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Search Results: 1 - 10 of 481797 matches for " M. 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.
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.
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.
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.
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.
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.
Is Methanol Using Co2 From the Atmosphere a New Fuel to Replace Gasoline?  [PDF]
John OM. Bockris
Smart Grid and Renewable Energy (SGRE) , 2011, DOI: 10.4236/sgre.2011.22017
Abstract: The recent disaster in the Gulf has drawn attention to the longevity of the oil supply and what alternative to gasoline is the appropriate fuel to which we should turn. The suggestion of Methanol as a substitute for gasoline as been greatly strengthened by George Olah in his publication UBeyond Oil and Gas: The Methanol EconomyU. However, there remained the question of burning methanol without special attention to its method of synthesis which would not add to the CO2 content of the atmosphere. Hydrogen has often been suggested as an alternative fuel because it burns clean. A comparison is made of Hydrogen and Methanol synthesized with hydrogen and CO2 from the atmosphere or biomass. The cost of the methanol as prepared would be $28 to $31 per GJ. Development is needed in the method by which to obtain the CO2from the atmosphere Uin a streamU. Three possible methods are outlined. Only one has been subject to detailed system analysis. However, two independent calculations give highly similar costs. Water, air and wind to pro-duce hydrogen for electrolysis of water, are the only resources necessary to make the methanol required. Changing over to any alternative fuel will impact the Oil companies. However, a change to methanol could be a long term solu-tion for them; whereas a trend towards electricity as the overall medium of energy would not be.
Detailing the Structure of Liquid THF Based on an EPSR Study  [PDF]
Alexandre Borges, Jo?o M. M. Cordeiro
Computational Chemistry (CC) , 2015, DOI: 10.4236/cc.2015.31001
Abstract: The structure of pure liquid tetrahydrofuran (THF) has been investigated via Monte Carlo simulations in the wake of a previous Empirical Potential Structure Refinement (EPSR) study on that liquid (Bowron, D.T.; Finney, J.L.; Soper, A.K. (2006) J. Am. Chem. Soc., 128, 5119). The molecules are allatoms rigid structures and the intermolecular potential used is described for the classical 6-12 Lennard-Jones plus Coulomb in the NPT ensemble at 1 atm and 25°C. THF is a poorly structured liquid. Typical preferred orientation of molecules has been explored and calculations shown different types of molecular pairs exist concurrently in the liquid. The geometry of those pairs was deeply investigated and its influence in the liquid structure discussed. The lack of molecular organization in the liquid is closely related to the existence of that diversity of molecular pairs. Its geometry changes from antiparallel up to T-like depending on the distance between the molecules in the pairs.
Selec o de Sistemas CRM Utilizando AHP
Cruz-Cunha, Maria Manuela,Varajo, José Eduardo
Teoria e Prática em Administra??o (TPA) , 2011,
Abstract: Managers are often faced with the need to select one of several suppliers of a similar product or service, characterized by a set of parameters of whose weighting and analysis the selection depends. One technique for doing this is the Analytic Hierarchy Process (AHP). This paper proposes the application of this technique to the process of CRM (customer relationship management) systems selection, presenting a set of criteria and weightings, as well as the explanation of the various stages of implementation of the technique.
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