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81.
利用概率论方法、测度变换方法、偏微分方程的变量代换法、Green函数法、Fourier变换法,给出了一个期望E(e-r(T-t)(ST-K)+|St=S)的几种求解方法. 相似文献
82.
83.
Tadamasa Toma Yoshio Furuya Wataru Watanabe Kazuyoshi Itoh Junji Nishii Kenichi Hayashi 《Optical Review》2000,7(1):14-17
It is known that local refractive index change occurs when femtosecond laser pulses with extremely high peak power are launched into glass. We focused 130-femtosecond laser pulses of 800 nm into the bulk of glass and examined the shape of the induced refractive index change. We found that the length of the spot of the refractive index change along the optical axis reached about 30 μm despite the diameter being about 2 μm. To estimate the distribution of induced refractive index change, we fabricated Bragg grating by scanning the focused spot and calculated the amount of the change by applying Kogelnik’s coupled mode theory to the measured diffraction efficiencies of the higher order diffracted beams. 相似文献
84.
Polycrystalline perovskite La0.67Ca0.33MnO3 was synthesized by a sol–gel method. Its adiabatic temperature change ΔTad induced by a magnetic field change was measured directly. At 268 K, near its Curie temperature TC, ΔTad of La0.67Ca0.33MnO3 induced by a magnetic field change of 2.02 T reaches 2.4 K. The latent heat Q and magnetic entropy change −ΔSM induced by a magnetic field change were calculated from the temperature dependence of ΔTad and zero-field heat capacity Cp. The maximum values of Q and −ΔSM in La0.67Ca0.33MnO3 induced by a magnetic field change of 2.02 T are 1.85 J g−1 and 6.9 J kg−1 K−1, respectively. The former is larger than the phase transition latent heat of heating or cooling, which is about 1.70 J g−1. 相似文献
85.
86.
Using the daily precipitation data of 740 stations in China from 1960 to 2000, the analysis on the variations and distributions of the frequency and the percentage of extreme precipitation to the annual rainfall have been performed in this paper. Results indicate that the percentage of heavy rains (above 25mm/day) in the annual rainfall has increased, while on average the day number of heavy rains has slightly reduced during the past 40 years. In the end of 1970s and the beginning of 1980s, both the number of days with extreme precipitation and the percentage of extreme precipitation abruptly changed over China, especially in the northern China. By moving t test, the abrupt change year of extreme precipitation for each station and its spatial distribution over the whole country are also obtained. The abrupt change years concentrated in 1978-1982 for most regions of northern China while occurred at various stations in southern China in greatly different/diverse years. Besides the abrupt change years of extreme precipitation at part stations of Northwest China happened about 5 years later in comparison with that of the country's average. 相似文献
87.
提出并利用高频CO2激光脉冲在普通单模通信光纤上写出了包层旋转折变型长周期光纤光栅(R-LPFG). 在分析R-LPFG波导结构和双折射特性的基础上,对光栅周期数和折变旋转度分别为50和7.2°/周期的R-LPFG进行了实验研究.结果表明,这种类型的光栅可极大地降低其谐振波长对横向负荷不同作用方向所表现出的方向相关性,并且其谐振峰幅度横向负荷灵敏度在任意方向下均高达0.37dB/(g·mm-1) ,是普通LPFG横向负荷灵敏度的9倍左右.利用R-LPFG的温度线性响应特性和独特的横向负荷特性,设计并实验研究了一种动态增益均衡器,用其平坦掺铒光纤放大器增益谱,在C波段32nm范围内,其平坦度小于±0.5dB,可满足实际环境对通信系统的平坦应用要求.
关键词:
光纤通信技术
长周期光纤光栅
动态增益均衡
旋转折变 相似文献
88.
89.
Investigations were carried out for laser-effected darkening and damage-free laser marking on thermoplastic elastomers (TPEs). Titanium dioxide (TiO2) was studied as the laser-sensitive additive to the TPEs for its role in enhancing laser marking contrast and its effect on the TPE properties. Laser beam characteristics, processing variables and percentage loading of TiO2 in the TPEs were found to have significant effect on the marking contrast. Surface damage-free and high contrast marking have been achieved with short pulse UV lasers. The laser-effected darkening was found to penetrate into the material in the order of a few tens of microns. XPS analysis was carried out to understand the laser-effected darkening mechanism. Potential applications of the technique are highlighted. 相似文献
90.
共形整流罩像差特性分析及校正方法 总被引:2,自引:1,他引:2
共形结构不仅具有良好的空气动力学性能,且不存在由于表面不连续造成的热梯度等问题,因而采用该结构的导弹整流罩更有利于导弹系统作战性能的提高。但共形结构中采用的非球面罩曲面使整流罩表现出许多不同于球形结构的动态特性,这给导引头中光学系统的设计带来很多困难。在分析共形结构一阶特性的基础上,利用矢量像差理论详细分析该结构中初级像差产生的原因及特点,并提出通过控制元件的倾斜和偏心来平衡所有观察视场中像差的方法。软件分析结果表明:加入倾斜偏心元件后可适当放大小观察视场中的像差,共形整流罩在各观察视场中具有较为稳定的像差特性,有效地改善了该结构的成像质量。 相似文献