Irreversible Phenomena Research Articles

A Lagrangian variational formulation for nonequilibrium thermodynamics. Part I: Discrete systems

In this paper, we present a Lagrangian variational formulation for nonequilibrium thermodynamics. This formulation is an extension of Hamilton’s principle of classical mechanics that allows the inclusion of irreversible phenomena. The irreversibility is encoded into a nonlinear phenomenological constraint given by the expression of the entropy production associated to all the irreversible processes involved. From a mathematical point of view, our variational formulation may be regarded as a generalization to nonequilibrium thermodynamics of the Lagrange–d’Alembert principle used in nonlinear nonholonomic mechanics, where the conventional Lagrange–d’Alembert principle cannot be applied since the nonlinear phenomenological constraint and its associated variational constraint must be treated separately. In our approach, to deal with the nonlinear nonholonomic constraint, we introduce a variable called the thermodynamic displacement associated to each irreversible process. This allows us to systematically define the corresponding variational constraint. In Part I, our variational theory is illustrated with various examples of discrete systems such as mechanical systems with friction, matter transfer, electric circuits, chemical reactions, and diffusion across membranes. In Part II of the present paper, we will extend our variational formulation of discrete systems to the case of continuum systems.

A model for moisture-induced dimensional instability in printing paper

The dimensional stability of printing paper is strongly related to changes in moisture content. This represents a major issue in the field of digital ink-jet printing, where moisture induced reversible and irreversible deformations may compromise printing quality and runnability. This paper proposes a two-dimensional hygro-mechanical model for paper, that focuses on the prediction of moisture induced out-of-plane deformations, due to inhomogeneous moisture variations in the plane. The model is based on a discrete network of beams. The adopted constitutive model, whose input parameters are calibrated to available experimental data for homogeneous moisture cycling, allows to describe typical irreversible phenomena related to the history of the production of paper, such as the release of dried-in strains. The deformation of paper in the wet and in the dry state predicted by the model is compared with experiments, in which the paper is subjected to a moisture cycle under different types of mechanical constraint. The results of the model capture well the experimental response of paper in terms of buckling patterns and of out-of-plane displacement wavelengths and amplitudes.

An Online-Applicable Model for Predicting Health Degradation of PEM Fuel Cells With Root Cause Analysis

This paper proposes a new prognostic method for the health state of proton exchange membrane (PEM) fuel cells. The method is designed to predict the state-of-health (SOH) of PEMs and provide root cause analysis of the predicted health degradation. In this method, an equivalent circuit model (ECM) is built to emulate the impedance spectrum of PEM fuel cells. Because the key degradation parameters in the ECM cannot be measured in situ , this method instead estimates the parameters indirectly using the output voltage. The estimation is based on the linear relationship between the key ECM parameters and the output voltage. Using the constructed ECM and the estimated parameters, an impedance spectrum at the current moment is produced. The historical voltage evolution is then extrapolated using linear and exponential models that represent the irreversible and reversible phenomena, respectively. The models are used to predict future ECM parameters and, eventually, the impedance spectrum at any moment in the future. Through these steps, the proposed method provides an online estimation of the current SOH and predicts the level of future degradation. The primary novel feature of the proposed method is its ability to diagnose the root causes of potential degradation using data from nondisruptive online monitoring.

Plasticity coupled with thermo-electric fields: Thermodynamics framework and finite element method computations

A consistent thermodynamic-based theoretical framework and three-dimensional finite element formulation is presented, capable of coupling elastic, thermal and electric fields. The complete set of governing equations is obtained from conservation principles for electric charge, energy and momentum. The second principle of thermodynamics is taken into account to introduce the irreversible phenomena, such as plastic dissipation or Joule heating. The constitutive relations are derived consistently from the Helmholtz free-energy potential for each corresponding dual variable in terms of the defined set of state variables. We consider the case of linear isotropic hardening model for plasticity, and provide the consistent form of the tangent thermo–electro–elastoplastic modulus through dual variable computations. The latter plays the crucial role in ensuring fast convergence properties of the finite element computations with the proposed coupled plasticity model. The implementation is carried out in a research version of the well-known computer code FEAP. Several numerical simulations are presented in order to illustrate the proposed model and formulation capabilities for providing an enhanced formulation of an important practical application in terms of Peltier cells.

