Hasil untuk "Thermodynamics"

Denny A. Jones

M. Winter, R. Brodd

S. Kauffman

J. Bekenstein

There are a number of similarities between black-hole physics and thermodynamics. Most striking is the similarity in the behaviors of black-hole area and of entropy: Both quantities tend to increase irreversibly. In this paper we make this similarity the basis of a thermodynamic approach to black-hole physics. After a brief review of the elements of the theory of information, we discuss black-hole physics from the point of view of information theory. We show that it is natural to introduce the concept of black-hole entropy as the measure of information about a black-hole interior which is inaccessible to an exterior observer. Considerations of simplicity and consistency, and dimensional arguments indicate that the black-hole entropy is equal to the ratio of the black-hole area to the square of the Planck length times a dimensionless constant of order unity. A different approach making use of the specific properties of Kerr black holes and of concepts from information theory leads to the same conclusion, and suggests a definite value for the constant. The physical content of the concept of black-hole entropy derives from the following generalized version of the second law: When common entropy goes down a black hole, the common entropy in the black-hole exterior plus the black-hole entropy never decreases. The validity of this version of the second law is supported by an argument from information theory as well as by several examples.

M. Biot

P. G. Hill, C. R. Peterson

S. Hawking

S. L. Dixon

A. Khan, R. Singh

C. J. Adkins

Katrin Himmelseher, Alexander Lampkowski, Stefan Sterlepper et al.

Abstract Hydrogen presents a promising opportunity for the reduction of CO2 emissions in combustion processes. Due to its wide ignition limits, operation in lean mode is possible, which significantly reduces NO x emissions. However, this lean operation also leads to a reduction in the resulting torque. In contrast, stoichiometric operation increases maximum power output but leads to increased NO x emissions. In particular, a cost-effective three-way catalyst can be used in stoichiometric operation, enabling effective emission control. This investigation proposes an innovative approach that involves lean-burn operation at part load conditions and switching to stoichiometric operation at full load. The transition between these two modes has a considerable impact on overall NO x emissions. To optimize this process, new functions were developed that implement countermeasures such as lambda control, ignition timing adjustment, catalyst purging, and shortening the switching range through the use of variable valve timing and variable turbine geometry. The results show that nitrogen oxide (NO x ) emissions downstream of the three-way catalyst are kept below $${\text{c}}_{{{\text{NO}}_{x} }} = 100\,{\text{ppm}}$$ in the lean operating range and below $${\text{c}}_{{{\text{NO}}_{x} }} = 30\;{\text{ppm}}$$ in the stoichiometric operating range. By optimizing the transition between the two operating modes and using advanced emission control technologies, it is possible to reduce NO x emissions by 84% while maintaining power efficiency under different load conditions. In addition, the almost torque-neutral switching between the two operational modes ensures that the vehicle’s drivability is not impaired. By incorporating additional dosing of a urea-water solution in an active SCR system, a significant improvment in NO x reduction is attained, achieving levels comparable to those of diesel internal combustion engines. This dual-mode operation strategy improves the feasibility of hydrogen as a viable fuel alternative in future energy systems.

Khairul Habib Alam, Yumnam Rohen, Anita Tomar et al.

This study presents an innovative iterative method designed to approximate common fixed points of generalized contractive mappings. We provide theorems that confirm the convergence and stability of the proposed iteration scheme, further illustrated through examples and visual demonstrations. Moreover, we apply <i>s</i>-convexity to the iteration procedure to construct orbits under convexity conditions, and we present a theorem that determines the condition when a sequence diverges to infinity, known as the escape criterion, for the transcendental sine function <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo form="prefix">sin</mo><mo>(</mo><msup><mi>u</mi><mi>m</mi></msup><mo>)</mo><mo>−</mo><mi>α</mi><mi>u</mi><mo>+</mo><mi>β</mi></mrow></semantics></math></inline-formula>, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>u</mi><mo>,</mo><mi>α</mi><mo>,</mo></mrow></semantics></math></inline-formula><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>β</mi><mo>∈</mo><mi mathvariant="double-struck">C</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>m</mi><mo>≥</mo><mn>2</mn></mrow></semantics></math></inline-formula>. Additionally, we generate chaotic fractals for this orbit, governed by escape criteria, with numerical examples implemented using MATHEMATICA software. Visual representations are included to demonstrate how various parameters influence the coloration and dynamics of the fractals. Furthermore, we observe that enlarging the Mandelbrot set near its petal edges reveals the Julia set, indicating that every point in the Mandelbrot set contains substantial data corresponding to the Julia set’s structure.

