Cette thèse s'inscrit en amont de la problématique de production d'hydrogène (H2) à partir de l'eau. Les réactions impliquées (oxydation de l'eau, WOR et réaction d'évolution de l'hydrogène, HER) requièrent des catalyseurs tels que des nanoparticules (NPs) métalliques. Cette catalyse peut être photoactivée en associant un photosensibilisateur (PS) aux NPs conduisant à des hybrides PS-NPs. Un tel assemblage peut se faire via des groupements acides carboxyliques. Ce travail de doctorat repose sur la combinaison d'outils expérimentaux et théoriques en vue de développer de nouveaux nanocatalyseurs au ruthénium. Notre contribution a consisté à définir une cartographie précise de la surface de Ru NPs stabilisées par des acides carboxyliques avec des chaînes alkyles de longueur différente comme systèmes modèles de catalyseurs PS-NPs pour la photoproduction d'H2 à partir d'H2O. Parmi les principaux objectifs était visée une meilleure compréhension des relations structure/propriétés à l'échelle nanométrique afin d'expliquer les propriétés de surface des NPs et leur viabilité catalytique. Les RuNPs ont été synthétisées par voie organométallique à partir du complexe [Ru(COD)(COT)] comme source de Ru et des acides carboxyliques (éthanoïque, pentanoïque et octanoïque) comme stabilisants. Cette méthode permet la formation de NPs bien contrôlées, fournissant ainsi des systèmes de choix pour des études comparatives fines. Des populations homogènes de RuNPs de taille 1.1 à 1.7 nm ont été obtenues. L'état de surface des NPs a été sondé par différentes techniques analytiques (IR, RMN et WAXS). L'optimisation du ratio [ligand) / [Ru] a permis de disposer de NPs de tailles similaires, et donc de systèmes comparables quel que soit l'acide carboxylique utilisé. Des calculs DFT ont été effectués en parallèle sur un modèle de NP Ru55, dont certains ont alimenté un modèle thermodynamique permettant de s'approcher des conditions expérimentales de température, de pression et de concentration. Une analyse systématique des propriétés des liaisons, des charges atomiques et des états électroniques (DOS, COHP, MPA) a été réalisée. Les calculs des modes de vibration des modèles à base de Ru55 et des déplacements chimiques RMN de clusters [Ru6] ont corroboré et facilité les attributions spectroscopiques expérimentales. Les données spectroscopiques et des études mécanistiques DFT ont montré que les acides carboxyliques interagissent sur la surface métallique sous forme carboxylate. En bon accord, les titrages expérimentaux et théoriques ont montré l'efficacité de l'approche suivie pour cerner l'influence du ligand et de la longueur de la chaîne alkyle sur les propriétés de RuNPs. L'énergie libre de Gibbs de l'adsorption d'hydrogène, un paramètre de référence pour déterminer la viabilité de matériaux pour la catalyse HER, a été calculée par DFT sur des modèles Ru55. Le meilleur nanocatalyseur doit présenter à la fois une surface métallique moyennement encombrée et un ligand avec une longueur de chaîne alkyle intermédiaire, indiquant ainsi comme système le plus prometteur les RuNPs stabilisées par l'acide pentanoïque. Des études d'échange de ligands à la surface de RuNPs stabilisées par l'acide octanoïque ont été réalisées afin de modéliser l'ancrage du PS par un groupe acide carboxylique et complétées par des études théoriques. Les résultats obtenus ont démontré la potentialité de cette approche. Une originalité de ce travail réside dans la combinaison d'études expérimentales et théoriques menées de front pour mieux comprendre la relation structure/propriétés de RuNPs stabilisées par des acides carboxyliques et leur viabilité catalytique pour la production d'H2 à partir d'H2O. Les données obtenues et des résultats catalytiques préliminaires devraient permettre de concevoir des nanocatalyseurs efficaces. Si l'intérêt d'une telle approche a été démontré sur des RuNPs modèles pour le craquage de l'eau, ce travail ouvre d'autres perspectives en nanocatalyse. / This PhD thesis is an upstream study regarding the production of hydrogen (H2) via the water splitting process. The reactions involved (water oxidation, WOR and hydrogen evolution reactions, HER) require efficient catalysts and nanoparticles (NPs) can act so. Such catalysis can be photoactivated by combining photosensitizers (PS) with the NPs leading to hybrid PS-NPs systems, and effective assembling is able via carboxylic acid groups. This work relies on a combination of experimental and