排序方式: 共有16条查询结果,搜索用时 390 毫秒
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DESIGNING A DIFFRACTIVE OPTICAL ELEMENT FOR CONTROLLING THE BEAM PROFILE IN A THREE-DIMENSIONAL SPACE USING THE SIMULATED ANNEALING ALGORITHM 总被引:4,自引:0,他引:4 下载免费PDF全文
We have designed a spatially quantized diffractive optical element (DOE) for controlling the beam profile in a three-dimensional space with the help of the simulated annealing (SA) algorithm. In this paper, we investigate the annealing schedule and the neighbourhood which are the deterministic parameters of the process that warrant the quality of the SA algorithm. The algorithm is employed to solve the discrete stochastic optimization problem of the design of a DOE. The objective function which constrains the optimization is also studied. The computed results demonstrate that the procedure of the algorithm converges stably to an optimal solution close to the global optimum with an acceptable computing time. The results meet the design requirement well and are applicable. 相似文献
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Ultrafast electron diffraction (UED) is a rapidly advancing technique capable of recording the atomic-detail structural dynamics in real time. We report the establishment of the first UED system in China. Employing this UED apparatus, both the coherent and the concurrent thermal lattice motions in an aluminium thin-film, trigged by ultrafast laser heating, have been observed. These results demonstrate its ability to directly measure a sub-milli-angstrom lattice spacing change on a sub-picosecond time scale. 相似文献
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Triggering and guiding of high voltage discharge by using femtosecond laser filaments with different parameters 下载免费PDF全文
This paper demonstrates the triggering and guiding of the stationary high voltage(HV) discharges at 5-40 kV by using plasma filaments generated by femtosecond laser pulses in air.A significant reduction of the breakdown voltage threshold due to the pre-ionization of the air gap by laser filamentation is observed.The discharge experiments are performed by using laser pulses with different energy from 15-60 mJ.The electron density of filaments is detected by sonography method.The influence of the electron density of laser filaments on the triggering and guiding HV discharge is experimentally investigated.The results have shown that the behaviour of plasma filaments can strongly affect the effciency of triggering and guiding HV discharge. 相似文献
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利用皮秒和飞秒激光研究了激光在空气中聚焦产生单个等离子体通道的条件.研究发现,能量为8—12mJ皮秒激光被焦距为15cm的透镜聚焦后,可以产生较为稳定的单个通道.通过横向纵向阴影成像分析发现,通道的管壁对聚焦产生的自发光具有箍缩作用,而通道内部却有利于光的传输.同时还发现,当采用短焦距透镜时,能量低于10mJ的飞秒激光在空气中较易形成单个等离子通道.
关键词:
等离子体通道
皮秒激光
飞秒激光
阴影成像 相似文献
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介绍了在体观测肿瘤内注射吲哚氰绿 (ICG) ,一种激光吸收染剂前后X射线衰减的实验结果。实验采用已种植两周的骨髓瘤细胞 (SP2 / 0 ) ,质量为 15~ 2 0g的BALB/c小鼠作为动物模型 ,采用数字X射线成像系统作为监测药物在肿瘤内扩散的机制。系统工作在 33kVp ,0 .3mA下 ,曝光时间 4s,采用 1.5×放大倍率。实验研究的是通过灰度值反应出不同区域的X射线衰减 ,和周围正常组织和图像中没有物体的背景区域相比较 ,注射ICG前后肿瘤内的灰度值发生了明显的变化。实验证明 ,使用数字X射线成像系统能够动态、有效、非侵入地监测ICG在肿瘤组织内的扩散 ,从而达到优化治疗结果的作用。 相似文献
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超快电子衍射(UED)技术因其同时具有亚皮秒的时间分辨和亚毫埃的空间分辨能力,成为研究物质瞬态结构变化,特别是研究晶格材料超快动力学的有力工具.应用国内首台自行研制的UED系统,我们实时测量了超快激光脉冲激发下,20 nm金属Al多晶薄膜产生的相干声子和晶格热运动.实验结果显示,在晶格热运动加剧的同时,热应力的作用使晶格产生了相干振荡,并最终膨胀达到新的平衡位置.实验中测得的振荡周期以及晶格上升的温度与理论计算的结果符合较好,展示了UED技术在超快晶格动力学研究方面的广阔应用前景
关键词:
超快电子衍射
相干声子
晶格热运动 相似文献
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