Filter by type:

Sort by year:

Propagation of surface waves at the interface between nonlinear MTMs and anisotropic materials

Journal paper
Hala J. El-Khozondar, Rifa J. El-Khozondar, Said Zouhdi
Applied Physics A: Material Science and processing, Volume 115, Issue 2, 2014, Pages 439-442

Abstract

Metamaterials (MTMs), which have both negative permeability and negative permittivity, have potential applications in optoelectronics and communications. These materials are fabricated in laboratories which is an added advantage. The focus of this work is on the propagation of surface waves at the interface between nonlinear MTMs and anisotropic materials in the optical range. The dispersion equation is derived from Maxwell’s equations. The dispersion equation is solved numerically to study the characteristics of the propagated wave. Only TE modes are considered. The results display the dependence of the propagating waves on the characteristics of the structure composite materials.

Keywords

Metamaterials, surface waves, nonlinear, dispersion equation, nisotropic materials

Numerical simulation of grain size distribution in two-phase polycrystalline materials

Journal paper
Rifa J. El-Khozondar, Dana Zӧllner, Klaus Kassner
International Journal of Materials Science and Applications, Volume 3, Issue 6, December 2014, Pages 381-390

Abstract

Numerical simulations based on the Monte Carlo Potts model are used to study the temporal change of the grain size
distribution of two-phase polycrystalline materials, where both phases grow simultaneously. After a sufficiently long time, grain growth in such two-phase systems can be characterized by a self-similar scaled grain size distribution function and an associated growth law. In particular, the grain size distribution is analyzed for a broad range of second phase volume fractions and found to vary with the volume fraction such that the size distribution becomes narrower and higher peaked with decreasing volume fraction of the second phase, where particularly the normal distribution function describes the simulation results very well. On the other hand, for one-phase systems the grain size distribution is in excellent agreement with an analytical grain size distribution function based on a statistical mean-field theory of grain growth that is completely compatible with the principal physical condition of total volume conservation.

Keywords

Monte Carlo, Grain Growth, Grain Size Distribution, Grain Structure, Polycrystalline Materials

Tunable MTMs consists of a single-walled nanotube thin film waveguide covered by nonlinear cladding

Journal paper
Hala J. El-Khozondar, Rifa J. El-Khozondar, Said Zouhdi
Applied Physics A: Material Science and processing, Volume 119, Issue 2, January 2015, Pages 451-453

Abstract

A theoretical approach to study fabrication of tunable metamaterials (MTMs) consists of a single-walled nanotube film sandwiched between nonlinear cladding and linear substrate. In the proposed waveguide, the dispersion equation is derived. Numerical calculation is carried out to draw the effective refractive index for transverse electric modes. The effective refractive index as function of frequency is plotted at different values of nonlinearity. Based on the results, the proposed structure can be used as tunable MTMs.

Keywords

Tunable, metamaterials, nanotube, nonlinear, waveguide, dispersion, refractive index

Matlab/Simulink Modeling to study the effect of partially shaded condition on Photovoltaic array's Maximum Power Point

Journal paper
Khaled Matter, Hala J. El-Khozondar , Rifa J. El-Khozondar, Teuvo Suntio
International Research Journal of Engineering and Technology (IRJET), Volume 02, ssue 02, May 2015, Pages 697-703

Abstract 

Solar energy is an important source of renewable energy due to the easy access to the source. One drawback in this system is achieving the maximum efficiency of the system. The photovoltaic (PV) cell is the fundamental unit in the power conversion of the solar system. The extracted maximum output power of PV cell reduces when it exposes to partial shading causing remarkable reduction in the efficiency of the system. In this work, PV modules under various shading condition is simulated using Matlab/Simulink. Results show that the power-voltage (P-V) characteristic of PV modules exhibit several local maximum power points (MPP) in comparison with unique MPP in case of full insolation causing more complication to the system and a noticeable reduction in the efficiency of the system.

Keywords

PV, MPP, Partial shading, Matlab simulation.

Towards a successful startup company: Best successful team components

Journal paper
Teejan T. El-Khazendar, Rifa J. El-Khozondar
American Journal of Theoretical and Applied Statistics, Volume 4, Issue 1-1, December 2014, Pages 9-14

Abstract

Entrepreneurship became an important sector in the Arab world. A lot of young entrepreneurs have ambitious projects and creative ideas, which they hope to get fund and incubation to implement these ideas. There are three incubators in Gaza which provide the required incubation, training and fund. Entrepreneurs personality characters have a big effect on the success of their startup companies; moreover, the startup companies category plays a big role on the success of their startup companies especially in small markets such as in Gaza. So we have to find a way to discover which is the most successful ideas and under which category can be classified with paying tight attention for the characters of the team members for each idea. They should have some traits which qualify this team seems to be successful. In the present paper, we are using computing approach based on data mining techniques to study one of the business fields to produce a business technique that helps in extraction the association rules for the incubated startup companies in Gaza. Moreover, we will study these association rules to understand and help the incubators in Gaza to avoid the failed ideas and teams as possible as it could be. Therefore, the incubators will be able to improve the incubation and entrepreneurship sector and increase the number of successful startup companies in Gaza and reduce the wasted fund and time on failed startups

