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OPTIMAL ERROR ESTIMATES FOR NEDELEC EDGE ELEMENTS FOR TIME-HARMONIC MAXWELL'S EQUATIONS

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Journal of Computational Mathematics 2009年第5期27卷 563-572页

作者： Liuqiang Zhong Shi Shu gabriel Wittum Jinchao Xu School of Mathematical and Computational Sciences Xiangtan University Xiangtan 411105 China Simulation and Modelling Goethe- Center for Scientic Computing Goethe-University Kettenhofweg 139 60325 Frankfurt am Main Germany Department of Mathematics Pennsylvania State University University Park PA 16802 USA

In this paper, we obtain optimal error estimates in both L^2-norm and H（curl）-norm for the Nedelec edge finite element approximation of the time-harmonic Maxwell＇s equations on a general Lipschitz domain discretized on quasi-uniform meshes. One key to our proof is to transform the L^2 error estimates into the L^2 estimate of a discrete divergence-free function which belongs to the edge finite element spaces, and then use the approximation of the discrete divergence-free function by the continuous divergence-free function and a duality argument for the continuous divergence-free function. For Nedelec＇s second type elements, we present an optimal convergence estimate which improves the best results available in the literature.

关键词： Edge finite element Time-harmonic Maxwell's equations.

Fluidization of binary mixtures of sisal residue and sand:A new model for deriving the final fluidization velocity

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Particuology 2018年第5期16卷 10-22页

作者： David Vasconcelos gabriele Batalha Luis gabriel Pereira Carlos Augusto Pires Chemical Reaction Engineering Laboratory Federal University of Bahia40.210-910SalvadorBABrazil

The influence of different factors on the fiuidization of a binary mixture of sisal residue and sand was *** particle sizes of the sand and sisal residue were varied from 0.2to 0.8mm and the biomass mass fractions from 2% to 9%.Some segregation was noted,and a significant relationship was found among the final fluidization velocity (Uff),the biomass and sand sizes,and the biomass mass fraction.A novel model was developed for predicting Uff,leading to an average discrepancy of 12.69% between the measured and predicted Uff compared with the best match of 15.32% when using a model from a previous *** new model was applied to data from studies using other biomass and a broad range of particle *** average divergences from measured values when using the new model were 7.9% for corn cob and walnut shell,and 20.5% for sweet sorghum bagasse,tobacco residue, and soy *** were superior to the values derived using other *** results confirm the accuracy of the model developed in this work and show that it represents a viable alternative way to calculate Uff for a binary mixture of sand and biomass.

关键词： Fluidization Binary mixture Sisal residue Final fluidization velocity model

Experimental and numerical study of pseudo-2D circulating fluidized beds

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Particuology 2016年第6期14卷 48-59页

作者： Adam Klimanek Wojciech Adamczyk Sirpa Kallio Pawet Kozolub gabriel Wecel Institute of Thermal Technology Silesian University of TechnologyKonarskiego 22 44-100 Gliwice Poland Technical Research Centre of Finland Ltd P.O. Box 1000 FI-02044 VTT Finland Amec Foster Wheeler Staszica 31 41-200 Sosnowiec Poland

We present experimental investigations and numerical simulations of a pseudo-2D riser. Experiments were performed for various airflow rates, particle types/diameters, and particle size distributions. Pres- sure distributions along the wall of the riser were measured, Additional measurements from a smaller pseudo-2D riser （Kallio et al., 2009; Shah et al., 2012） were used to analyze horizontal solids volume fraction profiles. The experimental data were compared with simulation results carried out using an Euler-Euler approach, A mesh sensitivity study was conducted for numerical simulations and effects associated with simplifying real 3D geometry to a 2D model were examined. In addition, the effect of using an algebraic equation to represent the granular temperature versus a full partial differential equation also was examined for numerical simulations. Results showed small but significant near-wall sensitivity of the flow variables to mesh size. Substantial differences in mean pressure, solids distribution, and solid velocities were obtained, when 2D and 3D simulation results were compared. Finally, applying the simplified granular temperature equation for turbulent fluidization and for dilute-phase transport can lead to incorrect predictions in models,

