Molecular thermodynamic models and the properties of fluid phase equilibria are necessary to the design, running, control and optimization of industrial process and furthermore its precision and reliability are directly related to the modeling and optimization results of process simulation. In this context, an equation of state with variable range for square⁃well potential (SWCF⁃VR) was developed based on the statistical association fluid theory and applied to represent the thermodynamic properties like vapor⁃liquid equilibria (VLE), liquid⁃liquid equilibria, solid⁃liquid equilibria, enthalpy of vaporization or mixing and so on for traditional fluids, associated fluids, electrolyte solutions, ionic liquids, polymers, etc. At the same time, the equation of sate combining with surface tension and viscosity can be used to predict and calculate the transfer properties of the mixture such as surface tension and viscosity successfully. The salient feature in our model was that transferable molecular parameters fitted from experimental phase equilibria data or predicted from group contribution method or solvation calculation were used. Meanwhile, the test of theoretical model and determination of molecular parameters in SWCF⁃VR were carried out always based on experimental thermodynamic data. Thus, an online platform for fluid phase equilibria (www.equilibria.cn) were developed, where the details about phase behavior conception, classification and applications were summarized, and data searching systems and some softwares for VLE calculation provided. The mentioned thermodynamic model and online platform in this work could be well used for process design, modeling and optimization.

The vertical and horizontal heterogeneity of the reservoir in Bohai Q oilfield is strong, so it is difficult to accurately establish the geological model, and there is a problem of low fitting accuracy in the history of reservoir numerical simulation in ultra⁃high water cut period. Based on the theory of percolation mechanics, production logging data and streamline simulation are combined. The combination of the pipe method and the use of production log data to provide the amount of liquid production and water content and stratified injection amount to determine the residual oil saturation and its distribution at any point in the reservoir. By using this method, the measures of flow field regulation of water injection unit and water blockage of local well group are proposed. The output of oil wells is increased by 14 times, and the annual oil production of oilfield is negatively decreasing. The practice shows that the combination of production logging data and streamline simulation can effectively identify the remaining oil distribution, and provide scientific theoretical basis for the development and adjustment of highly heterogeneous reservoirs in ultra⁃high water cut stage.

In this paper, based on the background of hydrogen photolysis of water, adapts the computational fluid dynamics software combined with secondary development to numerically analyze the heat transfer process inside the solar photocatalytic reactor. A high⁃quality structured hexahedral photocatalytic reactor grid was established to analyze the temperature distribution characteristics of the solar photocatalytic reactor model numerically, compile the Gaussian heat flow and validate the model combined with the solar photocatalytic water activity evaluation system for hydrogen production. This article will focus on the effect of solar radiation on the temperature distribution of the fluid inside the reactor and the reactor under full spectrum, and study the differences in temperature distribution and causes under different conditions.

This paper briefly introduces the measuring principle and structure of the liquid level standard device, which is based on the double-frequency laser interferometer equipment for measuring the liquid level. An uncertainty evaluation mathematical model for the liquid level standard device has been established. In the studies, various uncertainty affecting the liquid level standard device were analyzed. Based on this, the uncertainty components of different influence factors were calculated. The results show that the uncertainty value of the liquid level standard device was 0.045 588 mm, and the expanded uncertainty was 0.091 176 mm.

The pretreatment of spent lubricating oil to remove part of the water and impurities was carried out firstly, then the flash device are used for further removal of water, followed by the distillation in atmospheric and vacuum distillation unit. A lowfreezingpoint, high stable light diesel were produced in the atmospheric distillation zone; different kinds of lubricating base oils which are all available resources were produced by vacuum distillation segment combined with complex agent refiningalkaline cleaningclay refining process. Additives were added finally to improve the oil quality. The additional purification process conditions were identified: the mass fraction of acid solvent 4.5% which contains the mass fraction complexing agent 1.5% for pickling; 1% NaOH aqueous solution with its mass fraction of 40% were added for alkaline cleaning at 40 ℃, then 3% clay was added and stirred for 25～30 min at the temperature less than 120 ℃. This processing technology not only reduces the pollution effectively, but also greatly improves the reutilization of waste oil.

 

 

Gd ₂O ₂S:Dy ³⁺  phosphors were synthesized by a homogeneous precipitation method from Gd ₂O ₃, Dy ₂O ₃, H ₂SO ₄ and Urea starting materials. The characterizations of Gd ₂O ₂S:Dy ³⁺  phosphors were investigated by means of XRD, FE-SEM and PL spectra. XRD analysis shows that the precursor can be transformed into pure Gd ₂O ₂S powder by calcining at 900 ℃ for 1 h in hydrogen. FE-SEM observation shows that the Gd ₂O ₂S powder particles are quasi-spherical in shape, with a mean particle size of about 300~500 nm. Photoluminescence (PL) spectroscopy reveals that the main and second emission peaks are located at 579 nm and 488 nm under 270 nm UV light excitation, which corresponds to the  ⁴ F _9/2→ ⁶H _13/2 and the ⁴F _9/2→ ⁶H _15/2 transitions of Dy ³⁺ ions, and both transitions of Dy ³⁺ ions have a single exponential decay behavior. The quenching concentration of Dy ³⁺ ions is 1 %. The CIE coordinate and the color temperature of (Gd _0.99,Dy _0.01) ₂ O ₂S phosphor are (0.308, 0.379, 0.313）and 6 464 K respectively.

