Two-phase flow in porous media is an important subsurface process that has significant impacts on the global economy and environments. To study two-phase system in porous media, capillary pressure (Pc ), relative permeability (Kr), bulk electrical conductivity (σb) and bulk relative permittivity (εb) are often employed as characterization parameters. Interestingly, all of these parameters are functions of water saturation (S). However, the non-uniqueness in the Pc -S, Kr-S,σb-S and εb-S relationships pose considerable challenges in employing them for effective monitoring and control of the two-phase flow processes. In this work, laboratory scale experiments and numerical simulations were conducted to investigate the factors and conditions contributing to the non-uniqueness in the above relationships for silicone oil-water and supercritical CO2-water flow in porous media, with a special emphasis on geological carbon sequestration. Specifically, the dynamic capillary pressure effect, which indicates the dependence of the Pc - S relationship on the rate of change of saturation (αS/αt) during two-phase flow in porous media was investigated. Using a silicone oil-water system, the dynamic capillary pressure effect was quantified in term of the parameter named the dynamic coefficient, τ , and it was found to be dependent on the domain scale and the viscosity ratio of the two fluids. It was found that τ increases with the domain scale and the viscosity ratio. It is inversely affected by αS αt , which is related to the degree of resistance to the fluid motion, namely, viscosity. In almost all cases, τ was found to decrease monotonically with an increase in water saturation, S. An order increase in magnitude of τ was observed as the domain scale increases from 4cm scale to 8cm in height. A similar order of increase in τ was observed in the 12cm high domain scale. There is an order increase in the value of τ for the silicone oilwater system as the viscosity ratio increases from 200 to 500. For the supercritical CO2 (scCO2) and water system in porous media, the experiments and numerical simulations showed that τ increases with rising system temperature and decreasing porous media permeability. Dimensionless analysis of the silicone oil-water experimental results showed that by constructing non-dimensional groups of quantities expressing a relationship among different variables on which τ depends, it is possible to summarise the experimental results and determine their functional relationship. A generalised scaling relationship for τ was derived from the dimensionless analysis which was then validated against independent literature data. The exercise showed that the τ-S relationship obtained from the literature and the ii scaling relationship match reasonably well. This work also demonstrated the applicability of an artificial neural network (ANN) as an alternative computational platform for the prediction of the domain scale dependence of τ . The dependence of the Kr-S relationship on αS/αt was also investigated. The results showed that the Kr-S curve under dynamic flow condition is different from that under the quasi-static condition. Kr for water (Krw) increases with increasing water saturation and decreases with the increase in viscosity ratio while Kr for silicone oil (Krnw) increases with decreasing water saturation as well as with the increase in viscosity ratio. Also, Krw decreases while Krnw increases with the increasing boundary pressure. However, the εb-S and σb-S relationships were found to be independent of αS/αt for the scCO2-water system in carbonate and silicate porous media. Nevertheless, the εb and σb values decrease as the water saturation decreases in the two porous media samples. While εb decreases with increase in temperature in silica sand, the trend in the limestone showed a slight increase with temperature, especially at high water saturation. Also, the εb-S relationship is shown to be affected by pressure in silica sand increasing with the pressure of the domain. On the contrary, the σb-S relationship increases as the temperature increases with more significance at higher water saturation in the silica sand sample. This work further demonstrated the application of a membrane in the monitoring of the CO2 in geological sites used for carbon sequestration. Commercial silicone rubber coupled with a pressure transducer showed potential in the detection of CO2 leakage from geological sites. The response of the device in terms of the mass of permeated gas, permeability and gas flux were investigated for both CO2 and N2. In addition, the monitoring of potable water contamination in a shallow aquifer by the migrating or leaking of CO2 is demonstrated with the combination of the pH analysis, geoelectrical measurement techniques and the membrane-sensor system. Overall, the work in this PhD research demonstrated robust applications of two-phase systems'characterization parameters under different scenarios in the porous media. Implications of the findings in this work to the monitoring and control of two-phase systems in porous media are expatiated.

