Nonequilibrium Thermodynamic State Research Articles

Radiation gas dynamics of Martian space vehicles

.The first part of the paper contains brief description of the models. The second part describes numerical simulation results obtained with the use of the two dimensional code NERAT-2D. Numerical investigation of radiative aerothermodynamics of Pathfinder is performed for several points of entering trajectory, which are correspond non-equilibrium and quasi-equilibrium thermodynamic conditions. Distinguishing feature of obtained data is the comparison of convective and radiative heating of Pathfinder’s surface from forward up to backside stagnation line. It is demonstrated that radiative heating of Pathfinder space vehicle has its origin in presence of molecules CO2, CO, N2, O2, CN in shock layer and in wake. The third part of the paper presents analysis of two-dimensional radiative aerothermodynamic characteristics of space vehicle Exomars at different parts of Martian entry trajectories. Radiative heating of the spacecraft surface is predicted with the use of two methods of the radiation heat transfer theory. The first one is the half-moment method, which is applied to plane layer above windward surface. The second one is the ray-tracing method, which allows determine radiative heat flux over all Exomars’ surface. The final part of the paper contains results of three dimensional calculations of convective and radiative heating of Exomars under angle of attack 15 0 . Calculations were performed with the use of multigroup spectral model taking into account most significant radiative mechanisms of absorption and emission.

Workplace Health Promotion Program on Using Dietary Antioxidants (Anthocyanins) in Chemical Exposed Workers

Workplace health promotion is a business management system that aims to promote and improve the health situations of all employees in a comprehensive and sustainable mode, and should be seen as an equal partner for occupational health and safety. Certain industrial hazards (in particular chemical agents) display oxidant capacity in the human body acting via oxidative stress, caused by a cellular excess of reactive oxygen and nitrogen species. Species like superoxide and hydrogen peroxide are involved in protein kinase regulation, while nitric oxide and peroxynitrite inactivate phosphatases as well as activating kinases, which are key agents for translating signals of cell needs into metabolic change through enzyme action, gene transcription, protein synthesis, and biochemical flux. These reactions are permanently balanced by the redox system, a nonequilibrium thermodynamic state as a basic part of aerobic life, determined by relative and constantly changing amounts of oxidative and antioxidative (reductive) agents. Review of a large number of studies shows that external sources of antioxidants, mainly fruits and vegetables, are a real benefit for human defense mechanisms, considering now that sufficient scientific evidence exists for public health policy to promote a plant-rich diet. In our investigation, we focused on anthocyanins, as highly potent phytochemical antioxidants expected to protect us from oxidative injury. Furthermore, these specific antioxidants were found to act against lipoperoxidation and oxidative stress induced by industrial chemicals like carbon tetrachloride, paraquat or heavy metals. Anthocyanin extracts of Vaccinium Myrtillus (bilberry) improve night vision and eye strain caused by excessive computer use. Because of the antioxidant skin protection against UVB radiation, these phytochemicals can be used (both local and oral administration) by workers from oil-bearing platforms, furnaces or agriculture. We think that such important findings may be used for workplace health promotion projects in chemical industry, in order to prevent occupational diseases or work-related diseases. The individual approach of workplace health promotion focuses on the health-related behaviors of employees, and is called risk factor reduction (educational approach). We focused our initiative on using dietary natural antioxidants by running health campaigns, and raising awareness of the harmful effects of chemical agents and xenobiotics, addressed both to employees and managers. We propose a one year project sustaining behavior change mainly through educational and informative sessions, based on assessment of workers’ needs and also on developing healthy lifestyles. We also want to encourage company managers to offer antioxidant supplements/fresh fruits/berries juices to those employees who are working in harmful conditions, considering a daily estimated intake of 200 mg anthocyanins. Health promotion on consuming anthocyanins-rich fruits and vegetables may contribute in reducing age-related neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease, age-related metabolic diseases (especially cardiovascular diseases), and not at least, cancer. Designing potent antioxidant phytococktails and standardised mixtures of anthocyanins for human consumption will be a great challenge on essentially inter-disciplinary research topic involving interaction of nutritionists, physicians, chemists, pharmacists and others.

