977 resultados para Direct Urca Process
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Dissertação de mestrado em Direito das Crianças, Família e Sucessões
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This work focused on how different types of oil phase, MCT (medium chain triglycerides) and LCT (long chain triglycerides), exert influence on the gelation process of beeswax and thus properties of the organogel produced thereof. Organogels were produced at different temperatures and qualitative phase diagrams were constructed to identify and classify the type of structure formed at various compositions. The microstructure of gelator crystals was studied by polarized light microscopy. Melting and crystallization were characterized by differential scanning calorimetry and rheology (flow and small amplitude oscillatory measurements) to understand organogels' behaviour under different mechanical and thermal conditions. FTIR analysis was employed for a further understanding of oil-gelator chemical interactions. Results showed that the increase of beeswax concentration led to higher values of storage and loss moduli (G, G) and complex modulus (G*) of organogels, which is associated to the strong network formed between the crystalline gelator structure and the oil phase. Crystallization occurred in two steps (well evidenced for higher concentrations of gelator) during temperature decreasing. Thermal analysis showed the occurrence of hysteresis between melting and crystallization. Small angle X-ray scattering (SAXS) analysis allowed a better understanding in terms of how crystal conformations were disposed for each type of organogel. The structuring process supported by medium or long-chain triglycerides oils was an important exploit to apprehend the impact of different carbon chain-size on the gelation process and on gels' properties.
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Relatório de estágio de mestrado em Ensino de Inglês e de Espanhol no 3ºciclo do Ensino Básico e Ensino Secundário
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Tese de Doutoramento em Tecnologias e Sistemas de Informação.
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Tese de Doutoramento em Ciências da Comunicação.
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Tese de Doutoramento em Biologia Molecular e Ambiental (área de especialização em Biologia Molecular e Saúde).
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Dissertação apresentada na Universidade de Lisboa - Faculdade de Arquitetura, para obtenção do Grau de Mestre em Arquitetura.
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Dissertação apresentada na Universidade de Lisboa - Faculdade de Arquitetura, para obtenção do Grau de Mestre em Arquitetura.
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A presente investigação examina a importância do recess enquanto parte integrante do quotidiano escolar, deslindando o seu contributo ao nível da aprendizagem, da capacidade de trabalho e do sucesso académico. A premissa de que a aprendizagem dos alunos sai beneficiada pela introdução de pausas no seio de longos períodos de trabalho intelectual, é comum a um sem número de teorias gizadas na literatura que, no entanto, deixam por esclarecer se o benefício provém do conteúdo da pausa, ou meramente da sua existência. De forma a contribuir para este debate, centra-se a presente investigação numa abordagem alternativa: partindo do pressuposto de que as características individuais dos alunos, nomeadamente o estatuto sociométrico, a idade e o género, condicionam a forma como ocupam o tempo que passam no recreio, constituiu-se uma amostra, seleccionada mediante a aplicação de um questionário sociométrico, e levou-se a cabo a observação das actividades por ela desenvolvidas no recreio e da performance por ela conseguida na sala de aula, antes e depois do intervalo. Concluiu-se que a forma como as crianças vivem o recess é fortemente influenciada pelas três variáveis chave (status sociométrico, género e nível de ensino), e que o conteúdo do intervalo, mais do que a sua simples existência, é determinante para a subsequente atitude na sala de aula. Ressalve-se, em particular, que os alunos cuja actividade no recreio se revela fisicamente intensa e socialmente Cooperativa e Associativa, por excelência os alunos Populares, experimentam maiores dificuldades de atenção e concentração no regresso à aula do que aqueles que vivem um recess marcado por níveis moderados de actividade física e por um comportamento social menos expansivo. Mais, constatou-se que a dimensão social do comportamento durante o recess monopoliza o seu conteúdo influenciando, como tal, o desempenho na sala de aula.
