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Dahl, Wivecke. "Contribution à l'étude des métabolites secondaires chez les lichens fructiculeux Cladina stellaris et Cladina rangiferina /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2003. http://theses.uqac.ca.
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McClelland, Rebecca Elizabeth Mooneyhan. "Ground Layer Response to Disturbance in the Pine-Dominated Eastern Foothill Region of West-Central Alberta, Canada." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/dissertations/436.
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The canopy cover of the Pinus contorta forests of west-central Alberta, dictates colonization of the forest floor ground layer. This dynamic ground layer is a mosaic of feather mosses and reindeer lichens in a system driven by disturbance. In this project, anthropogenic was used to control canopy cover change and study its effects on the ground layer. Timber companies selectively mechanically thinned sections producing three experimental areas with uncut controls. Data were collected from 182, 6.5 m2 plots located in the four thinning areas. Six general areas of inquiry were posed around determining ground layer responses to canopy opening: 1) vegetation, 2) plant species richness, 3) plant abundance, 4) diaspore availability, 5) environmental limiting factors, 6) moss and lichen establishment. In 1997, three timber companies were involved in selective tree removal at three different stand percentages (20/40/60%), however, these were not consistent when measured in 2005. This variation in operational logging along with changes over the seven year time period, resulted in strong disparity for each of the thinning regimes. Percent canopy cover change for all thinned plots was ranked and three new groups created; least, moderate, most canopy change. These new groups formed the basis for the data presented in Chapter 3. The three thinning groups had little to no effect on species richness, but overall showed a small decrease from measurements taken pre-harvest. Numbers of locally rare species were similar to pre-harvest levels, but there were some gains and losses of species between pre-harvest and seven years post-harvest. In contrast to the lack of change in diversity, the abundance of dominant species and major vegetation components underwent dramatic changes. Dominant species of both vascular plants and bryophytes decreased with increasing canopy openness, with vascular plants being gradually affected while mosses were more affected at less intense canopy opening. Abundances of lichens showed no change. When measuring limiting factors (biotic and abiotic) for ground layer mosses and lichens, diaspores (spores and fragments) were plentiful in all stands, but differed in abundance at the micro-scale. The position of feather mosses and reindeer lichen in the forest floor mosaic appears to be due to an intermingling of environmental influences (at both the meso- and micro-scale). With less environmental constraints on lichens and the widespread availability of lichen fragments, lichens are more tolerant to the conditions evoked by thinning than are mosses. Mosses are more restricted by environmental conditions and have more constrained diaspore dispersal than lichens. Thus, mosses are more limited both by diaspore dispersal and by harsh environmental conditions in open canopy habitats. Whereas relative humidity (RH) did not differ at the stand level, moss dominated areas had higher RH no matter where they occurred, lichen-dominated areas did not--suggesting the moss occurrence is at least partially controlled by micro-scale level factors. Moss establishment is effected by the "ghosts" of past events and substrates. Mosses are widespread in formerly moss-dominated areas that contain organic substrates and high canopy cover. Lichen establishment is limited in previously moss-dominated areas. Species interactions weighed more heavily on moss establishment than on that of lichens. Therefore, the effects of canopy change on the ground layer are variable corresponding to moss decreases, but not lichens. Seven years post-harvest species diversity is unchanged, but vegetation, as a whole, has been affected.
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Srivastava, Raghvendra Mohan. "Electroslag cladding." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611300.
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Roturier, Samuel. "La gestion des pâtures de lichen au cours de la régénération forestière : associer les savoirs locaux des éleveurs de rennes Sami et la sylviculture." Phd thesis, Museum national d'histoire naturelle - MNHN PARIS, 2009. http://tel.archives-ouvertes.fr/tel-00483086.
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En Suède boréale, les techniques de régénération forestière utilisées par la foresterie moderne, notamment les préparations de sols précédant la plantation, endommagent les pâtures de lichen terricoles (Cladina spp.), et sont devenues une source de conflit entre forestiers et éleveurs de rennes Sami. L'objet de cette thèse est d'étudier des stratégies de régénération forestière pouvant réduire les perturbations et promouvoir le ré-établissement du lichen des rennes. Les savoirs et les pratiques des éleveurs Sami sur la ressource en lichen sont également analysés. Les effets de préparations de sol moins perturbatrices sur le ré-établissement du tapis de lichen, le pâturage des rennes et l'établissement de plants de Pinus sylvestris furent étudiés. L'utilisation de l'HuMinMix, technique mélangeant le couvert de lichen avec la couche d'humus et le sol minéral, est favorable à la régénération du tapis de lichen par comparaison aux préparations de sols conventionnelles. Cependant, l'établissement des jeunes pins est supérieur suivant une préparation exposant seulement le sol minéral. L'occurrence de dégâts mécaniques, possiblement causés par le piétinement des rennes, est un argument pour éviter la plantation dans les parcelles fortement fréquentées par les rennes, au profit de la régénération naturelle ou de l'ensemencement afin d'éviter les conflits avec les propriétaires forestiers. La régénération complète du tapis de lichen suivant la préparation de sol HuMinMix est estimée à une dizaine d'année comparé à plus de cinquante ans suivant les techniques conventionnelles. Les possibilités de dispersion artificielle du lichen, par exemple dans des parcelles fortement endommagées par les préparations de sol, sont également étudiées. La nature du substrat s'avère être un facteur clé pour l'établissement du lichen dispersé. Le sol minéral se révèle être un substrat ne permettant pas l'immobilisation des fragments de lichen, alors que les substrats organiques sont favorables à l'établissement et à la croissance du lichen. Au cours du suivi de 17 parcelles en régénération, toutes les espèces du genre Cladina furent observées colonisant naturellement les sols scarifiés. Néanmois la présence d'espèces de lichen pionnières semble favoriser l'établissement des lichens du genre Cladina. Toutes les méthodes de dispersion testées résultèrent en un établissement effectif du lichen. Néanmoins l'établissement suivant la transplantation de thalles lichéniques entiers, non-fragmentés, fût sévèrement réduit par le pâturage des rennes, alors que l'établissement à partir de thalles fragmentés le fût beaucoup moins. Une étude ethnolinguistique permit également de démontrer que, contrairement à son usage dans la culture occidentale où le mot ‘pâture' est associé à une communauté végétale spécifique, l'usage par les éleveurs Sami du même mot (guohtun en Sami) inclut l'effet de la neige sur les pâtures de lichen et leur pâturage par les rennes. Les éleveurs de rennes Samis utilisent leurs savoirs sur l'influence de la végétation forestière sur les conditions de neige, et donc les conditions de pâturage, pour élaborer des stratégies de pâturage au cours de l'hiver. C'est pourquoi il est nécessaire d'intégrer le savoir des éleveurs Sami sur les pâturages hivernaux en tenant compte des conséquences de la régénération forestière sur le développement et la structure du peuplement, afin d'améliorer la compréhension des effets de la production forestière sur le pâturage hivernal des rennes, et pour développer des stratégies qui satisfassent les gestionnaires forestiers et les éleveurs de rennes.
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Lin, Jehnming. "Characterisation of coaxial laser cladding." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367284.
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Paramonova, Ekaterina (Ekaterina D. ). "CRUD resistant fuel cladding materials." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82447.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2013."June 2013." Cataloged from PDF version of thesis.
Includes bibliographical references (pages 27-29).
CRUD is a term commonly used to describe deposited corrosion products that form on the surface of fuel cladding rods during the operation of Pressurized Water Reactors (PWR). CRUD has deleterious effects on reactor operation and currently, there is no effective way to mitigate its formation. The Electric Power Research Institute (EPRI) CRUD Resistant Fuel Cladding project has the objective to study the effect of different surface modifications of Zircaloy cladding on the formation of CRUD, and ultimately minimize its effects. This modification will alter the surface chemistry and therefore the CRUD formation rate. The objective of this study was to construct a pool boiling facility at atmospheric pressure and sub-cooled boiling conditions, and test a series of samples in simulated PWR water with a high concentration of nanoparticulate CRUD precursors. After testing, ZrC was the only material out of six that did not develop dark, circular spots, which are hypothesized to be the beginnings of CRUD boiling chimneys. Further testing will be needed to confirm that it is indeed more CRUD resistant, even under realistic PWR conditions in a parallel testing facility.
by Ekaterina Paramonova.
S.B.
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Murphy, M. L. "Rapid prototyping by laser surface cladding." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284268.
