采用吸收修正Bronnikov算法的有机复合样品的X射线显微计算机层析研究

有机复合样品如大多数由低原子序数物质构成的多聚物组合材料、生物软组织等具有混合相位和振幅特性,采用传统吸收计算机层析(CT)或纯相位重构算法难以达到较高密度分辨的目的。采用基于吸收修正的Bronnikov相位恢复算法的X射线同轴相衬CT技术对高分子混合组份材料和药物医学样品进行了实验研究。结果表明该相位恢复算法可以实现多聚物组合材料的无损分辨和精确测量,能够清晰辨别各组份材料的电子密度分布;验证了药物样品多孔性结构三维测量的可行性,能够有效提供孔隙测量的阈值选择。该方法在材料科学尤其是聚合物组合材料、泡沫多孔材料都会发挥很好的作用;单距的低辐射优势,尤其适用于生物医学样品三维无损成像。     

308nmXeCl准分子激光双侧面对称泵浦之形腔染料激光器研究

描述了用３０８ｎｍＸｅＣｌ准分子激光双侧面对称泵浦之形腔染料激光器，重点探讨了这种激光器的输出光束质量改善问题，实验发现这种双侧面对称泵浦较传统的横向泵浦，光束质量有较好的改善，对于２×１０－３ｍｏｌ／ｌ浓度的ｃｏｕｍａｒｉｎ４６０染料甲醇溶液，在波长４６０ｎｍ处，实验得到１１．７％的能量转换效率     

长焦距光学系统杂光系数测试仪

报告了一种新的长焦距光学系统杂光系数测量装置,该装置除具有避免了制作大直径积分球的优点外,还能精确测量轴外杂光系数,分析各部分杂光源对杂光系数的影响.     

Changes in surface morphology and work function caused by corrosion in aluminum alloys

Corrosion behavior of a material is complicated and can affect strongly its surface physical and chemical properties. In this study, the effect of corrosion on surface morphology and electron work function (EWF) of various Al alloys was comparatively investigated using a scanning electron microscopy and a scanning Kelvin probe. The experimental results showed that the change in EWF with corrosion time was not linear, but firstly increased and then decreased. The theoretical treatments demonstrated that such a change in EWF did not only depend on the surface roughness, but also correlate with oxide layers formed at the surfaces of Al alloys. The present results can also be used to reasonably explain the correlation between surface roughness and EWF reported previously.     

Performance study and assessment of phase noise suppression by incoherent addition in a mode-locked fiber laser system

This paper investigates the effectiveness of phase noise suppression by incoherent addition in a passively mode-locked fiber laser. Incoherent addition is achieved by using an interferometer external to the mode-locked laser. Two different types of interferometers, Mach–Zehnder and ring, are investigated experimentally for different background phase noise levels. Measurements show that both types of interferometers can achieve good phase noise reduction for a background phase noise level above ? 130 dBc/Hz. Effects of dispersion management and pulse train intensity ratio in the interferometers are also discussed. Multi-stage cascaded interferometers are proposed for supermode noise suppression of harmonically actively mode-locked lasers.     

Critical behavior of higher cumulants of order parameter in the 3D-Ising universality class

QCD deconfinement phase transition is supposed to be the same universality class as the 3D-Ising model. According to the universality of critical behavior, the Binder-like ratios and ratios of higher cumulants of order parameter near the critical temperature in the 3D-Ising model are studied. The Binder-like ratio is shown to be a step function of temperature. The critical point is the intersection of the ratios of different system sizes between two platforms. The normalized cumulant ratios, like the Skewness and Kurtosis, do not diverge with correlation length, contrary to the corresponding cumulants. Possible applications of these characters in locating critical point in relativistic heavy ion collisions are discussed.     

基于区域分解和逐级光线分裂的杂散光分析

针对蒙特卡罗法运算量大的问题,通过引入区域分解和逐级光线分裂技术,减少杂散光线与表面交点求解时所涉及的表面数及跟踪光线数,降低计算量.区域分解时,考虑子区域与表面数的匹配关系;并基于杂散光传播过程的模拟信息,逐级确定光线分裂倍数.以大衰减比抑制结构和多传感器系统为例,进行杂散光分析.结果表明,对复杂系统杂散光传播的蒙特卡罗法模拟,应用区域分解和逐级光线分裂技术,可以在保持计算精度的前提下,有效地提高计算效率.     

基于材料反射率谐振特性测试电磁参数的自由空间法

自由空间法具有非接触、非破坏性测试特点,适于材料的电磁参数测试．根据材料反射率扫频测试的特性,提出了一种基于谐振特性测试材料电磁参数的新的自由空间法．通过理论分析,研究了发生相消和相长干涉的条件,给出了应用干涉位置和材料厚度测试材料介电常数实部的理论计算公式．利用谐振峰,谷的位置及其相互关系可以计算材料介电常数虚部,而利用波谷比值法比驻波比值法容易达到更高的计算精度．     

微腔等离子体放电过程的数值研究

采用2维自洽完全流体模型,数值研究了阳极为通孔的高气压微腔放电结构中等离子体参数的变化过程。模拟结果获得了当氩气压强为13.3 kPa时,放电中的电势分布、等离子体密度分布、径向电场分布和电子温度分布等重要参数的演化过程。模拟结果表明在放电过程中,阴极附近的电场由轴向电场逐步转变为径向电场,等离子体密度最大值位于放电腔中间处,并随时间推移由阳极附近向阴极附近移动,电子温度的最大值出现在阴极环形鞘层区域。     

Irreversibility of a quantum walk induced by controllable decoherence employing random unitary operations

Quantum walk is different from random walk in reversibility and interference. Observation of the reduced re- versibility in a realistic quantum walk is of scientific interest in understanding the unique quantum behavior. We propose an idea to experimentally investigate the decoherence-induced irreversibility of quantum walks with trapped ions in phase space via the average fidelity decay. By introducing two controllable decoherence sources, i.e., the phase damping channel (i.e., dephasing) and the high temperature amplitude reservoir (i.e., dissipation), in the intervals between the steps of quantum walk, we find that the high temperature amplitude reservoir shows more detrimental effects than the phase damping channel on quantum walks. Our study also shows that the average fidelity decay works better than the position variance for characterizing the transition from quantum walks to random walk. Experimental feasibility to monitor the irreversibility is justified using currently available techniques.