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Öğe Computation of corona effects in transmission lines using state-space techniques(Pergamon-Elsevier Science Ltd, 2003) Herdem, S; Mamis, MSIn this paper, state-space method is applied to compute transients in power transmission lines by considering corona effects. Transmission line is modeled by lumped parameter identical sections to simulate the distribution nature of the line and nonlinear corona branches are combined with these sections'. The whole system is composed of RLC elements, sources and switches. The response of the system is calculated using state-space method which has been developed for the analysis of nonlinear power electronic circuits with periodically operated switches. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe A fast algorithm to compute the steady-state solution of nonlinear circuits by piecewise linearization(Pergamon-Elsevier Science Ltd, 2002) Herdem, S; Köksal, MIn the last few decades, many types of nonlinear components that operate in switching modes have appeared in electrical and electronics engineering. These components are conveniently modeled by piece-wise linearization which results with linear circuits containing switches. Hence, the analysis of such circuits has gained more importance. In this paper, a fast algorithm for the steady-state solution of the nonlinear circuits of this type is considered. This algorithm implements maximum advantage when the lonlinearities are discrete and strong as in most of the power electronics semiconductor devices, (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Filtration model of high gradient magnetic filters with granular matrix(Elsevier Science Sa, 1999) Herdem, S; Abbasov, T; Köksal, MConsidering the flow regime of the fluid through the pores of a magnetic filter having a granular matrix composed of ferromagnetic spheres and the accumulation process of the captured particles. the filtration mechanism is investigated. The effect of the different parameters of the filtration system on the efficiency of the magnetic filter is identified. New mathematical expressions are obtained to explain some events which take place in the filtration mechanism and which have not been described completely in the literature so far. The efficiency of the magnetic filter is expressed in terms of the ratios of the magnetic and static pressures which can be measured or identified easily. The theoretical results are compared with the experimental data and it is concluded that they are in good agreement. (C) 1999 Elsevier Science S.A. All rights reserved.Öğe Mathematical modeling of the magnetic filtration processes(Ios Press, 2003) Köksal, M; Abbasov, T; Herdem, SA mathematical model is proposed for the determination of non-stationary characteristics of the cleaning process of industrial liquids in magnetic filters. The theoretical investigation which provides the determination of the variation of the captured particles both with time and along the filter matrix is based on the general filtration equations. Considering the properties of the magnetic filtration process, non-stationary filtration equations involve the capturing and detachment coefficients of the particles in the filter matrix. The effect of the filter length on the magnetic filter performance is also presented. The obtained expressions make possible to compare the experimental and the expected theoretical results.Öğe Model for predicting filtration efficiency and pressure drop in axial magnetic filters(Taylor & Francis Inc, 2000) Herdem, S; Köksal, M; Abbasov, TThe theory of filtration efficiency and filter impedance in axially ordered magnetic filters in conditions of laminar flow is described. The now profile of the suspension that flows axially along the longitudinally ordered wires is determined by the Kuwabara-Happel cell model. Expressions for both filter impedance and filtration efficiency are obtained. In general, they are different from those predicted by previous filtration theories in ideal flow conditions. The derived theoretical formulas are simplified so they can be used easily in engineering applications. The results are compared with the experimental ones presented in the literature, and it is seen that they are consistent with each other.Öğe Modelling of distributed parameter nonlinear systems by differential Taylor method(Polish Acad Sciences Systems Research Inst, 1999) Abbasov, T; Herdem, S; Köksal, MModelling, solution, control and even design of many ecological and engineering systems involve dealing with nonlinear partial differential equations of which analytic solutions are rarely available and numerical approach with or without linearization, or approximation is inevitable most of the time. ill this paper the possibility of analysing such systems by using a fairly new method known as Differential Taylor (DT) Transform and its advantages are proved. The results obtained by this method are compared with the experimental results and shown to be within good agreement with them. It is emphasised that DT Transform is not effective for only filtration systems, but can also be used equally well for absorption, heat and mass transfer, convective diffusion and similar systems.