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911.
912.
913.
914.
In the present work, a further numerical simulation of the starting flow around a flat plate normal to the direction of motion
in a uniform fluid has been made by means of the discrete vortex method. The secondary separation occurring at rear surface
of the plate is explored, and predicted approximately using Thwait's method. The calculated results show that in the early
stages of the flow secondary separation does occur. The evolution of flow field, the vortex growing process and the characteristics
of secondary vortices have been described. The time dependent drag coefficients, the vorticity shed from the edges and rear
surface, and the separation positions are calculated as well as the distributions of velocity and pressure on the plate. In
the case of flow normal to the plate, the calculated secondary vortices are weak. Their existence will change the local velocity
distributions and affect pressure distributions. However, the effect on drag coefficient is negligible. 相似文献
915.
推拉型偶氮化合物的三阶非线性和光学双稳效应 总被引:9,自引:0,他引:9
本文报道从推拉型偶氮化合物中测得了非常高的三阶非线性极化率,X~(3)~6×10~(→3)esu.这对于引起光学双稳现象是至关重要的.利用波长为488nm的氩离子激光为光源,从这类材料掺杂的玻璃态聚合物薄膜的Kretschmann型态中,进一步观察到了光学双稳现象.与此同时,联系这类材料的顺反异构化反应历程,从电子吸收机制或光诱导的折射率变化机制对有关问题进行了讨论. 相似文献
916.
集成光学Mach—Zehnder型模数转换器 总被引:2,自引:0,他引:2
简述了M-Z干涉调制器型A/D转换器的原理,报道了实验样品的设计参数、制备工艺和实验现象观察,介绍了性能测试的方法和结果. 相似文献
917.
Ling Guocan 《Acta Mechanica Sinica》1988,4(3):211-222
In the present paper the mechanism involved in vortex shedding flows is investigated in detail. In the early stage of the
unsteady separated flow the interaction between secondary vortices and primary vortices is quite strong. In the later stage
of the flow, corresponding to the vortex shedding the recirculating flow region on each side of the aft body goes through
such a cycle: growth-contraction-growth, the secondary separation occurs periodically rather than continuously. The reduction
of circulation is taken into account in three cases with different decay factors to study its influence on the prediction
of main flow characteristics. Results show that to simulate vortex shedding flow it is necessary to include the reduction
of circulation to bring the calculated results into good agreement with experiments. An improved discrete vortex model is
suggested in which both the secondary separation and the reduction are incorporated. The processes of vortex shedding, the
forces prediction and other flow characteristics are given and some discussions are made.
Porject is supported by National Natural Science Foundation of China. 相似文献
918.
ZHANG Zhi-qian 《应用数学和力学(英文版)》2005,26(8):1064-1071
IntroductionAs one of the meshfree methods, multiple scale reproducing kernel particle method(RKPM)[1,2]bears, besides the common features of all meshfree methods, a uniqueinherent feature of multiresolution analysis by which the structural response can b… 相似文献
919.
Ming‐Zheng Wang Feng‐Xia Liang Biao Nie Long‐Hui Zeng Ling‐Xia Zheng Peng Lv Yong‐Qiang Yu Chao Xie Yang Yang Li Lin‐Bao Luo 《Particle & Particle Systems Characterization》2013,30(7):630-636
Schottky junctions made from a titanium dioxide nanotube (TiO2NT) array in contact with a monolayer graphene (MLG) film are fabricated and utilized for UV light detection. The TiO2NT array is synthesized by the anodization and the MLG through a simple chemical vapor deposition process. Photoconductive analysis shows that the fabricated Schottky junction photodetector (PD) is sensitive to UV light illumination with good stability and reproducibility. The corresponding responsivity (R), photoconductive gain (G), and detectivity (D*) are calculated to be 15 A W?1, 51, and 1.5 × 1012 cm Hz1/2 W?1, respectively. It is observed that the fabricated PD exhibits spectral sensitivity and a simple power‐law dependence on light intensity. Moreover, the height of the Schottky junction diode is derived to be 0.59 V by using a low temperature I–V measurement. Finally, the working mechanism of the TiO2NT array/MLG film Schottky junction PD is elucidated. 相似文献
920.
�� ��������������������κѧ�������������� �� 《核聚变与等离子体物理》2013,33(3):262-266
A three-channel far-infrared (FIR) HCN laser interferometer has been developed to measure the line averaged electron density on EAST tokamak. Detectors with the properties of high sensitivity, high signal-to-noise ratio, small volume and stability are needed in interferometer device. The application of new Schottky barrier diode (SBD) detector has made the density signal and the signal-to-noise ratio greatly improved. The disturbance caused by the lower hybrid wave can be eliminated by using double copper foil shield and narrow band pass filter. The improved detectors have worked well during the long pulse discharge and H mode discharge. 相似文献