共查询到20条相似文献,搜索用时 3 毫秒
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X.Q. ZHUS.S. LAW 《Journal of sound and vibration》2002,251(4):697-716
The dynamic loading on a multi-lane continuous bridge deck due to vehicles moving on top at a constant velocity is investigated. The bridge is modelled as a multi-span continuous orthotropic rectangular plate with line rigid intermediate supports. The vehicle is simulated as a two-axle three-dimensional vehicle model with seven degrees of freedom according to the H20-44 vehicle design loading (AASHTO LRFD Bridge Design Specifications 1998 American Association of State Highway and Transportation Officials [1]). The dynamic behavior of the bridge deck under single and several vehicles moving in different lanes is analyzed using the orthotropic plate theory and modal superposition technique. The dynamic loading is studied in terms of the dynamic impact factor of the bridge deck. The impact factor is found varying in an opposite trend as the dynamic responses for the different loading cases under study. 相似文献
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运动电磁媒质中的推迟势 总被引:5,自引:3,他引:2
求解了运动媒质中电磁势方程的格林函数,给出了无界空间的推迟势,结果表明,运动电磁媒质中的格林函数仍具有δ函数形式,场点对源点的时间响应特性不仅与媒质参量有关,而且与媒质运动速度有关。 相似文献
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运动介质反向散射波的演化谱 总被引:3,自引:0,他引:3
声呐、雷达和声达测量的运动介质反向散射波在补偿了能量衰减之后仍是非平稳随机过程。演化谱是描述它的良好手段,不平稳因子At(ω)和特征宽度BL有重要意义。当与散射体积元对应的时间尺寸小于BL时,反向散射过程的功率谱呈单峰特性;当超过BL时,功率谱呈双峰特性。选用具有平缓变化的模糊度函数的发射信号,可以减弱不平稳因子的作用。 相似文献
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本文根据学生学习的实际需求,从磁场做功和能量转换的角度论证了载流回路受磁场作用的一般运动趋势. 相似文献
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量子力学若干基本问题研究的新进展 总被引:5,自引:0,他引:5
首先回顾了量子力学诠释的各种研究的思想起源.以量子测量问题为核心,通过介绍和分析最近5年完成的相关实验(如用腔QED展示的量子退相干过程实验和超冷原子which-way实验等),系统地评述了量子力学若干基本问题研究(包括宏观物体相干性,量子测量的冯*诺伊曼链问题)的新进展,并阐明了其作用与意义.指出了量子力学基本问题的探讨已经走出纯哲学思辨的范畴,开始了大规模的实验检验,而且其研究结果对信息科学有重要的潜在应用.通过基本观念的正确阐释,对量子测量理解方面的某些误解(如超光速现象)给予一定程度的澄清.最后,通过介绍霍夫特(G.′tHooft)最近在量子力学方面的工作,展望了量子力学今后的可能发展. 相似文献
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量子理论若干基本问题研究的新进展 总被引:9,自引:0,他引:9
本结合最后的典型量子物理实验,如用冷原子Bragg散射实现的“which-way”实验,量子退相干过程的微腔QED检验和C60分子的量子干涉等,比较系统地介绍了量子理论基本问题若干研究的新进展,特别强调了处于其核心的量子测量问题及其相关的基本概念和基本思想,如EPR佯谬和Bell不等式,量子退相干和量子纠缠,从理论和实验结合的角度本阐述了被测系统和测量仪器的相互作用怎样导致量子测量的一般动力学过程,由此还讨论了外部环境和内部运动怎样诱导量子退相干和量子耗散,对“薛定谔猫佯谬”和“宏观物体空间局域化描述”给出了可能的物理解释,最后,通过具体例子,本简单地讨论了量子物理基本问题的研究结果对量子信息的应用。 相似文献
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This paper extends a moving screw dislocation theory in a conventional crystal to a one-dimensional hexagonal quasicrystal in the framework of the Landau theory. By introducing two functions φ and ψ which satisfy wave equations, respectively, a general solution is suggested in terms of φ and ψ. The analytical expressions for displacement and stress fields induced by a moving screw dislocation as well as the energy are found. The results obtained here when imposing the condition that the phason fields is absent reduce to those for a moving screw dislocation in a crystal. 相似文献
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We study the breakdown of conformal symmetry in a conformally invariant gravitational model. The symmetry breaking is introduced by defining a preferred conformal frame in terms of the large scale characteristics of the universe. In this context we show that a local change of the preferred conformal frame results in a Hamilton-Jacobi equation describing a particle with adjustable mass. In this equation the dynamical characteristics of the particle substantially depends on the applied conformal factor and local geometry. Relevant interpretations of the results are also discussed. 相似文献
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运用重构混沌吸引子的嵌入技术,开发了提取混沌时间序列信息的宏观信息熵方法,用以判定时滞的存在性和时滞的大小.仿真实验说明了本文方法的有效性
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单模光纤连接损耗研究 总被引:7,自引:0,他引:7
本文从单模光纤高斯模场解析分析法入手,推出了单模光纤归一化频率与高斯模场直径的解析表达式,此后,导出了单模光纤连接中同时存在横向偏移,轴线倾斜,端面间隙,以及光纤直径不匹配时的连接损耗更加完整而普通的计算公式,从而为单模光纤连接器及单模光纤熔接机对准系统的设计提供了依据。 相似文献
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本文研究电子与体纵光学声子耦合弱、与表面光学声子耦合强的半无限晶体中的表面极化子的性质.采用改进了的线性组合算符法和微扰法导出了半无限晶体中的慢速运动极化子的有效哈密顿量.在计及电子在反冲效应中发射和吸收的不同波矢的声子之间的相互作用时,讨论了对有效哈密顿量,诱生势和有效质量的影响.对AgBr晶体进行了数值计算,结果表明反冲效应中发射和吸收的不同波矢的声子之间的相互作用对有效质量和诱生势的影响随耦合常数αt的增加而增加,对有效质量的影响随坐标z的增加而减小的更多,对诱生势的影响随z的增加而增加的更多. 相似文献
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IDENTIFICATION OF MULTIPLE FAULTS IN ROTOR SYSTEMS 总被引:7,自引:0,他引:7
Many papers are available in the literature about identification of faults in rotor systems. However, they generally deal only with a single fault, usually an unbalance. Instead, in real machines, the case of multiple faults is quite common: the simultaneous presence of a bow (due to several different causes) and an unbalance or a coupling misalignment occurs often in rotor systems. In this paper, a model-based identification method for multiple faults is presented. The method requires the definition of the models of the elements that compose the system, i.e., the rotor, the bearings and the foundation, as well as the models of the faults, which can be represented by harmonic components of equivalent force or moment systems. The identification of multiple faults is made by a least-squares fitting approach in the frequency domain, by means of the minimization of a multi-dimensional residual between the vibrations in some measuring planes on the machine and the calculated vibrations due to the acting faults. Some numerical applications are reported for two simultaneous faults and some experimental results obtained on a test-rig are used to validate the identification procedure. The accuracy and limits of the proposed procedure have been evaluated. 相似文献