碳化钨颗粒增强钢基复合材料的冲蚀磨损性能研究

以直径为188～250 μm的石英砂为磨料,在自制颗粒冲蚀磨损试验机上对WC颗粒增强ZG45钢基表层复合材料的气-固两相冲蚀磨损性能进行研究,采用扫描电子显微镜观察其磨损表面形貌.结果表明,在相同冲蚀角条件下,增强相WC颗粒的直径越大,复合材料的耐磨性越差,复合材料在冲蚀角为45°时的冲蚀磨损率最大;而ZG45钢在冲蚀角为15°～30°范围内的冲蚀磨损率达到最大值,此后随着冲蚀角增加而减小;复合材料抗冲蚀磨损性能在较小冲蚀角(15°左右)下优于ZG45钢,在较大冲蚀角(≥30°)时劣于ZG45钢.     

层状类钙钛矿结构新铌酸盐KSr2Nb3O10

A new niobate compound KSr₂Nb₃O₁₀ was synthesized for the first time. The chemical compositions, crystal structure, optical property, density and melting point of the new compound were characterized by EPMA, TEM, XRD, DTA and so on. KSr₂Nb₃O₁₀ crystallizes the orthorhombic system with unit cell parameters a=0.7816(1) nm, b=0.7764(2) nm, c=2.9995(2) nm, V=1.8114(4) nm³, and space group P2₁2₁2₁, Z=8. The structure may be described as treble perovskite sheets ［Sr₂Nb₃O₁₀］^- interleaved with K⁺. Further, it was found that KSr₂Nb₃O₁₀ has intercalation phenomenon. Na⁺, Li⁺, H⁺, NH⁺₄ could exchange the interlayer cations K⁺ of KSr₂Nb₃O₁₀, and n-hexylamine also could intercalate into the place between the layers of ［Sr₂Nb₃O₁₀］^-.     

一种基于Mumford-Shah模型的红外图像边缘检测方法

Chan-Vese模型是一种优秀的简化Mumford-Shah模型。然而Chan-Vese模型是以两个同质区域为基础建立的,这并不符合红外图像的特点,导致直接应用该模型处理红外图像时可能失败。针对这一问题,提出了一种适用于红外图像边缘检测的改进Mumford-Shah模型,并对该模型中目标边缘的保持、停止准则的建立及算法速度的提高作了详细讨论。实验表明,改进Mumford-Shah模型能够克服Chan-Vese模型在对红外图像边缘检测时不能跨越过渡区域的缺点,有效地检测出目标边缘。     

一种高双折射光子晶体光纤中的脉冲俘获分析

数值模拟分析了一种新型高双折射光子晶体光纤中的脉冲俘获现象,以及泵浦脉冲入射条件对脉冲俘获效果的影响机理.结果表明:泵浦脉冲和信号脉冲处于零色散点附近,且分别处于光子晶体光纤的反常和正常色散区,其走离参量的数值小于10-12 s/m时,可以实现脉冲俘获;泵浦脉冲和信号脉冲的时域中心延迟对泵浦脉冲光谱红移量和信号脉冲光谱...     

锂离子电池的电化学阻抗谱分析

电化学阻抗谱(EIS)是研究电极/电解质界面发生的电化学过程的最有力工具之一,广泛应用于研究锂离子在锂离子电池嵌合物电极活性材料中的嵌入和脱出过程。本文从分析嵌合物电极的EIS谱特征入手,探讨了电化学阻抗谱中各时间常数的归属问题,重点讨论了与锂离子嵌脱过程相关的动力学参数,如电荷传递电阻、活性材料的电子电阻、扩散以及锂离子扩散迁移通过固体电解质相界面膜(SEI膜)的电阻等,对电极极化电位和温度的依赖关系。     

双零色散光子晶体光纤中超连续谱的产生及控制

通过数值模拟飞秒脉冲在具有双零色散波长的光子晶体光纤中的传输过程,详细分析了超连续谱的产生和控制机制.结果表明:中心波长处于反常色散区的泵浦脉冲在高阶非线性和高阶色散等作用的调制下,将演化为基孤子和正常色散区的两个色散波;该色散波进而经与之相位匹配的基孤子相干加强而使频谱展宽形成超连续谱,同时两个色散波上出现了干涉引起的振荡现象.进一步对比三种结构的光子晶体光纤中超连续谱的特点,定量分析了两色散波对超连续谱的限制作用,阐述了结构参量对超连续谱的影响.基于上述结论,结合对色散波的中心波长与光子晶体光纤的色散曲线、结构参量之间关系的分析,提出了设计光子晶体光纤的结构来控制超连续谱的方法.作为例证,通过优化光子晶体光纤结构理论上实现了频谱分量覆盖可见光区的平坦超连续谱.     

更新随机指标分枝过程的大偏差

研究了时间指标为一般更新过程的随机指标分枝过程.在每个粒子至少有两个分枝(Bottcher情形)以及更新分布满足Cramer条件的情况下,得到了更新随机指标分枝过程的大偏差原理.     

The effects of post-thermal annealing on the optical parameters of indium-doped ZnO thin films

Indium-doped ZnO thin films are deposited on quartz glass slides by RF magnetron sputtering at ambient temper- ature. The as-deposited films are annealed at different temperatures from 400 C to 800 C in air for 1 h. Transmittance spectra are used to determine the optical parameters and the thicknesses of the films before and after annealing using a nonlinear programming method, and the effects of the annealing temperatures on the optical parameters and the thickness are investigated. The optical band gap is determined from the absorption coefficient. The calculated results show that the film thickness and optical parameters both increase first and then decrease with increasing annealing temperature from 400 C to 800 C. The band gap of the as-deposited ZnO:In thin film is 3.28 eV, and it decreases to 3.17 eV after annealing at 400 C. Then the band gap increases from 3.17 eV to 3.23 eV with increasing annealing temperature from 400 C to 800 C.     

铌酸盐Ba_3NaBiNb_(10)O_(30)的结构与介电特性

A niobate was synthesized by doping Bi3＋ in the ternary system BaO Na2O Nb2O5. The crystal structure was determined by X ray powder diffraction,and it belongs to tetragonal tungsten bronze structure at room temperature with unit cell parameters a=1.24777 (2) nm,c=0.39266(1) nm,α =β =γ =90° .Measurements of dielectric properties indicate that phase transitions of Ba3NaBiNb10O30 from paraelectric to ferroelectric occurs at 400℃ ,which is lower than that of Ba2NaNb5O30.     

Analysis of Electrical Properties of Post-Annealed Polycrystalline CaCu3Ti4O12 Films by Impedance Spectroscopy

Impedance spectroscopy is performed to establish the electrical property and microstructure relations of the asdeposited and post-annealed polycrystalline CaCu3Ti4O12 （CCTO） films. Our results show that the resistance and capacitance of the grains and grain boundaries could be tuned by changing the annealing atmosphere and temperature. The simple resistor-capacitor equivalent circuit and the modified constant phase element （CPE） circuit are used to describe the impedance spectroscopy, and excellent agreement between the calculated and measured curves is obtained in the CPE circuit. Based on the experimental results, it is suggested that the origin of the semiconductivity of the grains in CCTO polycrystalline films originates from their oxygen-loss, while the grain boundaries are close to oxygen- stoichiometry.