One of the most important boron minerals, colemanite is reacted with sulfuric acid to produce boric acid. During this reaction, gypsum (calcium sulfate dihydrate) is formed as a byproduct. In this study, the boric acid production was handled both in a batch and four continuously stirred slurry reactors (4-CFSSR&rsquo / s) in series system. In this reaction system there are at least three phases, one liquid and two solid phases (colemanite and gypsum). In a batch reactor all the phases have the same operating time (residence time), whereas in a continuous reactor all the phases may have different residence time distributions. The residence time of both the reactant and the product solids are very important because they affect the dissolution conversion of colemanite and the growth of gypsum crystals. The main aim of this study was to investigate the dynamic behavior of continuous flow stirred slurry reactors. By obtaining the residence time distribution of the solid and liquid components, the non-idealities in the reactors can be found. The experiments performed in the continuous flow stirred slurry reactors showed that the reactors to be used during the boric acid production experiments approached an ideal CSTR in the range of the stirring rate (500-750 rpm) studied. The steady state performance of the continuous flow stirred slurry reactors (CFSSR&rsquo / s) in series was also studied. During the studies, two colemanites having the same origin but different compositions and particle sizes were used. The boric acid production reaction consists of two simultaneous reactions, dissolution of colemanite and crystallization of gypsum. The dissolution of colemanite and the gypsum formation was followed from the boric acid and calcium ion concentrations, respectively. The effect of initial CaO/ SO42- molar ratio (1.00, 1.37 and 2.17) on the boric acid and calcium ion concentrations were searched. Also, at these initial molar ratios the colemanite feed rate was varied (5, 7.5, 10 and 15 g/min) to change the residence time of the slurry. Purity of the boric acid solution was examined in terms of the selected impurities, which were the magnesium and sulfate ion concentrations. The concentrations of them were compared at the initial molar ratios of 1.00 and 1.37 with varying colemanite feed rates. It was seen that at high initial CaO/ SO42- molar ratios the sulfate and magnesium ion concentrations decreased but the calcium ion concentration increased. The gypsum crystals formed in the reaction are in the shape of thin needles. These crystals, mixed with the insolubles coming from the mineral, are removed from the boric acid slurry by filtration. Filtration of gypsum crystals has an important role in boric acid production reaction because it affects the efficiency, purity and crystallization of boric acid. These crystals must grow to an appropriate size in the reactor. The growth process of gypsum crystals should be synchronized with the dissolution reaction. The effect of solid hold-up (0.04&ndash / 0.09), defined as the volume of solid to the total volume, on the residence time of gypsum crystals was investigated and the change of the residence time (17-60 min) on the growth of the gypsum was searched. The residence time at each reactor was kept constant in each experiment as the volumes of the reactors were equal. The growth of gypsum was examined by a laser diffraction particle size analyzer and the volume weighted mean diameters of the gypsum crystals were obtained. The views of the crystals were taken under a light microscope. It was observed that the high residence time had a positive effect on the growth of gypsum crystals. The crystals had volume weighted mean diameters of even 240 &micro / m. The gypsum crystal growth model was obtained by using the second order crystallization reaction rate equation. The residence time of the continuous reactors are used together with the gypsum growth model to simulate the continuous boric acid reactors with macrofluid and microfluid models. The selected residence times (20-240 min) were modeled for different number of CSTR&rsquo / s (1-8) and the PFR. The simulated models were, then verified with the experimental data. The experimentally found calcium ion concentrations checked with the concentrations found from the microfluid model. It was also calculated that the experimental data fitted the microfluid model with a deviation of 4-7%.

