Orientador: Antonio Celso de Oliveira Braga / Banca: Vagner Roberto Elis / Banca: César Augusto Moreira / Resumo: Estudos ambientais envolvendo investigação e mapeamento do meio geológico por meio de métodos geoelétricos apresentam resultados satisfatórios para contaminantes iônicos (chorume) que sugerem eficácia no emprego desses métodos em situações que apresentem alterações dos componentes do subsolo devido à presença de combustíveis, como o etanol. Integrando a aplicação dos métodos geofísicos da eletrorresistividade, polarização induzida e potencial espontâneo, por meio das técnicas de caminhamento elétrico e perfilagem elétrica foi monitorada a variação temporal dos parâmetros físicos resistividade, cargabilidade elétrica e potencial espontâneo em sedimentos arenosos alterados devido à contaminação controlada de etanol, contidos em um tanque de monitoramento. O tanque de monitoramento contém um sistema de controle do nível de saturação, possibilitando análises das variações nos parâmetros geoelétricos investigados em dois extratos geoelétricos: insaturado e saturado. O presente trabalho objetiva avaliar o comportamento do etanol num experimento que simula condições hidrogeológicas reais, bem como caracterizar as variações temporais nos parâmetros geoelétricos analisados. Este tipo de pesquisa objetiva também a geração de subsídios técnico/científico que auxiliem a compreensão de estudos de caso em ambientes naturais / Abstract: Environmental studies involving research and mapping of geological environment by geoelectrical methods present satisfactory results for ionic contaminants (leachate) that suggest effectiveness in their use in situations that present changes in components of the basement due to the presence of fuels such as ethanol. Integrating the application of geophysical methods of resistivity, induced polarization and spontaneous potential, through the techniques of electrical profiling and electrical profiling was monitored temporal variation of physical parameters, resistivity, chargeability and electrical spontaneous potential in sandy sediments changed due to contamination of controlled ethanol contained in a tank monitoring. The tank contains a monitoring system to control the saturation level, allowing analysis of variations in geoelectrical parameters investigated in two extracts geoelectrical: unsaturated and saturated. This study aims to evaluate the behavior of ethanol in an experiment that simulates actual hydrogeological conditions and to characterize temporal variations in geoelectrical parameters analyzed. This type of research also aims to generate subsidies technical / scientific understanding to help the case studies in natural environments / Mestre

Molibdatos têm atraído grande atenção devido à existência de compostos com caráter elétrico unidimensional como conseqüência da presença de cadeias contendo ligações de Mo-O ou Mo-Mo em suas estruturas cristalinas. Com o objetivo de estudar molibdatos com esta característica, amostras policristalinas do sistema K-Mo-O foram preparadas pelo método de reação de difusão no estado sólido e caracterizadas por difratometria de raios x, propriedades elétricas e magnéticas. Estes resultados demonstram a existência de uma nova fase neste sistema com estequiometria KxMoO2-&#948;. Medidas da resistência elétrica em função da temperatura deste material mostram comportamento metálico anômalo que está relacionado a um ordenamento antiferromagnético. Foi observado ainda que a anomalia na resistência elétrica em baixas temperaturas (T < TM) comporta-se segundo uma lei de potência com expoente próximo de 0,5, o que sugere que o comportamento elétrico do KxMoO2-&#948; pode ser descrito por um mecanismo de condutividade unidimensional. / Molybdates have attracted great attention due to the existence of compounds which show one-dimensional electrical behavior as consequence of the channel containing Mo-O or Mo-Mo bonds in their crystalline structure. In order to study molybdates exhibiting onedimensional conductivity, polycrystalline samples of the K-Mo-O system were prepared using the solid state diffusion reaction method and characterized by X-ray powder diffractometry, electrical and magnetic properties. These results demonstrate the existence of a new phase in this system with KxMoO2-&#948; stoichiometry. Electrical resistance as a function of temperature measurements for this compound have shown anomalous metallic behavior which is related to an antiferromagnetic ordering. It has been also observed that the anomaly in the electrical resistance at low temperatures (T < TM) is fitted by power law temperature dependence with an exponent near 0.5 which suggests that the electrical behavior of the KxMoO2-&#948; can be well described by the one-dimensional conducting mechanism.