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In recent years rapid prototyping technology has been implemented in many spheres of industry, particularly the field of product development. Existing process provide the capability to rapidly produce a tangible solid part, directly from three dimensional CAD data, from a range of nonmetallic materials. In many situations the desired end product of a development cycle is a metallic object, whether a component or a tool. The development of a system capable of the direct manufacture of fully dense, metal parts is therefore seen as an important landmark in the evolution of rapid prototyping technology. A unique experimental project has been carried out to investigate the potential of laser surface cladding by pneumatic powder delivery to form the basis for such a process. A layered manufacturing part building strategy is proposed, in which laser cladding is used to deposit the near net shape of each layer. Conventional machining techniques are then used to trim each layer to the exact dimensions specified by the CAD data. A multi-kilowatt carbon dioxide laser was integrated with a four axis machine tool to create an opto-mechanical workstation on which to perform the process. A detailed study of the effects of cladding process parameters on the geometry of the deposited metal was carried out and quantitative relationships derived. These relationships are used to select process parameters appropriate to the geometry of the deposition required. A numerical method to fully describe the deposited clad geometry was developed in order that efficient cutter paths could be generated for the back machining cycle. These relationships are also used to determine the minimum size of deposited bead from which the required layer section may be machined, in order to optimise process efficiency. The application of the technique to the generation of a variety of simple geometries was investigated and the potential problems identified. A preliminary investigation into the process accuracy is made, relating specifically to the predictability of the geometry of multiple layer depositions and the distortion of parts as subsequent layers are deposited. The limits of geometrical complexity possible with the current apparatus, and the unsatisfactory build times involved, suggest that the most attractive application of this technique is as part of a hybrid process, adding a novel additive dimension to existing automated fabrication techniques.
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Sexton, Cornelius Leo. "Rapid Alloy Scanning by laser cladding." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320605.
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Gojan, Agnieszka. "Advanced Modeling of Pellet-Cladding Interaction." Thesis, KTH, Fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192843.
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Ji, Junhua. "Cladding-pumped Raman fibre laser sources." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/186035/.
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In this thesis, I investigate cladding-pumped Raman fibre lasers and amplifiers. Such devices, offering a novel way to generate Raman gain, combine the advantages of the hugely successful cladding-pumped rare-earth doped fibre lasers with those of stimulated Raman scattering. They not only inherit most advantages of conventional fibre devices, such as flexibility, high efficiency, compactness, and robustness, but also provide their own advantages and distinct properties relative to conventional fibre sources, i.e., wavelength flexibility and nearly instantaneous gain without energy storage. Cladding-pumped Raman fibre laser sources utilise double-clad Raman fibres as the gain medium. These are similar to a rare-earth doped double-clad fibre except that there is no laserion doping of the core. With double-clad fibres, the high-power output from low-cost multimode pump sources can be converted into diffraction-limited signal beams, e.g., through stimulated Raman scattering. Thus, cladding-pumped Raman fibre laser sources are a kind of brightness enhancers. In the beginning of this thesis, I theoretically analyse various factors that limit the brightness enhancement of such devices. One of the limits is unwanted 2nd-Stokes generation, which restricts the area ratio between the inner cladding and core. By designing a new DCRF with a W-type core, I successfully relax this restriction by nearly five times. Combined with other factors, i.e., core damage threshold, walk-off, numerical aperture, and background loss, a brightness enhancement of more than 3500 for the designed fibre could be achieved in such devices shown by a model with right pump sources and parameters. Secondly, I focus on the conversion efficiency of such devices. A well-designed fibre with inner-cladding-to-core area ratio around six was used as a double-clad Raman fibre, pumped by a source with nearly rectangular pulse shapes. The nearly rectangular pulses were obtained from an erbium and ytterbium co-doped master optical power oscillator through prepulse shaping. A sufficiently short piece was chosen to reduce the background loss and walk-off. The highest peak power conversion into the 1st Stokes was 75% and the energy conversion efficiency was over 60% in a pulsed cladding-pumped Raman fibre amplifier. Thirdly, I study the power scalability. Theoretically, I analyse the achievable power of such devices. The core size turns out to be a critical factor in most cases. The ultimately output power is limited to around 24 kW by thermal lensing if the core is large enough and enough pump power available. Experimentally, in collaboration with co-workers, a 100 W claddingpumped Raman fibre laser was demonstrated at 1116 nm. The output beam was nearly diffraction-limited. It shows the potential of power scalability of such devices and the ability of generating high power diffraction-limited sources at wavelengths outside the conventional range that rare-earth doped fibres offer. Since a large core size is a critical factor for power scaling, new double-clad Raman fibres with large-mode areas were introduced. They were experimentally demonstrated to work as efficiently as the previous fibre. An Nd:YAG laser was used to pump one of these fibres, and a 1 mJ Raman fibre source with good beam quality was thus demonstrated. This shows that double-clad Raman fibres offer another approach to obtaining high-brightness high-energy sources. In addition, based on a cladding-pumped Raman fibre converter, a simple and efficient method was proposed to generate supercontinuum sources.
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Silva, Bárbara Cibelli Gusmão da. "Efeitos de contaminantes sobre Cladonia verticillaris." Universidade Federal de Pernambuco, 2013. https://repositorio.ufpe.br/handle/123456789/10402.
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O crescimento econômico fundamentado na exploração indiscriminada dos recursos naturais resulta em transtornos ambientais que afetam diretamente a população. O desenvolvimento tecnológico mudou o estilo de vida da sociedade moderna, aumentando a necessidade do consumo de bens não duráveis que produzem grande quantidade de resíduos. Além disso, a queima de combustíveis fósseis, o uso compostos químicos como conservantes, desinfetantes e coagulantes, têm trazido inúmeros riscos a saúde humana. Desta forma o ambiente tem sido tema central de inúmeras discussões devido a sua importância para a manutenção da vida, levando a criação de leis no intuito de minimizar os danos a ele causados, porém estas leis necessitam de fiscalização, bem como um adequado monitoramento das fontes poluidoras. Este quando realizado com equipamentos torna-se muito oneroso, sendo o uso de indicadores biológicos mais barato e eficiente. Liquens são considerados monitores padrão em vários países e, no Nordeste do Brasil, a espécie Cladonia verticillaris tem desempenhado este papel com eficácia comprovada. Por esta razão, neste trabalho objetivou-se avaliar efeitos de contaminantes utilizados em processo de tratamento de água em grande parte do Brasil, bem como com composto encontrado em edificações com sistemas fechados de ventilação sobre a estrutura e metabolismo de C. verticillaris. Para isso o líquen foi submetido a Sulfato de Alumínio, Policloreto de Alumínio e Formaldeído em condições de laboratório. Durante e após o período de tratamento foram determinados os teores de pigmentos fotossintéticos, fenóis totais, e compostos principais da espécie. As amostras expostas ao formaldeído tiveram ainda observadas sua estrutura externa e integridade celular utilizando o azul de Evans (AE) e, a quantificação da vitalidade/mortalidade celular da alga pelo método do vermelho neutro. Os resultados obtidos revelaram uma diminuição na produção de clorofila, aumento na produção de fenóis totais, porém com interrupção da síntese do ácido fumarprotocetrárico (FUM), com acúmulo de produtos intermediários de sua síntese, sobretudo o ácido protocetrárico (PRO) e compostos degradados. Os estudos da estrutura externa do talo liquênico indicaram danos visíveis, intensamente corados com AE, alguns deles perceptíveis à vista desarmada. A avaliação da vitalidade celular da alga exibiu grande quantidade de células mortas nas amostras coletadas ao final do experimento, chegando a não serem encontradas células vivas em uma delas. As respostas encontradas na pesquisa confirmam dados encontrados na literatura, expressando os efeitos nocivos da exposição a poluentes amplamente utilizados nos dias atuais, sendo considerado o formaldeído o contaminante mais agressivo dentre os avaliados.
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Gedda, Hans. "Laser cladding : an experimental and theoretical investigation /." Luleå, 2004. http://epubl.luth.se/1402-1544/2004/41/LTU-DT-0441-SE.pdf.
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Baird, Andrew. "Seismic performance of precast concrete cladding systems." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2014. http://hdl.handle.net/10092/9997.
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Structural engineering is facing an extraordinarily challenging era. These challenges are driven by the increasing expectations of modern society to provide low-cost, architecturally appealing structures which can withstand large earthquakes. However, being able to avoid collapse in a large earthquake is no longer enough. A building must now be able to withstand a major seismic event with negligible damage so that it is immediately occupiable following such an event. As recent earthquakes have shown, the economic consequences of not achieving this level of performance are not acceptable.
Technological solutions for low-damage structural systems are emerging. However, the goal of developing a low-damage building requires improving the performance of both the structural skeleton and the non-structural components. These non-structural components include items such as the claddings, partitions, ceilings and contents. Previous research has shown that damage to such items contributes a disproportionate amount to the overall economic losses in an earthquake. One such non-structural element that has a history of poor performance is the external cladding system, and this forms the focus of this research.
Cladding systems are invariably complicated and provide a number of architectural functions. Therefore, it is important than when seeking to improve their seismic performance that these functions are not neglected. The seismic vulnerability of cladding systems are determined in this research through a desktop background study, literature review, and postearthquake reconnaissance survey of their performance in the 2010 – 2011 Canterbury earthquake sequence.