Waste stabilisation ponds (WSP) are a popular form of wastewater treatment worldwide, especially for rural-based manufacturing plants and small community sewage treatment. Ponds offer a robust and operationally simple technology, which are inexpensive where land is available, and have the potential to provide a considerable degree of treatment. However the continued use of WSP is being undermined by their inconsistent performance relative to current discharge requirements, particularly with respect to suspended solids, pathogen and nutrient removal. In a climate of increased public awareness of pollution, and the ever more stringent environmental protection regulations, novel pond designs need to be developed, and existing ponds retro-fitted, to improve their performance. This dissertation investigated the hydraulic modelling of non-mechanically mixed ponds, and produced a modelling framework from which improved pond designs could be evaluated. Computational fluid dynamics (CFD) simulations were used to develop models which were able to predict the hydraulics of arbitrarily shaped, non-mechanically mixed ponds under controlled conditions. The models represent an important departure from traditional pond modelling techniques, which are based on either historical experience or simple hydraulic and reaction models. The CFD approach overcomes the main limitation of these models, as it accounts for spatial variations of parameters within a pond such as fluid velocity, or pollutant concentration. This allows for the prediction of pond hydraulics based on the pond geometry (such as inlet configuration, pond shape or baffle placement), pond inlet boundary conditions and the fluid properties. Thus CFD models allow the rapid investigation of the effect of design modifications on pond performance. The WSP models were designed using a two stage process. The first stage, a steady state simulation, calculated the velocity and turbulence fields for the pond; the second stage, a transient numerical tracer, utilised the underlying steady state results to calculate the advection and diffusion of a tracer species. The species concentration at the outlet was then integrated to produce residence time distributions (RTD) and other quantities which were used to characterise the pond hydraulics, and quantitatively compare the models with experimental results to assess the pond¡¦s performance. These techniques could be applied to any numerical pond flow model, and are a discerning test of the model¡¦s consistency. RTD generated from two-dimensional (2-D) CFD simulations were compared to experimental RTD derived by Mangelson and Watters (1972). In one of the three geometries simulated, the 2-D CFD model successfully predicted the experimental RTD. However, the flow patterns in the other two geometries were not well described, due to the difficulty of representing a three dimensional (3-D) inlet in the 2-D CFD model. As no general relationship could be found for approximating a 2-D inlet in 3-D, full 3-D simulations were used to model the unsuccessful cases. The 3 D simulations provided much improved results, predicting all the major features of the RTD over the first residence time, and matching exponential decay of the RTD after this period. Due to the uncertainty in the exact experimental inlet dimensions, a range of inlet depths were simulated. This showed that the CFD model was sensitive to changes in the inlet configuration, and using the appropriate inlet depth, the simulated RTD matched the experimental results well. A sensitivity analysis of the effect of the inlet turbulent boundary conditions and tracer molecular diffusivity for the k-ƒÕ turbulent model, showed the RTD was insensitive to these properties, thereby confirming similar results in related systems (Benelmouffok, 1989; De Vantier and Larock, 1987). This is significant for future pond modelling, as these properties are difficult to measure experimentally or predict reliably. Tracer studies were performed in this dissertation on five full-scale pond systems. In Tasmania three identical sewage ponds with different inlet and baffle configurations were investigated. However wind conditions in this locality masked any effect of these modifications. Tracer studies were also performed on sugar mill ponds near Mackay. While the models predicted qualitative consistent RTD results, they did not match the experimentally measured RTD due to uncontrolled environmental mixing factors and the long residence times of these ponds. A preliminary investigation of the effect of wind mixing was undertaken by imposing a velocity to the top surface of the model. These results confirmed the strong influence of even small wind velocities due to the large surface area of the ponds. Practical experience has indicated that the pond hydraulics are often the limiting factor in pond performance. Both experimental and simulation results have confirmed this through the presence of short circuiting and dead zones within the pond. Three baffle designs were assessed, all of which improved the pond hydraulics by either dispersing the inlet jet, or utilising the jet to generate specific pond mixing. Finally the work in this thesis has highlighted a number of other areas for future investigation. These include reservations over the use of RTD to characterise full-scale pond hydraulics, and considerations regarding the most efficient use of the inlet mixing in ponds. The hydraulic models developed in this dissertation can be extended to include solids, stratification and reaction models, which would enable the direct validation of the model based on physical or chemical parameters. In addition, a coupled flow and reaction model would provide a tool that could be used to truly optimise pond performance. This offers the possibility of tailoring the design of ponds for specific reactions, such as improved biological nutrient removal.

