激光测头光束质量分析与控制

建立了光束质量控制的数学模型,提出了一种可定量评价光束质量的参数优化选择方法。针对激光测头进行了两片式光束质量控制光学系统的优化设计,并与光束聚焦控制、准直控制方法进行对比实验。激光结果证明:该优化光束控制系统在测量范围内既保持了光束的均匀性,光斑尺寸较小(光腰尺寸为34 μm),又保证了光束的精细度,有效地抑制了光束质量引入的测量误差,在±5 mm测量范围内,其均方根误差仅为6.3 μm,测量精度明显优于聚焦控制和准直控制系统。     

时空非相干光孤子的传播和相干特性

研究了时空非相干椭圆形高斯光束在饱和对数型非线性介质中的自陷行为,得到了孤子的形成条件并分析了其相干特性,讨论了光束自陷的变化形式,发现光束的初态和材料非线性对其有决定性的影响, 并进一步获得了光束半径和光束相干半径的解析表达式,发现光束的相干特性不但会随传播距离产生周期性的变化,且随组份频率的增大而减弱.     

高斯光束通过像散透镜后光束参数的变化

以二阶矩和环围功率作为束宽定义,对高斯光束通过像散透镜后光束参数,包括束宽和远场发散角作了解析和数值研究。结果表明：因像散引入束宽和远场发散角的相对误差与像散因子、瑞利尺寸、透镜焦距有关。对于束宽而言,相对误差还与传输距离z有关。在几何焦面处x和y方向束宽的相对误差相等。     

激光辐照InSb(PV)型探测器的热损伤

在建立高斯型连续激光辐照InSb(PV)型探测器物理模型的基础上,采用近似解析解的形式计算了圆柱形InSb靶板的2维温度场。通过数值分析得出了在激光辐照时,InSb(PV)型探测器的温升与时间的关系,并计算出相应的损伤阈值。研究表明：在强激光连续辐照下,半导体材料InSb会发生熔融损伤,且最早发生于迎光面的光斑中心,激光的功率密度越高,造成破坏所需要的时间越短;对于一定厚度胶层的InSb(PV)型探测器,只有强度大于一定阈值的连续激光辐照才可能发生熔融损伤,越薄的胶层对应的损伤阈值越大。为了增加InSb(PV)型探测器抗激光辐照能力,应该减小胶层厚度。采用该理论计算得到不同功率下的InSb熔融时间为1.57 s和4.54 s,与实验得到的2 s和 4~5 s基本吻合。     

基于最小二乘法的卫星相机MTF测量

对于对地观察卫星而言,为了定量评定其成像质量,对其MTF进行测量是非常重要的,它为比较不同卫星的性能提供了理论依据。一般的在轨MTF测量主要是对已知目标进行成像,由于天气和图像混叠的影响,这种方法对星载程序带来了很大限制。本文提出使用最小二乘法测量星载相机的MTF．对同一景物两次成像．一次采用高分辨率模式．另一次使用低分辨率模式,当两者分辨率比值足够高时,就可以通过将高分辨率图像与一个点扩散函数卷积和乏采样模拟得到低分辨率图像．并通过迭代使模拟图像与实测低分辨率图像的差在最小二乘意义下达到最小,以此得到点扩散函数。一旦迭代过程收敛,通过对点扩散函数进行傅立叶变换即可得到待测低分辨率图像的MTF。     

Steering Witness and Steering Criterion of Gaussian States

Quantum steering is an important quantum resource, which is intermediate between entanglement and Bell nonlocality. In this paper, we study steering witnesses for Gaussian states in continuous-variable systems. We give a definition of steering witnesses by covariance matrices of Gaussian states, and then obtain a steering criterion by steering witnesses to detect steerability of any (m+n)-mode Gaussian states. In addition, the conditions for two steering witnesses to be comparable and the optimality of steering witnesses are also discussed.     

Accurate conformation analysis in solution: NMR and DFT/PCM study of the S-3-(1-naphthoyl)-4-isopropyl-2,2-dimethyloxazolidin-5-one in CDCl3

The title molecule has been synthesised and the low temperature NMR spectrum recorded in CDCl₃. The spectrum shows that four conformers lie within 0.08 eV at 210 K. We show that an accurate conformation analysis can be obtained with a full and consistent use of the DFT (B3LYP) and PCM methods. If the polarised Stuttgart-Dresden basis and a PCM cavity with individual spheres on the hydrogen atoms are used, if the thermal and PCM non-electrostatic contributions are taken into account, and if a demanding convergence is achieved, then the rms error on the energy differences amounts to 0.002 eV. The 6-31+g(d) basis is larger and yields a larger rms error: 0.006 eV.     

On the α-q-Mutual Information and the α-q-Capacities

The measures of information transfer which correspond to non-additive entropies have intensively been studied in previous decades. The majority of the work includes the ones belonging to the Sharma–Mittal entropy class, such as the Rényi, the Tsallis, the Landsberg–Vedral and the Gaussian entropies. All of the considerations follow the same approach, mimicking some of the various and mutually equivalent definitions of Shannon information measures, and the information transfer is quantified by an appropriately defined measure of mutual information, while the maximal information transfer is considered as a generalized channel capacity. However, all of the previous approaches fail to satisfy at least one of the ineluctable properties which a measure of (maximal) information transfer should satisfy, leading to counterintuitive conclusions and predicting nonphysical behavior even in the case of very simple communication channels. This paper fills the gap by proposing two parameter measures named the α-q-mutual information and the α-q-capacity. In addition to standard Shannon approaches, special cases of these measures include the α-mutual information and the α-capacity, which are well established in the information theory literature as measures of additive Rényi information transfer, while the cases of the Tsallis, the Landsberg–Vedral and the Gaussian entropies can also be accessed by special choices of the parameters α and q. It is shown that, unlike the previous definition, the α-q-mutual information and the α-q-capacity satisfy the set of properties, which are stated as axioms, by which they reduce to zero in the case of totally destructive channels and to the (maximal) input Sharma–Mittal entropy in the case of perfect transmission, which is consistent with the maximum likelihood detection error. In addition, they are non-negative and less than or equal to the input and the output Sharma–Mittal entropies, in general. Thus, unlike the previous approaches, the proposed (maximal) information transfer measures do not manifest nonphysical behaviors such as sub-capacitance or super-capacitance, which could qualify them as appropriate measures of the Sharma–Mittal information transfer.     

自相似模型仿真ATM网络VBR视频源研究

仿真过程采用了一种新的异步传输模式（ATM）视频源建模方法，即长期相关性分析和自相似模型方法，使用了自相似模型中的分形高斯噪声（FGN）模型。FGN过程的产生采用了Hosking算法和反变换法。在仿真具体实现过程中改进了现有FGN模型仿真算法的不足，从而使产生的过程既充分考虑到实际可变比特率（VBR）视频源序列的长期相关性，又兼顾了序列的短期相关性，同时给出了仿真结果与实际源统计特性的比较和验证。比较结果表明，自相似模型是一种理想的VBR视频源模型。     

平稳高斯序列超过数点过程与部分和的联合渐近分布

｛Ｘｎ｝为标准化平稳高斯序列，Ｎｎ为Ｘ１，Ｘ２，，Ｘｎ对水平ｕｎ（ｘ）的超过数形成的点过程，ｒｎ＝ＥＸ１Ｘｎ＋１，Ｓｎ＝∑ｎｉ＝１Ｘｉ．ｒｎｌｏｇｎ→０时，在一定条件下得到Ｎｎ与Ｓｎ的渐近独立性．