Showing papers on "Entropy (classical thermodynamics) published in 2020"

Radiative MHD Casson Nanofluid Flow with Activation energy and chemical reaction over past nonlinearly stretching surface through Entropy generation

Abstract: In the present research analysis we have addressed comparative investigation of radiative electrically conducting Casson nanofluid. Nanofluid Flow is assumed over a nonlinearly stretching sheet. Heat transport analysis is carried via joule dissipation, thermal behavior and convective boundary condition. To employ the radiative effect radiation was involved to show the diverse states of nanoparticles. Furthermore entropy optimization with activation energy and chemical reaction are considered. Thermodynamics 2nd law is applied to explore entropy generation rate. Nonlinear expression is simplified through similarity variables. The reduced ordinary system is tackled through optimal approach. Flow pattern was reported for wide range of scrutinized parameters. Computational consequences of velocity drag force, heat flux and concentration gradient are analyzed numerically in tables. Results verify that conduction mode augments with enhance of magnetic parameter.Increasing radiation boosts the temperature and entropy. Activation energy corresponds to augmented concentration. Heat transmission rate augments with the consideration of radiation source term.

Natural convection and entropy production in hybrid nanofluid filled-annular elliptical cavity with internal heat generation or absorption

Abstract: This study is an attempt to understand the characteristics of heat transfer by natural convection, flow, and entropy generation of Cu-Al2O3/H2O based hybrid nanoliquid filled-annulus delimited by two elliptic cylinders considering internal heat generation or absorption (IHG/A) phenomenon The buoyancy-driven flow is induced by a thermal gradient between isothermal and differentially heated inner and outer cylinders A numerical solution of the governing equations in the dimensionless and non-primitive form is performed using the technique of finite volume discretization Impacts of diverse parameters of the study such as copper-alumina nanoparticles volumic concentration, Rayleigh number, and dimensionless internal heat generation or absorption parameter on the thermohydrodynamic characteristic and entropy generation are examined An analysis of the results showed that the combined effects of internal heat generation/absorption and hybrid nanoliquid significantly alter the hydrothermal characteristics, heat transfer rate, and entropy generation within the annulus

Black Holes in 4D N = 4 Super-Yang-Mills Field Theory

Abstract: Black-hole solutions to general relativity carry a thermodynamic entropy, discovered by Bekenstein and Hawking to be proportional to the area of the event horizon, at leading order in the semiclassical expansion. In a theory of quantum gravity, black holes must constitute ensembles of quantum microstates whose large number accounts for the entropy. We study this issue in the context of gravity with a negative cosmological constant. We exploit the most basic example of the holographic description of gravity (AdS/CFT): type IIB string theory on AdS5×S5, equivalent to maximally supersymmetric Yang-Mills theory in four dimensions. We thus resolve a long-standing question: Does the four-dimensional N=4 SU(N) Super-Yang-Mills theory on S3 at large N contain enough states to account for the entropy of rotating electrically charged supersymmetric black holes in 5D anti–de Sitter space? Our answer is positive. By reconsidering the large N limit of the superconformal index, using the so-called Bethe-ansatz formulation, we find an exponentially large contribution which exactly reproduces the Bekenstein-Hawking entropy of the black holes. Besides, the large N limit exhibits a complicated structure, with many competing exponential contributions and Stokes lines, hinting at new physics. Our method opens the way toward a quantitative study of quantum properties of black holes in anti–de Sitter space.

Entropy Measures in Machine Fault Diagnosis: Insights and Applications

Abstract: Entropy, as a complexity measure, has been widely applied for time series analysis. One preeminent example is the design of machine condition monitoring and industrial fault-diagnostic systems. The occurrence of failures in a machine will typically lead to nonlinear characteristics in the measurements, caused by instantaneous variations, which can increase the complexity in the system response. Entropy measures are suitable to quantify such dynamic changes in the underlying process, distinguishing between different system conditions. However, notions of entropy are defined differently in various contexts (e.g., information theory and dynamical systems theory), which may confound researchers in the applied sciences. In this article, we have systematically reviewed the theoretical development of some fundamental entropy measures and clarified the relations among them. Then, typical entropy-based applications of machine fault-diagnostic systems are summarized. Furthermore, insights into possible applications of the entropy measures are explained, as to where and how these measures can be useful toward future data-driven fault diagnosis methodologies. Finally, potential research trends in this area are discussed, with the intent of improving online entropy estimation and expanding its applicability to a wider range of intelligent fault-diagnostic systems.

