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以聚醚多元醇,玻璃纤维(G)及多次甲基多苯基多异氰酸酯为原料,采用一步法制备了玻纤增强硬质聚氨酯复合材料(RPU-G).对RPU-G的力学性能进行了研究,结果表明,随着G含量(m)的增加,其拉伸强度呈先升后降的变化趋势;当m为10%[长径比(n)为20~40]时,RPU-G20~4010 的力学性能达到最佳.由于G的n不同,其增强效果差异显著,以RPU-G20~4010的拉伸强度最大(0.80 MPa),与RPU相比提高了95%.压缩强度因G的n不同出现不同的趋势,仍以n为20~40的G增强效果最为明显,RPU-G20~405的压缩强度增加了10%. 相似文献
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在初中物理"浮力"一章的教学过程中,为了激发学生学习物理的兴趣,提高学生科学探究的意识,培养学生的自学能力和实践动手能力,我们提前组织了一次造船比赛,收到了意想不到的效果,也使我们首次体会到创新真的能带来巨大的效益. 相似文献
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Secondary ion mass spectroscopy was used to study the chemical diffusivity of 018 in c-textured YBa2Cu3O7-δ/SrTiO3 epitaxial thin film. By fitting experimental data to the one- dimensional diffusion curve, the apparent diffusivity along the c-axis was obtained to be equal to l.02×1014cm2/sec when the temperature was 350℃. A computer analysis method was put forward to calculate the "spiral diffusion" process, and the diffusivity anisotopy of films with different mosaic size obtained. For a film of 7000×7000?2 mosaic size, Dab was found to be ~3.55×10-5xexp((-1.03 ev)/kT) cm2/sec. The calculated results reveal that the variation of the results of Dc is not the result of diffusivity anisotropy but of the difference in mosaic size. 相似文献