Hasil untuk "Thermodynamics"

N. Saunders, P. Miodownik

Y. Fung, S. Cowin

D. Son, Piotr Surówka

We consider the hydrodynamic regime of theories with quantum anomalies for global currents. We show that a hitherto discarded term in the conserved current is not only allowed by symmetries, but is in fact required by triangle anomalies and the second law of thermodynamics. This term leads to a number of new effects, one of which is chiral separation in a rotating fluid at nonzero chemical potential. The new kinetic coefficients can be expressed, in a unique fashion, through the anomaly coefficients and the equation of state. We briefly discuss the relevance of this new hydrodynamic term for physical situations, including heavy-ion collisions.

Douglas Mundarain, Kevin Araya‐Sossa, Mario Miranda‐Rojas

Abstract In this work, a quantum bound is derived for the efficiency of a heat engine operating with two‐level quantum systems as the working substance. This bound is found by using the extension of the monotonicity of quantum relative entropy in terms of Petz recovery maps.

Callum Gray, Samir Chitnavis, Tamara Buja et al.

Yanling Zhao, Ruiqing Shi

This paper constructs a fundamental mathematical model to depict the therapeutic effects of two drugs on breast cancer patients. The model is described by fractional order differential equations with two control variables. Two scenarios are considered: the constant control and the optimal control. For the constant control scenario, the existence and uniqueness of the solution of the system are proved by using the fixed point theorem and combining with the Caputo–Fabrizio fractional derivative; then, the sufficient conditions for the existence and stability of the system’s equilibriums are derived. For the optimal control scenario, the optimal control solution is obtained by using the Pontryagin’s maximum principle. To further validate the effectiveness of the theoretical results, numerical simulations were conducted. The results show that the parameters have significant sensitivity to the dynamic behavior of the system.

Xiaowei Shi, Xingrong Huang, Le Fang

The interaction between the ship hull and the propeller’s rotational motion causes the propeller to operate under non-uniform inflow conditions. In reality, the ship’s effective wake constitutes a complex nonlinear superposition of multiple wave numbers. However, existing studies often neglect these multi-scale interactions. In this work, Unsteady Reynolds-Averaged Navier–Stokes (URANS) simulations with a two-scale inflow model are conducted to investigate the fluid–structure interaction of a propeller under multi-scale inflow. The model introduces large-scale and small-scale Fourier modes together with transverse perturbations, allowing systematic variation of inflow characteristics. The results reveal that large-scale modes amplify unsteady thrust fluctuations and enhance vortex fragmentation, while small-scale modes produce similar but weaker effects, mainly influencing the high-frequency components of unsteady thrust. In contrast, transverse perturbations reduce inflow non-uniformity, effectively suppress single blade thrust fluctuations, and preserve the coherent vortex structures of the wake. This study highlights the importance of multi-scale effects in the unsteady hydrodynamic characteristics of marine propellers and provides useful insights for the optimization of propeller design and energy-saving devices.

Qiulu GAO, Peng DIAO

Advanced water electrolysis powered by renewable energy is the most ideal and environmentally friendly approach for hydrogen production, serving as a technological foundation for large-scale hydrogen energy applications. This process can significantly reduce environmental pollution from energy consumption and support China’s carbon neutrality goals. However, the high energy demands and costs of noble metals pose challenges to scaling up hydrogen production from water electrolysis. To enhance efficiency, developing low-cost yet highly efficient noble metal-free electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial. Understanding the mechanisms behind HER and OER helps identify factors affecting electrocatalyst efficiency and design strategies to improve performance. Moreover, replacing the energy-intensive OER with more energy-efficient reactions offers another promising way to promote hydrogen production. This review summarizes recent advancements in nonprecious transition metal-based electrocatalysts for water electrolysis. Compared to noble metal-based electrocatalysts, nonprecious transition metal-based electrocatalysts like Fe, Co, and Ni-based oxides, (oxy) hydroxides, chalcogenides, and their derivates offer abundant reserves, lower costs, and adjustable catalytic properties, making them viable alternatives for large-scale water splitting. Understanding how these materials catalyze HER and the OER in different electrolytes is key to designing strategies, such as element doping, hetero-structuring, lattice defect construction, carbon composite coupling, and surface reconstruction, to reduce energy costs of electrochemical water splitting. The mechanisms behind these strategies for enhancing water electrolysis are explained through the thermodynamics of absorbed intermediates and the reaction kinetics. Beyond reducing overpotentials, another strategy involves replacing OER with the anodic oxidation reaction of organic molecules, effectively lowering the overall voltage. This review highlights recent progress and strategies for designing efficient electrocatalysts for the anodic oxidation of diverse organics, including urea, amine, hydrazine, alcohol, aldehyde, and sulfates, in substitution of water molecules. This review also addresses the gap between lab-scale research and industry-scale application of hydrogen production. It considers research on water splitting mechanisms, catalyst development, and OER-substituting electrooxidation reactions alongside electrolyzer design, synthesis costs, working conditions, and evaluation criteria. It also compares recent advancements in state-of-the-art water electrolysis technologies and summarizes their application prospects in hydrogen production. The review aims to provide theoretical guidance for designing and synthesizing advanced transition-metal-based electrocatalysts for HER, OER, and substitution anodic reactions for energy-efficient hydrogen production while also shedding light on opportunities for energy-efficient hybrid water-splitting applications.

