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General Solutions for Hydromagnetic Free Convection Flow over an Infinite Plate with Newtonian Heating, Mass Diffusion and Chemical Reaction

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Communications in Theoretical Physics 2017年第12期67卷 768-782页

作者： Constatin Fetecau Nehad Ali Shah Dumitru Vieru academy of romanian scientists Abdus Salam School of Mathematical Sciences GC University Lahore Technical University of Iasi

The problem of hydromagnetic free convection flow over a moving infinite vertical plate with Newtonian heating, mass diffusion and chemical reaction in the presence of a heat source is completely solved. Radiative and porous effects are not taken into consideration but they can be immediately included by a simple rescaling of Prandtl number and magnetic parameter. Exact general solutions for the dimensionless velocity and concentration fields and the corresponding Sherwood number and skin friction coefficient are determined under integral form in terms of error function or complementary error function of Gauss. They satisfy all imposed initial and boundary conditions and can generate exact solutions for any problem with technical relevance of this type. As an interesting completion, uncommon in the literature, the differential equations which describe the thermal, concentration and momentum boundary layer, as well as the exact expressions for the thicknesses of thermal, concentration or velocity boundary layers were *** results have shown that the thermal boundary layer thickness decreases for increasing values of Prandtl number and the concentration boundary layer thickness is decreasing with Schmidt number. Finally, for illustration,three special cases are considered and the influence of physical parameters on some fundamental motions is graphically underlined and discussed. The required time to reach the flow according with post-transient solution(the steady-state),for cosine/sine oscillating concentrations on the boundary is graphically determined. It is found that, the presence of destructive chemical reaction improves this time for increasing values of chemical reaction parameter.

关键词： hydromagnetic free convection Newtonian heating heat source mass diffusion chemical reaction general solutions

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Evaluation on the corrosion resistance, antibacterial property and osteogenic activity of biodegradable Mg-Ca and Mg-Ca-Zn-Ag alloys

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Journal of Magnesium and Alloys 2022年第12期10卷 3380-3396页

作者： Hewei Chen Bo Yuan Rui Zhao Xiao Yang Zhanwen Xiao Antoniac Aurora Bita Ana Iulia Xiangdong Zhu Antoniac Vasile Iulian Xingdong Zhang National Engineering Research Center for Biomaterials Sichuan UniversityChengdu 610064China Faculty of Materials Science and Engineering University Politehnica of BucharestBucharest 060042Romania academy of romanian scientists Bucharest 050094Romania

The rapid degradation of magnesium(Mg)-based implants in physiological environment limits its clinical applications, and alloying treatment is an effective way to regulate the degradation rate of Mg-based materials. In the present study, three Mg alloys, including Mg-0.8Ca(denoted as ZQ), Mg-0.8Ca-5Zn-1.5Ag(denoted as ZQ71) and Mg-0.8Ca-5Zn-2.5Ag(denoted as ZQ63), were fabricated by alloying with calcium(Ca), zinc(Zn) and silver(Ag). The results obtained from electrochemical corrosion tests and in vitro degradation evaluation demonstrated that the three Mg alloys exhibited distinct corrosion resistance, and ZQ71 exhibited the lowest degradation rate in vitro among them. After addition of Zn and Ag, the antibacterial potential of Mg alloys was also enhanced. The in vitro cell experiments showed that all the three Mg alloys had good biocompatibility. After implantation in a rat femoral defect, ZQ71 showed significantly higher osteogenic activity and bone substitution rate than ZQ63 and ZQ, due to its higher corrosion resistance as well as the stimulatory effects of the released metallic ions. In addition, the average daily degradation rate of each Mg alloy in vivo was significantly higher than that in vitro, as could be due to the implantation site located in the highly vascularized trabecular region. Importantly, the correlations between the in vitro and in vivo degradation parameters of the Mg alloys were systematically analyzed to find out the potential predictors of the in vivo degradation performance of the materials. The current work not only evaluated the clinical potential of the three biodegradable Mg alloys as bone grafts but also provided a feasible approach for predicting the in vivo degradation behavior of biodegradable materials.

