Structure and Evolution of the Central Gas-dust Disks in Nearby Galaxies by Dr. Chi Yuan (Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan)   This talk comprises two parts. The first part is about using wavelet methods to probe the central regions of nearby Disk galaxies. More than 40 galaxies are analyzed. All data used come from the HST archive. Galaxies are grouped by with or without a major bar, or by with or without nuclear activities, including starburst-rings. The majority of the galaxies in our sample have a nuclear bar or an oval distortion in the center, despite whether they have a major bar or not. The nuclear bar appears to be a separate system independent of the major bar. However, there are galaxies such as NGC5383 and NGC1512, which do not have a nuclear bar, but have distinct spirals extending all the way to the center. All the Seyfert galaxies in our group have nuclear bar or oval distortion with associated spiral structures. In the second part of the talk , we will discuss the resonance excitation mechanism to show how a pair of spirals can be excited by a rotating bar potential, a mechanism responsible for the spiral-bar structures in the galactic central regions. To demonstrate how the mechanism works and how the disk evolves in such a mechanism, a few numerical simulations will be displayed.