Dissertations / Theses on the topic 'Leaf seal'

Advanced rotating shaft seals have the potential to significantly increase the efficiency and performance of steam and gas turbines. Two such seals, brush and leaf seals, rely on the use of thousands of flexible filaments to close clearances between rotating components and their static casings. The current life of the components is poor compared to the rest of the gas turbine, limiting the seals' deployment, particularly in the jet engine at high temperature and pressure. Poor understanding of the seal installation response to frictional heat generated at the point of filament-rotor contact during operation has limited the ability to predict engine closures and hence seal behaviour and life. The resulting temperature rises may compromise the mechanical integrity of the engine rotor in extremis leading to a shaft failure. This thesis considers the heat transfer mechanisms that govern frictional heating, of both the fluid and solid components in the vicinity of such seals, characterising the process both experimentally and using numerical models. Through the identification of key features of the heat transfer a simple numerical methodology is shown to predict the thermal behaviour of the seal installation sufficiently accurately for engine design purposes. A low order heat transfer model, using a simple electrical analogy for heat transfer is used to investigate frictional heat generation. When contact occurs between the rotor surface and the seal filaments, mechanical energy is dissipated as heat at the interface. This is conducted into the rotor and the seal filaments in proportions that depend on the heat transfer characteristics of both contacting bodies (thermal resistances). To calculate the heat partition ratio and the resulting contact temperature, the thermal resistances of both rotor and seal need to be known. To that end, a new test facility, the Seal Static Thermal Test Facility (SSTTF), is developed. This is first used to study the convective heat transfer occurring in the vicinity of the seal; heat transfer coefficients based on appropriate, scalable, gas reference temperatures are reported. Importantly the results show a larger area on the rotor surface affected by the presence of the seal than was assumed by previous workers. The test rig is further modified to generate heating in a static test rig equivalent to the frictional heating at the filament tips. The test rig allows the contact temperature between rotor and seal, a critical previously unknown parameter to be measured in a well-conditioned environment. The presence of many thousands of vanishingly small flow passages in filament seals makes their explicit modelling unfeasible for engine design purposes. Thus the results from the experimental campaign are used to develop a simple computational fluid dynamic model of the seal, including empirically derived frictional heating, and seal porosity models, to achieve similar leakage and surface heat transfer to the rotor as was seen in the static experiments. The low order CFD methodology presented in the thesis is finally employed to model the transient operation of a brush seal under engine representative rotor surface speeds and differential pressures. Experimental data were generated in the Oxford Engine Seal Test Facility for a typical brush seal rubbing against a high growth rotor. These experiments were modelled using CFD and finite element analysis using parameters derived from static tests for the porous modelling of the seal leakage. Comparison of results shows that, without further tuning, the thermal behaviour is captured well with a moderate conservative overestimation of rotor heating with increased differential pressure across the seal allowing the strategy to be used as an engine design tool.

Threshold leak sizes and leak rates were calculated for a number of liquid food products exhibiting a wide range of surface tension and viscosity values. From this data, one can see that mathematically, under typical pressure differentials generated in food packages (less than or equal to ±34.5 kPa), a leak will never start through a 2 μm defect. The calculated leak rates were compared to calculated evaporation rates. The evaporation rate exceeds the leak rate at lower sized microholes (2, and 5 μm diameter) under typical pressure differentials found in food packages. If the liquid, typically aqueous in food products, is evaporating off faster than the leak itself, then there will be solids left behind that could effectively plug the leak.

The critical leak size is the size micro-defect that allows microbial penetration into the package. The critical leak size of air-filled defects was found to be 7 μm at all pressures tested. This size is considerably important to food packagers because this is when sterility of the package is lost. Previous leak studies have shown that the critical leak size for liquid-filled defects coincide with the threshold leak size and pressure. If this is in fact true, then air-filled defects should exhibit a larger critical leak size than the liquid-filled defects. In this study, air-filled defects were examined. A bioaerosol exposure chamber was used to test micro-defects, nickel microtubes of known diameters 2, 5, 7, 10, 20, and 50 μm hydraulic diameters, against pressure differentials of 0, -6.9, -13.8, and -34.5 kPa.
Master of Science

