Resumo em Inglês:

Abstract This article proposes a testing device to quickly and reliably estimate the gas permeability of bentonite-based clay barriers used in landfill cover systems. The testing methodology is based on a transient gas flow regime that passes through the barrier, therefore not requiring the use of sophisticated equipment that aim to maintain constant differential pressure and measure the gas flow, common requirements for testing methods under a permanent flow regime. To confirm the feasibility of the proposed technique, tests were performed on a pure hydrated bentonite layer, which subsequently encompassed samples of geosynthetic clay liner (GCL) at different moisture contents. Geosynthetic clay liners are often selected as a part of the barrier layer for cover systems in solid waste landfills to prevent infiltration of rainfall and migration of biogas into the atmosphere. The results confirmed the equipment reliability and differentiate the different responses of the gas flow barriers studied, considering their different compositions and different moistures.

Resumo em Inglês:

Abstract The Pedra Dourada Granulite (PDG) occurs at the southeastern portion of the Araçuaí Belt, north of the town of Ponte Nova. It comprises bodies up to 45 km2 inserted into amphibolite-facies gneisses of the Mantiqueira Complex. Motivated by the discrepancy of metamorphic grade with surrounding rocks, this paper presents results of the petrographic and geochemical investigation of the PDG. The unit is comprised of meta-igneous and metasedimentary rocks. Meta-igneous rocks dominate and include felsic granulites (biotite ± garnet-bearing and orthopyroxene-bearing) and subordinate mafic granulites. Metasedimentary rocks are aluminous granulites with Al-rich mineral assemblages (garnet, sillimanite, spinel). Geochemical data show that most of felsic protoliths are peraluminous rocks including granites, granodiorites and diorites of calc-alkaline character, chemically similar to granitoids of convergent tectonic settings. Mafic protoliths are metaluminous rocks comprised of gabbros and subordinate diorites of tholeiitic affinity, compositionally similar to plate margin basalts. Aluminous protoliths may be peraluminous pelitic rocks and wackes, analogous to sediments from convergent environments. The mineral assemblages indicate that these rocks were metamorphosed under medium-P granulite-facies conditions. Coronitic garnet textures suggest a near-isobaric cooling (IBC-path) after metamorphic peak.

Resumo em Inglês:

Abstract Reservoir static modelling plays a fundamental role in the evaluation phase of a petroleum field. Integrated modelling allows a better understanding of how the local geology and depositional systems are related through the distribution of facies and petrophysical properties within the reservoir. In this study, geological static models of the siliciclastic Carapebus Formation of Campos Basin were built using subsurface data. The applied methodology was divided into five phases: (1) establishment of a conceptual model, (2) building of a structural model, (3) generation of 100 realizations of lithofacies using sequential indicator simulation, (4) generation of 100 realizations of porosity and permeability using sequential Gaussian simulation, and (5) validation of models by targeting both statistical and geological consistency. The obtained models are consistent and honor the conditioning data. A lithofacies constraint is crucial to better characterize the petrophysical properties distribution of the reservoir. A Dykstra-Parsons coefficient of V=0.52 characterizes this reservoir as moderately homogeneous.

Resumo em Inglês:

Abstract Soil erosion is a major problem observed in terrestrial ecosystems. Monitoring and identifying potential areas for erosion becomes extremely important for the better management of these areas. The main aim of this study was to develop a Geographic Information System script tool based on the universal soil loss equation (USLE), which calculates soil loss in three large agricultural sub-basins. Algorithms were implemented in the graphical interface of ModelBuilder and later in Python programming language, thus allowing the creation of a specific script to calculate soil loss in an automatic way. The "USLE Paracatu Watershed" script was validated and proved to be effective in estimating erosion in the three sub-basins with an average processing time of half second per km2. This can be added via "ArcToolbox" toolbox in ArcGIS software, so that the user only has to add the variables of the USLE equation and the software will process the algorithms in an automatic way, generating the final map with the soil loss value (t/ha.year). The friendly interface of the script allows it to be used in any area, only requiring the user to enter the updated data of parameters that compose the equation.

