Theoretical Studies on Critical Properties of Binary System with Supercritical Carbon Dioxide

A new expression of mixing rule is suggested according to the Mayson′s mixing rule in this paper, which adopts the Redlich Kwong cubic equation of state and the modified Chueh Prausnitz method to calculate the experiment critical points of six binary mixtures CO 2+toluene, CO 2+cyclohexane, CO 2+ n butanal, CO 2+ i butanal , CO 2+methanol, CO 2+ethanol. The coefficients of interaction parameter in the expression of mixing rule were optimized from experimental data. The calculated results of critical temperature and critical pressure meet the experiment data well. The maximum relative errors of temperature and pressure between the calculation results and experiment data are 1 493% and 5 2236% respectively, indicating that the proposed expression of mixing rule is reasonable. This may provide a fundamental method for studying and predicting the properties of supercritical fluids.

A New Group-Contribution Method for Critical Properties

In the paper, an estimating method for critical properties in group-contribution method is presented.For eliminating the influence of adjacent group and distinguishing isomers, the new method including first-level group-contribution method and second-level group-contribution method is proposed. The new method demonstrates significant improvement in accuracy.

Critical Properties of Mixed Ising Spin System with Different Trimodal Transverse Fields in the Presence of Single-Ion Anisotropy

Within the framework of an effective field approximation, the effects of single-ion anisotropy and different trimodal transverse fields of two sublattices on the critical properties of the mixed spin-1/2 and spin-1 Ising system are investigated on the simple cubic lattice. A smaller single-lon anisotropy can magnify magnetic ordering phases and a larger one can depress magnetic ordering phase for T-Ω1/2 space at low temperatures, while a smaller single-ion anisotropy can hardly change the value of critical transverse field for T-Ω1 space. On the other hand, influences of two different trimodal transverse fields concentrations on tricritical points and magnetic ordering phases take on some interesting results in T-D space. The main reason comes from the common action of single-ion anisotropy, different transverse fields and two trimodal distributions.

Critical behaviours and magnetic properties of three-dimensional bond and anisotropy dilution Blume-Capel model in the presence of an applied field

This paper studies the critical behaviours and magnetic properties of three-dimensional bond and anisotropy dilution Blume-Capel model （BCM） in the presence of an applied field within the effective field theory. The trajectory of tricritical point, reentrant transitions and degenerate patterns of anisotropy are obtained both for the bond and the anisotropy dilutions. The global phase diagrams demonstrate unusually reentrant phenomena. The temperature dependences of magnetization curves undergo remarkable spin glass behaviour at low temperatures, and transform from ferromagnetism to paramagnetism at high temperature in applied fields. Temperature dependence of magnetic susceptibility curve is in qualitative agreement with experimental result.

Critical Properties of a Generalized Planar Rotator Model

The critical properties of the planar rotator model with chiral Dzyaloshinsky-Moriya interaction are analyzed using a hybrid Monte Carlo method.Simulations on different lattices conform an observation that there is an XY-like Berezinskii-Kosterlitz-Thouless (BKT) phase transition in this model.The ground state and some thermodynamics properties are also discussed.

Critical temperatures and pressures of reacting mixture in synthesis of dimethyl carbonate with methanol and carbon dioxide

Critical temperatures and pressures of nominal reacting mixture in synthesis of dimethyl carbonate （DMC） from methanol and carbon dioxide （quaternary mixture of carbon dioxide ＋ methanol ＋ water ＋ DMC） were measured using a high-pressure view cell. The results suggested that the critical properties of the reacting mixture depended on the reaction extent as well as its initial composition （initial ratio of carbon dioxide to methanol）. Such information is essential for determining the reaction conditions when one intends to carry out the synthesis of DMC with CO2 and methanol under supercritical conditions.

Iso-propyl caprylate and iso-propyl linolenate synthetic fluids as novel alternatives in deep-water drilling operations:Critical fluid properties and aerobic biodegradability assessments

