Optical fiber acoustic sensing multiplexing system based on TDM/SFDM

We propose a system of time-division multiplexing(TDM) and spatial frequency-division multiplexing(SFDM). Extrinsic Fabry–Perot interferometric sensors are applied to detect weak acoustic signals. The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers. Experimental results show that the equivalent noise pressure spectrum level is-97.2 d B re 1 rad/√Hz below 1250 Hz, and the cross talk between two sensors in one TDM channel is-32.7 d B with a cavity length difference of 60 μm. The number of sensors in this multiplexing system can theoretically reach 160.     

A DFT Study on the Adsorption of CO_2 Molecules on CaO(001) Surface at Different Coverages

The CO_2 adsorption on CaO(001) surface at different coverages from 1/9 monolayer(ML) to 1 ML has been investigated using density functional theory calculations. With the analysis of the most stable adsorption structures at different coverages, the mechanism of CaO(001)surface carbonating into CaCO_3 has been explored. At low coverages(≤1/3 ML), CO_2 molecule prefers sitting in parallel pattern on the CaO(001) surface, while the structure of the CaO(001)surface remains unchanged. At medium coverage(4/9 ～ 2/3 ML), the repulsive interactions between oxygen atoms of CO_2 become stronger, and the calcium carbonation structure appears on the CaO(001) surface. At high coverage( ≥ 7/9 ML), the structure of the CaO(001) surface is deeply damaged, and a few CO_2 molecules have penetrated into the surface and bound to the O atom of the second layer(sub-surface), eventually forming the layered structure of CaCO_3.Additionally, herein has discussed the simulation of HREELS and thermodynamical stability of these structures at different coverages.     

基于阈值因子的结构可靠性解耦优化方法

基于结构可靠性理论,引入阈值因子的概念,其物理意义为当前最优解满足可靠性约束需将阈值增减的幅度。随着迭代的进行,对于有效约束,阈值因子收敛于1,能够使得最可能失效点快速向满足可靠性约束的极限状态曲面靠拢,优化效率得以提升。解耦模型中,优化变量可为随机变量也可为非随机变量,当优化变量为随机变量时,采取优化变量拆解方式进行计算。数值算例表明,本文方法对优化变量拆解方式不敏感,对有效约束和非有效约束均能够获得满意的优化结果,且计算效率明显高于经典方法。     

Spin determination by in-plane angular correlation analysis in various coordinate systems

In the excitation of the resonant state followed by the sequential cluster-decay,the in-plane angular correlation method is usually employed to determine the spin of the mother nucleus.However,the correlation pattern exhibited in a two-dimensional angular-correlation spectrum depends on the selected coordinate system.In particular,the parity-symmetric and axial-symmetric processes should be presented in a way to enhance the correlation pattern,whereas the non-symmetric process should be plotted separately to reduce the background.In this study,three coordinate systems previously adopted for correlation patterns in the literature are described and compared to each other.The consistency among these systems is evaluated based on the experimental data analysis for the 10.29-MeV state in ~(18) O.A spin-parity of 4~+ is obtained for all three coordinate systems.     

Hybrid OCS/OBS interconnect in intra-data-center network

We report on a data center network(DCN) architecture based on hybrid optical circuit switching(OCS) and optical burst switching(OBS) interconnect for dynamic DCN connectivity provisioning. With the combination of the centralized and distributed control of the software-defined optical networks, the proposed interconnect can achieve unprecedented flexibility in dealing with both mice and elephant flow in the DCN. Numerical simulation is employed to investigate the performance of the proposed architecture. The results show that the OBS module has preferable performance in dealing with a larger burst packet, and the throughput is constrained by the capacity of the server random access memory module.