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Frequency Dependent Parameters (frequency + dependent_parameter)
Selected AbstractsCable model with frequency dependent parameters calculated by using subconductorsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2003L. Hofmann A cable model with frequency dependent parameters in the time domain for the simulation of transients in the short time range is presented. The model is based on the division of the transmission line into m short lossless delay line segments of length ,xk = l/m, which are connected to each other by damping-networks consisting of constant ohmic resistances and by distortion-networks simulating the frequency dependence of the series impedance per unit length. The damping-networks consider ohmic line losses as well as leakage losses by shunt conductances. The distortion-networks are represented by state space equations in the time domain. One advantage of the model in comparison to generally used models is the direct determination of the model parameters from the geometrical dimensions of the line-ground configuration. This model also provides a fast and accurate algorithm. [source] A hybrid integral equation and neural network approach for fast extraction of frequency dependent parameters of multiconductor transmission linesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2002G. Pan Abstract Multiconductor transmission lines (MTL) have been modeled by the distributed parameters R, L, C, and G in many commercial CAD packages, where most of the parameters are assumed to be frequency independent or at most . At gigahertz frequencies, such assumptions may introduce significantly large errors in the waveform simulation and timing. In this article, we present a new and fast technique based on a combination of neural network techniques and the integral equation method (IEM) to evaluate frequency dependences accurately, while dramatically reducing the computation time. © 2002 John Wiley & Sons, Inc. Int J RF and Microwave CAE 12: 37,50, 2002. [source] Spatial and spectral heterogeneity of time-varying shear stress profiles in the carotid bifurcation by phase-contrast MRIJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2006Bradley D. Gelfand BSE Abstract Purpose To determine the heterogeneity of the time-varying shear stress profiles in the human carotid bifurcation, a region prone to atherosclerosis. Materials and Methods Lagrangian bicubic interpolation of phase-contrast MRI images was used to determine the shear stress profiles for three adult healthy male volunteers. Frequency spectra for the common and internal carotid artery (CCA and ICA, respectively)-derived shear stresses were examined in order to determine the presence of significant heterogeneity in the intensity distribution. Results Hemodynamic characteristics (peak, minimum, average shear stress, and oscillatory shear index [OSI]) were highly heterogeneous both along the length of the vessel as well as circumferentially around the CCA and ICA. In the frequency domain, intensities below 4 Hz were significantly higher in the CCA compared to the sinus region of the ICA, indicating that shear stress heterogeneity can be detected in the frequency domain. The harmonic index, a measure of the relative contributions of dynamic and static components of the shear stress signal, colocalizes with OSI, which implies a relationship between specific frequency components and atherosclerosis development. Conclusion These findings indicate that the time and frequency dependent parameters of in vivo shear stress have important implications for regional development of atherosclerosis. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||