Optimal preparation of Bose and Fermi atomic gas mixtures of ^(87)Rb and ^(40)K in a crossed optical dipole trap

We report on the optimal production of the Bose and Fermi mixtures with ^(87) Rb and ^(40)K in a crossed optical dipole trap(ODT).We measure the atomic number and lifetime of the mixtures in combination of the spin state |F=9/2,m_(F)=9/2> of^(40)K and |1,1>of ^(87) Rb in the ODT,which is larger and longer compared with the combination of the spin state |9/2,9/2> of^(40)K and 12,2) of ^(87)Rb in the ODT.We observe the atomic numbers of ^(87)Rb and ^(40)K shown in each stage of the sympathetic cooling process while gradually reducing the depth of the optical trap.By optimizing the relative loading time of atomic mixtures in the MOT,we obtain the large atomic number of ^(40)K(~6 ×10^(6)) or the mixtures of atoms with an equal number(~1.6 × 10^(6)) at the end of evaporative cooling in the ODT.We experimentally investigate the evaporative cooling in an enlarged volume of the ODT via adding a third laser beam to the crossed ODT and found that more atoms(8 × 10^(6)) and higher degeneracy(T/T_(F)=0.25) of Fermi gases are obtained.The ultracold atomic gas mixtures pave the way to explore phenomena such as few-body collisions and the Bose-Fermi Hubbard model,as well as for creating ground-state molecules of ^(87)Rb^(40)K.

Features of Combustion of a Mixture of a Hydrogen Microjet with Various Gases

The objective of the present study is an experimental investigation of diffusion combustion of round microjets,i.e.,mixtures of hydrogen with methane,helium,and nitrogen.It is found that the evolution of burning microjets is associated with generation of a“bottleneck flame region”close to the nozzle exit,as it was observed earlier during hydrogen combustion.Combustion of a mixture of hydrogen and methane with increasing flow velocity occurs with the transformation of the torch.At first,a torch stabilized on the nozzle is observed,then it is divided into a stabilized part in contact with the nozzle and into a raised part of the torch.The combustion process occurs in two areas.A further increase in velocity promotes the breakdown of the raised torch,but maintains combustion in the nozzle area.The results on hydrogen/methane combustion are obtained in a smaller range of the microjet velocity than those of a hydrogen microjet.Somewhat similar data are derived for other gas additives.To make combustion of gas mixtures more stable with increasing microjet velocity,one has to increase the portion of hydrogen in the gas mixture or reduce the fractions of other gas additives.

Distribution performance of gas–liquid mixture in the shell side of spiral-wound heat exchangers

The non-uniformity of gas–liquid mixture is a critical issue which leads to the heat transfer deterioration of spiralwound heat exchangers(SWHEs).Two-phase mass flow rate and the content of gas are important parameters as well as structural parameters which have prominent influences on flow distribution uniformity of SWHE shell side.In order to investigate the influences of these parameters,an experimental test system was built using water and air as mediums and a novel distributor named"tubes distributor"was designed.The effects of mass flow rate and the content of gas on two-phase distribution performance were analyzed,where the mass flow rate ranged from 28.4 to 171.9 kg·h-1 and the content of gas changed from 0.2 to 0.8,respectively.The results showed that the mixture mass flow rate considerably influenced the liquid distribution than that of gas phase and the larger mass flow rate exhibited the better distribution uniformity of two-phase flow.It was also found that the tubes distributor had the better two-phase uniformity when the content of gas was around 0.4.Tube diameter played an important role in the distribution of gas phase and slit width was more significant for the uniformity of liquid phase.

The effect of membrane pores wettability on CO_2 removal from CO_2/CH_4 gaseous mixture using NaOH, MEA and TEA liquid absorbents in hollow fiber membrane contactor

