The modern science and technology and the information industries rapid development , causes the tourism to undergo a wave wave impact tide which the information technology brings 现代科学技术与信息产业的迅速发展,使旅游业正在经受着信息技术带来的一波一波的冲击浪潮。
Point originally possessed the harmful interference of the frequency s every kind of times . enlarge 1 khz sine wave the hour will produce 2 khz of two times wave with 3 khz of three times wave wave for and much higher time 指原有频率的各种倍频的有害干扰。放大1khz正弦波时将会产生2khz的二次谐波和3khz的三次谐波以及许多更高次的谐波。