Second law analysis of magneto-natural convection in a nanofluid filled wavy-hexagonal porous enclosure

Abstract: Natural convection heat transfer analysis can be completed using entropy generation analysis. This study aims to accomplish both the natural convection heat transfer and entropy generation analyses for a hexagonal cavity loaded with Cu-H2O nanoliquid subjected to an oriented magnetic field.,Control volume-based finite element method is applied to solve the non-dimensional forms of governing equations and then, the entropy generation number is computed.,The results portray that both the average Nusselt and entropy generation numbers boost with increasing aspect ratio for each value of the undulation number, while both of them decrease with increasing the undulation number for each amplitude parameter. There is a maximum value for the entropy generation number at a specified value of Hartmann number. Also, there is a minimum value for the entropy generation number at a specified value of angle of the magnetic field. When the volume fraction of nanoparticles grows, the average Nusselt number increases and the entropy generation number declines. The entropy generation number attains to a maximum value at Ha = 14 for each value of aspect ratio. The average Nusselt number ascends 2.9 per cent and entropy generation number decreases 1.3 per cent for Ha = 0 when ϕ increases from 0 to 4 per cent.,A hexagonal enclosure (complex geometry), which has many industrial applications, is chosen in this study. Not only the characteristics of heat transfer are investigated but also entropy generation analysis is performed in this study. The ecological coefficient of performance for enclosures is calculated, too.

Reflected entropy for an evaporating black hole

Abstract: We study reflected entropy as a mixed state correlation measure in black hole evaporation. As a measure for bipartite mixed states, reflected entropy can be computed between black hole and radiation, radiation and radiation, and even black hole and black hole. We compute reflected entropy curves in three different models: 3-side wormhole model, End-of-the-World (EOW) brane model in three dimensions and two-dimensional eternal black hole plus CFT model. For 3-side wormhole model, we find that reflected entropy is dual to island cross section. The reflected entropy between radiation and black hole increases at early time and then decreases to zero, similar to Page curve, but with a later transition time. The reflected entropy between radiation and radiation first increases and then saturates. For the EOW brane model, similar behaviors of reflected entropy are found. We propose a quantum extremal surface for reflected entropy, which we call quantum extremal cross section. In the eternal black hole plus CFT model, we find a generalized formula for reflected entropy with island cross section as its area term by considering the right half as the canonical purification of the left. Interestingly, the reflected entropy curve between the left black hole and the left radiation is nothing but the Page curve. We also find that reflected entropy between the left black hole and the right black hole decreases and goes to zero at late time. The reflected entropy between radiation and radiation increases at early time and saturates at late time.

Impact of Entropy Generation and Nonlinear Thermal Radiation on Darcy–Forchheimer Flow of MnFe2O4-Casson/Water Nanofluid due to a Rotating Disk: Application to Brain Dynamics

Abstract: The present article candidly states the incremental impact of nonlinear thermal radiation on heat transfer enhancement due to Darcy–Forchheimer flow of spinel-type MnFe2O4-Casson/water nanofluids due to a stretched rotating disk. In present contest, the entropy generation approach is highlighted specially as a powerful tool for the analysis of the brain function, in accordance with the theological and philosophical approach of Saint Thomas Aquinas. The some of the results of the present study that strengthening of permeability and Casson parameter contribute to the diminution of radial and tangential velocity profiles and yield shrinkage of the related boundary layers. An increase in thermal radiation leading to more heat propagating into the fluid thereby improves the TBL. Fluids with non-Newtonian behavior contribute greater entropy generation rate compared to Newtonian fluids. The most significant outcome is that the entropy generation makes a real contribution to the brain function or analysis of the function of the brain.

