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来源:Advances in Materials Science and Engineering , 2015

作者:Algazy Zhauyt, Janat Musayev

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Stress waves propagate in soil in case of earthquake and man-made effects (traffic flow, buried explosions, shield-driven pipes and tunnels, etc.). The wave point-sources are those located at the distances equal to more than two waves lengths, which significantly simplifies solving of a problem of these waves’ strength evaluation. Distribution of stress and displacement by the stress waves propagation in elastic medium is a complex pattern. The stress distribution in propagating waves depends on the type and form of source, conditions of the source contact with medium, and properties of mediums in the vicinity of the source. The point-sources and their combinations are selected in such a way to model an influence of machines and processes on soil body in case of shield-driven pipes (tunnels).

    来源:Advances in Materials Science and Engineering , 2015

    作者:Dingjun Xiao;Jun Xie;Zheming Zhu;等

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    A mixed failure criterion, which combined the modified maximum principal stress criterion with the damage model of tensile crack softening, was developed to simulate crack propagation of rock under blasting loads. In order to validate the proposed model, a set of blasting models with a crack and a borehole with different incident angles with the crack were established. By using this model, the property of crack propagation was investigated. The linear equation of state (EOS) was used for rock, and the JWL EOS was applied to the explosive. In order to validate the numerical simulation results, experiments by using PMMA (polymethyl methacrylate) with a crack and a borehole were carried out. The charge structure and incident angle of the blasting experimental model were the same as those in the numerical models. The experiment results agree with the numerical simulation results.

      来源:Advances in Materials Science and Engineering , 2015

      作者:Junying Ma;Bingjun Wang;Lili Cao;等

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      Four cellulose solvents including [C2mim][CH3COO] + DMSO, [C4mim][CH3COO] + DMSO, [C6mim][CH3COO] + DMSO, and [C8mim][CH3COO] + DMSO were prepared by adding dimethyl sulfoxide DMSO in 1-ethyl-3-methylimidazolium acetate [C2mim][CH3COO], 1-butyl-3-methylimidazolium acetate [C4mim][CH3COO], 1-hexyl-3-methylimidazolium acetate [C6mim][CH3COO], and 1-octyl-3-methylimidazolium acetate [C8mim][CH3COO], respectively. The solubilities of cellulose in these solvents were determined at 25°C. The effect of the alkyl chain length in imidazolium cation on cellulose solubility was investigated. With increasing alkyl chain length in imidazolium cation, the solubility of cellulose increases, but further increase in alkyl chain length results in decreases in cellulose.

        来源:Advances in Materials Science and Engineering , 2015

        作者:Seung Goo Lee;Won Ho Park;Ji Eun Lee;等

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        This study suggested the optimum conditions for the stable dispersion of cellulose microparticles in PAN spinning dope, which was prepared for spinning the fiber. Many research studies have investigated methods for preparing a variety of carbon fiber precursors in an attempt to control their characteristics according to the applications. In order to prepare PAN fiber that contains fine cellulose particles, it is important to create a uniformly dispersed spinning dope. Minimization of the cellulose particle size was subjected to heat treatment at various temperatures in order to reduce the cohesive force from the hydrogen bonds between the cellulose molecules. Carbonized cellulose microparticles were obtained for efficient dispersion using the physical method and the sedimentation method. Several instrumental analyses were conducted to study the characteristics of the particles and solutions with SEM, FT-IR, XRD, and a particle size analyzer. From the results, the dispersion of the PAN spinning dope with a chemical treatment was superior to the milling method followed by heat treatment. In this study, heat-treating cellulose microparticles at 400°C was found to be the most effective method.

          来源:Advances in Materials Science and Engineering , 2015

          作者:Yan-Huei Li, Chi-Chang Hsieh

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          LED lamps are characterized by high energy efficiency, high luminance, and long lifespans. However, the heat radiation problem caused by the extra high power shortens the lifespan and reduces the luminous efficiency of such lamps. This study introduced the development of a novel cooling fin structure for LED lamps and compared its performance with those of commercially available products. The objective of the design was to reduce the maximum temperature and temperature difference on the fin, the amount of aluminum required for fin manufacturing, and CO2 emissions to save energy. The study employed the Taguchi method for experiment planning and used gray relational analysis and principal component analysis to determine the optimal parameter combination for cooling fins. The results showed that the maximum temperature on the fin surface dropped by 2.62°C in environments without forced convection, which indicated improved lighting efficiency. Furthermore, the amount of aluminum used per unit volume for fins was reduced by 15%, which effectively reduced CO2 emissions during the manufacturing process.

            来源:Advances in Materials Science and Engineering , 2015

            作者:Hongsig Kang, Kwangkuk Ahn

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