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Circuit Models (circuit + models)

Distribution by Scientific Domains
Engineering87%

Selected Abstracts

Evaluation of electromagnetic interference on telecommunication cables from an AC railway line: Measurements and calculations

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2003
G. Lucca
The paper describes the main results of a field measurement campaign of the electromagnetic interference produced by a 25 kV - 50 Hz railway line on nearby telecommunication cables; the results of the measurements were compared with the results of calculations based on suitable circuit models for studying the inducing and induced systems. The results of the comparison were deemed satisfactory. [source]

On circuit models for quantum-classical networks,

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 5-6 2007
Árpád I. Csurgay
Abstract Physics is not scale invariant, and today the scale of atoms and molecules challenges designers of machines in which quantum effects have dominant sway. What role could circuit theory play in designing machines described by quantum-classical models? Classical equivalent circuits do exist for systems composed of metal contacted and wired devices, such as resonant tunneling diodes, single electron transistors, metal,insulator,metal diodes, etc. circuits, but not for quantum-entangled networks, such as multi-quantum-state atoms. If devices were not contacted and wired by macroscopic metals, i.e. devices were classically field coupled, then generalized circuit models can be introduced. Case studies have been presented on the role of circuit models in quantum-classical systems. However, there are no ideal circuit elements capable of capturing the port properties of quantum-mechanical and/or quantum-optical subsystems and their coupling to classical waveguides or cavities. Copyright © 2007 John Wiley & Sons, Ltd. [source]

TLM models of waves in moving media: refinements and dispersion analysis

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2003
William J O'Connor
Abstract Two recent papers about transmission line matrix (TLM) models of waves in moving media used notional diodes to achieve the appropriate direction-dependent wave speeds. Despite the algorithm's demonstrated success, the operation of the diodes might be criticized for being non-physical from a circuit theory perspective. Alternative circuit models are here developed that avoid this objection, being based on wave two-ports and standard circuit theory components. Their operation obeys the same numerical algorithm derived using the diodes, thereby confirming the validity of the original computational scheme. Furthermore these circuits lead more easily to the direction-dependent wave speed expressions and provide exact analytic results for dispersion and attenuation effects, which are here presented and discussed. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Analysis and characterization of package resonance

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2005
El-Badawy El-Sharawy
Abstract This article presents FDTD analysis and prediction of the overall effects of the resonance in ceramic and plastic packages. Practical structures that result in strong resonance effects are investigated, such as coupled cross lines with a via transition and multiple via transitions on a single line. A detailed study of the mutual coupling, including resonance effects, is also performed and presented. The results of the analysis indicate that the package performance can be very sensitive to the resonance effects. A broadband equivalent-circuit model for multiple transition discontinuities (two via holes) on a single line has been developed and presented. Good agreement between the frequency response of the FDTD and the circuit models has been achieved over a broad band of frequencies. The analysis presented in this article provides insight about the limits at which coupling effects on the overall package performance can be neglected. The equivalent-circuit model presented in this article can greatly simplify the analysis and simulation of a complex package, including several transition discontinuities, assuming that the coupling is small. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source]

Analysis and modeling of microstrip-to-coplanar flip chip package interconnects

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2001
Hussein H. M. Ghouz
Abstract In this paper, the discontinuity of a flip chip transition between a microstrip line and a coplanar waveguide is investigated and modeled using the finite-difference time-domain method (FDTD) to predict the overall S -parameters of the package. Effects of the bump and via interconnects on the package performance are investigated and discussed. This includes the effects of different staggered transitions and ground connects on the package performance. A reduction of about 10 dB in the bump and via reflections can be achieved by staggering the signal (bump) and the ground connects (bump/via). A staggering distance of about twice the slot width gave minimum reflection over a wide band of frequencies. Moreover, the larger the relative distance between the ground and the center connects the less the reflection due to the discontinuity. Finally, the computed S -parameters of the flip chip package using the FDTD solution are used to develop an equivalent circuit model for the transition discontinuity over a wide frequency band. The equivalent circuit model of the microstrip to coplanar waveguide discontinuity includes more elements and is more complex than other types of transitions. A TEE or PI circuit model has been used to approximate the general circuit model of the discontinuity. Good agreement has been obtained between the S -parameters of the FDTD model and the equivalent circuit models over a wide frequency band. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 202,211, 2001. [source]

In Vitro and In Vivo Evaluation of Albumin Synthesis Rate of Porcine Hepatocytes in a Flat-Plate Bioreactor

ARTIFICIAL ORGANS, Issue 7 2001
Masaya Shito
Abstract: Several configurations of extracorporeal bioartificial liver devices have been developed for the potential treatment of fulminant hepatic failure or as a bridge to liver transplantation. Recently, we developed a microchannel flat-plate bioreactor with an internal membrane oxygenator in which porcine hepatocytes are cultured as a monolayer on the bottom glass surface. In the present study, we investigated synthetic function of porcine hepatocytes in the bioreactor in both in vitro and in vivo flow circuit models. In vitro, albumin synthesis was stable in the bioreactor for up to 4 days of perfusion. In vivo, with the extracorporeal connection of the bioreactor to rat vasculature, porcine albumin was detectable for 24 h in the rat plasma. We also developed a simple mathematical model to predict the in vivo porcine albumin concentration in rat plasma. These results indicate that this configuration of a microchannel flat-plate bioreactor has potential as a liver support device and warrants further investigation. [source]