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Search Results: 1 - 10 of 498238 matches for " Karim H. M. Youssef "
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Low Voltage Ride through Control Capability of a Large Grid Connected PV System Combining DC Chopper and Current Limiting Techniques  [PDF]
Ronald Ntare, Nabil H. Abbasy, Karim H. M. Youssef
Journal of Power and Energy Engineering (JPEE) , 2019, DOI: 10.4236/jpee.2019.71004
Abstract: This paper presents the development and performance capability of a comprehensive Low voltage ride through (LVRT) control scheme that makes use of both the DC chopper and the current limiting based on the required reactive power during fault time. The study is conducted on an 8.5 MW single stage PV power plant (PVPP) connected to the Rwandan grid. In the event of fault disturbance, this control scheme helps to overcome the problems of excessive DC-link voltage by fast activation of the DC chopper operation. At the same instance, AC current is limited to the maximum rating of the inverter as a function of the injected reactive current. This helps overcome AC-over- current that may possibly lead to damage or disconnection of the inverter. The control scheme also ensures voltage support and power balance through the injection of reactive current as per grid code requirements. Selected simulations using MATLAB are carried out in the events of different kinds of fault caused voltage dips. Results demonstrate the effectiveness of the proposed LVRT control scheme.
The Solution of Optimal Two-Impulse Transfer between Elliptical Orbits with Plane Change  [PDF]
M. H. A. Youssef
International Journal of Astronomy and Astrophysics (IJAA) , 2017, DOI: 10.4236/ijaa.2017.73010
Abstract: The optimizing total velocity increment Δv needed for orbital maneuver between two elliptic orbits with plane change is investigated. Two-impulse orbital transfer is used based on a changing of transfer velocities concept due to the changing in the energy. The transferring has been made between two elliptic orbits having a common centre of attraction with changing in their planes in standard Hohmann transfer with the terminal orbit which is elliptic orbit and not circular. We develop a treatment based on the elements of elliptic orbits a1,e1, a2,e2, and?aT,eT of the initial orbit, final orbit and transferred orbit respectively. The first impulse Δv1 at the perigee induces a rotation of the orbital plane by \"\"?which will be minimized. The second impulse Δv2 at apogee is induced an angle \"\"?to product the final elliptic orbit. The total plane change required \"\". We calculate the total impulse Δv and minimize by optimizing angle of plane’s variation \"\". We obtain a polynomial equation of six degrees on the two transfer angles between neither two elliptic orbits \"\"?and \"\". The solution obtained numerically, using programming code of MATHEMATICA V10, with no condition on the eccentricity or the semi-major axis of the initial, transformed, and the final orbits. We find that there are constrains on the transfer angles \"\"and α. For α it must be between 40° and 160°, and there is no solution if α is less than 40° and bigger than 160° and \"\"?takes the values less than 40°. The minimum total velocity increments obtained at the value of \"\"?less than 25° and& alpha; equal to 160°. This is an interesting result in orbital transfer problem in which the change of orbital plane is necessary for the transferring.
Short-Period and Long-Period Effects of Weak Gravitational Waves  [PDF]
M. H. A. Youssef
International Journal of Astronomy and Astrophysics (IJAA) , 2017, DOI: 10.4236/ijaa.2017.73019
Abstract: We compute the long-term orbital variation of a test particle orbiting a central body acted upon by normal incident of plane gravitational wave. We use the tools of celestial mechanics to give the first order solution of canonical equations of long-period and short-period terms of the perturbed Hamiltonian of gravitational waves. We consider normal incident of plane gravitational wave and characteristic size of bound—two body system (earth’s satellite or planet) is much smaller than the wavelength of the wave and the wave’s frequency nw is much smaller than the particle’s orbital np. We construct the Hamiltonian of the gravitational waves in terms of the canonical variables (l,g,h,L,G,H)?and we solve the canonical equations numerically using Runge-Kutta fourth order method using language MATHEMATICA V10. Taking Jupiter as practical example we found that there are long period perturbations on ω,Ω and i?and not changing with revolution and the short period perturbations on a, e and M?changing with revolution during the interval of time (tt0 ) which is changing from 04π.
Solar Radiation Pressure and Gravitational Waves Effects on Sun-Synchronous Orbits  [PDF]
M. H. A. Youssef
World Journal of Mechanics (WJM) , 2018, DOI: 10.4236/wjm.2018.82002
Abstract: For certain values of semi-major axis and eccentricity, orbit plane precession caused by Earth oblate is synchronous with the mean orbital motion of the apparent Sun (a sun-synchronism). Many forces cause slow changes in the inclination and ascending node of sun-synchronous orbits. In this work, we investigate the analytical perturbations due to the direct solar radiation pressure and gravitational waves effects. A full analytical solution is obtained using technique of canonical Lie-transformation up to the order three in (the oblateness of the Earth). The solar radiation pressure and gravitational waves perturbations cause second order effects on all the elements of the elliptic orbit (the eccentricity, inclination, ascending node, argument of perigee, and semi-major axis) consequently these perturbations will cause disturbance in the sun-synchronism. Also we found that the perturbation or the behavior of gravitational waves almost the same as the perturbation or the behavior of solar radiation pressure and their coupling will incorporate the sun-synchronism through the secular rate of the ascending node precession.
