Cross median crashes have become a serious problem in recent years. Most of the median cross sections used for divided highways have terrains with steep slopes. Traffic barriers, frequently used on slopes, are generally designed based on the findings obtained from crash tests performed on flat terrain. For barriers placed on roadside and median slopes, vehicle impact height varies depending on the trajectory of the vehicle along the ditch section and lateral offset of the barrier. Thus depending on the placement location on a relatively steep slope, a barrier can be impacted by an errant vehicle at height and orientation more critical compared to those considered during its design. Hence, detailed study of performance of barriers on roadside and median slopes is needed to achieve acceptable safety performance. In this study, performances of modified G4(1S) W-beam, Midwest Guardrail System (MGS), modified Thrie-beam, modified weak post W-beam, and box-beam guardrail systems on sloped terrains are investigated using numerical simulations. A procedure is developed that provide guidance for their placement on roadside and median slopes. The research approach consists of nonlinear finite element analyses and multi-rigid-body dynamic analyses approach. Detailed finite element representation for each of the barriers is developed using LS-DYNA. Model fidelity is assessed through comparison of simulated and measured responses reported in full scale crash test studies conducted on flat terrain. LS-DYNA simulations of vehicle impacts on barriers placed on flat terrain at different impact heights are performed to identify performance limits of the barriers in terms of acceptable vehicle impact heights. The performances of the barriers are evaluated following the guidelines provided in NCHRP Report 350. Multi-rigid-body dynamic analysis code, CARSIM, is used to identify trajectories of the vehicles traversing various roadside and median cross-slopes. After analyzing vehicle trajectories and barrier performance limits, a guideline has been prepared with recommendations for the placement of barriers along roadside and median slopes. This guideline is then verified and refined using the responses obtained from full-scale LS-DYNA simulations. These simulations capture the full encroachment event from departure of the vehicle off the traveled way through impact with the barrier.

<p>X-ray and neutron crystallography are the predominant methods for obtaining atomic-scale information on bimolecular macromolecules. Despite the success of these techniques, generating well diffracting crystals critically limits going from protein to structure. In practice, the crystallization process proceeds through knowledge-informed empiricism. Better physico-chemical understanding remains elusive because of the large number of variables involved, hence little guidance is available to systematically identify solution conditions that promote crystallization. </p><p>The fields of structural biology and soft matter have independently sought out fundamental principles to rationalize protein crystallization. Yet the conceptual differences and limited overlap between the two disciplines may have prevented a comprehensive understanding of the phenomenon to emerge. Part of this dissertation focuses on computational studies of rubredoxin and human uniquitin that bridge the two fields.</p><p>Using atomistic simulations, the protein crystal contacts are characterized, and patchy particle models are accordingly parameterized. Comparing the phase diagrams of these schematic models with experimental results enables the critical review of the assumptions behind the two approaches, and reveals insights about protein-protein interactions that can be leveraged to crystallize proteins more generally. In addition, exploration of the model parameter space provides a rationale for several experimental observations, such as the success and occasional failure of George and Wilson's proposal for protein crystallization conditions and the competition between different crystal forms.</p><p>These simple physical models enlighten the connection between protein phase behavior and protein-protein interactions, which are, however, remarkably sensitive to the protein chemical environment. To help determine relationships between the physico-chemical protein properties and crystallization propensity, statistical models are trained on samples for 182 proteins supplied by the Northeast Structural Genomics consortium. Gaussian processes, which capture trends beyond the reach of linear statistical models, distinguish between two main physico-chemical mechanisms driving crystallization. One is characterized by low levels of side chain entropy and has been extensively reported in the literature. The other identifies specific electrostatic interactions not previously described in the crystallization context. Because evidence for two distinct mechanisms can be gleaned both from crystal contacts and from solution conditions leading to successful crystallization, the model offers future avenues for optimizing crystallization screens based on partial structural information. The availability of crystallization data coupled with structural outcomes analyzed through state-of-the-art statistical models may thus guide macromolecular crystallization toward a more rational basis.</p><p>To conclude, the behavior of water in protein crystals is specifically examined. Water is not only essential for the correct functioning and folding of proteins, but it is also a key player in protein crystal assembly. Although water occupies up to 80% of the volume fraction of a protein crystal, its structure has so far received little attention and it is often overly simplified in the structural refinement process. Merging information derived from molecular dynamics simulations and original structural information provides a way to better understand the behavior of water in crystals and to develop a method that enriches standard structural refinement.</p> / Dissertation

