Dissertations / Theses on the topic 'Gaz radon'

Radon gas may be a major air quality hazard issue inside the home. Radon (222Rn) comes from the natural breakdown of radioactive uranium (238U) via radium (226Ra) in soil, rocks, and water. Radon and its progeny contribute more than 50% of the total radiation dose to the human population due to inhalation; it can result in severe and fatal lung disease. This investigation has determined the radon concentrations in seventy-seven domestic houses in a mountainous area of Hamadan in Iran which were monitored using track-etch detectors of type CR-39 exposed for three month periods. The arithmetic mean radon concentration in Hamadan buildings was determined to be 80 Bqm-3 and also an average indoor annual effective dose equivalent for the Hamadan city population was calculated as 1.5 mSv. Maximum radon concentrations were noted during the winter and spring season. In addition to this, 28 water wells were monitored by utilizing a Sarad Doseman detector at hourly intervals over extended periods. Radon measurements were also carried out in the nearby Alisadr show cave, using Solid State Nuclear Track etch Detectors (SSNTDs) during the winter and the spring periods. In the cave, the average annual effective geometric and arithmetic mean dose for guides was 28.1 and 34.2 mSv respectively. The dose received by visitors was very low. Hamadan city is built on alluvial fan deposits which are the source of the local water supply. The data from the wells shows that the groundwater in these alluvial deposits influences the flux of radon. The atmospheric radon concentration measurement in wells above the water surface ranged from 1,000 Bqm-3 to 36,600 Bqm-3. There is evidence that radon-rich ground waters play a significant role in the transport of radon through the alluvial fan system. There is evidence that the radon concentrations in homes in Hamadan are greatly influenced by the porous nature of the underlying geology and the movement of groundwater within the alluvial fan.

In an EPA/DOE meeting in the U.S. in 1986, concerns on quantifying radon availability and the indoor radon concentration were highlighted (Hopke 1986). This work addressed some of their recommendations in a study on radon levels in S.W. England. This thesis presents: i) investigations into the correlation between indoor and soil gas radon concentrations, by the acquisition of new data from S. W. England. ii) investigations into the influence of geology, meteorological variables, spatial and depth variation on the measured radon levels. iii) a propsed protocol for obtaining soil gas measurements, suitable for use as an indication of potential inddor radon concentrations in S.W. England. iv) a discussion of the applicability of existing prediction models and proposals for the parameters to be included in any models applied to S.W. England. Several geological faults in S.W. England were delineated using radon measurements. Jointing was found to create anomalously high levels of [sup]222 Rn in the soil gas. A previous theory on the movement of ground water in convection cells was found to be unsupported. A dependence of both indoor and soil gas radon concentrations on the local geology was observed. Granite produced the highest levels as expected, and the influence of its metamorphic aureole was clearly detected. The increased fracturing of the rock was found to increase radon concentrations. Significant differences in soil gas radon levels were measured between the various sedimentary rock types. The two factors that were identified as chiefly responsible for any perturbation of a soil gas concentration, associated with a particular geology, are its moisture content and the inhomogeneity of soil permeability. Only a very weak correlation was obtained between the overall [sup]222 Rn concentration in soil gas and inside the home. However, for high soil gas concentrations a stronger correlation with the indoor level was observed. Typically the soil gas concentration was between a factor of 10 and 1000 times greater than that indoors. Levels as low as 10 kBq m[sup]-3 in the soil could produce an indoor concentration above the Action Level of 200 Bq m[sup]-3, The magnitude of influence of the various controlling parameters prevented the construction of a simple algorithm to predict the indoor radon concentration from that in the soil gas. However, in some cases, factors were identified that increased the probability that a house was above the Action Level. For a soil gas concentration in excess of 100 kBq m[sup]-3, it was found that over 70% of homes were above the Action Level, if located above and/or constructed from granite.

<p>Measurements of radon (&sup2<br>&sup2<br>&sup2<br>Rn) concentration in soil gas are routinely used to locate geological fault zones. This study was undertaken to investigate the systematic effects that influence radon soil-gas measurements, in preparation for the first such fault zone measurements in South Africa.</p>

Thesis (M.Phil.)--City University of Hong Kong, 2006.<br>"Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Master of Philosophy" Includes bibliographical references (leaves 106-116)

Earthquakes are amongst the most destructive of natural phenomena and have been the subject of significant research effort over many decades, to predict the onset of seismic events. Electromagnetic emissions detected prior to earthquakes provide a potential data source for seismic predictions and research suggests that specific pre-seismic electromagnetic activity can be directly related to specific earthquakes although it is still an open issue as to the precise links between these electromagnetic emissions and subsequent earthquakes. In this research, findings of the long memory or the self-organization of several pre-earthquake MHz electromagnetic time-series provide significant outcomes regarding the earthquake prediction. It is also recognised that enhanced radon gas emission has an equally long history as being associated with seismic activity. In general, several anomalous soil radon emissions have been observed prior to earthquakes and this has been recorded all over the world. The abnormal soil radon exhalation from the interior of the earth has been associated with earthquakes and is considered as an important field of research. The research reported in this thesis compared and contrasted the merits of combining electromagnetic emission data and radon exhalation data as precursors of earthquakes with the aim of enhancing earthquake prediction methodology. The findings from the long-memory analysis of radon disturbances in the soil indicated a very significant issue: the radon disturbances in the soil prior to earthquakes exhibit similar behaviour as the MHz RF disturbances of general failure. So, the radon precursors and the MHz electromagnetic correspond to the same pre-earthquake phase. Geological explanations were proposed in view of the asperity model. Persistent and anti-persistent MHz anomalies were due to the micro-cracking of the heterogeneous medium of the earth's crust which may have led the system's evolution towards the global failure. Fractal methods have been used on historical data, to investigate MHz electromagnetic time-series spectra on emissions preceding major earthquakes over the period 2007 to 2014 and the characteristics of enhanced radon emissions have been studied over the period 2008 to 2015 for seismic events occurring in the Aegean Region. It has been found that both the electromagnetic emissions and the radon exhalation data exhibit similar fractal behaviour and are associated with impending seismic activity. Hence both phenomena are relevant to earthquake predictions and should both be employed in any systematic approach to this problem as the varying geological and geographic conditions under which earthquakes can occur, might preclude one or other data from being measurable. According to the several techniques applied in this thesis, all should be employed in sequential steps, albeit the power-law spectral fractal analysis is the most significant to trace long-memory patterns of 1/f processes as those of the processes of earthquakes.