Under the preconditioned matrix P=I+R, the new USSOR iterative method was put forward. By the theory of matrix, it proved the convergence of the preconditioned USSOR iterative method when the coefficient matrix is a M-matrix or an H-matrix, gave a comparison theorem between the preconditioned USSOR iterative method and the classic USSOR iterative method when the coefficient matrix is a M-matrix, and disclosed precondition iterative method accelerates the convergence speed of the USSOR iterative method. Then a numerical example was used to demonstrate the validity.

The higher-order moment of sum of independent and identically distributed exponential random variables was investigated. The higher-moment of exponential random variable was computed by mathematical induction method. Base on this result, combining the multinomial theorem and the knowledge about the partition of integer in combinatorics, the higher-order moment of sum of independent and identically distributed exponential random variables was computed and the computation formula was got. At last, the conclusion was illustrated by numerical example.

 

Stock ownership is the key elements of board governance that relates to the corporate performance. The positive correlation of the stock ownership and corporate performance was analyzed using three variables as stock ownership including stock proportion, amount and worth. The positive correlation was more marked for corporation share when ownership structure was considered. Finally, a series of suggestions for enhancing the efficiency of corporate performance were put forward.

High temperature composite flooding systems with oil-washing, profile-controlling, viscosity-reduction functions were developed. It is used to solve the severe problems which were faced in the late development stage such as heavy oil reservoirs pressure declining greatly and ineffective steam channeling in high permeability zones, etc. FCY high temperature multifunctional foamer was researched as foaming agent of high temperature composite flooding systems, and plugging capacity of foam was measured by stable method. Effects of percolation velocity on plugging pressure differential and gas percolation mechanism under the existence of foam were researched by percolation experiments. Moreover, the resistance factor foam percolation model was built up based on experiment results of foam percolation mechanism. Good consistency between results from model and experiment results was found, and shear-thinning behavior of foam is described preferably. Effect of whole parameters, such as critical water saturation, capillary number, on gas percolation was also performed, and theory support is provided for steam-foam flooding in heavy oil reservoirs. 

The modified Flory-Huggins formula was adopted to calculate the free energy in mixing old asphalt with rejuvenator, and discussed their phase behavior. The solubility parameters and ratio of aromatic carbon of three aged asphalts are more than that of their materials. The mixing free energy of Caltex aged asphalt and rejuvenator R1 is above 0.0 (ΔGM＞0) at 25 ℃, their process of mixing is not spontaneity, so their mixing can’t form the homogeneous phase system. The mixing free energies of R2, R3, composite rejuvenator and aged asphalt are all below 0.0 (ΔGM＜0) at 25 ℃, their processes of mixing are spontaneity, so their mixing can form the homogeneous phase system.

The low flow rate of crude oil pipelines is ubiquitous. When the transportation quantity becomes lower than allowed minimum quantity, intermittent transportation technique can be used to solve this problem. In the course of intermittent transportation, if shutdown time is too long and crude oil temperature of pipeline decreases to a certain value, pipeline restart confronts tremendous difficulties, and further probably results in the accidents of pipeline condensation. According to of heating and water power character of pipelines from Tieling to Dalian, based on intermittent transportation, the mathematical models of temperature drop, restart temperature rising and restart pressure were established. By adopting finite difference method, partial differential equation of heat conduction is transferred to linear equations system and comes into solution by iterative method. Taking two sections of pipelines covering Anshan to Da Shiqiao and Da Shiqiao to Xiongyue as examples, simulation calculations of shut-down and restart were conducted. The result shows that pipeline may work safely during winters by this way that pipelines restart and continue work for two days after 8 days shut-down when the oil flow is 23 300 t/d and outgoing temperature is 45 ℃. The method is successfully applied for Tieling-Dalian pipeline.

Conside ring the complexity on calculating the binomial distributio n moments on the origin o f hig her -o rder with definition , Stirling number o f the second kind o f combina to rics w as applied to pro bability .And a method in which Stir ling numbe r of the second kind w as used w as given to so lve this pro blem :EXm = Σm l =0 S(m , l)[ n] l p l .M oreo ver , the method w as tested by an example .

Internal thermal of cold wall hydrogenation reactor often may become invalidation as a result of factors such as construction quality and working conditions. It leads to the reactor partially temperature extremely high. Because of the existence of thermal stress, overheating partial wall temperature is extremely disadvantageous to the equipment safe operation. The reactor in axial and circumferential thermal stress analysis and the calculation problem were studied. The stress analysis and computational method were put forward when ultra- warm spot is the square, the circular, the ring, the ellipse etc.