The concept of degree of similarity(η),is proposed to quantitatively describe the similarity of a parameter(e.g.the maximum amplitude Rmax)of a solar cycle rel
This special issue consists of 12 invited reviews on the frontier areas of as-tronomy and astrophysics, and is aimed at a timely, in-depth evaluation of the cur
It has long remained an open question as to the geometry of the broad line region (BLR) in active galactic nuclei (AGNs). The reverberation mapping technique wh