Rem-Revista Escola De Minas最新文献_第10页

Influence of thermal parameters on the dendritic arm spacing and the microhardness of Al-5.5wt.%Sn alloy directionally solidified 热参数对Al-5.5wt枝晶臂间距和显微硬度的影响。%Sn合金定向凝固

Rem-Revista Escola De Minas Pub Date : 2014-06-01 DOI: 10.1590/S0370-44672014000200007

A. Vasconcelos, Cibele Vieira Arão da Silva, A. Moreira, Maria Adrina Paixão de Sousa da Silva, O. Rocha

{"title":"Influence of thermal parameters on the dendritic arm spacing and the microhardness of Al-5.5wt.%Sn alloy directionally solidified","authors":"A. Vasconcelos, Cibele Vieira Arão da Silva, A. Moreira, Maria Adrina Paixão de Sousa da Silva, O. Rocha","doi":"10.1590/S0370-44672014000200007","DOIUrl":"https://doi.org/10.1590/S0370-44672014000200007","url":null,"abstract":"As ligas Al-Sn sao amplamente utilizados em aplicacoes tribologicas. Nesse estudo, analises termica, microestrutural e dureza (HV) foram realizadas ao longo de um lingote da liga Al-5,5%Sn, obtido por solidificacao direcional horizontal transitoria. Os principais parâmetros analisados incluem a velocidade de deslocamento da isoterma liquidus (VL) e a taxa de resfriamento (TR). Esses parâmetros termicos desempenham um papel fundamental na formacao da microestrutura. A microestrutura dendritica foi caracterizada atraves dos espacamentos dentriticos primarios (λ1), os quais foram determinados, experimentalmente, e correlacionados com VL, e TR. O comportamento apresentado pela liga Al- 5,5% Sn, durante a solidificacao,e semelhante ao de outras ligas de aluminio, isto e, observa-se rede dendritica mais grosseira com a diminuicao da taxa de resfriamento, indicando que a imiscibilidade entre o aluminio e estanho nao tem um efeito significativo sobre o relacao entre o espacamento dendritico primario e taxa de resfriamento. A dependencia da microdureza em VL, TR e no λ1 foi tambem analisada. Verificaram-se menores valores de HV para maiores TR. Por outro lado, os valores HV aumentam com valores crescentes de λ1.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"334 1","pages":"173-179"},"PeriodicalIF":0.0,"publicationDate":"2014-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76376221","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: 7

Iterative strategies associated with the normal flow technique on the nonlinear analysis of structural arches 结构拱非线性分析中与正流技术相关的迭代策略

Rem-Revista Escola De Minas Pub Date : 2014-06-01 DOI: 10.1590/S0370-44672014000200003

Dalilah Pires Maximiano, Andréa R. D. Silva, R. Silveira

{"title":"Iterative strategies associated with the normal flow technique on the nonlinear analysis of structural arches","authors":"Dalilah Pires Maximiano, Andréa R. D. Silva, R. Silveira","doi":"10.1590/S0370-44672014000200003","DOIUrl":"https://doi.org/10.1590/S0370-44672014000200003","url":null,"abstract":"A large part of the numerical procedures for obtaining the equilibrium path or load-displacement curve of structural problems with static nonlinear behavior is based on the Newton-Raphson iterative scheme to which are coupled the path-following methods. In this context, this study uses one technique, referred to as normal flow, in the process of obtaining the approximate nonlinear static response of struc tural systems. Basically, this technique is an adaptation made with in the NewtonRaphson iterative scheme in an attempt to speed up the nonlinear solution process and/or remove convergence problems. To overcome the critical points and to trace the whole nonlinear equilibrium path, three different strategies are used in association with the normal flow technique: the cylindrical arc-length, the minimum residual dis placement norm and the generalized displacement. With this procedure, the performance of these strategies when associated with the normal flow technique is valued. Two arches with highly nonlinear load-displacement curves are used in the study. The results obtained demonstrated that the association of the generalized displacement strategy with the normal flow technique contributes to the improvement of the non linear solution methodology.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"362 1","pages":"143-150"},"PeriodicalIF":0.0,"publicationDate":"2014-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74884470","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: 13

Synthesis and characterization of the Fe-Zn intermetallic phases using the Rietveld Method 用Rietveld法合成和表征Fe-Zn金属间相

Rem-Revista Escola De Minas Pub Date : 2014-06-01 DOI: 10.1590/S0370-44672014000200008

L. A. Santos, L. Lopes, P. Wendhausen

引用次数: 5

Diamonds from Borrachudo river, São Francisco basin (Tiros, MG): morphologic and dissolution aspects 来自<s:1>奥弗朗西斯科盆地(Tiros, MG) Borrachudo河的钻石:形态和溶解方面

Rem-Revista Escola De Minas Pub Date : 2014-06-01 DOI: 10.1590/S0370-44672014000200005

