, no entanto, nos concentramos no reescalonamento em tempo real para o caso de quebras definitivas de veículos. A principal contribuição é a abordagem eficiente do reescalonamento sob uma quebra. A abordagem com redução de espaço de estados, solução inicial e método de geração de colunas possibilitou uma ação realmente em tempo real. Em menos de cinco minutos, reescalonando todas as viagens restantes.
In this dissetation we presented a three articles compilation in urban bus transportation optimization. The main objective was to study and implement heuristic solutions method based on Operations Research to optimizing offline and online vehicle (re)scheduling problems considering multiple depots and heterogeneous fleet. In the first paper, a fast heuristic approach to deal with the multiple depot vehicle scheduling problem was proposed. We think the main contributions are the column generation framework for large instances and the state-space reduction techniques for accelerating the solutions. In the second paper, we added complexity when considering the heterogeneous fleet, denoted as "the multiple-depot vehicle-type scheduling problem" (MDVTSP). Although the MDVTSP importance and applicability, mathematical formulations and solution methods for it are still relatively unexplored. We think the main contribution is the column generation framework for instances with heterogeneous fleet since no other proposal in the literature has been identified at moment by the authors. In the third part of this dissertation, however, we focused on the real-time schedule recovery for the case of serious vehicle failures. Such vehicle breakdowns require that the remaining passengers from the disabled vehicle, and those expected to become part of the trip, to be picked up. In addition, since the disabled vehicle may have future trips assigned to it, the given schedule may be deteriorated to the extent where the fleet plan may need to be adjusted in real-time depending on the current state of what is certainly a dynamic system. Usually, without the help of a rescheduling algorithm, the dispatcher either cancels the trips that are initially scheduled to be implemented by the disabled vehicle (when there are upcoming future trips planned that could soon serve the expected demand for the canceled trips), or simply dispatches an available vehicle from a depot. In both cases, there may be considerable delays introduced. This manual approach may result in a poor solution. The implementation of new technologies (e.g., automatic vehicle locators, the global positioning system, geographical information systems, and wireless communication) in public transit systems makes it possible to implement real-time vehicle rescheduling algorithms at low cost. The main contribution is the efficient approach to rescheduling under a disruption. The approach with integrated state-space reduction, initial solution, and column generation framework enable a really real-time action. In less than five minutes rescheduling all trips remaining.

We demonstrate that pulses derived using Optimal Control Theory (OCT) techniques can be used to significantly enhance the robustness of the Carr-Purcell-Meiboom-Gill sequence (CPMG) [1,2] to inhomogeneities in the static BB0 field. By numerically inverting the Liouville - von Neumann equation, OCT pulses were derived that can be used directly in place of hard pulses in the CPMG sequence to greatly improve the bandwidth of refocusing. To retain the echo stability achieved by the Meiboom-Gill correction to the Carr-Purcell sequence, the refocusing pulses were designed to perform a unitary π-rotation as opposed to just a state inversion transfer. To illustrate this approach we present an example of optimized pulses that show an improved CPMG-like behavior with complete excitation and multiple refocusing over a bandwidth of +/- 2.6 γB1,max B with a pulse duration limited to 10 t180.

A ship scheduling problem in optimization of water-borne crude oil transportation has been investigated. The classic optimization problem the most closely related to the problem at hand is the Multi-Vehicle-Pick-up-and-Delivery Problem with Time Windows (m-PDPTW). In addition to the basic characteristics of the m-PDPTW, the studied problem has an additional degree of freedom due to having pick-ups and deliveries that are not matched. This extra freedom gives new possibilities when creating effective heuristics when dealing with transportation problems. The studied problem has been presented in relation to carefully selected background literature. On this basis a proposed heuristic has been developed, and implemented using some already existing structures in the commercial decision support system TurboRouter. The studied problem is an industrial shipping problem, an operational mode where the shipper owns the cargo to be transported. No income is therefore made directly from transporting goods. Therefore the objective function chosen was net income, which in this mode is the same as minimizing the net expenses. A multi-start local search with pre-matching of pick-ups and deliveries heuristic was chosen based on an assessment of problem size, problem type, real life applicability and existing software. This heuristic consists of three main parts. First the pick-ups and deliveries are matched and merged in a pre-matching heuristic, and then a large number of initial solutions are generated by an insertion heuristic. The best initial solutions are then improved by a local search. Two strategies were developed for pre-matching and then tested. The one with the best test results was subsequently used in the heuristic. This multi-start local search with pre-matching of pick-ups and deliveries heuristic has been subject to rigorous testing and was compared to a single-start local search and multiple initial solutions heuristic. The solutions generated by the multi-start local search heuristic were superior compared to those of the other heuristics, but the computation time necessary was high and higher than those of the heuristics which it was compared to. This high computation time is partially believed to be a result of flexible data sets resulting in broad solution spaces. In addition some computationally expensive heuristics were deployed, increasing the computation time. In real life applications, finding a solution relatively quickly is of importance. Therefore the heuristic may need to be simplified and used on "tighter" data sets than some sets used in testing to be real life applicable.

This study aims to improve transportation held between six auction centers, Inter-Auction Transportation, of FloraHolland. FloraHolland serves ninety eight percent of the Dutch market and is the largest auction in floriculture industry. The company wants to give the best sale opportunities with the costs as low as possible and this is the main initiative of this study. In this line of thought, FloraHolland wants to have a improvement on its current routing and scheduling mechanism. Exact models do not work due to the complexity and the size of the problem. Therefore, we developed a two-stage approach specific to this study. With this approach, we split exact approach into two, a mathematical model followed by a heuristic. In the exact approach, trucks are routed and scheduled at the same time. On the other hand, our solution approach first determines most efficient routes to be followed with Cycle Assignment Model and then, with Scheduling Heuristic, trucks are assigned to the routes, so within day transportation is planned in detail. Overall, each stage of this approach works in harmony and brings good solutions in a short CPU time.

Mestrado em Engenharia Eletrónica e Telecomunicações
Nesta dissertação, é estudado o problema de dimensionamento das redes óticas e é descrito o desenvolvimento de uma ferramenta de planeamento e otimização. A ferramenta desenvolvida é capaz de otimizar redes reais heterogenias, em termos de capacidade e custo, permite o uso de diferentes equipamentos terminais com diferentes taxas de linha e inclui as funcionalidades de colocação de regeneradores, de multi-hop grooming e de multiplexagem inversa. Esta ferramenta de otimização foi desenvolvida de forma a tirar partido da geração atual de computadores com processadores mútiplos na abordagem multi-thread, em particular quando é implementado um mecanismo de partilha de informação entre todas as threads. Por fim, a heurística implementada na ferramenta desenvolvida, bem como as soluções geradas, são também alvo de estudo e de análise nesta disserta ção. A ferramenta desenvolvida poderá servir de base para o estudo do comportamento da rede para diferentes soluções de equipamentos, testar os limites da capacidade da rede, detetar ligações superfluas ou congestionadas, possibilitar a aglomeração ou desaglomeração de tráfego, determinar a importância de ligações distintas e selecionar locais a intervir, determinar custos de implementação de componentes ou economizar recursos.
In this dissertation, the problem of dimensioning optical networks is addressed and the development of a tool for planning and optimization is described. The developed tool is able to optimize real heterogeneous networks, in terms of capacity and cost, allowing the use of different terminal equipment with different line rates and including different features such as regenerators placement, multi-hop grooming and inverse-multiplexing. This optimization tool was developed in order to make the most out of the current generation of computers with multiple processors in a multithreaded approach, particularly when a mechanism of information sharing is implemented among all threads. Finally, the heuristic implemented in the tool and the solutions generated for a set of case studies are studied and analysed in this dissertation. The developed tool can be used in the future for the study of the network behaviour for different equipment solutions, for testing the limits of network capacity, detecting redundant or congested links, enabling grooming or inverse multiplexing of traffic, determining the importance of different links, selecting network places for intervention, determining implementation costs of components or saving resources.

The ever-increasing demand for broadband services by end-user devices utilising 3G/4G/LTE and the projected 5G in the last mile will require sustaining broadband supply from fibre-linked terminals. The eventual outcome of the high demand for broadband is strained optical and electronic devices. The backbone optical fibre transport systems and techniques such as dense wavelength division multiplexing (DWDM), higher modulation formats, coherent detection and signal amplification have increased both fibre capacity and spectrum efficiency. A major challenge to fibre capacity and spectrum efficiency is fibre-faults and optical impairments, network management, routing and wavelength assignment (RWA). In this study, DWDM and flexible spectrum techniques such as wavelength assignment and adjustment, wavelength conversion and switching, optical add and drop multiplexing (OADM) and bitrate variable transmission have been experimentally optimized in a laboratory testbed for short- and long-haul optical fibre networks. This work starts by experimentally optimising different transmitters, fibre-types and receivers suitable for implementing cost effective and energy efficient flexible spectrum networks. Vertical cavity surface-emitting lasers (VCSELs) and distributed feedback (DFB) lasers have been studied to provide up to 10 Gb/s per channel in 1310 nm and 1550 nm transmission windows. VCSELs provide wavelength assignment and adjustment. This work utilises the non-return-to-zero (NRZ) on-off keying (OOK) modulation technique and direct detection due to their cost and simplicity. By using positive intrinsic negative (PIN) photo-receivers with error-free BER sensitivity of -18±1 dBm at the acceptable 10-9-bit error rate (BER) threshold level, unamplified transmission distances between 6 km and 76 km have been demonstrated using G.652 and G.655 single mode fibres (SMFs). For the first time, an all optical VCSEL to VCSEL wavelength conversion, switching, transmission at the 1550 nm window and BER evaluation of a NRZ data signal is experimentally demonstrated. With VCSEL wavelength conversion and switching, wavelength adjustments to a spectrum width of 4.8 nm (600 GHz) can be achieved to provide alternative routes to signals when fibre-cuts and wavelength collision occurs therefore enhancing signal continuity. This work also demonstrates a technique of removing and adding a wavelength in a bundle of DWDM and flexible channels using an OADM. This has been implemented using a VCSEL and a fibre Bragg grating (FBG) providing a wavelength isolation ratio of 31.4 dB and ~0.3 𝑑𝐵 add/drop penalty of 8.5 Gb/s signal. As a result, an OADM improves spectrum efficiency by offering wavelength re-use. Optical impairments such as crosstalk, chromatic dispersion (CD) and effects of polarization mode dispersion (PMD) have been experimentally investigated and mitigated. This work showed that crosstalk penalty increased with fibre-length, bitrate, interfering signal power and reduced channel spacing and as a result, a crosstalk-penalty trade-off is required. Effects of CD on a transmitted 10 Gb/s signal were also investigated and its mitigation techniques used to increase the fibre-reach. This work uses the negative dispersion fibres to mitigate the accumulated dispersion over the distance of transmission. A 5 dB sensitivity improvement is reported for an unamplified 76 km using DFB transmitters and combination of NZDSF true-wave reduced slope (TW-RS) and submarine reduced slope (TW-SRS) with + and – dispersion coefficients respectively. We have also demonstrated up to 52 km 10 Gb/s per channel VCSEL-based transmission and reduced net dispersion. Experimental demonstration of forward Raman amplification has achieved a 4.7 dB on-off gain distributed over a 4.8 nm spectral width and a 1.7 dB improvement of receiver sensitivity in Raman-aided 10 Gb/s per wavelength VCSEL transmission. Finally, 4.25-10 Gb/s PON-based point to point (P2P) and point to multipoint (P2MP) broadcast transmission have been experimentally demonstrated. A 10 Gb/s with a 1:8 passive splitter incurred a 3.7 dB penalty for a 24.7 km fibre-link. In summary, this work has demonstrated cost effective and energy efficient potential flexible spectrum techniques for high speed signal transmission. With the optimized network parameters, flexible spectrum is therefore relevant in short-reach, metro-access and long-haul applications for national broadband networks and the Square Kilometre Array (SKA) fibre-based signal and data transmission.

