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71.
72.
73.
设计了3套针对“神光-Ⅱ”倍频激光直接驱动的透镜阵列均匀辐照系统,并对冲击波的平面性进行了实验研究。结果表明,冲击波的平面性与透镜阵列参数、平面靶厚度、靶面位置等有关,采用列阵元数为121的透镜阵列进行激光束匀滑驱动的冲击波平面性最好,间接说明它在靶面的激光辐照是最均匀的;另外,随着靶厚的增加,冲击波平面性变差,平面区变小;而且冲击波平面性随靶面离焦位置的变化成一定的周期性变化,第2套透镜阵列焦点处的冲击波平面性最好。 相似文献
74.
This paper reports a comparative study of shear banding in BMGs resulting from thermal softening and free volume creation.
Firstly, the effects of thermal softening and free volume creation on shear instability are discussed. It is known that thermal
softening governs thermal shear banding, hence it is essentially energy related. However, compound free volume creation is
the key factor to the other instability, though void-induced softening seems to be the counterpart of thermal softening. So,
the driving force for shear instability owing to free volume creation is very different from the thermally assisted one. In
particular, long wave perturbations are always unstable owing to compound free volume creation. Therefore, the shear instability
resulting from coupled compound free volume creation and thermal softening may start more like that due to free volume creation.
Also, the compound free volume creation implies a specific and intrinsic characteristic growth time of shear instability.
Finally, the mature shear band width is governed by the corresponding diffusions (thermal or void diffusion) within the band.
As a rough guide, the dimensionless numbers: Thermal softening related number B, Deborah number (denoting the relation of instability growth rate owing to compound free volume and loading time) and Lewis
number (denoting the competition of different diffusions) show us their relative importance of thermal softening and free
volume creation in shear banding. All these results are of particular significance in understanding the mechanism of shear
banding in bulk metallic glasses (BMGs).
Supported by the Chinese Academy of Sciences under the project “Multi-Scale Complex System” (Grant No. KJCX-SW-L08), the National
Natural Science Foundation of China (Grant Nos. 10725211 and 10721202), and the Doctorial Start-up Fund of Hunan University
of Science and Technology (Grant No. E50840) 相似文献
75.
用低杂波的可的性条件,参量不稳定条件和功率耦合谱分析了低杂波电流驱动。由于波的可近性条件限制耦合谱中平行相速度较大的波进入等离子体中心,参量不稳定性使平行相速度较低的波与离子相互作用,随着等离子体密度的增中,这些作用越来越明显,最终导致低杂波不能在中心与电子相互作用,驱动电流消失,这就是所谓密度极限。在本文建立的模型基础上的计算结果与实验结果符合较好。 相似文献
76.
77.
R. J. Emrich 《Shock Waves》1996,5(6):327-339
Recollections of activities in the Physics Department of Princeton University leading to the construction and use of the SHOCK
TUBE are recorded. Walker Bleakney was the leader of these activities from 1940 to 1979, and his methods and attitude are
described. Original interferograms made at Princeton show some results obtained. 相似文献
78.
79.
Cerisier P Porterie B Kaiss A Cordonnier J 《The European physical journal. E, Soft matter》2005,18(1):85-93
The motion of particles moving under gravity in the velocity field of a liquid in a Bénard hexagonal cell is studied experimentally
and numerically for Stokes flow conditions. We then explain the settlement of particles in the centers of cells to form a
regular quincunx. It is found that sedimentation also occurs preferentially along the lines connecting the centers of adjacent
cells to form a triangle deposition tessellation. Finally, it is explained why particles occupy the central part of each convective
cell while the peripheral part of the cell quickly becomes limpid. Numerical results are in agreement with the experimental
observations of Bénard and those of the present study. 相似文献
80.
According to standard textbooks on compressible fluid dynamics, a shock wave is formed by an accumulation of compression waves. However, the process by which an accumulated compression wave grows into a shock wave has never been visualized. In the present paper, the authors tried to visualize this process using a model wedge with multiple steps. This model is useful for generating a series of compression waves and can simulate a compression process that occurs in a shock tube. By estimating the triple-point trajectory angle, we demonstrated visually that an accumulated compression wave grows into a shock wave. Further reflection experiments over a rough-surface wedge confirmed the tendency for the triple point trajectory angle to reach the asymptotic value
s in the end.This work was first presented at the Symposium on Shock Waves, Japan 2002 相似文献