光学复用大视场成像研究

为了简化光学复用成像系统复杂度和降低对编码方式的要求,基于反射镜旋转完成通道编码,构建了结合分束镜和光学成像系统实现双通道混叠成像的实验装置.为实现混叠图像的有效解混叠,提出了利用特征点检测与匹配方法实现多幅混叠图像之间平移量的自动识别,进而构建出具有亚像素精度的双通道光学复用成像系统的系统复用矩阵,并采用梯度投影稀疏重建算法完成基于多幅图像的双通道图像重建,最终实验实现了光学成像系统视场角的2倍放大.此外,对所提方法在其他场景的适应性也进行了实验验证,表明了其可在不改变焦平面探测器的情况下实现光学成像系统视场角的有效放大,大大节约了大视场光学成像系统的研制成本.     

Aeroacoustic Simulations Using Compressible Lattice Boltzmann Method

This paper presents a lattice Boltzmann (LB) method based study aimed at numerical simulation of aeroacoustic phenomenon in flows around a symmetric obstacle. To simulate the compressible flow accurately, a potential energy double-distribution-function (DDF) lattice Boltzmann method is used over the entire computational domain from the near to far fields. The buffer zone and absorbing boundary condition is employed to eliminate the non-physical reflecting. Through the direct numerical simulation, the flow around a circular cylinder at $Re$=150, $M$=0.2 and the flow around a NACA0012 airfoil at $Re$=10000, $M$=0.8, $α$=$0^◦$ are investigated. The generation and propagation of the sound produced by the vortex shedding are reappeared clearly. The obtained results increase our understanding of the characteristic features of the aeroacoustic sound.     

Tail wavelets in merger of binary compact objects

We present a model for tail wavelets, a phenomenon known as "echo" in the literature. The tail wavelet may appear in signal reconnaissances in the merger of binary compact objects, including black holes and neutron stars. We show that the dark matter surrounding the compact objects lead to a speculated tail wavelet following the main gravitational wave(GW). We demonstrate that the radiation pressure of the main wave is fully capable of pushing away the surrounding matter to some altitude, and splashing down of the matter excites the tail wavelet after ringing down of the main wave. We illustrate this concept in a simplified model, where numerical estimations are conducted on the specific distribution of dark matter outside the black hole horizon and the threshold values in accordance with observations. We study the full back reaction of the surrounding dark matter to the metric and find that the effect on to the tail wavelets is insignificant. We reveal the fine difference between the tail wavelets of a dressed and a bare black hole. We demonstrate that the tail wavelet can appear as a natural phenomenon in the frame of general relativity, without invoking modified gravities or quantum effects.     

火焰原子吸收光谱法测定鸭粪中铜和锌的含量

采用火焰原子吸收光谱法测定白洋淀生态养鸭场中饲料及鸭粪中的铜和锌含量,测定结果为饲料中的铜含量范围在9.7-61.55mg/kg,锌含量范围在63.14-149.07mg/kg,在禽类饲料中铜、锌含量属于较低的类型;鸭粪中铜含量范围在13.71-94.74mg/kg,锌含量范围在156.98-346.31mg/kg,参...     

Adsorption of CO, NH3 and O2 on Fe site of La0.875Sr0.125FeO3 (0 1 0) surface by density function theory calculation

The adsorption of CO, NH₃ and O₂ gas molecules on Fe site of La_0.875Sr_0.125FeO₃ (0 1 0) surface has been investigated based on the density functional theory (DFT) with the spin polarized generalized gradient approximation (GGA). The optimal adsorption orientations as well as the adsorption energies for these molecules adsorption on Fe site of La_0.875Sr_0.125FeO₃ (0 1 0) surface are derived. Results show that adsorption configurations with C-down for CO, N-down for NH₃ are stable. For the O₂ molecule adsorption, the mode with an angle about 120° between the oxygen molecule and La_0.875Sr_0.125FeO₃ (0 1 0) surface is stable.     

Multilayer thin-film inspection through measurements of reflection coefficients

A vibration-insensitive interferometer is described to measure the thickness, refraction index and surface profile of thin-film stack at normal incidence. By satisfying the continuous boundary conditions of electric and magnetic fields at interfaces in a multilayer film stack, the reflection coefficient phase of the thin-film stack can be distinguished from the phase of spatial path difference, thus thickness and refraction index can be extracted. The experiment results showed that the measurement precision is significantly increased after the phase analysis was added into the reflectance analysis.     

端部周期加热下管内气温奇异分布的实验研究

设计搭建了端部周期加热时管内气体热声对流的实验平台,对端部周期加热引起的气体热声对流作用下管内气体的温度分布进行了实验研究。该实验以氩气为工质,利用三极管控制加热电路实现周期性加热;测量了不同加热频率下管内的气体温度,并与常热流加热时的温度分布进行对比,结果表明端部周期加热时管内气体的温度分布与同功率下常热流加热时存在明显的差异,并且在某些测点出现了温度的奇异分布。本实验验证了超温现象的存在,为管内气体热声对流现象的进一步研究奠定了基础。     

Energy Band and Josephson Dynamics of Spin-Orbit Coupled Bose——Einstein Condensates

We theoretically investigate the energy band structure and Josephson dynamics of a spin-orbit coupled Bose-Einstein condensate in a double-well potential. We study the energy band structure and the corresponding tunneling dynamics of the system by properly adjusting the SO coupling, Raman coupling, Zeeman field and atomic interactions. The coupled effects of SO coupling, Raman coupling, Zeeman field and atomic interactions lead to the appearance of complex energy band structure including the loop structure. Particularly, the emergence of the loop structure in energy band also depends on SO coupling, Raman coupling, Zeeman field and atomic interactions. Correspondingly, the Josephson dynamics of the system are strongly related to the energy band structure. Especially, the emergence of the loop structure results in complex tunneling dynamics, including suppression-revival transitions and self-trapping of atoms transfer between two spin states and two wells. This engineering provides a possible means for studying energy level and corresponding dynamics of two-species SO coupled BECs.     

Fast Generation of GHZ States with Bose–Einstein Condensate in a Cavity

It is shown that strong coupling of Bose–Einstein condensates to an optical cavity can be realized experimentally. With an additional driven microwave field, we show that a highly nonlinear coupling among atoms in a Bose–Einstein condensate can be induced with the assistance of the cavity mode. With such interaction, we can investigate the generation of many body entangled states. In particularly, we show that multipartite entangled GHZ states can be obtained in such architecture with current available techniques.     

Temperature or strain induced adjustable-chirp characteristics of uniform fibre grating with tapered metal coating

Temperature and strain characteristics of uniform fibre grating with tapered metal coatings have been analysed theoretically, by which adjustable chirp characteristics of such gratings are shown. Electroplating is adopted to fabricate such gratings, and the tapered metal coating is obtained by gradually drawing the fibre grating out of the solution during the process of electroplating. The gradually changing cross-sectional area of the metal coating is calculated by a newly suggested numerical method. By combining the theoretical and numerical simulation analyses, the gratings' characteristics are given at various temperatures and strains. The results obtained using such a method are also testified by experiments.