The present paper renders a modeling and a 2D numerical simulation for the removal of CO_2from CO_2/CH_4gaseous stream utilizing sodium hydroxide(NaOH),monoethanolamine(MEA)and triethanolamine(TEA)liquid absorbents inside the hollow fiber membrane contactor.Counter-current arrangement of absorbing agents and CO_2/CH_4gaseous mixture flows are implemented in the modeling and numerical simulation.Non-wetting and partial wetting modes of operation are considered where in the partial wetting mode,CO_2/CH_4gaseous mixture and liquid absorbents fill the membrane pores.The deteriorated removal of CO_2in the partial wetting mode of operation is mainly due to the mass transfer resistance imposed by the liquid in the pores of membrane.The validation of numerical simulation is done based on the comparison of simulation results of CO_2removal using Na OH and experimental data under non-wetting mode of operation.The comparison illustrates a desirable agreement with an average deviation of less than 5%.According to the results,MEA provides higher efficiency for CO_2removal in comparison with the other liquid absorbents.The order for CO_2removal performance is MEAN Na OHN TEA.The influence of non-wetting and partial wetting modes of operation on CO_2removal are evaluated in this article as one of the novelties.Besides,the percentage of CO_2sequestration as a function of gas velocity for various percentages of membrane pores wetting ranging from 0(non-wetting mode of operation)to 100%(complete wetting mode of operation)is studied in this research paper,which can be proposed as the other novelty.The results indicate that increase in some operational parameters such as module length,membrane porosity and absorbents concentration encourage the removal percentage of CO_2from CO_2/CH_4gaseous mixture while increasing in membrane tortuosity,gas velocity and initial CO_2concentration has unfavorable influence on the separation efficiency of CO_2.

Densities and viscosities for ionic liquids [BMIM][BF4] and [BMIM][Cl] and their binary mixtures at various temperatures and atmospheric pressure

The density and viscosity of 1-butyl-3-methylimidazolium tetrafluoroborate[BMIM][BF4]and 1-butyl-3-methylimidazolium chloride[BMIM][Cl]and their binary mixtures within the temperatures from 303.15 K to323.15 K and at ambient pressure were determined in this work.The temperature dependences of density and viscosity were satisfactorily described with the linear model and the Vogel-Tammann-Fulcher type equation,respectively.The molar volume and viscosity of binary IL mixtures were predicted through ideal mixing rules showing that almost null deviations for IL mixtures were observed and their mixing was remarkably close to linear ideal behavior in the molar volumes,while comparatively large errors in viscosity occurred.Additionally,the molar volume of the investigated pure ILs and their mixtures could well be predicted by a predictive model presented by Valderrama et al.(Fluid Phase Equilib.,275(2009)145).

EXISTENCE AND REGULARITY OF SOLUTIONS TO MODEL FOR LIQUID MIXTURE OF ^3HE-^4HE

Existence and regularity of solutions to model for liquid mixture of 3He-4He is considered in this paper. First, it is proved that this system possesses a unique global weak solution in H^1 （Ω, C ×R） by using Galerkin method. Secondly, by using an iteration procedure, regularity estimates for the linear semigroups, it is proved that the model for liquid mixture of 3He-4He has a unique solution in H^k（Ω, C × R） for all k ≥ 1.

The effective ionization coefficients and electron drift velocities in gas mixtures of CF_3I with N_2 and CO_2 obtained from Boltzmann equation analysis

The electron swarm parameters including the density-normalized effective ionization coefficients（α-η）/N and the electron drift velocities V e are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend（SST） experiment.The overall density-reduced electric field strength is from 100 Td to 1000 Td（1 Td = 10-17V·cm2）,while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%.From the variation of（αη）/N with the CF3I mixture ratio k,the limiting field strength（E/N） lim for each CF3I concentration is derived.It is found that for the mixtures with 70% CF3I,the values of（E/N） lim are essentially the same as that for pure SF 6.Additionally,the global warming potential（GWP） and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment.

First Binary Mixture Ionic Liquids Containing EMIMBr and IM

A new series of binary mixture ionic liquids comprising 1-ethyl-3-methylimidozalium bromide (EMIMBr) and imidazole (IM) have been synthesized. The melting points of the ionic liquids vary with the different content of IM while they still keep satisfactory conductivity and viscosity. According to the analysis of its phase diagram, the eutectic point is about 16.5C with the mass percentage of IM 29%.

Investigation of the performance of CF3I/c-C4F8/N2 and CF3I/c-C4F8/CO2 gas mixtures from electron transport parameters

