220 resultados para Resistividade


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Pós-graduação em Química - IQ

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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In this work we study the behavior of the falling motion of neodymium magnets, inside conductive a metallic duct made of copper, aluminum, brass and bronze. We obtain, analyze and present results involving relationships between material and dynamical properties of falling neodymium magnets with the mechanical and electrical properties of conductive materials, such as mass, electrical resistivity, electrical conductivity, length and external diameter

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The contamination of the physical environment occurs as a result of the lack of planning and inadequate management of hazardous products. Due to the difficulty of the characterization and study of soil and groundwater, the contamination has been long neglected. The characterization of these areas by research techniques through direct methods such as physical and chemical analysis, are widely used in the diagnosis and monitoring. However, despite presenting quantitative results, this method is not representative in spatial terms. The purpose of this work is to bring geophysical complementation with the diagnosis, bringing the spatial element for the detection of the contamination plume. In the study area, there was a railway accident in 1999 in which three wagons fell and spilled 240,000 L of diesel onto the soil. The main objective is to assess the presence of contaminants in the residual phase and dissolved in the subsurface, using the technique of Electrical Tomography (ETR), understand the effects of natural attenuation process in the degradation of hydrocarbons and changes in electrical properties in soil and groundwater. The results allowed the definition of three distinct patterns of resistivity region with presence of dissolved phase, set in a historical chemical analyzes: low values (> 60Ω.m) associated with the presence of hydrocarbons in an advanced stage of degradation, intermediate values (260Ω.me 511Ω .m) indicative of coexistence of residual hydrocarbons and dissolved phase, and high values (> 1000Ω.m), which reveal the prevalence of residual phase with incipient degradation, possibly in high toxicity concentrations for effective action of biodegradation processes. The diagnostic of areas with potential accumulation of residual phase can subsidize the planning of remediation techniques and promote the complete decontamination of the area

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Geophysical survey is an important method for investigation of contaminated areas used in the characterization of contrasting physical properties in the presence of pollutants. This work applied the geophysical methods of Electrical Resistivity and Self Potential in waste landfill, located in Caçapava do Sul city, RS. The landfill is located over fractured metamorphic rocks. Eight lines of electrical profiling with 288 measures of self potential were done. In addition, 83 measurements of direction and dip of fractures were taken. The application of spontaneous potential method permitted to detect the direction of groundwater flow. The electrical resistivity measurements allowed the identification of low-intensity anomalies associated with the presence of leachate. There is a relationship between anomalous zones and the directions of fractures.

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Currently has few studies today concerning the behavior of the ethyl alcohol hydrated combustible in the geological environment, results of eventual spill or leaks in a wide transport chain and distribution. This work discusses the results of an experiment in laboratorial scale, that involves the monitoring of alterations in physical properties a simulate leak of alcohol in a tank with sand saturated in water, during 4920 hours. Are applied electrical resistivity, induced polarization and spontaneous potential geophysical methods. The electric resistivity is clearly correlating to the ethanol degradation pattern. The chargeability demonstrated sensibility to this pattern, while the natural electric potential revealed direct association with the oscillations of groundwater level. The variability of the physical parameters monitoring probable control for ethanol degradation process in environment study.

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The geophysical methods may be employed in aquifer system studies, as determination of groundwater level, soil/rock contact, beyond estimative of the aquifer thickness horizon. The geoeletric methods are particularly relevant in evaluations of the oilfields systems, due to directs relations between porosity and electrical resistivity, which allow inferences about oil and gas production. The indirect estimative of the productions in free aquifers system is something complex before of the diverse variables responsible for factors or physical phenomena, as clays minerals, which conditioned the physical parameters by electric geophysical methods. This paper present analyzed correlation among electrical resistivity, chargeability and direct measure flow in shallow wells, for determination of statistical relationships between parameters and evaluation of the geological constraints evolved. The study count with the 23 shallow wells located in free aquifer, constituted by alteration materials of the granites localized in Caçapava do Sul (RS). The geophysical data are acquired by vertical electric sounding in Schlumberger array. The correlations between electrical resistivity and flow, chargeability and flow, thickness of the soil/saprolite and flow indicated relationships between physical and hydrogeologic parameters, with variations conditioned by factors as porosity, permeability, besides intrinsic geological heterogeneities such soil variable thickness and rock fragments with several alteration degrees.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Geophysical methods are widely used in mineral exploration for several types of mineral deposits. When combined with direct studies as geochemistry, a substantial increase in the probability of ore discovery is possible in mineral exploration activities. Electrical geophysical methods are particularly promising in studies related to the search of sulphides due to the contrast of physical properties electric resistivity and chargeability. This paper presents the results obtained from the application of Resistivity (DC) and Induced Polarization methods, through the electrical profiling technique, aiming at evaluating the potential mineral of a gabbro intruded in a metasedimentary sequence, in an area where several occurrences of gold and copper were described. This gabbro is ranked on the Basic-Ultrabasic stratiform bodies, which gather peridotites, gabbros, and layered anortosites. Three radial lines of electrical profiling were performed, spaced of 60° and crossing at the area center, with readings of electric resistivity and chargeability in Wenner-Schlumberger array. The association of low resistivity and high chargeability areas has allowed defining potentially mineralized zones related to structures that condition the drainage net in the gabbro domain. Grains of gold detected through geochemical prospection of alluvial sediments dowstream from the gabbro may have originated from leaching of ores deposited in fractures through the action of river waters within the gabbro domain, possibly consisting of sulphides and gold.

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The mineral sector is of utmost importance for Brazilian economic growth, an area which depends on basic geological research to enlarge known deposits and in process of mining, besides discovering new occurrences and mineral deposits. This set of activities is named mineral research, which planning involves economy concepts, market demands and use of methods and techniques for geological evaluation, direct and indirect. This paper aim at performing geophysical detailing on occurrences of supergenic manganese located in the northwest portion of the State of São Paulo, Itapira, for spatial dimensioning of mineral targets, besides the attempt to correlate among the content on physical parameter measured by geophysics. The lack of scientific publications by Brazilian researchers in this theme, availability of previous studies for the selected targets, commercial importance of the mineral goods for the Brazilian Trade Balance, justify the performance of the present research project

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Interventions in nature made by man are very common since the beginnings of human history, especially in the case regarding the storage of water. The construction of dams have been and still are fundamental in maintaining human life due to the vital importance that water plays. The size of these structures vary according to need, such as water catchment, fish-farming or electricity generation. Embankment dams are the most common type of these structures. Can be defined as dams natural material obtained from loan chambers located near the dam site. This type of barrier may be divided into earth dams and rockfill dams. The study area covers an earth dam located in Cordeirópolis (SP) and is essentially composed of diabases altered soil of the Serra Geral Formation of the Paraná Basin. With the aid of geophysics, more specifically of the Electrical Resistivity method, the aim is to check any water infiltration zones in the dam's body. Given the risks associated with water seepage in earth dams, that may generate breakdown structures, erosion, and consequently accidents and / or harmful factors in the nearby areas. One of the main structural problems married by water infiltration is the possible generation of pipes that could jeopardize the dam structure. This work aims to contribute towards the evaluation of the effectiveness of using an indirect technique of research and monitoring in aid to direct research techniques such as piezometers and drive stakes. The results are presented in the form of 2D and 3D geophysical models, the analysis shows a low resistivity zone with typical values of the presence of humidity originating upstream of the dam and downstream bottleneck trend, that are the basis for interpretation by percolation or not water in the dam