[en] In this thesis we apply perturbative QCD to make precise predictions for some observables in high-energy processes involving bottom-quark. Our first application is a prediction for the energy spectrum of b-flavored hadrons in top quark decay. For that purpose we calculate at NLO the OCD corrections for bottom fragmentation in top decay. The b-quark in the top quark decay is considered once as a massless and once as a massive particle in our calculations. The difference between the differential width calculated in both cases can give us the perturbative fragmentation function of the b-quark. After that using the obtained differential widths and applying ZM-VFNS and GM-VFNS, we make some predictions for the spectrum of B-hadrons produced in top quark decay. The comparison of both approaches shows that the mass effect of the b-quark in the top quark decay is negligible. We also investigate the mass effect of B-hadron in the energy distribution obtained in the previous calculations and we show that this increases the value of the differential width when the energy taken away by the produced parton in top decay is small. Our second application is to obtain the helicity contributions of the W⁺-boson in the energy distribution of b-flavored hadrons in top quark decay. For this reason we study the angular decay distribution for the cascade decay of the top-quark (t→ b+W⁺(→e⁺+ν_e)). Using ZM-VFNS we make predictions for the NLO contributions of the longitudinal, the transverse-minus and the transverse-plus helicity of the W⁺-boson in the energy distribution of B-hadron. (orig.)