A.A. Araújo Filho, N. Heidari, A. Övgün

This work explores both classical and quantum aspects of an axisymmetric black hole within a non–commutative gauge theory. The rotating solution is derived using a modified Newman–Janis procedure. The analysis begins with the horizon structure, ergospheres, and angular velocity. The thermodynamic properties are examined through surface gravity, focusing on the Hawking temperature, entropy, and heat capacity. In addition, the remnant mass is calculated. The Hawking radiation is treated as a tunneling process for bosonic and fermionic particles, along with the corresponding particle creation density. Geodesic motion is explored, emphasizing null geodesics, radial accelerations, the photon sphere, and black hole shadows. Finally, the gravitational lensing in the strong deflection limit is investigated.

Yowe Kidwe, Djakba Raphaël, Wangmene Bagamla et al.

Compatible and environmentally clean activated carbon material was prepared via physicochemical method and used for harmful pollutant removal from aqueous solution. The performance of the pristine cottonseed cakes and its activated carbon was examined towards copper ions removal as targeted pollutant through adsorption process. The physicochemical properties of adsorbents were evaluated by numerous experimental techniques such as Fourier transform infra-red spectroscopy, Raman spectroscopy, scanning electron microscopy, the point of zero charge, iodine number and specific surface area. The effect of several key operational parameters such as contact time, adsorbent dose, pH, concentration and temperature were considered. Results of the adsorption tests exhibited significant sensitivity towards copper ions elimination at optimum conditions; the copper uptake capacity was enhanced with time up to equilibrium of 30 min with a minimum adsorbent dose of 0.1 g at alkaline pH of 10 for maximum concentration of 50 mg/L at room temperature (25 °C) and achieved appropriate adsorbed quantities of 51.56 mg/g for cottonseed cakes activated carbon (CCAC) and 48.5 mg/g for cottonseed cakes biosorbent (CCB). The values of point of zero charge are 2.63 and 6.32 for CCB and CCAC respectively which present high electrostatic attraction between positive charge of copper ions and negative charge of the surface at basic medium. Iodine number of 30.35 and 41.92 mg/g indicates random distribution of micropores. The specific surface area of CCAC (30.35 m2/g) is higher than the one of CCB (11.94 m2/g). FTIR shows good surface chemistry with various functional groups while Raman spectroscopy and SEM analyses revealed myriad morphological features and carbon phases (graphite and diamond). The adsorption of copper ions was described by pseudo second order kinetic model and favoured by Redlich Peterson isotherm corresponding to physisorption on CCB while the one CCAC involves chemical bonding and can be qualified as chemisorption mechanism as confirm by ΔH° of both materials.

Cristian Hernandez-Blick

Originating from nineteenth century physics, the concept of entropy—a measure of disorder, randomness, and/or the dissipation of useful energy—underlay a cosmology where order and complexity were seen as highly improbable phenomena in a universe tending toward chaos and disorganisation. Nearly a century later, theoretical frameworks were developed for understanding the production of entropy as an enabling feature of self-organized complexity in the natural world. These ideas would contribute to establishing connections between the origins, development, and evolution of life and the principles of a thermodynamic universe. For some, they also supplied the conceptual foundations for theorizing about a universal natural tendency driving the development of increasingly complex and ordered systems which amplify processes of entropy production and energy dissipation and dispersal. In this paper I chart a path through the aforementioned ideas and present their relevance in framing a relationship between our technological civilization and the Earth system. I then speculate about the prospect of a technosphere whose constitution and activity are aligned with thermodynamic principles of dissipation and entropy-production, drawing on theoretical biology and recent developments in bioengineering to envision a paradigm where technology becomes living matter itself.

Г.У. Билл, Д.С. Ахметсадык, А.М. Ильин et al.

The adsorption of O3 molecules (ozone) on graphene, N-doped graphene, Ga-doped graphene, and -Ga-N- co-doped graphene with an emphasis on O3 detection was examined in this work. The physical characteristics of -Ga-N-co-doped graphene are significantly altered upon O3 adsorption, which makes it a suitable choice for O3 detection molecular sensors. The interaction between the O3 molecule and the adsorbent is explained on the basis of their adsorption energy, adsorption distance and charge transfer. It was found that the adsorption of ozone molecules on the -Ga-N- co-doped graphene was more favorable in energy than that on the pristine one, representing the superior sensing performance of -Ga-N- co-doped system. In our work, we estimated the charge transfer between the O3 molecule and doped graphene nanostructures based on Mulliken population analysis. The calculated adsorption energy value shows the ozone molecule more firmly adsorbs on the surface of -Ga-N- co-doped graphene nanostructures (Eads = –1.74 eV) than that of pristine graphene (Eads = –0.41 eV), deriving from a stronger covalent bond between the ozone molecule and the -Ga- N- co-doped graphene nanostructures. Our findings thus suggest that -Ga-N- co-doped graphene could be a highly efficient gas sensor device for O3 detection in the environment.

Zhida Jiang, Haowen Zhu, Jiawei Sun et al.

