This paper presents an innovative method for an efficient characterization of relevant characteristics of nonlinear overvoltage protection elements in low-voltage applications. Standard measuring equipment was modifie...
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This paper presents an innovative method for an efficient characterization of relevant characteristics of nonlinear overvoltage protection elements in low-voltage applications. Standard measuring equipment was modified to enable an efficient and repeatable experimental procedure in order to investigate characteristics of overvoltage diodes and varistors, in particular volt-ampere characteristic, volt-ohm characteristic, coefficient of nonlinearity, and dissipating energy. Furthermore, the pseudoempiric method using the "area law" has been developed to determine a pulse characteristic of a gas-filled surge arresters (GFSA). An innovative aging estimate algorithm was additionally used. The justification of the suggested method on commercial nonlinear overvoltage components was checked. Its protective characteristics were examined by both the classical approach and the new suggested method. The obtained results from both methods showed minimal discrepancies.
In this paper, we suggest the use of a convergent rotating slat collimator in a SPECT system that contains strip-shaped CdZnTe detectors. This CdZnTe imaging device is able to provide better energy resolution than a c...
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In this paper, we suggest the use of a convergent rotating slat collimator in a SPECT system that contains strip-shaped CdZnTe detectors. This CdZnTe imaging device is able to provide better energy resolution than a conventional NaI(Tl) detector. A convergent imaging geometry has a higher detection sensitivity than a parallel imaging geometry when imaging a small object. A novel design method and reconstruction technique are proposed for use in this system.
The nonlinear system of equations for solving GPS atmospheric sounding's bending angles are normally solved using Newton's method. Because of the nonlinear nature of the equations, Newton's method applies ...
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The nonlinear system of equations for solving GPS atmospheric sounding's bending angles are normally solved using Newton's method. Because of the nonlinear nature of the equations, Newton's method applies linearization and iterations. The method assumes the refraction angle to be small enough such that the dependency of the doppler shift on these angles are linear. The bending angles are then solved iteratively. Since the approach assumes the dependency of doppler shift on bending angles to be linear, which in actual sense is not, some small nonlinearity error is incurred. The Newton's iterative method is often used owing to the bottleneck of solving in exact form the nonlinear system of equations for bending angles. By converting this system of trigonometric nonlinear equations into algebraic, the present contribution proposes an analytic (algebraic) algorithm for solving the bending angles and presents the geometry of the solution space. The algorithm is tested by computing bending angles of three CHAMP occultation data and the results compared to those of iterative Newton's approach. Occultation 133 of 3rd May 2002 is selected as it occurred during diurnal solar radiation maximum past afternoon. During this time, the effect of ionospheric noise is high. Occultations number 3 of 14th May 2001 and number 6 of 2nd February 2002 were selected since they occurred past mid-night, a time of low solar activity and thus less effect of ionospheric noise. The results for occultation 133 of 3rd May 2002 indicate that the nonlinearity errors in bending angles increase with decrease in height to a maximum absolute value of 0.00069degrees (0.1%) for the region 5-40 km during period of high solar activity. Such nonlinearity errors are shown to impact significantly on the computed impact parameters to which the bending angles are referred. During low solar activity period, the nonlinearity error was relatively small for occultation number 3 of 14th May 2001 with maximum absolute
A slat collimator in single photon emission computed tomography consists of a set of parallel slats. As the collimator spins, the detector measures a one-dimensional projection data set. A complete data set can be obt...
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A slat collimator in single photon emission computed tomography consists of a set of parallel slats. As the collimator spins, the detector measures a one-dimensional projection data set. A complete data set can be obtained by rotating the detector/collimator assembly around the object (patient) while the collimator spins continuously, The measured projection data are assumed to be weighted planar integrals of the object. This paper describes the development of an approximate three-dimensional image reconstruction algorithm for a rotating/spinning slat collimator. This algorithm is in filtered backprojection form. Computer simulations were performed to verify the effectiveness of the algorithm. (C) 2002 American Association of Physicists in Medicine.
An analytical algorithm is presented to compute the network completion time distribution function, where each are has a continuous, defined, and independent completion time distribution function. Through a transformat...
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An analytical algorithm is presented to compute the network completion time distribution function, where each are has a continuous, defined, and independent completion time distribution function. Through a transformation method, the algorithm is simplified into simple multiple integrals. Then Gaussian quadrature formula is generalized for numerical solution of these integrals. Also the generalized Gaussian quadrature formula is applied for conditional Monte Carlo simulation to increase its speed and develop its domain of application. A suitable criterion is presented for the efficiency of conditional Monte Carlo simulation. For variance reduction in estimation, the antithetic random variates are used for simulation methods, conditional Monte Carlo simulation and crude Monte Carlo simulation. Several examples are presented and solved through generalized Gaussian quadrature formula, conditional Monte Carlo simulation, and crude Monte Carlo simulation. For the aspects of speed and accuracy, different methods are compared, where analytical solutions are provided and used for comparison purposes. Finally, conclusions and recommendations are made. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
The scattering from an arbitrarily shaped cylinder for the general oblique incident case is characterised by its induced field ratio (IFR) and its co-polarised and cross-polarised scattering patterns, The paper descri...
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The scattering from an arbitrarily shaped cylinder for the general oblique incident case is characterised by its induced field ratio (IFR) and its co-polarised and cross-polarised scattering patterns, The paper describes how a unique focused-beam measurement system is used to determine experimentally the scattering characteristics of an arbitrarily shaped cylinder for an obliquely incident plane wave. The fields of the transmitting and receiving antennas of the focused-beam measurement system are approximated by equivalent fundamental Gaussian beams. An analytical algorithm, based on computation of the coupling between the transmit and receive Gaussian beams of the focused-beam measurement system and the scattered field of the cylinder, is used to determine the IFR and the co-polarised and cross-polarised scattering patterns of the cylinder. The experimental results obtained by this method for typical dielectric and metal cylinders agree well with the theoretical scattering characteristics computed numerically by the method of moments (MOM) and the finite element method (FEM).
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