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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

Fatigue damage accumulation under torsion and non-proportional push-pull interruption loading

Wheelhouse, Keith January 2002 (has links)
A new testing facility for fully reversed tension-torsion high cycle fatigue testing has been designed. The specimens used for the test programme were solid and made from a medium carbon steel. The test programme involved a tension-torsion multiaxial non-proportional loading sequence i.e. fully reversed torsion followed by a push-pull load interruption and then the continuation of the same torsion loading to failure. The push-pull load interruption represented a significantly low damage i.e. 4% damage according to Miner's linear damage theory, and was applied after different prior torsion cycle ratios. The tests were conducted with various interruption stress amplitudes all of which had fatigue lifetimes in the high cycle fatigue region. The torsion fatigue life was found to change significantly due to the application of push-pull load interruption which was considered to cause only a minor damage due to Miner's rule. Miner's linear damage theory cannot account for the predicted cumulative fatigue damage (Sigman/N[f]) for the push-pull interrupted torsion fatigue loading sequences used in the current test programme. The fatigue life was markedly enhanced when the interruption was applied at an early stage of torsion loading whilst the effect was less prominent when the interruption was applied at a later stage of torsion loading. At higher interruption stress amplitudes the torsion fatigue lifetime was reduced considerably and the damage summation was well below the unity predicted by the Miner's rule. The inability to predict damage accumulation by Miner's rule can be attributed to the complexity in the crack growth associated with the application of push-pull interruption. Crack growth equations to represent microstructural short crack (MSC) and the physically small crack (PSC) growth were determined for the material of the form;MSC - da/dN = C[m](d[i] - a)...(1) and PSC - da/dN = C[p]a-D ...(2). Material parameters for the models were derived using torsion and uniaxial constant amplitude fatigue S-N data, no crack coalescence, branching or re-initiation was considered. The crack growth model was able to predict the fatigue life in loading cases which were dominated by an uninterrupted crack growth. However, such a model was shown to significantly underestimate the torsion fatigue life in situations where the fatigue life was affected by secondary crack initiation due to the push-pull load interruption.
312

Characterising Human Capital in the Craft Industry

Kragulj, Florian January 2018 (has links) (PDF)
Small and medium enterprises (SMEs) play a significant role in Europe's economy. Since SMEs have distinct organisational practices and structures (e.g. owner-run, continuity over several generations, regional engagement), their intellectual capital (IC) differs from large enterprises. However, there is little research on IC in SMEs. Placing special attention on the craft industry, this research aims at closing this gap. It will present a cross-disciplinary review of research on craft to explore the role of knowledge and human capital in the craft industry. The findings point to overall characteristics which can guide future research and inform policy-making in the craft industry.
313

Využití meristémových kultur ve šlechtění česneku kuchyňského (\kur{Allium sativum}) / Meristem cultures in garlic (Allium sativum) breeding

ŠVEHLOVÁ, Eva January 2017 (has links)
The diploma thesis deals with the use of meristem cultures in garlic (Allium sativum) breeding. The source material was used variety Tantalum of garlic. The using material, before the isolation of meristem, was tested for the occurrence of viral diseases by immunological tests ELISA (Enzyme-Linked Immuno-Sorbent Assay), also known as EIA (Enzyme Immunoassay). The method used to detect antibodies and antigens. The material was tested for viruses onion yellow dwarf (OYDV - Onion Yellow Dwarf Virus) and virus genus Carlavirus (GCLV - Common Garlic Latent Virus). Then the sound material was sterilized, cultured and then it was obtained meristem. Cultivation of preparation meristem was realised according available methodologies. After preparation meristem put on MS medium with vitamins and growth regulator IAA, NAA and BAP.
314

Potencial toxigênico de Aspergillus flavus testado em diferentes meios e condições / Aspergillus flavus toxigenic potenmtial tested in different media and conditions

