Dissertations / Theses on the topic 'Heat cured'

The curing of flue-cured tobacco (Nicotiana tabacum L.) is an energy intensive process and represents a significant portion of the overall cost of production. Given the goal of the industry to reduce the environmental footprint of tobacco production and the energy demand of curing, attention has been directed to explore options for the use of renewable fuels for heating tobacco barns. A two-year study conducted at the Virginia Tech Southern Piedmont Center evaluated the effectiveness and cost of curing flue-cured tobacco with a wood pellet burner. Additionally, field studies were conducted to evaluate the feasibility of on-farm production of biomass fuel crops as well as on-farm manufacture of biomass fuel pellets. The first time use of a wood pellet burner with an air-to-air heat exchanger in a bulk curing barn proved to be a viable alternative to a conventional propane fueled burner. Curing cost averaged $0.05 with the pellet burner compared to $0.04 per kilogram of tobacco with the propane burner. The increase in cost was offset by a 90 percent reduction of CO2 emissions with the use of wood pellets. The use of low lignin grass varieties did have an impact on biomass pellet properties. Pellet testing revealed high ash and chloride levels which could be problematic using a high efficiency wood pellet burner. Full maturity harvest of annual grasses fertilized with 112 kg per ha N resulted in higher yields. However, fertilizing for maximum yield would increase the CO2 footprint for biomass fuel pellet production.
Master of Science

Content: “Red heat” is an industry term that describes the appearance of mostly red-pink coloured macroscopic microbial colonies on salt-cured hides and skins. Red heat-affected stock is undesirable as the resultant leather often shows obvious defects; but why this contamination is only superficial in other instances remains unclear. Previous work has focused on pigmented halophiles (‘salt-loving’ microbes) isolated from curing salts as the primary culprit. However, the identity of causative agents remains unspecified. Also, the involvement of non-pigmented microbes, and of microbes native to hides and skins, could be better understood. Thus, an investigation of the microbial communities that inhabit untreated bovine hide, curing salt, unaffected salt-cured bovine hide, and red heat-affected cured hide is proposed to uncover the microbial agents responsible for this contamination. This project aims to define these microbial communities using both a culture-dependent and –independent approach. Methods of microbe identification focus on marker gene amplification and sequencing. This is in contrast to earlier work which was restricted solely to phenotypic analyses. The 16S ribosomal RNA gene marker is used to identify members of Bacteria and Archaea, while the 18S and ITS2 regions of the fungal ribosomal RNA operon are targeted to detect fungi. Metagenomic amplicon sequencing using the Illumina MiSeq platform employs these same markers to determine taxonomic composition and relative abundance. Preliminary results from culturing identified different dominant species in curing salts screened for microbial growth. In agreement with earlier culture-based studies, these isolates were mostly pigmented, highly salt-tolerant members of the halophilic archaea of family Halobacteriaceae, as determined by marker gene sequencing. However, in agreement with more recent work within food preservation technology, nonpigmented isolates of halophilic archaea of genus Natrinema and bacterial genus Chromohalobacter were also found. It was also revealed that non-pigmented, quick-growing, salt-tolerant, proteolytic microbes were easily cultured from red heat-affected hide, most of the isolates were identified by marker gene sequencing as bacterial Pseudomonas halophila or Salicola. To determine red heat-causing microbes, future work involves the screening of isolates for extracellular enzyme activity; the most likely cause of red heat-associated damage. Sterile-salted hide samples will be inoculated with selected individual and combinations of isolates, and then further examined using confocal microscopy to check for reproducibility of red heat-associated damage. Take-Away: Different microbial species are found in different curing salts. Not all microbes involved in 'red heat' contamination are pigmented. The purpose is the possibility to overcome all the restrictions connected with the pin-wheel machine, the improvement of actual EN ISO methods of leather measurement and a better instrument to define tolerances considering the couple leather-machine.

The purpose of this study was to determine the cementitious parameters and placement temperature that impact internal sulfate attack in concrete. Concrete structures make up a large percentage of the infrastructure and multifamily housing. Durability is very important. Cements can be formulated to reduce the impact of external environmental exposure such as high salinity from marine environments or high sulfate levels from soils or surface waters. Concrete is also subject to internal attack such as alkali aggregate reaction, (AAR), and delayed ettringite formation, (DEF). This study focused on some of the cement chemistry issues that determine susceptibility of cement to DEF. Expansion due to DEF can weaken the concrete matrix resulting in microcracks that in some cases may progress to severe matrix cracking. The end result is loss of load carrying capacity and costly repairs. In this study, mortar bars were made with the as received cement chemistry and using additions of sulfate, and alkalis. The bars were then heat cured at various temperatures and stored in a saturated lime solution at room temperature. Measurements were made at predetermined time intervals. The series of mixes were made to determine the effect of varying sulfate levels, heat curing temperature, and alkali content in order to isolate the effect of these constituents. The cements were selected on the basis of tricalcium aluminate, alkali content, sulfate levels, C3S levels and fineness. The results indicate that a relationship exists between the rate and level of expansion experienced by the mortar bars and cementitious parameters, namely, alkali content, sulfate content, C3S levels and heat curing temperature.

Traditionally, dough moulding compounds (DMCs) have been based on unsaturated polyester resins (UPR), fillers and glass fibre reinforcements. Such systems however are inflammable and will emit dense, toxic smoke on combustion. Phenolic resins, on the other hand, have excellent flame retardant properties, but slightly inferior mechanical properties. Phenolic DMCs are based on mineral fillers and glass fibre reinforcements, compounded into a phenolic resol (heat cure) resin. Compounding these systems using a co-rotating twin screw extruder, instead of the traditional method using a Z-blade mixer, results in long fibre DMCs which have better mechanical properties than short fibre DMCs. In this study, a wide range of inorganic materials, their pH being one of the selection factors, have been investigated as potential phenolic DMC fillers. Viscosity measurements were carried out on resin/filler mixtures, while on the cured samples flexural and impact properties were investigated. Producing DMCs using a twin screw compounder, the effects of filler loading, types of glass fibre, glass fibre loading and machine output on flexural and impact properties were investigated. Phenolic dough moulding compounds containing 20 wt % high integrity glass fibres and small amounts of aminosilane treated china clays (40 phr filler) had superior mechanical properties. These systems have a flexural strength of more than 120 MPa, which would allow them to compete with traditional UPR-based DMCs.

Lo scopo primario di questa tesi e' l’analisi di una nuova procedura di regolarizzazione di path integral su spazi curvi, presentata inizialmente dal fisico J. Guven e applicata al caso di una teoria di campo scalare , ma mai utilizzata per svolgere ulteriori calcoli espliciti. Questa procedura, se corretta, permetterebbe di utilizzare il formalismo di path integral su spazi piatti anche nel caso in cui la varieta' di background risulti localmente curva. Tale procedura trasforma di fatto un modello sigma non lineare in un modello efficace lineare, permettando pertanto di aggirare le usuali complicazioni dovute alla generalizzazione di path integral. Una prova diretta della correttezza della procedura di Guven sembra mancare in letteratura: per questo motivo in questa tesi verranno eseguiti vari test volti a tale verifica. Alcuni errori sono stati riscontrati nella proposta iniziale, tra i quali un termine di potenziale che risulta essere non corretto. Ad ogni modo siamo stati in grado di identificare un potenziale che permetta di riprodurre correttamente i primi due coefficienti dell’espansione in serie dell’heat kernel. Utilizzando lo stesso metodo abbiamo poi cercato di ottenere il successivo coefficiente dell’espansione (cubico in termini di curvatura): il risultato ottenuto non risulta essere corretto, cosa che segnala il fallimento di tale metodo ad ordini superiori. Visti tali risultati preliminari, siamo stati indotti a considerare una classe speciale di spazi curvi, quella degli spazi massimamente simmetrici, trovando invece che su tali spazi la procedura di Guven riproduce i risultati corretti. Come verifica abbiamo ottenuto la parte diagonale dell’heat kernel, che ́ stata poi utilizzata per riprodurre l’anomalia di traccia di tipo A per campi scalari in dimensioni arbitrarie fino a D = 12. Questi risultati sono in accordo con quelli attesi. Viene pertanto fornita una prova della validita' di tale procedura su questi spazi.

