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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.
151

Application of Numerical Methods to Study Arrangement and Fracture of Lithium-Ion Microstructure

Stershic, Andrew Joseph January 2016 (has links)
<p>The focus of this work is to develop and employ numerical methods that provide characterization of granular microstructures, dynamic fragmentation of brittle materials, and dynamic fracture of three-dimensional bodies.</p><p>We first propose the fabric tensor formalism to describe the structure and evolution of lithium-ion electrode microstructure during the calendaring process. Fabric tensors are directional measures of particulate assemblies based on inter-particle connectivity, relating to the structural and transport properties of the electrode. Applying this technique to X-ray computed tomography of cathode microstructure, we show that fabric tensors capture the evolution of the inter-particle contact distribution and are therefore good measures for the internal state of and electronic transport within the electrode. </p><p>We then shift focus to the development and analysis of fracture models within finite element simulations. A difficult problem to characterize in the realm of fracture modeling is that of fragmentation, wherein brittle materials subjected to a uniform tensile loading break apart into a large number of smaller pieces. We explore the effect of numerical precision in the results of dynamic fragmentation simulations using the cohesive element approach on a one-dimensional domain. By introducing random and non-random field variations, we discern that round-off error plays a significant role in establishing a mesh-convergent solution for uniform fragmentation problems. Further, by using differing magnitudes of randomized material properties and mesh discretizations, we find that employing randomness can improve convergence behavior and provide a computational savings.</p><p>The Thick Level-Set model is implemented to describe brittle media undergoing dynamic fragmentation as an alternative to the cohesive element approach. This non-local damage model features a level-set function that defines the extent and severity of degradation and uses a length scale to limit the damage gradient. In terms of energy dissipated by fracture and mean fragment size, we find that the proposed model reproduces the rate-dependent observations of analytical approaches, cohesive element simulations, and experimental studies.</p><p>Lastly, the Thick Level-Set model is implemented in three dimensions to describe the dynamic failure of brittle media, such as the active material particles in the battery cathode during manufacturing. The proposed model matches expected behavior from physical experiments, analytical approaches, and numerical models, and mesh convergence is established. We find that the use of an asymmetrical damage model to represent tensile damage is important to producing the expected results for brittle fracture problems.</p><p>The impact of this work is that designers of lithium-ion battery components can employ the numerical methods presented herein to analyze the evolving electrode microstructure during manufacturing, operational, and extraordinary loadings. This allows for enhanced designs and manufacturing methods that advance the state of battery technology. Further, these numerical tools have applicability in a broad range of fields, from geotechnical analysis to ice-sheet modeling to armor design to hydraulic fracturing.</p> / Dissertation
152

Vendor-Independent Software-Defined Networking : Beyond The Hype / Leverantörsoberoende Mjukvarudefinerade Nätverk

Pagola Moledo, Santiago January 2019 (has links)
Software-Defined Networking (SDN) is an emerging trend in networking that offers a number of advantages such as smoother network management over traditional networks. By decoupling the control and data planes from network elements, a huge amount of new opportunities arise, especially in network virtualization. In cloud datacenters, where virtualization plays a fundamental role, SDN presents itself as the perfect candidate to ease infrastructure management and to ensure correct operation. Even if the original SDN ideology advocates openness of source and interfaces, multiple networking vendors offer their own proprietary solutions. In this work, an open-source SDN solution, named Tungsten Fabric, will be deployed in a virtualized datacenter and a number of SDN-related use-cases will be examined. The main goal of this work is to determine whether Tungsten Fabric can deliver the same set of use-cases as a proprietary solution from Juniper, named Contrail Cloud. Finally, this work will give some guidelines on whether open-source SDN is the right candidate for Ericsson.
153

A tipologia dos edifícios de apartamentos e sua relação com o tecido urbano da cidade: um estudo de suas transformações nos últimos 40 anos / The typology of housing buildings and their relationship with the urban fabric of the city a case study of their transformations in the last forty years.