This study identified that precast concrete claddings present a significant life-safety risk to pedestrians, and that the effect they have upon the primary structure is not well understood. The main objective of this research is consequently to better understand the performance of precast concrete cladding systems in earthquakes. This is achieved through an experimental campaign and numerical modelling of a range of precast concrete cladding systems.
The experimental campaign consists of uni-directional, quasi static cyclic earthquake simulation on a test frame which represents a single-storey, single-bay portion of a reinforced concrete building. The test frame is clad with various precast concrete cladding panel configurations. A major focus is placed upon the influence the connection between the cladding
panel and structural frame has upon seismic performance.
A combination of experimental component testing, finite element modelling and analytical derivation is used to develop cladding models of the cladding systems investigated. The cyclic responses of the models are compared with the experimental data to evaluate their accuracy and validity. The comparison shows that the cladding models developed provide an excellent representation of real-world cladding behaviour.
The cladding models are subsequently applied to a ten-storey case-study building. The expected seismic performance is examined with and without the cladding taken into consideration. The numerical analyses of the case-study building include modal analyses, nonlinear adaptive pushover analyses, and non-linear dynamic seismic response (time history) analyses to different levels of seismic hazard. The clad frame models are compared to the bare frame model to investigate the effect the cladding has upon the structural behaviour. Both the structural performance and cladding performance are also assessed using qualitative damage states. The results show a poor performance of precast concrete cladding systems is expected when traditional connection typologies are used. This result confirms the misalignment of structural and cladding damage observed in recent earthquake events.
Consequently, this research explores the potential of an innovative cladding connection. The outcomes from this research shows that the innovative cladding connection proposed here is able to achieve low-damage performance whilst also being cost comparable to a traditional cladding connection. It is also theoretically possible that the connection can provide a positive value to the seismic performance of the structure by adding addition strength, stiffness and damping.
Finally, the losses associated with both the traditional and innovative cladding systems are compared in terms of tangible outcomes, namely: repair costs, repair time and casualties. The results confirm that the use of innovative cladding technology can substantially reduce the overall losses that result from cladding damage.
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Engström, Hans. "Theoretical and practical aspects of laser cladding." Licentiate thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17807.
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Moor, Christian. "Analytical and experimental evaluation of advanced cladding connections." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/21441.
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Salehi, Dariush, and ds_salehi@yahoo com. "Sensing and control of Nd:YAG laser cladding process." Swinburne University of Technology, 2005. http://adt.lib.swin.edu.au./public/adt-VSWT20050915.142812.
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Surface engineering provides solutions to wear and corrosion degradation of engineering components. Laser cladding is a surfacing process used to produce wear and corrosion resistant surfaces by covering a particular part of the substrate with another material that has superior properties, producing a fusion bond between the two materials with minimal dilution of the clad layer by the substrate. The advantages of laser cladding compared to conventional techniques include low and controllable heat input into the workpiece, a high cooling rate, great processing flexibility, low distortion due to the low heat input to the workpiece and minimal post-treatment. The main processing parameters of laser cladding include laser power, laser spot size, processing speed, and powder feed rate. Within an optimized operational window, all these variables have some effect on the temperature of the clad interaction zone. The laser cladding technique is very complicated because it involves metallurgical and physical phenomena, such as laser beam-materials interaction, heat transfer between the clad and the substrate, and the interdiffusion of the clad and the substrate materials. Laser cladding is currently an open-loop process, relying on the skills of the operator and requiring dedication to specialty to make it successful. Unless the required expertise is provided, attempts to make the process successful will be futile. The objective in conducting the project was to investigate and develop prototype sensors to monitor and control Nd:YAG laser cladding process. Through a LabVIEW software based monitoring program, real-time process monitoring of optical emissions in the form of light and heat radiation was carried out, and correlated with the properties of the produced clad layers. During various experiments, single- and multiple-track laser cladding trials were performed. The responses of such sensors to the selected conditions were examined and an in depth analysis of detected heat and optical radiation signals was carried out. The results of these experiments showed the ability of such sensors to recognize changes in process parameters, and detected defects on layer surfaces along with the presence of oxides. A multi-function closed-loop laser power and CNC motion table feed rate control interface based on a LabVIEW platform has been designed and built, which is capable of accepting and interpreting sensors� data and adjusting accordingly the laser power and CNC motion table feed rate to produce sound clad layers. The developed dual control strategy utilized in this study forms a relatively inexpensive and less-complicated system that allows end-users to achieve lower failure rates during laser cladding (within its own limitations) and, therefore, through successful concurrent control of melt pool temperature and motion table feed rate provide better productivity and quality in the experimentally produced clad layers.
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Inculet, D. "The design of cladding against wind-driven rain." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58218.pdf.
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Gedda, Hans. "Analysis and development of the laser cladding process." Licentiate thesis, Luleå, 2002. http://epubl.luth.se/1402-1757/2002/13.
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Uniacke, Henry. "Design of a low cost ventilated photovoltaic cladding." Thesis, Cardiff University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496972.
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Du, Qiang. "Integrated decision-making in the cladding supply chain." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507764.
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The cladding industry is relatively independent and complex, having contemporary features in a rapidly changing sector of the construction industry. The increasing complexity of the cladding procurement and fragmentation of the supply chain bring challenges for making informed decisions. The purpose of this research was to study the cladding design and procurement process, in particular the decision making process. It was hoped to develop an integrated decision making mechanism within the context of the cladding supply chain. Based on preliminary exploration, a conceptual model of integrated communication and decision-making (ICDM) was proposed. Within this model, an Information and Communication (I&C) Hub acts as the pivotal platform of the information supply and communication in the supply chain and is managed by an industry level third party. It provides an effective and secure approach to information exchange and collaborative decision making. A questionnaire survey was the key method of this research, while industry meetings and informal interviews were employed to provide in-depth understanding of the communication related issues in the industry. It was found that the participants of the cladding supply chain were experiencing difficulties of identifying information sources and accessing information, and that an industry level third party acting as an independent information source could be accepted by the cladding industry. Therefore, the I&C Hub gained its necessity and partial feasibility. It was also found that training opportunity for practitioners was limited and the usage of ICT had a large potential for improvement. A number of modifications on the I&C Hub and information flows within the ICDM were proposed to enhance its practicality, and the enhanced model was presented and evaluated by an industry meeting. The conceptual model can only be completely validated by real cases; therefore, this study concluded with a recommendation for testing the framework in future pilot projects.
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Selvas-Aguilar, Romeo de Jesus. "Cladding-pumped neodymium and ytterbium doped fibre lasers." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/41526/.
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This thesis details my work on both high-power neodymium-doped fibre lasers (at around 1.1 μm and around 0.9 μm) and ytterbium-doped fibre lasers (at 980 nm). The main subjects were the study of efficient three-level compact continuous-wave fibre lasers and their power scaling.Ytterbium-doped fibre lasers (YDFLs) with emission at 980 nm were also investigated. I, in collaboration, obtained the highest reported output power from any compact single-mode 980 nm laser to this point. For this, speciality fibres, with special core and inner-cladding designs, were developed, notably the jacketed-air-clad (JAC) fibre, with properties that are not attainable in conventional double-clad fibres. The JAC structure allows for a small pump waveguide (inner cladding) with a high NA. This is an essential advantage for lasers operating on a transition to the ground state, such as YbThere are many considerations involved with making practical, reliable, and usable 980 nm fibre devices. The integration of all required functions into a single fibre device with a small, high-NA, inner cladding is a challenge that required a large research effort to solve. A thorough and careful design and characterisation effort led to the milestone achievement of an all-fibre pigtailed fibre laser at 980 nm, which later on was used in practice as a pump source for an 8-channel DFB fibre laser transmitter array. In addition, a 980 nm Q-switched fibre laser is realised in a cladding-pumped configuration for the first time.Furthermore, a fibre laser cladding-pumped by a high brightness intra-cavity beam-combined diode was demonstrated. Here, a multi-stripe, multi-mode diode was set-up for intra-cavity beam combination and used for cladding-pumping of fibre lasers with a small inner cladding. This high-brightness pumping scheme with a multi-emitter diode appears very attractive for power scaling of three-level fibre lasers.
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Li, Lin. "Intelligent laser cladding control system design and construction." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/7683.
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Tibblin, Fritjof. "Characterization of a newly developed martensitic stainless steel powder for Laser and PTA cladding." Thesis, KTH, Materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-163788.