关键词： Mg alloys Degradability Antibacterial property Osteogenic ability Bone defect repair

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Magnesium-based alloys with adapted interfaces for bone implants and tissue engineering

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Regenerative Biomaterials 2023年第1期10卷 1632-1692页

作者： Iulian Antoniac Veronica Manescu(Paltanea) Aurora Antoniac Gheorghe Paltanea Faculty of Material Science and Engineering National University of Science and Technology POLITEHNICA Bucharest060042 BucharestRomania academy of romanian scientists 050094 BucharestRomania Faculty of Electrical Engineering National University of Science and Technology POLITEHNICA Bucharest060042 BucharestRomania

Magnesium and its alloys are one of the most used materials for bone implants and tissue *** are characterized by numerous advantages such as biodegradability,high biocompatibility and mechanical properties with values close to the human ***,the implant surface must be adequately tuned,or Mg-based alloys must be alloyed with other chemical elements due to their increased corrosion effect in physiological *** article reviews the clinical challenges related to bone repair and regeneration,classifying bone defects and presenting some of the most used and modern therapies for bone injuries,such as Ilizarov or Masquelet techniques or stem cell *** implant interface challenges are related to new bone formation and fracture healing,implant degradation and hydrogen release.A detailed analysis of mechanical properties during implant degradation is extensively described based on different literature studies that included in vitro and in vivo tests correlated with material properties’***-based trauma implants such as plates and screws,intramedullary nails,Herbert screws,spine cages,rings for joint treatment and regenerative scaffolds are presented,taking into consideration their manufacturing technology,the implant geometrical dimensions and shape,the type of in vivo or in vitro studies and fracture *** technologies that modify or adapt the Mg-based implant interfaces are described by presenting the main surface microstructural modifications,physical deposition and chemical conversion *** last part of the article provides some recommendations from a translational perspective,identifies the challenges associated with Mg-based implants and presents some future *** review outlines the available literature on trauma and regenerative bone implants and describes the main techniques used to control the alloy corrosion rate and the cellular environment of the implant.

关键词： adapted interfaces bone tissue engineering fracture healing Mg-based alloys surface modifications

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Results in Sizing and Simulation of PV Applications Based on Different Solar Cell Technologies

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Journal of Power and Energy Engineering 2017年第1期5卷 63-74页

作者： Alexandru Diaconu Laurentiu Fara Paul Sterian Dan Craciunescu Silvian Fara University Politehnica Bucharest Romania academy of romanian scientists Bucharest Romania

Modeling and simulation of photovoltaic (PV) systems represents an essential task for the integration of PV panels in current power applications. At the present time, there are sizing tools of photovoltaic systems available on the market, taking into account the proposed energy consumption, site localization and system cost. An advanced specialized program (PVSyst) was considered. The sizing and simulations of two PV important applications were developed using PV modules based on three different technologies: monocrystalline and polycrystalline silicon, as well as CIS. Our results showed how different types of solar cell technologies influenced the final power output and performances for a PV LED lighting, as well as for a PV water pumping system, in terms of overall yield, efficiency and system availability.

关键词： Photovoltaic Simulations Monocrystalline Polycrystalline Copper Indium Selenide Solar Cells Photovoltaic Lighting Photovoltaic Water Pumping System

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Numerical Analysis of an Industrial Polycrystalline Silicon Photovoltaic Module Based on the Single-Diode Model Using Lambert W Function

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Journal of Power and Energy Engineering 2019年第7期7卷 29-38页

作者： Mihai Razvan Mitroi Valerica Ninulescu Laurentiu Fara Dan Craciunescu University Politehnica of Bucharest BucharestRomania academy of romanian scientists BucharestRomania

It is adopted the single-diode solar cell model and extended for a PV module. The current vs. voltage (I-V) characteristic based on the Lambert W-function was used. The estimation parameters for the simulation approach of the photovoltaic (PV) module make use of Levenberg-Marquardt method. It was considered an industrial polycrystalline silicon photovoltaic (PV) module and the simulated results were compared with the experimental ones extracted from a specific datasheet. The I-V characteristic for the analysed PV module and its maximum output power are investigated for different operating conditions of incident solar radiation flux and temperature, as well as parameters related to the solar cells material and technology (series resistance, shunt resistance and gamma factor). The analysis gives indications and limitations for design and optimization of the performance for industrial PV modules. This study can be implemented in any type of PV module.