Symmetry resolved entanglement: Exact results in 1D and beyond

Abstract: In a quantum many-body system that possesses an additive conserved quantity, the entanglement entropy of a subsystem can be resolved into a sum of contributions from different sectors of the subsystem's reduced density matrix, each sector corresponding to a possible value of the conserved quantity. Recent studies have discussed the basic properties of these symmetry-resolved contributions, and calculated them using conformal field theory and numerical methods. In this work we employ the generalized Fisher-Hartwig conjecture to obtain exact results for the characteristic function of the symmetry-resolved entanglement ("flux-resolved entanglement") for certain 1D spin chains, or, equivalently, the 1D fermionic tight binding and the Kitaev chain models. These results are true up to corrections of order $o(L^{-1})$ where $L$ is the subsystem size. We confirm that this calculation is in good agreement with numerical results. For the gapless tight binding chain we report an intriguing periodic structure of the characteristic functions, which nicely extends the structure predicted by conformal field theory. For the Kitaev chain in the topological phase we demonstrate the degeneracy between the even and odd fermion parity sectors of the entanglement spectrum due to virtual Majoranas at the entanglement cut. We also employ the Widom conjecture to obtain the leading behavior of the symmetry-resolved entanglement entropy in higher dimensions for an ungapped free Fermi gas in its ground state.

Entropy Generation and Consequences of MHD in Darcy–Forchheimer Nanofluid Flow Bounded by Non-Linearly Stretching Surface

Abstract: Present communication aims to inspect the entropy optimization, heat and mass transport in Darcy-Forchheimer nanofluid flow surrounded by a non-linearly stretching surface. Navier-Stokes model based governing equations for non-Newtonian nanofluids having symmetric components in various terms are considered. Non-linear stretching is assumed to be the driving force whereas influence of thermal radiation, Brownian diffusion, dissipation and thermophoresis is considered. Importantly, entropy optimization is performed using second law of thermodynamics. Governing problems are converted into nonlinear ordinary problems (ODEs) using suitably adjusted transformations. RK-45 based built-in shooting mechanism is used to solve the problems. Final outcomes are plotted graphically. In addition to velocity, temperature, concentration and Bejan number, the stream lines, contour graphs and density graphs have been prepared. For their industrial and engineering importance, results for wall-drag force, heat flux (Nusselt) rate and mass flux (Sherwood) rate are also given in tabular data form. Outputs indicate that velocity reduces for Forchheimer number as well as for the porosity factor. However, a rise is noted in temperature distribution for elevated values of thermal radiation. Entropy optimization shows enhancement for larger values of temperature difference ratio. Skin-friction enhances for all relevant parameters involved in momentum equation.

Thermodynamics of 4D dilatonic black holes and the weak gravity conjecture

Abstract: Taking a thermodynamic perspective, we study the weak gravity conjecture in the context of four-dimensional Einstein-Maxwell-dilaton theory. We find closed-form expressions for the corrected thermodynamic quantities in the presence of four-derivative terms in the action, and in particular the charge-to-mass ratio and entropy, for several families of solutions of special magnetic-to-electric charge ratio or dilaton coupling constant. Assuming that dyonic black holes themselves are the conjectured charged states, this places constraints on the Wilson coefficients of the theory which we show are satisfied for several generic UV completions.

Magnetohydrodynamic Mixed Convection and Entropy Analysis of Nanofluid in Gamma-Shaped Porous Cavity

Abstract: The entropy generation due to magnetohydrodynamic mixed convection flow and heat transfer in a Gamma-shaped porous cavity is explored in this research by the finite volume technique There exists a

