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On special Curves According to Darboux Frame in the Three Dimensional Lorentz space

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Computers, Materials & Continua 2018年第3期54卷 229-249页

作者： h.s.abdel-aziz M.Khalifa saad Math.Dept. Faculty of ScienceSohag University82524 SohagEgypt. Math.Dept. Faculty of ScienceIslamic University of Madinah170 El MadinahKSA

In the light of great importance of curves and their frames in many differentbranches of science, especially differential geometry as well as geometric properties andthe uses in various fields, we are interested here to study a special kind of curves calledsmarandache curves in Lorentz 3-space. Then, we present some characterizations for thesecurves and calculate their Darboux invariants. Moreover, we classify TP, TU, PU andTPU-smarandache curves of a spacelike curve according to the causal character of thevector, curve and surface used in the study. Besides, we give some of differential geometricproperties and important relations between that curves. Finally, to demonstrate ourtheoretical results a computational example is given with graph.

关键词： smarandache curves spacelike curve timelike surface Darboux frame

some Geometric Invariants of Pseudo-spherical Evolutes in the hyperbolic 3-space

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Computers, Materials & Continua 2018年第12期57卷 389-415页

作者： h.s.abdel-aziz M.Khalifa saad A.A.abdel-salam Mathematics Department Faculty of ScienceSohag University82524SohagEgypt Mathematics Department Faculty of ScienceIslamic University of Madinah170 El-MadinahKSA

In this paper,we study the pseudo-spherical evolutes of curves in three dimensional hyperbolic *** use techniques from singularity theory to investigate the singularities of pseudo-spherical evolutes and establish some relationships between singularities of these curves and geometric invariants of curves under the action of the Lorentz ***,we defray with illustration some computational examples in support our main results.

关键词： Pseudo-spherical evolutes evolute curves hyperbolic 3-space

Crosstalk between androgen signaling and the chemokine receptor CXCR4:a novel strategy to promote myelin regeneration

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Neural Regeneration Research 2025年第9期20卷 2581-2582页

作者： Marianne Bardy-Lagarde Narimène Asbelaoui abdel Mouman Ghoumari UMR1195 “Diseases and Hormones of the Nervous System”Inserm and University Paris-SaclayKremlin-BicêtreFrance

Multiple sclerosis(Ms)is the most common chronic disease of the central nervous system(CNs)in young adults and represents the first cause of severe handicap,originally non-traumatic(Oh et al.,2018).Ms is chara cterized by the infiltration of auto reactive lymphocytes specific to myelin through the blood-brain barrier,which results in the appearance of inflammatory demyelinating lesions caused by the death of the central nervous system myelinating cells,oligodendrocytes(Oh et al.,2018).There is a prevalence sexual with a ratio of three times more affected women than men.

关键词： myelin CXCR4

Two paths, one goal: mechanism of calcium homeostasis to balance plant growth and immunity

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science China Life sciences 2025年第1期 306-308页

作者： aziz Ul Ikram Yanping Jing huan Chen Jian Chen International Genome Center Jiangsu University Joint Center for single Cell Biology School of Agriculture and BiologyShanghai Jiao Tong University

Calcium(Ca2+) is an essential nutrient and a cellular signal in plants. The level of free Ca2+in the apoplast is ～10,000-fold higher than that in the cytoplasm at the resting state. This large Ca2+level gradient across the membrane between the interior and exterior can cause Ca2+overload and toxicity. Plants have evolved mechanisms to export Ca2+out of the cytoplasm or store it in intracellular organelles, such as endoplasmic reticulum（ER）, mitochondria, and vacuole.

