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Aspects Of Radar Polarimetry, Ernst Luneburg
Aspects Of Radar Polarimetry, Ernst Luneburg
Turkish Journal of Electrical Engineering and Computer Sciences
This contribution is a tutorial introduction to the phenomenological theory of radar polarimetry for the coherent scatter case emphasizing monostatic backscattering and forward scattering (transmission). Characteristic similarities and differences between radar polarimetry and optical polarimetry and the role of linear and antilinear operators (time-reversal) are pointed out and typical polarimetric invariants are identified.
Two-Dimensional Photonic Crystal L-Shaped Bent Waveguide And Its Application To Wavelength Multi/Demultiplexer, Yoshihiro Naka, Hiroyoshi Ikuno
Two-Dimensional Photonic Crystal L-Shaped Bent Waveguide And Its Application To Wavelength Multi/Demultiplexer, Yoshihiro Naka, Hiroyoshi Ikuno
Turkish Journal of Electrical Engineering and Computer Sciences
The bent waveguide is a key element for integrated optical signal processing waveguide devices. We propose a new type of two-dimensional photonic crystal L-shaped bent waveguides with additional pillars at the corner. Using the FDTD method based on the principle of multidimensional wave digital filters we simulate its transmission characteristics and show an excellent transmission of light in L-shaped bent waveguide. As an application we design compact size multi/demultiplexer composed of the L-shaped bent waveguides and directional couplers and realize multi/demultiplexer with low-insertion loss and high extinction ratio device whose size is of the order of the wavelength of light.
Discrete Array Representation Of Continuous Space-Time Source Distributions, Amir Shlivinski, Ehud Heyman
Discrete Array Representation Of Continuous Space-Time Source Distributions, Amir Shlivinski, Ehud Heyman
Turkish Journal of Electrical Engineering and Computer Sciences
We consider the realization of a continuous space-time source distributions using a sparse non-uniform point-source array. The construction determines the largest possible cells corresponding to the local source parameters in order to obtain a sparse array, while meeting an error criterion on the pulsed radiation pattern. The scheme is applied for the realization of collimated short-pulse beam fields. The error criterion is imposed within the main beam direction, while outside this region the relative realization error can be large but it is negligible since the field there is small compared to the main beam field.
Development Of A Cylindrical Waveguide Antenna Array With A High Isolation Between Receive - Transmit Sub Arrays: Theory And Experiment, Vladimir I. Okhmatovsky, Konstantina S. Nikita, Stavros Koulouridis, Nikolaos K. Uzunoglu
Development Of A Cylindrical Waveguide Antenna Array With A High Isolation Between Receive - Transmit Sub Arrays: Theory And Experiment, Vladimir I. Okhmatovsky, Konstantina S. Nikita, Stavros Koulouridis, Nikolaos K. Uzunoglu
Turkish Journal of Electrical Engineering and Computer Sciences
The possibility of developing an antenna system consisting of transmit and receive arrays and being able to work simultaneously in full duplex mode at the same frequency is a very attractive task. This could only be achieved if the isolation between the transmit and receive arrays is sufficiently high not to cause a parasitic oscillation which will ruin the proper operation of a transponder system to which the arrays will be connected. Specifically, in this paper the operation of two peripheral open waveguide arrays placed on a cylindrical surface and being isolated with a radial line operating as a space …
2d Complex Point Source Radiation Problem I. Complex Distances And Complex Angles, E. Gago-Ribas, M. J. Gonzalez Morales
2d Complex Point Source Radiation Problem I. Complex Distances And Complex Angles, E. Gago-Ribas, M. J. Gonzalez Morales
Turkish Journal of Electrical Engineering and Computer Sciences
A methodology based on the complex spaces analysis, which allows to generalize the study of wave radiation and scattering problems is presented in this paper. From the analytic continuation of functions defined in the real domain (real propagation or scattering spaces) into the complex space (space of complex coordinates), general non homogeneous phase field solutions are obtained for a particular wave problem. From these general solutions, other common solutions obtained under different approximations will arise. This procedure allows to obtain a complete classification of the solutions for the wave problem under analysis, and also to study both the ranges of …