Free liquid-jet impingement is well researched due to its high heat transfer ability and ease of implementation. This study considers both the steady state and transient heating of a patterned plate under slot-free-liquid jet impingement. The primary working fluid was water (H2O) and the plate material considered was silicon. Calculations were done for Reynolds number (Re) ranging from 500 to 1000 and indentation depths from 0.000125 to 0.0005 m for three different surface configurations. The effect of using different plate materials and R-134a as the working fluid were explored for the rectangular step case. The distributions of the local and average heat-transfer coefficient and the local and average Nusselt number were calculated for each case. A numerical model based in the FIDAP computer code was created to solve the conjugate heat transfer problem. The model used was developed for Cartesian coordinates for both steady state and transient conditions. Results show that the addition of surface geometry alters the fluid flow and heat transfer values. The highest heat-transfer coefficients occur at points where the fluid flow interacts with the surface geometry. The lowest heat-transfer coefficients are found in the indentations between the changes in geometry. The jet velocity has a large impact on the heat transfer values for all cases, with increasing jet velocity showing increased local heat-transfer coefficients and Nusselt number. It is observed that increasing the indentation depth for the rectangular and sinusoidal surfaces leads to a decrease in local heat transfer whereas for triangular patterns, a higher depth results in higher heat-transfer coefficient. The transient analysis showed that changing surface geometry had little effect on the time required to reach steady state. The selection of plate material has an impact on both the final maximum temperatures and the time required to reach steady state, with both traits being tied to the thermal diffusivity (α) of the material.

O presente trabalho trata da modelagem da condução de calor transiente com geração de calor em meios heterogêneos, e tem o objetivo de desenvolver um modelo multiescala adequado a esse fenômeno. Já existem modelos multiescala na literatura relacionados ao problema proposto, e que são válidos para os seguintes casos: (a) o elemento de volume representativo tem tamanho desprezível quando comparado ao comprimento característico macroscópico (e como consequência, a microescala tem inércia térmica desprezível); ou (b) a geração de calor é homogênea na microescala. Por outro lado, o modelo proposto nesta tese, o qual é desenvolvido utilizando uma descrição variacional do problema, pode ser aplicado a elementos de volume representativos finitos e em condições em que a geração de calor é heterogênea na microescala. A discretização temporal (diferenças finitas) e as discretizações espaciais na microescala e na macroescala (método dos elementos finitos) são apresentadas em detalhes, juntamente com os algoritmos necessários para implementar a solução do problema. Nesta tese são apresentados casos numéricos simples, procurando verificar não só o modelo teórico multiescala desenvolvido, mas também a implementação feita. Para tanto, são analisados, por exemplo, (a) casos em que considera-se a microescala um material homogêneo, tornando possível a comparação da solução multiescala com a solução convencional (uma única escala) pelo método dos elementos finitos, e (b) um caso em um material heterogêneo para o qual a solução completa, isto é, modelando diretamente os constituintes no corpo macroscópico, é obtida, tornando possível a comparação com a solução multiescala. A solução na microescala para vários casos analisados nesta tese sofre grande influência da inércia térmica da microescala. Para demonstrar o potencial de aplicação do modelo multiescala, simula-se a cura de um elastômero carregado com negro de fumo. Embora a simulação demonstre que a inércia térmica não precise ser considerada para esse caso em particular, a aplicação da presente metodologia torna possível modelar a cura do elastômero diretamente sobre a microescala, uma abordagem até então não utilizada no contexto de métodos multiescala. Essa metodologia abre a possibilidade para futuros aperfeiçoamentos da modelagem do estado de cura.
This work deals with the modeling of transient heat conduction with heat generation in heterogeneous media, and its objective is to develop a proper multiscale model for this phenomenon. There already exist multiscale models in the literature related to this proposed problem, and which are valid for the following cases: (a) the representative volume element has a negligible size when compared to the characteristic macroscopic size (and, as a consequence, the microscale has a negligible thermal inertia); or (b) the heat generation is homogeneous at the microscale. On the other hand, the model proposed in this thesis, which is developed using a variational description of the problem, can be applied to finite representative volume elements and in conditions in which the heat generation is heterogeneous at the microscale. The time discretization (finite difference) and the space discretizations at both the microscale and the macroscale (finite element method) are presented in details, together with the algorithms needed for implementing the solution of the problem. In this thesis, simple numerical cases are presented, aiming to verify not only the theoretical multiscale model developed, but also its implementation. For this, it is analyzed, for instance, (a) cases in which the microscale is taken as a homogeneous material, making it possible the comparison of the multiscale solution with the conventional solution (one single scale) by the finite element method, and (b) a case in a heterogeneous material for which the full solution, that is, modeling all constituents directly on the macroscale, is obtained, making it possible the comparison with the multiscale solution. The solution at the microscale for several cases analyzed in this thesis suffers a large influence of the microscale thermal inertia. To demonstrate the application potential of the multiscale model, the cure of a carbon black loaded elastomer is simulated. Although the simulation shows that the thermal inertia does not have to be considered for this case in particular, the application of the present methodology makes it possible to model the cure of the elastomer directly at the microscale, an approach not used in multiscale methods context until now. This methodology opens the possibility for future improvements of the state of cure modeling.

Regardless of scientific field computers have become pivotal tools for data analysis and the field of structural biology is not an exception. Here, computers are the main tools used for tasks including structural calculations of proteins, spectral analysis of nuclear magnetic resonance (NMR) spectroscopy data and fitting mathematical models to data. As results reported in papers heavily rely on software and scripts it is of key importance that the employed computational methods are robust and yield reliable results. However, as many scientific fields are niched and possess a small potential user base the task to develop necessary software often falls on researchers themselves. This can cause divergence when comparing data analyzed by different measures or by using subpar methods. Therein lies the importance of development of accurate computational methods that can be employed by the scientific community. The main theme of this thesis is software development applied to structural biology, with the purpose to aid research in this scientific field by speeding up the process of data analysis as well as to ensure that acquired data is properly analyzed. Among the original results of this thesis are three user-friendly software: COMPASS - a resonance assignment software for NMR spectroscopy data capable of analyzing chemical shifts and providing the user with suggestions to potential resonance assignments, based on a meticulous database comparison. CDpal - a curve fitting software used to fit thermal and chemical denaturation data of proteins acquired by circular dichroism (CD) spectroscopy or fluorescence spectroscopy. PINT - a line shape fitting and downstream analysis software forNMRspectroscopy data, designed with the important purpose to easily and accurately fit peaks in NMR spectra and extract parameters such as relaxation rates, intensities and volumes of peaks. This thesis also describes a study performed on variants of the life essential regulatory protein calmodulin that have been associated with the congenital life threatening heart disease long QT syndrome (LQTS). The study provided novel insights revealing that all variants are distinct from the wild type in regards to structure and dynamics on a detailed level; the presented results are useful for the interpretation of results from protein interaction studies. The underlying research of this paper makes use of all three developed software, which validates that all developed methods fulfil a scientific purpose and are capable of producing solid results.

