Space product assurance - verification and approval of automatic machine wave soldering 航天产品保险.自动机械波焊的检定和验收
2.
The content of the investigation concerns basic concepts in mechanics , dc circuit and mechanical waves 内容涉及动力学、直流电路和机械波中的基本概念。
3.
Ultrasonic is a kind of mechanical wave that frequency is upper 20khz . ultrasonic may be generated by many ultrasonic transducers 超声波是频率高于20khz的机械波，它可由多种能量转换器转变而成。
4.
Ultrasound is a kind of high frequency mechanical wave which can effectively improve mass transfer and heat transfer , change physical - chemistry phase equilibrium , fasten chemistry reaction rate 超声波是一种高频机械波，利用超声振动、超声空化能有效强化传质、传热，改变物理化学相平衡，加快化学反应速率。
5.
Mechanics course mainly includes the description of movement of objects , the instantaneous effect of strength , spatial build - up effect of strength , temporal build - up effect of strength , nonindividual body mechanics , mechanical wave and sound , relativity , inalterability and covariability and mechanics foundation of the theory of relativity 力学主要内容包括物体运动的描述，力的瞬时效应，力的空间累积效应，力的时间累积效应，连续体力学，机械波和声，相对性、不变性与协变性和相对论力学基础等。
6.
The research shows that students misunderstand the relation between force and motion . gravity and action / reaction ; that in dc circuit , students of different age groups have the belief of " consumption of current " , " clashing currents " and " the battery as a constant current generator " ; that in understanding the concepts of electricity students lack th e knowledge of relating the micro with the macro ; and that students have serious difficulties in understanding the propagation of mechanics wave , the speed of wave and superposition , and do not make a distinction between the initial conditions and the medium properties of the system 具体表现在：学生对力和运动的关系、重力和平衡、作用力与反作用力存在一些误解；对直流电路，不同年龄的学生不同程度地存在电流消耗、碰撞电流、恒定电流源等观念，而且对电学概念的理解缺乏宏观与微观的联系；学生在机械波的传播、波速、波的叠加上存在严重的困难，对于机械波的传播学生不能区分初始条件和媒质特性，并错误地将动力学某些观念与机械波进行类比。