Keywords

Entrepreneurship, Entrepreneurs, Incubation, Data Mining, Fund, Startup

Monte Carlo Potts Simulation of Grain Growth of Solid Grains Dispersed in a Liquid Matrix

Journal paper
Rifa J. El-Khozondar, Hala J. El-Khozondar
JOURNAL OF ENGINEERING RESEARCH AND TECHNOLOGY, March 2015, Volume 2, Issue 1, Pages 7-14

Abstract

Liquid phase sintering is a process in which solid grains coexist with a liquid matrix. This
process has important applications in processing of several engineering materials. Examples of these
applications are high-speed metal cutting tools, alumina substrates for packaging silicon chips and barium
titanate electrical capacitor. Grain growth in liquid phase sintered materials occurs by Ostwald ripening. The
purpose of this paper is developing Monte Carlo Potts model to simulate Ostwald ripening in liquid-phase
sintered materials. Ostwald ripening is simulated by treating two phases, solid grains dispersed in a liquid
matrix as a two-dimensional square array of sites. Each site of the solid-phase grains (phase A) is given a
random positive number between 1 and Q where Q=100 for all the simulation. The sites of the liquid phase
(phase B) are assigned only one negative number, qB = -1. It is found that the grain growth is controlled by
volume diffusion for volume fraction of the solid grains ranging from 40% to 90%. The grain growth
exponent has the value, n=3, in agreement with the theoretical value of Ostwald ripening.
Keywords

Monte Carlo, Potts model, grain growth, grain size, sintering, Ostwald ripening.

Simulation and Implementation of Incremental Conductance Maximum Power Point Tracking Algorithm for Photovoltaic System

Journal paper
Hala J. El-Khozondar, Rifa J. El-Khozondar, and Khalid H. Matter
Journal of Mechatronics, Volume 3, Issue 2, 2015, Pages 174–178

Abstract

In this work, we simulate a photovoltaic (PV) array to obtain maximum power point (MPP) of the
system. We used an incremental conductance (IC) algorithm to track MPP. We gave a detailed
explanation of IC tracking system algorithm. In addition, we used MATLAB simulation results. Simulation results show the accuracy of the results since we obtained output power equals 200.13 W.
We expected 200.143 W. Also, we did not get any oscillation around the output value. Thus we
recommend IC for fast and accurate results.
Keywords

photovoltaic, Incremental Conductance, maximum power point, output power, MATLAB simulation

Parameters influence on MPP value of the photo voltaic cell

Journal paper
Hala J. El-Khozondar, Rifa J. El-Khozondar, Khaled Matter
Energy Procedia, Volume 74, 2015, Pages 1142 – 1149

Abstract

Solar energy is an important alternate to traditional energy sources to generate electrical power. Electrical power is extracted from solar energy via photovoltaic (PV) cell. However, PV cell maximum output power (MPP) depends on different parameters including weather conditions and internal components of the system. To achieve MPP, we used MatLab simulation to study the effect of the various parameters on PV performance. Results showed that MPP strongly depends on sun irradiance, shunt resistance, series resistance, temperature and ideal factor. These results might be used as a guide to PV system users.

Keywords

Solar energy, electrical power, photovoltaic, weather conditions, maximum output power, sun irradiance

Metamaterial-dielectric photonics crystal waveguide structure

Journal paper
Hala J. El-Khozondar, Rifa J. El-Khozondar, Mohammed M. Shabat
Optics. Special Issue: Optical Engineering & Applications, Volume 4, issue 1-2, January 2015, pages 1-4

Abstract

Photonic crystals (PCs) are a revolutionary science that has a great impact on the field of photonics. In purpose of extend the applications of PCs, we introduce a new photonic structure which is composed of alternating lamellae of MTMs and Dielectric. The electromagnetic waves propagating through photonic crystal structures are numerically investigated. Results show improvement in the characteristics of the photonic crystal.

Keywords

Photonic crystals, lamellae, Metamaterials, Dielectric, electromagnetic waves

Design of Voltage control Oscillator using Nonlinear Composite Right/Left-Handed Transmission Line

Journal paper
Hala J. El-Khozondar, Mahmoud Abu-Marasa, Rifa J. El-Khozondar, Mady Elbahri, Said Zouhdi
ADVANCED ELECTROMAGNETICS, Volume 5, issue 1, March 2016, 15-21

Abstract

In the present work, we propose a voltage control oscillator (VCO) at high frequency consists of nonlinear composite
right/left-handed transmission line (CRLH-TL) loaded with Resonant Tunneling Diode (RTD). We designed three
prototype device examples. The first one consists of one cell with short circuit at the beginning of the cell between
ground and patch, and 50 Ω load resistance were added at the end of the cell between ground and patch. The second
one is similar to the first prototype but with open circuit at the beginning of the cell instated of short circuit. The third prototype consists of one cell with two 50 Ω load resistances added between ground and patch at the beginning and at the end of the cell. The proposed VCO models are capable of generating oscillations at frequencies between 4.87- 14.9 GHz.
In our simulations, we used OrCAD and ADS software to analyze the proposed circuit.