2d Complex Point Source Radiation Problem Ii.~Complex Beams, M. J. Gonzalez Morales, E. Gago-Ribas
2d Complex Point Source Radiation Problem Ii.~Complex Beams, M. J. Gonzalez Morales, E. Gago-Ribas
Turkish Journal of Electrical Engineering and Computer Sciences
The complex point source analytic continuation, and the analysis into the spaces of complex distances, angles, and other related magnitudes, may be applied to describe a wide variety of 2D wave propagation problems. This step will be essential in order to establish a complete complex methodology which may be applied to obtain general descriptions of more practical problems involving the scattering of waves under some kind of field incidence. A particular application of the methodology presented in Part I will be used in Part II. The specific problem under analysis in these papers will be the general complex beam solution …
An Efficient Preconditioner For Iterative Solvers, V. V. S. Prakash, Raj Mittra
An Efficient Preconditioner For Iterative Solvers, V. V. S. Prakash, Raj Mittra
Turkish Journal of Electrical Engineering and Computer Sciences
The method of moments solution of the Maxwell's equations leads to a dense system of complex equations. Direct solution of these equations using LU factorization becomes unwieldy as the size of the scatterer increase in terms of wavelength. Iterative solvers, such as those based on Krylov projection methods, offer an alternative approach for solving large system of equations. Most often, the iterative methods are used in combination with some kind of preconditioning to improve the condition number of the system matrix A in order to acheive accelerated convergence [1-2]. This paper discusses the application of Multi-Frontal Preconditioners (MFPs) for the …
A Note On The Poisson Summation Formula And Its Application To Electromagnetic Problems Involving Cylindrical Coordinates, Anastassios H. Panaretos, Hristos T. Anastassiu, Dimitra I. Kaklamani
A Note On The Poisson Summation Formula And Its Application To Electromagnetic Problems Involving Cylindrical Coordinates, Anastassios H. Panaretos, Hristos T. Anastassiu, Dimitra I. Kaklamani
Turkish Journal of Electrical Engineering and Computer Sciences
A modified version of the Poisson Summation Formula is derived,involving the Fourier-Bessel Transform of the kernel function, as opposed to the conventional Fourier Transform engaged in the standard formula. This novel form can be applied to problems employing cylindrical coordinates, such as the fast evaluation of the dyadic Green's function in a waveguide or cavity of circular cross-section.
A Time Domain Uniform Geometrical Theory Of Slope Diffraction For A Curved Wedge, Prabhakar H. Pathak, Paul R. Rousseau
A Time Domain Uniform Geometrical Theory Of Slope Diffraction For A Curved Wedge, Prabhakar H. Pathak, Paul R. Rousseau
Turkish Journal of Electrical Engineering and Computer Sciences
A time domain version of the uniform geometrical theory of diffraction (TD-UTD) is developed to describe, in essentially closed form, the field which is produced via slope diffraction at a perfectly conducting, arbitrarily curved wedge excited by a time impulsive wave that exhibits a rapid spatial variation near the edge of the wedge. This TD-UTD slope diffracted field for a curved wedge is obtained by a Fourier inversion of the corresponding frequency domain UTD expression. An analytical signal representation of the transient fields is used since it is convenient, and because it circumvents some of the difficulties, which especially arise …
A Novel Mom Approach For Obtaining Accurate And Efficient Solutions In Optical Rib Waveguide, Namik Yener, Ercan Topuz
A Novel Mom Approach For Obtaining Accurate And Efficient Solutions In Optical Rib Waveguide, Namik Yener, Ercan Topuz
Turkish Journal of Electrical Engineering and Computer Sciences
The optical rib waveguide (ORW) plays an important role in the design of several integrated optical devices. Various methods have been proposed for obtaining the modal field solutions in ORW. However, to the best of our knowledge none of them is capable of providing accurate full-wave benchmark solutions. Here we present a novel MoM approach wherein the modes of a loaded rectangular waveguide are utilized as basis functions and demonstrate that this approach is very efficient and yields highly accurate full-wave results which can serve as benchmark solutions in assessing the quality of the data reported in the literature.
