PYTHIA status report
Recent improvements in the PYTHIA event generator are summarized: new hard subprocesses, γ*γ* physics, QCD final-state showers, and more.
The Lund Model
Preface 1. Relativistic kinematics, electromagnetic fields and the method of virtual quanta 2. The harmonic oscillator and the quantum field 3. The vacuum as a dielectric medium and renormalisation 4. Deep inelastic scattering and the parton model 5. The classical motion of the massless relativistic string 6. The decay kinematics of the massless relativistic string 7. A stochastic process for string decay 8. The properties of the Lund model fragmentation formulae: external part formulas 9. The internal part fragmentation formulae and their relations to the unitarity equations of Regge theory 10. The dynamical analogues of the Lund model fragmentation formulae 11. Flavour and transverse momentum generation, and the vector to pseudoscalar meson ratio 12. Heavy quark fragmentation and Baryon production 13. The Hanbury-Brown-Twiss-effect and polarisation in the Lund model 14. The Lund gluon model, the kinematics and the decay properties 15. Gluon emission via the Bremsstrahlung process 16. Multigluon emission, the dipole moment and parton coherence cascade models 17. The lambda measure in the leading log, and the modified lead log approximation of perturbative QCD 18. The parton model and QCD 19. Inelastic lepto-production in the Lund model, the soft radiation model and heretical structure functions 20. Hadronic interaction models References Index.
Effect of superficial gas velocity on the particle temperature distribution in a fluidized bed with heat production
The heat transfer behavior of particles and gas in an olefin polymerization fluidized bed was numerically analyzed using an in-house developed 3-D computational fluid dynamics discrete element model (CFD-DEM). First the implementation of the model was verified by comparing simulation results with analytical results. A constant volumetric heat production rate was implemented in the particle energy equation to mimic the heat production due to the polymerization reaction. It was found that the probability density function (PDF) of the particle temperature becomes more homogeneous with increasing superficial gas velocity. Furthermore, instantaneous snapshots of the thermal driving force (the difference between the single particle temperature and bed-average gas temperature, Tp− ) for different heat production rates provide detailed insight in the particle temperature distribution inside the fluidized bed. The time- and bed-averaged particle convective heat transfer coefficient, which was calculated by Gunn׳s correlation, was found to be independent of the superficial gas velocity. This is explained by the fact that the relative velocity of gas and particles in the emulsion phase, where most of the particles and gas interact, is hardly influenced when increasing the gas superficial velocity. From the spatial distribution of Nusselt number, it becomes apparent that the high heat transfer regions are found in the wake of rising bubbles, whereas low heat transfer rates are found in the clouds of the bubbles.