关键词： Circulating fluidized bed Euler-Euler approachGas-solid flow Kinetic theory of granular flow Particle size distribution 2D vs 3D

Fuzzy logic controller implementation on a microbial electrolysis cell for biohydrogen production and storage

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Chinese Journal of Chemical Engineering 2021年第12期34卷 149-159页

作者： gabriel Khew Mun Hong Mohd Azlan Hussain Ahmad Khairi Abdul Wahab Department of Chemical Engineering Faculty of EngineeringUniversiti Malaya50603 Kuala LumpurMalaysia Department of Biomedical Engineering Faculty of EngineeringUniversiti Malaya50603 Kuala LumpurMalaysia Centre for Separation Science and Technology(CSST) Faculty of EngineeringUniversiti Malaya50603 Kuala LumpurMalaysia

This work presents the implementation of fuzzy logic control(FLC) on a microbial electrolysis cell(MEC).Hydrogen has been touted as a potential alternative source of energy to the depleting fossil fuels. MEC is one of the most extensively studied method of hydrogen production. The utilization of biowaste as its substrate by MEC promotes the waste to energy initiative. The hydrogen production within the MEC system, which involves microbial interaction contributes to the system's nonlinearity. Taking into account of the high complexity of MEC system, a precise process control system is required to ensure a wellcontrolled biohydrogen production flow rate and storage application inside a tank. Proportionalderivative-integral(PID) controller has been one of the pioneer control loop mechanism. However, it lacks the capability to adapt properly in the presence of disturbance. An advanced process control mechanism such as the FLC has proven to be a better solution to be implemented on a nonlinear system due to its similarity in human-natured thinking. The performance of the FLC has been evaluated based on its implementation on the MEC system through various control schemes progressively. Similar evaluations include the performance of Proportional-Integral(PI) and PID controller for comparison purposes. The tracking capability of FLC is also accessed against another advanced controller that is the model predictive controller(MPC). One of the key findings in this work is that the FLC resulted in a desirable hydrogen output via MEC over the PI and PID controller in terms of shorter settling time and lesser overshoot.

关键词： Fuzzy logic control Process control Nonlinear Microbial electrolysis cell Renewable energy Hydrogen

A MIXED VIRTUAL ELEMENT METHOD FOR THE BOUSSINESQ PROBLEM ON POLYGONAL MESHES

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Journal of Computational Mathematics 2021年第3期39卷 392-427页

作者： gabriel N.Gatica Mauricio Munar Filander A.Sequeira CI^2 MA and Departamento de Ingenieria Matemitica Universidad de ConcepcionCasilla 160-CConcepcionChile Escuela de Matemaitica Universidad NacionalCampus Omar DengoHerediaCosta Rica

In this work we introduce and analyze a mixed virtual element method(mixed-VEM)for the two-dimensional stationary Boussinesq *** continuous formulation is based on the introduction of a pseudostress tensor depending nonlinearly on the velocity,which allows to obtain an equivalent model in which the main unknowns are given by the aforementioned pseudostress tensor,the velocity and the temperature,whereas the pressure is computed via a postprocessing *** addition,an augmented approach together with a fixed point strategy is used to analyze the well-posedness of the resulting continuous *** the discrete problem,we follow the approach employed in a previous work dealing with the Navier-Stokes equations,and couple it with a VEM for the convection-diffusion equation modelling the *** precisely,we use a mixed-VEM for the scheme associated with the fluid equations in such a way that the pseudostress and the velocity are approximated on virtual element subspaces of H(div)and H^(1),respectively,whereas a VEM is proposed to approximate the temperature on a virtual element subspace of H^(1).In this way,we make use of the L^(2)-orthogonal projectors onto suitable polynomial spaces,which allows the explicit integration of the terms that appear in the bilinear and trilinear forms involved in the scheme for the fluid *** the other hand,in order to manipulate the bilinear form associated to the heat equations,we define a suitable projector onto a space of polynomials to deal with the fact that the diffusion tensor,which represents the thermal conductivity,is ***,the corresponding solvability analysis is performed using again appropriate fixed-point ***,Strang-type estimates are applied to derive the a priori error estimates for the components of the virtual element solution as well as for the fully computable projections of them and the postprocessed *** corresponding rates of convergence are als