Effects Of Substrate Temperature On Properties Of A-Sin_X:H Films, Tayyar Güngör, Hüseyi̇n Tolunay
Effects Of Substrate Temperature On Properties Of A-Sin_X:H Films, Tayyar Güngör, Hüseyi̇n Tolunay
Turkish Journal of Physics
Hydrogenated amorphous silicon nitride films were prepared in an rf glow-discharge system by the decomposition of silane + nitrogen gas mixture at various substrate temperatures. The effects of substrate temperature on the electrical and optical properties of the films have been studied.
Cover And Contents
Turkish Journal of Veterinary & Animal Sciences
No abstract provided.
Effect Of Rf Power On The Electrical Properties Of Glow-Discharge A-Si:H, Hüseyi̇n Tolunay
Effect Of Rf Power On The Electrical Properties Of Glow-Discharge A-Si:H, Hüseyi̇n Tolunay
Turkish Journal of Physics
Hydrogenated amorphous silicon films were prepared in an rf glow-discharge system by decomposing undiluted silane at various rf power densities. Dark conductivity and photoconductivity of the films have been measured in the temperature range 420K-100K at four different photon fluxes. It was observed that both dark conductivity and photoconductivity increase with increasing rf power density.
Plane Wave Diffraction By A Dielectric Loaded Open Parallel Thick Plate Waveguide, Bahatti̇n Türetken, Ali̇ Alkumru
Plane Wave Diffraction By A Dielectric Loaded Open Parallel Thick Plate Waveguide, Bahatti̇n Türetken, Ali̇ Alkumru
Turkish Journal of Electrical Engineering and Computer Sciences
A uniform asymptotic high-frequency solution for a two-dimensional diffraction problem of plane electromagnetic waves by a dielectric loaded open parallel thick plate waveguide is investigated rigorously using the Fourier transform technique in conjunction with the mode matching method. This mixed method of formulation gives rise to scalar modified Wiener-Hopf equations of the second kind for which the solution contains a set of infinitely many constants satisfying an infinite system of linear algebraic equations. A numerical solution of this system is obtained for various values of plate thickness, incidence angle and permittivity, and the effect of these parameters on the diffraction …
Array Pattern Nulling By Phase And Position Perturbations With The Use Of A Modified Tabu Search Algorithm, Ali̇ Akdağli, Keri̇m Güney
Array Pattern Nulling By Phase And Position Perturbations With The Use Of A Modified Tabu Search Algorithm, Ali̇ Akdağli, Keri̇m Güney
Turkish Journal of Electrical Engineering and Computer Sciences
A useful and flexible method based on the tabu search algorithm for the pattern synthesis of linear antenna arrays with the prescribed nulls is presented. Nulling of the pattern is achieved by controlling both the phase and the position of each array element. To show the versatility of the present method, some design specifications such as the maximum sidelobe level and the null depth level are considered by introducing a set of weighting factors in the cost function constructed for the tabu search algorithm. Several illustrative examples of a Chebyshev pattern with the imposed single, multiple and broad nulls are …
Scalar Wave Diffraction By Perfectly Soft Thin Circular Cylinder Of Finite Length; Analytical Regularization Method, Eylem Özkan, Fati̇h Di̇kmen, Yury Alexanderovich Tuchkin
Scalar Wave Diffraction By Perfectly Soft Thin Circular Cylinder Of Finite Length; Analytical Regularization Method, Eylem Özkan, Fati̇h Di̇kmen, Yury Alexanderovich Tuchkin
Turkish Journal of Electrical Engineering and Computer Sciences
A new mathematically rigorous and numerically effective method for solving the boundary value problem of scalar wave diffraction by an infinitely thin circular cylindrical screen of finite length is proposed. The method is based on the combination of the Orthogonal Polynomials Approach, and on the ideas of the methods of analytical regularization. As a result of the suggested regularization procedure, the initial boundary value problem is equivalently reduced to the infinite system of the linear algebraic equations of the second kind, i.e. to an equation of the type (I + H)x = b in the space \ell _{2} of square …
Active Clamped Zvs Forward Converter With Soft-Switched Synchronous Rectifier, A. Açik, Işik Çadirci
Active Clamped Zvs Forward Converter With Soft-Switched Synchronous Rectifier, A. Açik, Işik Çadirci
