A non-classical model for transversely isotropic magneto-electro-elastic circular Kirchhoff plates is established based on the extended modified couple stress theory.The Gibbs-type variational principle is used to obt...A non-classical model for transversely isotropic magneto-electro-elastic circular Kirchhoff plates is established based on the extended modified couple stress theory.The Gibbs-type variational principle is used to obtain the governing equations and boundary cond计ions.To illustrate the newly derived model,the static bending problem of a clamped circular plate subjected to a uniformly distributed constant load is solved numerically by Fourier-Bessel series.The numerical results show that the values of transverse displacement,electric and magnetic potentials predicted by the current model are always smaller than those of the classical model,and the differences are diminishing as the plate thickness increases.In addition,it is shown that the magneto-electro-elastic coupling effect plays an important role in the transverse displace-ment,elec trie pot ential and magnetic pot ential of the magne to-elec tr o-elastic circular Kirchhoff plates.Furthermore,several reduced specific models are provided for simpler cases.展开更多
This work deals with the modeling of the unsteady Newtonian fluid flow associated with an open cylindrical reservoir.This reservoir presents a hole on the right bottom wall.Fluid volume variation,heat and mass transfe...This work deals with the modeling of the unsteady Newtonian fluid flow associated with an open cylindrical reservoir.This reservoir presents a hole on the right bottom wall.Fluid volume variation,heat and mass transfers are neglected.The unsteady governing equations are based on the conservation of mass and momentum.A finite volume technique is used to solve the non-dimensional equations and related boundary conditions.The algebraic system of equations resulting from the discretization process are solved by means of the THOMAS algorithm.For pressure-velocity coupling,the SIMPLE algorithm(Semi Implicit Method for Pressure Linked Equations)is used.Results for laminar flow(Re<1000),including the pressure and velocities profiles as well as the streamlines in the reservoir are presented.Moreover,the effects of the D/d and H0/D ratios and Reynolds number Re on the fluid flow are discussed.It is shown that the velocities and pressure depend essentially on the reservoir size.To validate the model,the present results have been compared with Zhou et al.’s results,Poiseuille’s and Bernoulli’s exact solution.展开更多
Normally large amounts of particles are required to accurately simulate the metal cutting process,which consumes a lot of computing time and storage.Adaptive techniques can help decrease the number of particles,hence ...Normally large amounts of particles are required to accurately simulate the metal cutting process,which consumes a lot of computing time and storage.Adaptive techniques can help decrease the number of particles,hence reducing the runtime.This paper presents a novel adaptive smoothed particle hydrodynamics(SPH)method for the metal cutting simulation.The spatial resolution changes adaptively according to the distance to the tool tip by the particle splitting and merging.More particles are selected in the region where the workpiece and the tool are in contact.Since the contact region constantly changes during the cutting process,two quadrilateral frames are adopted in the adaptive algorithm to dynamically change the distribution of particles.One frame for the refinement,the other for the coarsening.These frames move at the same speed as the tool.To test the computational efficiency,the metal cutting process is simulated by using SPH with three different adaptive approaches.Numerical results show that the proposed adaptive algorithm with dynamic refinement and coarsening can significantly optimize the runtime.展开更多
A finite element model is proposed permitting prediction of elastic wave bandgaps of periodic composite microplates incorporating flexoelectric effect.In this model,we applied curvature-based flexoelectricity and Mind...A finite element model is proposed permitting prediction of elastic wave bandgaps of periodic composite microplates incorporating flexoelectric effect.In this model,we applied curvature-based flexoelectricity and Mindlin plate theories and derived a finite element formulation that has been implemented for bandgap analysis.The finite element model utilizes a three-node triangle element with 30 degrees of freedom satisfying Mindlin kinematics assumptions.It is based on a non-conforming interpolation scheme which provides nodal C^(1) continuity and ensures compatibility with curvature-based flexoelectricity.The approach accounts for microstructure effects and,owing to the triangular element topology,can be used to assist the design of microplates with complex microstructures.Validation of the approach is performed through comparison with both analytical and numerical models,in which the effect of flexoelectricity on the bandgap is studied based on cases demonstrating size dependence.展开更多
The aim of this study was to assess the physico-chemical and mineralogical quality of surface waters used by populations for their domestic and agro-pastoral activities in the Nyanga district in the south-west of the ...The aim of this study was to assess the physico-chemical and mineralogical quality of surface waters used by populations for their domestic and agro-pastoral activities in the Nyanga district in the south-west of the Republic of the Congo.Descriptive statistics,hydrochemistry(Piper diagram),Principal Component Analysis(PCA)and hierarchical ascending classification(HAC)were used to determine the quality,chemical facies and mineralization phenomena of surface waters.Physico-chemical analyses were carried out on 6 samples taken in May 2023.The results showed that the waters studied are acidic,with a pH between 4.99 and 5.76.They are poorly mineralized,with an average electrical conductivity of 12.37μS/cm.In the study area,the water is chloride-calcium-magnesium and bicarbonate-calcium-magnesium.Analysis of heavy metals shows that all values,with the exception of iron and nitrate,comply with WHO guidelines on water potability,with the exception of the point sampled at the confluence of the Nyanga,where values were slightly higher than normal,i.e.0.06μg/L for manganese and 0.03μg/L for nitrate.Other heavy metals such as Lead(Pb)and Copper(Cu)were analyzed and confirmed that their concentration was within the authorized detection limits.Water mineralization is controlled by phenomena such as soil rainwashing,acid hydrolysis of rocks and input from high rainfall.This study shows that water resources in the Nyanga watershed are not subject to anthropogenic pressure,but to a totally natural phenomenon.Given its acidity,untreated consumption of this water could present health risks for the population.展开更多
基金The work reported here is funded by the National Natural Science Foundation of China[Grant Numbers 12002086 and 11672099]。
文摘A non-classical model for transversely isotropic magneto-electro-elastic circular Kirchhoff plates is established based on the extended modified couple stress theory.The Gibbs-type variational principle is used to obtain the governing equations and boundary cond计ions.To illustrate the newly derived model,the static bending problem of a clamped circular plate subjected to a uniformly distributed constant load is solved numerically by Fourier-Bessel series.The numerical results show that the values of transverse displacement,electric and magnetic potentials predicted by the current model are always smaller than those of the classical model,and the differences are diminishing as the plate thickness increases.In addition,it is shown that the magneto-electro-elastic coupling effect plays an important role in the transverse displace-ment,elec trie pot ential and magnetic pot ential of the magne to-elec tr o-elastic circular Kirchhoff plates.Furthermore,several reduced specific models are provided for simpler cases.