Carvalho, Jorge Pessoa de 09 May 2008 (has links)
Esta dissertação analisa os principais fatores que influenciaram a tipologia arquitetônica dos empreendimentos residenciais produzidos pela configuração produtiva incorporação imobiliária na cidade de São Paulo nos últimos 40 anos. Analisa também como a produção deste setor imobiliário vem alterando os tecidos urbanos pré-existentes da cidade com empreendimentos que alteram a sua tipologia arquitetônica original e o uso do espaço público no entorno das edificações, mantendo inalterado o traçado viário e demais espaços da cidade em outras palavras, as conseqüências do uso novo do traçado velho. / This dissertation analyzes the main factors that influenced the architectural typology of housing development projects built by real estate development corporations in the city of São Paulo in the last forty years. It also analyzes how the real estate sector\'s production has changed the city\'s pre-existent urban fabric with development projects that alter the architectural typology and the land use of the public space surrounding the new buildings, while at the same time keeping unchanged the road system and the remaining city spaces in other words, the consequences of the new use of the old grid.
154

Vigas de concreto armado com telas soldadas: análise teórica e experimental da resistência à força cortante e do controle da fissuração / Reinforced concrete beams with welded wire mesh: theoretical-experimental analysis of the shear strength and the control of cracking

Silva, Reginaldo Carneiro da 11 February 2003 (has links)
Este trabalho apresenta uma análise teórica e experimental do desempenho de vigas de concreto armado com telas soldadas com relação à resistência, à força cortante e ao controle da fissuração. O programa experimental englobou cinco séries de vigas com variação dos seguintes parâmetros: largura e altura das vigas, taxa de armadura transversal, taxa de armadura lateral e tipo de ancoragem dos fios verticais da tela no bordo comprimido da viga. Os modelos experimentais foram constituídos por doze vigas VQ (15 x 40 x 305), relação a/d= 2,78 e sete vigas VS (20 x 70 x 540), a/d= 2,66, ambas com seção T (bf = 50 cm e hf = 10 cm). O esquema de ensaio foi de uma viga simplesmente apoiada, com duas forças concentradas aplicadas. A formulação proposta, elaborada com base na teoria do cisalhamento-atrito, considerando a contribuição da armadura lateral na resistência à força cortante, foi analisada mediante os resultados obtidos nos ensaios. Analisaram-se também as aberturas das fissuras de cisalhamento na alma. A contribuição da armadura lateral da tela soldada deve-se à alteração em dois mecanismos resistentes alternativos: aumento da parcela de engrenamento dos agregados afetada pelas menores aberturas das fissuras de cisalhamento na alma e pelo efeito de pino dos fios da armadura lateral nos pontos em que são interceptados pelas fissuras diagonais. De modo geral, as vigas armadas com telas soldadas apresentaram menores aberturas de fissuras de cisalhamento na alma, um panorama de fissuração mais sistemático e maior reserva de resistência nas proximidades do colapso. / This work presents a theoretical-experimental analysis of performance shear design and cracking control in reinforced concrete beams with welded wire mesh. The experimental program consisted of five series of beams with variation of the following parameters: width and depth of the beam, transversal reinforcement ratio, lateral reinforcement ratio and type of stirrup anchorage in beam compression zone. The tested specimens comprised of twelve beams VQ (15 x 40 x 305), shear span-to-depth a/d= 2,78 and seven beams VS (20 x 70 x 540), a/d= 2,66, both with T transversal section (bf = 50 cm e hf = 10 cm). The test setup was a simply supported beam, with two concentrated forces applied. The proposed model was based on shear friction, which took account of the lateral reinforcement contribution on shear design. This model was compared with the test results. It was also studied the shear crack widths on the web beam. The lateral reinforcement contribution is provided by two alternative strength mechanisms: the increasing of portion agreggate interlock affected by smaller diagonal crack widths and the dowel effect of lateral reinforcement wires intercepted by diagonal plane failure. Generally, the welded wire fabric beams presented smaller inclined shear cracks, a better cracking configuration and higher strength reserve close to colapse.
155