Ces dernières années, les problèmes environnementaux sont fortement associés à l'industrie des transports, les modes de transport de marchandises deviennent plus que la contribution la plus importante entre les autres secteurs. Malgré les avantages du transport intermodal, il a toujours des impacts négatifs, qui sont associés aux émissions. Cependant, la pollution est devenue intéressante entre les secteurs académique et industriel. Ainsi, pour atténuer les impacts négatifs du transport de marchandises, cela gagne de plus en plus en pertinence dans le domaine de la logistique. Pour répondre à ces enjeux et défis, pour identifier les apports de la logistique verte à l'optimisation du transport de marchandises, augmenter l'efficacité des opérations d'optimisation liées à la plateforme de transport multimodal.Le fonctionnement optimal du transport de conteneurs est particulièrement important lorsque le transport de marchandises de manière écologique peut être réalisé en combinant différents modes de transport et en coordonnant des activités telles que la recherche du chemin le plus court. Dans le système de transport multimodal de conteneurs, la sélection du mode de transport et de l'itinéraire a un effet important sur le processus de transport des conteneurs de transport. Dans cette thèse, pour organiser le transport multimodal de manière plus efficace, le facteur de routage des conteneurs est considéré avec le facteur de trajet du mode de transport. On étudie l'influence des caractéristiques incertaines du fonctionnement du nœud sur le mode de transport et le choix de l'itinéraire dans le processus de conversion du mode de transport du transport multimodal conteneurisé. Pour minimiser le coût total, un modèle de programmation mixte avec des contraintes de temps est introduit. La transformation graphique est utilisée pour transformer le problème en modèle de chemin le plus court avec des caractéristiques aléatoires et des contraintes de temps de transport dans les opérations de nœud. En vérifiant et en analysant les résultats, le chemin obtenu est acceptable d'un point de vue coût et temps. Ainsi, cela réduit la congestion du trafic et minimise les émissions. Dans le contexte de la congestion du trafic et de la réduction des émissions, cette thèse propose une technologie de peloton pour améliorer la consommation de carburant, la flexibilité routière et optimiser les opérations de transport de conteneurs. Dans cette thèse, un système de téléphérique pour le transport de petites marchandises est proposé et analysé afin de réduire la congestion du trafic dans la zone urbaine.La recherche conclue à l'optimisation des plates-formes de transport multimodal vise à réduire les impacts négatifs sur l'environnement et à maximiser la rentabilité en maximisant les services offerts qui minimisent le coût total de transport ainsi que le temps de transport entre chaque paire de nœuds Origine-Destination (OD) dans le réseau de transport. Ces travaux contribuent également à réduire les émissions de dioxyde de carbone en diminuant la consommation de carburants et en réduisant les coûts d'exploitation. Sur la base de ces travaux, des plates-formes de transport de conteneurs plus efficaces et efficientes peuvent être réalisées. Cette thèse introduit la base théorique de l'optimum de transport multimodal qui permet l'intégration entre différents modes. Parallèlement, il contribue à la logistique de l'efficacité du transport multimodal / intermodal
In recent years, environmental issues are highly associated with the transport industry, modes of goods transport become more than contribution as largest between other sectors. Despite the benefits of intermodal transport, it still has negative impacts, which are associated with emission. However, pollution has become interesting between academic and industrial sectors. Thus, to mitigate the negative impacts caused by goods transport, that gains more and more relevance in the logistics domain. To meet these issue and challenges, to identify the contributions that green logistics to the optimization of freight transport, the increase the efficiency of the multimodal transport platform related optimization operations.The optimal operating of container transport is particularly important where goods transport in an environmentally way can be achieved by combining different modes of transport and coordinating activities such as finding the shortest path. In the multimodal container transport system, the selection of the transport mode and route has a large effect on the transport container transport process. In this thesis, to organize multimodal transport in a more efficient manner the container routing factor is considered along with the path factor of transport mode. The influence of the uncertain characteristics of the node operation on the transport mode and route choice in the process of converting the transport mode from containerized multimodal transport is studied. To minimize the total cost, an integer mixed programming model with time constraints is introduced. The graphical transformation is used to transform the problem into the shortest path model with random characteristics and transport time constraints in the node operations. By verifying and analyzing the results, the path obtained is acceptable from a cost and time perspective. Thus, this reducing traffic congestion and minimizing emissions. In the context of traffic congestion and emissions reduction, in this thesis a platoon technology is proposed to improve to reduce fuel consumption, road flexibility and optimize container transport operations. In this thesis, a ropeway system for the transport of small-scale goods is proposed and analyzed to reduce the traffic congestion within the urban area.The research concluded to optimization multi-modal transport platforms aims to reduce negative impacts on the environment and maximize profitability maximizing the services offered that minimize the total transportation cost as well as minimize the transportation time between each pair of Origin-Destination (O-D) nodes in the transport network. This work also contributes to reducing carbon dioxide emissions by decreasing consumption fuels and reducing operating costs. Based on this work, more effective and efficient container transport platforms can be achieved. This thesis introduces the theoretical base of optimal of multi-modal transport which can integration between different modes. Meanwhile, it contributes to logistics of multi/inter-modal transport efficiency

The objective of this research is to examine how to design low-noise transport aircraft using Multidisciplinary Design Optimization (MDO). The subject is approached by designing for low-noise both implicitly and explicitly. The explicit design approach involves optimizing an aircraft while explicitly constraining the noise level. An MDO framework capable of optimizing both a cantilever wing and a Strut-Braced-Wing (SBW) aircraft was developed. The framework employs aircraft analysis codes previously developed at the Multidisciplinary Design and Analysis (MAD) Center at Virginia Tech (VT). These codes have been improved here to provide more detailed and realistic analysis. The Aircraft Noise Prediction Program (ANOPP) is used for airframe noise analysis. The objective is to use the MDO framework to design aircraft for low-airframe-noise at the approach conditions and quantify the change in weight and performance with respect to a traditionally designed aircraft. The results show that reducing airframe noise by reducing approach speed alone, will not provide significant noise reduction without a large performance and weight penalty. Therefore, more dramatic changes to the aircraft design are needed to achieve a significant airframe noise reduction. Another study showed that the trailing-edge (TE) flap can be eliminated, as well as all the noise associated with that device, without incurring a significant weight and performance penalty. To achieve approximately 10 EPNdB TE flap noise reduction the flap area was reduced by 82% while the wing reference area was increased by 12.4% and the angle of attack increased from 7.6 degrees to 12.1 degrees to meet the required lift at approach. The wing span increased by approximately 2.2%. Since the flap area is being minimized, the wing weight suffers only about a 2,000 lb penalty. The increase in wing span provides a reduction in induced drag to balance the increased parasite drag due to a lower wing aspect ratio. As a result, the aircraft has been designed to have minimal TE flaps without any significant performance penalty. If noise due to the leading-edge (LE) slats and landing gear are reduced, which is currently being pursued, the elimination of the flap will be very significant as the clean wing noise will be the next 'noise barrier'. Lastly, a comparison showed that SBW aircraft can be designed to be 10% lighter and require 15% less fuel than cantilever wing aircraft. Furthermore, an airframe noise analysis showed that SBW aircraft with short fuselage-mounted landing gear could have similar or potentially a lower airframe noise level than comparable cantilever wing aircraft. The implicit design approach involves selecting a configuration that supports a low-noise operation, and optimizing for performance. A Blended-Wing-Body (BWB) transport aircraft has the potential for significant reduction in environmental emissions and noise compared to a conventional transport aircraft. A BWB with distributed propulsion was selected as the configuration for the implicit low-noise design in this research. An MDO framework previously developed at the MAD Center at Virginia Tech has been refined to give more accurate and realistic aircraft designs. To study the effects of distributed propulsion, two different BWB configurations were optimized. A conventional propulsion BWB with four pylon mounted engines and two versions of a distributed propulsion BWB with eight boundary layer ingestion inlet engines. A 'conservative' distributed propulsion BWB design with a 20% duct weight factor and a 95% duct efficiency, and an 'optimistic' distributed propulsion BWB design with a 10% duct weight factor and a 97% duct efficiency were studied. The results show that 65% of the possible savings due to 'filling in' the wake are required for the 'optimistic' distributed propulsion BWB design to have comparable $TOGW$ as the conventional propulsion BWB, and 100% savings are required for the 'conservative' design. Therefore, considering weight alone, this may not be an attractive concept. Although a significant weight penalty is associated with the distributed propulsion system presented in this study, other characteristics need to be considered when evaluating the overall effects. Potential benefits of distributed propulsion are, for example, reduced propulsion system noise, improved safety due to engine redundancy, a less critical engine-out condition, gust load/flutter alleviation, and increased affordability due to smaller, easily-interchangeable engines.
Ph. D.

Road freight transportation is subject to several legal requirements having direct impact on the practical applicability of routes and schedules. The vast majority of vehicle routing literature, so far, has largely focused on physical constraints such as capacity limits, or customer requirements such as time windows for pickups and deliveries. This paper studies legal requirements for long-distance haulage in the European Union, identifies some major gaps in the current state-of-the-art in vehicle routing, presents approaches for overcoming this gap, and analyzes the impact of the legal requirements studied.

