Hasil untuk "Thermodynamics"

Iskandar Raufov, Dilshod Nematov, Saidjafar Murodzoda et al.

This study presents a first principles investigation of the structural, thermodynamic, electronic, optical and thermoelectric properties of aluminum antimonide (AlSb) in its cubic (F-43m) and hexagonal (P63mc) phases. Both structures are dynamically and mechanically stable, as confirmed by phonon calculations and the Born Huang criteria. The lattice constants obtained using the SCAN and PBEsol functionals show good agreement with experimental data. The cubic phase exhibits a direct band gap of 1.66 to 1.78 eV, while the hexagonal phase shows a band gap of 1.48 to 1.59 eV, as confirmed by mBJ and HSE06 calculations. Under external pressure, the band gap decreases in the cubic phase and increases in the hexagonal phase due to different s p orbital hybridization mechanisms. The optical absorption coefficient reaches 1e6 cm-1, which is comparable to or higher than values reported for other III V semiconductors. The Seebeck coefficient exceeds 1500 microV per K under intrinsic conditions, and the thermoelectric performance improves above 600 K due to enhanced phonon scattering and lattice anharmonicity. The calculated formation energies (-1.316 eV for F-43m and -1.258 eV for P63mc) confirm that the cubic phase is thermodynamically more stable. The hexagonal phase exhibits higher anisotropy and lower lattice stiffness, which is favorable for thermoelectric applications. These results demonstrate the strong interplay between crystal symmetry, phonon behavior and charge transport, and provide useful guidance for the design of AlSb based materials for optoelectronic and energy conversion technologies.

Victor E. Ambrus, Aleksandar Gecić

We consider the thermodynamic properties of a rotating gas of fermions. We begin by constructing the thermodynamic potential $Φ$ and its associated current $φ^μ$ within the grand canonical ensemble of a macroscopic rigidly rotating body, where the ensemble parameters are the temperature $T_0$ and chemical potential $μ_0$ on the rotation axis, as well as the rotation angular velocity $Ω_0$. We then consider the problem of local thermodynamics, where the thermodynamic state is defined by the local temperature $T$ and chemical potential $μ$, as well as the local spin potential tensor, $Ω_{μν}$. We find the thermodynamic pressure $P$, given as the sum of the usual classical (non-quantum) pressure and other corrections due to the spin potential and the kinematic state of the fluid. We compute the associated entropy, charge and spin densities, and show they are consistent with the Euler relation.

Miroslav Grmela, Michal Pavelka

In this paper, we review and compare some geometric frameworks for dissipation in non-equilibrium thermodynamics. We start with a brief overview of classical irreversible thermodynamics and gradient dynamics. Then we discuss several specific frameworks including Rayleigh dissipation potential and the dissipative d'Alembert framework, showing their relations with gradient dynamics. Finally, we discuss frameworks for dissipative evolution generated from Poisson brackets.

François Gay-Balmaz

Extended irreversible thermodynamics is a theory that expands the classical framework of nonequilibrium thermodynamics by going beyond the local-equilibrium assumption. A notable example of this is the Maxwell-Cattaneo heat flux model, which introduces a time lag in the heat flux response to temperature gradients. In this paper, we develop a variational formulation of the equations of extended irreversible thermodynamics by introducing an action principle for a nonequilibrium Lagrangian that treats thermodynamic fluxes as independent variables. A key feature of this approach is that it naturally extends both Hamilton's principle of reversible continuum mechanics and the earlier variational formulation of classical irreversible thermodynamics. The variational principle is initially formulated in the material (Lagrangian) description, from which the Eulerian form is derived using material covariance (or relabeling symmetries). The tensorial structure of the thermodynamic fluxes dictates the choice of objective rate in the Eulerian description, and plays a central role in the emergence of nonequilibrium stresses - arising from both viscous and thermal effects - that are essential to ensure thermodynamic consistency. This framework naturally results in the Cattaneo-Christov model for heat flux. We also investigate the extension of the approach to accommodate higher-order fluxes and the general form of entropy fluxes. The variational framework presented in this paper has promising applications in the development of structure-preserving and thermodynamically consistent numerical methods. It is particularly relevant for modeling systems where entropy production is a delicate issue that requires careful treatment to ensure consistency with the laws of thermodynamics.

Ti-Wei Xue, Zeng-Yuan Guo

Abstract Since the ideal gas equation of state (EOS) was established in 1840, a wide variety of EOS theories have been developed. However, due to the diversity of material structures and the complexity of intermolecular interactions, numerous EOS either have complex forms or have empirical coefficients without physical meaning, which severely limits their applications. This paper builds a simple and universal EOS model by means of a fully macroscopic thermodynamic approach. Firstly, two single variable thermodynamic functions as a function of pressure only and as a function of temperature only, respectively, are constructed. On this basis, two EOS in the forms of P–V–T and P–S–T are obtained by thermodynamic derivation, which are almost as simple as the ideal gas EOS. There are no assumptions about material structures and intermolecular interactions involved here. Therefore, the model is universal. Moreover, the coefficients in these two EOS have clear thermodynamic significance and thus can be calculated directly without fitting. The model is shown to characterize the thermodynamic properties of substances well and may play an important role in high-density and supercritical applications. This work may provide a new way of developing EOS theory and enrich the fundamentals of thermodynamics.