This research involved the study of sediment cores from Loch Etive, Loch Long, Loch Goil and Loch Fyne with the aims of investigating the geochemistry of natural, and manmade radionuclides and heavy metals within the sea loch environment. The main aims of the research were to determine accumulation rates and the extent of mixing within these sediments and to assess the fluxes, sources and temporal variations in input of pollutant heavy metals to these environments. In recent years it has been suggested that Pb is mobile in sea loch sediments which questions the validity of applying ²¹⁰Pb dating in this environment. This has important implications with respect to interpreting sediment cores to assess temporal trends of pollutant inputs and investigating the rates of physical and biogeochemical processes that are taking place in the coastal environment. Hence, one of the aims of this research was to determine whether Pb was mobile in these sediments. The ²⁰⁶Pb/²⁰⁷Pb isotope ratio can potentially be used to determine the extent of pollutant Pb input from leaded petrol to the environment and a further objective of the work was to investigate the isotopic signature of pollutant Pb in the sediment. Concentration of ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra, ²²⁸Th, ²³⁸U, ¹³⁷Cs, ¹³⁴Cs and ²⁴¹Am in the sediments were analysed using gamm a spectroscopy and the heavy metals, Pb, Zn and Cu were determined using X-ray Fluorescence. Stable Pb isotope ratios were determined using Inductively coupled plasma Mass spectrometry. The results obtained indicated that Pb is not subject to diagenetic mobility in these sediments and that ²¹⁰Pb profiles can be used to determine sedimentation rates for most of the sediment cores. lt was not possible to determine accumulation rates for the two cores from Loch Fyne by ²¹⁰Pb dating, and in this case the sedimentation rate was assessed by correlating the maximum concentration of ¹³⁷Cs in the sediments with the maximum ¹³⁷Cs discharge from Sellafield, BNFL's reprocessing plant located on the Cumbrian coast. The flux of ²¹⁰Pb to the lochs varied significantly suggesting that there has been sediment focusing of fine and/or organic rich material to the deeper sites, resulting in an enhanced flux of ²¹⁰Pb to these sediments. Sellafield waste radionuclides also provided useful chronologies by relating sediment maximum concentrations to maxima in the discharges. ¹³⁷Cs was observed to be subject to diffusive movement, invalidating the use of its total depth of penetration as a chronological indicator. The temporal trends of pollutant metal input agreed well with known historical trends and the Pb isotope profiles indicated that the onset of deposition from pollutant Pb from petrol occurred in the late 1920's. The maximum input of Pb from petrol peaked in the early 1980's and since then there has been a decrease in this input. The two sea lochs which were closest to the industrial centre of Glasgow exhibited a large anthropogenic pollutant input, confirming that these sediments have been highly perturbed by human activities, either directly as a result of sludge dumping or due to changes in land use (eg. road construction, deforestation, etc.) in the catchment. All the sea lochs reflected a change in the supply of material to the sediments over the last eighty years, indicating that increased anthropogenic activity has had an effect on these environments.

Les sceaux de plomb sont des artefacts relativement inconnus mais très importants comme sources d’information sur les textiles et leur consommation aux XVIIe et XVIIIe siècles. Ces étiquettes en plomb souvent attachées aux textiles ont servi comme indicateurs de qualité, de possession et de paiement des impôts sur ces textiles et autres biens commerciaux. Trouvés sur plusieurs sites archéologiques en Amérique du Nord, ces sceaux sont des indicateurs des origines éuropéennes des textiles ainsi que des réseaux marchands nécessaires pour les transporter vers la Nouvelle-France, un espace colonial fort dépendant de la métropole. Cette étude vise à découvrir de nouveaux détails sur les formes de consommation textile uniques de trois sites différents par leur localisation, leurs fonctions et leur population en utilisant les sceaux de plomb qui s’y trouvent. Les sceaux de trois sites français de l’époque coloniale seront examinés; le fort Saint-Joseph (Niles, MI), fort Ticonderoga (à Ticonderoga, NY, aussi connu sur le nom de fort Carillon) et la forteresse de Louisbourg (Louisbourg, NÉ).
Lead seals are relatively unknown artifacts, but are important as sources of information concerning textiles and their consumption in the seventeeth and eighteenth centuries. These lead tags were often attached to textiles and were proof of quality, ownership, and payment of taxes on textiles and other commercial goods. Found at many archaeological sites in North America, these seals are indicators of the European origins of imported textiles as well as merchant networks needed in order to transport them to New France, a colonial territory that was very dependent on the metropole. This study aims to discover new details concerning the unique consumption patterns present as three sites with different functions, locations, and populations, using the lead seals found at these sites. Seals from three French sites from the colonial period will be examined; Fort St. Joseph (Niles, MI), Fort Ticonderoga (Ticonderoga, NY, also known as Fort Carillon), and Fortress Louisbourg (Louisbourg, NS).