Manufacturing induced shape distortions is a common problem for composite materials. Due to the non-isotropic nature of carbon fibre reinforced polymers (CFRP) unavoidable deformations occur during part production. During fabrication of polymer composites, the material obtains its final shape at elevated temperatures. The curing process involves a transition from the liquid state to the solid, glassy state, allowing bonding between fibres and matrix. As the material cools the mismatch in thermal expansion coefficients and cure shrinkage obtained during the matrix polymerization leads to residual stresses on the mechanical level within composite part. There is a great interest from the aircraft and automotive industries, to increase the ability to understand development of shape distortions and residual stresses during the cure, since these deformations often lead to dissatisfaction of tolerances and it is essential to predict the deformations beforehand in order to compensate time and cost.  In this context, a study of residual stresses during the curing process of thermosetting resin composites is presented. A methodology is proposed for predicting the formation and development of manufacturing- induced residual stresses. The present project reports on a comprehensive experimental study on the dependency of different short curing cycles on the build-up of residual stresses in a carbon fibre/fast-curing epoxy system and evaluate of post-curing methods through induction heating and oven post-curing with unidirectional [904] and unsymmetrical [9020] laminates. It includes characterization in thermo-elastic properties and degree-of-cure of the material by Thermal bending test, thermal expansion test, mechanical tensile test and Differential Scanning Calorimetry (DSC) in non-post-cured and post-cured laminates. The results showed slight variation in the thermal properties and not effect in the mechanical properties at different cure and post-curing conditions. Analytical data by Laminate Analysis program validated the experimental thermo-elastic data with analytical simulations. In addition, it is shown improvements in the temperature distributions in the post-curing by induction heating with different experimental set-ups, however, oven post-curing showed a more systematic system, higher heat efficient a low cure temperature, with more consistent mechanisms of shape distortions and residual stresses compared to induction heating. These findings are relevant for the future development of prediction methods for process induced deformations of Fast Curing Epoxy Resins (FCER).

Une augmentation de la température à jeune âge du béton peut être causée par la chaleur d’hydratation dans le cas d’éléments massifs ou par l’application d’un traitement thermique dans l’industrie de la préfabrication. Lorsque le couple critique température maximale/durée de maintien est dépassé, il y a formation différée de l’ettringite (DEF) expansive pouvant fissurer les pièces. Les travaux présentés dans ce mémoire ont pour but principal d’établir une limite sécuritaire pour des mélanges V-S pour béton de masse et V-P pour béton préfabriqué régulièrement utilisés par le Ministère des Transports du Québec. Ces bétons utilisent des liants binaires composés de fumée de silice de type GUb-SF et des liants ternaires composés de fumée de silice et de cendres volantes ou de laitier de haut-fourneau. La norme canadienne actuelle (CSA A23.1-14 et CSA A23.4-16) impose une limite fixe de température qui ne dépend ni de la durée de traitement ni du type de liant utilisé. Le lien, souvent énoncé dans la littérature, entre la réponse d’un liant à un traitement thermique et sa composition chimique et minéralogique, déterminé respectivement par fluorescence X et diffraction des rayons X couplée par la méthode de calcul Rietveld, a pu être confirmé. Le rapport SO3 solubles/Al2O3 est notamment ce qui permet la meilleure estimation de la sensibilité d’un liant. Le processus de formation différée de l’ettringite est lent et peut prendre plusieurs années. Donc, pour étudier le phénomène, des méthodes d’essais accélérés ont été testées. Des méthodes ont ainsi pu être proposées pour de futurs tests. Une méthode d’essai rapide d’expansion de barres de mortier permet d’identifier les liants les plus sensibles à la DEF. La formation de la DEF dans les liants les moins sensibles peut être appréciée par le gain de masse de prismes de béton et leur observation microstructurale au microscope électronique à balayage (MEB). Une méthode sur bétons de masse et bétons préfabriqués permet de classer le degré de sensibilité d’un liant face à la DEF selon le gain de masse des prismes de béton. Les liants ternaires montrent une bonne résistance face à la DEF. La sensibilité des liants binaires dépend du rapport SO3 solubles/Al2O3 du liant.
Abstract : A heat cure for concrete can be caused by hydration in massive structures or by thermal treatment in prefabrication industry. When the limit couple maximum temperature/duration of treatment is exceeded, the delayed formation of ettringite occurs and leads to cracking in concrete. The main goal of the work presented in this essay is to establish a safe batch limit for some mixtures, VS (mass concrete) and V-P (precast concrete) which are often used by MTQ. These concretes use some cements blended with silica fume and ternary blended cements with silica fume and fly ash or blast furnace slag. Indeed, the current Canadian standard (CSA A23.1) set a limit which doesn’t depend on duration of the treatment nor the type of bender. However, the link between composition of the used bender, with can be determined by X-ray fluorescence and X-ray diffraction, and the response to a thermal treatment has been confirmed. The soluble SO3/Al2O3 ratio allows to estimate if a bender is sensitive to heat cure. The delayed formation of ettringite is a long process which can last a decade. In order to study this phenomenon, several accelerated test methods have been used. Some of them are available for some future tests. An accelerated expansion method using mortar bar allows to spot the DEF-sensitive benders. Delayed ettringite formation in the less sensitive bender can be estimated by weight gain in concrete prisms and by observation with scanning electron microscope (SEM). The sensitivity level of a bender can by estimated using a method based on weight gain. Ternary blended cements show a greater ability to withstand DEF. The sensibility of binary blended cements depends on soluble SO3/Al2O3 ratio.

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The effects of curvature and the resulting centrifugal instabilities on local heat transfer distributions are studied in a curved channel at Dean numbers ranging from 50 to 200. The channel has a rectangular cross section of 1.27 cm by 50.1 cm giving an aspect ratio of 40 to 1. Flow is heated in a straight portion of the channel prior to the curved portion in order to obtain flow which is hydrodynamically and thermally fully developed. All baseline tests confirm techniques employed and qualify flow behavior. These consist of energy balance checks and comparison of results from the straight section to numerical and analytic solutions. Nusselt numbers in the curved section initially show an abrupt decrease after the imposition of the stabilizing influences of convex curvature. These are followed by a gradual increase as centrifugal instabilities and Dean vortices form and develop. Spatially resolved results also show significant surface Nusselt number variations across the span of a vortex pair, especially on the concave surface. On the convex surface, local Nusselt numbers are much more apt to be spanwise uniform.

