Hasil untuk "Thermodynamics"

M. Koper

Özgür Ökcü

In this paper, combining the thermodynamical arguments of the horizon with the quadratic generalised uncertainty principle (GUP), we heuristically obtain the modified equipartition law of energy. Employing this modified equipartition law of energy, we derive the Friedmann equations in Verlinde’s entropic gravity. We find a maximum energy density at the beginning of the Universe. Remarkably, this feature emerges not only for positive GUP parameter but also for negative GUP parameter. From the initial acceleration, we deduce that the negative GUP parameter is more preferable. We also obtain maximum Hubble parameter from the first Friedmann equation, indicating a universe without initial singularity. Moreover, we compute the Kretschmann curvature scalar, again indicating a non-singular universe. Interestingly, we find that GUP-modified Friedmann equations share some similarities with braneworld cosmolgy where the quadratic term in energy density appears. We also compute the deceleration parameter. Finally, we revisit the gravitational baryogenesis and show that the GUP-modified equipartition law of energy provides a mechanism for generating baryon asymmetry. Moreover, we constrain the GUP parameter from observations.

Francesco Calise, Francesco Liberato Cappiello, Luca Cimmino et al.

This study addresses the critical challenge of performing a detailed calculation of energy savings in buildings by implementing suitable actions aiming at reducing greenhouse gas emissions. Given the high energy consumption of buildings’ space heating systems, optimizing their performance is crucial for reducing their overall primary energy demand. Unfortunately, the calculations of such savings are often based on extremely simplified methods, neglecting the dynamics of the emitters installed inside the buildings. These approximations may lead to relevant errors in the estimation of the possible energy savings. In this framework, the present study presents a novel 0-dimensional capacitive model of a radiator, the most common emitter used in residential buildings. The final scope of this paper is to integrate such a novel model within the TRNSYS 18simulation environment, performing a 1-year simulation of the overall building-space heating system. The radiator model is developed in MATLAB 2024b and it carefully considers the impact of surface area, inlet temperature, and flow rate on the radiator performance. Moreover, the dynamic heat transfer rate of the capacitive radiator is compared with the one returned by the built-in non-capacitive model available in TRNSYS, showing that neglecting the capacitive effect of radiators leads to an incorrect estimation of the heating consumption. During the winter season, with a heating system turned on from 8 a.m. to 4 p.m. and from 6 p.m. to 8 p.m., the thermal energy is underestimated by roughly 20% with the commonly used non-capacitive model.

Arif Hussain, Bertram Thoning Hvass Søgaard, Konstantinos Anastasakis

This study examines the significance of thermodynamic model selection to improve predictions when modeling a wet oxidation (WO) process. WO is a promising technology for treating the highly concentrated process water stream from hydrothermal liquefaction (HTL) while generating heat, due to the exothermic oxidation reactions, leading to a potential integrated HTL-WO autothermal process. However, the harsh process conditions employed fail to describe oxygen solubility accurately, leading to major deviations in predicted COD reduction, heat generation, vapor fraction, and final design. To accurately capture oxygen solubility at elevated temperatures and pressures, experimental oxygen solubility data were regressed using activity coefficient models. This yielded improved oxygen solubility predictions at 280–350 °C, more realistic vapor fractions and heat outputs, and COD reduction close to experimental values.

Clive B. Beggs, Rabia Abid, Fariborz Motallebi et al.

COVID-19 is an airborne disease, with the vast majority of infections occurring indoors. In comparison, little transmission occurs outdoors. Here, we investigate the airborne transmission pathways that differentiate the indoors from outdoors and conclude that profound differences exist, which help to explain why SARS-CoV-2 transmission is much more prevalent indoors. Near- and far-field transmission pathways are discussed along with factors that affect infection risk, with aerosol concentration, air entrainment, thermal plumes, and occupancy duration all identified as being influential. In particular, we present the fundamental equations that underpin the Wells–Riley model and show the mathematical relationship between inhaled virus particles and quanta of infection. A simple model is also presented for assessing infection risk in spaces with incomplete air mixing. Transmission risk is assessed in terms of aerosol concentration using simple 1D equations, followed by a description of thermal plume–ceiling interactions. With respect to this, we present new experimental results using Schlieren visualisation and computational fluid dynamics (CFD) based on the Eulerian–Lagrangian approach. Pathways of airborne infection are discussed, with the key differences identified between indoors and outdoors. In particular, the contribution of thermal and exhalation plumes is evaluated, and the presence of a near-field/far-field feedback loop is postulated, which is absent outdoors.

