O presente trabalho teve como objetivo determinar as vantagens e limitações do método geofísico de resistividade capacitiva na identificação de materiais enterrados de diferentes tamanhos e propriedades físicas e em diversas profundidades, localizados no Sítio Controlado de Geofísica Rasa II (SCGR-II), em frente ao IAG-USP. Para isso, a COMGAS, em parceria com o IAG-USP adquiriu o equipamento OhmMapper, possibilitando a aquisição de dados através do método capacitivo. Anteriormente à aquisição dos dados de campo, foram adquiridos os valores de resistividade aparente referentes ao background da área, para então realizar a instalação dos alvos. Após a instalação do sítio controlado, determinou-se a melhor técnica de aquisição em relação ao objetivo proposto, mostrando-se a técnica de aquisição contínua, com marcação de posição a cada 10m a mais adequada para o projeto em questão. Com a definição da melhor técnica de aquisição de dados, foi realizada a modelagem sintética dos alvos para que os resultados fossem confrontados com os obtidos em campo; a modelagem demonstrou que o método sintético utilizado (descrito no item 6.2) é capaz de definir contrastes de resistividade em profundidades inferiores a 0,8m e em alvos que apresentem dimensões de no mínimo 10cm. Para a avaliação do método capacitivo, realizou-se após a aquisição dos dados, uma análise 2D e 3D das anomalias. A análise dos dados reais demonstrou boa correlação com os ensaios sintéticos, exceto para alvos metálicos que apresentaram forte anomalia condutiva, enquanto que os mesmos alvos apresentaram anomalias resistivas no modelo criado. A análise das seções 2D do SCGR-II demonstrou boa resposta do método capacitivo utilizado para a caracterização geoelétrica de tambores de plástico cheios de água, tambores de aço vazios , cano metálico e tubos de cerâmica e PVC com água anomalias condutivas, tambores de plástico vazios, manilhas de concreto de grande diâmetro e vazias, caixa de areia acoplada a tubo vertical de PVC, vasos de cerâmica vazios, caixa com material cerâmico, caixa com brita de granito, tubos de PEAD vazios e tubos de polietileno e PVC de pequeno diâmetro e em até 0,5m de profundidade anomalias resistivas. Os dados 3D sumarizam as anomalias apresentadas nas diversas seções 2D, auxiliando na visualização dos contornos condutivos e resistivos do SCGR-II. Recomenda-se que a caracterização dos alvos pontuais seja, sempre que possível, realizada com o uso mútuo de no mínimo dois equipamentos distintos em suas técnicas e métodos, de forma a se evitar a interpretação precipitada das anomalias observadas e a reduzir os erros implícitos a interpretação, garantindo boa correlação com os dados diretos de campo. / The present work had as objective to determine the advantages and limitations of the capacitive resistivity method in the identification of buried materials with different dimensions, physical properties and located at different depths, at the Shallow Controlled Geophysical Site II (SCGR-II) IAG-USP. For this, the enterprise COMGAS, in partnership with the IAG-USP, acquired the capacitive equipment OhmMapper, enabling a data acquisition through the capacitive method. Previously to the acquisition of field data for the SCGR-II targets, the background apparent resistivity of the area were acquired, and then the targets were installed. After the installation of the targets, several acquisitions of test data were performed to define the best acquisition technique for the proposed objective, showing the technique of continuous acquisition, with mark spacing every 10m, the most appropriate for the project. After setting the best technique data acquisition, a synthetic modeling of the targets was done so that the results were compared with the field data; The modeling showed that the synthetic method used (described in item 6.2) is able to define resistivity contrasts in depths lower than 0.8m and in targets that have dimensions of at least 10cm. For the evaluation of the capacitive method, a 2D and 3D analysis of the anomalies was performed with the field data. The results showed a good correlation with the synthetic model, except to metallic targets that presented strong conductive anomaly, whereas the same targets at the modeling presented resistive anomalies. The analysis of the 2D sections at SCGR-II demonstrated that the capacitive method used for the geoelectric characterization got good responses for water filled plastic drums, empty steel drums, metal pipe and ceramic and PVC pipes with water - conductive anomalies, empty plastic drums, empty concrete sleeves with large diameter, sandbox coupled with a vertical PVC pipe, empty ceramic pots, box with ceramic material, box with crushed granite, empty PEAD pipes and tubes of polyester and small diameter PVC that is located up to 0.5m depth - resistive anomalies. The 3D data summarized the anomalies presented in the 2D sections, contributing to a better evaluation of the conductive and resistive contours observed on the sections of SCGR-II. It is recommended that the characterization of punctual targets, whenever possible, carried out with the mutual use of at least two different equipments which work with distinct techniques and methods, in order to avoid a hasty interpretation of the observed anomalies and to reduce the implicit errors in the interpretation, improving the geophysical correlation with direct field data.