Made available in DSpace on 2016-06-02T19:29:32Z (GMT). No. of bitstreams: 1 3436.pdf: 3258339 bytes, checksum: 7033f00ca9eab7b49ec141759f62e980 (MD5) Previous issue date: 2010-05-04 / Financiadora de Estudos e Projetos / The methodology of the accelerated aging test controlled deterioration to achieve the physiological quality of Lafoensia glyptocarpa Koehne seeds, separated into light and dark seeds, and to correlate if these seeds have their color due to different stages of maturation or whether the color is original phenotypic. The initial quality of the seeds was obtained through the tests of moisture content, conductivity and seedling emergence in greenhouse. The accelerated aging test was conducted at 40ºC during 24, 48, and 72 hours, using the traditional, NaCl saturated solution and controlled deterioration. The research was conducted in a completely randomized design. The saturated salt accelerated aging test and controlled deterioration was efficient for vigor evaluation of Lafoensia glyptocarpa Koehne seeds, and the period of 48hours at 40ºC was considered as the most adequate procedure to evaluate seed vigor levels, leading to the belief that colored seeds come from different stages of maturation. / O presente trabalho teve por objetivo avaliar as diferentes formas de se efetuar o teste de envelhecimento acelerado e deterioração controlada para avaliação do potencial fisiológico de sementes de Lafoensia glyptocarpa Koehne, separadas em sementes claras e sementes escuras, e correlacionar se estas sementes têm sua coloração devido a diferentes estádios de maturação ou se a coloração é de origem fenotípicas. A avaliação inicial dessas sementes consistiu na determinação do grau de umidade, condutividade e emergência de plântulas em casa de vegetação. O envelhecimento artificial foi implementado a 40ºC durante 24, 48, e 72 h, com e sem uso de solução saturada de NaCl, e para o teste de deterioração controlada as sementes foram umedecidas até 20% de umidade e posterior envelhecimento em câmara úmida a 40°C durante 24, 48 e 72h. O experimento foi conduzido em delineamento inteiramente casualizado. Dentre os procedimentos adotados no teste de envelhecimento artificial e o período de exposição de 48 horas a 40ºC com uso de solução saturada de NaCl, e deterioração controlada revelou-se adequado para a avaliação do potencial fisiológico de sementes de Lafoensia glyptocarpa Koehne, levando a crer que a coloração das sementes provem de estádios de maturação diferentes.

Submitted by Richardson Barbosa Gomes da Silva (richardsonunesp@gmail.com) on 2017-05-29T13:50:49Z No. of bitstreams: 1 Tese Richardson Barbosa Gomes da Silva.pdf: 3182502 bytes, checksum: 8fa9597a7aad6e3e72ed5c66cdde181e (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-05-31T16:32:20Z (GMT) No. of bitstreams: 1 silva_rbg_dr_bot.pdf: 3182502 bytes, checksum: 8fa9597a7aad6e3e72ed5c66cdde181e (MD5) / Made available in DSpace on 2017-05-31T16:32:20Z (GMT). No. of bitstreams: 1 silva_rbg_dr_bot.pdf: 3182502 bytes, checksum: 8fa9597a7aad6e3e72ed5c66cdde181e (MD5) Previous issue date: 2017-03-29 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Em muitos viveiros, a experiência pessoal dos viveiristas é o principal método utilizado para determinar quando e quanto tempo irrigar. Os viveiros produzem diversas espécies simultaneamente numa mesma área. Entre as espécies, há muita variação na arquitetura foliar, especificamente nos ângulos foliares. A falta de conhecimento sobre a lâmina adequada e como os ângulos foliares afetam a interceptação e captura da água, limitam a eficiência da irrigação e, consequentemente, a qualidade das mudas florestais. Este estudo teve como objetivo avaliar se o ângulo foliar das mudas de nove espécies florestais nativas e as lâminas de água aplicadas no viveiro afetam a qualidade morfológica, fisiológica e nutricional das mudas; a fração de lixiviação e a condutividade elétrica da solução lixiviada; e a qualidade morfológica das plantas após o plantio em vaso. As avaliações foram realizadas ao final do ciclo de produção de cada espécie no viveiro, através das variáveis: altura da