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991.
992.
研究了均匀等离子体中超短脉冲激光在传输过程中的脉宽、峰值功率随时间,空间变化的解析式,结果表明,对于25fs左右的超短脉冲,由等离体色散引起的脉宽变长及峰值功率降低效应是明显的。 相似文献
993.
Laser drilling of thick material using femtosecond pulse with a focus of dual-frequency beam 总被引:1,自引:0,他引:1
Laser drilling is one of the basic, most frequently performed, material removal processes. The drilling aspect ratio is theoretically limited by the size and the focal depth of the machining laser spot. The aspect ratio can be improved by using dual focus. In this paper we describe a focus of two different frequencies based on the longitudinal chromatic aberration arisen when polychromatic collimated light is incident on a positive lens element. In the experiments, a Ti:Sapphire laser of 800 nm wavelength and 150 fs pulse duration was used as a source. Two tightly focused laser spots few hundred micrometers apart from each other were formed by focusing a combined collimated laser beam which contains the fundamental optic frequency and the second harmonic optic frequency. The focus of dual-frequency beam was used to drill a 3 mm thick PMMA plate. The drilling aspect ratio of a dual-frequency beam was compared to that of a focus of single frequency beam. Experimental results reveal that dual-frequency beam increases the aspect ratio and improves the drilling quality in terms of profile of the produced features. 相似文献
994.
用失晕法测试了纳米锌镀层和0^#锌片在0.2mol/L硫酸介质中的腐蚀性能.结果表明纳米锌镀层的耐腐蚀性要远优于锌片,且在一定的实验条件下,纳米锌镀层的腐蚀速率为一常数.另外,本文还研究了溴化十六烷基吡啶和吡啶及其甲基衍生物在硫酸介质中对纳米锌镀层和0^#锌片的缓蚀性能.其中溴化十六烷基吡啶和3-甲基吡啶的缓蚀性能较好.并用密度泛函B3LYP方法和Onsager溶剂化模型,在6-31G水平上优化了溴化十六烷基毗啶、3-甲基吡啶和4-甲基毗啶分子的几何构型,用其电子结构数据探讨了它们的缓蚀机理。 相似文献
995.
Jing Yin FEI Guo Zheng LIANG Wen Li XIN Jiang Hong LIU 《中国化学快报》2005,16(8):1097-1100
Pulse plating of Zn-Co alloys was studied using square pulse containing reverse current.The surface morphologies of Zn-Co alloy deposits were examined using scanning elecron microscopy (SEM), and an attendant energy dispersive X-ray analyzer (EDA) was used to analyze the composition of Zn-Co alloy deposits. Results obtained showed that the average current density and reverse current density amongst all the variables investigated had very strong effects on the cobalt content and surface morphologies of Zn-Co alloy deposits. It is possible to elecrodeposit Zn-Co alloy coatings with a very wide cobalt content range of 10-90 wt% by modulating pulse parameters. 相似文献
996.
磁脉冲压缩器用脉冲变压器的设计 总被引:4,自引:3,他引:1
本文简要说明了磁脉冲压缩器的工作原理。着重介绍了其输入、输出脉冲变压器的等效回路设计法。并将该方法用于实例进行验证。结果说明,这种设计方法是非常成功的,而且可以推广到一般情况下的脉冲变压器的设计。 相似文献
997.
本文介绍一种为MNI-1U中性注入器研制的大功率长脉冲高压稳定电源。电路的技术指标为:输出脉冲电压50kV,脉冲电流30A,脉冲宽度50ms,上升下降时间小于25μs,平顶稳定度优于0.5%,调整响应时间30μs。当作直流高压稳压和稳流电源使用时,输出电压1-80kV,电流0.5—5A,电压或电流的稳定度可优于0.1% 相似文献
998.
Magnetic field measurements above type-II superconductor films in a remanent magnetization state have been used to determine
two dimensional surface current distributions. Using the Biot-Savart law for the surface current density, integral equations
(of 2-D convolution type) for two components of current have been obtained. These equations have been solved by employing
Tikhonov's method of generalized discrepancy, and the surface current pattern in superconductors as well as the magnetic field
distribution on the film surface have been obtained. Current peculiarities related to various kinds of inhomogeneities, specific
character of the film form, and a laser pulse effect have been observed. In particular, it was discovered that a laser pulse
can signficantly redistribute the film currents without changing the total number of current vortices in the film. 相似文献
999.
报道了脉冲钛宝石激光器的双波长可调谐运转,双汉总能量达到41.8mJ,调谐范围大于100nm并且研究了双波长运转时的竞争效应,增益损耗的影响,时域特性等。 相似文献
1000.
Compression of powerful microwave frequency-modulated e-polarized pulses by autocollimative gratings
N. G. Kazakova E. V. Koposova M. I. Petelin S. N. Vlasov 《International Journal of Infrared and Millimeter Waves》1997,18(3):675-685
Electromagnetic pulse compressors using gratings in autocollimation regime for the central frequency of a pulse for p- polarization
having greater electrical reliability are theoretically investigated. The theory is built on the basis of the numerical decision
of electromagnetic field equations by a method of the integral equation. A case of aberrationless approximation of bell-like
pulse compression with quadratically modulated phase is analytically considered. The numerical experiment shows the presence
of strong distortions of a pulse at compression, caused by cubic and senior members in decomposition of phase frequent dependence,
got by a wave in the compressor. Conditions of optimum pulse compression with the account of aberrations are investigated. 相似文献