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1

Efficient nitrate adsorption from water by aluminum powder. Kinetic, equilibrium and influence of anion competition studies

Fakhri Y., Kakavandi B., Safaei Z., Asadi A., Mohseni S. M., Golestanifar H.

Environment Protection Engineering

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2018

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Vol. 44, nr 3

19--31

EN

The feasibility of aluminum powder (with particle size of 75–150 μm) for nitrate removal from aqueous solutions has been investigated. Adsorption was examined in function of initial nitrate concentration, contact time, pH and influence of other interfering anions. Maximum nitrate removal occurred at equilibrium pH of 10. The kinetics of adsorption of nitrate ions was discussed based on three kinetic models, namely: the pseudo-first order, the pseudo-second order and the intraparticle diffusion model. The experimental data fitted the pseudo-second order kinetic model very well; the rate constant was 4x10–4 g/ (mg·min) at the concentration of NO3- of 100 mg/dm3. The adsorption data followed both Langmuir (R2 = 0.808) and Freundlich (R2 = 0.865) isotherms probably due to the real heterogeneous nature of the surface sites involved in the nitrate uptake. The maximum sorption capacity of aluminum powder for nitrate adsorption was found to be ca. 45.2 mg/g at room temperature. The results indicate that aluminum powder is an interesting alternative for nitrate removal from the water.

2

Numerical modelling of the competition between the adaptive immune system and virus

Kolev M.

Control and Cybernetics

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2011

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Vol. 40, no 3

763-778

EN

We present and analyze numerically a mathematical model of interactions between adaptive immune system and viral infection. The model is a bilinear system of partial integro-differential equations of Boltzmann type. It is a generalization of the recently proposed kinetic models that consider particular (namely, the cellmediated and the humoral) immune mechanisms used in the fight against viral infections. We use Matlab to solve complicated system of equations, present the results of computer simulations and explain their immunological meaning. The results show that the model can describe in a better way (in comparison with the previous kinetic models) real biological situations and is able to illustrate various methods of therapy.

3

One-dimensional ultrasound propagation in stratified gas

Leble S., Solovchuk M.

Archives of Acoustics

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2009

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Vol. 34, No. 2

215-229

EN

The system of hydrodynamic-type equations is derived by two-sided distribution function for a stratified gas in gravity field and applied to the problem of ultrasound. The theory is based on the generalized Gross-Jackson kinetic equation, the solution of which is built by means of locally equilibrium distribution function with different local parameters for molecules moving "up" and "down". The problem of propagation of the sound wave from an oscillating plane is explored. The linearized version of the obtained system is studied and compared with other results and experiments for a wide range of Knudsen numbers (Kn). The discrepancy with experiment in attenuation behavior at big Kn range forced us to use generalized kinetic description leading to the Alexeev-Boltzmann equation. Its use essentially improves the results.

4

A non-linear constitutive relation for flowing granular materials

Massoudi M., Rao C. L.

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 2

457-471

EN

We study the flow of granular materials down an inclined plane. We assume steady fully developed conditions. The constitutive relation is that of Rajagopal and Massoudi (1990), where the material parameters are given by the theory of Boyle and Massoudi (1990). We do not consider the effects of ?granular temperature? (a measure of the fluctuating component of the velocity of the grains). The material parameters are given in this model as functions of volume fraction, particle diameter, restitution coefficient, and the excluded volume. The momentum equations are non-dimensionalized and the resulting coupled non-linear ordinary differential equations are solved numerically; the results are presented for the volume fraction and velocity profiles for different dimensionless numbers.