Дисертації з теми "Core parameters"

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 39).
The limiting factor in current designs for fast reactors is not only the reactivity, but also the maximum permissible fast-neutron fluence in the cladding, especially for reduced uranium enrichment cores using high-albedo MgO reflectors. The intent of this thesis was to determine the best design parameters - fuel type, fuel compound, fuel arrangement, and coolant - while observing these limitations. The ERANOS code was used to determine the flux values for each design option. A curve was fitted to the fluxes taken at beginning of life, middle of life, and end of life. This curve was then integrated progressively until the clad fluence limit of 4 x 1023 fast neutrons/cm 2 was reached. The different design options were compared with emphasis on minimizing enrichment and maximizing burnup. Sodium was chosen as a coolant because of its extensive experience based compared to the other options, as well as its heat transfer properties. Inverted fuel was found to be better neutronically, in both clad lifetime and burnup than conventional pin-type fuel, but the requirement of fuel venting may discourage use of this option. Uranium carbide was found to be superior to nitride, oxide or metal fuel in its clad lifetime, especially if pin cell fuel is used. If inverted fuel is used, uranium oxide is also a valid choice from a burnup and cost perspective, especially should re-cladding not be feasible or desired, since the reactivity and clad fluence lifetimes of oxide fuel are similar to each other.
by Alyssa Kersting.
S.B.

The build–up of 6Li and 3He, that is, the strong thermal neutron absorbers or the so called "neutron poisons", in the beryllium reflector changes the physical characteristics of the reactor, such as reactivity, neutron spectra, neutron flux level, power distribution, etc.; furthermore,gaseous isotopes such as 3H and 4He induce swelling and embrittlement of the reflector. The SAFARI–1 research reactor, operated by Necsa at Pelindaba in South Africa, uses a beryllium reflector on three sides of the core, consisting of 19 beryllium reflector elements in total. This MTR went critical in 1965, and the original beryllium reflectors are still used. The individual neutron irradiation history of each beryllium reflector element, as well as the impact of beryllium poisoning on reactor parameters, were never well known nor investigated before. Furthermore, in the OSCAR{3 code system used in predictive neutronic calculations for SAFARI–1, beryllium reflector burn–up is not accounted for; OSCAR models the beryllium reflector as a non–burnable, 100% pure material. As a result, the poisoning phenomenon is not accounted for. Furthermore, the criteria and hence the optimum replacement time of the reflector has never been developed. This study presents detailed calculations, using MCNP, FISPACT and the OSCAR{3 code system, to quantify the influence of impurities that were originally present in the fresh beryllium reflector, the beryllium reflector poisoning phenomenon, and further goes on to propose the reflector's replacement criteria based on the calculated fluence and predicted swelling. Comparisons to experimental low power flux measurements and effects of safety parameters are also established. The study concludes that, to improve the accuracy and reliability of the predictive OSCAR code calculations, beryllium re flector burn–up should undoubtedly be incorporated in the next releases of OSCAR. Based on this study, the inclusion of the beryllium reflector burn–up chains is planned for implementation in the currently tested OSCAR–4 code system. In addition to beryllium reflector poisoning, the replacement criteria of the reflector is developed. It is however crucial that experimental measurements on the contents of 3H and 4He be conducted and thus swelling of the reflector be quantifed. In this way the calculated results could be verified and a sound replacement criteria be developed. In the absence of experimental measurements on the beryllium reflector, the analysis and quantifcation of the calculated results is reserved for future studies.
Thesis (M.Sc. Engineering Sciences (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

Power transformers are a key element in the transmission and distribution of electrical energy and as such need to be highly reliable and efficient. In power system networks, transformer core saturation can cause system voltage disturbances or transformer damage or accelerate insulation ageing. Low frequency switching transients such as ferroresonance and inrush currents, and increasingly what is now known as geomagnetic induce currents (GIC), are the most common phenomena to cause transformer core saturation. This thesis describes extensive simulation studies carried out on GIC and switching ferroresonant transient phenomena. Two types of transformer model were developed to study core saturation problems; one is the mathematical transformer magnetic circuit model, and the other the ATPDraw transformer model. Using the mathematical transformer magnetic circuit model, the influence of the transformer core structure on the magnetising current has been successfully identified and so have the transformers' responses to GIC events. By using the ATPDraw transformer model, the AC system network behaviours under the influence of the DC bias caused by GIC events have been successfully analysed using various simulation case studies. The effects of the winding connection, the core structure, and the network parameters including system impedances and transformer loading conditions on the magnetising currents of the transformers are summarised. Transient interaction among transformers and other system components during energisation and de-energisation operations are becoming increasingly important. One case study on switching ferroresonant transients was modelled using the available transformer test report data and the design data of the main components of the distribution network. The results were closely matched with field test results, which verified the simulation methodology. The simulation results helped establish the fundamental understanding of GIC and ferroresonance events in the power networks; among all the influential parameters identified, transformer core structure is the most important one. In summary, the five-limb core is easier to saturate than the three-limb transformer under the same GIC events; the smaller the side yoke area of the five-limb core, the easier it will be to saturate. More importantly, under GIC events a transformer core could become saturated irrespective of the loading condition of the transformer.

One of the main objectives of this work was to investigate the applicability and accuracy of artificial neural networks for estimating special core analysis (SCAL) parameters from minimal core training data and wireline logs. The SCAL data was obtained from measurements on core plugs undertaken at the Libyan Petroleum Institute (L.P.I). Previous neural network studies have attempted to predict routine core analysis parameters, such as permeability, but not SCAL parameters such as true formation resistivity (Rt), resistivity index (RI), water saturation (Sw), saturation exponent (n) and Amott-Harvey Wettability Index (IA/H). Different combinations of wireline logs were used to train a variety of neural network predictors. Some of the predictors were trained using a large dataset from the entire cored interval of the training well. Other genetically focused neural network (GFNN) predictors were trained just from one short representative genetic unit (RGU) in the training well. The predictors were then tested in an adjacent well in the same oil field and also in another well in a different oil field. Significantly the performance of the GFNN predictors was as good (and in most cases better) than the predictors trained on the much larger dataset. This demonstrated the useful of the GFNN approach, which is very cost effective in terms of the minimal core that is required, and the reduced computer processing time. Moreover, this is the first time that these GFNN predictors have been used to predict SCAL parameters in the studied area, the Nubian Sandstone Formation in North Africa. These neural network predictors are particularly useful in this area due to the limited amount of SCAL data that is currently available. Quantitative statistical measures of heterogeneity were also examined on the reservoir samples, followed by a comparative analysis of hydraulic units (HUs) with a newer approach of global hydraulic elements (GHEs) to characterize the reservoir units in the studied area. The GHEs were then applied to select minimal representative core training data to train the genetically focused neural networks (GFNNs) to predict the SCAL parameters. The thesis also describes the factors affecting SCAL resistivity parameters. Laboratory measurements on the Nubian Sandstone reservoir rock samples showed changes in the formation resistivity factor (F) and cementation exponent (m) between ambient conditions and at overburden pressures. Changes were also observed in the saturation exponent (n) before and after wettability measurement. The experimental results also showed that there was a good relation between resistivity and the type of pore system which is consistent with study result from Swanson (1985) confirming earlier work.

Electrospinning or electrostatic fibre spinning employs electrostatic force to draw fibres from a liquid, either a polymeric solution or a polymer melt in the form of a charged jet. The jet solidifies and is deposited on a collector in the form of a non-woven fibrous mat. Electrospun fibres have diameters between several nanometres to a few microns, which is one of the main advantages of the process, as materials at the nanoscale have shown great potential in a wide range of healthcare and energy applications. The initial selection of solvents to dissolve the polymer for production of electrospun defect-free nanofibres has generally been based on experience from similar polymer-solvent systems. The selection of a solvent is important to control the fibre surface morphology that would eventually determine the field of application for the electrospun nanofibrous structures. However, little attempt has been made to study the correlation between the solubility behaviour of the polymer in different solvents and the electrospinnability of the polymer solutions. From this perspective, the first part of this thesis focused on the selection of different solvents for the production of poly (lactic acid) (PLA) nanofibres. Solution properties were measured and the electrospun nanofibrous structures were analysed in terms of morphology and nanofibre diameter. Understanding the molecular interactions between polymer and solvents enables the correct solvent selection to ensure the desired nanofibrous structure. Solubility is not the only criterion for nanofibre formation from a polymer solution. Polymer concentration is one of the main factors affecting electrospinning. For this reason, a relationship between PLA concentration and nanofibre morphology was determined by solution property measurements. A three step systematic methodology has been proposed in this thesis in order to select appropriate solvent and polymer concentration for the production of homogeneous electrospun mats made of defect-free nanofibres. This methodology was validated for PLA nanofibres, but it can be used for a wide range of polymers. It simplifies the solvent selection process and can significantly improve the trial and error approaches used at present. Despite several models for electrospinning having been proposed to predict the behaviour of the electrospun jet, there are no simple methods for a priori prediction of the final morphology of the electrospun mat from the knowledge of solution properties and electrospinning process parameters. Moreover the prediction of nanofibre diameter is still a difficulty and little research has been done on this. For these reasons, the second part of this thesis is dedicated to understanding the effect of some process parameters on the jet electric current and hence on the morphology of PLA nanofibres. The values of current measured were used to verify an equation proposed in the literature for the prediction of the final diameter. The experimental diameter of the PLA nanofibres was compared with the predicted value. In the last chapter coaxial electrospinning was employed to produce PLA nanofibres with a core shell structure for the incorporation of a model hydrophilic drug in the nanofibre core. The large surface area to volume ratio of nanofibres offers the great advantage of higher efficiency of encapsulation and better control of the release profile compared with other drug delivery systems. Even though successful encapsulation of drug and proteins have been reported, it is not clear how to verify the continuous drug distribution in the core throughout the whole length of the fibre. The solution properties of both core and shell strongly affect the outcome of the electrospinning process. For this reason, several techniques have been used to verify the formation of a core shell structure and proper encapsulation of the drug. In addition, the efficiency of drug encapsulation was evaluated and drug release studies were performed.

