Almir Silva - Academia.edu (original) (raw)

Papers by Almir Silva

Journal of Magnetism and Magnetic Materials

Abstract In this work, the dynamic losses of modern high-permeability grain-oriented (HGO) electr... more Abstract In this work, the dynamic losses of modern high-permeability grain-oriented (HGO) electrical steel were investigated as a function of the clearance used during the shear cutting process and the frequency of the applied magnetic field from 3 up to 1000 Hz. The strips were shear cut at clearances of 0.01, 0.04, 0.05, 0.10 and 0.15 mm, and after cutting the samples were heat treated at 850°C for 1 hour. The edge regions were analysed using optical microscopy before and after the heat treatment, and a significant mechanical deformation and consequently a deterioration of magnetic properties was observed, which can be restored through stress-relief annealing. Clearances of 0.01, 0.04, 0.05 and 0.10 mm exhibit the same total magnetic loss; however, for the clearance of 0.15 mm, it increases by ≈ 10 % due to the crack in the fracture zone and greater rollover region. The heat treatment improves the magnetic performance of the as-cut HGO steel strips by ≈ 8 % and ≈ 15 % for 1.5 and 1.7 T, respectively, at frequency of 60 Hz. Finally, a detailed study of the dependence of the losses (hysteresis Ph, classical eddy current Pc, and excess Pe) on frequency and maximum induction was performed. Interestingly, it was observed that Ph is much more influenced by clearance than other losses. In addition, the role of the maximum induction Bmax on each loss component was investigated as a function of frequency. Our findings show that below 0.2 T Pc is larger than Pe and Ph, however, above this threshold there is an inversion where Pe is larger than the other two components in the entire frequency range, even with 1.5 T of magnetic induction. This can indicate that different physical mechanisms that constitute the permeability spectrum exhibit different relaxation times, therefore, they are activated at different frequencies and magnetic field intensities.

This study aims to discuss the school physical education and the myth and reality issues. The goa... more This study aims to discuss the school physical education and the myth and reality issues. The goal is to investigate whether the physical education aware people about the importance of physical activity for a better quality of life. The methodological procedure used was a mixed questionnaire containing tem questions applied to a hundred high school students. The concepts studied was some such as myth, reality, teaching practice, healthy habits, among others, guide the theoretical framework. To conclude, the physical education fulfils its role in the student’s awareness to the benefits of your practice.

O ano de 2010 comecou de forma interessante para os alunos do 4o semestre do curso de bacharel em... more O ano de 2010 comecou de forma interessante para os alunos do 4o semestre do curso de bacharel em Teologia da classe de Teologia pratica II. Um dos primeiros textos a serem estudados foi “Os varios olhares do educador cristao” de autoria de Esdras Bentho da revista Educador Cristao, Ano 10, no 40 da CPAD em que discute a respeito da figura do educador cristao. Entretanto, durante a discussao em sala de aula nos deparamos com as colocacoes do autor em que ora se referia a pessoa que ensina na igreja como educador, ora como professor. Ficamos a nos perguntar a diferenca entre ser professor e ser educador. Tal questionamento nos instigou a buscarmos respostas entre os professores de EBD de nossas igrejas que atendessem a nossa inquietacao. Saberiam eles qual a diferenca entre ser professor e ser educador? O objetivo deste projeto foi, apos o estudo em classe do texto, buscar conhecer a opiniao de professores de EBD sobre a questao: Ha diferenca entre ser um professor e ser um educador?...

Acta Veterinaria Brasilica, 2015

Nexos Econômicos, 2013

Esse artigo analisa o impacto do crédito rural no Produto Interno Bruto (PIB) agropecuário da eco... more Esse artigo analisa o impacto do crédito rural no Produto Interno Bruto (PIB) agropecuário da economia brasileira no período 1995 a 2009. Os resultados dos modelos econométricos demonstraram a causalidade bidirecional entre o crédito rural como proporção do PIB real agropecuário e esse último. Analizam-se também as modalidades de crédito rural destinadas ao investimento, custeio e comercialização da produção rural, além das séries de crédito rural para à agricultura e pecuária. O crédito rural para a comercialização e à agricultura em relação ao PIB real do setor agropecuário impactou positivamente esse último. Um choque positivo de 4,23% no crédito para a comercialização em relação ao PIB real desse setor tende a impactar o PIB real agropecuário em 1,89%. Já um choque de 1,90% no crédito destinado à agricultura em relação ao PIB real impacta o PIB real agropecuário em 0,79%.