theoretical tools to develop novel ruthenium-based nanocatalysts for the water splitting process. Our contribution aimed at achieving a precise mapping of the surface of ruthenium nanoparticles (RuNPs) stabilized by carboxylic acids with an alkyl chain of different length as model systems for the design of PS-NPs catalysts for H2 photoproduction from water. One of the main aims of this PhD was to bring a better understanding of structure/properties relationship at the nanoscale to explain the surface properties of RuNPs stabilized by carboxylic acids and their catalytic viability. RuNPs were synthesized by the organometallic approach using the [Ru(COD)(COT)] complex as metal source and ethanoic, pentanoic and octanoic acids as stabilizers. This synthesis method allows the formation of well-controlled metal NPs, thus providing nanosystems of choice for fine comparative studies. TEM characterization revealed the formation of homogeneous populations of RuNPs in a size range of 1.1 - 1.7 nm. The surface state of the NPs was probed by complementary analytical techniques like IR, NMR and WAXS, leading to a precise mapping of their surface. Optimization studies of the ligand/[Ru] ratio to get NPs with a similar size allowed to have comparable nanosystems whatever the carboxylic acid used as stabilizer and thus to determine the influence of the alkyl chain length. DFT calculations were performed in parallel according to a thermodynamic model fed with DFT energies. Also, a systematic analysis of the bond properties and of the electronic states (Density of States, Crystal Orbital Hamilton Population, atomic charges) was carried out using a Ru55 NP model. DFT calculations of the vibrational features of model RuNPs and of the chemical shifts of model Ru clusters also allowed to secure the spectroscopic experimental assignations. Spectroscopic data and DFT mechanistic studies evidenced that the carboxylic acids lie on the metal surface as carboxylates, together with hydrogen atoms. The results of experimental and theoretical titrations are in good agreement, thus showing the approach followed to be an efficient step to build a model in order to understand the ligand influence on RuNPs properties. Hydrogen adsorption Gibbs free energy, which is a reference parameter to determine the viability of materials for HER catalysis, has been calculated for optimized RuNP structures. The best nanocatalyst revealed to have both, intermediate crowded metal surface and intermediate alkyl chain length for the capping ligand, indicating the RuNPs stabilized by pentanoic acid as the most promising catalyst. Experiments on ligand exchange at the surface of octanoic acid-stabilized RuNPs were also performed in order to model the PS anchoring onto RuNPs through carboxylic acid groups completed by theoretical studies. Results obtained demonstrated the potentiality of this approach. The originality of this work lies with the combination of experimental and theoretical studies in parallel to achieve a better understanding of structure/properties relationship of RuNPs stabilized by carboxylic acids and their catalytic viability for the water-splitting process. Preliminary catalytic results are encouraging, and the data obtained should now allow to design appropriate nanocatalysts. Finally, the interest of this combined approach has been demonstrated through the study of RuNPs for water splitting, but this work opens new opportunities of research in nanocatalysis.

Cette thèse montre comment l'astérosismologie, basée sur l'observation et la modélisation, peut rendre compte de la structure interne d'une étoile naine blanche DAV, notamment comment il est possible de déduire la masse de son enveloppe d'hydrogène résiduel. Nous avons étudié 2 ZZ Ceti: HL Tau 76 (bord rouge de la bande d'instabilité) et G 185-32 (bord bleu). La modélisation indique que ces 2 étoiles possèdent une enveloppe d'hydrogène de masse sensiblement identique: M(H)= 2.0(+/-0.3)x 10e-4 Mstar. Cela suggèrerait une possible constance de la masse de cette enveloppe pour l'ensemble des étoiles DA et par là même d'éventuelles implications pour la cosmochronologie et les mécanismes de l'évolution stellaire. Par ailleurs, cette thèse illustre comment la modélisation permet de révéler certaines caractéristiques physiques comme une rotation de l'étoile non-uniforme, un couplage non-linéaire au sein d'un triplet de modes résonants, une intéraction entre les pulsations et la convection.