Thermodynamic restrictions on linear reversible and irreversible thermo-electro-magneto-mechanical processes.

A unified thermodynamic framework for the characterization of functional materials is developed. This framework encompasses linear reversible and irreversible processes with thermal, electrical, magnetic, and/or mechanical effects coupled. The comprehensive framework combines the principles of classical equilibrium and non-equilibrium thermodynamics with electrodynamics of continua in the infinitesimal strain regime.In the first part of this paper, linear Thermo-Electro-Magneto-Mechanical (TEMM) quasistatic processes are characterized. Thermodynamic stability conditions are further imposed on the linear constitutive model and restrictions on the corresponding material constants are derived. The framework is then extended to irreversible transport phenomena including thermoelectric, thermomagnetic and the state-of-the-art spintronic and spin caloritronic effects. Using Onsager's reciprocity relationships and the dissipation inequality, restrictions on the kinetic coefficients corresponding to charge, heat and spin transport processes are derived. All the constitutive models are accompanied by multiphysics interaction diagrams that highlight the various processes that can be characterized using this framework.

Gellan gum hybrid hydrogels for the cleaning of paper artworks contaminated with Aspergillus versicolor

The degradation of archive materials is related to irreversible phenomena induced by light, temperature, humidity, air pollution, micro-organisms, and use. Among biological factors, fungi can induce harmful effects in paper artworks. Further forms of damage (e.g. artwork swelling, fibre lifting and sheet delamination) can be caused by water immersion, which is one of the most commonly used methods for cleaning paper. To avoid damage it is necessary to control the amount and absorption rate of water by paper. Recently, gellan gum hydrogels have been proposed as effective tools to allow contaminant removal from paper supports, owing to the controlled water release and adhesive properties of gellan gum. In this study hybrid hydrogels were fabricated by doping gellan gum either with calcium compounds (calcium sulphate, hydroxide, chloride, and acetate) or titanium dioxide nanoparticles in order to evaluate their ability in cleaning different types of paper samples affected by spots originating from Aspergillus versicolor. The best decolourization results were obtained by calcium acetate/gellan gum hydrogels and titanium dioxide nanoparticle/gellan gum hydrogels, while no synergistic effect was found in paper samples treated with calcium acetate/titanium dioxide/gellan gum hydrogels. Hybrid hydrogels were tested on a case-study book.

The possible source of the causal time arrow in geo-historical explanations

My argument in this article, will be that nature, in general, and human nature in particular, suggests that, in principle, it is possible to derive the causal time arrow from several physical time arrows existing in nature and appearing to be unidirectional and irreversible phenomena. A more concrete argument will be that the assumption of a causal time arrow to which geologists resort in all geo-historical explanations, apparently originates in geo-historical time arrows concealed in unidirectional and irreversible physical-geological processes. I will illustrate this claim with a few examples of geo-historical explanations in the theory of plate tectonics, most of which are based on irreversible geo-physical processes. My final argument is a broader, of an epistemological nature, according to which the causal time arrow assumption used in logical-causative explanations in everyday life and in science, apparently “derives” in a way from the geo-historical time arrow. I will base this argument on the causal relationship and mutual influence that occurs in nature between geo-historical and evolutionary processes in animals, including developmental processes of the human brain and mind. From this reductionist argument, nicely integrated in the framework of evolutionary epistemology (EEM), it is possible to derive a wider naturalistic argument according to which, on principle, the laws of geo-historical physics can be reduced to the laws of logic and causality.

