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191.
对于多台固体激光器抽运的脉冲染料激光主振荡-功率放大(MOPA)链,在放大器中,抽运激光与染料种子激光不仅在空间上要求匹配,而且激光脉冲在时间上也要求匹配。为此,提出了进行激光脉冲时序的控制方法。该方法采用光纤、光开关和随机重复采样等技术实现快速激光脉冲的计算机数据采集。根据实验,抽运和染料激光脉冲的时间匹配最好时,它们的峰值几乎是重合的,由此提出以脉冲峰值处作为延迟时间的测量点来排除脉宽变化的影响,以及采用二次多项式曲线拟合的数据处理技术来排除峰值处延迟时间的测量干扰,实现抽运激光脉冲时序纳秒级的测量和闭环控制。控制系统的手动单步控制误差和延迟时间测量误差小于±0.2 ns,闭环控制精度可达±1 ns。 相似文献
192.
Scattering of SH wave from an interface cylindrical elastic inclusion with a semicircular disconnected curve is investigated.The solution of dynamic stress concentration factor is given using the Gteen's function and the method of complex variable functions.First,the space is divided into upper and lower parts along the interface.In the lower half space,a suitable Green's function for the problem is constructed.It is an essential solution of the displacement field for an elastic half space with a semi-cylindrical hill of cylindrical elastic inclusion while bearing out-plane harmonic line source load at the horizontal surface.Thus,the semicircular disconnected curve can be constructed when the two parts are bonded and continuous on the interface loading the undetermined anti-plane forces on the horizontal surfaces.Also,the expressions of displacement and stress fields are obtained in this situation.Finally,examples and results of dynamic stress concentration factor are given.Influences of the cylindrical inclusion and the difierence parameters of the two mediators are discussed. 相似文献
193.
Comparative analysis of phase extraction methods based on phase-stepping and shifting curve in grating interferometry 下载免费PDF全文
Two phase extraction methods which are based separately on
phase-stepping and shifting curve are mainly used in
phase-sensitive imaging in gating interferometry to determine the
x-ray phase shift induced by an object in the beam. In this paper,
the authors perform a full comparative analysis and present the main
virtues and limitations of these two methods according to the
theoretical analysis of the grating interferometry. 相似文献
194.
195.
Lithium borate (Li2B4O7) is a low Zeff, tissue equivalent material that is commonly used for medical dosimetry using the thermoluminescence (TL) technique. Nanocrystals of lithium borate were synthesized by the combustion method for the first time in the laboratory. TL characteristics of the synthesized material were studied and compared with those of commercially available microcrystalline Li2B4O7. The optimum pre-irradiation annealing condition was found to be 300 °C for 10 min and that of post-irradiation annealing was 300 °C for 30 min. The synthesized Li2B4O7 nanophosphor has very poor sensitivity for low doses of gamma up to 101 Gy whereas from 101 to 4.5×102 Gy this phosphor exhibits a linear response and then from 4.5×102 to 103 Gy it shows supralinearity. Thermoluminescence properties of Li2B4O7 nanophosphor doped with Cu has also been investigated in this paper. It shows low fading and a linear response over a wide range of gamma radiation from 1×102 to 5×103 Gy. Therefore the synthesized lithium borate nanophosphor doped with Cu may be used for high dose measurements of gamma radiations. 相似文献
196.
首先制备了不同周期的染料掺杂全息液晶/聚合物光栅并进行激光抽运实验, 得到了激光器的调谐曲线,确定了激光器在574 nm到685 nm的谱带里均可以实现激光输出, 即激光器具有110 nm左右的可调谐范围. 之后, 通过温控仪控制样品的温度, 对周期为610 nm的染料掺杂全息液晶/聚合物光栅进行激光抽运, 探测不同温度下的输出激光光谱, 观察到随着温度由20℃升高到65℃, 激光器的中心波长由627.9 nm减小到623 nm, 产生了4.9 nm的波长蓝移. 相似文献
197.
This work deals with the Paschen law in electrical breakdown of gases at pd values around the Paschen minimum. From the Townsend model, it is possible to deduce theoretical forms of the coefficients in Paschen's law, of which our calculated values are in the range of the tabulated values from the literature. These formulae show that the breakdown voltage must be influenced by the inter‐electrode distance, while the product pd remains a key parameter. This is confirmed by the Paschen curves measured in an argon discharge for inter‐electrode distances varying from 2 to 9 cm (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
198.
应用于密码学的椭圆曲线研究 总被引:1,自引:0,他引:1
雷信生 《信息安全与通信保密》1995,(4)
本文解决了椭圆曲线在密码学中应用的一个有关问题,即任意给定一个素数m,及一个有限域F_p,从F_p上任取一条椭圆曲线,使m是其有理点群阶的一个素因子的概率是多少?我们给出了这一概率的计算公式。 相似文献
199.
G.D. Roston M.S. Helmi 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,101(2):201-204
As the ground state potential curve is strongly related to spectral line shapes, the minumum position of the ground state potential is obtained from the experiemental absorption profile k(Δν, T) at high density of the radiating atoms. The temperature dependence of the absorption processes of Hg and Cd lines 253.65 and 326.1 nm, respectively perturbed by inert gases (Xe, Kr, Ar and Ne) had been carefully studied over a wide spectral range. Using the point of the maximum temperature dependence Δνm in each case, we are able to calculate the position of the ground state potential Rm using a simple formula. 相似文献
200.
V.J. Logeeswaran F.E.H. Tay M.L. Chan F.S. Chau Y.C. Liang 《Analog Integrated Circuits and Signal Processing》2003,37(1):17-33
In this paper, the response to the first harmonic component (2f) of the electrostatic force in single terminal driven electrostatic comb-drive and parallel-plate drive was used as a signal to extract device parameters, namely, the Q-factor and resonant frequency instead of the fundamental (1f) resonance response. It is shown that the difficulty in motional measurement due to electrical cross-talk (parasitics) using 1f measurement can be overcome with a higher signal-to-noise ratio of the 2f signal. Both atmospheric (low-Q) and reduced pressure environment were investigated using off-chip electronics and lock-in amplifier. The measurements were done on the electrostatic comb-drive and capacitive parallel plate sensing plates that form the two core modules of a yaw rate sensor (dual-axis resonator). The effects of AC and DC bias voltages on the measured response have been investigated. Experimental amplitude and phase response data have been analysed using the Lorentzian curve-fit, Resonance Curve Area (RCA) method, the half-power bandwidth method (3 dB) and the Nyquist plot for data fitting and determination of the Q-factor and resonance frequency. 相似文献