This PhD study, developed at Universitat Politècnica de València (UPV), aims to cover the first phase of the benchmark released by the expert group on Uncertainty Analysis in Modeling (UAM-LWR). The main contribution to the benchmark, made by the thesis' author, is the development of a MATLAB program requested by the benchmark organizers. This is used to generate neutronic libraries to distribute among the benchmark participants. The UAM benchmark pretends to determine the uncertainty introduced by coupled multi-physics and multi-scale LWR analysis codes. The benchmark is subdivided into three phases: 1. Neutronic phase: obtain collapsed and homogenized problem-dependent cross sections and criticality analyses. 2. Core phase: standalone thermohydraulic and neutronic codes. 3. System phase: coupled thermohydraulic and neutronic code. In this thesis the objectives of the first phase are covered. Specifically, a methodology is developed to propagate the uncertainty of cross sections and other neutronic parameters through a lattice physics code and core simulator. An Uncertainty and Sensitivity (U&S) analysis is performed over the cross sections contained in the ENDF/B-VII nuclear library. Their uncertainty is propagated through the lattice physics code SCALE6.2.1, including the collapse and homogenization phase, up to the generation of problem-dependent neutronic libraries. Afterward, the uncertainty contained in these libraries can be further propagated through a core simulator, in this study PARCSv3.2. The module SAMPLER -available in the latest release of SCALE- and DAKOTA 6.3 statistical tool are used for the U&S analysis. As a part of this process, a methodology to obtain neutronic libraries in NEMTAB format -to be used in a core simulator- is also developed. A code-to-code comparison with CASMO-4 is used as a verification. The whole methodology is tested using a Boiling Water Reactor (BWR) reactor type. Nevertheless, there is not any concern or limitation regarding its use in any other type of nuclear reactor. The Gesellschaft für Anlagen und Reaktorsicherheit (GRS) stochastic methodology for uncertainty quantification is used. This methodology makes use of the high-fidelity model and nonparametric sampling to propagate the uncertainty. As a result, the number of samples (determined using the revised Wilks' formula) does not depend on the number of input parameters but only on the desired confidence and uncertainty of output parameters. Moreover, the output Probability Distribution Functions (PDFs) are not subject to normality. The main disadvantage is that each input parameter must have a pre-defined PDF. If possible, input PDFs are defined using information found in the related literature. Otherwise, the uncertainty definition is based on expert judgment. A second scenario is used to propagate the uncertainty of different thermohydraulic parameters through the coupled code TRACE5.0p3/PARCSv3.0. In this case, a PWR reactor type is used and a transient control rod drop occurrence is simulated. As a new feature, the core is modeled chan-by-chan following a fully 3D discretization. No other study is found using a detailed 3D core. This U&S analysis also makes use of the GRS methodology and DAKOTA 6.3.
Este trabajo de doctorado, desarrollado en la Universitat Politècnica de València (UPV), tiene como objetivo cubrir la primera fase del benchmark presentado por el grupo de expertos Uncertainty Analysis in Modeling (UAM-LWR). La principal contribución al benchmark, por parte del autor de esta tesis, es el desarrollo de un programa de MATLAB solicitado por los organizadores del benchmark, el cual se usa para generar librerías neutrónicas a distribuir entre los participantes del benchmark. El benchmark del UAM pretende determinar la incertidumbre introducida por los códigos multifísicos y multiescala acoplados de análisis de reactores de agua ligera. El citado benchmark se divide en tres fases: 1. Fase neutrónica: obtener los parámetros neutrónicos y secciones eficaces del problema específico colapsados y homogenizados, además del análisis de criticidad. 2. Fase de núcleo: análisis termo-hidráulico y neutrónico por separado. 3. Fase de sistema: análisis termo-hidráulico y neutrónico acoplados. En esta tesis se completan los principales objetivos de la primera fase. Concretamente, se desarrolla una metodología para propagar la incertidumbre de secciones eficaces y otros parámetros neutrónicos a través de un código lattice y un simulador de núcleo. Se lleva a cabo un análisis de incertidumbre y sensibilidad para las secciones eficaces contenidas en la librería neutrónica ENDF/B-VII. Su incertidumbre se propaga a través del código lattice SCALE6.2.1, incluyendo las fases de colapsación y homogenización, hasta llegar a la generación de una librería neutrónica específica del problema. Luego, la incertidumbre contenida en dicha librería puede continuar propagándose a través de un simulador de núcleo, para este estudio PARCSv3.2. Para el análisis de incertidumbre y sensibilidad se ha usado el módulo SAMPLER -disponible en la última versión de SCALE- y la herramienta estadística DAKOTA 6.3. Como parte de este proceso, también se ha desarrollado una metodología para obtener librerías neutrónicas en formato NEMTAB para ser usadas en simuladores de núcleo. Se ha realizado una comparación con el código CASMO-4 para obtener una verificación de la metodología completa. Esta se ha probado usando un reactor de agua en ebullición del tipo BWR. Sin embargo, no hay ninguna preocupación o limitación respecto a su uso con otro tipo de reactor nuclear. Para la cuantificación de la incertidumbre se usa la metodología estocástica Gesellschaft für Anlagen und Reaktorsicherheit (GRS). Esta metodología hace uso del modelo de alta fidelidad y un muestreo no paramétrico para propagar la incertidumbre. Como resultado, el número de muestras (determinado con la fórmula revisada de Wilks) no depende del número de parámetros de entrada, sólo depende del nivel de confianza e incertidumbre deseados de los parámetros de salida. Además, las funciones de distribución de probabilidad no están limitadas a normalidad. El principal inconveniente es que se ha de disponer de las distribuciones de probabilidad de cada parámetro de entrada. Si es posible, las distribuciones de probabilidad de entrada se definen usando información encontrada en la literatura relacionada. En caso contrario, la incertidumbre se define en base a la opinión de un experto. Se usa un segundo escenario para propagar la incertidumbre de diferentes parámetros termo-hidráulicos a través del código acoplado TRACE5.0p3/PARCSv3.0. En este caso, se utiliza un reactor tipo PWR para simular un transitorio de una caída de barra. Como nueva característica, el núcleo se modela elemento a elemento siguiendo una discretización totalmente en 3D. No se ha encontrado ningún otro estudio que use un núcleo tan detallado en 3D. También se usa la metodología GRS y el DAKOTA 6.3 para este análisis de incertidumbre y sensibilidad.
Aquest treball de doctorat, desenvolupat a la Universitat Politècnica de València (UPV), té com a objectiu cobrir la primera fase del benchmark presentat pel grup d'experts Uncertainty Analysis in Modeling (UAM-LWR). La principal contribució al benchmark, per part de l'autor d'aquesta tesi, es el desenvolupament d'un programa de MATLAB sol¿licitat pels organitzadors del benchmark, el qual s'utilitza per a generar llibreries neutròniques a distribuir entre els participants del benchmark. El benchmark del UAM pretén determinar la incertesa introduïda pels codis multifísics i multiescala acoblats d'anàlisi de reactors d'aigua lleugera. El citat benchmark es divideix en tres fases: 1. Fase neutrònica: obtenir els paràmetres neutrònics i seccions eficaces del problema específic, col¿lapsats i homogeneïtzats, a més de la anàlisi de criticitat. 2. Fase de nucli: anàlisi termo-hidràulica i neutrònica per separat. 3. Fase de sistema: anàlisi termo-hidràulica i neutrònica acoblats. En aquesta tesi es completen els principals objectius de la primera fase. Concretament, es desenvolupa una metodologia per propagar la incertesa de les seccions eficaces i altres paràmetres neutrònics a través d'un codi lattice i un simulador de nucli. Es porta a terme una anàlisi d'incertesa i sensibilitat per a les seccions eficaces contingudes en la llibreria neutrònica ENDF/B-VII. La seua incertesa es propaga a través del codi lattice SCALE6.2.1, incloent les fases per col¿lapsar i homogeneïtzar, fins aplegar a la generació d'una llibreria neutrònica específica del problema. Després, la incertesa continguda en la esmentada llibreria pot continuar propagant-se a través d'un simulador de nucli, per a aquest estudi PARCSv3.2. Per a l'anàlisi d'incertesa i sensibilitat s'ha utilitzat el mòdul SAMPLER -disponible a l'última versió de SCALE- i la ferramenta estadística DAKOTA 6.3. Com a part d'aquest procés, també es desenvolupa una metodologia per a obtenir llibreries neutròniques en format NEMTAB per ser utilitzades en simuladors de nucli. S'ha realitzat una comparació amb el codi CASMO-4 per obtenir una verificació de la metodologia completa. Aquesta s'ha provat utilitzant un reactor d'aigua en ebullició del tipus BWR. Tanmateix, no hi ha cap preocupació o limitació respecte del seu ús amb un altre tipus de reactor nuclear. Per a la quantificació de la incertesa s'utilitza la metodologia estocàstica Gesellschaft für Anlagen und Reaktorsicherheit (GRS). Aquesta metodologia fa ús del model d'alta fidelitat i un mostreig no paramètric per propagar la incertesa. Com a resultat, el nombre de mostres (determinat amb la fórmula revisada de Wilks) no depèn del nombre de paràmetres d'entrada, sols depèn del nivell de confiança i incertesa desitjats dels paràmetres d'eixida. A més, las funcions de distribució de probabilitat no estan limitades a la normalitat. El principal inconvenient és que s'ha de disposar de les distribucions de probabilitat de cada paràmetre d'entrada. Si és possible, les distribucions de probabilitat d'entrada es defineixen utilitzant informació trobada a la literatura relacionada. En cas contrari, la incertesa es defineix en base a l'opinió d'un expert. S'utilitza un segon escenari per propagar la incertesa de diferents paràmetres termo-hidràulics a través del codi acoblat TRACE5.0p3/PARCSv3.0. En aquest cas, s'utilitza un reactor tipus PWR per simular un transitori d'una caiguda de barra. Com a nova característica, cal assenyalar que el nucli es modela element a element seguint una discretizació totalment 3D. No s'ha trobat cap altre estudi que utilitze un nucli tan detallat en 3D. També s'utilitza la metodologia GRS i el DAKOTA 6.3 per a aquesta anàlisi d'incertesa i sensibilitat.¿
Mesado Melia, C. (2017). Uncertainty Quantification and Sensitivity Analysis for Cross Sections and Thermohydraulic Parameters in Lattice and Core Physics Codes. Methodology for Cross Section Library Generation and Application to PWR and BWR [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86167
TESIS

