环氧树脂及其增强材料回顾

本文回顾了PCB制造常用的环氧树脂及其增强材料的性能和用途。同时,还介绍了代用树脂材料和代用增强材料的最新进展,如改性环氧树脂、无卤树脂、Thermount、PTFE、氰酸酯等,并就其性能进行了探讨。     

一种高精度位置环系统

简要叙述了高精度位置环系统的组成方法,详细阐述了光电编码器在位置环中的应用原理和速度修正方法。概述了单片机及串行D／A的应用。     

Grain growth of high Tc YBa2Cu3O7−x

Grain growth during sintering of the polycrystalline high onset temperature superconductor YBa₂Cu₃O_7−x has been examined by measuring grain sizes at various temperatures for different times above 900°C. The grain size distribution is found to be predominately lognormal after some sintering time. The mean grain size increases with both temperature and time. The standard deviation of the grain size distribution increases with temperature, but appears to be independent of time. The grain growth law may have an exponent of five. The grain growth rate may be affected by the grain size of the calcined powder.     

掺Tb_2O_3法拉第旋转玻璃

本文研究了掺Tb_2O_3的法拉第旋转玻璃的组成、物理化学性质及制备技术,实验结果表明维尔德常数V随着Tb_2O_3浓度的增大而增大,硼硅酸盐玻璃中Tb_2O_3含量大于20％(mol)时,维尔德常数可以达到-0.0030min/A/m·cm,从熔制试验结果0.5L铂坩埚可以获得质量较好的φ50×25mm的样品。     

Sol－Gel法制备的CoMnNiMgO热敏元件老化特性的研究

假设老化是从亚稳态到稳态的变化，利用反应动力学理论对Ｓｏｌ－Ｇｅｌ法制备的ＣｏＭｎＮｉＭｇＯ热敏元件的老化特性进行了研究，推导出老化公式△Ｒ／Ｒｏ＝Σｒｉ［１－ｅｘｐ（－ｔ／τｉ）］其中：τｉ＝τｏｉｅｘｐ（Ｅｉ／ｋＴ））。结果表明理论与实验能很好地一致，对于本文所研究的热敏元件，符合公式ＡＲ／Ｒｏ＝ｒ１［１－ｅｘｐ（－ｔ／τ１）］＋ｒ２［１－ｅｘｐ（－ｔ／τ２）］，该式中：，ｒ１＝１１．７６７×１０－３；ｒ２＝２０．６７３５×１０－３；τ１＝６．４５７８×１０－３ｅｘｐ（６１９０．８９／Ｔ）；τ２＝１．０４６１×１０－６ｅｘｐ（８ｌｌ６．２４／Ｔ）。     

有耗介质覆盖平面导体表面波传播特性的计算

本文推导了圆柱坐标系下有耗介质涂覆平面导体表面波的场函数和本征方程、每波长径向衰减常数;分析了介质特性参数、介质层厚度与的关系;指出磁损耗介质比电损耗介质有更好的抑制表面波的效果。     

Design of pseudo-ternary and quaternary alloys by superlattices consisting of (zn,cd)(s,se) binary ii–vi compounds

Theoretical design of pseudo-ternary and quaternary alloys by superlattice structures consisting of (Zn,Cd)(S,Se) binary II–VI compounds has been studied. For pseudo-ternary ZnCdS and ZnCdSe alloys, the superlattices with two layers in a cycle, i.e., ZnS/CdS and ZnSe/CdSe are considered, and for pseudo-quaternary ZnCdSSe alloy, the two superlattice structures with more than two layers in a cycle are considered. In order to design and evaluate these superlattices, the expression for the equilibrium in-plane lattice constant of these superlattices has been derived by minimizing the total elastic strain energy in the cycle. The combinations of layer thicknesses in a cycle and the effective bandgap of these superlattices have been calculated while the elastic strain effect was included. The usefulness of these superlattice structures has been evaluated.     

地物介电常数测量和分析

详细分析了基于矢量风络分析仪的同轴线探头介电常数测量系统和地物介电常数的测量方法。给出了几种典型地物（沙子、岩石、树木、棉叶）介电常数的测量和分析结果，并在模型进行了比较。本文实测数据可用于地物散射和辐射特性研究。     

在具有相关性的离散随机介质中波场的二阶矩

利用建立在多次散射基础上的Ｄｙｓｏｎ方程和Ｂｅｔｈｅ－Ｓａｌｐｅｔｅｒ方程，讨论了在考虑随机分布的散射间的对相关而忽略高阶相关的情况下标量波声波场的传播问题。认为在波传播方向散射体的相关性具有马尔科夫近似，同时运用前向散射近似，得到了在相关性离散随机介质中的等效传播常数，吸收截面和互相干函数的解析解。     

基于STM32的真空玻璃传热参数测试装置的研制

真空玻璃传热参数测试装置是一种专门测量真空玻璃传热参数的仪器设备。真空玻璃传热参数表征真空玻璃隔热保温、隔音降噪、防结霜结露等特性。以国标JC/T1079-2008为依据,并根据真空玻璃传热参数测试装置的组成结构,分别对其内部模块、电路控制系统、检测系统平台进行了研究、设计及制作;对真空玻璃在恒温条件下进行多次测试并研究分析了影响真空玻璃传热参数的一系列因素,测试出相应待测真空玻璃样品的传热参数。