Rem-Revista Escola De Minas最新文献

A Geostatistical Framework for Estimating Compositional Data Avoiding Bias in Back-transformation 一种避免反变换偏倚的成分数据估计地质统计学框架

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672015690041

R. Rubio, J. Costa, M. Bassani

{"title":"A Geostatistical Framework for Estimating Compositional Data Avoiding Bias in Back-transformation","authors":"R. Rubio, J. Costa, M. Bassani","doi":"10.1590/0370-44672015690041","DOIUrl":"https://doi.org/10.1590/0370-44672015690041","url":null,"abstract":"Estimation of some mineral deposits involves chemical species or a granulometric mass balance that constitute a closed constant sum (e.g., 100%). Data that add up to a constant are known as compositional data (CODA). Classical geostatistical estimation methods (e.g., kriging) are not satisfactory when CODA are used, since bias is expected when estimated mean block values are back-transformed to the original space. CODA methods use nonlinear transformations, and when the transformed data are interpolated, they cannot be returned directly to the space of the original data. If these averages are back-transformed using the inverse function, bias is generated. To avoid this bias, this article proposes geostatistical simulation of the isometric logratio ratio (ilr) transformations back-transforming point simulated values (instead of block estimations), with the averaging being postponed to the end of the process. The results show that, in addition to maintaining the mass balance and the correlations among the variables, the means (E-types) of the simulations satisfactorily reproduce the statistical characteristics of the grades without any sort of bias. A complete case study of a major bauxite deposit illustrates the methodology.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"9 1","pages":"219-226"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82657543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Surface drainage system for dry docks in shipyards - Case study of Estaleiro Rio Grande (Technical Note) 船厂干船坞地面排水系统- Estaleiro Rio Grande案例研究(技术说明)

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672014690210

C. B. Martinez, A. Saliba, Marcio Figueiredo de Resende, Eder Daniel Teixeira, M. Marques

引用次数: 0

Damage evolution in a tensile specimen of a ductile stainless steel 延性不锈钢拉伸试样的损伤演化

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672015690183

G. Faria, L. Godefroid, Fernando Victor Nery

{"title":"Damage evolution in a tensile specimen of a ductile stainless steel","authors":"G. Faria, L. Godefroid, Fernando Victor Nery","doi":"10.1590/0370-44672015690183","DOIUrl":"https://doi.org/10.1590/0370-44672015690183","url":null,"abstract":"This paper presents a study about the fracture mechanism of a ferritic stainless steel (UNS S44400 type) during a tensile test. The applied materials for the experimental procedures were 25 specimens of the steel, machined in the rolling direction. Each specimen was submitted to standard polishing procedures. One of the samples, in the original state, was structurally characterized by reflected light optical microscopy. The other samples were submitted to tensile tests with a constant displacement rate. Three samples were tested until failure (complete tests) and the others just until specific strain values, when the tests were interrupted and the samples were characterized by using optical and scanning electron microscopy. The main objective of these characterizations was to evaluate the structural damage evolution and to identify the fracture mechanism for the tested conditions. A methodology to quantify the damage evolution by surface roughness, identified by optical microscopy, was proposed. A new index - Damage by Diffuse Reflection Index (DRI) - was proposed to quantify the damage evolution in function of the specimen deformation. It was possible to confirm the ductile behavior of the studied steel and that the main fracture mechanism was the traditional dimpled rupture.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"80 1 1","pages":"175-183"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89560345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

Slope stability analysis at highway BR-153 using numerical models BR-153高速公路边坡稳定性数值模型分析