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A newly developed martensitic stainless steel powder, called “powder A”, designed for surface coating with laser cladding and PTA cladding was characterized. The purpose with powder A is to achieve both good corrosion resistance and wear resistance in a stainless steel grade. The investigation of powder A was divided into cladding characterization, microstructural investigation and a property comparison to existing grades 316 HSi and 431 L. Powder A was successfully deposited with laser cladding, exhibiting a wide process window, and PTA cladding. In both cases no preheating was required and no cracks were formed. The microstructure examination indicates that powder A has a martensitic structure possibly containing small amounts of ferrite in the grain boundaries. Thermodynamic calculations in computer software Thermo-Calc 4.1 supported this theory. The microstructure of powder A proved to be very stable over a wide range of cladding parameters. Powder A was significantly harder than 316 HSi and 431 L and had better corrosion resistance than 431 L in a chloride environment. Powder A had similar corrosion properties as 316 HSi in the experiments made .The wear performance of the powder A coatings was similar to 431 L. This was surprising since the hardness of the powder A coatings is significantly higher compared to 431 L.
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Cristina, Barroso Martins de Almeida Mônica. "Atividade antimicrobiana e citotóxica de extratos orgânicos e ácido barbático de Cladia aggregata." Universidade Federal de Pernambuco, 2005. https://repositorio.ufpe.br/handle/123456789/1978.
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Previous issue date: 2005O efeito da atividade biológica in vitro dos extratos orgânicos e o ácido barbático purificado de Cladia aggregata foi avaliado sobre microrganismos patógenos e células cancerígenas. Os extratos orgânicos foram obtidos a partir de 50g do talo liquênico in natura, através de extrações por esgotamento a frio e a quente, obedecendo a série eluotrópica éter, clorofórmio e acetona. Os extratos etéreos apresentaram cromatografia em camada delgada (CCD) e líquida de alta eficiência (CLAE) com menor número de bandas e picos respectivamente com rendimento total de 1,690g para o extrato frio e 2,183g para a quente. O ácido barbático foi purificado a partir do extrato etéreo a quente, através de várias lavagens com clorofórmio, cuja concentração demonstrada na CLAE foi de aproximadamente 96%. A atividade antimicrobiana foi verificada através de screening em disco, biocromatograma e concentração mínima inibitória (CMI).O teste em disco foi feito contra bactérias Gram-positivas, Gram-negativas e fungo. O biocromatograma e a CMI apenas com Gram-positivas. Os discos de papel foram impregnados com 21μL das soluções dos extratos, a uma concentração de 43mg/mL e, do ácido barbático purificado dissolvido em éter e água na mesma concentração. Os resultados demonstraram atividade contra Staphylococcus aureus e o ácido barbático purificado dissolvido em água apresentou o melhor halo de inibição, 13,5mm. Os resultados dos biocromatogramas dos extratos orgânicos e ácido barbático purificado contra S. aureus, apresentaram sinergismo entre as substâncias, verificando-se a presença de um único halo de inibição ao redor do cromatograma. O ácido barbático purificado foi submetido a diluições em 9 partes a 2mg/mL e a CMI contra S. aureus ficou entre 200 - 50μg/mL. Para os testes citotóxicos foram usados o extrato etéreo a quente a 50; 25; 12,5 e 6,5 μg/mL e o ácido barbático a 20; 10; 5 e 2,5 μg/mL , obtidos conforme metodologia anterior contra as seguintes linhagens de células cancerígenas: Hep-2, NCI-H292 e KB. O extrato etéreo a quente inibiu o crescimento celular em 78; 72; 70 e 60% Hep-2; 63; 61; 36 e 42% NCI- H292; 80; 80; 52 e 47% KB com CI50: < 6,5 μg/mL para Hep-2 e 6,5 12,5 μg/mL para NCI- H292 e KB. O ácido barbático purificado inibiu Hep-2 em 61; 66; 54 e 49%; NCI H292 63,4; 61,1; 36,7 e 42%; KB 77; 71; 53 e 43%, com CI50: 2,5 - 5 μg/mL para Hep-2 e KB e 5 μg/mL para NCI- H292. Os resultados demonstraram que os extratos orgânicos e o ácido barbático purificado apresentaram atividade antimicrobiana frente a S. aureus e atividade citotóxica para as células cancerígenas testadas
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ROSSI, JESUALDO L. "Efeito de tratamentos mecanotermicos na fluencia de aco inoxidavel austenitico estabilizado com niobio." reponame:Repositório Institucional do IPEN, 1987. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9872.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Bézivin, Carine. "Evaluation de l'activité cytotoxique d'extraits et de molécules lichéniques : étude particulière de cladonia convoluta (Lam.) Anders et de cladonia rangiformis Hoffm., Cladoniaceae." Rennes 1, 2002. http://www.theses.fr/2002REN10112.
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Dans le but de découvrir de nouvelles molécules actives dans le domaine de la cancérologie, nous avons entrepris un criblage sur six lignées cancéreuses humaines et murines d'extraits obtenus avec huit espèces lichéniques. Deux espèces de Cladonia se sont avérées spécialement actives avec une CI50 << 20 æg/ml. Une étude lichénochimique et morphologique, par microscopie à balayage, de Cladonia convoluta et de C. Rangiformis ont alors été réalisées. A la suite d'une extraction successive par solvants de polarité croissante, le travail de séparation a permis l'isolement et l'identification de 9 composés lichéniques (dérivé du dibenzofurane, depside, depsidones, stéroi͏̈de, polyols) dont certains sont décrits pour la première fois dans le lichen. L'origine naturelle ou non de ces composés est discutée ainsi que leur intérêt chimiotaxonomique. Hormis les polyols, ces différents composés isolés ont ensuite été évalués pour leur cytotoxicité sur le panel de cellules cancéreuses ainsi que pour leur activité inhibtrice de la protéine kinase CDK1 cycline B dépendante utilisés pour le criblage. Ces deux tests ayant fait particulièrement ressortir l'activité de l'acide usnique-(-), nous avons réalisé une étude sur son mécanisme d'action comparativement à celui de son énantiomère acide usnique-(+) et de l'étoposide. L'observation de cellules L1210 testées avec ces produits en microscopie à fluorescence a mis en évidence, une fragmentation de l'ADN caractéristique des cellules apoptotiques pour l'acide usnique (+) et (-) à des concentrations comprises entre 17,4 et 34,8 æM. Une nette diminution du nombre de cellules en phase S est apparente en cytométrie de flux pour l'acide usnique.
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Xiao, Di-Chen. "Manufacture of novel bearings by laser." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321252.
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Wolz, Michael W. "Nonlinear interaction between building structural systems and nonstructural cladding." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/20129.
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Yevko, Vladimir. "Cladding formation in laser-beam fusion of metal powder." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0007/MQ33971.pdf.
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Palermo, Antonio. "Influence of cladding on robustness of multi-storey buildings." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/6003/.
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In this dissertation the influence of a precast concrete cladding system on structural robustness of a multi-storey steel-composite building is studied. The analysis follows the well-established framework developed at Imperial College London for the appraisal of robustness of multi-storey buildings. For this scope a simplified nonlinear model of a typical precast concrete façade-system is developed. Particular attention is given to the connection system between structural frame and panel, recognised as the driving component of the nonlinear behaviour of the façade-system. Only connections involved in the gravity load path are evaluated (bearing connections).
Together with standard connection, a newly proposed system (Slotted Bearing Connection) is designed to achieve a more ductile behaviour of the panel-connection system. A parametric study involving the dimensions of panel-connection components is developed to search for an optimal configuration of the bearing connection.
From the appraisal of structural robustness of the panelised frame it is found that the standard connection systems may reduce the robustness of a multi-storey frame due to a poor ductile behaviour while the newly proposed connection is able to guarantee an enhanced response to the panelised multi-storey frame thanks to a higher ductility.
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Yang, Wen Fu. "Laser cladding surface treatment for enhancement of mechanical properties." Thesis, Peninsula Technikon, 2003. http://hdl.handle.net/20.500.11838/1267.
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Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2003Systematic laser cladding experiments were performed using a mixture of a Nickel base alloy powder mixed with tungsten carbide powder (percentage contents of tungsten carbide from 10% to 40%) on EN8 steel substrate with pre-placed powder method. Laser cladding of the Nickel base alloy powder + 50% tungsten carbide powder on EN9 steel substrate was performed with powder injection method as well. A Finite Element Method for calculating the surface temperature distribution was used to help prediction of temperature distribution laser cladding results. Composition of cladding materials was designed; a sticking agent was chosen for the pre-placed powder method. Clad coatings were obtained for different process parameters for laser cladding, and a detailed study of the affects of these parameters has been carried out. The characteristic microstructure and properties of the clad layers and interface were investigated by using an optical microscope, a micro hardness tester and a makeshift wear test. A comprehensive review is presented on the dilution of the coating and the typical problems experienced with the coating substrate interface. The results show that microstructure of clad layers comprise three zones: the cladding layer, bonding zone and heat-affected zone. The results showed that tungsten carbide particles increased the hardness and wear resistance as expected. Wear resistance of laser cladding coating is 3.5 times than that of substrate. The micro hardness range of the cladding layer is from RV 981.5 to RV 1187, which is 2-3 times than that of substrate. The micro hardness varies from cladding coating to transition layer then to heat affected zone and substrate along a gradient.
