The Experts below are selected from a list of 590052 Experts worldwide ranked by ideXlab platform
Q S Wang - One of the best experts on this subject based on the ideXlab platform.
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active buckling Control of beams using piezoelectric actuators and strain gauge sensors
Smart Materials and Structures, 2010Co-Authors: Q S WangAbstract:In this paper, a finite element model incorporating active Control techniques has been developed to stabilize the first two buckling modes of both a simply supported and a cantilevered beam. The goal is to increase the corresponding beam buckling loads by using piezoelectric actuators along with optimal feedback Control. The uniform beams are bonded with two pairs of segmented piezoelectric actuators at the top and bottom. Resistive strain gauges are attached to the centres of the actuators as sensors. Measurements are taken using these, to estimate the system states. The beams are simply supported or cantilevered and subjected to a slowly increasing axial compressive load. Finite element formulations based on the classical Euler–Bernoulli beam theory and linear piezoelectric constitutive equations for the actuators are presented. The associated reduced-order modal equations and the state-space equations are derived for the design of a standard linear quadratic regulator (LQR). The finite element analysis and the active Control Simulation results are consistent with both theoretical analysis results and experimental data. The designed full state feedback LQR Controller is shown to be successful in stabilizing the first two buckling modes of the beams. Also the Control Simulation shows that the present optimally located segmented actuator pairs along the beam are more effective for buckling Control.
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active buckling Control of beams using piezoelectric actuators and strain gauge sensors
Smart Materials and Structures, 2010Co-Authors: Q S WangAbstract:In this paper, a finite element model incorporating active Control techniques has been developed to stabilize the first two buckling modes of both a simply supported and a cantilevered beam. The goal is to increase the corresponding beam buckling loads by using piezoelectric actuators along with optimal feedback Control. The uniform beams are bonded with two pairs of segmented piezoelectric actuators at the top and bottom. Resistive strain gauges are attached to the centres of the actuators as sensors. Measurements are taken using these, to estimate the system states. The beams are simply supported or cantilevered and subjected to a slowly increasing axial compressive load. Finite element formulations based on the classical Euler–Bernoulli beam theory and linear piezoelectric constitutive equations for the actuators are presented. The associated reduced-order modal equations and the state-space equations are derived for the design of a standard linear quadratic regulator (LQR). The finite element analysis and the active Control Simulation results are consistent with both theoretical analysis results and experimental data. The designed full state feedback LQR Controller is shown to be successful in stabilizing the first two buckling modes of the beams. Also the Control Simulation shows that the present optimally located segmented actuator pairs along the beam are more effective for buckling Control.
James W Hurrell - One of the best experts on this subject based on the ideXlab platform.
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variability of the atlantic meridional overturning circulation in ccsm4
Journal of Climate, 2012Co-Authors: Gokhan Danabasoglu, Stephen Yeager, Youngoh Kwon, Joseph Tribbia, Adam S Phillips, James W HurrellAbstract:AbstractAtlantic meridional overturning circulation (AMOC) variability is documented in the Community Climate System Model, version 4 (CCSM4) preindustrial Control Simulation that uses nominal 1° horizontal resolution in all its components. AMOC shows a broad spectrum of low-frequency variability covering the 50–200-yr range, contrasting sharply with the multidecadal variability seen in the T85 × 1 resolution CCSM3 present-day Control Simulation. Furthermore, the amplitude of variability is much reduced in CCSM4 compared to that of CCSM3. Similarities as well as differences in AMOC variability mechanisms between CCSM3 and CCSM4 are discussed. As in CCSM3, the CCSM4 AMOC variability is primarily driven by the positive density anomalies at the Labrador Sea (LS) deep-water formation site, peaking 2 yr prior to an AMOC maximum. All processes, including parameterized mesoscale and submesoscale eddies, play a role in the creation of salinity anomalies that dominate these density anomalies. High Nordic Sea densi...