Studies on life styles ha ve driven us to consider three studies which analyse the concept and its relationship with other psychological variables. The first study presents an analysis of the activities carried out by a person, asan operational definition of life styles using ADIT self-registering (Self-Registeringof Time Distribution, SRTD), considering individuals who interact with subject in those activities. In the second study, modifications to the original self-record are suggested; eg, the sectionthat registers where and with whom are carried out the activities was eliminated. In the third study, the relationships among life styles, life satisfaction and personality variables are analysed. Therewere 84 persons in the sample assigned to 6 groups, depending on the relationships among these three concepts, as was previously suggested by other studies / Los estudios sobre estilos de vida (EV) conducen a plantear tres investigaciones que analizan elc oncepto y sus relaciones con otras variables psicológicas. Primero, se presenta el análisis de las actividades realizadas por la persona, como operativización de los estilos de vida a partir del autorregistro ADIT (Autorregistro de Distribución del Tiempo) en relación con las personas con las que lossujetos realizan dichas actividades. Segundo, se plantean modificaciones del autorregistro original; por ejemplo, se eliminó el apartado que registra dónde y con quién se realiza las actividades. Tercero.se analizan las relaciones entre los EV, la satisfacción vital y las variables de personalidad en 84 personas. Estas se organizan en seis grupos, de acuerdo con las relaciones entre estos tres conceptos,como se ha venido apuntando en trabajos previos

This paper considers Psychological Style (PS) as a supraordinal category in the personality organization andas an approach of change. The PS organizes behavior, has an eminet global character, is essential for interpretation, and could be considered as a set of guidelines. Given its encompassing nature, PS is useful in many fields. An empírica! research on Life Styles (LS) is presented, in which is proposed its operativization through time distribution. An original instrument on time distribution is given (AD IT). The data collected indicated that time distribution can be used as an operativisation of LS, since the profiles found have a clear psychological significance and the relation with demographic variables also have a psychological meaning. / Este estudio considera el Estilo Psicológico (EP) como categoría supraordinal en la organización de la personalidad y como base del enfoque del cambio. El estilo organiza la conducta, tiene un carácter eminentemente global, es imprescindible para el mantenimiento adaptativo del individuo y puede considerarse como un conjunto de pautas de interpretación, donación de significados y respuestas. Dado su carácter globalizador, el EP es aplicable a muchos campos. Se presenta un trabajo empírico sobre estilos de vida (EV), proponiéndose su operativización mediante la distribución del tiempo. Se presenta el instrumento original creado (ADIT). Los datos indicaron que podemos utilizar la distribución del tiempo como operativización del EV, puesto que los perfiles encontrados tienen un claro sentido psicológico y las relaciones con las variables demográficas tienen también sentido psicológico.

The Swedish National Testing and Research Institute is maintaining the Swedish realization of the world time scale UTC, called UTC(SP). One area of research and development for The Swedish National Laboratory of Time and Frequency is time synchronization and how UTC(SP) can be distributed in Sweden. Dissemination of time information by SP is in Sweden mainly performed via Internet using the Network Time Protocol (NTP) as well as via a modem dial up service and a speaking clock (Fröken Ur). In addition to these services, time information from the Global Positioning System (GPS) and from the long-wave transmitter DCF77 in Germany, is also available in Sweden. This master’s thesis considers how different available commercial communication systems could be used for multicast time distribution. DECT, Bluetooth, Mobile Telecommunication and Radio Broadcasting are different techniques that are investigated. One application of Radio Broadcasting, DARC, was found to be interesting for a more detailed study. A theoretical description of how DARC could be used for national time distribution is accomplished and a practical implementation of a test system is developed to evaluate the possibilities to use DARC for multicast time distribution. The tests of DARC and the radio broadcast system showed that these could be interesting techniques to distribute time with an accuracy of a couple of milliseconds. This quality level is not obtained today but would be possible with some alterations of the system.