Fast descent routes from within or near the stratosphere to the surface at Fukuoka, Japan, studied using <sup>7</sup>Be measurements and trajectory calculations

Abstract. By using high concentrations of 7Be as an indicator, we clarify fast descent routes from within or near the stratosphere to Earth's surface, with the study site being in Fukuoka, Japan. Most routes arise from high latitudes through the following processes. First, the descent associated with a tropopause fold occurs, followed by southward movement with slow descent at the rear side of a strong trough. Because this motion occurs along an isentropic surface, the descending air parcels nearly conserve the potential temperature. As an extension, a strong descent associated with a sharp drop in the isentropic-surface height occurs at the southern edge of the trough; this transports air parcels to low altitudes. This process involves irreversible phenomena such as filamentation and cutoff of potential vorticity. Finally, upon meeting appropriate near-surface disturbances, parcels at low altitudes are transported to Earth's surface.In some cases, parcels descend within midlatitudes. In such routes, because the potential temperature is much higher at high altitudes than at low altitudes, descent with conservation of the potential temperature is impossible, and the potential temperature decreases along the trajectories through mixing.The prevalence of the high-latitude route is explained as follows. In the midlatitude route, because parcels at high and relatively low altitudes mix, the high concentrations of 7Be included in high-altitude parcels are difficult to maintain. Therefore, for parcels to arrive at low altitudes in the midlatitude while maintaining high concentrations of 7Be, i.e., conserving the potential temperature, their area of origin should be high altitudes in high latitudes where the potential temperature is almost the same as that in the arrival area.In spring, tropopause folds are frequent in high latitudes, disturbances in the southward transport of parcels are strong, and disturbances occur by which parcels descend to the surface. Therefore, high concentrations of 7Be occur most frequently in spring.

Absorptive viscoelastic coatings for full field vibration coverage measurement in vibrothermography

Vibrothermography is a rapidly emerging nondestructive evaluation technique for detecting fatigue cracks in aircraft components. Externally applied mechanical vibrations in a specimen generate crack heating between vibrating crack faces due to friction or other irreversible phenomena. Crack heating in vibrothermography depends on the vibrational stresses, and therefore the amount of vibration generated in the specimen. A method to measure the vibration distribution from the hysteretic heating of viscoelastic polymer adhesive applied to a specimen surface is described. The heat generated by the adhesive coating maps directly to the vibrational strain distribution in the substrate. This is a fast method of vibration coverage measurement for vibrothermographic testing.

Security threats and risk management: European and Chinese responses to the climate disruption

Most academics and policy makers agree upon irreversible phenomena affecting planet Earth’s climate – we have finally faced a climate disruption. As triggered by humans, environmental degradation ultimately threatens not only the security but even the survival of individuals, communities, states and perhaps even the international system as a whole. This paper addresses differences with regards to risk assessment of climate disruption in Europe and in China. Its departure point is that the divergence between European and Chinese approaches is based on structural and institutional distinctions. Specifically, it tries to assess those distinctions (importance of sovereignty and non-interference) with regards to methods (assessment of vulnerability) and principles (transparency and inclusiveness) of risk assessment. Initial analysis leads to a tentative conclusion, which confirms the importance of political culture in national responses to security threats (be it traditional or non-traditional). In this respect EU-China strategic partnership is suggested as one of the possibly effective platforms for future cooperation.

Dysregulation of protein methyltransferases in human cancer: An emerging target class for anticancer therapy.

Protein methylation is one of the important post‐translational modifications. Although its biological and physiological functions were unknown for a long time, we and others have characterized a number of protein methyltransferases, which have unveiled the critical functions of protein methylation in various cellular processes, in particular, in epigenetic regulation. In addition, it had been believed that protein methylation is an irreversible phenomenon, but through identification of a variety of protein demethylases, protein methylation is now considered to be dynamically regulated similar to protein phosphorylation. A large amount of evidence indicated that protein methylation has a pivotal role in post‐translational modification of histone proteins as well as non‐histone proteins and is involved in various processes of cancer development and progression. As dysregulation of this modification has been observed frequently in various types of cancer, small‐molecule inhibitors targeting protein methyltransferases and demethylases have been actively developed as anticancer drugs; clinical trials for some of these drugs have already begun. In this review, we discuss the biological and physiological importance of protein methylation in human cancer, especially focusing on the significance of protein methyltransferases as emerging targets for anticancer therapy.

On the theory of nonlinear thermal conductivity

A nonlinear differential equation of thermal conductivity is derived phenomenologically from the general principles of construction of functional Q invariant to the inversion operation I(r →–r), and the temperature evolution dynamics is analyzed in the nonstationary case. The proposed method makes it possible to reveal some general regularities in the physical behavior of such systems for describing irreversible phenomena in self-organization processes. It is noted that an analogous situation may take place, for example, in strongly inhomogeneous structures with stochastic internal heat fluxes.