Thomas L Delworth - One of the best experts on this subject based on the ideXlab platform.
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impact of the atlantic meridional overturning circulation amoc on arctic surface air temperature and sea ice variability
Journal of Climate, 2011Co-Authors: Salil Mahajan, Rong Zhang, Thomas L DelworthAbstract:AbstractThe simulated impact of the Atlantic meridional overturning circulation (AMOC) on the low-frequency variability of the Arctic surface air temperature (SAT) and sea ice extent is studied with a 1000-year-long segment of a Control Simulation of the Geophysical Fluid Dynamics Laboratory Climate Model version 2.1. The simulated AMOC variations in the Control Simulation are found to be significantly anticorrelated with the Arctic sea ice extent anomalies and significantly correlated with the Arctic SAT anomalies on decadal time scales in the Atlantic sector of the Arctic. The maximum anticorrelation with the Arctic sea ice extent and the maximum correlation with the Arctic SAT occur when the AMOC index leads by one year. An intensification of the AMOC is associated with a sea ice decline in the Labrador, Greenland, and Barents Seas in the Control Simulation, with the largest change occurring in winter. The recent declining trend in the satellite-observed sea ice extent also shows a similar pattern in t...
Dan Mihailescu - One of the best experts on this subject based on the ideXlab platform.
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atomic detail peptide membrane interactions molecular dynamics Simulation of gramicidin s in a dmpc bilayer
Biophysical Journal, 2000Co-Authors: Dan Mihailescu, Jeremy C SmithAbstract:Molecular dynamics Simulations have been performed of the sequence-symmetric cyclic decapeptide antibiotic gramicidin S (GS), in interaction with a hydrated dimyristoylphosphatidylcholine (DMPC) bilayer, and the results compared with a "Control" Simulation of the system in the absence of GS. Following experimental evidence, the GS was initially set in a single antiparallel beta-sheet conformation with two Type II' beta-turns in an amphiphilic interaction with the membrane. This conformation and position remained in the 6.5 ns Simulation. Main-chain dihedrals are on average approximately 26 degrees from those determined by NMR experiment on GS in dimethylsulfoxide (DMSO) solution. Sequence-symmetric main-chain and side-chain dihedral angle pairs converge to within approximately 5 degrees and approximately 10 degrees, respectively. The area per lipid, lipid tail order parameters, and quadrupole spin-lattice relaxation times of the Control Simulation are mostly in good agreement with corresponding experiments. The GS has little effect on the membrane dipole potential or water permeability. However, it is found to have a disordering effect (in agreement with experiment) and a fluidifying effect on lipids directly interacting with it, and an ordering effect on those not directly interacting.
Gokhan Danabasoglu - One of the best experts on this subject based on the ideXlab platform.
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variability of the atlantic meridional overturning circulation in ccsm4
Journal of Climate, 2012Co-Authors: Gokhan Danabasoglu, Stephen Yeager, Youngoh Kwon, Joseph Tribbia, Adam S Phillips, James W HurrellAbstract:AbstractAtlantic meridional overturning circulation (AMOC) variability is documented in the Community Climate System Model, version 4 (CCSM4) preindustrial Control Simulation that uses nominal 1° horizontal resolution in all its components. AMOC shows a broad spectrum of low-frequency variability covering the 50–200-yr range, contrasting sharply with the multidecadal variability seen in the T85 × 1 resolution CCSM3 present-day Control Simulation. Furthermore, the amplitude of variability is much reduced in CCSM4 compared to that of CCSM3. Similarities as well as differences in AMOC variability mechanisms between CCSM3 and CCSM4 are discussed. As in CCSM3, the CCSM4 AMOC variability is primarily driven by the positive density anomalies at the Labrador Sea (LS) deep-water formation site, peaking 2 yr prior to an AMOC maximum. All processes, including parameterized mesoscale and submesoscale eddies, play a role in the creation of salinity anomalies that dominate these density anomalies. High Nordic Sea densi...