Naima Hakkar, Rajesh Dhayal, Amar Debbouche et al.

We herein report a new class of impulsive fractional stochastic differential systems driven by mixed fractional Brownian motions with infinite delay and Hurst parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mover accent="true"><mi mathvariant="script">H</mi><mo>^</mo></mover><mo>∈</mo><mrow><mo>(</mo><mn>1</mn><mo>/</mo><mn>2</mn><mo>,</mo><mn>1</mn><mo>)</mo></mrow></mrow></semantics></math></inline-formula>. Using fixed point techniques, a <i>q</i>-resolvent family, and fractional calculus, we discuss the existence of a piecewise continuous mild solution for the proposed system. Moreover, under appropriate conditions, we investigate the approximate controllability of the considered system. Finally, the main results are demonstrated with an illustrative example.

Nehad Ali Shah, Bander Almutairi, Dumitru Vieru et al.

This article investigates the effects of thermal memory and the moving line thermal shock on heat transfer in biological tissues by employing a generalized form of the Pennes equation. The mathematical model is built upon a novel time-fractional generalized Fourier’s law, wherein the thermal flux is influenced not only by the temperature gradient but also by its historical behavior. Fractionalization of the heat flow via a fractional integral operator leads to modeling of the finite speed of the heat wave. Moreover, the thermal source generates a linear thermal shock at every instant in a specified position of the tissue. The analytical solution in the Laplace domain for the temperature of the generalized model, respectively the analytical solution in the real domain for the ordinary model, are determined using the Laplace transform. The influence of the thermal memory parameter on the heat transfer is analyzed through numerical simulations and graphic representations.

Adnan Darwish Ahmad, Nelson K. Akafuah, Jason Forthofer et al.

The authors are a team of fire whirl researchers who have been actively studying whirls and large-scale wildland fires by directly observing them through fire-fighting efforts and applying theory, scale modeling, and numerical simulations in fire research. This multidisciplinary research-background team previously conducted scale model experiments to reconstruct hazardous large-scale fires in the laboratory, then conducted numerical simulations and developed fundamental theories to translate these findings into a basic understanding of combustion science and fluid dynamics. This article, a mix of reviews of the state of art experiments, theories, numerical modeling and artificial intelligence, and two case studies, is intended to address some safety concerns and raise awareness of large-scale fire whirls and forest fires with knowledge of thermodynamics, chemical kinetics, fluid dynamics, design, and practical fire-fighting experience, offering gaps that should be filled and future research to be conducted in each field, and crucial new observations and insights on large-scale fire incidents. We believe, this timely topic is of interest not only to fire research community but also to general readers, as the frequency and intensity of large-scale forest fires and fire whirls have increased, possibly due to the continuing global warming trend and human-induced changes in fuels. Each section and case study was written by one or two individual researchers based on their field of expertise which allows them to critically review progress made in their section of large-scale fire-whirls and forest-fires. Crucial observations and insights on the historical Great-Kanto-Earthquake-generated Hifukusho-Ato Fire-whirl (HAFW) and the slow rotations observed during recent forest firefighting efforts are presented. The first case study occurred in downtown Tokyo on 1 September 1923, as a result of the Great-Kanto-Earthquake, which claimed over 38,000 deaths within 15 min. The second case study discusses large-scale slow rotations observed during recent forest fires, which might had been responsible for the injuries and deaths of experienced firefighters.

