Hasil untuk "Thermodynamics"

Sasti Handayani Wakhidyah, Imam Mudakir, Sri Wahyuni

Higher order thinking skills are skills that 21st century students should have in order to compete globally. Higher-order thinking skills involve complex thinking processes, including analysing, evaluating and creating. This study aims to analyse students' higher order thinking skills in solving heat and thermodynamics problems. The samples used in this study were grade 12 students in the 2024/2025 academic year, as many as 64 students. Data collection was carried out through the results of high thinking ability tests on heat and thermodynamics material with Bloom's tachnosomy domain levels C4, C5, and C6. The method used is quantitative method with purposive sampling technique. The results of this study, students have the ability to analyse (C4) by 61.34%, the ability to evaluate (C5) by 26%, and the ability to create (C6) by 12.66%. The conclusion of this study is that students are in the good category in the analysing aspect, the less category in the evaluating aspect and the very less category in the creating aspect. This means that students can complete the completion stage but are less able to compile information so that they are unable to produce perfect answers.

J. Thuburn

<p>A new computational fluid dynamics code for large eddy simulation (LES) of the atmospheric boundary layer and convection is presented and made available. A key novelty is that moist thermodynamics is formulated in terms of thermodynamic potentials, ensuring thermodynamic consistency. Despite the apparent complexity of the thermodynamic potential approach, the model's performance demonstrates that it is feasible and effective at reasonable computational cost for three-dimensional simulations. Semi-implicit semi-Lagrangian numerical methods are used; such methods are unusual for simulating boundary layer and convective flows and are more typical of global atmospheric models. Moreover, the model includes no explicit scheme to represent subgrid-scale fluxes of scalars and momentum but relies instead on the mixing and dissipation resulting from the numerical methods used; in other words, it employs implicit LES (ILES). Sample results from several standard LES test cases show that the model's ability to capture the main aspects of the flows is comparable to other LES models. At the same time, the results highlight limitations of the ILES approach near the bottom boundary and suggest that ILES might need to be augmented in some way, for example, by distributing the convergence of surface fluxes over several model layers. Also, results for a marine stratocumulus case show a significant sensitivity to different options for the numerical methods and parameters used. Further development and application of the code would benefit from a deeper understanding of both the bottom boundary behaviour and the sensitivities to numerics.</p>

Guillermo Fernández-Anaya, Francisco A. Godínez, Rogelio Valdés et al.

Fractional variable order systems with unusual dynamics in the order are a little-studied topic. In this study, we present three examples of very simple fractional systems with unusual dynamics in the derivative order. These cases involve different approaches to define the variable-order dynamics: (1) an integer-order differential equation that includes the state variable, (2) a differential equation that incorporates the state variable and features both integer- and fractional-order derivatives, and (3) fractional variable-order differential equations nested in the derivative orders. We prove a result that shows how the extended recursion of the last case is generalized. These examples illustrate the richness that simple dynamical systems can reveal through the order of their derivatives.

Leslie Glasser

S.V. Chuprov, A.V. Babkin

Background. With the increasing digitalization of the Russian economy, understanding the dominant trends in the distribution and protection of information flows in a non-stationary space is gaining theoretical and practical significance. An evolving industrial system immersed in such environments is characterized by highly disturbed processes and metamorphoses displayed by nonlinear phenomena, measures of chaos and order of its behavior. On this basis, taking into account the discussed phenomena, the article is aimed at analyzing and ensuring the stability of the industrial system in the face of the impact of both flows of technological and product innovations of the digitalized economy and geopolitical and economic threats that aggravate the behavior of the system. Materials and methods. The theoretical and methodological basis of the study was formed by the doctrines of thermodynamics, statistical physics, nonlinear dynamics, concepts and methods of theories catastrophe, communication and information, cybernetics and synergetics, evolutionary and innovative economics and production management. Results. Using their ideas and analytics, the concepts of entropy, chaos and the effect of the functioning of the system supported by the control information coming into it are revealed. Within the framework of information theory, the influence of signal and noise parameters on information processes in the economy, the features of their transmission and distortion are characterized. In the context of the statistical dependence of the effect of the economic system's activity on the control information accumulated in it, the transformation and interpretation of this exponential dependence with measures of the order of behavior of the industrial system are performed. Nonlinear phenomena of this dependence and the evolution of the industrial system are interpreted in order to achieve its stable effect. Conclusions. The study complements theoretical ideas about the factors ensuring the stability of the functioning of modernized industrial systems and argues for the need for a symbiosis of natural and economic sciences to deepen the analysis and interpretation of the phenomena of the evolution of chaotic industrial systems in a digitalized economy.