Present drilling fluids for deep water wells have severe degenerative effect on the environment with high operational and disposal costs.Thus,making them less desirable in recent times.Ester synthetic drilling fluid provides a novel environmentally friendly alternative but conventional ester-based drilling fluids exhibit high viscosities in deep-water wells causing excessive equivalent circulating density(ECD)and increased risk of lost circulation owing to narrow mud density window.This study experimentally investigates the critical fluid properties and aerobic biodegradability potentials of two newly developed deep-water synthetic ester drilling fluids namely:iso-propyl caprylate(COIPE)and iso-propyl linolenate(LOIPE)synthetic fluids and their comparison with synthetic-paraffin(SP-SBF)and isomerized-olefin(IOSBF)synthetic hydrocarbon fluids.The esters of iso-propyl caprylate and iso-propyl linolenate were produced from the isolation of ester mixtures that were obtained from the homogeneous catalytic transesterification of coconut and linseed plant oil biomass respectively.The COIPE was isolated from the coconut oil iso-propyl ester mixture by low-pressure fractional distillation technique.While fractional distillation and crystallization were used to isolate the LOIPE ester from the linseed oil iso-propyl ester mixture.Meanwhile,the aerobic biodegradation investigation was conducted by a modified oxygen consumption respirometry technique.The GC-MS analysis of the COIPE and LOIPE showed that the former contains essentially of lower saturated carbon compounds(C8).Whereas the latter contains higher molecular weight and unsaturated carbon compounds(C18+).The COIPE and LOIPE kinematic viscosity values are in good agreement with that of the reference synthetic hydrocarbon fluid samples(SP-SBF and IO-SBF).Although,the COIPE synthetic ester has lower viscosity value owing to the presence of shorter chain and saturated carbon atoms(C8 esters).Similarly,the linolenic oil iso-propyl ester has excellent cold flow characteristics for deep-water well drilling owing to lower values of cloud and pour points as a result of higher concentration of poly-unsaturated linolenic esters.The iso-propyl caprylate and the iso-propyl linolenate ester synthetic fluids are readily biodegradable in the sea water inoculum under aerobic condition.However,the iso-propyl caprylate is inherently biodegradable because its degradation level and that of the reference chemical sample were already above 60%during the 10-day window period.The SP-SBF and the IO-SBF synthetic fluids have lower aerobic biodegradation values because they contain little quantity of poly aromatic hydrocarbons as evident in their GC-MS profiles.Finally,esters and unsaturated synthetic-based fluid are more rapidly biodegradable than paraffinic synthetic fluids and the rate of biodegradation of organic compounds decreases as molecular weight increases.

Phase Equilibrium of Isobutanol in Supercritical CO2

Vapor-liquid phase equilibrium data including composition,densities,molar volume and equilibrium constant of isobutanol in supercritical carbon dioxide from 313.2K to 353.2K were measured in a variable-volume visual cell.The properties of critical point were obtained by extrapolation.The results showed that critical temperature,critical pressure and critical compressibility factor of CO2-isobutanol system decreased with the increase of critical CO2 content.The phase equilibrium model was established by Peng-Robinson equation of state and van der Waals-2 mixing regulation,and model parameters were determined by optimization calculation of nonlinear least square method.The correlation between calculated values and the experimental data showed good agreement.

Influence of the gassing materials on the dielectric properties of air

Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and validated. Then the species compositions of the air–organic vapor mixtures were calculated based on the Gibbs free energy minimization. Finally, the Townsend ionization coefficient, the Townsend electron attachment coefficient and the critical reduced electric field strength were derived from the calculated electron energy distribution function by solving the Boltzmann transport equation. The calculation results indicated that H;O with large attachment cross sections has a great impact on the critical reduced electric field strength of the air–organic vapor mixtures. On the other hand, the vaporization of gassing materials can help to increase the dielectric properties of air circuit breakers to some degree.

Measurements of the Critical Temperature and Pressure of Ethylene+Benzene+Ethylbenzene Mixture

Critical temperature (Tc) and critical pressure (pc) of the ternary mixture of ethylene+benzene+ethylbenzene (the mole ratio of ethylbenzene to benzene was fixed at 0.95:0.05) were measured by using a high=pressure view cell with direct visual observation.The interaction coefficients obtained from the critical properties of the relevant binary systems were used to predict the critical properties (Tc,pc) of the ternary mixture.The agreement between the prediction and experiments is satisfactory.