Nanoporous materials for gas purification and thermal insulation have been studied and developed for application in many areas. It is known that a single adsorbent may not adequately control multiple contaminants. Further the utilization of nanoporous material as thermal insulator in building applications is limited due to high cost. Moreover, in view of the global environmental movement for clean air and reduction of heating energy consumption in built environment, the development of new and better nanoporous materials will not only facilitate major advances in gas adsorption and thermal insulation technology, but also meet the new challenges that cannot be met with the nanoporous materials that are currently available. This thesis presents a synthesis of new nanoporous silica based materials, and the characterization and application of these materials for molecular filtration and thermal insulation. Commercial nanoporous materials have been used for benchmarking for the pore properties, the applicability, and the performance of these new materials. First a double metal-silica adsorbent has been synthesized. The preparation procedure is based on the use of sodium silicate coagulated with various ratios of magnesium and calcium salts which yields micro-meso porous structures in the resulting material. The results show that molar ratios of Mg/Ca influence the pore parameters as well as the structure and morphology. The bimodal pore size can be tailored by controlling the Mg/Ca ratio. In the second synthesis, pure mesoporous silica, SNP has been prepared using glycerol as pore forming agent and monovalent salts as coagulant. This leads to material with large surface area and uniformed pore size centred at 43 or 47 nm.  The materials further exhibits a low bulk density in the range of 0.077 to 0.122 g/ml and possess a high porosity in the range of 95-97%. The influence of acid type (organic or inorganic) on the pore parameters and on the tapped density has also been investigated.   A synthesis method has also been developed for the preparation of carbon-silica composites. The method involves a number of routes, which can be summarised as addition of activated carbon particles to (I) the paste, (II) the salt solution, or (III) with the sodium silicate solution. In route II and III the activated carbon is present before coagulation. The routes presented here leads to carbon-silica composites possessing high micro porosity, meso porosity as well as large surface areas. The results further shows that pore size distribution may be tailored based on the route of addition of the carbon particles. Following route I and III a wide pore size (1-30 nm) was obtained whereas by route II a narrow pore size (1-4 nm) was observed.     MgCa-silica chemisorbents were also developed using either potassium hydroxide or potassium permanganate as impregnate chemicals. A direct or post-impregnation procedure was employed. The results revealed that the impregnate route and amount cause a reduction in both specific surface area and pore volume. Finally the thermal conductivity and dynamic adsorption of H2S, SO2 andtoluene were measured. Results show that at room temperature and atmospheric pressure, a thermal conductivity of 28.4 and 29.6 mW/m.K were obtained for the SNP mesoporous silicas. The dynamic adsorption behaviour of the chemisorbents and composites indicate their ability to absorbed H2S, SO2 andtoluene respectively. The highest H2S uptake corresponds to chemisorbents with 11.2-13.6 wt% KMnO4. The effect of impregnation route, amount of KMnO4 and its location in the pore system are likely the key factors in achieving a large H2S uptake. For SO2 adsorption, the highest uptake capacity was observed for MgCa-68/32-KOH. The results further suggest that the key to large SO2 uptake is as a result of the synergetic effect between large mesopore diameter and extensive mesopore volumes. Carbon-silica composites with carbon content 45 wt % exhibits high toluene adsorption with composite via route I having the highest toluene adsorption capacity (27.6 wt % relative to carbon content). The large uptake capacity of this composite was attributed to the presence of high microporosity volume and a wide (1-30 nm) bimodal pore system consisting of extensive mesopore channels (2-30 nm) as well as large surface area. These capacity values of carbon-silica composites are competitive to results obtained for commercial coconut based carbon (31 wt %), and better than commercial alumina-carbon composite (9.5 wt %).

QC 20130408

This thesis presents the project for the optimization of the APOLLO3® neutronic calculation scheme applied to the 4th generation fast neutron reactor ASTRID. APOLLO3® is the new multipurpose neutronic platform developed by the CEA. It incorporates many of the previous generation codes used in the French reactor core design supply chain. Like all deterministic codes, APOLLO3® solves the neutron transport equation with a discretization of the variables of interest: multi-group method for the energy, discrete ordinates and spherical harmonics for the angular variable, collision probabilities and characteristics methods for the spatial variable. The resolution of the transport equation handles useful quantities such as the neutron flux and multiplication factor, fission rates and cross sections to understand the physical behaviour of the reactor core. Currently it is not possible to use deterministic codes to simulate an entire reactor with a heterogeneous 3D geometry and a fine energy description, so to simplify the study of complete neutron field at core level, the calculation scheme is divided into two phases: lattice and core calculation. The main purpose of this work is to find an optimal degree of approximations of the calculation scheme for the evaluation of a desired physical effect and of the user constraints. In order to reach this optimum, several studies have been carried out with different levels of approximations. The results have been benchmarked with the ones obtained using the stochastic code TRIPOLI4®, used as a reference and to ensure a good accuracy. Furthermore, several sensitivity studies have been carried out to understand how the different approximations affect the macroscopic cross sections evaluation, because these dependences are not yet fully understood.

Cette thèse est une contribution à l´économie du travail. En particulier, nous analysons la demande de travail des entreprises sous plusieurs aspects. En termes de méthodes, nous utilisons des données administratives, des données d'enquêtes et des modèles théoriques dans la lignée de la théorie de l'appariement. Dans un premier chapitre, nous étudions les mouvements sur le marché du travail au niveau macroéconomique en utilisant de nouvelles données microéconomiques sur les entreprises et leurs salariés. Nous montrons l'importance des caractéristiques des entreprises pour comprendre les flux d'emploi. Dans un deuxième chapitre, nous étudions l´organisation du travail suite à un choc d'offre de travail au niveau de l'entreprise. Nous utilisons le registre des hospitalisations et des décès pour confectionner une base de données qui permet d’exploiter les méthodes les plus récentes économétriques. Nous montrons l’importance de l'ajustement des heures de travail des collègues pour quantifier les couts de rotation de la main d'œuvre. Dans un troisième chapitre, nous analysons les stratégies des ressources humaines des entreprises. Nous utilisons la première enquête européenne qui permet de mieux comprendre le processus d’embauche et de formations des entreprises. Un des résultats de notre analyse et le lien compétition sur le marché des biens et les stratégies de recrutements
There are three main matters regarding employers’ decisions: employment, compensation, and training. We contribute to the economic literature on employment and compensation. Specifically, the economic question of this thesis is: how do firms adjust their employment to shocks? Disruptive innovation, employee departure or supplier shutdown are a few of the many shocks that force firms to adjust their employment. These adjustments are costly, and significant differences in firm characteristics make them respond differently to similar shocks. The idea that it takes time and effort for workers to find desirable employers and firms to find suitable employees is present throughout this work. To understand how firms respond to shocks of various kinds, we combine empirical methods with theory. On the empirical side, we create unique datasets using several data sources from Denmark. Danish data has the distinctive property that sources such as administrative records, surveys, or big data from private firms can be linked. Linking information from various sources allow, among other things, to find shocks and draw causal links between economic relationships. In one project, we also draw on theoretical models where various distortions (e.g., search frictions) prevent immediate matching between employees and employers. Concretely, we bring together datasets and structural models to estimate economic outcomes (e.g, hiring costs) that are not directly observed in datasets. In the chapter entitled "Firm Adjustment to Unexpected Departures", we use quasi-experimental variation in firms’ employment to provide a new way of estimating turnover costs. In another chapter, entitled "Firm Labor Demand Over the Business Cycle" we study how, over more than 30 years, firms grow and shrink when the macroeconomic environment changes. Finally, contrary to the first two chapters that used as primary input large administrative datasets, the last chapter, "International Evidence on Hiring Practices", uses a recent survey. This is another angle to understanding firm labor demand

The presented thesis focused on the study of effect of temperature and different loading condition of an inductive current transformer for medium voltage purposes. Equivalent circuit parameters behavior of the current transformer is analyzed for two different temperatures 24°C and 60°C and varying working conditions (current and voltage). Application of Short Circuit and Open circuit test is done for the current transformer under test with varying loading conditions and two temperatures of interest. Interesting behavior of the shunt parameters of the current transformers are of most attention and can be implemented during modeling a current transformer.

Background: In a computed protein multiple sequence alignment, the coreness of a column is the fraction of its substitutions that are in so-called core columns of the gold-standard reference alignment of its proteins. In benchmark suites of protein reference alignments, the core columns of the reference alignment are those that can be confidently labeled as correct, usually due to all residues in the column being sufficiently close in the spatial superposition of the known three-dimensional structures of the proteins. Typically the accuracy of a protein multiple sequence alignment that has been computed for a benchmark is only measured with respect to the core columns of the reference alignment. When computing an alignment in practice, however, a reference alignment is not known, so the coreness of its columns can only be predicted. Results: We develop for the first time a predictor of column coreness for protein multiple sequence alignments. This allows us to predict which columns of a computed alignment are core, and hence better estimate the alignment's accuracy. Our approach to predicting coreness is similar to nearest-neighbor classification from machine learning, except we transform nearest-neighbor distances into a coreness prediction via a regression function, and we learn an appropriate distance function through a new optimization formulation that solves a large-scale linear programming problem. We apply our coreness predictor to parameter advising, the task of choosing parameter values for an aligner's scoring function to obtain a more accurate alignment of a specific set of sequences. We show that for this task, our predictor strongly outperforms other column-confidence estimators from the literature, and affords a substantial boost in alignment accuracy.

When modeling a neuron, modelers often focus on the values of parameters that produce a desired output. However, if these parameters are not unique, there could be a number of parameter sets that produce the same output. Thus, even though the values of the various maximum conductances, half activation voltages and so on differ, as a set they can produce the same spike height, firing rates, and so forth. To examine whether or not parameter sets are unique, a 3-compartment motoneuron model was created that has 15 target outputs and 59 parameters. Using parameter searches, over one hundred parameter sets were created for this model that produced the same output (within tolerances). Parameter values vary between parameter sets and indicate that the parameter values are not unique. In addition, some parameters are more tightly constrained than others. Principal component analysis is used to examine the dimensionality of the input and output spaces. However, neurons are more than static output generators. For example, a variety of neuromodulatory influences are known to shift parameter values to alter neuronal output. Thus the question arises as to whether this non-uniqueness extends from model outputs to the models sensitivities to its parameters. In this work, the non-unique parameter sets are further analyzed using sensitivity analyses and output correlations to show that these values vary significantly between these parameter sets. Therefore, each of these models will react to parameter variation differently. This work concludes that parameter sets are non-unique but have varying sensitivity analyses and output correlations. The ramifications of this are discussed for both modelers and neuroscientists.

