La congestion routière est le résultat d’un excès de la demande sur l’offre. Sur le réseau autoroutier en particulier, la congestion apparaît soit en section courante, soit au niveau des bretelles d’accès, des bretelles de sortie ou des zones d’entrecroisement qui sont généralement appelées les discontinuités ou nœuds du réseau routier. Les objectif de la thèse sont (i) d'apporter des éclairages sur la phénoménologie du trafic au droit des discontinuités du réseau autoroutier et (ii) de proposer des modèles macroscopiques pour en prédire le fonctionnement et évaluer des stratégies d'optimisation de l'écoulement du flux. Contrairement aux modèles existants, les modèles proposés dans cette thèse prennent en compte les phénomènes physiques du trafic en intégrant explicitement les comportements individuels des usagers. Après avoir présenté les outils méthodologiques et expérimentaux mobilisés, la thèse propose une analyse empirique des changements de voie à partir de données individuelles de trajectoires. Sur la base des résultats empiriques, la thèse présente ensuite les modèles analytiques développés qui sont utilisés dans une dernière partie pour proposer des stratégies d'optimisation de l'écoulement du flux du trafic. / The congestion occurs when the demand is higher than the supply. On the highway network, the congestion forms on the diverges, the merges and the weaving section which are generally named the discontinuities of the network. The thesis aims at (i) investigating the traffic phenomenology at the discontinuities of the highway network and (ii) developing macroscopic traffic flow model to forecast their operation and evaluate traffic regulations. Those models will explicitly integrate the drivers' microscopic behaviors. The thesis presents first the methodological and experimental tools. Then, it proposes an empirical analysis of the lane-changes at two merges and one weaving sections. The thesis describes the analytical models while it ends with operational applications of those models.

The research on optimal reinsurance design dated back to the 1960’s. For nearly half a century, the quest for optimal reinsurance designs has remained a fascinating subject, drawing significant interests from both academicians and practitioners. Its fascination lies in its potential as an effective risk management tool for the insurers. There are many ways of formulating the optimal design of reinsurance, depending on the chosen objective and constraints. In this thesis, we address the problem of optimal reinsurance designs from an insurer’s perspective. For an insurer, an appropriate use of the reinsurance helps to reduce the adverse risk exposure and improve the overall viability of the underlying business. On the other hand, reinsurance incurs additional cost to the insurer in the form of reinsurance premium. This implies a classical risk and reward tradeoff faced by the insurer. The primary objective of the thesis is to develop theoretically sound and yet practical solution in the quest for optimal reinsurance designs. In order to achieve such an objective, this thesis is divided into two parts. In the first part, a number of reinsurance models are developed and their optimal reinsurance treaties are derived explicitly. This part focuses on the risk measure minimization reinsurance models and discusses the optimal reinsurance treaties by exploiting two of the most common risk measures known as the Value-at-Risk (VaR) and the Conditional Tail Expectation (CTE). Some additional important economic factors such as the reinsurance premium budget, the insurer’s profitability are also considered. The second part proposes an innovative method in formulating the reinsurance models, which we refer as the empirical approach since it exploits explicitly the insurer’s empirical loss data. The empirical approach has the advantage that it is practical and intuitively appealing. This approach is motivated by the difficulty that the reinsurance models are often infinite dimensional optimization problems and hence the explicit solutions are achievable only in some special cases. The empirical approach effectively reformulates the optimal reinsurance problem into a finite dimensional optimization problem. Furthermore, we demonstrate that the second-order conic programming can be used to obtain the optimal solutions for a wide range of reinsurance models formulated by the empirical approach.

The research on optimal reinsurance design dated back to the 1960’s. For nearly half a century, the quest for optimal reinsurance designs has remained a fascinating subject, drawing significant interests from both academicians and practitioners. Its fascination lies in its potential as an effective risk management tool for the insurers. There are many ways of formulating the optimal design of reinsurance, depending on the chosen objective and constraints. In this thesis, we address the problem of optimal reinsurance designs from an insurer’s perspective. For an insurer, an appropriate use of the reinsurance helps to reduce the adverse risk exposure and improve the overall viability of the underlying business. On the other hand, reinsurance incurs additional cost to the insurer in the form of reinsurance premium. This implies a classical risk and reward tradeoff faced by the insurer. The primary objective of the thesis is to develop theoretically sound and yet practical solution in the quest for optimal reinsurance designs. In order to achieve such an objective, this thesis is divided into two parts. In the first part, a number of reinsurance models are developed and their optimal reinsurance treaties are derived explicitly. This part focuses on the risk measure minimization reinsurance models and discusses the optimal reinsurance treaties by exploiting two of the most common risk measures known as the Value-at-Risk (VaR) and the Conditional Tail Expectation (CTE). Some additional important economic factors such as the reinsurance premium budget, the insurer’s profitability are also considered. The second part proposes an innovative method in formulating the reinsurance models, which we refer as the empirical approach since it exploits explicitly the insurer’s empirical loss data. The empirical approach has the advantage that it is practical and intuitively appealing. This approach is motivated by the difficulty that the reinsurance models are often infinite dimensional optimization problems and hence the explicit solutions are achievable only in some special cases. The empirical approach effectively reformulates the optimal reinsurance problem into a finite dimensional optimization problem. Furthermore, we demonstrate that the second-order conic programming can be used to obtain the optimal solutions for a wide range of reinsurance models formulated by the empirical approach.

