Neste trabalho avaliou-se o comportamento reológico dos 11 molhos comerciais para salada, tratados pelo processo de irradiação por raios gama, nas doses: 3 kGy e 5 kGy. Essa avaliação foi realizada por meio de reogramas traçados por medidas de viscosidade e tensão de cisalhamento por taxa de cisalhamento. Parâmetros matemáticos, obtidos destas medidas, também contribuiram para a conclusão do comportamento apresentado e do melhor modelo matemático aplicável a cada molho. As medidas foram realizadas em um viscosímetro de Brookfield modelo LVDV III. O banho térmico Neslab foi empregado para manter a tempertura ambiente durante toda a análise. Realizou-se o protocolo de estudo em duas fases. Na fase 1, a avaliação ocorreu logo após as amostras terem sido irradiadas, as quais se encontravam próximas a suas datas de fabricação. Na fase 2 as amostras foram reavalidas após um período de armazenamento, próximo a data de expiração de suas validades. Paralelamente realizou-se medida de pH para avaliar sua estabilidade diante dos tratamentos e análises sensoriais, de dois dos onze molhos estudados, a fim de verificar a aceitação desses diante da irradiação. O comportamento pseudoplástico foi confirmado para todos os molhos através do modelo matemático, da lei da potência, que melhor se aplica a este, nas duas fases das análises. A irradiação, nas doses absorvidas estudadas, não influênciou nesse comportamento. Os resultados da análise sensorial indicaram boa aceitação dos molhos irradiados, pelos provadores. / This study evaluated the rheological behavior of 11 salad dressings ready to eat, processed by gamma irradiation, at doses: 3 kGy and 5 kGy. This assessment was made by rheograms traced by measurements of viscosity and shear stress by shear rate. Mathematical parameters obtained from these measures also contributed to the conclusion of the behavior exhibited and for choosing the best mathematical model applicable to them. The measurements were performed on a Brookfield viscometer Model LVDV - III. The Neslab thermal bath was used to maintain ambient temperature during the whole analysis. This study protocol was done in two stages. In step 1, the evaluation was performed soon after the samples have been irradiated when these were close to their dates of manufacture. In phase 2 the samples were reassessed after a period of storage, near the expiration date of their validity. Simultaneously pH measurement was performed to evaluate their stability in the face of treatment and sensory analyzes of two salad dressings were studied, in order to verify the acceptance of these when submitted to irradiation. The shear-thinning behavior was confirmed for all dressings through the mathematical model, the power law, that best model apply to this, in both phases. The irradiation at the absorbed doses studied did not influence this behavior. The results of sensory evaluation indicated good acceptance of irradiated sauces for the tasters.

Magneto-rheological damper is a nonlinear system. In this case study, system has been identified using Neural Network tool. Optimization between number of neurons in the hidden layer and number of epochs has been achieved and discussed by using multilayer perceptron Neural Network.

A new type of viscoelastic amphoteric surfactants (amidoamine oxide) has been examined as a diverting agent during acidizing treatment. Rheological properties of viscoelastic surfactants are a function of surfactant concentration, acid additives, pH, temperature and shear rate. A HPHT rheometer was used to test the effect of common acid additives and organic acids/chelating agents on the apparent viscosity of amidoamine oxide-based acids. The compatibility and thermal stability of surfactants with corrosion inhibitor were also investigated. Rotating disk apparatus was used to examine the kinetic studies of surfactant-based acids with limestone. The results show that the apparent viscosity of surfactant solutions prepared in deionized water, live acid, and spent acid was found to be a function of temperature. Apparent viscosity of live surfactant-based acids was also found to be a function of HCl concentration. Most of acid additives could adversely affect the rheological properties of spent acids. Compatibility tests should be done prior the field application. Cryo-TEM studies show the changes of rod-like micelle structures with the addition of additives. The reaction between surfactant-based acid and limestone was found to be mass transfer limited at 170 degrees F.

