Orientador: João Carlos Dourado / Banca: Carlos Alberto Mendonça / Banca: Walter Malagutti Filho / Resumo: Este trabalho discute a aplicabilidade do método geofísico Eletromagnético Transiente (TEM) a partir de análise comparativa com o método de Eletrorresistividade, em uma área industrial contaminada por derivados de petróleo e atualmente sob processos de Atenuação Natural. Dentre os contaminantes presentes no solo e água subterrânea estão o Benzeno, Tolueno, Xileno, 1,2 Dicloroetano, Sódio, Cloreto e Sulfato. A remediação da área é realizada exclusivamente por Atenuação Natural, ou seja, ação de processos físicos, químicos e biológicos responsáveis pela degradação, dispersão e diluição dos contaminantes. Foram utilizadas as técnicas de sondagem eletromagnética de "loop" central, caminhamento eletromagnético, sondagem elétrica vertical e caminhamento elétrico. Os resultados apresentam uma anomalia de baixa resistividade adjacente aos poços de injeção, e anomalias de alta resistividade sob estes poços. A grande área abrangida pela anomalia de baixa resistividade é fruto principalmente da biodegradação dos contaminantes de fase líquida leve não aquosa - LNAPL, cujas sucessivas quebras em compostos mais simples por ação de microorganismos resulta em ácidos orgânicos que corroem grãos minerais, que são liberados ao meio sob a forma iônica. A pequena área abrangida pela anomalia de alta resistividade é produto da concentração de contaminantes pouco degradados, caracterizados por elevada resistividade em relação á água. O TEM se mostrou aplicável no estudo de áreas contaminadas e o processo de Atenuação Natural está sendo eficaz na remediação da área. / Abstract: This work discuss the applicability of the Transient Electromagnetic Method (TEM) from comparative analysis with the Electrical Method, in an industrial area contaminated by oil derived and currently under processes of Natural Attenuation. Amongst the contaminants presents in the soil and groundwater they are the Benzene, Toluene, Xylene, 1,2 Dichloroetene, Sodium, Chloride and Sulphate. A remediation of the area is carried through exclusively by Natural Attenuation, or either, action of physical, chemical and biological processes responsible for the degradation, dispersion and dilution of contaminants. The techniques of electromagnetic sounding of central loop, electromagnetic tomography, vertical electric sounding and electric tomography had been used. The results present an anomaly of low adjacent resistivity to the injection wells, and anomalies of high resistivity under these wells. The great area enclosed for the anomaly of low resistivity is fruit mainly of the biodegradation of the contaminants of light non-aqueous phase liquid - LNAPL, whose successive breakings in simpler composites for action of microorganisms result in acid organic that corrode mineral grains, that are set free to the way under the ionic form. The small area enclosed for the anomaly of high resistivity is product of the concentration of contaminants little degraded, characterized for raised resistivity in relation a water. The TEM if it showed applicable in the study of contaminated areas and the process of Natural Attenuation is being efficient in the remediation of the area. / Mestre