The project has been concerned with the study of radon and other natural radionuclides in the U-238 decay series in the environment. The contribution made by radon and its daughter radionuclides to population radiation dose both in the air and in water supplies has been investigated. The natural radioactivity of the river water, stream water, sediments and freshwater mussels have been measured using a thick source alpha counting technique and γ-spectrometry (water samples were preconcentrated by manganese dioxide precipitation method). The ^226Ra activity ranged from 10-20 Bq m^-3 in the river and 4-30 Bq m^-3 in stream water. The highest values were found close to the source of the river where the water flowed through an area of igneous rocks. Such granite type rocks are enriched in uranium and thorium. Concentrations of radon and its daughters were measured, indoors and outdoors, using a grab sample technique. Outdoor concentrations were 10-30 Bq m^-3 depending on underlying rocks, meteorological condition (pressure, temperature, snow, rain), while indoor values ranged between 20 and 600 Bq m^-3 depending on radon input rate (source strength, ventilation rate and pressure inside the building). The relationship between the indoor ^222Rn concentration and ventilation rate was investigated. The radiation dose and the consequent risk due to inhalation of radon and its daughters were estimated. The annual effective dose equivalent ranged from 0.12 to 11 mSv. The radon concentrations in well waters were measured and were found to range between 3 and 76 Bq ℓ-1. This variation can be associated with different bedrock. A model predicting average indoor increments due to this source is presented and supported by a series of measurements made in the houses which were supplied by well water. The maximum annual effective dose equivalent from inhalation and ingestion was found to be 0.27 and 0.054 mSv respectively.

Magister Scientiae - MSc<br>The prospect of unconventional shale-gas development in the Karoo Basin (South Africa) has created the need to obtain baseline data on natural radioactivity in Karoo groundwaters. The Karoo Basin groundwater radiological baseline developed through this study could serve as a reference to research potential future radiological contamination effects due to hydraulic fracturing. The major naturally occurring radioactive material (NORM) studied was radon (222Rn), in particular in-water activity concentrations; however, supplementary radium (226Ra and 228Ra) in-water activity concentrations and uranium (238U) in-water concentrations measurements were also made. A total of 53 aquifers across three provinces were sampled for groundwater and measured, with three measurement series from 2014 to 2016. The aquifers were categorized as shallow, mixed, or deep source. The radon-in-water baseline of the Karoo Basin can be characterised by a minimum of 0.6 ± 0.9 Bq/L, a maximum of 183 ± 18 Bq/L and mean of 41 ± 5 Bq/L. The radon-in-water levels from shallow sources (with water temperature < 20 °C) were systematically higher (40 Bq/L) than for deep sources (with water temperature > 20 °C). The natural fluctuations in radon-in-water levels were predominantly associated with shallow aquifers compared to almost none observed in the deep sources. The uranium in-water baseline can be characterised by a minimum of below detection level, a maximum of 41 μg/L, and the mean of 5.10 ± 0.80 μg/L. Similar to radon-in-water levels, uranium in-water levels for shallow sources were systematically higher than for deep sources. The limited (six aquifers) radium (228Ra and 226Ra) in-water activity-concentration measurement results were very low, with a maximum of 0.008 Bq/L (226Ra) and 0.015 Bq/L (228Ra). The 228Ra/226Ra ratio baseline were characterised by a minimum of 0.93, a mean of 3.3 ± 1.3, and a maximum of 6.5. The radium isotopes’ activity concentration ratio is an isotopic tracer for hydraulic fracturing wastewater. Pollution and contamination (radiological), due to unconventional shale gas development, in water resources has been noticed in the Marcellus Basin (United States). Consequently, developing and improving continuous baseline monitoring are of importance to study the environmental radiological effect of hydraulic fracturing.

