Cálculo y predicción de coeficientes de fugacidad y actividad en mezclas binarias mediante el algoritmo de búsqueda armónica con ancho de banda autoajustable

El presente artículo de investigación propone el uso de la nueva variante del algoritmo hs (Harmony Search), esto es, el sfhs (Self-Regulated Fretwidth Harmony Search Algorithm) para el cálculo y predicción de coeficientes de fugacidad y actividad en mezclas binarias. La selección de los parámetros de ejecución del algoritmo sfhs se realizó con base en pruebas preliminares con diferentes funciones de prueba estándar. Se seleccionaron sistemas previamente reportados en la literatura, a 25 ºC y 40 ºC, y a presiones bajas y moderadas. Adicionalmente, se seleccionaron dos solutos diferentes: dióxido de carbono y etano. Se tomaron diferentes solventes, polares y no polares, con propósitos comparativos. Los coeficientes de actividad y fugacidad se calcularon utilizando la ecuación de estado Redlich-Kwong y la regla de Lewis, junto con el algoritmo sfhs para los dos solutos en fase vapor. La consistencia de los coeficientes de actividad se analizó mediante la estrategia de Redlich-Kister. Se obtuvieron resultados muy cercanos a los encontrados experimentalmente por otros autores y en su mayoría, no difirieron en más de una unidad porcentual.This research article proposes the use of a novel variant of the HS algorithm (harmony search), i.e. SFHS (self-regulated fret width harmony search algorithm), for calculating and predicting fugacity and activity coefficients in binary mixtures. Parameter selection was carried out based on preliminary results with different standard test functions. Different previously reported systems were selected, at 25 ° C and 40 ° C, and at low and moderate pressure levels. Moreover, two solutes were selected: carbon dioxide and ethane. Different solvents, both polar and nonpolar, were selected with comparative purposes. Activity and fugacity coefficients were calculated using the Redlich-Kwong state equation and Lewis rule, along with the sfhs algorithm, assuming both solutes in vapor phase. Consistency of the activity coefficients was analyzed by the Redlich-Kister strategy. Results were very close to those found experimentally by other authors, and most of them did not differ in more than one percentage unit

