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991.
Although the nonlinear effects of the ship motions, wave-induced loads and structural responses of conventional vessels have been investigated experimentally and numerically in recent years, similar studies on the wave-piercing tumblehome (WPTH) vessels are rare, in spite of the urgent necessary due to their extensive applications. This paper experimentally investigated the nonlinear effects of the vertical motions and vertical bending moment (VBM) for a WPTH vessel based on a hydro-elastic segmented model test. The model test was carried out in head regular waves for three amplitudes, in the towing tank at Harbin Engineering University. Based on the band-pass filter technique, four kinds of decomposed harmonics are defined by mean offset, linear wave-frequency response, nonlinear wave-frequency response and nonlinear high-frequency vibration. Meanwhile, based on mean offset, three kinds of combined responses are defined by considering linear wave-frequency response, nonlinear wave-frequency response and nonlinear high-frequency vibrations step by step. The transfer functions of vertical motions and VBM are presented as function of the incident wave frequency, and the measured data and VBM were compared with numerical calculations for validation. With the method proposed above, the results of VBM are analyzed by focusing on the influences of decomposed harmonics on the amplitudes and asymmetry of combined responses. Strong nonlinear effects are observed in the VBM. The nonlinearity of VBM can be identified by the significant amplitudes of decomposed harmonics, variation of amplitude with the wave amplitude and remarkable asymmetry about the zero axis. The hogging VBM of WPTH vessel can be even larger than the sagging VBM, which is in contrast to the general experiences from conventional vessels. Combined the calculated relative motion with the decomposed and combined histories of VBM, the occurrence of the transient impact and its characteristics are discussed, and these are then used to analyze the unconventional asymmetry of VBM. Furthermore, the influences of the bow shape over the vertical motions and VBM are discussed. At the end of the paper, the uncertainties in the test are provided. 相似文献
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993.
杨晋阳 《辽宁省交通高等专科学校学报》2013,(5):32-34
全面建设"畅、安、舒、美"公路体系,科学提高公路养护工程质量和管理技术水平。路况评定系统已是公路养护管理工作的重要组成部分。通过采集实地数据录入系统分析得出养护科学决策可降低养护成本,评定系统的应用全面促进了公路检测技术、数据管理技术、数据分析技术、养护决策技术、养护规划及养护计划技术的进步。确保公路畅通、快速、安全和舒适的运营效能,逐步实现公路养护管理的科学化、规范化和制度化。 相似文献
994.
The accuracy and time scale invariance of value-at-risk (VaR) measurement methods for different stock indices and at different confidence levels are tested. Extreme value theory (EVT) is applied to model the extreme tail of standardized residual series of daily/weekly indices losses, and parametric and nonparametric methods are used to estimate parameters of the general Pareto distribution (GPD), and dynamic VaR for indices of three stock markets in China. The accuracy and time scale invariance of risk measurement methods through back-testing approach are also examined. Results show that not all the indices accept time scale invariance; there are some differences in accuracy between different indices at various confidence levels. The most powerful dynamic VaR estimation methods are EVT-GJR-Hill at 97.5% level for weekly loss to Shanghai stock market, and EVT-GARCH-MLE (Hill) at 99.0% level for weekly loss to Taiwan and Hong Kong stock markets, respectively. 相似文献
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成本管理是高速公路工程施工项目管理中的重要组成部分。文章分析了高速公路施工项目成本管理所存在的问题,提出了作业成本法应用于高速公路施工项目的理念,并分析了作业成本法在高速公路施工项目中应用的有利因素与不利因素。 相似文献
999.
由于使命或功能要求的不同,有些船型具有复杂的舱室划分和结构,其节点的结构形式和数量众多,在设计分析过程中发现节点的应力集中和疲劳问题突出.因而,在对具有复杂舱室的船舶进行疲劳强度评估时,需要考虑的疲劳校核部位相应增多.针对疲劳校核部位选取的问题,本次研究提出基于全船有限元基本网格节点进行疲劳节点筛选的方法.另外,本文以由上述筛选方法筛选出的船舶强框架结构位置处的热点为例,给出了该结构处圆弧过渡位置的4种细化方式;并参照中国船级社2015版《船体结构疲劳指南》,给出了复杂舱室船舶节点结构疲劳强度评估的整套方法. 相似文献
1000.
The circulation system of a slurry shield is composed of a transportation system and a processing system.For shield construction, correct selection of the circulation system for the slurry shield is directly related to construc-tion speed. Using the Nanjing Yangtze tunnel as an example, the material balance calculation of the circulation sys-tem, sieving effect analysis, and analysis of the muck carrying ability of the dredging pipe are conducted for various strata. The practical results show that above mentioned calculations and analysis method provide a good reference for the proper selection of a slurry separation system and dredge pipe. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献