La démarche « matériaux numériques », développée au CEA Le Ripaut, consiste à optimiser numériquement une structure, à l’aide de codes de calcul permettant de réaliser des expériences numériques, afin de répondre le plus précisément possible à un cahier des charges. La mise en œuvre de ces structures optimisées, aux formes pouvant être complexes, n’est parfois pas réalisable avec les procédés de fabrication actuels. Cependant, la progression rapide de l’impression 3D semble maintenant pouvoir concrétiser cette démarche. Le but de cette thèse est d’étudier cette faisabilité de fabrication, à travers une application concrète : l’optimisation des récepteurs volumétriques des Centrales Solaires Thermodynamiques (CST).Actuellement, la conception de ces récepteurs en Carbure de Silicium (SiC) est restreinte par les techniques existantes de fabrication, et leurs morphologies se limitent donc principalement à des mousses ou des canaux parallèles. Or, ce type de structure ne permet pas d’exploiter tout le caractère 3D proposé par les récepteurs, en raison notamment d’une absorption trop hétérogène du rayonnement solaire dans le volume. Dans ce travail de thèse, afin de rechercher la répartition de l’absorption la plus homogène possible dans l’ensemble du volume, de nombreuses structures aux formes variées sont générées virtuellement. Une simulation de l’éclairement solaire reçu est réalisée sur l’ensemble de ces structures, grâce à un code de calcul développé spécialement pour cette application, permettant ainsi d’en retenir trois répondants au mieux aux critères du cahier des charges. Ces structures potentiellement optimisées ont ensuite été fabriquées en SiC par impression 3D, par un procédé de projection de liant sur lit de poudre. Elles ont été ensuite testées sur un banc d’essai expérimental du laboratoire PROMES, reproduisant les conditions d’une CST. Les résultats ont montrés que ces structures, aux formes totalement différentes de mousses ou de canaux parallèles, sont capables de produire au maximum de l’air à 860°C en sortie de récepteur, et avec des rendements énergétiques proches de 0,65. Enfin, un code de calcul thermique couplé conducto-radiatif, amélioré durant ce travail, a permis d’analyser ces résultats expérimentaux et servira pour les futurs travaux d’optimisation de la géométrie d’un récepteur. / The "numerical materials" approach, developed at CEA Le Ripaut, consists to numerically optimize a structure, by using calculation codes that allow to realize numerical experiments, in order to answer, as precisely as possible, to a set of specifications. The manufacturing of these optimized structures, whose shapes can be complex, is sometimes not feasible with current manufacturing processes. However, the rapid progress of 3D printing now seems to be able to concretize this approach. The aim of this thesis is to study this manufacturing feasibility, through a concrete application: the optimization of the volumetric receivers of Concentrated Solar Power Plants (CSP). Currently, the design of these silicon carbide (SiC) receptors is restricted by the existing manufacturing techniques, and their morphologies are therefore mainly limited to foams or parallel channels. However, this type of structure does not allow to exploit all the 3D character proposed by the receivers, due in particular to a heterogeneous absorption of solar radiation in the volume. In this work, in order to find the distribution of the most homogeneous absorption possible in the whole volume, many structures with various shapes are generated virtually. A simulation of the solar irradiance received is carried out on all these structures, thanks to a calculation code developed especially for this application, thus allowing to choose three of them, respondents at best to the criteria of the specifications. These potentially optimized structures were then manufactured in SiC by 3D printing, by a binder jetting process. They were then tested on an experimental test bench of the PROMES laboratory, reproducing the conditions of a CSP. Results showed that these structures, where their shapes are totally different from foams or parallel channels, are able to produce a maximum air temperature of 860°C at the output of the receiver, and with efficiencies close to 0.65. Finally, a conducto-radiative coupled thermal computational code, improved during this work, made it possible to analyze these experimental results and will be used for the future work of optimization of the geometry of a receiver.