Patagonian toothfish (Dissostichus eleginoides) or "Chilean sea bass" support a valuable and controversial fishery, but the life history is little known and longevity estimates range from ~20 to more than 40 or 50 yr. In this study, lead-radium dating provided validated age estimates from juveniles to older adults, supporting the use of otoliths as accurate indicators of age. The oldest age groups were near 30 yr, which provided support for age estimates exceeding 40 or 50 yr from grow zone counts in otolith sections. Hence, scale reading, which rarely exceeds 20 years, has the potential for age underestimation. Lead-radium dating revealed what may be minor differences in age interpretation between two facilities and findings may provide an age-validated opportunity for the CCAMLR Otolith Network to reassess otolith interpretations. Orange roughy (Hoplostethus atlanticus) support a major deep-sea fishery and stock assessments often depend on age analyses, but lifespan estimates range from ~20 to over 100 yr and validation of growth zone counts remained unresolved. An early application of lead-radium dating supported centenarian ages, but the findings were met with disbelief and some studies have attempted to discredit the technique and the long lifespan. In this study, an improved lead-radium dating technique used smaller samples than previously possible and circumvented assumptions that were previously necessary. Lead-radium dating of otolith cores, the first few years of growth, provided ratios that correlated well with the ingrowth curve. This provided robust support for age estimates from otolith thin sections. Use of radiometric ages as independent age estimates indicated the fish in the oldest group were at least 93 yr. Lead-radium dating has validated a centenarian lifespan for orange roughy. To date, radium-226 has been measured in otoliths of 39 fish species ranging from the northern Pacific and Atlantic Oceans to the Southern Ocean. In total, 367 reliable radium-226 measurements were made in 36 studies since the first lead-radium dating study on fish in 1982. The activity of radium-226 measurements ranged over 3 orders of magnitude (<0.001 to >1.0 dpm.g⁻¹). An analysis revealed ontogenetic differences in radium-226 uptake that may be attributed to changes in habitat or diet. Radiometric age from otolith core studies was used to describe a radium-226 uptake time-series for some species, which revealed interesting patterns over long periods. This synopsis provides information on the uptake of radium-226 to otoliths from an environmental perspective, which can be used as a basis for future studies.

This diploma project deals with the production line in the selected company. The theoretical part is dealing with lean production, followed by the company description and description of the production line itself. The diploma project looks at the production line from a variety of perspectives and looks for the most appropriate points to optimize. The most important aspects are the efficiency of production and ergonomics. After finding critical points, different solutions are proposed and they are further elaborated, evaluated and the most appropriate one is recommended.

Purpose The purpose of the study was to determine the level of agreement between OCR regional directors, SEA directors and LEA directors on the effectiveness of mediation in resolving special education complaints. The specific problem was to determine the major factors contributing to the effectiveness of mediation as an approach to conflict resolution in special education. Methods and procedures Two instruments were developed to collect data. Prior to administration to five OCR directors, 20 SEA directors and 65 LEA directors, the instruments were piloted on a group which included state consultants, LEA coordinators, LEA directors and a legal assistant. Four research questions were answered using descriptive and inferential statistics. A frequency distribution, along with percentages of data, was used to indicate the status of mediation as related to the mediator, reductions of hearings and hearing issues resolved. The chi-square test of significance was used to test the significance of data reported for large and small school systems. Results Mediation is used at the federal level and by a large percentage of local school systems. A small percentage of the SEA directors reported that mediation is a requirement of local school systems. There was disparity in responses of SEA and LEA directors on the length of time mediation has been required. Although both SEA and LEA directors reported a reduction in hearing, the LEA directors were more inclined to attribute the reduction to mediations. The issues of identification, evaluation, placement and related services can be resolved through mediation. The primary handicaps of learning disabilities, behavior disorders, and mentally handicapped appeared most frequently in mediations. A significant difference, in favor of large school systems, was indicated relative to the use of mediation. No significant difference was apparent between large and small school systems relative to the development of guidelines and the requirement of mediation. Conclusions The federal agency of OCR, state education agencies and school systems have made some efforts to include some form of mediation as part of their appeals process. The variables of issues and types of handicaps, while important for influencing the request for mediation, do not appear to be contributing factors for mediation effectiveness. Limited documentation was found at federal, state and local levels. Therefore, generalizations drawn from the study should be applied cautiously.

