熔石英亚表面杂质颗粒附近光场调制的三维模拟

熔石英亚表面缺陷是光学材料低损伤阈值的主要因素之一.本文建立了熔石英亚表面三维球形杂质颗粒模型,采用三维时域有限差分方法对杂质附近的光场进行了数值模拟,分析了杂质的介电常数与尺寸对光强增强因子的影响,结果显示:介电常数小于熔石英的杂质,其光强增强因子不随尺寸、介电常数的改变而改变,均保持为4左右;当介电常数为6.0时,半径为1.5λ,2λ及2.5λ的杂质,相应的光强增强因子分别为50.1588,73.3904及102.9953,即增强因子随杂质尺寸的增大而增大;恰 关键词： 杂质颗粒 三维时域有限差分 数值计算 光强增强因子     

Neural network applied to reconstruction of complex objects based on fringe projection

The neural network has been introduced into the reconstruction of the complex object based on fringe projection. In this method, the neural network with powerful property of approximation is used to get the continuous approximate function of a discrete fringe pattern captured by an image frame grabber. The depth-related phase of the measured object modulated into the fringe pattern can be demodulated by dealing with the approximate function. Compared with the Fourier transform profilometry (FTP), in the network method, one deformed fringe pattern is needed to reconstruct the tested object, and a high spatial resolution is maintained for no filtering process. Therefore, this method performs better than FTP in the measurement of the complex object. Moreover, the network method is capable of demodulating more depth-related phase even in the case that the local shadow exists in the fringe pattern. Computer simulations and experiments validate the feasibility of this method.     

品质因数的多重内涵及其教学探讨

从正弦激励下线性二阶系统的微分方程出发,结合阻尼振子的受迫振动以及RLC串联、并联谐振电路等具体物理情境,剖析了品质因数Q在频率特性、能量转换以及系统各物理参数等多个层次上的内涵,进而探讨如何更好地为工科各专业学生讲授品质因数这一概念.     

High pressure X-ray diffraction study of SrMnO3 perovskite

Using a diamond anvil cell device and synchrotron radiation, the in-situ high-pressure structure of SrMnO3 has been investigated. At pressure up to 28.6 GPa, no pressure-induced phase transition is observed. The lattice parameters as a function of pressure is reported, and the relationship of the axial compression coefficients is β<,a>> β<,c>. The isothermal bulk modulus K<,298>=266(4) GPa is also obtained by fitting the pressure- volume data using the Murnaghan equation of state.     

Analysis of superconducting cavity quench events at SSRF

Quench is important and dangerous to superconducting RF cavities. This paper illustrates the mechanism of quench and how a quench detector works, and analyzes the quench events happening during beam operations and cavity conditioning. We find that the quench protection is mostly triggered by some reasons such as fluctuation of cavity voltage, multipacting or arc, rather than a real cavity thermal breakdown. The results will be beneficial to optimize the operation parameters of superconducting cavities, to discover the real reasons for beam trip by quench interlock, and to improve the operation stability of superconducting RF systems.     

Reference-free Shack-Hartmann wavefront sensor

The traditional Shack-Hartmann wavefront sensing (SHWS) system measures the wavefront slope by calculating the centroid shift between the sample and a reference piece, and then the wavefront is reconstructed by a suitable iterative reconstruction method. Because of the necessity of a reference, many issues are brought up, which limit the system in most applications. This Letter proposes a reference-free wavefront sensing (RFWS) methodology, and an RFWS system is built up where wavefront slope changes are measured by introducing a lateral disturbance to the sampling aperture. By using Southwell reconstruction two times to process the measured data, the form of the wavefront at the sampling plane can be well reconstructed. A theoretical simulation platform of RFWS is established, and various surface forms are investigated. Practical measurements with two measurement systems-SHWS and our RFWS-are conducted, analyzed, and compared. All the simulation and measurement results prove and demonstrate the correctness and effectiveness of the method.     

铬的电离势及类氦Cr~(22 )的E2和M1光谱跃迁的全相对论计算

基于相对论多组态自洽场方法 ,计算了CrⅠ至CrⅩⅩⅣ离子的基态能量和各价电离势 ,类氦Cr2 2 离子的电四极矩和磁偶极矩光谱跃迁数据。计算中考虑了核的有限体积效应、Berit修正、QED修正和轨道极化效应。计算结果与文献的实验和计算值进行了比较。     

遗传算法在离心压缩机参数优化中的应用

遗传算法是当今世界上应用比较广泛的优化算法之一,特别是在处理有界多极值复杂函数方面有着明显的优势．在流体机械行业中,设计参数的优化问题往往涉及求解一些复杂隐函数在约束区间内的极值问题．因此将遗传算法应用到流体机械的设计参数优化当中有明显的现实意义．本文介绍了遗传算法在离心压缩机参数优化中的应用,并与传统的复合型法所获得的优化结果进行了比较,对比的结果显示出了遗传算法的优越性．     

图形衬底对多周期InGaAs量子点自组装生长的影响

量子点器件技术广泛应用于量子计算和光电器件上.成核位置的均匀性、有序性和尺寸一致性,可以有效提高光电器件性能.为了实现阵列量子点的可控性,本文采用湿法刻蚀制备图形化衬底,理论上解释了铟原子在图形化衬底上成核现象,产生有序的量子点分布特征,发现图形衬底的缺陷诱导在平台边缘和沟壑边缘成核,形成较大的量子点.在Stranski-Krastanow模式下图形衬底制备多周期量子点,发现多周期生长可以弱化台阶结构对量子点分布的限制作用.     

三代微光和超二代微光夜视技术的研究和开发

介绍三代微光和超二代微光夜视技术的发展概况：阐明了它们各自的原理、技术特点和关键课题；着重指出了两者间的异同和相互联系。