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151.
在神光Ⅱ第9路ICF高功率激光装置中,采用可调法布里-珀罗(F-P)滤波器对幅度调制效应进行补偿,根据补偿装置的技术要求,提出一种应用nm量级精度的电容式位移传感器对可调F-P滤波器间距稳定度进行监控的系统,详细论述了监控系统的结构与工作原理。给出了电容式位移传感器的驱动电路及数据处理与控制软件的设计方案,并对电容式位移传感器的精度进行了标定。实验结果表明,该位移监控系统能够使可调F-P滤波器的间距稳定度保持在15 nm/h以内,使幅度调制效应的调制深度优于4%。 相似文献
152.
153.
Stress intensity factors for asymmetric branched cracks in plane extension by using crack-tip displacement discontinuity elements 总被引:3,自引:1,他引:3
Xiangqiao Yan 《Mechanics Research Communications》2005,32(4):375-384
Stress intensity factors are important in the analysis of cracked materials. They are directly related to the fracture propagation and fatigue crack growth criteria. Based on the analytical solution (Crouch, S.L., 1976. Solution of plane elasticity problems by displacement discontinuity method, Int. J. Numer. Methods Eng. 10, pp. 301–343; Crouch, S.L., Starfield, A.M., 1983. Boundary Element Method in Solid Mechanics, with Application in Rock Mechanics and Geological Mechanics, London, Geore Allon and Unwin, Bonton, Sydney) to the problem of a constant discontinuity in displacement over a finite line segment in the x, y plane of an infinite elastic solid, recently, the crack-tip displacement discontinuity element which can be classified as the left and right crack-tip displacement discontinuity elements are developed by the author Yan, X., (in press. A special crack-tip displacement discontinuity element, Mechanics Research Communications) to model the crack-tip fields to more accurately compute the stress intensity factors of cracks in general plane elasticity. In the boundary element implementation the left or the right crack-tip displacement discontinuity element is placed locally at the corresponding left or right crack tip on top of the ordinary non-singular displacement discontinuity elements that cover the entire crack surface and the other boundaries. To prove further the efficiency of the suggested approach and provide more results of the stress intensity factors, in this study, analysis of an asymmetric branched crack bifurcated from a main crack in plane extension is carried out. 相似文献
154.
155.
H.-M. Zhu Y.-Y. Wu W.-H. Zheng Z.-W. Huang 《Archive of Applied Mechanics (Ingenieur Archiv)》2006,75(8-9):521-526
When an object moves, ultrasonic speckles backscattered from its surface will follow the object to move. From the Kirchhoff
diffraction theory and the correlation principles of random signals, the necessary condition for keeping the correlativity
between the speckle fields before and after the objective displacement was deduced. Based on this condition, the formulas
for the relationship between the speckle displacement and the objective displacement were obtained. Practical measurement
was performed. Ultrasonic digital speckle correlation method was used to measure the in-plane displacement and out-of-plane
displacement of an object. The displacements of the objective surface were evaluated after the displacements of the speckles
were determined.This method can be also used to measure the displacements of an inner objective surface. A mountain-climbing
search method was proposed, which enabled us to find the maximum correlation coefficient in the correlation operation quickly
and efficiently. The experimental results showed good agreement with the theoretical predictions. 相似文献
156.
Xiangqiao Yan 《Mechanics Research Communications》2004,31(2):263
In this paper, a numerical analysis of perpendicular cracks under general in-plane loading is performed by using a hybrid displacement discontinuity method which consists of the non-singular displacement discontinuity element presented by Crouch and Starfied and the crack tip displacement discontinuity elements by the author. In the boundary element implementation the left or the right crack tip displacement discontinuity element is placed locally at corresponding left or right crack tip on top of the ordinary non-singular displacement discontinuity elements that cover the entire crack surface and the other boundary. The present numerical results show that the numerical approach is simple, yet very accurate for calculating numerically stress intensity factors for perpendicular cracks under general in-plane loading. 相似文献
157.
K. Arakawa T. Mada H. Komatsu T. Shimizu M. Satou K. Takehara G. Etoh 《Experimental Mechanics》2007,47(2):277-282
The oblique impact between a golf ball and a polymethyl methacrylate (PMMA) target with smooth transparent surfaces was studied
using a high-speed video camera. Video images of the impact were recorded from the backside of the target and were used to
determine the contact time, contact area, and the displacement and rotation of the ball along the target. The average tangential
and angular velocities were determined as functions of the inbound ball velocity. As the inbound ball velocity increased,
the contact area and average tangential and angular velocities also increased while the contact time decreased. An oiled PMMA
target was used to study the effect of reduced friction between the ball and target. The results were compared with earlier
data for a steel target with relatively rough surfaces. The contact area and time were unaffected by friction, but the average
tangential velocity increased while the average angular velocity decreased as the friction decreased. 相似文献
158.
Guoyan Ma Yiding Shen Ruimin Gao Xiaorong Wang Zhe Wu 《Journal of Dispersion Science and Technology》2017,38(10):1459-1464
An ultralow interfacial tension (IFT) oil displacement agent, which was a surfactant combinational system (HCS) with good salt and heat resistance, was synthesized using amphoteric betaine (AMS)/anionic sulfonate (AKS)/nonionic alkyl amide (NIS). The interface tensiometer was used to test the IFT. The results showed that the oil–water IFT could be as low as 10?4 mN/m when the salinity is 10,000~50,000?mg/L, the concentration is 1~5?g/L, and the temperature is 40~80°C. The surfactant system has good emulsification stability. The displacement simulation experiments demonstrated that the increment of the recovery ratio can be up to 14.1%. The surfactant system could meet the demands of site operation. 相似文献
159.
A fixed point theorem for directional multi-valued k(·)-contractions acting m a complete metric space is established which extends similar results both for k(·)-contractions and directional contractions. Such theorem enables to obtain fixed points theorems for the former class of set-valued maps from those valid for the latter one without metrical convexity or proximinality assumptions, thereby contributing to unify the current setting of the theory. Connections with several recent advances on this subject are also examinated.Mathematics Subject Classifications (2000): 47H10, 54H25 相似文献
160.