Numerical Studies of Resonance and Secular Effects of Gravitational Waves  [PDF]
M. H. A. Youssef
World Journal of Mechanics (WJM) , 2018, DOI: 10.4236/wjm.2018.85013
Abstract: This work deals with the numerical solution of the gravitational waves effects on the orbital elements of the planets in case of commensurability between the wave’s frequency ng and the planet’s mean motion np. Taking Mercury and Pluto as practical examples for low frequency and high frequency, the variations of the orbital elements of Mercury due to resonance of gravitational wave are different and small than the perturbation on Pluto. The amount of changing in the orbital elements under the effects of gravitational waves is different from planet to planet according to the planet’s mean motion np. For low frequency ng, the secular variation in orbital elements will be negative (i.e. decreasing) in the inclination, semi-major axis and the eccentricity (i, a, e) like as Pluto. For high frequency ng like Mercury, the secular variation in all the orbital elements will be positive (i.e. increasing). The perturbation on all the orbital elements of two planets is changing during each revolution except the eccentricity e of Mercury and the mean anomaly M of Mercury and Pluto during the time.
Vibration of gold nanobeam with variable thermal conductivity: state-space approach
H. M. Youssef
Applied Nanoscience , 2013, DOI: 10.1007/s13204-012-0158-9
Abstract: The non-Fourier effect in heat conduction and the coupling effect between temperature and strain rate are the two significant effects in the nanoscale beam. In the present work, the solution of vibration of gold nanobeam resonator induced by thermal shock is developed in the context of generalized thermoelasticity with variable thermal conductivity. State-space and Laplace transform methods are used to determine the lateral vibration, the temperature, the displacement, the strain, the stress, and the strain–stress energy. The numerical results have been studied and represented graphically with some comparisons to stand on the effects of the variability of thermal conductivity.
Secular Effect of Geomagnetic Field and Gravitational Waves on Earth’s Satellite Orbits  [PDF]
M. H. A. Youssef
Journal of Applied Mathematics and Physics (JAMP) , 2019, DOI: 10.4236/jamp.2019.78116
Abstract: In this work we study the perturbation and the change in the orbital elements due to the earth’s magnetic field and the gravitational waves. The acceleration components are derived in the radial, transverse to it and normal to the orbital plane. The equation for the rates of variation of the elements is formed and solved to find the secular variation in the element for polar and equatorial satellites.
Implementation of High Performance Electronic Circuits for Zero Suppression and Encoding of Digital Signals  [PDF]
Ashraf H. Yahia, Amr Radi, Salwa M. Youssef
Journal of Signal and Information Processing (JSIP) , 2015, DOI: 10.4236/jsip.2015.63022
Abstract: This paper presents a design of a data processing circuit for receiving digital signals from front end-electronic board chips of a specific nuclear detector, encoding and triggering them via specific optical links operating at a specific frequency. Such processed signals are then fed to a data acquisition system (DAQ) for analysis. Very high-speed integrated circuit hardware description language (VHDL) algorithms and codes were created to implement this design using field programmable gate array (FPGA) devices. The obtained data were simulated using international standard simulators.
Generalized Minimum Perpendicular Distance Square Method of Estimation  [PDF]
Rezaul Karim, Morshed Alam, M. M. H. Chowdhury, Forhad Hossain
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.312266
Abstract: In case of heteroscedasticity, a Generalized Minimum Perpendicular Distance Square (GMPDS) method has been suggested instead of traditionally used Generalized Least Square (GLS) method to fit a regression line, with an aim to get a better fitted regression line, so that the estimated line will be closest one to the observed points. Mathematical form of the estimator for the parameters has been presented. A logical argument behind the relationship between the slopes of the lines and has been placed.
Evolutions of the Ruled Surfaces via the Evolution of Their Directrix Using Quasi Frame along a Space Curve  [PDF]
M. A. Soliman, Nassar H. Abdel-All, R. A. Hussien, Taha Youssef
Journal of Applied Mathematics and Physics (JAMP) , 2018, DOI: 10.4236/jamp.2018.68149
Abstract: In this paper, evolutions of ruled surfaces generated by the quasi normal and quasi binormal vector fields of space curve are presented. These evolutions of the ruled surfaces depend on the evolutions of their directrix using quasi frame along a space curve.
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