The role of compound lens in optimizing the irradiation uniformity in longitudinal pumping laser

In order to optimize the axial irradiation uniformity of a laser in plasma, this paper investigates the role played by the compound lens using a ray-tracing method. Obtained results show that the adoption of the compound lens is capable of increasing the axial line-focus length. Meanwhile, after the energy attenuation in the plasma has been considered, moderating the optical parameter of the compound lens to obtain the corresponding energy output to compensate for the attenuation optimizes the irradiation uniformity along the focal line.     

冲压板材拉伸筋阻力的一种有效数值计算方法

将弹塑性有限变形的拟流动角点本构理论和厚向各向异性屈服函数引入弹塑性动力显式有限元列式,对板材通过拉伸筋的变形过程及拉伸筋阻力进行了数值模拟,并与有关实验结果进行了比较很好的一致性,表明了该计算方法的有效性。进而,数值研究了拉伸筋形状、界面摩擦状况以及材料的厚向各向异性对拉伸筋阻力的影响,为实际覆盖件冲压成形中拉伸筋的设置提供了重要的定量依据。     

结构力学分析方法在南海水平井钻进预测中的应用

本文探讨了结构力学分析方法-非线性有限元性在预测水平井钻进中的工程应用,在钻探水平井尤其是大位移水平井中,事先较准确地预测出钻柱的钻进扭矩及钻头前进的方向,是取得水平井成功的关键条件之一。利用非线性有限元理论,着重分析了水平井实际钻进中的钻柱大变形非线性及钻柱与井壁的接触非线性问题,并导出了一套非线性有限元钻柱力学模式,在此基础上编制了一套非线性力学计算程序软件,并在海洋石油南海西部石油公司一个钻井平台水平井钻井进行了五口井的实际验证,获得了一些有启迪性的结论。     

极大倾角光纤光栅悬臂梁振动传感器性能优化

提出一种利用极大倾角光纤光栅(Ex-TFG)谐振峰的3 dB点进行悬臂梁低频振动检测的优化方法。对Ex-TFG的轴向应变和弯曲应变特性进行理论分析和实验验证;对基于光强调制的Ex-TFG振动传感的光谱响应特性进行理论分析,采用Ex-TFG谐振峰的3 dB点对振动进行实验研究。实验结果表明:1)Ex-TFG在轴向应变和弯曲应变条件下,其谐振波长均发生蓝移,横电(TE)模和横磁(TM)模的轴向应变灵敏度分别为-2.8 pm/με和-1.8 pm/με,透射强度基本不变,在0～0.4 m~(-1)的曲率范围内基于光强变化的弯曲应变灵敏度分别为2.6 dB/m~(-1)和1.2 dB/m~(-1),基于波长漂移的弯曲应变灵敏度分别为-3.34 nm/m~(-1)和-2.53 nm/m~(-1);2)在低频振动的检测中,Ex-TFG的TE模和TM模的谐振峰3 dB点的振动加速度灵敏度分别为113.54 mV/g和100.93 mV/g,比谐振峰的峰值波长点(100%点)的振动加速度灵敏度高2倍多,且信噪比(SNR)高约10 dB。此外,SNR随悬臂梁厚度的增大而增大;3)在相同条件下,TE模具有比TM模更高的振动响应灵敏度,但TM模比TE模具有更好的输出稳定性。     

轴向运动层合圆柱壳体的振动特性

研究了轴向运动层合圆柱壳体的振动特性．基于Donnell壳体理论,建立了轴向运动层合圆柱壳体的横向振动方程,使用Galerkin方法求解该振动方程,得到其固有频率,通过与有限元结果对比说明方法的有效性．分析了轴向速度、纤维方向角、长径比和厚径比对壳体振动特性的影响．研究表明：当纤维方向角为 (15?/-15?)s时,轴向运动柱壳前3阶固有频率达到最大值．     

轴向磁场对环形浅液池内硅熔体热毛细对流的影响

为了更好地了解轴向磁场对温度梯度作用下Marangoni-热毛细对流的影响,采用有限差分法对环形浅液池内硅熔体制单晶的流动进行了数值模拟.研究了三种不同边界条件下,Ha数分别为0、10、20、30对应下硅熔体内部流动强度和自由表面速度.结果表明,轴向磁场对浅液池内的Marangoni对流、热毛细对流和耦合的Marangoni-热毛细对流都有较好的抑制作用,且随着磁场强度的增强,抑制作用增加,更有利于提高晶体的结晶质量.当磁场强度和底部热流密度一定时,随着水平温度梯度的增加,靠近内壁的流动得到增强,外壁附近流动反而减弱.     

采用变焦液体透镜的共焦检测系统的设计与仿真

共焦显微技术越来越广泛地应用于微机电系统和半导体器件的三维轮廓测量。设计一种新型采用变焦透镜作为轴向扫描方式的共焦显微系统,利用变焦透镜的焦距变化来代替传统的轴向位移扫描。系统实现了无机械运动的轴向扫描,消除了传统共焦系统中由位移台移动带来的振动,不仅减小了系统的复杂度,而且降低了成本。进一步设计了基于位移台和变焦透镜的两种共焦检测系统,并且对其进行了仿真实验。实验结果表明:基于位移台和基于变焦透镜的共焦系统的聚焦成像和离焦成像结果类似,并且光强的轴向分布曲线也基本相同,表明此方法可行。     

Asymptotic analysis on weakly forced vibration of axially moving viscoelastic beam constituted by standard linear solid model

The weakly forced vibration of an axially moving viscoelastic beam is investigated.The viscoelastic material of the beam is constituted by the standard linear solid model with the material time derivative involved.The nonlinear equations governing the transverse vibration are derived from the dynamical,constitutive,and geometrical relations.The method of multiple scales is used to determine the steady-state response.The modulation equation is derived from the solvability condition of eliminating secular terms.Closed-form expressions of the amplitude and existence condition of nontrivial steady-state response are derived from the modulation equation.The stability of nontrivial steady-state response is examined via the Routh-Hurwitz criterion.     

轴向运动三参数黏弹性梁弱受迫振动的渐近分析

研究了轴向运动三参数黏弹性梁的弱受迫振动．建立了轴向运动三参数黏弹性梁受迫振动的控制方程．使用多尺度法渐近分析了运动梁的稳态响应,导出了解稳定性边界方程、稳态振幅的表达式以及稳态响应非零解的存在条件．依据Routh-Hurwitz定律决定了非线性稳态响应非零解的稳定性．     

Dynamics of Motorized Vehicle Flow under Mixed Traffic Circumstance

To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a car-following model based on the principle of collision free and cautious driving is proposed. Lateral friction and overlapping driving are introduced to describe the interactions between motorized vehicles and non-motorized vehicles. By numerical simulations, the flux-density relation, thetemporal-spatial dynamics, and the velocity evolution are investigated in detail. The results indicate non-motorized vehicles have a significant impact on the motorized vehicle flow and cause the maximum flux to decline by about 13%. Non-motorized vehicles can decrease the motorized vehicle velocity and cause velocity oscillation when the motorized vehicle density is low. Moreover,non-motorized vehicles show a significant damping effect on the oscillating velocity when the density is medium and high, and such an effect weakens as motorized vehicle density increases. The results also stress the necessity for separating motorized vehicles from non-motorized vehicles.