parte aérea, diâmetro do colo, massa seca aérea, radicular e total, índice de qualidade de Dickson, área de projeção da copa, conformação do sistema radicular, potencial hídrico foliar, índice SPAD, transpiração diária, teores dos pigmentos foliares clorofila a, b, carotenoides e antocianinas, fração de lixiviação, condutividade elétrica da solução lixiviada e acúmulo nutricional. A qualidade morfológica das plantas após o plantio em vaso foi avaliada em intervalos de 30 dias, durante 120 dias, através das variáveis altura da parte aérea e diâmetro do colo. Aqui mostramos que, nas espécies com ângulos foliares maiores, a aplicação de lâminas menores resulta em mudas com maior qualidade. Nas espécies com ângulos menores, é necessária a aplicação de lâminas maiores, exceto quando a área de projeção da copa é pequena. A partir desse conhecimento, o ângulo foliar poderá começar a ser adotado entre os critérios para agrupar as espécies no viveiro, a fim de que a irrigação praticada evite o desperdício de água e fertilizantes, bem como aumente a qualidade morfológica, fisiológica e nutricional das mudas florestais. / In many nurseries, the personal experience of nurseries is the primary method used to determine when and how much time to irrigate. Nurseries produce several species simultaneously in the same area. Among the species, there is much variation in foliar architecture, specifically in the leaf angles. The lack of knowledge about the proper water depth and how the leaf angles affect the interception and capture of water, limit irrigation efficiency and consequently seedlings quality. The objective of this study was to evaluate if the leaf angle of nine species of tree seedlings and the water depths applied in the nursery affect the morphological, physiological and nutritional seedlings quality; the leaching fraction and the electrical conductivity of the solution leached; and the morphological quality of the plants after planting in pot. The evaluations were performed at the end of the production cycle of each species in the nursery, through the following variables: height, stem diameter, shoot, root and total dry mass, Dickson quality index, crown projection area, conformation root system, leaf water potential, SPAD index, daily perspiration, leaf chlorophyll a, b, carotenoids and anthocyanins, leaching fraction, electrical conductivity of the solution leached and nutritional accumulation. The morphological quality of the plants after planting was evaluated at intervals of 30 days, during 120 days, through the variables height of and stem diameter. Here we show that, in species with larger leaf angles, the application of smaller water depths results in seedlings with higher quality. In species with smaller angles, it is necessary to apply larger water depths, except when crown projection area of seedling is small. From this knowledge, leaf angle can begin to be adopted among the criteria to group the species in the nursery, so that the irrigation practiced avoids the waste of water and fertilizers, as well as increase the morphological, physiological and nutritional tree seedlings quality. / FAPESP: 2013/17447-8

Devido à importância do monitoramento da composição iônica da solução do solo, no que diz respeito ao meio ambiente e ao manejo da fertirrigação, associada às limitações práticas dos métodos tradicionais de sua determinação é crescente a procura por um método confiável que possibilite o monitoramento desta composição em tempo real e em curtos intervalos de tempo. Neste sentido a TDR tem sido uma alternativa viável. O presente trabalho objetivou, pelo uso da TDR, avaliar o desempenho de sete modelos na determinação da CEw; relacioná-los com a concentração dos íons potássio nitrato e cloreto avaliando os modelos em determinar a concentração dos íons; e por fim monitorar e determinar a concentração destes íons na água lixiviada em coluna de solo não saturado. O trabalho foi divido em dois experimentos, no primeiro os modelos foram calibrados em colunas de solo sendo formado por 24 tratamentos composto por 4 faixas de umidade volumétrica e 6 concentrações da solução de