O presente trabalho teve como objetivo determinar as vantagens e limitações do método geofísico de resistividade capacitiva na identificação de materiais enterrados de diferentes tamanhos e propriedades físicas e em diversas profundidades, localizados no Sítio Controlado de Geofísica Rasa II (SCGR-II), em frente ao IAG-USP. Para isso, a COMGAS, em parceria com o IAG-USP adquiriu o equipamento OhmMapper, possibilitando a aquisição de dados através do método capacitivo. Anteriormente à aquisição dos dados de campo, foram adquiridos os valores de resistividade aparente referentes ao background da área, para então realizar a instalação dos alvos. Após a instalação do sítio controlado, determinou-se a melhor técnica de aquisição em relação ao objetivo proposto, mostrando-se a técnica de aquisição contínua, com marcação de posição a cada 10m a mais adequada para o projeto em questão. Com a definição da melhor técnica de aquisição de dados, foi realizada a modelagem sintética dos alvos para que os resultados fossem confrontados com os obtidos em campo; a modelagem demonstrou que o método sintético utilizado (descrito no item 6.2) é capaz de definir contrastes de resistividade em profundidades inferiores a 0,8m e em alvos que apresentem dimensões de no mínimo 10cm. Para a avaliação do método capacitivo, realizou-se após a aquisição dos dados, uma análise 2D e 3D das anomalias. A análise dos dados reais demonstrou boa correlação com os ensaios sintéticos, exceto para alvos metálicos que apresentaram forte anomalia condutiva, enquanto que os mesmos alvos apresentaram anomalias resistivas no modelo criado. A análise das seções 2D do SCGR-II demonstrou boa resposta do método capacitivo utilizado para a caracterização geoelétrica de tambores de plástico cheios de água, tambores de aço vazios , cano metálico e tubos de cerâmica e PVC com água anomalias condutivas, tambores de plástico vazios, manilhas de concreto de grande diâmetro e vazias, caixa de areia acoplada a tubo vertical de PVC, vasos de cerâmica vazios, caixa com material cerâmico, caixa com brita de granito, tubos de PEAD vazios e tubos de polietileno e PVC de pequeno diâmetro e em até 0,5m de profundidade anomalias resistivas. Os dados 3D sumarizam as anomalias apresentadas nas diversas seções 2D, auxiliando na visualização dos contornos condutivos e resistivos do SCGR-II. Recomenda-se que a caracterização dos alvos pontuais seja, sempre que possível, realizada com o uso mútuo de no mínimo dois equipamentos distintos em suas técnicas e métodos, de forma a se evitar a interpretação precipitada das anomalias observadas e a reduzir os erros implícitos a interpretação, garantindo boa correlação com os dados diretos de campo. / The present work had as objective to determine the advantages and limitations of the capacitive resistivity method in the identification of buried materials with different dimensions, physical properties and located at different depths, at the Shallow Controlled Geophysical Site II (SCGR-II) IAG-USP. For this, the enterprise COMGAS, in partnership with the IAG-USP, acquired the capacitive equipment OhmMapper, enabling a data acquisition through the capacitive method. Previously to the acquisition of field data for the SCGR-II targets, the background apparent resistivity of the area were acquired, and then the targets were installed. After the installation of the targets, several acquisitions of test data were performed to define the best acquisition technique for the proposed objective, showing the technique of continuous acquisition, with mark spacing every 10m, the most appropriate for the project. After setting the best technique data acquisition, a synthetic modeling of the targets was done so that the results were compared with the field data; The modeling showed that the synthetic method used (described in item 6.2) is able to define resistivity contrasts in depths lower than 0.8m and in targets that have dimensions of at least 10cm. For the evaluation of the capacitive method, a 2D and 3D analysis of the anomalies was performed with the field data. The results showed a good correlation with the synthetic model, except to metallic targets that presented strong conductive anomaly, whereas the same targets at the modeling presented resistive anomalies. The analysis of the 2D sections at SCGR-II demonstrated that the capacitive method used for the geoelectric characterization got good responses for water filled plastic drums, empty steel drums, metal pipe and ceramic and PVC pipes with water - conductive anomalies, empty plastic drums, empty concrete sleeves with large diameter, sandbox coupled with a vertical PVC pipe, empty ceramic pots, box with ceramic material, box with crushed granite, empty PEAD pipes and tubes of polyester and small diameter PVC that is located up to 0.5m depth - resistive anomalies. The 3D data summarized the anomalies presented in the 2D sections, contributing to a better evaluation of the conductive and resistive contours observed on the sections of SCGR-II. It is recommended that the characterization of punctual targets, whenever possible, carried out with the mutual use of at least two different equipments which work with distinct techniques and methods, in order to avoid a hasty interpretation of the observed anomalies and to reduce the implicit errors in the interpretation, improving the geophysical correlation with direct field data.