关键词： Boussinesq problem Pseudostress-based formulation Augmented formulation Mixed virtual element method.High-order approximations

A short climatology of black and brown carbon and their sources at a suburban site impacted by smoke in Brazil

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Journal of Environmental Sciences 2024年第2期136卷 498-511页

作者： Admir Creso Targino Patricia Krecl gabriel Yoshikazu Oukawa Eva Maria Mollinedo Graduate Program in Environmental Engineering Federal University of TechnologyAv.Pioneiros 3131LondrinaPR 86036-370Brazil Department of Environmental Engineering Federal University of TechnologyAv.Pioneiros 3131LondrinaPR 86036-370Brazil

Emissions from biomass burning challenge efforts to curb air pollution in cities downwind of fire-prone regions,as they contribute large amounts of brown carbon(Br C)and black carbon(BC)*** investigated the patterns of Br C and BC concentrations using Aethalometer data(atλ=370 and 880 nm,respectively)spanning four years at a site impacted by the outflow of *** data required to be post processed for the shadowing effect since,without correction,concentrations would be between 29%and 35%*** Br C concentrations were consistently higher than the BC concentrations,indicating the prevalence of aerosols from biomass *** results were supported by the Angstrom coefficient(A_(370/880)),with values predominantly larger than 1(mean±standard deviation:1.25±0.31).A_(370/880)values below 1 were more prevalent during the wet season,which suggests a contribution from fossil fuel *** observed sharp Br C and BC seasonal signals,with mean minimum concentrations of 0.40μg/m^(3)and 0.36μg/m^(3),respectively,in the wet season,and mean maximum concentrations of 2.05μg/m^(3)and 1.53μg/m^(3)in the dry *** largest concentrations were observed when northerly air masses moved over regions with a high density of fire *** burning of residential solid waste and industrial combustion caused extreme Br C and BC concentrations under favourable wind *** neither pollutant is included in any ambient air quality standards,our results suggest that transboundary smoke may hamper efforts to meet the World Health Organization guidelines for fine particles.

关键词： Light-absorbing carbonaceous matter Black carbon Wildfires Biomass burning Aethalometer

FINITE ELEMENT METHOD ON NUMERICAL SIMULATION OF STRATUM CORNEUM'S PENETRATION PROPERTY

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Applied Mathematics and Mechanics(English Edition) 2006年第4期27卷 469-475页

作者：刘宇红乔爱科 Dirk Feuchter gabriel Wittum 曾衍钧 Biomechanics and Medical Information Institute Beijing University of Technology Beijing 100022P. R. China Technical Simulation Group of the Interdisciplinary Center for Scientific Computing of University Heidelberg Im neuen Heimerfeld 36869120Germany Technical Simulation Group of the Interdisciplinary Center for Scientific Computing of University Heidelberg Im neuen Heimerfeld 368 69120Germany

How the outer substance could penetrate through the skin lies in the stratum corneum, because it is the main barrier in the multi-layers of the skin. Supposing the keratin cell with a special geometry as tetrakaidecahedron, the penetration property of stratum corneum was the key problem which was numerically simulated with finite element method. At first the discretization of the stratum corneum region was given in two steps： first, the discretization of the keratin cell; second, the discretization of fattiness that surrounds the keratin. Then there was the work of numerical simulation. In this procedure, the finite element method and the multi-grid method were used. The former was to obtain the discretization of basic elements; the latter was to decrease the high frequency error. At last the visualization of the numerical simulation was shown.