Correlating thermal conductivity of pure hydrocarbons and aromatics via perceptron artificial neural network (PANN) method

Accurate estimation of liquid thermal conductivity is highly necessary to appropriately design equipments in different industries. Respect to this necessity, in the current investigation a feed-forward artificial neural network(ANN) model is examined to correlate the liquid thermal conductivity of normal and aromatic hydrocarbons at the temperatures range of 257–338 K and atmospheric pressure. For this purpose, 956 experimental thermal conductivities for normal and aromatic hydrocarbons are collected from different previously published literature.During the modeling stage, to discriminate different substances, critical temperature(Tc), critical pressure(Pc)and acentric factor(ω) are utilized as the network inputs besides the temperature. During the examination, effects of different transfer functions and number of neurons in hidden layer are investigated to find the optimum network architecture. Besides, statistical error analysis considering the results obtained from available correlations and group contribution methods and proposed neural network is performed to reliably check the feasibility and accuracy of the proposed method. Respect to the obtained results, it can be concluded that the proposed neural network consisted of three layers namely, input, hidden and output layers with 22 neurons in hidden layer was the optimum ANN model. Generally, the proposed model enables to correlate the thermal conductivity of normal and aromatic hydrocarbons with absolute average relative deviation percent(AARD), mean square error(MSE), and correlation coefficient(R^2) of lower than 0.2%, 1.05 × 10^(-7) and 0.9994, respectively.

A generalized set of correlations for plus fraction characterization

The importance of accurate determination of the critical properties of plus fractions in prediction of phase behaviour of hydrocarbon mixtures by equations of state is well known in the petroleum industry. It has been stated in various papers （Elsharkawy, 2001） that using the plus fraction as a single group in equation of state calculations reduces the accuracy of the results. However in this work it has been shown that using the proper values of critical temperature and pressure for the plus fraction group can estimate the properties of hydrocarbon mixtures, and they are accurate enough to be used in reservoir engineering and enhanced oil recovery calculations. In this paper, a new method is proposed for calculating the critical properties of plus fractions of petroleum fluids. One can use this method either in predicting critical pressure and temperature of single carbon numbers （SCNs） after the splitting process or in predicting critical pressure and temperature of the plus fraction as a single group. A comparison study is performed against Riazi-Daubert correlation （Riazi and Daubert, 1987） and Sancet correlations （Sancet, 2007） for 25 oil samples taken from 14 fields from southwest Iran. The results indicate the superiority of the proposed method to the Riazi-Daubert and Sancet correlations.

Mechanics of Twisted DNA Molecule Adsorbed on a Biological Membrane

DNA is the carrier of all cellular genetic information and increasingly used in nanotechnology. The study of DNA molecule achieved in vitro while submitting the DNA to all chemicals agent capabilities to destabilize links hydrogen, such as pH, temperature. In fact, the DNA enveloped in the membrane cellular, so it is legitimate to study the influence of membrane undulations. In this work, we try to show that the fluctuations of the membrane can be considerate as a physics agent is also capable to destabilize links hydrogen. In this investigation, we assume that each pair base formed an angle an with the membrane’s surface. We have proposed a theoretical model, and we have established a relationship between the angle formed by the pair base θeq and an angle formed by the membrane and each pair base. We assume that DNA and biomembrane interact via a realistic potential of Morse type. To this end, use is made of a generalized model that extends that introduced by M. Peyrard and A. R. Bishop in the past modified by M. Zoli. This generalized model is based on the resolution of a Schrödinger-like equation. The exact resolution gives the expression of the ground state, and the associated eigenvalue (energy) that equals the free energy, in the thermodynamic limit. First, we compute the denaturation temperature of DNA strands critical temperature. Second, we deduce all critical properties that mainly depend on the parameters of the model, and we quantify the effects of the membrane undulations. These undulations renormalize all physical quantities, such as harmonic stacking, melting temperature, eigenfunctions, eigenvalues and regular part of specific heat.

Quantitative properties of ground-states to an M-coupled system with critical exponent in R^N

In this paper, we consider the ground-states of the following M-coupled system:where p_(ij)+q_(ij)=2*:=2 N/(N-2)(N≥3). We prove the existence of ground-states to the M-coupled system. At the same time, we not only give out the characterization of the ground-states, but also study the number of the ground-states, containing the positive ground-states and the semi-trivial ground-states, which may be the first result studying the number of not only positive ground-states but also semi-trivial ground-states.

Quantitative and Qualitative Analysis of Bose—Einstein Condensation in Harmonic Traps

A simple and direct approach to handle summation is presented. With this approach, we analytically investigate Bose–Einstein condensation of ideal Bose gas trapped in an isotropic harmonic oscillator potential. We get the accurate expression of which is very close to (0.43% larger than) the experimental data. We find the curve of internal energy of the system vs. temperature has a turning point which marks the beginning of a condensation. We also find that there exists specific heat jump at the transition temperature, no matter whether the system is macroscopic or finite. This phenomenon could be a manifestation of a phase transition in finite systems.