Les observations actuelles semblent soutenir la théorie selon laquelle l'onde de choc des restes de supernova accélère des électrons (représentant 1 % des rayons cosmiques) du milieu interstellaire jusqu'à des énergies de l'ordre de 10^15 eV. En revanche il n'y a pas encore de preuves solides que les restes de supernova accélèrent aussi des protons (composant majoritaire des rayons cosmiques). Les observations en rayons X de ces restes de supernova par le satellite XMM-Newton permettent d'apporter des informations cruciales sur les mécanismes d'accélération et sur cette population de particules accélérées. Cette thèse présente l'analyse en rayons X des restes de supernova RX J1713. 7-3946 et SN 1006 pour lesquels il a été démontré qu'ils accéléraient efficacement des électrons. Pour le premier objet, j'ai construit, grâce à de nouvelles observations XMM-Newton, la première mosaïque à haute résolution angulaire de la totalité du reste de supernova. J'ai ensuite comparé l'émission en rayons X et en rayons gamma de cet objet dans le but de comprendre la nature de l'émission gamma. Cette comparaison morphologique et spectrale m'a permis de discuter les deux origines possibles de ce rayonnement (émis par les électrons ou bien par les protons). Pour SN 1006, je me suis intéressé à la densité du milieu ambiant dans laquelle l'onde de choc se propage. Cette densité est un paramètre clé pour l'évolution hydrodynamique du reste de supernova et pour l'étude d'une future détection en rayon gamma. L'étude de l'émission en rayons X du gaz chauffé par l'onde de choc m'a permis de mieux estimer cette valeur de la densité jusqu'ici mal contrainte pour cet objet<br>The current observations seem to support the theory that the shock wave of supernova remnants accelerate electrons (representing 1 % of cosmic rays) of the interstellar medium up to energies of about 10^15 eV. However there is still no solid evidence that supernova remnants also accelerate protons (major component of cosmic rays). The X-ray observations of those supernova remnants with the satellite XMM-Newton can provide crucial information on the acceleration mechanisms and on this population of accelerated particles. This thesis presents the X-ray analysis of the supernova remnants RX J1713. 7-3946 and SN 1006 for which it has been shown that they accelerate electrons efficiently. As a result, these objects are very good targets to compare the theoretical models of acceleration to the observation. For the first object, I constructed through new XMM-Newton observations, the first high-angular resolution mosaic of the entire supernova remnant. I then compared the X- and gamma-ray emission of this object in order to understand the nature of the gamma-ray emission. This spectral and morphological comparison allowed me to discuss the two possible origins of the gamma-ray radiation (issued by electrons or by protons). For SN 1006, I studied the density of the ambient medium in which the shock wave propagates. This density is a key parameter for the hydrodynamical evolution of the remnant and for studying a future gamma-ray emission. The study of X-ray emission of the gas heated by the shock wave allowed me to better estimate of the value of the density so far poorly constrained for this object

Philosophiae Doctor - PhD<br>In Africa as well as in the world, South Africa plays an important role in the mining industry which dates back almost 120 years. Mining activities in South Africa mainly take place in Gauteng Province. Every year millions of tons of rocks are taken from underground, milled and processed to extract gold. Uranium is one of the minerals which is mined as a by-product of gold. The uranium bearing tailings are then placed on large dumps which are usually one or more kilometres in diameter in the environment. There are approximately 250 gold mine tailings dumps covering a total area of about 7000 ha. These gold mine tailings dumps contain considerable amounts of radium (226Ra) and have therefore been identified as large sources of radon (222Rn). Radon release from these tailings dumps pose health concerns for the surrounding communities. This study reports on the 222Rn soil-gas concentrations and exhalations measurements which were conducted at a non-operational mine dump (Kloof) which belongs to Carletonville Gold Field, Witwatersrand, South Africa. Radon soil-gas concentrations were measured using a continuous radon monitor (the Durridge RAD7). The radon soil gas concentration levels were measured at depths starting from 30 cm below ground/air interface up to 110 cm at intervals of 20 cm. These radon soil-gas measurements were performed at five different spots on the mine dump. The concentrations recorded ranged from to kBq.m-3. Furthermore, thirty four soil samples were taken from these spots for laboratory-based measurement. The soil samples were collected in the depth range 0-30 cm and measured using the low-background Hyper Pure Germanium (HPGe) -ray detector available at the Environmental Radioactivity Laboratory (ERL), iThemba LABS, Western Cape Province. The weighted average activity concentrations in the soils samples were Bq.kg-1, Bq.kg-1 and Bq.kg-1 for 238U, 40K and 232Th, respectively. 1 26 23 472 7 308 5 2551 18 The activity concentration of 40K and the decay series of 238U and 232Th for the top 30 cm of the accessible parts of the mine dump were measured using the MEDUSA (Multi-Element Detector for Underwater Sediment Activity) -ray detection system which was mounted on the front of a 44 vehicle, 0.6 m off the ground. The spectra acquired by the MEDUSA system were analysed and the activity concentrations were extracted using the Full Spectrum Analysis approach. The average activity concentrations obtained were 25975 Bq.kg-1 for 40K, 30940 Bq.kg-1 for 238U series and 185Bq.kg-1 for 232Th series for 2002 survey while 26075 Bq.kg-1 for 40K, 31040 Bq.kg-1 for 238U series and 20 5 Bq.kg-1 for 232Th series were recorded for 2010 survey. Moreover, a novel technique by means of the MEDUSA -ray detection system was utilised to map radon exhalation from the Kloof mine dump. In this technique the 214Bi concentration in the top 30 cm of the dump, which is used as a proxy for the 238U or 226Ra concentration, is measured even though there is not secular equilibrium between the radium and bismuth because radon has escaped. The actual activity concentrations of 40K and 226Ra are obtained from soil samples which were collected, sealed and measured in the laboratory settings after attaining secular equilibrium since radon gas does not escape. By comparing the ratios of the activity concentrations of the 214Bi obtained in the field using the MEDUSA -ray detector system to the activity concentrations of the 214Bi obtained in the laboratory using the HPGe -ray detector system yields a reasonable radon exhalation for a particular location in the mine dump. In this case it is assumed that the 40K and 232Th series activity concentrations are not or hardly affected by radon exhalation. By applying this new technique an average normalised radon flux of 0.120.02 and 0.120.02 Bq.m-2.s-1 were obtained for 2002 and 2010 surveys, respectively. The electrets and the IAEA standard formula were also utilised to calculated radon fluxes yielding 0.060.02 and 0.120.02 Bq.m-2.s-1 respectively.