Transitional areas, between inland and coastal environments, represent an important habitat for their environmental and natural value. They act as a natural buffer for all those chemicals which are produced by diffused sources of pollutants (run-off rain water from agriculture) or from hidden sources (sewers not connected to a wastewater treatment plant). Pollutants produced by this type of sources can lead, if not conveniently treated, to eutrophication and to other water quality problems along coastal areas. Traditional wastewater treatment methods appear to be not effective in these conditions because of the big volumes of water and the relatively low concentration of dissolved pollutants to be treated. Since traditional wastewater treatment plants can not be used, it becomes important to better understand transport phenomena in transitional environments (rivers and wetlands) and all the removal processes in such zones in order to manage them to treat all the chemicals before they arrive to the coastal areas. Particular attention must be therefore stressed on retention processes and on the formulation of predictive models which allow scientists and engineers to better manage and design these buffer areas. In Chapter 1, the role of different transport processes is analyzed focusing the attention on different spatial and temporal scales. Principal modeling approaches are discussed underlining the role of each term on the mass balance equation and the most classical model closures are described in this chapter. In Chapter 2, retention characteristics of three different rivers are analyzed, relating different model closures with planimetric features of the rivers, their vegetational cover and bottom permeability. The analysis is carried on using STIR (Solute Transport In Rivers) model, a one-dimensional solute transport model that describes concentration breakthrough curves implementing a wide set of retention phenomena characterized by different time scales, represented by a specific residence time distribution in each retention domain. Comparison of modeling results and experimental data shows the capability of the model to characterize, with an inverse analysis, retention processes that occur in a river. In Chapter 3 a two-dimensional schematic wetland is studied with a numerical model that solves, with a shallow water approach, hydrodynamic and mass transport equations. A specific processing of the numerical results is used to determine numerical residence time distributions of the wetland as a function of a particular vegetation distribution that reproduces a central channel delimited by two lateral, more densely vegetated, banks. To each different density ratio it corresponds a specific shape of the residence time distribution, that present a clear bimodality below a critical value. To model this specific phenomenon, typical in natural environments, a simple and a more easy to use one-dimensional model approach is implemented in the former STIR model. The new version is called STIR-DTD. In Chapter 4 a new innovative optimization approach to wetland design is defined. Numerical solution of a two-dimensional shallow water model using the open-source suite TELEMAC2D, is integrated with an evolutionary optimization algorithm. At the initial stage of the evolution strategy, the removal efficiency of a random population of individuals (each individual represents a specific distribution of vegetated patches over the wetland domain) is evaluated numerically solving a shallow water hydrodynamic model coupled with a solute transport model. Once the removal efficiency is known, the evolutionary algorithm, using a wide range of selection operators that mimic natural evolution, evolve the initial population to an individual that maximizes the pollutant mass removal. Performed tests show how the optimized distribution tends to cover the maximum wetland available area or, if a maximum vegetated area is kept fixed, how the distribution tends to lengthen the flow paths between the inlet and the outlet section of the wetland. Chapter 5 shows results of a preliminary analysis on the removal efficiency of randomly distributed vegetation characterized by a Gaussian spatial probability density function. Vegetation density is treated as a random variable characterized by a mean, a variance and an homogeneous correlation length. The effect of each distribution on the removal efficiency is numerically evaluated by a coupled hydrodynamic and solute transport that accounts for the pollutant decay. Results show how removal efficiency is correlated with the statistical parameters of the space probability density function used to generate the random filed.
Le zone di transizione tra entroterra e mare costituiscono una porzione di territorio molto importante dal punto di vista ambientale e naturalistico. Esse rappresentano un naturale filtro per tutte quelle specie chimiche che sono prodotte da fonti di inquinamento diffuse (dilavamento di suoli agricoli) o occulte (scarichi non collettati o irregolari) che possono creare, se non opportunamente trattate, problemi di eutrofizzazione e di qualità delle acque lungo le coste. I tradizionali metodi di depurazione si rivelano poco efficaci nel trattare questo tipo di effluenti, per le grandi portate da gestire e per le relativamente basse concentrazioni di inquinanti. Risulta importante quindi, nell'impossibilità di impiegare i tradizionali impianti di depurazione, comprendere le dinamiche di trasporto negli ambienti naturali (fiumi e aree umide) e i meccanismi di rimozione degli inquinanti in tali zone, in modo da poterle utilizzare per riassorbire, in modo sostenibile e naturale, il carico di inquinanti che altrimenti raggiungerebbe direttamente le coste. A questo scopo è necessario focalizzare l'attenzione sui processi di ritenzione e sulla formulazione di appropriati strumenti modellistici che consentano ai tecnici e ai modellisti una comprensione sufficientemente ampia dei fenomeni e forniscano loro degli strumenti pratici che aiutino nella gestione e riprogettazione di queste aree tampone. Nel Capitolo 1 viene analizzato il ruolo di differenti processi di trasporto focalizzando l'attenzione su diverse scale spaziali e temporali di analisi e descrivendo i principali approcci modellistici utilizzati per trattare ciascun fenomeno. E' evidenziato il contributo di ciascun termine al bilancio di massa e sono prese in considerazione le chiusure modellistiche più classiche oggi adottate. Nel Capitolo 2 si analizzano le caratteristiche dei processi di ritenzione in tre diversi corsi d'acqua mettendo in relazione le diverse chiusure modellistiche adottate in funzione delle caratteristiche planimetriche degli alvei, della loro composizione vegetazionale e delle caratteristiche di permeabilità del fondo. L'analisi \'e eseguita utilizzando il modello di trasporto monodimensionale STIR (Solute Transport In Rivers) che si presta a descrivere le curve di concentrazione implementando una vasta gamma di fenomeni di ritenzione a diverse scale temporali, descritte da specifiche distribuzioni dei tempi di residenza del soluto in ciascun comparto di ritenzione. L'accordo dei dati sperimentali con le curve di concentrazione mostra come si possa, tramite analisi inversa, caratterizzare un fiume dal punto di vista della ritenzione. Il Capitolo 3 prende in considerazione un'area umida bidimensionale di cui si risolvono, con un approccio modellistico alle acque basse, l'idrodinamica e il trasporto di massa. Una opportuna procedura di analisi dei risultati numerici è utilizzata per determinare le distribuzioni dei tempi di residenza dell'area umida in funzione di una particolare distribuzione di vegetazione che riproduce un canale principale delimitato da due zone laterali a maggiore densità di vegetazione. A diversi rapporti di densità corrisponde una specifica forma della distribuzione che presenta, al di sotto di uno specifico valore di soglia, una evidente bimodalità. Per rappresentare opportunamente tale fenomeno, comune negli ambienti naturali, con un approccio modellistico mono-dimensionale di più semplice utilizzo, è proposta in questo capitolo, una nuova versione del modello STIR denominata STIR-DTD. Il Capitolo 4 presenta un approccio innovativo di ottimizzazione alla progettazione di un'area umida. La risoluzione numerica di un modello bidimensionale alle acque basse tramite il modello TELEMAC2D è integrata infatti con un algoritmo evolutivo di ottimizzazione. Allo stadio iniziale dell'evoluzione, è definita, in modo casuale, una popolazione di individui (ciascun individuo rappresenta una specifica distribuzione di zone vegetate) di cui il modello valuta l'efficienza depurativa. A partire dal livello di efficienza depurativa dimostrata da ciascuna distribuzione, l'algoritmo evolutivo, tramite specifici operatori genetici che mimano i processi di selezione naturali, evolve la popolazione verso la distribuzione di vegetazione che massimizza l'abbattimento di inquinanti. I test effettuati mostrano come la distribuzione ottimale evolva verso configurazioni che tendono a coprire tutta l'area vegetata disponibile o, qualora questa sia fissata, a prolungare il più possibile i percorsi di flusso all'interno delle aree vegetate. Il Capitolo 5 riporta i risultati di una prima analisi eseguita su campi random di vegetazione, descritti da una opportuna funzione densità di probabilità spaziale (Gaussiana). La risoluzione tramite un modello bidimensionale accoppiato ad uno di trasporto e decadimento mostra come l'efficienza depurativa e la portata siano correlabili con i parametri (densità media, varianza e lunghezza di correlazione) che caratterizzano la particolare distribuzione statistica di vegetazione adottata.

1. GasnIkov A. V., Klenov S. L., NurmInskIy E. A., Holodov Ya. A., Shamray N. B. Vvedennya v matematichne modelyuvannya transportnih potokIv. - M.: MTsNMO, 2013. 2. VuchIka V. R. Transport v mIstah, zruchnih dlya zhittya. - M .: TeritorIya maybutnogo, 2011. - [OrigInal: Vuchic V. R. Transportation for Livable Cities, 1999].
Transport is sometimes called the circulatory system of a country’s economy. Railway, automobile, sea, river, air - these are just general names for a well-known list of modes of transport. Huge numbers of people and essential goods move on land, in the air, and on water. All this is important to do on time and with minimal cost.

De nos jours, le transport joue un rôle clé dans la vie des pays modernes, en particulier pour les flux de marchandises. La logistique des flux entre régions, pays et continents a bénéficié d’innovations technologiques et organisationnelles assurant efficacité et efficience. Il n’en a pas été de même à l’échelle urbaine, plus particulièrement dans les centres-villes : la gestion des flux dans un environnement caractérisé par une forte densité démographique n’a pas encore véritablement trouvé son modèle d’organisation. Aujourd’hui, la logistique urbaine ou encore la gestion "du dernier kilomètre" constitue donc un enjeu de premier plan, tant socio politique et environnemental qu’économique. La logistique urbaine est caractérisée par la présence de plusieurs acteurs (chargeurs ou propriétaires de marchandises, clients, transporteurs, autorités publiques, …) ayant chacun des priorités différentes (réduction de la pollution, amélioration de la qualité de service, minimisation de la distance totale parcourue, …). Pour relever ces défis, un des leviers possibles consiste à optimiser les tournées de distribution et/ou collecte de marchandises, dans le contexte et sous les contraintes de la ville.Le but de ce travail de thèse réside alors dans la planification de la distribution des marchandises dans un réseau logistique, abordée sous un angle de collaboration entre les chargeurs. Cette collaboration consiste à regrouper les demandes de divers chargeurs pour optimiser le taux de chargement des camions et obtenir de meilleurs prix de transport. Ici, la gestion du « dernier kilomètre » s’apparente à ce que l’on identifie dans la littérature comme le Pickup and Delivery Problem (PDP). Dans le cadre de cette thèse, nous nous intéressons à des variantes de ce problème plus adaptées au contexte urbain. Après avoir réalisé un état de l’art sur les problèmes d’optimisation combinatoire autour du transport et les méthodes utilisées pour leur résolution, nous étudions deux nouvelles variantes du problème de collecte et de livraison : le Selective PDP with Time Windows and Paired Demands et le Multi-periods PDP with Time Windows and Paired Demands. La première permet aux transporteurs de livrer le maximum de clients dans une journée par exemple ; avec la seconde, et en cas d’impossibilité de livraison dans cette période, on détermine la meilleure date de livraison en minimisant la distance parcourue. Chacune d’elles fait l’objet d’une description formelle, d’une modélisation mathématique sous forme de programme linéaire, puis d’une résolution par des méthodes exacte, heuristiques et métaheuristiques, dans des cas mono-objectif et multi-objectifs. La performance de chaque approche a été évaluée par un nombre substantiel de tests sur des instances de différentes tailles issues de la littérature et/ou que nous avons générées. Les avantages et les inconvénients de chaque approche sont analysés, notamment dans le cadre de la collaboration entre chargeurs
Nowadays, transportation plays a key role in our modern countries’life, in particular for the goods flows. The logistics of flows between regions, countries and continents have benefited from technological and organizational innovations ensuring efficiency and effectiveness. It has not been the same at the urban scale, especially in city centers: the management of flows in a high population density environment has not yet found its organizational model. Today, urban logistics or "last mile" management is therefore a major issue, both socio-political and environmental as well as economic. Urban logistics is characterized by several actors (shippers or owners of goods, customers, carriers, public authorities, ...) each with different priorities (reduction of pollution, improvement of service quality, minimization of total distance traveled, ...). To overcome these challenges, one possible lever is to optimize the distribution and/or collection of goods in the context and under the constraints of the city.The goal of this PhD work is then to plan the distribution of goods in a logistics network, approached from a collaboration angle between shippers. This collaboration consists in grouping the demands of several shippers to optimize the loading rate of the trucks and to obtain better transport prices. Here, managing the "last mile" is similar to what is known in the literature as the Pickup and Delivery Problem (PDP). In this thesis, we are interested in variants of this problem more adapted to the urban context. After having realized a state of the art on the combinatorial optimization problems around the transport and the methods used for their resolution, we study two new variants of the problem of collection and delivery: the Selective PDP with Windows and Paired Demands and the Multi-period PDP with Windows and Paired Demands. The first allows carriers to deliver the maximum number of customers in a day for example; with the second, and in case of impossibility of delivery in this period, we determine the best delivery date by minimizing the distance traveled. Each of them is the subject of a formal description, of a mathematical modeling in the form of a linear program, then of a resolution by exact methods, heuristics and metaheuristics, in single-objective and multi-objective cases. The performance of each approach was evaluated by a substantial number of tests on instances of different sizes from the literature and / or that we generated. The advantages and drawbacks of each approach are analyzed, in particular in the context of collaboration between shippers

Thesis (M.S.)--University of West Florida, 2009.
Submitted to the Dept. of Computer Science. Title from title page of source document. Document formatted into pages; contains 66 pages. Includes bibliographical references.