关键词： stratum corneum tetrakaidecahedron discretization finite element method multi-grid method

Preparation and Characterization of Fe-Based Metallic Glasses with Pure and Raw Elements

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Chinese Physics Letters 2012年第11期29卷 207-210页

作者： Nassima Seghairi Badis Bendjemil gabriel Lavorato Alberto Castellero Marcello Baricco Dipartimento di Chimica I.F.M/NIS/CNISM/INSTM Universitàdi TorinoVia Giuria 910125 TrinoItaly University of Larbi Ben M'hidi Oum El BouaghiAlgeria LASEA Faculty of SciencesDepartment of ChimistryUniversity of AnnabaAlgeria University of Guelma P.O.Box 1224000 GuelmaAlgeria

Amorphous alloys with a composition(at.%)Fe_(48)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2) were prepared by using either pure elements(alloy B1)or a commercial AISI430 steel as a base material(B2).When prepared from pure elements,alloy(B1)could be cast in plate form with a fixed thickness of 2 mm and variable lengths between 10 and 20 mm by means of copper-mold injection in an air *** the case of alloy B2,prepared by using commercial grade raw materials,rods of 2 mm diameter are ***(B1 and B2)of width 5 mm and thickness about 30μm are prepared from the arc-melted ingots using a single roller melt spinner at a wheel speed of 40 m/*** thermal and structural properties of the samples are measured by a combination of differential scanning calorimetry(DSC),x-ray diffraction and scanning electron *** compositions are checked by energy dispersive spectroscopy analysis.X-ray diffraction and scanning electron microscopy observations confirm that an amorphous structure is obtained in all the samples.A minor fraction of crystalline phases(oxides and carbides)is detected on the as-cast *** of hardness and Young modulus were measured by nanoindentation for both the *** effects of adverse casting conditions(such as air atmosphere,non-conventional injection copper mold casting and the partial replacement of pure elements with commercial grade raw materials)on the glass formation and properties of the alloy are discussed.

关键词： alloy casting roller

Anti-viral and anti-inflammatory effects of kaempferol and quercetin and COVID-2019:A scoping review

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Asian Pacific Journal of Tropical Biomedicine 2021年第8期11卷 327-334页

作者： Mohammad Reza Khazdair Akbar Anaeigoudari gabriel A.Agbor Cardiovascular Diseases Research Center Birjand University of Medical SciencesBirjandIran Department of Physiology Jiroft University of Medical SciencesJirofIran Center for Research on Medicinal Plants and Traditional Medicine Institute of Medical Research and Medicinal Plants StudiesMinistry of Scientific Research and InnovationsYaoundeCameroon

Severe acute respiratory syndrome coronavirus type 2(SARS-CoV-2)is a novel coronavirus identified at the end of *** is recognized as the causative agent of coronavirus disease 2019(COVID-19).Flavonoids have been shown to exhibit therapeutical effect on complications related to *** present study reviews possible therapeutic benefits of flavonoids on *** Web of Science,PubMed,Scopus,and Google Scholar were searched using keywords:“COVID-19”,“SARS-CoV-2”,“Kaempferol”and“Quercetin”in the Title/*** published articles in the English language until August 2020 were *** and quercetin showed antiviral properties such as inhibition of protein kinase B and phosphorylation of protein kinase and blocking effects on a selective channel(3a channel)expressed in SARS-CoV infected *** also reduced the level of reactive oxygen species,expression of inducible nitric oxide synthase,pro-inflammatory mediators including TNF-α,IL-1α,IL-1β,IL-6,IL-10,and IL-12 p70,and *** and quercetin might exert beneficial effects in the control or treatment of COVID-19 because of their antiviral,antioxidant,anti-inflammatory,and immunomodulatory effects.

关键词： SARS-CoV-2 Flavonoids Kaempferol Quercetin Immunomodulation Anti-inflammatory Antiviral effects