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Coupling Model (coupling + model)
Selected AbstractsDynamic stiffness of deep foundations with inclined pilesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2010L. 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] FEM simulation of turbulent flow in a turbine blade passage with dynamical fluid,structure interactionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2009Lixiang Zhang Abstract Results are described from a combined mathematical modeling and numerical iteration schemes of flow and vibration. We consider the coupling numerical simulations of both turbulent flow and structure vibration induced by flow. The methodology used is based on the stabilized finite element formulations with time integration. A fully coupled model of flow and flow-induced structure vibration was established using a hydride generalized variational principle of fluid and solid dynamics. The spatial discretization of this coupling model is based on the finite element interpolating formulations for the fluid and solid structure, while the different time integration schemes are respectively used for fluid and solid structure to obtain a stabilized algorithm. For fluid and solid dynamics, Hughes' predictor multi-corrector algorithm and the Newmark method are monolithically used to realize a monolithic solution of the fully coupled model. The numerical convergence is ensured for small deformation vibrating problems of the structure by using different time steps for fluid and solid, respectively. The established model and the associated numerical methodology developed in the paper were then applied to simulate two different flows. The first one is the lid-driven square cavity flow with different Reynolds numbers of 1000, 400 and 100 and the second is the turbulent flows in a 3-D turbine blade passage with dynamical fluid,structure interaction. Good agreement between numerical simulations and measurements of pressure and vibration acceleration indicates that the finite element method formulations developed in this paper are appropriate to deal with the flow under investigation. Copyright © 2009 John Wiley & Sons, Ltd. [source] CFD simulations of hydrodynamic/thermal coupling phenomena in a bubble column with internalsAICHE JOURNAL, Issue 9 2010Cédric Laborde-Boutet Abstract CFD simulations have been carried out in a full three-dimensional, unsteady, Eulerian framework to simulate hydrodynamic/thermal coupling in a bubble column with internals. A first part of the study, dedicated to the hydrodynamic/thermal coupling in liquid single-phase flows, showed that assuming constant wall temperature on the internals constitutes a reasonable approximation in lieu of comprehensive simulations encompassing shell flow and coolant flow together. A second part dealing with the hydrodynamics of gas,liquid flows in a bubble column with internals showed that a RNG k,, turbulence model formulation accounting for gas-induced turbulence was a relevant choice. The last part used these conclusions to build a hydrodynamic/thermal coupling model of a gas,liquid flow in a bubble column with internals. With a per-phase RNG k,, turbulence model and assuming constant wall temperature, it was possible to simulate heat transfer phenomena consistent with experimentally measured heat transfer coefficients. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Electronic Security Systems and Active Implantable Medical DevicesPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2002WERNER IRNICH IRNICH, W.: Electronic Security Systems and Active Implantable Medical Devices. How do active implantable medical devices react in the presence of strong magnetic fields in the frequency range between extremely low frequency (ELF) to radiofrequency (RF) as they are emitted by electronic security systems (ESS)? There are three different sorts of ESSs: electronic article surveillance (EAS) devices, metal detector (MDS) devices, and radiofrequency identification (RFID) systems. Common to all is the production of magnetic fields. There is an abundance of literature concerning interference by ESS gates with respect to if there is an influence possible and if such an influence can bear a risk for the AIMD wearers. However, there has been no attempt to study the physical mechanism nor to develop a model of how and under which conditions magnetic fields can influence pacemakers and defibrillators and how they could be disarmed by technological means. It is too often assumed that interference of AIMD with ESS is inevitable. Exogenous signals of similar intensity and rhythm to heart signals can be misinterpreted and, thus, confuse the implant. Important for the interference coupling mechanism is the differentiation between a "unipolar" and a "bipolar" system. With respect to magnetic fields, the left side implanted pacemaker is the most unfavorable case as the lead forms approximately a semicircular area of maximum 225 cm2 into which a voltage can be induced. This assumption yields an interference coupling model that can be expressed by simple mathematics. The worst-case conditions for induced interference voltages are a coupling area of 225 cm2 that is representative for a large human, a homogeneous magnetic field perpendicular to the area formed by the lead, and a unipolar ventricular pacemaker system that is implanted on the left side of the thorax and has the highest interference sensitivity. In bipolar systems the fields must be 17 times larger when compared to a unipolar system to have the same effect. The magnetic field for interfering with ICDs must be 1.7 stronger than that of the most sensitive unipolar pacemaker. The lowest interference thresholds measured over the last 10 years in the low frequency range (16 2/3 Hz,24 kHz) together with thresholds > 24 kHz that were supplied by the CETECOM study are listed. Both sets of data together with the coupling model, allow for judging which fields of ESSs could influence AIMDs. From measurements at gate antennas, it is possible to derive a "maximum allowed field" curve over the whole frequency range, below which no interference will occur. Comparison of data from literature with these maximum allowed fields confirm the correctness of the calculations. Thus, it is possible to predict interference situations in gates if the magnetic field is known. If all future pacemakers were to have the immunity against interference of the better 50% of today's pacemakers, the magnetic field ceiling values could be at least four times higher. The same is true if the ventricular sensitivity is routinely set at 7 mV. Pacemaker manufacturers should consider filter improvement with modern technology, but gate manufacturers should not claim the privilege of being out of bounds. [source] A comparative study of La0.67Ca0.33MnO3 composites with different secondary phasesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2009Guang Ming Ren Abstract Two kinds of composites with the nominal composition of (1 , x)La0.67Ca0.33MnO3 (LCMO)/x MgO and (1 , x)LCMO/ x SrO were investigated. Different electrical and magnetic transport properties were observed between the two kinds of composites. For the LCMO/MgO composites, the insulator,metal transition temperature (Tp) decreases rapidly with the increase of MgO content and a remarkably enhanced magnetoresistance (MR) peak is observed near Tp. However, for the LCMO/SrO composites, the SrO content has little effect on Tp and the low-field MR is enhanced over almost the whole temperature range. Moreover, a two-step magnetization behavior was observed in the LCMO/MgO composites. By calculating in terms of a ferromagnetic grain coupling model, we attribute this difference to the different effects of the secondary phases on the ferromagnetic coupling between the neighboring LCMO grains, which results from the formation of the different interfacial phases at the grain boundary in the two kinds of composites. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Exciton dephasing in quantum dots: Coupling to LO phonons via excited statesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2008E. A. Muljarov Abstract We have found a novel mechanism of spectral broadening and dephasing in quantum dots (QDs) due to the coupling to longitudinal-optical (LO) phonons. In theory, this mechanism comes into play only if the complete manifold of exciton levels (including those in the wetting-layer continuum) is taken into account. We demonstrate this nontrivial dephasing in different types of QDs, using the exactly solvable quadratic coupling model, here generalized to an arbitrary number of excitonic states. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||