Molibdatos têm atraído grande atenção devido à existência de compostos com caráter elétrico unidimensional como conseqüência da presença de cadeias contendo ligações de Mo-O ou Mo-Mo em suas estruturas cristalinas. Com o objetivo de estudar molibdatos com esta característica, amostras policristalinas do sistema K-Mo-O foram preparadas pelo método de reação de difusão no estado sólido e caracterizadas por difratometria de raios x, propriedades elétricas e magnéticas. Estes resultados demonstram a existência de uma nova fase neste sistema com estequiometria KxMoO2-&#948;. Medidas da resistência elétrica em função da temperatura deste material mostram comportamento metálico anômalo que está relacionado a um ordenamento antiferromagnético. Foi observado ainda que a anomalia na resistência elétrica em baixas temperaturas (T < TM) comporta-se segundo uma lei de potência com expoente próximo de 0,5, o que sugere que o comportamento elétrico do KxMoO2-&#948; pode ser descrito por um mecanismo de condutividade unidimensional. / Molybdates have attracted great attention due to the existence of compounds which show one-dimensional electrical behavior as consequence of the channel containing Mo-O or Mo-Mo bonds in their crystalline structure. In order to study molybdates exhibiting onedimensional conductivity, polycrystalline samples of the K-Mo-O system were prepared using the solid state diffusion reaction method and characterized by X-ray powder diffractometry, electrical and magnetic properties. These results demonstrate the existence of a new phase in this system with KxMoO2-&#948; stoichiometry. Electrical resistance as a function of temperature measurements for this compound have shown anomalous metallic behavior which is related to an antiferromagnetic ordering. It has been also observed that the anomaly in the electrical resistance at low temperatures (T < TM) is fitted by power law temperature dependence with an exponent near 0.5 which suggests that the electrical behavior of the KxMoO2-&#948; can be well described by the one-dimensional conducting mechanism.

In regions where chloride-based deicing salts are applied to bridge decks, corrosion of the interior steel reinforcement is a major problem. Vertical electrical impedance (VEI) is an effective measurement technique to quantitatively assess the cover protection on bridges against aggressive chemical penetration of reinforced concrete. In its current form, traditional vertical electrical impedance is time-consuming and destructive because a direct connection to the reinforcing steel is required to provide a ground reference. A new method using a large-area electrode (LAE) permits VEI measurement without a direct electrical connection to the steel reinforcement. The LAE creates a nondestructive, semi-direct, low impedance connection between the measurement electronics and the reinforcing steel. In this work, numerical simulations are performed on common electrode arrangements to demonstrate the effectiveness of the LAE when significant variations in concrete conductivity exist. Physical experiments of a large-area electrode are carried out in the laboratory and field to validate the numerical simulations and to provide additional comparisons with the traditional tapped steel reinforcement method. The results of this study are a set of important design considerations for VEI utilizing a LAE to connect to the underlying rebar. Using these design considerations, the large-area electrode method was validated using both an analytical and a finite-element model, laboratory experiments, and field experiments on two bridges in Utah. The validation results indicate the LAE can replace the direct connection to the reinforcing steel. As a result of this work, a multichannel VEI scanner which uses the LAE method was built which can provide VEI information for bridge engineers and managers to better rehabilitate deteriorating reinforced concrete.

