Level statistics for nearly integrable systems

We assume that the level spectra of quantum systems in the initial phase of transition from integrability to chaos are approximated by superpositions of independent sequences. Each individual sequence is modeled by a random matrix ensemble. We obtain analytical expressions for the level spacing distribution and level number variance for such a system. These expressions are successfully applied to the analysis of the resonance spectrum in a nearly integrable microwave billiard.Comment: 10 pages, 4 figure

Demulsification techniques of water-in-oil and oil-in-water emulsions in petroleum industry

The difficulties associated with transportation and refining of crude oil emulsions and produced water discharge limitations are among the conspicuous clues that have led the oilfield researchers to probe into practical demulsification methods for many decades. Inconsistent research outcomes observed in the literature for a particular demulsification method of a typical emulsion (i.e., water-in-oil or oil-in-water) arise not only from the varied influential parameters associated (such as salinity, temperature, pH, dispersed phase content, emulsifier/demulsifier concentration, and droplet size) but also from the diverse types of emulsion constituents (namely oil, surfactant, salt, alkali, polymer, fine solids, and/or other chemicals/impurities). Being the main component in formation of stabilizing interfacial film surrounding the dispersed phase droplets, surfactant is the most predominant contributor to emulsion stability, extent of which depends on its nature (being ionic or nonionic, and its degree of hydrophilicity/lipophilicity), concentration, and interaction with other surface-active agents in the emulsion as well as on the salinity, temperature, and pH of the system. In this paper, it is endeavored to overview some of the most commonly exploited demulsification techniques (i.e., chemical, biological, membrane, electrical, and microwave irradiation) of both oilfield and synthetic emulsions, taking into account the emulsion-stabilizing and -destabilizing effects with regard to the dominant parameters plus the emulsion composition. Further, the variations occurring in interfacial properties of emulsions by demulsification process are discussed. Finally, the mechanism(s) involved in emulsions resolution achieved by each method is elucidated. Clearly, the most efficient demulsification approach is the one able to attain desirable separation efficiency while complying with the environmental regulations and imposing the least economic burden on the petroleum industry

Investigation of Multistage Circulating Fast Fluidized Bed Membrane Reformers for Production of Ultraclean Hydrogen and Syngas

A rigorous mathematical model is implemented to simulate multistage circulating fast fluidized bed membrane reformers (CFFBMRs) for production of ultraclean hydrogen and a high-grade syngas. Discrete physically well-mixed catalysts are employed in this study. It has been shown that enhancement of the water–gas shift reaction (WGS) by addition of CO in the feed coupled with the heat release from the partial oxidation reactions substantially improved the total H₂ yield by 27.60% in the first CFFBMR_1. At the best operating conditions, it was found that the total H₂ yield is significantly increased by 48.75% in the first CFFBMR₁ and by 59.66% in the second CFFBMR_2. The simulation results show that CO₂ concentration can be reduced by 96.39% to a very low level. The results also reveal that the heat integration and energy saving can be realized through coupling endothermic and exothermic reactions reinforced by catalyst patterns