Marlene Crone, Michael Türk

Supercritical fluid reactive deposition is an environmentally friendly technique for the synthesis of supported mono- or bimetallic nanoparticles. Experimental results show that the adsorption of a precursor on a substrate is the crucial process step that controls the loading and the size of the deposited metal nanoparticles. In this review, an overview of experimental and modeling work is given and selected experimental data were correlated with the following adsorption isotherm models: Henry, Freundlich, Langmuir, Toth, and Langmuir–Freundlich equations. As a result, in the case of precursors with a low CO₂ solubility and therewith low uptake, the adsorption behavior can be described with sufficient accuracy by the Henry approach. Furthermore, the Freundlich and Langmuir equations enable sufficiently accurate descriptions of the experimental data. In the end, strategies for overcoming the knowledge gaps for essential future research directions are suggested.

Adam Gadomski, Natalia Kruszewska

This commentary tackles the subtle at-the-edge problem of passing locally by a mesoscopic matter-aggregating system from a classical stochastic to a quantum stochastic description. A <i>d</i>-dimensional entropy-productive aggregation of the matter is taken as the starting point. Then, a dimensional reduction towards a one-dimensional quantum-wire type matter-aggregation system is proposed, resulting in postponing surface-tension conditions for the effectively <i>d</i> = 1-dimensional quantum-wire type or nanorod-like cluster/polycrystal, which is qualitatively consistent with a physical-metallurgical (high-temperature) Louat’s grain growth model. A certain recuperative interplay based on maneuvering between subtle temperature rises applied to the system under study while maintaining its quantum character (the so-called Nelson’s quantum-stochastic procedure) within the limits of a vanishing Planck’s constant, involved in the diffusivity measure of the aggregation, is discussed. Certain applications towards the formation of <i>d</i> = 1-dimensional semiconductors and other nanostructures (possibly using soft materials or (bio)polymeric materials such as nanofibers) are envisioned. As a special example, one may propose a nanotechnological process which is termed the Van der Waals heteroepitaxy. The process itself contains the main quantum vs. classical crossover due to the involvement of weak repulsion (quantum) vs. attraction (treated classically) interactions, which are represented by a Lennard-Jones-type potential.

Sergey Il’ich Kruglov

Spherically symmetric solution in 4D Einstein–Gauss–Bonnet gravity coupled to modified logarithmic nonlinear electrodynamics (ModLogNED) is found. This solution at infinity possesses the charged black hole Reissner–Nordström behavior. We study the black hole thermodynamics, entropy, shadow, energy emission rate and quasinormal modes. It was shown that black holes can possess the phase transitions and at some range of event horizon radii black holes are stable. The entropy has the logarithmic correction to the area law. The shadow radii were calculated for variety of parameters. We found that there is a peak of the black hole energy emission rate. The real and imaginary parts of the quasinormal modes frequencies were calculated. The energy conditions of ModLogNED are investigated.

Abbas Shahrabadi, Allahyar Daghbandan, Mohsen Arabiyoun

Nowadays, the application of materials, such as surfactants and nanoparticles in enhanced oil recovery (EOR) projects has been widely studied. So, the adsorption process of these substances is one of the important methods to increase the oil recovery factor from carbonate oil reservoirs. However, understanding how the surfactant-nanoparticle combination interacts through the adsorption process onto the carbonate reservoir rocks surface is not well discussed. In this paper, the adsorption process of saponin extracted from the Glycyrrhiza glabra plant as a natural non-ionic surfactant (GG surfactant) with the presence of hydrophilic titanium dioxide nanoparticles (HITNPs) onto the carbonate reservoir rock (adsorbent) surface has been investigated for mobilizing the crude oil remaining to increase the oil recovery factor. Hence, this study highlights the equilibrium adsorption rate and the adsorption kinetics of these materials in aqueous solutions for chemical EOR schemes. Also, analyses of X-ray diffraction (XRD) spectrometry, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy have been applied to confirm and determine the physicochemical changes and properties of materials. To evaluate the adsorption rate and the relationship between surfactant concentration with the presence of nanoparticles and adsorption density on the adsorbent surface in the aqueous phase, batch adsorption tests under atmospheric conditions at different concentrations and times have been used to comprehend the impact of adsorbate dose on the sorption efficiency. Therefore, the electrical conductivity (EC) technique was used for measuring the adsorption rate of surfactant with the presence of HITNPs in the aqueous phase on the adsorbent surface. The adsorption kinetics process was experimentally investigated at laboratory temperature (25 °C) by monitoring the uptake of solutions on the adsorbent surface as a function of time. The experimental adsorption data were also examined by different equilibrium and kinetic models of adsorption. Hence, the adsorption parameters were determined for each model. Langmuir isotherm was the best model according to the higher values of the correlation coefficient (R2) for GG surfactant and surfactant nanofluid solutions on the adsorbent surface. Furthermore, the pseudo-second-order kinetic model could satisfactorily estimate the adsorption kinetics of GG surfactant and surfactant nanofluid solutions on the adsorbent surface. Results indicated that the adsorption process of GG surfactant and surfactant nanofluid solutions on the adsorbent surface is characterized by a short period of rapid adsorption, followed by a long period of slower adsorption. Moreover, the results of the IFT experiment of these materials showed that GG surfactant and surfactant nanofluid solutions could significantly reduce the IFT value between oil and water system. Finally, the results obtained from this study can help in selecting appropriate surfactants and metal oxide nanoparticles for the design of EOR projects, especially reservoir simulation schemes and chemical flooding processes for carbonate oil reservoirs.

