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Search Results: 1 - 10 of 774197 matches for " A. M.;Varaj?o "
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Viabilidade do uso de argilas cauliníticas do Quadrilátero Ferrífero para a indústria ceramica
Peralta-Sánchez, M. G.;Morales-Carrera, A. M.;Varajo, A. F. D. C.;Ferreira, M. M.;
Ceramica , 2011, DOI: 10.1590/S0366-69132011000300002
Abstract: seven samples from three kaolin deposits of the quadrilátero ferrífero were characterized by physical, mineralogical and chemical analyses in order to determine their use in the ceramic industry. despite the predominant presence of kaolinite, the variations in the fe2o3 content from 2 to 44%, due to presence of goethite and hematite, resulted in different colors, namely: white (acm and db), yellow (r5), yellowed red (fs) and red (dv, r1 and am). specimens were burned at 900 and 1100 °c and they almost didn't change color. however, only specimens made with dv and r1 samples reached the technical specifications for the ceramic industry, without fractures and with values of compression strength of 96.2 and 64.2 mpa, respectively. the other samples were made by mixing phyllite in the proportions of 5, 10, 15, 20 and 25% and burned at 900 and 1100 °c. the bricks made with acm+15f, db+5f, r5+5f, fs+5f, am+5f and burned at 900 oc reached the technical specifications for ceramic industry, without fractures and with values of compression strength between 69.15 and 29.6 mpa.
Altera??o superficial e pedogeomorfologia no sul do Complexo Ba??o - Quadrilátero Ferrífero (MG)
Figueiredo, M. A.;Varajo, A. F. D. C.;Fabris, J. D.;Loutfi, I. S.;Carvalho, A. P.;
Revista Brasileira de Ciência do Solo , 2004, DOI: 10.1590/S0100-06832004000400012
Abstract: this study defines some aspects of superficial alteration processes and their reflexes on the quaternary pedogeomorphology in the sub-basin of the upper maracujá river, in the complexo ba??o, ferriferous zone, state of minas gerais, brazil. characteristics related to the dynamic evolution of three gneiss-underlayered toposequences (1, 2, and 3) at different erosion stages were investigated. in the top slope segments of the toposequences 1 and 2 the soil profiles are little developed and present an in situ evolution. in toposequence 3, the soil profile of the same top slope segment is a well developed oxisol with allochthonous features. similarly, in the mid slope segments of the three toposequences, the soil profiles are thick, latosolic, originated from the colluvial sediments that descended from the top slope. however, there is a rupture in the sediment transport and deposition process in the low slope segments. the soil profile of toposequence 2 is an autochthonous cambic oxisol, while the toposequences 1 and 3 profiles were developed from alluvial - colluvial materials deposited on the gneiss saprolite basement. despite the fact that dynamic evolution of the top and mid slope segments of the three toposequences corroborate the tropical geomorphological models up to the mid slope segment, the rupture in colluvial deposition to the lower slope segments suggests a recent morphodynamic imbalance. besides, the micromorphological and mineralogical features do not present any correlation with the differentiated erosive susceptibility verified in the area.
Argilas bentoníticas da península de Santa Elena, Equador: pilariza??o, ativa??o ácida e seu uso como descolorante de óleo de soja
Morales-Carrera, Ana M.;Varajo, Angélica F. D. C.;Gon?alves, Marcos A.;Stachissini, Ant?nia S.;
Química Nova , 2009, DOI: 10.1590/S0100-40422009000900009
Abstract: two samples of calcic bentonite of the santa elena peninsula, ecuador, were pillared with al13 ions in the ratio of 10, 15 and 20 meq of al g-1 of clay, calcinated at 573, 723 and 873 ok and acid activated with 4, 6 and 8 mol l-1 h2so4. analyses by x-ray diffraction, x-ray fluorescence, differential and gravimetric thermal, density, surface area and porosity, were applied in order to study the modifications occurred in the crystalline structure of the montmorillonite. the 8 mol l-1 h2so4 acid-activated 15 meq of al g-1 of clay at 573 ok al-pillared samples indicated the best results in the bleaching of the soybean oil measured by uv-visible spectrophotometer.
Transforma??es mineralógicas e cristaloquímicas decorrentes dos ensaios termais em argilas cauliníticas ferruginosas
Ferreira, M. M.;Varajo, A. F. D. C.;Morales-Carrera, A. M.;Peralta-Sánchez, M. G.;Costa, G. M. da;
Ceramica , 2012, DOI: 10.1590/S0366-69132012000100017
Abstract: mineralogical and crystallochemical transformations of representative ferruginous kaolinitic clay samples were investigated in specimens burned at 800, 1000 and 1200 °c. x-ray diffraction and differential thermal and thermogravimetric analyses showed that kaolinite was the predominant mineral in the raw samples. the m?ssbauer spectroscopy results showed that the high iron content (22.5 wt.%), as determined by x-ray fluorescence, is related to the presence of goethite (18 wt.%) and hematite (16 wt.%). however, after fe was extracted using a dithionite-citrate system buffered with sodium bicarbonate, a residue of this element (fe3+ and fe2+) was found in the structure of the kaolinite. the sintering process showed the destruction of kaolinite, as well as the transformation of the goethite into hematite, the crystals growing as the temperature increases. the hematite crystal size at 1200 °c is five times larger than in the raw sample. the mullite formation at 1000 °c is comprised of a solid solution of fe2o3 and al2o3, which results in a resistant product with a higher thermal stability.