A variable-complexity design strategy with combined aerodynamic and structural optimization procedures is presented for the high speed civil transport design (HSCT). Variable-complexity analysis methods are used to reduce the computational expense. A finite element-model based structural optimization procedure with flexible loads is implemented to evaluate the wing bending material weight. Static aeroelastic effects, evaluated through the comparison of rigid and flexible wing models, are found to be small in the HSCT design. The results of structural optimization are compared with two quasi-empirical weight equations. Good correlation is obtained between the structural optimization and one of the weight equations. Based on this comparison, an interlacing procedure is developed to combine both the simple weight equations and structural optimization in the HSCT design optimization, at modest computational cost. HSCT designs based on the interlacing procedure reveal that the aerodynamic optimizer may take advantage of weaknesses in weight equation. However, the optimizer may be unable to escape the local minimum due to the noisy of aerodynamic response and the lack of derivative information for the interlacing procedure.
Ph. D.

Aujourd'hui, toutes les grandes métropoles de France, d'Europe et du reste du monde souffrent de graves problèmes de congestion et de saturation des infrastructures routières, qui concernent à la fois les transports individuels et publics. Les systèmes de transport actuels atteignent leurs limites de capacité et semblent incapables d'absorber l'augmentation des flux de passagers à l'avenir.Dans ce contexte, l'un des principaux défis à relever concerne la création de méthodologies dédiées pour l'analyse des données de transport géo-localisées pour le stockage instantané, l'analyse, la gestion et la diffusion de flux de données massives. Les algorithmes associés doivent être capables de gérer des listes d'événements de plusieurs dizaines de minutes pour calculer des trajectoires réelles, des occupations instantanées, des cycles de changement de feux de circulation ainsi que des prévisions de flux de circulation de véhicules.Dans cette thèse, nous abordons deux différentes problématiques liées à ce sujet.Une première contribution concerne l'optimisation des systèmes de feux tricolores. L'objectif est de minimiser le temps de trajet total des véhicules présents dans une certaine partie d'une ville. Dans ce but, nous proposons une technique d’optimization de type PSO (Particle Swarm Optimization). Les résultats expérimentaux obtenus montrent qu'une telle approche permet d'obtenir des gains importants (5.37% - 21.53%) en termes de temps de parcours moyen global des véhicules.La deuxième partie de la thèse est consacrée à la problématique de la prédiction des flux de trafic. En particulier, nous nous concentrons sur la prédiction de l'heure d'arrivée des bus dans les différentes stations présentes sur un itinéraire donné. Ici, nos contributions concernent tout d'abord l'introduction d'un nouveau modèle de données, appelé TDM (Traffic Density Matrix), qui capture dynamiquement la situation du trafic tout au long d'un itinéraire de bus donné. Ensuite, nous montrons comment différentes techniques d'apprentissage statistique peuvent exploiter une cette structure de données afin d'effectuer une prédiction efficace. L'analyse des résultats obtenus par les méthodes traditionnelles (régression linéaire, SVR avec différents noyaux…) montre que l'augmentation du niveau de non-linéarité permet d’obtenir des performences supérieures. En partant de ce constat, nous proposons différentes techniques de deep learning avec des réseaux conçus sur mesure, que nous avons spécifiquement adaptés à nos objectifs. L'approche proposée inclut des réseaux de neurones récurrents, des approches de type LSTM (Long Short Time Memory), des réseaux entièrement connectés et enfin convolutionnels. L'analyse des résultats expérimentaux obtenus confirme notre intuition initiale et démontre que ces techniques hautement non-linéaires surpassent les approches traditionnelles et sont capables de prendre en compte les singularités qui apparaissent dans ce type de données et qui, dans notre cas, correspondent à des embouteillages localisés qui affectent globalement le comportement du système.En raison du manque de disponibilité de ce type d'informations géo-localisées qui très sensibles et soumises à des réglementations variées, toutes les données prises en compte dans nos expériments ont été générées à l'aide du simulateur microscopique SUMO (Simulation of Urban Mobility). Nous montrons notamment comment SUMO peut être exploité pour construire des scénarios réalistes, proches de situations réelles et exploitables à des fins d'analyse.Enfin, une dernière contribution concerne l’élaboration et la mise en œuvre de deux applications de visualisation différentes, une première dédiée aux opérateurs et la seconde aux clients. Pour assurer le déploiement et la compatibilité de ces applications sur différents terminaux (PC, ordinateurs portables, smartphones, tablettes…), une solution scalable est proposée
Today all major metropolises in France, Europe and the rest of the world suffer from severe problems of congestion and saturation of infrastructures, which concern both individual and public transport. Current transportation systems are reaching capacity limits and appear unable to absorb increases in passenger flows in the future. The transport of the future is part of the various so-called Smart City initiatives and should be ”intelligent”, that is to say not only react to the demands but anticipate them, relying on the data exchanged between the end user and the information system of transportation operators.Within this context, one of the main challenges is the creation of appropriate methodologies for analysis of geo-localized transport data for instantaneous storage, analysis, management and dissemination of massive (typically thousands of instant geo-localizations , with a refresh rate of the order of a few seconds) data flows. The related algorithms must be capable of managing event lists of several tens of minutes to calculate real trajectories, instantaneous occupations, traffic lights changing cycles as well as vehicular traffic flow forecasts.In this thesis, we address two different issues related to this topic.A first contribution concerns the optimization of the traffic lights systems. The objective is to minimize the total journey time of the vehicles that are present in a certain part of a city. To this purpose, we propose a PSO (Particle Swarm Optimization) technique. The experimental results obtained show that such an approach makes it possible to obtain significant gains (5.37% - 21.53%) in terms of global average journey time.The second part of the thesis is dedicated to the issue of traffic flow prediction. In particular, we focus on prediction of the bus arrival time in the various bus stations existent over a given itinerary. Here, our contributions first concern the introduction of a novel data model, so-called TDM (Traffic Density Matrix), which captures dynamically the situation of the traffic along a given bus itinerary. Then, we show how different machine learning (ML) techniques can exploit such a structure in order to perform efficient prediction. To this purpose, we consider first traditional ML techniques, including linear regression and support vector regression with various kernels. The analysis of the results show that increasing the level of non-linearity can lead to superior results. Based on this observation, we propose various deep learning techniques with hand-crafted networks that we have specifically adapted to our objectives. The proposed approach include recurrent neural networks, LSTM (Long Short Time Memory) approaches, fully connected and convolutional networks. The analysis of the obtained experimental results confirm our intuition and demonstrate that such highly non-linear techniques outperform the traditional approaches and are able to deal with the singularities of the data that in this case correspond to localized traffic jams that globally affect the behavior of the system.Due to the lack of availability of such highly sensitive type of geo-localized information, all the data considered in our experiments has been produced with the help of the SUMO (Simulation of Urban Mobility) microscopic simulator. We notably show how SUMO can be exploited to construct realistic scenarios, close to real-life situations and exploitable for analysis purposes.Interpretation and understanding the data is of vital importance, nevertheless an adequate visualization platform is needed to present the results in a visually pleasing and understandable manner. To this purpose, we finally propose two different visualization application, a first one dedicated to the operators and the second one to clients. To ensure the deployment and compatibility of such applications on different devices (desktop PCs, Laptops, Smartphones, tablets…) a scalable solution is proposed

Mestrado em Engenharia Eletrónica e Telecomunicações
Nesta dissertação é apresentada uma introdução as redes de transporte oticas multicamada. Foram caracterizados os dois elementos principais da rede: nós e ligações. Ao nível das ligações foi feita uma abordagem baseada nos seus elementos físicos principais. Ao nível dos nós foram tidos em consideração o tráfego de cliente (baixo débito) e o tráfego de linha (alto débito), bem como os componentes necessários para os transportar. A forma como o tráfego de cliente e agregado e o encaminhamento do mesmo na rede, exigem a elaboração de uma arquitetura que minimize os recursos necessários. A necessidade de otimizar este processo de dimensionamento da rede levou a construção e validação de métodos de agregação de tráfego e encaminhamento baseados em topologias lógicas da rede. Assim, proponho nesta dissertação algoritmos de agregação e encaminhamento aplicados a um software livre, previamente validados por modelos de programação linear baseados em restrições e funções objectivo adequadas a topologia pretendida. A apresentação detalhada dos resultados considerando o CAPEX, bem como a sua análise são considerados na dissertação. Por fim, são apresentadas conclusões e sugerido o trabalho científico que ainda pode ser realizado neste âmbito.
In this dissertation an introduction is presented to the multilayer optical transport networks. The two main elements of the network were characterized: nodes and links. Regarding the connections it was made a shallower approach based on its key physical elements. In terms of nodes client traf- c (low bandwith) and the line tra c (high bandwith) were considered as well as the components necessary to carry them. The way the client tra c is aggregated and its forwarding in the same network requires an architecture which makes use of the minimum resources. The need of optimizing this network design process led to the construction and validation of tra c aggregation methods and routing based on logical network topologies. I therefore propose in this dissertation routing and grooming algorithms applied to a open source software, previously validated by linear programming models based on constraints and objective functions suitable to the desired topology. A detailed presentation of the results considering the CAPEX and its analysis are also taken into account. Finally, conclusions are presented and the scienti c work that can still be done in this area is suggested.