This work is dedicated to the theoretical and numerical study of nonlinear phononic crystals. The studied nonlinearities are those due to the second (quadratic) and third (cubic) order elastic constants of the materials that constitute the crystals. Nonlinear effects are studied by the means of finite element methods, used to simulate the propagation of an elastic wave through the crystals. A first research project concerns the study of a bone structure, namely the dispersion of elastic waves in a structure composed of collagen and hydroxy apatite alternate constituent layers. Simulations showed that it exists a strong link between bones hydration and their ability to dissipate the energy. The second study relates to an elastic resonator. A structure composed of steel inclusions in a silica matrix shows a switch behavior when the cubic nonlinearities of steel are taken into account. This strong nonlinear effect appears when the amplitude of the incident wave reaches a threshold. A full analytical model is provided. The last study demonstrates the design of composite materials with both strong cubic nonlinearities and weak quadratic nonlinearities. The derivation of the mixing laws of the elastic parameters of a nonlinear material inside a linear one is performed up to order three. Equations show a strong amplification of the nonlinear parameters of the material for some concentrations. Numerical simulations allow to conclude that the above mentioned resonator can be produced. For this thesis, an innovative tool based on the Discontinuous Galerkin (DG) finite element method is developed for the simulation of elastic wave propagation, in linear and nonlinear systems and in finite and semi-infinite media. The implementation of this DG code for 2D and 3D simulations benefits from the efficient exploitation of modern computer infrastructure (GPU units, clusters) using the property of massive parallelization of DG algorithms. This thesis is part of a joint agreement for an international Ph.D. degree between École Centrale de Lille and the Materials Science and Engineering department of the University of Arizona at Tucson. Ce travail porte sur l'étude théorique et numérique des cristaux phononiques non-linéaires. Les non-linéarités étudiées sont celles dues aux constantes élastiques d'ordre deux (quadratiques) et trois (cubiques) des matériaux constituant les cristaux. Les effets non-linéaires sont étudiés grâce á des méthodes d'éléments finis en simulant la propagation d'une onde élastique á travers les cristaux. Un premier projet de recherche a porté sur l'étude d'une structure osseuse, et plus spécifiquement sur la dispersion des ondes élastiques dans une structure constituée d'une alternance de couches de collagène et d'hydroxy apatite. Les simulations montrent qu'il existe un lien étroit entre l'hydratation des os et leur capacité à dissiper l'énergie. La seconde étude réalisée concerne un résonateur élastique. Une structure constituée d'inclusions d'acier dans de la silice présente un comportement de commutateur (switch) lorsque les non-linéarités cubiques de l'acier sont prises en compte. Cet effet fortement non-linéaire apparaît lorsque l'amplitude de l'onde incidente dépasse un certain seuil. Un modèle analytique complet est fourni. La dernière étude réalisée montre la conception de matériaux composites possédant de fortes non-linéarités cubiques mais de faibles non-linéarités quadratiques. La dérivation des lois de mélange des paramètres élastiques d'un matériau non-linéaire dans un matériau linéaire est effectuée à l'ordre trois. Les équations montrent une forte amplification des paramètres non-linéaires du matériau résultant pour certaines concentrations. Les simulations permettent de conclure que le résonateur mentionné ci-dessus peut effectivement étre réalisé. Pour cette thèse, un outil numérique innovant basé sur la méthode des éléments finis de type Galerkin Discontinu (DG) est développé pour la simulation de la propagation d'ondes élastiques, dans des systèmes linéaires et non-linéaires et dans des milieux finis et semi-infinis. L'implémentation de ce code DG pour des simulations 2D et 3D tire parti des infrastructures de calcul actuelles (processeurs graphiques, clusters) grâce à la propriété de parallélisation massive des algorithmes DG. Cette thèse s'est déroulée dans le cadre d'une cotutelle entre l'École Centrale de Lille et le département de Science et ingénierie des matériaux de l'Université d'Arizona, à Tucson.