KCl. Para cada coluna de solo era realizada uma leitura com a TDR ( e CEa) e a CEw na solução do solo era determinada por condutivímetro de mesa, nesta solução foram determinadas as concentrações de potássio e cloreto. No segundo experimento o mesmo procedimento foi realizado, entretanto, foi aplicado KNO3 e determinados potássio e nitrato. Desta forma, foi possível calibrar os modelos para a estimativa da CEw, e para determinação das concentrações dos íons potássio, nitrato e cloreto. Os modelos foram avaliados pelos coeficientes de determinação (R²) e exatidão (d), pela estimativa do erro padrão (EEP) e, ainda, foram classificados de acordo com o índice c, produto dos dois coeficientes citados. Os resultados mostram que os modelos de Rhoads et al. (1976) e Vogeler et al. (1996) se ajustam melhor para solos com características texturais argilosas sendo classificados como Ótimos métodos para a determinação da CEw, tanto pela aplicação de KCl como pela aplicação de KNO3 via água de irrigação. Na estimativa da CEw no solo arenoso os modelos de Munõz-Carpena et al. (2005), Mualen e Friedman (1991), Vogeler et al. (1996) e Rhoads et al. (1976) apresentam melhores ajustes na determinação da CEw, sendo classificados com Muito bom. Na determinação do potássio pelos modelos avaliados o melhor ajuste se dá pela associação da relação K-CEw do tipo potência aplicada para solos argilosos e linear para solos arenosos, apresentando classificação de: Ótimo e Muito bom, respectivamente. Para o cloreto e o nitrato o melhor ajuste se dá pela relação de CEw-Cl e CEw-NO do tipo linear, apresentando classificação de Muito Bom e Ótimo respectivamente. A TDR é uma técnica confiável no monitoramento da concentração dos íons potássio e cloreto lixiviados no perfil do solo. / There is a growing demand for a reliable method applied to monitoring ionic composition of soil solution in real-time and short time intervals, due the importance to environmental sustainability and fertigation management and limitations of traditional methods for determination. Time domain reflectometry (TDR) is often considered a viable alternative to traditional methods. Consequently, this research looks for using TDR evaluate the performance of seven mathematical models for determining electrical conductivity (CEw) by comparing simulated and measured concentrations of potassium, nitrate and chloride, and to monitor and determine the concentration of these ions in water leached from unsaturated soil columns. The research was carried out under two experiments conditions. In the first experiment the models were calibrated with input data from 24 soil columns consisting of four soils with six different KCl concentrations. For each soil column CEw was determined by both TDR ( and CEa readings) and the CEw of soil solution was determined by direct measurements of potassium and chloride concentrations. In the second experiment the procedure was the same, but with KCl being replaced with KNO3. This was possible to calibrate the models to estimate the CEw, and to determine potassium, nitrate and chloride ions concentrations. The models were ranked using the c-index, the coefficient of determination (R²) and estimated standard error (ESE). The results showed were Rhoads et al. (1976) and Vogel et al. (1996) classified as \"Great\" for the CEw determination associated with the application of both KCl and KNO3 to irrigation water in clay soils. For estimating CEw in sandy soils, the models Muñoz-Carpena et al. (2005), Mualen and Friedman (1991), Vogel et al. (1996) and Rhoads et al. (1976) were classified as \"Very Good.\" The relationship between CEw and potassium concentration was best represented by a power function in clay soils, and a linear function in sandy soils, with index of \"Great\" and \"Very Good\", respectively. For chloride and nitrate, the best fits were obtained by representing the CEw-Cl and CEw-NO3 relationships with linear functions, which were classified as Very Good and Good, respectively. TDR proved to be a reliable technique for monitoring the concentration of potassium and chloride ions leached in soil profiles.