Dans un diagramme d'etat de type zenz, le regime d'ecoulement discontinu gaz-solide se caracterise par de grandes fluctuations de pression et de faibles vitesses superficielles de la phase porteuse. Il se situe entre les regimes de saltation, les lits de particules mobiles et represente par consequent une famille d'ecoulements de type transitoire. De nombreux travaux ont ete consacres a la caracterisation fondamentale de ce regime en conduite horizontale et verticale, mais le cas des singularites reste a ce jour peu etudie. Ainsi, l'objectif des travaux presentes dans ce memoire est la mise en evidence du role des changements de direction sur l'organisation de l'ecoulement dans les circuits et la mise en uvre des hypotheses necessaires a la modelisation des efforts appliques aux coudes, au passage de l'ecoulement. Pour ce faire une premiere partie est consacree a la revue generale bibliographique dans laquelle on s'attache a mettre en evidence les proprietes principales caracterisant l'ecoulement discontinu gaz-solide en conduite droite ainsi que l'influence de la presence de changements de direction sur les ecoulements diphasiques. Une seconde partie apparait a la fois comme une analyse qualitative et quantitative du comportement de l'ecoulement au voisinage d'un changement de direction a rayon de courbure nul, place dans une configuration geometrique horizontale-verticale et en utilisant des techniques de visualisation. Cette partie de l'etude permet de formuler certaines des hypotheses necessaires a la modelisation des efforts provoques par le passage de l'ecoulement dans la singularite. Toutefois, devant les limites des techniques de visualisation, une derniere partie est consacree au developpement et a la validation d'une instrumentation specifique formant un systeme de detection et de reconnaissance des formes principales de l'ecoulement discontinu gaz-solide. Cette methode appliquee en conduite droite horizontale au voisinage de changements de direction a rayon de courbure constant, permet de mettre en evidence les principales proprietes de l'ecoulement qui sont confrontees aux resultats bibliographiques connus et aux resultats obtenus grace a l'instrumentation d'un site reel de grande longueur fonctionnant en regime discontinu et pour lequel les effets de singularites peuvent etre negliges. Enfin, une synthese est proposee pour mettre en evidence les modeles adaptables aux problemes poses par le passage de l'ecoulement dans les changements de direction et la contribution apportee par le systeme de detection est analysee.

La arquitectura subterránea ha dado cobijo y protegido al hombre desde muchos siglos atrás, evolucionando tipológicamente y perdurando con el paso del tiempo hasta la actualidad. La presente necesidad de incidir en propuestas bioclimáticas de bajo coste hace indispensable el estudio de esta arquitectura más primitiva puesto que, además de formar parte de la vivencia colectiva del habitar humano, es un referente en cuanto al aprovechamiento de los condicionantes naturales mediante propuestas sencillas que se benefician de la inercia térmica del terreno. El objetivo de la presente tesis doctoral es identificar, analizar y poner de manifiesto la evolución tipológica de la vivienda excavada a nivel mundial y su adaptación, en cada caso, a la geografía regional tanto como solución arquitectónica individual como sistema de agrupación urbanístico. Investigación que se concreta en el estudio pormenorizado de los asentamientos de casas-cueva existentes hoy en día en el municipio de Crevillente en Alicante (España) mostrando, en primer lugar, la benevolencia de la solución subterránea como espacio habitable mediante un análisis del origen, la condiciones históricas y las tipologías de estas viviendas excavadas; y, en segundo lugar, mostrando la problemática derivada de la influencia del terreno donde se asientan mediante un estudio sobre las condiciones de calidad ambiental de los espacios excavados en relación al gas radiactivo radón.

A presente tese se baseia no estudo das rochas ornamentais e de revestimento em relação aos seus aspectos de alterabilidade que irá influenciar diretamente no aumento da adição do gás radioativo radônio no interior de um ambiente com o passar do tempo de uso, fato devido as interações com o meio de onde é instalado a rocha, como exemplo da sua manutenção e limpeza, que implicará no seu padrão estético e na qualidade do ar do ambiente interior. Temas como a qualidade do ar interior relacionado a qualidade de vida do usuário, a radioatividade natural, o perigo do gás radiotivo radônio no interior do ambiente e as rochas ornamentais como composição e uso na arquitetura são apresentados para embasamento da Tese e auxiliando no entendimento dos ensaios realizados. Para isso, cinco rochas ornamentais foram escolhidas e realizados ensaios de alterabilidade química, ensaios tecnológicos de caraterização e ensaios de caracterização radiométrica a fim de prever o comportamento de uma dada rocha em seu ambiente ao ser aplicado na arquitetura. O ataque do ácido HCl nas rochas diminuiu sua resistência e aumentou a quantidade de radônio exalado relacionado diretamente ao aumento direto na porosidade, aumentando também a eficiência de exalação da rocha. O ataque do álcali KOH apesar de diminuir a resistência da rocha, interferiu na porosidade e diminuindo assim a quantidade de radônio exalado em alguns casos. Isso demonstra que mesmo conhecendo o material e a sua contribuição na adição do Rn no interior do ambiente, com o passar do tempo a rocha irá aumentar sua exalação quando não conservadas podendo aumentar o nível de radônio acumulado no ambiente. Com isso, a tese realça a importância de conhecer o material que irá compor o interior do ambiente afim de prevenir futuros danos à saúde da edificação e dos usuários, facilitando assim o entendimento desses materiais e como interfere na qualidade do ambiente construído.<br>This thesis is based on the study of dimension stone in relation to aspects of changeability which will directly influence the increased addition of radon radioactive gas within an environment over time of use, a fact due to interactions with the environment where it is installed rock, as an example of its maintenance and cleaning, which will result in its aesthetic standard and quality of indoor air environment. Topics such as the quality of the related indoor air to the user\'s quality of life, natural radioactivity, the danger of radiotivo radon gas into the atmosphere and dimension stone as composition and use in architecture are presented to foundation this Thesis and aiding in the understanding of tests. For this, five ornamental stones were chosen and performed chemical tests changeability, technological characterization of assays and radiometric characterization tests to predict the behavior of a given rock in your environment to be applied in architecture. The attack of the HCl acid in the rocks decreased its strength and increased the amount of exhaled radon related directly to the direct increase in porosity, also increasing exhalation efficiency of the rock. The attack KOH alkali spite of reducing the resistance of the rock, and interfere with the porosity thereby decreasing the amount of radon vented in some cases. This shows that even knowing the material and its contribution to the addition of Rn into the environment, with the passage of time the rock will increase your exhalation when not maintained can increase the level of accumulated radon in the environment. Thus, the thesis highlights the importance of knowing the material that will form the inside of the environment in order to prevent further damage to the health of the building and users, thus facilitating the understanding of these materials and how it interferes in the quality of the built environment.