Discrete dynamic system models that track, maintain, utilize, and evolve virtual time are referred to as virtual time systems (VTS). The realization of VTS using virtual machine (VM) technology offers several benefits including fidelity, scalability, interoperability, fault tolerance and load balancing. The usage of VTS with VMs appears in two ways: (a) VMs within VTS, and (b) VTS over VMs. The former is prevalent in high-fidelity cyber infrastructure simulations and cyber-physical system simulations, wherein VMs form a crucial component of VTS. The latter appears in the popular Cloud computing services, where VMs are offered as computing commodities and the VTS utilizes VMs as parallel execution platforms. Prior to our work presented here, the simulation community using VM within VTS (specifically, cyber infrastructure simulations) had little awareness of the existence of a fundamental virtual time-ordering problem. The correctness problem was largely unnoticed and unaddressed because of the unrecognized effects of fair-share multiplexing of VMs to realize virtual time evolution of VMs within VTS. The dissertation research reported here demonstrated the latent incorrectness of existing methods, defined key correctness benchmarks, quantitatively measured the incorrectness, proposed and implemented novel algorithms to overcome incorrectness, and optimized the solutions to execute without a performance penalty. In fact our novel, correctness-enforcing design yields better runtime performance than the traditional (incorrect) methods. Similarly, the VTS execution over VM platforms such as Cloud computing services incurs large performance degradation, which was not known until our research uncovered the fundamental mismatch between the scheduling needs of VTS execution and those of traditional parallel workloads. Consequently, we designed a novel VTS-aware hypervisor scheduler and showed significant performance gains in VTS execution over VM platforms. Prior to our work, the performance concern of VTS over VM was largely unaddressed due to the absence of an understanding of execution policy mismatch between VMs and VTS applications. VTS follows virtual-time order execution whereas the conventional VM execution follows fair-share policy. Our research quantitatively uncovered the exact cause of poor performance of VTS in VM platforms. Moreover, we proposed and implemented a novel virtual time-aware execution methodology that relieves the degradation and provides over an order of magnitude faster execution than the traditional virtual time-unaware execution.

No description available.

Dans le modèle standard de cosmologie ΛCDM, environ 72% de la densité d'énergie totale de l'Univers se présente sous la forme d'énergie sombre qui causerait la présente accélération de l'Univers. Parmi les sondes cosmologiques couramment utilisées, l'effet de lentille gravitationnel forte dans les amas est une technique prometteuse fournissant des contraintes orthogonales sur les paramètres cosmologiques. Le programme HFF a permis une amélioration significative de l'estimation de la distribution de masse des amas. Cependant, la modélisation de l'effet de lentille forte dans les amas semble ne pas atteindre la résolution angulaire des observations HST. Cette thèse fournit une meilleure compréhension de l'impact des erreurs systématiques dans la modélisation paramétrique de l'effet de lentille forte dans les amas de galaxies et, donc, sur la détermination des paramètres cosmologiques. Premièrement, j'ai analysé deux amas de galaxies simulés, ayant les mêmes caractéristiques que les amas du programme HFF, Ares et Hera. J'ai utilisé plusieurs estimateurs afin d'évaluer la qualité de nos reconstructions obtenues, permettant de quantifier l'impact des erreurs systématiques dues, au choix des profils de densité et configurations et, ensuite, de la disponibilité d'images multiples dans la détermination de paramètres cosmologiques. Deuxièmement, en utilisant deux amas de galaxies, j'ai testé quatre modèles cosmologiques pour lesquels l'équation d'état de l'énergie sombre, w(z), est paramétrisée en fonction du redshift. J'ai réalisé plusieurs modélisations pour quantifier l'impact des erreurs systématiques liées à la position des images multiples sur les paramètres cosmologiques. / In the standard cosmological model ΛCDM, about 70% of the energy density of the Universe is in the form of a dark energy that would cause the current acceleration of the Universe. Among the extensively used cosmological probes, using strong lensing features in galaxy clusters is a promising technique yielding orthogonal constraints on cosmological parameters. The program HFF has led to a significant improvement of cluster mass estimates. However, strong lensing modelling appears to be still unable to match the HST observations angular resolution.This thesis provides a better understanding of how systematic errors impact the retrieval of cosmological parameters in order to use strong lensing clusters as reliable cosmological probes. Firstly, I have analyzed two simulated HFF-like clusters, Ares and Hera, I use several estimators to assess the goodness of our reconstructions by comparing our multiple models, with the input models. This allows to quantify the impact of systematic errors arising from the choice of different density profiles and configurations and, secondly, from the availability of constraints in the parametric modelling of strong lensing clusters and therefore on the retrieval of cosmological parameters. Secondly, I probe four cosmological models in which the equation of state of dark energy, w(z), is parameterized as a function of redshift using strong lensing features in two galaxy clusters. To quantify how the cosmological constraints are biased due to systematic effects in the strong lensing modelling, I carry out several modelling attempts considering different uncertainties for the multiple images positions.