On s'intéresse dans cette thèse à l'étude de méthodes numériques pour les systèmes de réaction-diffusion. Tout d'abord, on étudie le schéma par régularisation du résidu et ses extrapolations; ce schéma introduit un préconditionneur en espace lors de la discrétisation en temps. On prouve la stabilité en norme usuelle et la convergence en norme d'énergie de cette méthode et on l'applique au préconditionnement de méthodes spectrales par des méthodes d'éléments finis. Cette application nécessite le calcul d'asymptotiques précises des polynômes de Legendre et de leurs extrema. On prouve aussi la convergence et l'ordre deux d'une méthode de splitting semi-discrétisée en temps pour les systèmes de réaction-diffusion, l'approximation de Peaceman-Rachford. Enfin, on applique ces méthodes à la simulation d'une équation parabolique non linéaire pour modéliser la croissance de grains et à une équation parabolique non locale venant de la mécanique statistique et modélisant les systèmes autogravitants de fermions.

La simulation numérique est aujourd'hui un outils majeur dans la conception des objets aérodynamiques, que ce soit dans l'aéronautique, l'automobile, l'industrie navale, etc... Un des défis majeurs pour repousser les limites des codes de simulation est d'améliorer leur précision, tout en utilisant une quantité fixe de ressources (puissance et/ou temps de calcul). Cet objectif peut être atteint par deux approches différentes, soit en construisant une discrétisation fournissant sur un maillage donné une solution d'ordre très élevé, soit en construisant un schéma compact et massivement parallélisable, de manière à minimiser le temps de calcul en distribuant le problème sur un grand nombre de processeurs. Dans cette thèse, nous tentons de rassembler ces deux approches par le développement et l'implémentation de Schéma Distribuant le Résidu (RDS) d'ordre très élevé et de compacité maximale. Ce manuscrit commence par un rappel des principaux résultats mathématiques concernant les Lois de Conservation hyperboliques (CLs). Le but de cette première partie est de mettre en évidence les propriétés des solutions analytiques que nous cherchons à approcher, de manière à injecter ces propriétés dans celles de la solution discrète recherchée. Nous décrivons ensuite les trois étapes principales de la construction d'un schéma RD d'ordre très élevé : \begin{itemize} \item la représentation polynomiale d'ordre très élevé de la solution sur des polygones et des polyèdres; \item la description de méthodes distribuant le résidu de faible ordre, compactes et conservatives, consistantes avec une représentation polynomiale des données de très haut degré. Parmi elles, une attention particulière est donnée à la plus simple, issue d'une généralisation du schéma de Lax-Friedrichs (LxF); \item la mise en place d'une procédure préservant la positivité qui transforme tout schéma stable et linéaire, en un schéma non linéaire d'ordre très élevé, capturant les chocs de manière non oscillante. \end{itemize} Dans le manuscrit, nous montrons que les schémas obtenus par cette procédure sont consistants avec la CL considérée, qu'ils sont stables en norme $\L^{\infty}$ et qu'ils ont la bonne erreur de troncature. Même si tous ces développements théoriques ne sont démontrés que dans le cas de CL scalaires, des remarques au sujet des problèmes vectoriels sont faites dès que cela est possible. Malheureusement, lorsqu'on considère le schéma LxF, le problème algébrique non linéaire associé à la recherche de la solution stationnaire est en général mal posé. En particulier, on observe l'apparition de modes parasites de haute fréquence dans les régions de faible gradient. Ceux-ci sont éliminés grâce à un terme supplémentaire de stabilisation dont les effets et l'évaluation numérique sont précisément détaillés. Enfin, nous nous intéressons à une discrétisation correcte des conditions limites pour le schéma d'ordre élevé proposé. Cette théorie est ensuite illustrée sur des cas test scalaires bidimensionnels simples. Afin de montrer la généralité de notre approche, des maillages composés uniquement de triangles et des maillages hybrides, composés de triangles et de quadrangles, sont utilisés. Les résultats obtenus par ces tests confirment ce qui est attendu par la théorie et mettent en avant certains avantages des maillages hybrides. Nous considérons ensuite des solutions bidimensionnelles des équations d'Euler de la dynamique des gaz. Les résultats sont assez bons, mais on perd les pentes de convergence attendues dès que des conditions limite de paroi sont