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Schweitzer, Luiz Guilherme de Souza. "Laser cladding for epitaxial nickel base superalloys turbine blades." reponame:Repositório Institucional da UFSC, 2014. https://repositorio.ufsc.br/xmlui/handle/123456789/129625.
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A prosperidade e larga utilização da aviação como meio de transporte civil, nacional e internacional, exige seriedade no condicionamento das aeronaves. A manutenção preventiva é um ponto fundamental para que sejam evitados desastres aéreos. A verificação dos motores é indispensável e, devido ao alto valor agregado, corresponde aos custos mais elevados de recondicionamento. As turbinas, por estarem sujeitas a elevada temperatura e pressão, geralmente apresentam o maior número de componentes danificados. Por esta razão há o interesse no desenvolvimento de técnicas para o reparo eficaz de pás de turbina. Erosão e formação de trincas são danos comuns que necessitam de recondicionamento. A recente aplicação de pás monocristalinas (SX), no lugar de policristalinas, apresenta vantagens por suportar melhor as elevadas temperaturas e com isto aumentar a eficiência dos motores [1, 2]. No entanto, não há um método reconhecido para o reparo das pás monocristalinas. A proposta deste trabalho consiste na aplicação de laser cladding com injeção de pó, devido a características como o tratamento localizado e controle de material fornecido. Este processo é apropriado devido principalmente à flexibilidade e baixo nível de diluição. Foram desenvolvidos dois métodos para promover o reparo de tais defeitos. Um método consiste na remoção completa de camadas de material onde estão situadas as trincas. O outro prevê a remoção de apenas um pequeno volume da estrutura afetada, através de um entalhe que retira o volume danificado. Com isto, a perda de material, o tempo de trabalho e os custos de manutenção podem ser drasticamente reduzidos. O entalhe tem de ser soldável e também permitir a solidificação de material no mesmo plano orientado como a microestrutura inicial. Para isto, um gradiente de temperatura deve ser introduzido a fim de orientar o crescimento de grão. No entanto, existem desafios para alcançar uma estrutura de cristal único sem rachaduras e poros, devido à distribuição de energia no interior do entalhe. Progressos atingidos e novos desafios são apresentados neste trabalho.
Abstract : The prosperity and widespread use of aviation as a civil national and international transport requires seriousness in the aircraft conditioning. Preventive maintenance is the key to avoid disasters. For that, is essential the check of engines, which corresponds to the higher reconditioning costs. The turbines, due to elevated temperature and pressure, usually have the highest number of damaged parts. For this reason, there is an interest in developing techniques for the efficient repair of turbine blades. Erosion and crack formation are common damages that require refurbishing. The recent application of single crystal (SX) turbine blades, instead of polycrystalline, present better withstands in high temperatures and thus increases the efficiency of the engines [1, 2]. However, a recognized method for the repair of SX turbine blades has to be developed. The proposal of this work involves the application of laser cladding with powder injection, due to characteristics such as localized treatment and control of the material injected. This process is particularly suitable due to flexibility and low dilution levels. There are two techniques developed to promote the repair of such defects. One way is by the removal of complete layers in which the cracks are located. Another possibility is to remove just a small volume of the affected microstructure. Therewith the loss of material and working time may be drastically reduced as well as the maintenance costs. The notch must be weldable and permit the material solidification in the same oriented plane as the original structure. For that, a temperature gradient has to be introduced in order to guide the grain growth. However, there are challenges to achieve a SX structure without cracks and pores due to energy distribution inside the notch. Current achievements and further challenges are presented in this work.
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Lundgren, Emil. "A new model for Pellet Cladding Interaction risk assessment." Thesis, KTH, Fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-263048.
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Stevenson, Elizabeth Victoria. "The design and evaluation of building integrated thermal cladding." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/27935/.
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The project aim was to investigate the potential of a large scale, inexpensive, solar thermal façade in the UK climate. Profiled steel cladding was utilised as a solar absorber, with the channels used to form a series of parallel ducts when covered by a glass surface. Air was considered to flow through the ducts in two modes; forced or buoyant convection. The factors affecting air flow were investigated in a laboratory experiment. The factors affecting solar heat transfer to the air were investigated using prototypes in field conditions. Three models for forced convection and two for buoyant were found in the literature. These were developed and compared against the experimental results to establish appropriate design models. The design models were used to optimise the duct geometry for three desirable outputs; mass flow, temperature output or power output. Optimal duct geometry was found to depend on the flow mode assumed. In addition, the optimal geometry also depended on the required output. Thus it was determined that an optimal hybrid system which could switch modes as required, could not be configured; the function and utility of the system must be decided at the design stage and not reconfigured afterwards. The annual performance of a building-scale south facing façade fitted with such a system (optimised for power output) was modelled for forced and buoyant convection modes. It was found that both flow modes had the potential to generate significant amounts of heat energy which could be used, for instance, to preheat ventilation air. The buoyant system also showed the potential for the generation of significant natural ventilation. However the forced convection system would have the advantage of being more controllable, have a better seasonal distribution of performance and have a greater potential for higher air exit temperatures to be achieved in winter.
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Schnier, Gladys. "Development and validation of a fatigue-resistant cladding technology." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=26011.
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Knowledge and understanding of residual stresses has been and remains a complex area of study, the determination of these stresses crucial in appreciating the state of the component both prior to and during operation. In the case of dissimilar joints, the interaction of materials increases the complexity of the residual stress state resulting due to the applied joining process. A fatigue-resistant cladding technology is presented in this thesis, with the aim of inducing compressive residual stresses in the clad layer. Through the generation of these beneficial compressive residual stresses an improvement in fatigue performance can be achieved in an erosive-corrosive environment. Characterisation of clad and substrate materials allows an understanding of the interaction of materials and the resulting residual stress distribution due to a weld cladding process, both experimentally and through finite element modelling. Finite element modelling of the weld cladding process utilised an elastic-perfectly plastic material model throughout the investigation of the modelling process. Good correlation between experimental and simulation residual stresses is presented, with factors influencing residual stress distributions discussed. The accurate capturing of residual stresses due to weld cladding is a complex process due to, for example, material metallurgy and properties. Laser cladding provides an alternative method of generating residual stresses indicating that the fatigue-resistant cladding technology is not limited to weld cladding. Furthermore, weld cladding is not a process that must be applied exclusively, with the application of autofrettage post-cladding providing a means of favourably modifying tensile residual stresses obtained through the weld cladding process. The fatigue-resistant weld cladding technology has been successfully developed and validated, with recommendations provided for further development and the implementation of this concept. Although this research was primarily focussed on the weld cladding of a hydraulic fracturing pump, the application of this technology is not limited to this component therefore presenting the potential to improve the fatigue performance of any component operating under cyclic loading conditions in an erosive-corrosive environment.
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Andrews, Michael Robert. "The interaction of deposition promoters with AGR fuel cladding surfaces." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244466.
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Nguyen, Quan Viet. "Seismic Energy Dissipation of Steel Buildings Using Engineered Cladding Systems." Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/theses/373/.
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Ranalli, Juan Manuel. "Relationship between microstructure and corrosion of pressure vessel cladding materials." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8333/.
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Type 347L and Type 309L stainless steels used as weld cladding materials of nuclear reactor pressure vessels were investigated under realistic conditions of fabrication and service. Electron backscatter diffraction and metallographic observations were used in combination with double loop electrochemical potentiokinetic reactivation (DLEPR) test and ASTM-262-A test to determine the precipitation behaviour and its influence on intergranular corrosion (IGC) resistance as a function of post welding heat treatment (PWHT) time at 600 oC and after simulated service ageing at 425 °C. It was shown that during the first stage of PWHT, M23C6 carbides precipitate in both alloys as a result of δ ferrite decomposition. This increased sensitization of the materials is due to the creation of a chromium-depleted zone, which was found to be replenished after 40 h of treatment, recovering the resistance of the materials to IGC. After combined treatment of PWHT + simulated service, 309L was shown to be re-sensitized whereas 347L remained resistant. Sigma phase was found to precipitate during the last stages of PWHT with a higher tendency on 309L. Two characteristic reactivation potentials were found for both materials. A specific split-cycle DLEPR was applied to show that this technique can be further developed to identify deleterious phases in austenitic stainless steel welds. Micro hardness and Charpy impact tests showed an increase in hardness and a decrease in absorbed energy of materials without PWHT after ageing at 425 oC.
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Jarvis, Jennifer Anne. "Hydrogen entry in Zircaloy-4 fuel cladding : an electrochemical study." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103730.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 291-297).