L'objectif de ce projet de recherche est la mise au point et l'utilisation de charges inorganiques barrière aux rayonnements infrarouge pour la préparation de matériaux d'enduction à base de plastisols PVC. Dans un premier temps, cette étude a été consacrée à la caractérisation rhéologique, morphologique et optique de la matrice PVC et à l'élaboration de nouvelles formulations, en incorporant dans le plastisol des charges commerciales de natures chimiques différentes (nacre, billes de verre, alumine, oxyde de Zinc, TiO2 …). Ensuite, des mesures radiatives sur des films de plastisols chargés à différents taux massiques ont été réalisées dans le but de sélectionner les charges présentant les meilleures performances optiques. Enfin, les formulations optimales ont été enduites sur un textile polyester et la stabilité des revêtements soumis à des rayonnements UV a été suivie par plusieurs techniques analytiques. Diverses caractérisations mécaniques, esthétiques et morphologiques sont venues compléter cette étude. Dans un second temps, un modèle de transfert radiatif permettant de simuler la propagation du rayonnement dans les systèmes de protection développés a été testé / This project aims to develop new filled PVC plastisol composite offering enhanced optical properties. Different types of inorganic fillers were tested and added to the PVC matrix. Rheological, morphological and optical characterization of the PVC matrix and development of new formulations by incorporation of different fillers (nacre, glass beads, alumina, zinc oxide, TiO2 ...) were the subject of the first phase of the project. Then, radiative measurements on plastisol films loaded at different mass ratios were performed in order to select the fillers having the best optical performance. The second phase was dedicated to the validation and the testing of the optimal formulations coated on polyester textile substrate. Different analytic technics were used in order to rank the UV stabilization as a function of the tested formulations. In addition, mechanical, aesthetic and morphological characterizations were used to complete this study. Finally, radiative transfer model was developed to simulate the radiative behavior of the different formulations

Indiana University-Purdue University Indianapolis (IUPUI) / This dissertation focuses on quantification of submicroscopic iron of different sizes, mineral abundance and grain size of lunar soils using Hapke's radiative transfer model. The main objective is to explore implications of these results for assessing the relative importance of solar wind implantation versus micrometeorite impacts for lunar space weathering as well as three hypotheses (solar wind deflection, comet impact and dust transport) for swirl formation on the Moon. Results from this study can help to make connections between ordinary chondritic meteorites and asteroids, and put physical and chemical constraints on heating processes in the early solar system.

Die hier vorgestellte Untersuchung des radiativen elektroschwachen "Pinguin"-Zerfalls B->K*(892)Gamma, der durch den "Schleifen"-Übergang b->sGamma stattfindet, stellt einen wichtigen Test des Standardmodells und einen Kandidaten für die Suche nach Neuer Physik dar. Der benutzte Datensatz wurde auf der Y(4S)-Resonanz mit dem BABAR-Detektor am asymmetrischen Elektron-Positron-Speicherring PEP-II des Stanford Linear Accelerator Centers (SLAC) aufgezeichnet. Die B->K*Gamma Verzweigungsverhältnisse wurden in vier K*-Zerfallskanälen gemessen. Eine Suche nach direkter CP-Verletzung im B->K*Gamma Kanal wurde ebenfalls durchgeführt. / The presented study of the radiative electroweak "penguin"-decay B->K*(892)gamma, proceeding by the b->sgamma "loop"-transition, provides an important test of the Standard Model and a candidate of the search for New Physics. The used data sample has been recorded at the Y(4S) resonance with the BABAR detector at the asymmetric electron-positron- collider PEP-II of the Stanford Linear Accelerator Center (SLAC) in California. The B->K*gamma branching fractions are measured in four K*-decay modes. A search for direct CP-violation in the B->K*gamma mode has also been carried out.

