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J T Devreese - One of the best experts on this subject based on the ideXlab platform.
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pseudogap and preformed pairs in the imbalanced fermi gas in two dimensions
New Journal of Physics, 2012Co-Authors: S N Klimin, J Tempere, J T DevreeseAbstract:The physics of the pseudogap state is intimately linked with the pairing mechanism that gives rise to superfluidity in quantum gases and to superconductivity in high-Tc cuprates, and therefore, both in quantum gases and in superconductors, the pseudogap state and preformed pairs have been under intensive experimental scrutiny. Here, we develop a path integral treatment that provides a divergence-free description of the paired state in two-dimensional Fermi gases. Within this formalism, we derive the pseudogap Temperature and the pair fluctuation spectral function, and compare these results with a recent experimental measurement of the pairing in the two-dimensional Fermi gas. The removal of the infrared divergence in the number equations is shown both numerically and analytically, through a study of the long-wavelength and low-energy limit of the pair fluctuation density. Besides the pseudogap Temperature, the pair Formation Temperature and the critical Temperature for superfluidity are also derived. The latter corresponds to the Berezinski–Kosterlitz–Thouless (BKT) Temperature. The pseudogap Temperature, which coincides with the pair Formation Temperature in the mean field, is found to be suppressed with respect to the pair Formation Temperature by fluctuations. This suppression is strongest for large binding energies of the pairs. Finally, we investigate how the pair Formation Temperature, the pseudogap Temperature and the BKT Temperature behave as a function of both binding energy and imbalance between the pairing partners in the Fermi gas. This allows us to set up phase diagrams for the two-dimensional Fermi gas, in which the superfluid phase, the phase-fluctuating quasicondensate and the normal state can be identified.
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pseudogap and preformed pairs in the imbalanced fermi gas in two dimensions
arXiv: Quantum Gases, 2012Co-Authors: S N Klimin, J Tempere, J T DevreeseAbstract:The physics of the pseudogap state is intimately linked with the pairing mechanism that gives rise to superfluidity in quantum gases and to superconductivity in high-Tc cuprates, and therefore, both in quantum gases and superconductors, the pseudogap state and preformed pairs have been under intensive experimental scrutiny. Here, we develop a path integral treatment that provides a divergence-free description of the paired state in two-dimensional Fermi gases. Within this formalism, we derive the pseudogap Temperature and the pair fluctuation spectral function, and compare these results with the recent experimental measument of the pairing in the two-dimensional Fermi gas. The removal of the infrared divergence in the number equations is shown both numerically and analytically, through a study of the long-wavelength and low-energy limit of the pair fluctuation density. Besides the pseudogap Temperature, also the pair Formation Temperature and the critical Temperature for superfluidity are derived. The latter corresponds to the Berezinski-Kosterlitz-Thouless (BKT) Temperature. The pseudogap Temperature, which coincides with the pair Formation Temperature in mean field, is found to be suppressed with respect to the pair Formation Temperature by fluctuations. This suppression is strongest for large binding energies of the pairs. Finally, we investigate how the pair Formation Temperature, the pseudogap Temperature and the BKT Temperature behave as a function of both binding energy and imbalance between the pairing partners in the Fermi gas. This allows to set up phase diagrams for the two-dimensional Fermi gas, in which the superfluid phase, the phase-fluctuating quasicondensate, and the normal state can be identified.
S E Borisovsky - One of the best experts on this subject based on the ideXlab platform.