Orientador: Lucia Galvão de Albuquerque
Coorientador: Gerardo Alves Fernandes Júnior
Banca: Henrique Nunes de Oliveira
Banca: Raphael Bermal Costa
Resumo: A habilidade de permanência (HP), que pode ser definida como a probabilidade de uma vaca parir numa determinada idade, dado que ela teve esta oportunidade, é uma característica reprodutiva de grande importância em bovinos de corte, estando diretamente relacionada à produtividade do rebanho. O objetivo deste trabalho foi estimar parâmetros genéticos e identificar possíveis regiões do genoma que estejam associadas com a expressão fenotípica da HP de vacas da raça Nelore. Os componentes de variância foram estimados por inferência bayesiana utilizando um modelo de limiar no qual foram considerados os efeitos sistemáticos de grupos de contemporâneos e precocidade sexual, e os efeitos aleatórios de animal e resíduo.Os efeitos dos SNPs foram estimados por meio da metodologia ssGBLUP, sendo utilizados na análise 2838 animais genotipados com o painel de alta densidade da Illumina (Bovine HD Assay Illumina, San Diego, CA, USA). A variância explicada por janelas formadas por 200 SNPs consecutivos foi utilizada na identificação das regiões de maior efeito sobre a expressão da característica HP. A herdabilidade encontrada utilizando a matriz A (pedigree) foi de 0,11±0,01 e utilizando a matriz H( matriz de parentesco que combina a informação de pedigree e dos SNPs) de 0,14±0,01. Foram encontrados 147 genes candidatos para a característica habilidade de permanência em regiões dos cromossomos 1, 2, 5, 6, 9, 20 e no cromossomo sexual X. Novas regiões candidatas para a característica habilida... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Stayability, which can be defined as the probability of a cow calving to a certain age since it has this opportunity, is a reproduction trait of great importance in beef cattle and is directly related to the productivity of the herd. The objective of this study was to estimate variance components through single-step G-BLUP methodology, and use the solutions of the SNPs effects to identify possible regions of the genome that are associated with the phenotypic expression of stayability in Nellore cows. The variance components were estimated by Bayesian inference using a threshold model in which were considered the fixed effects of precocity and contemporary groups, and the random effects of residue and animal. The effects of SNP were estimated by ssGBLUP methodology being used for the analysis 2838 animals genotyped with the Illumina panel of high density ( HD Assay Bovine Illumina, San Diego, CA, USA ). A Manhattan plot containing the variance explained by the windows formed by 200 SNPs consecutive was used to identify regions of greatest effect on the expression of stayability trait. The heritability found using the A matrix was 0.11 ± 0.01 and using the H matrix was 0.14 ± 0.01. 147 potential genes for stayability were found in regions of chromosomes 1,2,5,6,9,20 and sexual chromosome X. New candidate regions for stayability were detected and most of them are related to reproductive, immune and nervous system.
Mestre

Le graphe de taches (gdt) est un modele tres utilise pour la prediction de performance et l'optimisation d'applications paralleles. Il presente cependant deux desavantages. La taille d'un gdt depend de la valeur des parametres de l'application qu'il modelise. Un algorithme d'ordonnancement statique prend en entree un gdt et affecte, a chaque tache, un processeur et une date de debut d'execution. La duree du calcul de l'ordonnancement ainsi que le cout memoire dependent de la taille du graphe et donc de la valeur des parametres de l'application. Une telle approche n'est pas extensible car pour les grandes valeurs des parametres le graphe de taches correspondant peut ne pas tenir en memoire. Cette methode n'est pas non plus adaptative car un changement de machine cible ou des parametres du programme impose de recalculer l'ordonnancement. Pour apporter une reponse a ces deux problemes nous avons etudie un modele intermediaire : le graphe de taches parametre (gtp). Un gtp est une representation compacte et symbolique des graphes de taches issus de certaines applications de calcul scientifique. Il utilise les parametres du programme qui doivent etre instancies pour construire le gdt. Nos travaux se decomposent en trois volets. (1) nous avons concu un algorithme d'ordonnancement du gtp. Le cout memoire de l'ordonnancement se trouve alors grandement reduit. Cet algorithme est integre dans un schema dynamique pour permettre la construction de programmes generiques. (2) nous presentons une heuristique d'allocation symbolique du gtp appelee slc. Nous garantissons que cette allocation forme des grappes lineaires. Le temps et le cout memoire de l'allocation sont alors independants de la valeur des parametres. (3) nous avons realise un prototype de generateur de code qui produit un programme multithreade se conformant a l'allocation trouvee par slc. Nous obtenons ainsi un code parallele portable et generique qui fonctionne pour toutes les valeurs des parametres du programme.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O conhecimento da estrutura de uma população é importante quando se deseja manter a variabilidade genética em programas de melhoramento genético. As estimativas dos parâmetros genéticos permitem identificar as características de interesse econômico que podem responder a seleção direta ou indireta. Neste trabalho, objetivou-se avaliar a estrutura genética populacional e estimar os parâmetros genéticos para as características peso corporal da fêmea na entrada (PEP) e na saída (PSP) da primeira estação de monta, idade ao primeiro parto (IPP), peso corporal da vaca ao primeiro parto (PPP), peso corporal da vaca ao primeiro desmame (PPD) e perímetro escrotal aos 378 dias (PE378) em bovinos da raça Caracu, para avaliar critérios de seleção e os procedimentos de acasalamento para manter a variabilidade genética da população. A estrutura genética da população foi avaliada pelo tamanho efetivo (Ne), número efetivo de fundadores (fe), número efetivo de ancestrais (fa), intervalos de geração, coeficiente de endogamia (F), coeficiente de parentesco médio (AR) e integridade do pedigree. Os parâmetros genéticos foram estimados pelo método de máxima verossimilhança restrita (REML) por meio de modelo animal multi-característica. Os resultados obtidos para Ne na geração máxima, completa e equivalente, foram 180,90; 57,39; e 92,38, respectivamente. O valor para fe foi de 199 e para fa de 27. O coeficiente de endogamia médio e o parentesco médio foram 2,14% e 5,72%, respectivamente. Na avaliação da integridade do pedigree foram identificados 94,83% das mães e 93,82% dos pais com registros de origem. As estimativas de herdabilidade para as características de peso corporal variaram de 0,37 ± 0,09 (PPP) a 0,46 ± 0,08 (PPD). Para as características reprodutivas, as estimativas de herdabilidade foram 0,31 ± 0,10 para PE378 e 0,10 ± 0,06 para IPP. As correlações genéticas variaram de -0,37 ± 0,30 (PE378 e IPP) a 0,94 ± 0,06 (PSP e PPP). As correlações genéticas entre os pesos corporais medidos durante o primeiro ciclo reprodutivo e IPP indicaram que a seleção visando controlar o peso corporal nesse período não irá afetar a idade ao primeiro parto. A correlação genética favorável obtida entre PE378 e IPP (-0,37±0,30) indicou que a seleção para PE378 nos machos poderá favorecer a redução de idade ao primeiro parto das fêmeas. A partir dos parâmetros populacionais, concluiu-se que a variabilidade genética da população tem sido mantida, assim como os níveis de endogâmia, em decorrência do controle dos acasalamentos no decorrer das gerações.
The knowledge of the structure of the population is important to desired to maintain genetic variability in breeding programs. The genetic parameters estimates allow identifying economic interest traits that can respond to direct or indirect selection. The goal of this study was to evaluate the population genetic structure and to estimate the genetic parameters for the body weight of the cow at the beginning (WBF) and at the end (WEF) of the first breeding season, age at first calving (AFC), body weight of cow at first calving (WFC), body weight of cow at first weaning (WFW) and scrotal circumference measured at 378 days (SC378) in Caracu beef cattle, to assess the selection criteria and to indicate mating procedures to maintain the genetic diversity of the population. The genetic structure of the population was verified of the effective population size (Ne), the effective number of the founders (fe), the effective number of the ancestors (fa), the generational intervals, the inbreeding coefficient (F), the average relatedness (AR) and of the pedigree integrity. The restricted maximum likelihood method (REML) was used to estimate the genetic parameters under multitrait animal model. The maximum, complete and equivalent generation for Ne was 180.90; 57.39 and 92.38, respectively. For the fe were 199 and for fa 27. The average of the inbreeding coefficient and the AR were 2.14% and 5.72%, respectively. The integrity of the pedigree identified was 94.83% of the dam and 93.82% of the sire with known initial records Estimates of heritability for body weight traits ranged from 0.37 ± 0.09 (WFC) to 0.46 ± 0.08 (WFW). For the reproductive traits, the heritability estimates were 0.31 ± 0.10 for SC378 and 0.10 ± 0.06 for AFC. Genetic correlations ranged from -0.37 ± 0.30 (SC378 and AFC) to 0.94 ± 0.06 (WEF and WFC). Genetic correlations between body weights measured during the first reproductive cycle and the AFC indicated that selection to control body weight in this period will not affect age at first calving. The favorable genetic correlation obtained between SC378 and AFC (-0.37 ± 0.30) indicated that selection for SC378 of males may reduce the age at first calving of females. The population parameters showed that the genetic variability of the population has been maintained, as well as the levels of the inbreeding due to the control of mating during the generations.

El presente proyecto de investigación a nivel laboratorio tiene por objetivo caracterizar y evaluar los parámetros significativos de operación en los procesos de Lixiviación (LIX), extracción por solvente (SX) y la electroobtención (EW) a fin de obtener cobre fino. El mineral de cabeza utilizado en las pruebas, es un sulfuro de cobre (calcopirita asociado con escalerita y pirita), para poder lixiviarlos se hizo una tostación oxidante a 650 °C. Luego la calcina producida con un Ley de cobre de 4.48%, fue sometida a una lixiviación ácida (10 g/l H2SO4). Se obtuvo un PLS de una concentración de 8.1 g/l a partir de la lixiviación de la calcina de cobre. En las pruebas de extracción por solvente (SX) se empleó el LIX 612N-LV, de elevada selectividad del Cu2+ obteniéndose en la etapa de reextracción una solución acuosa de más de 27 gr/l Cu y otra de más de 46 g/l Cu. Estas soluciones concentradas fueron utilizadas como electrolito en la electroobtención de cobre (EW), los electrodos empleados son de Pb-Sn (ánodo) y Acero AISI 316-L (cátodo). La calidad del cobre electro obtenido fue de 99.969 %, bajo condiciones de operación similares utilizadas a nivel industrial. Sin embargo los elementos críticos (S, Fe, Pb) que determinan la calidad del cátodo de cobre de GRADO 1 COMEX sobrepasaron los límites aceptados. Debido en gran medida a las limitaciones del laboratorio, los arrastres físicos incurridos en las etapas de extracción por solventes (SX) y electro-obtención (EW). Sin embargo la calidad del cobre producido es valida para otras aplicaciones que no sean conductores eléctricos, como piezas de aleaciones no ferrosas
Tesis

