Two methods were used to solve the convection-diffusion equation which appropriate to straight single-tube Flow Injection Analysis(FIA)system without chemical reaction,and the concentration distribution of the slug-injected sample after dispersing in the tube was obtained. F-Curve was thereby obtained.

The locally implicit finite element scheme is a new numerical algorithm In this paper, it is given for the model equation, convection diffuse equation Then, the TVD property is analyzed, and the numerical experiment is done for the Riemann discontinuous questions It is proved that the locally implicit finite element scheme does have the TVD property

Based on central difference scheme, explicit upwind scheme, Samarskii scheme and modified Dennis scheme, some new alternating group explicit methods and alternating direction explicit methods are constructed for solving convection diffusion equation. Their experimental model and results of numerical comparison are given.

It is proved that they are unconditionally stable. As shown by numerical results, besides AGE scheme based on central difference scheme and alternatively difference explicit scheme, the rest of AGE schemes and relevant ADE schemes are well matched in accuracy. They are also effective to higher Reynolds numbers.

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.