Directions: In this section, you will hear ten short conversations At the end of each conversation a question will be asked about what was said. Both the conversation and the question will be spoken only once. After each question there will be a pause. During the pause, you must read the four choices marked A), B), C)and d),and decide which is the best answer. Then mark the corresponding letter on the Answer Sheet with a single line through the

Directions: In this section you will hear ten short conversations At the end of each conversation, a question will be asked about what was said. Both the conversation and the question will be spoken only once. After each question there will be a pause. During the pause, you must read the four choices marked A), B), C)and D), and decide which is the best answer. Then mark the corresponding letter on the answer sheet with a single line through

Directions: In this section, you will hear ten short conversations. At the end of each conversation, a question will be asked about what was said. Both the conversation and the question will be spoken only once.After each question there will be a pause. During the pause you must read the four choices marked A),),C) and D),and decide which is the best answer

本书作为高职高专层次的国际贸易专业的系列教材之一,由对外经济贸易大学公共管 理学院海关管理系海关实务和海关法教学领域的学科带头人郑俊田教授和张红教授编著, 是海关实务类课程几十年教学研究成果的结晶,堪称我国海关专业教材编撰园地的一朵奇 葩。 全书的内容包括:海关与对外贸易、海关与海关法、海关的各项通关业务制度、通关 中的违法行为及其责任追究、通关中与海关发生行政争议的解决途径等

第13章微机的操作和维护较件 出于软件维护的需要,本章简要介绍了DOS和 Windows操作系统的使用,并着重介绍了常用的系统维护软件工具。 13.1MS-D6.22的基本操作和维护软 13.2 Windows9597)的维护软件 13.3 Windows98的维护软件 13.4 Windows2000的维护软件

第12章微机系统软件安装 本章介绍了硬盘的初始化操作:硬盘分区、格式化、DOS盘结构和双系统引导盘建立等。还介绍了DOS和 Windows操作系统的安装方法。 12.1硬盘初始化 12.2D的盘结约 12.3安装系统软件

简谐振动的合成( combination of simple harmonic motions) 常见的简谐振动的合成有 同一直线上同频率的简谐振动的合成 同一直线上不同频率的简谐振动的合成 相互垂直的同频率的简谐振动的合成 相互垂直的不同频率的简谐振动的合成 我们讨论同一直线上即两个同方向同频率简谐运动的合成

当波源与观察者相对静止时观察者接受波的频率和波源发射的频率相等。 多普勒效应(Doppler Effect):当或接收器(观察者)R,或S、R都相对媒质运动 时,接收器所测得的频率不等于波源振动频率的现象(对机械波) 多普勒效应

1掌握平面简谐波的波动方程及其物理意义,理解波形图。掌握平面简谐波的特征量。掌握由已知质点的简谐振动方程建立波动方程的方法。 2理解谐波的能流和能流密度的概念

一、力牛顿第三定律 从现代的观点来看,经典力学中力的概念其实是更为普遍的动量守恒定律的 推论。我们用现代的观点重新审视力学中力的概念 我们考察两个粒子间的相互作用力 如果两个粒子除了相互作用外,不与其它物体发生相互作用