不同厚度有耗左手材料板中的电磁波研究

 基于有损耗的Lorentz模型的时域有限差分（FDTD）方法，模拟了有耗左手材料（LHM）平板对波源的图像聚焦特性。分别计算了不同宽度的左手材料平板结构。通过比较说明电磁波在不同厚度左手材料板中传播方式相同。材料板越薄，其聚焦点的位置越往板边缘靠近。当左手材料板的厚度不满足聚焦尺寸时，该聚焦点将会消失。     

超短电子脉冲在聚焦强激光场中的三维有质动力散射

采用三维测试粒子模拟(test-padicle simulation)的方法，研究了聚焦的飞秒脉冲强激光与超短电子束进行有质动力的散射过程.详细讨论了超短电子束经过不同激光延迟下有质动力散射的空间分布特征和能谱特征.提出了通过测量电子束的空间分布和能谱分布实现对超短脉冲电子束的脉冲宽度测量的方法. 关键词： 有质动力散射 聚焦的飞激光 飞秒电子束     

克尔效应对高斯光束聚焦特性的影响

利用菲涅尔—基尔霍夫衍射积分公式，研究薄片近似情况下的Kerr效应带来的波前畸变对高斯光束聚焦特性的影响.在相位延迟为－2~2 rad的范围内进行的模拟计算表明：正Kerr效应能提高高斯光束的聚焦强度、增大相对焦移量、提高聚焦光束的焦平面桶中功率和降低几何焦平面的峰值光强；而负Kerr效应，则会降低聚焦强度、增大相对焦移量、降低聚焦光束的焦平面桶中功率和几何焦平面的峰值光强.可以通过增大光束菲涅尔数来抑制Kerr效应对聚焦特性的影响.     

一种飞秒电子衍射系统的设计与分析

设计了飞秒电子衍射系统,详细分析了影响系统时间分辨率的因素,如阴极的材料及厚度、阴极附近场强、聚焦方式、偏转灵敏度及扫描速度等.设计的电子枪采用35 nm厚的Ag阴极,阴栅之间场强为10 kV/mm,磁线圈聚焦,偏转灵敏度为26.3 mm/kV的平折扫描板,5.5 kV/ns的扫描电压斜率,最终获得了1.45×108 m/s的扫描速度.计算出系统总的时间分辨率为500 fs左右.     

Monte Carlo Study on Focus Properties of Portable Ultrabright Microfocus X-Ray Sources

The construct and electrode potential of emitting systems are very important for the portable ultrahigh brightness microfocus x-ray sources. The ratio of Dw/H （Dw is the diameter of Wehnelt grid aperture and H is the setting height of the cathode） and the grid bias are determinative parameters for the emission current and focus properties of an electron beam. The Monte Carlo method is used to numerically calculate the electron beam trajectories within a microfocus x-ray tube. The calculated results indicate that an optimum source system with the electron beam focal spot diameter smaller than 10μm at the anode, reasonable short focal length of about 76mm and the cathode emission current of more than 30mA can be attained under conditions of Dw/H = 5 and grid bias Vg = -0.6 k V.     

Theoretical and Experimental Investigation of Ultrasonic Focusing with Annular Phased Array

The focused acoustic field generated by an annular array interface are investigated theoretically and experimentally. transducer and its reflection field on a solid-liquid Theoretically, the concise analytic expressions about the radiation and reflection acoustic fields of the annular phased array are obtained by the ray approach method （saddle-point method）. In experiment, an annular transducer with 8 equal-area elements is designed and fabricated, and a series of experiments about the radiation acoustic field and its reflection on the liquid-solid interface are carried out. The experimental characteristics of the transducer are in good agreement with the numerical ones. It shows the correctness of the theoretical result and the feasibility of dynamic focusing of the experiment system. With the maximum amplitude and its emergence time of the reflection wave, we can acquire the information and the imaging of the reflection interface by the annular phased array dynamic focusing.     

双原子分子多光子电离强场效应的含时波包动力学研究

强激光非线性条件下分子的多光子电离过程呈现出较为明显的强场效应.由于这种效应不能用传统的量子微扰论来处理,“缀饰态”模型方法提供了物理图象清晰的处理光与物质相互作用的方案.本文基于含时波包动力学的基本理论,将激光场看作经典场,利用“缀饰态”模型研究了强场下双原子分子(NO、RbI等)的多光子电离过程.研究表明,激光场的强度、泵浦-探测脉冲延迟时间等对多光子电离光电子能谱的形状有着重要的影响,而这种影响是由光诱导势引起的.另外,在研究具有两个连续态的RbI体系时,自电离现象的发生也与势能面的交叉密切相关,并受外场强度的影响.本文计算模拟外场中分子的光电子能谱时所得到的强场效应对理解和实现原子分子过程的激光操控具有重要的意义.     

Theoretical Prediction of the Acoustical Nonlinear Field Radiated from a Concave Focusing Source with a Wide Aperture Angle

We propose a time-domain theoretical approach to predict the acoustic nonlinear field radiated from a concave focusing spherical source with a wide aperture angle. The nonlinear sound propagation is theoretically described by an accurate mathematical model including the continuity and momentum equations. Numerical calculation is implemented by using the finite difference time domain algorithm in the oblate spheroidal coordinate system. To examine the validity of the theoretical model, we calculate the sound fields radiated from concave spherical focusing transducers with aperture angles 30° and 40° and the results are compared with those obtained by the SBE solution.     

一种自适应的自动聚焦算法

自动聚焦是图像测量和计算机视觉中的重要技术。研究发现,以前的一些自动聚焦算法,在没有噪声的影响下,效果较好,但一旦有噪声的影响,算法可能会失效,因此,提出了一种自适应的自动聚焦方法。首先通过一个基于局部小窗口的自适应门限将边缘像素和非边缘像素区别开来,然后再加上一个全局门限来进一步滤除噪声的影响,最后用一些自动聚焦算法来计算经过自适应处理后的图像,画出它们的聚焦曲线。经过大量的实验,结果表明,该算法不仅具有单峰性强,无偏性好,灵敏度高等特点,而且还具有很好的抗噪声性能。     

毛细管柱表面鸡卵清蛋白快速改性并用于等电聚焦电泳分离蛋白质

开发了一种利用鸡卵清蛋白改性毛细管柱内表面的快速方法。改性后的毛细管柱可避免蛋白质样品的吸附作用，在较温和的条件下，柱性能有很好的稳定性，可适用于等电聚焦电泳分离生物样品的需要。