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Search Results: 1 - 10 of 359 matches for " Ahsan Illahi "
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On the Effects of Complex Conjugate Medium on TM Scattering by a Strip  [PDF]
Amjad Imran, Ahsan Illahi
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2011, DOI: 10.4236/jemaa.2011.37043
Abstract: In this paper, Method of Kobayashi Potential is used to determine the scattering behavior of a strip which is placed at the air-complex conjugate medium interface. And discussion is presented that how the complex conjugate medium mod-ify the scattering properties of the strip. A comparison is also given with that if we replace the conjugate medium with standard dielectric medium. E-polarized electromagnetic plane wave is supposed to be obliquely incident upon the ge-ometry. Scattered fields in both the half spaces are supposed in terms of unknown weighting functions. Discontinuous properties of Weber-Schafheitlin integral and orthogonal properties of Jacobi’s polynomials are used to determine these unknown weighting functions. Far scattered fields have been calculated using Saddle Point Method and computed for different parameters of interest.
Scattering of Dipole Field by a Perfect Electromagnetic Conductor Cylinder
Ahsan Illahi;M. Afzaal;Qaisar Abbas Naqvi
PIER Letters , 2008, DOI: 10.2528/PIERL08051601
Abstract: Scattering of dipole field by a perfect electromagnetic conductor (PEMC) cylinder is studied theoretically. Electric dipole and magnetic dipole are considered separately as source of excitation. Plots are given for different values of admittance parameter of the PEMC cylinder.
Scattering of Dipole Field by a Finite Conducting and a Finite Impedance Cylinder
Ahsan Illahi;Qaisar Abbas Naqvi;Kohei Hongo
PIER M , 2008, DOI: 10.2528/PIERM08013001
Abstract: Scattering of a spherical wave by a finite PEC and a finite impedance cylinder is studied theoretically. Source of excitation is spherical wave is produced by a dipole with arbitrary orientation. First we derive surface fields induced on an infinite cylinder when it is illuminated by an arbitrary oriented dipole. By the use of the currents on the infinite cylinder excited by an arbitrarily oriented dipole, approximate expressions for two components of the far-zone scattered electric field of a finite PEC and a finite impedance cylinder are derived. The validity of the approximation depends on the conditions that the cylinder must be long compared to the wavelength. The theoretical results are compared to the available results in the literature.
Scattering of an Arbitrarily Oriented Electric Dipole Field from an Infinitely Long Db Circular Cylinder
Abid Mahmood;Ahsan Illahi;Aqeel Abbas Syed;Qaisar Abbas Naqvi
PIER M , 2012, DOI: 10.2528/PIERM11120105
Abstract: Analytic expressions for the scattered magnetic vector potential from an infinitely long DB circular cylinder are presented. An arbitrarily oriented electric dipole is considered as a source of excitation that induces surface currents on the DB circular cylinder. Approximate far field expressions for magnetic vector potential are also derived in this setting. Numerical results of the scattering from the DB cylinder are also presented and compared with those of the PEC cylinder.
Fractional Parallel Plate DB Waveguides Using Fractional Curl Operator
Akhtar Hussain,Sajid Abbas Naqvi,Ahsan Illahi,Q. A. Naqvi
Physics , 2011,
Abstract: DB boundary conditions have been simulated in terms of perfect electric conductor (PEC) boundary for transverse electric modes and perfect magnetic conductor (PMC) for transverse magnetic modes. Electric and magnetic fields inside the dielectric region of a parallel plate DB boundary waveguide have been derived and fractional curl operator has been utilized to study the fractional parallel plate DB waveguide. Field behavior as well as transverse impedance of the guide walls have been studied with respect to the fractional parameter describing the order of fractional curl operator. The results are also compared with the corresponding results for fractional waveguides with PEC walls.