Les techniques de réalisation des reconstitutions prothétiques en Odontologie ont été profondément modifiées par l'avènement et le développement de la Conception et Fabrication Assistées par Ordinateur (CFAO). La qualité d'une prothèse fixée est caractérisée par la bonne adaptation de celle-ci sur son pilier dentaire afin d'assurer la longévité de l'assemblage dentoprothétique. L'évaluation de l'adaptation marginale et interne par l'analyse du hiatus est un élément essentiel du contrôle de leur qualité. Cependant, la littérature rapporte de nombreuses méthodes d'évaluation de l'adaptation compromettant d'autant la comparaison pertinente et la validité des valeurs de ces hiatus. Le but de cette thèse est la mise au point d'une méthode de mesure du hiatus dento-prothétique qui bénéficierait de qualités métrologiques suffisantes pour rendre pertinente la comparaison et l'analyse des différentes chaînes de mesure accessibles sur le marché. L'étude des besoins métrologiques de l'évaluation du hiatus et des méthodes de mesure recensés dans la littérature a permis de retenir une chaîne de mesure, dénommée "Triple scan". Grâce aux résultats obtenus au cours de ces travaux, cette méthode semble pertinente pour évaluer tridimensionnellement le hiatus dento-prothétique. Elle a été comparée à d'autres méthodes documentées et validées dans la littérature telles que la méthode des répliques en élastomère et celle utilisant la microtomographie Rx. Les résultats obtenus conduisent à conclure que la méthode "Triple scan" serait plus appropriée dans les expertises approfondies sur les performances des systèmes de CFAO en termes de fidélité aux paramètres fixés et de reproductibilité de leur fabrication<br>Techniques for producing prosthetic reconstitutions in odontology have undergone radical change due to the emergence and development of Computer Aided Design and Manufacturing (CAD/CAM). The quality of a fixed prosthesis is characterised by its correct adaptation on its dental abutment to ensure the longevity of the dento-prosthetic assembly. Evaluating the marginal and internal adaptation by analysing the gap is essential for controlling its quality. However, the numerous methods reported in the literature make it difficult to perform a pertinent and valid analysis of the values of these gaps. The purpose of this thesis is the development of a method of measuring the dento-prosthetic gap endowed with sufficient metrological capacities to ensure the pertinence of comparisons and analyses of the different measurement systems available on the market. The study of metrological requirements for evaluating the gap and the measurement methods identified in the literature has led to the selection of measurement system known as II Triple scan". The results obtained during these works demonstrated the pertinence of this method for the 3-dimensional evaluation of the dento­-prosthetic gap. It was compared to other methods documented and validated in the literature such as the elastomer replica method and that using X-ray microtomography. The results obtained lead to the conclusion that the "Triple scan" is the most appropriate for in-depth analysis of the performances of CAD/CAM systems in terms of fidelity to the parameters determined and the reproducibility of fabrication