Geocronologia e petrotrama de quartzo milonitos do duplex transcorrente de Lavras da Mangabeira / Geochronology and milonites quartz fabric of the strike-slip duplex from Lavras da Mangabeira

Freimann, Marcelo de Almeida 15 September 2014 (has links)
Fatias de rochas compreendendo granitóides, gnaisses bandados, anfibolitos, quartzitos e metapelitos formam um sistema imbricado situado na porção oeste do Lineamento Patos (Província Borborema, NE do Brasil). A estrutura situada no sul do estado do Ceará, inserida no Bloco Assaré, nesse momento ainda carece de estudos geológicos que permitam a sua melhor compreensão. Neste contexto, o presente trabalho foi realizado com o objetivo de trazer novos dados geocronológicos e estruturais para acrescentar no entendimento do duplex transcorrente. Datações de rochas situadas no interior das escamas imbricadas em zircões (U-Pb) via LA-ICP-MS indicam que o duplexé constituído por unidades (escamas) de idades diferentes. Gnaisses bandados, diques de anfibolito e metaultramáficas da unidade Granjeiro forneceram idades arqueanas (gnaisses: c. 2.8 Ga, LM10; c. 3.2 Ga, LM3; dique: c. 3.0 Ga, LM2). Idades siderianas e riacianas foram encontradas em gnaisses e anfibolitos a oeste de Cajazeiras (c. 2.4 Ga, LM1; c.2.4, LM13) e em augen gnaisses a sul de Cedro (c. 2.2 Ga, LM11), respectivamente. Essas sequencias do embasamento encontram-se em contato alóctone com metapelitos e quartzitos agrupados na Formação neoproterozoica Lavras da Mangabeira. Critérios cinemáticos derivados doestudo das microestruturas e das tramas cristalográficas de milonitos ricos em quartzo mostram que a sequência metassedimentar foi empurrada para nordeste. Eixos-c e eixos- de quartzo indicam a ativação de sistemas de deslizamento de alta temperatura durante o desenvolvimento da trama. Estimativas de temperaturas baseadas na abertura de ângulo da trama de eixos-c e em contatos suturados entre grãos de quartzo indicam que a deformação dúctil ocorreu entre 500 e 700 °C. A formação do duplex transcorrente, que constitui uma estrutura única na Província Borborema, possivelmente foi facilitada pela presença de rochas arqueanas que provavelmente se comportaram de forma mais rígida durante a deformação facilitando o cavalgamento oblíquo dos conjuntos litológicos. O arranjo estrutural das fatias imbricadas é portanto consistente com um duplextranscorrente compressivo induzido pela deformação cisalhante destral. / Slices of metaplutonic rocks, banded gneiss, amphibolites and metasedimentary sequences form a strike-slip duplex situated in the west portion of the Patos Lineament (Borborema Province, Northeastern Brazil). U-Pb (LA-ICP-MS) data in zircons from the imbricate slices indicate they are constituted by rocks of different ages. Banded gneiss, orthogneisses and metaultramafic dikes assembled in the Granjeiro Complex yielded Archean ages between 2.8 and 3.2 Ga. In contrast, biotite gneisses and amphibolites produced a Siderian (ca. 2.4 Ga) age and an augen gneiss apparently intrusive in the Siderian sequences yielded a Rhyacian (ca. 2.2 Ga) age. These basement sequences are in allochtonous contact with metapelites and quartzites grouped in the Lavras da Mangabeira Formation of Neoprotrozoic age. Kinematic criteria deduced from the study of the microstructures and crystallographic fabric of quartz-rich mylonites show that the metasedimentary sequence was thrusted to the northeast direction. Crystalligraphic c- and a- axis of quartz indicated that medium- to high temperature slip-systems were active during the fabric development. Temperature estimations based on the opening-angle of the c-axis fabric and the sutured contacts between quartz-quartz grains indicated that the ductile deformation occurred at 500 and 700°C. The development of the tectonic duplex was likely facilitated by the occurrence of Archean rocks involved in the shear deformation. They would have acted as a rigid (competent) material that induce the stacking of the sequences during the bulk dextral transcurrent deformation of the Patos Lineament.
156

