438 research outputs found
Sistema de monitoramento de din?mica de rocha (SMDR) aplicado ao controle geot?cnico de uma cavidade natural subterr?nea no munic?pio de S?o Gon?alo do Rio Abaixo - MG.
Programa de P?s-Gradua??o em Geotecnia. N?cleo de Geotecnia, Escola de Minas, Universidade Federal de Ouro Preto.As atividades de minera??o s?o imprescind?veis para a economia brasileira, tendo em
vista a enorme influ?ncia desse setor na gera??o de empregos, no PIB e no equil?brio
econ?mico nacional. Por?m, nos ?ltimos anos ocorreram mudan?as na legisla??o
ambiental do Brasil que estipularam um raio de prote??o no entorno das cavidades
naturais subterr?neas, determinado de forma emp?rica, no valor de 250 metros, onde n?o
se pode ocorrer nenhum impacto ambiental irrevers?vel a caverna, podendo inviabilizar o
aproveitamento de grande parte das jazidas minerais. Dessa forma, com o intuito de
verificar a influ?ncia do desmonte com uso de explosivos na estabilidade f?sica da
cavidade BRU_0034, nas proximidades da Mina de Brucutu da empresa Vale S.A., foram
propostos, por interm?dio desse estudo, monitoramentos sismogr?ficos e de
deslocamento atrav?s do uso do Sistema de Monitoramento de Din?mica de Rocha
(SMDR). No que se refere aos resultados obtidos com o SMDR, foi poss?vel verificar
atrav?s dos dados sismogr?ficos e dos desmontes que o modelo de atenua??o proposto,
apesar de possuir uma pequena popula??o amostral, ? estatisticamente aceito. Al?m disso,
com base na an?lise dos dados de deslocamento, pode-se concluir que n?o houve uma
grande movimenta??o aparente nos sensores durante o monitoramento, atestando assim
uma boa estabilidade geomec?nica da cavidadeMining activities are essential for the Brazilian economy, in view of the enormous
influence of the sector in job creation, PIB and the national economic balance. However,
in recent years there have been changes in brazil's environmental legislation that
stipulate a protective radius around the underground natural cavities, determined
empirically, in the amount of 250 meters, where no irreversible environmental impact
can occur at the cave and may make it impossible to use most of the mineral deposits.
Thus, in order to verify the influence of the rock blasting with the use of explosives on
the physical stability of the BRU_0034 cavity, near the Brucutu Mine of Vale S.A.,
seismographic and displacement monitoring stemming from the use of the Rock
Dynamics Monitoring System (SMDR) were proposed through this study. Regarding the
results obtained with the SMDR, it was possible to verify through the seismographic data
and the rock blasting that the proposed attenuation model, despite having a small sample
population, is statistically accepted. In addition, based on the analysis of displacement
data, it can be concluded that there was no major apparent movement in the sensors during
monitoring, thus attesting to a good geomechanical stability of the cavity
A-DInSAR technique applied to the surface displacements of the GW sector of the Brucutu mine – Quadrilátero Ferrífero
A mina de Brucutu encontra-se na porção nordeste do Quadrilátero Ferrífero, no município de São Gonçalo do Rio Abaixo, a aproximadamente 120 km a leste de Belo Horizonte, Minas Gerais. Nesse local, a empresa Vale S.A. opera uma das maiores minas de ferro do Brasil. O minério de ferro encontra-se alojado nos itabiritos e em corpos de hematita da Formação Cauê. Essas rochas têm diferentes comportamentos geomecânicos, visto que elas ocorrem em contatos com rochas intrusivas e encontram-se brechadas, intensamente foliadas e fortemente intemperizadas. Os taludes das cotas 1.030 a 1.000 m, do setor GW da cava de Brucutu, vem registrando instabilidades nos últimos anos. O presente estudo visou analisar os deslocamentos superficiais e discutir os prováveis fatores controladores. Utilizou-se a técnica Advanced Differential Radar Interferometry (A-DInSAR) a partir de imagens do sensor COSMO-SkyMed em modo StripMap para monitorar os deslocamentos. Os períodos abrangidos para o desenvolvimento do presente trabalho foram de junho de 2018 a agosto de 2019 e de junho de 2019 a novembro de 2020. As imagens utilizadas foram fornecidas e processadas