Hasil untuk "Thermodynamics"

W. Israel

I. Sanchez, R. Lacombe

S. Sandler

D. Kondepudi, I. Prigogine

A. Chamblin, R. Emparan, Clifford V. Johnson et al.

The physical properties of Reissner-Nordstrom black holes in (n11)-dimensional anti-de Sitter spacetime are related, by a holographic map, to the physics of a class of n-dimensional field theories coupled to a background global current. Motivated by that fact, and the recent observations of the striking similarity between the thermodynamic phase structure of these black holes ~in the canonical ensemble! and that of the van der Waals-Maxwell liquid-gas system, we explore the physics in more detail. We study fluctuations and stability within the equilibrium thermodynamics, examining the specific heats and electrical permittivity of the holes, and consider the analogue of the Clayperon equation at the phase boundaries. Consequently, we refine the phase diagrams in the canonical and grand canonical ensembles. We study the interesting physics in the neighborhood of the critical point in the canonical ensemble. There is a second order phase transition found there, and that region is characterized by a Landau-Ginzburg model with A3 potential. The holographically dual field theories provide the description of the microscopic degrees of freedom which underlie all of the thermodynamics, as can be seen by examining the form of the microscopic fluctuations. @S0556-2821~99!06820-4#

E. Schneider, J. Kay

A. Feld, Gallagher Mikrowellen-Anregung, unabhangige Grundgrö

B. Eu

G. Lebon, D. Jou, J. Casas-Vazquez

V. Schmidt, J. V. Wittemann, U. Gösele

Christopher S. Henry, L. Broadbelt, V. Hatzimanikatis

Miroslav Grmela, Michal Pavelka

Classical and multiscale non-equilibrium thermodynamics have different histories and different objectives. In this Note we explain the differences and review some topics in which the multiscale viewpoint of mesoscopic time evolution of macroscopic systems helped to advance the classical non-equilibrium thermodynamics. Eventually, we illustrate the Braun-Le Chatelier principle in dissipative thermodynamics.

Serges Bruno Lemoupi Ngomade, Cyrille Donlifack Atemkeng, Aymard Didier Tamafo Fouegue et al.

This study examined the thermal breakdown of Podocarpus falcatus oil (PFO) and its derived biodiesel (BPFO) under dynamic heating conditions. PFO and BPFO were characterized by spectroscopic, computational, and thermo-gravimetric analysis coupled with differential thermo-gravimetric analysis (TGA/DTA). PFO and BPFO's kinetic and thermodynamic properties were examined using Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Starink isoconversional kinetic models. The conversion limit was restricted from 0.1 to 0.9 at different heating rates of 5, 7 and 10 °C.min−1. The FWO isoconversional model was properly fitted by the TGA/DTA analytical data, with the highest R2 values of 0.941. Average activation energies were 224.50 kJ.mol−1 for PFO and 108.60 kJ.mol−1 for BPFO. Nonspontaneous and endothermic thermal breakdown was confirmed by positive standard enthalpy (∆H) and standard Gibbs free energy(∆G) values. In contrast, the negative standard entropy (ΔS) indicated a more ordered process. Using density functional theory (DFT) in conjunction with the M05–2X hybrid functional, the computing study was conducted on the two most abundant FAMEs (Fatty acid methyl ester) to achieve the optimum geometry, topology analysis, and electronic properties. There was a good correlation between the computation and experimental results. This study showed that biodiesel's thermal and oxidation stability with regard to time could be accurately predicted using the TGA/DTA approach.

B. Andresen

Mingnan Ding, Jun Wu, Xiangjun Xing

In this work, we study the stochastic thermodynamics of micro-magnetic systems. We first formulate the stochastic dynamics of micro-magnetic systems by incorporating noises into Landau-Lifshitz (LL) equation, which describes the irreversible and deterministic dynamics of magnetic moments. The resulting stochastic Landau-Lifshitz (sLL) equation obeys detailed balance, which guarantees that, with the external field fixed, the system converges to thermodynamic equilibrium with vanishing entropy production and with non-vanishing probability current. We then discuss various thermodynamic variables both at the trajectory level and at the ensemble level, and further establish both the first and the second laws of thermodynamics. Finally, we establish fluctuation theorems, and verify them using numerical simulations.

