927 resultados para Polyester and vinylester thermoset matrices


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Mode of access: Internet.

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Includes bibliographical references.

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Mode of access: Internet.

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Bibliography: p. 35.

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"This work was supported in part by the Department of Computer Science, University of Illinois, Urbana, Illinois, and in part by the Advanced Research Projects Agency as administered by the Rome Air Development Center under contract no. US AF 30(602)4144."

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Thesis (Master's)--University of Washington, 2016-06

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The chemical structure, synthesis, morphology, and properties of polyurethane elastomers are briefly discussed. The current understanding of the effect of chemical structure and the associated morphology on the stability of polyurethanes in the biological environments is reviewed. The degradation of conventional polyurethanes appears as surface or deep cracking, stiffening, and deterioration of mechanical properties, such as flex-fatigue resistance. Polyester and poly( tetramethylene oxide) based polyurethanes degrade by hydrolytic and oxidative degradation of ester and ether functional groups, respectively. The recent approaches to develop polyurethanes with improved long-term biostability are based on developing novel polyether, hydrocarbon, polycarbonate, and siloxane macrodiols to replace degradation-prone polyester and polyether macrodiols in polyurethane formulations. The new approaches are discussed with respect to synthesis, properties and biostability based on reported in vivo studies. Among the newly developed materials, siloxane-based polyurethanes have exhibited excellent biostability and are expected to find many applications in biomedical implants.

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Column-based refolding of complex and highly disulfide-bonded proteins simplifies protein renaturation at both preparative and process scale by integrating and automating a number of operations commonly used in dilution refolding. Bovine serum albumin (BSA) was used as a model protein for refolding and oxido-shuffling on an ion-exchange column to give a refolding yield of 55 % after 40 Ih incubation. Successful on-column refolding was conducted at protein concentrations of up to 10 mg/ml and refolded protein, purified from misfolded forms, was eluted directly from the column at a concentration of 3 mg/ml. This technique integrates the dithiothreitol removal, refolding, concentration and purification steps, achieving a high level of process simplification and automation, and a significant saving in reagent costs when scaled. Importantly, the current result suggests that it is possible to controllably refold disulfide-bonded proteins using common and inexpensive matrices, and that it is not always necessary to control protein-surface interactions using affinity tags and expensive chromatographic matrices. Moreover, it is possible to strictly control the oxidative refolding environment once denatured protein is bound to the ion-exchange column, thus allowing precisely controlled oxido-shuffling. (c) 2005 Elsevier B.V. All rights reserved.

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Sparse code division multiple access (CDMA), a variation on the standard CDMA method in which the spreading (signature) matrix contains only a relatively small number of nonzero elements, is presented and analysed using methods of statistical physics. The analysis provides results on the performance of maximum likelihood decoding for sparse spreading codes in the large system limit. We present results for both cases of regular and irregular spreading matrices for the binary additive white Gaussian noise channel (BIAWGN) with a comparison to the canonical (dense) random spreading code. © 2007 IOP Publishing Ltd.

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O desenvolvimento de métodos adequados que permitam o monitoramento de resíduos e contaminantes em alimentos é de suma importância pois é a única forma de garantir a segurança dos alimentos evitando danos à saúde do consumidor. Para isso, fazse necessário que estes métodos sejam rápidos, fáceis e de baixo custo, capazes de detectar a presença de resíduos em concentrações baixas e em diferentes matrizes. Este trabalho consistiu no desenvolvimento de método para determinação de 5 sedativos e 14 β-bloqueadores em amostras de rim suíno e posterior análise por Cromatografia Líquida Acoplada à Espectrometria de Massas em Série (LC-MS/MS). O procedimento de extração que melhor se adequou para análise destes compostos consistiu na pesagem de 2 g de amostra e adição de 10 mL de acetonitrila seguida de homogeneização com auxílio de Ultra-Turrax e mesa agitadora. Após extração, as amostras foram submetidas a duas técnicas de clean-up, sendo elas, congelamento do extrato à baixa temperatura e extração em fase sólida dispersiva (d-SPE) utilizando como sorvente Celite® 545. Uma etapa de concentração foi realizada com auxílio de concentrador de amostras sob fluxo de N2 e temperatura controlada. As amostras secas foram retomadas com metanol e analisadas utilizando sistema LC-MS/MS com Ionização por Eletrospray (ESI), operando no modo MRM positivo, coluna Poroshell 120 EC-C18 (3,0 x 50 mm, 2,7 μm) para separação dos analitos, e gradiente de fase móvel composta por (A) solução aquosa acidificada com 0,1% de ácido fórmico (v/v) e (B) metanol 0,1% ácido fórmico (v/v). Os parâmetros de validação avaliados foram linearidade, seletividade, efeito matriz, precisão, veracidade, recuperação, limite de decisão, capacidade de detecção, incerteza da medição, robustez, limite de detecção e de quantificação. Além disso foram observados os critérios de desempenho aplicáveis à detecção por espectrometria de massas e estabilidade dos compostos. A recuperação foi avaliada em 10 μg kg-1 e a veracidade em 5, 10 e 15 μg kg-1 apresentando resultados satisfatórios entre 70 - 85% e 90 - 101%, respectivamente. O limite de quantificação determinado foi de 2,5 μg kg-1 , exceto para carazolol que foi de 1,25 μg kg- 1 . O estudo de linearidade foi realizado entre 0 e 20 μg kg-1 apresentando coeficientes de determinação superiores a 0,98. Estes procedimentos foram realizados através de análise de matriz branca fortificada. Além disso, o presente método foi utilizado para analisar carazolol, azaperone e azaperol em amostras de ensaio colaborativo de rim suíno, apresentando resultados muito próximos aos reais. Portanto, é possível concluir que o método desenvolvido é adequado para análise de sedativos e β-bloqueadores através de extração dos compostos e limpeza do extrato eficientes utilizando procedimentos rápidos, fáceis e de baixo custo, garantindo resultados seguros e confiáveis.