While restoring hyporheic flowpaths has been cited as a benefit to stream restoration structures, little documentation exists confirming that constructed restoration structures induce hyporheic exchange comparable to natural stream features. This study compares a stream restoration structure (cross-vane) to a natural feature (riffle) concurrently in the same stream reach using time-lapsed electrical resistivity (ER) tomography. Using this hydrogeophysical approach, I am able to quantify hyporheic extent and transport beneath the cross-vane structure and riffle. I interpret from the geophysical data that the cross-vane and natural riffle induced spatially and temporally unique hyporheic extent and transport, and the cross-vane created both spatially larger and temporally longer hyporheic flowpaths than the natural riffle. Tracer from the 4.67-hr injection was detected along flowpaths for 4.6-hrs at the cross-vane and 4.2-hrs at the riffle. The spatial extent of the hyporheic zone at the cross-vane was 12% larger than at the riffle. I compare ER results of this study to vertical fluxes calculated from temperature profiles and conclude significant differences in the interpretation of hyporheic transport from these different field techniques. Results of this study demonstrate a high degree of heterogeneity in transport metrics at both the cross-vane and riffle and significant differences between the hyporheic flowpath networks at the two different features. Our results suggest that restoration structures may be capable of creating sufficient exchange flux and residence times to achieve the same ecological functions as natural features, but engineering of the physical and biogeochemical environment may be necessary to realize those benefits.

Insulators used in the construction of spacecraft are irradiated with high-energy electrons in the space environment and this sometimes causes the insulators to charge to very high voltages. Such charged insulators can generate spontaneous electric partial-discharge pulses of the order of mA to tens of A. These pulses sometimes last enough time to destroy the expensive micro-circuitry present in the spacecraft. In evaluating the threat to the spacecraft due to these discharges, calculation of the resistivity becomes a critical parameter since it determines how accumulated charge will distribute across the spacecraft and how rapidly charge imbalance will dissipate. So far, resistivity values for the insulators for spacecraft applications have been simply imported from tabulated results measured using standard American Society for Testing and Materials (ASTM) and International Electro-technical Commission (IEC) methods. This thesis work provides the details of the charge storage method which has been found to be more appropriate in calculating the resistivity of spacecraft insulators by emulating the space environment better. This method is based on the concept that the resistivity is better measured as the decay of the charge deposited on the surface of an insulator, rather than by the flow of current across two electrodes around the sample which is the case with the classical method of measurements. From the results obtained from the charge storage method, it has been found that the ASTM resistivity values for thin film insulating spacecraft materials have been found to under-predict charge transport values applicable to many spacecraft charging problems, by 10 to 104 times. The charge storage method has only one side of the insulator in vacuum exposed to charged particles, light and plasma, with a metal electrode attached to the other side of the insulator. The chamber for measuring the charge storage decay has been designed with the capability to measure 32 samples simultaneously. The details of the apparatus, instrumentation, test methods, data acquisition methods, and data analysis for measuring resistivity of the spacecraft insulators are given here. Details about the vacuum environment, sample mounting, isolation of the samples, charging of the samples, measurement of the surface charge, rotary motion of the sample carousel, etc., are also given. The report also includes differences between the classical methods and the charge storage method both in terms instrumentation and methodology. The results obtained from both methods are tabulated showing the superiority of the charge storage method. Recommendations for future work are also included.