Clinical evaluation and urodynamic study observation in post-menopausal female: a comparative study

Background: Menopause is an irreversible and age related phenomenon and serves as an objective sign of reproductive senescence. Atrophic changes within the urogenital tract may occur due to estrogen deficiency and is associated with genitourinary symptoms. Methods: A total of 66 women who attained natural and surgical menopause with more than twelve months with urogenital symptoms were selected for study. Results: Age of patients selected for study was between 35-70 years. Majority of the patients 52/66 (78.7%) were presented after minimum 5 yrs of menopause. Among genital symptoms vaginal discharge was significantly higher (p 0.05). Among urinary symptoms frequency was the most common symptom in both the groups, 15 (44.12%) in natural menopause and 22 (68.75%) in surgical menopause, more prevalent in surgical group. Urgency was seen in 38.23% in natural menopause and 56.25% in surgical menopause. Incontinence was present in 47.05% in natural menopause and 62.51% in surgical menopause. Among incontinence stress incontinence was most common in the groups, 20.59% in natural group and 37.5 % in surgical group, statistically significant in surgical group. Mixed incontinence was observed in 5.58% in natural menopause; statistically significant in surgical group. Prevalence of urge incontinence was observed more in natural menopause 20.59% and 3.12 % in surgical menopause. There was no statistically significant difference in uroflowmetry parameters between both the groups. In cystometry parameters, volume at first bladder sensation was significantly less in patients with urgency and urge incontinence in both groups. Maximum bladder capacity was less in detrusor overactivity in both the groups. Compliance was poor in patient with urge incontinence in both the groups. Conclusions: Hypoestrogenism could be an etiological factor in urogenital dysfunction in postmenopausal women with spontaneous menopause and surgical menopause.

Conservative and dissipative phenomena in thermodynamical systems stability

Abstract: The entropy production of thermodynamical systems with reversible (conservative) and irreversible (dissipative) phenomena is used as a Lyapunov candidate function to address stability properties. First, based on the conjugated variables of the extensive properties, the dissipative and conservative phenomena are identified, then, the dynamic behavior of entropy production is obtained. Based on the properties of the entropy function Hessian, it is found that dissipative phenomena contribute to stability and attraction of the thermodynamical equilibrium. In particular, when only dissipative phenomena are present, the entropy production is a Lyapunov function that guarantees global or local stability, depending on the nonlinearities. Complex behaviors, for instance transitory increments of the entropy production, are due to both conservative phenomena and, far from equilibrium, non linearities of dissipative phenomena. Finally, a case study consisting in a gas-piston system is presented to illustrate these ideas.

Densification and deformation during uniaxial cold compaction of stainless steel powder with different particle size

The behaviour of austenitic stainless steel powder column during uniaxial cold compaction was investigated in this work. Powders with different particle size were compacted to the same green density in a hydraulic press, also providing different H/D ratios in order to account for the influence of geometry. The analysis of the data continuously recorded by the press allowed distinguishing the contribution of the reversible phenomena (elastic deformation of powders and tools) and of the irreversible phenomena (rearrangement and plastic deformation of the powders). An analytical model for densification was proposed, considering both density and increase in density versus the applied pressure. The trend of reversible and permanent deformations versus the applied pressure was evaluated, also proposing an analytical model. The comparison between the densification curves and the curves of permanent deformation allowed highlighting the physical meaning of the model describing the increase in density for the different particle size.

Customizing residential buildings for people with dysfunction of motion

According to the national census conducted in 2002, the number of people with disabilities in Poland is 5456.7 thous., PONAD 14 percent of the population of the country. This means that every seventh citizen is a person with a disability or for such a thought. Polish society, in addition, like other societies in Europe, subject to irreversible phenomenon of an aging population. This is related to a significant increase in people with reduced mobility. Research on ergonomics and the development of techniques and materials in recent years has gone so far that basically revolutionized many areas of life. Is it the same in adapt to the needs of residential buildings to people with reduced mobility? Does such persons may still face impediments in areas where every day they live? In the article the author presents solutions that help adapt to the needs of residential buildings by persons with reduced traffic, especially for wheelchair access and the elderly.

