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Etude du dépôt de radionucléides par les gouttelettes de brouillards et de nuages sur les végétaux à partir d'expérimentations in situ / Deposition of radionuclides on plants by fog and cloud dropletsTav, Jackie 12 October 2017 (has links)
Pour les besoins du refroidissement de leurs réacteurs, les CNPE1 sont placés à proximité immédiate de cours d’eau ou du littoral. Ils sont de ce fait exposés à des bancs de brouillards, en particulier à l’automne et au cours de l’hiver. Or les modèles opérationnels de dispersion atmosphérique/dépôt, utilisés pour simuler la contamination radioactive de l’environnement à la suite d’un accident nucléaire, considèrent uniquement les dépôts par temps sec et ceux par temps de pluie. Faut-il tenir compte de la présence des brouillards comme terme additionnel de dépôt de radionucléides en cas d’accident nucléaire ? Pour répondre à cette question, une étude expérimentale a été conduite sur plusieurs sites exposés aux brouillards ou aux nuages (principalement la plateforme d’observation atmosphérique de l’ANDRA à Houdelaincourt ainsi que la station de recherche atmosphérique de l’OPGC/CNRS2 au sommet du Puy de Dôme et la plateforme d’étude atmosphérique SIRTA3 de l’IPSL4 à Palaiseau). La collecte d’eau de brouillard et la mesure des quantités d’eau déposées sous forme de gouttelettes sur différents types de végétaux, ont été réalisées respectivement grâce à collecteurs à fils et des pesées de précision. En mesurant le contenu en eau liquide dans l’air ainsi que la masse d’eau déposé sur les plantes, il a été possible de calculer des vitesses de dépôt des gouttelettes de brouillard pouvant atteindre plusieurs dizaines de cm.s-1 dans le cas d’un brouillard composé de grosses gouttelettes (diamètre médian volumique moyen de 20 µm). Ces vitesses élevées mettent en évidence l’importance des processus gravitationnels mais aussi turbulents notamment dans le cadre du dépôt sur des végétaux à structure foliaire tridimensionnelle comme les conifères. L’effet d’auto-écrantage lié à une densité de biomasse foliaire élevée a également été quantifié. Les concentrations en radionucléides à l’état de traces ont montré que l’eau de brouillard pouvait être jusqu’à 20 fois plus concentrée que l’eau de pluie, du fait de la dilution par condensation de vapeur d’eau sur les gouttelettes au cours de leur grossissement. Les mesures des masses d’eau déposées par les brouillards et de la concentration en radionucléides dans les gouttelettes sur le site d’Houdelaincourt, permettent d’estimer ces dépôts habituellement qualifiés d’occultes car trop faibles pour être quantifiés par des pluviomètres ou des radars météorologiques. Sur l’ensemble d’une saison de brouillard, le dépôt occulte de radionucléides a représenté jusqu’à 25% des dépôts par temps secs et par temps de pluie. En cas de rejet accidentel, la présence de brouillard pourrait contribuer à hauteur de 14% du dépôt par temps sec. Ces résultats mettent en évidence la nécessité de prendre en compte ce processus de dépôt pour mieux quantifier les retombées radioactives sur des territoires en contact avec des brouillards ou des nuages (en ce qui concerne les sites d’altitudes), en particulier en situation post-accidentelle. Un schéma simple de type dépôt sec, considérant le diamètre médian des gouttelettes dérivé de la visibilité, permet à minima de mieux simuler le processus de dépôt par sédimentation des gouttelettes. Ces travaux restent à compléter pour quantifier la contribution de la turbulence induite par l’écoulement de l’air au voisinage des obstacles comme des végétaux de grandes tailles et incorporer un schéma spécifique dans les modèles de dépôt. / For the purpose of cooling off their reactors, nuclear power plants are located near rivers, ponds or in coastal areas. In temperate regions and during fall and winter, they are frequently exposed to fogs. Operational models of atmospheric dispersion and deposition used to estimate radioactive contamination of the environment after a nuclear accident, consider dry deposition and wet deposition by rain. Should we take into account the deposition by fog droplets as an additional process in term of deposition? To answer this question, an experimental study has been setup on several sites often exposed to fogs or clouds. Fogwater collection and measurement of fogwater deposited on plants were realized with string collectors and precision balances, respectively. Different plant types were used for this study: small conifers, cabbage, grass plus a bare soil as a reference deposition surface. By measuring the liquid water content (LWC) and the mass of water deposited on plants, fog droplet deposition velocities can be calculated. In the case of fog composed mainly of big droplets (mean median volume diameter of 20 µm), deposition velocities of these droplets can reach several tens cm.s-1. These high deposition velocities highlight the fact that gravitational but also turbulent processes are both contributing to the deposition on plants especially with a tri-dimensional structure such as conifers. The edge effect linked to a strong density of trees has also been identified and quantified during our experiments. The radionuclides found in trace amounts in fogwater showed that fogwater could be up to twenty times more concentrated in radionuclides than rain water. It is due to the activity dilution during the condensation phase of the droplets, when the droplets are growing. Based on measurements of the mass of