Orientador: Ariene G. F. Van Dender
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Neste trabalho otimizou-se o processo de obtenção do requeijão cremoso longa vida (UHT) com teor integral de gordura e desenvolveu-se o processo tecnológico de fabricação do requeijão cremoso light UHT, de modo a obter produtos com características similares às versões tradicional e light obtidas com tratamento térmico normal. Os requeijões cremosos foram processados a partir de massa obtida por acidificação direta a quente de leite desnatado. Creme de leite, sal emulsificante e cloreto de sódio foram adicionados a massa antes de iniciar o processo de fusão. No caso das versões light a gordura foi parcialmente substituída pelo concentrado de proteína de soro (WPC 34%). Os requeijões obtidos foram envasados em copos de vidro (requeijão cremoso e requeijão cremoso light) ou esterilizados em processo UHT (143ºC/3-5 segundos) e envasados assepticamente em embalagens Tetra Pak de 125 mL (requeijão cremoso UHT e light UHT). Os requeijões obtidos foram avaliados e comparados em relação às características: físicas e químicas, microbiológicas, perfil de textura (TPA), sensoriais (aceitabilidade, ADQ, estudo de vida de prateleira), perfil eletroforético das proteínas, microscopia eletrônica de varredura (SEM) e cor (instrumental). Não houve diferença significativa (p < 0,05) na composição química do requeijão cremoso (RC) e requeijão cremoso UHT (RCUHT). Os requeijões cremosos light (RCL) e light UHT (RCLUHT) apresentaram composição bastante similar. Ao longo do período de estocagem de 90 dias a 5ºC os valores de pH e lactose dos requeijões cremosos (RC e RCUHT) não apresentaram diferença significativa. Os índices de oxidação lipídica pelo método de ácido 2-tiobarbitúrico (TBA) do RC foram significativamente maiores do que os do RCUHT em 30, 60 e 90 dias de estocagem a 5ºC. Não houve diferença significativa no índice de TBA do RCUHT (estocado a 5 e 25ºC) durante o período de estocagem de 180 dias, exceto após 135 dias de estocagem. Nenhuma alteração foi observada no RC e RCL (acondicionados em copo), mantidos a 4-5ºC durante 90 dias, os quais apresentaram qualidade microbiológica satisfatória e de acordo com a legislação vigente. Quando submetidos ao teste de incubação (35-37ºC/7dias), RCUHT e o RCLUHT não apresentaram crescimento microbiano, alteração no pH e na aparência visual sendo, portanto considerados microbiológicamente seguros e adequados ao consumo. Houve diferença significativa (p < 0,05) em todos os parâmetros do perfil de textura (firmeza, adesividade, elasticidade e coesividade) entre o RC e o RCUHT durante 90 dias a 5ºC. Em geral não houve diferença significativa nos atributos de textura do requeijão cremoso UHT e do requeijão cremoso light UHT quando estocados nas temperaturas de 5 e 25ºC. Não houve diferença significativa (p < 0,05) nos parâmetros de cor (Luminosidade, cor amarela e índice de brancura) dos requeijões (RC e RCUHT, e RCL e RCLUHT) durante 90 dias de estocagem a 5ºC, dos requeijões (RCUHT e RCLUHT estocados a 5 e 25ºC) durante 180 dias de estocagem. A interação entre as amostras (RC e RCUHT) e o tempo de estocagem não foi significativa, ou seja, o tratamento térmico aplicado às amostras não afetou significativamente, o pH e o teor de lactose, os parâmetros de textura e os parâmetros de cor dos requeijões durante 90 dias a 5ºC. Para o RCL e o RCL UHT, a interação entre as amostras e o tempo de estocagem não foi significativa para os parâmetros de textura e de cor dos requeijões. Não houve interação significativa entre as amostras (estocadas a 5 e 25ºC) e o tempo de estocagem, ou seja, as temperaturas de estocagem dos requeijões (5 e 25ºC) não afetaram significativamente o índice de TBA, os parâmetros de cor e os parâmetros de textura do RCUHT e do RCLUHT durante 180 dias a 5 e 25ºC. Na microscopia eletrônica de varredura observaram-se diferenças na microestrutura do RC e do RCUHT e também na microestrutura do RCL e RCLUHT. Tais diferenças provavelmente se devem aos efeitos dos tratamentos (térmico e mecânico) inerentes ao processo UHT. Apesar da composição química similar, as diferenças observadas na textura e na microestrutura dos requeijões cremosos (UHT e light UHT) foram desejáveis e necessárias de forma que o produto pudesse ser acondicionado na embalagem e manipulado facilmente para seu consumo. O perfil eletroforético dos requeijões (RC e RCUHT) apresentou as frações da ß-CN, as1-CN e ?-CN. No requeijão cremoso (RC) observou-se também a presença da fração as1 - I CN, além das outras frações. Não houve diferença no perfil eletroforético das proteínas no requeijão cremoso light e requeijão cremoso light UHT, os quais apresentaram as frações de ß-CN, as1-CN e ?-CN. Ao longo do período de estocagem de 90 dias para o requeijão cremoso e light e 180 dias para o requeijão cremoso UHT e light UHT não houve alteração no perfil eletroforético, indicando que não ocorreu proteólise ou degradação das frações de caseína ao longo do tempo. No teste de aceitabilidade das amostras de RC e RCUHT em comparação com amostras comerciais observou-se que todas as amostras obtiveram boas médias de aceitação global. Quanto à consistência e espalhabilidade observaram-se elevadas porcentagens de rejeição da amostra UHT em relação às demais, sendo sua consistência de menor aceitação. Por outro lado, as amostras de RCL e RCLUHT comparadas com amostras de requeijões cremosos light comerciais no teste de aceitabilidade foram as de maior aceitação global. Quanto à consistência e espalhabilidade, houve destaque positivo para aceitação das amostras de RCLUHT e RCL em relação às demais. Em relação ao sabor, o RCLUHT obteve o maior índice de aceitação entre as amostras. Na Análise descritiva quantitativa verificou-se que a amostra de RCUHT em relação ao RC apresentou (ao nível de erro de 5%) cor branco-creme mais escura, menos consistência, mais fluidez, mais escorrimento no pão, menor sensação de corpo/consistência oral e gosto ácido levemente mais intenso. Estas amostras apresentaram igual intensidade de aroma e de sabor característico de requeijão e de creme de leite, de aroma de queijo maturado e de gostos salgado e amargo. A amostra de RCLUHT em relação ao RCL somente diferiu (ao nível de erro de 5%) quanto à intensidade do sabor característico de requeijão, considerada levemente menor. De acordo com o estudo da vida de prateleira e tendo em mente a necessidade de uma margem de segurança que garanta a qualidade do produto sugere-se os seguintes prazos de validade; (1) requeijão cremoso UHT (longa vida): 6 meses sob refrigeração até 10º C; 5 meses a 25º C e 2 meses para estocagem a 35º C; (2) requeijão cremoso light UHT (longa vida): 6 meses sob refrigeração até 10º C; 4 meses a 25º C e 2 meses para estocagem a 35º C. O emprego do processo UHT na produção de requeijão cremoso visa aumentar a durabilidade do produto devido ao tratamento térmico (UHT) e a embalagem asséptica e simplificar o sistema de transporte e estocagem do mesmo, sem a necessidade de refrigeração. Portanto, esta nova tecnologia desenvolvida visa oferecer uma nova alternativa ao mercado consumidor
Abstract: This research study describes the optimization of the manufacturing process of UHT full fat requeijão cremoso (long-life) as well as the development of a process to manufacture reduced fat version of UHT requeijão cremoso (long-life), in a way such as to obtain final products with characteristics similar to those of traditional commercial requeijão cremoso produced with the normal heat treatment. The processed cheeses were all made from fresh curds obtained by direct acidification of heated skim milk. Milk cream, emulsifying salt and sodium chloride were added to the curds before initiating the melting process. In the case of the reduced fat versions, milk fat was partially replaced by a fat substitute (WPC 34). The final products were hot-filled into glass containers (full fat and reduced fat requeijão cremoso) or sterilized by UHT processing (143ºC/3-5 seconds) before being aseptically filled into 125 mL Tetra Pak packages (full fat UHT requeijão cremoso and reduced fat UHT requeijão cremoso). The processed cheeses were evaluated and compared for physical-chemical, microbiological, texture profile analysis (TPA) and sensory (acceptability, DQA, shelf life study) characteristics, protein electrophoretic profile, scanning electron microscopy (SEM) and color (instrumental). No statistically significant (p < 0,05) differences were found in the chemical composition of the requeijão cremoso types investigated (traditional heat and UHT processing). The traditional reduced fat and UHT reduced fat requeijão cremoso presented quite similar chemical compositions. During storage for 90 days at 5ºC, the pH value and lactose levels of the traditional and UHT full fat requeijão cremoso samples did not show any significant differences (p < 0,05). Lipids oxidation as measured by TBA method was found to be significantly higher in the samples of requeijão cremoso (glass containers) compared to UHT requeijão cremoso after 30, 60 and 90 days storage. No statistically significant (p < 0,05) differences were found in the TBA values of the full fat UHT requeijão cremoso (stored at 5 and 25ºC) during the180 days storage period studied, except after the 135 days. In addition to being of satisfactory microbiological quality and in compliance with all applicable standards, the glass-packed requeijão cremoso samples (full fat and reduced fat) did not present any microbiological changes after 90 days storage at 4-5ºC. The results of the incubation test clearly show that the long-life processed cheeses (UHT full fat and UHT reduced fat requeijão cremoso) were also considered microbiologically safe and fit for human consumption as they did not present bacterial growth, change of pH value and visual appearance after incubation at 35-37ºC for 7 days. The texture profile parameter values (firmness, adhesiveness, elasticity and cohesiveness) of the glass-packed full-fat requeijão cremoso samples were significantly (p < 0,05) different from those of the UHT full fat cheeses during 90 days at 5ºC. In general, no significant differences (p < 0,05) were found between texture profile attributes of UHT full fat and UHT reduced fat processed cheeses when stored at 5 and 25ºC. No significant changes in the color parameters values (L*, b*, IB) of the glass-packed full fat and reduced fat requeijão cremoso, and UHT full fat and UHT reduced fat requeijão cremoso were observed throughout 90 days storage at 5C. Also in the case of UHT full fat and UHT reduced fat requeijão samples stored at 5 and 25ºC, the color parameter values did not measurably change during 180 days storage. No statistically significant differences (p < 0,05) were detected as to interaction between the samples (full fat and UHT full fat requeijão cremoso) and the storage period investigated, thus the heat treatment to which the different RC types were exposed during the manufacturing process did not produce any significant differences in terms of pH value, lactose levels, texture profile parameter values and color parameters values during 90 days at 5ºC. No statistically significant differences (p < 0,05) were detected as to interaction between the samples and the storage period investigated relative to the color parameters values and the texture profile parameter values of reduced fat and UHT reduced fat requeijão cremoso. No significant differences (p < 0,05) were found between the samples (stored at 5 and 25ºC) and the storage period, thus, storage temperatures did not significantly affect the TBA values, the color parameters values and the texture profile attributes of UHT full fat requeijão cremoso and UHT reduced fat requeijão cremoso during 180 days at 5 and 25ºC. Images generated by scanning electron microscopy (SEM) showed marked differences between the microstructure of glass-packed full fat and UHT full fat requeijão cremoso on one hand, and between the microstructure of glass-packed reduced fat and UHT reduced fat requeijão cremoso on the other. These differences are probably due to effects of the heat and mechanical treatments inherent to UHT processing. In spite of having similar chemical compositions, the differences in texture and microstructure of the UHT full fat and UHT reduced fat requeijão cremoso versions are desirable and necessary, not only to enable the product to be filled into the package, but also to facilitate its consumption. The electrophoretic profiles of the full fat requeijão cremoso versions (glass-packed and UHT-processed) exhibited fractions of ß-CN, as1-CN e ?-CN. In addition to these fractions, the electrophoretic profile of glass-packed full fat requeijão cremoso shows also the presence of the as1 - I CN fraction. There was no difference between the electrophoretic profiles of the proteins present in the glass-packed reduced fat requeijão cremoso and that of the UHT reduced fat product, both of which contained the ß-CN, as1-CN and ?-CN fractions. No perceptible changes were observed in the electrophoretic profiles of the glass-packed requeijão samples (full fat and reduced fat) during the 90-day storage period studied, nor in the profile of the UHT full fat and UHT reduced fat cheeses during 180 days storage, thereby indicating that none of the four requeijão cremoso types studied was affected by proteolysis or casein fraction breakdown with time. The results of sensory acceptability analysis showed that both the glass-packed and UHT full fat requeijão cremoso samples received a high percentage of good ratings for overall sensory acceptability. The consistency and spreadability attributes of the UHT full fat requeijão cremoso samples received high percentages of rejection compared to the other sample types, with consistency receiving the lowest scores of acceptability. On the other hand, the samples of glass-packed reduced fat requeijão cremoso and UHT reduced fat requeijão cremoso obtained good percentage ratings for overall acceptability and received higher ratings for this attribute as compared to 2 different brands of commercial reduced fat requeijão. As for consistency and spreadability, particularly the samples of glass-packed and UHT reduced fat cheese which obtained consistently higher ratings compared to all the other samples types analysed. As for the attribute taste, UHT reduced fat requeijão cremoso received the highest scores for acceptability. The results of quantitative descriptive analysis show that (5% error level), compared to the glasspacked full fat product, the UHT full fat requeijão cremoso presented a darker tone of creamy white color, less firm and more fluid consistency, smoother and more fluid cheese flow on bread, less mouthfeel & body and a more intense acidic note. These samples exhibited similar intensity of aroma and typical requeijão and milk cream taste, ripened cheese aroma and salty and bitter flavor notes. Compared to the glass-packed reduced fat requeijão, the UHT reduced fat requeijão cremoso samples were found to exhibit only less intense taste of typical requeijão (5% error level). Based on the results of the shelf-life study and considering the need for a safety margin that would guarantee the safety of the product, the following shelf life times are suggested: (1) UHT full fat requeijão cremoso (long-life): 6 months when stored under refrigeration at up to 10º C; 5 months when stored at up to 25º C and 2 months when stored at up to 35º C; (2) UHT reduced fat requeijão cremoso (long-life): 6 months when stored under refrigeration at up to 10º C; 4 months when stored at a temperature of 25º C and 2 months when stored at up to 35º C. The use of UHT processing in the manufacture of requeijão cremoso aims at extending the shelf life of the product as a result of both the higher efficiency of the UHT process as compared to the traditional heat treatment and the advantages of the aseptic package that not only eliminates the need of refrigeration but also facilitates handling throughout the distribution chain. Thus, this new technology provides a new and technically & economically feasible alternative for large-scale dairy plants
Doutorado
Doutor em Tecnologia de Alimentos

