扫描型热像系统均匀性校正方法研究

随着热像系统时域噪声等效温差（NETD）的不断下降,残余固定图形噪声（RFPN）的不稳定性成为制约系统性能,特别是制约系统识别能力的一个关键因素。通过分析热像系统响应非均匀性产生的机理,介绍一种扫描型热像系统获得场景平均辐照度点的方法,实现了以场景平均辐照度点为校正基准点的动态校正。采用该方法研制的热像系统在（0～50）℃场景动态范围内可使系统的RFPN小于15mK。通过样机冬、夏两季外场试验以及各种环境试验,验证了该校正方法在热像系统温度发生变化以及场景辐照度发生变化时具有良好的适应性。     

射频离子源束流特性分析

介绍了为HL-2A 装置设计的引出束功率为1MW 的射频离子源研制情况。目前,在测试平台上,该离子源已经成功引出了束能量和束电流分别为35keV 和12.4A、束质子比为79%、脉宽为100ms 的氢离子束,达到了其设计束功率的44%。用红外热成像的方法测量了离子束能量密度分布。结果表明,在距离引出系统地电极 1.3m 处,束密度分布遵循高斯分布。引出束的最佳导流系数为1.689×10^–6A•V^-3/2 左右,随射频功率改变有较小的变化。根据这些实验结果,采取了相关改进措施来改善离子源的引出束性能。     

The spreading behaviour of perfluoropolyether droplets on solid surfaces

The spread of perfluoropolyether （PFPE） droplets on solid surfaces has been measured from the top-down view through a microscope system. Effects of substrates, molecular weight and end-group functionality on spreading of the PFPE droplets have been studied experimentally and the results were compared with those by molecular dynamics （MD） simulations. Silicon wafer and diamond-like carbon （DLC） substrates were used to study the effect of substrates on spreading. Two types of PFPE, Z-dol and Z-tetraol, with the same chain structure and various molecular weights （2000 and 4000 g/mol） were employed in experiments. Effect of molecular weight has been investigated through comparing the spreading of Z-dol 2000 and Z-dol 4000, and it is found that the increase of molecular weight will decrease the mobility of PFPE. Comparison between spreading of Z-dol and Z-tetraol of the same molecular weight proved that functional end group plays a significant role on the spreading of PFPE, which confirmed the MD simulation results.     

Local Unitary Invariants for Multipartite States

We study the invariants of arbitrary dimensional multipartite quantum states under local unitary transformations. For multipartite pure states, we give a set of invariants in terms of singular values of coefficient matrices. For multipartite mixed states, we propose a set of invariants in terms of the trace of coefficient matrices. For full rank mixed states with non-degenerate eigenvalues, this set of invariants is also the set of the necessary and sufficient conditions for the local unitary equivalence of such two states.     

Theoretical and experimental study of single mode-locking pulse generation with low repetition rate in a dual-loss-modulated QML YVO4/Nd:YVO4 laser with EO and GaAs

Using electro-optic (EO) modulator and GaAs saturable absorber, a diode-pumped doubly Q-switched and mode-locked (QML) YVO₄/Nd:YVO₄ laser at 1.06 μm is realized. The experimental results show that the number of the mode-locking pulses underneath the Q-switched envelope decreased with increasing pump power. With an output coupling of 6.5 %, the single mode-locking pulse underneath the Q-switched envelope with 1 kHz repetition rate was obtained when the pump power exceeded 4.65 W. At a pump power of 8.25 W for an output coupling of 10 %, a stable mode-locking pulse train at a repetition rate of 1 kHz was achieved with pulse energy as high as 582 μJ and pulse duration of about 580 ps, corresponding to a peak power of 1 MW. Using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled rate equations for diode-pumped doubly QML YVO₄/Nd:YVO₄ laser are given and the numerical solutions of the equations are basically in accordance with the experimental results.     

非下采样小波变换红外光谱数据去噪

为了降低噪声对实测红外光谱信号的影响,引入了一种非下采样小波变换的红外光谱数据去噪方法。采用非下采样小波变换对原始光谱信号进行多尺度分解,提取信号的多尺度细节特征;根据光谱信号和噪声在不同尺度上的差异,通过应用变分偏微分方程方法调整分解后的各子带系数;重构各子带就可以将原始光谱信号中真实信号和噪声分离,从而达到剔除噪声的目的。通过两组实验对比传统小波和该方法针对红外光谱数据的消噪效果,实验结果表明:非下采样小波变换在红外光谱数据去噪方面具有明显的优势,不仅能够有效地去除噪声,很好地保持信号的形状,并且均方误差较小;在实际的红外光谱数据处理中能够获得较好的去噪效果。     

激光能量叠加过程中对准精度对焦斑的影响

利用多光束激光输出耦合叠加是一种提高激光器输出功率的有效方法。采用两束矩形激光对准系统,分析两光束不同对准情况下的焦斑特性。完全对准的情况下,两束光的远场焦斑重合在一起,焦斑能量是两光束能量之和。在实际光束对准系统中,讨论了三种常见的对准误差,并比较了这些误差对焦斑特性的影响。利用ZEMAX软件对设计系统进行了模拟分析,并进行了实验验证。结果表明,元件的位置误差会使远场焦斑能量集中度降低,焦斑半径增大。     

初态对光波导阵列中连续量子行走影响的研究

本文使用近邻耦合模型得到的解析解,分析了周期性波导中输入态对量子行走的粒子数的概率分布函数 和二阶相干性的影响.结果表明:输入态的对称性质对量子行走过程的二阶相干度有影响, 而对粒子数的概率分布函数影响不大. 关键词： 周期性光波导阵列 量子行走 二阶相干度 纠缠态     

电子磁矩对同步辐射频谱的修正

本文从偶极子辐射场的Heaviside-Feynman表达式出发, 用经典的电动力学方法推导了考虑内禀磁矩影响后的相对论电子辐射频谱分布的表达式, 并对做匀速圆周运动的极端相对论性电子的同步辐射, 计算了两个偏振方向上的考虑磁矩修正后的辐射谱. 计算结果表明对于特征频率为ω_c的同步辐射, 如果ħω_c≥10 keV, 内禀磁矩对辐射的修正是可观的. 通过同步辐射的内禀磁矩修正, 本文讨论了电子束极化度与辐射场偏振度的依赖关系, 并基于此关系提出一种测量电子束极化度的新方法. 关键词： 同步辐射 电子内禀磁矩 同步辐射偏振度 束流极化度     

大气波导条件下雷达海杂波功率仿真

考虑近海面大气折射率垂直梯度的变化, 采用曲面波频谱估计方法(CWSE)计算掠射角, 并结合修正的GIT海表反射率模型和雷达距离方程对大气波导条件下雷达海杂波功率进行仿真, 最后通过数值实验及与实测数据比较, 验证了CWSE方法的可行性. 关键词： 大气波导 雷达海杂波 曲面波频谱估计