water deposited by fog and concentrations of radionuclides in fog droplets on the site of Houdelaincourt, occult deposition that cannot be quantify by rain gauges or meteorological radar can be estimated. Over a whole season of fog, occult deposition can represent up to 25% of the total deposition (dry and wet by rain) of radionuclides. In case of an accidental release, fog could contribute to 14% of the total deposition if no rain event occurs. Those results highlight the fact that fog deposition should be considered to better quantify radioactive fallouts in areas embedded by fog (or clouds for high altitude sites), particularly in post-accident situation. A simple model of dry deposition to simulate the droplets deposition by sedimentation can be developed, using the median diameter of droplets derived from the visibility. This work still needs to be completed to quantify the turbulence contribution induced by the air flow near obstacles such as large plants and to implement a specific scheme into deposition model.
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Uppfångning och kvarhållning av 134Cs och 85Sr i olika växtutvecklingsstadier / Interception and retention of 134Cs and 85Sr at different growth stagesMårtensson, Anna-Lisa January 2012 (has links)
Emissions of radionuclides to the atmosphere can lead to wet deposition on plants in theevent of rainfall. An increased level of radioactivity in the plants may occur due tointerception and retention of the radionuclides. If the content of the plants is above thethreshold limit value, entire yields may have to be destroyed. In order to preventcontamination or decrease the content countermeasures can be taken. The impact of thebiomass, leaf area index (LAI) and growth stage of the plant on the interception andretention is important to know in order to decide which countermeasures to use.Weather may also be an important factor. In this work the interception and retention of 134Cs and 85Sr by spring wheat, ley andspring oil-seed rape was studied. The impact of the biomass, LAI and growth stage ofthe plant and precipitation after deposition was also studied. The work was conducted asa field study with plots of the size 1 x 1 m. The plants were wet deposited with 134Cs and 85Sr by using a rain simulator. A total activity of 40 kBq/m2 for both radionuclideswas deposited on each plot. Depositions were performed during four different growthstages and the plants were sampled approximately four hours, one and five days afterdeposition. Activities of the dried plant samples were measured with a High PurityGermanium (HPGe) detector. Finally the interception fraction and the retention factorwere calculated. The study showed that the interception fraction was highest for the third growth stagefor both wheat and oil-seed rape; dough ripeness for wheat and ripening for oil-seedrape. Ley, which was harvested after two depositions, had the highest interceptionfraction at the second growth stage, flowering. Oil-seed rape and ley seemed to have aslightly higher interception fraction for 85Sr at all growth stages. There was a positiverelationship for the biomass and interception fraction, for the LAI and interceptionfraction the relationship wasn’t significant. The retention showed a weak trend ofdecreasing with time, with the decrease being largest during the first day after theinterception. However, the standard deviation was large and consequently the values uncertain. / Utsläpp av radionuklider till atmosfären kan genom regn leda till att de våtdeponeras påväxter. Radionukliderna kan då fångas upp av växterna och hållas kvar vilket kanresultera i förhöjda halter av radioaktivitet hos växterna. Om detta leder till attgränsvärden överskrids kan kassering av växter som används vid livsmedelsproduktionvara nödvändig. Motåtgärder kan vidtas för att undvika kontaminering eller minskahalterna. För att veta vilka motåtgärder som ska användas är det viktigt att veta hurväxtens biomassa, bladyteindex (LAI), utvecklingsstadium samt väderförhållandenpåverkar uppfångningen och kvarhållningen. I detta arbete undersöktes uppfångningen och kvarhållningen av 134Cs och 85Sr hosvårvete, vall och vårraps. Inverkan av växtens biomassa, LAI och utvecklingsstadiumsamt nederbörd efter deponering undersöktes också. Arbetet genomfördes som ettfältförsök med försöksrutor med storleken 1 x 1 m. Växterna våtdeponerades med 134Csoch 85Sr med hjälp av en regnsimulator. En total aktivitet på 40 kBq/m2 för bådaradionukliderna deponerades per försöksruta. Deponeringar skedde under fyra olikaväxtutvecklingsstadier och växtprover togs ungefär fyra timmar efter deponering samtett och fem dygn senare. Aktiviteten hos de torkade växtproverna mättes med en HighPurity Germanium (HPGe) detektor. Därefter beräknades uppfångningsfraktioner ochkvarhållningsfaktorer. Försöket visade att uppfångningsfraktionen var störst vid det tredjeväxtutvecklingsstadiet för både vete och raps; degmognad för vete och fröutveckling förraps. Vallen, som slogs av efter två deponeringar, uppvisade störst uppfångningsfraktionvid andra växtutvecklingsstadiet, blomning. Hos raps och vall verkadeuppfångningsfraktionen för 85Sr vara något högre vid samtliga växtutvecklingsstadier.För biomassan och uppfångningsfraktionen fanns ett positivt samband, för LAI ochuppfångningsfraktionen var sambandet inte signifikant. Kvarhållningen visade en svagtrend att minska med tiden, minskningen var störst under det första dygnet efteruppfångningen. Dock var standardavvikelsen stor och värden därmed osäkra.
