μ介子氢原子在双色激光场驱动下产生单个仄秒脉冲

本文利用强场近似理论研究了一束强度稍弱的X射线脉冲辅助另一束强X射线脉冲作用于μ介子氢原子产生高次谐波的过程.研究发现当弱X射线的频率为强X射线频率的一半时,可以生成超宽高次谐波频谱.通过合成高次谐波的连续谱,得到宽度为130 zs的单个仄秒脉冲.单个仄秒脉冲为超快变化过程的研究提供了工具.     

不均匀场中氢分子离子高次谐波产生的理论研究

在非Born-Oppenheimer近似下，通过求解含时薛定谔方程的方法，对氢分子离子在不均匀场中高次谐波的产生进行了理论研究.计算结果显示，同均匀场相比，电离的电子在不均匀场中加速会获得更多的能量，从而更有利于得到宽频谱.此外,通过优化不均匀场中的空间不均匀度，长量子路径被明显的抑制，最终通过叠加110阶到150阶谐波，获得一个60as的孤立阿秒脉冲.同时，通过库仑势和激光场的相互作用势以及时频分布图解释了其中的物理机制.     

Optical pulse shaper with integrated slab waveguide for arbitrary waveform generation using optical gradient force

Integrated optical pulse shaper opens up possibilities for realizing the ultra high-speed and ultra wide-band linear signal processing with compact size and low power consumption. We propose a silicon monolithic integrated optical pulse shaper using optical gradient force, which is based on the eight-path finite impulse response. A cantilever structure is fabricated in one arm of the Mach–Zehnder interferometer（MZI） to act as an amplitude modulator. The phase shift feature of waveguide is analyzed with the optical pump power, and five typical waveforms are demonstrated with the manipulation of optical force. Unlike other pulse shaper schemes based on thermo–optic effect or electro–optic effect, our scheme is based on a new degree of freedom manipulation, i.e., optical force, so no microelectrodes are required on the silicon chip,which can reduce the complexity of fabrication. Besides, the chip structure is suitable for commercial silicon on an insulator（SOI） wafer, which has a top silicon layer of about 220 nm in thickness.     

电除尘器的脉冲电源研究北大核心CSCD

为解决电除尘器脉冲电源存在的负载上脉冲拖尾、电容剩余电压积累、负载上电压振荡问题,在充电二极管两端反向并联了一个辅助开关。详细分析了电路的工作原理,给出了选取影响负载上脉冲波形的关键元器件参数的理论依据,仿真分析和低压试验验证了解决方案的正确性。脉冲电源的改进,有利于进一步提高除尘效率和能量利用率。     

考虑防御系统延迟使其预测误差最大的突防弹道设计

对中段多脉冲机动突防弹道的设计问题进行了研究。采用的原理与方法有别于成熟的航天器多脉冲变轨,而是基于路径规划的思想对弹道设计问题简化。考虑敌方防御系统延迟,改进多脉冲点火模型,并基于变射面的思想对关机点参数进行了设计及优化。然后,从使敌方预测误差最大的角度提出评价函数,并利用遗传算法进行优化。最后,给出了一种同时满足导弹机动突防与打击精度要求的多脉冲弹道设计方法。从模型的可行性,方法的有效性、灵活性、迭代效率及精度等方面进行了仿真验证分析。在PC机仿真中,20 s内就设计出一条保证打击精度的中段突防弹道。结果表明,建立的模型是可行的,提出的突防弹道设计方法是快速有效的。     

一个带有脉冲效应的高阶积分边值问题的正解

研究了一个带有脉冲效应的高阶积分边值问题的正解.在与相应的线性算子第一特征值有关的条件下,通过运用Krasnoselskii-Zabreiko不动点定理,获得了单个和多重正解的存在性结果.     

Investigations of ionization-induced injection of laser wake field acceleration using phenomenological model

We develop a phenomenological model to investigate dynamics of ionization-induced injection. In the ＂bubble＂ regime of laser wakefield acceleration （LWFA）, it is found that there is an upper limit for laser intensity of ionization-induced injection. In the plane perpendicular to the laser polarization, when the laser pulse is linearly polarized, ionization-induced injected electrons exhibit a filamented structure and semi-coherent betatron oscillation.     

Impacts of air pressure on the evolution of nanosecond pulse discharge products

Based on the nonequilibrium plasma dynamics of air discharge, a dynamic model of zero-dimensional plasma is established by combining the component density equation, the Boltzmann equation, and the energy transfer equation. The evolution properties of nanosecond pulse discharge (NPD) plasma under different air pressures are calculated. The results show that the air pressure has significant impacts on the NPD products and the peak values of particle number density for particles such as O atoms, O3 molecules, N2(A3) molecules in excited states, and NO molecules. It increases at first and then decreases with the increase of air pressure. On the other hand, the peak values of particle number density for N2(B3) and N2(C3) molecules in excited states are only slightly affected by the air pressure.     

脉冲电磁波在对称双槽上的散射特性研究

本刊讯随着亚波长光学的发展，人们对电磁波在具有凹槽的金属平面上发生的散射和共振进行了广泛而深入的研究，希望通过这些工作洞悉亚波长结构与电磁波作用的物理过程，并将成果应用于光学集成和人工材料的制造。为了简化问题，过去的研究绝大多数都是针对单色连续电磁波进行的，而对于更实际的脉冲电磁波鲜有涉及。