Quantum maximum-entropy principle for closed quantum hydrodynamic transport within a Wigner function formalism

By introducing a quantum entropy functional of the reduced density matrix, the principle of quantum maximum entropy is asserted as fundamental principle of quantum statistical mechanics. Accordingly, we develop a comprehensive theoretical formalism to construct rigorously a closed quantum hydrodynamic transport within a Wigner function approach. The theoretical formalism is formulated in both thermodynamic equilibrium and nonequilibrium conditions, and the quantum contributions are obtained by only assuming that the Lagrange multipliers can be expanded in powers of h(2). In particular, by using an arbitrary number of moments, we prove that (1) on a macroscopic scale all nonlocal effects, compatible with the uncertainty principle, are imputable to high-order spatial derivatives, both of the numerical density n and of the effective temperature T; (2) the results available from the literature in the framework of both a quantum Boltzmann gas and a degenerate quantum Fermi gas are recovered as a particular case; (3) the statistics for the quantum Fermi and Bose gases at different levels of degeneracy are explicitly incorporated; (4) a set of relevant applications admitting exact analytical equations are explicitly given and discussed; (5) the quantum maximum entropy principle keeps full validity in the classical limit, when h → 0.

Generalized Kinetic Equation for Far-from-Equilibrium Many-Body Systems

A kinetic equation for the single particle distribution function in an open many-body system, when in far away from equilibrium conditions is derived in the context of a Non-Equilibrium Thermo-Statistics of ample scope. It consists of a generalization of traditional kinetic equations in that no restrictions are imposed on the characteristics of the nonequilibrium thermodynamic state of the system. This kinetic equation do contain some contributions that become relevant in systems with a nonlinear kinetics when driven sufficiently far from equilibrium (certain complex systems). Moreover, the handling of the kinetic equation in a multiple-moment approach provides a generalized nonlinear higher-order thermo-hydrodynamics.

High-power terahertz electromagnetic wave emission from high-T_c superconducting Bi_2Sr_2CaCu_2O_8+δ mesa structures

In this paper, we report intense electromagnetic wave emissions generated by the rectangular mesa structure of intrinsic Josephson junctions with high-T(c) superconducting Bi2Sr2CaCu2O(8+δ). The radiated power is an order of magnitude stronger than that of the previously observed power of a few μW. Two emission regions, reversible (R-type) and irreversible (IR-type), with comparable intensities can be observed at different I-V curve locations in the same mesa. We find peculiar temperature dependences of the emission power in both the R- and IR-type radiations, suggesting that a non-equilibrium thermodynamic state may be realized through the dc input current. The R-type emission is quite stable, whereas the IR-type emission is rather unstable. Although the emitted frequency for both cases obey the cavity resonance conditions, this sharp contrast in emission stability is indicative of two different states in a multi-stacked intrinsic Josephson junction system.

Molecular structural property and potential energy dependence on nonequilibrium-thermodynamic state point of liquid n-hexadecane under shear

Extensive computer experiments have been conducted in order to shed light on the macroscopic shear flow behavior of liquid n-hexadecane fluid under isobaric-isothermal conditions through the nonequilibrium molecular dynamic methodology. With respect to shear rates, the accompanying variations in structural properties of the fluid span the microscopic range of understanding from the intrinsic to extrinsic characteristics. As drawn from the average value of bond length and bond angle, the distribution of dihedral angle, and the radius distribution function of intramolecular and intermolecular van der Waals distances, these intrinsic structures change with hardness, except in the situation of extreme shear rates. The shear-induced variation of thermodynamic state curve along with the shear rate studied is shown to consist of both the quasiequilibrium state plateau and the nonequilibrium-thermodynamic state slope. Significantly, the occurrence of nonequilibrium-thermodynamic state behavior is attributed to variations in molecular potential energies, which include bond stretching, bond bending, bond torsion, and intra- and intermolecular van der Waals interactions. To unfold the physical representation of extrinsic structural deformation, under the aggressive influence of a shear flow field, the molecular dimension and appearance can be directly described via the squared radius of gyration and the sphericity angle, R(g)(2) and ϕ, respectively. In addition, a specific orientational order S(x) defines the alignment of the molecules with the flow direction of the x-axis. As a result, at low shear rates, the overall molecules are slightly stretched and shaped in a manner that is increasingly ellipsoidal. Simultaneously, there is an obvious enhancement in the order. In contrast to high shear rates, the molecules spontaneously shrink themselves with a decreased value of R(g)(2), while their shape and order barely vary with an infinite value of ϕ and S(x). It is important to note that under different temperatures and pressures, these three parameters are integrated within a molecular description in response to thermodynamic state variable of density and rheological material function of shear viscosity.