Jan Karbowski

This paper provides a perspective on applying the concepts of information thermodynamics, developed recently in non-equilibrium statistical physics, to problems in theoretical neuroscience. Historically, information and energy in neuroscience have been treated separately, in contrast to physics approaches, where the relationship of entropy production with heat is a central idea. It is argued here that also in neural systems information and energy can be considered within the same theoretical framework. Starting from basic ideas of thermodynamics and information theory on a classic Brownian particle, it is shown how noisy neural networks can infer its probabilistic motion. The decoding of the particle motion by neurons is performed with some accuracy and it has some energy cost, and both can be determined using information thermodynamics. In a similar fashion, we also discuss how neural networks in the brain can learn the particle velocity, and maintain that information in the weights of plastic synapses from a physical point of view. Generally, it is shown how the framework of stochastic and information thermodynamics can be used practically to study neural inference, learning, and information storing.

Samuel Plesnik, Maria Violaris

We compare how the impossibility of a universal work extractor from coherence arises from different approaches to quantum thermodynamics: an explicit protocol accounting for all relevant quantum resources, and axiomatic, information-theoretic constraints imposed by constructor theory. We first explain how the impossibility of a universal work extractor from coherence is directly implied by a recently proposed constructor-theoretic theorem based on distinguishability, which is scale- and dynamics- independent. Then we give an explicit demonstration of this result within quantum theory, by proving the impossibility of generalising a proposed quantum protocol for deterministically extracting work from coherence. We demonstrate a new connection between the impossibility of universal work extractors and constructor-based irreversibility, which was recently shown using the quantum homogenizer. Finally we discuss additional avenues for applying the constructor-theoretic formulation of work extraction to quantum thermodynamics, including the irreversibility of quantum computation and thermodynamics of multiple conserved quantities.

ZHAO Xuewei, YANG Yi, WEI Xiaoxiao et al.

ObjectiveTo propose a method for modifying the existed isotherm model based on molecular thermodynamics.MethodsThe phantom model in polymer physics field was borrowed to predict the chemical potential of water from swelling effect. Isothermal adsorption and desorption of wheat flour measured using a dynamic vapor sorption system at 20，30，40 ℃ were used as a case to verify our improving approach after analyzing the reasonability of best fitted parameter values.ResultsThe modified model can describe the adsorption and desorption of wheat flour very well, give reasonable parameter values, and predict logically the variation of bound water and adsorbed water contents with water activity and the contributions of mixing, swelling and adsorption effects to the chemical potential of water.ConclusionOur approach for modifying the molecular thermodynamic isotherm model is effective and reasonable.

Lawal Abubakar, Nor Azah Yusof, Abdul Halim Abdullah et al.

Due to the release of hazardous heavy metals from various industries, water pollution has become one of the biggest challenges for environmental scientists today. Mercury Hg(II) is regarded as one of the most toxic heavy metals due to its ability to cause cancer and other health issues. In this study, a tailor-made modern eco-friendly molecularly imprinted polymer (MIP)/nanoporous carbon (NC) nanocomposite was synthesized and examined for the uptake of Hg(II) using an aqueous solution. The fabrication of the MIP/NC nanocomposite occurred via bulk polymerization involving the complexation of the template, followed by polymerization and, finally, template removal. Thus, the formed nanocomposite underwent characterizations that included morphological, thermal degradation, functional, and surface area analyses. The MIP/NC nanocomposite, with a high specific surface area of 884.9 m²/g, was evaluated for its efficacy towards the adsorptive elimination of Hg(II) against the pH solution changes, the dosage of adsorbent, initial concentration, and interaction time. The analysis showed that a maximum Hg(II) adsorption effectiveness of 116 mg/g was attained at pH 4, while the Freundlich model fitted the equilibrium sorption result and was aligned with pseudo-second-order kinetics. Likewise, thermodynamic parameters like enthalpy, entropy, and Gibbs free energy indicated that the adsorption was consistent with spontaneous, favorable, and endothermic reactions. Furthermore, the adsorption efficiency of MIP/NC was also evaluated against a real sample of condensate from the oil and gas industry, showing an 87.4% recovery of Hg(II). Finally, the synthesized MIP/NC showed promise as a selective adsorbent of Hg(II) in polluted environments, suggesting that a variety of combined absorbents of different precursors is recommended to evaluate heavy metal and pharmaceutical removals.