Microporosity of BIF hosted massive hematite ore, Iron Quadrangle, Brazil
VARAJO, CéSAR A.C.;BRUAND, ARY;RAMANAIDOU, ERICK R.;GILKES, ROBERT J.;
Anais da Academia Brasileira de Ciências , 2002, DOI: 10.1590/S0001-37652002000100008
Abstract: massive hematite ore (mho) is a special high-grade iron ore, used as lump ore in the process of obtaining direct reduction iron (dri). the influence of porosity on the reducibility of mho from the capit?o do mato mine (iron quadrangle, brazil) was investigated using optical and scanning electron microscopes on drill core and open pit samples. hematite is the main component of the samples and occurs as granular crystals (10 mm), microplates (1 mm) and euhedral martite (10 to 30 mm). quartz, maghemite, kenomagnetite and goethite are minor components. primary micropores (? to 1 mm) are associated with microplaty crystals that fill cavities between granular hematite. secondary micropores (? to 5 mm) related to euhedral martite crystals, are the most important. the total porosity of weathered samples, measured using nitrogen adsorption and mercury injection, attains values up to 11%, whereas unweathered samples have a porosity less than 2.5%. reducibility is strongly enhanced by porosity, but inhibited by structure (bedding).
Microporosity of BIF hosted massive hematite ore, Iron Quadrangle, Brazil
VARAJO CéSAR A.C.,BRUAND ARY,RAMANAIDOU ERICK R.,GILKES ROBERT J.
Anais da Academia Brasileira de Ciências , 2002,
Abstract: Massive hematite ore (MHO) is a special high-grade iron ore, used as lump ore in the process of obtaining direct reduction iron (DRI). The influence of porosity on the reducibility of MHO from the Capit o do Mato Mine (Iron Quadrangle, Brazil) was investigated using optical and scanning electron microscopes on drill core and open pit samples. Hematite is the main component of the samples and occurs as granular crystals (10 mum), microplates (1 mum) and euhedral martite (10 to 30 mum). Quartz, maghemite, kenomagnetite and goethite are minor components. Primary micropores ( to 1 mum) are associated with microplaty crystals that fill cavities between granular hematite. Secondary micropores ( to 5 mum) related to euhedral martite crystals, are the most important. The total porosity of weathered samples, measured using nitrogen adsorption and mercury injection, attains values up to 11%, whereas unweathered samples have a porosity less than 2.5%. Reducibility is strongly enhanced by porosity, but inhibited by structure (bedding).
QUALIDADE DO SOLO COMO UM ATRIBUTO PARA UMA METODOLOGIA DE MANEJO DE TRILHAS DO PARQUE NACIONAL DA SERRA DO CIPó, MG
Ricardo Eustáquio Fonseca Filho,Angélica Fortes Drummond Chicarino Varajo,Múcio do Amaral Figueiredo
Revista Brasileira de Ecoturismo , 2011,
Abstract: As Unidades de Conserva o, em especial as que permitem o uso público como Parques, s o áreas naturais protegidas e propícias ao ecoturismo, segmento turístico muito procurado na atualidade o que acarreta impactos ambientais n o somente à biodiversidade, mas também à geodiversidade. Os geoindicadores, ferramentas para identificar mudan as rápidas no ambiente natural, podem auxiliar no manejo destas áreas, especificamente nas trilhas. A Capacidade de Carga Turística (CCT) utiliza-se dos chamados Fatores de Corre o como erodibilidade e acessibilidade para ajudar na determina o da capacidade máxima de visitas em um local. Contanto, a compacta o do solo, também estreitamente associada a condi es e características específicas de cada local n o é considerada na metodologia. O Parque Nacional da Serra do Cipó (PNSC), localizado na por o central de MG recebe grande número de visitantes havendo pouco controle da visita o e monitoramento das condi es das vias que levam aos atrativos naturais locais, as trilhas. Este trabalho tem como objetivo verificar a compacta o do solo – geoindicador qualidade do solo – como fator de corre o para auxílio no manejo da visita o e uso das trilhas. Utilizando-se um penetr metro de solo com anel dinamométrico obteve-se a medida de resistência do solo em diversos pontos ao longo da trilha da Cachoeira da Farofa e entorno. Os resultados mostraram que o solo do leito da referida trilha se encontra mais compactada do que o entorno, assim como as áreas em que há tráfego de veículos automotores. Observou-se ainda que nos pontos mais compactados, havendo declividade mais acentuada (medida através de clin metro), áreas mais sujeitas à reten o hídrica, ausência de serapilheira e bioma cerrado, há maior eros o do solo. Os resultados, associados a outras análises de impactos bióticos e abióticos, podem auxiliar na gest o da Unidade de Conserva o para redu o das altera es ambientais, em que as trilhas costumam ser tratadas somente como um meio de deslocamento a atrativos turísticos naturais. Neste sentido, a sua apropriada conserva o agregaria valor à experiência do visitante. Outra contribui o se dá através de outro olhar para a metodologia CCT, além do foco somente no número de turistas.
