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机械钟表已有近四百年的历史。这四百年来,无数富有聪明才智的制表师们做出了许多美妙的设计。然而,岁月如梭,现在不少设计只能在古董店中偶然一见,甚至已经只能在旧书中找到。另一方面,计算机技术不断进步,虚拟现实已进入日常生活,动漫到处可见。机械表是动的,看书不如看动画。因此,我们想到了要做一个虚拟的机械表图书馆,以飨爱好机械钟表的人们。 相似文献
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单层曲面复眼成像系统的优化设计 总被引:2,自引:1,他引:1
与传统曲面复眼结构不同,提出了在曲面基底上设计非均一微透镜阵列的构想.整个透镜阵列呈环状对称分布,沿径向排列的各级透镜其焦距由所处位置决定,与基底到光探测阵列的距离相吻合.根据几何光学成像原理计算了各级透镜的设计参数并通过光线追迹加以验证.仿真结果表明,这种设计可对全视场在光探测阵列上聚焦,解决了传统曲面复眼边缘视场成像质量急剧下降的问题.同时还论证了采用光刻胶热熔法在曲面基底上制作非均一微透镜阵列的可行性. 相似文献
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In contrast to the traditional interpretation of shear bands in sand as a bifurcation problem in continuum mechanics,shear bands in sand are considered as high-strain phase(plastic phase) of sand and the materials outside the bands are still in low-strain phase(elastic phase),namely,the two phases of sand can coexist under certain condition.As a one-dimensional example,the results show that,for materials with strain-softening behavior,the two-phase solution is a stable branch of solutions,but the method to find two-phase solutions is very different from the one for bifurcation analysis.The theory of multi-phase equilibrium and the slow plastic flow model are applied to predict the formation and patterns of shear bands in sand specimens,discontinuity of deformation gradient and stress across interfaces between shear bands and other regions is considered,the continuity of displacements and traction across interfaces is imposed,and the Maxwell relation is satisfied.The governing equations are deduced.The critical stress for the formation of a shear band,both the stresses and strains inside the band and outside the band,and the inclination angle of the band can all be predicted.The predicted results are consistent with experimental measurements. 相似文献
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