1,354,859 research outputs found
Four loop stochastic perturbation theory in 3d SU(3)
No full textDi Renzo F, Mantovi A, Miccio V, Schroeder Y. Four loop stochastic perturbation theory in 3d SU(3). Nucl. Phys. Proc. Suppl. 2004;129-130:590-592
3-d lattice QCD free energy to four loops
No full textDi Renzo F,, Mantovi A,, Miccio V,, Schroeder Y. 3-d lattice QCD free energy to four loops. JHEP. 2004;2004(05):006.We compute the expansion of the 3-d Lattice QCD free energy to four loop order by means of Numerical Stochastic Perturbation Theory. The first and second order are already known and are correctly reproduced. The third and fourth order coefficients are new results. The known logarithmic divergence in the fourth order is correctly identified. We comment on the relevance of our computation in the context of dimensionally reduced finite temperature QCD
On the mechanism of coal-biomass slurry fluidized bed gasification
No full textTwo pumpable, water-based, coal-biomass slurries were prepared, bottom-injected and tested in an experimental program at pilot-scale for atmospheric bubbling bed gasification with air. The bed was made of either alumina particles or alumina-supported catalysts of the same size and operated at about 850°C. The equivalence ratio, which was selected as the main operating variable, was in the range =0.3-0.49. The fluidization velocity was U=0.4 m/s; the jetting ratio, which was the ratio of the air flow rate for slurry dispersion to the overall air flow rate, was J=0.25.
The complex slurry gasification mechanism determines poor gasification efficiency. The switch from a bed of non-catalytic solids to one of Ni-supporting -alumina particles is effective in converting within the bed up to half of the generated tars. However, this advantage is offset by an enhanced carbon loss from the bed of the gasifier
A theoretical investigation on the effects of product inhibition in a chemostat
No full textIl presente articolo si propone di studiare le condizioni di regime di un chemostato la cui popolazione microbica si sviluppa secondo una cinetica di inibizione da prodotto. Il bioreattore è descritto mediante un modello matematico non strutturato impiegando la cinetica di Aiba & Shoda [1]. Per condurre quest’analisi, si è fatto ricorso alla teoria delle singolarità che permette di definire la relazione tra i parametri del modello e la presenza di biforcazioni statiche. A questo scopo, sono stati tracciati i diagrammi delle singolarità che permettono di ricavare in maniera semplice gli intervalli di valori dei parametri per cui è possibile rilevare una molteplicità di stati stazionari. Infine, si è dimostrato che il sistema non possiede alcun punto di biforcazione dinamica per qualunque valore fisicamente coerente dei parametri coinvolti
GATA factor transcriptional activity: Insights from genome‐wide binding profiles
No full textThe members of the GATA family of transcription factors have homologous zinc fingers and bind to similar sequence motifs. Recent advances in genome-wide technologies and the integration of bioinformatics data have led to a better understanding of how GATA factors regulate gene expression; GATA-factor-induced transcriptional and epigenetic changes have now been analyzed at unprecedented levels of detail. Here, we review the results of genome-wide studies of GATA factor occupancy in human and murine cell lines and primary cells (as determined by chromatin immunoprecipitation sequencing), and then discuss the molecular mechanisms underlying the mediation of transcriptional and epigenetic regulation by GATA factors
The leading non-perturbative coefficient in the weak-coupling expansion of hot QCD pressure
No full textDi Renzo F, Laine M, Miccio V, Schroeder Y, Torrero C. The leading non-perturbative coefficient in the weak-coupling expansion of hot QCD pressure. JHEP. 2006;2006(07):026.Using Numerical Stochastic Perturbation Theory within three-dimensional pure SU(3) gauge theory, we estimate the last unknown renormalization constant that is needed for converting the vacuum energy density of this model from lattice regularization to the MS scheme. Making use of a previous non-perturbative lattice measurement of the plaquette expectation value in three dimensions, this allows us to approximate the first non-perturbative coefficient that appears in the weak-coupling expansion of hot QCD pressure
Modeling homogeneous combustion in bubbling beds burning liquid fuels
No full textThis paper introduces a model for the description of the homogeneous combustion of various fuels in fluidized bed combustors (FBC) at temperatures lower than the classical
value for solid fuels, i.e., 850 °C. The model construction is based on a key bubbling fluidized bed feature: A fuel-rich (endogenous) bubble is generated at the fuel injection point, travels inside the bed at constant pressure, and undergoes chemical conversion in the presence of mass transfer with the emulsion phase and of coalescence with air (exogenous) bubbles formed at the distributor and, possibly, with other endogenous
bubbles. The model couples a fluid-dynamic submodel based on two-phase fluidization theory with a submodel of gas phase oxidation. To this end, the model development takes full advantage of a detailed chemical kinetic scheme, which includes both the low and high temperature mechanisms of hydrocarbon oxidation, and accounts for about 200 molecular and radical species involved in more than 5000 reactions. Simple hypotheses
are made to set up and close mass balances for the various species as well as enthalpy balances in the bed. First, the conversion and oxidation of gaseous fuels (e.g., methane)
were calculated as a test case for the model; then, n-dodecane was taken into consideration to give a simple representation of diesel fuel using a pure hydrocarbon. The model predictions qualitatively agree with some of the evidence from the experimental data reported in the literature. The fate of hydrocarbon species is extremely sensitive to temperature
change and oxygen availability in the rising bubble. A preliminary model validation was attempted with results of experiments carried out on a prepilot, bubbling combustor fired by underbed injection of a diesel fuel. Specifically, the model results confirm that heat release both in the bed and in the freeboard is a function of bed temperature. At lower emulsion phase temperatures many combustible species leave the bed unburned, while post-combustion occurs after the bed and freeboard temperature considerably increases. This is a well-recognized undesirable feature from the viewpoint of practical application and emission control
- …
