Cette thèse aborde l'étude du vieillissement thermique du système Fe-Cr. Nous avons étudié le mécanisme de diffusion de la lacune dans le cadre de la théorie de la fonctionnelle de la densité (Density Functional Theory - DFT) et examiné la capacité d'un potentiel empirique de la classe EAM (Embedded Atom Method) à reproduire les résultats DFT. Nous avons montré que l'énergie de migration de la lacune dépend fortement de l'environnement atomique du point de col où les interactions chrome-chrome et chrome-lacune déterminent en partie l’énergie de point de col. Nous avons proposé trois approches pour la paramétrisation d'un modèle Monte Carlo Cinétique (MCC) atomique : l’une entièrement basée sur le potentiel EAM, les autres partiellement basées sur nos calculs DFT. Les simulations par MCC du vieillissement thermique des alliages Fe-20% at. Cr et Fe-25% at. Cr à 773 K montrent la formation de précipités riches en chrome dont la croissance avec le temps suit une loi de puissance avec un exposant 1/3, en accord avec la théorie de Lifshitz-Slyozov-Wagner. La paramétrisation des simulations par MCC entièrement basée sur le potentiel EAM prédit une taille moyenne des précipités supérieure à celle observée expérimentalement, alors que cette dernière est sous-estimée par les paramétrisations partiellement basées sur nos calculs DFT. Ce désaccord semble avoir une origine cinétique plutôt que thermodynamique. La composition de la phase riche en chrome varie au cours de la séparation de phase, indiquant ainsi que la démixtion se produit par nucléation non-classique ou par décomposition spinodale. Des précipités interconnectés sont plus susceptibles de se former dans le système Fe-25% at. Cr plutôt que dans l’alliage Fe-20% at. Cr suggérant ainsi que, lorsque la concentration en soluté augmente, le mécanisme de démixtion se rapproche de la décomposition spinodale. / In this thesis, we address the study of the microstrucutre evolution of the Fe-Cr system under thermal ageing. The vacancy diffusion mechanism was investigated in the framework of the density functional theory (DFT) and the capability of a recently developed embedded atom method (EAM) empirical cohesive model to reproduce the DFT results was examined. We have shown that the vacancy migration energy strongly depends on the saddle point atomic environment where the chromium-chromium and the chromium-vacancy interactions partially determine the saddle point energy. We proposed three approaches for the parameterisation of an atomistic kinetic Monte Carlo (AKMC) model: one fully based on the EAM potential, the others partially based on our DFT calculations. The AKMC simulations of the thermal ageing of the Fe-20 at.%Cr and Fe-25 at.%Cr alloys at 773 K show the formation of chromium-rich precipitates whose growth with time follows a power law with exponent 1/3. This is consistent with the Lifshitz-Slyozov-Wagner theory of coarsening. The AKMC parameterisation fully based on the EAM potential predicts a mean precipitate size higher than the experimentally observed one, whereas the parameterisations partially based on our DFT calculations underestimate it. This disagreement seems to have a kinetic rather than thermodynamic origin. The composition of the precipitating phase varies during the phase separation thus indicating that the unmixing is driven by either a non-classical nucleation or a spinodal decomposition. Interconnected precipitates are more likely to form in the Fe-25 at.%Cr alloy than in the Fe-20 at.%Cr thus suggesting that, as the solute concentration increases, the spinodal decomposition is more likely to occur.