A porção sul do Leque Aluvial do Taquari, chamada Nhecolândia, é uma sub-região do Pantanal Mato-Grossense, que apresenta um complexo sistema de lagoas arredondadas, vazantes, cordilheiras, corixos e pequenas depressões. Estudos anteriores mostraram que os fluxos de águas subsuperficiais dependem da intensidade das cheias, e da presença e forma dos horizontes verdes argilosos, localmente cimentados, que limitam fortemente a permeabilidade, e comandam os fluxos laterais. Inicialmente associados a ambientes alcalinos das salinas, esses horizontes também ocorrem em ambientes diluídos, como as pequenas depressões. O objetivo geral deste trabalho é compreender o funcionamento hídrico de três pequenas depressões, em relação com as características morfológicas dos solos. Métodos de indução eletromagnética foram utilizados para mapear a condutividade elétrica aparente (CEa); complementados por métodos de descrições das características morfológicas dos solos, e de análises granulométricas e mineralógicas em laboratório. Estes trabalhos foram complementados por análises físico-químicas das águas nas depressões; e pelo monitoramento do nível do lençol freático entre uma depressão e uma baía. O horizonte verde argiloso, mais ou menos endurecido, aparece na base das sequências de solos nas três pequenas depressões, ao qual se superpõem horizontes arenosos superficiais e subsuperficiais. As principais diferenciações morfológicas observadas referem-se aos processos de redistribuição de ferro e da matéria orgânica, ligados ao regime hídrico. No período seco, quando ocorre um rebaixamento do nível freático, o horizonte verde argiloso funciona como uma soleira e fragmenta o lençol, que passa a funcionar como dois segmentos, um ligado à Depressão Fechada, e outro à Baía. Ao longo do ano, a Depressão Fechada acumula água apenas temporária e fugazmente. Na maior parte do tempo, ela funciona como área dispersora de água às unidades morfológicas adjacentes, salientando sua importância funcional na Nhecolândia. / The southern part of the Taquari alluvial fan, called Nhecolândia, is a sub-region of the Pantanal of Mato-Grosso exhibiting a complex of round shape lakes, draining fields, forested sandy areas, small watercourses and small depressions. Former studies have shown that the sub-superficial water fluxes depend on the intensity of the flood and on the presence and shape of a sandy clay loam greenish horizon, locally cemented, which acts as an impervious layer and drives lateral fluxes. Although its presence has always been associated to the alkaline-saline parts of this singular landscape, it also occurs below small freshwater depressions. The objective of this study is to understand the hydrological functioning of these small depressions in relation to the soil cover layout. Electromagnetic induction methods were used to draw apparent electrical conductivity (CEa) maps, crossed with direct auger holes and pits observations, and laboratory analysis (grain size distribution and mineralogy). Physico-chemical analysis of the ground water in the depressions and a monitoring of the groundwater fluctuation along one year were also performed. The greenish horizon, more or less cemented, occurred at the base of the soil system in all the studied depressions. It was overlaid by more sandy horizons. The main pedological differentiation was organic matter and iron redistribution along the soil sequences, in relation with the hydrological regime. During the dry season, the watertable goes down and the greenish horizon acts as a threshold, disconnecting various watertables in the different parts of the landscape. Along the year, the closed depressions accumulate the water only temporarily and fleetingly. Most of the time, they work as areas of water redistribution towards the surrounding landscape units, and therefore have a essential function in the Nhecolândia.

Ce travail propose une optimisation de la conductivité électrique transverse des composites structuraux matrice/fibres de carbone. L'influence de la fonctionnalisation électrique de l'ensimage sur la conductivité des composites est particulièrement étudiée. Des feuillets submicroniques d'argent (AgNpts) ont été élaborés en présence de citrate de sodium (TSC). Leur morphologie plane est particulièrement adaptée à une dispersion dans un ensimage. Les feuillets ont été dispersés dans une matrice modèle. Le seuil de percolation électrique des feuillets est déterminé à 5,9 %. Cette valeur est cohérente avec un facteur de forme modéré, compris entre 12 et 28. L'ensimage fonctionnalisé a ensuite été déposé sur une mèche de fibres de carbone, elle-même imprégnée par une matrice PAEK hautes performances. Avant imprégnation des fibres de carbone, des fils submicroniques d'argent ont été introduits dans la matrice PAEK. Des composites matrice-fils submicroniques d'argent/fibres de carbone avec ensimage conducteur ont été mis en œuvre. Leur conductivité électrique est élevée (7 S.m-1), alors que la fraction volumique en particules d'argent (fils et feuillets) est inférieure à 1 % en volume. / This PhD thesis deals with the optimization of transverse electrical conductivity of Thermoplastic Carbon Fiber Reinforced Polymer. The influence of an electrically conductive sizing has been investigated. Silver nanoplates (AgNpts) have been successfully synthesized by a soft chemical reduction, with trisodiumcitrate (TSC) as surfactant. Silver nanoplates have been dispersed into a model matrix, percolation threshold has been determined near 5.9 % in volume fraction. This value is consistent with their moderate aspect ratio (between 12 and 28). Size and morphology of silver nanoplates are suitable for their dispersion in the sizing. Carbon fiber has been coated with conductive sizing. Carbon fiber will be further impregnated by a PAEK thermoplastic matrix. A higher conductivity level has been achieved by introducing silver nanowires in the PAEK matrix. Structural composites consisting of matrix-silver nanowires / continuous carbon fiber sized with conductive sizing have been elaborated. Their electrical conductivity reached 7 S.m-1 for a total silver volume fraction of 1 %.vol.

