振幅和相位涨落对锁模脉冲列特性的影响

用傅里叶变换的方法分析了锁模激光器中模式间的相位和振幅涨落对锁模脉冲列特性的影响。将锁模激光器中各模式的相位和振幅涨落作傅里叶展开,再通过增益谱抽样的傅里叶变化得到其时域行为。分析结果表明振幅系统涨落及随机涨落均不引起脉宽的明显变化,只引起脉冲间背景的加大,但相位涨落随机会使脉冲列强度产生波动。所用物理图像简明,结果对获得稳定的锁模脉冲列的实验研究有参考意义。     

振幅和相位涨落对锁模脉冲列特性的影响

 用傅里叶变换的方法分析了锁模激光器中模式间的相位和振幅涨落对锁模脉冲列特性的影响。将锁模激光器中各模式的相位和振幅涨落作傅里叶展开，再通过增益谱抽样的傅里叶变化得到其时域行为。分析结果表明振幅系统涨落及随机涨落均不引起脉宽的明显变化，只引起脉冲间背景的加大，但相位涨落随机会使脉冲列强度产生波动。所用物理图像简明，结果对获得稳定的锁模脉冲列的实验研究有参考意义。     

Measurement of the structure coefficient of refractive index fluctuations in a turbulent premixed butane-air flame by means of a laser-based interferometer technique

With a view to measuring the structure coefficient of refractive index fluctuations in a turbulent premixed butane-air flame, a thin laser beam is sent into the flame perpendicular to the flow direction. The laser beam generally undergoes fluctuations of direction, phase, and amplitude. Only the random deflections of the laser beam may be taken into account. After having traversed the flame, the perturbed laser beam enters into an interferometric system. Materials and experimental procedure are described. In the unperturbed interference pattern, the zones only sensitive to fluctuations of the angle-of-arrival of the laser beam are detected. From the random displacements of the central bright fringe, the structure coefficient of refractive index fluctuations in the flame is measured. To prove that the method of measurement is satisfactory, the result obtained is applied for computing the power spectral density of the angle-of-arrival of the laser beam from the formula of correlations of the laser beam deflection angles which we have demonstrated in previous works. This computed power spectral density is compared to that measured from the effective position of the detector. A good agreement is observed between the two results.     

基于MILO结构的一种单边multipactor模型分析

根据高功率微波源相互作用腔的物理结构特性,以磁绝缘传输线振荡器（MILO）为例,建立了一种单边二次电子倍增效应（mulitpactor）模型.采用概率统计和蒙特卡罗（MC）模拟方法,计算了敏感曲线和二次电子的时间演化规律,分析了射频场参数对二次电子倍增效应的影响,并提出了减小和抑制二次电子倍增效应的具体措施. 关键词： 单边二次电子倍增效应 敏感曲线 二次电子的时间演化     

Surface structure analysis based on the exclusive use of the specular LEED spot – a theoretical study

The exclusive use of the specularly reflected beam (the (0,0) spot) may be a more practical way of collecting data for a LEED I–V structure analysis under certain experimental conditions. In this paper we discuss the special properties of the (0,0) spot intensity and test its sensitivity towards structural changes for the model system CO/Ni(1 1 1) within the framework of a R factor analysis. It is found that the (0,0) spot can, indeed, be used for a reliable structure determination if the energy range is increased by collecting data at different polar and azimuthal angles of incidence. The R factor contrast is, however, reduced with respect to a conventional LEED I–V analysis.     

基于特定混沌系统微弱谐波信号频率检测的理论分析与仿真

为更完整地研究一类特定的Duffing-Holmes方程所建立的混沌系统用于确定微弱谐波未知频 率，论证了方程存在周期解并且该解唯一；利用稳定相态周期轨迹特征成功地进行了确定谐 波频率的仿真实验；从1Hz至200Hz变阻尼比（α）计算了检测误差|Δω|；结果表明，不同 频率带宽、不同频率相应的α值选择需要经过细致仿真实验去加以确定. 关键词： 特定混沌系统 混沌系统周期解 稳定相态周期 阻尼比