Ritter, Ana Carolina January 2007 (has links)
A avaliação da capacidade produtora de micotoxinas vem sendo utilizada como uma importante ferramenta na identificação de espécies conhecidamente toxigênicas. Poucos são os métodos rápidos e alternativos disponíveis para a determinação do potencial toxigênico de espécies do gênero Aspergillus. Neste contexto, o objetivo deste trabalho foi avaliar a capacidade produtora de aflatoxina B1, em diferentes condições de cultivo, por três isolados de Aspergillus flavus, produtores de aflatoxina B1. O delineamento experimental baseou-se em um planejamento 2³ completo, tendo como variáveis independentes a temperatura (20-40°C), o tempo de incubação (7-21 dias) e o pH (2,0-6,0) nos meio sintéticos (YES, CYA e Sabouraud). As melhores condições encontradas foram aplicadas em testes com meio natural (arroz) e isolados a principio não-aflatoxigênicos. Aflatoxina B1 foi extraída diretamente dos meios sintéticos com clorofórmio e do arroz com metanol. A identificação e quantificação do composto foi realizada por Cromatografia em Camada Delgada e Fotometria Fotográfica. O meio YES se mostrou o melhor para detecção do potencial toxigênico, seguidos de melhor pH 4,0 e 5,2, e temperatura de 20º e 25ºC e tempo de incubação de 11 e 14 dias. O isolado A43, em temperatura de 25º, pH 5,2 e tempo de incubação de 11 dias, mostrou a maior produção de aflatoxina B1, com 206,05 ng. No arroz, os isolados revelaram produção de aflatoxina, apenas a partir do 14ºdia. Dos 30 isolados a princípio não-aflatoxigênicos testados inicialmente em agar coco, 12 apresentaram resultado positivo nos meios e condições aqui apresentados. / Mycotoxins producing capacity evaluation has being used as an important tool, in the identification of toxigenic species. A few of them are available as alternative rapid methods for the determination of the toxigenic potential of species Aspergillus. The objective of this work was to evaluate the aflatoxin B1 producing capacity in different conditions of culture by three Aspergillus flavus. The experimental delineation was based on a 2³ factorial design. To test the effect of three independent variables, the temperature (20-40°C), the incubation time (7-21 days) and pH (2,0 -6,0) in the synthetic medium (YES, CYA and Sabouraud) were applied in the program STATISCA 7.0. The best joined conditions had been applied in tests with natural medium (rice) and isolated tested as nonaflatoxigenics. Aflatoxin B1 was extracted directly from sintetic mediuns by chloroform and from rice by methanol. Thin-layer chromatography (TLC) and Photometric Photography were the methods utilized for the identification and quantification of aflatoxin B1. YES was the best medium for the detention of toxigenic potential, at pH 4,0 and 5,2, temperature of 20º and 25ºC and incubation time of 11 and 14 days. The isolated A43, at temperature of 25ºC, pH 5,2 and incubation time of 11 days showed the biggest aflatoxin B1 production (206,05 ng). Aflatoxin production in rice occurred only after 14 days. 12 of the 30 non aflatoxigenic isolates showed aflatoxin production in the media and conditions tested.
315

GREEN ROOF PLUG GERMINATION AND GROWTH WITH DIFFERENT BASE MEDIA AND TREATMENTS

Caulkins, Afton Michelle 01 May 2017 (has links)
The germination rates of four plant species (Allium schoenoprasum L., Dianthus gratianopolitanus ‘Grandiflorus’ Vill., Sedum kamtschaticum Fisch. & C.A. Mey. Spp. ellacombianum (Praeger) R.T. Clausen, and Talinum calycinum Engelm.) were compared with six fertility treatments (control, fertilizer - once a week, double fertilizer - twice a week, mycorrhizae, vermicompost, and green roof mix) that also evaluated a peat based greenhouse medium verses a lightweight aggregate medium integrated. The greenhouse medium had higher germination rates than the lightweight aggregate medium. The control, fertilizer, and double fertilizer, which were not applied until a month into the study, provided similar germination results. The seedlings obtained from the germination study were grown into 3.81cm x 7.62cm plugs, with plant height, leaf count/width, and dry weight taken three months later. The greenhouse medium treatments control, fertilizer, and double fertilizer had the most leaves, and provided the tallest and widest leaves as well as the greatest biomass. The lightweight aggregate medium control displayed the lowest growth in this study. The fertility treatment that showed the most potential was the green roof mix. This mix significantly improved plant growth in the lightweight aggregate medium, which indicates the potential to improve greenhouse medium based plug establishment on extensive green roofs with aggregates.
316