Ces onze dernières années ont vu apparaitre les pérovskites organiques inorganiques hybrides (HOIPs) comme un passionnant domaine de recherche pour leur application potentielle dans les technologies du photovoltaïque (PV) en raison de leurs exceptionnelles propriétés optoélectroniques et de leur facilité de mise en oeuvre. Cependant, les matériaux HOIPs ont plusieurs inconvénients dont leur manque de stabilité en conditions opérationnelles. Améliorer celle-ci est l'un des plus grands défis à relever avant commercialisation. La formule générale est (A1,A2,A3,A4)Pb(X1,X2)3, où les sites A occupés par une distribution de 1 à 4 cations métalliques/organiques et les sites X par celle d’anions halogénures. Les défauts lacunaires natifs sont considérés comme une cause possible de dégradation des cellules solaires HOIPs. L'objectif de ce travail est de comprendre le rôle des défauts dans la stabilité à long terme des matériaux PV HOIPs. A cette fin, des défauts primaires ont été introduits de manière contrôlée par irradiation avec des électrons de haute énergie (1MeV) dans des lots de couches et cellules solaires (SCs) à base de divers composés HOIPs. Il s'agit notamment du prototype PV HOIPs, MAPbI3 (A1PbX13), et de nouveaux composés mixtes d’halogénures à triple ou quadruple cations, (CsMAFA)Pb(I1-xBrx)3 (A3PbX23) ou (GACsMAFA)Pb(I1-yBry)3 (A4PbX23). Les couches sont fabriquées selon la même procédure que les couches actives SCs et, ensuite, traitées dans des conditions similaires. Pour A1PbX13/A3PbX23, la structure SC est de type p-i-n avec des couches organiques pour le transport des trous et des électrons (HTL/ETL). Les couches sont déposées sur le substrat verre/ITO/HTL (PEDOT:PSS) sans ou avec couche supérieure ETL (PCBM). Pour A4PbX23, la structure SC est de type n-i-p avec des couches ETL inorganiques (TiO2) et HTL organiques (Spiro-OMeTAD). Les couches sont directement déposées sur du verre.La spectroscopie d'annihilation de positons donne une évidence directe de l'existence de défauts lacunaires natifs et induits par irradiation dans chaque composé. Les spectres d’absorbance en fonction de l’énergie montrent que le vieillissement naturel et après irradiation génère différentes populations de défauts dans chaque composé. De plus, celles-ci pour A1PbX13 et A3PbX23 diffèrent selon l'absence ou la présence de la couche supérieure ETL. Les populations de défauts évoluent pendant au moins 3 mois. Le vieillissement modifie (i) la bande interdite, (ii) les queues de bande de conduction/valence et (iii) l'absorption optique via des niveaux électroniques profonds. Les effets d’illumination sous laser varient aussi en fonction du vieillissement. L’asymétrie des pics de photoluminescence (PL) dans chaque composé sous illumination laser continue reflète une superposition de raies d’émission gaussiennes à énergie, FWHM et hauteur évoluant avec le temps d'illumination. Les transitions d'émission impliquent des niveaux électroniques localisés peu profonds dans A3PbX23/A4PbX23 et résonnants dans A1PbX13. De tels effets durent au moins 3 mois dans A4PbX23. Ces niveaux électroniques sont attribués à des populations de défauts spécifiquement induits par illumination. Le vieillissement naturel et après irradiation donne des spectres PL à décroissance temporelle résolue en une ou deux exponentielles. Le nombre et la durée de vie sont fortement influencés par l’irradiation initiale et la composition. Une amélioration frappante du fonctionnement PV pour le type SC p-i-n est induite par le vieillissement dû à l'irradiation. Le rendement quantique externe et les performances PVs ont des valeurs plus élevées pour l’état irradié que de référence durant 6 à 12 mois de vieillissement. Cela prouve que l'ingénierie des défauts par irradiation d'électrons à haute énergie a le potentiel de fournir des voies de traitement innovantes pour améliorer la stabilité à long terme des performances photovoltaïques HOIPs
During the last eleven years, Hybrid Organic Inorganic Perovskites (HOIPs) materials have emerged as an exciting topic of research for potential application in solar cell technologies due to their outstanding optoelectronic properties and processing advantages. However, HOIPs materials suffer from several drawbacks with, in peculiar, their lack of stability under operational conditions (light, bias, environment…). To improve this stability is one of the biggest challenges to be addressed before commercialization. The general formula for HOIPs is (A1,A2,A3,A4)Pb(X1,X2)3, where the A sites can be occupied by a distribution of 1 to 4 metallic/organic cations and X sites with halide anions. The role of native vacancy defects has been questioned as a possible cause for HOIPs solar cells degradation. The aim of this work is to understand the defect role in long term stability of HOIPs materials for photovoltaics. For this reason, primary defects were introduced in a controlled way via high energy electron irradiation (1MeV) in sets of layers and solar cells (SCs) fabricated using various HOIPs compounds. Those include the photovoltaic HOIPs prototype, MAPbI3 (A1PbX13), and emergent triple or quadruple cation mixed halide HOIPs, (CsMAFA)Pb(I1-xBrx)3 (A3PbX23) or (GACsMAFA)Pb(I1-yBry)3 (A4PbX23). The HOIPs layers are fabricated according to the same procedure as the HOIPs active SC layers and, subsequently, treated in similar conditions. For A1PbX13 and A3PbX23, the solar cells are of the p-i-n structure with organic hole and electron transport layer (HTL/ETL). The HOIPs layers are deposited on the glass/ITO/HTL (PEDOT:PSS) substrate without or with the top ETL layer (PCBM). For A4PbX23, the solar cells are of the n-i-p type with inorganic ETL (TiO2) and organic HTL (Spiro-OMeTAD) layers. The layers are directly deposited on glass without the ETL layer.Positron Annihilation Spectroscopy (PAS) gives direct evidence for native vacancy-type defects and irradiation induced ones in layers of each HOIP compound. The energy dependence of absorbance shows that natural and after irradiation ageing generates different defect populations in each HOIP compound. These populations strikingly also differ depending on the absence or presence of the top ETL layer for the A1PbX13 and A3PbX23 compounds. The defect populations evolve over ageing duration as long as 3 months. The prominent effects of ageing include (i) band gap modification, (ii) tailing of conduction/valence band extrema and (iii) optical absorption via deep subgap electronic levels. Illumination effects under laser also vary with ageing for each HOIP compound. Asymmetric photoluminescence (PL) peaks in each compound under continuous laser illumination reflect that radiative emission involves Gaussian emission rays with energy, FWHM and height evolving with illumination time. The emission transitions involve shallow localized electronic levels in A3PbX23 and A4PbX23 and resonant ones in A1PbX13. These electronic levels are attributed to specifically illumination-induced defect populations. Natural and after irradiation ageing result in PL decay lifetime spectra resolved into one or two exponential decay components. The decay components number and lifetime are strongly affected by the initial production of irradiation defects and HOIPs composition. Such effects last over 3 months at least in A4PbX23. The p-i-n solar cells exhibit most striking irradiation ageing induced photovoltaics performance. The External Quantum Efficiency (EQE versus photon energy) and the photovoltaic performance (I-V under illumination) of the irradiated solar cells have higher values than those in the reference SCs after 6 to 12 months of ageing. This gives evidence that defect engineering via high energy electron irradiation has a potential for providing innovative processing pathways to enhance the long-term stability of HOIPs photovoltaic performance

