探头软保护膜和硬保护膜相比,突出的优点是() ["A、透声性能好","B、材质声衰减小","C、有利消除耦合差异","D、以上全部"]
窄脉冲探头和普通探头相比() ["A、Q值较小","B、灵敏度较低","C、频带较宽","D、以上全部"]
调节探伤仪面板上的“抑制”旋钮会影响探伤仪的() ["A、垂直线性","B、动态范围","C、灵敏度","D、以上全部"]
脉冲反射式超声波探伤仪中,产生时基线的电路单元叫做() ["A、触发电路","B、扫描电路","C、同步电路","D、发射电路"]
脉冲反射式超声波探伤仪中,产生触发脉冲的电路单元叫做() ["A、发射电路","B、扫描电路","C、同步电路","D、标距电路"]
试分别叙述冒口设计中“模数法”和“缩管法”的原理与步骤?