A aplicação de micronutrientes nas sementes pode constituir alternativa interessante para a disponibilização destes elementos às plantas, reduzindo perdas e disponibilizando-os no início do desenvolvimento das mesmas, favorecendo sua utilização. O nutripriming da semente é uma técnica em que há hidratação das sementes com solução aquosa de nutrientes, associando os benefícios do priming com a disponibilização de elementos essenciais à nutrição vegetal. Assim, foi avaliada a adequação do priming para as sementes de trigo, do nutripriming com a aplicação do cobre e do manganês e a interferência desses procedimentos na qualidade da semente e no desenvolvimento da plântula; foram utilizados os cultivares Quartzo e Supera, avaliados em cinco épocas: inicial e aos 45, 90, 135 e 180 dias. Para a avaliação das sementes foram determinados o teor de água, a germinação (total e primeira contagem), a emergência da plântula (total e índice de velocidade), os comprimentos da plântula (manualmente e com o software SVIS®), a condutividade elétrica e os índices de vigor e uniformidade de plântulas O experimento foi conduzido em esquema fatorial 7 x 2 (controle e doses de micronutrientes x sementes sem priming e com nutripriming), em delineamento experimental inteiramente casualizado. Independentemente do cultivar, o nutripriming em sementes de trigo, utilizando doses superiores a 100 mg de Cu/kg de semente, afeta negativamente o desenvolvimento da plântula reduzindo o crescimento das raízes. A aplicação na semente de trigo, doses 10 e 33 mg de Cu/kg de semente, sem priming ou utilizando nutripriming, não causa redução da qualidade da semente e não compromete o desenvolvimento da plântula. A utilização do manganês, independentemente do cultivar e da forma de aplicação, não interfere negativamente na qualidade da semente e no desenvolvimento da plântula.
Micronutrient application through seeds may consist in an interesting alternative to provide these elements to plants, reducing losses and making them available at their initial growth stages, which may favor their utilization. Nutripriming is a technique that involves seed hydration in aqueous nutrient solution, which combines the priming benefits with the supply of essential elements for plant nutrition. Thus, this research evaluated the adequacy of priming for wheat seeds, the application of copper and manganese through nutripriming and the interference of these procedures on seed quality and seedling development. Wheat cultivars Quartzo and Supera were used; the evaluations were performed in five periods: initial (day 1), 45, 90, 135 and 180 days. Seeds were evaluated by water content, germination (total and first count), seedling emergence (total and speed index), seedlings length (manually and with SVIS® software), electrical conductivity and vigor and uniformity indices seedlings. The experiment was conducted in a completely randomized factorial design 7 x 2 (control and doses of micronutrients x non-primed and primed seeds). Regardless the cultivar, nutripriming of wheat seeds, at doses higher than 100 mg Cu / kg seed, negatively affects seedling development, reducing root length. The application of doses 10 and 33 mg Cu / kg seed, via seed dressing or nutripriming, does not affect seed quality and seedling development. The use of manganese, regardless the cultivar and application type, does not interfere on seed quality and seedling development.

Spinal cord injury (SCI) is a medical condition that occurs as a result of trauma, sickness or brain injury and as a result the connection between the brain and some part of the body is lost. This will result in tremendous changes in the daily life of the individual affected. Secondary complications arising from SCI are of very importance as well since some of them if left unattended, will result in life treating conditions. Functional electrical stimulation (FES) is one of the methods developed by researchers in order to get paralysed limbs functional with the help of electrical stimulation once again but the issue of muscle fatigue is limiting the efficiency of this method. In this thesis the primary and secondary matters arising from SCI are discussed and a CAD-based VN4D humanoid model integrated with Matlab/ Simulink, for use as a platform for analysis, design and evaluation of the developed strategies and approaches in this research is developed. Muscle models using different methodologies are developed in order to represent the reaction of the paralysed muscle to electrical stimulation and their output torque once moved. It was decided that the best model to represent the muscle is the proposed ANFIS model which was then integrated into the VN4D model. One of the main limitations of FES which is rapid muscle fatigue is studied in depth and the stimulation parameters which are having the greatest impact on the muscle fatigue are identified. It was determined that frequency modulation results in faster muscle fatigue therefore the controlled parameter is set to be pulse width after an experiment on 15 SCI individuals. Different control methodologies, including PID, fuzzy, adaptive neuro-fuzzy and iterative learning control (ILC) to move the simulated paralyzed model previously build using VN4D are explained and has been suggested that fuzzy and PID resulted in fatigue happening later once compared with adaptive and iterative learning control. This is made possible by the study of the trend of changes in pulse width and the amount of energy induced to the muscles. While all four control methods are showing great results once compared to a reference trajectory, adaptive and ILC controllers have induced greater amount of energy to the muscles resulting in faster fatigue. Two practical FES exercise activities including FES leg extension exercise and FES rowing are designed and controlled in a feedback control setting. It is realised that by employing mechanical facilitators in an FES activity a smoother performance is derived and less fatigue is induced in the muscles resulting in the individual being able to exercise for a longer period of time without damaging any tissue or bone. In summary, this work resulted in development of a new generalised accurate muscle model which was then used to display that how the issue of premature fatigue is affecting the performance of an FES exercise machine and how the control parameters and the choice of control strategy will result in different amount of energy induced in the muscles which in return results in fatigue showing in the earlier cycles of the movement. Further experiments are carried out on a group of spinal cord injured individuals and two FES exercise facilities, FES leg extension exercise machine and FES rowing machine, are further developed.

THE THESIS FOCUSES ON A CONSTRUCTION DESIGN OF A NEW DRILLING HEAD DESIGNED TO REPLACE THE ORIGINAL ONE IN A MULTIDRILL HYNDAGA DRILLING RING. THE SUBSTITUTION IS SUPPOSED TO PROVIDE A SOLUTION TO THE SHORTCOMINGS OF THE CURRENTLY USED DRILLING HEAD. THE THESIS ANALYSES PARAMETERS OBTAINED FROM THE MANUFACTURER, NEW PRODUCTION REQUIREMENTS AND PROPOSES TWO TYPES OF MOTORS INNOVATIVE METHODS HAD BEEN IMPLEMENTED IN CALCULATIONS OF CONCEPTUAL PARAMETERS OF THE NECESSARY COMPONENTS. THE OUTCOME IS A NEW F-TYPE DRILLING HEAD.

This research focuses on modelling reflectors in typical material testing reactors (MTRs). Reflectors present some challenges to the usual approach to full-core calculational models. Diffusion theory is standardly used in full-core calculations and is known to be inaccurate in regions where the flux is anisotropic, for example within the reflectors. Thus, special consideration should be given to reflector models. In this research, normalised generalised equivalence theory is used to homogenise cross-sections and calculate equivalent nodal parameters and albedo boundary conditions for the reflector surrounding a typical MTR reactor. Various studies have shown that equivalence theory can be used to accurately generate equivalent nodal parameters for the core and reflector regions of large reactors, such as pressurised and boiling water reactors, in one dimension and for two neutron energy groups. This has not been tested for smaller reactors where leakage, environment sensitivity and multi-group spectrum dependency are much larger. The SAFARI-1 MTR reactor is modelled in this work. A thirty day operational cycle is simulated for this reactor, using the nodal diffusion code MGRAC. NGET reflector equivalent nodal parameters are calculated using the codes NEWT and EQUIVA. The impact of different reflector models are evaluated, based on their effect on the core power, flux distribution, reactivity and neutron leakage over the duration of the operational cycle. It is found that homogenisation introduces some environment dependencies in the reflector parameters, particularly in the corners of the reactor core. In full-core calculations, the reflector parameters show some sensitivity to the in-core reflector structures, but not the fuel composition. A practical reflector model for SAFARI-1 is proposed, which proves that NGET equivalence theory can be used for multi-group reflector modelling in a small MTR reactor. This approach to reflector modelling simplifies the core model, increases the accuracy of a diffusion calculation, and increases the efficiency (shorter calculational time and better convergence behaviour) of computer simulations.
Thesis (MSc (Engineering Sciences in Nuclear Engineering))--North-West University, Potchefstroom Campus, 2013.

An empirically-based classification of lower Paleozoic carbonate-bearing rocks was created for field-based geotechnical applications. Geotechnical parameters were subsequently correlated to that classification. Seven hundred seventy-seven samples were used as the basis for the classification. Thirteen categories based on visual and tactile properties and a hydrochloric acid test were created. Samples were from central, north-central, and south-central Kentucky and represented the majority of Ordovician exposures in the state, and some Mississippian exposures. Few Silurian and Devonian units were included in the sample set. Geotechnical parameters, including density as well as elastic constants (shear and compression wave velocities, Poisson’s ratio, Young’s modulus, and shear modulus), were calculated for 113 representative samples from the classification. Compression strength testing was completed on 29 samples and the slake durability index was calculated for 18 samples. Testing values were correlated to the classification system in an attempt to use the classification as a predictive and comparative tool for geotechnical applications. Despite samples being heterogeneous and isotropic, each of the 13 categories behaved differently and predictably, with the sharpest contrast in siliciclastic and carbonate rocks.

Orientador: Denis Jose Schiozer
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: O controle da produção de água é uma tarefa difícil e muito estudada por profissionais da área de engenharia de petróleo. O controle pode ser feito de várias maneiras. Uma delas é a modificação da relação de mobilidade entre os fluidos através da utilização de polímeros e agentes tensoativos. Uma outra maneira é a utilização de barreiras artificiais para modificar a distribuição de potencial de pressão no reservatório. Existe ainda, a utilização do controle de parâmetros de produção para evitar o fenômeno de cone de água. É neste tipo de controle que este trabalho se enquadra. Este trabalho tem como objetivo principal desenvolver uma metodologia de otimização de parâmetros de produção para controlar o crescimento do cone de água. Esta otimização consiste em se determinar a localização e comprimento da completação e a vazão de produção através da maximização de uma função-objetivo que utiliza o valor presente da receita da produção de óleo, subtraindo as despesas decorrentes da produção de água. A metodologia, que consistiu em um processo iterativo com otimizações separadas de vazão de produção e completação, foi testada para três exemplos encontrados na literatura como problemas em que ocorre o cone de água. Finalmente, foi testada a eficácia da completação dupla no controle de cone em um dos exemplos, avaliando-se seus efeitos na produção acumulada de óleo e água
Abstract: The water production control is a difficult task and it can be controlled by many techniques. One of these techniques is to change the water-oil mobility ratio by using polymers and surface-active agents. Another technique is the use of barriers to obstruct the water fluxoThe technique investigated in this work is the control of production rate and completion interval to avoid water conning effects. The objective of this work is to develop an optimization routine to find the best values of production rate and completion interval in order to maximize an objective function which represents the net present value of oil production. The methodology used for this optimization is an iterative procedure with separated optimization of production rate and completion interval, resulting in a computer program that uses a reservoir simulator to optimize the objective function. by simulations This methodology was tested in three examples found in literature as problems of water coning, showing good results. The efficiency of dual completion was tested in one of the examples
Mestrado
Mestre em Engenharia de Petróleo

The Cone Penetration Test (CPT) is widely used for determining in-situ properties of soil because of its continuous data measurement and repeatability at relatively low cost. The test is even more attractive in cohesionless soils such as sands, silts and most tailings due to difficulties associated with retrieving undisturbed samples in such soils. Behaviour of soils is highly dependent on both density and stress level. The state parameter is widely accepted to represent the soil behaviour encompassing both density and stress effects. Hence, determining the in-situ state parameter from CPT is of great practical interest. The CPT was analysed using a large strain spherical cavity expansion finite element code using a critical state soil model (NorSand) capable of accounting for both elasticity and plastic compressibility. The constitutive model was calibrated through triaxial tests on reconstituted samples. The state parameter was then interpreted from CPT tip resistance, and the results were verified against an extensive database of calibration chamber tests. The efficiency of the method was further investigated by analysing two well documented case histories confirming that consistent results could be obtained from different in-situ testing methods using the proposed framework. Consequently, cumbersome and expensive testing methods can be substituted by a combination of triaxial testing and finite element analysis producing soil specific correlations. One of the difficulties in analysing the cone penetration problem is the less researched effect of high stresses developing around the cone on the behaviour of the soil. A hypothesis was put forward on the particle breakage process at the particle level and its implications for the behaviour of sands at higher stress levels were discussed. A series of triaxial tests were performed, focusing on the effects of particle breakage on the location of the critical state line. The hypothesis was used to explain the observed behaviour. Particle breakage was shown to cause additional compression and a parallel downward shift in the critical state line. The magnitude of the shift was linked to the amount of breakage and it was argued that significant breakage starts after the capacity for compression due to sliding and rolling is exhausted.