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coexisting bournonite seligmannite and tennantite tetrahedrite solid solutions of the darasun gold deposit eastern transbaikalia russia estimation of the mineral Formation Temperature
Geology of Ore Deposits, 2019Co-Authors: N G Lyubimtseva, N S Bortnikov, S E BorisovskyAbstract:Mineral associations, intergrowth features, chemical composition and Sb and As distribution in coexisting fahlore and bournonite-seligmanite solid solutions in the Darasun gold deposit were studied. For the first time the almost complete solid solution was found between bournonite and seligmanite with a continuous isomorphism between Sb and As in the range of Sb/(Sb + As) ratios from 0.21 to 1.00 in the Darasun deposit by EMPA. The composition of the fahlore coexisting with bournonite varies widely: Sb/(Sb + As) ratios 0.03-0.96 and Fe/(Fe + Zn) ratios 0.36-0.87. The coupled compositional evolution from early antimony to late arsenic in coexisting solid solutions has been established. Based on the investigation of the Sb and As distribution between coexisting fahlore and bournonite-seligmanite, the Temperatures of their joint deposition and, as a result, of the productive stage, in which they are closely associated with native gold and tellurides (90–335 °С), are estimated.
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coexisting bournonite seligmannite and tennantite tetrahedrite solid solutions of the darasun gold deposit eastern transbaikalia russia estimation of the mineral Formation Temperature
Geology of Ore Deposits, 2019Co-Authors: N G Lyubimtseva, N S Bortnikov, S E BorisovskyAbstract:Mineral assemblages, the peculiarities of intergrowths, chemical composition, and Sb and As distribution in coexisting fahlore and bournonite-seligmannite solid solutions of the Darasun gold deposit are studied. The almost complete solid solution between bournonite and seligmannite with continuous Sb–As isomorphism for Sb/(Sb + As) ratios from 0.21 to 1.00 is identified for the first time for the Darasun deposit using a microprobe. The composition of fahlore coexisting with bournonite widely varies: Sb/(Sb + As) ratio 0.03–0.96 and Fe/(Fe + Zn) ratio 0.36–0.87. The mutual compositional evolution from early Sb to late As coexisting solid solutions is identified. Based on the Sb and As distribution between coexisting fahlore and bournonite-seligmannite, the Temperatures of their joint crystallization are estimated, as well as those of the productive stage, where they are associated with native gold and tellurides (90–335°C).
Derek Dunnrankin - One of the best experts on this subject based on the ideXlab platform.
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ammonium bisulfate Formation and reduced load scr operation
Fuel, 2017Co-Authors: Lawrence Muzio, Sean Bogseth, Richard Marshall Himes, Yuchien Chien, Derek DunnrankinAbstract:Abstract Primary NOx control methods used on coal fired utility boilers utilize ammonia- and urea-based processes. These processes result in some ammonia exiting the treatment zone, which can react with SO3/H2SO4 in the coal fired flue gas to form ammonium bisulfate (ABS). This ABS Formation can lead to potential balance of plant operational issues: • deposition on the SCR NOx control ammonia injection components in cases of insufficiently heated dilution air for ammonia transport • deposition on catalyst surfaces during low load operation, reducing catalyst activity • deposition in the cold end baskets of the air preheater Mitigating these impacts requires an accurate understanding of the ABS Formation Temperature as a function of flue gas composition. Five past studies of ABS Formation Temperature exhibit a very large variation. This paper provides a critical review of these studies, along with new experimental data, in order to show that ABS Formation is best described by recent laboratory work, with the ABS Formation Temperature effectively described by the equation: (1) P NH 3 ( atm ) ∗ P SO 3 ( atm ) = 2.97 ∗ 10 13 ∗ e ( - 54 , 950 / RT ) where R is the universal gas constant (1.987 cal/K-mol) and T is the flue gas Temperature in degrees Kelvin (K). With the increase in renewable fuel sources and the increasing use of natural gas for electricity generation, coal fired boilers are called upon to operate over a broader load range. Using the above expression, this work shows that the generally accepted value for ABS Formation Temperature is nominally 5% (14 K or 25°F) too high. While this difference may seem small, from a practical perspective it can represent substantial operating cost savings, as a large coal fired plant can operate at a lower minimum load than is currently required by the catalyst vendor‘s prescribed SCR minimum operating Temperature based on ABS Formation Temperature from prior work.