The use of remote sensing techniques can eliminate the need for extensive sampling in the field, reducing the cost of sampling and increase the accuracy of the results. In this context, the present study had the following objectives: I-evaluate the effectiveness of an optical sensor for determining the nitrogen nutritional status of cotton crop subjected to different doses of N and correlate with the crop yield. II- to determine the electrical conductivity in two fields of classification Oxisols by using a sensor and relate this index with other chemical soil parameters and productivity of corn. Regarding the first objective, the experiment was conducted in the agricultural year of 2012/13 on a Oxisol with the cotton crop. The experimental design was a randomized block design with seven treatments and three replications. Treatments consisted of the following N rates: 0, 45, 90, 130, 150, 180 and 220 kg ha-1 applied at 43 days after sowing (DAS). The vegetation index readings were taken at three different times, corresponding to 63, 75 and 97 DAE with the optical sensor N-Sensor ALS ® (YARA). Concerning the objective II electrical conductivity was evaluated of two areas using the Veris ® 3100 sensor to depths of 0-30 cm and 0-90 cm. The evaluations were conducted in the agricultural year 2012/13, the cultivated culture, in both areas, was the corn. Chemical parameters of the soil and the electrical conductivity were compared by method of multiple regression 'stepwise'. Regarding the first objective, the vegetation index reading by sensor showed high correlation with N rates in three stages evaluated, this correlation was also found with the parameters plant height, dry matter and N absorbed. The highest yield of cotton was achieved with rate of 152 kg ha-1 of N. Regarding the objective II, the EC of Area 1, for 0-30 cm layer, was explained by factors V% and Mg and in the layer of 0-90 cm by SB factor. For Area II, the EC in the 0-30 cm layer, was explained by clay contente, CTCpH7,0 and SB and for 0-90 cm layer by clay content. Increasing productivity of Area 1 showed a quadratic fit with increasing EC at both depths evaluated, in Area 2 increased productivity correlated linearly with increasing EC at both depths. / O uso de técnicas de sensoriamento remoto pode eliminar a necessidade de extensivas amostragens na lavoura diminuindo o custo da amostragem além de aumentar a acurácia dos resultados obtidos. Nesse contexto, o presente trabalho teve os seguintes objetivos: I- avaliar a eficácia de um sensor óptico na determinação do estado nutricional nitrogenado na cultura do algodoeiro submetido a diferentes doses de N e correlacionar com a produtividade da cultura. II- determinar a condutividade elétrica em duas áreas de classificação Latossolos, através do uso de sensor e relacionar esse índice com os demais parâmetros químicos do solo e com a produtividade da cultura do milho. Em relação ao objetivo I, o experimento foi conduzido no ano agrícola de 2012/13 em um Latossolo Vermelho Amarelo com a cultura do algodoeiro. O Delineamento experimental foi em blocos ao acaso, com sete tratamentos e três repetições. Os tratamentos consistiram das seguintes doses de N: 0, 45, 90, 130, 150, 180 e 220 kg ha-1 aplicados aos 43 dias após semeadura (DAS). As leituras de índice de vegetação foram realizadas em três épocas, correspondentes aos 63, 75 e 97 DAE com o sensor óptico N-Sensor ALS® (YARA). Em relação ao objetivo II foi avaliada a condutividade elétrica de duas áreas com uso do sensor Veris® 3100, para as profundidades de 0-30 cm e 0-90 cm. As avaliações foram realizadas no ano agrícola de 2012/13 e a cultura cultivada, em ambas as áreas, foi a do milho. Os parâmetros químicos do solo e a condutividade elétrica foram comparados pelo método de regressão múltipla do tipo stepwise‟. Sobre o objetivo I, a leitura do índice de vegetação do sensor apresentou alta correlação com as doses de N nos três estágios avaliados, essa correlação também foi verificada com os parâmetros altura de planta, massa seca e N absorvido. A maior produtividade da cultura do algodão foi alcançada com a dose de 152 kg ha-1 de N. Com relação ao objetivo II, a CE da Área 1 para a camada de 0-30 cm foi explicada pelos fatores V% e Mg e para a camada de 0-90 cm pelo fator SB. Para a Área II a CE na camada de 0-30 cm foi explicada pela argila, CTCpH7,0 e SB e para a camada de 0-90 cm pelo teor de argila. O aumento da produtividade da Área 1, apresentou ajuste quadrático com o aumento da CE em ambas as profundidades avaliadas, já na Área 2, o aumento da produtividade se correlacionou linearmente com o aumento da CE em ambas as profundidades.

