The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Lucas Duffrene - One of the best experts on this subject based on the ideXlab platform.
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Temperature Dependence of the High‐Frequency Viscoelastic Behavior of a Soda‐Lime‐Silica Glass
Journal of the American Ceramic Society, 2005Co-Authors: Lucas Duffrene, J. E. Masnik, John C. Kieffer, Jay D. BassAbstract:The high-frequency Viscoelastic Behavior of a soda-lime-silica glass has been investigated using the Brillouin scattering technique. The temperature dependence of instantaneous elastic constants and very short-time relaxation mechanisms have been measured in a temperature range between 100° and 1000°C. Variations in the elastic constants in the transition region are significant, and have to be taken into account for numerical computations of tempering and annealing of glasses. A complex thermorheological Behavior is observed for very fast relaxation mechanisms in the transition range, whereas intermediate and slow relaxation mechanisms exhibit a simple thermorheological Behavior. The Viscoelastic Behavior of this glass can be adequately represented by assuming a different thermorheological Behavior in the alpha- and β-relaxation regimes.
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Viscoelastic Behavior of a soda-lime-silica glass: inadequacy of the KWW function
Journal of Non-crystalline Solids, 1997Co-Authors: Lucas Duffrene, H. Burlet, R. PiquesAbstract:Abstract The Viscoelastic Behavior of a soda-lime-silica glass has been experimentally investigated in the glass transition range using shear and uniaxial creep-recovery experiments. No departure of linearity and thermorheological simplicity is found in the investigated stress and temperature ranges, respectively. The shear and uniaxial Viscoelastic constants and retardation functions have been precisely measured from the recovery part. An attempt to model the shear and uniaxial Viscoelastic Behaviors with KWW functions is made and it is shown that this model cannot be a good representation of the linear Viscoelastic Behavior of the investigated glass.
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Multiaxial linear Viscoelastic Behavior of a soda–lime–silica glass based on a generalized Maxwell model
Journal of Rheology, 1997Co-Authors: Lucas Duffrene, H. Burlet, R. PiquesAbstract:The multiaxial linear Viscoelastic Behavior of a soda–lime–silica glass has been investigated in the transition range using shear and uniaxial creep-recovery experiments. The shear and uniaxial Viscoelastic constants and retardation functions have been precisely measured. The no-stress and the no-temperature dependence of the Viscoelastic constants show, respectively, linear Viscoelastic and simple thermorheological Behaviors of the glass. The deviatoric part of the Viscoelastic Behavior is first investigated from the shear experimental data. A generalized Maxwell model with one set of parameters is shown to correctly simulate the shear creep-recovery experiments. Using the deviatoric part of the model, the spheric part of the Viscoelastic Behavior is deduced from the uniaxial experimental data. In particular, we show experimental measurements of the bulk equilibrium modulus and the temperature dependence of the hydrostatic pressure Viscoelastic Behavior for a soda–lime–silica glass. A second set of parameters of the generalized Maxwell model is determined for the hydrostatic pressure Viscoelastic Behavior.
Arash Kheradvar - One of the best experts on this subject based on the ideXlab platform.
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Aging does not affect radial Viscoelastic Behavior of the left ventricle.
Cardiology, 2013Co-Authors: Jan O. Mangual, Daniela Föll, Bernd Jung, Gianni Pedrizzetti, Arash KheradvarAbstract:Objectives: This study investigates the effect of aging on the radial Viscoelastic Behavior of the left ventricle (LV) based on a previously validated model that
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Modeling Radial Viscoelastic Behavior of Left Ventricle Based on MRI Tissue Phase Mapping
Annals of Biomedical Engineering, 2010Co-Authors: Jan O. Mangual, Bernd Jung, James A. Ritter, Arash KheradvarAbstract:The Viscoelastic Behavior of myocardial tissue is a measure that has recently found to be a deterministic factor in quality of contraction. Parameters imposing the Viscoelastic Behavior of the heart are influenced in part by sarcomere function and myocardial composition. Despite the overall agreement on significance of cardiac Viscoelasticity, a practical model that can measure and characterize the Viscoelastic Behavior of the myocardial segments does not yet exist. Pressure–Volume ( P – V ) curves are currently the only measure for stiffness/compliance of the left ventricle. However, obtaining P – V curves requires invasive cardiac catheterization, and only provides qualitative information on how pressure and volume change with respect to each other. For accurate assessment of myocardial mechanical Behavior, it is required to obtain quantitative measures for Viscoelasticity. In this work, we have devised a model that yields myocardial elastic and viscous damping coefficient functions through the cardiac cycle. The required inputs for this model are kinematic information with respect to changes in LV short axes that were obtained by Magnetic Resonance Imaging (MRI) using a tissue phase mapping (TPM) pulse sequence. We evaluated Viscoelastic coefficients of LV myocardium in two different age groups of 20–40 and greater than 60. We found that the magnitude of stiffness coefficients is noticeably greater in the older subjects. Additionally, we found that slope of viscous damping functions follow similar patterns for each individual age group. This method may shed light on dynamics of contraction through MRI in conditions where composition of myocardium is changed such as in aging, adverse remodeling, and cardiomyopathies.