Maritime transportation emits about 3% of global greenhouse gas, International Maritime Organization (IMO) aims to reduce shipping’s emissions by 50% with respect to 2008 levels. Proton exchange membrane fuel cells (PEMFCs) are considered among the most promising clean technologies for decarbonizing the maritime sector. One of the challenges for commercial application of PEMFCs is their limited durability. The purpose of this thesis was to assess the most significant degradation mechanisms and operating conditions of the PEMFC in marine applications, including membrane and catalyst layer degradation during idle, start-stop cycles, and dynamic load cycles, and to build a model to forecast the lifetime.A semi-empirical approach was developed to evaluate the PEMFC lifetime through a 2D COMSOL model. The model takes into account the empirical relationships for membrane conductivity loss and electrochemical surface area (ECSA) decay as functions of cycling numbers, aging process, and idling time. The 2D model has been validated with the experimental data in the literature and are also compared with a previous 1D model. The polarization curves show the voltage output against current density, lifetime is evaluated using a 10% voltage reduction criterion at the current density 0.6 A/cm2.An improved ECSA degradation model with variable load levels increases the lifetime of the ferry in Case 5 from 5500 hours to 7500 hours. Load cycling and idling cause the most severe degradation, but the impact can be reduced by a hybrid system with battery supplement and onshore charging. The lifetime of the ferry in Case 5 has been significantly further improved from 7500 hours to 22500 hours, which is comparable to the 20000-hour lifetime of commercial products for marine applications. Furthermore, membrane thickness effect analysis showed that fuel cells with thinner membranes (such as NR211) have better performance before degradation due to higher proton conductivity, but degrade faster during load cycling due to hydrogen crossover. The results of this research can be extended to help optimize fuel cell, stack and power system designs to avoid worst-case operating conditions and thereby limit fuel cell degradation. / Sjötransporter släpper ut cirka 3% av de globala växthusgaserna, International Maritime Organization (IMO) har som mål att minska sjöfartens utsläpp med 50 % jämfört med 2008 års nivåer. PEM-bränsleceller anses vara bland de mest lovande rena teknikerna för att minska koldioxidutsläppen i den maritima sektorn. En av utmaningarna för kommersiell användning av PEM-bränsleceller är deras begränsade hållbarhet. Syftet med denna avhandling var att bedöma de viktigaste nedbrytningsmekanismerna och driftsförhållandena för PEM-bränsleceller i marina applikationer, inklusive nedbrytning av membran och katalysatorskikt under tomgång, start-stopp-cykler och dynamiska belastningscykler, och att bygga en modell för att förutsäga livslängd.En semi-empirisk metod utvecklades för att utvärdera PEMFC:s livslängd genom en 2D COMSOL-modell. Modellen tar hänsyn till de empiriska sambanden för membrankonduktivitetsförlust och den elektrokemisk ytareans (ECSA) sönderfall som funktioner av cyklingstal, åldrandeprocess och tomgångstid. 2D-modellen har validerats med experimentella data i litteraturen och jämförs även med en tidigare 1D-modell. Polarisationskurvorna visar utspänningen mot strömtätheten, livslängden utvärderas med ett 10 % spänningsreduktionskriterium vid strömtätheten 0.6 A/cm2.En förbättrad modell för nedbrytning av elektrokemisk yta med varierande lastnivåer ökar färjans livslängd i fall 5 från 5500 timmar till 7500 timmar. Lastcykling och tomgång orsakar den allvarligaste försämringen, men påverkan kan minskas genom ett hybridsystem med batteritillägg och landladdning. Färjans livslängd i fall 5 har förbättrats avsevärt ytterligare från 7500 timmar till 22500 timmar, vilket är jämförbart med 20000 timmars livslängd för kommersiella produkter för marina applikationer. Vidare visade membrantjocklekseffektanalys att bränsleceller med tunnare membran (som NR211) har bättre prestanda före nedbrytning på grund av högre protonledningsförmåga, men bryts ned snabbare under belastningscykler på grund av väteövergång. Resultaten av denna forskning kan utökas för att hjälpa till att optimera designen av bränsleceller, stack och kraftsystem för att undvika värsta driftsförhållanden och därigenom begränsa nedbrytningen av bränsleceller.

The primary objective of this research was to quantify the improvement in service life of a flexible pavement constructed using full-depth reclamation (FDR) in conjunction with cement stabilization when specified reductions in the spatial variability of specific construction-related parameters are achieved. This study analyzed pavement data obtained through field and laboratory testing of a reconstruction project in northern Utah. Data analyses included multivariate regression, Monte Carlo simulation, and mechanistic-empirical analyses of a model pavement structure. The results of the research show a steadily increasing trend in 28-day unconfined compressive strength of the cement-treated base (CTB) layer with increasing reductions in variability for cement content, moisture content, and reclaimed asphalt pavement (RAP) content across each of five different reliability levels. The most significant increases in CTB strength occurred with reductions in the standard deviations of moisture content and RAP content. Decreasing the variability of cement content did not provide significant additional strength to the CTB layer. Therefore, when involved on FDR projects, members of the pavement industry should focus energy on reducing the variability of both moisture content and RAP content, which both significantly impact pavement life, to achieve high-quality, long-lasting pavements.