Os métodos geofísicos têm sido utilizados para definir a extensão em área e em profundidade de contaminações causadas por compostos orgânicos ou inorgânicos, uma vez que tais contaminações alteram as propriedades físicas do meio. Este trabalho abrangeu o desenvolvimento de ensaios realizados em laboratório e em campo para verificar a aplicabilidade de minissonda de resistividade, que utiliza quatro eletrodos dispostos segundo o arranjo Wenner em conjunto com uma fonte de corrente e dois multímetros, o que torna possível a execução de uma medida convencional de resistividade em diferentes profundidades à medida que a sonda é cravada no solo. Uma eventual aplicação desta minissonda seria sua utilização na avaliação de salinização secundária de solos. A agroindústria, principalmente no estado de São Paulo, vem utilizando cada vez mais estufas para a produção de frutos e flores, principalmente. Os processos de irrigação, e o microclima criados dentro das estufas, têm causado o incremento da quantidade de sais no solo, uma vez que o solo não é naturalmente lixiviado pela água da chuva. Isto pode comprometer a utilização dessas estufas para fins ligados à agricultura. A salinidade refere-se à presença de sais dissolvidos no solo, na água superficial e subterrânea. A salinização do solo pode estar ligada a processos naturais como a pedogênese do solo ou ao clima local por exemplo, ou pode ter origem secundária, podendo estar relacionada às atividades antrópicas capazes de alterar esta propriedade do meio. O presente trabalho visou testar a aplicabilidade da minissonda de resistividade para a avaliação da salinização secundária de solos. O trabalho foi inicialmente desenvolvido em laboratório, onde foram efetuados experimentos em amostras de solo saturadas com soluções de NaCl em diferentes concentrações. Os resultados obtidos nestes ensaios utilizando um meio arenoso totalmente saturado mostraram que a condutividade elétrica aumenta em função da concentração de NaCl utilizado na solução. Observou-se ainda a relação inversa entre a resistividade aparente calculada e a concentração da solução utilizada. Os ensaios de campo foram executados em duas estufas distintas, que utilizam diferentes técnicas de cultivo, localizadas nos municípios de Holambra e Elias Fausto, e não indicaram correlação entre a condutividade elétrica calculada a partir das resistividades obtidas e a condutividade elétricas medidas em laboratório, nas amostras de solo encaminhadas para análise. Foram analisados também os íons Al, Ba, Ca, Cr, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Zn, e cloretos. Nas duas estufas observa-se correlação entre as condutividades obtidas e alguns dos íons analisados. As diferenças observadas entre as condutividades elétricas calculada e medida, podem estar relacionadas às condições de campo, uma vez que nas duas estufas observou-se porções porosas no solo, a presença de solo argiloso nas estufas, principalmente em Holambra, e à presença dos metais presentes no solo local, conforme mostram os resultados analíticos obtidos. Adicionalmente, durante a realização dos ensaios em laboratório o meio encontrase totalmente saturado, o que não ocorreu nos ensaios realizados em campo, uma vez que na estufa em Holambra o solo estava úmido e na estufa em Elias Fausto apresentava-se bastante seco. As diferenças de umidade também podem ter interferido nos resultados obtidos. Os trabalhos realizados evidenciaram que a minissonda pode ser aplicada para medida de resistividade in situ, porém, seu uso deve se limitar à avaliação de áreas onde o solo é mais arenoso e pouco compactado. / Geophysical methods have been used to define the extension and depth of contaminations caused by organic and inorganic compounds spills. This is because those contaminations change the physical properties of the underground materials. This study presents the tests results performed both in laboratory and field of a small probe that allows the in situ measurement of the resistivity, avoiding the need of installation of monitoring wells and allowing low cost and fast measurements. It consists in a probe with four electrodes according a Wenner array, a current source and two multimeters. It makes possible to take in situ resistivity measurements in different depths while the probe is inserted in the soil. An eventual application for that mini probe would be for evaluation of secondary salinity of the soil. The agro industry, mainly in the São Paulo state, has been using greenhouses to increase the production mainly of fruits and flowers. The irrigation processes used and the microclimate generated in the greenhouse have been causing an increasing salt quantity in the soil. This happens because the natural lixiviation (by the rain) does not occur. That increasing salinization may prejudice the use of such greenhouses for agricultural purposes. Salinization refers to a build up of salts in soil, in the superficial water and groundwater. It may be due to natural process, like e.g. the pedogenesis or the local climate, or it may have a secondary origin, normally related to antropic activities that are capable to modify such property. This study aimed at testing the applicability of the resistivity mini probe to evaluate the secondary salinization of the soil. It was performed firstly in laboratory, using soil samples saturated with NaCl solutions of different concentrations. The results of those experiments showed that the electrical conductivity increases as function of the NaCl concentration and, naturally, the inverse relation with the apparent and calculated resistivity. Field tests were performed in two different greenhouses where distinct techniques are used. They are located in the Holambra and Elias Fausto municipalities. These tests did not indicate correlation between the electrical conductivity calculated from the measures resistivities and the electrical conductivities measured in the soil samples sent to the laboratory. In those samples the ions Al, Ba, Ca, Cr, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Zn, and chloride were also analyzed. For both greenhouses, some ions presented correlation with the electrical conductivities. The observed differences between the electrical conductivity calculated and measured may be related to the field conditions, since that in both greenhouses the soil was porous (avoiding the perfect coupling of the probe), the presence of clay that sticks in the probe between the electrodes, or the presence of metals in the soil, shown by the chemical analysis. In addition, during the laboratory tests, the soil was completely saturated, what was not the case in the field. In Holambra the soil was wet and Elias Fausto it was completely dry. So, the humidity differences may have interfered in the results. Finally, the tests results showed that the mini probe may be applied to measure the resistivity in situ but, its use may be limited to the evaluation of areas where the soil is more sandy and relatively loose.