Md Shazzad Hossain, Ibrahim Sultan, Truong Phung et al.

In this work, an artificial neural network (ANN)-based model is proposed to describe the input–output relationships in a Limaçon-To-Circular (L2C) gas expander with an inlet valve. The L2C gas expander is a type of energy converter that has great potential to be used in organic Rankine cycle (ORC)-based small-scale power plants. The proposed model predicts the different performance indices of a limaçon gas expander for different input pressures, rotor velocities, and valve cutoff angles. A network model is constructed and optimized for different model parameters to achieve the best prediction performance compared to the classic mathematical model of the system. An overall normalized mean square error of 0.0014, coefficient of determination (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi>R</mi><mn>2</mn></msup></semantics></math></inline-formula>) of 0.98, and mean average error of 0.0114 are reported. This implies that the surrogate model can effectively mimic the actual model with high precision. The model performance is also compared to a linear interpolation (LI) method. It is found that the proposed ANN model predictions are about 96.53% accurate for a given error threshold, compared to about 91.46% accuracy of the LI method. Thus the proposed model can effectively predict different output parameters of a limaçon gas expander such as energy, filling factor, isentropic efficiency, and mass flow for different operating conditions. Of note, the model is only trained by a set of input and target values; thus, the performance of the model is not affected by the internal complex mathematical models of the overall valved-expander system. This neural network-based approach is highly suitable for optimization, as the alternative iterative analysis of the complex analytical model is time-consuming and requires higher computational resources. A similar modeling approach with some modifications could also be utilized to design controllers for these types of systems that are difficult to model mathematically.

Seth Kermausuor, Eze R. Nwaeze

All types of inequalities play a very important role in various aspects of mathematical analysis, such as approximation theory and differential equation theory [...]

Zoi Salta, Nicola Tasinato, Joel F. Liebman et al.

Despite being one of the best-known families of organic compounds, the fact that hydrocarbons exhibit a rich variety of structures owing to branching, cyclization, and the presence of multiple bonds, means that many of their properties are yet to be determined accurately, or even at all. Among cyclic hydrocarbons, those with three-membered rings are particularly interesting because of their strain energy. In this paper, we report accurate calculations of the enthalpy of formation of three-membered carbocycles, whose experimental values have not been obtained by direct measurement of the heat of combustion. For this purpose, we used several accurate composite methods to obtain the gas-phase enthalpies of atomization and derived from them the gas-phase enthalpies of formation, using experimentally determined accurate values for the atoms. Moreover, to minimize the inaccuracy that can possibly arise in this procedure, we also used homodesmotic reactions designed to balance systematic errors in the geometric and electronic structure of some of the species. A careful analysis of the results shows that some of the indirectly derived values reported in the literature are far from the most accurate theoretical outcomes, and we suggest that these new ones should be adopted.

Goziya W. Dzarma, Chinedu M. Agu, Kenechi Nwosu-Obieogu et al.

