Under the consideration of harmonic fluctuations of initial tension and axially velocity, a nonlinear governing equation for transverse vibration of an axially accelerating string is set up by using the equation of mo...Under the consideration of harmonic fluctuations of initial tension and axially velocity, a nonlinear governing equation for transverse vibration of an axially accelerating string is set up by using the equation of motion for a 3-dimensional deformable body with initial stresses. The Kelvin model is used to describe viscoelastic behaviors of the material. The basis function of the complex-mode Galerkin method for axially accelerating nonlinear strings is constructed by using the modal function of linear moving strings with constant axially transport velocity. By the constructed basis functions, the application of the complex-mode Galerkin method in nonlinear vibration analysis of an axially accelerating viscoelastic string is investigated. Numerical results show that the convergence velocity of the complex-mode Galerkin method is higher than that of the real-mode Galerkin method for a variable coefficient gyroscopic system.展开更多
为解决实振型分解反应谱法采用强迫解耦处理调谐质量阻尼器(tuned mass damper,TMD)减震结构具有非比例的阻尼矩阵及计算精度较差的问题,引入复模态理论,利用复振型在状态空间中的正交性和叠加性,并基于复完全平方组合(complex complete...为解决实振型分解反应谱法采用强迫解耦处理调谐质量阻尼器(tuned mass damper,TMD)减震结构具有非比例的阻尼矩阵及计算精度较差的问题,引入复模态理论,利用复振型在状态空间中的正交性和叠加性,并基于复完全平方组合(complex complete quadratic combination,CCQC)法和反应谱,提出一套适用于剪切型TMD减震结构的复振型分解反应谱方法。为匹配抗震规范,基于复振型的复共轭特性以及参数矩阵与状态方程系数矩阵间的关系,推导出实数形式的标准地震作用表达。通过数值分析比较实振型和复振型2种反应谱法的误差发现,实振型误差大于10%,复振型误差在5%以内。研究表明:复振型方法考虑了非比例阻尼和振型速度的影响,比实振型方法具有更高的计算精度和稳定性。匹配规范形式的标准地震作用表达式,可使用设计反应谱,形式简单易用。展开更多
为全面评估航空器小于管制规定间隔事件中的管制员工作状态,提出1种管制员工作状态量化评估方法。首先,基于关键词的词频和共现频率挖掘小于管制规定间隔事件的致因,并在此基础上改进人因分析和分类系统(human factors analysis and cla...为全面评估航空器小于管制规定间隔事件中的管制员工作状态,提出1种管制员工作状态量化评估方法。首先,基于关键词的词频和共现频率挖掘小于管制规定间隔事件的致因,并在此基础上改进人因分析和分类系统(human factors analysis and classification system,HFACS)模型,构建小于管制规定间隔事件的管制员工作状态评估指标体系,合并相同致因因素以最终得到该事件的致因链条。其次,分析各层指标之间的关系,并构建事件致因复杂网络,通过网络的度中心性、介数中心性和PageRank值计算指标的综合权重,进而通过线性加权量化管制员工作状态的危险指数。最后,基于中国民用航空安全信息系统实际案例分析验证管制员工作状态量化评估方法。研究结果表明:繁忙空域/流量大、硬件设备故障、现场管理缺位是综合权重排名前3的关键致因因素;改进的HFACS模型能够全面揭示导致小于管制规定间隔事件发生的人为因素及其耦合关系,最终得到了341条事件致因链条;管制员工作状态评估结果与事件调查报告的结论基本一致,可验证本文所提方法的合理性。研究结果可为管制员工作状态评估提供参考。展开更多
基金Project supported by the National Natural Science Foundation of China (No. 10472060)Shanghai Leading Academic Discipline Project (No.Y0103)the Natural Science Foundation of Shanghai (No.04ZR14058)the Outstanding Youth Program of Shanghai Municipal Commission of Educatio(No.04YQHB088)
文摘Under the consideration of harmonic fluctuations of initial tension and axially velocity, a nonlinear governing equation for transverse vibration of an axially accelerating string is set up by using the equation of motion for a 3-dimensional deformable body with initial stresses. The Kelvin model is used to describe viscoelastic behaviors of the material. The basis function of the complex-mode Galerkin method for axially accelerating nonlinear strings is constructed by using the modal function of linear moving strings with constant axially transport velocity. By the constructed basis functions, the application of the complex-mode Galerkin method in nonlinear vibration analysis of an axially accelerating viscoelastic string is investigated. Numerical results show that the convergence velocity of the complex-mode Galerkin method is higher than that of the real-mode Galerkin method for a variable coefficient gyroscopic system.
