第一性原理研究[112]硅锗异质结纳米线的电子结构与光学性质

基于密度泛函理论体系下的广义梯度近似,本文利用第一性原理方法着重研究了[112]晶向硅锗异质结纳米线的电子结构与光学性质.能带结构计算表明:随着锗原子数的增加,[112]晶向硅锗纳米线的带隙逐渐减小;对Si_(36)Ge_(24)H_(32)纳米线施加单轴应变,其能量带隙随拉应变的增加而单调减小.光学性质计算则表明:随着锗原子数的增加,[112]硅锗纳米线介电函数的峰位和吸收谱的吸收边均向低能量区移动;而随着拉应变的增大,吸收系数峰值呈现出逐渐减小的趋势,且峰位不断向低能量区移动,上述结果说明锗原子数的增加与施加拉应变均导致[112]硅锗纳米线的吸收谱产生红移.本文的研究为硅锗异质结纳米线光电器件研究与设计提供一定的理论参考.     

Study on transition process of vacuum arc under transverse magnetic field

The transverse magnetic field (TMF) drives the vacuum arc to move along the surface of the contacts to prevent the local overheating and melting of the contact surfaces. The arcing process has great influence on the breaking capacity of short‐circuit current. In this paper, the arcing process between three types of TMF contacts was investigated. The transition process of an arc from the ignition stage to the diffusion stage was discussed. The transition moment, transition gap distance, and transition current were obtained. It was found that the axial magnetic field component of TMF contacts affected the arc transition process.     

Structures,stabilities and adsorption mechanisms of nitrogen adsorbed on Mon (n = 1–8) clusters

Configurations, stabilities and adsorption mechanisms of ground-state Mo_nN and Mo_nN₂ (n?=?1–8) clusters are calculated by using the density functional method within the PBE level. Evidently, N atoms tend to approach more Mo atoms. Doping with two N impurity prefers to occupy symmetrical position of the host Mo_n (n?=?1–8) cluster except for Mo₂N₂ clusters. Mo₄N, Mo₆N, Mo₂N₂, Mo₄N₂ and Mo₆N₂ clusters have higher structural stabilities than their neighbors by the second derivative of total binding energy. Mo₂N, Mo₄N and Mo₇N, Mo₂N₂, Mo₅N₂ and Mo₇N₂ clusters have higher kinetic reactivity than their neighbors by the HOMO–LUMO gaps. The adsorption capacity of a N atom to Mo₄ cluster is stronger than the other Mo–N clusters.     

用电流源法测量非线性元件的伏安特性

本文报导了一种新的用于测量非线性元件伏安特性的实验电路，该电路采用的是以电流为信号变量的电流模式测量电路，并分析与比较了该电路与传统的以电压作为信号变量的电压模式测量电路的不同．     

30M-35kV/2000A高温超导电缆制冷系统

本文介绍了我国新研制成的首条并网运行的热绝缘型30M-35KV/2000A高温超导电缆制冷系统。该制冷系统主要有液氮泵箱、过冷箱、高真空输液管道、液氮贮槽、辅助减压抽空系统、泵箱及气动阀门供气系统、监控系统所组成。冷却方式是过冷液氮循环,制冷方式是G-M制冷机和减压抽空(备用)。给出了制冷系统的运行结果。     

Characterization of Er3+-doped Na2O-WO3-TeO2 glass for ion-exchanged waveguide amplifiers and lasers

Er3+-doped Na2O-WO3-TeO2 glass consistent with standard ion-exchange technology has been fabricated and characterized. The measured absorption and emission spectra of the glass were analyzed by the JuddOfelt and McCumber theories. The intensity parameters are Ω2 = 7.01 × 10-20 cm2, Ω4 = 1.80 × 10-20 cm2, Ω6 = 1.03 × 10-20 cm2. The maximum emission cross-section is 0.91 × 10-20 cm2 at 1.533 μm, and a broad 1.5-μm emission spectrum of 65-nm full width at half-maximum (FWHM) is demonstrated. Glass transition temperature, crystallization onset temperature, density, refractive index are also reported for reference in the design and modelling of the ion-exchange process.     

Propagation characteristics of TM Gaussian beam

The propagation characteristics of TM polarized Gaussian beam, which is the rigorous solution of an eigenfunction problem for a confocal resonator, have been investigated using the nonparaxial vectorial moment theory of light beam propagation. The analytical expressions of the beam propagation factors are given by means of Fourier transform. Both the transversal second-order moment beam widths follow a simple hyperbolic variational law. For nonparaxial case, however, beam has different propagating features in the two transversal directions. As to paraxial case, its propagation approximately reduces to that of scalar Gaussian beam TEM₀₀ mode.     

Four-channel coarse WDM for inter- and intra-satellite optical communications

A polymer volume grating-based four-channel coarse wavelength division multiplexer (WDM) for inter- and intra-satellite optical communication application is reported for the first time. This compact four-channel WDM device working at 0.83, 1.06, 1.34 and 1.55 μm is designed to build a complete optical link between two satellites, where wavelengths of 0.83 and 1.55 μm are used for data stream channels, 1.06 and 1.34 μm are used for inter- and intra-satellite connection. It is for the first time reported that a WDM device can cover such a large wavelength range in a single substrate. For transverse electric (TE) wave, the channel efficiencies at 0.83, 1.06, 1.34 and 1.55 μm are 55%, 40%, 35% and 45%, respectively. Channel efficiencies for transverse magnetic (TM) waves are 20% lower than those of TE waves on average. Wavelength shifts due to Doppler effect, temperature variations and radiation effects in space can be adequately accommodated.     

加群(Pk-1,P)型的Pk(k>3)阶结合环的同构分类

本文给出加群(p^k-1,p)型的p^k(k>3)阶结合环的同构分类,类数如下表:(?)并按幂零和非幂零分别列表举出一个全体代表团。     

Study of shear transfer in Al/epoxy joint by digital photoelasticity

An improved six-step phase-shifting method is proposed for calculating full-field shear stress based on a four-step color phase-shifting method in digital photoelasticity. The method was verified using a disk under diametral compression and then applied to an aluminum alloy/epoxy joint for studying the shear transfer behavior. Experimental results revealed that the isochromatic fringe order and shear stress at the bonding interface are distributed continuously and increased with compression. In particular, an antisymmetric thermal residual shear stress appears at the bonding interface, because of the difference in the thermal expansion coefficients of Al and the resin. This indicates that the thermal residual shear stress at the bonding interface is self-balanced and reaches a peak at the edges of the bonding interface. The load transfer is realized by the shear band from the bonding interface to the bottom support. Basically, the bonding interfacial shear stress is balanced with the load.