Luis Alberto de Deus Borges, M. Chaves, J. Karfunkel

{"title":"Diamonds from Borrachudo river, São Francisco basin (Tiros, MG): morphologic and dissolution aspects","authors":"Luis Alberto de Deus Borges, M. Chaves, J. Karfunkel","doi":"10.1590/S0370-44672014000200005","DOIUrl":"https://doi.org/10.1590/S0370-44672014000200005","url":null,"abstract":"A representative set of diamonds from the Borrachudo River (114 stones) was described for the first time as to their physical characteristics, among them weight, morphology, dissolution figures, and abrasion. Most samples are low in weight (~51% less than 0.30 ct) and only ~3.5% are above 3.0 ct. However, considering the total weight, ~47% of it is concentrated in the range above 3 ct. On the other hand, there even occur diamonds with dozen of carats. The most common crystallographic forms are originated from the octahedral form by dissolution, although irregular shapes like chips and flats also occur. The diamonds show differences in form compared to their weight ranges; those up to 0.30 ct have various shapes; in the range of 0.31 to 1 ct the most common are octahedral forms and their descendants; and in stones larger than 1 ct chips and flats predominate. The general habitus of the crystals, identified by their final tetrahexahedroid shapes, chips and flats, corroborated by the dissolution figures, indicate that the diamond were submitted to strong dissolution in a magmatic environment. Residual hillocks and holes represent the final stage of dissolution. The study indicates that the abrasion by the fluvial transport was not expressive enough to cause mechanical wear, thus ca. 97% shows no sign of wear. This fact suggests a proximal source for most of these diamonds.","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"1 1","pages":"159-165"},"PeriodicalIF":0.0,"publicationDate":"2014-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80418680","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: 0

Nickel ore grinding energy determination 镍矿磨矿能测定

Rem-Revista Escola De Minas Pub Date : 2014-05-14 DOI: 10.1590/S0370-44672014000200009

Alaine Moreira Imbelloni, José Pedro da Silva, C. Pereira

引用次数: 0

The application of sampling theory in bauxite protocols 抽样理论在铝土矿协议中的应用

Rem-Revista Escola De Minas Pub Date : 2014-05-14 DOI: 10.1590/S0370-44672014000200014

D. A. Bortoleto, A. C. Chieregati, Antônio Henrique Rietra Pereira, Raiza Cavalcante Oliveira

引用次数: 5

Metal bioavailability potential of São Francisco river sediments in Três Marias (Minas Gerais - Brazil) 巴西米纳斯吉拉斯州Três Marias地区<s:1> o Francisco河沉积物金属生物利用潜力

Rem-Revista Escola De Minas Pub Date : 2014-05-14 DOI: 10.1590/S0370-44672014000200004

A. H. Martins, D. Almeida, Luciano Rodrigo Gomes Santos, T. Moreira

{"title":"Metal bioavailability potential of São Francisco river sediments in Três Marias (Minas Gerais - Brazil)","authors":"A. H. Martins, D. Almeida, Luciano Rodrigo Gomes Santos, T. Moreira","doi":"10.1590/S0370-44672014000200004","DOIUrl":"https://doi.org/10.1590/S0370-44672014000200004","url":null,"abstract":"Sediment contamination by metals is very common and frequently researched worldwide with the objective of assessing the environmental impact of these contaminants. The bulk metal concentration in sediments is not enough for assessing toxicity and therefore, needs additional research and assays. To estimate the potentially bioavailable fraction of the metals in the sediment, the acid-volatile sulfides / simultane ously extracted metals (AVS/SEM) method was used. Seven samples in duplicate were collected from the Sao Francisco River and its tributary, near a zinc metallurgical plant in the city of Tres Marias (MG). The AVS/SEM results suggest that, although the bulk metal concentrations are above TEL (Threshold Effects Level: A chemical concentration above which some adverse effect to biota is expected), samples from the Sao Francisco River presented relatively low potential for bioavailability (uncertain toxicity). These results should be taken into consideration before deciding about contaminated sediment management. Keyword: AVS-SEM, bioavailability, metals, Sao Francisco River","PeriodicalId":54498,"journal":{"name":"Rem-Revista Escola De Minas","volume":"18 6","pages":"151-157"},"PeriodicalIF":0.0,"publicationDate":"2014-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1590/S0370-44672014000200004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72368273","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: 0

Iron removal by precipitate flotation 沉淀法浮选除铁

Rem-Revista Escola De Minas Pub Date : 2014-05-14 DOI: 10.1590/S0370-44672014000200012

Denise Fontoura Morosini, C. Baltar, A. C. Duarte-coelho

引用次数: 5

Use of depressants in the direct flotation of a silicate-carbonate phosphate ore 抑制剂在硅酸盐-碳酸盐磷矿石正浮选中的应用

Rem-Revista Escola De Minas Pub Date : 2014-05-14 DOI: 10.1590/S0370-44672014000200010

A. L. Souza, R. Albuquerque, F. Lameiras, Plínio Eduardo Praes, A. Peres

引用次数: 8

Performance of direct and reverse Samarco grinding circuits 直接和反向萨马尔科磨削电路的性能

Rem-Revista Escola De Minas Pub Date : 2014-05-14 DOI: 10.1590/S0370-44672014000200011

A. Rosa, H. Delboni

引用次数: 0