La contamination des aquifères de proche subsurface par les intrants d'origine agricole (nitrates) est un problème mondial.L'utilisation excessive d'engrais depuis plusieurs décennies a impacté la qualité des masses d'eau souterraines et soulève des enjeux pour la santé humaine comme pour celle des écosystèmes. Les nitrates dans les aquifères peuvent être réduits en diazote gazeux par l'activité microbienne hétérotrophique (la biomasse microbienne obtenant l'énergie nécessaire à ce processus via le carbone organique issu de la surface) et/ou par l'activité autotrophique (la biomasse microbienne obtenant cette fois ci son énergie depuis une source proche, lithologique). Les taux de dénitrification sont très variables spatialement, et sont régulés par l'interaction entre la structure des flux d'eau souterrains avec l'activité biogéochimique. Localiser l'activité biogéochimique dans les aquifères est difficilement réalisable à l'échelle des bassins versants, mais paraît crucial pour la gestion des masses d'eau souterraines. Bien que les processus de l'activité microbienne ne puissent pas être entièrement résolus à l'échelle locale, ce manuscrit de thèse propose une caractérisation des taux de dénitrification à l'échelle du bassin versant, basée sur l'analyse de données et sur une approche de modélisation intégrée. Cette thèse propose d'utiliser de manière extensive des traceurs conservatifs et réactifs associés aux flux d'eau souterraine et des modèles de transport afin d'identifier les contrôles géologiques et biogéochimiques sur les capacités de dénitrification dans les aquifères. Cette méthodologie a été appliquée à un aquifère libre cristallin de 76 km² situé en Bretagne. A partir des concentrations en CFC-12, O2, NO3- et N2 dissous mesurées dans 16 puits, il a été possible de reconstituer les chroniques d'apports de nitrate dans la zone saturée et de définir les variations spatio-temporelles de la dénitrification. Il est prouvé ici que la dénitrification est en premier lieu contrôlée par la position des donneurs d'électron. Ce travail propose un cadre d'interprétation général sur la base de l'utilisation combinée et complémentaire des traceurs et sur la modélisation semi-explicite pour estimer à l'échelle régionale les capacités de dénitrification et les stocks de nitrates dans les aquifères. / Unconfined shallow aquifers in agricultural areas are contaminated by nitrates worldwide. Excessive fertilization over the last decades has affected groundwater quality as well as human and ecosystem wellbeing. Nitrate in groundwater can be microbially reduced to dinitrogen gas by heterotrophic (microbes obtaining their energy from surface-derived organic carbon) and autotrophic (microbes obtaining their energy from a lithological source) processes. However, denitrification rates are highly spatially variable, following involved interactions between groundwater flow structures and biogeochemical activity. The location of biogeochemical activity in the aquifer is difficult to access at the catchment scale, but of vast importance to gain predictive capabilities for groundwater management. Even though microbial processes cannot be resolved at the local scale, this dissertation proposes a catchment scale characterization of denitrification rates based on an integrated model- and data-driven approach. The dissertation proposes an extensive use of conservative and reactive tracers combined with groundwater flow and transport models to identify the geological and biogeochemical controls on aquifer denitrification capacities. The methodology is applied to a crystalline unconfined aquifer of 76 km2 size in Brittany, France. Based on CFC-12, O2, NO3-, and dissolved N2 concentrations measured in 16 wells, it is possible to reconstruct historical nitrate inputs to the saturated zone and to define spatiotemporal denitrification activity. It is shown that denitrification is primarily controlled by the location of electron donors. The dissertation proposes a general interpretation framework based on tracer information combined with complementary semi-explicit lumped parameter models to assess regional denitrification capacities and nitrate legacy.

La torréfaction est un traitement thermique à basse température (250 à 300 °C) en atmosphère inerte qui permet de modifier les propriétés de la biomasse. La biomasse torréfiée est alors plus dense énergétiquement, plus hydrophobe et plus fragile. Dans cette étude, un modèle numérique de torréfaction en four tournant à une dimension a été développé. Le transport des plaquettes de bois, les transferts thermiques, le séchage ainsi que les cinétiques de torréfaction ont été modélisés séparément. Après confrontation aux résultats expérimentaux, ces différents sous-modèles ont été assemblés dans un modèle global. Le modèle prédit alors l’évolution de la température et de la perte de masse des plaquettes le long du four. Les résultats numériques montrent une adéquation satisfaisante avec les valeurs obtenues lors d’expériences de torréfaction sur un four tournant pilote. Les solides torréfiés ont été analysés et leurs propriétés ont été corrélées à la perte de masse. Il a en particulier été démontré que l'énergie de broyage de la biomasse torréfiée était fortement réduite. / Torrefaction is a thermal treatment at low temperature (250-300°C) used to improve biomass properties. Torrefied biomass has a higher energy density, it is more hydrophobic and more brittle. In this study, a one-dimensional numerical model of torrefaction in a rotary kiln has been developed. The wood chips flow, the thermal transfers, the drying step and the torrefaction kinetics have been modelled separately. These submodels have been experimentally validated before being implemented together. The model can thus predict the temperature and the mass loss of wood chips along the kiln. These results are in good agreement with values obtained during torrefaction experiments in the pilot-scale rotary kiln. In parallel, torrefied biomass has been analysed in terms of composition, heating value and structural properties with emphasis on the decrease of grinding energy consumption.