Corrosion and hydrogen pickup of zirconium alloy fuel cladding in water cooled nuclear reactors are life-limiting phenomena for fuel. This thesis studies the fate of hydrogen liberated by waterside corrosion of Zircaloy-4 fuel cladding in Pressurized Water Reactors (PWRs): are the adsorbed protons incorporated into the oxide and eventually the metal, or are they evolved into molecular hydrogen and released into the coolant? Water chemistry modeling was used to understand effects of radiolysis and CRUD. Density functional theory (DFT) was used to investigate the role of oxidized Zr(Fe,Cr)2 second phase particles. Chemical potentials and the electron chemical potential were used to connect these two modeling efforts. A radiolysis model was developed for the primary loop of a PWR. Dose profiles accounting for fuel burnup, boron addition, axial power profiles, and a CRUD layer were produced. Dose rates to the bulk coolant increased by 21-22% with 12.5-75 pim thick CRUD layers. Radially-averaged core chemistry was compared to single-channel chemistry at individual fuel rods. Calculations showed that local chemistry was more oxidizing at high-power fuel and fuel with CRUD. Local hydrogen peroxide concentrations were up to 2.5 ppb higher than average levels of 5-8 ppb. Radiolysis results were used to compute chemical potentials and the corrosion potential. Marcus theory was applied to compare the band energies of oxides associated with Zircaloy-4 and the energy levels for proton reduction in PWR conditions. Hydrogen interactions with Cr203 and Fe203, both found in oxidized precipitates, were studied with DFT. Atomic adsorption of hydrogen was modeled on the Cr and Feterminated (0001) surfaces. Climbing Image-Nudged Elastic Band calculations were used to model the competing pathways of hydrogen migration into the subsurface and molecular hydrogen formation. A two-step mechanism for hydrogen recombination was identified consisting of: reduction of an adsorbed proton (H+) to a hydride ion (H-) and H2 formation from an adjacent adsorbed proton and hydride ion. Overall, results suggest that neither surface will be an easy entrance point for hydrogen ingress and that Cr203 is more likely to be involved in hydrogen evolution than the Fe203.
by Jennifer Anne Jarvis.
Ph. D.
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Lee, Youho. "Safety of light water reactor fuel with silicon carbide cladding." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/86866.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 303-314).
Structural aspects of the performance of light water reactor (LWR) fuel rod with triplex silicon carbide (SiC) cladding - an emerging option to replace the zirconium alloy cladding - are assessed. Its behavior under accident conditions is examined with an integrated approach of experiments, modeling, and simulation. High temperature (1100°C~1500°C) steam oxidation experiments demonstrated that the oxidation of monolithic SiC is about three orders of magnitude slower than that of zirconium alloys, and with a weaker impact on mechanical strength. This, along with the presence of the environmental barrier coating around the load carrying intermediate layer of SiC fiber composite, diminishes the importance of oxidation for cladding failure mechanisms. Thermal shock experiments showed strength retention for both [alpha]-SiC and [beta]-SiC, as well as A1₂O₃ samples quenched from temperatures up to 1260°C in saturated water. The initial heat transfer upon the solid - fluid contact in the quenching transient is found to be a controlling factor in the potential for brittle fracture. This implies that SiC would not fail by thermal shock induced fracture during the reflood phase of a loss of coolant accident, which includes fuel-cladding quenching by emergency coolant at saturation conditions. A thermo-mechanical model for stress distribution and Weibull statistical fracture of laminated SiC cladding during normal and accident conditions is developed. It is coupled to fuel rod performance code FRAPCON-3.4 (modified here for SiC) and RELAP-5 (to determine coolant conditions). It is concluded that a PWR fuel rod with SiC cladding can extend the fuel residence time in the core, while keeping the internal pressure level within the safety assurance limit during steady-state and loss of coolant accidents. Peak burnup of 93 MWD/kgU (10% central void in fuel pellets) at 74 months of in-core residence time is found achievable with conventional PWR fuel rod design, but with an extended plenum length (70 cm). An easier to manufacture, 30% larger SiC cladding thickness requires an improved thermal conductivity of the composite layer to reduce thermal stress levels under steady-state operation to avoid failure at the same burnup. A larger Weibull modulus of the SiC cladding improves chances of avoiding brittle failure.
by Youho Lee.
Ph. D.
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Paul, James. "Joining of silicon carbide for accident tolerant PWR fuel cladding." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/joining-of-silicon-carbide-for-accident-tolerant-pwr-fuel-cladding(f9851a0a-ef68-465e-8029-a31ab77fab27).html.
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Following two previous nuclear reactor accidents involving light water reactors, there is a renewed interest in accident tolerant fuels. These accident tolerant fuels should not oxidise in a steam atmosphere during loss of coolant accidents. One such accident tolerant fuel that has been suggested is the use of ceramic composite cladding material as a replacement for the current zircaloy cladding. The high temperature stability of silicon carbide, together with its high resistance to corrosion may make it preferable to zircaloy during accident conditions. Furthermore, if the neutron absorption cross section of the cladding is less than the current zircaloy, extended life might be available when compared with current fuels. One of the main difficulties in using ceramic cladding materials as nuclear fuels is the lack of a reliable joining process to manufacture end caps for the cladding tubes. A manufacturing method would need to be developed to produce ceramic joint that is able to withstand a PWR environment. Two methods of ceramic joining have been proposed. Firstly, silicon carbide deposition process that is used to infill the gap between two ceramic components and secondly a ceramic soldering technique. A silicon carbide deposition process has been developed. The deposit was confirmed to be 3C silicon carbide which has preferable irradiation response to the other polytypes. The deposit was found to be carbon rich which was largely removed through the use of a thermal treatment step. The deposit was used to coat metallic surfaces for increased hardness, reduced sliding wear and corrosion resistance. Silicon carbide joints were produced using an oxide powder frit of silicon dioxide, yttrium oxide and aluminium oxide. Tubular samples were joined, however they contained circumferential cracking resulting in a join that was not hermetically sealed. The thermal conductivity of each joint varied from sample to sample. X-ray computed tomography showed there were large inconsistencies in the volume of joined material present in each sample giving rise to the large variation in thermal conductivity.
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Rodrigues, Silva Alexandre. "Cladonia verticillaris (Raddi) Fr. como agente tripanocida sobre Trypanosoma cruzi." Universidade Federal de Pernambuco, 2009. https://repositorio.ufpe.br/handle/123456789/665.
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Previous issue date: 2009Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
A doença de Chagas continua a ser um problema de Saúde Pública relevante e, o único tratamento, o Benznidazol, acarreta severos efeitos colaterais e possui limitações terapêuticas. Diante disso, objetivou-se analisar o efeito do extrato acetônico (ACE) e dos ácidos fumarprotocetrárico (FUM) e protocetrárico (PRO) do líquen Cladonia verticillaris (Raddi) Fr.. contra Trypanosoma cruzi, in vitro. O extrato acetônico foi obtido mediante a uma seqüência eluotrópica de solventes orgânicos. Posteriormente foram obtidos os compostos isolados (FUM) e (PRO). Foram realizados leituras cromatográficas para confirmação e determinação do grau de pureza das substâncias. Os bioensaios foram conduzidos com formas epimastigotas e tripomastigotas sangüínea incubadas durante 72 e 24 horas respectivamente, na ausência ou presença de 75 a 300ig.mL-1das substâncias testes. Foram determinadas nesse período a IC50 e IL50. As análises foram realizadas em triplicatas em três experimentos independentes. As formas tripomastigotas revelaram maior susceptibilidade aos metabólitos secundários, com 100% de lise dos parasitas tratados com 300 ig·mL-1 de PRO, após 24 horas de incubação. A análise ultraestrutural de tripomastigotas tratadas revelaram desorganização de organelas, retração nuclear e danos ao cinetoplasto e a mitocôndria. Estas alterações foram mais evidentes nos tratamento com PRO. Concluindo, os resultados obtidos estimulam estudos futuros para elucidar os mecanismos de ação destes compostos bem como avaliar seus efeitos sobre formas amastigotas intracelulares. Estes resultados também apontam para o uso do PRO como agente potencial contra Trypanosoma cruzi
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Dalvina, Correia da Silva Michele. "Uma Lectina do líquen Cladonia verticillaris : purificação e caracterização parcial." Universidade Federal de Pernambuco, 2004. https://repositorio.ufpe.br/handle/123456789/2059.
