Hasil untuk "Thermodynamics"

A. Katchalsky, P. Curran

R. Swalin, J. Arents

F. Millero

In the next ten years, a number of studies on the carbonate system are planned as part of the JGOFS/WOCE programs. The carbon dioxide system will be studied by measuring at least two of the controlling parameters; pH, total alkalinity (TA), total inorganic CO2 (TCO2), and the fugacity of CO2 (fCO2). The other parameters can be calculated using thermodynamic relations. In the present paper the thermodynamic equations necessary to characterize the CO2 system in the oceans as a function of salinity and temperature are given. This includes equations for the dissociation of carbonic acid, boric acid, phosphoric acid, silicic acid, water, hydrogen sulfide, and ammonia in seawater as a function of temperature (0 to 45°C) and salinity (0 to 45). The equations are of the form ln Ki = A + BT + C ln T, where A, B, and C are functions of salinity. Equations are also given for calculating the effect of temperature and salinity on the fugacity and pH of seawater using the carbonic acid constants of Roy et al. (1993a).

C. Beck, F. Schögl

M. Grmela, H. C. Öttinger

J. Connolly

B. Dolan

The mass of a black hole is interpreted, in terms of thermodynamic potentials, as being the enthalpy, with the pressure given by the cosmological constant. The volume is then defined as being the Legendre transform of the pressure, and the resulting relation between volume and pressure is explored in the case of positive pressure. A virial expansion is developed and a van der Waals like critical point determined. The first law of black hole thermodynamics includes a PdV term which modifies the maximal efficiency of a Penrose process. It is shown that, in four-dimensional spacetime with a negative cosmological constant, an extremal charged rotating black hole can have an efficiency of up to 75%, while for an electrically neutral rotating black hole this figure is reduced to 52%, compared to the corresponding values of 50% and 29% respectively when the cosmological constant is zero.

E. Feireisl, A. Novotný

S. Guenneau, C. Amra, D. Veynante

We adapt tools of transformation optics, governed by a (elliptic) wave equation, to thermodynamics, governed by the (parabolic) heat equation. We apply this new concept to an invibility cloak in order to thermally protect a region (a dead core) and to a concentrator to focus heat flux in a small region. We finally propose a multilayered cloak consisting of 20 homogeneous concentric layers with a piecewise constant isotropic diffusivity working over a finite time interval (homogenization approach).

M. Ku, A. Sommer, L. Cheuk et al.

Nailing Down the Superfluid Transition A gas of fermions, the class of particle that protons, neutrons, and electrons belong to, can be found in contexts as different as neutron stars and a block of metal. When the interaction between fermions is on the brink of forming fermion pairs, the thermodynamics of the gas become dependent only on the gas temperature and density. Ku et al. (p. 563, published online 12 January; see the Perspective by Zwerger) measured this universal thermodynamics with high precision in an ultracold Fermi gas, observing the predicted transition into a superfluid state through the characteristic lambda-shaped transition in the gas's specific heat. Thermodynamic quantities for the superfluid transition of a strongly interacting atomic Fermi gas were measured. Fermi gases, collections of fermions such as neutrons and electrons, are found throughout nature, from solids to neutron stars. Interacting Fermi gases can form a superfluid or, for charged fermions, a superconductor. We have observed the superfluid phase transition in a strongly interacting Fermi gas by high-precision measurements of the local compressibility, density, and pressure. Our data completely determine the universal thermodynamics of these gases without any fit or external thermometer. The onset of superfluidity is observed in the compressibility, the chemical potential, the entropy, and the heat capacity, which displays a characteristic lambda-like feature at the critical temperature Tc/TF = 0.167(13). The ground-state energy is 35 ξN EF with ξ = 0.376(4). Our measurements provide a benchmark for many-body theories of strongly interacting fermions.

J. Schneider, H. Jia, J. Muckerman et al.

Călin Gheorghe Buzea, Florin Nedeff, Diana Mirila et al.

Generative Adversarial Networks (GANs) perform well on natural images but often fail in domains governed by strict geometric or symbolic constraints. This work focuses on convolutional GANs and studies how their inductive biases interact with two contrasting types of synthetic image data: fractal patterns, characterized by self-similarity and scale-invariant local structure, and Euclidean shapes, defined by simple geometric primitives and rigid global constraints. Using multiple convolutional GAN architectures (DCGAN, WGAN-GP, and SNGAN), two resolutions (64 × 64 and 128 × 128), and a suite of evaluation metrics, we compare adversarial training behavior on these datasets under tightly controlled conditions. Fractal datasets yield stable training dynamics and perceptually plausible generations, whereas Euclidean shape datasets consistently exhibit structural failure modes that persist under higher resolution, smoother shape representations, and architectural stabilization. Geometry-aware metrics reveal severe violations of global shape consistency in Euclidean outputs that are not reliably captured by standard perceptual or distributional measures such as FID, SSIM, or LPIPS. We argue that these findings reflect a fundamental inductive bias of convolutional generative models toward a locally rich, scale-repeating structure rather than globally constrained geometry. Rather than indicating that fractals are intrinsically easier to model, our results show that Euclidean geometry exposes limitations of adversarial generative learning that remain hidden under conventional evaluation. From this perspective, fractal datasets serve as informative diagnostic benchmarks for probing how adversarially trained convolutional generators handle scale-invariant structure versus globally constrained geometry, and our results highlight the need for domain-aware metrics and alternative architectural biases when applying generative models to structured or symbolic data.

