Yasin Khan

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Electromagnetic waves scattering from a sphere of complex conjugate medium

Journal of the European Optical Society: Rapid Publications, Jun 7, 2019

A boundary value problem involving the scattering of electromagnetic waves from a sphere of compl... more A boundary value problem involving the scattering of electromagnetic waves from a sphere of complex conjugate medium (CCM) is studied. The sphere is placed in free space. The source of excitation for the sphere in our case is a plane wave. Incident, scattered and transmitted fields are formulated. The unknown coefficients in the scattered and transmitted fields are found using boundary conditions. From these electromagnetic fields, the Mie efficiencies are determined. The technique used in studying the scattering of electromagnetic waves from CCM is analytical and a closed form solution is obtained. It is shown by numerical results that the scattering is enhanced in case of CCM sphere as a target. Results for the limiting cases are also derived to compare the validity of our formulation with the published work.

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Insulation Performance Analysis of Field Aged and New MV XLPE Cables Using Various Diagnostic Techniques

E3S Web of Conferences

Cross-linked polyethylene (XLPE) cables are widely used in the distribution and transmission netw... more Cross-linked polyethylene (XLPE) cables are widely used in the distribution and transmission networks of power systems. The insulation materials of these cables are stressed by the over voltages and are also exposed to various environmental conditions. This leads the power cables to degrade during their normal life span. Therefore, it would be advantageous for the power utilities to acquire the cable’s insulation condition frequently during their operation. In this paper, experimental studies were carried out on short sections of field aged as well as un-aged medium voltage (MV) XLPE cables to investigate the insulation condition using non-destructive diagnostic techniques such as Dissipation Factor (DF), Isothermal Relaxation Current (IRC), and Partial Discharge (PD) characteristics at 60Hz. From this set of experiments, different parameters will be used to analyze the dielectric response and the insulation condition. Finally, the results show how the VLF dissipation factor works e...

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The Estimation of Lightning Impulses Superimposed onto Pre-Stressed DC Breakdown Voltages Using the Leader Propagation Method

Energies, 2022

The impulse breakdown attributes are of rudimentary importance in the insulation coordination in ... more The impulse breakdown attributes are of rudimentary importance in the insulation coordination in the gas-insulated switchgear (GIS). The critical voltage waveshape for the insulation is the surge over voltages. Usually, such over-voltages will emerge on the electrical equipment while these are burdened under DC or AC working voltages. Therefore, during relatively small-time intervals, the undermined devices are exposed to surge voltages that are superimposed upon the already running DC or AC voltages. From a safety point of view, and for providing reliable power to the consumer, we need to study the breakdown characteristics under such over-voltages, with reference to normal operating voltages (DC or AC). The breakdown mechanism of the GIS under compressed SF6 gas is known to be controlled by a stepped leader propagation method. Although different experimental studies have been conducted by many researchers for different experimental conditions under DC, AC, or impulse high voltages...

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Electromagnetic Wave Reflectance, Transmittance, and Absorption in a Graphene-Covered Uniaxial Crystal Slab

Progress In Electromagnetics Research M, 2018

A theoretical investigation of the interaction of electromagnetic plane waves with a uniaxial cry... more A theoretical investigation of the interaction of electromagnetic plane waves with a uniaxial crystal slab bounded by two graphene layers from both sides placed in free space is presented in this paper. An 8×8 matrix method is developed using boundary conditions at a grapheneuniaxial anisotropic crystal interface and a uniaxial anisotropic crystal-graphene interface. The developed matrix is used to find reflection and transmission coefficients by Crammer's rule. Numerical results are presented to demonstrate the effect of frequency of the incident wave, thickness of the uniaxial crystal slab, and Fermi energy of the graphene on the reflected and transmitted energies. The presented formulations and results are confirmed by published results of some limited cases.

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Electromagnetic Energy Surface Modes in Metamaterial-Filled Bi-layer Graphene Structures

Plasmonics, 2021

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Optical characterization of non-thermal plasma jet energy carriers for effective catalytic processing of industrial wastewaters

Scientific Reports, 2021

An argon plasma jet was sustained in open air and characterized for its chemical composition. The... more An argon plasma jet was sustained in open air and characterized for its chemical composition. The optically characterized plasma jet was used to treat industrial wastewater containing mixed textile dyes and heavy metals. Since plasma jet produces UV-radiations, the photocatalytic TiO2 was used to enhance plasma treatment efficiency especially for degradation of dyes. Mixed anatase and rutile phases of TiO2 (5.2–8.5 nm) were produced through surfactant assisted sol–gel approach. The emission spectrum confirmed the presence of excited argon, OH, excited nitrogen, excited oxygen, ozone and nitric oxide in the plasma jet. The spectral lines of excited Ar, NO, O3, OH−, N2, $${\mathrm{N}}_{2}^{+}$$ N 2 + , O, $${\mathrm{O}}_{2}^{+}$$ O 2 + and O+ species were observed at wavelength of 695–740 nm, 254.3 nm, 307.9 nm, 302–310 nm, 330–380 nm, 390–415 nm, 715.6 nm, 500–600 nm and 400–500 nm. These reactive species decompose the organic pollutants and separate the heavy metals from the water s...

