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Conduction properties of condensed lanthanum phosphates:La(PO_3)_3 and LaP_5O_(14)

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Journal of Rare Earths 2010年第3期28卷 321-328页

作者： Ines Hammas Karima Horchani-Naifer mokhtar férid Research Unit of Rare Earth Materials National Research Center in Sciences of MaterialsB.P.95 Hammam-Lif2050Tunisia

Single crystals of LaP3O9·3H2O were prepared using a classical method of aqueous chemistry whereas those of the ultraphosphate LaP5O14 were obtained by flux *** treatment of LaP3O9·3H2O up to 700 °C allowed us to obtain the lanthanum polyphosphate La(PO3)*** conductivity as well as the vibrational study of the lanthanum ultraphosphate and polyphosphate were analysed in order to explain the mechanism of *** energies of 0.45 and 0.84 eV,deduced from the Arrhenius relation,were r...

关键词： condensed lanthanum phosphates electrical conductivity Grotthuss mechanism rare earths

Combustion synthesis and luminescence properties of LaPO4： Eu （5%）

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Journal of Rare Earths 2009年第2期27卷 182-186页

作者： Mounir ferhi Karima Horchani-Naifer mokhtar férid Research Unit of Rare Earth Materials National Research Center in Sciences of Materials B.P. 95 Hammam-Lif 2050 Tunisia

Rare earth doped materials are an important type of phosphors due to their excellent performance such as stability at high temperature and light emission covering the entire visible domain. The combustion synthesis at acid pH of the monoclinic LaPO4： Eu（5%） powders was described. A mixture of La（NO3）3·6H2O, EuCly6H2O and （NH4）2HPO4 was used as anion precursor and glycin as fuel. The synthesis was followed by structure, morphology characterisation and luminescent properties of the obtained compound. The room temperature emission measurements under ultraviolet excitation at 254 nm were made for the emission transition ^5D0→^7fJ of this phosphor. The CIE （Commission Intemationale de L＇Eclairage） chromatic coordinates, dominant wavelength and colour purity were determined and compared to other luminescent materials obtained by other methods.

关键词： rare earth phosphates combustion optical materials luminescence chromaticity

Crystal structure and infrared spectrum of thallium holmium polyphosphate, TlHo(PO_3)_4

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Journal of Rare Earths 2008年第6期26卷 765-769页

作者： Karima Horchani-Naifer Jaouher Amami mokhtar férid Unité de Recherches de Matériaux de Terres Rares Centre National de Recherches en Sciences des Matériaux

Crystals of thallium-holmium polyphosphate T1Ho（PO3）4 were grown by flux method technique and characterized by single crystal X-ray diffraction. Structure of T1Ho（PO3）4 was solved for the first time, and it crystallized in the monoclinic P21/n space group with the following unit-cell dimensions： a=1.02225（3） nm, b=0.88536（2） nm, c=1.09541（4） nm, β=105.888（1）°, V=0.95354（5） nm^3 and Z=4. The crystal structure was solved from 2174 independent reflections with final R1（f^2）=0.0442 and Rw（f^2）=0.0861 refined with 164 parameters. The atomic arrangement could be described as a long chain polyphosphate organization. Holmium atoms had eightfold coordination. The structure of T1Ho（PO3）4 consisted of HoO8 polyhedra sharing oxygen atoms with phosphoric group PO4. Infrared spectrum was investigated at room temperature in the frequencies range, 350--4000 cm^-1, showing some characteristic vibration bands of infinite chain structure of PO4 tetrahedra linked by bridging oxygen.