The purpose of this research project was to identify the extent that concrete resistivity measurements (bulk and/or surface) can be used as a performance based lab test to improve the quality of concrete in Utah bridge decks. By allowing UDOT to specify a required resistivity, concrete bridge deck quality will increase and future maintenance costs will decrease. This research consisted of two phases: the field phase and the lab phase. In the field phase, concrete samples were gathered from local concrete producers in Utah. These concrete samples were made with common concrete mixes used in bridge decks across the state of Utah. Testing multiple mix designs allowed the research team to investigate several variations of concrete constituents, for instance, water to cement ratio, common Utah supplementary cementitious materials, curing type, and aggregate type. Mechanical and durability testing was performed on concrete of different ages. These tests included strength, surface resistivity, bulk resistivity, rapid chloride permeability, and freeze and thaw tests. In the lab phase, one of the field mixes was selected as the control mix. This mix was then duplicated in the lab in order to see the performance differences of each mix in the controlled and field experiments. In addition, changes were made to the lab control mix, to see the effect of different materials on the resistivity and durability of concrete.

A bulk silicon temperature sensor is fabricated in this work. The objective is to develop a low-cost high resolution temperature sensor. The target applications are a Conductivity-Temperature-Depth (CTD) sensor for oceanic applications and a magnetocaloric microcooler. The properties of silicon are modified by thermal diffusion of gold. Gold is a fast diffuser in silicon and its diffusion contributes to the increase in resistivity of silicon. The addition of gold to n-type silicon creates a negative temperature coefficient device. The effect of the diffusing environment was investigated by diffusing in oxygen and nitrogen ambient at various temperatures. The influence of area of gold diffusion was also investigated. The effect of temperature on resistance was measured and was used to calibrate the sensor. Although the sensors fabricated in an oxygen environment have an exponential type response, they can be used in the CTD application because of enhanced sensitivity in the 10˚C - 30˚C temperature range. Sensors fabricated in a nitrogen environment are found to have linear response with sensitivity ranging from 7Ω/˚C to 3000Ω/˚C and can be used for both applications. The fabricated sensors have a 0.1˚C resolution.

The most common method of monitoring and mapping groundwatercontaminants is to extract and analyse a number of groundwatersamples from wells in the investigation area. However, thereare a number of limitations with this type of point-wiseinvestigation, as it is hard to acquire an adequate picture ofa heterogeneous and anisotropic subsurface using a fewpoints. To overcome the limitations of point investigations and toimprove ground monitoring investigations in a cost-effectiveway, support can be provided by direct current resistivitymeasurements, which give a characterisation of the electricalproperties of a ground volume. The main objective with this work was to investigate theusability of the resistivity method as a support in monitoringgroundwater contaminants in glaciated terrains and underdifferent seasons, both in long-term monitoring programmes andintracer tests. The work comprised field investigations at several differentsanitary landfills and four tracer tests in differentgeological environments, around the Stockholm region. The maininvestigations have been done at Högbytorp, Stockholmwhich has been used for long-term investigations of theresistivity variation, together with a field set up formonitoring and measurements on seasonal variation in soilmoisture, ground temperature and precipitation. It can be concluded that the use of resistivity measurementssupplies valuable information in the case of mapping andmonitoring conductive groundwater contaminants andfurthermore: The variation in resistivity (in shallow investigations<1 m) can be extensive between different seasons (around30 % compared to a mean value in till and clay soils) andshould be considered, so that anthropogenic affects can beseparated from natural resistivity variation. For deeperinvestigations (>5 m) the seasonal resistivity variationwas more moderate (around 15% compared to a mean value intill and clay soils). Soil moisture variation shows a strong relationship toresistivity variation in the investigated clay and tillsoils. Together with temperature correction 47 to 65% of thevariation has been explained. Three types of monitoring systems can be applied:Permanently installed, partly installed and fully mobilesystems. For the actual measurements, all three types can useeither high-density techniques such as CVES (ContinuousVertical Electrical Sounding) or low-density measuring withone or some different electrode spacings. The suggested evaluation tool for monitoring programmesshowed that it was possible to detect a decrease of 15 % inthe mean value at a specific site using Modified Double Masscalculations between resistivity time series and time seriesat a reference site with a comparable seasonalvariation. Resistivity measurements may be used as a valuablecomplement to groundwater sampling in tracer tests. Adecrease in resistivity, a minimum and a recovery phasereflect the passage of a NaCl-solution, which can be used toestimate flow velocity and flow patterns of the investigatedaquifer. The achieved recovery of NaCl in the tracer testscarried out was estimated to 20 to 70 %. The measurement system for long-term monitoring or tracertests, which should be chosen with regard to layout andfrequency, depends on the purpose of measurement and onsite-specific conditions and therefore no standard solutioncan be proposed. Key words:Resistivity, Direct Current, Monitoring,Groundwater, Contaminant, Tracer test, Geophysics.