In this work, EPDM rubber was compounded with increasing amount of filler (FEF N 550 type carbon black), process oil (saturated mineral oil), vulcanizing agent [di (t-butylperoxy) diisopropyl benzene, i.e., BBPIB] and diene [5-ethylidenebicyclo(2.2.1)-hept-2-ene, i.e., ENB] in order to investigate mechanical and rheological properties. Effect of Increasing amount of filler was investigated by using FEF N 550 type carbon black in 35, 70, 87.5, 105 phr. Decrease in scorch times of vulcanization reactions, ts2 (25, 21, 19, and 18 s, respectively) and slight increase in rate constants for vulcanization reactions (0.0270, 0.0274, 0.0301 and 0.0302 s-1, respectively) were explained in terms of nature of semi-active filler. Effect of increasing amount of process oil was investigated by using saturated mineral oil (TUDALEN 3909) in 15, 30, 45 phr. Scorch time for vulcanization reaction and rate constants were measured as 95, 103, 97 s and 0.0277, 0.0274, 0.0291 s-1, respectively. Effect of increasing amount of vulcanizing agent was investigated by using BBPIB (PERKADOX 14/40 MB-gr) in 2.5, 5, 7.5, 10 phr. The compound with 5 phr vulcanizing agent gave optimum rheometer data, crosslink density,, ultimate tensile strength, hardness, deflection and damping. Vulcanization reaction rate constant reached 0.0335 s-1 with 7.5 phr vulcanizing agent. Effect of increasing ENB ratio was investigated by using 4 different EPDM with ENB ratios 5.0, 5.6, 7.5, 8.9%. With two different cure systems, compounds with 5.6 and 7.5% ENB ratio gave optimum results. Vulcanization cure time, reaction rate constant and compression set properties changed in irregular manner.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2009. / Härtill 3 uppsatser.

O comportamento reológico de suspensões concentradas heterogêneas como concretos e argamassas possui influência direta na energia requerida e na produtividade durante o processamento e aplicação destes materiais, além de ser um fator determinante na obtenção de um produto final qualidade. De um modo geral pode-se dizer que a fluidez destas suspensões está diretamente relacionada à facilidade de movimentação das partículas, logo pode-se inferir que a redução dos fenômenos atrito é um fator determinante para o bom desempenho destas suspensões durante o fluxo. Deste modo, este trabalho buscou por meio de modelos ideais de esferas e silicone líquido avaliar a influência do coeficiente de atrito dos agregados e da viscosidade da matriz no comportamento reológico de suspensões concentradas. O coeficiente de atrito de agregados esféricos com diferentes granulometrias foi determinado experimentalmente através do ensaio de cisalhamento direto, também conhecido como shear box, e o comportamento reológico de suspensões compostas por estes agregados e silicones líquidos de diferentes viscosidades foram avaliadas por meio do ensaio de squeeze flow. Os resultados revelam que a distribuição granulométrica possui um influência no coeficiente de atrito dos agregados e que esta propriedades está relacionada a área e ao tipo de contato entre as partículas. Entretanto, para o tipo de fluxo e para as velocidades as suspensões, não houve uma relação direta entre o coeficiente dos agregados e a viscosidade da suspensão. Além disto, apesar de alterar o comportamento reológico das suspensões a viscosidade da matriz não apresentou uma relação direta com viscosidade da suspensão, o que em partes ser explicados pela provável ocorrência de um fluxo não homogêneo das suspensões nas condições aqui estudadas. / The rheological behavior of concentrated suspensions like concrete and mortars plays an important hole during their processing and application, and also has a great influence on the final product quality. The flowability of these suspensions is directly related to the ease of particle motion in the system, therefore reduction of friction phenomena contributes for a good flow behavior. The aim of this work was to determine the influences of aggregates friction coefficient and the liquid viscosity of the fluid matrix on the rheological behavior of concentrated suspensions. The friction coefficient of glass spheres with different particle size distributions were determined by shear box tests, while the rheological behavior of concentrated suspensions composed by these glass spheres and silicone oils was evaluated by squeeze flow tests. Results revealed that the particle size distribution influences the coefficient of friction, and this property is determined by the type and the area of contact between the particles. However, for the kind of flow and the speed used in the experiments, there was no relation between friction coefficient and the suspension viscosity. Additionally, matrix viscosity has an impact on the rheological behavior of the system, but no clear relation was identified, which may be caused by the occurrence of heterogeneous flow under the applied experimental conditions.