Vito Antonio Cimmelli

We propose a thermodynamic model describing the thermoelastic behavior of composition graded materials. The compatibility of the model with the second law of thermodynamics is explored by applying a generalized Coleman–Noll procedure. For the material at hand, the specific entropy and the stress tensor may depend on the gradient of the unknown fields, resulting in a very general theory. We calculate the speeds of coupled first- and second-sound pulses, propagating either trough nonequilibrium or equilibrium states. We characterize several different types of perturbations depending on the value of the material coefficients. Under the assumption that the deformation of the body can produce changes in its stoichiometry, altering locally the material composition, the possibility of propagation of pure stoichiometric waves is pointed out. Thermoelastic perturbations generated by the coupling of stoichiometric and thermal effects are analyzed as well.

Shabir Ahmad, Salma Haque, Khalid Ali Khan et al.

In this study, we analyze the transmission of the COVID-19 model by using a piecewise operator in the classical Caputo sense. The existence along with the uniqueness of the solution of the COVID-19 model under a piecewise derivative is presented. The numerical scheme with Newton polynomials is used to obtain a numerical solution to the model under consideration. The graphical illustrations for the suggested model are demonstrated with various fractional orders. The crossover behavior of the considered system is observed in the graphical analysis. Furthermore, the comparison of simulations with real data for three different countries is presented, where best-fitted dynamics are observed.

Sampath Bharadwaj Kota, Seik Mansoor Ali, Sreenivas Jayanti

During the 2011 nuclear catastrophe at Fukushima Daiichi, Unit 3 had a sharper increase in containment pressure than Unit 2, with thermal stratification of the suppression pool cited as one of the contributing factors. In the present work, the buoyancy-induced circulation consequent to steam condensation in a large, toroidal pool of water is studied using computational fluid dynamics (CFD) simulations with a view to understanding the role of important design parameters of the suppression pool system. The tunnelling phenomenon observed in the development of the thermal stratification process is delineated in terms of the establishment of a thermocline. The effects of the number of steam injection points and the cross-section of the pool on thermal stratification characteristics have been investigated through a number of case studies. In all the cases, the surface temperature, which is responsible for over-pressurization of the containment, is found to be significantly higher than the bulk pool temperature. Multiple injection points with the same overall steam flow rate are found to lead to higher surface temperatures due to a shortened circulation path. For the same volume of pool water, the simulations show that a deeper and narrower pool gives rise to significantly higher temperatures than a wider and shallower pool. This is attributed to the relatively deeper penetration of the buoyancy-induced circulation into the pool.

Jane K.J. Lee, Yun-Tao Liu, Jason J. Hu et al.

Propionyl-CoA carboxylase (PCC) is a multienzyme complex consisting of up to six α-subunits and six β-subunits. Belonging to a metabolic pathway converging on the citric acid cycle, it is present in most forms of life and irregularities in its assembly lead to serious illness in humans, known as propionic acidemia. Here, we report the cryogenic electron microscopy (cryoEM) structures and assembly of different oligomeric isomers of endogenous PCC from the parasitic protozoan Leishmania tarentolae (LtPCC). These structures and their statistical distribution reveal the mechanics of PCC assembly and disassembly at equilibrium. We show that, in solution, endogenous LtPCC β-subunits form stable homohexamers, to which different numbers of α-subunits attach. Sorting LtPCC particles into seven classes (i.e., oligomeric formulae α0β6, α1β6, α2β6, α3β6, α4β6, α5β6, α6β6) enables formulation of a model for PCC assembly. Our results suggest how multimerization regulates PCC enzymatic activity and showcase the utility of cryoEM in revealing the statistical mechanics of reaction pathways.

肖丙政, 谢海平, 魏刚武 et al.

The production process of steelmarking bearing steel by 100 t converter is studied and analyzed with tlhermody namics. The co-operating control process of carbon preservation, dephosphorization, and temperature control (C-P-T) in converter steelmaking process is optimized and established and applied to produce bearing steel. The results show that the dephosphorization reaction in furnace does not stop immediately when the selective oxidation temperature of phosphorus and carbon comes but has a slow decay process. In order to meet the need of deep dephosphorization, the optimal time of first slagging out in early stage of the new process should be controlled between 350 s and 380 s, and the temperature range is 1 360-1 437 ℃. The decarburization rate model predicts that the decarburization rate of bearing steel in the late stage of smelting is (0. 21% -0. 28% )/min. In order to keep the requirement of carbon preservation and temperature control, the catch carbon and reblow can be adopted in the end phase of blowing to further accurately control the temperature of liquid steel. According to the production data statistics of a furnace service period, the heat ratio of end carbon, phosphorus and temperature hit the target at the same time accounts for 76.67% , and the purity of liquid steel is greatly improved.