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents the analysis, design and implementation of an active-clamped, ZVS forward converter equipped with a soft-switched synchronous rectifier (ACFC-SR) proposed for high-efficiency, low output voltage dc-dc converter applications. The converter efficiency is maximized due to the soft-switching of the main, active clamp, synchronous rectifier and freewheeling MOSFET switches. The operating principles of the ACFC-SR are analyzed in detail and the converter performance is compared with the alternative forward converter schemes employed in low output voltage dc-dc converters. Experimental results are presented for a converter with a dc input voltage of 48 V, an output voltage of 5 V, …
A Comparison Of Erythrocyte Superoxide Dismutase And Catalase Activity In Patients With Hepatitis C Infection, Aysun Bay Karabulut, Emi̇ne Sönmez, Yaşar Bayindir, Engi̇n Gözükara
A Comparison Of Erythrocyte Superoxide Dismutase And Catalase Activity In Patients With Hepatitis C Infection, Aysun Bay Karabulut, Emi̇ne Sönmez, Yaşar Bayindir, Engi̇n Gözükara
Turkish Journal of Medical Sciences
Hepatitis C virus (HCV) infection remains important due to difficulties in treatment up to a chronic state. It is considered that free radicals, lipid peroxidation and antioxidant defense play a role in various tissue damages, just as in certain types of viral hepatitis. Since only limited data has been reported concerning oxidative stress in viral hepatitis, a comparative study was planned for patients with hepatitis C. In this study, we searched for erythrocyte superoxide dismutase (SOD) and catalase (CAT) activities in patients with HCV infection who had received and not received recombinant interferon alpha. Four groups of patients [Group I: …
Glycine Transport Through A Charged Polysulfone Cation Exchange Membrane, Nuri̇ Ünlü, Hüseyi̇n Kara, Mustafa Ersöz
Glycine Transport Through A Charged Polysulfone Cation Exchange Membrane, Nuri̇ Ünlü, Hüseyi̇n Kara, Mustafa Ersöz
Turkish Journal of Chemistry
The transport of glycine through a charged polysulfone cation exchange membrane was studied as a function of pH at different initial conditions of less than pH 5.9 and the glycine permeability was explained under the experimental conditions as pH dependent interfacial transport. The glycine permeability increases with a decreasing pH in the receiver phase. The largest permeability was obtained if the initial pH on the source side was pH 5.9 and that on the opposite side was pH 2.0. The transport phenomena can be explained by the interfacial transport based on the interfacial chemical reaction (protonation, deprotonation or ion-exchange) between …
The Effects Of Benzoic Acid In Chloride Solutions On The Corrosion Of Iron And Aluminum, Si̇bel Zor
The Effects Of Benzoic Acid In Chloride Solutions On The Corrosion Of Iron And Aluminum, Si̇bel Zor
Turkish Journal of Chemistry
In this work, the corrosion behavior of iron and aluminum was investigated in 0.1 M NaCl solutions with an initial pH value of 8 and containing various concentrations (0, 30, 150, 300 ppm) of benzoic acid. For this purpose, the anodic and cathodic semilogarithmic current-potential curves, weight loss and pH of the solution were determined over time. The changes in the concentrations of benzoic acid in the solutions with time were determined by a UV spectrophotometer. According to the results obtained in this investigation, benzoic acid in 0.1 M NaCl acts on iron and aluminum as an inhibitor. This effect …
Production Of Mesophase Pitch From Coal Tar And Petroleum Pitches Using Supercritical Fluid Extraction, Mustafa Zafer Özel, Keith D. Bartle
Production Of Mesophase Pitch From Coal Tar And Petroleum Pitches Using Supercritical Fluid Extraction, Mustafa Zafer Özel, Keith D. Bartle
Turkish Journal of Chemistry
Supercritical fluid extraction (SFE) is currently being investigated as a possible technique in the production of high quality mesophase pitch from coal tar and petroleum pitches. Mesophase pitch is used to make high technology products, such as carbon fibre. The conventional production of mesophase pitch initially involves the removal of low molecular weight species from coal tar and petroleum pitches. The remaining residue is then transformed into a mesophase pitch through a polymerisation process. The aim of this study involves the extraction of light molecular weight species using SFE. Both petroleum and coal tar pitch contain complex aromatic molecules with …