A three-dimensional computational tool was developed that simulates the heat and mass transfer interaction in a soil-root-stem system (SRSS) for a tree in a seasonally varying deciduous forest. The development of the SRSS model involved the modification and coupling of existing heat and mass transport tools to reproduce the three-dimensional diurnal internal and external temperatures, internal fluid distribution, and heat flow in the soil, roots, and stems. The model also required the development of a parallel Monte-Carlo algorithm to simulate the solar and environmental radiation regime consisting of sky and forest radiative effects surrounding the tree. The SRSS was tested, component-wise verified, and quantitatively compared with published observations. The SRSS was applied to simulate a tree in a dense temperate hardwood forest that included the calculations of surface heat flux and comparisons between cases with fluid flow transport and periods of zero flow. Results from the winter simulations indicate that the primary influence of temperature in the trunk is solar radiation and radiative energy from the soil and surrounding trees. Results from the summer simulation differed with previous results, indicating that sap flow in the trunk altered the internal temperature change with secondary effects attributed to the radiative energy from the soil and surrounding trees. Summer simulation results also showed that with sap flow, as the soil around the roots become unsaturated, the flow path for the roots will be changed to areas where the soil is still saturated with a corresponding increase in fluid velocity.

No description available.

The goal of this Master thesis is to demonstrate Witteńs mechanism in selected extensions of the Standard model based on the Pati-Salam gauge group. The purpose of this mechanism is to obtain an extremely large Majorana mass term for right-handed neutrinos at the two-loop level and consequently light physical masses of neutrinos using the type I see-saw mechanism. The existence of corresponding Feynman diagrams without any interactions of vector bosons is presented. While it is impossible to construct this type of corrections in minimal SO(10) or SU(5)xU(1) model in Pati-Salam model they may be even dominant. Subsequently, implications of possible partial gauge coupling unification or even embedding of the Pati-Salam group into a gauge group of "Great Unified Theory" are considered. At the end the possibility of unacceptably fast proton decay is inspected. The discussed models are concluded to be potentially realistic but only at the cost of predictivity, since completely unknown Yukawa couplings appear in numerous key relations. 1

The inductively coupled plasma mass spectrometer (ICP-MS) has been used in laboratories for many years. The majority of the improvements to the instrument have been done empirically through trial and error. A few fluid models have been made, which have given a general description of the flow through the mass spectrometer interface. However, due to long mean free path effects and other factors, it is very difficult to simulate the flow details well enough to predict how changing the interface design will change the formation of the ion beam. Towards this end, Spencer et al. developed FENIX, a direct simulation Monte Carlo algorithm capable of modeling this transitional flow through the mass spectrometer interface, the transitional flow from disorganized plasma to focused ion beam. Their previous work describes how FENIX simulates the neutral ion flow. While understanding the argon flow is essential to understanding the ICP-MS, the true goal is to improve its analyte detection capabilities. In this work, we develop a model for adding analyte to FENIX and compare it to previously collected experimental data. We also calculate how much ambipolar fields, plasma sheaths, and electron-ion recombination affect the ion beam formation. We find that behind the sampling interface there is no evidence of turbulent mixing. The behavior of the analyte seems to be described simply by convection and diffusion. Also, ambipolar field effects are small and do not significantly affect ion beam formation between the sampler and skimmer cones. We also find that the plasma sheath that forms around the sampling cone does not significantly affect the analyte flow downstream from the skimmer. However, it does thermally insulate the electrons from the sampling cone, which reduces ion-electron recombination. We also develop a model for electron-ion recombination. By comparing it to experimental data, we find that significant amounts of electron-ion recombination occurs just downstream from the sampling interface.

In the past few years, studies regarding new bio-based materials have led to an increased attention in the nanoscale product of cellulose, called nanocellulose. This biodegradable and renewable material has interesting physical, optical and thermal properties. The optical properties could be affected by tuning the nanostructure of the material, which makes it interesting for further investigation. The promising properties of nanocellulose can be useful in many different applications. The aim of this work was therefore to study the optical properties of nanocellulose, and to examine if the material is suitable for spectral design of camouflage or in passive cooling applications. The optical properties of a nanocellulose, specifically cellulose nanofiber (CNF), have been studied. Freestanding CNF films and CNF films deposited on glass substrates were made and characterized by spectroscopy, ellipsometry, BRDF measurements, and optical microscopy. The freestanding samples were examined with different CNF concentrations of 0.52% and 1.0%, and different thicknesses. The samples on glass substrates all had a concentration of 1.0% CNF, but with different amount deposited solution which was either drop or spin coated. The freestanding CNF samples show high transmission in the visual region and relatively high emissivity in the atmospheric windows. This implies that it can be used as an effective material for passive radiative cooling. A thicker sample could also be used to increase the emissivity in the atmospheric windows and improve the ability for passive cooling. The low reflectance, and high emissivity in the atmospheric windows can be promising for use in camouflage applications, according to earlier studies. However, the suitable properties are very dependent on the spectral response of the background. Additional measurements need to be performed and more specified scenarios are necessary to draw any further conclusions.