Nell’ultimo decennio si è posta sempre maggiore attenzione ai diversi aspetti condizionanti il fabbisogno energetico degli edifici, al fine di ridurre sempre di più i dispendi di energia, soprattutto nei periodi estivi. Questa ricerca, in particolare, si è focalizzata sugli studi dei materiali ad alto indice di riflettanza solare (SRI, Solar Refletance Index). Si sono svolte ricerche bibliografiche sui materiali già studiati e sulle tecniche di applicazione e si è dedicata particolare attenzione alla loro classificazione e comparazione. Si è voluto andare oltre i così detti “cool roofs”, ovvero i tetti rivestiti con materiali cool (ad alto SRI), per studiare il comportamento di un’eventuale applicazione di questi materiali anche per altri elementi opachi dell’involucro e, più nello specifico, quelli che possono essere rivestiti con piastrelle ceramiche. Per indagare in questo senso, si è studiata l’applicazione dei pigmenti cool presenti sul mercato sia per la colorazione in massa di piastrelle sia negli smalti di piastrelle in grès porcellanato. Si è inoltre eseguita un’analisi della durabilità delle proprietà radiative delle piastrelle ceramiche con lo scopo di dimostrarne i vantaggi rispetto ad altri materiali cool presenti sul mercato.

The energy crisis together with greater environmental awareness, has increased interest in the construction of low energy buildings. Fabric thermal storage systems provide a promising approach for reducing building energy use and cost, and consequently, the emission of environmental pollutants. Hollow core ventilated slab systems are a form of fabric thermal storage system that, through the coupling of the ventilation air with the mass of the slab, are effective in utilizing the building fabric as a thermal store. However, the benefit of such systems can only be realized through the effective control of the thermal storage. This thesis investigates an optimum control strategy for the hollow core ventilated slab systems, that reduces the energy cost of the system without prejudicing the building occupants thermal comfort. The controller uses the predicted ambient temperature and solar radiation, together with a model of the building, to predict the energy costs of the system and the thermal comfort conditions in the occupied space. The optimum control strategy is identified by exercising the model with a numerical optimization method, such that the energy costs are minimized without violating the building occupant's thermal comfort. The thesis describes the use of an Auto Regressive Moving Average model to predict the ambient conditions for the next 24 hours. A building dynamic lumped parameter thermal network model, is also described, together with its validation. The implementation of a Genetic Algorithm search method for optimizing the control strategy is described, and its performance in finding an optimum solution analysed. The characteristics of the optimum schedule of control setpoints are investigated for each season, from which a simplified time-stage control strategy is derived. The effects of weather prediction errors on the optimum control strategy are investigated and the performance of the optimum controller is analysed and compared to a conventional rule-based control strategy. The on-line implementation of the optimal predictive controller would require the accurate estimation of parameters for modelling the building, which could form part of future work.

Orientador: Amauri Garcia
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: A macroestrutura de solidificação de peças fundidas ou lingotes pode apresentar-se na forma de grãos completamente colunares ou totalmente equiaxiais, dependendo da composição química da liga e das condições de solidificação. Uma forma estrutural mais complexa, típica de solidificação em moldes de maiores difusividade de calor como moldes metálicos e refrigerados, é composta pelas duas zonas estruturais. Essa forma mista de solidificação ocorre quando os grãos equiaxiais encontram condições de nuclear e crescer no líquido, à frente da fronteira colunar de crescimento, provocando a transição colunar/equiaxial. A previsão da transição colunar/equiaxial é de grande interesse na programação das propriedades mecânicas de produtos solidificados. Peças com estruturas completamente equiaxiais são mais apropriadas para inúmeras aplicações, uma vez que apresentam isotropia de propriedades fisicas e mecânicas. Por outro lado, a anisotropia das propriedades das estruturas colunares permite aplicações tecnológicas importantes, como por exemplo, no crescimento de lâminas de turbinas de motores a jato. Uma série de experiências é realizada para analisar a transição colunar/equiaxial durante a solidificação direcional de ligas Al-Cu e Sn-Pb em condições transitórias de fluxo de calor para diferentes superaquecimentos e coeficientes variáveis de transferência de calor na interface meta/molde. Uma abordagem teórico-experimental é desenvolvida para a determinação quantitativa de parâmetros térmicos de solidificação: coeficientes variáveis de transferência de calor meta/molde, velocidades de crescimento da ponta da dendrita, gradientes térmicos e taxas de resfriamento. Os resultados de simulações numéricas, confrontados com resultados experimentais obtidos, mostram que critérios para a transição colunar/equiaxial (TCE), baseados ou na velocidade de crescimento ou no gradiente de temperatura na ponta da dendrita isoladamente, não são capazes de determinar a transição estrutural. A análise indica que um critério mais realista deveria envolver ambos os parâmetros térmicos através da taxa de resfriamento na ponta da dendrita. O crescimento colunar deve prevalecer ao longo do fundido para uma taxa de resfriamento maior do que um determinado valor crítico, e que depende do sistema binário. Estas taxas críticas atingem valores de cerca de 0,2 K/s, para ligas Al-Cu e 0,014 K/s, para ligas Sn-Pb, no presente trabalho. As influências de parâmetros de solidificação, como superaquecimento no metal líquido, concentração de soluto e coeficientes de transferência de calor metal/molde na posição da transição colunar/equiaxial são também investigadas
Abstract: The macroestructure of cast ingots can be characterized by either a completely columnar structure or an equiaxed structure, depending on alloy composition and solidification conditions. A more complex structure, typical of solidification in molds of high heat diffusivity, like chill and cooled molds, both structural forms. This mixed mode of solidification occurs when equiaxed grains can nucleate and grow ahead of the columnar front provoking the columnar to equiaxed transition. The prediction of such transition is of great interest for the evaluation and design of the mechanical properties of casting products. On the other hand, the anisotropy of mechanical properties, typical of columnar structures, enables technological applications of great importance like growing of blades for jet engmes. Experiments are conducted to analyze the columnar to equiaxed transition (CET) during the upward unsteady state directional solidification of Al-Cu and Sn-Pb alloys, under different conditions of superheat and heat transfer efficiencies at the metal/mold interface. A combined theoretical and experimental approach is developed to quantitatively determine the solidification thermal parameters: transient heat transfer coefficients, tip growth rates, thermal gradients and cooling rates. A numerical procedure combined with experimental results does not give support to CET criteria based either on tip growth rate or on temperature gradients at the dendrite tips. Rather, the analysis has indicated that a more convenient criterion should encompass both thermal parameters through the tip cooling rate. The columnar growth is expected to prevail throughout the casting for a tip cooling rate higher than a critical value, which depends only on the alloy system and observed to be about 0.2 K/s, for Al-Cu alloys and 0.014 K/s, for Sn-Pb alloys in this investigation. The effects of solidification parameters like melt superheat, solute concentration and metal/mold heat transfer coefficient on the CET position are also investigated.
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica

A finalidade deste estudo foi avaliar o uso de rações contendo grão de milho flint processado através da moagem ou floculação combinados com dietas contendo 4; 7; 10 ou 13% de FDN do bagaço de cana in natura (BIN) (% da MS) e suas interações. Foram conduzidos 2 experimentos. No experimento 1: Os 240 tourinhos Nelore (PC=350±37,36 kg) foram alocados aleatoriamente em 32 baias em um arranjo fatorial 2 × 4. Os animais foram blocados com base no PC inicial. Os dados foram analisados pelo PROC MIXED do SAS. Não houve interação entre as concentrações de FDN de volumoso (FDNv) e métodos de processamento sobre o desempenho, características de carcaça, medidas morfométricas de papilas, energia das dietas, amido e comportamento ingestivo. A moagem do milho proporcionou maior ingestão de matéria seca (IMS), amido fecal, número de papilas, área de superfície absortiva do rúmen e representatividade das papilas na superfície absortiva e menor ingestão de energia, peso final, ganho de peso diário, pior eficiência alimentar, menor peso de carcaça, tempo de ruminação, energia nas dietas, digestibilidade do amido no trato total, energia do milho que a floculação. O aumento na concentração de FDNv nas dietas causaram efeito quadrático para IMS, redução linear no rendimento de carcaça, na energia das dietas e aumento linear no tempo de ruminação e mastigação. Houve interação entre as concentrações de FDNv e métodos de processamento para a medida de largura de papilas. Os resultados indicam que a floculação foi superior à moagem do milho para otimizar o desempenho dos tourinhos Nelore. No experimento 2: Foram utilizados 16 touros da raça Nelore (PC 443,52±24,80kg) canulados no rúmen, alocados aleatoriamente em 16 baias por dois períodos, em arranjo fatorial 2 x 4. Os dados foram analisados pelo PROC MIXED do SAS. Não houve interações entre processamento e concentrações dietéticas de FDNv. A floculação aumentou na digestibilidade da MS, dos carboidratos totais (CHOT), dos carboidratos não fibrosos (CNF), do amido, no %NDT nas dietas, na concentração de propionato no rúmen e na eficiência microbiana e gerou maior volume final da degradação de CNF, taxa de degradação de CNF e redução no N-NH3 no rúmen, na ingestão de N, N ureico no plasma, N urina, na excreção de N total e no lag time. O aumento do teor de volumoso nas dietas causou resposta quadrática para IMS e na ingestão e absorção de N e redução linear na digestibilidade da MS, dos CHOT, na proporção de propionato e concentração de AGV total e aumentos lineares no tempo de ruminação e mastigação. Em conclusão a floculação foi superior à moagem em melhorar a digestibilidade da MS, em aumentar a energia do milho e das dietas e em melhorar o metabolismo de N. Aumentos nos teores de FDNv estimulam a ruminação, mas diminui a eficiência da produção de energia no rúmen.
The purpose of this study was to evaluate the use of feed containing flint corn grain processed by ground or steam-flaked combined with diets containing 4; 7; 10 or 13% roughage NDF (DM basis) using sugarcane bagasse as source of fiber and their interactions. Two experiments were conducted. In experiment 1: 240 Nellore bulls (BW=350±37,36 kg) were randomly divided into 32 pens in a factorial 2 × 4 arrangement of. The animals were blocked based on their initial BW. The data were analyzed using PROC MIXED of SAS. There was no interaction between the concentrations of sugarcane bagasse NDF and processing methods on performance, carcass characteristics, morphometric measures of papillae, energy diets, starch and feeding behavior. Ground corn provided higher dry matter intake (DMI), fecal starch, number of papillae, rumen absorptive surface area of the papillae and representativeness of the absorptive surface and lower energy intake, body weight, daily weight gain, worse feed efficiency, lower carcass weight, rumination time, energy in the diet, total-tract starch digestibility energy corn than steam-flaked. The increase in the concentration of NDF of BIN in the diets caused a quadratic effect for IMS, linear reduction in carcass yield, energy diets and linear increase in rumination and chewing. There was interaction between NDF concentrations and processing methods for papillae width measurements. The results indicate that the steam-flaked was higher than ground corn to optimize the performance of Nellore bulls. In experiment 2: sixteen Nellore bulls (BW=443,52±24,80 kg) fitted with rumen cannula, randomly allocated to 16 pens for two periods in a 2 x 4 factorial arrangement. The data were analyzed using PROC MIXED of SAS. There were no interactions between corn processing and dietary concentrations of sugarcane bagasse NDF. Steam-flaking increased in DM digestibility, total carbohydrates (TCHO), non-fiber carbohydrates (NFC), of starch, dietary TDN concentration, of rumen propionate concentration and microbial efficiency and provided higher final volume of degradation CNF, CNF degradation rate and decreased rumen N-NH3 concentration, N intake, N urea in plasma (PUN), N urine, total N excretion and lag time. Increasing dietary sugarcane bagasse NDF caused a quadratic response for DMI, N intake and N absorption and linear decrease in total tract apparent digestibility of DM and of TCHO, concentration of propionate and total VFA and linear increases in rumination and chewing. In conclusion, steam-flaking was greater than the ground corn to improve the digestibility of DM, to increase energy value of flint corn and feeding and improve N metabolism. Increasing dietary sugarcane bagasse NDF stimulate rumination, but decreases the efficiency of production energy in the rumen.