utilisées. Ce problème nécessite encore d'être étudié. Nous présentons alors l'implémentation parallèle du schéma. Celle-ci est analysée et illustrée à travers des cas test tridimensionnel de grande taille. Du fait de la relative nouveauté et de la complexité des problèmes tridimensionels, seuls des remarques qualitatives sont faites pour ces cas test : le comportement global semble être bon, mais plus de travail est encore nécessaire pour définir les propriétés du schémas en trois dimensions. Enfin, nous présentons une extension possible du schéma aux équations de Navier-Stokes dans laquelle les termes visqueux sont traités par une formulation de type Galerkin. La consistance de cette formulation avec les équations de Navier-Stokes est démontrée et quelques remarques au sujet de la précision du schéma sont soulevées. La méthode est validé sur une couche limite de Blasius pour laquelle nous obtenons des résultats satisfaisants. Ce travail offre une meilleure compréhension des propriétés générales des schémas RD d'ordre très élevé et soulève de nouvelles questions pour des améliorations futures. Ces améliorations devrait faire des schémas RD une alternative attractive aux discrétisations classiques FV ou ENO/WENO, aussi bien qu'aux schémas Galerkin Discontinu d'ordre très élevé, de plus en plus populaires.

Ideal magnetohydrodynamics (MHD) simulations are known to have problems in satisfying the solenoidal constraint (i.e. the divergence of magnetic field should be equal to zero, $ ablacdotvec{B} = 0$). The simulations become unstable unless specific measures have been taken. In this thesis, a solenoidal constraint satisfying technique that allows discrete satisfaction of the solenoidal constraint up to the machine accuracy is presented and validated with a variety of test cases. Due to its inspiration from Chorin's artificial compressibility method developed for incompressible CFD applications, the technique was named as extit{artificial compressibility analogy (ACA)} approach. It is demonstrated that ACA is a purely hyperbolic, stable and consistent technique, which is moreover easy to implement. Unlike some other techniques, it does not pose any problems of the sort that $ ablacdotvec{B}$ errors accumulate in the vicinity of the stagnant regions of flow. With these crucial properties, ACA is thought to be a remedy to the drawbacks of the most commonly used solenoidal constraint satisfying techniques in the literature namely: Incorrect shock capturing and poor performance of the convective stabilization mechanism in regions of stagnant flow for Powell's source term method; exceedingly complex implementation for constrained transport technique due to the staggered grid representation; computationally expensive nature due to the necessity of a Poisson solver combined with hyperbolic/elliptic numerical methods for classical projection schemes. In the first chapter of the thesis, general background knowledge is given about plasmas, MHD and its history, a certain class of upwind finite volume methods, namely Riemann solvers, and their applications in MHD, the definition, constituents, formation mechanisms and effects of space weather and some of the space missions that are and will be performed in its prediction. Secondly, detailed analysis of the compressible ideal MHD equations is given in the form of the derivation of the equations, their dimensionless numbers which will be of use to specify the flows in the following chapters, and finally, the presentation of the MHD waves and discontinuities, which indicates the complexity of the system of ideal MHD equations and therefore their further numerical analysis. The next discussion is about the main subject of the thesis, namely the solenoidal constraint satisfying techniques. First of all, the definition and significance of the solenoidal constraint is given. Afterwards, the most common solenoidal constraint satisfying techniques in the literature are reviewed along with their abovementioned drawbacks. Moreover, particular emphasis is given to the Powell's source term approach which was also implemented in the upwind finite volume MHD solver developed. In addition, the hyperbolic divergence cleaning technique is presented in detail together with the resemblance and differences between it and ACA. Some other solenoidal constraint satisfying techniques are briefly mentioned at this stage. After these, ACA is presented in the following way: The point of inspiration, which is the analogy made with Chorin's artificial compressibility method developed for incompressible