基于AT89C51RC的以太网数据采集器设计与实现

提出一种基于AT89C51RC单片机和RTL8019AS网络驱动芯片的以太网数据采集器的设计方案,介绍其软硬件结构.重点介绍系统软件各个子模块的设计.数据采集器以AT89C51RC为核心,嵌入TCP/IP协议栈,实现对智能仪表数据的采集、存储和以太网传输等任务.该数据采集器的功能已在建筑能耗数据采集系统中得到验证.     

城市水资源可持续发展公众化评价研究

城市水资源可持续发展微观尺度的评价系统一直是环境可持续发展理论领域的空白。本研究提出了城市水资源可持续发展公众化的概念,讨论了城市水资源可持续发展公众化系统组成,构建了城市水资源可持续发展公众化评价指标体系、计算方法与评价等级。提出通过多边形包络评价法进行城市的社会经济科技发展水平评价计算,作为验证手段检验本理论与方法正确性。最后指出,进行城市水资源可持续发展公众化评价理论及其体系研究对城市科学发展的重要意义。     

Growth and characterization of 0.8-μm gate length AlGaN/GaN HEMTs on sapphire substrates

GaN-based high electron mobility transistors (HEMTs) are promising devices for high power and high temperature applications[1―4]. Improvements over the years in material growth and device design have produced state-of-the-art AlGaN/GaN HEMTs with con- tinuous output power densities greater than 30 W/mm[3]. However, despite the impres- sive achievements, there exist some problems in developing the devices for application purposes, such as the current leakage through the GaN buffer layer[…