Mixed convolved action principles in linear continuum dynamics

The paper begins with an overview of several of the classical integral formulations of elastodynamics, which highlights the natural appearance of temporal convolutions in the reciprocal theorem for such problems. This leads first to the formulation of a principle of virtual convolved action, as an extension of the principle of virtual work to dynamical problems. Then, to overcome the key shortcomings of Hamilton’s principle, the concept of mixed convolved action is developed for linear dynamical problems within the context of continuum solid mechanics. This new approach is broadly applicable to both reversible and irreversible phenomena without the need for special treatments, such as the artificial definition of Rayleigh dissipation functionals. The focus here is on linear elastic and viscoelastic media, which in the latter case is represented by classical Kelvin–Voigt and Maxwell models. Remarkably, for each problem type, the stationarity of the mixed convolved action provides not only the governing partial differential equations, but also the specified boundary and initial conditions, as its Euler–Lagrange equations. Thus, the entire initial/boundary value problem definition is encapsulated in a scalar mixed convolved action functional written in terms of displacements and stress impulses. The resulting formulations possess an elegant structure that provides a versatile framework for the development of novel computational methods, involving finite element representations in both space and time. We present perhaps the simplest approach by employing linear three-node triangular elements for two-dimensional analysis, along with linear shape functions over the temporal domain. Numerical examples are included to verify the formulation and to explore concepts of stress wave attenuation.

Advanced and delayed filling or emptying of pore entities by vapor sorption or liquid intrusion in simulated porous networks

Recently, a combination of successive experimental sorption and intrusion processes, developed in the same porous material, has been found very useful to ascertain the mechanisms by which a specified fluid can fill or empty (cooperatively or not) the porous entities that constitute the substrate in question. Here, we have chosen porous substrates, modeled through the Dual Site-Bond Model, in order to simulate either sorption or intrusion–extrusion phenomena inside them. Afterwards, we have assessed the results obtained from these two techniques to describe the occurrence of cooperative phenomena during the filling or emptying of pore entities with a given fluid. The void entities involved in the development of irreversible phenomena (e.g. advanced adsorption, delayed intrusion, etc.) can be identified in each of these substrates in terms of their sizes and topology (i.e. the specific way by which these pores are interconnected to the other ones). The possible interrelation between assorted cooperative phenomena, taking place in the same porous adsorbent, is studied according to the type of porous material in hand.

Dielectric properties of human diabetic blood: Thermodynamic characterization and new prospective for alternative diagnostic techniques

In this paper, we will show the possibility of studying physical properties and irreversible phenomena that occur in blood by applying the dielectric Kluitenberg's nonequilibrium thermodynamic theory. Namely, we shall use some recent extensions of this theory that allow to infer its main characteristic parameters from experimental measures. Applying these results to the study of normal and diabetic blood we show, by comparing them, that it is possible to determine the difference, in some details, of the amount of particular phenomena occurring inside them and give a biological meaning to these phenomena. Moreover, observing a correspondence between a particular value of the frequency for which state coefficients are equal and glucose levels we introduce an alternative diagnostic method to measure the values of the glucose in the blood by determining only this frequency value. The thermodynamic description will be completed by determining the trend of the entropy production.

A novel construction of thermodynamically compatible models and its correspondence with Boltzmann-equation-based moment-closure hierarchies

Abstract In this article, we propose a novel approach to construct macroscopic balance equations and constitutive equations describing various irreversible phenomena. It is based on the general principles of non-equilibrium thermodynamics and consists of four basic steps: picking suitable state variables, choosing a strictly concave entropy function, properly separating entropy fluxes and production rates, and determining a dissipation matrix. Our approach takes advantage of both extended irreversible thermodynamics and GENERIC formalisms and shows a direct correspondence with Levermore's moment-closure hierarchies for the Boltzmann equation. As a direct application, a new ten-moment model beyond the classical hierarchies is constructed and is shown to recover the Euler equations in the equilibrium state. These interesting results may put various macroscopic modeling approaches, starting from the general principles of non-equilibrium thermodynamics, on a solid microscopic foundation based on the Boltzmann equation.