CFD, the introduction of the modified system of ideal MHD equations due to ACA, the derivation of the wave equation governing the propagation of $ ablacdotvec{B}$ errors and the analytical consistency proof. Having finished the core discussion of the thesis, the solver developed and its constituents are given in the fourth chapter. Furthermore, a brief overview of the platform into which this solver was implemented, namely COOLFluiD, is also given at this point. Afterwards, a thorough numerical verification of the ACA approach has been made on an increasingly complex suite of test cases. The results obtained with ACA and Powell's source term implementations are given in order to numerically analyse and verify ACA and compare the two methods and validate them with the results from literature. The sixth chapter is devoted to further validation of ACA performed with a variety of more advanced space weather-related simulations. In this chapter, also the $vec{B}_{ extrm{0}} + vec{B}_{ extrm{1}}$ splitting technique used to treat planetary magnetosphere is presented along with its application to ACA and Powell's source term approaches. This technique is utilized in obtaining the solar wind/Earth's magnetosphere interaction results and is based on suppressing the direct inclusion of the Earth's magnetic field, which is a dipole field, in the solution variables. In this way, problems are avoided with the energy equation that could arise from the drastic change of the ratio of the dipole field and the variable field computed by the solver (i.e. $frac{lvertvec{B}_{ extrm{0}}lvert}{lvertvec{B}_{ extrm{1}}lvert}$) in the computational domain. Finally, conclusions and future perspectives related to the material presented in the thesis are put forward.

Single self-assembled semiconductor quantum dots (QDs) are able to emit single-photons and entangled-photons pairs. They are therefore considered as potential candidate building blocks for quantum information processing (QIP) and communication. To exploit them fully, the ability to precisely control their optical properties is needed due to several reasons. For example, the stochastic nature of their growth ends up with only little probability of finding any two or more QDs emitting indistinguishable photons. These are required for two-photon quantum interference (partial Bell-state measurement), which lies at the heart of linear optics QIP. Also, most of the as-grown QDs do not fulfil the symmetries required for generation of entangled-photon pairs. Additionally, tuning is required to establish completely new systems, for example, 87Rb atomic-vapors based hybrid semiconductoratomic (HSA) interface or QDs with significant heavy-hole (HH)-light-hole (LH) mixings. The former paves a way towards quantum memories and the latter makes the optical control of hole spins much easier required for spin- based QIP. This work focuses on the optical properties of a new type of QDs optimized for HSA experiments and their broadband tuning using strain. It was created by integrating the membranes, containing QDs, onto relaxor-ferroelectric actuators and was quantified with a spatial resolution of ~1 µm by combining measurements of the µ-photoluminescence of the regions surrounding the QDs and dedicated modeling. The emission of a neutral exciton confined in a QD usually consists of two fine-structure-split lines which are linearly polarized along orthogonal directions. In our QDs we tune the emission energies as large as ~23meV and the fine-structure-splitting by more than 90 µeV. For the first time, we demonstrate that strain is able to tune the angle between the polarization direction of these two lines up to 40° due to increased strain-induced HH-LH mixings up to ~55%. Compared to other quantum emitters, QDs can be easily integrated into optoelectronic devices, which enable, for example, the generation of non-classical light under electrical injection. A novel method to create sub-micrometer sized current-channels to efficiently feed charge carriers into single QDs is presented in this thesis. It is based on focused-laserbeam assisted thermal diffusion of manganese interstitial ions from the top GaMnAs layer into the underlying layer of resonant tunneling diode structures. The combination of the two methods investigated in this thesis may lead to new QDbased devices, where direct laser writing is employed to preselect QDs by creating localized current-channels and strain is used to fine tune their optical properties to match the demanding requirements imposed by QIP concepts.