Intensive tillage and monoculture cropping practices reduce soil C accumulation hence increasing soil vulnerability to chemical, physical and biological degradation. This study focussed on enhancing biomass production of wheat and oat winter cover crops as a means of increasing C sequestration in the low organic C soils of the central part of Eastern Cape Province. The specific objectives were (i) to evaluate the short-term effects of no till and cereal-fallow based crop rotations on; soil organic matter related parameters, pH and electrical conductivity, (ii) soil bulk density, water retention and aggregate stability, (iii) soil microbial biomass C and N, mineralizable N, soil respiration, and dehydrogenase enzyme activity, (iv) grain yield, soil nutrient concentration (N, P and K) and their uptake by maize, and (v) to identify soil parameters with high sensitivity to tillage under maize-fallow-maize, maize-wheat-maize and maize-oat-maize rotational cover cropping practices. The experiment was laid out as a split-plot arrangement in a randomized complete block design with 4 replicates. Tillage treatments (CT and NT) were applied on the main plots which measured 8 × 18 m while crop rotation treatments were applied in the subplots which measured 8 × 6 m. The rotation treatments were maize-fallow-maize (MFM), maize-wheat-maize (MWM) and maize-oat-maize (MOM). Weed control in NT plots involved preplant application of glyphosate to control mainly the grass weeds while post emergence weed management was done using Atrazine (485 atrazine and 15 g l-1 triazines). Initial weed control in CT plots was achieved through ploughing to a depth of 20 cm followed by disking while post emergence weed iii management was done by hand hoeing. Soil parameters measured were; (i) particulate organic matter (POM), soil organic carbon (SOC), total nitrogen (TN), pH and electrical conductivity (EC), (ii) soil bulk density (b), moisture at field capacity (FC), aggregate mean weight diameter (MWD) determined by fast wetting (FW), slow wetting (SW), mechanical breakdown by shaking (MB) and the stability index (SI), (iii) soil microbial biomass C (MBC) and N (MBN), mineralizable N (MN), soil respiration (SR), and dehydrogenase enzyme activity (DHEA). No-till increased POM and TN compared to CT in Lenye and Burnshill, respectively. The MWM and the MOM rotations increased TN relative to the MFM rotation in Lenye. The MWM and MOM rotations enhanced SOC relative to MFM in all sampled soil depths at Burnshill and similar observations were made under MOM rotation in the 5-20 cm depth in Lenye. The MWM and MOM rotations tended to depress soil pH relative to the MFM rotation in both sampled soil depths in Lenye while NT reduced soil pH relative to CT on the surface soil layer in Burnshill. Soil EC and pH varied with depth across tillage practices but both parameters remained within the ideal range for successful crop production over the study period. Soil stability index (SI) and aggregate MWD determined by FW, SW and MB were higher in Lenye compared to Burnshill. The MOM rotation enhanced the SI relative to MFM and MWM rotations at both sites. Scanning electron microscope (SEM) showed that more organic C was incorporated into the soil under NT and MOM rotation compared to CT and MFM rotation which had few organic coatings on the soil particles. Microbial properties varied with plant biomass input as influenced by tillage and type of rotational cover crop at both sites. Like in other past studies, NT showed higher levels of MBC, MBN, NM and SR at the soil surface layer compared to CT in Burnshill. No till increased MN iv relative to CT in both sampled soil depths in Lenye and resulted in higher DHEA compared to CT in Burnshill. The MOM rotation increased MBC, MBN, MN relative to MFM rotation especially within surface soil layer. Similar observations were made with respect to MN and SR in both sampled soil layers at Lenye. By contrast, the DHEA was higher under the MFM relative to the MWM and MOM rotations in Lenye but similar under the MFM and MOM rotations in Burnshill. Maize grain yield was not affected by both tillage and crop rotations but varied with cropping season. Comparable grain yields observed under the two tillage practices with similar fertilizer application rates indicated the advantage of NT over CT in saving on labour costs in maize production without compromising yields. High plant biomass retention under NT relative to CT contributed to high soil N and P levels under the former compared to the latter tillage practice especially on soil surface layer at both study sites. Principal component analysis (PCA) revealed that soil chemical and biological parameters closely linked to organic matter, namely SOC, MN, MBC and MBN showed the highest sensitivity to tillage and crop rotation treatments. Soil aggregate MWD determined by SW and b were the physical parameters which were highly altered by agronomic management practice. The MWM and MOM rotations were clustered together and clearly separated from the MFM rotation and this observed trend only applied to the 0-5 and 5-20 cm depths in Lenye site only. No till, MWM and MOM rotations enhanced POM, SOC and TN relative to CT and MFM rotation suggesting these practices have greater potential to improve soil chemical properties compared to intensive tillage and maize monoculture based production practices. Reduced soil b under MOM rotation and improved SI under NT compared to MFM and CT, respectively v indicate that these practices have the potential to improve degraded soils. Although not significantly different, NT values for MBC, MBN, MN, SR and DHEA were higher compared to CT indicating the potential of the practice to improve soil biotic activity relative to conventional tillage practices. No till enhanced surface soil nitrate N and extractable P compared to CT at both sites revealing the long-term potential of NT in improving the supply of these essential plant nutrients compared to CT. Principal component analysis showed that SOC, MN, K, P, MBC, MBN, soil aggregate MWD determined by SW and b were the most sensitive parameters to tillage and crop rotations. Therefore, these parameters could constitute the minimum data set for assessments of the impact of selected CA practices on soil quality attributes.

Flux distribution in transformer core has a significant effect on vibration-born-noise of the ferromagnetic core. The grade of electrical steel and the geometry of the core joints as well as the manufacturing and utilisation parameters affect the flux distribution in the core, mainly in the joints. Understanding the effect of materials and the manufacturing parameters on flux density distribution would enable transformer design engineers to improve the core performance. In this study, localised search coils were used to measure the flux density distribution in a linear joint assembled from different grades of electrical steel and the results were verified using COMSOL Multiphysics software with a 2D model. The flux density distribution was also measured in a mitred corner joint and the effect of the variability of the airgaps was investigated. A 3D laser scanning vibrometer was deployed to measure the vibration of the mitred joint and the results were compared with the flux density distribution. The front surface of a three phase three limb production transformer core was scanned using the 3D laser scanner and the emitted noise was measured in the same induction level to find a correlation between the noise and vibration. The flux in the limb is non-uniform due to the longitudinal airgaps in the joints and the length of this non-uniformity greatly depends on the airgap length and the permeability of electrical steel. The peak value of the interlaminar flux density was found to be higher in NO steel than GO and the flux density in the rolling direction in the NO assembly was more uniform than GO. The flux in the outer layers of the stacked transformer core was found to be higher than in the central layers and increasing the height of stack made the flux more uniform. The calculated Maxwell forces and mechanical deformation in the joint had a good correlation with flux distribution and the scanned vibration data. A reasonable correlation was found between the surface vibration acceleration and the emitted noise of the production transformer core with frequency domain analyses.

Le caratteristiche superficiali influenzano molte proprietà di un materiale. Nel caso dei materiali da pavimentazione le proprietà superficiali influiscono sulla scivolosità e sulla sicurezza delle persone. A fronte di un panorama internazionale caratterizzato da una varietà di metodi di valutazione della resistenza allo scivolamento, l’obiettivo del presente studio di tesi è quello di individuare un metodo univoco e oggettivo per la valutazione della scivolosità basato sullo studio della tessitura superficiale. Questa ricerca, effettuata presso il Centro Ceramico di Bologna, parte dall'indagine di campioni di piastrelle di ceramica tramite strumenti di profilometria ottica. Tramite l'analisi dei profili di rugosità e di ondulazione sono stati individuati quei parametri più significativi che meglio descrivono la struttura superficiale. Questi dati sono stati successivamente confrontati con i vari metodi di prova di resistenza allo scivolamento previsti da normativa al fine di ricercare eventuali correlazioni. I risultati ottenuti convalidano altre ricerche in merito alla resistenza allo scivolamento e mostrano come i parametri più idonei risultino essere "Rz" e "sPk". I risultati ottenuti sono particolarmente promettenti sia dal punto di vista scientifico che tecnico e aprono strade interessanti alla progettazione di superfici con resistenza allo scivolamento predeterminata.

Orientador: Geraldo Nonato Telles
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Nesta pesquisa determinou-se modelo matemático para distribuição racional das diversas "passadas" para corte de roscas em tomos à CNC. Através de ensaios tecnológicos avaliou-se o modelo e os diferentes métodos de corte de roscas (mergulho radial, de flanco e flanco alternado) de forma a possibilitar proposta para otimização dos parâmetros geométricas para essa operação. Essa otimização permite, com sua racionalização, além da redução de custos operacionais, melhor controle dos esforços de corte e conseqüente melhoria da qualidade
Abstract: A mathematical model for rational "infeed" distribution for threading in CNC lathes was determined, in this research. By means of technological experiments the model proposed and threading cutting methods (radial, flank and changing flank "infeed") were analyzed in such a way to obtain the otimization of geometrical parameters setting for threading. The otimization allowas, through rationalization not only the reduction cost , but also improved cutting force control in threading operations and consequently an increase in quality
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

The master's thesis deals and introduces a single-phase inductions machines, the principle of operation, types of design and operating conditions. This thesis includes analysis of individual losses in the machine and reduce the possibility of different ways. After a theoretical proposal for reducing losses are measured by mass-produced single-phase induction machine. Further machine modifications proposed for reducing losses in the stator windings and designed a prototype machine with the adjustment of the magnetic circuit to reduce iron losses made by ATAS elektromotory Nachod a.s. The results are supplemented by a simulation using software Maxwell RMxprt and finite element method (FEM). Finally, they are compared to each machines modifications mainly in terms of energy consumption.