The grain-size dependences of thermal conductivity and electrical resistivity of polycrystalline and nanocrystalline nickel were measured by the flash method and four-point probe method, respectively. Nanocrystalline nickel was made by the pulsed-current electrodeposition process, while polycrystalline nickel was commercially available Ni 200 in annealed condition. The grain sizes of the materials examined ranged from 28 nanometers to 57 micrometers. Noticeable changes in thermal conductivity and electrical resistivity with grain size were observed in particular for samples with grain sizes less than 100 nm. These results can be explained on the basis of the rapid increase in the intercrystalline grain boundary and triple junction volume fractions at very small grain sizes. The relationship between thermal conductivity and electrical resistivity of nanocrystalline nickel follows the classic Wiedemann-Franz law.

The grain-size dependences of thermal conductivity and electrical resistivity of polycrystalline and nanocrystalline nickel were measured by the flash method and four-point probe method, respectively. Nanocrystalline nickel was made by the pulsed-current electrodeposition process, while polycrystalline nickel was commercially available Ni 200 in annealed condition. The grain sizes of the materials examined ranged from 28 nanometers to 57 micrometers. Noticeable changes in thermal conductivity and electrical resistivity with grain size were observed in particular for samples with grain sizes less than 100 nm. These results can be explained on the basis of the rapid increase in the intercrystalline grain boundary and triple junction volume fractions at very small grain sizes. The relationship between thermal conductivity and electrical resistivity of nanocrystalline nickel follows the classic Wiedemann-Franz law.

Presented in this thesis are two studies that apply nondestructive testing methods to civil engineering problems. The first study examines the relationship between the small-strain and large-strain properties of exhumed cast iron water pipes. Nondestructive and destructive testing programs were performed on eight pipes varying in age from 40 to 130 years. New applications of frequency domain analysis techniques including Fourier and wavelet transforms of ultrasonic pulse velocity measurements are presented. The effects of Lamb wave propagation on the ultrasonic testing results are investigated. Microstructure evaluation revealed two different types of cast iron within the pipes sampled: grey cast iron and ductile iron. A low correlation between wave propagation and large-strain measurements was observed. However, the wave velocities were consistently different between ductile and grey cast iron pipes (14% to 18% difference). Lamb waves were found to contribute significantly to the frequency content of the ultrasonic signals possibly resulting in the poor correlations observed. Therefore, correlations between wave velocities and large strain properties obtained using samples from exhumed water pipes must be used with caution in the condition assessment of aged water pipes especially for grey cast iron pipes. The second study presented in this thesis was performed to evaluate the effectiveness of three geophysical methods for geotechnical site characterization in swamps and environmentally sensitive wetland areas. The geophysical methods evaluated were electrical resistivity imaging (ERI), seismic refraction (SR), and multiple-channel analysis of surface waves (MASW). The geophysical test results were verified against the results from borehole and CPT logs. The ERI results were best for determining the depth to the glacial till. The SR results overestimated the depth to the till because of the presence of a stiffness reversal. The MASW results predicted the depth to the refusal till layer less accurately than the ERI method. However, this method was able to detect the three distinct layers above the till. These methods can be used as a basis for further development to optimize a procedure to reduce the number of boreholes required for conventional site investigations in areas that are environmentally sensitive or where access is restricted.