En utfackningsvägg är en icke bärande väggkonstruktion, ofta av trä som har för syfte att minimera energiförbrukningen för byggnader i betong. Inuti konstruktionen används ibland stålpelare för att bära ovanliggande konstruktioner. Stålpelarna utsätts för laster som de måste dimensioneras för. Över och under pelarna svetsas plåtar fast för att öka den belastade arean och hindra brott i betongen. I detta examensarbete har därför en datormodell i programmet Excel framtagits. Modellen dimensionerar kantpelare i stål enligt Eurokoderna. De brottsfall som ingår i modellen är genomstansning, prägling, spjälkning, avstånd till betongkant, reducering vid håltagning i betong, tryckkraftskapacitet för fot respektive topplåtarna och böjmoment för plåtarna.   Genomstansning är ett koniskt sprött brott som sker i betongen, det spröda brottet sker direkt utan förvarning och betongplattas bärförmåga sjunker snabbt vilket kan leda till ras.  Prägling är en lokal krossning av betongen och spjälkningen innebär att på grund av tryckkraften så uppstår en horisontell dragkraft i betongen vilket kan leda till brott. Då det är svårt att uppfatta i Eurokoderna för hur avståndet mellan plåtarna och betongkanten påverkar hållfastheten har därför en beräkningsmetod framställts, likvärdigt gäller för påverkan av håltagning nära en pelare. Exempel på hål kan vara trappor, hissar eller håltagning för värmestammar till radiatorer. Plåtarna beräknas i tvärsnittsklass tre. Modellen är uppbygg så att olika dimensioner och kvalitéer väljs, hållfastheten för konstruktionen beräknas och sedan redovisa om lasten klaras eller inte. I och med det så kan till exempel olika dimensioner och kvalitéer testas fram för att få en så optimal konstruktionslösning som möjligt. Avgränsningar har gjorts. Modellen beräknar bara de olika brottsfall som ovan nämns och berör endast kvadratiska VKR- profiler och plåtar. Pelare har beräknats som ledat infäst i båda upplagen där endast tryckkrafter dimensionerat betongen och plåtarna. Under det första skedet av arbetet så har fakta inhämtning för det olika brottsfallen gjort. Fakta har hämtats från litteratur, rapporter, undersökningar, forskningar, tidigare lösningar, diskussion med branscherfarna och tidigare respektive nyare regelverk. Därefter har datormodellen gjorts, målet med modellen är att få ett snabbt resultat och en komplett redovisning. Därför är modellen uppbygg så att varje brottsfall har en egen flik och kan redovisas enskilt.  För att modellen ska kunna användas av utomstående har standardbeteckningar, bilder och kommentarer använts. Modellen har kontrollerats med diverse beräkningsexempel och program för att få ett trovärdigt/användbart resultat. Slutsats: En väl fungerande modell har tagits fram och som kan användas av utomstående byggnadsingenjörer med minst gymnasieingenjörsutbildning. / A infill wall is a non-bearing wall construction, often is made af wood, which has the aim of minimizing the energy consumption of buildings in concrete. The inside the construction is sometimes steel designed for supporting the overlyingstructures. Steel studs are subjected to loads that they must be dimensioned to support. Above and below the colums plates are welded to increase the loaded area and prevent damages to the concrete. In this thesis a computer program in Excel has been created, the program dimensions border pillars in steel that follows the Eurocodes. Included in the program is punching, local pressure, splitting, distance to concrete, reduction when drilling in concrete, compression load capacity of foot and top plates, and bending torque the plates. Punching is a conical damage that occurs in the concrete, the damage occurs without warning and the concrete’s bearing capacity decreases rapidly which can lead to collapse. Local pressure is a local damage of the concrete and splitting, meaning that because of the pressure force arising can lead to a horizontal thrust in the concrete, which can lead to injuries. Since it is difficult to perceive the distance between the plates and the concrete edge of structural strength in the Eurocodes a calculation method has been made, equally applies to the consequences when drilling near a pillar. Examples of holes can be stairs, elevators or holes for heat strain for radiators. The plates are calculated in cross-section class three. The program is built so that different dimensions and qualities is selected, then the program calculates the strength of the structure and reports if will support the load. Different dimensions and qualities can be tested to get the optimal structure sollution. Limits have been set, the program only calculates the various injuries mentioned above and applies only to square VKR-sections and plates. Pillar has been calculated as articulated in both secured repository where the only pressure forces dimensioned concrete and plates. During the first phase of the work, gathering facts for the various types of damages has been done. Facts have been gathered from literature, reports, studies, researches, previous solutions, discussions with industry experienced and previous and more recent regulations. Since then, the computer program has been made, the goal of the program is to get a quick result and a complete report. Therefore, the program is made so that all damages is on different tabs and can be reported separately. So that the program can used by third parties standard names, images and comments are used. The program has been checked with various calculation examples and applications to achieve a credible / useful result. Conclusion: A well-functioning model has been developed and can be used by structural engineers with a education at least of technical college.