Orientadores: Rosiane Lopes da Cunha, Fernanda Yumi Ushikubo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-24T20:14:36Z (GMT). No. of bitstreams: 1 Oliveira_DaviRochaBernardesde_M.pdf: 18877035 bytes, checksum: 1668d21b0c81ea31f26e9d7c85a25644 (MD5) Previous issue date: 2014 / Resumo: A emulsificação em dispositivos microfluídicos destaca-se pela sua capacidade em gerar gotas de maneira individual em um processo totalmente controlado. Através dele, é possível a obtenção de emulsões com coeficientes de variação de tamanho de gotas inferiores a 5%. Soluções de glicerol (fluidos Newtonianos) com concentrações variando entre 10 e 75% (m/m) foram utilizadas como fase dispersa para obtenção de emulsões água em óleo em microcanais planares com junções do tipo T e Y. Como fase contínua foi utilizado óleo de soja contendo 5% (m/m) de emulsificante PGPR. Como condições de processo, quatro diferentes razões entre as vazões das fases contínua e dispersa foram avaliadas. Paralelamente, quatro soluções de goma xantana (fluidos não-Newtonianos) com concentrações variando de 0,05 a 0,50% (m/m) foram avaliadas como fase dispersa num microcanal com junção em Y, e submetidas às mesmas condições das soluções de glicerol. Em todos os sistemas avaliados, a razão entre as fases foi o fator de maior influência no tamanho das gotas formadas. Em relação aos fluidos Newtonianos, a emulsificação no canal em T se mostrou menos sensível às propriedades físicas dos fluidos, enquanto na geometria em Y, notou-se, através do cálculo dos números adimensionais de Weber e Capilar, grande influência da tensão interfacial sobre o tamanho das gotas formadas, superando a ação das forças viscosas. Em relação aos fluidos não-Newtonianos, foi observada grande diferença no processo de formação das gotas e nas características da emulsão. Gotas com elevada polidispersão foram obtidas, em especial nas soluções mais concentradas e nas maiores razões entre as vazões das fases. Esse fato se deu devido à formação das gotas ter ocorrido longe da junção dos canais, através da formação de um jato de fase dispersa. Esse jato foi intensificado nas soluções de goma xantana de maior concentração e nas condições de maiores velocidades da fase contínua. Ensaios reológicos extensionais confirmaram que, de fato, a viscosidade elongacional da solução de goma xantana aumenta com a concentração e também com a taxa de deformação elongacional, o que explicaria a formação do jato. Na solução de menor concentração de goma xantana foi possível a obtenção de gotas altamente monodispersas, embora tenha ocorrido a formação do jato no rompimento das gotas, estando essa solução numa região de transição do regime de jateamento para o regime de gotejamento. Dessa forma, pode-se verificar que no regime de gotejamento, típico dos fluídos Newtonianos, a monodispersão é uma característica bem definida. No caso do uso de fluídos viscoelásticos na fase dispersa, a obtenção de gotas monodispersas é um desafio, devido ao efeito da elevada viscosidade elongacional. Assim, torna-se necessária a avaliação de condições de processo e geometria de canal mais adequadas a esta situação de forma a diminuir a polidispersidade desses sistemas / Abstract: Emulsification in microfluidic devices is distinguished by its ability to generate droplets in a controlled and individual way, in which it is possible to obtain emulsions with polydispersity lower than 5%. Glycerol solutions (Newtonian fluids) at concentrations ranging from 10 to 75% (w/w) were used as dispersed phase in order to obtain water in oil emulsions, using Y - and T - junction microchannels. As continuous phase, soybean oil containing 5% (w/w) of emulsifier PRPG was used. Four different ratios of the flow rates of continuous and dispersed phases were evaluated in both microfluidic devices. Similarly, four xanthan gum solutions (non-Newtonian fluids) with concentrations ranging from 0,05 to 0,50% were evaluated as dispersed phase in a Y ¿ junction microchannel. In all systems, the ratio of the flow rates of the phases was the most influential factor in the size of the droplets. Regarding Newtonian fluids, the T ¿ junction microchannel was less sensitive to the fluids physical properties, while in Y ¿ junction geometry it was noted that the interfacial tensions played the main role in droplet size, overcoming the viscous forces. Regarding the non-Newtonian fluids, a large difference in the droplet generation was observed. Droplets with high polydispersity were obtained, especially in the most concentrated xanthan gum solution, when high shear forces were applied. This fact may have occurred due to the formation of a jet of the dispersed phase, from which droplets were detached without any control. This jet was intensified in xanthan solutions of higher concentration and under high velocities of the dispersed phase. Indeed, extensional rheology confirmed that the elongational viscosity of xanthan gum solution increases with concentration and also with the rate of elongational deformation, which would explain the formation of the jet. In the solution at lower concentration of xanthan, it was possible to obtain highly monodisperse droplets, although the droplets detachment still occurred in the jetting regime. This solution is herefore in a transition region between jetting and dripping regime. Thus, it was verified that the dripping regime, typical of Newtonian fluids, the monodispersity is a well-defined characteristic. On the other hand, when using viscoelastic fluids as dispersed phase, obtaining monodispersed droplets is still a challenge, due to the effect of high elongational viscosity of this fluids. In this way, it becomes necessary evaluate new process conditions and microchannel geometries in order to reach emulsions with low polydispersity / Mestrado / Engenharia de Alimentos / Mestre em Engenharia de Alimentos