Algoritmos para o encaixe de moldes com formato irregular em tecidos listrados

Alves, Andressa Schneider January 2016 (has links)
Esta tese tem como objetivo principal a proposição de solução para o problema do encaixe de moldes em tecidos listrados da indústria do vestuário. Os moldes são peças com formato irregular que devem ser dispostos sobre a matéria-prima, neste caso o tecido, para a etapa posterior de corte. No problema específico do encaixe em tecidos listrados, o local em que os moldes são posicionados no tecido deve garantir que, após a confecção da peça, as listras apresentem continuidade. Assim, a fundamentação teórica do trabalho abrange temas relacionados à moda e ao design do vestuário, como os tipos e padronagens de tecidos listrados, e as possibilidades de rotação e colocação dos moldes sobre tecidos listrados. Na fundamentação teórica também são abordados temas da pesquisa em otimização combinatória como: características dos problemas bidimensionais de corte e encaixe e algoritmos utilizados por diversos autores para solucionar o problema. Ainda na parte final da fundamentação teórica são descritos o método Cadeia de Markov Monte Carlo e o algoritmo de Metropolis-Hastings. Com base na pesquisa bibliográfica, foram propostos dois algoritmos distintos para lidar com o problema de encaixe de moldes em tecidos listrados: algoritmo com pré-processamento e algoritmo de busca do melhor encaixe utilizando o algoritmo de Metropolis-Hastings. Ambos foram implementados no software Riscare Listrado, que é uma continuidade do software Riscare para tecidos lisos desenvolvido em Alves (2010). Para testar o desempenho dos dois algoritmos foram utilizados seis problemas benchmarks da literatura e proposto um novo problema denominado de camisa masculina. Os problemas benchmarks da literatura foram propostos para matéria-prima lisa e o problema camisa masculina especificamente para tecidos listrados. Entre os dois algoritmos desenvolvidos, o algoritmo de busca do melhor encaixe apresentou resultados com melhores eficiências de utilização do tecido para todos os problemas propostos. Quando comparado aos melhores resultados publicados na literatura para matéria-prima lisa, o algoritmo de busca do melhor encaixe apresentou encaixes com eficiências inferiores, porém com resultados superiores ao recomendado pela literatura específica da área de moda para tecidos estampados. / This thesis proposes the solution for the packing problem of patterns on striped fabric in clothing industry. The patterns are pieces with irregular form that should be placed on raw material which is, in this case, the fabric. This fabric is cut after packing. In the specific problem of packing on striped fabric, the position that patterns are put in the fabric should ensure that, after the clothing sewing, the stripes should present continuity. Thus, the theoretical foundation of this project includes subjects about fashion and clothing design, such as types and rapports of striped fabric, and the possibilities of rotation and the correct place to put the patterns on striped fabric. In the theoretical foundation, there are also subjects about research in combinatorial optimization as: characteristics about bi-dimensional packing and cutting problems and algorithms used for several authors to solve the problem. In addition, the Markov Chain Monte Carlo method and the Metropolis-Hastings algorithm are described at end of theoretical foundation. Based on the bibliographic research, two different algorithms for the packing problem with striped fabric are proposed: algorithm with pre-processing step and algorithm of searching the best packing using the Metropolis-Hastings algorithm. Both algorithms are implemented in the Striped Riscare software, which is a continuity of Riscare software for clear fabrics developed in the Masters degree of the author. Both algorithms performances are tested with six literature benchmark problems and a new problem called “male shirt” is proposed here. The benchmark problems of literature were iniatially proposed for clear raw material and the male shirt problem, specifically for striped fabrics. Between the two developed algorithms, the algorithm of searching the best packing has shown better results with better efficiencies of the fabric usage for all the problems tested. When compared to the best results published in the literature for clear raw material, the algorithm of searching the best packing has shown packings with lower efficiencies. However, it showed results higher than recommended for the specific literature of fashion design for patterned fabrics.
157