L’entrée des polluants gazeux du sol (Radon, COV,…) dans les environnements intérieurs peut occasionner des risques sanitaires significatifs. Or les modèles d’évaluation de risques sanitaires liés à ces polluants gazeux du sol contiennent beaucoup d’incertitudes qui peuvent conduire à une mauvaise appréciation des risques. Dans un premier temps, cette thèse contribue à l’amélioration des modèles d’évaluation des risques. Dans un second temps, elle propose le développement d’un modèle de dimensionnement des Systèmes de Dépressurisation du Sol (SDS) passifs utilisés pour protéger les bâtiments des pollutions gazeuses venant du sol. L’amélioration des modèles a porté sur la prise en compte des principaux phénomènes de convection et diffusion à l’interface entre le sol et le bâtiment, en tenant compte des différentes typologies de soubassement. La première contribution porte sur le développement de modèles analytiques fournissant les débits d’air dus à la convection à travers le sol pour différents types de soubassement : dallage indépendant, dalle portée, vide sanitaire et cave. Les bâtiments avec des murs enterrés et les soubassements avec un lit de gravier sous le plancher bas sont également traités. Une méthodologie permettant la prise en compte de la fissuration et des points singuliers du plancher bas est aussi proposée. La deuxième contribution porte sur la prise en compte du transfert couplé des polluants des sols par convection et diffusion auprès des fondations. Une étude numérique a permis une meilleure compréhension du comportement des polluants à l’interface sol/bâtiment. Sur la base de cette compréhension, des lois semi-empiriques d’estimation des flux d’entrée de polluant dans les bâtiments sont proposées. Les différents modèles développés ont été validés numériquement avec un modèle CFD et expérimentalement avec des données issues de la littérature. La confrontation de ces modèles avec ceux existants a montré les améliorations apportées. L’impact de la typologie du soubassement sur le transfert de polluants gazeux des sols a été constaté. Une première application des modèles est illustrée par leur intégration dans un code de simulation thermo-aéraulique multizone afin de pouvoir étudier l’impact de ces polluants sur la qualité de l’air intérieur. Ce travail se termine par le développement d’un modèle de dimensionnement des Systèmes de Dépression du Sol (SDS) passifs. Ce modèle aéraulique de dimensionnement des SDS a été validé par des mesures effectuées au CSTB dans une maison expérimentale. Les premières applications du modèle de dimensionnement portent notamment sur l’impact de la météorologie (vent et tirage thermique) sur le fonctionnement du SDS passif et sur l’impact des stratégies de ventilation du bâtiment sur le fonctionnement du SDS passif. On voit ainsi l’intérêt de l’utilisation d’un tel modèle pour tester l’aptitude de ce système de protection des bâtiments dans des situations environnementales données<br>Transfer of soil gas pollutants (Radon, VOC) into buildings can cause significant health risks. However, analytical models used today to estimate health risks associated with these pollutants contain many uncertainties which can lead to poor risk assessment. Initially, the main objective of this thesis is to contribute to the improvement of these models for risk assessment. Secondly, we propose the development of air flow model for passive Sub slab Depressurization Systems (SDS) design used to protect buildings. The improvement of models focused on the inclusion of the main phenomena of convection and diffusion at building/soil interface, taking into account different types of building substructures. The first improvement concerns the assessment of convection phenomenon through the development of analytical models to quantify air flow rates entering through many kinds of building substructures: floating slab, bearing slab, crawl space and basement. Buildings with buried walls and substructures with a sub slab gravel layer are also treated. A methodology taking into account the presence of cracks, holes and singular leakages of the slab is also proposed. The second improvement of the models is the inclusion of coupled transfer of convection and diffusion near foundations. A numerical study allowed a better understanding of the behavior of pollutants at soil / building interface. Based on this understanding, semi-empirical laws for estimating soil gas pollutants entry rate into buildings are proposed. The various models developed have been validated numerically using a CFD model and experimentally with data from the literature when available. The impact of building substructure on pollutant transfer has been highlighted. A first application of the model is illustrated by their integration into a multizone simulation code to study the impact of these transfers on indoor air quality. Finally, the work ends with the development of a model for designing passive sub slab depressurization systems. The design model developed is validated with in situ experimental data. Preliminary applications using this model focused at first on the impact of meteorological conditions (stack effect, wind) on the sub slab system running. At second, the impact of ventilation strategies on sub slab depressurization performance is studied. Thus, we see the potential interest of this model to test the effective running of passive sub slab depressurization systems in given configuration

This thesis is a study of naturally occurring radioactive materials (NORM) activity concentration, gamma dose rate and radon (222Rn) exhalation from the waste streams of large-scale onshore petroleum operations. Types of activities covered included; sludge recovery from separation tanks, sludge farming, NORM storage, scaling in oil tubulars, scaling in gas production and sedimentation in produced water evaporation ponds. Field work was conducted in the arid desert terrain of an operational oil exploration and production region in the Sultanate of Oman. The main radionuclides found were 226Ra and 210Pb (238U - series), 228Ra and 228Th (232Th - series), and 227Ac (235U - series), along with 40K. All activity concentrations were higher than the ambient soil level and varied over several orders of magnitude. The range of gamma dose rates at a 1 m height above ground for the farm treated sludge had a range of 0.06 0.43 µSv h 1, and an average close to the ambient soil mean of 0.086 ± 0.014 µSv h 1, whereas the untreated sludge gamma dose rates had a range of 0.07 1.78 µSv h 1, and a mean of 0.456 ± 0.303 µSv h 1. The geometric mean of ambient soil 222Rn exhalation rate for area surrounding the sludge was mBq m 2 s 1. Radon exhalation rates reported in oil waste products were all higher than the ambient soil value and varied over three orders of magnitude. This study resulted in some unique findings including: (i) detection of radiotoxic 227Ac in the oil scales and sludge, (ii) need of a new empirical relation between petroleum sludge activity concentrations and gamma dose rates, and (iii) assessment of exhalation of 222Rn from oil sludge. Additionally the study investigated a method to determine oil scale and sludge age by the use of inherent behaviour of radionuclides as 228Ra:226Ra and 228Th:228Ra activity ratios.

In intense laser – cluster interaction, the experimental results show a strong energetic coupling between radiation and matter. We have measured absolute x – ray yields and charge state distributions under well control conditions as a function of physical parameters governing the interaction; namely laser intensity, pulse duration, wavelength or polarization state of the laser light, the size and the species of the clusters (Ar, Kr, Xe). We have highlighted, for the first time, an intensity threshold in the x – ray production very low (~ 2.1014 W/cm2 for a pulse duration of 300 fs) which can results from an effect of the dynamical polarisation of clusters in an intense electric field. A weak dependence with the wavelength (400 nm / 800 nm) on the absolute x – ray yields has been found. Moreover, we have observed a saturation of the x – ray emission probability below a critical cluster size.