Electroanalysis, 2016

This work describes the sequential determination of amlodipine (AML) and atenolol (ATN) by batch ... more This work describes the sequential determination of amlodipine (AML) and atenolol (ATN) by batch injection analysis (BIA) with pulsed amperometric detection (BIA-PAD). Boron doped diamond (BDD) was used as working electrode. AML was detected at +1.00 V and ATN at +1.65 V. The proposed BIA method is simple, robust, precise (RSD 70 injections h−1), generates reduced volume of waste (without use of organic solvent) and requires minimal sample manipulation (dissolution and dilution in electrolyte). The limits of detection were 0.074 and 0.073 µmol L−1 for AML and ATN, respectively. The results obtained with the proposed BIA method were compared to those obtained by HPLC and similar results were obtained (at 95% of confidence level).

Um adesivo de baixa viscosidade foi desenvolvido para atuar na colagem de grandes areas. O sistem... more Um adesivo de baixa viscosidade foi desenvolvido para atuar na colagem de grandes areas. O sistema de laminacao epoxi AR300 foi nanomodificado por particulas de grafeno e utilizado como adesivo. A resistencia aparente ao cisalhamento de juntas single-lap foi medida e apresentou valores comparaveis aos de adesivos estruturais comerciais. A adicao de 2% de grafeno foi responsavel por um aumento de capacidade de carga de 57,7%. A baixa viscosidade do AR300 facilita o espalhamento da resina na area a ser colada. Isso permite a sua utilizacao em reparos de tubulacoes, paineis, cascos de barcos, fuselagem de avioes e tambem para a fabricacao de estruturas sanduiche. Alem disso, o processo de dispersao do grafeno foi facilitado pela baixa viscosidade e processos como a mistura por alto cisalhamento e ultrassom passaram a ser possiveis. A caracterizacao do novo adesivo nanoestruturado pela difracao de raios X indicou a existencia de nanoestruturas lamelares com tamanho medio de 17 nm e espacamento basal de aproximadamente 0,34 nm. Por meio do metodo de nanoindentacao foi possivel medir o modulo de elasticidade do adesivo com e sem nanoparticulas. O aumento da rigidez do material foi de 22,3% com a adicao de 2% de grafeno.

ABSTRACT The goal of this paper is to investigate the effect of graphene nanosheets addition to l... more ABSTRACT The goal of this paper is to investigate the effect of graphene nanosheets addition to laminated composites (carbon fibers/epoxy). A set of graphene based nanocomposites, up to 3 wt%, are synthesized using a high shear mixer and sonication. The results from XRD and SEM have showed that nano-structures formed are mostly into the exfoliated condition. The Hybrid laminates were evaluated using three point bending tests. The results have shown that graphene based hybrid nanocomposites lead to peak stresses around 139% higher than control samples. A decrease on glass transition temperature with the addition of graphene was observed. Furthermore, the thermal stability was compromised, as the temperature on 5% weight loss dropped around 30%.

Aerospace, 2006

A new nanocomposite is prepared by cold direct mixing. To investigate how this new nanocomposite ... more A new nanocomposite is prepared by cold direct mixing. To investigate how this new nanocomposite behaves under low velocity impact loads, a set of plates with 16 layers and 65% fiber volume fraction is manufactured by vacuum assisted wet lay-up. The fibers have a plain-weave configuration, while the epoxy system is ARALDITE M/HY956. The nanoclay is an organically modified montmorillonite ceramic and it is dissolved into the epoxy system in a 1%, 2%, 5% and 10% ratio in weight with respect to the matrix. X-ray diffraction tests indicate that rather than exfoliated, these nanocomposites are mostly in intercalated form, with possible presence of immiscible nano systems at 10% concentration. The impact tests are based on the ASTM D5628-01 standard. For the 20 joules impact energy condition, the energy absorption by delamination increases close to 48%, while for larger energies, i.e. 40 and 60 joules, the average improvement into energy absorption is around 15%. Even for larger energies ...