Summoning the Spirit of Obsolescence in Media and Performance: A Posthuman Sèance

Greer, Lindsay Patrice 01 December 2017 (has links)
In this dissertation, I explore the fantasies and paradoxical desires belying spiritual medium performances of the late-nineteenth and early-twentieth centuries and new media practices of remediation. Forming the organizing construct of this dissertation, spiritual medium performance gives me a medium to explore fantasy as a means of suspending and manipulating audience belief. Through the use of my performance persona, Lucida Fox, I further connect the spiritual medium’s communication with the dead to the practices of remediation meant to summon the influences of obsolete media. Through Lucida, I remediate the past (Chapter 2), future (Chapter 3), and experiment with several spiritualist techniques in the present (Chapter 4). In the final chapter, I address the implications of this research on current discussions within the field of performance studies and conclude by offering future direction of this research.
317

Perverse Fascination: Medium, Identity, and Performativity in the Art of Kara Walker

DiTillio, Jessica 11 July 2013 (has links)
Kara Walker is one of the most successful and widely known contemporary African-American artists today--remarkable for her radical engagement with issues of race, gender, and sexuality. Walker is best known for her provocative installations, composed of cut-paper silhouettes depicting fantastic and grotesque scenes of the antebellum South. This thesis examines Walker's work in silhouettes, text, and video in order to establish the unifying logic that unites her media. Walker's use of racist stereotypes has incited vehement criticism, and the debate over the political meaning of her work has been worked and reworked in the voluminous literature on her artistic practice. This thesis focuses on how Walker's defense and explanation of her own work functions as a performative and political component of the art itself. Walker's construction and performance of an artistic identity is an integral and intentional part of her overall practice and a key component to the interpretation of her work.
318

Etude expérimentale de l'ébullition en masse dans un milieu poreux modèle / Pore-scale experimental study of boiling in a model porous medium

Sapin, Paul 14 May 2014 (has links)
Ce travail propose une étude expérimentale de l'ébullition en masse dans une structure poreuse modèle. L'objectif est d'approfondir la compréhension des transferts de chaleur dans un écoulement diphasique avec changement de phase liquide-vapeur en milieu poreux, en liaison avec la problématique de la gestion des accidents graves dans les réacteurs nucléaires. A la suite d'un dysfonctionnement sur le circuit de refroidissement d'un réacteur nucléaire, l'augmentation de la température au sein du cœur provoque l'effondrement des tubes contenant le combustible. Il en résulte la formation d'un lit de débris chaud, assimilable à un milieu poreux dégageant une puissance thermique importante, qui peut être refroidi efficacement par renoyage avec de l'eau. Cela engendre des mécanismes d'ébullition intenses qu'il convient de modéliser proprement pour estimer les chances de succès du renoyage. Notre étude vise à caractériser les échanges de chaleur à l'échelle du pore en fonction des caractéristiques de l'écoulement local. Une partie importante du travail a été consacrée à la mise au point du dispositif expérimental. Le cœur du dispositif est un milieu poreux bidimensionnel formé de cylindres disposés aléatoirement entre deux plaques de céramique. Chaque cylindre est une sonde à résistance de platine, utilisée non seulement pour fournir la puissance thermique désirée mais aussi pour mesurer la température de l'élément : chaque élément chauffant est contrôlé individuellement ou en groupe à l'aide d'un système d'asservissement temps réel. La plaque supérieure étant transparente, la distribution des phases au sein du poreux est obtenue par visualisation haute vitesse. L'acquisition d'images et les mesures thermiques permettent de caractériser l'échange de chaleur effectif local en fonction du régime d'ébullition. Deux configurations principales ont été étudiées. Dans la première, le milieu est initialement saturé en liquide et chauffé jusqu'à l'apparition de la vapeur et l'obtention de différents régimes d'ébullition. Ceci a notamment permis d'établir des courbes de Nukiyama en milieu confiné. Dans la seconde, dite de renoyage, le liquide est injecté dans le milieu sec et surchauffé initialement. Ceci a permis de caractériser la dynamique du renoyage et de visualiser les régimes d'écoulement rencontrés. Les résultats sont discutés en relation avec le modèle macroscopique à non-équilibre thermique local actuellement le plus avancé pour l'étude de ces différentes situations d'ébullition. / This manuscript presents a pore-scale experimental study of convective boiling heat transfer in a two-dimensional porous medium. The purpose is to deepen the understanding of thermohydraulics of porous media saturated with multiple fluid phases, in order to enhance management of severe accidents in nuclear reactors. Indeed, following a long-lasting failure in the cooling system of a pressurized water reactor (PWR) or a boiling water reactor (BWR) and despite the lowering of the control rods that stops the fission reaction, residual power due to radioactive decay keeps heating up the core. This induces water evaporation, which leads to the drying and degradation of the fuel rods. The resulting hot debris bed, comparable to a porous heat-generating medium, can be cooled down by reflooding, provided a water source is available. This process involves intense boiling mechanisms that must be modelled properly. The experimental study of boiling in porous media presented in this thesis focuses on the influence of different pore-scale boiling regimes on local heat transfer. The experimental setup is a model porous medium made of a bundle of heating cylinders randomly placed between two ceramic plates, one of which is transparent. Each cylinder is a resistance temperature detector (RTD) used to give temperature measurements as well as heat generation. Thermal measurements and high-speed image acquisition allow the effective heat exchanges to be characterized according to the observed local boiling regimes. This provides precious indications precious indications for the type of correlations used in the non-equilibrium macroscopic model used to model reflooding process.
319