L’accès aux données de base, que sont les sections efficaces, constitue le principal goulot d’étranglement aux performances dans la résolution des équations du transport neutronique par méthode Monte Carlo (MC). Ces sections efficaces caractérisent les probabilités de collisions des neutrons avec les nucléides qui composent le matériau traversé. Elles sont propres à chaque nucléide et dépendent de l’énergie du neutron incident et de la température du matériau. Les codes de référence en MC chargent ces données en mémoire à l’ensemble des températures intervenant dans le système et utilisent un algorithme de recherche binaire dans les tables stockant les sections. Sur les architectures many-coeurs (typiquement Intel MIC), ces méthodes sont dramatiquement inefficaces du fait des accès aléatoires à la mémoire qui ne permettent pas de profiter des différents niveaux de cache mémoire et du manque de vectorisation de ces algorithmes.Tout le travail de la thèse a consisté, dans une première partie, à trouver des alternatives à cet algorithme de base en proposant le meilleur compromis performances/occupation mémoire qui tire parti des spécificités du MIC (multithreading et vectorisation). Dans un deuxième temps, nous sommes partis sur une approche radicalement opposée, approche dans laquelle les données ne sont pas stockées en mémoire, mais calculées à la volée. Toute une série d’optimisations de l’algorithme, des structures de données, vectorisation, déroulement de boucles et influence de la précision de représentation des données, ont permis d’obtenir des gains considérables par rapport à l’implémentation initiale.En fin de compte, une comparaison a été effectué entre les deux approches (données en mémoire et données calculées à la volée) pour finalement proposer le meilleur compromis en termes de performance/occupation mémoire. Au-delà de l'application ciblée (le transport MC), le travail réalisé est également une étude qui peut se généraliser sur la façon de transformer un problème initialement limité par la latence mémoire (« memory latency bound ») en un problème qui sature le processeur (« CPU-bound ») et permet de tirer parti des architectures many-coeurs
Monte Carlo (MC) neutron transport simulations are widely used in the nuclear community to perform reference calculations with minimal approximations. The conventional MC method has a slow convergence according to the law of large numbers, which makes simulations computationally expensive. Cross section computation has been identified as the major performance bottleneck for MC neutron code. Typically, cross section data are precalculated and stored into memory before simulations for each nuclide, thus during the simulation, only table lookups are required to retrieve data from memory and the compute cost is trivial. We implemented and optimized a large collection of lookup algorithms in order to accelerate this data retrieving process. Results show that significant speedup can be achieved over the conventional binary search on both CPU and MIC in unit tests other than real case simulations. Using vectorization instructions has been proved effective on many-core architecture due to its 512-bit vector units; on CPU this improvement is limited by a smaller register size. Further optimization like memory reduction turns out to be very important since it largely improves computing performance. As can be imagined, all proposals of energy lookup are totally memory-bound where computing units does little things but only waiting for data. In another word, computing capability of modern architectures are largely wasted. Another major issue of energy lookup is that the memory requirement is huge: cross section data in one temperature for up to 400 nuclides involved in a real case simulation requires nearly 1 GB memory space, which makes simulations with several thousand temperatures infeasible to carry out with current computer systems.In order to solve the problem relevant to energy lookup, we begin to investigate another on-the-fly cross section proposal called reconstruction. The basic idea behind the reconstruction, is to do the Doppler broadening (performing a convolution integral) computation of cross sections on-the-fly, each time a cross section is needed, with a formulation close to standard neutron cross section libraries, and based on the same amount of data. The reconstruction converts the problem from memory-bound to compute-bound: only several variables for each resonance are required instead of the conventional pointwise table covering the entire resolved resonance region. Though memory space is largely reduced, this method is really time-consuming. After a series of optimizations, results show that the reconstruction kernel benefits well from vectorization and can achieve 1806 GFLOPS (single precision) on a Knights Landing 7250, which represents 67% of its effective peak performance. Even if optimization efforts on reconstruction significantly improve the FLOP usage, this on-the-fly calculation is still slower than the conventional lookup method. Under this situation, we begin to port the code on GPGPU to exploit potential higher performance as well as higher FLOP usage. On the other hand, another evaluation has been planned to compare lookup and reconstruction in terms of power consumption: with the help of hardware and software energy measurement support, we expect to find a compromising solution between performance and energy consumption in order to face the "power wall" challenge along with hardware evolution

Les performances de transport dans l'Internet mobile sont cruciales pour l'expérience utilisateur et affectent directement les revenus des fournisseurs d'applications Internet. Cette thèse se concentre sur l'accès au réseau et le contrôle de la congestion, deux facteurs clés affectant les performances de transport, et mène des recherches sous trois aspects : la mesure de l'accès au réseau, le contrôle de la congestion à trajet unique et le contrôle de la congestion à trajets multiples. Pour la mesure de l'accès au réseau, nous menons une étude de mesure dans quatre villes pour analyser les caractéristiques de la connectivité basée sur le WiFi géré par le fournisseur dans des scénarios mobiles. Pour le contrôle de la congestion à chemin unique, nous proposons un algorithme BBRv2 amélioré basé sur les informations de retard pour améliorer les performances de BBRv2 dans les scénarios mobiles. Pour le contrôle de la congestion par trajets multiples, nous proposons un mécanisme de sélection d'algorithme de contrôle de la congestion par trajets multiples, qui s'appuie sur l'apprentissage automatique pour sélectionner dynamiquement des algorithmes de contrôle de congestion appropriés pour les sous-flux afin d'améliorer les performances du transport par trajets multiples
The transport performance in Mobile Internet is crucial to user experience and directly affects the revenue of providers for Internet applications. This dissertation focuses on network access and congestion control, two key factors affecting transport performance, and conducts research from three aspects: network access measurement, single-path congestion control, and multipath congestion control. For network access measurement, we conduct a measurement study across four cities to analyze the characteristics of the connectivity based on provider-managed WiFi in mobile scenarios. For single-path congestion control, we propose an enhanced BBRv2 algorithm based on delay information to improve the performance of BBRv2 in mobile scenarios. For multipath congestion control, we propose a multipath congestion control algorithm (CCA) selection mechanism, which leverages machine learning to dynamically select suitable CCAs for subflows to improve the performance of multipath transport

Research into the improvement of the Aircraft ConceptualDesign process by the application of MultidisciplinaryOptimization (MDO) is presented. Aircraft conceptual designanalysis codes were incorporated into a variety of optimizationmethods including Orthogonal Steepest Descent (full-factorialstepping search), Monte Carlo, a mutation-based EvolutionaryAlgorithm, and three variants of the Genetic Algorithm withnumerous options. These were compared in the optimization offour notional aircraft concepts, namely an advanced multiroleexport fighter, a commercial airliner, a flying-wing UAV, and ageneral aviation twin of novel asymmetric configuration. Tobetter stress the methods, the commercial airliner design wasdeliberately modified for certain case runs to reflect a verypoor initial choice of design parameters including wingloading, sweep, and aspect ratio.

MDO methods were evaluated in terms of their ability to findthe optimal aircraft, as well as total execution time,convergence history, tendencies to get caught in a localoptimum, sensitivity to the actual problem posed, and overallease of programming and operation. In all, more than a millionparametric variations of these aircraft designs were definedand analyzed in the course of this research.

Following this assessment of the optimization methods, theywere used to study the issue of how the computer optimizationroutine modifies the aircraft geometric inputs to the analysismodules as the design is parametrically changed. Since thiswill ultimately drive the final result obtained, this subjectdeserves serious attention. To investigate this subject,procedures for automated redesign which are suitable foraircraft conceptual design MDO were postulated, programmed, andevaluated as to their impact on optimization results for thesample aircraft and on the realism of the computer-defined"optimum" aircraft. (These are sometimes called vehicle scalinglaws, but should not be confused with aircraft sizing, alsocalled scaling in some circles.)

This study produced several key results with application toboth Aircraft Conceptual Design and MultidisciplinaryOptimization, namely:

    MDO techniques truly can improve the weight and cost ofan aircraft design concept in the conceptual design phase.This is accomplished by a relatively small "tweaking" of thekey design variables, and with no additional downstreamcosts.In effect, we get a better airplane for free.

    For a smaller number of variables (<6-8), adeterministic searching method (here represented by thefull-factorial Orthogonal Steepest Descent) provides aslightly better final result with about the same number ofcase evaluations

    For more variables, evolutionary/genetic methods getclose to the best final result with far-fewer caseevaluations. The eight variables studied herein probablyrepresent the practical upper limit on deterministicsearching methods with today’s computer speeds.

    Of the evolutionary methods studied herein, the BreederPool approach (which was devised during this research andappears to be new) seems to provide convergence in the fewestnumber ofcase evaluations, and yields results very close tothe deterministic best result. However, all of the methodsstudied produced similar results and any of them is asuitable candidate for use.

    Hybrid methods, with a stochastic initial optimizationfollowed by a deterministic final "fine tuning", proved lessdesirable than anticipated.

    Not a single case was observed, in over a hundred caseruns totaling over a million parametric design evaluations,of a method returning a local rather than global optimum.Even the modified commercial airliner, with poorly selectedinitial design variables far away from the global solution,was easily "fixed" by all the MDO methods studied.

    The postulated set of automated redesign procedures andgeometric constraints provide a more-realistic final result,preventing attainment of an unrealistic "better" finalresult. Especially useful is a new approach defined herein,Net Design Volume, which can prevent unrealisticallyhigh design densities with relatively little setup andcomputational overhead. Further work in this area issuggested, especially in the unexplored area of automatedredesign procedures for discrete variables.

This work contributes to the rapid approximation of solutions to optimization problems that are constrained by iteratively solved transport simulations. Given an objective function, a set of candidate decision variables and a black-box transport simulation that is solved by iteratively attaining a (deterministic or stochastic) equilibrium, the proposed method approximates the best decision variable out of the candidate set without having to run the transport simulation to convergence for every single candidate decision variable. This method can be inserted into a broad class of optimization algorithms or search heuristics that implement the following logic: (i) Create variations of a given, currently best decision variable, (ii) identify one out of these variations as the new currently best decision variable, and (iii) iterate steps (i) and (ii) until no further improvement can be attained. A probabilistic and an asymptotic performance bound are established and exploited in the formulation of an efficient heuristic that is tailored towards tight computational budgets. The efficiency of the method is substantiated through a comprehensive simulation study with a non-trivial road pricing problem. The method is compatible with a broad range of simulators and requires minimal parametrization.

We demonstrate that pulses derived using Optimal Control Theory (OCT) techniques can be used to significantly enhance the robustness of the Carr-Purcell-Meiboom-Gill sequence (CPMG) [1,2] to inhomogeneities in the static BB0 field. By numerically inverting the Liouville - von Neumann equation, OCT pulses were derived that can be used directly in place of hard pulses in the CPMG sequence to greatly improve the bandwidth of refocusing. To retain the echo stability achieved by the Meiboom-Gill correction to the Carr-Purcell sequence, the refocusing pulses were designed to perform a unitary π-rotation as opposed to just a state inversion transfer. To illustrate this approach we present an example of optimized pulses that show an improved CPMG-like behavior with complete excitation and multiple refocusing over a bandwidth of +/- 2.6 γB1,max B with a pulse duration limited to 10 t180.

