To solve numerical dissipation and dispersion in numerical solution of convection-diffuson equation, a numerical procedure for simulating the convection-diffusion movement has been developed. The procedure is based on a governing equation which can be divided into Euler type convection equation and Lagrange type diffusion equation.

Based on the convection-diffuse equation, a numerical-simulation system of urban vehicle emissions is built, which simulated the diffuse of vehicle emiss ions by 50-metre grid.

This paper is devoted to the development of stabilized finite element methods by empolying local bubble functions for adveetive-diffusive models which has the form σu+a·(?) u-k△u =f. We show this methodology is stable independent of σ or Peclet-number and its globle optimal convergence order,from the problem with a=0 or σ=0.

At present, the methods of calculating pollution load are approximately classified as the sum of each section load, product of section average concentration and section water amount, sum ofload distributing frequency and convection-diffuseness model.

In order to solve the two-point boundary value problems of one-dimensional steady diffusion-convection equation with large Peclet number,a numerical method using the arc length of the solution aa a parameter has been presented in this paper. It has been successfully applied to solve some difficult problems with boundary layer shock layer and air-pocket using the shooting technique (single or multi-segments).

The convection-dispersion processes, by which the crest of mound is flatted and moved shoreward at the same time, are generated by the present numerical model very well.

Moreover, two solute transport models [convection-dispersion equation model (CDE) and two-site non-equilibrium model (TSN)] were used to simulate heavy metal movement in soil on a laboratory column scale.

Three models of convection-dispersion equation (CDE), transfer functional model (TFM) and Back-Progation Network (BP Network) were used to simulate the transportation process of bromide ion.

Mean flow velocity and vertical dispersion were estimated by an analytical best-fit method using one-dimensional convection-dispersion model.

The model accounts for heat transport by diffusion and by convection, while the modeling of the displacement of nitrate and ammonium in the soil is based on the convection-dispersion equation.

An investigation of the kinetics of the reactions between liquid slags and carbonsaturated iron including the reduction of FeO, MnO, CrO and V_2O_3 by carbon and the desulphurization of iron leads to the conclusion that the chemical reactions come to equilibrium rapidly at the slag-metal interface, while the controlling step is convective diffusion. It has been found that the reactions are of the first order when the melt is kept in a rotational motion, caused by the use of a rotating crucible or stirrer, and...

An investigation of the kinetics of the reactions between liquid slags and carbonsaturated iron including the reduction of FeO, MnO, CrO and V_2O_3 by carbon and the desulphurization of iron leads to the conclusion that the chemical reactions come to equilibrium rapidly at the slag-metal interface, while the controlling step is convective diffusion. It has been found that the reactions are of the first order when the melt is kept in a rotational motion, caused by the use of a rotating crucible or stirrer, and are of second order when the melt is kept in a stationary crucible and stirred by CO gas bubbles only. The thickness of the diffusion boundary layer δ, obtained from a treatment of Chipman's desulphurization data and Philbrook's data on the reduction of FeO, which correspond to the two fore-mentioned cases respectively, has been found to be inversely propertional to ω~(1/2), the square root of the angular velocity, and C_(FeO), the concentration of FeO in the slag phase.The present problem has been treated on the basis of the principle of convective diffusion across a solid-liquid interface according to Levich. It has been found that our findings can be satisfactorily explained by an application of this principle. An exceptional case is the reduction of SiO_2 from slags, which is probably controlled by interfacial chemical reaction.

A star is an open system that exchanges energy and matter with its exterior. A star is also a themodynamic system far from the equilibrium state. For such a thermo-dynamic system, we could use the criterion of excess entropy production in non-linear and non-equilibrium thermodynamics provided by Ⅰ. Prigogine et al. to study the stability of the stellar structure. Following paper, in this paper we have reexamined the stability of stars located at the upper part of the main sequence, for which the reaction of...

A star is an open system that exchanges energy and matter with its exterior. A star is also a themodynamic system far from the equilibrium state. For such a thermo-dynamic system, we could use the criterion of excess entropy production in non-linear and non-equilibrium thermodynamics provided by Ⅰ. Prigogine et al. to study the stability of the stellar structure. Following paper, in this paper we have reexamined the stability of stars located at the upper part of the main sequence, for which the reaction of C-N-O cycle is their main energy source. We assume that the star is in hydro-statii equilibrium, the temperature in the region of nuclear reaction is a constant, and the convection and diffusion are unimportant. The formulae (3) are the reaction equations of C-N-0 cycle, in which x1, . . ., x6 are the mass densities of H1, C12, C13, N14, N15 and He4 respectively, kij are defined by (4), where NA is Avogodro's number, <σ,v>ij is the reaction section between particle i and j, and Ai is the atomic weight of particle i. The local excess entropy production is decided by the formulae (8), (12) and (13). According to the nonlinear and non-equilibrium thermodynamics, the system is stable if δxσ> 0, and unstable if δxσ< 0. We have obtained five conditions for the stability, that is, the formula (14). The first three conditions are satisfied for a star. But the last two conditions, that is, the formulae (15) and (16), contradict each other. Therefore, the thermodynamic system is unstable. We have discussed the reasons about the contradiction, and shown that the convection, diffusion, temperature change and the cycle reaction other than C-N-O cycle, i.e. formula (17), are important, and their effects on stability of the stellar structure must be considered.

The effective distance of acid penetration along a fracture is an important parameter for acid fracturing design and treatment.Up to now, it has not yet been taken into account at home and abroad that the decreasing acid concentration and the increasing reaction products influence the effective mass transfer of hydrogen ions in the flowing acid reacting with carbonate rocks. In our research, we have found that the influence of the common ion effect on the effective mass transfer coefficient of hydrogen ions...

The effective distance of acid penetration along a fracture is an important parameter for acid fracturing design and treatment.Up to now, it has not yet been taken into account at home and abroad that the decreasing acid concentration and the increasing reaction products influence the effective mass transfer of hydrogen ions in the flowing acid reacting with carbonate rocks. In our research, we have found that the influence of the common ion effect on the effective mass transfer coefficient of hydrogen ions is considerable. It is an important factor to be considered.By means of reaction of flowing hydrochloric acid of various concentrations with Yang Xin limestone of Permian age from Sichuan, we have got some curves which express the relationship between the transfer coefficient with the partially spent acid concentration and the flowing Reynolds number.With the help of mathematical statistics an experience equation expressing dimentionless relation of them has been obtained. When we substitute it into the convection-diffusion equation and solve the latter, the distance of acid penetration can be claculated. In the calculation the change of acid concentration and the common ion effect are taken into account. This distance may be also estimated by superposing the results of calculating section by section.