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El proceso cultural en las Sierras de Córdoba fue habitualmente concebido como marginal con respecto al Noroeste Argentino. Tras el establecimiento del esquema básico de la secuencia prehispánica, a mediados del siglo pasado, se definió una etapa agroalfarera de cronología tardía, que continuaba a una extensa etapa precerámica cuyos límites se aproximaban a la transición Pleistoceno-Holoceno. Se hacía referencia, de este modo, al advenimiento de un modo de vida agrícola y aldeano, que reemplazaba a otro basado en la caza y recolección. Dicha transformación, alternativamente atribuida a la población cazadora local o a una migración de grupos agricultores desde regiones vecinas, se habría consumado hacia 1500 AP, fijando uno de los límites de la dispersión de la agricultura andina. Es necesario destacar la extremada escasez y el carácter indirecto de las evidencias arqueológicas utilizadas para sustentar la ocurrencia de tal proceso. Asimismo, la vigencia de supuestos que han comenzado a mostrar inconsistencias con los resultados de las recientes investigaciones. Entre ellos, principalmente, el que asume que la introducción de la agricultura dio paso a una transformación radical de las sociedades prehispánicas, constituyendo un hito fundamental en su devenir histórico, el comienzo de una nueva etapa. Nuestros últimos estudios en el sector central de las Sierras de Córdoba apuntaron, entre otros objetivos, a reconocer indicadores arqueológicos directos de producción agrícola, así como de la manipulación y consumo de plantas cultivadas. Los primeros resultados nos permiten vislumbrar un escenario complejo que desafía los modelos vigentes. El consumo de maíz, por ejemplo, parece haber antecedido por muchos siglos a la adopción de prácticas agrícolas. El acceso a este cultígeno, sumado a otros elementos, indicaría cambios entre los cazadores-recolectores serranos, promovidos por su integración en redes macrorregionales que los vincularon con sociedades agricultoras de la vertiente oriental andina y quizás del Chaco Santiagueño, por lo menos desde 2500 AP. En definitiva, la agricultura no parece haber sido adoptada rápidamente ni provocado transformaciones profundas e inmediatas en la organización de los grupos prehispánicos. Se ha observado, por el contrario, la incorporación gradual de distintas innovaciones que incluso permiten relacionar la manipulación y más tarde el cultivo de plantas domesticadas, con procesos de intensificación productiva de mayor escala temporal. Uno de nuestros objetivos en este proyecto consiste, básicamente, en profundizar las investigaciones en curso a fin de ampliar el cuerpo de datos con el cual analizar y discutir el problema de la dispersión agrícola en la región. Ello implica el tratamiento de diferentes líneas de evidencia, en particular: 1) la distribución regional de sitios arqueológicos y las modalidades de ocupación de las tierras cultivables; 2) la búsqueda de superficies de cultivo en sitios estratificados; y 3) estudios arqueobotánicos, polínicos y de isótopos estables. Se entiende que no le corresponde a la arqueología asumir apriorísticamente el significado histórico de la introducción de la agricultura, sino establecerlo en cada caso puntual a través de la investigación concreta. Nuestro segundo objetivo consiste, por lo tanto, en delinear los cambios (económicos, tecnológicos, políticos, sociales) que acompañaron al proceso de dispersión agrícola. Ello implica el tratamiento de diferentes problemas, entre otros: 1) las prácticas de apropiación de los recursos silvestres; 2) la continuidad y cambio tecnológico; 3) la movilidad y la articulación microambiental; y 4) los aspectos políticos y sociales ligados a prácticas como la molienda grupal y la producción del arte rupestre. The radical chage of societies from hunter-gatherers to farmers in 1500 BP was considered a milestone whitin the cultural process of pre-hispanic societies in Cordoba Hill. But there is a shortage of archaeological remains to support this change and there are weak hypotheses of absolute transformations. During the last years, our studies carried out on the central area of Cordoba Hill have tried to recognize direct archaeological signs of agriculture production as well as the handling and consumption of crops. The first results show a complex set that challenges the current theoretical models. For example, the corn was probably eatten prior to its adoption for farm practices. Our first main consists in increasing a corpus of data about the spread of agriculture in Cordoba region that we have been researching for the last years. These researches involve different lines of evidence: 1-regional location of archaeological sites and kinds of occupation on cultivable lands; 2-the search for plots at archaeological sites; 3-archaeobotanical, pollen and stable isotopes studies. Our second main consists in outlining changes within the spread of agriculture. It implies to considering different problems: 1-the practices to gatherer wild resources; 2-the continuity and changes of technologies; 3-the mobility and the articulation on the micro-environment; 4-political and social aspects in connection with activities such as groupal grinding and rock art productions.
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As digital imaging processing techniques become increasingly used in a broad range of consumer applications, the critical need to evaluate algorithm performance has become recognised by developers as an area of vital importance. With digital image processing algorithms now playing a greater role in security and protection applications, it is of crucial importance that we are able to empirically study their performance. Apart from the field of biometrics little emphasis has been put on algorithm performance evaluation until now and where evaluation has taken place, it has been carried out in a somewhat cumbersome and unsystematic fashion, without any standardised approach. This paper presents a comprehensive testing methodology and framework aimed towards automating the evaluation of image processing algorithms. Ultimately, the test framework aims to shorten the algorithm development life cycle by helping to identify algorithm performance problems quickly and more efficiently.