Öğe Modelling of the buildup process of particles in pores of high-gradient magnetic filters using the Fokker-Planck education(Iop Publishing Ltd, 1999) Herdem, S; Abbasov, T; Köksal, MThe stochastic model of the accumulation of particles in a filter matrix composed of magnetized ferromagnetic spheres is considered. The distribution function, which gives the time dependence of the saturation radius that is characterized by both the capturing and detachment events occurring in the capture region, is determined. Taking into account the motional properties of the particles in the capture region, the distribution is evaluated from the solution of the Fokker-Planck equation. The results obtained are compared with, and shown to be similar to, the results of the other methods and some experiments reported in the literature.Öğe Ordinary differential equations with strong nonlinearities and their numerical solutions with abrupt changes(Elsevier Science Inc, 2001) Köksal, M; Herdem, SIn the last few decades many types of nonlinear components that operate in switching modes have appeared in electrical and electronics engineering. Exact modeling of systems containing such components usually Leads to sophisticated differential equations of which analytic solutions can hardly be found, or cannot be computed in many cases. On the other hand, the numerical solutions involve computational errors either due to the wide-spread time constants or very small damping ratios which usually lead to overcontinuing oscillations. This paper is aimed to show the ease in treating the switching type strong nonlinearities by using piecewise linearization in conjunction with the switching equations evaluating the discontinuities. (C) 2001 Elsevier Science Inc, All rights reserved.Öğe Particle capture in axial magnetic filters with power law flow model(Iop Publishing Ltd, 1999) Abbasov, T; Herdem, S; Köksal, MA theory of capture of magnetic particle carried by laminar flow of viscous non-Newtonian (power law) fluid in axially ordered filters is presented. The velocity profile of the fluid flow is determined by the Kuwabara-Happel cell model. For the trajectory of the particle, the capture area and the filter performance simple analytical expressions are obtained. These expressions are valid for particle capture processes from both Newtonian and non-Newtonian fluids. For this reason the obtained theoretical results make it possible to widen the application of high-gradient magnetic filtration (HGMF) to other industrial areas. For Newtonian fluids the theoretical results are shown to be in good agreement with the experimental ones reported in the literature.Öğe Performance of high gradient magnetic filters with granular matrix(Marcel Dekker Inc, 1999) Abbasov, T; Herdem, S; Köksal, MThe performance characteristics of high gradient magnetic filters composed of spherical ferromagnetic granules are determined in terms of dimensionless parameters for a wide range of system parameters. The results obtained are used to overcome some contradictions seen in the literature related to magnetic filters. They are in a good agreement with the experimental data given in the literature for the filters used in laboratories and industry.Öğe Simulation of the magnetic filtration process of technological liquids and gases by a nonlinear electrical circuit(Iop Publishing Ltd, 2001) Herdem, S; Köksal, M; Abbasov, TA general model that explains the mechanisms of the cleaning process of technological liquids and gases, and that estimates and controls the results of these processes, has not yet been found. It is possible to simulate the magnetic filtration of a technological medium by using electrical circuit theory. Characteristics of filtration processes under different regimes can be easily obtained by an appropriate change of nonlinearity parameters of the circuit, Furthermore, the presented model seems to be promising for non-magnetic filtration and other processes similar to filtration, such as separation, absorption, flotation and classification.Öğe A theoretical model for estimation of drag force in the flow of non-newtonian fluids around spherical solid particles(Elsevier Science Sa, 1999) Ceylan, K; Herdem, S; Abbasov, TA theoretical approach for estimation of the drag correlation coefficients in the flow of Newtonian or weak non-Newtonian liquids around spherical solid particles is presented. Some new analytical relations are derived by using a stream function and the energy dissipation equation to approximate the drag coefficients to the experimental data. It is shown that these relationships can be applicable in a wide range of Reynolds number, Re, up to Re < 1000 for the liquids with a flow behavior index, n, in the range of 0.5 < n < 1. The predicted coefficients from these relationships are in very good agreement with the experimental data given in the literature. (C) 1999 Elsevier Science S.A. All rights reserved.Öğe Theory of high-gradient magnetic filter performance(Ieee-Inst Electrical Electronics Engineers Inc, 1999) Abbasov, T; Koksal, M; Herdem, SA unique general model for high-gradient magnetic filters is presented. The functional dependence of the filter performance on the system's physical and geometrical parameters is derived. The derived theoretical expression makes it possible to explain both of the two different, apparently opposite, experimental results reported in the literature. The new quality factor does not include the suspension viscosity, but instead depends on the suspension density, which leads to the application of the formula for a larger class of filtration media including liquids, gases, and vapors.