Lei Wu, Chun Wang, Chuanhui Wang et al.

This study aims to predict the carbon sequestration capacity of Chinese grasslands to address climate change and achieve carbon neutrality goals. Grassland carbon sequestration is a crucial part of the global carbon cycle. However, its capacity is significantly impacted by climate change and human activities, making its dynamic changes complex and challenging to predict. This study adopts a fractional-order accumulation grey model, using 11 provinces in China as samples, to analyze and forecast grassland carbon sequestration. The study finds significant differences in grassland carbon sequestration trends across the sample regions. The carbon sequestration capacity of the grasslands in Xizang (Tibet) and Heilongjiang province is increasing, while it is decreasing in other provinces. The varying prediction results are influenced not only by regional climatic and natural conditions, but also by human interventions such as overgrazing, irrational reclamation, excessive mineral resource exploitation, and increased tourism development. Therefore, more region-specific grassland management and protection strategies should be formulated to enhance the carbon sequestration capacity of grasslands and promote the sustainable development of ecosystems. The significance of this study lies not only in providing scientific guidance for the protection and sustainable management of Chinese grasslands, but also in contributing theoretical and practical insights into global carbon sequestration strategies.

Zulayat Abliz, Rena Eskar, Moldir Serik et al.

In this paper, we will introduce a compact alternating direction implicit (ADI) difference scheme for solving the two-dimensional (2D) time fractional nonlinear Schrödinger equation. The difference scheme is constructed by using the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>L</mi><mn>1</mn><mo>−</mo><mn>2</mn><mo>−</mo><mn>3</mn></mrow></semantics></math></inline-formula> formula to approximate the Caputo fractional derivative in time and the fourth-order compact difference scheme is adopted in the space direction. The proposed difference scheme with a convergence accuracy of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>O</mi><mrow><mo>(</mo><msup><mi>τ</mi><mrow><mn>1</mn><mo>+</mo><mi>α</mi></mrow></msup><mo>+</mo><msubsup><mi>h</mi><mrow><mi>x</mi></mrow><mn>4</mn></msubsup><mo>+</mo><msubsup><mi>h</mi><mrow><mi>y</mi></mrow><mn>4</mn></msubsup><mo>)</mo></mrow><mrow><mo>(</mo><mi>α</mi><mo>∈</mo><mrow><mo>(</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>)</mo></mrow><mo>)</mo></mrow></mrow></semantics></math></inline-formula> is obtained by adding a small term, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>h</mi><mi>x</mi></msub></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>h</mi><mi>y</mi></msub></semantics></math></inline-formula> are the temporal and spatial step sizes, respectively. The convergence and unconditional stability of the difference scheme are obtained. Moreover, numerical experiments are given to verify the accuracy and efficiency of the difference scheme.

Georg Elsinger, Herman Oprins, Vladimir Cherman et al.

With ever increasing integration density of electronic components, the demand for cooling solutions capable of removing the heat generated by such systems grows along with it. It has been shown that a viable answer to this demand is the use of direct liquid jet impingement. While this method can generally be scaled to the cooling of large areas, this is restricted by the necessity of coolant flow rate scaling. In this study, the benefits and restrictions of using increased nozzle pitch to remedy the increasing demand for overall flow rate are investigated. To this end, a model is validated against experimental findings and then used for computational fluid dynamics simulations, exploring effects of the pitch change for micro-scale nozzle diameters and nozzle-to-target spacings. It is found that while this method is efficient in adjusting the tradeoff between total coolant flow rate and pressure drop up to a certain pint, the occurrence of a hydraulic jump in the cavity causes a deterioration of its effect for large nozzle pitches.

Ivana Weber, Tina Borić, Josipa Mardešić et al.

