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191.
LD泵浦固体激光器基模振荡光的场分布噪音 总被引:3,自引:3,他引:0
通过调整泵浦光直径,使得LD端面泵浦固体激光器的振荡光工作于基模.在排除高阶横模的条件下,测量了由于热透镜的不稳定引起的光场场分布的噪音.实验发现,基模振荡光的高斯半径、光束指向角都在波动,而且光斑存在畸变波动.对一个未采取抑制措施的2W连续LD端面泵浦Nd:YAG固体激光器进行了测量.结果表明,在总功率不变的情况下,激光束峰值点附近的光强波动达到6.3%;激光的高斯半径波动达到5.8%;激光的指向角波动达到0.3mrad. 相似文献
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194.
Spectral and Pseudospectral Approximations Using Hermite Functions: Application to the Dirac Equation 总被引:1,自引:0,他引:1
We consider in this paper spectral and pseudospectral approximations using Hermite functions for PDEs on the whole line. We first develop some basic approximation results associated with the projections and interpolations in the spaces spanned by Hermite functions. These results play important roles in the analysis of the related spectral and pseudospectral methods. We then consider, as an example of applications, spectral and pseudospectral approximations of the Dirac equation using Hermite functions. In particular, these schemes preserve the essential conservation property of the Dirac equation. We also present some numerical results which illustrate the effectiveness of these methods. 相似文献
195.
196.
中国股票市场风险的实证分析研究 总被引:6,自引:1,他引:5
本文从实证角度说明了上证指数和深证成份指数存在着GARCH现象 ,并建立了沪、深两市股指波动率的IGARCH(1,1) M模型与EGARCH(1,1) M模型。将估计的IGARCH(1,1) M模型与EGARCH(1,1) M模型比较得出 ,对上证指数的波动率 ,IGARCH(1,1) M模型与EGARCH(1,1) M模型的模拟效果基本相同 ,而对深证成份指数的波动率 ,IGARCH M模型要略优于EGARCH M模型。同时还对两市的股指收益的波动率进行了预测分析 相似文献
197.
Nongelatin dichromated holographic film(NGD) is a new holographic recordingmaterial.Holograms recorded on this material have better environmental stability, higherdiffraction efficiency and stronger real time effect, etc..An experimental study to ascertainthe influence of two electron donors, namely,N,N-dimethylformamide(DMF) and dimethyl-sulfoxide(DMSO),on the real time diffraction efficiency(RTDE) of NGD holograms is car-ried out.The pressence of electron donors not only improves the sensitivity,but also enhancesthe real time effect greatly.RTDE of above 60% at±1 orders of NGD plane transimissiongrating is achieved by introducing electron donors. 相似文献
198.
X.X. Guo 《Surface science》2004,549(3):211-216
We studied parallel conductivities of pure BaF2 films with thicknesses ranging from 35 to 300 nm, epitaxially grown on Al2O3(0 1 2) substrates by molecular beam epitaxy technique. The overall conductivities of the films are found to increase with decreasing thickness. The detailed investigation of the overall conductance as a function of the thickness permits the deconvolution of bulk and boundary effects, the latter being attributed to distinct space charge effects in the interface between BaF2 film and Al2O3 substrate. The (extrinsic) Debye length (λ) is estimated to be about 8 nm at T=593 K, which corresponds to an impurity content of 1018/cm3 (singly ionized dopant assumed). This is consistent with the fact that we observed a constant boundary contribution for all investigated films (film thickness >4λ). It is also consistent with the Debye length observed in a previous report on CaF2/BaF2 heterolayers fabricated by the same technique, in which the low temperature enhancement was also attributed to space charges in BaF2 [Nature 408 (2000) 946]. Only at low temperatures (below 370 °C), the conductance seems to be influenced by strain effect. 相似文献
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This paper is devoted to the long time behavior for the Drift-diffusion semi-conductor equations. It is proved that the dynamical system has a compact, connected and maximal attractor when the mobilities are constants and generation-recombination term is the Auger model; as well as the semigroup S(t) defined by the solutions map is differential. Moreover the upper bound of Hausdorff dimension for the attractor is given. 相似文献