Many real life problems can be formulated as constraint satisfaction problems <i>(CSPs)</i>. Backtracking search algorithms are usually employed to solve <i>CSPs</i> and in backtracking search the choice of branching strategies can be critical since they specify how a search algorithm can instantiate a variable and how a problem can be reduced into subproblems; that is, they define a search tree. In spite of the apparent importance of the branching strategy, there have been only a few empirical studies about different branching strategies and they all have been tested exclusively for numerical constraints. In this thesis, we employ the three most commonly used branching strategies in solving finite domain <i>CSPs</i>. These branching strategies are described as follows: first, a branching strategy with strong commitment assigns its variables in the early stage of the search as in k-Way branching; second, 2-Way branching guides a search by branching one side with assigning a variable and the other with eliminating the assigned value; third, the domain splitting strategy, based on the least commitment principle, branches by dividing a variable's domain rather than by assigning a single value to a variable. In our experiments, we compared the efficiency of different branching strategies in terms of their execution times and the number of choice points in solving finite domain <i>CSPs</i>. Interestingly, our experiments provide evidence that the choice of branching strategy for finite domain problems does not matter much in most cases--provided we are using an effective variable ordering heuristic--as domain splitting and 2-Way branching end up simulating k-Way branching. However, for an optimization problem with large domain size, the branching strategy with the least commitment principle can be more efficient than the other strategies. This empirical study will hopefully interest other practitioners to take different branching schemes into consideration in designing heuristics.

This thesis focuses on decision support for regional LTL carriers. The basic operating characteristics of regional LTL carriers are similar to those of national LTL carriers, i.e., they operate linehaul networks with satellites, breakbulks, and relays to consolidate freight so as to be able to cost-effectively serve their customers. However, there are also key differences. Most importantly, because the area covered by a regional carrier is smaller, a regional carrier handles less freight (sometimes significantly less) and therefore typically has fewer consolidation opportunities, which results in higher handling and transportation costs per unit of freight. Consequently, competing with national carriers on price is difficult. Therefore, to gain or maintain market share, regional carriers have to provide better service. To be able to provide better service, regional carriers have to be more dynamic, e.g., they have to be able to deviate from their load plan when appropriate, which creates challenges for decision makers. Regional carriers deliver about 60% of their shipments within a day and almost all of their shipments within two days. Furthermore, most drivers get back to their domicile at the end of each day. Therefore, the focus of the thesis is the development of effective and efficient decision models supporting daily operations of regional LTL carriers which provide excellent service at low cost. This thesis presents an effective solution approach based on two optimization models: a dynamic load planning model and a driver assignment model. The dynamic load planning model consists of two parts: an integer program to generate the best paths for daily origin-destination freight volumes and an integer program to pack freight into trailers and trailers into loads, and to determine dispatch times for these loads. Techniques to efficiently solve these integer program solution are discussed in detail. The driver assignment model is solved in multiple stages, each stage requiring the solution of a set packing models in which columns represent driver duties. Each stages determines admissible driver duties. The quality and efficiency of the solution approach are demonstrated through a computational study with real-life data from one of the largest regional LTL carriers in the country. An important "technique" for reducing driver requirements is the use of meet-and-turn operations. A basic meet-and-turn operation involves two drivers meeting at a location in between terminals and exchange trucks. A parking lot or a rest area suffices as a meet-and-turn location. This ensures that drivers return to the terminal where they started. More sophisticated meet-and-turn operations also exist, often called drop and hook operations. In this case, drivers do not exchange trucks, but one of their trailers. The motivation in this case is not to get drivers back to their domicile, but to reduce load- miles. The thesis presents analytical results quantifying the maximum benefits of using meet and turn operations and optimization techniques for identifying profitable meet-and-turn opportunities.