L’établissement correspond à la formation d’une population pérenne dans l’aire d’introduction. Les populations introduites ayant des effectifs faibles, elles sont sujettes à plusieurs mécanismes augmentant leurs risques d’extinction. La structure spatiale de l’aire d’introduction, une mosaïque hétérogène de patchs d’habitat appelée « paysage », peut affecter la persistance de la population introduite. L’objectif de cette thèse est d’étudier l’interaction entre cette structure spatiale et ces mécanismes, ainsi que leur impact sur l’établissement. Les recherches entreprises ont été conduites en utilisant des modèles stochastiques afin de simuler des invasions et faire émerger des prédictions, et en testant expérimentalement ces prédictions grâce à des introductions artificielles de Trichogramma chilonis en microcosmes. Ces travaux ont permis d’identifier un effet fort de la connectivité du site d’introduction, qui peut diminuer les chances d’établissement au niveau local en favorisant l’émigration depuis le site d’introduction, et augmenter les chances d’établissement à un niveau plus large en permettant la colonisation d’autres patchs dans l’aire d’introduction. Au niveau du paysage, nous avons identifié l’impact des hubs, des patchs concentrant les flux de dispersion, qui accroissent fortement la vitesse de colonisation mais diminuent le taux d’établissement. L’établissement était également favorisé par l’agrégation de la ressource et la colonisation par sa dissémination à travers le paysage. La nature stochastique des dynamiques de colonisation est telle qu’il est nécessaire de les prendre en compte pour étudier l’établissement. / Establishment is an important stage of biological invasions, which corresponds to the formation of a persistent population in the introduction area. It is not trivial, as introduced populations are often small, and subject to various specific mechanisms, which increase extinction risks. The spatial structure of the introduction area, which is usually a heterogeneous mosaic of habitat patches called a “landscape”, can interact with those mechanisms and impact the introduced population persistence. This thesis objective is to study the interaction between this spatial structure and those mechanisms, as well as their impact on establishment. On the one hand, we used stochastic models to simulate invasions and formulate predictions. On the other hand, we tested these predictions by performing artificial introductions of Trichogramma chilonis in laboratory microcosms. We were able to identify the impact of the introduction site connectivity, which could decrease establishment probabilities at a local level by increasing the emigration rate from the introduction site, and increase establishment at the landscape level by increasing the colonisation rate of other patches in the introduction area. At the landscape level, we identified the impact of hubs, i.e. patches concentrating dispersal fluxes. They strongly increased colonisation speed, but also decreased establishment. The clustering of resources increased establishment, while its scattering increased colonization. Our results show that introduced population dynamics are highly sensitive to their size. The stochastic nature of colonization dynamics is also necessary to study establishment.

La déformation plastique des matériaux cristallins classiques est surtout dominée par des dislocations et leurs interactions mutuelles. Pour les métaux nanocrystallines (nc), des mécanismes de joints de grains différents peuvent exister en plus des mécanismes basés sur la dislocation. La dépendance à l’égard, entre autres, la forme du grain, l’orientation des grains, la densité de dislocations initiale, la structure des joints de grains et conditions extérieures favorise un ou deux mécanismes de déformation par rapport aux autres. Ces mécanismes dominants dictent la réponse globale du métal nc. L’influence des caractéristiques de microstructure doit être mieux comprise individuellement et collectivement. Dans le cadre de cette thèse, des simulations de dynamique des dislocations discrète 3D (DD) ont été effectuéessur trois grains individuels de taille micronique de même volume, mais qui diffèrent leurs rapports d’aspect. La diminution de la localisation de la déformation plastique avec l’augmentation de rapport d’aspect du grain à été observée. En raison du mécanisme inter-dérapant amélioré, des grains ayant rapport de un aspect plus elevé. La réponse plastique anisotrope des grains allongés a été quantifiée en terme d’ampleur du back-stress sur chaque système de glissement. En outre, une version polycristalline de dynamique des dislocations couple avec des éléments finis a été utilisée pour étudier le comportement mécanique des couches minces de palladium libre avec des grains colonnaires. La densité de dislocations initiale prise en compte dans les simulations est proche de celle mesurée expérimentalement. Les simulationsde DD d’un polycristal avec 12 grains hexagonaux de tailles égales reproduisent correctement le comportement d’écrouissage. L’augmentation de la résistance observée avec la diminution de l’épaisseur du film a été capturé en