Proceedings of the 11th CONTECSI International Conference on Information Systems and Technology Management, 2014

Atualmente as redes de computadores no âmbito empresarial possuem sistemas e equipamentos essenci... more Atualmente as redes de computadores no âmbito empresarial possuem sistemas e equipamentos essenciais ao negocio sendo que qualquer parada nao planejada acarretara em diversos problemas e prejuizos, comprometendo o resultado e desempenho produtivo das companhias (HEEGAARD, 2009: 1215). Esforcos na literatura concentram-se em potencializar a disponibilidade da rede e dos servicos nela contidos, bem como prover um rapido reestabelecimento da mesma em caso de falhas (WU, 2012: 421) (ORLOWSKI, 2010: 277) (YOUNIS, 2009:64). Neste trabalho e apresentado um metodo para a classificacao, diagnostico e tratamento dos incidentes a partir de processos para rastreamento de problemas na rede, identificacao dos ambientes criticos ao negocio do cliente. Contempla o acompanhamento executivo em crises decorrentes de incidentes em tais ambientes e uma proposta de fluxo para uma estrutura de atendimento que aplique todos esses processos integrados com as melhores praticas do ETOM-ITIL. Full Paper PDF: http://www.contecsi.fea.usp.br/envio/11contecsi-files/papers/842/submission/director/842-2505-1-DR.pdf

54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2013

This paper addresses the effect of graphene dispersion into epoxy adhesives and its aging by UVA ... more This paper addresses the effect of graphene dispersion into epoxy adhesives and its aging by UVA light exposure. To achieve this goal, two approaches were employed. The first one was direct exposure of the nano-modified AR300/AH15 samples to UVA light for four hundred hours. After the aging process, nanoindentation tests were performed. The second approach was based on tensile tests of aged single lap joints (SLJ). The graphene nanostructures formed inside the AR300/AH15 nano-modified adhesive seems to block the aging process, as none of the specimens presented a decrease on stiffness. The forcedisplacement curves obtained by nanoindentation seem to indicate a good dispersion process, as the large majority of the curves laid down at the same path. When the single lap joints were tested the results also indicated an average increase on bearing-load capacity of 40.96% and 72.03% for 1 wt. % and 2 wt. %, respectively for one hundred hours aging. When the aging reached two hundred hours, there is a decrease on load capacity when compared against the 100 hours results. Even though, the average load capacity was 27.03% and 58.19% higher than the not aged AR300/AH15 single lap joints. At 400 hours there is another increase on load capacity, i.e. 32.06% and 74.43% for 1 wt. % and 2 wt. % graphene, respectively. A finite element simulation revealed that peel and shear stresses at adhesive edge increased by 82%. The Fourier Transformed Infrared tests revealed that chemical changes on hydroxyl, carbonyl and epoxy components could be the reason for this behavior. The graphene dispersion into the epoxy adhesives seems to have a double folded effect, in one hand it is increase the bonded joint capacity and on the other hand block the aging effect of UVA light.

52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 2011

Revista Brasileira de Zootecnia, 2006

Avaliaram-se o consumo, as digestibilidades total, ruminal e intestinal dos nutrientes, a taxa de... more Avaliaram-se o consumo, as digestibilidades total, ruminal e intestinal dos nutrientes, a taxa de passagem da digesta ruminal e as concentrações de amônia e pH ruminal de dietas contendo silagens de milho e sorgo, com e sem inoculante microbiano. Utilizaram-se quatro animais Holandês x Zebu fistulados no rúmen e no abomaso, distribuídos em um quadrado latino 4 x 4 (duas silagens x dois inoculantes). Adotou-se uma relação volumoso:concentrado de 63:37%, na MS. O consumo e as digestibilidades total e ruminal dos nutrientes não foram influenciados pelas dietas experimentais. Para os consumos de MS, PB e NDT, registraram-se, respectivamente, valores médios de 6,61; 0,75 e 3,96 kg/dia. Obtiveram-se valores médios de 61,17 e 61,91; 61,43 e 13,21 e 52,13 e 92,96% para as digestibilidades total e ruminal da MS, PB e FDN, respectivamente. Quanto à digestibilidade intestinal dos nutrientes, detectou-se efeito do tipo de silagem apenas na FDN, observando-se maior valor para a dieta à base de s...

International Journal of Impact Engineering, 2011

This paper focuses on ballistic tests of a new class of composite materials, i.e. hybrid nanocomp... more This paper focuses on ballistic tests of a new class of composite materials, i.e. hybrid nanocomposites. The two hybrid nanocomposites studied are fiber glass/epoxy/nanoclay and fiber glass/epoxy/nanographite. The fiber glass used is a plain weave 200 g/m2, while the nanoclay is an organically modified montmorillonite ceramic (Nanomer I30E). The expandable graphite used to generate the graphene nanosheets was from Graftech (grade

International Journal of Impact Engineering, 2007