pela empresa Telespazio Brasil. Foram utilizadas também ortoimagens provenientes de Aeronave Remotamente Pilotada (ARP), dados geológicos-geotécnicos de campo e dados pluviométricos. Os resultados obtidos por meio do monitoramento A-DInSAR mostram que foram identificadas taxas de deslocamento consideráveis (até -76,3 mm/ano) no período chuvoso. As instabilidades presentes na área de estudo são condicionadas pelos seguintes fatores: contato entre rochas intrusivas (IN) e itabirito friável (IF); atitude desfavorável da foliação; e índices pluviométricos elevados que produzem o desmantelamento (erosão) da face dos taludes.The Brucutu mine is in the northeast portion of the Quadrilátero Ferrífero, in the municipality of São Gonçalo do Rio Abaixo, approximately 120 km east of Belo Horizonte, Minas Gerais. In this place, Vale S.A. operates one of the largest iron ore mines in Brazil. Iron ore is housed in itabirite and hematite bodies of the Cauê Formation. These rocks have different geomechanical behaviors, since they occur in contact with intrusive rocks and are breached, intensely foliated and strongly weathered. The slopes of the quotas 1,030 to 1,000, of the GW sector of the Brucutu pit, have been registering instabilities in recent years. The present study aimed to analyze the superficial displacements and discuss the probable controlling factors. The Advanced Differential Radar Interferometry (A-DInSAR) technique was used from images of the COSMO-SkyMed sensor in StripMap mode to monitor the displacements. The periods covered for the development of this work were from June 2018 to August 2019 and from June 2019 to November 2020. The images used were provided and processed by the company Telespazio Brasil. Orthoimages from Remotely Piloted Aircraft (RPA), field geological-geotechnical data, and rainfall data were also used. The results obtained through A-DInSAR monitoring show that considerable displacement rates (up to -76.3 mm/year) were identified in the rainy season. The instabilities present in the study area are conditioned by the following factors: contact between intrusive rocks (IN) and friable itabirite (FI); unfavorable attitude of foliation; and high rainfall rates that produce the dismantling (erosion) of the slope face. 
Técnica A-DInSAR aplicada aos deslocamentos superficiais do setor GW da mina de Brucutu – Quadrilátero Ferrífero
A mina de Brucutu encontra-se na porção nordeste do Quadrilátero Ferrífero, no município de São Gonçalo do Rio Abaixo, a aproximadamente 120 km a leste de Belo Horizonte, Minas Gerais. Nesse local, a empresa Vale S.A. opera uma das maiores minas de ferro do Brasil. O minério de ferro encontra-se alojado nos itabiritos e em corpos de hematita da Formação Cauê. Essas rochas têm diferentes comportamentos geomecânicos, visto que elas ocorrem em contatos com rochas intrusivas e encontram-se brechadas, intensamente foliadas e fortemente intemperizadas. Os taludes das cotas 1.030 a 1.000 m, do setor GW da cava de Brucutu, vem registrando instabilidades nos últimos anos. O presente estudo visou analisar os deslocamentos superficiais e discutir os prováveis fatores controladores. Utilizou-se a técnica Advanced Differential Radar Interferometry (A-DInSAR) a partir de imagens do sensor COSMO-SkyMed em modo StripMap para monitorar os deslocamentos. Os períodos abrangidos para o desenvolvimento do presente trabalho foram de junho de 2018 a agosto de 2019 e de junho de 2019 a novembro de 2020. As imagens utilizadas foram fornecidas e processadas pela empresa Telespazio Brasil. Foram utilizadas também ortoimagens provenientes de Aeronave Remotamente Pilotada (ARP), dados geológicos-geotécnicos de campo e dados pluviométricos. Os resultados obtidos por meio do monitoramento A-DInSAR mostram que foram identificadas taxas de deslocamento consideráveis (até -76,3 mm/ano) no período chuvoso. As instabilidades presentes na área de estudo são condicionadas pelos seguintes fatores: contato entre rochas intrusivas (IN) e itabirito friável (IF); atitude desfavorável da foliação; e índices pluviométricos elevados que produzem o desmantelamento (erosão) da face dos taludes