CF3I gas mixtures have attracted considerable attention as potential environmentally-friendly alternatives to SF6 gas,owing to their excellent insulating performance.This paper attempts to study the CF3I ternary gas mixtures with c-C4F8 and buffer gases N2 and CO2 by considering dielectric strength from electron transport parameters based on the Boltzmann method and synergistic effect analysis,compared with SF6 gas mixtures.The results confirm that the critical electric field strength of CF3I/c-C4F8/70%CO2 is greater than that of 30%SF6/70%CO2 when the CF3I content is greater than 17%.Moreover,a higher content of c-C4F8 decreases the sensitivity of gas mixtures to an electric field,and this phenomenon is more obvious in CF3I/c-C4F8/CO2 gas mixtures.The synergistic effects for CF3I/c-C4F8/70%N2 were most obvious when the c-C4F8 content was approximately 20%,and for CF3I/c-C4F8/70%CO2 when the c-C4F8 content was approximately 10%.On the basis of this research,CF3I/c-C4F8/70%N2 shows better insulation performance when the c-C4F8 content is in the15%–20%range.For CF3I/c-C4F8/70%CO2,when the c-C4F8 content is in the 10%–15%range,the gas mixtures have excellent performance.Hence,these gas systems might be used as alternative gas mixtures to SF6 in high-voltage equipment.

A Statistical Thermodynamic Model of Vapor-Liquid Interfacial Tension for Liquid Mixtures at High Pressure

1 INTRODUCTIONInterfacial tension of pure fluids and their mixtures is an important property for the development,design and simulation of many chemical processes.The interfacial behavior has important prac-tical applications in material science,environment science and chemical engineering separationprocesses as well as in secondary or tertiary recovery of petroleum.Although interfacial phenom-ena are rather complicated,interfacial tension of free vapor-liquid interface is considered as a firstand fundamental step of the study.For example,enhanced carbon dioxide“flooding”

Investigation of the hydrate formation process in fine sediments by a binary CO2/N2 gas mixture

To obtain the fundamental data of CO2/N2 gas mixture hydrate formation kinetics and CO2 separation and sequestration mechanisms,the gas hydrate formation process by a binary CO2/N2 gas mixture(50:50)in fine sediments(150–250μm)was investigated in a semibatch vessel at variable temperatures(273,275,and 277 K)and pressures(5.8–7.8 MPa).During the gas hydrate reaction process,the changes in the gaseous phase composition were determined by gas chromatography.The results indicate that the gas hydrate formation process of the binary CO2/N2 gas mixture in fine sediments can be reduced to two stages.Firstly,the dissolved gas containing a large amount of CO2 formed gas hydrates,and then gaseous N2 participated in the gas hydrate formation.In the second stage,all the dissolved gas was consumed.Thus,both gaseous CO2 and N2 diffused into sediment.The first stage in different experiments lasted for 5–15 h,and>60%of the gas was consumed in this period.The gas consumption rate was greater in the first stage than in the second stage.After the completion of gas hydrate formation,the CO2 content in the gas hydrate was more than that in the gas phase.This indicates that CO2 formed hydrate easily than N2 in the binary mixture.Higher operating pressures and lower temperatures increased the gas consumption rate of the binary gas mixture in gas hydrate formation.

Ultrasonic study on organic liquid and binary organic liquid mixtures by using Schaaffs＇ collision factor theory

Based on Schaaff＇s collision factor theory （CFT） in liquids, the equations for nonlinear ultrasonic parameters in both organic liquid and binary organic liquid mixtures are deduced. The nonlinear ultrasonic parameters, including pressure coefficient, temperature coefficients of ultrasonic velocity, and nonlinear acoustic parameter B/A in both organic liquid and binary organic liquid mixtures, are evaluated for comparison with the measured results and data from other sources. The equations show that the coefficient of ultrasonic velocity and nonlinear acoustic parameter B/A are closely related to molecular interactions. These nonlinear ultrasonic parameters reflect some information of internal structure and outside status of the medium or mixtures. From the exponent of repulsive forces of the molecules, several thermodynamic parameters, pressure and temperature of the medium, the nonlinear ultrasonic parameters and ultrasonic nature of the medium can be evaluated. When evaluating and studying nonlinear acoustic parameter B/A of binary organic liquid mixtures, there is no need to know the nonlinear acoustic parameter B/A of the components. Obviously, the equation reveals the connection between the nonlinear ultrasonic nature and internal structure and outside status of the mixtures more directly and distinctly than traditional mixture law for B/A, e.g. Apfel＇s and Sehgal＇s laws for liquid binary mixtures.

Predicting the Dielectric Strength of c-C_4F_8 and SF_6 Gas Mixtures by Monte Carlo Method

An improved Monte Carlo method was used to simulate the motion of electrons in c-C4F8 and SF6 gas mixtures for pulsed townsend discharge. The electron swarm parameters such as effective ionization coefficient, -↑α and drift velocity over the E/N range from 280～700 Td（1Td=10^-21 V·m^2） were calculated by employing a set of cross sections available in literature. From the variation cure of -↑α with SF6 partial pressure p, the limiting field （E/N）lim of gas mixture at different gas content was determined. It is found that the limiting field of c-C4F8 and SF6 gas mixture is higher than that of pure SF6 at any SF6 mixture ratio. Simulation results show excellent agreement with experiment data available in previous literature.