Fields in Fractional Parallel Plate Db Waveguides
Akhtar Hussain;Sajid Abbas Naqvi;Ahsan Illahi;Aqeel Abbas Syed;Qaisar Abbas Naqvi
PIER , 2012, DOI: 10.2528/PIER11120701
Abstract: Time harmonic electric and magnetic fields inside a parallel plate DB boundary waveguide are derived and fractional curl operator is utilized to study the fractional parallel plate DB waveguides. The DB boundary conditions are incorporated by assuming the behavior of boundary as perfect electric conductor (PEC) for transverse electric mode and perfect magnetic conductor (PMC) for transverse magnetic mode. For this purpose a general wave propagating inside the parallel plate wave waveguide is assumed and decomposed into TE and TM modes. Behavior of the fields and transverse impedances of the walls of guide are studied with respect to the fractional parameter describing the order of the fractional curl operator. The results are compared with the corresponding results for fractional waveguides with PEC walls.
Scattering of a Radially Oriented Hertz Dipole Field by a Perfect Electromagnetic Conductor (PEMC) Sphere
Abdul Ghaffar;Nasir Mehmood;Muhammad Shoaib;Muhammad Yasin Naz;Ahsan Illahi;Qaisar Abbas Naqvi
PIER B , 2012, DOI: 10.2528/PIERB12052704
Abstract: PEMC medium is a special type of metamaterial which generalizes the pre-existing concepts of perfect electric conductor (PEC) and perfect magnetic conductor (PMC). PEMC medium is described by a special parameter named as admittance and denoted as M. This admittance parameter acts as a base in order to extract the nature of medium as PEC or PMC. Electromagnetic fields scattered by a PEMC sphere are investigated theoretically. A Hertz dipole as a source of excitation is considered. Co-polarized as well as cross-polarized component of the scattered fields are taken into consideration. A general solution of fields scattered by the PEMC sphere has been sought.
Mammalian Fauna and Conservational Issues of the Baraiyadhala National Park in Chittagong, Bangladesh  [PDF]
Rezaul Karim, Farid Ahsan
Open Journal of Forestry (OJF) , 2016, DOI: 10.4236/ojf.2016.62011
Abstract: Mammals were studied at the Baraiyadhala National Park, Chittagong from August 2012 to July 2013. Twenty nine species of mammals belonging to 26 genera, 17 families and 9 orders were recorded. Of the recorded species, 2 were primates, 10 rodents, 1 lagomorph (hare), 5 chiropterans (bats), 1 manid, 7 carnivores and 3 ungulates. Rodentia appeared as the largest family contained 10 speices. The overall mammalian population density was 239.12/km2. Irrawardy squirrel (Callosciurus pygerythrus) scored the highest density (112.97/km2) and several species attained the lowest (1/km2 each). Local status (relative abundance) of mammals assessed where 15 (51.72%) species were rare, and according to National Conservation Status, 13 (44.82%) were remarked as threatened species of that area. There were some major threats to the park such as forest fire, encroachment of forest and forest edges by both tribal and landless people, illegal exploitation of forest resources, grazing of livestock and unavailable water reservoirs.
Inflow Outflow Effect and Shock Wave Analysis in a Traffic Flow Simulation  [PDF]
Ahsan Ali, Laek Sazzad Andallah
American Journal of Computational Mathematics (AJCM) , 2016, DOI: 10.4236/ajcm.2016.62007
Abstract: This paper investigates the effect of inflow, outflow and shock waves in a single lane highway traffic flow problem. A constant source term has been introduced to demonstrate the inflow and outflow. The classical Lighthill Whitham and Richards (LWR) model combined with the Greenshields model is used to obtain analytical and numerical solutions. The model is treated as an IBVP and numerical solutions are presented using Lax Friedrichs scheme. Godunov method is also used to present shock wave analysis. The numerical procedures adopted in this investigation yield results which are very much consistent with real life scenario in terms of traffic density and velocity.
Some torsion theoretical characterizations of rings
Javed Ahsan
International Journal of Mathematics and Mathematical Sciences , 1984, DOI: 10.1155/s0161171284000302
Abstract: Rings whose torsion free modules are quasi-injective, quasi-projective or coflat have been characterized in the context of certain torsion theories.
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