Wegen der zunehmenden Menge an LIBS-Daten von der Marsoberfläche sowie deren speziellen Herausforderungen bei der Analyse untersucht diese Arbeit, wie die Modellierung und Simulation von solchen LIBS-Spektren genutzt werden kann. Das Ziel ist es, Einblicke in die Eigenschaften von LIBS-Plasmen auf dem Mars zu erhalten und Modelle zu entwickeln, die bei der Analyse von realen Missionsdaten helfen können. Die Modellierung basiert sich auf einem stationären Plasma im lokalen thermischen Gleichgewicht (LTE). Das Plasma wird dabei in eine Reihe homogener Zonen unterteilt und Spektren werden mit dem Strahlungstransfer entlang einer eindimensionalen Sichtlinie durch diese Plasmazonen simuliert. Die Ergebnisse dieser Arbeit zeigen, dass auf LTE basierende Modelle gut auf LIBS-Spektren angewendet werden können, die unter Marsbedingungen gemessen wurden. Für zeitaufgelöste Daten kann die Anpassung eines Zwei-Zonen-Modells verwendet werden, um Einblicke in das Plasma zu erhalten und um die Elementkonzentrationen mit einer höheren Genauigkeit zu bestimmen, als es mit der Saha-Boltzmann-Methode möglich wäre. Allerdings sollten Nicht-Gleichgewichtseffekte in den frühesten und spätesten Phasen der Plasmalebensdauer berücksichtigt werden. Für zeitlich integrierte Spektren, wie sie bei aktuellen Marsmissionen gemessen werden, sind Anpassungen durch ein Zwei-Zonen-Modell aufgrund von zu langen Rechenzeiten nicht durchführbar. Stattdessen kann durch die Methode der spektralen Entmischung eine Überlagerung von Spektren unterschiedlicher Temperaturen und Dichten verwendet werden. Diese Methode ermöglicht keine direkten quantitativen Bestimmungen der Elementkonzentrationen, ist aber ein hervorragendes Werkzeug, um einen Überblick über die große Menge an Informationen zu erhalten, die in den Spektren enthalten sind. / Motivated by existing challenges in analysing LIBS spectra and the increasing quantity of Martian LIBS data, this thesis investigates the modelling and simulation of LIBS spectra for the application to LIBS data in Martian atmospheric conditions. This is done with the aim of providing insights into the characteristics of Martian LIBS plasmas as well as developing tools to assist the analysis of real mission data. The modelling of LIBS spectra is based on a stationary plasma in local thermal equilibrium (LTE). The plasma is then divided into a series of homogeneous zones and spectra are simulated using radiative transfer along a one-dimensional line-of-sight through the plasma zones. The results of this thesis show that spectral modelling based on LTE can be well applied to LIBS data in Martian atmospheric conditions. For time-resolved data, fits of a two-zone plasma model can be used to obtain insights into the plasma as well as improved concentration estimates compared to the Saha-Boltzmann plot method. However, attention to non-equilibrium effects should be given at the earliest and latest stages of the plasma lifetime. For time-integrated spectra, i.e. real mission data, fits of the two-zone model are not feasible due to too long computation times. Instead, a superposition of spectra of different temperatures and densities, i.e. the spectral unmixing method, can be used. Although not directly allowing for quantitative concentration estimates, the method is a great tool to overview the large amount of information contained in the spectra.