Les coûts de transport représentent une grande partie des coûts d'exploitation des entreprises de recyclage du bois. Le problème que nous étudions est le problème du transport avec retour en charge, au sein duquel une entreprise doit décider comment connecter ses points d'approvisionnement et de demande en utilisant des itinéraires. Dans ce mémoire, le problème résolu est un cas particulier du problème de transport dans lequel le producteur n'a qu'une seule usine. Ce cas spécial est rarement étudié dans la littérature scientifique. Nous utilisons un modèle de programmation linéaire pour résoudre ce problème. Nous présentons les résultats obtenus lorsque nous appliquons cette approche aux données d’une entreprise de recyclage du bois. Nous étudions l'effet de l'horizon temporel de planification en comparant la planification annuelle des transports à la planification hebdomadaire. Nous comparons aussi l’effet de différents calculs de distance, différents types de camion et différents objectifs d’optimisation. Les résultats montrent 42% d'économies de temps de déplacement pour la planification annuelle et 36% d'économies pour la planification hebdomadaire. Nous analysons également la répartition des économies entre un ensemble de transporteurs et rapportons que 49% des économies impliquent le transporteur priorisé par la société de recyclage. Lorsque nous ajoutons des contraintes aux types de camions pouvant effectuer des retours en charge, les économies chutent à 17%. Ces contraintes résultent du fait que les entreprises de recyclage du bois utilisent différentes catégories de matériaux et nécessitent par conséquent des configurations de camions spécifiques. Enfin, une analyse des coûts de transport et des revenus de la société de recyclage montre que notre modèle peut potentiellement augmenter considérablement les revenus de transport.
Transportation costs represent a large portion of the operation costs for wood recycling companies. The problem we study is the transportation with backhaul problem in which a company must decide how to connect its supply and demand points using routes. In this master’s thesis, the problem solved is a special case of the transportation problem where the producer only has one mill. This special case is rarely studied in the scientific literature. We use a linear programming model to solve these problems. We present results obtained when applying this approach to data from a wood recycling company. We investigate the effect of the planning time horizon by comparing yearly transportation planning against weekly planning. We also compare the effect of different distance calculations, different types of trucks and different optimization goals. The results show 42% in traveled time savings for yearly planning and 36% in savings for weekly planning. We also analyse the distribution of the backhaul savings among a set of carriers and report that 49% of the savings involved the recycling company’s prioritized carrier. When we add constraints on truck types that can perform backhauls, savings drop to 17%. These constraints result from the fact that wood recycling companies handle different categories of materials and therefore require specific truck configurations. Finally, an analysis of the recycling company’s transportation costs and revenues show that our model has the potential to substantially increase transportation revenues.

Praktinėje žmonių veikloje (transporto sistemoje, valdyme, projektuojant konstrukcijas ir kt.) dažnai reikia rinktis vieną sprendinį iš kelių galimų. Iškyla uždavinys – rasti geriausią sprendinį. Pavyzdžiui, įmonėje reikia taip organizuoti gamybą, kad pelnas, gautas už pagamintą produkciją, būtų didžiausias; reikia taip suplanuoti produktų išvežimą iš siuntimo punktų (sandėlių, bazių) į paskirties punktus (parduotuves, statybos aikšteles ir t. t.), kad bendrosios transportavimo išlaidos būtų mažiausios. Darbo tikslas išanalizuoti optimizavimo uždavinius transporte, sprendžiant transporto uždavinius įvairiais būdais, naudojant skirtingas programas ir atitinkamus jų modelius. Palyginti programų interfeisus, susipažinti su jų aplinka ir padaryti išvadas, su kuria programa yra patogu ir optimalu spręsti specializuotus uždavinius. Šio darbo teorinėje dalyje pirmiausiai buvo susipažinta su pagrindinėmis sąvokomis, kurios yra naudojamos nagrinėjant šią problemą. Buvo susipažinta su Solver, WinQSB ir Simplex programomis. Išnagrinėjome, kaip reikia dirbti su Solver, WinQSB ir Simplex programomis, kad būtų galima surasti optimalų sprendinį konkrečių uždavinių transporto sferoje. Darbe taip pat buvo susipažinta su pagrindinėmis Network Modeling programos Transportation Problem (transporto uždavinių sprendimo modulio) – darbo principais, kuris priklauso WinQSB programai. Šią problemą domėtis bei galvoti kaip ją spręsti ir tobulinti turimas žinias nusprendžiau dirbdama transporto... [toliau žr. visą tekstą]
Fairly often it is necessary choose one solution out of several possible ones in the practical human activities (in transport system, management, design of structures, etc.). Naturally, then it is necessary to find the best solution. For example, a company has to arrange its production so as to maximise the profit from the production; product transportation from dispatch points (storehouses, centres) to destination (shops, construction sites, etc.) is to be planned so as to minimise the overall transportation costs. The objective of the work is to analyse the methods of linear programming when solving transportation problems by applying various tools, using different software and their respective models, to compare the software interfaces, get acquainted with their environment and to conclude which of the programmes is the most convenient and optimum for the solution of specific problems. The theoretical part of the work, first of all, introduces the main definitions used in the analysis of the problem. Solver, WinQSB and Simplex software was introduced. It was analysed, how one is to work with Solver, WinQSB and Simplex software to find an optimum solution when dealing with a particular problem of the transport sector. The work also introduces the main principles when working with Transportation Problem module of Network Modelling, which is a part of WinQSB software. I had decided to analyse the problem and improve my knowledge while working in the transport sector – then... [to full text]

The objective of this project is to improve productivity and efficiency for the inbound material handling operations in the warehouse of DC Älmhult. After three weeks pre-study in place of the distribution center, the authors have observed several problems existing in the current production, among which three types of wastes are found and analyzed by using VSM that are pick and drop, operator waiting time and inefficient transport. Two typical cases chosen from the inbound production are analyzed to reflect the current process and address problems. Fish-bone tool is used to identify wastes and roots. To eliminate or reduce the wastes, recommendations and solutions are developed by creating continuous flow combining with internal transport optimization. Future-state VSMs are drawn based on the suggested changes in line with continuous flow. Different productions models are simulated by elaborately developed excel sheets. A „distance table‟ is developed by using Microsoft Excel to help the loading or unloading leaders with the gate steering function so as to minimize internal transport distance. A new layout of the conveyor system is also suggested to lower the idle transport rate.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001.
Includes bibliographical references.
(cont.) The vectorial energy transfer design of sensory films to harvest and direct energy to the surface detection layer toward ultimate signal amplification has been discussed. Third, the role of chemical structure of a sensory polymer in the selectivity of a conjugated polymer-based fluorescent sensor has been examined. In two different sensory systems for the detection of potassium ions and a nitroaromatic explosive TNT, respectively, key chemical design parameters governing their selectivity have been rationalized. Finally, the combination of the conclusions of this thesis provided an idealized structure of a fluorescent conjugated polymer-based sensory film with optimized sensitivity and selectivity.
A sensor is one of the many important applications of conjugated polymers. Poly(p-phenylene ethynylene)s (PPEs) have been studied for fluorescence-based sensor applications. The chemical structure and nano-structure of a polymer in the solid-state are two critical parameters that determine sensitivity and selectivity of a conjugated polymer-based sensor. In this thesis, both parameters have been systematically investigated. First, the Langmuir-Blodgett method was used to control the nano-structure of PPEs in the solid-state. Rational design of surfactant PPEs made it possible to control the conformation of a single polymer strand and interpolymer spatial arrangement at the air-water interface. In situ UV-Vis and fluorescence spectroscopy on the Langmuir film in controlled nano-structures revealed the effects of conformation and spatial arrangement of conjugated polymers on their intrinsic optical properties. Since the controlled structure of a monolayer at the air-water interface can be transferred to a solid substrate, structurally well-defined multilayer LB films of PPEs with confined optical properties were fabricated. This made it possible to study the role of interpolymer aggregation in the photophysical properties of conjugated polymer films. The results provided a general design principle to make a highly emissive conjugated polymer film. Second, an ideal thickness of a sensory film for optimizing sensitivity was determined by experimental and theoretical analysis of energy transport phenomena in multilayer PPE films.
y Jinsang Kim.
Ph.D.

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 77-78).
This thesis explores the strategies, methodologies and tools for an optimal management of Reusable Transport Items, such as containers or chassis, in an extensive multi-depots network. We use an ocean shipping company operating globally to propose a broad, comprehensive and integrated system for an optimal management of the fleet, embracing technology, processes and monitoring system. The ability to track these assets is the first step to visibility and fleet optimization and we will question the opportunity for a company to invest in a real time tracking technology. In highly complex logistic networks, the challenge is to get the right equipment at the right place at the right time, in a cost efficient manner and with a fleet size as small as possible. Beyond increased visibility through tracking capabilities, we show that choosing an appropriate utilization metrics helps identify and quantify other areas of improvement. Using actual data, we evaluate to what extent the fleet size can be reduced by improving asset utilization and how leasing also impacts operating costs. We also show how the structural imbalance of trade (some regions being net exporters while others are net importers) impacts both global repositioning policy and local inventory policy, with depots of different profiles requiring different policies. Understanding this systematic and systemic approach of fleet management, we assess the contribution of tracking technology capabilities to these potential improvements.
by Jean-Marie Lefebvre and Dameng Yue.
M.Eng.in Logistics

Video is foreseen to be the dominant type of data traffic in the Internet. This vision is supported by a number of studies which forecast that video traffic will drastically increase in the following years, surpassing Peer-to-Peer traffic in volume already in the current year. Current infrastructures are not prepared to deal with this traffic increase. The current Internet, and in particular the mobile Internet, was not designed with video requirements in mind and, as a consequence, its architecture is very inefficient for handling this volume of video traffic. When a large part of traffic is associated to multimedia entertainment, most of the mobile infrastructure is used in a very inefficient way to provide such a simple service, thereby saturating the whole cellular network, and leading to perceived quality levels that are not adequate to support widespread end user acceptance. The main goal of the research activity in this thesis is to evolve the mobile Internet architecture for efficient video traffic support. As video is expected to represent the majority of the traffic, the future architecture should efficiently support the requirements of this data type, and specific enhancements for video should be introduced at all layers of the protocol stack where needed. These enhancements need to cater for improved quality of experience, improved reliability in a mobile world (anywhere, anytime), lower exploitation cost, and increased flexibility. In this thesis a set of video delivery mechanisms are designed to optimize the video transmission at different layers of the protocol stack and at different levels of the cellular network. Upon the architectural choices, resource allocation schemes are implemented to support a range of video applications, which cover video broadcast/multicast streaming, video on demand, real-time streaming, video progressive download and video upstreaming. By means of simulation, the benefits of the designed mechanisms in terms of perceived video quality and network resource saving are shown and compared to existing solutions. Furthermore, selected modules are implemented in a real testbed and some experimental results are provided to support the development of such transport mechanisms in practice.
Il traffico video sarà il tipo di applicazione dominante in Internet nei prossimi anni. Già in questi anni assistiamo al sorpasso del traffico video mobile rispetto al Peer-to-Peer. Le infrastrutture attuali non sono preparate ad affrontare questo aumento di traffico video. Internet, e in particolare Internet mobile, non è stata progettata sulla base di requisiti video e, di conseguenza, la sua architettura è inefficiente nel gestire questo tipo di traffico. Quando il traffico è associato all'intrattenimento multimediale, la maggior parte dell'infrastruttura mobile è utilizzata in un modo inefficiente pur fornendo un servizio semplice, saturando in tal modo l'intera rete cellulare e portando il servizio a livelli di qualità non adeguati a sostenere quella che gli utenti si aspettano di ricevere. L'obiettivo principale dell'attività di ricerca in questa tesi è quello di evolvere l'architettura di Internet mobile per un efficiente supporto del traffico video. Poiché il video è previsto rappresentare la maggior parte del traffico, l'architettura di rete deve supportare in modo efficiente le esigenze di questo tipo di traffico e miglioramenti specifici dovrebbero essere introdotti a tutti i livelli dello stack protocollare. Questi miglioramenti hanno lo scopo di incrementare la qualità percepita del servizio, di dare una maggiore affidabilità in un mondo mobile, di abbassare i costi di servizio e di aumentare la flessibilità della rete. In questa tesi una serie di meccanismi di trasmissione video sono progettati per ottimizzare la consegna di applicazioni video su reti cellulari di nuova generazione a diversi livelli dello stack protocollare ed a differenti livelli della rete cellulare. Sulla base di queste scelte architetturali, sistemi di allocazione delle risorse sono implementati per supportare una gamma di applicazioni video che copre il video broadcast/multicast in streaming, video on demand, streaming in tempo reale, il video download progressivo e il video upstreaming. Tramite campagne di simulazioni, i benefici sotto forma di qualità percepita e di risorse di rete risparmiate sono riportati attraverso il confronto con soluzioni pre-esistenti. Inoltre moduli selezionati sono implementati in un vero e proprio banco di prova e alcuni dei risultati sperimentali conseguiti sono usati per sostenere lo sviluppo di nuovi meccanismi di trasporto video nelle reti mobili future.