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Previous issue date: 2004Lectinas são proteínas ou glicoproteínas de origem não imunológica que possuem sítios de ligação para carboidratos e/ou glicoconjugados. Uma lectina do líquen Cladonia verticillaris foi purificada através de cromatografia de exclusão molecular. O líquen triturado foi submetido à extração e uma purificação parcial por fracionamentos utilizando sulfato de amônio. As amostras foram submetidas a ensaios de atividade hemaglutinante (AH) e suas concentrações protéicas foram estimadas. A fração mais ativa, F1 (0-30 %), foi submetida a ensaios de inibição, a ensaios de estabilidade térmica e de dependência de íons divalentes, assim como a ensaios cromatográficos para a purificação e caracterização lectínica. ClaveLL foi isolada através de cromatografia de exclusão molecular de F1, e submetida aos mesmos ensaios; foi também avaliada quanto à estabilidade da AH em valores de pH compreendidos de 2 a 12. F1 e ClaveLL foram analisadas em eletroforeses em gel de poliacrilamida (PAGE) para proteínas nativas ácidas e básicas, assim como para proteínas desnaturadas. F1 foi inibida parcialmente por carboidratos (N-acetil-D-glicosamina, xilose, arabinose, ramnose e manose) e glicoproteínas (fetuína, caseína, ovalbumina e peroxidase) ou totalmente (glicoproteínas presentes em soro fetal bovino e em soro de coelho). ClaveLL foi inibida parcialmente por carboidratos (N-acetil-D-glicosamina, galactose, ramnose, manose, glicose e trealose) e ovalbumina, e inibida totalmente por fetuína, asialo-fetuína, caseína, asocaseína e glicoproteínas presentes em colostro, soro de coelho e soro fetal bovino. F1 foi termoestável, mantendo sua AH a 80°C, enquanto ClaveLL foi sensível ao aumento de temperatura. F1 e ClaveLL não foram dependentes de íons, mas MnCl2, BaCl2, CaCl2 e MgCl2 estimularam sua AH. ClaveLL foi mais ativa nos valores de pH ácido (5,5) ou básico (11,0). PAGE contendo SDS resolveu F1 e ClaveLL como única banda polipeptídica (glicosilada) com peso molecular menor que 14 kDa. F1 glicosilada pode ter resíduos glicose/manose uma vez que se ligou à Cramoll 1,4-Sepharose, uma matriz de afinidade com a lectina de semente de Cratylia mollis, isoformas 1 e 4 glicose/manose específica, imobilizada à Sepharose CL-4B. PAGE para proteínas nativas ácidas detectou em ClaveLL uma única banda que migrou junto com a frente de corrida; o mesmo foi observado em PAGE para proteínas nativas básicas. Cromatografia de ClaveLL através de filtração em gel em sistema ÄKTA-FPLC, resolveu três picos distintos com AH, que sugeriram formas de agregados moleculares para a lectina nativa, com pesos moleculares estimados em 170, 110 (pico principal) e 82 kDa. Concluindo, ClaveLL glicosilada altamente purificada é estável a pH e principalmente inibida por glicoproteínas
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Phuah, Chin Heng. "Corrosion of thermally-aged Advanced Gas-Cooled Reactor fuel cladding." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/10550.
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The microstructure of Advanced Gas-Cooled Reactor (AGR) fuel cladding that underpins its corrosion behaviour has been established, contributing to an understanding of long-term control, monitoring practice and storage decisions for this fuel. AGR fuel cladding specimens sourced from Sellafield Ltd, cut and individually heat treated at temperatures from 400 to 800°C for 24 to 192h were attempts to approximate irradiated AGR fuel cladding and characterised both in terms of their corrosion behaviour and of microstructure. Niobium carbide (NbC) second phases are the primary local corrosion sites. Bulk austenite-γ cladding metal (50.3±1.7 at% Fe, 21.0±1.1 at% Cr and 21.0±0.4 at% Ni) around NbC precipitates exhibited extensive corrosion even though the precipitate themselves appear unchanged. Corrosion observed from the specimen surface took the form of lacy covers around an NbC precipitate at the cover centre (~10 to 25 μm dia. depending on the site) and in the subsurface were voids (~0.1 μm pin-holes), cavities (~2 to 5 μm), an envelope of dissolved-metal region along NbC peripheries (~1 μm thick with austenite-γ composition decreased by on average 20% Fe, 21% Cr and 17% Ni) or a large, smooth concave pit bottom comparable to the cover dimension. These observations collectively suggest that AGR cladding corrosion is a diffusion-controlled phenomenon where the NbC precipitate may act as the cathode in a local galvanic couple and the adjacent austenite-γ metal is the anode that undergoes preferential oxidation. The primary contributing factors to NbC-induced AGR cladding corrosion are high NaCl concentration of the electrolyte solution, large NbC precipitates, small austenite-γ grains and presence of stress in the microstructure. Specifically, corrosion potential measurements in the 0.001M electrolyte NaCl are ~800mV (v.s. Ag|AgCl reference electrode) more noble than in the 0.1M electrolyte, suggesting that cladding wet storage requires maintenance with lowest chloride concentration practically achievable. Specimens with comparatively large NbC precipitates (~5 μm) and small austenite-γ grains (~10 μm) that result from heat treatment are ~810mV more corrosion susceptible than the as-received specimens with ~0.1 dia. NbC precipitate and ~25 μm austenite-γ grains. Increased dislocation densities were observed adjacent to the grown-NbC precipitate, imparting a stress-corrosion effect on the AGR cladding corrosion.
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Rudyk, Martin. "Porovnání navařování svazkem elektronů a plazmou." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231419.
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This diploma thesis deals with plasma cladding and electron beam cladding. The theoretical part is divided into several chapters which is focused on description of these methods of cladding process. In the practical part the particular experiment of electron beam cladding (EBC) and plasma cladding (PC) is described. In the conclusion overall results were assessed, both methods were compared each other and possible exploitation in industry was described.
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TIGRE, Rafaela Carvalho. "Atividade alelopática de Cladonia verticillaris (Raddi) Fr. sobre a germinação e o crescimento inicial de Lactuca sativa L." reponame:Repositório Institucional da UFPE, 2009. https://repositorio.ufpe.br/handle/123456789/14000.
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DISSERTAÇÃO Rafaela Carvalho Tigre.pdf: 8383179 bytes, checksum: 4faaf34d6442f38ca981fd651b1fa042 (MD5)Made available in DSpace on 2015-05-19T16:49:25Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO Rafaela Carvalho Tigre.pdf: 8383179 bytes, checksum: 4faaf34d6442f38ca981fd651b1fa042 (MD5) Previous issue date: 2009-02-16
CAPES
Os aleloquímicos liquênicos, têm um importante papel na ecologia dos liquens, podendo afetar o desenvolvimento de outros organismos ao seu redor. O objetivo deste trabalho foi avaliar o potencial alelopático do talo de Cladonia verticillaris, seus extratos e suas substâncias principais, os ácidos fumarprotocetrárico (FUM) protocetrárico (PRO) sobre a germinação e o desenvolvimento inicial de Lactuca sativa. Os extratos foram obtidos com éter dietílico, clorofórmio e acetona. O FUM foi extraído a partir do extrato acetônico. Ensaios cromatográficos foram realizados para detecção dos fenóis. O experimento foi conduzido em placas de Petri contendo extratos, ou FUM ou PRO (0,01; 0,1; 1,0; 2,5mg/mL). Nos bioensaios in vivo foram borrifadas soluções de uréia (0,1; 1,0 e 10mg/mL) sobre o líquen. Observou-se que o talo e todas as soluções testadas não afetaram a germinabilidade, mas os extratos causaram alterações no tempo de germinação. Os parâmetros biométricos foram mais sensíveis aos aleloquímicos obtendo-se diferentes respostas dependendo da concentração. As alterações morfológicas das plântulas indicaram modificações no balanço hormonal das plântulas, com indução da formação de pêlos, raízes laterais, aumento do diâmetro radicular e inibições do sistema radicular. Notou-se que a adição de uréia (0,1mg/mL) e água deionizada ativa a urease causando diferentes efeitos alelopáticos. As análises cromatográficas revelaram a presença de FUM e PRO nos extratos indicando serem estas as substâncias responsáveis pelas alterações observadas.
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Stephan, Hendrik Christoffel. "Investigation of a testing approach for trapezoidal crest fastened metal cladding." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80018.
