Capability of Uranium Heap Leaching From Gattar and El Missikat Area, Eastern Desert, Egypt: A Kinetic Approach

Detailed studies of uranium heap leaching from different uranium mineralization resources situated in Eastern Desert of Egypt were investigated using sulfuric acid via batch experiments, followed by using the obtained optimum condition on bench scale leaching tests using small column. The previous optimum parameters were implemented on another large scale column in order to make more condition control and evaluate the time and reagents needed while transferring from small to large scale. The obtained data shows that leaching efficiency of GII mineralization attained about 78.3% with consumed acid amount about 34 kg/ton in a 44 days as leaching time, on the other hand, leaching efficiency of uranium from El-Missikat mineralization higher than GII mineralization and attained about 86.6% and the consumed as lower than G-II about 28kg/ton in a 40 days leaching time. Kinetics reaction models of column tests have been investigated to optimize the column leaching behavior. Based on the leaching results of the two mineralized occurrences, the rate of the uranium dissolution is controlled by both the chemical reaction and the diffusion reaction but diffusion reaction control was more predominate than a chemical reaction.

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On a Robust and Efficient Numerical Scheme for the Simulation of Stationary 3-Component Systems with Non-Negative Species-Concentration with an Application to the Cu Deposition from a Cu-(β-alanine)-Electrolyte

Algorithms ◽

10.3390/a14040113 ◽

2021 ◽

Vol 14 (4) ◽

pp. 113

Author(s):

Stephan Daniel Schwoebel ◽

Thomas Mehner ◽

Thomas Lampke

Keyword(s):

Augmented Lagrangian ◽

Computation Time ◽

Species Distributions ◽

Chemical Processes ◽

Diffusion Reaction ◽

Augmented Lagrangian Methods ◽

Major Question ◽

Component Systems ◽

Reaction Models ◽

Reaction Equations

Three-component systems of diffusion–reaction equations play a central role in the modelling and simulation of chemical processes in engineering, electro-chemistry, physical chemistry, biology, population dynamics, etc. A major question in the simulation of three-component systems is how to guarantee non-negative species distributions in the model and how to calculate them effectively. Current numerical methods to enforce non-negative species distributions tend to be cost-intensive in terms of computation time and they are not robust for big rate constants of the considered reaction. In this article, a method, as a combination of homotopy methods, modern augmented Lagrangian methods, and adaptive FEMs is outlined to obtain a robust and efficient method to simulate diffusion–reaction models with non-negative concentrations. Although in this paper the convergence analysis is not described rigorously, multiple numerical examples as well as an application to elctro-deposition from an aqueous Cu2+-(β-alanine) electrolyte are presented.

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Reliable Efficient Difference Methods for Random Heterogeneous Diffusion Reaction Models with a Finite Degree of Randomness

Mathematics ◽

10.3390/math9030206 ◽

2021 ◽

Vol 9 (3) ◽

pp. 206

Author(s):

María Consuelo Casabán ◽

Rafael Company ◽

Lucas Jódar

Keyword(s):

Stochastic Process ◽

Finite Difference ◽

Coming Out ◽

Finite Difference Methods ◽

Diffusion Reaction ◽

Finite Difference Schemes ◽

Finite Degree ◽

Mean Square Stability ◽

Reaction Models ◽

Difference Methods

This paper deals with the search for reliable efficient finite difference methods for the numerical solution of random heterogeneous diffusion reaction models with a finite degree of randomness. Efficiency appeals to the computational challenge in the random framework that requires not only the approximating stochastic process solution but also its expectation and variance. After studying positivity and conditional random mean square stability, the computation of the expectation and variance of the approximating stochastic process is not performed directly but through using a set of sampling finite difference schemes coming out by taking realizations of the random scheme and using Monte Carlo technique. Thus, the storage accumulation of symbolic expressions collapsing the approach is avoided keeping reliability. Results are simulated and a procedure for the numerical computation is given.

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Polarization-Independent Circulator Based on Composite Rod of Ferrite and Plasma in Photonic Crystal Structure

Nanomaterials ◽

10.3390/nano11020381 ◽

2021 ◽

Vol 11 (2) ◽

pp. 381

Author(s):

Mi Lin ◽

Lixin Fu ◽

Shakeel Ahmed ◽

Qiong Wang ◽

Yaoxian Zheng ◽

...