Malgré la prédominance actuelle du mode routier, pour le transport de marchandises en milieu urbain, une alternative durable est nécessaire, au vu des enjeux environnementaux et sociétaux. Dans cette thèse, nous proposons l’étude d’une des perspectives possibles, pour absorber une partie de ce flux de marchandises toujours plus dense, en utilisant le réseau ferroviaire urbain, initialement dédié aux voyageurs. Une méthodologie intégrant le fret dans ce dernier est proposée, avec comme première étape, l'identification et la classification de tous les niveaux de mixité fret / voyageurs possibles. Le niveau le plus contraint est retenu, car sa faisabilité induira celle des autres. Notre seconde contribution est relative à une approche par décomposition du problème d’insertion du flux de fret en plusieurs sous-problèmes interdépendants, selon les trois horizons temporels (long, moyen et court). Dans le but d’évaluer la capacité du système global, à absorber un flux supplémentaire de nature différente, le problème de détermination du meilleur plan de transport des marchandises est identifié comme central et critique. La troisième contribution concerne la simulation du système de transport, puis sa formalisation par un PL en variables mixtes, pour affecter chaque commande à un train, en déterminant le moment auquel elle sera chargée et en minimisant les temps d’attente cumulés des commandes. Plusieurs variantes de colonies de fourmis sont développées, pour la résolution d’instances de grande taille. La quatrième contribution concerne le couplage du modèle de simulation, qui permet l’évaluation des performances de cette nouvelle solution de transport, avec les différents algorithmes optimisant le plan de transport. Enfin, nous proposons une approche de replanification par horizon glissant, pour absorber les perturbations de la demande, en minimisant les changements du plan de transport
Urban freight transport is almost exclusively carried out by truck. Beyond the drawbacks caused in the city, this transport mode is nearly saturated. This study discusses an alternative way of transporting freight by using urban rail infrastructure. The first contribution deals with the identification and classification of all different sharing possibilities of mixing freight with passenger’s traffic using rail network. The second contribution is the definition of global freight/passenger transport problem, which is decomposed into several optimization interdependent sub-problems with different temporal decision horizon. In order to show the capacity of the global system to absorb an additional flow with different nature, the Freight Rail Transport Schedule Problem “FRTSP” is identified as the bottleneck of transportation system and is formalized with MIP model. As third contribution, this problem determines train and loading time for each demand to be assigned respecting several constraints while minimizing total waiting time. The fourth contribution deals with a discrete event simulation approach, which studies this alternative and validates several proposed decision algorithms. Finally, the fifth contribution consists in a dynamic approach based on a rolling horizon, which is proposed in order to update the initial plan. The updated plan allows to determine a new assignment regarding new demand such as the modifications from the previous plan are minimized

Les gestionnaires des réseaux de transport d'électricité doivent adapter leurs outils d'aide à la décision aux avancées technologiques du XXIième siècle. Une opération sous-jacente à beaucoup d'outils est de calculer les flux en actif/réactif qui minimisent les pertes ou les coûts de production. Mathématiquement, il s'agit d'un problème d'optimisation qui peut être décrit en utilisant seulement l'addition et la multiplication de nombres complexes. L'objectif de cette thèse est de trouver des solutions globales. Un des aboutissements de ce projet doctoral hautement collaboratif est d'utiliser des résultats récents en géométrie algébrique pour calculer des flux optimaux dans le réseau Européen à haute tension
Transmission system operators need to adapt their decision-making tools to the technological evolutions of the twenty first century. A computation inherent to most tools seeks to find alternating-current power flows that minimize power loss or generation cost. Mathematically, it consists in an optimization problem that can be described using only addition and multiplication of complex numbers. The objective of this thesis is to find global solutions, in other words the best solutions to the problem. One of the outcomes of this highly collaborative doctoral project is to use recent results from algebraic geometry to compute globally optimal power flows in the European high-voltage transmission network

Les ports maritimes se confrontent à des exigences rigoureuses imposées par l'évolution de la taille de la flotte mondiale des porte-conteneurs et des zones de stockage qui arrivent à des niveaux de saturation élevés. Pour répondre à ces défis, plusieurs ports ont décidé de créer des terminaux multimodaux qui jouent le rôle de méga-hubs pour les terminaux maritimes, en vue de libérer les zones de stockage de ces terminaux, de développer la part du transport massifié de conteneurs et de réduire les émissions des gaz à effet de serre en utilisant des modes alternatifs à la route. Néanmoins, la gestion de ces nouveaux schémas logistiques est laborieuse. Cela s’explique par plusieurs facteurs, entre autres, la nature dynamique et distribuée de ces systèmes, la diversité des opérations et le manque des informations nécessaires au contrôle de flux. La finalité de cette thèse est de développer des approches capables de répondre aux besoins des opérateurs portuaires dans un terminal multimodal, avec prise en compte des différentes sources d’incertitudes. Deux problèmes d'optimisation sont principalement considérés dans cette thèse, à savoir : l'optimisation de tournées de navettes ferroviaires (The Rail Shuttle Routing Problem) et l'ordonnancement de grues de quai (The Quay Crane Scheduling Problem). En vue d'aborder la complexité et l’aspect incertain de ces problèmes, nous proposerons des modélisations mathématiques, ainsi que des approches de résolution basées sur l’optimisation par colonies de fourmis, l’optimisation robuste et le couplage Simulation-Optimisation. Les différents tests numériques effectués ont prouvé l’efficacité des algorithmes proposés et leur robustesse
Today, seaports face increasingly stringent requirements imposed by the considerable growth of goods transited by sea. Indeed, the organization of the port sector has evolved rapidly and has caused several negative impacts, including pollution and congestion of terminals, which constitute today the major concerns of port operators. To address those challenges, several ports have decided to build multimodal terminals that act as mega-hubs for maritime terminals, in order to free the storage areas on the maritime terminals, to promote the use of consolidated container modes of transfer and to reduce greenhouse gas emissions by using alternative modes to the road. Nevertheless, the management of these new logistic systems is laborious. This is due to several factors, including the dynamic and distributed nature of these systems, the variety of operations, and the lack of information needed to control flow. The aim of this thesis is to develop approaches capable of meeting the needs of port operators in a multimodal terminal, taking into account the different sources of uncertainty. Two optimization problems are mainly considered in this thesis, namely : the Rail Shuttle Routing Problem(RSRP) and the Quay Crane Scheduling Problem(QCSP). To address the complexity and uncertainties of these problems, we propose new mathematical models, as well as some heuristics approaches based on ant colony optimization, robust optimization and Simulation-Optimization. The various numerical tests carried out proved the effectiveness and the robustness of the proposed algorithms

This thesis concerns the security of tomorrow’s peer-to-peer real-time communication in heterogeneous networks. Because of the additional delay caused by inband handshake and the poor compatibilities of some transport protocols, it was determined that existing security protocols such as transport layer security (TLS) and datagram transport layer security (DTLS) are not suitable in such a user scenario and a new security protocol should be designed. This new security protocol is called transport encapsulation security payload (TESP). TESP not only has the advantage of low initialization delay, but also fully supports transport protocols including TCP, UDP, stream control transmission protocol (SCTP), and datagram congestion control protocol (DCCP). Also a security analysis of TESP was carried out and no security flaws were found.
Denna uppsats behandlar säkerheten för morgondagens "peer-to-peer" (P2P) realtidskommunikation i heterogena nät. På grund av den adderade fördröjning som orsakas av inbandssignalering och dålig kompabilitet hos många transportprotokoll, så kan man fastställa att existerande säkerhetsprotokoll, såsom "(Datagram) Transport Layer Security" (TLS och DTLS), inte är lämpade för denna typ av kommunikation och att ett nytt säkerhetsprotokoll bör tas fram. "Transport Encapsulation Security Payload" (TESP) är ett sådant protokoll. TESP har inte bara fördelar såsom låg uppstartsfördröjning, utan har också stöd för många transportprotokoll, t.ex. "Transport Control Protocol" (TCP), "User Datagram Protocol" (UDP), "Stream Control Transmission Protocol" (SCTP) och "Datagram Congestion Control Protocol" (DCCP). Även en säkerhetsanalys av TESP har gjorts, där inga säkerhetsproblem har kunnat påvisas.