Melhoria do processo de produção de tecidos metálicos na fabricação de pneus

Rodrigues, Jordana Roider January 2014 (has links)
A melhoria de processos é um tema abordado em diversos setores. Este trabalho concentrou-se na melhoria do processo de produção de tecidos metálicos usados como material de reforço na fabricação de pneus radiais. O estudo foi realizado em uma indústria fabricante de pneus, em uma calandra de configuração Z e teve como objetivo aprofundar os conhecimentos a respeito deste processo identificando oportunidades de melhorias para reduzir perdas causadas por problemas qualitativos. Além disso, buscou melhorar a qualidade percebida pelo cliente interno sem afetar a qualidade do produto final, percebida pelo cliente externo. Para tanto, foi realizado um mapeamento do processo produtivo em questão, seguido de um estudo do efeito das temperaturas neste processo. O mapeamento mostrou que muitas etapas possuem influência direta na qualidade dos tecidos, as oportunidades de melhoria foram destacadas durante e após o mapeamento e estão relacionadas principalmente ao controle das temperaturas da calandra e dos moinhos, à automatização do processo, aos procedimentos operacionais e à instalação de dispositivos de controle e alerta. Uma vez que o controle das temperaturas de toda a linha da calandra resultou ser um fator crítico para o processo, realizou-se um estudo do efeito das temperaturas usadas durante a produção, a partir do uso da metodologia de Projeto de Experimentos com a aplicação de um Projeto Fatorial 25-1 sem repetição Quatro variáveis de resposta foram estudadas: quantidade de grumos pré-vulcanizados, aderência tecido-tecido, reversão de enxofre e adesão borracha-metal. Os fatores controláveis usados foram: temperatura dos moinhos alimentadores, temperatura dos cilindros 1 e 4, temperatura dos cilindros 2 e 3, temperatura dos tambores de resfriamento e temperatura do aquecimento das cordas metálicas. Pela otimização das variáveis de resposta, chegou-se aos valores ótimos para o processo, sendo todos eles no seu nível alto, com exceção da temperatura dos cilindros 2 e 3 que apresentou o melhor valor no nível baixo. Os resultados deste trabalho aprofundaram os conhecimentos num processo que, apesar de muito antigo, ainda possui poucos textos publicados a respeito. Adicionalmente, forneceu uma otimização experimental para as afirmações encontradas na literatura sobre a importância do controle de temperaturas no processo de fabricação de tecidos metálicos. / The process improvement is a topic widely used in several sectors. In this work this topic deals with improving the production process of metallic fabrics used as reinforcement material for radial tires. The study was carried out in a tire industry in a Z configuration calender and aims to deepen the knowledge about this process by identifying improvement opportunities to reduce losses caused by quality problems in metallic fabrics. It also seeks to improve the quality perceived by internal costumer without affecting the quality of the final product, perceived by the external customer. Thus, a mapping of the production process in question was made, followed by a study of the effect of temperature in this manufacturing process. The mapping shown that many steps have direct influence on fabric quality, the opportunities for improvement were highlighted during and after the mapping and are related mainly to control the temperature of the calender and mills, to process automation, operational procedures and the installation of devices for control and alert. Since the temperature control of whole calender line proved to be a critical factor in the process, a study of the effect of the temperatures used during the production was performed from the use of the design of experiments methodology with the application of a factorial design 25-1, without replication Four response variables were studied: number of pre vulcanized lumps, tack, sulfur reversion and steel-rubber adhesion. The controllable factors chosen were: feeder mills temperature, temperature of rolls 1 and 4 of the calender, temperature of rolls 2 and 3 of the calender, temperature of cooling drums and heating temperature of steel cords. By the optimization of the response variables, it was reached the optimum values for the process, all of which are in its high level except for the temperature of the rolls 2 and 3 which showed the best value in the low level. These results obtained deepened knowledge in a process which, though very old, still has a few articles published. Additionally, it provided quantitative data to the statements found in the literature about the importance of temperature control in the manufacturing process of metallic fabrics.
158