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The mixed metal oxides constitute an important class of catalytic materials widely investigated in different fields of applications. Studies of rare earth nickelates have been carried by several researchers in order to investigate the structural stability afforded by oxide formed and the existence of catalytic properties at room temperature. So, this study aims synthesize the nanosized catalyst of nickelate of lanthanum doped with strontium (La(1-x)SrxNiO4-d; x = 0,2 and 0,3), through the Pechini method and your characterization for subsequent application in the desulfurization of thiophene reaction. The precursor solutions were calcined at 300ºC/2h for pyrolysis of polyester and later calcinations occurred at temperatures of 500 - 1000°C. The resulting powders were characterized by thermogravimetric analysis (TG / DTG), surface area for adsorption of N2 by BET method, X-ray diffraction (XRD), scanning electron microscopy (HR_SEM) and spectrometry dispersive energy (EDS). The results of XRD had show that the perovskites obtained consist of two phases (LSN and NiO) and from 700ºC have crystalline structure. The results of SEM evidenced the obtainment of nanometric powders. The results of BET show that the powders have surface area within the range used in catalysis (5-50m2/g). The characterization of active sites was performed by reaction of desulfurization of thiophene at room temperature and 200ºC, the relation F/W equal to 0,7 mol h-1mcat -1. The products of the reaction were separated by gas chromatography and identified by the selective detection PFPD sulfur. All samples had presented conversion above 95%

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As dificuldades de aprendizagem são tema de grande relevância no campo da educação, pelas repercussões que têm no desenvolvimento das crianças que as possuem, quer a nível pessoal, familiar, escolar e social. A compreensão das competências sócio-emocionais destas crianças surge como objecto de estudo desta investigação. A amostra é constituída por 74 crianças com dificuldades de aprendizagem do 1° Ciclo do Ensino Básico. Os instrumentos utilizados foram: o Inventário de Quociente Emocional Bar-On: Versão para crianças (EQ-i:YV; versão portuguesa; Candeias et al., 2008), o Teste de Resolução de Problemas lnterpessoais da Inteligência Social para Crianças (PRPI - 6/11; Candeias et al., 2008), o Teste de Competências Sociais para Crianças (PACS - Socialmente em Acção 6/11, Candeias et al., 2008), o Teste de Percepção de Emoções (Franco & Candeias, 2008) e as Matrizes Progressivas Coloridas de Raven (MPCR, Raven, 1965). Estudaram-se as relações entre a inteligência social, inteligência emocional, competência social e variáveis sócio-demográficas como a idade, o nível sócio-económico e a participação social destas crianças. Conclui-se que, quanto mais elevada é a competência emocional destes alunos, menores serão as suas dificuldades em termos de competência social. Estes achados permitem aumentar o conhecimento teórico sobre esta problemática, possibilitando a aplicação prática na intervenção psicológica e psicopedagógica. / ABSTRACT: Learning difficulties are the subject of great relevance in education, the impact they have on the development of children who have, whether for personal, familial, educational and social. Understanding of the socio-emotional skills of these children appears to be the subject of this research study. This study used a sample of 74 children with learning difficulties the first cycle of the cities of Évora and Montemor-o­ Novo. We applied: Emotional Quocient lnventory Bar-On: young version (EQ-i: YV; Candeias et al., 2008); Perception and Recognition Emotions (Franco & Candeias, 2008); Cognitive Test of Social lntelligence for Children (PRPI-6/11; Candeias et al., 2008); Social Competence Test for Children (PACS-6/11; Candeias et al., 2008) and Coloured Progressive Matrices (CPM, Raven, 1965). We studied the relationship between social intelligence, emotional intelligence, social competence and socio-demographic variables such as age, socio-economic and social participation of these children. lt was concluded that, the higher the emotional competence of these students, lower their difficulties in terms of social competence. These findings increase the theoretical knowledge on this issue, enabling the practical application in psychological and pedagogic. This study leaves open some suggestions for future work.