Estimativa da distribuição longitudinal das pressões a jusante de comportas tipo segmento invertida

Kempka, Mariane January 2014 (has links)
O uso de comportas ou válvulas em condutos para efetuar o controle de fluxo em estruturas hidráulicas é bastante usual. Uma das aplicações deste tipo de dispositivo de controle de vazões é para fazer o enchimento e esvaziamento de câmaras de eclusas de navegação. Entretanto, a sua aplicação deve ser feita com cuidado em função da complexidade do escoamento, o qual pode apresentar grandes variações de velocidade e pressões junto à base e ao teto da galeria a jusante da comporta. O gradiente de pressão pode variar no tempo e no espaço podendo vir a ocasionar danos por erosão (desgaste) e/ou cavitação. Assim, torna-se fundamental obter critérios para a estimativa de previsão do valor dessas pressões para, então, poder inferir a possibilidade de danos junto à superfície sólida, permitindo que se determinem as condições críticas de operação que devem ser evitadas ou minimizadas durante as operações de esvaziamento ou de enchimento da câmara da eclusa. Esta pesquisa procura apresentar o estado da arte em relação à distribuição longitudinal das pressões a jusante de comportas tipo segmento invertida e os resultados e análises desenvolvidas em um modelo físico de laboratório. Estes estudos permitiram compreender o comportamento das pressões e verificar se o método sugerido por Batistton (2013), para estimar os valores da distribuição longitudinal das pressões junto à base e o teto da galeria a jusante da comporta, podem ser aplicados para todas as aberturas da comporta. As análises desenvolvidas consentiram observar que as situações críticas ocorrem para aberturas entre 40% e 60% e que as pressões mínimas ocorrem em uma distância adimensional ( ) em torno de 2 a 6. Destaca-se que todos os resultados apresentados na presente pesquisa são válidos para coeficiente de pressão média para abertura de 100% da comporta, CP* 100%, entre 2,8 e 65,9. / The practice of using of gates or valves in conduits to control the flow in hydraulic structures is a common one. One of the applications for this type of device is the flow control for filling and emptying navigation locks. However proper care should be taken when applying those due to the inherit complexity of the flows, which can present significant pressure and velocity fluctuation in the regions next to the floor and ceiling downstream of these gates. Fluctuations in the pressure gradients can cause damage by erosion and/or cavitation. For these reasons its of interest the understanding of criteria for the estimative of those pressures to then infer the possibility of damage in the solid boundaries, allowing the determination of critical operation conditions which to avoid or minimize during the emptying and filling operations of lock chambers. This research aims to present the state of art regarding the longitudinal pressure distribution downstream of inverted tainter gates and the results of experimental data obtained in a physical model. These study allowed to comprehend the behavior of the aforementioned pressures and to verify the method proposed by Battiston (2013) to estimate longitudinal pressure distributions next to the ceiling and floor of those types of structures. The developed analysis showed that the critical conditions occur in between the 40% and 60% opening and that the minimum pressures occur in between a dimensionless distance (Ladm) 2 and 6. The presented results are valid for a mean pressure coefficient of 100% gate opening, CP*100%, between 2,81 and 65,9.
320

