Adele Manes

Minimum free energy in linear thermoelectromagnetism

A closed expression is given for the minimum free energy of a linear thermoelectromagnetic conductor, whose constitutive equations relative to the electric current density and to the heat flux have memory effects. This expression, derived in the frequency domain, is related to the maximum recoverable work, which can be obtained from a given state of the material. Another equivalent expression of the minimum free energy is deduced; it allows us to give explicit formulae for the case of a discrete spectrum model.

A Heat Conductor with Fading Memory: Dissipation and Free Energies

Some expressions for the free energies of differential systems connected with a rigid heat conductor with memory are studied. The properties of these materials are given by a dynamical system, where the state is expressed in terms of the past histories of the temperature and of its gradient. Finally, the internal dissipations, corresponding to each of these free energies, are also evaluated.

A note on the reference configurations of a thermoelastic solid

SommarioSi ammette comunemente che, comunque si scelga un valore della temperatura in un certo intervallo, esiste una configurazione di riferimento naturale e a temperatura uniforme, rispetto alla quale un solido termoelastico sia omogeneo ed isotropo. In questa nota si fa vedere che basta supporre che esiste una sola di tali configurazioni per potere affermare che, sotto ipotesi facilmente ammissibili, di tali configurazioni ne esistono infinite al variare della temperatura in un opportuno intorno.SummaryWe show that in Continuum Thermodynamics if one natural reference configuration at uniform temperature exists, for which the solid is homogeneous and isotropic, there is an endless number of these configurations, temperatures of which vary in a given range.