关键词： polyphosphate holmium crystal structure infrared spectroscopy rare earths

Wave propagation of a functionally graded plate via integral variables with a hyperbolic arcsine function

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Earthquake Engineering and Engineering Vibration 2024年第3期23卷 547-561页

作者： mokhtar Ellali mokhtar Bouazza Ashraf M.Zenkour Smart structures Laboratory University of Ain TemouchentAin Temouchent 46000Algeria Department of Civil Engineering University Tahri Mohamed of BecharBechar 08000Algeria Department of Mathematics Faculty of ScienceKing Abdulaziz UniversityJeddah 21589Saudi Arabia Laboratory of Materials and Hydrology(LMH) University of Sidi Bel AbbesSidi Bel Abbes 22000Algeria Department of Mathematics Faculty of ScienceKafrelsheikh UniversityKafrelsheikh 33516Egypt

Several studies on functionally graded materials(fGMs)have been done by researchers,but few studies have dealt with the impact of the modification of the properties of materials with regard to the functional propagation of the waves in *** work aims to explore the effects of changing compositional characteristics and the volume fraction of the constituent of plate materials regarding the wave propagation response of thick plates of *** model is based on a higher-order theory and a new displacement field with four unknowns that introduce indeterminate integral variables with a hyperbolic arcsine *** fGM plate is assumed to consist of a mixture of metal and ceramic,and its properties change depending on the power functions of the thickness of the plate,such as linear,quadratic,cubic,and inverse *** utilizing Hamilton’s principle,general formulae of the wave propagation were obtained to establish wave modes and phase velocity curves of the wave propagation in a functionally graded plate,including the effects of changing compositional characteristics of materials.

关键词： fGM plate effects of material properties wave propagation indeterminate integral variables inverse sinus hyperbolic function

Viscous falling film instability around a vertical moving cylinder

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Acta Mechanica Sinica 2012年第2期28卷 253-265页

作者： Kadry Zakaria yasser Gamiel Department of Mathematics Faculty of ScienceTanta UniversityTantaEgypt Department of Engineering Mathematics and Physics Faculty of EngineeringTanta UniversityTantaEgypt

The present work discusses both the linear and nonlinear stability conditions of a viscous falling film down the outer surface of a solid vertical cylinder which moves in the direction of its axis with a constant velocity. After studying the linear conditions, a generalized nonlinear kine- matic model is then derived to present the physical system. Applying the boundary conditions, analytical solutions are obtained using the long-wave perturbation method. In the first step, the normal mode method is used to characterize the linear behaviors. In the second step, the nonlinear film flow model is solved by using the method of multiple scales, to obtain Ginzburg-Landau equation. The influence of some physical parameters is discussed in both linear and nonlinear steps of the problem, and the results are displayed in many plots showing the stability criteria in various param- eter planes.

关键词： Newtonian fluids Viscous fluids falling filmstability Ginzburg-Landau equation

Evaluation of the remaining lateral torsional buckling capacity in corroded steel members

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第11期11卷 887-897页

作者： yasser SHARIfI Reza RAHGOZAR Department of Civil Engineering Kerman University

Corrosion is one of the main causes of deterioration in steel structures. Loss of thickness in flanges and web of corroded steel beams leads to reduction in section properties which can reduce the lateral torsional buckling capacity of the member. In this paper, thickness loss data were compiled from four samples of corrosion damaged I-beams removed from a petro-chemical plant. Visual examination of the four corroded beams showed that they were corroded uniformly. To improve the accuracy of the results, a large number of measurements for surface roughness were taken for each beam, totally 770 values to obtain the average thickness of flanges and web of each beam. The data was used to develop a corrosion decay model in order to calculate the percentage remaining lateral torsional buckling capacity of long and short span beams which are laterally unrestrained. To estimate the percentage of remaining lateral torsional buckling capacity in the corroded damaged I-beams, the readily available minimum curves for different types of universal beams in conjunction with information on the thickness loss were used. The results can be used by practicing engineers for better estimation on the service life of deteriorated steel structures.

关键词： Corrosion Steel structures Lateral torsional buckling Beams

Dynamics of Optical Bistability with Kerr-nonlinear Blackbody Radiation Reservoir

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Communications in Theoretical Physics 2017年第4期67卷 435-442页

作者： yasser A.Sharaby Suez University Faculty of SciencesPhysics DepartmentSuezEgypt

In this paper we investigate the nonlinear dynamics for optical bistabile(OB) model of homogeneously broadened two-level atomic medium interacting with a single mode of the ring cavity in the presence of a Kerr-nonlinear blackbody(KNB) radiation reservoir. We show the impact of the relative temperature of the reservoir on the transition between the dynamical states via bifurcation diagrams that represents the relation between maximum values of the output field and the relative temperature for fixed input field. Specifically, decreasing the relative temperature(T_b)causes the system to bifurcate from periodic to chaotic behavior and in turn reverts back to periodic behavior with further decrease of T_b. Varying atomic detuning leads to a change in the nature of the dynamic transition between the system's states from self pulsing to chaotic behavior.