This study investigated the effect of extraction parameters such as particle size, temperature, and time on yield alongside the kinetic and thermodynamics variables for Chrysophyllum albidum. For the extraction, the oil yield increased as the extraction temperature and time increased, but the reverse was observed as the particle size increased. At the temperature of 55 °C, particle size of 0.55 mm, and extraction time of 150 min, the maximum oil yield of 14.98% was obtained. The extracted oil was analyzed and was found to have a saponification value of 134.64 mgKOH/kg, Iodine value of 82.53 mg I/g, peroxide value of 5mEq/kg, and acid value of 14.47 mg KOH/mg. In addition, the oil viscosity and specific gravity were 54.54 mm2 s−1 and 0.941, respectively. Hyperbolic, second-order, and Elovich's kinetic models were used to fit the data gotten from experimental findings. The three models fitted the experimental data suitably, with hyperbolic kinetic model giving the best fit (R2=0.93288, RMS=0.12133, and SD=0.02715) followed by Elovich's model kinetic model (R2=0.92172, RMS=0.205329, and SD=0.039349) and (R2=0.92968, RMS=0.66867, and SD=0.542885) in that order. Thermodynamic parameters ∆H and ∆S for ASA seed oil extraction were evaluated at temperature of 318 K. The enthalpy values for the five particle sizes used were 19.35, 22.24, 26.08, 29.57 and 49.98 KJ/mol and the Entropy 0.08, 0.09 0.10 0.11 and 0.17 KJ/mol respectively. These positives values for the enthalpy and entropy change shows that the extraction is endothermic and irreversible in nature. The Gibbs free energy change (∆G) for the extraction was found to be below zero showing that the extraction was a spontaneous process. Using ANOVA and Tukey's post hoc HSD analyses, extraction time variation was found to significantly affect oil yield. Particle size and extraction temperature variations were statistically insignificant.

Qing-Zhu Sun, Chul-Ho Kim

As the core powertrain component of electric vehicles, batteries release heat when charging and discharging due to the chemical reactions between the battery elements and internal resistance. To avoid problems resulting from abnormal temperatures, such as performance and lifespan issues, an effective battery cooling system is required. This paper presents a fundamental study of battery module liquid cooling through a three-dimensional numerical analysis. CFD numerical tests as conducted here are based on the heat transfer characteristics and on the liquid cooling theory, and the temperature distribution and thermal conductivity are analyzed qualitatively and quantitatively using Simcenter STAR CCM+ version 2016 (Siemens Digital Industries Software, Plano, TX, USA). A simulation uses a square-shell lithium-ion battery-made module with two different liquid cooling systems at different positions of the module. The results of the numerical study indicate that the bottom cooling system shows a better battery module temperature difference that is approximately 80% less than that of the side cooling system. For the side cooling system, it is better in terms of the maximum temperature of the battery module, which is approximately 20% lower than that in the bottom cooling system, but this system does not offer very good control of the temperature difference, which is also its greatest shortcoming compared to the bottom cooling system.

Dongqing Li

A. Torres-Hernandez, F. Brambila-Paz

Considering the large number of fractional operators that exist, and since it does not seem that their number will stop increasing soon at the time of writing this paper, it is presented for the first time, as far as the authors know, a simple and compact method to work the fractional calculus through the classification of fractional operators using sets. This new method of working with fractional operators, which may be called fractional calculus of sets, allows generalizing objects of conventional calculus, such as tensor operators, the Taylor series of a vector-valued function, and the fixed-point method, in several variables, which allows generating the method known as the fractional fixed-point method. Furthermore, it is also shown that each fractional fixed-point method that generates a convergent sequence has the ability to generate an uncountable family of fractional fixed-point methods that generate convergent sequences. So, it is presented a method to estimate numerically in a region <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Ω</mi></semantics></math></inline-formula> the mean order of convergence of any fractional fixed-point method, and it is shown how to construct a hybrid fractional iterative method to determine the critical points of a scalar function. Finally, considering that the proposed method to classify fractional operators through sets allows generalizing the existing results of the fractional calculus, some examples are shown of how to define families of fractional operators that satisfy some property to ensure the validity of the results to be generalized.

