The first full - color two - way video teleconferencing service is offered . the development of tfm ( time frequency multiplexing ) . the first compact disk players are available for sale in the u . s 第一个全彩色双向电视电话会议业务开通。开发tfm （时间频率多路复用） 。美国开始出售第一个光盘播放器。
2.
We successfully apply the two - fluid model ( tfm ) to the study of two dimensional and three dimensional dense gas - solid flow characteristics . the results show some rules on the particle collisions and gas particle interactive influence of the vertical upward pipe 在对高浓度气固两相流的研究中，成功的运用双流体模型对两维和三维垂直立管段进行了研究，揭示了垂直立管内的高浓度气固流动的颗粒碰撞以及气相和颗粒相的相互影响的一些规律。