Aplicação do Sistema de Monitoramento de Dinâmica de Rocha (SMDR) para Controle Geotécnico Contínuo de Cavidade Natural Subterrânea no Quadrilátero Ferrífero (MG)
Nos últimos anos uma série de estudos tem sido conduzida sobre cavidades naturais subterrâneas em formações ferríferas. Esses estudos decorrem da necessidade de se preservar as cavidades naturais e, ao mesmo tempo, viabilizar de forma sustentável, a operação de uma mina de minério de ferro. Isso ocorre pelo fato da legislação ambiental do Brasil estipular, empiricamente, um raio de proteção de 250 m, de forma a evitar dano ambiental irreversível às cavernas, que por sua vez, bloqueia a lavra de considerável fração de minério de ferro. Dessa forma, com o intuito de verificar a influência do desmonte com uso de explosivos na estabilidade física da cavidade BRU_0034, nas proximidades da Mina de Brucutu da empresa Vale S.A., foram propostos, por intermédio desse estudo,monitoramentos sismográficos e de deslocamento através do uso do Sistema de Monitoramento de Dinâmica de Rocha (SMDR). No que se refere aos resultados obtidos com o SMDR, foi possível verificar por meio dos dados sismográficos e de deslocamento que não houve uma grande movimentação aparente nos sensores durante o monitoramento de desmontes de rochas por explosivos realizados em distâncias inferiores a 250 m
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Charge separation relative to the reaction plane in Pb-Pb collisions at TeV
Measurements of charge dependent azimuthal correlations with the ALICE
detector at the LHC are reported for Pb-Pb collisions at TeV. Two- and three-particle charge-dependent azimuthal correlations in
the pseudo-rapidity range are presented as a function of the
collision centrality, particle separation in pseudo-rapidity, and transverse
momentum. A clear signal compatible with a charge-dependent separation relative
to the reaction plane is observed, which shows little or no collision energy
dependence when compared to measurements at RHIC energies. This provides a new
insight for understanding the nature of the charge dependent azimuthal
correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286
A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE
In this small note we are concerned with the solution of Forward-Backward
Stochastic Differential Equations (FBSDE) with drivers that grow quadratically
in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem
is a comparison result that allows comparing componentwise the signs of the
control processes of two different qgFBSDE. As a byproduct one obtains
conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at , 2.76 and 7 TeV
Measurements of the sphericity of primary charged particles in minimum bias
proton--proton collisions at , 2.76 and 7 TeV with the ALICE
detector at the LHC are presented. The observable is linearized to be collinear
safe and is measured in the plane perpendicular to the beam direction using
primary charged tracks with GeV/c in . The
mean sphericity as a function of the charged particle multiplicity at
mid-rapidity () is reported for events with different
scales ("soft" and "hard") defined by the transverse momentum of the leading
particle. In addition, the mean charged particle transverse momentum versus
multiplicity is presented for the different event classes, and the sphericity
distributions in bins of multiplicity are presented. The data are compared with
calculations of standard Monte Carlo event generators. The transverse
sphericity is found to grow with multiplicity at all collision energies, with a
steeper rise at low , whereas the event generators show the
opposite tendency. The combined study of the sphericity and the mean with multiplicity indicates that most of the tested event generators
produce events with higher multiplicity by generating more back-to-back jets
resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with
tune PERUGIA-2011 exhibits a noticeable improvement in describing the data,
compared to the other tested generators.Comment: 21 pages, 9 captioned figures, 3 tables, authors from page 16,
published version, figures from
http://aliceinfo.cern.ch/ArtSubmission/node/308
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