Ruppeiner thermodynamic geometry for the Schwarzschild-AdS black hole

Abstract: Due to the nonindependence of entropy and thermodynamic volume for spherically symmetric black holes in the anti--de Sitter (AdS) spacetime, when applying the Ruppeiner thermodynamic geometry theory to these black holes, we often encounter an unavoidable problem of the singularity about the line element of thermodynamic geometry. In this paper, we propose a basic and natural scheme for dealing with the thermodynamic geometry of spherically symmetric AdS black holes. We point out that enthalpy, not internal energy, is the fundamental thermodynamic characteristic function for the Ruppeiner thermodynamic geometry. Based on this fact, we give the specific forms of the line element of thermodynamic geometry for the Schwarzschild AdS (SAdS) black hole in different phase spaces, and the results show that the thermodynamic curvatures obtained in different phase spaces are equivalent. It is shown that the thermodynamic curvature is negative which may be related to the information of attractive interaction between black hole molecules for the SAdS black hole. Meanwhile we also give an approximate expression of the thermodynamic curvature of the Schwarzschild black hole which shows that the black hole may be dominated by repulsion on the low temperature region and by attraction on the high temperature region phenomenologically or qualitatively.

Thermodynamic Routes to Ultralow Thermal Conductivity and High Thermoelectric Performance

Abstract: Thermoelectric (TE) research is not only a course of materials by discovery but also a seedbed of novel concepts and methodologies. Herein, the focus is on recent advances in three emerging paradigms: entropy engineering, phase-boundary mapping, and liquid-like TE materials in the context of thermodynamic routes. Specifically, entropy engineering is underpinned by the core effects of high-entropy alloys; the extended solubility limit, the tendency to form a high-symmetry crystal structure, severe lattice distortions, and sluggish diffusion processes afford large phase space for performance optimization, high electronic-band degeneracy, rich multiscale microstructures, and low lattice thermal conductivity toward higher-performance TE materials. Entropy engineering is successfully implemented in half-Huesler and IV-VI compounds. In Zintl phases and skutterudites, the efficacy of phase-boundary mapping is demonstrated through unraveling the profound relations among chemical compositions, mutual solubilities of constituent elements, phase instability, microstructures, and resulting TE properties at the operation temperatures. Attention is also given to liquid-like TE materials that exhibit lattice thermal conductivity at lower than the amorphous limit due to intensive mobile ion disorder and reduced vibrational entropy. To conclude, an outlook on the development of next-generation TE materials in line with these thermodynamic routes is given.

Effect of Collective Dynamics and Anharmonicity on Entropy in Heterogenous Catalysis: Building the Case for Advanced Molecular Simulations

Abstract: We present a perspective on the computational determination of entropy and its effects and consequences on heterogeneous catalysis. Special attention is paid to the role of anharmonicity (a result ...

RBFNN-Based Minimum Entropy Filtering for a Class of Stochastic Nonlinear Systems

Abstract: This paper presents a novel minimum entropy filter design for a class of stochastic nonlinear systems, which are subjected to non-Gaussian noises. Motivated by stochastic distribution control, an output entropy model is developed using a radial basis function neural network, while the parameters of the model can be identified by the collected data. Based upon the presented model, the filtering problem has been investigated, while the system dynamics have been represented. As the model output is the entropy of the estimation error, the optimal nonlinear filter is obtained based on the Lyapunov design, which makes the model output minimum. Moreover, the entropy assignment problem has been discussed as an extension of the presented approach. To verify the presented design procedure, a numerical example is given, which illustrates the effectiveness of the presented algorithm. The contributions of this paper can be summarized as follows: 1) an output entropy model is presented using a neural network; 2) a nonlinear filter design algorithm is developed as the main result; and 3) a solution of the entropy assignment problem is obtained, which is an extension of the presented framework.

Complexity for charged thermofield double states

Abstract: We study Nielsen’s circuit complexity for a charged thermofield double state (cTFD) of free complex scalar quantum field theory in the presence of background electric field. We show that the ratio of the complexity of formation for cTFD state to the thermo- dynamic entropy is finite and it depends just on the temperature and chemical potential. Moreover, this ratio smoothly approaches the value for real scalar theory. We compare our field theory calculations with holographic complexity of charged black holes and confirm that the same cost function which is used for neutral case continues to work in presence of U(1) background field. For t > 0, the complexity of cTFD state evolves in time and contrasts with holographic results, it saturates after a time of the order of inverse temper- ature. This discrepancy can be understood by the fact that holographic QFTs are actually strong interacting theories, not free ones.