Critical parameters near the ferromagnetic-paramagnetic phase transition in La_(0.67–x)Y_xBa_(0.23)Ca_(0.1)MnO_3 compounds(x=0.10 and x=0.15)

The critical properties of the mixed manganite La0.67–x Y x Ba0.23Ca0.1Mn O3 with x=0.10 and x=0.15 around the paramagnetic（PM）-ferromagnetic（FM） phase transition were investigated through various techniques. These involved modified Arrott plots, Kouvel-Fisher method and Widom scaling relation. Magnetic data, analyzed in the critical region, using the above methods, yielded the critical exponents for（x=0.10） La0.57Y0.10Ba0.23Ca0.1Mn O3（β=0.312±0.002 and γ=1.147±0.003 at T C=299.23±0.05 K）. Moreover, the estimated critical exponents of（x=0.15） La0.52Y0.15Ba0.23Ca0.1Mn O3 were β=0.286±0.004 and γ=0.943±0.002 at T C=289.53±0.06 K. The critical exponents＇ values were close to the theoretical values of 3D-Ising model and tricritical mean-field model. These results suggested that the present composition should be close to a tricritical point in the La0.67–x Y x Ba0.23Ca0.1Mn O3 phase diagram. Expressing the field dependence as ΔS M∝H n allowed us to establish a relationship between the exponent n and the critical exponents of the material and to propose a phenomenological universal curve for the field dependence of ΔS M.

Controlling the gelation temperature of biomimetic polyisocyanides

Thermosensitive polymers show an entropy-driven transition from a well-solvated to a poorly solvated polymer chain, resulting in a more compact globular conformation. The transition at the lower critical solution temperature（LCST） is often sharp, which allows for a wide range of smart material applications.At the LCST, oligo（ethylene glycol）-substituted polyisocyanides（PICs） form soft hydrogels, composed of polymer bundles similar to biological gels, such as actin, fibrin and intermediate filaments. Here, we show that the LCST of PICs strongly depends linearly on the length of the ethylene glycol（EG） tails; every EG group increases the LCSTand thus the gelation temperature by nearly 30 ℃. Using a copolymerisation approach, we demonstrate that we can precisely tailor the gelation temperature between 10 ℃ and 60 ℃and, consequently, tune the mechanical properties of the PIC gels.

Research advances in the formation poredynamics of sedimentary basins

In the 21st century,the geodynamics is developing towards quantitative researches.However,due to the irreversible geological processes,it was very difficult to recover the geological process.In particular,the restoration of geological parameter evolution process at the microscopic scale has become a major scientific problem in geology presently.Thereby,a concept of the formation poredynamics is revised and proposed,and the formation poredynamics is a fundamental discipline which focus on the mechanical characteristic of porous media,the pore evolution law,the dynamic genesis and the seepage property of pore fluid during the burial process of clastic rocks.Moreover,it is a new interdiscipline of underground diagenetic dynamics and pore fluid dynamics,and also is as an important part of sedimentary basin dynamics.Research advances were made in both basic theory and applied research.The advances in the basic theory include:(1)the static equilibrium principle of the formation pore,(2)the porosity evolution mechanism and quantitative model of sandstone during the burial diagenetic process,(3)the compaction characteristic and the porosity evolution quantitative model of mudstone,(4)the theoretical relationship between the underground pore fluid temperature and the pore fluid pressure,(5)the influence of the tectonism-induced additional geostress on the pore fluid pressure,and(6)the relationship between the mudstone compaction and the vitrinite reflectance(R_(o))of organic matter.The advances in the applied research include:(1)the geotemperature-geopressure system division of the sedimentary basin and the interpretation of the hydrocarbon distribution dynamic,(2)the modification of the strata pressure prediction model,(3)the construction of the reservoir critical properties and the reservoir dynamics evaluation system,(4)the simulation of the evolution process of the formation fluid pressure,(5)the numerical simulation and physical experimental simulation on the sandstone hydrocarbon charging dynamics,and(6)the dynamic process analysis of the hydrocarbon accumulation in tight sandstone.Through the integration between the pore genesis evolution and the pore fluid dynamic evolution,the formation poredynamics is one of the representative discipline branches that the geological dynamics research had developed toward the underground microscopic scale in recently 20 years,and it also is an inevitable result from the quantitative development of the formation and distribution mechanisms of sedimentary mineral deposits.Based on the formation poredynamics research,eight important research achievements are summarized,and the geological researches are extended from the macroscopic scale to the microscopic scale,to find out the pore parameter evolution law under control of the formation pore evolution during the burial process,and update and improve exploration and production application technologies.