Les inhalateurs à poudre sèche (DPI) sont une alternative attractive aux inhalateurs pressurisés à valve doseuse (pMDI) du fait de leur absence de gaz propulseur. Pour pénétrer dans les poumons profonds, la taille optimale du principe actif est généralement inférieure à 5 μm. Leur mélange avec un transporteur de taille plus importante, principalement le lactose alpha monohydrate, est classiquement utilisé pour améliorer leur écoulement, faciliter le remplissage dans les inhalateurs et améliorer leur dispersion. Cependant, la formulation et la production des mélanges de poudres pour inhalation demandent une optimisation adéquate pour des-agglomérer les particules cohésives de principe actif et assurer l’homogénéité de ces mélanges contenant un faible pourcentage de principe actif (1,5 à 2,5 %). De plus, l’amélioration de la performance aérodynamique de ces mélanges est nécessaire. Le contrôle des propriétés physico-chimiques du principe actif et du transporteur est critique pour atteindre et maintenir la qualité de la formulation des poudres pour inhalation. Dans cette étude, le lactose alpha monohydrate est utilisé comme transporteur. Des lactoses de grade et de qualité différents sont comparés. Le propionate de fluticasone et le sulfate de terbutaline sont utilisés comme principes actifs modèles. Différentes techniques sont utilisées pour caractériser les principes actifs et les transporteurs: la distribution granulométrique mesurée par la méthode de diffraction laser, les propriétés thermiques par la méthode de calorimétrie (DSC), l’analyse d’image par microscopie électronique à balayage (MEB), l’énergie de surface par la méthode de chromatographie gazeuse inverse (iGC)…Le mélange principe actif et transporteur est réalisé grâce au mélangeur type Turbula, l’influence des conditions opératoires a été étudiée. La performance aérodynamique est évaluée par l’impacteur à cascade en verre (Pharmacopée Européenne). Nous avons développé des techniques de caractérisation des mélanges : l’évaluation de l’adhésion par le tamiseur à dépression d’air, la perméabilité des poudres mesurée par le perméabilimètre de Blaine ; la taille des agglomérats de principe actifs déterminée par la méthode de diffraction laser en milieu liquide. Enfin, les propriétés rhéologiques de poudre et en particulier sa fluidisation sont évaluées par un nouveau rhéomètre, le Freeman FT4. La taille des particules de transporteur exerce une influence importante sur la performance des mélanges pour inhalation. La réduction de taille du transporteur diminue les interactions entre le principe actif et le transporteur. Le détachement du principe de son transporteur est ainsi facilité ce qui augmente le pourcentage de principe actif susceptible de pénétrer dans les poumons c’est-à-dire la fraction respirable de principe actif. Différents grades et qualités de lactose de répartition granulométrique similaire mais obtenus par différentes méthodes de production ont été étudiés et comparés. Ces lactoses différaient essentiellement par le procédé de préparation (broyage ou tamisage) et la teneur en fines particules de lactose. Le lactose broyé présente un potentiel d’adsorption mesuré par iGC supérieur à celui du lactose tamisé et sa teneur en fines particules de lactose est plus importante. Les fines particules de lactose peuvent former des agglomérats avec les particules de principe actif ce qui permet une libération plus facile du principe actif lors de la fluidisation car les forces d’adhésion entre ces particules sont moins importantes. Les mélanges ayant une teneur en fines particules de lactose plus importante permettent d’obtenir une fraction respirable de principe actif supérieure lors de l’évaluation aérodynamique du mélange. Dans ce cas, le pic maximal déterminé par iGC est décalé vers les valeurs supérieures de potentiel d’adsorption ce qui est en accord avec l’hypothèse d’agglomération. [...] / Dry Powder Inhalers (DPIs) are attractive alternatives of pressurized Metered Dose Inhalers (pMDI) in pulmonary delivery, thanks to its being free of CFC and ease of use. The typical size of respirable drug particles is generally less than 5 micrometers. Formulations with fine drug particles and coarse carrier particles, usually lactose have been commonly used to facilitate dispersion and flow. Nevertheless, DPI formulation and production require an adequate optimization in order to de-agglomerate the cohesive drug particles and to produce a uniform mixture with a coarser carrier. Furthermore, improvement of the aerodynamic performance of drug mixtures has recently drawn the great attention of pharmaceutical company. Indeed, the close control of drug and carrier physicochemical properties is crucial to obtain and to maintain the quality of formulation during development and manufacturing. In this study, lactose alpha monohydrate was used as carrier. Different grades and qualities of lactose were compared. Fluticasone propionate and terbutaline sulphate served as model drug. Different techniques were used to characterize the properties of drug and carrier: particle size distribution (by laser diffraction), thermal properties by differential scanning calorimetry (DSC), image analysis by Scanning Electronic Microscopy (SEM), and surface energy by inverse gas chromatography (iGC)... Drug and carrier