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991.
992.
In this paper, we evaluated the quasinormal modes of electromagnetic perturbation in a Schwarzschild black hole surrounded
by the static spherically symmetric quintessence by using the third-order WKB approximation when the quintessential state
parameter w
q
in the range of −1/3 < w
q
< 0. Due to the presence of quintessence, Maxwell field damps more slowly. And when at −1 < w
q
< −1/3, it is similar to the black hole solution in the ds/Ads spacetime. The appropriate boundary conditions need to be
modified. 相似文献
993.
We present in this paper a highly stable and efficient KTP-based intracavity optical parametric oscillator with a diode-end-pumped
Nd:YVO4/Cr:YAG passively Q-switched laser. At the incident diode pump power of 4 W, the signal (1.57 μm) and idler (3.29 μm) average
output powers up to 580 and 100 mW, respectively, have been achieved. The corresponding conversion efficiency from the input
diode pump power to the output signal power is 14.5%, while that to the total OPO output (signal+idler) reaches 17%. To the
best of our knowledge, these are the highest conversion efficiencies reported to date. After more than four hours of investigation,
the OPO power stability better than 2% has been obtained. In addition, efficient cavity dumping of the IOPO has inevitably
led to the short pulse duration (1.6 ns) and high peak power output (8.3 kW) at the signal wave. Additionally, the amplitude
and repetition rate fluctuations of the signal pulses are well within 5%.
PACS 42.55.Xi; 42.60.Gd; 42.60.Lh; 42.65.Yj 相似文献
994.
We present the effects of optical feedback from an anisotropic external cavity on the characteristics of the output intensities
in a single mode Nd:YAG laser. Due to the birefringence effect, the external cavity modulates laser intensities in the two
orthogonal directions with a phase difference, which is twice as large as that of the birefringence element in the external
cavity. Experimental results are presented, as well as a theoretical analysis. The potential applications of this phenomenon
are also discussed.
PACS 42.60.Jf; 42.62.Eh; 42.25.Lc; 42.60.By 相似文献
995.
996.
997.
在分析激光主动探测中回波信号的噪声特性和小波变换去噪原理的基础上,提出了一种基于最大信噪比准则的小渡阈值去噪方法。首先用最大信噪比准则对小波变换系数进行阈值选取,然后采用软阂值方法对小波系数进行量化处理后再重构。仿真结果表明最大信噪比准则小波去噪方法改善信噪比效果十分显著,检测下限达到-16.2dB。证明了该方法在激光主动探测系统回波信号检测中的有效性。 相似文献
998.
We formulate a global equilibrium model to describe the growth of one-dimensional nanostructures in the VLS process by including
also the chemical tension in addition to the physical tensions, i.e. surface energies. The chemical tension derives from the
Gibbs free energy change due to the growth of a crystal layer of an elementary thickness. The system global equilibrium is
arrived at via the balance of the static physical tensions and the dynamic chemical tension. The model predicts and provides
conditions for the growth of nanowires of all sizes exceeding a lower thermodynamic limit. The model also predicts the conditions
distinguishing the growth of nanohillocks from nanowires. These predictions will allow the verification of the model by future
experiments specifically designed for this purpose.
PACS 81.07.-b; 82.60.-s; 05.70.Np; 68.35.Md; 68.03.Cd 相似文献
999.
1000.
The polycrystalline Ti/TiNx multilayer films were deposited by magnetron sputtering, and the as-deposited multilayer coatings were annealed at 500-800 °C for 2-4 h in vacuum. We investigated the effects of annealing temperature and annealing time on the microstructural, interfacial, and mechanical properties of the polycrystalline Ti/TiNx multilayer films. It was found that the hardness increased with annealing temperature. This hardness enhancement was probably caused by the preferred crystalline orientation TiN(1 1 1). The X-ray reflectivity measurements showed that the layer structure of the coatings could be maintained after annealing at 500 °C and the addition of the Si3N4 interlayer to Ti/TiNx multilayer could improve the thermal stability to 800 °C. 相似文献