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Ireland’s remote position on the tip of Europe ensures that the country is vulnerable to uncertainty of supply. The reliance on conventional sources of electricity has ensured that escalated prices and high carbon emissions have been witnessed whilst opportunities that inherent resources provide, such as the wind, have not been capitalised upon. The intermittent nature of the wind make it difficult to maximise its potential as in many cases the highest wind speeds are highest when demand is low. The West of Ireland’s combination of wind speeds and unique topography makes it suitable for and innovative wind powered pumped storage system, which can essentially regulate the wind generated electricity and integrate further penetration of renewable energy. In addition, its location along the Atlantic Ocean provides further scope for innovation as seawater can be integrated into the system design. The construction of such an unprecedented project in combination with increased interconnectors has the potential to make Ireland a rechargeable battery for Europe. However, such ambitious plans are at the very early stages and are in direct contrast to current events in the Irish energy market. This study focuses on the feasibility of West of Ireland pumped storage systems. Entailed within this is an extensive desk study, a detailed site selection process and a feasibility study of grid connection. To increase opportunities to identify the best possible site, the feasibility study was focused on the Galway and Mayo areas solely.
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Surgeons may use a number of cutting instruments such as osteotomes and chisels to cut bone during an operative procedure. The initial loading of cortical bone during the cutting process results in the formation of microcracks in the vicinity of the cutting zone with main crack propagation to failure occuring with continued loading. When a material cracks, energy is emitted in the form of Acoustic Emission (AE) signals that spread in all directions, therefore, AE transducers can be used to monitor the occurrence and development of microcracking and crack propagation in cortical bone. In this research, number of AE signals (hits) and related parameters including amplitude, duration and absolute energy (abs-energy) were recorded during the indentation cutting process by a wedge blade on cortical bone specimens. The cutting force was also measured to correlate between load-displacement curves and the output from the AE sensor. The results from experiments show AE signals increase substantially during the loading just prior to fracture between 90% and 100% of maximum fracture load. Furthermore, an amplitude threshold value of 64dB (with approximate abs-energy of 1500 aJ) was established to saparate AE signals associated with microcracking (41 – 64dB) from fracture related signals (65 – 98dB). The results also demonstrated that the complete fracture event which had the highest duration value can be distinguished from other growing macrocracks which did not lead to catastrophic fracture. It was observed that the main crack initiation may be detected by capturing a high amplitude signal at a mean load value of 87% of maximum load and unsteady crack propagation may occur just prior to final fracture event at a mean load value of 96% of maximum load. The author concludes that the AE method is useful in understanding the crack initiation and fracture during the indentation cutting process.
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Univariate statistical control charts, such as the Shewhart chart, do not satisfy the requirements for process monitoring on a high volume automated fuel cell manufacturing line. This is because of the number of variables that require monitoring. The risk of elevated false alarms, due to the nature of the process being high volume, can present problems if univariate methods are used. Multivariate statistical methods are discussed as an alternative for process monitoring and control. The research presented is conducted on a manufacturing line which evaluates the performance of a fuel cell. It has three stages of production assembly that contribute to the final end product performance. The product performance is assessed by power and energy measurements, taken at various time points throughout the discharge testing of the fuel cell. The literature review performed on these multivariate techniques are evaluated using individual and batch observations. Modern techniques using multivariate control charts on Hotellings T2 are compared to other multivariate methods, such as Principal Components Analysis (PCA). The latter, PCA, was identified as the most suitable method. Control charts such as, scores, T2 and DModX charts, are constructed from the PCA model. Diagnostic procedures, using Contribution plots, for out of control points that are detected using these control charts, are also discussed. These plots enable the investigator to perform root cause analysis. Multivariate batch techniques are compared to individual observations typically seen on continuous processes. Recommendations, for the introduction of multivariate techniques that would be appropriate for most high volume processes, are also covered.
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The impending introduction of lead-free solder in the manufacture of electrical and electronic products has presented the electronics industry with many challenges. European manufacturers must transfer from a tin-lead process to a lead-free process by July 2006 as a result of the publication of two directives from the European Parliament. Tin-lead solders have been used for mechanical and electrical connections on printed circuit boards for over fifty years and considerable process knowledge has been accumulated. Extensive literature reviews were conducted on the topic and as a result it was found there are many implications to be considered with the introduction of lead-free solder. One particular question that requires answering is; can lead-free solder be used in existing manufacturing processes? The purpose of this research is to conduct a comparative study of a tin-lead solder and a lead-free solder in two key surface mount technology (SMT) processes. The two SMT processes in question were the stencil printing process and the reflow soldering process. Unreplicated fractional factorial experimental designs were used to carry out the studies. The quality of paste deposition in terms of height and volume were the characteristics of interest in the stencil printing process. The quality of solder joints produced in the reflow soldering experiment was assessed using x-ray and cross sectional analysis. This provided qualitative data that was then uniquely scored and weighted using a method developed during the research. Nested experimental design techniques were then used to analyse the resulting quantitative data. Predictive models were developed that allowed for the optimisation of both processes. Results from both experiments show that solder joints of comparable quality to those produced using tin-lead solder can be produced using lead-free solder in current SMT processes.