Les pompes permettent le transfert d’un produit (colle, lubrifiant, essence, etc.) jusqu’au système de pulvérisation sous pression. Etant présentes dans une multitude de secteur d’activité, leur fiabilité a une importance majeure pour la protection de l’environnement et de la santé. Nous étudions l’impact de l’état de surface sur la fonctionnalité (étanchéité, usure) de différents systèmes, au sein des pompes et systèmes de pulvérisation. Une méthode de caractérisation multi-échelle est ainsi mise en place afin de comprendre l’impact de l’état de surface des pièces sur la fonctionnalité de ces systèmes. Cette méthode est appliquée sur une première étude de caractérisation de l’étanchéité de buses réversibles. Il n’est pas toujours évident d’interpréter l’impact de la morphologie d’une surface sur sa fonctionnalité utilisant les paramètres de rugosité. Un modèle de contact et un outil de visualisation de répartition du contact sont donc développés. L’interface de contact est ainsi calculée pour mieux comprendre la répartition du contact et les chemins de fuite. La suite de la thèse a pour but de caractériser couple étanchéité/usure d’un piston hydraulique. Un banc de test est développé pour caractériser l’usure, l’étanchéité et la topographie des pièces étudiées. Ainsi, la dégradation de l’état de surface d’un piston est analysée en fonction de son étanchéité. Afin d’appliquer l’étude du couplage étanchéité/usure à d’autres contacts similaires, un modèle numérique, capable de calculer la conductance hydraulique d’un contact coulissant entre deux surfaces rugueuses, est en développement. Pour terminer, des revêtements susceptibles de remplacer le chrome dur sont testés en usure. L’utilisation du chromage dur étant fortement réglementée et sera amené à être interdite à l’avenir. Ainsi, l’étude comparative de la dégradation de différents revêtements dans les mêmes conditions d’usure est étudiée
Pumps allow the transfer of a product (glue, lubricant, petrol, etc.) to the pressurised spraying system. Being present in a multitude of industries, their reliability is of major importance for the protection of the environment and health. We study the impact of surface finish on the functionality (tightness, wear) of different systems, within pumps and spraying systems. A multi-scale characterization method is thus implemented in order to understand the impact of the surface finish of parts on the functionality of these systems. This method is applied on a first characterization study of the tightness of reversible nozzles. It is not always easy to interpret the impact of the morphology of a surface on its functionality using roughness parameters. A contact model and a contact distribution visualization tool are therefore developed. The contact interface is thus computed to better understand the contact distribution and leakage paths. The next part of the thesis aims to characterize the seal/wear torque of a hydraulic piston. A test bench is developed to characterize the wear, tightness and topography of the studied parts. Thus, the degradation of the surface state of a piston is analyzed as a function of its tightness. In order to apply the study of the seal/wear coupling to other similar contacts, a numerical model, capable of calculating the hydraulic conductance of a sliding contact between two rough surfaces, is being developed. Finally, coatings that could replace hard chromium are being tested for wear. The use of hard chromium plating is highly regulated and will be banned in the future. Thus, the comparative degradation of different coatings under the same wear conditions is being studied

