Inclusive neutron cross-sections at forward angles from Nb Nb and Au Au collisions at 800-MeV/nucleon

Inclusive neutron spectra were measured at 0°, 4°, 8°, 15°, 30°, and 42° from Nb-Nb and Au-Au collisions at 800 MeV/nucleon. A peak that originates from neutron evaporation from the projectile appears in the spectra at angles out to 8°. The shapes and magnitudes of the spectra are compared with those calculated from models of nucleus-nucleus collisions. The differential cross sections for Au-Au collisions are about four times those for Nb-Nb collisions. The predictions of the Vlasov-Uehling-Uhlenbeck (VUU) and QMD theories agree with the angular distributions of the differential cross sections except at small angles; the VUU prediction overestimates the angular distributions from a few degrees to about 20°, whereas the QMD prediction underestimates the angular distributions below 8°. The Firestreak model overestimates the angular distribution for Nb-Nb collisions and underestimates it for Au-Au collisions. Also, the VUU and QMD models agree with the measured double-differential cross sections in more angular and energy regions than the Firestreak and intranuclear cascade models; however, none of the models can account for the peaks at small angles (θ≤15°)

Unanticipated evolution in software product lines versus independent products: A case study

Real product families need to evolve in ways that are not always anticipated by a pre-planned design. Any given approach for software product lines will likely lead to both positive and negative consequences during unanticipated software evolution. Unfortunately, we know little about the evolvability characteristics of SPL approaches that concern both modelling and implementation, limiting our ability to make rational and disciplined decisions about adoption.We conduct a case study into the unanticipated evolution of a software product family using two approaches: separate products versus a common codebase using delta-oriented programming (DOP). We compare the ease of change within the two versions through a set of quantitative measurements and qualitative observations. We find that both versions have strengths and weaknesses: complexity and incomplete support from DOP tools versus significant duplication and error-proneness in the separate products