Meadows in the Sierra Nevada Mountains are an important ecological resource that have degraded in quality and distribution due to several environmental and anthropogenic stressors. The encroachment of conifers beyond forest meadow ecotones is largely responsible for the decline of meadow habitat throughout the past century. Currently, there is little research that quantifies the hydrologic response to removal of conifers encroaching meadows in terms of implicating successful meadow restoration. This study has implemented a before after control intervention (BACI) study design to determine the hydrologic response associated with the removal of conifers from a historic meadow encroached by conifers. The primary goals of this research were to: (1) establish a method to evaluate the weekly water balance of an encroached meadow before and after conifer removal (restoration) (2) characterize the hydrology of an encroached meadow and a nearby control meadow prior to restoration (3) assess the effectiveness of electrical resistivity tomography in improving the spatial interpretation of subsurface hydrology on our study site. A water budget approach was developed to quantify the hydrology of a control and study meadow (Marian Meadow) before and after restoration. In order to determine weekly changes in groundwater depth, 14 Odyssey water level capacitance instruments were installed to a 1.5 meter depth in PVC wells. In order to quantify changes in soil moisture storage, 14 soil moisture probes were installed to a ~1 ft (30 cm) depth. Both sets of instruments were installed using a spatially balanced random sampling approach. Electrical resistivity tomography was conducted on both meadows on three separate dates during: September 9-10 2013, May 5 2014 and September 6-7 2014. A method to quantify runoff from a stream that drains Marian Meadow (Marian Creek) was also established. The Priestley Taylor model was used to estimate daily evapotranspiration from both meadows. Electrical resistivity tomography improved the spatial interpretation of groundwater recharge and facilitated the use of a recession curve analysis to model groundwater recharge when the water table receded beyond instrument detection depths. Electrical resistivity also demonstrated a change in hydrologic characteristics across a forest –meadow ecotone. Analysis of the pre-removal hydrologic characteristics from September 2013 to December 2014 indicates that Marian Meadow may be a favorable candidate for restoration (in terms of hydrology). On Marian Meadow, volumetric soil moisture was higher than the Control Meadow from May-November 2014. Sufficient soil moisture in the summer months is thought to be critical to the maintenance of endemic meadow flora. The water table depth on Marian Meadow and the Control Meadow was similar throughout the analysis period, but Marian Meadow had a shallower water table during the summer months. The Control Meadow had near surface groundwater during short periods from February-April 2014 and December 2014. If conifer removal from Marian Meadow causes an increase in seasonal volumetric soil moisture and a decrease in seasonal groundwater depth, an augmented version of the stable hydrologic system already present on Marian Meadow may result in hydrologic conditions more favorable to meadow restoration.

Orientador: Walter Malagutti Junior / Resumo: Os cemitérios atualmente são considerados como potenciais fontes de contaminação, principalmente para as águas subterrâneas. Isso é devido ao líquido produzido durante a decomposição dos cadáveres, denominado necrochorume. Este trabalho investigou uma possível contaminação por necrochorume no subssolo do cemitério da Saudade situado no município de Monte Alto – São Paulo, Brasil. Assim foi aplicado o método da eletrorresistividade, técnica de imageamento elétrico, utilizando três tipos clássicos de arranjos: wernner, schlumberger e dipolo-dipolo. Com o intuito de também comparar os resultados gerados por cada tipo de arranjo. A técnica da sondagem elétrica vertical (SEV) foi utilizada para se indicar a profundidade do nível freático e o fluxo subterrâneo, que foram de 10 m e sentido SW respectivamente. Além da aplicação desses métodos geofísicos, foi realizada uma pesquisa documental nos registros de sepultamentos do cemitério. Obtendo-se um mapa que indica as quadras com maiores números de sepultamentos do cemitério. As seções (2D) resultantes das linhas de imageamento elétrico dos três tipos de arranjo, são muito semelhantes, com algumas poucas diferenças significativas para o arranjo dipolo-dipolo, principalmente em níveis mais profundos. As seções confirmam a presença de áreas de baixa resistividade que contrastam com o restante do meio, indicando possíveis alterações do meio físico causadas pelo necro-chorume. Para visualização em 3D e em mapa, foram confeccionados mapas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Actually, cemeteries are considered as potential sources of contamination, especially for underground water. This is due to the liquid produced during the decomposition of the corpses, called necrochorume. This work investigated a possible contamination by necro-manure in the subsoil of the Saudade cemetery located in the city of Monte Alto - São Paulo, Brazil. Thus, the method of electro resistivity was applied (eletric resistivity tomography), using three classical types of arrays: wernner, schlumberger and dipole-dipole. In order to also compare the results generated by each type of array. The technique of vertical electric sounding (SEV) was used to indicate the depth of the groundwater and the underground flow, which were 10 m and SW direction respectively. In addition to the application of these geophysical methods, a documentary research was carried out in the book records of the cemetery. Obtaining a map that indicates the blocks with greater numbers of burials of the cemetery. The sections (2D) resulting from the electric resistivity tomography, of the three types of arrays, are very similar, with a few significant differences for the dipole-dipole array, especially at deep levels. The sections confirm the presence of areas of low resistivity that contrast with the rest of environment, indicating possible changes in the physical environment caused by the necro-manure. For 3D and map visualization, maps of various levels of depth were made for the results of each arra... (Complete abstract click electronic access below) / Mestre

