Infrared superbroadband emission of Bi ion doped germanium-aluminum-sodium glass

The 96GeO-(3-χ)Al₂O₃-χNa₂O-1NaBiO₃ (χ = 0, 0.5, 1.5 molar percent designated as A1, A2 and A3) and 96GeO-(3.5-ψ)Al₂O₃-ψNa₂O-0.5Bi₂O₃ (ψ = 0.5, 1, 2 molar percent designated as B1, B2 and B3) glasses were prepared by conventional melting method with the measurement of their DTA curve, fluorescence decay curve, transmission, absorption and emission spectra. The near infrared superbroadband emission characteristics of the A1, A2, B1 and B2 glasses peak at ∼1220 nm were observed when pumped by an 800 nm laser diode. The stimulated emission cross section (σ_p) was obtained from the emission spectra. The result indicated that the introduction of Bi⁵⁺ in NaBiO₃ into raw materials could increase the emission intensity of the obtained glasses by 5.6 times than that of Bi³⁺ in Bi₂O₃, and the FWHM (Δλ) and emission lifetime (τ) at 1220 nm increased from 195 nm to 275 nm, and 280 μs to 434 μs. Meanwhile, it was found that the absorption edges were blue-shifted from 486 to 447 nm by comparing those of A1 and B1. The absorption edges were considered to be ascribed to the charge transfer from Bi³⁺ 6s² to Bi⁵⁺ 6s⁰. Therefore we could conclude that the content of Bi⁵⁺ ions in A1 was more than that in B1 glasses. It could be deduced from the emission and absorption spectra that the stronger emission intensity and wider FWHM were due to the higher concentration of Bi⁵⁺ ion in glass. In particular, the increase of Na₂O content was in proportion to the thermal stability and the value of σ_p × τ and σ_p × Δλ of glasses.     

Numerical solutions of general-relativistic field equations for rapidly rotating neutron stars

Stationary axial symmetric equilibrium configurations rapidly rotating with uniform angular velocity in the framework of general relativity are considered. Sequences of models are numerically computed by means of a computer code that solves the full Einstein equations exactly. This code employs Neugebauer’s minimal surface formalism, where the field equations are equivalent to two-dimensional minimal surface equations for 4 metric potentials. The calculations are based upon 10 different equations of state. Results of various structures of neutron stars and the rotational effects on stellar structures and properties are reported. Finally some limits to equations of state of neutron stars and the stability for rapidly rotating relativistic neutron stars are discussed.     

用数字干涉仪测量变形镜影响函数的实验研究

分析了变形反射镜面形影响函数的意义，鉴于自适应光学系统中波前探测大都以测量波前斜率为基础的特点，提出应研究斜率影响函数，并在此基础上构成波前复原矩阵。还介绍了用数字干涉仪测量变形镜影响函数的方法和结果，并对测量结果进行了分析，得到了影响函数的各种参数，例如：交连值，高斯指数，特征宽度等。并将干涉法测量斜率影响函数的结果与实际的哈特探测器的测试结果进行了比较。     

Absolute calibration of Hartmann-Shack wavefront sensor by spherical wavefronts

A method for absolute calibration of Hartmann-Shack wavefront sensor (HSWFS), in which the wavefront differences of several spherical wavefronts are used to determine parameters of HSWFS, is proposed in this paper. The calibration method is introduced and the experiment results and error analysis are presented. Across a pupil with diameter of 2.6 mm, a lenslet array of 20 × 20 sub-apertures with square configuration, and focal length 4 mm, is used to sample the incident wave. The results indicate the uncertainty of the Hartmann-Shack wavefront sensor calibrated by the proposed method, is improved to less than λ/60 PV value and λ/500 RMS value (λ = 635 nm) with modal reconstruction method. Furthermore, the factors affected the results are analyzed. The error analysis suggested that the influences of the factors on the accuracy of reconstruction can be controlled to an accept level.     