关键词： Single-Diode Model Electrical Modeling I-V Characteristic Numerical Analysis Industrial PV Module Performance

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Three-dimensional mixed convection stagnation-point fow past a vertical surface with second-order slip velocity

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Applied Mathematics and Mechanics(English Edition) 2023年第4期44卷 641-652页

作者： A.V.ROSCA N.C.ROSCA I.POP Department of Statistics-Forecasts-Mathematics Faculty of Economics and Business AdministrationBabes-Bolyai UniversityCluj-Napoca 400084Romania Department of Mathematics Faculty of Mathematics and Computer ScienceBabes-Bolyai UniversityCluj-Napoca 400084Romania academy of romanian scientists 3 Ilfov StreetBucharest 050044Romania

This study is concerned with the three-dimensional(3D)stagnation-point for the mixed convection flow past a vertical surface considering the first-order and secondorder velocity *** the authors’knowledge,this is the first study presenting this very interesting *** partial differential equations for the flow problem are transformed into nonlinear ordinary differential equations(ODEs)by using appropriate similarity *** ODEs with the corresponding boundary conditions are numerically solved by utilizing the bvp4c solver in MATLAB programming *** effects of the governing parameters on the non-dimensional velocity profiles,temperature profiles,skin friction coefficients,and the local Nusselt number are presented in detail through a series of graphs and ***,it is reported that the reduced skin friction coefficient decreases for the assisting flow situation and increases for the opposing flow *** numerical computations of the present work are compared with those from other research available in specific situations,and an excellent consensus is *** exciting feature for this work is the existence of dual *** important remark is that the dual solutions exist for both assisting and opposing flows.A linear stability analysis is performed showing that one solution is stable and the other solution is not *** notice that the mixed convection and velocity slip parameters have strong effects on the flow *** effects are depicted in graphs and discussed in this *** obtained results show that the first-order and second-order slip parameters have a considerable effect on the flow,as well as on the heat transfer characteristics.

关键词： three-dimensional(3D)mixed convection flow stagnation point flow first-order slip velocity second-order slip velocity numerical solution stability analysis

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Non-axisymmetric Homann stagnation-point flow of Walter’s B nanofluid over a cylindrical disk

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Applied Mathematics and Mechanics(English Edition) 2020年第5期41卷 725-740页

作者： M.KHAN M.SARFRAZ J.AHMED L.AHMAD C.FETECAU Department of Mathematics Quaid-i-Azam UniversityTaxila 47050Pakistan Department of Basic Sciences University of Engineering and TechnologySheringal Upper Dir 18000Pakistan Department of Mathematics Shaheed Benazir Bhutto UniversitySheringal Upper Dir 18000Pakistan academy of romanian scientists Bucuresti 050094Romania

The study of non-axisymmetric Homann stagnation-point flow of Walter’s B nanofluid along with magnetohydrodynamic(MHD) and non-linear Rosseland thermal radiation over a cylindrical disk in the existence of the time-independent free stream is considered. Moreover, the notable impacts of thermophoresis and Brownian motion are analyzed by Buongiorno’s model. The momentum, energy, and concentration equations are converted into the dimensionless coupled ordinary differential equations via similarity transformations, which are later numerically solved by altering the values of the pertinent parameters. The numerical and asymptotic solutions for the large shear-to-strain rate ratio γ =a/bfor the parameters of the displacement thicknesses and the wall-shear stress are computed by perturbative expansion and analyzed. Furthermore, the technique bvp4c in MATLAB is deployed as an efficient method to analyze the calculations for the non-dimensional velocities, temperature, displacement thickness, and concentration profiles. It is observed that the two-dimensional displacement thickness parameters α andβ are reduced due to the viscoelasticity and magnetic field effects. Moreover, when the shear-to-strain rate ratio approaches infinity, α is closer to its asymptotic value, while βand the three-dimensional displacement thickness parameter δ1 show the opposite *** outcomes of the viscoelasticity and the magnetic field on the skin friction are also determined. It is concluded that ■ reaches its asymptotic behavior when the shearto-strain rate ratio approaches infinity. Meanwhile, ■ shows different results.