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Os radionuclídeos naturais das séries radioativas do 238U e do 232Th têm sido aplicados com sucesso como traçadores de processos ambientais atuais e mudanças climáticas. O 210Pb (meia-vida de 22,2 anos) é empregado na técnica de datação geocronológica de testemunhos sedimentares dos últimos 100-150 anos e na determinação de taxa de sedimentação. As concentrações dos isótopos 226Ra e 228Ra (meia-vida de 1.600 anos e 5,75 anos, respectivamente) auxiliam no cálculo das atividades de 210Pb em excesso no sedimento e auxiliam na identificação de processos marinhos importantes, como, por exemplo, a intrusão de água subterrânea. Neste trabalho foram quantificadas as concentrações de atividade de 226Ra, 228Ra e 210Pb em quatro testemunhos marinhos curtos coletados desde a plataforma continental até o talude superior do Atlântico Sudoeste. A partir dos resultados obtidos, as taxas de sedimentação em cada local e as idades de cada fatia de sedimento foram determinadas pelo método de datação geocronológica com 210Pb. As amostras sedimentares sofreram digestão total ácida em microondas. A separação radioquímica sequencial de 226Ra, 228Ra e 210Pb foi realizada com a obtenção dos precipitados de Ba(Ra)SO4 e PbCrO4. As medidas α total do 226Ra e β total do 228Ra e do 210Pb a partir dos precipitados foram feitas em um detector proporcional de fluxo gasoso de baixa radiação de fundo. Com relação aos testemunhos analisados, as concentrações de atividade dos radionuclídeos variaram de 14 Bq.kg-1 a 154 Bq.kg-1 para o 226Ra; de 17 Bq.kg-1 a 45 Bq.kg-1 para o 228Ra; de 20 Bq.kg-1 a 2.073 Bq.kg-1 para o 210Pb. Valores altos de 210Pb foram encontrados no topo de todos os perfis sedimentares, proveniente principalmente da deposição atmosférica. Os dados coletados neste trabalho estão na mesma faixa de grandeza de outros relacionados a medições de 226Ra, 228Ra, 210Pb em áreas não contaminadas do Oceano Atlântico Sudoeste. As taxas de sedimentação diminuíram com o aumento da profundidade de coluna dágua, cujos valores variaram de 0,049 cm.ano-1 a 0,40 cm.ano-1.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

L'authenticité et la traçabilité des aliments gagnent un intérêt croissant au cours de la dernière décennie puisque la connaissance de la provenance des aliments est considérée comme une garantie supplémentaire de leur qualité. Les consommateurs ont également des inquiétudes et des préoccupations par l'origine de la nourriture qu'ils consomment car divers produits sont sujets à l'adultération ou à la fausse dénomination. L'intérêt accru à l’égard de la protection des consommateurs et de la lutte antifraude ont entraîné un accroissement de la recherche scientifique appliquée et le développement d'outils efficaces pour contrôler l'authenticité des produits alimentaires. Entre techniques analytiques appliquées à l'authenticité et à la traçabilité des aliments, les méthodes les plus prometteuses sont basées sur les empreintes d'éléments lourds mesurées par la spectroscopie atomique. La spectrométrie de masse à multicollection à couplage à plasma induit (MC-ICP-MS) est reconnue comme la méthode optimale pour effectuer des mesures de haute précision de nombreux éléments du tableau périodique en contrôlant simultanément les rapports entre leurs isotopes stables. Cette étude présente une nouvelle stratégie analytique basée sur des isotopes stables non-traditionnels combinés avec des éléments traces déterminés par ICP-MS. Les avantages de combiner les informations de deux systèmes isotopiques, l'un traçant le sol (Sr), et l'autre traçant la pollution environnementale ambiante (Pb), ont permis d'obtenir de nouvelles informations exceptionnelles sur la traçabilité et l'authenticité des matrices alimentaires sélectionnées : vins de Bordeaux, jambons secs et thé. En utilisant des techniques analytiques complémentaires telles que les empreintes des élémentaires traditionnelles, la spécification régionale, ainsi que le traçage du processus de préparation des aliments sont possibles. Traitée par la chimiométrie, cette approche analytique constitue un nouvel outil efficace et prometteur pour détecter des fraudes alimentaires, y compris l’imitation de produits de grande valeur, l’étiquetage erroné et la substitution par des produits moins cher
Food authenticity and traceability have received an increasing interest during the last decade since the knowledge of food provenance is regarded as an additional warranty of its quality. The world's globalization brought to the consumers is more and more concerned with the origin of the food they eat because various products are subjected to adulteration or false denomination. The augmentative interest in anti-fraud and consumer protection has led to the extension of scientific research and development of effective tools of food authenticity control. Among the analytical technics applied to food authenticity and traceability, one of the most rapidly developing and promising method is based on fingerprinting of heavy elements detected by atomic spectroscopy. The multicollection inductively coupled plasma mass spectrometry (MC-ICP-MS) is recognized as a method of choice for the high precision measurement of numerous elements of the periodic table as well as ratios of their stable isotopes. This study present a new analytical strategy based on combined non-traditional stable isotopes and trace elements determination by ICP-MS. The benefits of combining information from two isotopic systems, one tracing the soil (Sr), and the other tracing environmental ambient pollution (Pb), allowed to obtain an exceptional new information about traceability and authenticity of selected food matrixes: prestigious Bordeaux wines, dry-cured hams and tea. Using complementary analytical techniques such as traditional elemental fingerprinting, the regional specification, as well as tracing of the food preparation process are possible. When combined with chemometrics, these analytical advances constitute an efficient and promising tool to detect food frauds, including adulteration of high value products with cheaper substitutes, forgery and falsification

