基于压电探测判定激光支持燃烧波和爆轰波的点燃阈值

为了获得激光支持燃烧波和爆轰波的点燃阈值,采用压电探测器检测波长为1 064 nm的Nd:YAG激光作用在铝靶表面所产生的应变和冲压。从实验结果观察到压电信号的变化分为3个阶段,分别为光热弹性应变阶段、等离子体增强耦合阶段和激光支持爆轰波对靶表面的压力阶段,并从理论上研究了这3个阶段的激光与靶材料相互作用的机理,从而可以从压电信号是否发生跃变判断出激光支持燃烧波和激光支持爆轰波的点燃阈值,与其它方法所得到结果基本吻合。     

Ⅲ族氮化物异质结构二维电子气研究进展

本文总结了近年来Ⅲ族氮化物半导体异质结构二维电子气的研究进展。从Ⅲ族氮化物材料晶格结构和特有的极化性质出发,重点讨论了AlGaN/GaN异质结构中二维电子气的性质,总结分析了异质结构中Al组分、势垒层厚度、应变弛豫度、掺杂等对二维电子气浓度和迁移率的影响,同时还涉及AlGaN/GaN/AlGaN,AlGaN/AlN/GaN和AlGaN/InGaN/GaN等异质结构二维电子气性质。     

DECAY RATE OF SAINT-VENANT END EFFECTS FOR PLANE DEFORMATIONS OF PIEZOELECTRIC-PIEZOMAGNETIC SANDWICH STRUCTURES

This paper is concerned with the decay of Saint-Venant end effects for plane deformations of piezoelectric （PE）-piezomagnetic （PM） sandwich structures, where a PM layer is located between two PE layers with the same material properties or reversely. The end of the sandwich structure is subjected to a set of self-equilibrated magneto-electro-elastic loads. The upper and lower surfaces of the sandwich structure axe mechanically free, electrically open or shorted as well as magnetically open or shorted. Firstly the constitutive equations of PE mate- rials and PM materials for plane strain are given and normalized. Secondly, the simplified state space approach is employed to arrange the constitutive equations into differential equations in a matrix form. Finally, by using the transfer matrix method, the characteristic equations for eigen- values or decay rates axe derived. Based on the obtained characteristic equations, the decay rates for the PE-PM-PE and PM-PE-PM sandwich structures are calculated. The influences of the electromagnetic boundary conditions, material properties of PE layers and volume fraction on the decay rates are discussed in detail.     

雷鸣1540型组合扬声器投产

七九七厂新试制了一种高保真度、声场覆盖面积大的组合扬声器箱.该系统由一只大功率高顺性15英寸(约381mm)低音扬声器和一只指向性与频率无关的高频扬声器及分频衰减器组合而成.其箱体设计采用了声管倒相.该组合扬声器有较宽的频响,如图1所示.在较宽的频率范围内,指向性达到了较好的水平,如图2所示.经各方面有关人员主观试听,认为该组合音箱低音部分低沉浑厚,中音刚劲有力,高音清     

一般切割面的铋硅族氧化物光折变增益特性及动态光栅优化

利用耦合张量对光折变旋光，电光，压电及弹光铋硅族氧化物晶体中光波本征模的作用，在任意晶体切割面上求解了弱耦合的矢量波耦合方程, 并利用有效耦合概念处理了非旋光晶体 中的矢量波耦合问题. 进而计算旋光和非旋光材料中信号光的增益, 并分别比较各向同性耦 合和各向异性耦合对增益的影响. 对旋光材料优化增益，并把处理结果应用于BSO和BTO晶体 . 还讨论了压电和弹光效应对(110)，(111)及(112)切割面优化增益的影响. 关键词： 铋硅族氧化物 光折变 旋光效应 压电 弹光效应     

AlxGa1-xN/GaN异质结构中Al组分对二维电子气性质的影响

通过用数值计算方法自洽求解薛定谔方程和泊松方程,研究了Al组分对AlxGa1-xN/GaN异质结构二维电子气性质的影响,给出了AlxGa1-xN/GaN异质结构二维电子气分布和面密度,导带能带偏移以及子带中电子分布随AlxGa1-xN势垒层中Al组分的变化关系,并用AlxGa1-xN/GaN异质结构自发极化与压电极化机理和能带偏移对结果进行讨论分析.     

POLYNOMIAL SOLUTIONS TO PIEZOELECTRIC BEAMS (Ⅰ)——SEVERAL EXACT SOLUTIONS

IntroductionDue to its excellent piezoelectric properties,composites made of piezoelectric materialsare found widespread applications and attracted more attentions[1-10].Because of materialanisotropy and couplingbetween mechanical deformation and electric…