文摘This work deals with the modeling of the unsteady Newtonian fluid flow associated with an open cylindrical reservoir.This reservoir presents a hole on the right bottom wall.Fluid volume variation,heat and mass transfers are neglected.The unsteady governing equations are based on the conservation of mass and momentum.A finite volume technique is used to solve the non-dimensional equations and related boundary conditions.The algebraic system of equations resulting from the discretization process are solved by means of the THOMAS algorithm.For pressure-velocity coupling,the SIMPLE algorithm(Semi Implicit Method for Pressure Linked Equations)is used.Results for laminar flow(Re<1000),including the pressure and velocities profiles as well as the streamlines in the reservoir are presented.Moreover,the effects of the D/d and H0/D ratios and Reynolds number Re on the fluid flow are discussed.It is shown that the velocities and pressure depend essentially on the reservoir size.To validate the model,the present results have been compared with Zhou et al.’s results,Poiseuille’s and Bernoulli’s exact solution.
基金the National Natural Science Foundation of China(Grant Nos.12002290 and 11772274).
文摘Normally large amounts of particles are required to accurately simulate the metal cutting process,which consumes a lot of computing time and storage.Adaptive techniques can help decrease the number of particles,hence reducing the runtime.This paper presents a novel adaptive smoothed particle hydrodynamics(SPH)method for the metal cutting simulation.The spatial resolution changes adaptively according to the distance to the tool tip by the particle splitting and merging.More particles are selected in the region where the workpiece and the tool are in contact.Since the contact region constantly changes during the cutting process,two quadrilateral frames are adopted in the adaptive algorithm to dynamically change the distribution of particles.One frame for the refinement,the other for the coarsening.These frames move at the same speed as the tool.To test the computational efficiency,the metal cutting process is simulated by using SPH with three different adaptive approaches.Numerical results show that the proposed adaptive algorithm with dynamic refinement and coarsening can significantly optimize the runtime.
文摘A finite element model is proposed permitting prediction of elastic wave bandgaps of periodic composite microplates incorporating flexoelectric effect.In this model,we applied curvature-based flexoelectricity and Mindlin plate theories and derived a finite element formulation that has been implemented for bandgap analysis.The finite element model utilizes a three-node triangle element with 30 degrees of freedom satisfying Mindlin kinematics assumptions.It is based on a non-conforming interpolation scheme which provides nodal C^(1) continuity and ensures compatibility with curvature-based flexoelectricity.The approach accounts for microstructure effects and,owing to the triangular element topology,can be used to assist the design of microplates with complex microstructures.Validation of the approach is performed through comparison with both analytical and numerical models,in which the effect of flexoelectricity on the bandgap is studied based on cases demonstrating size dependence.
文摘The aim of this study was to assess the physico-chemical and mineralogical quality of surface waters used by populations for their domestic and agro-pastoral activities in the Nyanga district in the south-west of the Republic of the Congo.Descriptive statistics,hydrochemistry(Piper diagram),Principal Component Analysis(PCA)and hierarchical ascending classification(HAC)were used to determine the quality,chemical facies and mineralization phenomena of surface waters.Physico-chemical analyses were carried out on 6 samples taken in May 2023.The results showed that the waters studied are acidic,with a pH between 4.99 and 5.76.They are poorly mineralized,with an average electrical conductivity of 12.37μS/cm.In the study area,the water is chloride-calcium-magnesium and bicarbonate-calcium-magnesium.Analysis of heavy metals shows that all values,with the exception of iron and nitrate,comply with WHO guidelines on water potability,with the exception of the point sampled at the confluence of the Nyanga,where values were slightly higher than normal,i.e.0.06μg/L for manganese and 0.03μg/L for nitrate.Other heavy metals such as Lead(Pb)and Copper(Cu)were analyzed and confirmed that their concentration was within the authorized detection limits.Water mineralization is controlled by phenomena such as soil rainwashing,acid hydrolysis of rocks and input from high rainfall.This study shows that water resources in the Nyanga watershed are not subject to anthropogenic pressure,but to a totally natural phenomenon.Given its acidity,untreated consumption of this water could present health risks for the population.