Magister Scientiae Dentium - MSc(Dent)
Objectives:Substances leaching from denture- base polymers have been associated with cytotoxicity and allergic reactions. This study examined the effect of polishing,mixing ratios, water immersion temperatures and different thicknesses on the sorption and solubility of a heat-polymerized, denture-base polymer. The effect of different water immersion temperatures on the flexural strength of the denture base, was tested as well. The next component of this study, is the testing of the most significant sorption and solubility findings on in vitro cell viability. Materials and Methods:Disc shaped specimens from a heat-polymerized, denture-base polymer (Vertex®) were prepared, based on ISO 1567 specifications for sorption and solubility testing, following the manufacturers’ instructions. The following tests were performed: 1) Sorption and solubility of two groups (n = 12 each) of polished and unpolished discs were established and compared by means of the Mixed procedure; 2) Sorption and solubility of three groups (n = 12 each) with different mixing ratios were compared by means of the Mixed procedure; 3) Four groups (n = 14 each) were immersed in water at different temperatures, sorption and solubility were compared by means of pairwise comparison and the Median test; 4) Specimens with different thicknesses (n = 36) were compared, again, by means of pairwise comparison and the Median test; 5) To test the influence of different water-soaking temperatures on the flexural strength of the disc, strips were prepared from the disc used in test no. 3. The flexural strength was compared, by means of the Median test; 6) To test the influence of no postpolymerization treatment, polishing and water immersion on the cytotoxicity of mouse fibroblast cells, (n = 9) for each test group, were prepared. A preliminary test was performed beforehand, over a period of 24 hours, up to a maximum period of four weeks. The Balb/c 3T3 mouse fibroblast cells were cultured and incubated for 24 hours in Eagles medium. Eluates prepared from the disc and medium without any disc (control) replaced the medium. Cytotoxicity was assessed by MTT-assay. Optical density values were obtained at 24 and 48 hour intervals. The data was analyzed by means of the Means procedure.Results:In the entire thesis, the data was analyzed using SAS on a 0.01 probability level.Between polished and unpolished groups, no significant difference in water sorption (p> 0.01) was found, but there was a difference in solubility (p<0.01).Different mixing ratios did not alter sorption (p = 0.34) or solubility (p = 0.68).However, a difference (p<0.01) in sorption and solubility was found among the different temperature and thickness groups. Soaking the denture base in water at different temperatures did not alter its flexural strength (p = 0.48). Cell viability levels were noted in all the experimental groups in the MTT assay test. The analysis was a two-factor study, with one factor being the group, and the other, being time. The interaction between these factors was found to be significant, indicating that the effect of the groups varied by time (and vice versa).Conclusion:The processes of the soaking in warm water and the polishing of a denture-base polymer, reduce its solubility. Therefore, it is recommended that dentures are soaked in warm water before polishing. Within the limits of this study, the mixing ratios may be changed without affecting sorption or solubility. As solubility increases within the increasing denture-base thickness, it is recommended that unnecessarily thick dentures be avoided.Short- and long-term exposure to eluates of a PMMA, has a negative effect on cell viability. For water-stored and polished discs, this effect is time-dependent, with a higher viability for 48 hours’, than for 24 hours eluates. Polishing is associated with lower solubility. At 24 hours, the polished discs, indeed, had a lower cytotoxic effect than the untreated discs: it may be recommended that dentures be polished on the fitting surface as well.The cytotoxic potential of PMMA-eluates appears to fluctuate over time.