L'Electrolyse de la Vapeur d'eau à Haute Température (EVHT) est l'un des procédésde production d'hydrogène les plus prometteurs. Dans l'optique d'une économie del'hydrogène produit par EVHT, de nombreux verrous restent à lever. L'un d'entre euxporte sur l'étanchéité. En effet, dans un EVHT, la gestion des gaz est primordiale. Ilfaut pouvoir gérer et prévoir dans le temps le comportement des joints afin d'éviter unedégradation des performances. Or, en EVHT, les températures de fonctionnement sontélevées (classiquement autour de 800 °C), des phénomènes de fluage ou de relaxationapparaissent, le différentiel de dilatation thermique entre les cellules électrochimiques encéramique et les interconnecteurs métalliques doit être pris en compte. Enfin, il convientde maintenir l'étanchéité de l'empilement à faible niveau d'effort pour ne pas risquerd'endommager la partie céramique.L'objet du travail de cette thèse démarre par un constat simple : nous ne disposons pasd'outils de prédimensionnement des joints à haute température permettant de prévoirun débit de fuite. Dès lors que l'on est amené à changer un paramètre de fonctionnement,comme la température, la pression, la stratégie de chargement, la géométrie ou la naturedu joint, une nouvelle expérience doit être menée.A partir d'essais d'étanchéité et de simulations numériques aux éléments finis, un modèleoriginal est proposé. Ce modèle qui a été validé en fonction de différents paramètresexpérimentaux permet d'estimer le débit de fuite associé à un joint en Fecralloy (Fe-CrAl) selon sa forme, ses conditions de serrage et du temps de maintien. Offrant ainsila possibilité de concevoir à moindre coût des joints spécifiques pour l'application visée.

Leadership in stressful and dangerous situations is vitally important in terms of lives, property, and national strategic objectives. But our understanding of effective leadership in these and other contexts is limited. Part of the problem is that interactionist theoretical perspectives are not reflected in contemporary leadership thinking. In addition, the impact of individual differences on leadership is often misrepresented or hidden by linear correlations and regressions conducted on continuous scores. This study employed new, innovative, indirect conditional reasoning measures to assess the personalities of 627 leaders entering the militaryâ s most challenging and stressful combat leader development course (the US Army Ranger School). These innovative measures predicted compelling differences in leadership, attrition, and in the peer evaluations made during the training. Analyses conducted on the continuous personality scores demonstrate that these findings are misrepresented or hidden by linear correlations and regressions. As an alternative, I present a configural scoring scheme, couched in a poker analogy, to explain how these individual differences combine to predict the odds of success for each of the 18 personality types studied.

碩士
國立臺灣大學
機械工程學研究所
89
Leakage has been a difficult problem to tackle in fluid transmission systems, and the development of sealing technique is the key to solve it. Different seal mechanisms cause different fluid leaking paths. If leakage results from the micro voids on the interface between contact surfaces, the path is determined by the deformation of the surface roughness; if leakage results from gaps generated between contact surfaces, the path is determined by the size and distribution of the gaps generated. However, the deformation of surface roughness and gap generation are difficult to observe, and the leakage curves obtained from experiments are limited and cannot provide the foundation of improvement. Therefore, how to get the relationship between leakage and design factors is the major subject of this research. This research aims two kinds of fluid control components: diaphragm valve and ball valve, using finite element analysis to obtain interface deformation parameters, which are difficult to observe in experiments. According to different seal mechanisms, leakage prediction models are defined and established which can be provide as design tools to solve leakage problems of seal structures.