Cooperative and collective effects in light of the maximum energy dissipation principle

We compare the collective phenomena in physics and cooperative phenomena in biology/chemistry in terms of the variational description. The maximum energy dissipation employed and the cost-like functional was chosen according to an optimal control based formulation. Using this approach, the variational outline has been considered for non-equilibrium thermodynamic conditions. The differences between the application of the proposed approach to the description of cooperative phenomena in chemical/biochemical kinetics and the Landau free energy approach to collective phenomena in physics have been investigated.

Linear viscoelasticity and thermorheological simplicity of n-hexadecane fluids under oscillatory shear via non-equilibrium molecular dynamics simulations

A small amplitude oscillatory shear flows with the classic characteristic of a phase shift when using non-equilibrium molecular dynamics simulations for n-hexadecane fluids. In a suitable range of strain amplitude, the fluid possesses significant linear viscoelastic behavior. Non-linear viscoelastic behavior of strain thinning, which means the dynamic modulus monotonously decreased with increasing strain amplitudes, was found at extreme strain amplitudes. Under isobaric conditions, different temperatures strongly affected the range of linear viscoelasticity and the slope of strain thinning. The fluid's phase states, containing solid-, liquid-, and gel-like states, can be distinguished through a criterion of the viscoelastic spectrum. As a result, a particular condition for the viscoelastic behavior of n-hexadecane molecules approaching that of the Rouse chain was obtained. Besides, more importantly, evidence of thermorheologically simple materials was presented in which the relaxation modulus obeys the time-temperature superposition principle. Therefore, using shift factors from the time-temperature superposition principle, the estimated Arrhenius flow activation energy was in good agreement with related experimental values. Furthermore, one relaxation modulus master curve well exhibited both transition and terminal zones. Especially regarding non-equilibrium thermodynamic states, variations in the density, with respect to frequencies, were revealed.

Influence of the concentration, temperature and electric field intensity on the electron mobility in n-doped zinc sulphide

We have calculated the steady state electron mobility in n-doped zinc sulphide (in WZ and ZB phases), driven far away from equilibrium by an electric field. The dependence of the electron mobility (which depends on the nonequilibrium thermodynamic state of the sample) on the concentration, temperature and electric field strength was obtained and analyzed.

Optical properties of III-nitrides in electric fields

The influence of intermediate to high electric fields on the optical properties of direct-gap strongly-polar III-Nitrides is characterized. It is manifested through the dependence on the electric field of the nonequilibrium thermodynamic state of the system, which is characterized by a nonequilibrium effective temperature (quasi-temperature), quasi-chemical potentials and drift velocities of the excited carriers driven away from equilibrium, and the quasi-temperatures of the phonons in the different branches. In particular, we analyze the processes of absorption and luminescence, and a field-dependent Roosbroeck-Shockley relation is derived. It is shown that it is possible to measure the carriers’ drift velocity and quasi-temperature, in the steady state or with ultrafast time resolution, resorting to luminescence together with Raman scattering experiments.

Master curves and radial distribution functions for shear dilatancy of liquid n-hexadecane via nonequilibrium molecular dynamics simulations

Shear dilatancy, a significant nonlinear behavior of nonequilibrium thermodynamics states, has been observed in nonequilibrium molecular dynamics (NEMD) simulations for liquid n-hexadecane fluid under extreme shear conditions. The existence of shear dilatancy is relevant to the relationship between the imposed shear rate gamma and the critical shear rate gamma(c). Consequently, as gamma<gamma(c), the intermolecular equilibrium distance of the fluid remains unchanged, while the nonequilibrium state of the fluid approaches equilibrium. In contrast to gamma>gamma(c), the intermolecular distance is lengthened substantially by strong shear deformation breaking the equilibrium thermodynamic state so that shear dilatancy takes place. Notably, a characteristic shear rate gamma(m), which depends on the root mean square molecular velocity and the average free molecular distance, is found in nonequilibrium thermodynamics state curves. Studies of the variations in the intermolecular radial distribution function (RDF) with respect to the shear rate provide a direct measure of the variation in the degree of intermolecular separation. Additionally, the variations of the RDF curve in the microscopic regime are consistent with those of the nonequilibrium thermodynamic state in the macroscopic world. By inspecting the overall shape of the RDF curve, it can be readily corroborated that the fluid of interest exists in the liquid state. More importantly, both primary characteristic values, the equilibrium thermodynamic state variable and a particular shear rate of gamma(p), are determined cautiously, with gamma(p) depending on the gamma(m) value and the square root of pressure. Thereby, the nonequilibrium thermodynamic state curves can be normalized as temperature-, pressure-, and density-invariant master curves, formulated by applying the Cross constitutive equation. Clearly, gamma(c) occurs at which a reduced shear rate gamma/gamma(p) approaches 0.1. Furthermore, the trends in the rates of shear dilatancy in both the constant-pressure and constant-volume NEMD systems under isothermal conditions conform to the cyclic rule of pressure, as a function of density and shear rate.