Resumo em Inglês:

Abstract Industrialized closing systems appear as rational solutions in steel-structured construction. These closing systems, consisting of multi-layered panels, have been applied in projects where it is intended to obtain a high sound transmission loss without raising the cost and without using a lot of mass. However, acoustic isolation depends on several factors, including the type of connection between the panels, requiring a preliminary study of the acoustic performance of the closing system to prevent future interventions. This paper uses a simplified graphical method to evaluate the influence of the type of connection (line-line, line-punctual or punctual-punctual) of industrialized closing panels on the estimation of the sound transmission loss that occurs across the wall constituted by these panels. The panels are combined, forming multi-layered closings interleaved by a layer of air, either without or with a sound-absorbing material between them. The results show that it is necessary to check the effectiveness of each type of fastening of the closing systems because, for example, for the frequency range between 500 and 2,000 Hz, the sound transmission loss of a closing system consisting of cementitious plate with glass wool and line-punctual and punctual-punctual connections exceeds in 6.25% the sound transmission loss of the same system with line-line fastening. For a system composed of expanded polystyrene with glass wool, the sound transmission loss provided by line-line fastening exceeds in 7.0% the sound transmission loss of the same closing system with line-punctual and punctual-punctual fastenings.

Resumo em Inglês:

Abstract A numerical thermal model was developed to evaluate the heat flux which is conducted to a rectangular workpiece of steel plate ABNT 1020, thus making it possible to compute the maximum temperature in the grinding surface, taking into account the rectangular distribution of heat flux, the thermal properties of the grinding wheel conventional Al2O3, the piece to be machined and the lubri-refrigerating fluid. The finite volume method was employed for the discretization of the direct thermal problem from the heat diffusion equation associated with the two-dimensional problem of heat conduction in transient regime. The inverse thermal problem was solved by the Golden Section technique. The thermal flux, when compared to the conventional technique of method of application fluid, was reduced by 84.0% in the practices performed with cutting depth of 30µm, at 74.0% in practices with cutting depth of 45µm and 61.2% in the aggressive practices of 60µm, thus demonstrating the applicability of the optimized method for fluid application.

Resumo em Inglês:

Abstract The comfort conditions of a given environment can directly influence the performance of the activities performed therein. When considering the school space in relationship with the user, the environment is even more important, since it may reflect fully on the learning process. This article evaluates the thermal comfort perceptions of classroom users of the Federal University of Ouro Preto, specifically the School of Mining, the Institute of Physical and Biological Sciences and the Building Block of Classrooms. The research is conducted through questionnaires and measurements of environmental variables in loco simultaneously in the three areas throughout the months of June, July and September 2011. The results were statistically analyzed using the calculation of the standard deviation from the mean operative temperature and humidity to give comfort zone. Approximately 75% of the users were satisfied with the thermal environment.

Resumo em Inglês:

Abstract The quantification of nanometric precipitates in Al-Zn-Mg-Cu alloys has been performed by a series of experimental techniques. Especially in the AA7050 alloy, after ageing heat treatment, the particles responsible for the hardening become very thin. Typically, these precipitates of nanometric sizes are mainly characterized by transmission electron microscopy (TEM), which in this particular case, requires a very meticulous preparation. This study investigated a possible alternative quantification of the precipitates by atomic force microscopy (AFM) to complement the technique by TEM. For this, three conditions for heat treatment of an aged aluminium alloy AA7050 were therefore chosen to produce different density and sizes of precipitates. The experimental results showed that the AFM technique proved to be a valid qualitative tool and may complement the results obtained by TEM an exploratory analysis for the microstructures.

Resumo em Inglês:

Abstract The aim of this paper is to analyze mixtures of basic oxygen furnace slag and granite waste in order to produce Portland cement. X-ray patterns were carried out in both the basic oxygen furnace slag and granite waste. Then, mixtures were prepared to obtain the binary basicity of 0.5, 0.9 and 1.2. The mixtures were melted at 1500ºC. Two cooling steps were performed. The first cooling step was accomplished inside the furnace in order to determine the phases formed during the melting step. The second cooling process was carried out in water in order to obtain an amorphous structure. Images via scanning electrons microscopy and EDS spectrum were obtained for the mixtures cooling in water. The results showed that basic oxygen furnace slag contains a higher percent of CaO. A binary basicity of 4.6 was determined. The granite waste appeared as mainly a quartz phase. During the slow cooling step, silicates (akermanite and gehlenite) were formed. On the fast cooling step, amorphous structures were obtained. In addition, images obtained via scanning electrons microscopy showed glass structures. EDS spectrum indicated that the glass structures were composed for calcium silicates. Thus, the results suggest that mixtures using basic oxygen furnace slag and granite waste presented characteristics desirable for Portland cement production.