Keywords

voltage control oscillator, transmission line, nonlinear composite, Resonant Tunneling Diode, short circuit

Grain Size Distribution and topological correlations During Ostwald Ripening: Monte Carlo Potts model simulation

Journal paper
1. Rifa J. El-Khozondar, Hala J. El-Khozondar
Al-Aqsa University Journal, Volume 20, January 2016, Pages 44-60

Abstract

Practically most polycrystalline materials such as ceramics are sintered by liquid during processing; for example, tungsten carbide applied for cutting tools. In liquid sintering, grain structure is controlled by Ostwald ripening. In this work, the Monte Carlo Potts model is employed to simulate Ostwald ripening in solid-liquid mixture. Based on the computer simulation, the grain size distribution and the topological correlations were analyzed for a series of volume fraction of the solid grains varies between 40% – 90%.

It is found that after a long time within the quasi-stationary state, the scaled grain size distribution and the topological distribution of grain sides keep invariant with time. It is further shown that the scaled grain size distribution can be described very well with the normal distribution function. Whereas at high volume fractions, the scaled grain size distribution is in very good agreement with an analytical grain size distribution function based on a statistical mean-field theory of grain growth. Moreover, the grain size distribution is found to be dependent on the volume fraction of the solid grains. It becomes more peaked as the volume fraction increases.

Keywords

grain size distribution, Monte Carlo Potts model, polycrystalline materials, Ostwald ripening, topological correlations

Grain Size Distribution and topological correlations During Ostwald Ripening: Monte Carlo Potts model simulation

Journal paper
Rifa J. El-Khozondar, Hala J. El-Khozondar
International Journal of Engineering Science Invention, Volume 6, Issue 1, January 2017, Pages 29-37

bstract

Numerical simulations based on the Monte Carlo Potts model are used to study coupling of grain
growth and Ostwald ripening in two-phase polycrystalline materials. The ratio of the grain boundary energy to
the interphase boundary energy is used as an input parameter. It is shown that the grain growth in two-phase
polycrystalline materials is controlled by long-range diffusion and the change of the mean grain size with time
obeys the growth law, <R>n = <R>0n+kt where n is the grain growth exponent. The value of n is calculated for
a broad series of volume fractions. It is found that the inverse grain growth exponent, 1/n, in agreement with the
theoretical value, 1/n=1/3, noticed during computer simulations for volume fractions between 40% and 90%.
However, the value of 1/n is smaller than 1/3 for volume fractions between 10% and 30%. Furthermore, the
temporal development of the number of grains has been analyzed for the entire range of volume fractions. It is
also seen that the quasi-stationary state is advanced at varied aging times depending on the volume fractions.
Furthermore, it is shown that the simulated size distribution are symmetric and peaked at x=1 for volume
fractions differ between 50% and 90%; however, the simulated size distribution become asymmetric and skew to
smaller grains for lower volume fractions change between 10% and 40%.

Keywords

Monte Carlo, Ostwald Ripening, Polycrystalline Materials, Grain Growth, Volume Diffusion

Enhancing Sensor Sensitivity Using Graphene-MTM Interface

Journal paper
R. J. El-Khozondar, H. J. El-Khozondar, M. M. Shabat
American Journal of Nano Research and Applications, Volume 4, Issue 5, January 2017, Pages 43-46

Abstract

Sensitivity of a waveguide sensor consists of Graphene monolayer between metamaterials (MTMs) layer from below and dielectric layer from above is studied. In this work, we only considered Transverse Magnetic (TM) surface plasmon (SP) at terahertz (THz) range of frequency. Thus, Graphene is assumed to have constant surface conductivity with positive imaginary part. The homogenous sensitivity is derived from the dispersion equation and numerically calculated at different values of MTM parameter. Results show that this structure is valid as a very sensitive sensor that is capable of sensing small signals. Moreover, the sensitivity varies as MTM parameters varies at frequency ranges from 1-10 THz.

Keywords

Graphene, Metamaterials, Waveguide Sensor, Plasmon, TM, Sensitivity

A review study of photovoltaic array maximum power tracking algorithms

Journal paper
Hala J. El‑Khozondar, Rifa J. El‑Khozondar, Khaled Matter and Teuvo Suntio
Renewables: Wind, Water, and Solar, Volume 3, Issue 1, December 2016, Pages1-8.

Abstract

There are numerous maximum power point tracking (MPPT) algorithms for improving the energy efficiency of solar
photovoltaic (PV) systems. The main differences between these algorithms are digital or analog implementation,
simplicity of the design, sensor requirements, convergence speed, range of effectiveness, as well as hardware costs.
Therefore, choosing the right algorithm is very important to the users, because it affects the electrical efficiency of PV system and reduces the costs by decreasing the number of solar panels needed to get the desired power. This paper provides the comparison of 62 different techniques used in tracking the maximum power based on literature survey. This paper is intended to be a reference for PV systems users.

Keywords

Maximum power point tracking system (MPPT), Photovoltaic (PV), System efficiency