关键词： optical bistability Kerr-nonlinear blackbody reservoir bifurcation nonlinear dynamics self pulsing chaos

An Efficient fuzzy Logic fault Detection and Identification Method of Photovoltaic Inverters

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Computers, Materials & Continua 2021年第5期67卷 2283-2299页

作者： mokhtar Aly Hegazy Rezk Department of Electrical Engineering Aswan UniversityAswan81542Egypt Electronics Engineering Department Universidad Tecnica Federico Santa MariaValparaiso2390123Chile College of Engineering at Wadi Addawaser Prince Sattam Bin Abdulaziz UniversityWadi Addawaser11991Saudi Arabia Electrical Engineering Department Faculty of EngineeringMinia UniversityMinia61111Egypt

fuzzy logic control(fLC)systems have found wide utilization in several industrial *** paper proposes a fuzzy logic-based fault detection and identification method for open-circuit switch fault in grid-tied photovoltaic(PV)*** installations and ambitious plans have been recently achieved for PV systems as clean and renewable power generation sources due to their improved environmental impacts and availability *** converters represent the main parts for the grid integration of PV ***,PV power converters contain several power switches that construct their *** power switches in PV systems are highly subjected to high stresses due to the continuously varying operating ***,the grid-tied systems represent nonlinear systems and the system model parameters are changing ***,the grid-tied PV systems have a nonlinear factor and the fault detection and identification(fDI)methods based on using mathematical models become more *** proposed fuzzy logic-based fDI(fL-fDI)method is based on employing the fuzzy logic concept for detecting and identifying the location of various switch *** proposed fL-fDI method is designed and extracted from the analysis and comparison of the various measured voltage/current components for the control ***,the proposed fL-fDI method does not require additional components or measurement ***,the proposed method can detect the faulty condition and also identify the location of the faulty switch for replacement and maintenance *** proposed method can detect the faulty condition within only a single fundamental line period without the need for additional sensors and/or performing complex calculations or precise *** proposed fL-fDI method is tested on the widely used T-type PV inverter system,wherein there are twelve different switches and the fDI process represents a challenging *** results sho

关键词： fault detection and identification fuzzy logic T-type inverter photovoltaic(PV)

Portable device for the local three-dimensional deformation measurement using a single camera

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Science China(Technological Sciences) 2018年第1期61卷 51-60页

作者： MOHAMMED mokhtar Eisa SHAO XinXing HE XiaoYuan School of Civil Engineering Department of Engineering Mechanics Southeast University

The aim of this paper is to establish and validate a portable device for the local three dimensional deformation measurements using a single camera combined with a triangular prism mirror and two mirrors. The mirrors were utilized to convert a single camera into a stereo image system, which views a test object from two different directions and records the surface images of the test specimen on the two halves of the camera sensor in order to achieve a three-dimensional measurement. The proposed system consists of a single camera and the reflection system was integrated into a portable device to achieve a truly portable, low-cost, local three-dimensional deformation measurement, one-time calibration and easy implementation in situ. The optical design and measurement procedures to obtain the three-dimensional （3D） deformation measurements of the proposed system were described in detail. The efficiency and precision of the proposed system were verified by measuring the displacements of a translated fiat plate. As a practical application, the proposed system is used to measure the out-of-plane displacement of an aluminum circular plate with a central load. Moreover, the normal strain measurement of a plastic beam under symmetric four-point bending via an outer loading frame was also presented. The measurement results are in good accordance with the data obtained by strain gauges. The experimental results revealed that the proposed system was practicable and effective for the local three-dimensional deformation measurement. This system well-suited to both laboratory and field condition and will have significant application in the fields of engineering.

关键词： digital image correlation single camera strain analysis local 3D deformation