Thermodynamics is a theory based on phenomenological premises and has wide applicability in science and technology. However, it remains one of the most challenging subjects to understand and teach, which makes it an excellent candidate for research and development of teaching methods. In this research, a questionnaire was used to evaluate the current knowledge of Bachelor’s and Master’s physics students, analyzing their immediate understanding of the topic and exploring their reasoning and thought processes. The questionnaire is divided into three sections which sequentially examine high school knowledge of entropy and thermodynamics; understanding of (ir)reversible processes related to energy and entropy change; and the distinction between equilibrium and nonequilibrium states. Based on the analysis of the results, we identified difficulties in understanding and articulating and applying the learned concepts. In particular, misunderstandings of entropy changes in isothermal processes and isolated systems are observed among students at all levels. Additionally, students find it difficult to distinguish between the contributions of energy and entropy changes to a system and its environment in the processes. The difficulty in defining (non)equilibrium states is present among Bachelor’s second-year physics students. To address these challenges, we propose adjustments to the teaching approach, including discussions about entropy sources and process (ir)reversibility, incorporating more theoretical and everyday examples of various processes and (non)equilibrium states and allowing more time for student discussions.

Mriganka Dutta, Banibrata Mukhopadhyay

The theory of general relativity is often considered under the framework of modified Einstein gravity to explain different phenomena under strong curvature. The strong curvature effect plays a main role near black holes, where the gravitational field is strongest. The idea of black hole thermodynamics is to describe the strong field curvature properties of a black hole in the effective thermodynamical framework, e.g. entropy, temperature, heat capacity etc. In this paper, our aim is to explore how the effect of modified gravity changes the thermodynamic properties of black hole. We show that even a small modification to Einstein gravity affects the thermodynamical properties of a black hole.

Nobuyoshi Komatsu

The first and second laws of thermodynamics should lead to a consistent scenario for discussing the cosmological constant problem. In the present study, to establish such a thermodynamic scenario, cosmological equations in a flat Friedmann-Lemaître-Robertson-Walker universe were derived from the first law, using an arbitrary entropy $S_{H}$ on a cosmological horizon. Then, the cosmological equations were formulated based on a general formulation that includes two extra driving terms, $f_Λ(t)$ and $h_{\textrm{B}}(t)$, which are usually used for, e.g., time-varying $Λ(t)$ cosmology and bulk viscous cosmology, respectively. In addition, thermodynamic constraints on the two terms are examined using the second law of thermodynamics, extending a previous analysis [Phys. Rev. D 99, 043523 (2019) (arXiv:1810.11138)]. It is found that a deviation $S_Δ$ of $S_{H}$ from the Bekenstein-Hawking entropy plays important roles in the two terms. The second law should constrain the upper limits of $f_Λ(t)$ and $h_{\textrm{B}}(t)$ in our late Universe. The orders of the two terms are likely consistent with the order of the cosmological constant $Λ_{\textrm{obs}}$ measured by observations. In particular, when the deviation $S_Δ$ is close to zero, $h_{\textrm{B}}(t)$ and $f_Λ(t)$ should reduce to zero and a constant value (consistent with the order of $Λ_{\textrm{obs}}$), respectively, as if a consistent and viable scenario could be obtained from thermodynamics.

María Isabel Haro-Olmo, Inés Tejado, Blas M. Vinagre et al.

In this paper, two types of fractional-order damping are proposed for a single flexible link: internal and external friction, related to the material of the link and the environment, respectively. Considering these dampings, the Laplace transform is used to obtain the exact model of a slewing flexible link by means of the Euler–Bernoulli beam theory. The model obtained is used in a sensing antenna with the aim of accurately describing its dynamic behavior, thanks to the incorporation of the mentioned damping models. Therefore, experimental data are used to identify the damping phenomena of this system in the frequency domain. Welch’s method is employed to estimate the experimental frequency responses. To determine the best damping model for the sensing antenna, a cost function with two weighting forms is minimized for different model structures (i.e., with internal and/or external dampings of integer- and/or fractional-order), and their robustness and fitting performance are analyzed.

Vasile Preda, Răzvan-Cornel Sfetcu

We introduce fractal Tsallis entropy and show that it satisfies Shannon–Khinchin axioms. Analogously to Tsallis divergence (or Tsallis relative entropy, according to some authors), fractal Tsallis divergence is defined and some properties of it are studied. Within this framework, Lesche stability is verified and an example concerning the microcanonical ensemble is given. We generalize the LMC complexity measure (LMC is Lopez-Ruiz, Mancini and Calbert), apply it to a two-level system and define the statistical complexity by using the Euclidean and Wootters’ distance measures in order to analyze it for two-level systems.