In this work the relationships between penetrant structure, its transport properties, and its effects on the mechanical properties of a polymer matrix were investigated. Although there is a vast amount of data on the diffusion of low molecular weight molecules into polymeric materials and on the mechanical properties of various polymer-penetrant systems, no attempts have been made to inter-relate the two properties with respect to the chemical structure of the diffusant. Therefore, two series of penetrants - n-alkanes and esters - were examined in this context, with the goal of correlating molecular size, shape, and chemical nature of the penetrant to its final transport and matrix mechanical properties. These correlations have been demonstrated to allow quantitative prediction of one property, given a reasonable set of data on the other parameters. A series of n-alkanes (C6-C17) and esters (C5-C17) have been used to separate the effects of penetrant size and shape, from those due to polymer-penetrant interactions, in the diffusion through a polyamide polymeric adhesive. These effects have been taken into account in order to yield a qualitative relationship that allows for prediction of diffusivity based upon penetrant structural information. Transport properties have been analyzed using mass uptake experiments as well as an in-situ FTIR-ATR technique to provide detailed kinetic as well as thermodynamic information on this process. The phenomenon of diffusion and its effects on the resulting dynamic mechanical response of a matrix polymeric adhesive have been studied in great detail using the method of reduced variables. The concept of a diffusion-time shift factor (log aDt) has been introduced to create doubly-reduced master curves, taking into account the effects of temperature and the variations in the polymer mechanical response due to the existence of a low molecular weight penetrant. / Ph. D.

Many cities suffer from problems with high traffic flows in the city centers which leads to a desire to get more people to choose public transport over cars. For many car drivers, the main reason to take the car is the convenience and time efficiency; the price is often of less importance. The public transport providers should, therefore, strive to improve their Level of Service (LOS). A general process that can be used by public transport providers or other stakeholders to evaluate the LOS in a public transport system based on Automated Vehicle Location (AVL) data is developed and presented in this thesis.The process values the quality and suitability of the AVL data, propose which KPIs to use and how to use the results to find possible improvements. Four different types of erroneous data were discovered: outliers in position, outliers in speed, outliers in travel time and general errors. KPIs are developed in three main areas: on-time performance, travel time distribution and speed, where each KPI is divided into several sub-areas.