An information entropy based-clustering algorithm for heterogeneous wireless sensor networks

Abstract: This paper proposes a novel dynamic, distributive, and self-organizing entropy based clustering scheme that benefits from the local information of sensor nodes measured in terms of entropy and use that as criteria for cluster head election and cluster formation. It divides the WSN into two-levels of hierarchy and three-levels of energy heterogeneity of sensor nodes. The simulation results reveal that the proposed approach outperforms existing baseline algorithms in terms of energy consumption, stability period, and the network lifetime.

Black hole entropy function for toric theories via Bethe Ansatz

Abstract: We evaluate the large-N behavior of the superconformal indices of toric quiver gauge theories, and use it to find the entropy functions of the dual electrically charged rotating AdS5 black holes. To this end, we employ the recently proposed Bethe Ansatz method, and find a certain set of solutions to the Bethe Ansatz Equations of toric theories. This, in turn, allows us to compute the large-N behavior of the index for these theories, including the infinite families Ypq , Xpq and Lpqr of quiver gauge theories. Our results are in perfect agreement with the predictions made recently using the Cardy-like limit of the superconformal index. We also explore the index structure in the space of chemical potentials and describe the pattern of Stokes lines arising in the conifold theory case.

Simultaneous effects of nonlinear thermal radiation and Joule heating on the flow of Williamson nanofluid with entropy generation

Abstract: The present communication addresses the heat and mass transfer mechanism in MHD nanofluid flow of Williamson fluid over a stretching sheet taking the combined effects of Joule heating, nonlinear thermal radiation and viscous dissipation into consideration. For physical relevance we also analyzed the influence of chemical reactions on the flow field. The appropriate transformations are implemented to metamorphose the governing PDEs into a set of coupled ODEs. The shooting technique along with fourth order Runge–Kutta method has been implemented to get the solutions of obtained highly non-linear ODEs. The second law of thermodynamics is implemented to model the equation of entropy generation for the current analysis. Impact of different dominant parameters on velocity, temperature, concentration, entropy generation as well as Bejan number are described through graphs whereas the variation in the skin friction coefficient, heat transfer rate and mass transfer rate are studied using numerical data in the tabular form. It is observed from the obtained numerical data that the rate of heat transfer gets reduced with increase in Eckert number while the thermal radiation parameter tends to enhance it. Increase in Brinkman parameter leads to a rise in entropy generation while it (Brinkman parameter) has an adverse effect on Bejan number.

Second law analysis with effects of Arrhenius activation energy and binary chemical reaction on nanofluid flow.

Abstract: The Arrhenius activation energy and binary chemical reaction are taken into account to consider the magnetohydrodynamic mixed convection second grade nanofluid flow through a porous medium in the presence of thermal radiation, heat absorption/generation, buoyancy effects and entropy generation. The items composing of the governing systems are degenerated to nonlinear ordinary differential equations by adopting the appropriate similarity transformations which are computed through Runge-Kutta-Fehlberg (RKF) numerical technique along with Shooting method. The solution is manifested through graphs which provides a detailed explanations of each profile in terms of involved parameters effects. The compared results maintain outstanding approach to the previous papers.

An entropy approach of Williamson nanofluid flow with Joule heating and zero nanoparticle mass flux

Abstract: The important focus of this research is to investigate the features of MHD radiative Williamson nanofluid flow caused by a stretchable surface entrenched in a porous medium with Joule heating, convective heating and passive controls of nanoparticles. The heat flux is modelled based on the Christov–Cattaneo heat flux theory. Nanofluid contains thermophoresis and Brownian motion effects. Additionally, the entropy generation of Williamson nanofluid is calculated via the second law of thermodynamics. The governing partial differential equations are modified into nonlinear ordinary differential systems by applying appropriate similarity transformations. Homotopy progress is used to solve the nonlinear ordinary differential systems. Outcomes of magnetic field, Weissenberg number, radiation, Eckert number, Brownian motion, Bejan number and entropy generation of different parameters are discussed in detail. Moreover, skin friction, heat and mass transfer rates are evaluated. The comparison of skin friction and Nusselt number is validated, and the results have been reported.