In 1982, the Belgian Pilots' Guild raised the question of what effect exposure to radar radiation--for example, that encountered in passing a pilot launch's radar--might have on the human body. Recapitulating investigations of this question, this article states that in 25 years of experience with radar, there have been no known incidents of pilots being affected by radar waves. In the future, however, involvement by some pilots with Vessel Traffic Service shore-based radar could affect pilots somewhat differently from limited exposure to pilot launch radar. Pilots who find themselves in new working conditions close to an emitting source should exercise care all times.

About heat waves

A unifying thermomechanical framework is presented that reconciles several classes of gradient elastoviscoplasticity and damage models proposed in the literature during the last 40 years . It is based on the introduction of the micromorphic counterpart ϕχ of a selected state or internal variable ϕ in a standard constitutive model. In addition to the classical balance of momentum equation, a balance of micromorphic momentum is derived that involves generalized stress tensors. The corresponding additional boundary conditions are also deduced from the procedure. The power of generalized forces is assumed to contribute to the energy balance equation. The free energy density function is then chosen to depend on a relative generalized strain, typically ϕ- ϕχ , and the microstrain gradient ∇ ϕχ . When applied to the deformation gradient itself, ϕ≡ F , the method yields the micromorphic theory of Eringen and Mindlin together with its extension to finite deformation elastoviscoplasticity by Forest and Sievert. If...

Micromorphic Approach for Gradient Elasticity, Viscoplasticity, and Damage

http://users.auth.gr/users/0/3/022730/public_html/Update%20on%20a%20class%20of%20gradient%20theories.pdf

Update on a class of gradient theories

The conceptual problems arising in the definition and measurement of temperature in non-equilibrium states are discussed in this paper in situations where the local-equilibrium hypothesis is no longer satisfactory. This is a necessary and urgent discussion because of the increasing interest in thermodynamic theories beyond local equilibrium, in computer simulations, in non-linear statistical mechanics, in new experiments, and in technological applications of nanoscale systems and material sciences. First, we briefly review the concept of temperature from the perspectives of equilibrium thermodynamics and statistical mechanics. Afterwards, we explore which of the equilibrium concepts may be extrapolated beyond local equilibrium and which of them should be modified, then we review several attempts to define temperature in non-equilibrium situations from macroscopic and microscopic bases. A wide review of proposals is offered on effective non-equilibrium temperatures and their application to ideal and real gases, electromagnetic radiation, nuclear collisions, granular systems, glasses, sheared fluids, amorphous semiconductors and turbulent fluids. The consistency between the different relativistic transformation laws for temperature is discussed in the new light gained from this perspective. A wide bibliography is provided in order to foster further research in this field.

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Temperature in non-equilibrium states: a review of open problems and current proposals

The cornerstone of finite-time thermodynamics is all about the price of haste and how to minimize it. Reversible processes may be ultimately efficient, but they are unrealistically slow. In all situations-chemical, mechanical, economical-we pay extra to get the job done quickly. Finite-time thermodynamics can be used to develop methods to limit that extra expenditure, be it in energy, entropy production, money, or something entirely different. Finite-time thermodynamics also includes methods to calculate the optimal path or mode of operation to achieve this minimal expenditure. The concept is to place the system of interest in contact with a time-varying environment which will coax the system along the desired path, much like guiding a horse along by waving a carrot in front of it.

Current Trends in Finite‐Time Thermodynamics

The first part of this review replaces the concept of internal variables of state in the general context of non-equilibrium thermodynamics. This offers the slightest deviation from the classical Theory of irreversible processes (TIP) while exhibiting a flexibility and versatility that other attempts at generalizing TIP cannot sustain. Here the basic working hypotheses on which the application of internal-variable theory relies, are specified. The use of TIP, after introduction of the appropriate axiom of local equilibrium state, or of a pseudopotentia l of dissipation is emphasized. The role of internal state variables in describing miscrostructures and the current misunderstanding with internal degrees of freedom are clarified. However, the resemblance or identity with order parameters of phase-transition theory as well as essential differences with extended thermodynamics are acknowledged. In all, internal variables epitomize the use of systems of evolution in mathematical continuum physics.

Thermodynamics with Internal Variables. Part I. General Concepts

The second part of this synthetic work presents and discusses the most spectacular and successful applications of the irreversible thermodynamics with internal variables. These include viscosity in both fluids and solids (in the former case, in complex fluids and structurally complex flows), viscoplasticity and rate-independent plasticity in small and finite strains, damage and cyclic plasticity, electric and magnetic relaxation, magnetic and electric hysteresis, normal and semi-conduction, superconductivity of deformable solids, and ferrofluids. In all cases the internal variables of interest are given some physical significance in terms of quantities defined at a sublevel of description. The relevant internal variables may be as varied as second-order tensors, real or complex valued scalars, and polar or axial vectors. Furthermore, the role played by internal variables in wave-propagation problems is emphasized through appropriate examples. The presentation ends with reaction-diffusion problems. This is illustrated by damage, plastic-strain localization and models for nerve-pulse dynamics. Globally, we have all ingredients of a truly post-Duhemian irreversible thermodynamics of complex behaviors.

Thermodynamics with Internal Variables. Part II. Applications

Different formulations of non-equilibrium continuum thermodynamics are discussed: Thermodynamics of Irreversible Processes (TIP), Rational Thermodynamics (RAT), Extended Thermodynamics (ET), Mesoscopic Continuum Thermodynamics (MT), and the GENERIC version of thermodynamics. Concepts as constitutive quantity, state space, material frame indifference, exploiting dissipation inequality, mesoscopic variables, and GENERIC balance equations are taken into consideration.

A sketch of continuum thermodynamics

On the basis of well known empirems of classical thermodynamics, such as the First and Zeroth Laws, which lead to the definition of calorimeter systems by which heat exchanges can be measured, thermal interaction between thermally homogeneous systems is investigated by methods of set theory. In connexion with Carnap's axiom for a classical measuring quantity a thermodynamic analogue of the thermostatic temperature can be developed by generalized empirems which govern the thermal interaction between non-equilibrium and thermally homogeneous systems. An empirical identification of the contact temperature and its field formulation are given.

Wolfgang Muschik

Papers

Thermodynamics with Internal Variables. Part I. General Concepts

Thermodynamics with Internal Variables. Part II. Applications

A sketch of continuum thermodynamics

Empirical foundation and axiomatic treatment of non-equilibrium temperature

An Amendment to the Second Law