G. Gour, Markus P. Muller, Varun Narasimhachar et al.

We review recent work on the foundations of thermodynamics in the light of quantum information theory. We adopt a resource-theoretic perspective, wherein thermodynamics is formulated as a theory of what agents can achieve under a particular restriction, namely, that the only state preparations and transformations that they can implement for free are those that are thermal at some fixed temperature. States that are out of thermal equilibrium are the resources. We consider the special case of this theory wherein all systems have trivial Hamiltonians (that is, all of their energy levels are degenerate). In this case, the only free operations are those that add noise to the system (or implement a reversible evolution) and the only nonequilibrium states are states of informational nonequilibrium, that is, states that deviate from the maximally mixed state. The degree of this deviation we call the state’s nonuniformity; it is the resource of interest here, the fuel that is consumed, for instance, in an erasure operation. We consider the different types of state conversion: exact and approximate, single-shot and asymptotic, catalytic and noncatalytic. In each case, we present the necessary and sufficient conditions for the conversion to be possible for any pair of states, emphasizing a geometrical representation of the conditions in terms of Lorenz curves. We also review the problem of quantifying the nonuniformity of a state, in particular through the use of generalized entropies, and that of quantifying the gap between the nonuniformity one must expend to achieve a single-shot state preparation or state conversion and the nonuniformity one can extract in the reverse operation. Quantum state-conversion problems in this resource theory can be shown to be always reducible to their classical counterparts, so that there are no inherently quantum-mechanical features arising in such problems. This body of work also demonstrates that the standard formulation of the second law of thermodynamics is inadequate as a criterion for deciding whether or not a given state transition is possible.

Markus Fallmann, Lukas Stanger, Martin Fischer et al.

This paper presents the development and implementation of a broadly applicable Energy Management System (EMS) based on model predictive control (MPC) to optimize energy consumption in a real-world industrial food processing plant. The EMS, formulated as a Mixed-Integer Linear Programming (MILP) optimization problem, is designed to minimize energy use and switching operations- defined as the number of equipment on/off transitions per unit of energy delivered (switches/MWh) - while ensuring sufficient heating and cooling for production. The control structure is built upon a two-tiered MPC framework. At the higher level, an MPC algorithm optimizes energy efficiency over a 24-hour horizon, taking into account the production schedule, predicted energy demands, and the operation of thermal storage and heat pumps. The lower-level controller, with a faster sampling rate, focuses on short-term disturbance rejection and immediate system adjustments. The system was evaluated over 14 days of real-world economic plant operation, with results showing significant improvements in efficiency and in reducing switching operations and thus wear. On the cold process side, switching operations have been reduced while maximizing control performance under tight temperature constraints. On the hot side, the EMS achieved a remarkable 8 % increase in efficiency and 36 % reduction of switching operations.

Zhenyu Wu, Chuanjing Song

In this work, Noether symmetries and conserved quantities of a non-standard Birkhoffian system based on the Caputo <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Δ</mo></semantics></math></inline-formula> Pfaff–Birkhoff principle on time scales are studied. Firstly, equations of motion for Caputo <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Δ</mo></semantics></math></inline-formula> non-standard Birkhoffian systems are set up from Caputo <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Δ</mo></semantics></math></inline-formula> variational principle. Secondly, invariance of Caputo non-standard Pfaff action on time scales is demonstrated, thus giving rise to Noether symmetry criterions which establish Noether’s theorems for the corresponding system. The validity of the methods and results presented in the paper is illustrated by means of examples provided at the end of the article.

Tomás Basile, Karel Proesmans

In this paper, we study the thermodynamic cost associated with erasing a static random access memory. Using the framework of stochastic thermodynamics applied to electronic circuits, combined with optimization techniques based on machine learning, we demonstrate that memory erasure can be performed at arbitrarily fast speeds while maintaining finite heat dissipation. Our results suggests that heat dissipation must increase linearly with the speed of erasure. In addition, we identify optimized control protocols that minimize dissipation, providing explicit guidelines for the thermodynamically efficient design of future memory technologies. Our work thus establishes a concrete link between abstract thermodynamic theory and practical applications in electronic engineering.

