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991.
992.
实现动基座上动调陀螺仪启停锁定 总被引:1,自引:0,他引:1
本文在对动基座上DTG启停运动进行分析的基础上,介绍了实现动基座锁定的思想与方法,并具体实现了由单片机完成的动基座上动调陀螺仪的启停锁定。 相似文献
993.
In this paper, the forced response of a non-linear axially moving strip with coupled transverse and longitudinal motions is studied. In particular, the response of the system is examined in the neighborhood of a 3 : 1 internal resonance between the first two transverse modes. The equations of motion are derived using the Hamilton's Principle and discretized by the Galerkin's method. First, with the longitudinal motion neglected, the forced transverse response is investigated by applying the method of multiple scales to assess the effects of speed and the internal resonance. In general, the speed is shown to affect each mode differently. The internal resonance results in the constant solutions having transition to instability of both a saddle-node type and a Hopf bifurcation. In the region where the Hopf bifurcation occurs, steady-state periodic motion does not exist. Instead the stable motion is amplitude- and phase-modulated. When the coupled system with longitudinal motion is examined with internal resonance, results reveal that the modulated motions disappear. Thus, the presence of the longitudinal motion has a stabilizing effect on the transverse modes in the Hopf bifurcation region. The second longitudinal mode is shown to drift due primarily to a direct excitation of the first transverse mode. Effects of the longitudinal motion on the transverse response are shown to be significant for speeds both away from and close to the critical speed. 相似文献
994.
具有小密度差的两层流体中运动点源的二阶内波解 总被引:1,自引:0,他引:1
在具有自由面的两层流体中,运动点源生成的Kelvin船波存在两种模式,即表面波模式和内波模式。当上、下层流体密度比趋于1时,由内波模式计算的界面波幅趋于无穷大,这与实验事实相违背。为克服此困难,在自由面和界面作小波幅运动的假设,引入一个小密度差参数。研究了运动点源在无粘、不可压且具有小密度差的两层有限深流体中生成的高阶波动。首先利用摄动方法推导了各阶小参数满足的边值问题;其次,给出了小密度差情形下的可解性条件。证明了在密度比趋于1的极限情形,不存在导致界面波幅无穷大的内波模式;最后,利用Phillips的非线性共振相互作用理论,构造了具有自由面的两层有限深流体中Kelvin船波系的二阶一致有效波动解,并证明了该解在深水情形下退化为Newman关于均匀流体中自由面的二阶波动解。 相似文献
995.
本文研究了流体润滑状态下磨粒尺寸对液压泵磨损的影响。结果表明,在液压系统中,泵的磨损主要决定于磨粒与泵内关键运动副动态间隙之间的尺寸关系:尺寸小于动态间隙的磨粒影响很小;尺寸明显比动态间隙大的磨粒不会对泵产生磨损作用;尺寸与动态间隙很接近的磨粒能使泵发生严重磨损。作者还利用扫描电子显微镜对流体润滑状态下三体磨粒磨损中的磨屑形貌进行了观察与分析,并且提出了控制液压系统中磨粒损磨的可行施措。 相似文献
996.
997.
As a typical surface texture, microgrooves have broad prospects in the fields of mechanical engineering, bio-medicine, new energy and efficient heat dissipation of electronic products. Through-mask electrochemical micromachining (TMEMM) is widely used in the fabrication of micro-structures because of high processing efficiency and no residual stress. However, due to the edge effect of current distribution, there is often a serious dimension discrepancy problem in electrochemical machining of micro-structures. In order to weaken the influence of edge effect on the uniformity of microgrooves, the method that TMEMM with a moving cathode is presented. The current distribution in the electrochemical machining is constantly changed by the movement of the cathode. Thus, the uniformity of the micro-structure is improved. The method is studied through the combination of simulation and experimental verification. Firstly, the electrochemical machining process of TMEMM was analyzed theoretically. The theoretical analysis results show that the depth of electrolytic etching is proportional to the current density of electrolytic machining. To change the uniformity of the electrochemical machining, the most important thing is to improve the uniformity of the current distribution. On this theoretical basis, the current distribution and anodic contour of microgroove array during TMEMM are simulated by using the COMSOL finite element analysis software. The simulation results indicate that, compared with the conventional TMEMM, the TMEMM with moving cathode can obtain the microgrooves array with more uniform size. Secondly, on the basis of numerical simulation, the TMEMM experiment was carried out. The experimental results indicate that the TMEMM method of moving cathode can effectively improve the size uniformity of microgroove array. It can be observed by microscope that the microgroove array obtained by TMEMM with a moving cathode had good structural morphology and higher uniformity. Compared with conventional TMEMM, the uniformity of TMEMM with moving cathode has been improved by 68.3%. At the same time, under different experimental conditions, the trend of unevenness of microgroove array was calculated. With the increase of the distance between the cathode and anode, the microgroove depth heterogeneity showed a tendency of first decreasing and then increasing, when the distance between anode and cathode is about 1.3 mm, the unevenness of microgroove array reaches the minimum point. With the increases of cathode width and cathode speed, the depth inhomogeneities of microgroove increase and decrease gradually, respectively. The simulation results are basically consistent with the experimental results. It can be seen that the TMEMM with the moving cathode method can greatly improve the size uniformity. © 2021 Authors. All rights reserved. 相似文献
998.
Based on the Nagel-Schreckenberg model, we propose a new cellular automata model to simulate the urban rail traffic flow under moving block system and present a new minimum instantaneous distance formula under pure moving block. We also analyze the characteristics of the urban rail traffic flow under the influence of train density, station dwell times, the length of train, and the train velocity. Train delays can be decreased effectively through flexible departure intervals according to the preceding train type before its departure. The results demonstrate that a suitable adjustment of the current train velocity based on the following train velocity can greatly shorten the minimum departure intervals and then increase the capacity of rail transit. 相似文献
999.
1000.
Ming Jin 《Mechanics Research Communications》2001,28(3):305
In this paper, a mechanical model is proposed to study cavitation in solids. The material is elastic and obeys Hook's law. Logarithm strain and Cauchy stress in nonlinear elasticity is used. A sphere with a central hole is loaded under hydrostatic tension on surface. In spherical symmetry, closed form solution is got. As radius of the hole tends to zero, a pitchfork bifurcation appears on load-displacement curve. The pitchfork bifurcation indicates that there is a cavitation at center of solid sphere as load reaches a critical value. 相似文献