Sinaliza??o visual e Biologia Reprodutiva de Dendropsophus werneri (Anura: Hylidae) em área de Mata Atlantica no Estado do Paraná, Brasil
Miranda, Daniele Bazzo;Garey, Michel Varajo;Monteiro-Filho, Emygdio L.A.;Hartmann, Marília Teresinha;
Papéis Avulsos de Zoologia (S?o Paulo) , 2008, DOI: 10.1590/S0031-10492008002900001
Abstract: we studied the reproductive biology and visual signaling of dendropsophus werneri, whose distribution is limited to the atlantic rain forest. the fieldwork was carried out in the esta??o 2 do iapar, municipality of morretes, state of paraná, brazil, from august 2006 to march 2007. additional information on reproduction was gathered in the reserva natural salto morato, municipality of guaraque?aba, state of paraná, brazil, from september 2006 to march 2007. males were smaller than females. males called throughout all the study period in morretes, but were active only during three months in guaraque?aba; males called from low vegetation along the edge of temporary ponds in open areas. the visual signaling was observed in two contexts: (1) aggressive behaviors between two males and (2) during the reproduction, by amplectant males. in the territorial behavior, males exhibited both aggressive and mixed calls, visual signaling as well as physical combats. we also recorded satellite behavior in four males. the mean egg number per clutch was 244 ± 32 eggs, varying between 188 and 310 eggs. we observed two reproductive modes: mode 1 and mode 24. in the present study, dendropsophus werneri showed elaborated social interactions involving visual signaling, territorial behavior, mating bahavior with tactile stimuli, and two different reproductive modes, demonstrating its complex reproductive biology.
Software projects’ most important activities of quality management: A Delphi study
Márcia Filipa Lopes Catarino,Dulce Cristina dos Santos Iria Gon?alves,António Manuel de Jesus Pereira,Jo?o Eduardo Quintela Alves de Sousa Varajo
Communications of the IBIMA , 2009,
Abstract: Quality management is a very important contributor for the success of software project management. In quality management area we can find multiple activities to carry out, however organizations cannot always execute all those tasks and many times it is indispensable to make choices about what can and should be made. In order to help the organizations to identify the most important activities in quality management, we carried out a Delphi study with the participation of several senior project managers. The result is the identification of several groups of activities, ordered by importance for the project success.
óxidos de ferro de solos formados sobre gnaisse do Complexo Ba??o, Quadrilátero Ferrífero, Minas Gerais
Figueiredo, Múcio do Amaral;Fabris, José Domingos;Varajo, Angélica Fortes Drummond Chicarino;Couceiro, Paulo Rogério da Costa;Loutfi, Ivan Soares;Azevedo, Izabel de Souza;Garg, Vijayendra Kumar;
Pesquisa Agropecuária Brasileira , 2006, DOI: 10.1590/S0100-204X2006000200017
Abstract: the objective of this work was to characterize iron oxides from b-horizons of three soil profiles developing on gneiss of the ba??o complex geodomain in the quadrilátero ferrífero, minas gerais, brazil. samples were collected from the uppest, middle and lowest segments along the slope. the earth fine fractions (mean diameter, f = 2 mm) were separated for all samples. the chemical composition of the major elements was determined with the x-ray fluorescence technique; the mineralogical analysis was performed with powder x-ray diffractomer and m?ssbauer spectroscopy. all samples have similar mineralogical composition, with a general occurrence corresponding to the sequence quartz >> gibbsite > kaolinite > goethite. from the 4.2 k-m?ssbauer results, the coexistence of goethite (major) and hematite is confirmed. the isomorphic aluminum contents, as they were deduced from the hyperfine fields, lead to the following chemical formulas for goethites: afe0.79al0.21ooh (upslope), afe0.75al0.25ooh (midslope) and afe0.78al0.22ooh (downslope). the iron oxides transformation dynamics in b horizons along the slope is a useful indicator of the paleo-climatic oscillations in this area: aluminous goethite is an indicator of humid paleo-environments, whereas aluminous-poorer goethite reveals drier pedogenic conditions.
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