Ce travail de thèse est une contribution à l'étude du rayonnement UVX cohérent produit par génération des harmoniques d'ordre élevé d'une impulsion laser intense focalisée dans un gaz rare. <br />Dans une première partie, nous présentons une étude approfondie de l'optimisation du flux harmonique produit soit dans une fibre creuse soit dans un jet. Dans chacun des cas, nous déterminons les facteurs limitant l'émission : accord de phase, absorption, ionisation, défocalisation. La comparaison des profils d'émission avec les simulations démontre le rôle crucial de la phase du dipôle atomique pour la génération dans une fibre. L'optimisation dans un jet conduit à des efficacités de conversion allant de 10-5 à 50nm (1010 ph/imp) à 10-7 à 15nm (5.107 ph/imp). <br />Dans une deuxième partie, nous étudions la focalisation du rayonnement harmonique par une lentille de Bragg-Fresnel, qui permet une focalisation efficace hors axe, sans aberration. Nous mesurons pour l'harmonique 39 une tache focale de l'ordre de 2µm. Compte tenu du flux élevé et de la courte durée (femtoseconde) des harmoniques, des éclairements élevés dans l'UVX peuvent être atteints.<br />Finalement, nous présentons les premières expériences de diagnostic de plasma par interférométrie UVX utilisant le rayonnement harmonique. Une technique originale est développée à partir de 2 sources harmoniques mutuellement cohérentes séparées spatialement. L'analogue temporel de l'interférométrie spatiale, qui utilise 2 impulsions harmoniques séparées en temps, est également démontré. Cette interférométrie fréquentielle a permis le premier diagnostic UVX de l'évolution temporelle d'un plasma avec une résolution femtoseconde. Une extension du schéma de 2 à 4 impulsions permet de mesurer avec une sensibilité extrême un déphasage équivalent à une demi-période harmonique, soit des écarts temporels à l'échelle attoseconde (1as=10-18s).

Des anomalies géophysiques ont été observées avant des tremblements de terre. Ces signaux précurseurs ne sont pas systématiques et en général leur relation avec la sismicité ne peut pas être confirmée. Afin d'étudier si une relaton existe entre ces signaux géophysiques et les contraintes tectoniques au cours du cycle sismique, nous allons étudier le comportement géophysique d 'un milieu naturel en réponse à des sollicitations mécaniques. Le site choisi est le site de Sur-Frêtes en Savoie au voisinage des lacs artificiels de Roselend et La Gittaz. Les variations annuelles de niveau des lacs de plus de 50 m d'amplitude constituent le moteur de déformation cyclique sur le milieu. La réponse géophysique du site est étudiée principalement en termes de potentiel électrique, d'émanation de gaz radon, de niveau de puits et de déformation. Des variations de potentiel électrique ont été associées aux variations de niveau des lacs, avec un coefficient de couplage compris entre 0.6 et 4.2 mV /m d'eau. Nous montrons qu'elles sont produites par un mécanisme d'électrofiltration compatible avec les mesures en laboratoire réalisées sur des échantillons du site. Cette observation démontre que le phénomène d'électrofiltration est actif à l'échelle naturelle. De plus, cette expérience a mis en évidence des variations transitoires de potentiel électrique de l 'ordre de 20 mV associées à des pics d'émanation de gaz radon d'amplitude 5 à 40 fois supérieure au bruit de fond. Ces événements, dont la durée est comprise entre 1 et 10 semaines, sont corrélés à des déformations transitoires mesurées par inclinométrie, qui interviennent lors d'augmentation du taux de chargement du milieu. Des mesures en puits réalisées en fin d'expérience lors de la vidange décennale du lac de Roselend montrent que ces événements sont aussi associés à des surpressions de fluide de l'ordre de 1 bar. Les fluides jouent donc un rôle déterminant dans la génération des potentiels électriques et des pics de gaz radon. Nous proposons que ces signaux sont liés aux surpressions de fluide qui produisent localement une augmentation de la connectivité du milieu entrainant des circulations de fluide transitoires. Ces observations montrent la sensibilité des propriétés de transport de la roche aux variations du taux de déformation. Nous discutons sur la base de ces mécanismes la possibilité d'observer des précurseurs dans le cas du chevauchement actif Himalayen . Nos résultats suggèrent qu'une variation présismique du taux de déformation de la croûte pourrait produire des signaux géophysiques mesurables à l'aplomb de l 'extrémité de la zone sismogénique bloquée.

The relative contributions of bedrock geology, radiometric uranium, till permeability and surficial geology were assessed as predictors of radon in indoor air in the Halifax Regional Municipality (HRM), NS, Canada. Bedrock geology and radiometric uranium were statistically significant predictors (14.4%) of indoor radon, based on available indoor radon data. Permeability was not among the predictors, which was surprising given its importance in past studies. In a follow up field analogue study done in laboratory columns, the permeability and diffusivity, as gas transport mechanisms, were found, as suspected, to be important drivers on the concentrations of radon-222 detected. Given the variable thickness of till in the HRM (< 0.5 m to > 3 m), these experiments highlighted the significance of till thickness, composition, and permeability in predicting the radioactive radon-222 potential.

