Abstract: A one-dimensional model is established to simulate the axial flow patterns in a downer reactor. Based on the gas–solid continuity equation and the momentum equation, the model takes the variation of superficial gas velocity in the downer into account. The gas and solid velocity and the voidage distribution is emphatically studied. The simulation results show that there exists a remarkable disparity of axial flow pattern between variable superficial gas velocity and fixed gas velocity conditions. The linearly variable superficial velocity condition is more close to a downer reactor in practical operation.

Key words: downer, variable superficial gas velocity, one-dimensional model

摘要： 简要介绍了扫描探针显微术(Scanning Probe Microscopy, SPM)在纳米科学中的应用、研究现状及其发展趋势，特别介绍了电化学扫描隧道显微术(Scanning Tunneling Microscopy, STM)在此研究领域的重要作用以及所获成果等. 内容涉及STM技术的工作原理及特点、纳米结构的研究和表征、纳米结构的构筑及分子电子学器件的研究等.

关键词: 纳米科学, 扫描隧道显微术, 纳米结构, 分子电子学