Kun He, Yifan Wang, Huoxing Liu et al.

To meet requirements such as heat exchange capability and spatial compatibility, multiple sub-precoolers are integrated within a precooled engine. However, no effective solutions have been proposed to address the spatial issue of excessive axial dimensions in precoolers, and there is a notable absence of parametric study for parallel precoolers. In this study, the mechanisms underlying the performance degradation of a single precooler (baseline precooler) under non-uniform airflow conditions, as well as the performance advantages of parallel precoolers, were revealed. Meanwhile, a simplified simulation method was utilized to evaluate the performance of the precooled ducts based on the baseline precooler and the dual-parallel precoolers. The research demonstrated that, with rational central diameters design and coolant allocation of the sub-precoolers, parallel precoolers can almost entirely eliminate the adverse performance impacts caused by non-uniform airflow under the most ideal conditions. Furthermore, compared to the precooled duct based on the baseline precooler, the variable-diameter dual-parallel precoolers featuring a novel axially staggered layout achieves notable spatial contraction and total pressure benefits while maintaining comparable heat transfer performance. With a minor sacrifice of heat transfer power reduction below 0.39 %, it saves the axial space by 20 %–40 % and lowers the total pressure loss by 0.98 %–3.72 %.

Paul Skrzypczyk, A. J. Short, S. Popescu

Thermodynamics is traditionally concerned with systems comprised of a large number of particles. Here we present a framework for extending thermodynamics to individual quantum systems, including explicitly a thermal bath and work-storage device (essentially a ‘weight’ that can be raised or lowered). We prove that the second law of thermodynamics holds in our framework, and gives a simple protocol to extract the optimal amount of work from the system, equal to its change in free energy. Our results apply to any quantum system in an arbitrary initial state, in particular including non-equilibrium situations. The optimal protocol is essentially reversible, similar to classical Carnot cycles, and indeed, we show that it can be used to construct a quantum Carnot engine. Traditionally, thermodynamics deals with the study of macroscopic systems comprised of a large number of particles. Skrzypczyk et al. present a framework—including a thermal bath and work-storage device—to extract the optimal amount of work from individual quantum systems.

Runsheng Lv, Xinya Han, Gaofeng Liu et al.

Faults, as a kind of fracture tectonics, play a role in reservoir closure or provide oil and gas transportation channels. The accurate understanding of the distribution characteristics of faults is significant for oil and gas exploration. The traditional fractal dimension for fault number (<i>D_f3</i>) cannot comprehensively characterize the complexity and heterogeneity of fault network distribution. In this paper, a fractal characterization method on three-dimensional (3D) tortuosity of fault tectonics is proposed based on 3D seismic exploration. The methodology is described in detail to establish the model on the fractal dimension for the 3D tortuosity of fault tectonics. The results show the proposed method of estimation of the <i>D_T3</i> displaying high accuracy and rationality. Compared with the traditional fractal dimension <i>D_f3</i>, the proposed <i>D_T3</i> can comprehensively characterize the fractal characteristics of faults network systems in the 3D space. This study achieves a breakthrough in the fractal characterization of the 3D tortuosity of fault tectonics. It is worth further study for establishing an analytical fractal equation based on the <i>D_T3</i> and oil or gas transfer, which can provide the theoretical foundation and technical support for oil and gas exploration.

Alexander G. Tvalchrelidze

This article presents tangible geological evidence for coexistence of porphyry copper and epithermal gold systems within single polygenic deposits and provides a paleothermophysical model for their origins. Brief metallogenic analysis of the Southern Caucasus and Northern Iran has shown that such deposits are confined to long-living calc-alkaline island arcs and were formed during their orogenesis. Examples of complex Sonajil (Iran), Gharta, and Merisi (Georgia) deposits are considered. Investigation has shown that for combined porphyry and epithermal ore formation some preconditions are suggested to exist: (i) Source of anomalous energy, which exceeds thermodynamics of the enclosing environment; (ii) Existence of temperature gradient, which determines conventional flows of fluids composed of endogenous and meteoric constituents (proven by rhythmical zoning of ore lodes); (iii) Stability of such conditions for a period of sulfide ore formation. However, such a process of sulfide ore formation cannot explain formation of high sulfidation gold deposits. Mass precipitation of free gold requires phreatic collapse in the ore conduit channel already after formation of hydrothermally altered rocks, and this event results in creation of either hydrothermal breccias, often with jigsaw-fit texture or brecciated vuggy silica where host rocks and hydrothermally altered rocks are cemented by a gold-bearing quartz matrix.