Creating Nodes at Selected Locations in a Harmonically Excited Structure Using Feedback Control and Green’s Function

The paper deals with designing a control force to create nodal point(s) having zero displacements and/or zero slopes at selected locations in a harmonically excited vibrating structure. It is shown that the steady-state vibrations at desired points can be eliminated using feedback control forces. These control forces are constructed from displacement and/or velocity measurements using sensors located either at the control force position or at some other locations. Dynamic Green’s function is exploited to derive a simple and exact closed from expression for the control force. Under a certain condition, this control force can be generated using passive elements such as springs and dampers. Numerical examples demonstrate the applicability of the method in various cases.

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Green's function for steady-state heat conduction in a bimaterial composite solid

Computational Mechanics ◽

10.1007/s004660050509 ◽

2000 ◽

Vol 25 (6) ◽

pp. 627-634 ◽

Cited By ~ 11

Author(s):

J. R. Berger ◽

J. L. Skilowitz ◽

V. K. Tewary

Keyword(s):

Heat Conduction ◽

Steady State ◽

Green’S Function ◽

Green's Function ◽

State Heat ◽

Steady State Heat ◽

Composite Solid

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Keldysh Green’s function approach to coherence in a non-equilibrium steady state: connecting Bose-Einstein condensation and lasing

Optical Generation and Control of Quantum Coherence in Semiconductor Nanostructures - NanoScience and Technology ◽

10.1007/978-3-642-12491-4_12 ◽

2010 ◽

pp. 293-329 ◽

Cited By ~ 1

Author(s):

Jonathan Keeling ◽

Marzena H. Szymańska ◽

Peter B. Littlewood

Keyword(s):

Steady State ◽

Green’S Function ◽

Green's Function ◽

Function Approach ◽

Einstein Condensation ◽

Bose Einstein Condensation ◽

Bose Einstein ◽

Non Equilibrium

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On Selection of Control Parameters for H∞ Output Feedback

Volume 8: Seismic Engineering ◽

10.1115/pvp2005-71109 ◽

2005 ◽

Author(s):

Chang-Ching Chang ◽

Chi-Chang Lin

Keyword(s):

Control System ◽

Feedback Control ◽

Output Feedback ◽

Delay Time ◽

Output Feedback Control ◽

Feedback Gain ◽

Control Force ◽

Control Parameters ◽

Structural Responses ◽

Control Forces

In this paper, an H∞ direct output feedback control algorithm through minimizing the entropy, a performance index measuring the tradeoff between H∞ optimality and H2 optimality, is employed to design the control system in reducing structural responses due to dynamic loads such as earthquakes. The control forces are obtained from the multiplication of direct output measurements by a pre-calculated time-invariant feedback gain matrix. To achieve optimal control performance, the strategy to select both control parameters γ and α is extensively investigated. The decrease of γ or increase of α results in better control effectiveness, but larger control force requirement. For a single degree-of-freedom (SDOF) damped structure, exact solutions of output feedback gains and control parameters are derived. It can be proved analytically that the LQR control is a special case of the proposed H∞ control. Direct velocity feedback control is effective in reducing structural responses with very small number of sensors and controllers compared with the DOFs of the structure. In active control of a real structure, control force execution time delay cannot be avoided. Relatively small delay time not only can render the control ineffective, but also may cause system instability. In this study, explicit formulas to calculate maximum allowable delay time and critical control parameters are derived for the design of a stable control system. Some solutions are also proposed to increase the maximum allowable delay time.

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Pairon Green’s function for high-Tc superconductors

Modern Physics Letters B ◽

10.1142/s0217984921500809 ◽

2020 ◽

pp. 2150080

Author(s):

Radhika Chauhan ◽

B. D. Indu

Keyword(s):

Green’S Function ◽

Green's Function ◽

Quantum Dynamics ◽

Nodal Point ◽

Superconducting Gap ◽

Energy Relation ◽

Gap Equation ◽

Gap Ratio ◽

Many Body Quantum Dynamics ◽

The Many

Considering the many-body quantum dynamics, the pairon Green’s function has been developed via a Hamiltonian that encompasses the contribution of pairons, pairon-phonon interactions, anharmonicities, and defects. To obtain the renormalized pairon energy dispersion, the most relevant Born–Mayer–Huggins potential has been taken into account. The Fermi surface for the representative [Formula: see text] high-[Formula: see text] superconductor has been obtained via renormalized pairon energy relation. This revealed the [Formula: see text]-shape superconducting gap with a nodal point along [Formula: see text] direction. Further, the superconducting gap equation has been derived using the pairon density of states. The developed gap equation is the function of temperature, Fermi energy, and renormalized pairon energy. The temperature variation of the gap equation is found to be in good agreement with the BCS gap equation. Also, this reveals the reduced gap ratio ([Formula: see text] for [Formula: see text]) in the limit (5–8) of the reduced gap ratio designated for high-[Formula: see text] superconductors.

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