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Characteristics of hybrid surface plasmon polaritons at a chiral graphene metal interface in cylindrical waveguides

Optical and Quantum Electronics, 2021

A detailed theoretical analysis of the hybrid surface plasmon mode generation and propagation at ... more A detailed theoretical analysis of the hybrid surface plasmon mode generation and propagation at a chiral graphene metal (CGM) interface for a cylindrical structure is presented. The conductivity of graphene is modeled using the Kubo formalism and the dispersion relation for the hybrid surface waves is computed on the basis of the Kubo formalism and impedance matching boundary conditions. The hybrid mode consisting of lower and upper plasmon modes is witnessed due to the presence of the chiral medium. The frequency band gap between the lower and upper plasmon modes is found to be sensitive and tunable with respect to the chiral strength, radial distance of the waveguide, and chemical potential of graphene. The propagation length and effective refractive index can also be modulated by varying the chiral strength and chemical potential. For very high values of chirality and biasing voltage, the Goos-Hänchen effect is observed at the CGM interface. The cutoff values of chiral strength as a function of normalized frequency make the proposed structure applicable for chiroptical and chemical sensing and enantiomeric detection in the THz frequency regime. Key Word: Surface Plasmon Polaritons, Chiral, Graphene, Waveguide 1 2 in Eq. 15). The graph exhibits the sensitive behavior of plasmon modes toward optical and chemical changes in the chiral medium. The cutoff chiral values follow a linear and distinct relation for variation in refractive index values within a narrow frequency range. The frequency-dependent cutoff values for chiral media having different refractive indices enrich the sensitivity of the proposed design toward chiroptical and chemical sensing.

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Defect Localization Inside Simulated MV Switchgear Based on Cumulative Energy Curve Using Transient Earth Voltage Sensors

Energies, 2021

The partial discharge (PD) leads to catastrophic failure of the medium voltage (MV) switchgear in... more The partial discharge (PD) leads to catastrophic failure of the medium voltage (MV) switchgear insulation. Determination of the PD source (defect) location in high voltage (HV) equipment is very important in the maintenance procedures and in isolating the root cause of PD generation. In this paper, the transient earth voltage (TEV) detection method was used to acquire defect-initiated PD signals in a simulated MV switchgear model. An array of four TEV sensors were placed on the surface walls outside an MV switchgear tank to acquire the PD signals generated from the known location(s)/coordinates of sharp needle type defect inside the tank. The time difference of arrival (TDOA) between signals that are captured by the TEV sensors array was critically analyzed. Estimating the TDOA between PD signals generated by PD source at a known location with high accuracy is of great importance for accurate defect localization. The cumulative energy method (CEM) is used to estimate the onset time ...

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Electromagnetic surface waves supported by a resistive metasurface-covered metamaterial structure

Scientific Reports, 2020

This study examines the analytical and numerical solution of electromagnetic surface waves suppor... more This study examines the analytical and numerical solution of electromagnetic surface waves supported by a resistive metasurface-covered grounded metamaterial structure. To simulate the metamaterial, the Kramers–Kronig relation based on the causality principle is used, while the modeling of the resistive metasurface has been done by implementing the impedance boundary conditions. The analytical expressions for the field phasors of surface waves are developed for the transverse magnetic (TM) polarized mode and transverse electric (TE) polarized mode. The characteristic equations are computed for both modes, and the unknown propagation constant is evaluated numerically in the kernel. After computation, the dispersion curves, electric field profiles, effective mode index ($$N_{eff}$$Neff), and phase speeds ($$v_{p}$$vp) are presented for both the TM and TE polarized modes. To study the tunability of surface waves, the influence of the thickness of the metamaterial slab ($$d$$d), effecti...

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Transverse electric surface waves in ferrite medium surrounded by plasma layers

Journal of the European Optical Society-Rapid Publications, 2020

The theoretical analysis of transverse electric surface waves in ferrite medium surrounded by iso... more The theoretical analysis of transverse electric surface waves in ferrite medium surrounded by isotropic plasma layers is presented in this manuscript. Maxwell’s equations in differential form are used, and we impose the boundary conditions to acquire the dispersion relation to formulate the proposed structure. The influence of number density, separation distance between the layers of plasma, and dielectric permittivity of ferrite film on the normalized propagation constant is studied. It is concluded from the result obtained that if the number density and values of dielectric permittivity of ferrite film increases the propagation constant Re(β) tends to decreases whereas the increase in separation distance between the layers of plasma tends to increase the propagation constant Re(β). Furthermore, to verify the surface waves, the normalized field distribution for plasma medium as well as ferrite medium are also presented in this manuscript. The present work has potential applications...