High quality ammonium oxofluorotitanate discoid crystal is successfully grown on glass with an aqueous solution of ammonium hexafluorotitanate and boric acid at the molar ratio of 0.6. The concentration of hydrofluoric acid is less on the glass substrate surface and enhances the ammonium oxofluorotitanate nucleation growth. The growth rate is much higher than that grown on dioctadecyldimethylammonium. From the examinations of X-ray diffraction and high-resolution transmission electron microscopy, the crystal shows high crystalline quality and uniformity. Each titanium oxide octahedral is linked with fluorine and nitrogen atoms. Therefore, ammonium oxofluorotitanate has high potential to be thermally decomposed into high crystalline fluorine and nitrogen co-doped titanium oxide. A simple process for the preparation of nanocrystalline anatase phase titanium oxide converted from ammonium oxofluorotitanate by thermal treatment was developed. The nanocrystalline anatase phase titanium oxide shows a large bandgap reduction due to the co-doping of high concentrations of fluorine and nitrogen. Due to the excellent nanocrystalline quality and the co-doping of higher concentrations of fluorine and nitrogen at the thermal treatment temperature of 800 OC, it is 1.3 times the photocatalytic activities of P-25 due to the visble region usage of Hg lamp light source. The 11.2 times the visible photocatalytic activities of P-25 using blue light-emitting diode as the light source is obtained from thermal treatment temperature of 600 OC. There is one to one correspondence between carrier lifetime and photocatalytic activity. As a result, a highly reactive and visible-light-driven photocatalysis is achieved. The heterostructure of zinc selenide/titanium oxide and zinc sulfide/titanium oxide were prepared by metal-organic chemical vapor deposition on the above-prepared titanium oxide. The energy bandgap of zinc sulfide is much larger than that of titanium oxide and can act as a window for titanium oxide. It would not hinder titanium oxide absorption and preserve the role of fluorine and nitrogen co-doping. The energy bandgap of zinc selenide is near the maximum intensity of solar spectrum and acts as a sensitizer of titanium oxide. The lifetime of electron and hole pairs of heterostructure are about 240 and 207 nsec, which are longer than 65 nsec of titanium oxide prepared at 800 oC thermal treatment. Their photocatalytic activities are further improved to 2.0 and 1.5 times higher than that of commercial P-25. The photocatalysis of titanium oxide is very sensitive to the surface states. Titanium oxide surface defects can act as trapping sites for photo-induced holes and facilitate the separation of photo-induced carriers. Zinc selenide and zinc sulfide can passivate the surface well. It may say that titanium oxide surface defects removal has a negative impact. The density, height, diameter, PL wavelength and intensity of zinc selenide self-assembled quantum dots grown on zinc sulfide/gallium arsenide with the zinc sulfide thickness from 15 to 160 nm are studied. For a fixed 30 sec zinc selenide self-assembled quantum dots growth, it cannot be formed with the zinc sulfide thickness below 15 nm due to the close lattice match between zinc sulfide and gallium arsenide. The zinc sulfide/gallium arsenide is fully lattice relaxed with the zinc sulfide thickness higher than 130 nm examined by X-ray diffraction. The higher quality and density of zinc selenide self-assembled quantum dots can be obtained on zinc sulfide/gallium arsenide with the zinc sulfide thickness far beyond its critical thickness. The maximum zinc selenide self-assembled quantum dots density of 4.9 x 109 cm-2 with the strongest photoluminescence intensity is obtained at the zinc sulfide/gallium arsenide thickness of 130 nm. Clusters are formed on the surface of zinc selenide/gallium arsenide. The selenium segregation is the main mechanism for the formation of clusters. The dislocations will enhance the selenium segregation. Higher zinc selenide cluster corresponds to higher density of dislocations. The non-spherical cluster is formed from the mergence of the two clusters. High quality zinc oxide rods and zinc hydroxide slices are successfully grown on gallium arsenide with the aqueous solution of zinc nitrate and hexamethylenetetramine. The growth can be controlled by the appropriate nitric acid concentration incorporation in the solution. After thermal annealing, the zinc oxide slices transformed from zinc hydroxide slices can contribute much higher photocatalytic activity to 1.2 times to P-25.