  The AMS-02 experiment has reported precise measurements of energy spectra of
several cosmic-ray species in the range of ~(0.5-2000) GeV/n. An intriguing
finding is the differences in the spectral shape between the different species.
Protons exhibit the steepest spectrum of all the species, and helium, carbon,
oxygen and iron spectra are found to be harder than that of neon, magnesium and
silicon. These observations are difficult to explain as diffusive shock
acceleration, the currently most plausible theory for cosmic particle
acceleration at high energies, expects independence of the spectral index from
mass and charge of the accelerated particle. Moreover, propagation in the
Galaxy has been shown to not being able to compensate for this discrepancy. In
this work, we present an explanation based on two-component model for the
origin of cosmic rays in the Galaxy -- the first component originating from
regular supernova remnants in the interstellar medium and the second component
from Wolf-Rayet supernovae. Using recent results on cosmic-ray injection
enhancement at supernova shocks in the uniform interstellar medium and in the
wind environment of Wolf-Rayet stars, we show that the combination of the two
components may explain most of the behavior observed by the AMS-02 experiment.