Maxwell Aifer, Sebastian Deffner

While recent breakthroughs in quantum computing promise the nascence of the quantum information age, quantum states remain delicate to control. Moreover, the required energy budget for large scale quantum applications has only sparely been considered. Addressing either of these issues necessitates a careful study of the most energetically efficient implementation of elementary quantum operations. In the present analysis, we show that this optimal control problem can be solved within the powerful framework of quantum speed limits. To this end, we derive state-independent lower bounds on the energetic cost, from which we find the universally optimal implementation of unitary quantum gates, for both single and N -qubit operations.

Liang Li, Hongwei Wang, Jun Wu et al.

The thermomechanical coupling constitutive model of concrete is a critical subject for the theoretical investigation and numerical simulation of the mechanical behaviors of concrete members and structures at high temperature. This paper presents a thermomechanical coupling constitutive model for the description of the mechanical behaviors of concrete at different temperatures. The expression of the elastic strain increment is derived with the free energy function including the temperature variable. The expression of the plastic strain increment is derived from the yield function based on the Drucker–Prager strength criterion. The elastoplastic damage effect is included in this constitutive model. The damage variable is included in the yield function to consider the effect of the damage on the elastoplastic mechanical behaviors of concrete. The proposed constitutive model is validated by the comparison of the simulation results of the uniaxial compression tests of concrete at different temperatures with the corresponding test results. The simulation results accord well with the test results at different temperatures. This indicates that the proposed constitutive model can characterize the mechanical behaviors of concrete at different temperatures with considerable accuracy. The proposed constitutive model was applied to simulate an axially compressive concrete column. The simulation results are consistent with the essential mechanical response behaviors of concrete members at different temperatures.

Yi-Wen Han, Xiao-Xiong Zeng, Yun Hong

Abstract After studying the energy–momentum relation of charged particles’ Hamilton–Jacobi equations, we discuss the laws of thermodynamics and the weak cosmic censorship conjecture in torus-like black holes. We find that both the first law of thermodynamic as well as the weak cosmic censorship conjecture are valid in both the normal phase space and extended phase space. However, the second law of thermodynamics is only valid in the normal phase space. Our results show that the first law and weak cosmic censorship conjecture do not depend on the phase spaces while the second law depends. What’s more, we find that the shift of the metric function that determines the event horizon take the same form in different phase spaces, indicating that the weak cosmic censorship conjecture is independent of the phase space.

HUSSEIN KEHINDE OKORO, Oluwaseyi Ayika, Adedibu Tella et al.