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Se han desarrollado varios modelos prometedores para la captura digital de datos de movilidad, que pueden ser aplicados en la planificación urbana, de transporte y de ordenamiento territorial. Por ello el objetivo de este trabajo es desarrollar una metodología que recolecte información de movilidad con la cual se generen matrices Origen-Destino (OD) y de tiempos de viajes, además que identifique puntos de interés, modos y rutas frecuentes de viaje mediante el desarrollo e implementación de una aplicación para dispositivos móviles Android. Metodología: Se produjo una aplicación para dispositivos móviles con sistema operativo Android, en base a modelos existentes. Esta aplicación obtuvo datos de movilidad a partir de los sensores de localización incorporados en los móviles (GPS), para su posterior migración a una base de datos en la nube y consiguiente post proceso con herramientas de análisis como KNIME, Python y QuantumGis. La aplicación fue probada por 68 estudiantes voluntarios de la Universidad de Cuenca, durante 14 días del mes de enero de 2016. Resultados: Con la información completa de 44 participantes se obtuvieron matrices OD y de tiempos de viajes para diferentes períodos del día, las cuales permitieron identificar variaciones de interacción entre zonas, variaciones de número y tiempo de viajes. Fueron reconocidos también modos de transporte como caminata, bicicleta y motorizados para una sub muestra (n=6). Se detectaron los POIs Residencia (91%), Trabajo/Estudio (74%) y puntos intermedios (20% del total de POIs) y se logró observar comportamientos de movilidad atípico. Finalmente se compararon las rutas más frecuentadas por los usuarios con las rutas óptimas teóricas calculadas, encontrando que el 63.6% de los usuarios coincidían con el recorrido de estas últimas. Conclusiones: El método planteado presenta coherencia con trabajos previos, mostrando niveles de confianza equiparables. El mayor reto es la implementación masiva del modelo creado para la recolección de datos útiles para planes de movilidad.

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Pulsed electric field technology is one of the most attractive new non-thermal technology thanks to its lower energy consumption and short treatment times. It consists of an electric treatment of short duration (from several ns to several ms) with electric field strengths from 0.1 to 80 kV/cm that lead to an increase in the permeability of the cell membrane. In this PhD thesis, PEF technology was investigated with the aim of improving mass transfer in plant and animal foods by using it alone or in combination with conventional food processes. Different methods of evaluating electroporation for optimizing PEF processing parameters were investigated. In this respect, the degree of membrane permeabilization in plant and animal food matrices was investigated using electrical impedance spectroscopy, current-voltage measurements and magnetic resonance imaging. The research findings provided useful insights and calls for critical choice of electroporation assessment methods for the selection of adequate PEF treatment conditions. It was outlined that the effect of electroporation is highly dependent on the properties of the food matrix and secondary phenomena occurring in the cell structure undergoing PEF treatment, such as the water re-distribution in the tissue due to the exchange of fluids between intra- and extra-cellular environments. This study also confirmed the great potential of combining PEF technology with conventional food processes, with the main purpose of improving the quality of the food material and accelerating the kinetics of mass transfers, in both plant and animal tissues. Consistent reduction of acrylamide formation in potato crisps was achieved by monitoring key PEF process parameters and subsequent manufacturing steps. Kiwifruit snacks showed a significant reduction in drying kinetics when pre-treated with PEF, while their quality was well maintained. Finally, the research results showed that PEF pre-treatments can shorten the brine process as well as the rehydration kinetics of fish muscles.

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Glass fibre-reinforced plastics (GFRP), nowadays commonly used in the construction, transportation and automobile sectors, have been considered inherently difficult to recycle due to both the cross-linked nature of thermoset resins, which cannot be remoulded, and the complex composition of the composite itself, which includes glass fibres, polymer matrix and different types of inorganic fillers. Hence, to date, most of the thermoset based GFRP waste is being incinerated or landfilled leading to negative environmental impacts and additional costs to producers and suppliers. With an increasing awareness of environmental matters and the subsequent desire to save resources, recycling would convert an expensive waste disposal into a profitable reusable material. In this study, the effect of the incorporation of mechanically recycled GFRP pultrusion wastes on flexural and compressive behaviour of polyester polymer mortars (PM) was assessed. For this purpose, different contents of GFRP recyclates (0%, 4%, 8% and 12%, w/w), with distinct size grades (coarse fibrous mixture and fine powdered mixture), were incorporated into polyester PM as sand aggregates and filler replacements. The effect of the incorporation of a silane coupling agent was also assessed. Experimental results revealed that GFRP waste filled polymer mortars show improved mechanical behaviour over unmodified polyester based mortars, thus indicating the feasibility of GFRP waste reuse as raw material in concrete-polymer composites.