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Por um Brasil transparente: estudo sobre os efeitos da Lei De Acesso a Informação nos sítios das secretarias da fazenda dos estados e do distrito federalSantos, Gabriela Vieira dos 30 August 2016 (has links)
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GABRIELA VIEIRA - dissertação.pdf: 1989464 bytes, checksum: 7308a380120fbfe82c90fb4bee23652c (MD5) / Esta pesquisa tem como objetivo analisar a situação dos sítios das secretarias da fazenda nos 26 Estados Brasileiros e no Distrito Federal, após a regulamentação da Lei de Acesso à Informação Pública (Lei nº 12.527, de 18 de novembro de 2011). Para a realização dessa pesquisa foram percorridas três etapas. A primeira é o estudo de elementos como sociedade, estado, informação, gestão pública e transparência para construção do arcabouço teórico, relevante para o entendimento do desenvolvimento da pesquisa. A segunda é a coleta de dados para averiguação das conformidades com base em um roteiro de observação estruturada com os requisitos da Lei de acesso, detalhadas na metodologia. A terceira compreende a interpretação dos dados encontrados. Esta pesquisa se situa nesta relação de construção entre o papel do Estado e da Sociedade, a importância da informação e da transparência na Gestão Pública, cujos resultados demonstraram que as Secretarias da Fazenda estão fazendo esforços para cumprir a lei, mas ainda encontram grandes dificuldades para adaptar-se a essa nova realidade cultural. Dos 27 sítios analisados, apenas três não atingiram nem metade da pontuação total atribuída aos requisitos avaliados. Para explicar este cenário, buscou-se verificar possíveis variáveis que alteram os resultados desta pesquisa, como o desenvolvimento da infraestrutura das telecomunicações, o crescimento das TICS, o nível de alfabetização digital dos usuários brasileiros, o Índice de Desenvolvimento Humano (IDH) e o Produto Interno Bruto (PIB). / ABSTRACT- This research aims to analyze the situation of the websites of the Treasury Office in the 26 Brazilian states and the Federal District, after the regulation of the Access to Public Information Law (Law No. 12,527, of 18 November 2011). To carry out this research, three stages were followed. The first is the study of elements such as society, state, information, public administration and transparency, to build the theoretical framework, relevant for understanding the development of research. The second is the collection of data for investigation of compliance based on an observation structured script with the requirements of the access law, detailed in the methodology. The third comprises the interpretation of the data found. This research lies in this relationship building between the role of the state and society, the importance of information and transparency in public management, the results showed that the Secretariats of Finance are making efforts to comply with the law, but still find it very difficult to adapt to this new cultural reality. Of the 27 sítios analyzed, only 3 did not reach even half of the total score assigned to the assessed requirements. To explain this scenario, we sought to identify possible variables that alter the results of this research, the development of telecommunications infrastructure, the growth of ICT, the level of digital literacy of Brazilian users, the Human Development Index (HDI) and Gross Domestic product (GDP).