The remediation of cadmium and lead ions from their respective aqueous solutions was carried out with the use of metal-organic frameworks (MOFs) developed from copper and zinc with benzene-1,4-dicarboxylic acid (BDC). The experimental adsorption process was done in batches to determine the equilibrium characteristics, thermodynamics and kinetics of the sorption processes. The result was then tested using Langmuir, Freundlich, and Temkin isotherm equations with Langmuir being the best fitted isotherm, while the kinetics isotherm used were pseudo first order and pseudo second order. The result obtained shows that the MOFs are great potential adsorbent for the studied metals.

Dongjing Liu, Weiguo Zhou, Xu Song et al.

In flocculation processes, particulates randomly collide and coagulate with each other, leading to the formation and sedimention of aggregates exhibiting fractal characteristics. The diffusion-limited aggregation (DLA) model is extensively employed to describe and study flocculation processes. To more accurately simulate flocculation processes with the DLA model, the effects of particle number (denoting flocculation time), motion step length (denoting water temperature), launch radius (representing initial particulate concentration), and finite motion step (representing the motion energy of the particles) on the morphology and structure of the two-dimensional (2D) as well as three-dimensional (3D) DLA aggregates are studied. The results show that the 2D DLA aggregates possess conspicuous fractal features when the particle number is above 1000, motion step length is 1.5–3.5, launch radius is 1–10, and finite motion step is more than 3000; the 3D DLA aggregates present clear fractal characteristics when the particle number is above 500, the motion step length is 1.5–3.5, the launch radius is 1–10, and the finite motion step exceeds 200. The fractal dimensions of 3D DLA aggregates are appreciably higher than those of 2D DLA aggregates.

Romit Maulik, Omer San

Solving two-dimensional compressible turbulence problems up to a resolution of 16, 384^2, this paper investigates the characteristics of two promising computational approaches: (i) an implicit or numerical large eddy simulation (ILES) framework using an upwind-biased fifth-order weighted essentially non-oscillatory (WENO) reconstruction algorithm equipped with several Riemann solvers, and (ii) a central sixth-order reconstruction framework combined with various linear and nonlinear explicit low-pass spatial filtering processes. Our primary aim is to quantify the dissipative behavior, resolution characteristics, shock capturing ability and computational expenditure for each approach utilizing a systematic analysis with respect to its modeling parameters or parameterizations. The relative advantages and disadvantages of both approaches are addressed for solving a stratified Kelvin-Helmholtz instability shear layer problem as well as a canonical Riemann problem with the interaction of four shocks. The comparisons are both qualitative and quantitative, using visualizations of the spatial structure of the flow and energy spectra, respectively. We observe that the central scheme, with relaxation filtering, offers a competitive approach to ILES and is much more computationally efficient than WENO-based schemes.

Bogeun Gwak, Daeho Ro

We investigate herein the spin interaction during collisions between Kerr-(anti-)de Sitter black holes. The spin interaction potential depends on the relative rotation directions of the black holes, and this potential can be released as gravitational radiation upon collision. The energy of the radiation depends on the cosmological constant and corresponds to the spin interaction potential in the limit that one of the black holes has negligibly small mass and angular momentum. We then determine the approximate overall behaviors of the upper bounds on the radiation using thermodynamics. The results indicate that the spin interaction can consistently contribute to the radiation. In addition, the radiation depends on the stability of the black hole produced by the collision.

Zhengwen Xu, Yunlong Zhao, Jing Shi et al.

As new emerging pollutants, phthalic acid monoesters (PAMs) pose potential ecological and human health risks. In the present study, adsorption performance of monobutyl phthalate (MBP) onto two macroporous base anion-exchange resins (D-201 and D-301) was discussed. It was found that the adsorption isotherms were best fitted by the Langmuir equation while the adsorption kinetics were well described by pseudo-first-order model. Analyses of sorption isotherms and thermodynamics proved that the adsorption mechanisms for DBP onto D-201 were ion exchange. However, the obtained enthalpy values indicate that the sorption process of MBP onto D-301 is physical adsorption. The equilibrium adsorption capacities and adsorption rates of DBP on two different resins increased with the increasing temperature of the solution. D-301 exhibited a higher adsorption capacity of MBP than D-201. These results proved that D-301, as an effective sorbent, can be used to remove phthalic acid monoesters from aqueous solution.