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51.
基于ANSYS软件平台,在模态分析理论基础上,对某型舰载导弹贮存架结构进行了模态分析,得到了贮存架结构前十阶模态结果;着重分析了前五阶模态振型,指出了贮存架弯曲振动和扭转振动是其结构动态特性的主要表现形式;指出针对导弹贮存架结构进行的模态分析,可为贮存架结构的动力学研究工作提供基础和依据。 相似文献
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ABSTRACTShadows have long been a challenging topic for computer vision. This challenge is made even harder when we assume that the camera is moving, as many existing shadow detection techniques require the creation and maintenance of a background model. This article explores the problem of shadow modelling from a moving viewpoint (assumed to be a robotic platform) through comparing shadow-variant and shadow-invariant image features — primarily color, texture and edge-based features. These features are then embedded in a segmentation pipeline that provides predictions on shadow status, using minimal temporal context. We also release a public dataset of shadow-related image sequences, to help other researchers further develop shadow detection methods and to enable benchmarking of techniques. 相似文献
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Masaya Kimura Masanori Kawamura Katsuhiko Yamada 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(3):1336-1346
An analytical expression for distant retrograde orbits (DROs) is obtained in this study. Owing to the fact that a planar DRO is a closed orbit and can be expressed as an approximately elliptical orbit, respective geometries and periods of DROs are analytically calculated. A switching point, where various properties of planar DROs change abruptly with an increase in the orbital radius, is determined. The Mars–Deimos system is taken as a case study in this work. The proposed method can be applied to cases where the Hill’s approximation of the restricted three-body problem is valid. Numerical calculations are performed to validate the proposed method. 相似文献
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《中国航空学报》2023,36(1):324-341
Based on the growth mechanism of natural biological branching systems and inspiration from the morphology of plant root tips, a bionic design method called Improved Adaptive Growth Method (IAGM) has been proposed in the authors’ previous research and successfully applied to the reinforcement optimization of three-dimensional box structures with respect to natural frequencies. However, as a kind of ground structure methods, the final layout patterns of stiffeners obtained by using the IAGM are highly subjected to their ground structures, which restricts the optimization effect and freedom to further improve the dynamic performance of structures. To solve this problem, a novel post-processing geometry and size optimization approach is proposed in this article. This method takes the former layout optimization result as start, and iteratively finds the optimal layout angles, locations, and lengths of stiffeners with a few design variables by optimizing the positions of some specific node lines called active node lines. At the same time, thicknesses of stiffeners are also optimized to further improve natural frequencies of three-dimensional box structures. Using this method, stiffeners can be successfully separated from their ground structures and further effectively improve natural frequencies of three-dimensional box structures with less material consumption. Typical numerical examples are illustrated to validate the effectiveness and advantages of the suggested method. 相似文献
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通过重庆都市经济圈网格化深浅层土壤及评价样品的调查分析,阐述重金属Cd区域上的分布现状,并绘制土壤Cd元素环境质量分级图.研究区浅层土壤Cd背景平均值0.27μg/g,深层0.13μg/g.根据《土壤环境质量标准》对区内土壤进行统计分类,区内浅层土壤Cd元素Ⅱ类土及以上土类面积为83.97%.土壤Cd高含量值主要分布在金刀峡镇北、含谷—白市驿、木耳—王家和玉峰山镇等区域.含谷—白市驿、木耳—王家、西彭北等区域的高Cd含量受人类活动影响比较明显,其中含谷—白市驿区Cd主要来源于生活垃圾、排污底泥和降尘,而金刀峡镇北的高Cd含量属自然背景变化的范畴. 相似文献
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从《灌园叟晚逢仙女》译作的成功中 ,探讨汉译英时词义的选择、语境的分析、用语的变化、句型的转变和句子结构调整的方法与特点。 相似文献