Parvin Gharbani, Ali Mehrizad, Seyyed Amir Mosavi

Abstract In this study, the photocatalytic degradation of Methylene Blue was investigated using CdSe nanoparticles. CdSe nanoparticles were synthesized via a simple method and were characterized by FTIR, XRD, FESEM, BET, DRS and EDS techniques. The photocatalytic performance of the CdSe nanoparticles was optimized using Response Surface Methodology (RSM) under visible light. The independent variables involved initial pH, MB concentration, photocatalyst dosage, and irradiation time were evaluated and the optimum photodegradation efficiency of MB dye removal was achieved ˜ 92.80% at pH = 8, 20 mgL−1 of MB concentration, 0.02 g 50 mL−1 of CdSe dosage, and 20 min of irradiation time. Also, the photodegradation of MB by CdSe is obeyed pseudo-first-order kinetic model (k = 0.038 min−1). The thermodynamic results revealed that the photocatalytic degradation of MB is spontaneous and endothermic. Also, the evaluation of various scavengers confirmed that the MB photodegradation was mainly done by photogenerated holes and hydroxyl radicals.

Yanghuan Zhang, Xin Wei, Wei Zhang et al.

In this investigation, mechanical grinding was applied to fabricating the Mg-based alloys La7Sm3Mg80Ni10 + 5 wt.% M (M = None, TiO2, La2O3) (named La7Sm3Mg80Ni10–5 M (M = None, TiO2, La2O3)). The result reveals that the structures of as-milled alloys consist of amorphous and nanocrystalline. The particle sizes of the added M (M = TiO2, La2O3) alloys obviously diminish in comparison with the M = None specimen, suggesting that the catalysts TiO2 and La2O3 can enhance the grinding efficiency. What's more, the additives TiO2 and La2O3 observably improve the activation performance and reaction kinetics of the composite. The time required by releasing 3 wt.% hydrogen at 553, 573 and 593 K is 988, 553 and 419 s for the M= None sample, and 578, 352 and 286 s for the M = TiO2 composite, and 594, 366, 301 s for the La2O3 containing alloy, respectively. The absolute value of hydrogenation enthalpy change |ΔH| of the M (M = None, TiO2, La2O3) alloys is 77.13, 74.28 and 75.28 kJ/mol. Furthermore, the addition of catalysts reduces the hydrogen desorption activation energy (Eade).

Dheerandra Shanker Sachan, Shailesh Jaloree, Junesang Choi

The purpose of this paper is to develop some new recurrence relations for the two parametric Mittag-Leffler function. Then, we consider some applications of those recurrence relations. Firstly, we express many of the two parametric Mittag-Leffler functions in terms of elementary functions by combining suitable pairings of certain specific instances of those recurrence relations. Secondly, by applying Riemann–Liouville fractional integral and differential operators to one of those recurrence relations, we establish four new relations among the Fox–Wright functions, certain particular cases of which exhibit four relations among the generalized hypergeometric functions. Finally, we raise several relevant issues for further research.

Kaihong Zhao, Yue Ma

The existence of solutions for a class of nonlinear neutral Hadamard-type fractional integro-differential equations with infinite delay is researched in this paper. By constructing an appropriate normed space and utilizing the Banach contraction principle, Krasnoselskii’s fixed point theorem, we obtain some sufficient conditions for the existence of solutions. Finally, we provide an example to illustrate the validity of our main results.

Themis Matsoukas

The appeal of thermodynamics to problems outside physics is undeniable, as is the growing recognition of its apparent universality, yet in the absence of a rigorous formalism divorced from the peculiarities of molecular systems all attempts to generalize thermodynamics remain qualitative and heuristic at best. In this paper we formulate a probabilistic theory of thermodynamics and and set the basis for its application to generic stochastic populations.

Tomoki Nosaka, Tokiro Numasawa

Abstract We study various aspects of the mass deformation of the SYK model which makes the black hole microstates escapable. SYK boundary states are given by a simple local boundary condition on the Majorana fermions and then evolved in Euclidean time in the SYK Hamiltonian. We study the ground state of this mass deformed SYK model in detail. We also use SYK boundary states as a variational approximation to the ground state of the mass deformed SYK model. We compare variational approximation with the exact ground state results and they showed a good agreement. We also study the time evolution of the mass deformed ground state under the SYK Hamiltonian. We give a gravity interpretation of the mass deformed ground state and its time evolutions. In gravity side, mass deformation gives a way to prepare black hole microstates that are similar to pure boundary state black holes. Escaping protocol on these ground states simply gives a global AdS2 with an IR end of the world brane. We also study the thermodynamics and quantum chaotic properties of this mass deformed SYK model. Interestingly, we do not observe the Hawking Page like phase transition in this model in spite of similarity of the Hamiltonian with eternal traversable wormhole model where we have the phase transition.