Este trabalho apresenta a fabricação e a caracterização elétrica de contatos Al/Ti/Ni(Pt)Si sobre junções rasas N+P com aproximadamente 0,2 ìm de profundidade, sendo que o monosiliceto de níquel foi formado a partir da estrutura Ni(30nm)/Pt(1,5nm)/Si. O comportamento elétrico dos diodos obtidos no melhor processo foi adequado, com as seguintes médias e desvios padrões: corrente reversa por unidade de área de 33,8nA/cm2 ±12,3 nA/cm2 e corrente reversa por unidade de perímetro de 654pA/cm ±229pA/cm para tensão reversa de -5V, a resistência reversa dos diodos quadrados de 268,9G? ±97,7G? e a resistência reversa dos diodos serpentinas de 35,5G? ±11,5G?, a tensão de início de condução resultou entre 0,55V e 0,56V, a resistência série em condução de 4,7? ±1,3?, fator de idealidade de 1,15 ±0,03, e corrente de saturação de 1,1x10-11A para diodos quadrados (300ìm x 300ìm). O menor valor de resistividade do filme de (Ni(Pt)Si) resultou 25ì?cm e a resistência de folha de 3,13 ?/? foram obtidas após a formação do mono-siliceto de níquel na temperatura de 600 ºC durante 120 segundos. As estruturas Kelvin apresentaram resistividade de contato de 15,0ì?.cm2 ±3,3ì?.cm2 e comportamento ôhmico estável para diversos níveis de corrente. Após uma extensa análise sobre modelagem de contato, foi elaborado um programa computacional desenvolvido em MATLAB, baseado em um método bem conhecido, isto é, uma malha de resistores tridimensional, que analisa os efeitos do fenômeno de concentração das linhas de corrente lateral no contato. Este programa foi aplicado em contatos com siliceto de níquel, onde foram observadas reduções de até 32% na resistividade real do contato. / This work presents the fabrication and electrical characterization of Al/Ti/Ni(Pt)Si contacts having the nickel monosilicide formed from Ni(30nm)/Pt(1.5nm)/Si structure on shallow N+P junctions with about 0.2 ìm of depth. The diodes? electrical behavior achieved at the best process was considered good, with the following average and standard deviations: area diode leakage current of 33.8nA/cm2 ±12.3nA/cm2 and periphery diode leakage current of 654pA/cm ±229pA/cm for reverse voltage of -5V, the square diode reverse resistance of 268.9G? ±97.7G? and serpentine diode reverse resistance of 35.5G? ±11.5G?, forwardbias voltage between 0.55V and 0.56V, forward series resistance of 4.7? ±1.3?, ideality factor of 1.15 ±0.03, and reverse saturation current of 1.1x10-11A for square diodes (300ìm x 300ìm). The lowest film resistivity value (Ni(Pt)Si) of 25ì?cm and sheet resistance of 3.13 ?/? were obtained for the formation of nickel monosilicide under temperature of 600ºC for 120 seconds. The cross-bridge Kelvin resistors presented contact resistivity of 15.0 ì?.cm2 ±3.3 ì?.cm2 and stable ohmic behavior for several electrical current levels. After extensive analysis about contact modeling, a computer program was elaborated in MATLAB, based on a well-known three-dimensional resistor network, which analyses the lateral current crowding effects on contact. This program was applied for contacts with nickel silicide, where a decrease up to 32% at the real contact resistivity was observed.

