1,720,963 research outputs found
A porous thermoelastic diffusion theory of types II and III
No full textIn this paper, we derive a nonlinear theory of thermoelasticity with voids and diffusion according to the Green–Naghdi theory of thermomechanics of continua of types II and III. This theory permits propagation of both thermal and diffusion waves at finite speeds. The equations of the linear theory are also obtained. We prove the well-posedness of the linear model and the asymptotic behavior of the solutions by the semigroup theory of linear operators. Finally, we investigate the impossibility of the localization in time of solutions. The main idea to prove this result is to show the uniqueness of solutions for the backward in time problem
Well-posedness and exponential stability in binary mixtures theory for thermoviscoelastic diffusion materials
No full textA nonlinear theory is derived for a thermoviscoelastic diffusion composite which is modeled as a binary mixture consisting of two Kelvin–Voigt viscoelastic materials. First, the basic equations of the nonlinear theory of heat and diffusion conducting viscoelastic mixtures are derived in Lagrangian description. Then, the theory is linearized and field equations are given for both anisotropic and isotropic centrosymmetric materials. We establish the necessary and sufficient conditions to get a dissipation inequality for isotropic centrosymmetric materials. With the help of the semigroup theory of linear operators, we establish the suitable framework where the linear problem is well posed. Finally, we prove that generically the solution decreases exponentially thanks to the viscous dissipation effects of the constituents
A thermoelastic diffusion theory with microtemperatures and microconcentrations
No full textThis article is concerned with a nonlinear theory of thermodynamics for elastic materials in which the particles are subjected to classical displacement, temperature, and mass diffusion fields and whose microelements possess microtemperatures and microconcentrations. The equations of the linear theory are also obtained. It is shown that there exists coupling between temperature, chemical potential, microtemperatures, and microconcentrations even for isotropic bodies. With the help of the semigroup theory of linear operators, we prove the well-posedness of the linear anisotropic problem and we study the asymptotic behavior of the solutions
Thermoelastic theory with microtemperatures and dissipative thermodynamics
No full textIn this article we derive a nonlinear theory of thermoelastic materials with microtemperatures based on the entropy balance of type III postulated by Green and Naghdi. The work is motivated by an increasing use of materials which possess thermal variation at a microstructure level such that both thermal and microtemperatures waves can propagate with finite speeds and energy dissipation. The equations of the linear theory are also obtained. Then, we use a semigroup approach to derive an existence and uniqueness result for the solutions to the anisotropic problem and to study the asymptotic behavior. Finally, we investigate the impossibility of the localization in time of solutions
A bending theory of thermoelastic diffusion plates based on Green-Naghdi theory
No full textThis article is concerned with bending plate theory for thermoelastic diffusion materials under Green-Naghdi theory. First, we present the basic equations which characterize the bending of thin thermoelastic diffusion plates for type II and III models. The theory allows for the effect of transverse shear deformation without any shear correction factor, and permits the propagation of waves at a finite speed without energy dissipation for type II model and with energy dissipation for type III model. By the semigroup theory of linear operators, we prove the well-posedness of the both models and the asymptotic behavior of the solutions of type III model. For unbounded plate of type III model, we prove that a measure associated with the thermodynamic process decays faster than an exponential of a polynomial of second degree. Finally, we investigate the impossibility of the localization in time of solutions. The main idea to prove this result is to show the uniqueness of solutions for the backward in-time problem
A problem for an infinite elastic body with a spherical cavity in the theory of generalized thermoelastic diffusion
No full textAbstractIn this work, we study a one-dimensional problem in a generalized thermoelastic diffusion in infinite medium with a spherical cavity subjected to a time dependent thermal shock of its internal boundary which is assumed to be traction free. The chemical potential is also assumed to be a known function of time on the bounding cavity. Laplace transform techniques are used. The solution of the problem in the transformed domain is obtained by using a direct approach without the customary use of potential functions. By means of numerical Laplace inversion, the problem is solved in the physical domain. Numerical results predict finite speeds of propagation for thermoelastic and diffusive waves. To investigate the diffusions effects, a comparison is made with the results obtained in the thermoelastic problem
Generalized thermo-piezoelectric problems with temperature-dependent properties
No full textAbstractThe model of the equation of generalized thermo-piezoelectricity in an isotropic elastic medium with temperature-dependent mechanical properties is established. The modulus of elasticity is taken as a linear function of reference temperature. The state-space approach is adopted for the solution of one-dimensional problems in the absence or presence of heat sources. A numerical technique is employed to obtain the solution in the physical domain. The results are given and illustrated graphically. A comparison is made with results obtained in case of temperature-independent modulus of elasticity
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