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Experimental and Statistical Validation of Data on Mesh-Coupled Annular Distributor Design for Swirling Fluidized Beds

Processes, 2020

In this study, velocimetry and statistical analyses were conducted on a swirling fluidized bed. A... more In this study, velocimetry and statistical analyses were conducted on a swirling fluidized bed. A bed of spherical particles (4 mm) was fluidized by using an annular distributor covered with mesh. The angles of rectangular blades in the distributor were set at 30°, 45°, 60°, 75° and 90°, and the cell size of the mesh cover was 2.5 × 2.5 mm2. The weight was varied from 500 to 1250 g and the effect of each variable on bed velocity response was quantified through velocimetry and statistical analysis. The statistical analysis was conducted using NCSS statistical software. The blade angle, bed weight and superficial velocity for 4 mm particles were statistically optimized at 750 g, 58.26° and 1.45 m/s, respectively. On the experimental side, these parameters have been optimized at 750 g, 60° and 1.41 m/s, respectively. A small difference of 1.74° was noticed in experimental and statistical predictions for the blade angle. The bed weights and superficial velocities were found to be same i...

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Catalytic and Non-Catalytic Treatment of Industrial Wastewater under the Exposure of Non-Thermal Plasma Jet

Processes, 2020

Freshwater is only 2.5% of the total water on the Earth and rest is contaminated or brackish. Var... more Freshwater is only 2.5% of the total water on the Earth and rest is contaminated or brackish. Various physical and chemical techniques are being used to purify the contaminated water. This study deals with catalytic plasma treatment of contaminated water collected from different sites of Faisalabad-Pakistan. A non-thermal DC plasma jet technique was used to treat the water samples in the presence of TiO2 catalyst. The plasma-assisted catalytic treatment introduced some oxidative species (O3, H2O2, HO2−, OH−) in the water. These species reacted with pollutants and cause the degradation of harmful contaminants, especially dyes. The degradation of dye sample during plasma treatment was more pronounced as compared to other samples. pH, conductivity and TDS of dye containing sample decreased after catalytic plasma treatment. The degradation of organic pollutants increased due to presence of several oxidants, such as TiO2, ferrous ions and hydrogen peroxide. FT-IR analysis revealed the de...

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Characteristics of electromagnetic wave transmission and reflection from isotropic plasma coated circular nihility cylinder

AIP Advances, 2019

Theoretical investigation has been carried out to study the scattering and transmission of electr... more Theoretical investigation has been carried out to study the scattering and transmission of electromagnetic energy from isotropic plasma coated circular nihility cylinder. The physical modeling of the problem is done in frame work of classical scattering theory. All the fields are expanded in terms of cylindrical vector wave functions (CVWFs). The analytical as well as numerical solution for both Transverse Electric (TE) and Transverse Magnetic (TM) polarizations is presented. The unknown scattering coefficients are computed by implementing the boundary conditions at each interface (free space/plasma and plasma/nihility). The influence of plasma parameters i.e., plasma density (ND) and effective collision frequency (v) on the bistatic echo width is analyzed and it is concluded that the plasma coating can be used to control and tune the scattering amplitude. Further it is also concluded that for the case ω > ωp the scattering amplitude is much less than for the case ω < ωp. Unde...

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Structural Study on Nano-crystals of Spinel Mgx-Zn1-X-Fe2O4 Ferrite with and without Calcination

High Temperature Materials and Processes, 2017

This study investigated a series of single phase Mgx-Zn1-x-Fe2O4 spinel ferrites, prepared using ... more This study investigated a series of single phase Mgx-Zn1-x-Fe2O4 spinel ferrites, prepared using co-precipitation technique and sintered at 600 °C. The X-ray diffraction (XRD) patterns of the ferrite samples revealed the formation of impurity free single phase spinel structures. The formation of ferrite phases and face centered cubic structures was confirmed at Bragg angles of 35.9°, 54.3° and 62.7°. The lattice parameter increased with an increase in ‘x’ content in the ferrite composition. The grain size, estimated from SEM micrographs, was found in the range of 0.5–2 mµ. The lattice parameter of the ferrite samples exhibited an initial increase upto a certain extent, thereafter suddenly dropped down due to fracturing and re-welding processes. Overall, the lattice parameter ‘a’ varied from 0.80 to 0.85 nm, crystallite size from 34 to 80 nm, unit cell volume from 0.528 × 10−21 to 0.62 × 10−21 cm3 and X-ray density from 5.8 to 4.5 g/cm3.