Masters of Science / Understanding the hydrogeology of fractured or crystalline rocks is complicated because of complex structure and a porosity that is almost exclusively secondary. These types of geologies exhibit strong heterogeneities and irregularities contrasted in hydraulic properties, spacing and flow direction within fractured rock aquifers. Therefore it is important to develop a conceptual model based on site specific data such as the hydraulic roles between groundwater and nearby hillslope/surface water bodies in order to understand its movement within the environment. Therefore this study intends to develop a hydrogeological conceptual model associated with the dominant groundwater flow processes at a 3rd order scale within the Kruger National Park (KNP).

With the increasing use of fission-type nuclear power generation, particularly high-levels radioactive nuclear waste are generated, so the safe use of nuclear energy requires proper disposal of high-level radioactive nuclear waste. The selected treatment method is deep geological disposal. Therefore, underground research laboratory (URL) to prepare for deep geological disposal will also be carried out. Corrosion of metallic materials, which are closely related to the safety of URL, is the focus of this research project. This study selected monitoring techniques for URL and developed a rough monitoring scheme for temperature and resistivity in URL. In this study, corrosion-temperature and corrosion-resistivity monitoring experiments were carried out in different bentonite samples to simulate the experiments in URL. The results show that the self-compensating high-precision inductance corrosion monitoring system and multifunction soil corrosion rate measurer proved to be a good system for monitoring the corrosion-temperature and corrosion-resistivity of metals. However, the life span limitation makes them unable to meet the requirements of URL. The results also show that the corrosion rate of metal in bentonite is positively correlated with temperature. The existing electrochemical probes are suitable for monitoring the corrosion rate, but not suitable for soil corrosion rate monitoring.

Low temperature sintering has become a very important research area in ceramics processing and sintering as a promising process to obtain grain size below 100nm. For electronic ceramics, low temperature sintering is particularly difficult, because not only the required microstructure but also the desired electronic properties should be obtained. In this dissertation, the effect of liquid sintering aids and particle size (micrometer and nanometer) on sintering temperature and Positive Temperature Coefficient Resistivity (PTCR) property are investigated for Ba1-xSrxTiO3 (BST) doped with 0.2-0.3mol% Sb3+ (x = 0.1,0.2,0.3,0.4 and 0.5). Different sintering aids with low melting point are used as sintering aids to decrease the sintering temperature for micrometer size BST particles. Micrometer size and nanometer size Ba1-xSrxTiO3 (BST) particles are used to demonstrate the particle size effect on the sintering temperature for semiconducting BST. To reduce the sintering temperature, three processes are developed, i.e. 1 using sol-gel nanometer size Sb3+ doped powders with a sintering aid; 2 using micrometer size powders plus a sintering aid; and 3 using nanometer size Sb3+ doped powders with sintering aids. Grain size effect on PTCR characteristics is investigated through comparison between micrometer size powder sintered pellets and nanometer size powder sintered pellets. The former has lower resistivity at temperatures below the Curie temperature (Tc) and high resistivity at temperatures above the Curie temperature (Tc) along with higher ñmax/ñmin ratio (ñmax is the highest resistivity at temperatures above Tc, ñmin is the lowest resistivity at temperatures below Tc), whereas the latter has both higher ñmax and ñmin. Also, ñmax/ñmin is smaller than that of pellets with larger grain size. The reason is that the solid with small grain size has more grain boundaries than the solid with large grain size. The contribution z at room temperature and high temperature and a lower ñmax/ñmin ratio value.

