Techniques for the Thermodynamic Consistency of Constitutive Equations

The paper investigates the techniques associated with the exploitation of the second law of thermodynamics as a restriction on the physically admissible processes. Though the exploitation consists of the use of the arbitrariness occurring in the Clausius-Duhem inequality, the approach emphasizes two uncommon features within the thermodynamic analysis: the representation formula, of vectors and tensors, and the entropy production. The representation is shown to be fruitful whenever more terms of the Clausius-Duhem inequality are not independent. Among the examples developed to show this feature, the paper yields the constitutive equation for hypo-elastic solids and for Maxwell- Cattaneo-like equations of heat conduction. The entropy production is assumed to be given by a constitutive function per se and not merely the expression inherited by the other constitutive functions. This feature results in more general expressions of the representation formulae and is crucial for the compact description of hysteretic phenomena

Modelling of Electro-Viscoelastic Materials through Rate Equations

Models of dielectric solids subject to large deformations are established by following a thermodynamic approach. The models are quite general in that they account for viscoelastic properties and allow electric and thermal conduction. A preliminary analysis is devoted to the selection of fields for the polarization and the electric field; the appropriate fields are required to comply with the balance of angular momentum and to enjoy the Euclidean invariance. Next, the thermodynamic restrictions for the constitutive equations are investigated using a wide set of variables allowing for the joint properties of viscoelastic solids, electric and heat conductors, dielectrics with memory, and hysteretic ferroelectrics. Particular attention is devoted to models for soft ferroelectrics, such as BTS ceramics. The advantage of this approach is that a few constitutive parameters provide a good fit of material behaviour. A dependence on the gradient of the electric field is also considered. The generality and the accuracy of the models are improved by means of two features. The entropy production is regarded as a constitutive property per se, while the consequences of the thermodynamic inequalities are made explicit by means of representation formulae

Una experiència d’aprofitament de biomassa forestal per a ús energètic: cas de l’illa de Menorca

L'actual situació del mercat energètic juntament amb l'expansió de la superfície i del volum de biomassa forestal aprofitable als boscos de les balears, ha fet que hagin sorgit iniciatives privades a diferents finques de les illes per a l'aprofitament del bosc per a l'obtenció d'estella forestal amb finalitats energètiques. El present article pretén resumir les diferents actuacions realitzades a les finques de l'illa de Menorca durant els dos darrers anys, presentar els resultats i obtenir les principals conclusions preliminars de l’experiència des de l'òptica de l'administració forestal de la Comunitat Autònoma

Solidification and separation in saline water

Motivated by the formation of brine channels, this paper is devoted to a continuum model for salt separation and phase transition in saline water. The mass density and the concentrations of salt and ice are the pertinent variables describing saline water. Hence the balance of mass is considered for the single constituents (salt, water, ice). To keep the model as simple as possible, the balance of momentum and energy are considered for the mixture as a whole. However, due to the internal structure of the mixture, an extra-energy flux is allowed to occur in addition to the heat flux. Also, the mixture is allowed to be viscous. The constitutive equations involve the dependence on the temperature, the mass density of the mixture, the salt concentration and the ice concentration, in addition to the stretching tensor, and the gradient of temperature and concentrations. The balance of mass for the single constituents eventually result in the evolution equations for the concentrations. A whole set of constitutive equations compatible with thermodynamics are established. A free energy function is given which allows for capturing the main feature which occurs during the freezing of the salted water. That is, the salt entrapment in small regions (brine channels) where the cryoscopic effect forbid complete ice formation

Modeling of heat conduction through rate equations

Starting from a classical thermodynamic approach, we derive rate-type equations to describe the behavior of heat flow in deformable media. Constitutive equations are defined in the material (Lagrangian) description where the standard time derivative satisfies the principle of objectivity. The statement of the Second Law is formulated in the classical form and the thermodynamic restrictions are then developed following a variant of the Coleman-Noll procedure where the entropy production too is given by a non-negative constitutive equation. Both the free energy and the entropy production are assumed to depend on a common set of independent variables involving, in addition to temperature, both temperature gradient and heat-flux vector together with their time derivatives. This approach results in rate-type constitutive function for the heat flux that are intrinsically consistent with the Second Law and easily amenable to analysis. In addition to providing already known models (e.g., Maxwell-Cattaneo-Vernotte's and Jeffreys-like heat conductors), this scheme allows the formulation of new models of heat transport that are likely to apply also in nanosystems. This is consistent with the fact that higher-order time derivatives of the heat flux are in order when high-rate regimes occur

ONOS-Controlled Disaggregated Optical Networks

State-of-art, potentials and limitations of the ONOS controller applied to disaggregated optical networks are reported. Focus is on the on-going ODTN project. Results of experimental demonstrations are reported to prove the feasibility of proposed approach

La colonialidad de género y su influencia en la percepción de la masculinidad negra: un conflicto en el mensaje antiesclavista en Sab de Gertrudis Gómez de Avellaneda

This article examines gender coloniality and its influence on the perception of black masculinity in Gertrudis Gómez de Avellaneda’s Sab. In the novel, the Afro-descendant man is perceived as a threat to the colonial order and white femininity, which betrays the «black fear». Important themes are presented in a superficial tone, as the protagonist’s goal is not to abolish slavery, but to free himself in order to love Carlota. From this it is identified that the novel’s anti-slavery message is ineffective, as Sab is a spokesperson for the white feminist struggle and is denied her own liberation by presenting the antislavery struggle as an inferior concern to women’s liberation.En el presente artículo se examina la colonialidad de género y su influencia en la percepción de la masculinidad negra en Sab, de Gertrudis Gómez de Avellaneda. En la novela se percibe al hombre afrodescendiente como una amenaza para el orden colonial y la feminidad blanca, lo cual delata el «miedo negro». Se exponen temas importantes con un tono superficial, pues el objetivo del protagonista no es abolir la esclavitud, sino liberarse para amar a Carlota. A partir de ello se identifica que el mensaje antiesclavista de la novela es ineficaz, pues Sab es un portavoz de la lucha feminista blanca y se le niega su propia liberación al presentar la lucha antiesclavista como una preocupación inferior a la liberación femenina

La parcialidad hacia la mujer de color por su rol de género en Roque Moreno de Teresa González de Fanning

This article will analyze the biased position that the writer Teresa González de Fanning has with her character Chavelita, who is a woman of color that is part of the nineteenth-century novel Roque Moreno. We propose that this bias is because Chavelita fulfills the feminine-domestic ideal that the writer defended and professed from her position as an enlightened woman.En el presente artículo se analizará la postura parcializada que tiene la escritora Teresa González de Fanning con su personaje Chavelita, quien es una mujer de color que forma parte de la novela decimonónica Roque Moreno. Proponemos que esta parcialidad se debe a que Chavelita cumple con el ideal femenino-doméstico que defendía y profesaba la escritora desde su posición de mujer ilustrada