扬声器驱动热声制冷机设计研究

热声制冷机主要由声驱动器、共振管、板叠、高低温端换热器、声容等部件组成。它具有运动部件少、运行可靠、振动小和寿命长等优点 ,在军事、航天、微电子、低温物理等领域有着十分诱人的应用前景。文中运用经典线性热声理论对热声制冷机各个组成部件设计进行了介绍 ,在此基础上设计了一台扬声器驱动热声制冷机 ,并用专业计算软件进行了数值模拟验证 ,为热声制冷机进一步优化与发展提供了一个解决方案。     

聚氨酯／丙烯酸酯类树脂互穿网络的结构形态与力学性能研究

通过示差扫描量热计，扫描电与广角Ｘ－光衍射仪研究了由化二亚胺改性二苯基甲烷二异氰酸酯合成的聚氨酯（ＰＵ）与丙烯酸酯类树脂（ＶＥＲ）形成的同步互穿网络（ＳＩＮ）的结构，形态与力学性能，发现网络间的化学键对其影响极大，网络间没有化学键宫接的ＰＵ＝ＶＥＲＳＩＮｓ是一个热力学不相容体系，存在显示的相分离形态，后者同时与两个网络的形成速率与工程因素有关；对于网络间有化学键连接的ＰＵ／ＶＥＲＳＩＮｓ，两个网络     

In-Situ Conductivity Measurement of BaF2 under High Pressure and High Temperature

We perform the in-situ conductivity measurement on BaF2 at high pressure using a microcircuit fabricated on a diamond anvil cell. The results show that BaF2 initially exhibits the electrical property of an insulator at pressure below 25 GPa, it transforms to a wide energy gap semiconductor at pressure from 25 to 30 GPa, and the conductivity increases gradually with increasing pressure from 30 GPa. However, the metallization predicted by theoretical calculation at 30-33 GPa cannot be observed. In addition, we measure the temperature dependence of the conductivity at several pressures and obtain the relationship between the energy gap and pressure. Based on the experimental data, it is predicted that BaF2 would transform to a metal at about 87 GPa and ambient temperature. The conductivity of BaF2 reaches the order of 10^-3Ω^-1 cm^-1 at 37 GPa and 2400 K, the superionic conduction is not observed during the experiments, indicating the application of pressure elevates greatly the transition temperature of the superionic conduction.     

Growth and Annealing Study of Mg-Doped AlGaN and GaN/AlGaN Superlattices

Mg-doped AlGaN and GaN/AlGaN superlattices are grown by metalorganic chemical vapour deposition （MOCVD） Rapid thermal annealing （RTA） treatments are carried out on the samples. Hall and high resolution x-ray diffraction measurements are used to characterize the electrical and structural prosperities of the as-grown and annealed samples, respectively. The results of hall measurements show that after annealing, the Mg-doped AIGaN sample can not obtain the distinct hole concentration and can acquire a resistivity of 1.4 ×10^3 Ωcm. However, with the same annealing treatment, the GaN/AlGaN superlattice sample has a hole concentration of 1.7 × 10^17 cm-3 and a resistivity of 5.6Ωcm. The piezoelectric field in the GaN/AlGaN superlattices improves the activation efficiency of Mg acceptors, which leads to higher hole concentration and lower p-type resistivity.     

关于线性代数课教学的两点看法

就线性代数教学中解析几何与线性代数的互相渗透以及如何处理教材内容更新的问题,谈一些个人看法,欢迎批评指正.1解析几何与线性代数的互相渗透微积分,解析几何,线性代数之间的互相渗透体现了教材内容的“现代化”.正如文[1]所述,将解析几何与线性代数整合为一门课程已经得到不     

常压射频冷等离子体TEOS工艺沉积二氧化硅薄膜的光谱研究

常压射频冷等离子体是近年来广受关注的一种新兴技术,在薄膜沉积方面已体现出其巨大潜力,但由于等离子体本身反应的复杂性,使其在薄膜沉积方面的机理至今尚未完全清楚。本文旨在从光谱分析的角度,研究常压射频冷等离子体TEOS工艺沉积二氧化硅薄膜。实验中我们检测到了Si和C-H的特征峰,表明二氧化硅是由TEOS在等离子体中分解而形成的。同时还研究了不同输入功率下Si和C-H的特征峰强度的变化情况,并发现其变化规律与生长速率有着很好的相似性。在温度为200℃的条件下所生成的SiO2薄膜的折射率在1.47-1.48的范围内。     

Period and temperature tuning of cascaded opticalparametric oscillator based on periodically poled LiNbO3

We report the broadly tunable source by a cascaded optical parametric oscillator in the periodically poled LiNbO_3 (PPLN) with domain grating period and temperature tuning. The optical parametric oscillator was pumped by a passive Q-switched Nd:YVO_4 laser. Multi-wavelength outputs from visible to infrared were obtained. The temperature of the PPLN crystal changed within the range of 70－150℃ with different periods of PPLN. The tunable range covered from 433 to 1657nm.     

基于可拓集合的动态分类及其UML表示方法研究

可拓集合是分析事物的可变性和多变性的理论基础 .本文首先建立了物元与类之间的联系 ,在可拓集合零界的基础上建立了过渡类 ,为了形式化描述出多值分类 ,对关联函数进行约束 ,并利用可拓域与物元变换探讨了动态分类机制 ,最后采用 UML构造型扩展机制对动态分类的表示问题进行初步的研究 .     

“辨误教学”与高等数学基本理论教学

理工科院校部分学生对高等数学基本理论学习不够重视，因而对基本理论掌握不牢，而“辩误教学”是促使学生理解和掌握高等数学基本理论的有效方法之一。