Theoretical calculations of nonlinear electronic transport behavior in III‐nitrides: GaN and AlN

AbstractThe dependence of the mobility in n‐doped III‐nitrides on the electric field strength and the concentration of electrons and impurities is derived. Such dependence is determined by the nonequilibrium thermodynamic state of the system, which is led to far‐from equilibrium conditions by the action of intermediate to strong electric fields. It is shown that the mobility decreases with the increase of the electric field strength and the concentration of carriers, in a way evidencing the influence of the nonlinear transport involved. Dependence of the mobility with the concentration following two types of regimes characterized by exponential laws are evidenced. They can also be approximately described by fractional power laws. The influence of the thermal bath temperature is also analyzed. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

The nonequilibrium thermodynamic conditions and properties of materials

The basic principles for classifying the properties of materials, measured under nonequilibrium thermodynamic conditions, are formulated. It is proposed to supplement the nonlinear nonequilibrium thermodynamic mode of operation by new submodes, the area of action of which is determined by the dimensionless criteria introduced. The heat flux relaxation time and the temperature gradient time are considered as new nonlinear properties.

Shear thinning and shear dilatancy of liquid n-hexadecane via equilibrium and nonequilibrium molecular dynamics simulations: Temperature, pressure, and density effects

Equilibrium and nonequilibrium molecular dynamics (MD) simulations have been performed in both isochoric-isothermal (NVT) and isobaric-isothermal (NPT) ensemble systems. Under steady state shearing conditions, thermodynamic states and rheological properties of liquid n-hexadecane molecules have been studied. Between equilibrium and nonequilibrium states, it is important to understand how shear rates (gamma) affect the thermodynamic state variables of temperature, pressure, and density. At lower shear rates of gamma<1 x 10(11) s(-1), the relationships between the thermodynamic variables at nonequilibrium states closely approximate those at equilibrium states, namely, the liquid is very near its Newtonian fluid regime. Conversely, at extreme shear rates of gamma>1 x 10(11) s(-1), specific behavior of shear dilatancy is observed in the variations of nonequilibrium thermodynamic states. Significantly, by analyzing the effects of changes in temperature, pressure, and density on shear flow system, we report a variety of rheological properties including the shear thinning relationship between viscosity and shear rate, zero-shear-rate viscosity, rotational relaxation time, and critical shear rate. In addition, the flow activation energy and the pressure-viscosity coefficient determined through Arrhenius and Barus equations acceptably agree with the related experimental and MD simulation results.

Study of titanium nitride deposition by supersonic plasma spraying

In this study, titanium nitride (TiN) deposition by reactive spraying was carried out under a low-pressure environment using a DC arc plasma jet generator with a supersonic expansion nozzle. Titanium powders were injected using a hollow cathode with argon gas, and nitrogen or nitrogen and hydrogen mixture was used as the plasma gas. Microstructure and properties of the coatings were examined using scanning electron microscope and X-ray diffraction. A dense TiN coating with a Vickers hardness of 2000 Hv was formed at a substrate temperature of 700 °C with a low input power of 5.3 kW. The results showed that the supersonic plasma jet in thermodynamic and chemical nonequilibrium state exhibits high potentials for reactive spraying.