碩士
國立臺灣大學
臨床牙醫學研究所
106
Objective: The purpose of this in vitro study was to compare the denture base adaptation of conventionally manufactured (Pack & Press, injection molding), 3D printing and CAD/CAM milled techniques for fabricating complete dentures to determine which process produces the most accurate adaptation. Materials and Methods: Two edentulous maxillary and mandibular models were fabricated by cobalt-chrome alloy. Three reference spheres (4mmx4mmx4mm) were added on the bilateral tuberosities, anterior crest at the midline at maxillary ridge and on the bilateral posterior crests, anterior crest at the midline at mandibular ridge respectively. The models were scanned by 3Shape D900 scanner (3Shape, Copenhagen, Denmark) and designed with a 2mm thickness denture base (3Shape CAD Design Software). Denture bases were fabricated by four different manufacturing techniques and materials: CAD/CAM milled (POLYWAX & YAMAHACHI), 3D printing (BV005 & NextDent), injection molding and Pack & Press. Denture base adaptation was assessed by both conventional and digital method. In conventional way, coated the internal surface of each denture base with silicone impression material and placed onto the master model under a 5 kgf axial load. Adaptation of the reference location was assessed by measuring the thickness of intervening layer of silicone impression material with the dial thickness gauge (547-400S, Mitutoyo Corp., Tokyo, Japan) between the base and the master model. In digital way, the trueness of the intaglio surface was assessed by superimposition of the test and reference scanning data. Results: At maxilla, according to conventional method, no matter which technique was used the bilateral tuberosities showed the minimum thickness and the post dam area showed the maximum thickness. The CAD/CAM milled technique had the most accurate adaptation on the reference area. The 3D printing group showed larger gap than conventional group. At mandible, according to conventional method, 3D printing (BV005) group showed the best adaptation, followed by CAD/CAM (POLYWAX) group. Heat cured resin method had the least adapted result among all techniques. According to digital superimposition, the overall results showed that there was no significant difference in the trueness of the intaglio surfaces between CAD/CAM milled, injection molding and pack & press groups. 3D printing group showed the lowest trueness among all groups. Conclusions: Within the limitation of the study, the conclusions are The CAD/CAM milled and conventional heat cured methods were more accurate denture fabrication techniques when compared with 3D printing denture base processing technique.

Submitted in fulfillment of requirements of the degree of Master in Health Sciences: Dental Technology, Durban University of Technology, Durban, South Africa, 2016.
Pumice is used in the polishing of dental appliances to remove surface irregularities. It is usually used in a slurry form that is pumice powder mixed with water. In Nigeria, the increased cost of pumice as a result of its limited supply into the country has encouraged dental technicians to re-use pumice slurry for longer periods than advocated when polishing acrylic dentures, whether new or old dentures which have been worn in the mouth. Consequently, this is likely to increase cross-infection of communicable diseases in the dental technology laboratory. Although materials such as white sand, black sand and porcelnite can be used, literature documents that these materials are less effective in the polishing of acrylic dentures (Areeg 2011). The focus of this study was to use eggshells, a natural waste product, to develop and test the quality of an alternative material to reduce the surface roughness of heat-cured acrylic resins. A quantitative research paradigm and an experimental research strategy were adopted. The research design included two phases. In phase one of this study, different characterisation techniques such as Brunnae-Emmer Teller (BET); Fourier Transform Infrared Spectroscopy (FTIR); X-ray Diffraction (XRD); Energy Dispersive X-ray Spectroscopy (EDX) and Scanning Electron Microscope (SEM); Transmission Electron Microscopy (TEM); Laser Scattering Particle Size Distribution Analyser (PSA); Thermo-Gravimetric Analysis (TGA); and Induction-Coupling-Optical Emission Spectroscopy (ICP-OES) were used to assess the suitability of the new abrasive material (NAM). In addition, the level of microbial contamination of the NAM was assessed in line with the specified microbial limits for cosmetic products. In contrast, phase two investigated the product-based quality of the NAM as an abrasive material for removable dental appliances. There were two sample groups, that is, the NAM (test group) and Pumice (control), and each sample group had 50 PMMA acrylic specimens. The surface roughness (Ra) was measured using a Talysurf profilometer. An Independent Tukey test was used to analyse the Ra values (p=0.05). A Scanning Electron Microscope (SEM) and Optical Microscope (OEM) were further used to support the results of the profilometer in terms of the quality of surface finish and polish. Validity of the study was achieved following the ISO 20795-1 (2013) methods of preparation and fabrication of the acrylic specimens. The reliability was determined via reproducibility and repeatability of tests. The BET analysis showed that the NAM is predominantly a mesoporous powder. The FTIR and XRD analyses confirmed that the NAM is pure calcite with unique water absorbing characteristics, and is free of bacteria. The EDX and ICP-OES analyses revealed calcium, oxygen and carbon as the major elemental composition of the NAM. The SEM and TEM images revealed irregular shaped particles in the NAM. The PSA analysis of the particle distribution showed the NAM to be superfine (50nm to 0.3µm) and medium (44µm powder), respectively. The TGA analysis revealed a high-grade carbonate product in the NAM (>66.0 mass% of calcium carbonates). In addition, and in terms of in the qualities of the NAM in reducing the surface roughness of PMMA resins, the test group and the control group produced Ra values that were significant different (p<0.0001). The SEM and OEM analyses further confirmed the differences in the surfaces between the polished sample groups at different magnifications. Overall, the control showed the highest mean average (0.1056±0.03688µm), whereas the test group had the lowest Ra values (0.0476±0.01379). The lowest Ra values measured with the test group indicated that the NAM improves the surface smoothness of PMMA acrylic specimens. Notably, this study conclusively showed that the NAM effectively reduces the surface roughness to below the threshold limit value of 0.2µm. Significantly, and in associating the Ra values to the threshold limit value of 0.2µm, the NAM produced better results than pumice. Hence the use of the NAM as a polishing material for acrylic dentures is highly recommended. Finally and in line the NAM being a suitable alternative to pumice as it effectively reduces the surface roughness of PMMA specimens, future investigation into the use of eggshell nanoparticles to develop dental prophylaxes will be encouraged.
M