Three-dimensional graphene foam (3D GrF) is an interconnected, porous structure of graphene sheets with excellent mechanical, electrical and thermal properties, making it a candidate reinforcement for polymer matrices. GrF’s 3D structure eliminates nanoparticle agglomeration and provides seamless pathways for electron travel. The objective of this work is to fabricate low density GrF reinforced epoxy composites with superior mechanical and electrical properties and study the underlying deformation mechanisms. Dip coating and mold casting fabrication methods are employed in order to tailor the microstructure and properties. The composite’s microstructure revealed good interfacial interaction. By adding mere 0.63 wt.% GrF, flexural strength was improved by 56%. The addition of 2 wt.% GrF showed a surge in glass transition temperature (56oC), improvement in damping behavior (150%), and electrical conductivity 11 orders of magnitude higher than pure epoxy. Dip coated and mold casted composites showed a gauge factor of ~2.4 indicating electromechanically robust composite materials.

The cold test is one of the oldest and most acceptable vigour tests as it is used to simulate stress conditions commonly occurring in the field. In recent years, some of South Africa’s top maize hybrids, with high cold test scores, have shown emergence problems under cold, wet planting conditions. It resulted in major complaints from commercial maize producers with sizable claims involved. Therefore, the need arose to find a more sensitive vigour test that takes into account cold, wet conditions. In practice, South African maize producers would not plant if it is too cold and wet. However, cold, wet conditions are commonly experienced during planting time in the main maize production regions of South Africa, especially during October and even November. Furthermore, in most of the commercial maize production areas, such as the western Free State, chances of thunder and hailstorms are high during the planting period. These weather conditions are major causes for sudden drops in temperature and flooding which can expose maize seed and emerging maize seedlings to stress conditions The effects of cold, wet conditions on germination and emergence of nine maize hybrids were investigated in laboratory, glasshouse and field experiments. Growth chamber and glasshouse experiments were conducted under 10°C, 20°C and 30°C and 0, 24, 48 and 72 hours flooding. Field experiments were conducted under different climatic conditions, resulting in cool and wet, cold and wet and favourable conditions during planting. The objectives were to investigate the correlations between different laboratory vigour tests and field emergence of maize hybrids under cold, wet conditions in order to identify the most suitable laboratory vigour test for predicting field emergence under cold, wet conditions. Eight different vigour tests were conducted and each was compared with field emergence under cold, wet conditions. The eight tests conducted, were the cold test, soak test, complex stressing vigour test, electrical conductivity test, accelerated ageing test, tetrazolium test, fast green test and emergence rate test. The soak test was the most sensitive vigour test when considering cold, wet conditions, as it measures seed germination, based on the warm test, after a 48 hour soak in water at 27°C. Correlations found between the soak test and field emergence (53%) under cold, wet conditions was unexpected, since the soak test does not account for low temperatures. The complex stressing vigour test was conducted to study the effect of fluctuating soaking temperatures on germination of maize seed. Seeds of nine maize hybrids were soaked for 48 hours at a moderate temperature (25°C), followed by another 48 hours soak at a low temperature (5°C), and then planted in sand and grown for 4 days at 25°C, before evaluation. Highly significant correlations were found between the complex stressing vigour test and simulated field emergence under both controlled conditions in a glasshouse (89.9%) and cold, wet conditions in the field (90.0%). The complex stressing vigour test was the best test to predict field performance under a wide range of climatic conditions, especially cold, wet conditions. Implementation of the complex stressing test as a routine vigour test, will be to the advantage of maize seed companies, especially in being proactive in predicting emergence of maize hybrids under cold, wet conditions. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Plant Production and Soil Science / unrestricted