Os processos oxidativos avançados são promissores para a degradação de compostos orgânicos resistentes aos tratamentos convencionais, como o fenol. A fluidodinâmica computacional (CFD) tornou-se uma poderosa ferramenta para analisar processos fotoquímicos por resolver os balanços acoplados de quantidade de movimento, de massa e de radiação. O objetivo deste trabalho é investigar o processo UV/H2O2 num reator fotoquímico anular usando CFD e um modelo cinético mais realista. O modelo em CFD foi criado de forma progressiva. Inicialmente, foram determinados os campos de velocidade para três vazões (30, 60 e 100 L/h). Considerou-se dois diâmetros de lâmpada para reproduzir a configuração experimental do sistema. A discretização foi feita com malhas tetraédricas variando entre 390 000 e 1 200 000 elementos. Quatro modelos de turbulência RANS foram analisados: k-e, k-w, o shear stress transport (SST) e o modelo de tensões de Reynolds (RSM). O campo de velocidades foi validado comparando a DTR com seu levantamento experimental. A próxima etapa foi incluir o mecanismo de degradação de fenol proposto por Edalatmanesh, Dhib e Mehrvar (2008) no modelo em CFD. Trata-se de um modelo cinético baseado em equações dinâmicas para todas as espécies. O campo de radiação foi calculado pelo modelo radial e pela solução da equação de transporte de radiação através do método discrete transfer. As simulações reproduziram dados experimentais abrangendo uma larga gama de concentrações iniciais de fenol, razões molares H2O2/fenol e três potências de emissão das lâmpadas. O campo de velocidades obtido era dependente da vazão: o fluido pode manter movimento helicoidal sobre toda a extensão do reator ou se desenvolver como um escoamento pistonado. O modelo k-e não reproduziu bem o escoamento por não ser adequado para escoamentos rotativos. Os outros modelos geraram curvas de DTR com bom ajuste aos dados experimentais, especialmente o modelo k-w. O desvio médio entre as simulações de degradação de fenol e os dados experimentais é inferior a 8%. Verificou-se que, devido ao escoamento rotativo, os reagentes ficavam concentrados próximos à parede externa e migravam para a região da lâmpada ao longo do reator. A elevada intensidade de radiação na superfície da lâmpada criou uma camada ao seu redor na qual a fotólise do H2O2 ocorreu com grande taxa. Os radicais OH gerados nessa camada eram transportados para a região das paredes por convecção. Isso fez com que a maior parte do fenol fosse atacada na segunda metade do reator e gerou acúmulo do radical próximo à lâmpada na seção de saída do reator, já que o poluente já fora oxidado nessa área. O método discrete transfer previu intensidades de radiação maiores que o modelo radial, e, consequentemente, maior concentração de radicais OH. Os resultados satisfatórios indicam que CFD foi uma ferramenta adequada para analisar este escoamento reativo. / Advanced oxidation processes are a promising technology for degradation of organic compounds resistant to conventional treatments such as phenol. Computational fluid dynamics (CFD) has recently emerged as a powerful tool that allows a deeper understanding of photochemical processes in reactor engineering by solving the coupled momentum, mass and radiation balances. This work aimed to investigate the UV/H2O2 process in an annular photoreactor using CFD and a more realistic kinetic model. A progressive approach was used to develop the CFD reactor model. First, the velocity fields were determined for three volumetric flow rates (30, 60 and 100 L/h). Two lamp diameters were considered to reflect the experimental configuration of the system. Tetrahedral meshes varying form 390,000 to 1,200,000 elements were analyzed to achieve grid independence. For accounting turbulence effects, four RANS models were tested: k-e, k-w, the Shear Stress Transport (SST) and the Reynolds Stress models (RSM). The velocity field was validated through comparison to RTD experimental data. Next step was introducing the mechanism of phenol degradation proposed by Edalatmanesh, Dhib and Mehrvar (2008) into the CFD model. This kinetic model is based on dynamic equations for all species. The fluence rate field was calculated by the radial model and by solving the radiation transport equation with the discrete transfer method. Simulations reproduced experimental data spanning a wide range of initial phenol concentrations, H2O2/phenol molar ratios and three values for lamp power. It was found that the velocity field depends on the volumetric flow rate: either it maintains a swirling motion through the whole reactor or might develop like a plug flow. The k-e model did not represent the RTD data accurately, and the velocity field therefore, since it is not appropriate for swirling flows. The other turbulence models showed good match of RTD, especially the k-w model. Simulations of phenol degradation deviated less than 8% from experimental data. It was possible verified that, due to the swirling inlet effects, reactants got concentrated close to the outer wall and migrated on the lamp direction along the reactor path. High radiation intensities close to the lamp surface created a layer around it where photolysis of H2O2 took place with higher rates. OH radicals were generated in that layer and transported towards the outer wall by convection. This caused most of phenol to be consumed in the second half of the reactor and accumulation of the radical near the lamp and the reactor outlet, since the pollutant in this area was already oxidized. The discrete transfer method predicted higher incident radiation intensity than the radial model, and higher concentrations of OH radicals as a consequence. Satisfactory results indicated that CFD was an appropriate tool for analyzing this reactive flow.