Epoxy resins are widely used materials in the industry as electrical insulators, adhesives and in aircrafts structural components because of their high mechanical stiffness, strength and high temperature and chemical resistance properties. But still, the influence of water uptake due to moisture adsorption is not fully understood as it detrimentally modifies the electrical and chemical properties of the material. Here ,we investigate the influence of water moisture uptake on the neat epoxy material by monitoring the change in the volume resistivity and dielectric properties of epoxy material at three different thickness configurations: 0.250 mm, 0.50 mm and 1 mm thicknesses. Gravimetric analysis was done to monitor the mass uptake behaviour, Volume Resistivity was measured to monitor the change in conductivity of the material, and the dielectric properties were mapped to characterise the type of water mechanism available within the material during two ageing processes of sorption and desorption. Two-stage behaviours of diffusion and reaction have been identified by the mass uptake analysis. Moreover, the plot of volume resistivity versus mass uptake has indicated a non-uniform relationship between the two quantities. However, the analysis of the dielectric spectrum at medium range of frequency and time has showed a change in the dipolar activities and also showed the extent to which the water molecules can be segregated between bounding to the resin or existing as free water

Cognition of the hydraulic properties of soils is important in civil and environmental projects such as for water supply, geotechnical investigations and evaluation of pollutant spreading. This pilot project aims to develop and test a new method for characterization of the homogeneity and isotropy of different soils by using geophysical measurements. The method is based on geoelectrical (resistivity) measurements using a radial array. Using a radial array with electrode lines in various orientations crossing a midpoint at which water was infiltrated, it was possible to build a 3D-block model showing the water penetration into a soil body. Based on the infiltration pattern it was possible to evaluate the hydraulic heterogeneity and anisotropy of the material. Several common Swedish types of soils were tested. Measurement and evaluation techniques including software were developed. The project shows that geoelectrical measurements using a radial array and geoelectrical instruments available on the market can be used for rapid evaluation of the hydraulic heterogeneity and anisotropy of soils and rock.

Concrete has been used in a number of civil engineering applications due to its interesting fresh, hardened, and durability-related properties. 28-day compressive strength is the most important hardened state property and is frequently used as an indicator of the material’s quality. However, early-age mechanical properties are a key factor nowadays to enhance construction planning. Several advanced techniques have been proposed to appraise concrete microstructure and quality, and among those electrical resistivity (ER) is one of the most commonly used since it is a non-destructive and low-cost technique. Although recent literature data have shown that ER may be significantly influenced by a variety of parameters such as the test setup, material porosity and moisture content, binder type/amount and presence of supplementary cementing materials (SCMs) along with the nature of the aggregates used in the mix, further research must be performed to clarify the influence of the raw materials (i.e. SCMs and aggregate nature) on ER using distinct setups. Therefore, this work aims to appraise the influence of the coarse aggregate nature and binder replacement/amount on the concrete ER and compressive strength predictions models through ER. Twenty-four concrete mixtures were developed with two different coarse aggregate natures (i.e. granite and limestone), two different water-to-binder ratios (w/b; i.e. 0.6 and 0.4) and incorporating two different SCMs (i.e. slag and fly-ash class F) with different replacement levels. Moreover, three distinct ER techniques (e.g. bulk, surface, and internal) and compressive strength tests were performed at different ages (i.e. 3, 7, 14, and 28 days). Results indicate that the binder type and replacement amount significantly affect ER and compressive strength. Otherwise, the coarse aggregate nature presented only trivial influence for 0.6 w/b mixes, except for 50% fly-ash replacement samples; whereas for concrete specimens with enhanced microstructure (i.e. 0.4 w/b), the aggregate nature influence was statically significant especially for the binary mixtures with high SCMs replacement levels (i.e. 70% GGBS and 50% fly-ash). Finally, all ER test setups were considered to be quite suitable and reliable NDT techniques correlating themselves very well. Yet the internal resistivity setup demonstrated to be the device which yields the lowest variability amongst them.

No description available.