L’étude du comportement des composantes des intérieurs planétaires dans des conditions extrêmes de pression (megabar) et température (milliers de Kelvin) est essentielle afin de construire des modèles fiables décrivant l’évolution et la structure des planètes. Dans ce travail, nous avons étudié plusieurs composantes par compression par choc laser sur les installations LULI2000 (France) et GEKKO XII (Japon).Nous avons employé des chocs décroissants pour étudier des conditions de haute-pression / haute-température. Afin d’accéder à des conditions de température modérée, nous avons utilisé des techniques de pre-compression statique (couplage compression par choc — cellules à enclumes de diamant) et dynamique (génération de doubles chocs).Nous avons étudié l’équation d’état des mélanges eau-ethanol-ammoniac et de l’eau et ammoniac purs, d’intérêt pour la description des intérieurs des planètes géantes de glace. L’étude de l’ammoniac a été particulièrement délicate en raison de sa forte réactivité et donc de la complexité du design des cibles ; nous présentons les premières données obtenues par choc laser, dans un domaine de pression jamais exploré. Les données des mélanges confirment des calculs ab initio récents basés sur une approximation de mélange linéaire.Nous avons également mesuré la réflectivité des mélanges liquides et de la silice, une composante-clé des intérieurs des planètes terrestres. Nous avons ensuite estimé la conductivité électrique — un paramètre crucial pour modéliser la génération des champs magnétiques planétaires dans les intérieurs via un mécanisme dynamo — de ces composantes.Eau, ammoniac et mélanges eau-ethanol-ammoniac affichent des réflectivités différentes, ce qui suggère que l’eau pure ne peut pas être considérée comme représentative des mélanges planétaires dans les modèles dynamo.Par ailleurs, nous avons apporté une confirmation expérimentale de calculs ab initio récents selon lesquels la conductivité de la silice n’est pas monotone le long d’une ligne isotherme pour des températures modérées.Nos données supportent des calculs qui prédisent qu’une dynamo peut avoir lieu dans les océans de magma dans des super-Terres ainsi que dans la jeune Terre. / Characterising the behaviour of planetary interiors’ components at extreme conditions (megabar pressures, temperatures of a few thousand Kelvin) is essential to build reliable models describing the evolution and structure of planets. In this thesis, we investigated various components on a wide set of conditions using laser-driven shock compression techniques at the LULI2000 (France) and GEKKO XII (Japan) facilities.Single decaying shocks were employed to study high-pressure / high-temperature states. To reach moderate-temperature conditions, closer to planetary interior profiles, we employed static and dynamic pre-compression techniques coupling Diamond Anvil Cells to shock compression and generating double shocks, respectively.We studied the equation of state of water-ethanol-ammonia mixtures and of pure liquid water and ammonia, of interest for icy giant structure models. Pure ammonia measurements have been particularly challenging due to cell design complexity in reason of its reactivity; we provide the first data obtained with laser shocks, in a pressure domain up to now unexplored. Mixtures data are in agreement with recent ab initio calculations based on the linear mixing approximation.We measured the optical reflectivity of liquid mixtures and silica, a key component of rocky planets’ interiors. From reflectivity data we estimated the electrical conductivity of such components — a crucial parameter for modelling the generation of planetary magnetic fields in the interiors via a dynamo mechanism.Water, ammonia, and water-ethanol-ammonia mixtures exhibit different reflectivity (hence conductivity) behaviours as a function of pressure and temperature. This suggests that pure water should not be used in dynamo models as representative of the icy mixtures.Moreover, we provide the first experimental confirmation of recent ab initio studies showing that the conductivity of silica along isothermal lines is not monotonic at moderate temperatures. Our data provide experimental support for the calculations predicting a dynamo action to occur in super-Earths’ and early Earth’s magma oceans.