Electrical contacts to devices which pose low resistance continue to be of interest as the dimensions of devices decrease and nanotechnology demands better means of creating electrical access. Continued improvement in the performance of ohmic contacts requires techniques to better characterise and quantify the performance of such contacts. In order to study and estimate the resistance of such contacts or the resistance posed by the interface(s) in such contacts, accurate test structures and evaluation techniques need to be used. The resistance posed by an interface is quantified using its specific contact resistivity (SCR), which is denoted using ƒâc (units: £[cm2). Cross Kelvin resistor (CKR) test structures have been used for the measurement of low values of SCR. A simplified approach to this problem of SCR evaluation (developed previously at RMIT University) using the CKR test structures with varying contact sizes was used and during this work was shown to be accurate for the estimation of low values (less than10-8 £[cm2) of SCR. The silicides of interest in this study were titanium silicide (TiSi2) and nickel silicide (NiSi). These thin films are known for their low resistivity and low barrier heights to both n-type and p-type silicon. The research involved thin film formation and substantial materials characterisation of these thin films. The silicide thin films were formed by vacuum annealing metal thin films on silicon substrates. Silicide thin films formed from metal films deposited by DC magnetron sputtering and electron beam evaporation were compared. The composition, crystallographic orientation, and morphology of these thin films were studied using spectroscopy (AES, SIMS, RBS, in situ Raman spectroscopy), diffraction (Bragg-Brentano and glancing angle XRD, RHEED), and microscopy techniques (TEM, SEM, and AFM). TiSi2 and NiSi thin films were also found to be suitable for microsystems fabrication due to their ability to withstand wet etching of silicon using potassium hydroxide. The SCR of aluminium-titanium silicide ohmic contacts was evaluated to be as low as 6 x 10-10 ƒÇcm2, which is the lowest reported for any two- layer single-interface contact. Characterisation of ohmic contacts comprising of aluminium, nickel silicide, and doped silicon (with shallow implants) were also carried out using the same technique. SCR values as low as 5.0 x 10-9 ƒÇcm2 for contacts to antimony-doped silicon and 3.5 x 10-9 £[cm2 to boron-doped silicon were evaluated.

<p>Broadband extremely low-frequency wave emissions below the ion plasma frequency have been observed by a number of spacecraft and rockets on auroral field lines. The importance of these broadband emissions for transverse ion heating and electron acceleration in the auroral regions is now reasonably well established. However, the exact mechanism(s) for mediating this energy transfer and the wave mode(s) involved are not well known. In this thesis we focus on the identification of broadband waves by different methods. </p><p>Two wave analysis methods, involving different approximations and assumptions, give consistent results concerning the wave mode identification. We find that much of the broadband emissions can be identified as a mixture of ion acoustic, electrostatic ion cyclotron and, ion Bernstein waves, which all can be described as different parts of the same dispersion surface in the linear theory of waves in homogeneous plasma. </p><p>A new result is that ion acoustic waves occur on auroral magnetic field lines. These are found in relatively small regions interpreted as acceleration regions without cold (tens of eV) electrons.</p><p>From interferometry we also determine the phase velocity and k vector for parallel and oblique ion acoustic waves. The retrieved characteristic phase velocity is of the order of the ion acoustic speed and larger than the thermal velocity of the protons. The typical wavelength is around the proton gyro radius and always larger than the Debye length which is consistent with ion acoustic waves. </p><p>We have observed quasi-static parallel electric fields associated with the ion acoustic waves in regions with large-scale currents. Waves, in particular ion acoustic waves, can create an anomalous resistivity due to wave-particle interaction when electrons are retarded or trapped by the electric wave-field. To maintain the large-scale current, a parallel electric field is set up, which then can accelerate a second electron population to high velocities.</p>

The currently accepted method for assessing the resistance of concrete to penetration of chloride ions is ASTM C1202, commonly known as the “Rapid Chloride Permeability (RCP) Test.” The test is time-consuming, laborious, has rather high variability, and, is to a degree, user sensitive, making it problematic for inclusion in a performance-based specification. A potential alternative to the RCP test is the “Surface Resistivity (SR) Test”, a method which is dramatically easier, faster, and has less variability than the RCP test. The research reported herein was directed toward determining a correlation between RCP and SR test measurements for Tennessee bridge deck concrete, based on cylinders collected from concrete bridge decks being constructed across the state, and evaluating the appropriateness of the SR test as an alternative to the RCP test for inclusion in a performance-based specification. Results of the testing showed a clear correlation between the two methods and identified potential limits for possible inclusion in a performance-based specification.

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