Resumo em Inglês:

Abstract The influence of tellurium in the indium segregation of Ga1-xInxSb:Te ingots obtained by the conventional vertical Bridgman method (CVBM), under stirred and non-stirred conditions, was investigated. Three Te-doped ingots and three no-doped ingots were unidirectionally solidified at a constant speed of 2.0 mm/hour, inside quartz ampoules, closed under argon, and with a conical tip. The furnace temperature was set for overheating between 73.5 - 93ºC, and temperature gradients between 3.0 - 3.3ºC/mm. The tellurium doped ingots showed a smaller number of grains and no cracks in the middle region of the ingots, right after the tip, in comparison with the no-doped ingots. Moreover, when comparing the stirred with the non-stirred ingots, the EDS experimental profile of indium in Te-doped synthetized without melt stirring ingot showed a better agreement with the Scheil-Gulliver equation than the stirred Te-doped ingots. The Te-doped ingots when stirring the melt during synthesis showed a more constant axial indium distribution, up to 85% of their lengths. The constant lattice estimated from TEM diffraction images are respectively 6.29 Å for the non-doped sample and 6.17 Å for the Te-doped sample. A qualitative account for the increase of the lattice parameter and the Hall measurements results is that the tellurium compensates for the native acceptor defects, contributing to the microstructural quality in the Ga1-xInxSb ingots.

Resumo em Inglês:

Abstract In order to determine the exploitation potentiality of a kaolin deposit from Atacama in the north of Chile, two types of kaolin (K-1 and K-2) were characterized by XRD, XRF, SEM/EDXS, size distribution, whiteness and DSC. Kaolinite, quartz, muscovite and albite were recognized as main constituents of the ore deposit, and also a significant amount of impurities that negatively impacts on quality were detected. Results show that the low quality presented by the samples, especially K-2, impedes their industrial use as raw material and further mineral concentration processes are proposed. Finally, the results of thermal analysis confirm a conversion to metakaolin that could be the basis for an alternative processing route.

Resumo em Inglês:

Abstract In this paper, a detailed study of the influence of Mn2+ ions on quartz and hematite flotation (at pH 10.5 with starch/amine as depressor/collector) in the absence and presence of ethylenediaminetetraacetic acid (EDTA) is presented. By using zeta potential measurement and a careful analysis of manganese species present in water for dosages in which manganese hydroxide precipitated, we confirmed that the depression of both minerals by Mn2+ ions is due to the following: (i) the adsorption of Mn hydroxy complexes (Mn2(OH)3+ and Mn(OH)+); (ii) Mn2+ and mainly (iii) the precipitation of Mn(OH)2 on mineral surfaces. These effects hindered the adsorption of amine species on the surfaces of the minerals (quartz and hematite). EDTA was used to complex Mn2+ to restore the recoveries of both minerals. This was confirmed by the species distribution diagrams of Mn and EDTA-Mn in water. Conditioning with starch followed by amine at pH 10.5 enabled a selective separation of these minerals.

Resumo em Inglês:

Abstract In open pit mining, dilution is not always a factor systematically analyzed and calculated. Often it is only an adjusted number, for example, calculated or even empirically determined for a certain operational condition perpetuating along time in the form of a constant applied to calculating reserves or mine planning in attendance of audit requirements. Dilution and loss are factors that should be always considered for tonnage and grade estimates. These factors are always associated and can be determined considering several particularities of the deposit and the operation itself. In this study, a methodology was determined to identify blocks adjacent to the blocks previously planned to be mined. Thus, it is possible to estimate the dilution caused by poor operating efficiency, taking into account the inability of the equipment to perfectly remove each block, respecting its limits. Mining dilution is defined as the incorporation of waste material to ore due to the operational incapacity to efficiently separate the materials during the mining process, considering the physical processes, and the operating and geometric configurations of the mining with the equipment available.

Resumo em Inglês:

Abstract Data quality control programs used in the mineral industry normally define tolerance limits based on values considered as good practice or those that have previously been applied to similar deposits, although the precision and accuracy of estimates depend on a combination of geological characteristics, estimation parameters, sample spacing and data quality. This study investigates how the sample quality limits affect the estimates results. The proposed methodology is based on a series of metrics used to compare the impact on the estimates using a synthetic database with an increasing amount of error added to the original sample grades or positions, emulating different levels of precision. The proposed approach results lead to tolerance limits for the grades similar to those recommended in literature. The influence of the positional uncertainty on model estimates is at a minimum, because of the accuracy of current surveying methods that have a deviation in the order of millimeters, so its impact can be considered negligible.