Candelaria Tejada-Tovar, Ángel Villabona-Ortíz, Walter Cortina-Góngora et al.

The presence of heavy metals in aqueous media represents a severe threat to ecosystems because they are non-biodegradable, toxic, and carcinogenic. In the present work, the utilization of agro-industrial residues from obtaining plantain starch for removing Ni (II) was studied, establishing the effect of temperature, adsorption dose, and initial concentration. The kinetics, equilibrium, and thermodynamic parameters that determine the process were studied. For this purpose, tests were carried out in a batch system maintaining constant stirring (200 rpm), pH (2), and solution volume (100 mL). The remaining metal concentration was determined by atomic adsorption at 237 nm. It was found that the best adsorption conditions were given at 55 ºC, 0.6775 g, and 368 mg/L obtaining a maximum adsorption capacity of 47.57 mg/g corresponding to a removal of 87%. The kinetic model that best fits the experimental data was a pseudo-second-order model, and the isotherm that describes the process is Langmuir and Freundlich, so the adsorption is given by chemisorption and multilayers. The thermodynamic parameters determined suggest that the process is favourable, not spontaneous, endothermic, and irreversible under the studied conditions. The results show that the residual biomass from the obtaining of plantain starch is a good precursor for absorbing Ni (II) in an aqueous solution.

Hulya Durur, Esin Ilhan, Hasan Bulut

This manuscript focuses on the application of the <inline-formula><math display="inline"><semantics><mrow><mrow><mo>(</mo><mrow><mrow><mrow><mi>m</mi><mo>+</mo><mn>1</mn></mrow><mo>/</mo><msup><mi>G</mi><mo>′</mo></msup></mrow></mrow><mo>)</mo></mrow></mrow></semantics></math></inline-formula>-expansion method to the (2+1)-dimensional hyperbolic nonlinear Schrödinger equation. With the help of projected method, the periodic and singular complex wave solutions to the considered model are derived. Various figures such as 3D and 2D surfaces with the selecting the suitable of parameter values are plotted.

Yan Zhang, Qian Li, Xiaoliang Liu

Arsenopyrite (FeAsS) is often associated with gold, but pre-treatment is necessary prior to gold leaching, mainly due to the gold encapsulation in the matrix of FeAsS. Bio-oxidation is attractive and promising, largely due to its simplicity, low cost and environmental friendliness. A critical problem that still impedes the large-scale applications of this green technology is its slow leaching kinetics. Some metal ions such as Ag⁺ have previously been found to expedite the bioleaching process. In this paper, the role of Ag⁺ in the arsenopyrite bioleaching by <i>Acidithiobacillus ferrooxidans</i> was investigated in detail by bioleaching experiments and a series of analyses including thermodynamics, X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Experimental results suggested that addition of 5 mg/L Ag⁺ to the leaching system could significantly improve the final As leaching efficiency from 30.4% to 47.8% and shorten the bioleaching period from 19 days to 15 days. Thermodynamic analysis indicates that Ag⁺ destabilises As₂S₂, As₂S₃ and S⁰ via forming Ag₂S, which is confirmed by the XRD analysis on the phase transformation during bioleaching. SEM and XPS analyses further showed that Ag⁺ removed the passivating film consisting mainly of As₂S₂, As₂S₃ and S⁰ because Ag₂S formed on the arsenopyrite surface from the start bioleaching of 36 h. In the presence of Fe³⁺, Ag₂S could easily be dissolved to Ag⁺ again, likely leading to the establishment of the Ag⁺/Ag₂S cycle. The bacteria utilised the two synergistic cycles of Fe³⁺/Fe²⁺ and Ag⁺/Ag₂S to catalyse the bioleaching of arsenopyrite.

Anatoly SOKOLENKO, Olexandr SHEVCHENKO, Konstantin VASYLKIVSKY et al.