The region that served as the basis for this work is characterized by the abundance of different types of granite. In some places, the predominance of certain uraniferous minerals, the existence of faults and mines may even be responsible for the existence of very high levels of natural radioactivity, especially with regard to radon. The main motivation for studying the effects of population exposure to radon is based on the fact that this gas, radioactive, odorless, colorless and tasteless, has been recognized since 1988 by the World Health Organization as the 2nd leading cause of death from lung cancer for the general population, after tobacco. Approximately 80 % of the background radiation to which populations are exposed daily comes from natural sources, which can include radioactive materials of natural origin, NORM, present in the earth’s crust, in food, in some drinks and, including certain building materials. In December 2018, a new legislation was approved in Portugal, DL no 108/2018, transposed from European Directive 59/2013 / Euratom, which establishes uniform basic safety standards for the protection of the health of people subject to exposure professional, public and medical professionals against the dangers arising from ionizing radiation. The radon isotope, 222Rn, which results from radio disintegration, 226Ra, and one of the uranium decay products, 238U, is the main radionuclide of radiological interest in terms human health. This radioactive gas is spontaneously released from some rocks and, being slightly denser than air, it tends to accumulate in ground areas of closed spaces and is responsible for the majority of the radiation dose received by the population. Some traditional solutions have been applied in order to solve the problem, however, after the detection of the radon they do not use the data collected in order to combat and prevent the gas from accumulating in the interior spaces. In Portugal it is a problem that has not been given due attention. Taking into account the possible harmful effects of radon on the population, the main motivation of this work was the development of an IoT (Internet of Things) system with the objective of detecting, mitigating and predicting the levels of radon gas inside homes. Based on this assumption, it will be possible to create a healthier environment that will reduce health risks in closed environments. To achieve this goal, an IoT system was developed, consisting of a radon sensor and an automated switch, which allows the fans installed and / or switched off to be installed in the residence, as well as predicting and making decisions in the face of a potentially dangerous situation based on the records provided by the sensors. This system also includes a web application that allows the user to consult the statistical data related to the average radon concentration. On the other hand, through the web application, it is possible to not only activate the fans manually, but also to edit the limit at which the fans are activated. This system was tested in a real context and, therefore, it is possible to compare two radon gas mitigation methods and identify which would be the most effective. Once the method to be used was determined and after stabilizing the data obtained by the sensor, the results obtained by the system were analyzed, which allowed us to conclude that the system reduced considerably the levels of radon in the house. On average, there was a 93% reduction in the concentration of radon gas. This result demonstrates that the implementation of the system was successful and allows us to conclude that it can be applied on a larger scale.<br>A região que serviu de base para a realização deste trabalho é caracterizada pela abundância de diversos tipos de granitos. Em alguns locais, a predominância de determinados minerais uraníferos, a existência de falhas e minas podem, inclusivamente, ser responsáveis pela existência de níveis de radioatividade natural bastante elevados, especialmente no que se refere ao radão. A principal motivação para se estudar os efeitos da exposição das populações ao radão baseia-se no facto de este gás, radioativo, inodoro, incolor e insípido, ser desde 1988, reconhecido pela Organização Mundial de Saúde como a 2a causa de morte por cancro pulmonar para a população geral, depois do tabaco. Cerca de 80% da radiação de fundo a que as populações estão, diariamente, expostas tem origem em fontes naturais nas quais se podem incluir os materiais radioativos de origem natural, NORM, presentes na crosta terrestre, na comida, em algumas bebidas e, inclusivamente, em certos materiais de construção. Em dezembro de 2018, foi aprovada, em Portugal, uma nova legislação, o DL no 108/2018, transposta da Diretiva Europeia 59/2013/Euratom, que estabelece normas de segurança de base uniformes para a proteção da saúde de pessoas sujeitas a exposição profissional, da população e médica contra os perigos resultantes das radiações ionizantes. O isótopo radão, 222Rn, que resulta da desintegração do radio, 226Ra, e um dos produtos de decaimento do urânio, 238U, é o principal radionuclídeo com interesse radiológico em termos de saúde humana. Este gás radioativo liberta-se, espontaneamente de algumas rochas e, sendo ligeiramente mais denso do que o ar, tem tendência a acumular-se em zonas térreas de espaços fechados e é responsável pela maioria da dose de radiação recebida pela população. Algumas soluções tradicionais têm sido aplicadas de modo a resolver o problema, no entanto, depois da deteção do radão estas não usam os dados recolhidos de forma a combater e a prevenir que o gás se acumule nos espaços interiores. Em Portugal é um problema que não tem a devida atenção. Tendo em conta os possíveis efeitos nocivos do radão na população, a principal motivação deste trabalho consistiu no desenvolvimento de um sistema IoT (Internet das Coisas) com o objetivo de detetar, mitigar e prever os níveis do gás radão no interior das habitações. Partindo deste pressuposto, será possível criar um ambiente mais saudável que permitirá reduzir os riscos para a saúde em ambientes fechados. Para se concretizar este objetivo foi desenvolvido um sistema IoT que consiste em um sensor de radão e um interruptor automatizado, que permite ligar e/ou desligar os ventiladores instalados na residência, bem como prever e tomar decisões perante uma situação potencialmente perigosa com base nos registos fornecidos pelos sensores. Este sistema integra também uma aplicação web que permite ao utilizador consultar os dados estatísticos relativos à concentração média de radão. Por outro lado, através da aplicação web, é possível não só ativar os ventiladores manualmente, como também editar o limite em que os ventiladores são accionados. Este sistema foi testado num contexto real e, por isso, possível comparar dois métodos de mitigação do gás radão e identificar qual seria o mais eficaz. Uma vez determinado o método a ser utilizado e após a estabilização dos dados obtidos pelo sensor, analisaram-se os resultados obtidos pelo sistema que permitiram concluir que o sistema reduziu consideravelmente os níveis de radão na habitação. Foi verificada, em média, uma redução de cerca de 93% na concentração de gás radão. Este resultado demonstra que a implementação do sistema foi um sucesso e permite concluir que poderá ser aplicado numa escala maior.