The aim of this study was to determine the mean lethal concentration (96 h) for waterborne copper (LC50), as well as the effect of the exposure to copper on growth, metabolic parameters (glycogen, glucose, lactate, and protein) in some tissues, activity of acetylcholinesterase (AChE) (brain and muscle), amylase and maltase (intestine) in silver catfish (Rhamdia quelen). The LC50 for copper was 0.4 mg/L. On growth experiments fish were exposed to 10 and 20% LC50, i.e., 0.04 and 0.08 mg/L respectively. Exposure to copper did not change growth parameters (weight, length and biomass). In the liver, lactate levels increased in juveniles exposed to 0.04 mg/L and decreased in those maintained at 0.08 mg/L, while protein levels decreased in those exposed to both concentrations compared to unexposed specimens. Glycogen levels in the muscle were lower in fish exposed to both concentrations, glucose and lactate were higher in those exposed to 0.04 mg/L and decreased in juveniles maintained at 0.08 mg/L, while protein was higher in those exposed to 0.08 mg/L. Glucose and lactate plasma levels were higher in juveniles exposed to 0.04 mg/L, but protein levels were lower in those maintained at both copper concentrations. Amylase activity was lower in juveniles exposed to both concentrations, but maltase was higher in those exposed to 0.04 mg/L than control group. Brain AChE activity was lower in fish exposed to both concentrations while muscle AChE activity was not affected after 45 days of exposure. It can be concluded that copper can change several metabolic parameters and enzymes of toxicological and feeding interest even at sublethal concentrations.
O objetivo deste estudo foi verificar a concentração letal média em 96 h (CL50) para o cobre, bem como o efeito da exposição ao cobre sobre o crescimento, parâmetros metabólicos (glicogênio, glicose, lactato e proteína) em alguns tecidos (fígado, músculo e cérebro) e a atividade da acetilcolinesterase (AChE) (cérebro e músculo), amilase e maltase (intestino) em jundiás (Rhamdia quelen.). A CL50 para o cobre foi 0,4 mg/L. Nos experimentos de crescimento os peixes foram expostos durante 45 dias a 10 e 20% da CL50, ou seja, 0,04 e 0,08 mg/L respectivamente. A adição de cobre não alterou os parâmetros de crescimento avaliados (peso, comprimento e biomassa). No fígado, os níveis de lactato aumentaram nos exemplares expostos a 0,04 mg/L e diminuíram nos mantidos em 0,08 mg/L, enquanto que os níveis de proteína diminuíram em ambas as concentrações em relação ao grupo controle. No músculo houve redução na atividade do glicogênio nos exemplares mantidos nas duas concentrações testadas, a glicose e o lactato aumentaram nos expostos a 0,04 mg/L e diminuíram nos expostos a 0,08 mg/L, e a proteína aumentou nos mantidos em 0,08 mg/L. Os níveis de glicose e lactato no plasma foram maiores nos exemplares mantidos em 0,04 mg/L e diminuíram os níveis de proteína nos expostos a ambas as concentrações de cobre. A atividade da amilase foi menor nos juvenis expostos a ambas as concentrações, enquanto a da maltase foi maior em 0,04 mg/L quando comparada ao grupo controle. A atividade da AChE cerebral foi menor nos exemplares expostos a ambas concentrações, enquanto que a AChE muscular não sofreu alterações após os 45 dias de exposição. Conclui-se que o cobre mesmo em concentrações subletais pode alterar diversos parâmetros metabólicos e enzimas de interesse toxicológico e alimentar.

The determination, validation and understanding, and proper use of special core analysis relationships are paramount in the assessment of recovery efficiency of petroleum reservoirs. The most reliable information, resulting in representative relationships, such as for relative permeability and capillary pressure, may be obtained from laboratory experiments. However, being time-consuming and expensive, the number of core samples typically subjected to such investigations tends to be limited, often resulting in data deficiencies and hence improper understanding of the necessary relationships, which are essential for conducting detailed reservoir engineering and simulation studies, with the aim of maximising the extraction of petroleum. For the above reasons, over the past decades, the establishment of mathematical models to predict the required properties has received considerable attention from petroleum engineers, and is one of the active research areas today. In an attempt to predict valid relationships, difficulties are primarily related to complexity and variability of rocks, in terms of pore structure and mineralogy and associated fundamental properties: porosity, absolute permeability, and fluid saturation. Such variation is a function of the original deposition of grains and subsequent alteration or diagenesis of a geological formation, most notably rock. compaction upon burial, but also other significant alteration, for example the generation of different types of clays, filling part of the pore structure. In addition to pore structure variation, the second complication is associated with the surface chemistry between fluids and the varied rock grains, as well as the interaction between fluids themselves, for example oil and water contained in the pores. Thirdly, in conducting laboratory experiments, the precise experimental conditions may greatly influence results obtained: pressure, temperature and the types of fluids used and their properties, most notably fluid viscosity, flow velocity and interfacial tension. Investigations by co-researchers and others into single-phase flow and the identification of appropriate geological entities, or facies, representative of (homogeneous) flow behaviour, have led to the conclusion that the Carman-Kozeny model is ideally suited to bridge the gap between the differing views of geologists and engineers. As this model is able to elegantly unify the parameters for single phase flow for the majority of petroleum rocks, the formulation was subsequently extended to two phase flow situations by the principal supervisor. These concepts were then utilised in this research and further extended, and a number of new relationships were established, which may be used to validate experimental data and relationships or predict such relationships from more fundamental properties. In deriving the above formulations, an extensive database was utilised, semi-empirically fitting the data for establishing some of the relationships. In other cases the data was used to validate new models, comparing model-generated and experimental results. The database was created by utilising laboratory data generated by commercial laboratories and made available by several petroleum companies, covering onshore and offshore Australian hydrocarbon basins. Both, capillary pressure and relative permeability models were validated using this data, and the new models were demonstrated to have excellent performance in predicting two-phase flow relationships. In a further attempt to validate these models, comparison studies were also conducted with well-known models used by the oil and gas industry. The Brooks and Corey capillary pressure model was used for comparison with the newly established capillary pressure model, and the performance of the new relative permeability model was checked against that of the modified Brook and Corey model, also known as the power law model. Relative permeability and capillary pressure models depend on the primary parameters mentioned above but are actually formulated in terms of several secondary parameters, functions of primary parameters. As such irreducible water saturation is most significant. If this quantity has not been measured in the laboratory, it may be predicted. New models were established to predict irreducible water saturation, based on an artificial neural network approach. A semi-empirical model, based on trapping parameters, was also investigated, resulting in an alternate formulation for irreducible water saturation, and a universal analytical form that should be applicable to the range of geological formations. As mentioned above, relative permeability relationships are also controlled by wettability. For the purpose of predicting relative permeability, a new model to link the USBM wettability index to pore structure parameters was also established by this research. As with relative permeability, capillary pressure and irreducible water saturation models, the model was created and validated using the Australian database. However, the general form of the equation would lend itself for use with any data set. Finally, the ratio of effective (or relative) permeability endpoints may be taken as an indictor of wettability. Equations to predict effective permeability to oil at irreducible water saturation and effective permeability to water at residual oil saturation have been formulated. Both equations are extensions of the Carman-Kozeny formulation.
Thesis (Ph.D.) -- University of Adelaide, Australian School of Petroleum, 2006

碩士
國立臺灣科技大學
材料科學與工程系
104
In this study, interfaces between Ag and CeO2 of Ag@CeO2 core-shell nanoparticles (NPs) were investigated by using transmission electron microscopy (TEM) equipped with energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) with high energy resolution. Ag@CeO2 core-shell NPs were synthesized by two-steps chemical reduction method. Effects of process parameters on the feature of surface of Ag core as well as the subsequent deposition of CeO2 shell were studied at first. A native thin oxide layer on the surface of Ag core was observed. Structure of this thin oxide layer was closely related to the type of substrate, growth temperature and the size of Ag core. The existence of native thin oxide layer is essential to the subsequent deposition of CeO2 shell. In addition, according to EELS analysis, charge transfer between Ag core and CeO2 shell was seen, which results in the reduction of Ce4+. At last, it is found that the area affected by charge transfer was narrow and was not dependent on the thickness of CeO2 shell.

碩士
臺北市立教育大學
自然科學系碩士班
99
This study employs the western Philippine Sea MD06-3049 core (16.35 ° N, 124.39° E), collected by the 2006 Marco-Polo II cruise, to measure multi-magnetic parameters and to conduct grain size analysis for reconstruction of the paleoenvironment records. The water depth for the core is about 2498 meters and the total recovered length is 32.28 meters. We determine the Brunhes/Matuyama boundary, the Jaramillo subchron, the Olduvai subchron and the Reunion subchron from the characteristics declination and inclination curves in the nature remnant magnetization of the core. In addition, with supplement of the paleointensity low value for comparison, we can differentiate excursions as age control points to construct age model, suggesting that the age span of the core is about 2.4 Ma. The magnetic parameters analysis of the magnetic mineral composition in the core MD06-3049 indicates that the main magnetic mineral is the pseudosingle-domain titanomagnetite. The results of grain size analysis show that the mean grain size positively correlates with the magnetite grain size --- both are bigger during glacial and smaller during interglacial. By using the mean grain size of 10~63μm sediment as an indication of bottom flow speed, we also show that the bottom flow strengthen during glacial and decline during interglacial. The grain size of core MD06-3049 is affected by the changing velocity of the glacial-interglacial bottom flow. The characteristics of continuous records and stable sedimentary rates of marine cores are good for studying whether the paleointensity has orbital cycle or not. Using the anhysteresis remanent magnetization and paleointensity of the MD06-3049 core for spectrum analysis, we find that the anhysteresis remnant magnetization has a main cycle 100kyrs close to that of the Earth’s orbital eccentricity while the paleointensity has not. Although the ratio of nature remanent magnetization and anhysteresis remanent magnetization is used as relative variation of the paleointensity, the signal of anhysteresis remnant magnetization signal still controlled by the grain size of the magnetic mineral. It shows that the cyclical changes of paleointensity may result from changes of grain size, capturing the environmental messages.