The paper deals with the peculiarities of thermodynamic analysis of technological systems of food production with generation of secondary steam. System analysis is based on information about production, equipment operation, modern scientific achievements and modeling methods in chemical, physical, mathematical and other sciences. The information about applied energy and thermodynamic criteria, criteria of optimization of systems, list of sequence of actions on improvement of systems is given. Secondary energy resources of food industries are often represented by thermal energy of liquid media or secondary steam. Regeneration of the secondary steam allows, during its subsequent condensation, to return the heat potential of the steam to the media. This means that in the systems where the increase in the thermodynamic parameters of steam due to its compression, there is the use of Carno's return cycle. Such use occurs both in closed and open cycles. The description of the physical processes accompanying the work of the thermocompressors is subject to mathematical modeling based on the laws of conservation of energy, mass conservation and conservation of impulses. The assessment of the suitability for using secondary energy resources is based on exergy methods in order to determine the directions for their further improvement. For identical pressures in the mixing chamber, the efficiency of the actual compressor is higher than the ratio of the ejection coefficients of the real and ideal compressors, since internal irreversible losses along with the reduction of the ejection rate result in the increase of the specific exergy of the compressed flow.

Alexander Fuchs, Niclas Berg, Lisa Prahl Wittberg

Pulsatile flow in the abdominal aorta and the renal arteries of three patients was studied numerically. Two of the patients had renal artery stenosis. The aim of the study was to assess the use of four types of indicators for determining the risk of new stenosis after revascularization of the affected arteries. The four indicators considered include the time averaged wall shear stress (<i>TAWSS</i>), the oscillatory shear index (<i>OSI</i>), the relative reference time (RRT) and a power law model based in platelet activation modeling but applied to the endothelium, named endothelium activation indicator (EAI). The results show that the indicators can detect the existing stenosis but are less successful in the revascularized cases. The <i>TAWSS</i> and, more clearly, the EAI approach seem to be better in predicting the risk for stenosis relapse at the original location and close to the post-stenotic dilatation. The shortcomings of the respective indicators are discussed along with potential improvements to endothelial activation modeling and its use as an indicator for risks of restenosis.

A.S. Kudussov, I.A. Kudussova, O.B. Seldyugaev et al.

The paper presents a method of calculating the heat energy loss from the room through double and triple glazing. In this article algorithms of calculation of losses of energy through the processes of conduction, convection and radiation heat transfer. The article shows that the replacement of the standard double-glazed window (total thickness of the double-glazed 24 mm) with the upgraded triple-glazed window (total thickness of the upgraded glass 47 mm) leads to a reduction in heat energy losses by at least 50 percent; at the same time, with an increase in the difference between the temperature of the street and the temperature of the room, it leads to an increase in thermal energy savings. The article shows that the loss of thermal energy through the Windows is not dependent on the thickness of the glass, but there is a strong dependence of the flow of thermal energy going through the Windows into the street, the number of glasses in the glass and the distance between the glasses. The given article technique allows you to quickly calculate the energy loss through 1 m2 of doubleglazed glass; knowing the total area of Windows in the room, you can calculate the total energy loss through all the Windows and, if necessary, adjust the supply of heat energy to the room: for example, increase or decrease the number of ribs of heating batteries.

Hermann Stoever, C. Pesterfield

Richard Otis, Zi-Kui Liu

The pycalphad software package is a free and open-source Python library for designing thermodynamic models, calculating phase diagrams and investigating phase equilibria using the CALPHAD method. It provides routines for reading thermodynamic databases and solving the multi-component, multi-phase Gibbs energy minimization problem. The pycalphad software project advances the state of thermodynamic modeling by providing a flexible yet powerful interface for manipulating CALPHAD data and models. The key feature of the software is that the thermodynamic models of individual phases and their associated databases can be programmatically manipulated and overridden at run-time without modifying any internal solver or calculation code. Because the models are internally decoupled from the equilibrium solver and the models themselves are represented symbolically, pycalphad is an ideal tool for CALPHAD database development and model prototyping.