Direct measurements of wintertime surface heat fluxes between the ocean and atmosphere in lead and polynya environments in the Canadian Arctic are presented. Such environments can yield very large vertical temperature gradients during the winter months and are particularly dynamic micrometeorological environments. We found that sensible heat fluxes can exceed +100 W m-2 during the winter months, much larger than most regional estimates (~ 0 W m-2). In addition, large heat fluxes are shown to affect the characteristics of the near surface temperature inversion (temperature increases with height). The height, depth and strength of the characteristic wintertime inversion are shown to be influenced in cases where large surface fluxes were observed. Such findings are likely to have implications on the regional and planetary heat budget, general circulation models and larger scale weather processes, which most often omit local scale heat fluxes in their analyses and calculations.
February 2016

碩士
國立臺灣海洋大學
海洋生物研究所
103
Environmental pollutions do impact marine organisms, such as sea turtles, and threate their survivorhsip. It has proved that high concentration of heavy metals in sea turtles will reduce hatching success or decreased their immunity ability andaffect the health of sea turtle populations.This thesis is the first report on the heavy metal in the blood of sea turtle from bycatch, stranding alive, nesting or captive sea turtles in Taiwan. The purpose is to understand the relationship between heavy metal concentrations and the plasma biochemical of these sea turtles. Topics are divided into three parts, First part are the wild and stranded alive sea turtles, In this part, we find that the Cd、Se and Hg were higher in loggerhead turtle than green turtle(with carapace range from 70cm-90cm). In addition, hematocrit (PCV) does affect the concentration of heavy metals. In some special stranding cases : turtles swallowed tar ball or having eye infection, the blood contained high concentration of Hg、Cu and As. The second part are the nesting female.Higher concentration of Cd and Hg were found in turtles nest at Liouciou Island than Wangan and Lanyu Islands. The “Creatinine” values in plasma biochemistry were positively rrelated with Hg. The third part are the acptive and rehabilitated sea turtle, where the diet were different from the wild turtle.The As, Cu and Hg concentrations were higher than the wild turtles. The Pb concentration in the blood increased significantly with the duration of captive. The pond water in captivity; Da-Yi Temple had a higher concentration of Ni and found affected the captived sea turtles (Ni in blood concentration 3575.89µg / L ). The improper diets caused hyperphosphatemia and hypocalcemia of captive turtles have deteriorate the kidney fuction of the captive turtles. The damaged on this major metabolic organ will decrease the detoxification of sea turtles on heavy metals.. Even without direct evidence, the positive relationship between plasma biochemistry value with heavy metals suggests that the heavy metals do affect the health of sea turtles. This study emphasize the importance of pollutants control management, and can provide basline information for veterinarians and rehabilitation center to improve the captive environment and the diet of sea turtle.

Esta dissertação tem como objetivo analisar a espada medieval durante os séculos XIV e XV sobre as suas características, componentes, variáveis e, também, os diversos tratados sobre o uso desta arma deixados pelos mestres antigos. A dissertação inicia-se com a caracterização física da espada e os seus diversos componentes durante a Idade Média e continua com o estudo das tipologias de espadas, procurando integrar a questão sobre os locais de origem daquelas armas. Foi feito, também, um estudo sobre a produção e distribuição deste armamento na Europa, com o objetivo de descobrir os locais onde podem ser obtidas as matérias-primas para a produção deste armamento e os possíveis meios da sua distribuição. A pesquisa sobre o processo de produção e de distribuição procurou integrar os processos de decoração e de manutenção da arma. Na componente mais prática desta dissertação foi elaborado um estudo sobre quatro dos mais importantes tratados de esgrima medievais e os mestres que os escreveram. Através desta análise pretendeu-se, também, integrar e desenvolver a importância do estudo da biomecânica humana com o objetivo de explicar como as técnicas de combate apresentadas funcionavam da maneira como foram descritas. Também se procurou analisar o processo de combate com armadura e os tipos de equipamento utilizados no estudo destas técnicas de combate, que pertencem ao ramo das artes marciais europeias.
This dissertation has as an objective the analysis of the medieval sword during the XIV and XV centuries, in relation to its characteristics, components, variables, but also through the diverse treatises that were left by the ancient masters regarding the use of this weapon.. The dissertation begins with the physical characterization of the sword and its several components during the middle ages, and it continues with the study of the typologies of the sword, while trying to integrate the question of the birthplace of these weapons. A study was also made, regarding the production and distribution of this piece of armament in Europe, with the objective of discovering the locations of the primary resources used in the constructing of swords and for its possible means of distribution. The research about the process of productions and distribution also tried to integrate the processes of decoration and maintenance of the weapon. As for the practical component of this dissertation, a study was made about the four most important medieval fencing treatises and the masters who wrote them. Through this analysis it was also intended, to integrate and develop the importance of the study of human biomechanics, with the objective of explaining the reason, as to why the combat techniques that were described in these treatises, work in the way that they were described. It was also searched the process of combat with armour and the several types of equipment that should be used for the study of these combat techniques, which on itself belongs to the branch of Historical European Martial Arts.