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La physique des collisions d'ions lourds réunit deux domaines : la physique nucléaire et la physique des particules. Les progrès expérimentaux de ces dernières années donne l'opportunité d'étudier la nouvelle matière créée dans les collisions d'ions lourds qui s'appelle le plasma de quarks et de gluons.L'état initial de deux ions qui se collisionnent est affecté par les fluctuations créées par les fonctions d'ondes des nucléons. Ces fluctuations provoquent l'anisotropie de moments de la matière hadronique observée par les détecteurs. Le système créé dans une collision se comporte comme un fluide, donc l'état initial est connecté avec l'état final par l'évolution hydrodynamique. L’hydrodynamique relativiste est utilisée pour décrire l'évolution du fluide créé dans les collisions d'ions lourds. Nos résultats combinés avec les données expérimentales permettent de contraindre l'etat initial donc de faire la «rétro-ingénierie» des collisions d'ions lourds.L'observable qui caractérise l'anisotropie des moments est le flot anisotrope v_n. On présente les premières mesures du premier coefficient de la distribution de Fourier v_1 pour l'accélérateur LHC. v_1 s'appelle le flot dirigé. On effectue aussi les premiers calculs de v_1 à partir de l’hydrodynamique visqueuse. On trouve que v_1 est moins dépendent de la viscosité que les coefficients v_2 et v_3 qui sont respectivement les flots elliptique et triangulaire. On présente aussi les prédictions de v_1 pour l'accélérateur RHIC. Ces résultats ont été confirmés plus tard par les mesures de v_1 par RHIC. On propose aussi deux méthodes pour contraindre les modèles d’état initial: avec les données de v_1 et les données de v_2 et v_3. Ces méthodes donnent l'unique possibilité de contraindre les modèles Monte Carlo d'état initial. A la fin de cette thèse on montre les perspectives de ce domaine et on étudie les corrélations entre les plans des évènements qui ont été mesurées récemment et qui pourraient faire la lumière sur les fluctuations de l'état initial. / Ultra-Relativistic heavy-ion physics is a promising field of high energy physics connecting two fields: nuclear physics and elementary particle physics. Experimental achievements of the last years have provided an opportunity to study the properties of a new state of matter created in heavy-ion collisions called quark-gluon plasma. The initial state of two colliding nuclei is affected by fluctuations coming from wave- functions of nucleons. These fluctuations lead to the momentum anisotropy of the hadronic matter which is observed by the detectors. The system created in the collision behaves like a fluid, so the initial state is connected to the final state via hydrodynamic evolution. In this thesis we model the evolution with relativistic viscous hydrodynamics. Our results, combined with experimental data, give non trivial constraints on the initial state, thus achieving "reverse engineering" of the heavy-ion collisions. The observable which characterizes the momentum anisotropy is the anisotropic flow vn. We present the first measurements of the first harmonic of the anisotropic flow called directed flow v1 in Pb-Pb collisions at the LHC. We then perform the first viscous hydrodynamic modeling of directed flow and show that it is less sensitive to viscosity than higher harmonics. Comparison of these experimental data with the modeling allows to extract the values of the dipole asymmetry of the initial state, which provides constraints on the models of initial states. A prediction for directed flow v1 in Au-Au collisions is also made for RHIC. We then perform a similar modeling of the second and third harmonics of the anisotropic flow, called respectively elliptic v2 and triangular v3 flow. A combined analysis of the elliptic and triangular flow data compared with viscous hydrodynamic calculations allows us to put constraints on initial ellipticity and triangularity of the system. These constraints are then used as a filter for different models of initial state. At the end of this thesis, we show perspectives in the studies of the initial state which are opened by recent measurements of event-plane correlations which could shed light on the initial state fluctuations.

This thesis presents three searches for new resonances in dijet invariant mass spectra. The spectra are produced using √s = 13 TeV proton-proton collision data recorded by the ATLAS detector. New dijet resonances are searched for in the mass range 200 GeV to 6.9 TeV in mass. Heavy new resonances, with masses above 1.1 TeV, are targeted by a high mass dijet search. Light new resonances, with masses down to 200 GeV, are searched for in dijet events with an associated high momentum object (a photon or a jet) arising from initial state radiation. The associated object is used to efficiently trigger the recording of low mass dijet events. All of the analyses presented in this thesis search for an excess of events, localised in mass, above a data-derived estimate of the smoothly falling QCD background. In each search no evidence for new resonances is observed, and the data are used to set 95% C.L. limits on the production cross-section times acceptance times branching ratio for model-independent Gaussian resonance shapes, as well as benchmark signals. One particular benchmark signal which is considered in all of the searches is an axial-vector Z' dark matter mediator model whose parameter space is reduced due to the results presented in this thesis.

