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101.
本文采用应力波特征线方法详细分析了刚体撞击固支的弹性长杆的撞击过程,指出当撞块质量和长杆质量的比值满足一定条件时,在第一次撞击过程结束后会发生第二次撞击。 相似文献
102.
103.
考虑地基-结构-散粒体相互作用时贮仓结构的静、动力研究[Ⅱ]--有限元分析 总被引:1,自引:0,他引:1
对贮仓结构的静、动力问题进行了系统的分析计算:考虑到地基—结构—散粒体间的相互作用,引入新的计算模式,对不同地基上的贮仓结构模型进行了系统的有限元静、动力分析计算,并与作者所完成的试验结果进行了比较。结果表明,所提出的计算模式及有限元计算模型是正确的。 相似文献
104.
105.
Cargo Pendulation Reduction of Ship-Mounted Cranes 总被引:4,自引:0,他引:4
Ship-mounted cranes are used to transfer cargo from large container ships to smaller lighters when deep-water ports are not
available. The wave-induced motion of the crane ship can produce large pendulations of the cargo being hoisted and cause operations
to be suspended. In this work, we show that it is possible to reduce these pendulations significantly by controlling the slew
and luff angles of the boom. Such a control can be achieved with the heavy equipment that is already part of the crane so
that retrofitting existing cranes would require a small effort. Moreover, the control is superimposed on the commands of the
operator transparently. The successful control strategy is based on delayed feedback of the angles of the cargo-hoisting cable
in and out of the plane of the boom and crane tower. Its effectiveness is demonstrated in a fully nonlinear three-dimensional
computer simulation and in an experiment with a 1/24th-scale model of a T-ACS (The Auxiliary Crane Ship) crane mounted on
a platform moving with three degrees of freedom. The results demonstrate that the pendulations can be significantly reduced,
and therefore the range of sea conditions in which cargo-transfer operations can take place can be greatly expanded. 相似文献
106.
Jinzhi?LeiEmail author Pedro?J.?Torres Meirong?Zhang 《Journal of Dynamics and Differential Equations》2005,17(1):21-50
In this paper, we will give, for the periodic solution of the scalar Newtonian equation, some twist criteria which can deal with the fourth order resonant case. These are established by developing some new estimates for the periodic solution of the Ermakov–Pinney equation, for which the associated Hill equation may across the fourth order resonances. As a concrete example, the least amplitude periodic solution of the forced pendulum is proved to be twist even when the frequency acroses the fourth order resonances. This improves the results in Lei et al. (2003). Twist character of the least amplitude periodic solution of the forced pendulm. SIAM J. Math. Anal. 35, 844–867.Dedicated to Professor Shui-Nee Chow on the occasion of his 60th birthday. 相似文献
107.
The Nordic forest industry requires just-in-time wood deliveries. Operations must continue regardless of season, weather and terrain. Soil compaction and deep ruts must be avoided while providing high performance and a reasonable working environment for operators.The Xt28 pendulum arm forwarder is a full-size concept forwarder with six hydrostatic propelled wheels on pendulum arms built on a three-piece frame connected with two articulation joints. The Xt28 concept machine was tested according to Skogforsk standard machine tests. Rut depth test focused on soil interaction where rut depth was measured related to number of passes. Machine dynamics were measured using standardized test track with focus on operator comfort.The project proved the potential of pendulum arm technology in off-road transportation. Automatic pendulum arm levelling, equalized ground pressure between wheels and improved operator comfort through reducing adverse vibrations and roll angles, simultaneously reducing dynamic forces transferred to the forest floor. Pendulum arm technology improves travel speed in adverse terrain, providing unparalleled side slope capability and enhanced productivity. 相似文献
108.
高耸异型烟囱结构风压和风振系数试验研究 总被引:3,自引:0,他引:3
本文在模拟的大气边界层中,对某一发电厂高耸异型烟囱的刚性模型进行了测压试验研究,得到了这一结构的平均风压系数、最大和最小风压系数分布,以及该结构的风荷载体型系数;结果表明在烟囱外形明显变化的局部区域,风压绝对值较大,与理论分析一致。同时,对动态测力试验模型进行了高频动态天平测力试验研究,详细介绍了试验及数据处理方法,根据试验结果计算得到了该烟囱在风作用下的动力响应和风振系数;根据试验结果计算所得的风振系数值大于按规范公式估算值。这些结果不仅为结构的风荷载计算提供了依据,也有助于进一步认识该类异性烟囱结构的风荷载和风振特性。 相似文献
109.
110.
Fast determination of neighboring atoms is an essential step in molecular dynamics simulations or Monte Carlo computations, and there exists a variety of algorithms to efficiently compute neighbor lists. However, most of these algorithms are general, and not specifically designed for a given type of application. As a result, although their average performance is satisfactory, they might be inappropriate in some specific application domains. In this article, we study the case of detecting neighbors between large rigid molecules, which has applications in, e.g., rigid body molecular docking, Monte Carlo simulations of molecular self-assembly or diffusion, and rigid body molecular dynamics simulations. More precisely, we compare the traditional grid-based algorithm to a series of hierarchy-based algorithms that use bounding volumes to rapidly eliminate large groups of irrelevant pairs of atoms during the neighbor search. We compare the performance of these algorithms based on several parameters: the size of the molecules, the average distance between them, the cutoff distance, as well as the type of bounding volume used in the culling hierarchy (AABB, OBB, wrapped, or layered spheres). We demonstrate that for relatively large systems (> 100,000 atoms) the algorithm based on the hierarchy of wrapped spheres shows the best results and the traditional grid-based algorithm gives the worst timings. For small systems, however, the grid-based algorithm and the one based on the wrapped sphere hierarchy are beneficial. 相似文献