Submitted in fulfillment of the Degree of Master in Technology: Dental Technology in the Department of Dental Services Faculty of Health Sciences, Durban University of Technology, 2008.
Globally in the field of Dental Technology, polymethyl methacrylate (PMMA) resin continues to be the popular material for the fabrication of denture bases in removable prosthodontics. However, the mechanical strength of the denture base is a concern due to fractures occurring intra-orally or when accidentally dropped. The objective of this in vitro investigation was therefore to evaluate and compare the flexural strength and microstructure of stick® glass fibre and wire mesh reinforced PMMA resin after thermocycling. The selection of the materials used in this study was based primarily on their popularity and availability in South Africa. These materials were selected to ensure that the results of this study would have further implicational value in the commercial dental industry when published. This investigation was conducted by means of fabricating a total of 90 PMMA resin specimens and divided in three groups consisting of 30 specimens each. Sample groups 1 and 2 were reinforced with stick® glass fibres and wire mesh respectively. The un-reinforced sample group was the control. All 90 specimens were thermocycled in water at temperatures between 5˚C and 55˚C for 2100 cycles. The flexural strength of each specimen was tested using a universal testing machine and the microstructure of the fractured surfaces was then analysed using scanning electron microscopes (SEM). SPSS version 15.0 was used for data analysis. A p-value of <0.05 was considered as statistically significant. Data were analysed using parametric and non-parametric statistical methods. Statistically significant differences in flexural strength existed between the three sample groups (p<0.001) with the stick® glass fibre and wire mesh sample groups being significantly superior to the control. Furthermore there was a significant association between fracture modes and sample groups. Microscopic analysis revealed the presence of voids. Statistically, in terms of microstructure (% of voids present), a significant difference existed between all sample groups. With regards to surface texture of the compression and tension sides of the test specimens, significant differences existed between the three sample groups. Furthermore microscopic analysis revealed partial impregnation and distribution of the fibres to the PMMA resin matrix and un-bonding between the wire mesh and PMMA resin matrix. Statistically, the Mann-Whitney test was conducted to compare flexural strength between sample groups with and without voids. The flexural strength was higher in sample groups with voids than those without. This is an important finding from the clinical perspective because, in some structures of dentures, toughness is a desired property. Nevertheless in order to find the long-term data especially on clinical behaviour of these new fibre reinforcement systems, more studies should be conducted.

This thesis examines the underlying physics that gives rise to the Hawking and Unruh effects. The Rindler coordinate system is constructed from a physical argument that shows how an observer would actually go about building such a coordinate system out of scaffolding and clocks. Quantum theory is discussed in detail with particular relevance to quantum entanglement as this is an important issue relating to information loss in black holes. The thesis demonstrates the general impossibility of utilising quantum entanglement to transmit information faster than light. Bell's theorem is also reviewed from the perspective of anti-correlated spin-half particles. This theorem shows the impossibility of describing nature by a local hidden variable theory, and hence emphasises the importance of the topic of information loss in black holes as a bridge between general relativity and quantum theory. The Unruh effect is a purely quantum field theoretic effect that displays considerable mathematical similarities to the Hawking effect. The effects are nevertheless quite dissimilar in some respects and this thesis examines some of these differences. The other aim of the thesis is to discuss the possible loss of information in a black hole. The Hawking effect raises the possibility that a black hole may evaporate and potentially disappear completely. This raises a significant problem related to how the information that entered the black hole may escape, if at all. If information cannot escape the black hole then this implies a violation of one of the principles of quantum mechanics: a pure quantum state cannot undergo unitary evolution to become a thermal distribution of radiation but this is what the Hawking effect essentially predicts. These two conclusions are new and are important contributions to the understanding of the coupling between gravity and quantum theory. The thesis also looks at a number of subsidiary topics to do with the underlying physics of these effects along the way, always with an emphasis on the physical. In particular, the method for quantizing a field is developed in a physical manner by examining the continuum limit of a quantized discretely modelled string. Two other topics within the thesis that are of interest are a demonstration of the coordinate independence of the Euler-Lagrange equations and a heuristic method of 'deriving' the Lorentz transformation equations that is presented in an appendix. These two presentations are new and have not appeared elsewhere to my knowledge.
Doctor of Philosophy (PhD) (Science)

In our study, the Finite Volume Method (FVM) is successfully implemented to simulate thermal process of polymerization. This application is verified based on the obtained plots compared with those from other two methods as well as experimental data. After the verification, a method is developed to optimize heat history in order to reduce processing time and in the meantime to maintain the uniformity of cure state. Also sensitivities of cure state to different parameters are examined. Besides, a correlation between temperature and the degree of polymerization profile on sample surface is found using on-line monitoring method.

碩士
國立高雄海洋科技大學
輪機工程研究所
94
This experimental study examines the heat transfer of the reciprocating curved tube fitted with longitudinal fins with the attempts to evaluate the heat transfer augmentation generated by the longitudinal fins and to develop the heat transfer correlation for the design of piston cooling system. The circumferential heat transfer distributions along five cross-sections of the curved fin-tube were measured. Heat transfer tests were performed with five reciprocating frequencies of 0, 0.83, 1.25, 1.67 and 2 Hz for each tested Reynolds number of 5000, 10000, 15000, 20000, 24000. The selected heat-transfer results in this thesis illustrated the heat transfer physics inside the reciprocating curved tube fitted with longitudinal fins. The Nusselt numbers obtained from the reciprocating and static test-conditions were compared to unravel the influences of reciprocation on heat transfer. Within the parametric range studied, the ratios of Nusselt number between the reciprocating and static tubes were in the range of 0.67~1.12. A set of heat transfer correlations was derived to permit the evaluation of individual and interactive impacts of centrifugal force, inertial force, reciprocating force and reciprocating buoyancy on heat transfer, which provided the design reference for piston cooling system.