Potencial toxigênico de Aspergillus flavus testado em diferentes meios e condições / Aspergillus flavus toxigenic potenmtial tested in different media and conditions

Ritter, Ana Carolina January 2007 (has links)
A avaliação da capacidade produtora de micotoxinas vem sendo utilizada como uma importante ferramenta na identificação de espécies conhecidamente toxigênicas. Poucos são os métodos rápidos e alternativos disponíveis para a determinação do potencial toxigênico de espécies do gênero Aspergillus. Neste contexto, o objetivo deste trabalho foi avaliar a capacidade produtora de aflatoxina B1, em diferentes condições de cultivo, por três isolados de Aspergillus flavus, produtores de aflatoxina B1. O delineamento experimental baseou-se em um planejamento 2³ completo, tendo como variáveis independentes a temperatura (20-40°C), o tempo de incubação (7-21 dias) e o pH (2,0-6,0) nos meio sintéticos (YES, CYA e Sabouraud). As melhores condições encontradas foram aplicadas em testes com meio natural (arroz) e isolados a principio não-aflatoxigênicos. Aflatoxina B1 foi extraída diretamente dos meios sintéticos com clorofórmio e do arroz com metanol. A identificação e quantificação do composto foi realizada por Cromatografia em Camada Delgada e Fotometria Fotográfica. O meio YES se mostrou o melhor para detecção do potencial toxigênico, seguidos de melhor pH 4,0 e 5,2, e temperatura de 20º e 25ºC e tempo de incubação de 11 e 14 dias. O isolado A43, em temperatura de 25º, pH 5,2 e tempo de incubação de 11 dias, mostrou a maior produção de aflatoxina B1, com 206,05 ng. No arroz, os isolados revelaram produção de aflatoxina, apenas a partir do 14ºdia. Dos 30 isolados a princípio não-aflatoxigênicos testados inicialmente em agar coco, 12 apresentaram resultado positivo nos meios e condições aqui apresentados. / Mycotoxins producing capacity evaluation has being used as an important tool, in the identification of toxigenic species. A few of them are available as alternative rapid methods for the determination of the toxigenic potential of species Aspergillus. The objective of this work was to evaluate the aflatoxin B1 producing capacity in different conditions of culture by three Aspergillus flavus. The experimental delineation was based on a 2³ factorial design. To test the effect of three independent variables, the temperature (20-40°C), the incubation time (7-21 days) and pH (2,0 -6,0) in the synthetic medium (YES, CYA and Sabouraud) were applied in the program STATISCA 7.0. The best joined conditions had been applied in tests with natural medium (rice) and isolated tested as nonaflatoxigenics. Aflatoxin B1 was extracted directly from sintetic mediuns by chloroform and from rice by methanol. Thin-layer chromatography (TLC) and Photometric Photography were the methods utilized for the identification and quantification of aflatoxin B1. YES was the best medium for the detention of toxigenic potential, at pH 4,0 and 5,2, temperature of 20º and 25ºC and incubation time of 11 and 14 days. The isolated A43, at temperature of 25ºC, pH 5,2 and incubation time of 11 days showed the biggest aflatoxin B1 production (206,05 ng). Aflatoxin production in rice occurred only after 14 days. 12 of the 30 non aflatoxigenic isolates showed aflatoxin production in the media and conditions tested.

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