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Attitude dynamics and control of spacecraft using geomagnetic Lorentz force

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Research in Astronomy and Astrophysics 2015年第1期15卷 127-144页

作者： Yehia A.abdel-aziz Muhammad shoaib National Research Institute of Astronomy and Geophysics (NRIAG) Helwan Cairo 11721Egypt University of hail Department of Mathematics PO BOX 2440 Kingdom of Saudi Arabia

Attitude stabilization of a charged rigid spacecraft in Low Earth Orbit using torques due to Lorentz force in pitch and roll directions is considered. A spacecraft that generates an electrostatic charge on its surface in the Earth’s magnetic field will be subject to perturbations from the Lorentz force. The Lorentz force acting on an electrostatically charged spacecraft may provide a useful thrust for controlling a spacecraft’s orientation. We assume that the spacecraft is moving in the Earth’s magnetic field in an elliptical orbit under the effects of gravitational, geomagnetic and Lorentz torques. The magnetic field of the Earth is modeled as a non-tilted dipole.A model incorporating all Lorentz torques as a function of orbital elements has been developed on the basis of electric and magnetic fields. The stability of the spacecraft orientation is investigated both analytically and numerically. The existence and stability of equilibrium positions is investigated for different values of the charge to mass ratio（α＊）. stable orbits are identified for various values of α＊. The main parameters for stabilization of the spacecraft are α＊and the difference between the components of the moment of inertia for the spacecraft.

关键词： space vehicles atmospheric effects celestial mechanics kinematics and dynamics

Equilibria of a charged artificial satellite subject to gravitational and Lorentz torques

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Research in Astronomy and Astrophysics 2014年第7期14卷 891-902页

作者： Yehia A.abdel-aziz Muhammad shoaib National Research Institute of Astronomy and Geophysics (NRIAG) HelwanCairo 11721Egypt University of hail Department of MathematicsPO Box 2440Kingdom of Saudi Arabia

The attitude dynamics of a rigid artificial satellite subject to a gravity gradient and Lorentz torques in a circular orbit are considered. Lorentz torque is developed on the basis of the electrodynamic effects of the Lorentz force acting on the charged satellite＇s surface. We assume that the satellite is moving in a Low Earth Orbit in the geomagnetic field, which is considered to be a dipole. Our model of torque due to the Lorentz force is developed for an artificial satellite with a general shape, and the nonlinear differential equations of Euler are used to describe its attitude orientation. All equilibrium positions are determined and conditions for their existence are *** numerical results show that the charge q and radius ρ0of the center of charge for the satellite provide a certain type of semi-passive control for the attitude of the satellite. The technique for this kind of control would be to increase or decrease the electrostatic screening on the satellite. The results obtained confirm that the change in charge can affect the magnitude of the Lorentz torque, which can also affect control of the satellite. Moreover, the relationship between magnitude of the Lorentz torque and inclination of the orbit is investigated.

关键词： space vehicles -- atmospheric effects -- celestial mechanics -- kine-matics and dynamics

Encoderless Five-phase PMa-synRM Drive system Based on Robust Torque-speed Estimator with super-twisting sliding Mode Control

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CEs Transactions on Electrical Machines and systems 2023年第1期7卷 54-62页

作者： Ghada A.abdel aziz Rehan Ali Khan Power Electronics and Energy Conversion Department Electronics Research InstituteCairo11843Egypt Department of Electrical Engineering University of Science&TechnologyBannu28100Pakistan IEEE

In this paper,a robust torque speed estimator(RTsE)for linear parameter changing(LPC)system is proposed and designed for an encoderless five-phase permanent magnet assisted synchronous reluctance motor(5-phase PMa-synRM).This estimator is utilized for estimating the rotor speed and the load torque as well as can solve the speed sensor fault problem,as the feedback speed information is obtained directly from the virtual *** addition,this technique is able to enhance the 5-phase PMa-synRM performance by estimating the load torque for the real time *** stability analysis of the proposed estimator is performed via schur complement along with Lyapunov ***,for improving the 5-phase PMa-synRM performance,five super-twisting sliding mode controllers(sT-sMCs)are employed with providing a robust response without the impacts of high chattering problem.A super-twisting sliding mode speed controller(sT-sMsC)is employed for controlling the PMa-synRM rotor speed,and four super-twisting sliding mode current controllers(sT-sMCCs)are employed for controlling the 5-phase PMa-synRM *** stability analysis and the experimental results indicate the effectiveness along with feasibility of the proposed RTsE and the sT-sMsC with sT-sMCCs approach for a 750-W 5-phase PMa-synRM under load disturbance,parameters variations,single open-phase fault,and adjacent two-phase open circuit fault conditions.