博士
國防大學中正理工學院
國防科學研究所
94
In this study, the thermal-flow field characteristics on impingement plate and film cooled curved composite plate with double-rows of cylindrical or fan-shaped staggered injection holes are systematically discussed based on computational fluid dynamics and technique. The effect of blowing ratio on the heat transfer performance over adiabatic model and conjugate heat transfer model of film cooled concave and convex plates are considered. Governing equations adopted in this paper is steady-state Reynolds-averaged Navier-Stokes equations of steady state and turbulence model is two-equations Realizable k-e model. For cases of impingement cooling, the distributions of Nusselt number with three different crossflow directions as changing the impingement flow channel open ends are evaluated. For each exit orientation, computations are made at four jet Reynolds numbers ranging from 2440 to 14640 as well as three jet-to-plate spacings of Zn/dj = 1, 3, and 6. Results show that the flow exit crossflow direction significantly affects the developing jets and Nusselt number distributions on the target plate. Simulation results also show that spatially-averaged Nusselt number over the impingement plate increases with an increase of jet Reynolds number regardless of the crossflow orientation. Highest Nusselt numbers are obtained for an array of inline jets with a crossflow orientation where flow exits in both directions. An obvious enhancement in the thermal performance of impingement jets can be found when the jet-to-plate spacing decreased from 6 to 3. Further shortening the jet-to-plate spacing to 1 results in a visible non-uniform distributions of local Nusselt number over the target plate regardless of the crossflow orientations. To investigate the influences of hole configuration and blowing ratio on heat transfer distribution over the film cooled concave and convex composite plate surface, four different blowing ratios ranged from 0.5 to 2.0 and three different diffused angles of fan-shaped holes which are 8○, 15○and 21○ are tested. The simulation results of adiabatic model show that either film cooling effectiveness or net heat flux reduction close regins of to double-rows of jets increases as the diffused angle of hole increased.It means that laterally diffused angle design of injection holes can intensify the development of lateral jet flow on the concave surface. However, for cases of the blowing ratio is higher than 1.0, none of the three diffused angle designs can avoid the lift-off phenomena of coolant jet flow. Among the tested parameter combinations, area-averaged film cooling effectiveness is the highest when the diffused angle of the fan-shaped jet hole is 21○ and the blowing ratio is 1.0. On the concave surface, the film-cooling effectiveness and net heat flux reduction is better at blowing ratio 1.0, Due to the curved passage corner vortex effect, the fan-shaped hole which diffuse angle 8○ is better choice for convex plate. The Simulation results of conjugate model show that the net heat flux reduction on the concave plate is better at blowing ratio 0.5 and fan-shaped hole with diffuse angle 8○. On the convex surface, results reveal that the fan-shaped hole with diffuse angle of 8○ provides the best net heat flux reduction performance at blowing ratio of 1.0.

碩士
國立成功大學
航空太空工程學系
89
The research is to investigate the distribution of the radiation energy and the heat transfer mechanisms of an enclosure with heat source. We use Data Model Hd9221 Photo-Radiometer to measure the radiation of a heat source and the enclosure surface. We use K-type thermocouple and Inframetrics Model-60 IR Imager to measure the closed surface temperature of the enclosure. The temperature distribution of the flow field inside the enclosure is also measured. Results shows that radiation in visible range is higher for the case with high beam and low beam design. Foe example, visible radiation up to 30﹪of the total radiation is measure in the design with high beam and low beam together, while the visible radiation is only 10﹪for the case without high beam./low beam design .It is attributed to the spectrum of the source radiation, absorption and reflection of the material. Results also show that total radiation and the heat flux increase as the power of the heat source increases. However, there are two peaks of radiations in the vertical plane passing through the axis of the heat source, with the maximum radiation takes place at θ= -750. It is also found that the temperature distribution of the flow inside the enclosure is effected by the internal structure of the heat source. For example, there is a supporting wire above the heating element of the 9007 heat source and it results in a blockage effect on the radiation from the heating element, while the H-4 heat source has not such kind of mechanism. Hence the peak temperature of the hot plume from the H-4 heat source is at the center while those of the 9007 heat source are on the two side of the hot plume. The energy is then transferred to the outer surface of the heat source through conduction. The air near the outer surface of the heat source is heated up and results in a hot plume above the heat source. The energy is transferred to the inner surface of the enclosure by natural convection. The energy is transferred to the outer surface of the enclosure again by heat conduction and is further transferred to the air outside the enclosure . It is also found that the radiation heat transfer from the heat source to the enclosure can not be neglected temperature is as high as 580℃.

碩士
淡江大學
航空太空工程學系
88
To study the effect of fin radiator in a notebook, this research investigated the flow structure and heat transfer enhancement in a curved channel with longitudinal vortex generator (delta winglet). To observe how the secondary flow enhanced heat transfer in the channel delta winglets were set at various positions in a curved channel. The flow structure and the temperature field were computed. Enhancement of the heat transfer at the bottom wall of the channel was also calculated. Results showed that the delta winglets did improve the heat transfer with various degree of success while setting the winglets at different positions and angle of attack. It is also shown that heat transfer can be enhanced by 35.6 percent at 6 m/s inlet velocity with proper set up of winglets.

碩士
淡江大學
航空太空工程學系
91
The research experimentally investigates the heat transfer and the near-wall flow characteristics in strongly curved developing duct flows with and without turbulators. The cross section of the duct was fixed at 7 3.5 cm2 and the curved angles is 90o. A small wind tunnel was used to provide the uniform flow at the duct entrance. The Reynolds number is 14680 and the corresponding Dean number is 3687. A 45o delta-wing and a 45o trapezoid-wing were used as the turbulators. Sixteen heated plates, placed along two sides of the curved duct bottom-wall, were used as the heat transfer surfaces. The relations between the near-wall fluid flow and heat transfer were discussed in terms of three flow parameters, including the axial component of vorticity, the axial mean velocity and the turbulent kinetic energy. These studies include three-component mean and fluctuating velocity measurements at duct cross section and the near heat transfer surfaces, using the Doppler velocimetry. The Temperatures on the heat transfer surfaces were measured using thermocouples to obtain the Nusselt numbers. Results show that the delta-wing and trapezoid-wing turbulators had the effect to cause the increases in the turbulent kinetic energy and axial vorticity, and to augment the heat transfer, especially the trapezoid-wing turbulator. The turbulent kinetic energy played the most important role in the heat transfer distribution.

碩士
國立中山大學
機械工程學系
87
The curvature of a pipe can induce a secondary flow for the flow in the pipe. The effect of the secondary flow enhances the heat transfer rate significantly. Therefore, curved pipe is widely applied in heat transfer devices . However, in the literature, most of studies for the curved pipe flow is dealing with coroidal flow with constant curvature. There are few articles dealing with varying curvature curved pipe flow despite the fact that non-uniform curved pipes have as much practical use as coroidal. The solar collector with periodical s-shaped pipe is a practical example for varying curvature curved pipe flow and heat transfer. In this article, experiments were conducted in a double-pipe heat exchanger with water as the working medium. The heat transfer coefficients were obtained using the Wilson plot method. The effect of the Dean, Prandtl, Reynolds number and curvature ratio on the flow resistance , average heat transfer rate and friction factor are presented.

碩士
國立臺灣大學
機械工程學研究所
94
The object of this study is to expand the functions of the code with unstructured hp spectral element method. The developed code can simulate common heat transfer problems. Theses functions are element classification, the ability to deal with heat convectional boundary conditions, and making the code accommodate three dimensional curved geometry. Spectral element method is a high-order numerical method. If curved geometry is not interpolated with high-order method, it cannot reduce spectral accuracy. In this thesis, we get the mapping function of the curved element with boundary modes. And the code was validated by several examples. Finally, we take this code to simulate the heat transfer problem of a LED light bar.

碩士
中原大學
機械工程學系
88
There are three topics in this study. In the first part, the computational fluid dynamics software package FIDAP was chosen to analysis the phenomena of pressure drop and heat transfer effect for the 90°curved ducts. The numerical solution obtained from FIDAP is very close to the Kajishima's results, which was solved by the finite difference method. In the second part, FIDAP was applied to analysis the phenomena of pressure drop and heat transfer effect for 180°curved ducts in different curvature. Finally, FIDAP was applied to analysis the phenomena of pressure drop and heat transfer effect for two different types of the multi-channel plate heat exchangers, the results used in FIDAP and experimental results have the same phenomena of pressure drop and heat transfer effect. The numeral solution shows the TYPE-B(without grooves) have less pressure drop and more heat transfer than TYPE-A(with grooves).