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672015690040

R. Rubio, Jorge Flórez, A. Zingano

{"title":"Slope stability analysis at highway BR-153 using numerical models","authors":"R. Rubio, Jorge Flórez, A. Zingano","doi":"10.1590/0370-44672015690040","DOIUrl":"https://doi.org/10.1590/0370-44672015690040","url":null,"abstract":"An existing cut slope on Highway RS-471/BR-153 is studied. The slope is composed of the Serra Geral Formation's material: a highly altered volcanic breccia and above it a slightly altered and very fractured rhyolite. A numerical analysis of the slope is carried out in two dimensions. Fracturing of the rhyolite necessitates the use of a constitutive model for materials with families of discontinuities (Ubiquitous-joint). To simplify the analysis of the problem and to examine some of the most sensitive variables, two more analyses are made, replacing the initial model by a Mohr's constitutive model, which considers the material as continuous. The results obtained from the Ubiquitous-joint model provide an acceptable representation of the field conditions, showing a failure mechanism type of rockfall from the face of the slope in the rhyolite, and the rupture surface of the breccia, without propagation of surface failure. In the analysis, when considering both materials as continuous, it is not possible to take account the fault conditions simultaneously, and this analysis also requires values of the mechanical parameters different from those recommended in literature.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"232 1","pages":"185-191"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73250883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Microstructural analysis in the Fe-30.5Mn-8.0Al-1.2C and Fe-30.5Mn-2.1Al-1.2C steels upon cold rolling Fe-30.5Mn-8.0Al-1.2C和Fe-30.5Mn-2.1Al-1.2C冷轧钢组织分析

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672015690097

F. M. Souza, A. F. Padilha, I. Gutierrez-Urrutia, D. Raabe

{"title":"Microstructural analysis in the Fe-30.5Mn-8.0Al-1.2C and Fe-30.5Mn-2.1Al-1.2C steels upon cold rolling","authors":"F. M. Souza, A. F. Padilha, I. Gutierrez-Urrutia, D. Raabe","doi":"10.1590/0370-44672015690097","DOIUrl":"https://doi.org/10.1590/0370-44672015690097","url":null,"abstract":"Electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) were used to examine microstructural changes of the austenitic low-density Fe-30.5Mn-8.0Al-1.2C (8Al) and Fe-30.5Mn-2.1Al-1.2C (2Al) (wt.%) steels during cold rolling. As the strain increased, deformation mechanisms, such as stacking faults, slip, mechanical twinning, and shear banding were activated in both steels cold rolled up to strain of 0.69. Only slip was noted in these steels at low strain (e=0.11) and slip dominance was detected in the 8Al steel at higher strains. Shear banding became active at higher strain (e~0.7) in these materials. An inhomogeneous microstructure formed in both alloys at such strain level. More extensive mechanical twinning in the 2Al alloy than that in the 8Al alloy was observed. Fish bone-like structure patterns were revealed in the 8Al steel and a river-like structure in the 2Al steel. Detailed microstructure features as elongated and fragmented grains along the rolling direction (RD) were found for both steels, as already observed in other high-Mn steels. These deformed structures are composed by lamellar packets which can contain mechanical twins or slip lines and shear bands.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"42 1","pages":"167-173"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84548310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

A stochastic approach for the wind load effect on steel structures 风荷载对钢结构影响的随机方法

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672015690203

T. D. Santos, G. Siqueira, L. C. M. Junior

{"title":"A stochastic approach for the wind load effect on steel structures","authors":"T. D. Santos, G. Siqueira, L. C. M. Junior","doi":"10.1590/0370-44672015690203","DOIUrl":"https://doi.org/10.1590/0370-44672015690203","url":null,"abstract":"The Brazilian design load standard still provides a wind speed map developed in 1977. Since then, new data have been collected and new charts have been proposed in literature. The literature not only alerts to changes in short-term wind gust patterns, but it also warns that the wind speed values are higher than observed in the past. Many researchers have suggested that these differences are correlated to climate change effects. Besides the geophysical and societal impacts of climate change, there is a general concern between designers on the impacts of higher wind speeds on structural design. This paper aims to analyze the wind speed as a stochastic variable and its influence on the design of steel structures when changes in wind speed occur. A stochastic approach is used to evaluate expected stress values for a steel beam-column example. A Monte Carlo analysis is performed on a forty-story steel frame to compare the impact of different wind speed scenarios and types of analysis. In the analyses, the wind speed is approached by a Gumbel distribution and future wind scenarios are generated for sensitiveness evaluation. The analytical and Monte Carlo analyses indicate that greater attention shall be given to the consequences of using an average wind speed value instead of a probability distribution function.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"6 1","pages":"137-145"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87085419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Analisys of hot deformation behavior of super duplex stainless steel UNS S32760 through processing maps 通过加工图分析超级双相不锈钢S32760的热变形行为