In this work, Cu/1060Al bimetallic composite materials manufactured by high-temperature free-oxygen rolling process are reported. The results show that with the increase of rolling passes, the microstructure of Cu and 1060Al gradually extends and elongates in the rolling direction, and the interface that has few compounds is dominated by mechanical bonding. It is worth noting that layered fracture occurs during the tensile process. After annealing, the interface changes from mechanical bonding to metallurgical bonding, and the layered fracture is alleviated under the traction of the interface layer. With the increase of annealing time and temperature, the thickness of the interface compounds gradually increase, and the interface compounds from the copper layer to the aluminum layer are Cu9Al4, CuAl and CuAl2, respectively. Annealing at 350 °C for 2 h exhibits the best comprehensive performance, a tensile strength of 138 MPa and an elongation of 64 %. Tensile behavior in the rolled state and annealed state has been discussed based on failure theory, and compound growth after annealing has been analyzed on account of the theories of dynamics and thermodynamics.

Roberto da Silva, Sandra Denise Prado

This study explores the application of random matrices to track chaotic dynamics within the Chirikov standard map. Our findings highlight the potential of matrices exhibiting Wishart-like characteristics, combined with statistical insights from their eigenvalue density, as a promising avenue for chaos monitoring. Inspired by a technique originally designed for detecting phase transitions in spin systems, we successfully adapted and applied it to identify analogous transformative patterns in the context of the Chirikov standard map. Leveraging the precision previously demonstrated in localizing critical points within magnetic systems in our prior research, our method accurately pinpoints the Chirikov resonance overlap criterion for the chaos boundary at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>K</mi><mo>≈</mo><mn>2.43</mn></mrow></semantics></math></inline-formula>, reinforcing its effectiveness. Additionally, we verified our findings by employing a combined approach that incorporates Lyapunov exponents and bifurcation diagrams. Lastly, we demonstrate the adaptability of our technique to other maps, establishing its capability to capture the transition to chaos, as evidenced in the logistic map.

Ke Sun, Zhiyao Ma, Guowei Dong et al.

In this work, an adaptive fuzzy backstepping fault-tolerant control (FTC) issue is tackled for uncertain fractional-order (FO) nonlinear systems with sensor and actuator faults. A fuzzy logic system is exploited to manage unknown nonlinearity. In addition, a novel FO nonlinear filter-based dynamic surface control (DSC) method is constructed, effectively avoiding the inherent complexity explosion problem in the backstepping recursive process, and in the light of the construction of auxiliary functions, compensating the coupling term introduced by faults. On account of certain assumptions, the stability criterion of the FO Lyapunov function is applied to guarantee the stability of the closed-loop system. Finally, the simulation example verifies the validity of the presented control strategy.

V.N. Oparin

It is shown that modern achievements in the field of experimental and theoretical researches and developments of innovative measuring systems for monitoring of non-linear dynamic and kinematic characteristics allow to formulate basics of new academic discipline, designated as “geomechanical thermodynamics”. The following circumstances can be considered as the most important prerequisites for development of this new discipline.(1) Practical completeness of the classical thermodynamics, based on kinetic gas theory and molecular movements in solid bodies; (2) Creation of “formular construction tool” for the description of dynamic and kinematic characteristics of pendulum waves and energy conditions of their occurrence and propagation from dynamic sources, located in multi-phased stressed rock mass and geomaterials with block-hierarchical structure; (3) Principal opportunity to establish formal relations between substantial energy carriers of “packages” of non-linear pendulum waves (geoblocks of certain hierarchical levels according to their diameters) and “molecules”: their movement, velocity and acceleration of the “molecules” ↔ “geoblock”; “force interactions between molecules” ↔ “non-linear elastic interaction between geoblocks”, etc.The term of “geomechanical temperature” is introduced and its analytical expression, which is proportional to kinetic energy of movement of geoblocks with defined volume for their hierarchical subsequence at “confined” conditions of the stressed rock mass, is shown. The similar aspects are discussed, when emission acoustic-electromagnetic fields are fixed using corresponding coefficients of mechanical-electrical and mechanical-acoustic transformations. In order to quantitively describe the evolution of energy state of local zones of stress-strain concentration and surroundings of their non-linear influence from catastrophic events at the natural and mine-engineering systems (earthquakes, rock bursts, etc.), the terms of their geomechanical and thermodynamic stages are introduced and specified: Ti(i∈0,+,±,−,∗)‒ with background states (i∈0,∗) and three major stages (i∈+,±,−) outlined, where (+) is the concentration, (±, ‒) are the failure and relaxation and (∗) is the quasi-recovering up to “background” level after the occurred catastrophic event. Using certain examples, the existence of critical elastic energy content of local zones with “meta-stable state”, which is transforming to quasi-resonance process of failure and relaxation of “excessive” energy, is shown (T±).