were mixed by low-shear tumble blending mixer, the influence of operating conditions was studied. The aerodynamic performance of drug mixtures was determined by Twin Stage Impinger (European Pharmacopoeia). Several novel techniques were developed during this study in order to characterize drug mixtures. Drug – carrier adhesion was quantified by Alpine Air jet Siever. Powder permeability was measured by permeametry with the Blaine apparatus. Agglomerate size of drug in mixture was also determined by method developed based on laser diffraction in liquid. The rheological properties of powder were determined by Freeman FT4, a new powder rheometer. Carrier particle size plays an important role on the inhalation performance of interactive mixture. Decrease in carrier particle size leads to a decrease of particulate interaction between drug and carrier. The reduced adhesion between drug and carrier particles increased drug detachment, and thus increased the respirable fraction of drug. Different batches of lactose with similar particle size but different production method (milling or sieving) were investigated. Among the parameters tested, the differences are the preparation processes and the content of fine lactose particles. Lactose obtained by milling process shows a higher adsorption potential measured by iGC and it contains more fine particles which could form agglomerates with the drug. Because of their increased detachment mass, drug particles may be more easily detached from the coarse lactose in the air flow. With higher FPF values, which correspond to higher fines content, the peak maxima determined by IGC are shifted to higher adsorption potentials which support the agglomeration hypothesis. [...]

This diploma thesis deals with the characterization of rheological properties and biodegradation of a poly(3-hydroxy-co-4-hydroxybutyrate), a copolymer produced by a strain of Cupriavidus malaysiensis. The theoretical part focuses on the rheology and degradation of polymers in general. It also contains the basic characteristics of polyhydroxyalkanoates and deals in more details with the description of the studied copolymer, its properties, synthesis, decomposition and possibilities of its applications. In the experimental part, the given copolymer was investigated in its native form and also in the form of copolymer mixtures filaments, which were enriched with additives (stabilizers and plasticizers). In terms of rheology, the samples showed pseudoplastic behaviour, which was slightly limited by the plasticization of the material. The highest thermal stability observed as a function of changes in complex viscosity over time was observed in a sample of a copolymer mixture containing stabilizers and plasticizer Citrofol BII. The plasticization also caused significant changes in thermal properties, especially crystallinity, which decreased compared to the native copolymer. In vitro degradation studies of samples in the form of films prepared by dissolving copolymer mixtures in chloroform were performed in phosphate buffer with lipase, in simulated body fluid and in synthetic gastric juice. The course of the process itself was characterized by the method of determining the molecular weight (SEC-MALLS) and the weight loss over time (gravimetrically). The results showed that the analysed samples are subject to degradation in all used environments. The most considerable molecular weight loss after 105 days (76 %) was observed in the sample containing stabilizers and plasticizer Citrofol BII in the environment of synthetic gastric juice. The most extensive gravimetric weight loss was attributed to the sample with stabilizers and without plasticizers, in the environment of phosphate buffer with lipase, specifically by 79%.

This study is focused on modifying an existing solenoid valve based semi-active hydropneumatic spring-damper system using Magneto-Rheological (MR) fluid. The MR fluid's effective viscosity can be altered by application of a magnetic field. Therefore, using a magnetic/ MR valve makes it possible to change the state of the system by simply changing the applied magnetic field. A prototype MR valve was developed to determine whether a unit small enough for installation was possible. This prototype valve was designed from first principles and properties such as pressure drop over the valve (damping) and flow blocking (for switching between spring characteristics) were measured. The measured pressure drop over the valve was higher than what was design for which was due to an incorrect assumption for the viscosity of the thixotropic MR Fluid. The flow blocking ability of the valve was determined by constant force tests. Results showed that the valve could virtually block the flow of fluid for approximately a quarter of the vehicles weight. With the second prototype, the valve design and magnetic circuit design were improved. Two valves were constructed and implemented on a prototype suspension system. The damping characteristics of the system were lower than expected, however they can be improved by changing the valve geometry. The base spring characteristics are acceptable, however the higher spring characteristics fail when a high force is exerted on the strut that exceeds the valves flow blocking capability. The response time of the valve is not yet sufficient to make the system viable for real world implementation, especially under extreme conditions that can change more rapidly than the current valves. / Dissertation (MEng)--University of Pretoria, 2015. / Mechanical and Aeronautical Engineering / MEng / Unrestricted