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Impedance Functions (impedance + function)

Distribution by Scientific Domains
Engineering100%

Selected Abstracts

Synthesis of general impedance with simple dc/dc converters for power processing applications

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 3 2008
J. C. P. Liu
Abstract A general impedance synthesizer using a minimum number of switching converters is studied in this paper. We begin with showing that any impedance can be synthesized by a circuit consisting of only two simple power converters, one storage element (e.g. capacitor) and one dissipative element (e.g. resistor) or power source. The implementation of such a circuit for synthesizing any desired impedance can be performed by (i) programming the input current given the input voltage such that the desired impedance function is achieved, (ii) controlling the amount of power dissipation (generation) in the dissipative element (source) so as to match the required active power of the impedance to be synthesized. Then, the instantaneous power will be automatically balanced by the storage element. Such impedance synthesizers find a lot of applications in power electronics. For instance, a resistance synthesizer can be used for power factor correction (PFC), a programmable capacitor or inductor synthesizer (comprising small high-frequency converters) can be used for control applications. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Dynamic stiffness of deep foundations with inclined piles

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2010
L. A. Padrón
Abstract The influence of inclined piles on the dynamic response of deep foundations and superstructures is still not well understood and needs further research. For this reason, impedance functions of deep foundations with inclined piles, obtained numerically from a boundary element,finite element coupling model, are provided in this paper. More precisely, vertical, horizontal, rocking and horizontal,rocking crossed dynamic stiffness and damping functions of single inclined piles and 2 × 2 and 3 × 3 pile groups with battered elements are presented in a set of plots. The soil is assumed to be a homogeneous viscoelastic isotropic half-space and the piles are modeled as elastic compressible Euler,Bernoulli beams. The results for different pile group configurations, pile,soil stiffness ratios and rake angles are presented. Copyright © 2010 John Wiley & Sons, Ltd. [source]

A model for the 3D kinematic interaction analysis of pile groups in layered soils

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2009
Francesca Dezi
Abstract The paper presents a numerical model for the analysis of the soil,structure kinematic interaction of single piles and pile groups embedded in layered soil deposits during seismic actions. A finite element model is considered for the pile group and the soil is assumed to be a Winkler-type medium. The pile,soil,pile interaction and the radiation problem are accounted for by means of elastodynamic Green's functions. Condensation of the problem permits a consistent and straightforward derivation of both the impedance functions and the foundation input motion, which are necessary to perform the inertial soil,structure interaction analyses. The model proposed allows calculating the internal forces induced by soil,pile and pile-to-pile interactions. Comparisons with data available in literature are made to study the convergence and validate the model. An application to a realistic pile foundation is given to demonstrate the potential of the model to catch the dynamic behaviour of the soil,foundation system and the stress resultants in each pile. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Effect of soil interaction on the performance of liquid column dampers for seismic applications

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2005
Aparna Ghosh
Abstract The effects of soil,structure interaction (SSI) while designing the liquid column damper (LCD) for seismic vibration control of structures have been presented in this study. The formulation for the input,output relation of a flexible-base structure with attached LCD has been presented. The superstructure has been modelled by a single-degree-of-freedom (SDOF) system. The non-linearity in the orifice damping of the LCD has been replaced by equivalent linear viscous damping by using equivalent linearization technique. The force,deformation relationships and damping characteristics of the foundation have been described by complex valued impedance functions. Through a numerical stochastic study in the frequency domain, the various aspects of SSI on the functioning of the LCD have been illustrated. A simpler approach for studying the LCD performance considering SSI, using an equivalent SDOF model for the soil,structure system available in literature by Wolf (Dynamic Soil,Structure Interaction. International Series in Civil Engineering and Engineering Mechanics. Prentice-Hall: Englewood Cliffs, NJ, 1985) has also been presented. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Electromagnetic scattering from perfectly conducting periodic surfaces by transforming into equivalent boundary condition

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2008
Necmi Serkan TezelArticle first published online: 28 MAY 200
Abstract In this study, electromagnetic scattering from perfectly conducting periodic surface have been solved by means of transformation of problem into equivalent problem, that is scattering from plane represented by high order inhomogeneous impedance boundary condition (IBC). High order impedance functions are determined by function of the roughness of the surface. Then, transformed equivalent problem is solved by means of series expansion method using Floquet modes. This transformation makes the problem simple formulation and computational effectively without involving calculation of slowly converging periodic Green's function. Results and computational times obtained by transform method and those obtained by Method of Moment (MoM) technique are compared. Good agreements are observed in results. It is also observed that transform method needs much less computational time than MoM method. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1997,2000, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23567 [source]