网络教学模式的探讨

网络教学是网络支撑下的虚拟与现实相结合的一种学习情境。本文首先对网络教学的特点进行了阐述，然后针对一贯主宰课堂的教师在网络教学中所起的作用做了详细分析，并对网络教学的教学模式、解决方案和新技术应用进行了介绍，最后指出了网络教学的意义。     

Asynchronous cooperative transmission scheme using linear dispersion code

The cooperative diversity schemes can effectively create a virtual antenna array for combating multipath fading in wireless channels. However, a lot of cooperative diversity schemes require perfect synchronization which is, in practice, difficult and even impossible to be realized. In this paper, we propose an asynchronous cooperative diversity scheme based on the linear dispersion code (LDC). By adding the zero padding (ZP) between linear dispersion codewords, our scheme mitigates the effect of asynchronism effectively. The length of ZP is decided by relative timing errors between different relays. Besides, an easy decoding method of our scheme is given in this paper by restructuring the stacked channel matrix.     

一个新的基于时间Petri网的多媒体同步模型

多媒体同步是多媒体应用的一个重要需求。本文提出了一种基于时间Ｐｅｔｒｉ网的多媒体同步模型,以对具有时间约束关系的多媒体合成进行抽象和形式化描述,并给出了处理异步用户交互的算法