Crystal nucleation and growth in glass-forming melts: Experiment and theory

A critical overview on basic assumptions of the classical theory of crystal nucleation and growth is given. It is shown how the classical theory can be generalized in order to overcome contradictions between theoretical predictions and experimental data. These generalizations refer both to the kinetic prefactor as to the method of determination of the work of formation of clusters of sub-, super- and critical sizes being essential ingredients of the theoretical description. In particular, generalizing the classical Gibbs’ theory of heterogeneous systems to thermodynamic non-equilibrium states it is shown that the properties of the clusters change significantly in dependence on their sizes. In particular, it is shown that the properties of the critical clusters deviate, as a rule, from the properties of the newly evolving macroscopic phases. As one result it turns out that the classical nucleation theory overestimates the work of critical cluster formation and underestimates the value of the steady-state nucleation rate. The application of the generalized Gibbs approach to phase formation allows one in addition a new interpretation of a variety of phenomena in crystallization processes of glass-forming melts, which could not be given a satisfactory explanation in terms of the classical theory so far, retaining on the other side the advantages of the classical approach.

Nonlinear hole transport and nonequilibrium thermodynamics in group III-nitrides under the influence of electric fields

A theoretical study on the nonlinear transport of holes and of the nonequilibrium thermodynamic characteristics of p-doped wurtzite gallium nitride (GaN), aluminium nitride (AlN), and indium nitride (InN), under the influence of moderate to high electric fields, is presented. It is based on a nonlinear quantum kinetic theory which provides a description of the dissipative phenomena developing in the system. The ultrafast time evolution of the hole drift velocity and of the quasitemperatures of holes and longitudinal optical phonons are obtained. The steady state is analyzed by determining the dependence on the electric field of the nonequilibrium thermodynamic state and of the non-Ohmic mobility. A velocity overshoot is evidenced.

High shock release in ultrafast laser irradiated metals: Scenario for material ejection

We present one-dimensional numerical simulations describing the behavior of solid matter exposed to subpicosecond near infrared pulsed laser radiation. We point out to the role of strong isochoric heating as a mechanism for producing highly nonequilibrium thermodynamic states. In the case of metals, the conditions of material ejection from the surface are discussed in a hydrodynamic context, allowing correlation of the thermodynamic features with ablation mechanisms. A convenient synthetic representation of the thermodynamic processes is presented, emphasizing different competitive pathways of material ejection. Based on the study of the relaxation and cooling processes which constrain the system to follow original thermodynamic paths, we establish that the metal surface can exhibit several kinds of phase evolution which can result in phase explosion or fragmentation. An estimation of the amount of material exceeding the specific energy required for melting is reported for copper and aluminum and a theoretical value of the limit size of the recast material after ultrashort laser irradiation is determined. Ablation by mechanical fragmentation is also analyzed and compared to experimental data for aluminum subjected to high tensile pressures and ultrafast loading rates. Spallation is expected to occur at the rear surface of the aluminum foils and a comparison with simulation results can determine a spall strength value related to high strain rates.

Residual stress analysis with improved numerical methods for tempered plate glasses based on structural relaxation model

Glass has useful optical properties but shows unfavorable mechanical performance such as poor impact resistance. As a way to improve such inferior mechanical performance, glass undergoes tempering processes which introduce through-thickness residual stress. Here, the residual stress is numerically analyzed for a soda-lime silicate glass plate under the one-dimensional through-thickness symmetric boundary conditions. As for the constitutive law, the structural relaxation model was used to account for the non-equilibrium thermodynamic state of micro-structures in calculating volume change during cooling and also the visco-elastic nature of mechanical properties. Results obtained using improved numerical methods were compared with experiments as well as results available in previous literatures.

STATISTICAL APPROACH TO NON-FICKIAN DIFFUSION

Competing styles in statistical mechanics have been introduced to investigate physico-chemical systems displaying complex structures, when one faces difficulties to handle the standard formalism in the well-established Boltzmann–Gibbs statistics. After a brief description of the question, we consider the particular case of Renyi statistical approach, which is applied to the study of the "anomalous" (non-Fickian) diffusion that is involved in experiments of cyclic voltammetry in electro-physical chemistry. In these experiments, one is dealing with the fractal-like structure of the thin film morphology present in electrodes in microbatteries. Fractional-power laws are evidenced in the voltammetry measurements and in the analysis of the interphase width obtained using atomic force microscopy. The resulting fractional-powers are related to each other and to the statistical fractal dimension, and can be expressed in terms of the index on which Renyi's statistical approach depends. The important fact that this index, which is restricted to a given interval, provides a measure of the micro-roughness of the electrode surface, and is related to the dynamics involved, the nonequilibrium thermodynamic state of the system, and to the experimental protocol is clarified.