  We present a statistical study of a sample of 17 hub-filament-system (HFS)
clouds of high-mass star formation using high-angular resolution ($\sim$1-2
arcsecond) ALMA 1.3mm and 3mm continuum data. The sample includes 8 infrared
(IR)-dark and 9 IR-bright types, which correspond to an evolutionary sequence
from the IR-dark to IR-bright stage. The central massive clumps and their
associated most massive cores are observed to follow a trend of increasing mass
($M$) and mass surface density ($\Sigma$) with evolution from IR-dark to
IR-bright stage. In addition, a mass-segregated cluster of young stellar
objects (YSOs) are revealed in both IR-dark and IR-bright HFSs with massive
YSOs located in the hub and the population of low-mass YSOs distributed over
larger areas. Moreover, outflow feedback in all HFSs are found to escape
preferentially through the inter-filamentary diffuse cavities, suggesting that
outflows would render a limited effect on the disruption of the HFSs and
ongoing high-mass star formation therein. From the above observations, we
suggest that high-mass star formation in the HFSs can be described by a
multi-scale mass accretion/transfer scenario, from hub-composing filaments
through clumps down to cores, that can naturally lead to a mass-segregated
cluster of stars.