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Inversion des formes d'ondes LiDAR pour l'estimation des caractéristiques des cultures et des forêts par des techniques probabilistes et variationnelles / Lidar full waveform inversion for crop and forest caracteristics estimation by probabilistic and variational techniquesBen Hmida, Sahar 21 December 2018 (has links)
L'utilisation du LiDAR en télédétection permet une description précise de l'architecture du couvert végétal. L'objet de cette thèse est le développement des approches d'inversion de mesures LiDAR à l'aide d'une modélisation physique et statistique du signal dans le but d'estimer des propriétés biophysiques de cultures dominantes (blé, maïs) du Sud-Ouest de la France et d'un couvert forestier en Chine. Le travail a tout d'abord porté sur l'estimation du LAI et la hauteur des cultures par inversion de formes d'onde LiDAR à faible empreinte. Une base de données de simulations de formes d'onde réalistes des cultures est réalisée à l'aide du modèle de transfert radiatif (MTR) DART. L'inversion consiste à utiliser la technique de table de correspondance qui consiste à chercher la simulation la plus proche de l'observation réelle. Le travail a ensuite porté sur l'estimation du profil de LAI des arbres de la forêt. Une approche variationnelle d'estimation du profil de LAI par inversion de formes d'ondes est proposée. Elle repose sur un MTR simplifié et une technique de lissage du profil de LAI s'appuyant sur les chaines de Markov. La formulation bayésienne du problème, nous amène à une fonction de coût non-linéaire. Elle est minimisée à l'aide d'une nouvelle technique de gradient multi-échelle. Les approches développées montrent bien leurs performances en les appliquant sur des données réelles de cultures (maïs et blé) et de milieu forestier. / The use of LiDAR in remote sensing allows a precise description of the vegetation cover architecture. The aim of this thesis is the development of LiDAR data inversion approaches using physical and statistical signal modeling in order to estimate the biophysical properties of dominant crops (wheat, maize) of the South-West of France and a forest cover in China. The work firstly focused on estimating LAI and crop height by small footprint LiDAR waveforms inversion. A realistic crop waveform simulations database is performed using the Radiative Transfer Model (MTR) DART. The inversion consists in using the Look up Table technique which consists of looking for the closest simulation to the actual observation. The second inversion approach focused on LAI profile estimation of the forest trees. A variational approach to estimate LAI by waveform inversion is proposed. It relies on a simplified MTR and LAI profile smoothing technique based on Markov chains. The Bayesian formulation of the problem leads us to a non-linear cost function. It is minimized using a new multi-scale gradient technique. The developed approaches show clearly their performance by applying them to real crop data (corn and wheat) and forest.
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Modelling soil temperature and carbon storage changes for Swedish boreal forestsSvensson, Magnus January 2004 (has links)
<p>With the use of a process-orientated ecosystem model andmeasurements conducted at different Swedish coniferous forestsites, abiotic and biotic interactions between tree and soilwere identified and related to governing factors. Two differentmodelling approaches to describe soil temperatures at two sitesincluding hydrological transects were tested (I). The approachin which both canopy and soil were considered proved to be amore flexible tool to describe soil temperatures, especiallyduring snow-free winter periods. Five sites along a climatetransect covering Sweden were used to describe soil carbon poolchanges during an 80-year period simulation (II). The dynamicmodelling approach, with a feedback between abiotic and bioticsub-models, was successful in describing simplified patterns offorest stand dynamics and furthermore in differentiatingbetween climate and nitrogen availability factors. The largereffect of nitrogen availability compared to climate on soilcarbon pool changes was clearly shown.</p><p><b>Keywords:</b>SPAC; soil surface energy balance; Norwayspruce; canopy; LAI; climate; nitrogen; CoupModel</p>
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Couleurs et "couleurs de rhétorique" dans les formes brèves des XIIe et XIIIe sièclesAllard, Chantal January 2009 (has links)
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.