R. Piques - One of the best experts on this subject based on the ideXlab platform.
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Viscoelastic Behavior of a soda-lime-silica glass: inadequacy of the KWW function
Journal of Non-crystalline Solids, 1997Co-Authors: Lucas Duffrene, H. Burlet, R. PiquesAbstract:Abstract The Viscoelastic Behavior of a soda-lime-silica glass has been experimentally investigated in the glass transition range using shear and uniaxial creep-recovery experiments. No departure of linearity and thermorheological simplicity is found in the investigated stress and temperature ranges, respectively. The shear and uniaxial Viscoelastic constants and retardation functions have been precisely measured from the recovery part. An attempt to model the shear and uniaxial Viscoelastic Behaviors with KWW functions is made and it is shown that this model cannot be a good representation of the linear Viscoelastic Behavior of the investigated glass.
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Multiaxial linear Viscoelastic Behavior of a soda–lime–silica glass based on a generalized Maxwell model
Journal of Rheology, 1997Co-Authors: Lucas Duffrene, H. Burlet, R. PiquesAbstract:The multiaxial linear Viscoelastic Behavior of a soda–lime–silica glass has been investigated in the transition range using shear and uniaxial creep-recovery experiments. The shear and uniaxial Viscoelastic constants and retardation functions have been precisely measured. The no-stress and the no-temperature dependence of the Viscoelastic constants show, respectively, linear Viscoelastic and simple thermorheological Behaviors of the glass. The deviatoric part of the Viscoelastic Behavior is first investigated from the shear experimental data. A generalized Maxwell model with one set of parameters is shown to correctly simulate the shear creep-recovery experiments. Using the deviatoric part of the model, the spheric part of the Viscoelastic Behavior is deduced from the uniaxial experimental data. In particular, we show experimental measurements of the bulk equilibrium modulus and the temperature dependence of the hydrostatic pressure Viscoelastic Behavior for a soda–lime–silica glass. A second set of parameters of the generalized Maxwell model is determined for the hydrostatic pressure Viscoelastic Behavior.
Jan O. Mangual - One of the best experts on this subject based on the ideXlab platform.
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Aging does not affect radial Viscoelastic Behavior of the left ventricle.
Cardiology, 2013Co-Authors: Jan O. Mangual, Daniela Föll, Bernd Jung, Gianni Pedrizzetti, Arash KheradvarAbstract:Objectives: This study investigates the effect of aging on the radial Viscoelastic Behavior of the left ventricle (LV) based on a previously validated model that
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Modeling Radial Viscoelastic Behavior of Left Ventricle Based on MRI Tissue Phase Mapping
Annals of Biomedical Engineering, 2010Co-Authors: Jan O. Mangual, Bernd Jung, James A. Ritter, Arash KheradvarAbstract:The Viscoelastic Behavior of myocardial tissue is a measure that has recently found to be a deterministic factor in quality of contraction. Parameters imposing the Viscoelastic Behavior of the heart are influenced in part by sarcomere function and myocardial composition. Despite the overall agreement on significance of cardiac Viscoelasticity, a practical model that can measure and characterize the Viscoelastic Behavior of the myocardial segments does not yet exist. Pressure–Volume ( P – V ) curves are currently the only measure for stiffness/compliance of the left ventricle. However, obtaining P – V curves requires invasive cardiac catheterization, and only provides qualitative information on how pressure and volume change with respect to each other. For accurate assessment of myocardial mechanical Behavior, it is required to obtain quantitative measures for Viscoelasticity. In this work, we have devised a model that yields myocardial elastic and viscous damping coefficient functions through the cardiac cycle. The required inputs for this model are kinematic information with respect to changes in LV short axes that were obtained by Magnetic Resonance Imaging (MRI) using a tissue phase mapping (TPM) pulse sequence. We evaluated Viscoelastic coefficients of LV myocardium in two different age groups of 20–40 and greater than 60. We found that the magnitude of stiffness coefficients is noticeably greater in the older subjects. Additionally, we found that slope of viscous damping functions follow similar patterns for each individual age group. This method may shed light on dynamics of contraction through MRI in conditions where composition of myocardium is changed such as in aging, adverse remodeling, and cardiomyopathies.
Jay D. Bass - One of the best experts on this subject based on the ideXlab platform.
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Temperature Dependence of the High‐Frequency Viscoelastic Behavior of a Soda‐Lime‐Silica Glass
Journal of the American Ceramic Society, 2005Co-Authors: Lucas Duffrene, J. E. Masnik, John C. Kieffer, Jay D. BassAbstract:The high-frequency Viscoelastic Behavior of a soda-lime-silica glass has been investigated using the Brillouin scattering technique. The temperature dependence of instantaneous elastic constants and very short-time relaxation mechanisms have been measured in a temperature range between 100° and 1000°C. Variations in the elastic constants in the transition region are significant, and have to be taken into account for numerical computations of tempering and annealing of glasses. A complex thermorheological Behavior is observed for very fast relaxation mechanisms in the transition range, whereas intermediate and slow relaxation mechanisms exhibit a simple thermorheological Behavior. The Viscoelastic Behavior of this glass can be adequately represented by assuming a different thermorheological Behavior in the alpha- and β-relaxation regimes.