Diploma thesis is focused on the design of prestressed concrete membrane from the lightweight concrete. The concrete membrane is in the interaction with the bearing steel structure, which one is supported. I did only one variant of the solution, which was optimized. The goal of the design was determined the initial state of a membrane and ensure to in the end of design working life was the membrane in the compression state and the cracks couldn’t appear. The structure is modelled in the main (longitudinal) direction as a spatial frame in program ANSYS 17.2. This tool enables to perform analysis of the construction stages. The rheology is calculated manually and supplied to the model as relative strain. The whole structure is checked for ultimate limit state and serviceability limit state according to valid Eurocodes. Transverse direction is modelled by shell elements in program RFEM 5.12. Construction stages and global behaviour of the structure were analysed. The checks have been calculated manually and control in program IDEA StatiCa. The attachments of the thesis are drawings, visualisation and schemes of construction stages.

When monitoring a binary process proportion p, it is usually assumed that the binary observations are independent. However, it is very common that the observations are correlated with p being the correlation between two successive observations. The first part of this research investigates the problem of monitoring p when the binary observations follow a first-order two-state Markov chain model with p remaining unchanged. A Markov Binary GLR (MBGLR) chart with an upper bound on the estimate of p is proposed to monitor a continuous stream of autocorrelated binary observations treating each observation as a sample of size n=1. The MBGLR chart with a large upper bound has good overall performance over a wide range of shifts. The MBGLR chart is optimized using the extra number of defectives (END) over a range of upper bounds for the MLE of p. The numerical results show that the optimized MBGLR chart has a smaller END than the optimized Markov binary CUSUM. The second part of this research develops a CUSUM-pp chart and a GLR-pp chart to monitor p and p simultaneously. The CUSUM-pp with two tuning parameters is designed to detect shifts in p and p when the shifted values are known. We apply two CUSUM-pp charts as a chart combination to detect increases in p and increases or decreases in p. The GLR-pp chart with an upper bound on the estimate of p, and an upper bound and a lower bound on the estimate of p works well when the shifts are unknown. We find that the GLR-pp chart has better overall performance. The last part of this research investigates the problem of monitoring p with p remains at the target value when the correlated binary observations are aggregated into samples with n>1. We assume that samples are independent and there is correlation between the observations in a sample. We proposed some GLR and CUSUM charts to monitor p and the performance of the charts are compared. The simulation results show MBNGLR has overall better performance than the other charts. / Ph. D.