Impact of carbon dioxide on Ivanić oilfield in tertiary oil recovery phase

Godišnja proizvodnja nafte u Hrvatskoj s više od 30 naftnih polja je nešto veća od 500 000 tona. Tijekom proteklih 50 godina iz naftnih ležišta u Hrvatskoj ostvaren je prosječan iscrpak nafte od 32,6% utvrđenih rezervi nafte. Sadašnja cijena nafte na svjetskom tržištu potencira primjenu tercijarnih metoda povećanja iscrpka nafte. Ukoliko se iz postojećih ležišta nafte u Hrvatskoj uz te metode poveća iscrpak nafte za 3%, to dovodi do povećanja godišnje proizvodnje od 15 000 tona nafte. U svjetskoj praksi sve zastupljenija je proizvodnja nafte tercijarnim metodama pri čemu utiskivanje ugljičnog dioksida u naftna ležišta ima najveću primjenu. Na temelju laboratorijskih ispitivanja primjene tercijarnih metoda povećanja iscrpka iz naftnih ležišta u Hrvatskoj utiskivanje ugljičnog dioksida je odabrano kao najpovoljnija metoda povećanja iscrpka nafte iz ležišta naftnog polja Ivanić. Tijekom utiskivanja ugljičnog dioksida u naftno ležište mijenja se njegovo agregatno stanje iz kapljevitog u plinsko ili pregrijano stanje. Mjereni podaci o ugljičnom dioksidu u laboratorijskim uvjetima i uvjetima utiskivanja u ležište nažalost odstupaju. S obzirom na to da su mjerenja u bušotinskim uvjetima skupa, a neki puta i tehnološki neizvediva, za poznavanje stanja ugljičnog dioksida u bušotinskim uvjetima uzimaju se različite aproksimacije uz upotrebu raznovrsnih jednadžbi stanja. Izmjereni podaci o faznom stanju ugljičnog dioksida u širokom rasponu p,T uvjeta tijekom njegova utiskivanja u ležišta naftnog polja Ivanić tijekom pilot projekta željeli su se aproksimirati nekom od brojnih jednadžbi stanja i ne mogu se na nekom drugom ležištu koristiti. Od brojnih kubičnih jednadžbi stanja odabrane su van der Waalsova, Redlich-Kwongova, Soave-Redlich-Kwongova, Peng-Robinsonova, Valderrama-Cisternasova, Patel-Tejina, Lawal-Lake- Silberbergova i Martin-Houova jednadžba. Nakon sveobuhvatne analize mjerenih i računatih vrijednosti u širokom rasponu p,T uvjeta preporučene su jednadžbe stanja za proračunavanje faznih stanja ugljičnog dioksida kod njegova utiskivanja u ležišta naftnog polja Ivanić.Current annual oil production in Croatia on more than 30 oilfields, amounts to a little more than 0.5 million t per year. In the last 50 years, the realized oil recovery factor from the oil reservoirs has on average amounted to 32.6% of original oil in place. The currently favourable oil price increases the need for higher oil recovery from existing oilfields through the implementation of tertiary oil recovery methods. As for Croatia, a 3% increase in the oil recovery factor from current oil reservoirs, obtained due to the implementation of tertiary oil recovery methods, increases annual oil production by 15 000 t. Although tertiary oil recovery methods (EOR methods) are becoming more common worldwide, carbon dioxide injection in oil reservoirs is the most implemented EOR method. Based on the laboratory test results of the applications of tertiary oil recovery methods on oil reservoirs in Croatia, the carbon dioxide injection process was chosen as an appropriate method for increasing oil production on the Ivanić oil field. During the injection stage, carbon dioxide changes the state of the matter from liquid to gaseous or supercritical state. Unfortunately, the measured carbon dioxide injection results and laboratory test results differ. In situ measurements are very expensive and sometimes impractical; therefore, various approximations are taken into account with numerous equations of state. The aim was to approximate an equation of state on the measured data, for a wide range of p,T conditions, during a pilot project of carbon dioxide injection on the Ivanić oilfield reservoir. Among numerous cubic equations of state, van der Waals, Redlich-Kwong, Soave-Redlich-Kwong, Peng-Robinson, Valderrama-Cisternas, Patel-Teja, Lawal-Lake- Silberberg and Matin and Hou equation of state. After comprehensive comparisons and analysis of the values measured and calculated for a wide range of p,T conditions during carbon dioxide injection on the Ivanić oilfield, some of equations of state were recommended for determinations carbon dioxide changes of state

Probing the QCD phase diagram with fluctuations

The relevance of higher order cumulants of conserved charges for the analysis of freeze-out and critical conditions in heavy ion collisions at LHC and RHIC is discussed. Using properties of $O(4)$ scaling functions, the generic structure of these higher cumulants at vanishing baryon chemical potential is discussed. Chiral model calculations are then used to study their properties at non-zero baryon chemical potential. It is argued that the rapid variation of sixth and higher order cumulants at the phase boundary may be used to explore the QCD phase diagram in experiment. Moreover, results for the Polyakov loop susceptibilities in SU(3) lattice gauge theory as well as in (2+1) flavor lattice QCD are discussed. An analysis of the ratios of susceptibilities indicates that the deconfinement transition is reflected in characteristic modifications of these ratios.Comment: 14 pages, 6 figures. To appear in the G.E. Brown memorial volume in NP

Canonical aspects of strangeness enhancement

Strangeness enhancement (SE) in heavy ion collisions can be understood in the statistical model on the basis of canonical suppression. In this formulation,SE is a consequence of the transition from canonical to the asymptotic grand canonical limit and is predicted to be a decreasing function of collision energy. This model predictions are consistent with the recent NA49 data on $\Lambda$ enhancement at $p_{lab}=40, 80, 158$ GeV.Comment: 4 pages, 4 figures. To appear in the proceedings of Quark Matter 2002 (Nantes, France