关键词： Walter’s B fluid cylindrical disk nanofluid magnetic field non-linear thermal radiation stagnation-point flow

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A semiclassical perspective on nuclear chirality

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Frontiers of physics 2024年第2期19卷 39-52页

作者： Radu Budaca “Horia Hulubei”National Institute for R&D in Physics and Nuclear Engineering Str.Reactorului 30RO-077125POB-MG6 Bucharest-MǎgureleRomania academy of romanian scientists Splaiul Independenţei 54050044BucharestRomania

The application of the semiclassical description to a particle-core system with imbued chiral symmetry is *** classical features of the chiral geometry in atomic nuclei and the associated dynamics are investigated for various core deformations and single-particle *** dynamical characteristics are identified in specific angular momentum ranges,triaxiality and alignment *** observables will be extracted from the classical picture for a quantitative description of experimental data provided as numerical examples of the model’s performance.

关键词： chiral symmetry triaxial nuclei semiclassical description

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Peristaltic Flow of Couple Stress Fluid in a Non-Uniform Rectangular Duct Having Compliant Walls

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Communications in Theoretical Physics 2016年第1期65卷 66-72页

作者： R.Ellahi M.Mubashir Bhatti C.Fetecau K.Vafai Department of Mechanical Engineering University of California Riverside Riverside USA Department of Mathematics and Statistics FBAS IIUI Islamabad Pakistan Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200444 China Department of Mathematics Technical University of Iasi Romania Academy of Romanian Scientists 050094 Bucuresti Romania

The present study investigates the peristaltic flow of couple stress fluid in a non-uniform rectangular duct with compliant *** modeling is based upon the laws of mass and linear *** solutions are carried out by the eigen function expansion method under long-wavelength and low-Reynolds number *** features of the flow characteristics are analyzed by plotting the graphs of various values of physical parameters of *** bolus scheme is also presented through streamlines.

关键词： peristaltic flow couple stress fluid compliant walls eigen function expansion method analyticalsolutions

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Construction of a magnesium hydroxide/graphene oxide/hydroxyapatite composite coating on Mg-Ca-Zn-Ag alloy to inhibit bacterial infection and promote bone regeneration

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Bioactive Materials 2022年第12期7卷 354-367页

作者： Bo Yuan Hewei Chen Rui Zhao Xuangeng Deng Guo Chen Xiao Yang Zhanwen Xiao Antoniac Aurora Bita Ana Iulia Kai Zhang Xiangdong Zhu Antoniac Vasile Iulian Shen Hai Xingdong Zhang National Engineering Research Center for Biomaterials Sichuan UniversityChengdu610064China College of Biomedical Engineering Sichuan UniversityChengdu610064China Sichuan Provincial Orthopedic Hospital Chengdu610041China Faculty of Materials Science and Engineering University Politehnica of Bucharest060042BucharestRomania academy of romanian scientists 050094BucharestRomania

The improved corrosion resistance, osteogenic activity, and antibacterial ability are the key factors for promoting the large-scale clinical application of magnesium (Mg)-based implants. In the present study, a novel nanocomposite coating composed of inner magnesium hydroxide, middle graphene oxide, and outer hydroxyapatite (Mg(OH)_(2)/GO/HA) is constructed on the surface of Mg-0.8Ca-5Zn-1.5Ag by a combined strategy of hydrothermal treatment, electrophoretic deposition, and electrochemical deposition. The results of material characterization and electrochemical corrosion test showed that all the three coatings have high bonding strength, hydrophilicity and corrosion resistance. In vitro studies show that Mg(OH)2 indeed improves the antibacterial activity of the substrate. The next GO and GO/HA coating procedures both promote the osteogenic differentiation of MC3T3-E1 cells and show no harm to the antibacterial activity of Mg(OH)2 coating, but the latter exhibits the best promoting effect. In vivo studies demonstrate that the Mg alloy with the composite coating not only ameliorates osteolysis induced by bacterial invasion but also promotes bone regeneration under both normal and infected conditions. The current study provides a promising surface modification strategy for developing multifunctional Mg-based implants with good corrosion resistance, antibacterial ability and osteogenic activity to enlarge their biomedical applications.

关键词： Mg alloy Composite coating Corrosion resistance Antibacterial ability Osteogenic activity

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