热对流作用下筒壁涂层的边裂行为

边裂(边缘开裂)是涂层热致损伤的主要模式之一. 边缘裂纹穿透涂层后,常导致界面脱粘从而驱使涂层与基体剥离,最终丧失对基体的保护作用. 本文以热应力强度因子表征边缘裂纹的扩展驱动力,研究筒壁涂层在热对流作用下的边裂行为. 首先,利用拉普拉斯变换法,得到了瞬态温度场及热应力场的封闭解. 其次,运用Fett等的三参数法确定了筒壁涂层边缘裂纹的权函数. 最后,基于叠加原理和权函数方法计算了边缘裂纹的热应力强度因子. 探讨了无量纲时间、边缘裂纹深度、基体/涂层厚度比、热对流强度等参数对热应力强度因子的影响规律. 结果表明:热应力强度因子的峰值既非发生在热载荷初始时刻,也非发生在热稳态时刻,而出现在时间历程的中间时刻;增大热对流强度不仅可提高热应力强度因子的峰值,而且使峰值提前出现;其他条件相同时,热应力强度因子随着边缘裂纹长度的增大而降低;增大涂层厚度或减小基体厚度可增强涂层抵抗瞬态热载荷的能力.      

管内湍流旋流的数值计算

本文用有限差分法对直管内的湍流旋流进行了数值模拟。计算中采用Ｂｏｕｓｓｉｎｅｓｑ湍流涡粘性假设的基本思想和Ｋ－ε双方程模型来求解雷诺应力各分量。为了反映旋流中湍流转输的非均匀性和各向异性特征，对雷诺应力各分量及与之相主尖的各湍流粘性系数分别进行计算。计算结果表明该模型能较好地反映直管内湍流旋流的流动结构。     

Progress of pyrene-based organic semiconductor in organic field effect transistors

Thanks to the pure blue emitting, high planarity, electron rich and ease of chemical modification, pyrene has been thoroughly investigated for applications in organic electronics such as organic light emitting diodes (OLEDs), organic field effect transistors (OFETs), and organic solar cells (OSCs). Especially, great progresses have been made of pyrene-based organic semiconductors for OFETs in past decades. Due to the difference of molecular structure, pyrene-based organic semiconductors are divided into three categories, pyrene as terminal group, pyrene as center core and fused pyrene derivatives. This minireview gives a brief introduction of the structure-property relationship and application in OFETs about most of pyrene-based semiconducting materials since 2006, illustrating that pyrene is a good building block to construct semiconductors with superior transport property for OFETs. Finally, we provide a summary concerning the methodology to improve the transport property of the pyrene-based semiconducting materials as well as an outlook.     

Multicomponent dynamic covalent assembly of a rhombicuboctahedral nanocapsule

Molecular container compounds have a range of potential applications in chemical and biological sciences, most notably as nanoreactors, drug delivery devices, and storage materials. We report a highly efficient dynamic covalent chemistry approach for the synthesis of covalent rhombicuboctahedral nanocapsule 1 from 14 square- and triangular-shaped molecular components. The nanocapsule is obtained in a one-pot reaction in high yield and high purity, and has a solvodynamic diameter of 3.9 nm. In our approach, six formyl cavitands and eight 1,3,5-tris(p-aminophenyl)benzene molecules are assembled into a molecular rhombicuboctahedron through twenty four newly formed dynamic imine bonds. Binding studies show that 1 encapsulates tetraalkylammonium salts in toluene. We also discuss the growth mechanism of this nanocapsule.     

用于活体人眼视网膜观察的自适应光学成像系统

利用自适应光学技术,研制了两套活体人眼视网膜高分辨力成像系统,在实时校正人眼波前误差的基础上,实现活体人眼视网膜细胞尺度的高分辨力成像。这两套系统分别采用19和37单元小型压电变形反射镜作为波前校正元件,哈特曼-夏克(Hartmann-Shack)波前传感器测量波前误差,用眼底反射的半导体激光作为波前探测的信标。在用计算机控制自适应光学系统实现人眼波前误差校正后,触发闪光灯照明视网膜,用CCD相机记录视网膜的高分辨力图像。校正后的残余波前误差的均方根值已分别小于1／6和1／10波长,相当于视网膜上成像分辨力分别为3．4μm和2．6μm,接近衍射极限。试验表明37单元系统的成像质量更好。