Le travail présenté dans ce mémoire a pour objectif d'aboutir à une meilleure caractérisation expérimentale du comportement non drainé du sable d'Hostun à l'échelle locale, en relation avec les différentes méthodes de reconstitution utilisées. On vise en particulier à mettre en évidence la façon dont la microstructure influence les propriétés des sols granulaires, notamment vis-à-vis de l'instabilité de liquéfaction. Le point clé de ce travail consiste en l'utilisation de capteurs piézoélectriques pour mesurer les vitesses d'onde de cisaillement au sein d'éprouvettes triaxiales reconstituées par trois techniques différentes à savoir le damage humide, la pluviation à sec et la pluviation sous eau. Les résultats obtenus mettent en évidence l'influence considérable du mode de fabrication sur le comportement mécanique du sable. Ils montrent que pour une même densité initiale, et à même pression de confinement, le comportement mécanique observé est très différent selon les trois modes de préparation. Les valeurs de vitesses d'onde de cisaillement enregistrées sont différentes d'un mode de déposition à un autre. Concernant l'anisotropie, le matériau préparé par damage humide présente un certain degré d'anisotropie inhérente, qui est toutefois minimal. En revanche, la pluviation à sec et la pluviation sous eau induisent des structures initiales plus isotropes. / This work aims to achieve a better experimental characterization of the undrained behavior of the Hostun HN31 sand at the local scale, depending on the different procedures used for sample reconstitution. We particularly highlight the influence of the microstructure on the mechanical behavior of sand especially in relation to liquefaction instability. The key point of this work consists of the use of piezoelectric transducers to measure shear wave velocities within triaxial sand specimens. These specimens have been prepared by different methods, namely: moist tamping, dry pluviation and water pluviation. The obtained results highlight the considerable influence of the deposition mode on the mechanical behavior of sand. They show that for the same initial density, and at the same confining pressure, the mechanical behavior is very different from the three preparation methods. Furthermore, the values of shear wave velocity are different from one deposition mode to another. Concerning the anisotropy, the material prepared by moist tamping presents an inherent degree of anisotropy, which it is however minimal. On the other hand, dry pluviation and water pluviation induce more isotropic initial structures. Moreover, the initial anisotropy is less important than the anisotropy induced by loading. These experimental results indicate that the initial state of a granular medium can not be described by only couple of scalar variables of initial density and confining pressure: a variable that can reflect the initial microstructure and an evolution law of this variable are necessary to model the experimental observations.

Ultra-Relativistic heavy-ion physics is a promising field of high energy physics connecting two fields: nuclear physics and elementary particle physics. Experimental achievements of the last years have provided an opportunity to study the properties of a new state of matter created in heavy-ion collisions called quark-gluon plasma. The initial state of two colliding nuclei is affected by fluctuations coming from wave- functions of nucleons. These fluctuations lead to the momentum anisotropy of the hadronic matter which is observed by the detectors. The system created in the collision behaves like a fluid, so the initial state is connected to the final state via hydrodynamic evolution. In this thesis we model the evolution with relativistic viscous hydrodynamics. Our results, combined with experimental data, give non trivial constraints on the initial state, thus achieving "reverse engineering" of the heavy-ion collisions. The observable which characterizes the momentum anisotropy is the anisotropic flow vn. We present the first measurements of the first harmonic of the anisotropic flow called directed flow v1 in Pb-Pb collisions at the LHC. We then perform the first viscous hydrodynamic modeling of directed flow and show that it is less sensitive to viscosity than higher harmonics. Comparison of these experimental data with the modeling allows to extract the values of the dipole asymmetry of the initial state, which provides constraints on the models of initial states. A prediction for directed flow v1 in Au-Au collisions is also made for RHIC. We then perform a similar modeling of the second and third harmonics of the anisotropic flow, called respectively elliptic v2 and triangular v3 flow. A combined analysis of the elliptic and triangular flow data compared with viscous hydrodynamic calculations allows us to put constraints on initial ellipticity and triangularity of the system. These constraints are then used as a filter for different models of initial state. At the end of this thesis, we show perspectives in the studies of the initial state which are opened by recent measurements of event-plane correlations which could shed light on the initial state fluctuations.

The subject of this diploma thesis is design a cable-supported pedestrian bridge. Three different variants of the solution were created for the design. For detailed processing, variant no.2 was chosen - a suspended bridge with a pylon in the middle of the span. The main task is the static design of the supporting structure. The model for the lengthways is created in ANSYS. The SCIA engineer was used to solve crosswise. The assessment and dimensioning was done according to the limit state principles and valid standards.

The subject of this master thesis is to design a pedestrian bridge supported by cables. There are three variants of studies created for this case and for most suitable one, all documentations were produced. The primary focus of this work is on static design solution with an output of several drawings. Static model for results from load cases included construction stages and was created in Midas Civil. Design and checks were performed by hand calculations, complemented by checks of several sections by IDEA StatiCa software. Analysis and calculations are compliant to up-to-date codes and respect the fundamentals of analysis due to limit states.