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672014690176

C. Dias, O. Balancin

{"title":"Analisys of hot deformation behavior of super duplex stainless steel UNS S32760 through processing maps","authors":"C. Dias, O. Balancin","doi":"10.1590/0370-44672014690176","DOIUrl":"https://doi.org/10.1590/0370-44672014690176","url":null,"abstract":"The need for materials with higher strength and corrosion resistance in corrosive environments, such as in the oil extraction in saline media, has led to the use of super duplex stainless steels in projects such as the Pre-sal. The manufacture of these materials involves the step of thermomechanical processing, whose performance depends on the workability of the material. Processing conditions in which the super duplex stainless steel UNS S32760 can be worked safely and in which the material can fail were investigated in this presentation. The physical simulation was performed by means of hot torsion testing. The tests were performed at temperatures ranging from 900°C to 1200°C and strain rates of 0.01s-1 to 10s-1. The evolution of strain rate sensitivity of flow stress (m) for deformation of 0.5 at all temperatures investigated here was determined. After attaining the values of m for each deformation condition, the values of the power dissipation efficiency (η) were calculated, an instability criterion (ξ) was applied, and processing maps were constructed. Using these maps, the effects of deformation conditions on the power dissipation efficiency and the material plastic instability were discussed. The domains of processing maps, the observed microstructures and the shape of plastic flow stress curves were associated.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"44 1","pages":"155-160"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74141398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Dispersion degree and zeta potential of hematite 赤铁矿的分散度与zeta电位

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672014690073

Júnia Soares Alexandrino, A. Peres, G. M. Lopes, O. Rodrigues

引用次数: 12

Effects of hematite surface characteristicson filtration process 赤铁矿表面特性对过滤过程的影响

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672014690158

L. Graça, L. Lagoeiro, R. Galery, A. Peres

{"title":"Effects of hematite surface characteristicson filtration process","authors":"L. Graça, L. Lagoeiro, R. Galery, A. Peres","doi":"10.1590/0370-44672014690158","DOIUrl":"https://doi.org/10.1590/0370-44672014690158","url":null,"abstract":"In iron ore pelletizing plants a range of process parameters such as particle size distribution, specific surface area, and moisture, must be controlled to achieve optimized operation conditions. Particle size distribution and specific surface area are controlled during the grinding operations. Moisture, however, is controlled during filtration of the ground products. This work investigates the relationship between particle morphology, filter cake moisture and filter capacity. The samples were taken during the filtration tests and referred to three different blends presenting distinct mineralogical features and similar chemical compositions in order to investigate the effects of only the hematite surface characteristics. Six types of morphology are distinguished: granular hematite, tabular hematite, martitic hematite, polycrystalline hematite, hematite-goethite aggregates and goethite. For each filtration test, the filter cloth product was characterised. The characterisation analysis revealed that blends containing martitic hematite concentration above 11.45 percent increased substantially the filter capacity. However, it had also caused an increasing in final moisture content that reached values around 10.0 % compared with industrial moisture specification that can vary on the range of 8.5 to 9.5 %.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"PP 1","pages":"199-205"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85022028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Modelling and Simulation of the Santa Rita Mine Milling Circuit Santa Rita矿山选矿电路的建模与仿真

Rem-Revista Escola De Minas Pub Date : 2016-06-01 DOI: 10.1590/0370-44672014690186

L. F. D. S. Junior, H. D. Júnior

引用次数: 1