Fine quantitative characterization of high-H2S gas reservoirs under the influence of liquid sulfur deposition and adsorption

In order to clarify the influence of liquid sulfur deposition and adsorption to high-H2S gas reservoirs,three types of natural cores with typical carbonate pore structures were selected for high-temperature and high-pressure core displacement experiments.Fine quantitative characterization of the cores in three steady states(original,after sulfur injection,and after gas flooding)was carried out using the nuclear magnetic resonance(NMR)transverse relaxation time spectrum and imaging,X-ray computer tomography(CT)of full-diameter cores,basic physical property testing,and field emission scanning electron microscopy imaging.The loss of pore volume caused by sulfur deposition and adsorption mainly comes from the medium and large pores with sizes bigger than 1000μm.Liquid sulfur has a stronger adsorption and deposition ability in smaller pore spaces,and causes greater damage to reservoirs with poor original pore structures.The pore structure of the three types of carbonate reservoirs shows multiple fractal characteristics.The worse the pore structure,the greater the change of internal pore distribution caused by liquid sulfur deposition and adsorption,and the stronger the heterogeneity.Liquid sulfur deposition and adsorption change the pore size distribution,pore connectivity,and heterogeneity of the rock,which further changes the physical properties of the reservoir.After sulfur injection and gas flooding,the permeability of TypeⅠreservoirs with good physical properties decreased by 16%,and that of TypesⅡandⅢreservoirs with poor physical properties decreased by 90%or more,suggesting an extremely high damage.This indicates that the worse the initial physical properties,the greater the damage of liquid sulfur deposition and adsorption.Liquid sulfur is adsorbed and deposited in different types of pore space in the forms of flocculence,cobweb,or retinitis,causing different changes in the pore structure and physical property of the reservoir.

Numerical simulation for explosion wave propagation of combustible mixture gas

A two-dimensional multi-material code was indigenously developed to investigate the effects of duct boundary conditions and ignition positions on the propagation law of explosion wave for hydrogen and methane-based combustible mixture gas. In the code,Young's technique was employed to track the interface between the explosion products and air,and combustible function model was adopted to simulate ignition process. The code was employed to study explosion flow field inside and outside the duct and to obtain peak pressures in different boundary conditions and ignition positions. Numerical results suggest that during the propagation in a duct,for point initiation,the curvature of spherical wave front gradually decreases and evolves into plane wave. Due to the multiple reflections on the duct wall,multi-peak values appear on pressure-time curve,and peak pressure strongly relies on the duct boundary conditions and ignition position. When explosive wave reaches the exit of the duct,explosion products expand outward and forms shock wave in air. Multiple rarefaction waves also occur and propagate upstream along the duct to decrease the pressure in the duct. The results are in agreement with one-dimensional isentropic gas flow theory of the explosion products,and indicate that the ignition model and multi-material interface treatment method are feasible.

Calculation and characteristic analysis on synergistic effect of CF3I gas mixtures

CF3I is a potential SF6 alternative gas.In order to study the insulation properties and synergistic effects of CF3I/N2 and CF3I/CO2 gas mixtures,two-term approximate Boltzmann equations were used to obtain the ionization coefficient α,attachment coefficient η and the critical equivalent electrical field strength（E/N）（cr）.The results show that the（E/N）（cr）of CF3I gas at 300 K is 1.2 times that of SF6 gas,and CF3I/N2 and CF3I/CO2 gas mixtures both have synergistic effect occurred.The synergistic effect coefficient of CF3I/CO2 gas mixture was higher than that of CF3I/N2 gas mixture.But the（E/N）（cr）of CF3I/N2 is higher than that of CF3I/CO2 under the same conditions.When the content of CF3I exceeds 20%,the （E/N）（cr） of CF3I/N2 and CF3I/CO2 gas mixture increase linearly with the increasing of CF3I gas content.The breakdown voltage of CF3I/N2 gas mixture is also higher than that of CF3I/CO2 gas mixture in slightly non-uniform electrical field under power frequency voltage,but the synergistic effect coefficients of the two gas mixtures are basically the same.