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Comparative Study of Different Hill Climbing MPPT through Simulation and Experimental Test Bed

Research Journal of Applied Sciences, Engineering and Technology, 2014

Hill climbing MPPT technique is commonly used in photovoltaic systems in order to achieve maximum... more Hill climbing MPPT technique is commonly used in photovoltaic systems in order to achieve maximum power from it. Due to the massive numbers of the MPPT techniques in this field, it becomes essential to find and verify the most effective, simplest and reliable technique to be used. In this paper comparative studies of two different climbing MPPTs that are conventional perturb and observe and modified perturb and observe has been performed. The paper verifies their tracking performance through calculations. Simulations are also performed using MATLAB SIMULINK and results are analyzed. In addition, hardware implementation has been carried out which verifies simulation results. This study should serve as a strong evidence for practical feasibility of the modified perturb and observe method for MPPT.

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A Review of Frequency Response Analysis Methods for Power Transformer Diagnostics

Energies, 2016

Power transformers play a critical role in electric power networks. Such transformers can suffer ... more Power transformers play a critical role in electric power networks. Such transformers can suffer failures due to multiple stresses and aging. Thus, assessment of condition and diagnostic techniques are of great importance for improving power network reliability and service continuity. Several techniques are available to diagnose the faults within the power transformer. Frequency response analysis (FRA) method is a powerful technique for diagnosing transformer winding deformation and several other types of problems that are caused during manufacture, transportation, installation and/or service life. This paper provides a comprehensive review on FRA methods and their applications in diagnostics and fault identification for power transformers. The paper discusses theory and applications of FRA methods as well as various issues and challenges faced in the application of this method.

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Challenges in Detection of High Impedance Faults on Broken Conductors in MV Lines

Research Journal of Applied Sciences, Engineering and Technology, 2014

The weather conditions in Saudi Arabia are harsh and the inland areas are very hot, dry and sandy... more The weather conditions in Saudi Arabia are harsh and the inland areas are very hot, dry and sandy. Thousands of kilometers of medium voltage overhead lines (13.8 kV) are located in deep desert areas feeding loads that are located in remote desert areas. Such medium and low voltage distribution networks face difficulties regarding fault detection and localization. High Impedance Fault (HIF) resulting from a broken conductor in MV overhead lines represent the most challenging problem in such environments. Such condition may cause damage, fire or electric shock hazards resulting in life threatening situations. This study reports on a study of electrical characteristics of inland desert sand and typical characteristics of HIF fault when a MV line conductor breaks and touches such sand. It is shown that the arid desert sand has extremely high resistivity and it is difficult to detect the fault by using conventional protective devices. The study presents results of measurements and simulations and suggests that innovative approaches have to be employed to achieve the desired protection in such environments.

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Emission constrained economic dispatch for hybrid energy system in the presence of distributed generation and energy storage

Journal of Renewable and Sustainable Energy, 2015

Due to the concerns about the increasing price of fossil fuels, greenhouse gas emissions and ener... more Due to the concerns about the increasing price of fossil fuels, greenhouse gas emissions and energy supply sustainability, power utilities are being forced to examine their operational policies. The use of hybrid power system and the minimization of overall generation cost of such systems employing distributed generation and distributed energy storage facilities with limited amounts of pollutants emission is the main objective of the optimization carried out in this work. The analysis considers the generation cost of thermal, renewable and storage based hybrid power plants along with the cost paid for health and environmental damages caused by the emissions. The analysis is carried out using MATLAB simulations with sequential quadratic programming algorithm. It is shown that the actual cost of fossil fuel based electricity generation is higher than that of the renewable power generation if the hidden costs of conventional generation related to environmental impacts are considered as...

Optimized pit configuration for efficient grounding of the power system in high resistivity soils using low resistivity materials

2011 Fourth International Conference on Modeling, Simulation and Applied Optimization, 2011

Abstract In an electrical power system, the integrity of the grounding system is very important t... more Abstract In an electrical power system, the integrity of the grounding system is very important to maintain a reference point of potential for equipment and personnel safety, to provide a discharge point for lightning currents as well as to prevent excessive high voltages on the power system. Therefore, to maintain ground system effectiveness, proper design, installation and testing of grounding system is required. In Saudi Arabia, the weather is dry and the soil resistivity varies significantly from area to area because the geodetic terrain ...

Efficient use of low resistivity material for grounding resistance reduction in high soil resistivity areas

TENCON 2010 - 2010 IEEE Region 10 Conference, 2010

Abstract Power system is generally protected from lightning strokes by surge arresters which are ... more Abstract Power system is generally protected from lightning strokes by surge arresters which are provided with a low earth resistance connection to enable the large currents encountered to be effectively discharged to the general mass of earth. This offers some resistance to the flow of current which depends on electrode arrangements as well as the surrounding soil resistivity. In Saudi Arabia, the soil resistivity varies in a large range because the geodetic terrain varies from sea shore to the arid desert and dry mountains. ...

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