  The presence of nearby discrete cosmic-ray (CR) sources can lead to many
interesting effects on the observed properties of CRs. In this paper, we study
about the possible effects on the CR primary and secondary spectra and also the
subsequent effects on the CR secondary-to-primary ratios. For the study, we
assume that CRs undergo diffusive propagation in the Galaxy and we neglect the
effect of convection, energy losses and reacceleration. In our model, we assume
that there exists a uniform and continuous distribution of CR sources in the
Galaxy generating a stationary CR background at the Earth. In addition, we also
consider the existence of some nearby sources which inject CRs in a discrete
space-time model. Assuming a constant CR source power throughout the Galaxy,
our study has found that the presence of nearby supernova remnants (SNRs)
produces noticeable variations in the primary fluxes mainly above ~ 100 GeV/n,
if CRs are assumed to be released instantaneously after the supernova
explosion. The variation reaches a value of ~ 45% at around 10^5 GeV/n. Respect
to earlier studies, the variation in the case of the secondaries is found to be
almost negligible. We also discuss about the possible effects of the different
particle release times from the SNRs. For the particle release time of ~ 10^5
yr, predicted by the diffusive shock acceleration theories in SNRs, we have
found that the presence of the nearby SNRs hardly produces any significant
effects on the CRs at the Earth.