Biowęgiel z pofermentacyjnej pozostałości kukurydzy hybrydowej - tani i wydajny sorbent metali ciężkich

Biochar produced from fermentation residue of maize hybrid was used in untreated form as a sorbent for the removal of Cd(II), Pb(II) and Zn(II) from aqueous solution. The capability of biochar to immobilized ions was investigated by leaching test. Equilibrium between biochar sample and studied elements in solution was reached at a contact time 30 min for Zn(II) and 90 min for Pb(II) and Cd(II). The experimental data were described by pseudofirst-order and pseudo-second-order kinetic model, two- and three-parameter isotherms in non-linear form. The maximum sorption capacity achieved was 30.07 mg.g(-1) in the case of Cd(II) ions, 99.44 mg.g(-1) in the case of Pb( II) and 40.18 in the case of Zn(II). Biochar developed for this study is comparable to conventional biochar, low cost, non-toxic and experimental results show that is a suitable and efficient sorbent for Cd(II), Pb(II) and Zn(II) removal from aqueous solutions.Web of Science26475774

The canonical partition function for relativistic hadron gases

Particle production in high-energy collisions is often addressed within the framework of the thermal (statistical) model. We present a method to calculate the canonical partition function for the hadron resonance gas with exact conservation of the baryon number, strangeness, electric charge, charmness and bottomness. We derive an analytical expression for the partition function which is represented as series of Bessel functions. Our results can be used directly to analyze particle production yields in elementary and in heavy ion collisions. We also quantify the importance of quantum statistics in the calculations of the light particle multiplicities in the canonical thermal model of the hadron resonance gas.Comment: 10 pages, 2 figures; submitted for publication in EPJ

The strongest gravitational lenses: I. The statistical impact of cluster mergers

For more than a decade now, it has been controversial whether or not the high rate of giant gravitational arcs and the largest observed Einstein radii are consistent with the standard cosmological model. Recent studies indicate that mergers provide an efficient mechanism to substantially increase the strong-lensing efficiency of individual clusters. Based on purely semi-analytic methods, we investigated the statistical impact of cluster mergers on the distribution of the largest Einstein radii and the optical depth for giant gravitational arcs of selected cluster samples. Analysing representative all-sky realizations of clusters at redshifts z < 1 and assuming a constant source redshift of z_s = 2.0, we find that mergers increase the number of Einstein radii above 10 arcsec (20 arcsec) by ~ 35 % (~ 55 %). Exploiting the tight correlation between Einstein radii and lensing cross sections, we infer that the optical depth for giant gravitational arcs with a length-to-width ratio > 7.5 of those clusters with Einstein radii above 10 arcsec (20 arcsec) increases by ~ 45 % (85 %). Our findings suggest that cluster mergers significantly influence in particular the statistical lensing properties of the strongest gravitational lenses. We conclude that semi-analytic studies must inevitably take these events into account before questioning the standard cosmological model on the basis of the largest observed Einstein radii and the statistics of giant gravitational arcs.Comment: 23 pages, 18 figures; accepted for publication in Astronomy and Astrophysics; v2: minor corrections (added clarifying comments; added Fig. 19) to match the accepted versio

The influence of fluctuations on thermodynamics near chiral phase transition

We discuss the influence of fluctuations on thermodynamics near the chiral phase transition within Polyakov loop extended quark--meson model based on the functional renormalization group (FRG) method. We include the gluon fields in the FRG flow equation self-consistently on the mean-field level. We focus on the properties of the phase diagram and net-baryon number fluctuations.Comment: Invited talk at "New Frontiers in QCD 2010", Kyoto, Japan; to appear in Prog. of Theor. Phy