Analysis of Maximum Liquid Carrying Capacity Based on Conventional Tubing Plunger Gas Lift

China’s unconventional gas fields have a large number of low-productivity and low-efficiency wells, many of whichare located in remote and environmentally harsh mountainous areas. To address the long-term stable productionof these gas wells, plunger-lift technology plays an important role. In order to fully understand and accurately graspthe drainage and gas production mechanisms of plunger-lift, a mechanical model of plunger-liquid column uplift inthe plunger-lift process was established, focusing on conventional plunger-lift systems and representative wellboreconfigurations in the Linxing region. The operating casing pressure of the plunger-lift process and the calculationmethod for the maximum daily fluid production rate based on the work regime with the highest fluid recovery ratewere determined. For the first time, the critical flow rate method was proposed as a constraint for the maximumliquid-carrying capacity of the plunger-lift, and liquid-carrying capacity charts for conventional plunger-lift withdifferent casing sizes were developed. The results showed that for 23/8 casing plunger-lift, with a well depth ofshallower than 808 m, the maximum drainage rate was 33 m3/d;for 27/8 casing plunger-lift, with a well depth ofshallower than 742 m, the maximum drainage rate was 50.15 m3/d;for 31/2 casing plunger-lift, with a well depthof shallower than 560 m, the maximum drainage rate was 75.14 m3/d. This research provides a foundation for thescientific selection of plunger-lift technology and serves as a decision-making reference for developing reasonableplunger-lift work regimes.

A Surface Tension Model for Liquid Mixtures Based on NRTL Equation

A new equation for predicting surface tension is proposed based on the thermodynamic definition of surface tension and the expression of the Gibbs free energy of the system. Using the NRTL equation to represent the excess Gibbs free energy, a two-parameter surface tension equation is derived. The feasibility of the new equation has been tested in terms of 124 binary and 16 multicomponent systems(13-ternary and 3-quaternary) with absolute relative deviations of 0.59% and 1.55% respectively. This model is also predictive for the temperature dependence of surface tension of liquid mixtures. It is shown that, with good accuracy, this equation is simple and reliable for practical use.

Deformation and water/gas flow properties of claystone/bentonite mixtures

As a potential engineered barrier material for disposal of radioactive waste in clay formations,claystone aggregate excavated from the Opalinus clay(OPA),its mixture with bentonite MX80 in a mass ratio of 7/3,and pure bentonite were extensively investigated with respect to the hydro-mechanical properties and performances.With these materials,a series of parallel experiments was performed under sequentially applied conditions of hydration with synthetic porewater of the clay formation,consolidation and water flow under increased stresses,and gas injection into the water-saturated and compacted materials under loading.Significant responses of the clay mixtures were observed.Main findings include:(1)the hydration and induced swelling of the mixtures are mainly dominated by bentonite content and dry density;(2)the consolidation decreases the porosity and water permeability exponentially by 2-3 orders of magnitude to low values of 10^(-18)-10^(-20) m^(2) at stresses of 2-5 MPa,depending upon bentonite content;and(3)the gas penetration in the water-saturated and compacted bentonite is characterised by a cyclic pressure rising/dropping process limited in between the upper breakthrough and lower shut-off boundaries,whereas the compacted claystone and claystone/bentonite mixture allow for gas release at low and moderate pressures.The results are helpful for design of the engineered barriers for safe isolation of radioactive waste in repositories.

Phase behaviors of binary mixtures composed of electron-rich and electron-poor triphenylene discotic liquid crystals

Disk-like liquid crystals（DLCs） can self-assemble to ordered columnar mesophases and are intriguing onedimensional organic semiconductors with high charge carrier mobility.To improve their applicable property of mesomorphic temperature ranges,we exploit the binary mixtures of electronic donor-acceptor DLC materials.The electron-rich2,3,6,7,10,11-hexakis（alkoxy）triphenylenes（C4,C6,C8,C10,C12） and an electron-deficient tetrapentyl triphenylene-2,3,6,10-tetracarboxylate have been prepared and their binary mixtures have been investigated.The mesomorphism of the1：1（molar ratio） mixtures has been characterized by polarizing optical microscopy（POM）,differential scanning calorimetry（DSC）,and small angel x-ray scattering（SAXS）.The self-assembled monolayer structure of a discogen on a solid-liquid interface has been imaged by the high resolution scanning tunneling microscopy（STM）.The match of peripheral chain length has important influence on the mesomorphism of the binary mixtures.