The homogeneous field approximation of classical thermodynamics

1988 ◽  
Vol 101 (4) ◽  
pp. 349-363 ◽  
Author(s):  
W. A. Day
Keyword(s):  
Field Approximation ◽  
Homogeneous Field ◽  
Classical Thermodynamics

The Determination of the Magnetoelectric Coupling Coefficient in Ferroelectric–Ferromagnetic Composite Based on PZT–Ferrite

2013 ◽  
Vol 58 (4) ◽  
pp. 1401-1403 ◽  
Author(s):  
J.A. Bartkowska ◽  
R. Zachariasz ◽  
D. Bochenek ◽  
J. Ilczuk
Keyword(s):  
Dielectric Permittivity ◽  
Coupling Coefficient ◽  
Mean Field ◽  
Field Approximation ◽  
Theoretical Description ◽  
Magnetoelectric Coupling ◽  
Mean Field Approximation ◽  
Dielectric Measurements ◽  
Temperature Dependences ◽  
Multiferroic Composite

Abstract In the present work, the magnetoelectric coupling coefficient, from the temperature dependences of the dielectric permittivity for the multiferroic composite was determined. The research material was ferroelectric-ferromagnetic composite on the based PZT and ferrite. We investigated the temperature dependences of the dielectric permittivity (") for the different frequency of measurement’s field. From the dielectric measurements we determined the temperature of phase transition from ferroelectric to paraelectric phase. For the theoretical description of the temperature dependence of the dielectric constant, the Hamiltonian of Alcantara, Gehring and Janssen was used. To investigate the dielectric properties of the multiferroic composite this Hamiltonian was expressed under the mean-field approximation. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified.

Magnetic Field Approximation in MR Tomography

PIERS Online ◽  
2007 ◽  
Vol 3 (8) ◽  
pp. 1250-1253
Author(s):  
Michal Hadinec ◽  
Pavel Fiala ◽  
Eva Kroutilova ◽  
M. Steinbauer ◽  
Karel Bartusek
Keyword(s):  
Magnetic Field ◽  
Field Approximation ◽  
Mr Tomography

General Cluster Sorption Isotherm

2020 ◽  
Author(s):  
Christoph Buttersack
Keyword(s):  
Density Functional ◽  
Capillary Condensation ◽  
Cluster Formation ◽  
Full Range ◽  
Full Description ◽  
Cross Sectional ◽  
Macroporous Silica ◽  
Isotherm Equation ◽  
Type Iv ◽  
Classical Thermodynamics

<p>Adsorption isotherms are an essential tool in chemical physics of surfaces. However, several approaches based on a different theoretical basis exist and for isotherms including capillary condensation existing approaches can fail. Here, a general isotherm equation is derived and applied to literature data both concerning type IV isotherms of argon and nitrogen in ordered mesoporous silica, and type II isotherms of disordered macroporous silica. The new isotherm covers the full range of partial pressure (10<sup>-6</sup> - 0.7). It relies firstly on the classical thermodynamics of cluster formation, secondly on a relationship defining the free energy during the increase of the cluster size. That equation replaces the Lennard-Jones potentials used in the classical density functional theory. The determination of surface areas is not possible by this isotherm because the cross-sectional area of a cluster is unknown. Based on the full description of type IV isotherms, most known isotherms are accessible by respective simplifications. </p>

Formation of Barrier Oxide Film on Lead in Borate Solutions

1994 ◽  
Vol 59 (6) ◽  
pp. 1305-1310 ◽  
Author(s):  
Emad E. Abdel Aal ◽  
Mohamed M. Hefny
Keyword(s):  
Oxide Film ◽  
Current Density ◽  
High Field ◽  
Empirical Relation ◽  
Field Approximation ◽  
Ion Concentration ◽  
Solution Temperature ◽  
Oxide Growth ◽  
Rate Of Growth ◽  
Barrier Type

Galvanostatic anodization of lead in borate solutions reveals that lead can form a barrier type oxide film. The rate of growth, R, fulfils the empirical relation, R = aib within the current density i range from 1.16 .10-4 to 3.19 .10-4 A cm-2. The magnitudes of the parameters a and b are 6.9 . 103 and 1.6, respectively, it has been found that the high field approximation is applicable for the oxide growth on lead. The coefficients of the dependence of R on solution temperature, T, pH and borate ion concentration, c, viz. (∂R/∂T), (∂R/∂pH) and (∂R/∂log c) are -18 . 10-4, -0.13 and 0.41, respectively.

Temperature and its measurement

2017 ◽  
Author(s):  
Andrew Clarke
Keyword(s):  
Thermal Equilibrium ◽  
Isotope Fractionation ◽  
Thermodynamic Temperature ◽  
The Other ◽  
Deterministic Models ◽  
Triple Point Of Water ◽  
Temperature Scales ◽  
Classical Thermodynamics ◽  
The Relationship ◽  
Unit Of Temperature

Temperature is that property of a body which determines whether it gains or loses energy in a particular environment. In classical thermodynamics temperature is defined by the relationship between energy and entropy. Temperature can be defined only for a body that is in thermodynamic and thermal equilibrium; whilst organisms do not conform to these criteria, the errors in assuming that they do are generally small. The Celsius and Fahrenheit temperature scales are arbitrary because they require two fixed points, one to define the zero and the other to set the scale. The thermodynamic (absolute) scale of temperature has a natural zero (absolute zero) and is defined by the triple point of water. Its unit of temperature is the Kelvin. The Celsius scale is convenient for much ecological and physiological work, but where temperature is included in statistical or deterministic models, only thermodynamic temperature should be used. Past temperatures can only be reconstructed with the use of proxies, the most important of which are based on isotope fractionation.

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