W-Mo系复合材料的制备及其特性波阻抗

采用放电等离子烧结技术,在相同的温度(1473K)及压力(30MPa)下,制备出不同配比的致密的W Mo系复合材料样品。采用高精度超声波脉冲回波重合方法,精确测量了超声波在样品中传播的横、纵波声速,并由此得到样品的特性波阻抗值。对样品的相组成分析及电子探针分析的结果表明,W Mo系复合材料主要是以W、Mo机械混合的形式通过粘结相获得致密化的。因此,选用混合物模型对其特性波阻抗值进行了理论预测,与实测值的比较表明该模型能对W Mo系复合材料的特性波阻抗作出比较准确的预测。

Mo-Ti系复合材料的特性波阻抗

采用放电等离子烧结技术 ,在相同的温度 (14 73K)及压力 (30 MPa)下 ,制备出不同配比的致密的 Mo- Ti系复合材料。采用高精度超声波脉冲回波重合法 ,精确测量了样品的横、纵波声速 ,并由此计算得到其特性波阻抗的实验值。对样品的相组成分析及电子探针分析的结果表明 ,Mo- Ti系复合材料是通过 Mo和 Ti之间形成固溶体来实现烧结致密化的。选用混合物模型对其特性波阻抗值进行了理论预测 ,与实测值的比较表明该模型能对 Mo-

Study on mutual impedance characteristics between probes in a circular waveguide

The expression of mutual impedance between two probes in a circular waveguide is derived by means of a vector potential function, reaction concept and reciprocity theorem. The waveguide is semi-infinite, and one end of the waveguide is terminated to a load with a reflection coefficient. The contribution to the mutual resistance is found to come from the dominant mode, while the contribution to the mutual reactance comes from the dominant mode and the higher order modes. The major contribution to the mutual reactance is from the dominant mode, since the higher modes decay rapidly with the increasing the probes’ of separation distance. However, as the separation distance approaches zero, the higher modes become dominant, which results in a large value of the mutual reactance. The mutual impedance is dependent on the location and height of the probes, their separation distance and the location of the terminal plane.