关键词： Five-phase permanent magnet assisted synchronous reluctance motor Encoderless control supertwisting sliding mode control Torque-speed estimator

Adaptive Gain Tuning Rule for Nonlinear sliding-mode speed Control of Encoderless Three-phase Permanent Magnet Assisted synchronous Motor

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CEs Transactions on Electrical Machines and systems 2023年第3期7卷 301-310页

作者： Ghada A.abdel aziz Rehan Ali Khan IEEE Power Electronics and Energy Conversion Department Electronics Research InstituteCairo 11843Egypt Department of Electrical Engineering University of Science&TechnologyBannuPakistan.

In this paper, an adaptive gain tuning rule is designed for the nonlinear sliding mode speed control(NsMsC) in order to enhance the dynamic performance and the robustness of the permanent magnet assisted synchronous reluctance motor(PMa-syn RM) with considering the parameter uncertainties. A nonlinear sliding surface whose parameters are altering with time is designed at first. The proposed NsMsC can minimize the settling time without any overshoot via utilizing a low damping ratio at starting along with a high damping ratio as the output approaches the target set-point. In addition, it eliminates the problem of the singularity with the upper bound of an uncertain term that is hard to be measured practically as well as ensures a rapid convergence in finite time, through employing a simple adaptation law. Moreover, for enhancing the system efficiency throughout the constant torque region, the control system utilizes the maximum torque per ampere technique. The nonlinear sliding surface stability is assured via employing Lyapunov stability theory. Furthermore, a simple sliding mode estimator is employed for estimating the system uncertainties. The stability analysis and the experimental results indicate the effectiveness along with feasibility of the proposed speed estimation and the NsMsC approach for a 1.1-k W PMa-syn RM under different speed references, electrical and mechanical parameters disparities, and load disturbance conditions.

关键词： Permanent magnet assisted synchronous reluctance motor Nonlinear sliding mode speed control speed estimation Parameter uncertainties sliding mode estimator

Electromagnetic effects on the orbital motion of a charged spacecraft

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Research in Astronomy and Astrophysics 2014年第5期14卷 589-600页

作者： Yehia Ahmed abdel-aziz Khalil Ibrahim Khalil National Research Institute of Astronomy and Geophysics (NRIAG) Helwan Cairo 11721Egypt Department of Mathematics Hail University Hail 2440 Kingdom of Saudi Arabia

This paper deals with the effects of electromagnetic forces on the orbital motion of a spacecraft. The electrostatic charge which a spacecraft generates on its surface in the Earth＇s magnetic field will be subject to a perturbative Lorentz force. A model incorporating all Lorentz forces as a function of orbital elements has been developed on the basis of magnetic and electric fields. This Lorentz force can be used to modify or perturb the spacecraft＇s orbits. Lagrange＇s planetary equations in the Gauss variational form are derived using the Lorentz force as a perturbation to a Keplerian orbit. Our approach incorporates orbital inclination and the true anomaly. The numer- ical results of Lagrange＇s planetary equations for some operational satellites show that the perturbation in the orbital elements of the spacecraft is a second order perturba- tion for a certain value of charge. The effect of the Lorentz force due to its magnetic component is three times that of the Lorentz force due to its electric component. In addition, the numerical results confirm that the strong effects are due to the Lorentz force in a polar orbit, which is consistent with realistic physical phenomena that occur in polar orbits. The results confirm that the magnitude of the Lorentz force depends on the amount of charge. This means that we can use artificial charging to create a force to control the attitude and orbital motion of a spacecraft.

关键词： space vehicles -- atmospheric effects -- celestial mechanics -- kine-matics and dynamics