utilisant une distribution de taille de grains hétérogène du polycristal. L’élément essentiel est que la probabilité de grains plus petits sans dislocations initiales augmente avec la diminution de l’épaisseur du film. La différence dans les contributions en back-stress résultant de la distribution de la taille des grains dans le film a également été quantifiée. Enfin, en adaptant le modèle de Read, l’influence d’une dislocation statique électriquement chargée sur les propriétés électriques des semi-conducteurs a été étudiée. / Plastic deformation of classical crystalline materials is mostly dominated by dislocations and their mutual interactions. In nanocrystalline (nc) metals, different grain boundary mechanisms may exist in addition to the dislocation-based mechanisms. The dependency on, among other, the grain shape, grain orientation, initial dislocation density, grain boundary structure and external conditions will promote one or two deformation mechanisms over others. These dominant mechanisms dictate the overall response of nc metal. The influence of the microstructural features needs to be better understood individually and collectively. In the scope of the thesis, 3D discrete dislocation dynamics (DD) simulations were performed on three micron-sized single grains of same volume but differing in aspect ratios. Localization of plastic deformation was observed to decrease with increasing grain aspect ratio. Due to the enhanced cross-slip mechanism, grains with higher aspectratio exhibit a softer behavior. The anisotropic plastic response of elongated grains was quantified interms of the magnitude of back-stress on each slip system. Further, a polycrystalline version of dislocation dynamics code coupled with a finite elements was used, to study the mechanical behavior of free-standing palladium thin films with columnar grains. The initial dislocation density considered in the simulations is close to the one measured experimentally. DD simulations of a polycrystal with 12 equally sized hexagonal grains properly reproduce the strain hardening behavior. The increase in strength observed with decreasing film thickness was captured using a heterogenous grain size distribution of the polycrystal. The key element is that the probability of smaller grains with no inital dislocations is increasingwith decreasing thickness of the film. Difference in the back-stress contributions arising from the grain size distribution in the film was also quantified. Finally, by adapting Read’s model, the influence of a static, electrically-charged dislocation on electrical properties in semiconductors was studied.

.La densification du névé en glace est un processus essentiel à comprendre pour interpréter les enregistrements climatiques. Une bonne connaissance des mécanismes permet une datation précise de l'air capturé dans la glace lors de la fermeture des pores. Celle-ci est plus vieille que l'air capturé à cause du transport des gaz dans la colonne de névé plus rapide que la densification de celui-ci. Cette différence d'âge entre la glace et le gaz est généralement appelé le Δage. La densification de la neige consiste en un processus complexe de réarrangement de grains, de frittage et de déformation viscoplastique. Bien que le comportement viscoplastique du cristal de glace soit fortement anisotrope, les modèles de densification actuels ne tiennent pas compte de cette anisotropie. De plus, le caractère granulaire du névé affecte aussi sa densification. La relation entre la fermeture des pores et les mécanismes microstructuraux sous-jacents est encore méconnue. Le but de cette thèse est d'incorporer l'aspect granulaire ainsi que l'anisotropie du cristal de glace dans une approche de modélisation innovante de la densification. Des expériences sur l'indentation viscoplastique de cylindres monocristallins de glace ont été réalisées pour proposer une loi de contact basée sur la théorie de l'indentation, et prenant en compte la déformation préférentielle du cristal de glace sur les plans basaux. Cette loi de contact a été implémentée dans un code utilisant la méthode des éléments discrets pour prédire la densification du névé.La micro-tomographie aux rayons X a été utilisée pour caractériser ex situ le névé polaire en trois dimensions à différentes étapes de la densification (ρ= 0.55-0.88 g/cm3), i.e. pour différentes profondeurs (~23 à 130m). Une étude fine de la fermeture des pores et de différentes caractéristiques morphologiques et physiques a été réalisée pour les sites polaires Dome C et Lock In. Des essais mécaniques ont aussi été réalisés in situ sur du névé extrait de Dome C dans le but de modéliser la densification du névé. Les observations microstructurales des expériences ex situ et in situ révèlent d'importantes différences dues aux vitesses relativement importantes utilisées lors des essais mécaniques. Ces vitesses rapides permettent de découpler la contribution des cinétiques de diffusion de la contribution viscoplastique de la déformation. Les effets de ces contributions sur la morphologie des pores et leurs fermetures sont discutés. Pour caractériser la fermeture des pores, cette thèse propose un indice de