Neutral hydrogen clouds are known to exist in the Universe, however their
spatial distributions and physical properties are poorly understood. Such
missing information can be studied by the new generation Chinese radio
telescopes through a blind searching of 21-cm absorption systems. We forecast
the capabilities of surveys of 21-cm absorption systems by two representative
radio telescopes in China -- Five-hundred-meter Aperture Spherical radio
Telescope (FAST) and Tianlai 21-cm cosmology experiment (Tianlai). Facilitated
by either the high sensitivity (FAST) or the wide field of view (Tianlai) of
these telescopes, more than a thousand 21-cm absorption systems can be
discovered in a few years, representing orders of magnitude improvement over
the cumulative discoveries in the past half a century.Comment: 4 pages. Accepted for publication in Research in Astronomy and
Astrophysic