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Thesis (MscEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Low-rise buildings with crest fastenedmetal cladding are susceptible to failures in the vicinity of the fasteners during strongwind uplift conditions. These localised failures often lead to the progressive removal of cladding, which can cause disastrous building damage. In South Africa, the current metal cladding design approach is inadequate, since it solely relies upon manufacturer design specifications. These specifications are typically designated as broad design guidelines for the maximum allowable cladding support spacings which are independent from any specified design loads. This research focuses on the investigation of 0.50 mm ISQ550 IBR cladding systems to understand basic cladding behaviour during static wind uplift conditions and to quantify the uplift performance of IBR systems. The research investigation also included the improvement and performance evaluation of a full-scale cladding test method which applies an air-bag loading method to simulate static wind uplift conditions according to the revised SANS 10237:201X code of practice. This thesis may serve as a basis for further cladding research, and the development of suitable standardised metal cladding test methods in South Africa. Several experimental investigation methods and limited finite element analyses (FEA) were used to investigate IBR and the performance of the test methods. Tensile testing was used to determine the material properties of the cladding metal. The full-scale cladding assembly testing was used to investigate the behaviour of IBR and to evaluate the performance of the air-bag test rig. The localised behaviour of the cladding around the fasteners was also investigated with a small cladding subassembly test method. The FEA served as a supplementary investigation for IBR performance evaluation. The experimental investigation confirmed that the static wind uplift resistances of IBR systems are mainly governed by localised deformations of their fastened crests and fastener pull-through failures. The behaviour and performance of IBR systems are heavily dependent on the crest fastening arrangement. IBR systems with every crest fastening demonstrated a considerably higher wind uplift resistance than IBR systems with the standard alternate crest fastening arrangement. The measured fastener loads were independent from span length, whereas the overall uplift resistance of IBR reduced with increased span lengths. Load-span resistance data for 0.50 mm ISQ550 IBR was derived from testing to provide a rational framework for design. The FEA provided a reasonable simulation of IBR subjected to static wind uplift and confirmed the presence of high stress and strain concentrations around the fastener holes which cause fastener pull-through failures. Therefore, FEA can be used as an effective tool to investigate the behaviour of IBR. In conclusion, the air-bag test method used in this research investigation provided an effective method for evaluating the uplift performance of crest fastened metal cladding. However, the air-bag load method is not capable of accurately simulating a true uniformly distributed uplift load. It is recommended that direct air pressure testing be adopted for any further research or commercial testing ofmetal cladding because direct air pressure testing is an effective and proven test method for accurate simulation of static and cyclic wind uplift conditions.
AFRIKAANSE OPSOMMING: Metaalbekleding met kruinvashegting op lae geboue is geneig om te faal by die vashegters tydens toestande van sterkwind-opheffing. As vashegters faal kan bekleding progressief verwyderwordomrampspoedige skade aan die gebou te veroorsaak. Die huidige ontwerpmetode vir metaalbekleding in Suid-Afrika is onvoldoende, aangesien dit slegs gegrond is op vervaardigers se ontwerpspesifikasies. Spesifikasies word gewoonlik verklaar as breë ontwerpriglyne vir die maksimum toelaatbare spasiërings van ondersteunings sonder enige oorwegings vir ontwerpbelastings. Hierdie navorsing fokus dus op 0.50mm ISQ550 IBR metaalbekleding omdie basiese gedrag van bekleding tydens wind-opheffing beter te verstaan en die ophefweerstand van IBR te kwantifiseer vir ontwerpdoeleindes. Verder ondersoek hierdie navorsing ook die verbetering en evaluasie van ’n volskaalse bekledingstoetsmetode wat statiese wind-opheffing naboots met verspreide lugsakbelasting volgens die hersiende SANS 10237:201X gebruikskode. Hierdie proefskrif kan dien as ’n grondslag vir verdere navorsing en die ontwikkeling van geskikte standaard-toetsmetodes vir metaalbekleding in Suid-Afrika. Verskeie eksperimentele toetsmetodes en beperkte eindige-element-analises (EEA) is gebruik om die gedrag van IBR en die toets-opstellings te ondersoek. Trektoetse is gebruik om die meganiese eienskappe van die bekledingsmetaal te bepaal. Volskaalse toets-opstellings is gebruik om die weerstand van IBR te ondersoek en die lugsaktoetsmetode te evalueer. Die gelokaliseerde gedrag van die bekleding rondom die vashegters was ook ondersoek met klein toets-opstellings. EEA het gedien as ’n aanvullende ondersoek om die gedrag van IBR te evalueer. Die eksperimentele ondersoek het bevestig dat die wind-ophefweerstande van IBR-stelsels hoofsaaklik bepaal word deur gelokaliseerde deformasies van die vasgehegde kruine en die vashegters se deurtrekweerstand. Die gedrag en weerstand van IBR-stelsels is ook grootliks afhanklik van die toegepaste vashegtingsmetode. IBR stelsels met vashegting deur elke kruin het ’n hoër ophefweerstand verskaf as IBR-stelsels met die standaard vashegtingsmetode deur elke tweede kruin. Die gemete vashegterbelastings was onafhanklik van die spanlengtes, terwyl die algehele ophefweerstand van IBR verminder het vir langer spanlengtes. Toetsdata is gebruik om ophefweerstande vir 0.50mm ISQ550 IBR oor verskeie spanlengtes af te lei sodat ’n rasionele raamwerk vir ontwerp bewerkstellig kan word. Die EEA het die gedrag van IBR tydens toestande van statiese wind-opheffing redelik goed nageboots en het ook die teenwoordigheid van hoë spannings- en vervormingskonsentrasies rondom die vashegtergate, wat vashegters laat deurtrek, bevestig. Daarom kan EEA as ’n effektiewe instrument gebruik word om die gedrag van IBR te ondersoek. Ten slotte word dit afgelei dat die lugsaktoetsmetode van hierdie navorsingsondersoek ’n effektiewe metode verskaf het vir die gedrag-evaluering van kruinvasgehegte bekleding tydens wind-opheffing. Die lugsaktoetsmetode kan egter nie ’n ware gelykverspreide ophefbelasting naboots nie. Daarom word dit voorgestel dat toetsmetodes wat direkte lugdruk aanwend gebruik moet word vir enige verdere navorsing of kommersiële toetse van metaalbekleding, aangesien dit ’n effektiewe en bevestigde toetsmetode is wat statiese en sikliese opheftoestande akkuraat kan naboots.
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Segeťa, Petr. "Studium vlastností vrstvy uhlíkaté oceli navařené vysokovýkonným polovodičovým laserem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231513.
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The aim of my thesis is the analysis of properties of laser cladding. The theoretical part is focus on conventional methods of laser cladding, types and properties of lasers and its applications in industry. Then there is the description of preparing metallographic samples and its assessment, also there are types of wear enclosed. In the experimental part the nickel laser cladding were made by using semiconductor laser, in which the structure, the dilution, the EDS analysis and the hardness with respect to input parameters are assessed.
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Asselin, Matthew. "Optical Sensor for Measurement of Clad Height during Laser Cladding Process." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/874.
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The process of laser cladding consists of depositing successive layers of molten metallic powder to create a near-net shape. A high-power laser is used to melt incoming metallic powder, which forms a melt pool on the surface. As the latter moves beneath the laser, this newly created melt pool solidifies. By properly controlling the trajectory of deposition tracks, one can create a diverse range of shapes with varying complexities. However, the process is very sensitive to parameters, requiring constant attention from technicians. This lends itself perfectly to the addition of automatic controllers whereby supervision is minimal. In this thesis, an optical sensor is developed to monitor the process zone. The sensor will output a measurement of the height of solidified clad, which in turn can be used by a controller to adjust this geometrical feature. The thesis is divided into three main parts, each contributing to the final algorithm.
First, in Chapter 3 an analysis is performed on the light irradiating from the interaction zone (or melt pool). It is stated that the dominating source of light is governed by blackbody radiation from this molten metal. This is confirmed by analyzing a series of images captured through a digital camera, where various narrow bandpass filters were utilized to selectively view a portion of the CCD-sensor's spectrum. This investigation also leads to the selection of bandpass filter such that a stable, relatively intense melt pool is captured through the digital camera's CCD-sensor.
Second, in Chapter 4 the captured images are taken through a pair of image processing techniques, outputting a series of coordinates representating the melt pool's boundary. The image is first analyzed to calculate an optimal threshold level based on the minimization of fuzzy entropy. With this threshold selected, the grayscale image is converted into black-and-white, where the white pixels represent the melt pool. After this step, the melt pool's boundary is extracted through an 8-connectivity border tracing algorithm. This technique outputs a series of coordinates (in pixels) as though one were traveling along the melt pool in a clockwise rotation.
Last, Chapter 5 analyzes these pixel coordinates to extract the melt pool's height. The coordinates are first transformed into real-world coordinates, by use of a perspective transformation. This transformation essentially yields the melt pool's shadow, as created by a light-source coincident with the camera. As a result, the melt pool's height is estimated based upon a right-angle triangle, where the camera's angle is known, and the projected coordinates represent the shadow length (triangle's base).
The result of applying this series of steps to the estimation of clad heights is found at the end of Chapter 5. Results varied dramatically, from 4% error to 393%. Although the errors are large at times, they are mainly caused by a bias in the estimate. That is, the dynamics of the true clad formation are very well predicted by the algorithm, however, shifting by a certain amount. This amount varies both with substrate velocity, and the clad's direction of travel, relative to the camera. A partial explanation is given such that the clad's height is offset from the laser center-point, which is a function of both these parameters. However, the specific relationship requires further experimentation.
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Winter, Gerrard Martin. "Determination of the design strength of thin structural veneer cladding panels /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17531.pdf.
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