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Seasonal and Spatial Variation in Leaf Area Index, Litter Production, and Light Levels in Myrica Cerifera,Shrub Thickets Across a Barrier Island ChronsequenceBrantley, Steven T. 01 January 2005 (has links)
Leaf area index (LAI), litter production and understory light levels of Myrica cergera shrub thickets were assessed on Hog Island, Virginia to quantify spatial and seasonal variations in leaf area and light attenuation among four thickets representing a successional chronosequence and compare methods of estimating LA1 in shrub- dominated systems. Seasonal LA1 estimates were made seven times throughout the year with a portable integrating radiometer (Li-Cor LAI-2000) and three times by measurement of photosynthetically active radiation (PAR) and use of the Beer-Larnbert law. Leaf area index was also estimated through leaf litter collection and use of allometric relationships between stem diameter and leaf area. The oldest of the four thickets had the lowest LA1 and litter production throughout the year. Peak LA1 measurements with the portable integrating radiometer ranged from 2.0 ± 0.2 to 4.0 ± 0.3 for the oldest and youngest thickets, respectively which appear to be substantial underestimates of the actual values. According to annual litterfall, LA1 ranged from 4.1 ± 0.5 for the oldest thicket to 10.2 ± 0.4 for a 20 year old thicket. Leaf area index varied from 6.4 ± 0.2 for the oldest thicket to 1 1.4 ± 2.1 for the 40 year old thicket according to the allometric relationships, which may overestimate LA1 in stands with many large stems. The high light attenuation by the shrub canopy and heavy litterfall may contribute to the low diversity within thicket canopies by inhibiting germination and growth of other species. The study demonstrates that these low diversity shrub thickets have a higher LA1 and litter production, and thus higher potential for primary productivity, than many temperate forested systems and that stand age may be the major determinant of productivity.
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“We Require Regeneration Not Rebirth”: Cyborg Regeneration in Feminist Science and Speculative FictionHulan, Michelle 18 April 2019 (has links)
This thesis examines a recent trend in contemporary science and speculative fiction to produce new and/or alternative iterations of reproduction that are not limited by biology, gender, or species. Through Donna Haraway’s notion of “cyborg regeneration” and recent critical and theoretical revisionings of this concept, I investigate this trend in three key texts: Jeanette Winterson’s The Stone Gods, Nalo Hopkinson’s Midnight Robber, and Larissa Lai’s long poem “rachel” from her book of poetry Automaton Biographies. Each of these authors offers representations of reproduction that counter gender stereotypes and essentialism and produce new cyborg maternal or explicitly non-maternal figures unbound to patriarchal models of repronormativity and colonialist constructions of the mother. By portraying these nonunitary maternal figures and/or non-reproductive bodies, I argue that these sf texts present new forms of procreation that further feminist conversations about gender, the body, the limits of the human, future populations, and desire.
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Protokol pro sběr biofyzikálních parametrů vegetace v terénu / Field protocol for in-situ biophysical parameters collectionŠudová, Markéta January 2019 (has links)
Field protocol for in-situ biophysical parameters collection Abstract The main aim of diploma thesis is to design a unified protocol intended for collecting of in-situ biophysical parameters of vegetation based on an up-to-now published literature as well as on my own experimental measuring. The key for measuring of high- quality field data, that are suitable for a subsequent validation of remote sensing products, is an implementation of unified rules as well as all the phases of data collecting, a recommended preparation before the very measuring, the choice of a sampling scheme and a processing of measured data. Based on an accessible literature the current methods of LAI data measuring were evaluated and the basic protocol parameters were defined. For designing of a proper parameterization of this protocol an experimental field measurement was carried out. A determination of a suitable number of partial measurements within ESU is given by a relationship between the number of partial measurements and MSE value. The sampling schemes stated in a literature as well as my own designed sampling schemes are subsequently tested in order to determine a suitable sampling scheme. Based on achieved MSE values the most suitable sampling scheme that was later verified in field measuring was evaluated. Based on a field...
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'I Just Wanted You to Know': War Testifies through the CameraGurses, Seyda Aylin 16 October 2009 (has links)
This work is a textual analysis of selected documentary films whose common theme is the inevitable discrepancy between the realities of the Vietnam and the 2003 Iraq War from the perspectives of the veterans and soldiers, and the assumed reality that is constructed in the media. It is at this point that the inextricable link between documentary cinema and reality proved fundamental to the developing discourse of the entire study ahead. Since the manner in which the world is both transformed and depicted strongly depends upon the tools available to the director, the technological innovations and the emergence of portable cameras, by granting the documentary filmmaker flexibility, irreversibly solidified this link between non-fictional act of narrating and its approach and proximity to reality. Four works that are picked among a large body of documentary films are Winter Soldier (1972) directed by Winter Collective; Gunner Palace (2004) directed by Petra Epperlein and Michael Tucker; Full Battle Rattle (2008) directed by Tony Gerber and Jesse Moss and finally Standard Operating Procedure (2008) directed by Errol Morris. Even though the films are historically ordered, this study's concern is to be systematic thematically than chronologically. In the course of these analyses, discussions of notions like reality and truth, the relations of the makers of the films, the camera and editing process to the subjects of the films, will naturally emerge, as will issues related to the political and social roles of documentary cinema.
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