The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
R S Reneman - One of the best experts on this subject based on the ideXlab platform.
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relation between left ventricular cavity pressure and volume and systolic fiber stress and strain in the wall
Biophysical Journal, 1991Co-Authors: Theo Arts, P H M Bovendeerd, F M Prinzen, R S RenemanAbstract:Pumping power as delivered by the heart is generated by the cells in the myocardial wall. In the present model study global left-ventricular pump function as expressed in terms of cavity pressure and volume is related to local wall tissue function as expressed in terms of myocardial fiber stress and strain. On the basis of earlier studies in our laboratory, it may be concluded that in the normal left ventricle muscle fiber stress and strain are homogeneously distributed. So, fiber stress and strain may be approximated by single values, being valid for the whole wall. When assuming rotational symmetry and homogeneity of mechanical load in the wall, the Dimensionless Ratio of muscle fiber stress (sigma f) to left-ventricular pressure (Plv) appears to depend mainly on the Dimensionless Ratio of cavity volume (Vlv) to wall volume (Vw) and is quite independent of other geometric parameters. A good (+/- 10%) and simple approximation of this relation is sigma f/Plv = 1 + 3 Vlv/Vw. Natural fiber strain is defined by ef = In (lf/lf,ref), where lf,ref indicates fiber length (lf) in a reference situation. Using the principle of conservation of energy for a change in ef, it holds delta ef = (1/3)delta In (1 + 3Vlv/Vw).
M.h. Frese - One of the best experts on this subject based on the ideXlab platform.
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current and current density of a finite width space charge limited electron beam in two dimensional parallel plate geometry
Physics of Plasmas, 2001Co-Authors: John J. Watrous, J.w. Luginsland, M.h. FreseAbstract:The current carried by a steady-state, finite-width beam produced by space-charge-limited emission in two-dimensional parallel plate geometry is known to diverge strongly from estimates based on the classic one-dimensional Child–Langmuir problem. The two-dimensional problem presents formidable analytic difficulties, but a numerical approach to this problem has been developed. The approach simultaneously determines the electrostatic potential and the unknown current density profile. Calculations show that the total current is a function of the Dimensionless Ratio of beam width (w) to anode–cathode gap (d), but that the current density profile varies with both w and d separately.
Jiunnwei Chen - One of the best experts on this subject based on the ideXlab platform.
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bulk viscosity of a gas of massless pions
Physical Review C, 2009Co-Authors: Jiunnwei Chen, Juven WangAbstract:In the hadronic phase, the dominant configuRation of quantum chromodynamics (QCD) with two flavors of massless quarks is a gas of massless pions. We calculate the bulk viscosity ($\ensuremath{\zeta}$) using the Boltzmann equation with the kinetic theory generalized to incorporate the trace anomaly. We find that the Dimensionless Ratio $\ensuremath{\zeta}/s$, $s$ being the entropy density, is monotonic increasing below $T=120$ MeV, where chiral perturbation theory is applicable. This, combined with previous results, shows that $\ensuremath{\zeta}/s$ reaches its maximum near the phase-transition temperature ${T}_{c}$, while $\ensuremath{\eta}/s$, $\ensuremath{\eta}$ being the shear viscosity, reaches its minimum near ${T}_{c}$ in QCD with massless quarks.
Juven Wang - One of the best experts on this subject based on the ideXlab platform.
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bulk viscosity of a gas of massless pions
Physical Review C, 2009Co-Authors: Jiunnwei Chen, Juven WangAbstract:In the hadronic phase, the dominant configuRation of quantum chromodynamics (QCD) with two flavors of massless quarks is a gas of massless pions. We calculate the bulk viscosity ($\ensuremath{\zeta}$) using the Boltzmann equation with the kinetic theory generalized to incorporate the trace anomaly. We find that the Dimensionless Ratio $\ensuremath{\zeta}/s$, $s$ being the entropy density, is monotonic increasing below $T=120$ MeV, where chiral perturbation theory is applicable. This, combined with previous results, shows that $\ensuremath{\zeta}/s$ reaches its maximum near the phase-transition temperature ${T}_{c}$, while $\ensuremath{\eta}/s$, $\ensuremath{\eta}$ being the shear viscosity, reaches its minimum near ${T}_{c}$ in QCD with massless quarks.
Yongdong Li - One of the best experts on this subject based on the ideXlab platform.
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Two-dimensional Child–Langmuir law of planar diode with finite-radius emitter
2005Co-Authors: Yongdong Li, Hongguang WangAbstract:Abstract A planar diode with finite-radius emitter is studied with particle-in-cell simulations to extend the classical one-dimensional (1D) Child–Langmuir law to two-dimensions. It is found that the 2D space–charge-limited current density in units of the classical 1D value follows a monotonically decreasing function of the Dimensionless Ratio of emitter radius (R) to gap sepaRation (D), and the function can be extended to relativistic regime without significant modification. It is also verified that Lau's analytical prediction of the 2D Child–Langmuir law is in better agreement with the simulation results in comparison with Rokhlenko's.
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2D Child-Langmuir law for planar diode with finite-radius emitter
IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839), 2004Co-Authors: Yongdong Li, Feng HeAbstract:A planar diode with finite-radius emitter is studied with particle-in-cell simulations to extend the classical one-dimensional (1D) Child-Langmuir law to two dimensions. It is found that the 2D space-charge-limited current density in units of the classical 1D value follows a monotonically deceasing function of the Dimensionless Ratio of emitter radius (R) to gap sepaRation (D), and the function can be extended to relativistic regime without significant modification. It is also verified that Lau's analytical prediction of the 2D Child-Langmuir law is in good agreement with the simulation results in comparison with Rokhlenko's.