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871.
1MechhacalModelThefractUreproblemwhichisthesameasthatinpaper[I]isfurtherdiscussedinthispaper.TheanalysisoffractUrebehavioursnearcracktipforinfinitelinearelasticorthotropiccompositeplatewithacentralthroughcrackoflengthZaiscarriedout.ThegeometryandloadingcondihonsareshowninFig.1.Tosolvesuchaproblem,weneedtosolvethepanaldifferentialequationwiththefollowingboundaryconditions:wherewisdeflectionofcoddleplane;M.andM,arebendingmoment,Ma.istwistingmoment,andstiffnessmatrixFromthetheoryofplateL'],w… 相似文献
872.
本文对企业经营状况建立了一个具有吸收状态的马尔可夫链的数学模型,列举并分析了这种马氏链的一些性状,结合实际经济现象提出了若干具体问题并给出了相应的解决方法 相似文献
873.
This paper investigates the channel assignment problem of dual‐band PCS systems where single‐band and dual‐band handsets co‐exist. Load‐balancing channel assignment schemes are proposed to improve the system performance. To balance the loads of both bands, the BSC selects a band to serve a call request of a dual‐band handset based on the loads of both bands. In addition, a channel re‐assignment scheme is used to further improve the system capacity. Analytic models and computer simulations have been developed to evaluate the performance of the load‐balancing schemes. The results indicate that both load‐balancing and channel re‐assignment techniques significantly increase the system capacity as the percentage of dual‐band handsets increases. Furthermore, the load‐balancing with channel re‐assignment scheme that combines both techniques achieves the best system performance even when the percentage of dual‐band handset is as low as 25%. In addition, we describe an approach to reduce the signal overhead of the load‐balancing schemes. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
874.
The paper considers the limitation problem of the distillation column systems separating multicomponent mixtures with serial and parallel structures. The solution takes into account the irreversibility of processes. Using entropic balance conditions, the dependence of load on heat consumption is obtained for a binary distillation column. This dependence is parameterized through two characteristic coefficients–reversible efficiency and irreversibility factor. This dependence was used to solve problems of distribution of heat and raw material fluxes in parallel column structure and selection of optimal separation order in serial structure. The obtained results make it possible to estimate the minimum heat consumption for the separation of a given flow of raw materials, the maximum productivity, and efficiency of the system. 相似文献
875.
876.
将基于MPI平台的并行时域有限差分(FDTD)方法与基于完全磁导体(PMC)镜像法相结合,并结合CST模拟软件,模拟给出分布式负载垂直极化有界波电磁脉冲(EMP)的外泄场(包括侧泄场和后泄场)的分布规律。模拟结果与实验结果符合得很好。研究表明:在高度方向上,地面附近的外泄场峰值最大,但远离模拟器时,在1.5 m高的高度范围内,外泄场的峰值差别不大;不管采用何种双指数脉冲源,距离模拟器边缘位置比较近的测点在传输线段的侧泄场的幅值大于分布式负载段侧泄场的幅值,且两者都大于分布式负载末端的后泄场幅值,但随着测点与模拟器边缘的垂直距离的增加,分布式负载段的后泄场可能会比侧泄场大;对于电压峰值相同的双指数激励源而言,所含的高频分量越多,在一定范围内,从其分布式负载末端外泄的后泄场更大;模拟器下方大地的电导率增加,模拟器的外泄场增加。 相似文献
877.
不确定性移动载荷激励下的弹性梁振动是土木、机械和航空航天等工程领域普遍存在的一类重要问题。在许多实际工程中,不确定移动载荷的样本测试数据有限或测试成本较高,本文引入区间过程模型对此类动态不确定性参数进行描述,提出了一种求解不确定移动载荷激励下弹性梁振动响应边界的非随机振动分析方法。首先,介绍了确定性移动载荷激励下弹性梁的振动微分方程及其解析求解方法;其次,引入区间过程模型,以上下边界函数的形式对不确定性移动载荷进行度量,进而基于模态叠加法发展出弹性梁振动响应边界求解的非随机振动分析方法;最后,将上述非随机振动分析方法应用于车桥耦合振动问题。 相似文献
878.
879.
Long-span reticulated dome is often considered as a landmark building of a region, so it is very important to investigate the dynamic response and propose the damage assessment method of reticulated dome under blast loading. In this article, a fine finite element model of Kiewitt8 (K8) single-layer reticulated dome was established by using ANSYS/LS-DYNA. The effects of standoff distance, charge weight, rise–span ratio, span, and roof weight on the responses of K8 single-layer reticulated dome were numerically studied. The results showed that the blast-resistant performance of reticulated dome with smaller rise–span ratio and larger span under exterior blast load was more advantageous. Although the blast-resistant capacity of reticulated dome with large span and large roof weight was favorable, the plastic deformations of reticulated dome members were small and the utilization of material was low at failure state. According to the dynamic response characteristics of plentiful K8 single-layer reticulated domes at different damage levels, a damage model of K8 single-layer reticulated dome under exterior blast load was proposed in this article to indicate the damage level and determine the ultimate strength. Besides, a new damage criterion for K8 reticulated dome was also defined. This damage model was defined based on the physical phenomena at different damage levels, which made the strength failure criterion had definite physical meaning. Using the proposed damage criterion and a new search algorithm for pressure and impulse, the pressure–impulse diagrams for the typical K8 reticulated dome were derived from the numerical simulations to evaluate the damage level of reticulated dome under blast loading. Finally, a method to determine the safety standoff distance for reticulated dome under given TNT charge weight was also proposed. 相似文献
880.
敞开式空间结构的桁架由于直接受气流作用,其流场空间分布复杂,风荷载确定困难,且风洞试验受模型缩尺比限制难于获取桁架结构上的气动力.借助数值风洞技术,利用高性能计算平台,本文数值求解了敞开式桁架结构的空间流场及风荷载分布.敞开式空间桁架结构整体风荷载表现为水平向为主,竖向不显著的特点,该点与封闭式桁架结构整体通常表现出竖向较强吸力作用明显不同.敞开式空间桁架结构整体风荷载对风向角表现并不敏感,其原因在于敞开式空间桁架的流场多处分离且相互干扰严重,其整体特征紊流不易在某个风向角下特别占优. 相似文献