connectivité définit par le ratio entre le volume du plus gros pore sur la porosité totale. En effet, cet indice est plus approprié lors de l'utilisation de la tomographie aux rayons X que le ratio de pores fermés pour prédire la densité au close-off. / Densification from firn to ice is an essential phenomenon to understand for the interpretation of the climate record. A good knowledge of this mechanism enables the precise dating of the air embedded in the ice. The step at which the air becomes entrapped is the pore closure (or close-off). Because of gas flow in the firn column, the ice is older than the entrapped air. The difference between ice and gas is generally defined as Δage.Snow densification consists of grain rearrangements, sintering and viscoplastic deformation. Although the viscoplastic behaviour of the ice crystal is strongly anisotropic, densification models do not take into account this anisotropy. Firn also bears some granular characteristics that may affect its densification. The interactions between pore closure and microstructural mechanisms in the firn are still misunderstood.The aim of this PhD thesis is to incorporate both the granular aspect of firn and its anisotropy into an innovating approach of firn densification modelling. The mutual indentation of viscoplastic monocrystalline ice cylinders was experimentally carried out to propose a contact law that is based on indentation theory and that takes into account the preferential viscoplastic deformation on the basal plane. We have integrated this contact law into a DEM (Discrete Element Method) code for the prediction of firn densification.3D X-ray micro-tomography was performed on polar firn at different stages of the densification (ρ= 0.55-0.88 g/cm3) and depths (~23 to 130m). A thorough investigation of pore closure and of different morphological and physical parameters was achieved for the Dome C and the newly drilled Lock In polar sites. In addition to these ex situ analyses, in situ X-ray micro-mechanical experiments were carried out on firn extracted from Dome C in order to model its densification. Ex situ and in situ microstructural observations indicate significant differences that can be explained by the relatively large strain-rates imposed to the firn during in situ tests. These large strain rates allow for a decoupling of the effects of diffusion kinetics and of viscoplastic deformation. Their relative weights on the morphology of pores and on their closure are discussed. To measure pore closure, we propose a connectivity index, which is the ratio of the largest pore volume over the total pore volume. We show that this index is better suited for X-ray tomography analysis than the classic closed porosity ratio to predict the close-off density

La spectroscopie ro-vibrationelle de haute résolution de l’ion moleculaire H2+ par REMPD requiert une source sélective en état interne. Dans cette thèse nous présentons notre travail de conception et de réalisation d’une telle source utilisant la photo-ionisation multiphotonique résonante (REMPI) de H2 à l’aide d’un laser pulsé à 303 nm.Dans un deuxième temps nous présentons nos simulations numériques de refroidissement sympathique dans un piège de Paul linéaire, avec pour application principale le projet GBAR qui implique le refroidissement sympathique d’un ion d’antimatière H̄+ par des ions Be+ refroidis par laser. Nous avons dévelopé un code GPU utilisant un pas de temps variable permettant de décrire les interactions coulombiennes de façon efficace. Nous discutons de l’influence du chauffage RF et de lois d’échelles entre le temps de capture, l’énergie initiale et le nombre d’ions dans le cristal. Nous montrons que le refroidissement sympathique de H̄ requis pour GBAR pourrait fonctionner avec un cristal dissymétrique de Be+/HD+ qui semble plus efficace que le Be+ seul. Nous montrons qu’avec un tel cristal la capture du H̄+ pourrait être détectée expérimentalement par analyse de Fourier des données de fluorescence. / The high-resolution ro-vibrational spectroscopy of the H2+ molecular ion by resonance-enhanced multiphoton dissociation (REMPD) requires a state-selective source of H2+. In this thesis we present work on a functional state selective H2+ ion source using resonance enhanced multiphoton ionisation (REMPI) with a 303 nm pulsed laser.The second part of the thesis presents numerical simulations of sympathetic cooling in linear RF traps, whose main application is the GBAR project (Gravitational Behaviour of Antihydrogen at Rest) which involves sympathetic cooling of an antimatter H̄+ ion by laser-cooled Be+ ions. We developed a GPU code using a variable timestep technique enabling a fast description of Coulomb interactions. We discuss the influence of RF heating and scaling laws between cooling times, initial energy and ion numbers in the cooling crystal. We show that the H̄ sympathetic cooling step of GBAR could be feasible using a rotationally asymmetric two-component Be+/HD+ crystal which appears more effective than a single-component Be+ crystal. We find that the H̄+ ion’s capture by this crystal could be detected experimentally by Fourier analysis of the fluorescence data.