Kexin Liu, Xunjian Che, Xianshi Fang et al.

Twisted tri-lobed tubes have garnered attention due to their exceptional heat transfer efficiency and straightforward fabrication. Existing literature lacks comprehensive assessments of the overall heat transfer performance of twisted tri-lobed tubes from the perspective of energy loss and irreversibility. This research aims to investigate entropy generation during turbulent water flow within twisted tri-lobed tubes, examining the influence of geometric parameters on local and average entropy production. Findings indicate that larger small circle radius (r) and straight lengths (l), coupled with smaller transition circle radius (R) and twist pitch lengths (p), result in diminished local and average heat transfer entropy production while enhancing local and average frictional entropy production, with heat transfer entropy generation dominating the overall entropy production. Additionally, with increasing Reynolds numbers, all twisted tubes demonstrate an increasing trend in average frictional entropy production, except for some cases (Case 1-Case 4) that exhibit an initial rise followed by a decline in average heat transfer entropy generation. Among the examined Reynolds range, Case 4 displays lower overall irreversibility compared to a plain tube. Following the second law of thermodynamics, Case 4 is preferred. The findings and methodology contribute to enhancing the thermodynamic evaluation of convective heat transfer in twisted tri-lobed tubes.

Hajar Farhadi, Narjes Keramati

Abstract A novel exfoliated graphitic carbon nitride and clinoptilolite nanocomposites (Ex.g-C3N4/CP and g-C3N4/CP with a various ratios of g-C3N4 to CP) were prepared by facile method. This study evaluates the adsorption of methylene blue (MB) on the surface of synthesized adsorbents. The as-prepared composites were characterized by XRD, FT-IR, FESEM, BET and DRS. Batch experiments were carried out under various conditions, such as the amount of adsorbent and solution pH. The optimum batch experimental conditions were found under the response surface methodology. The Ex.g-C3N4/CP presented maximum removal of MB as compared to others. The removal efficiency of the as-prepared nanocomposite was significantly elevated owing to the synergistic effects. The adsorption capacities of MB (10 ppm) on Ex.g-C3N4/CP was 54.3 mg/g. The adsorption process by both composites (g-C3N4/CP and Ex.g-C3N4/CP) showed well-fitting with the Elovich kinetic model, and Langmuir isotherm. The thermodynamic study suggested that the adsorption of MB was a spontaneous and endothermic process. The reusability of g-C3N4/CP1:2 and Ex. g-C3N4/CP in removing of MB (10 ppm, pH = 9) was studied by photocatalytic regeneration under visible irradiation for three consecutive cycles. The results obtained from the experimental analyses showed that the removal of MB was easy treatment, eco-friendly, and high yield.

T. Koide, T. Kodama

We formulate thermodynamical relations based on the field degrees of freedom by introducing a work induced by the volume change in the function space, in addition to the usual work associated with the spatial volume change. The first and second laws of thermodynamics are defined for such a work inherent to the field theory by generalizing stochastic energetics (stochastic thermodynamics) to the classical real scalar field in contact with a heat bath. We further discuss the local equilibrium ansatz in the function space and show that it is possible to introduce a model of functional ideal hydrodynamics, which is consistent with the derived thermodynamical laws.

Sebastian A. Altmeyer

This paper investigates the impact of combined axial through flow and radial mass flux on Taylor–Couette flow in a counter-rotating configuration, in which different branches of nontrivial solutions appear via Hopf bifurcations. Using direct numerical simulation, we elucidate flow structures, dynamics, and bifurcation behavior in qualitative and quantitative detail as a function of axial Reynolds numbers (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mi>e</mi></mrow></semantics></math></inline-formula>) and radial mass flux (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>) spanning a parameter space with a very rich variety of solutions. We have determined nonlinear properties such as anharmonicity, asymmetry, flow rates (axial and radial) and torque for toroidally closed Taylor vortices and helical spiral vortices. Small to moderate radial flow <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> initially decreases the symmetry of the different flows, before for larger values, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>, the symmetry eventually increases, which appears to be congruent with the degree of anharmonicity. Enhancement in the total torque with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> are elucidated whereby the strength varies for different flow structures, which allows for potential better selection and control. Further, depending on control parameters, heteroclinic connections (and cycles) of oscillatory type in between unstable and topological different flow structures are detected. The research results provide a theoretical basis for simple modification the conventional Taylor flow reactor with a combination of additional mass flux to enhance the mass transfer mechanism.