S. Liang, R. L. Dong, W. W. Xu et al.

Film cooling protects high-temperature components and generates complex vortex structures through the interaction between the mainstream flow and the injected coolant. Additionally, the process of applying thermal barrier coatings introduces imperfect cooling holes. A numerical simulation study is conducted on two geometric configurations: inclined perfect and imperfect holes arranged in a single row on a flat plate to investigate the effects of flow field vortex structures and hole imperfections. The k-epsilon turbulent model is employed to analyse the impact of varying blowing ratios and defect positions on flow field structure and cooling efficiency, with vortex dynamics providing explanatory insights. As the blowing ratio increases, the kidney vortex associated with the perfect holes progressively detaches from the wall, reducing film cooling efficiency. The kidney vortex originates from the shear interaction between the mainstream and the impinging jet, predominantly influenced by the vortex stretching component. Imperfect holes influence the distribution state of the kidney vortex, with weakened roll-up phenomena observed at the IT4 defect location. Consequently, a noticeable enhancement in film cooling effectiveness is achieved near the proximal end of the hole. 

Johnson N. Naat, Yantus Neolaka, Yosep Lawa et al.

This study aims to examine histamine adsorption using Takari natural sand-based SiO2@BSA as the silica source. Silica was extracted using the hydrothermal and coprecipitation methods and then modified into SiO2@BSA adsorbent using the ultrasonication method. After that, the adsorbent was used to adsorb histamine. The results showed that the mass ratio of SiO2 and BSA to the histamine adsorption was 1:0.02 (qe=11.39 mg/g), with optimum adsorption pH of 5 (qe= 12.33 mg/g) and a contact time of 60 minutes (qe=12.36 mg/g). The percentage of histamine removal was 96%. The kinetic model was pseudo-second order type 1 with an adsorption rate constant of 6.3x103 g/mg, while the isotherm model was Langmuir with R2=0.997; qe=18 mg/g. Thermodynamic parameters indicated that the adsorption process was exothermic with a high degree of randomness, and the histamine adsorption by silica-based SiO2@BSA adsorbent from natural sand occurred chemically.

Georg J. Schmitz, Michael te Vrugt, Tore Haug-Warberg et al.

A gas in a box is perhaps the most important model system studied in thermodynamics and statistical mechanics. Usually, studies focus on the gas, whereas the box merely serves as an idealized confinement. The present article focuses on the box as the central object and develops a thermodynamic theory by treating the geometric degrees of freedom of the box as the degrees of freedom of a thermodynamic system. Applying standard mathematical methods to the thermodynamics of an empty box allows equations with the same structure as those of cosmology and classical and quantum mechanics to be derived. The simple model system of an empty box is shown to have interesting connections to classical mechanics, special relativity, and quantum field theory.

Carolina Aparicio-Fernández, M Eugenia Torner, Mar Cañada-Soriano et al.

Energy consumption in public education buildings depends on use and occupancy. To improve energy performance, energy audits are essential to identify specific solutions for each building. In this study, we conducted an energy audit of a historical building used as a public education centre. We collected gas and electricity bills and recorded indoor temperatures for over a year to determine heating and cooling set points and the schedules. Our analysis showed that 47.42% of the electricity bills were unused. To reduce energy demand and improve thermal comfort, we both developed and validated a Building Energy Modelling (BEM) approach using TRNSYS18 and weather data during year 2021. The BEM model allowed us to propose efficient measures to meet the Standard Passive requirements. Our results demonstrate the effectiveness of energy audits and BEM modelling in reducing energy consumption in public education buildings.

Anna Utkina, Andrey Kozelkov, Roman Zhuchkov et al.

The paper reports the results of a study concerned with the influence of the size of the leading edge laminar bubble on the aerodynamic characteristics of the HGR01 airfoil. The completely turbulent and transient flows are considered. The mechanism of the appearance and interaction of laminar and turbulent flow separation near the leading and trailing edges of the airfoil is studied in detail. In the paper, the dependence of aerodynamic forces on the critical Reynolds number for the HGR01 airfoil is discussed. It has been established that the separation bubble at the leading edge can only be obtained using the laminar–turbulent transition model. Fully turbulent models are not able to show this feature of the airfoil flow. Graphs of the lift coefficient as a function of the critical Reynolds number, as well as the pressure distribution as a function of the size of the laminar bubble, are shown.