Latest ArticlesThe R-p relationship of ZnO nanocrystals and bulk materials were determined by diamond anvil cell (DAC). Research results show that a phase transformation begins at the 7.9 GPa when the particle is 20 nm nanocrystals, whereas the phase transition of ZnO bulk materials at 5 GPa. The smaller particle has larger phase transition pressure, and transformation pressure of bulk materials determined by DAC is lower than that previously reported. The structural properties of ZnO were discussed, and the domain fracture of nanocrystals under pressure was investigated.
A new method for calculating cold energy, cold pressure and cohesive energy was poroposed. Cohesive energy calculations for 52 metals show that the calculated results using this method are consistent with the experimental data, especially for alkali metals. Comparison of Hugoniot curves calculated based on cold energy and cold pressure with the experimental Hugoniot data of aluminum, copper, zinc and silver, shows that this method can be applied to calculate cold energy and cold pressure of solid materials.
In this paper, the Monte Carlo (MC) method was used to investigate the optimization of pyrometer design and the uncertainty assessment for shock-induced temperature measurements. The statistic T90%, which was defined by p{｜T-Ttrue｜>T90%}=0.1, was calculated for 10 kinds of designs, and each case was simulated 2×105 times to make the statistical sample. Four conclusions are presented: (1) Using more channels in a pyrometer can surely, but slightly improves the measurement accuracy of shock-induced temperature. (2) In the most case, measurement accuracy evidently depends on the accuracy of each channel. Generally, when the channel uncertainty is reduced from 10% to 5%, the experimental accuracy can be increased by over 150%. (3) The measurement accuracy also obviously depends on the channel's wavelength range. (4) The measurement accuracy can be largely improved by using those wavelength channels at which the difference of the radiation energy measured is as large as possible.
The electronic structures of Mn2+ luminescence centers in Mn-doped ZnS are studied by using first-principles linear muffin-tin-orbital method combining atomic sphere approximation. The calculated results for ZnS:Mn2+ show that the property of impurity energy level for single bug satisfies the theory of crystal potential field, and the influence of impurity energy level caused by concentration of impurity is not evident, which is consistents with the experiment results.
In this dissertation, a model EPW is designed on the basis of theoretical analyses. Shell material and parameters of a projectile body, such as slenderness ratio and CRH (caliber radius head), were studied. Strength check and aerodynamic properties of a projectile body were investigated. The experimental examination of a projectile on penetrating semi-infinite concrete medium was performed. The values from theoretical prediction have good coincidence with the experimental data. Young equation can be applied to estimate the penetration depth.
A new system utilizing laser diode and PIN for gas-gun projectile velocity measurement were developed in 1997. The system is integrated in a barrel extension. It not only has the advantages of simple structure and vibration resistance but also has easiness of collimation. In addition, it is helpful to keep smaller tilt and to avoid projectile free-flying before it impacts the target. It has been used successfully to measure the velocity of irregular or nonmetallic projectile. The relative measurement uncertainty is less than 0.2%.
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