Keyword(s):

Photonic Crystal ◽

Large Scale ◽

Optimization Method ◽

Coupling Condition ◽

High Isolation ◽

Optimum Parameters ◽

Composite Rod ◽

Polarized Waves ◽

Two Dimensional Photonic Crystal ◽

Polarization Independent

We propose a type of polarization-independent circulator based on a composite rod of ferrite and plasma materials in a two-dimensional photonic crystal (PhC) slab. Only one composite rod was set at the center of the structure to provide circulation for both TE- and TM-polarized waves. Additionally, to improve the performance of the circulator, three additional rods were inserted to improve the coupling condition between the center magneto-optical microcavity and the corresponding waveguides. Finite element method was used to calculate the characteristics of the structure and the Nelder–Mead optimization method was employed to obtain the optimum parameters. The results show that a low insertion loss (~0.22 dB) and high isolation (~14 dB) can be achieved in our structure for waves of both TE and TM polarizations. The idea presented here may be useful for designing compact polarization devices in large-scale integrated photonic circuits.

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The formation and development of oblique detonation wave with different chemical reaction models

Aerospace Science and Technology ◽

10.1016/j.ast.2021.106964 ◽

2021 ◽

pp. 106964

Author(s):

Hongbo Guo ◽

Xiongbin Jia ◽

Ningbo Zhao ◽

Shuying Li ◽

Hongtao Zheng ◽

...

Keyword(s):

Detonation Wave ◽

Chemical Reaction ◽

Oblique Detonation Wave ◽

Reaction Models

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A methodology for the simultaneous development of linear and nonlinear chemical reaction models from a linearly designed experimental program

Chemometrics and Intelligent Laboratory Systems ◽

10.1016/0169-7439(95)80085-n ◽

1995 ◽

Vol 29 (1) ◽

pp. 125-131 ◽

Cited By ~ 1

Author(s):

Kent P. Steele ◽

Mark W. Zettler

Keyword(s):

Chemical Reaction ◽

Experimental Program ◽

Simultaneous Development ◽

Reaction Models ◽

Linear And Nonlinear

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Analysis and comparison of in-situ combustion chemical reaction models

Fuel ◽

10.1016/j.fuel.2021.122599 ◽

2021 ◽

pp. 122599 ◽

Cited By ~ 1

Author(s):

Timothy I. Anderson ◽

Anthony R. Kovscek

Keyword(s):

Chemical Reaction ◽

In Situ Combustion ◽

Reaction Models

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A computational model for diffusion-reaction-deformation coupled problems and its finite element implementation

Engineering Computations ◽

10.1108/ec-02-2021-0084 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Bao Qin ◽

Yexin Zhou ◽

Zheng Zhong

Keyword(s):

Finite Element ◽

Chemical Reaction ◽

Reaction Rate ◽

Diffusion Processes ◽

Diffusion Reaction ◽

Governing Equations ◽

Content Type ◽

Finite Element Software ◽

And Diffusion ◽

Reaction And Diffusion

PurposeA diffusion-reaction-deformation coupled model is employed and implemented as a user-defined element (UEL) subroutine in the commercial finite element software package ABAQUS.Design/methodology/approachChemical reaction and diffusion are treated as two distinct processes by introducing the extent of reaction and the diffusion concentration as two kinds of independent variables, for which the independent governing equations for chemical reaction and diffusion processes are obtained. Furthermore, an exponential form of chemical kinetics, instead of the linearly phenomenological relation, between the reaction rate and the chemical affinity is used to describe reaction process. As a result, complex chemical reaction can be simulated, no matter it is around or away from equilibrium.FindingsTwo numerical examples are presented, one for validation of the model and another for the modeling of the deflection of a plane caused by a chemical reaction.Originality/value1. Independent governing equations for diffusion and reaction processes are given. 2. An exponential relation between the reaction rate and its driving force is employed. 3. The UEL subroutine is used to implement the finite element procedure.

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