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ammonium bisulfate Formation Temperature in a bench scale single channel air preheater
Fuel, 2011Co-Authors: J Menasha, Derek Dunnrankin, Luca Muzio, J StallingsAbstract:Abstract Ammonium bisulfate (ABS) forms in coal-fired power plant exhaust systems when ammonia slip from the NO x control system reacts with the sulfur oxides and water in the flue gas. The critical Temperature range for ABS Formation occurs in the air preheater, where ABS is known to cause corrosion and pluggage that can require unplanned outages and expensive cleaning. To develop mitigation strategies for the deleterious effects of ABS in air preheaters, it is important to know its Formation Temperature and deposition process. This paper describes a bench-scale experimental simulation of a single-channel air preheater, with the appropriate Temperature gradient, used in conjunction with simulated coal combustion flue gas, including sulfur oxides, ammonia, and water vapor, to investigate the Formation of ABS. Formation was observed optically, and the Formation Temperature, as well as deposition characteristics for a realistic range of reactant concentrations are presented and compared with previous studies on ABS Formation. This study presents data at realistic concentrations not earlier tested, and the reported data has smaller experimental uncertainty than previously obtained. We found that the measured ABS Formation Temperatures under air preheater channel conditions lies between the Temperatures reported by others, and is in the range of 500–520 K for typical flue gas concentrations of ammonia and sulfur oxide species. The results also show that, at least for this experimental configuration, ABS forms predominantly as an aerosol in the gas phase rather than as a condensate on the channel walls.
Yingfeng Meng - One of the best experts on this subject based on the ideXlab platform.
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determining initial Formation Temperature considering radial Temperature gradient and axial thermal conduction of the wellbore fluid
Applied Thermal Engineering, 2019Co-Authors: Mou Yang, Yuanhang Chen, Gao Li, Xingguo Zhang, Daqian Tang, Yingfeng MengAbstract:Abstract It is crucial to verify how to accurately determine the initial Formation Temperature by investigating the heat exchange of wellbore fluid. The heat transfer models of initial Formation Temperature were established considering the effect of radial Temperature gradient and axial thermal conduction, which were solved using the implicit finite difference technique, and the calculated results from two Temperature measurement methods, including the cable and measurement while drilling, were compared. Results reveal that fluid radial Temperature gradient leads to a change of the initial Formation Temperature in the upper and lower sections of the wellbore of 0.03 °C and 0.32 °C, respectively, and the axial thermal conductivity of drilling fluid had little effect on the initial Formation Temperature. The identical initial Formation Temperature was calculated from both measurement methods after a long shut-in. Most relevant is that the model results matched actual field data better than other heat transfer models.
Lesley A James - One of the best experts on this subject based on the ideXlab platform.
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evaluation of gas hydrate Formation Temperature for gas water salt alcohol systems utilization of extended uniquac model and pc saft equation of state
Industrial & Engineering Chemistry Research, 2018Co-Authors: Javad Kondori, Sohrab Zendehboudi, Lesley A JamesAbstract:Naturally occurring gas hydrates are of great importance as a strategic energy source. Hydrates affect coastal sediment stability, global climate change, and ocean carbon cycling. It is vital to understand the thermodynamic conditions of gas hydrates to control/manage and inhibit hydrate Formation. A variety of equations of state (EOSs) have been utilized to model the thermodynamic behaviors of gas hydrates. In this study, the perturbed chain statistical association fluid theory (PC-SAFT) equation of state combined with van der Waals and Platteuw model is employed to determine the clathrate hydrate Formation Temperature of pure gases (e.g., methane, ethane, propane, isobutane, carbon dioxide, and hydrogen sulfide) and binary and ternary systems of hydrate gases. In addition, the gas hydrate Formation conditions are investigated where methanol, ethanol, glycerol, NaCl, KCl, CaCl2, and MgCl2 as inhibitors are present. The UNIQUAC model is utilized in this work to obtain the hydrate Formation conditions in s...