Knowledge,need and demand of eco-labelled upholstery fabrics at Svensson Markspelle, Ludvig Svensson

KORNELIUSSON, ULRIKA January 2010 (has links)
Due to greater awareness of the need to conserve the world&apos;s resources - one direction is to promote products with less environmental impact during manufacturing processes. There are different perspectives to understand what is driving this development towards environmental production. On one hand, producers manage their production with less environmental impact either of an integrated environmental management of the company or because of regulatory requirements in steering manufacturing, especially under circumstances in Sweden. The development may also be because of responding to market demand for eco-labelled prod-ucts. My case studies have two approaches of qualitative research in order to answer the research questions: The first angle, makes a description of how a company has adapted to environmental production conditions, and examine the product development process and the choice of implementing product groups in its range. The second angle is from a customer perspective, exploring choices of specific products. The study begins with the producer Lud-vig Svensson AB and their brand Svensson Markspelle of their eco-labelled furniture fabrics and then followed by a comparison of the different kind of customers within the brand. The findings of the thesis revealed that, Ludvig Svensson has adjusted to a sustainable production since before the implementation of an eco-label. It also shows that there is a need for greater information about the company’s environmental work out to customers as eco-labels is limited in its message as a communication tool, regardless whether the eco-label is part of the ongoing environmental work or not. More customer-oriented information could make a difference as an eco-label is a simple message for complex conditions. There is also an op-portunity to increase knowledge. However, it is important to emphasize that although the organization Ecolabelling Sweden has a responsibility to raise awareness about eco-labels they certify for. Findings of the customer study showed that the choices that govern the public environment are complex. At many times other requirements such as washability, durability and flame resistance are put higher than the choice of an upholstery fabric. To be envi-ronmental friendly in product selection is not just about choosing a product with minor envi-ronmental impact, but high quality is such as great environmental choice. The study also showed that there are general aspects that are problematic to make environmentally con-scious choices and the obstacles of lack of knowledge in some areas come from several directions with regard to conditions in the public procurement. / Program: Magisterutbildning i Applied Textile Management
159

Product Requirements for Fabric Sofa Covers in Accordance with Customer Life Situation at Home

Yusuf Kocer, Ahmet, Mahmood Zubair, Muhammad January 2010 (has links)
IKEA is a unique home furnishing retailer in selling water washable slip covers for living room sofa.The aim of this research is to set product requirements for sofa covers in accordance with the usage at home by customers.This was done by conducting consumer survey to understand need, reviewing existing quality, test methods and proposal of new requirements and test methods. The overall objective is every day quality guarantee and better communication with customers in store. / Program: Magisterutbildning i Applied Textile Management
160

To study how to improve the productivity of yarn and fabric production in a production mill

MUHAMMAD, ASIF January 2011 (has links)
Productivity in every sector is essential, Production areas like textile require more production, more profit with less cost. Everyone should play their own role in achieving better production rate in these working sectors.There are many factors which can improve the productivity, but here we will focus on some specific areas. By working on these issues or factors, we can achieve our productivity goal. There are challenges for production managers and they need to take healthy measures for the enhancement in their production rates e.g. to find the best raw material available, to train its team and keep them updated to the latest technologies etc.This thesis is comprised of different factors which can affect the productivity in textile field. Here we will discuss the textile sector of Pakistan. All the information and collection of data is taken out and is referenced to the textile industry of Pakistan. / Program: Magisterutbildning i Applied Textile Management

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