This study utilizes Multidisciplinary Design Optimization (MDO) techniques to explore the effectiveness of the truss-braced (TBW) and strut-braced (SBW) wing configurations in enhancing the performance of medium range, transonic transport aircraft. The truss and strut-braced wing concepts synergize structures and aerodynamics to create a planform with decreased weight and drag. Past studies at Virginia Tech have found that these configurations can achieve significant performance benefits when compared to a cantilever aircraft with a long range, Boeing 777-200ER-like mission. The objective of this study is to explore these benefits when applied to a medium range Boeing 737-800NG-like aircraft with a cruise Mach number of 0.78, a 3,115 nautical mile range, and 162 passengers. Results demonstrate the significant performance benefits of the SBW and TBW configurations. Both configurations exhibit reduced weight and fuel consumption. Configurations are also optimized for 1990â s or advanced technology aerodynamics. For the 1990â s technology minimum TOGW cases, the SBW and TBW configurations achieve reductions in the TOGW of as much as 6% with 20% less fuel weight than the comparable cantilever configurations. The 1990â s technology minimum fuel cases offer fuel weight reductions of about 13% compared to the 1990â s technology minimum TOGW configurations and 11% when compared to the 1990â s minimum fuel optimized cantilever configurations. The advanced aerodynamics technology minimum TOGW configurations feature an additional 4% weight savings over the comparable 1990â s technology results while the advanced technology minimum fuel cases show fuel savings of 12% over the 1990â s minimum fuel results. This translates to a 15% reduction in TOGW for the advanced technology minimum TOGW cases and a 47% reduction in fuel consumption for the advanced technology minimum fuel cases when compared to the simulated Boeing 737-800NG. It is found that the TBW configurations do not offer significant performance benefits over the comparable SBW designs.
Master of Science

In recent years, there has been a growing shift in the world towards sustainability. For civil aviation, this is reflected in the goals of several organizations including NASA and ACARE as significantly increased fuel efficiency along with reduced harmful emissions in the atmosphere. Achieving the goals necessitates the advent of novel and radical aircraft technologies, NASA's X-57, is one such concept using distributed electric propulsion (DEP) technology. Although practical implementation of DEP is achievable due to the scale invariance of highly efficient electric motors, the current battery technology restricts its adoption for commercial transport aircraft. A Hybrid Electric Distributed Propulsion (HEDiP) system offers a promising alternative to the all-electric system. It leverages the benefits of DEP when coupled with a hybrid electric system. One of the areas needing improvement in HEDiP aircraft design is the fast and accurate estimation of wing aerodynamic characteristics in the presence of multiple propellers. A VLM based estimation technique was developed to address this requirement. This research is primarily motivated by the need to have mature conceptual design methods for HEDiP aircraft. Therefore, the overall research objective is to develop an effective conceptual design capability based on a proven multidisciplinary design optimization (MDO) framework, and to demonstrate the resulting capability by applying it to the conceptual design of a regional transport aircraft (RTA) with HEDiP systems.
Master of Science

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 83-85).
The tally system in Monte Carlo neutron transport codes accounts for a significant fraction of the total execution time. This project studied the tally performance of a Monte Carlo neutron transport code (i.e., OpenMC) and implemented several optimizations to address the major bottlenecks. First, a comprehensive profiling analysis was carried out on modern Intel micro-architectures (i.e., Intel Xeon Phi and Intel Xeon Platinum 8180) to understand what hardware and settings configurations were optimal. The specific modules and subroutines that were responsible for the performance drop were also highlighted. The first round of optimizations were specific to the information that the profiling analysis provided. Both the nuclide and the reaction index searches were found to be inefficient. As a result, the two searches were improved with the implementation of direct address tables, which have a single search efficiency of O(1) and a small memory footprint.
Moreover, a linear array cache was also introduced to store the following cross-sections: (n, 2n), (n, 3n), (n, 4n), (n, p), (n, [alpha]), and (n, [gamma]). These cross-sections, together with (n; fission), are indispensable to solve the transition matrix of the Bateman equations during transmutation analysis. As a result, pre-computing and storing them before tally-time eliminated redundant computations in the case a high energy particle travels through multiple fuel regions without colliding. Overall, these optimizations resulted in speedups of 2.31x and 2.15x for the Xeon Platinum and Xeon Phi, respectively. Further, this project also presents an alternative method to compute reaction rate tallies. In general, tallying all of the aforementioned seven rates through a Monte Carlo simulation can be quite expensive for realistic light water reactors.
Another approach would be to collapse a very fine-group flux together with a pregenerated multigroup cross section (constructed with the same energy grid). While this approach does provide a 3x speedup in the OpenMC active cycles performance, it also introduces a considerable memory penalty. The issue is that thousands of groups are needed to accurately resolve the (n, [gamma]) rates, most notably that of 238U. This study explores a hybrid approach in which (n, [gamma]) and (n, fission) are handled with a standard reaction rate tally while the remaining reaction rates are computed through the flux tally route. This option provides more flexibility in reducing the total number of groups because the remaining reactions outside of (n, fission) and (n, [gamma]) usually have smoother shapes. Performance was tested on five benchmarks with depleted fuel and increasing geometrical complexity.
Results showed that the hybrid tally method provided decent speedups ranging from 1.30x to 1.75x in the active cycles across all benchmarks. Multiple error analyses were also carried out on the proposed hybrid method; the results show that even when going as low as 300 groups, the eigenvalue is still within 100 pcm of a traditional simulation.
by José Luis Salcedo-Pérez.
S.M.
S.M. Massachusetts Institute of Technology, Department of Nuclear Science and Engineering

Les problèmes de tournées de véhicules cumulatives avec capacité (CCVRP) sont étudiés dans cette thèse, où la minimisation de la somme des temps d'arrivée reflète mieux les objectifs stratégiques de la logistique humanitaire.Dans le problème de multiples tournées d’un véhicule cumulatif avec capacité (mt-CCSVRP), un seul véhicule est disponible et il peut effectuer plusieurs voyages. Un algorithme du plus court chemin avec contrainte de ressources est proposé pour résoudre ce problème, dans lequel les tournées deviennent des nœuds et les sites sont des ressources. Le réseau est orienté et acyclique en raison des propriétés particulières du mt-CCSVRP.Le problème de multiples tournées de véhicules cumulatives avec capacité (mt-CCVRP) est introduit, où plusieurs véhicules peuvent effectuer multiples voyages. Quatre programmes linéaires en nombre entiers (PLNE) sont proposés pour résoudre le CCVRP. Un PLNE pour le mt-CCVRP est proposé ainsi que trois métaheuristiques : une recherche locale itéré à démarrages multiples (MS-ILS), un algorithme mémétique avec gestion de la population (MA|PM) et une recherche locale évolutive à démarrages multiples (MS-ELS), qui appellent un algorithme de recherche local à voisinages variables (VND). Une méthode split à deux phases permet MA|PM et MS-ELS d'alterner entre deux espaces de solutions.Le problème de tournées de véhicules cumulatif avec capacité et des livraisons indirectes (CCVRP-ID) permet aux sites non visités si leurs demandes sont fournies par un véhicule auxiliaire. Un PLNE et un MS-ELS sont développés
The cumulative capacitated vehicle routing problems (CCVRP) are studied in this thesis, where the minimization of the sum of arrival times better reflects the strategic objectives of humanitarian logistics.In the multitrip cumulative capacitated single-vehicle routing problem (mt-CCSVRP), only one vehicle is available and it can perform multiple trips. An exact resource constrained shortest path algorithm is proposed for this problem, in which trips become nodes and sites are resources. The resulting network is proven to be directed and acyclic due to the special properties of the mt-CCSVRP.The multitrip cumulative capacitated vehicle routing problem (mt-CCVRP) is introduced, where several vehicles can do multiple trips. Four mixed integer linear programs (MILP) are proposed to solve the CCVRP. For the mt-CCVRP a MILP is also given as well as three metaheuristics: a multi-start iterated local search (MS-ILS), a memetic algorithm with population management (MA|PM) and a multi-start evolutionary local search (MS-ELS), which call a variable neighborhood descent algorithm (VND). A two phases split method allows MA|MS and MS-ELS to alternate between two spaces of solutions.The cumulative capacitated vehicle routing problem with indirect deliveries (CCVRP-ID) allows unvisited sites if their demands are provided by an auxiliary vehicle. An MILP and an MS-ELS are developed

El presente trabajo de tesis es una propuesta de solución para una empresa enfocada en el proceso de planificación y distribución de producto terminado, quienes a diferencia de otras empresas donde se externaliza la operación logística de transporte, esta lo realiza con recursos propios. Además, las leyes nacionales actuales se vuelven cada vez más estrictas en cuanto al transporte. Es por esto que surge la necesidad de tener sistemas automatizados de planificación de distribución de despacho para hacer uso óptimo del transporte en función a la carga a entregar. Para esto, los algoritmos, las matemáticas y la implementación de hardware son importantes, pues son la base para plantear una solución que considere todas las variables posibles en el negocio. El documento está divido en ocho capítulos. El primero corresponde a los fundamentos teóricos, así como un análisis de la organización objetivo y la identificación de la situación problemática. El segundo capítulo establece los objetivos del proyecto, así como su fundamentación. También detalla los beneficios del proyecto y compara la solución con diferentes propuestas del mercado. El tercer capítulo modela el negocio bajo el proceso de desarrollo de software RUP. El cuarto capítulo define los requerimientos del sistema, bajo el mismo proceso de desarrollo de software que en el modelado de negocio. El quinto capítulo define la arquitectura del software, identifica las metas, restricciones y mecanismos arquitectónicos que van a restringir la construcción del producto. En el sexto capítulo se describen los patrones de sistema de la solución propuesta, el modelo de datos, y la construcción propiamente del sistema. En el séptimo capítulo se describe el plan de calidad y las pruebas del software. Finalmente, el octavo y último capítulo detalla la aplicación de gestión de proyectos bajo la metodología establecida por el PMI®.
This thesis work is a proposal for a solution for a company focused on the process of planning and distribution of finished product, who unlike other companies where the logistics operation of transportation is outsourced, this is done with own resources. In addition, current national laws are becoming stricter in terms of transport. That is why the need arises to have automated dispatch distribution planning systems to make optimal use of transport according to the load to be delivered. For this, the algorithms, the mathematics and the hardware implementation are important, because they are the basis to propose a solution that considers all the possible variables in the business. The document is divided into eight chapters. The first corresponds to the theoretical foundations, as well as an analysis of the objective organization and the identification of the problematic situation. The second chapter establishes the objectives of the project, as well as its foundation. It also details the benefits of the project and compares the solution with different market proposals. The third chapter models the business under the RUP software development process. The fourth chapter defines the requirements of the system, under the same software development process as in business modeling. The fifth chapter defines the architecture of the software, identifies the goals, restrictions and architectural mechanisms that will restrict the construction of the product. The sixth chapter describes the system patterns of the proposed solution, the data model, and the construction of the system itself. In the seventh chapter, the quality plan and the software tests are described. Finally, the eighth and last chapter details the application of project management under the methodology established by the PMI®.
Tesis

O principal objetivo deste trabalho foi o desenvolvimento de um sistema informatizado para o auxílio na escolha modal pelos usuários de transporte público. Neste sistema, as alternativas a considerar e soluções geradas devem se basear nas solicitações do usuário e poderão ser usadas para o planejamento tático e/ou estratégico do sistema de transporte considerado. O sistema foi modelado para solução através do algoritmo de fluxo em rede Label Correcting, capaz de lidar com esse problema multimodal, implementado em uma linguagem de programação orientada a objetos. O sistema foi concebido como uma aplicação de internet e, embora seja voltado para um sistema de transporte genérico, foi aplicado e testado com base nas alternativas de transporte disponíveis e malha de ruas da Cidade Universitária Armando de Salles Oliveira.
The main target of this master of science research is the development of a tool to help on modal selection by the public transportation users, which will be implemented as an eletronic information system.Since the infomation must be provided in real time to the user,it is important to the system to be fast and easy to use.It is also a requirement that the system presents options and information to help the user on the selection of the best choice among all possible ones. The alternatives to be considered and generated solutions shall be based on the user requests related to origin and destination of the desired trip. The requests will be stored and could be used for tactic and/or strategic planning of the concerned system of transport. This multimodal problem will be modeled to be solved with the Label Correcting network flow algorithm and implemented using an object oriented language. Although addressed to a generic transport system,it will be implemented and tested based on the available transport alternatives and street mesh of the Cidade Universitaria Armando de Salles Oliveira. The system may be available to users through internet.