Hasil untuk "Thermodynamics"

Yassine Elyaakouby, Amine Tilioua

Reverse osmosis (RO) desalination has become an essential technology for providing freshwater in arid regions; however, its high energy demand remains a major operational and environmental concern. This study investigates the energy optimization of a full-scale RO desalination unit located in southern Morocco. Real operational data were collected and analyzed using a Python-based linear regression model to identify relationships between feed pressure, flow rate, conductivity, and specific energy consumption (SEC). Results show a strong correlation between energy use and operational scheduling, with an optimal operating window reducing SEC from 1.42 to 1.20 kWh m⁻³ and decreasing specific cost by approximately 0.015 USD m⁻³. Implementation of optimized control strategies led to an estimated 15 % reduction in energy consumption and 12 % decrease in CO₂ emissions. The proposed three-level methodology data acquisition, operational supervision, and AI-assisted optimization provides a replicable framework for improving the sustainability of desalination plants in energy-constrained arid environments.

Huizhen Qu, Tianwei Zhang, Jianwen Zhou

The Euler difference approach has become a prevalent tool in the research of integral order differential equations. Nevertheless, a review of the literature reveals a dearth of studies examining fractional order models using the exponential Euler difference approach. The present study employs an exponential Euler difference approach to examine the properties of nonlocal discrete-time oscillators with Mittag–Leffler kernels and piecewise features, with the aim of providing insights into a continuous-time nonlocal nonlinear system. By employing impulsive equations of variations in constants with different forms in conjunction with the Gronwall inequality, a controller that is capable of instantaneously responding and stabilizing the nonlocal discrete-time oscillator is devised. This controller is realized through an associated algorithm. As a case study, the primary outcome is applied to a problem of impulsive stabilization in nonlocal discrete-time Chua’s oscillator. This article presents a stabilizing algorithm for piecewise nonlocal discrete-time oscillators developed using a novel impulsive approach.

G.S. Gopika Krishnan, K. Muraleedharan

Understanding how the bis-urea macrocycle molecules can sense different invited anionic substances is becoming increasingly crucial. In this context, we have theoretically studied a new host-guest such as the interaction of 7,13-dibromo-1,4,8,11-tetraazacyclotetradecane-5,12‑dione (BUM) with the anions like SO42−, SO32−, CH3COO−, NO2−, and NO3−. DFT and TD-DFT are used to calculate thermodynamics, electronic structure, electric-field induced properties, and photo-physical characteristics in order to investigate the mechanism of selective sensing of these anions. The free energy change (ΔGads) and adsorption energies (Eads) suggest that these anionic interactions are thermodynamically feasible with strong to moderate adsorption energy with the receptor. The conductivity and sensitivity between the anions can be improved by the external electric field regulated investigation. Because of the intramolecular charge transfer transitions, internal conversions, and related configurational modifications, BUM-SO32− exhibits good fluorescence in the BUM-anion complexes, indicating its significance for practical utility.

Nayema Islam Nima, Mohammed Abdul Hannan

This study investigates mixed convection flow over a vertical thin needle with variable surface heat, mass, and microbial flux, incorporating the influence of gyrotactic microorganisms. The governing partial differential equations are transformed into ordinary differential equations using appropriate similarity transformations and then solved numerically by employing MATLAB’s Bvp4c solver. The primary focus lies in examining the influence of various dimensionless parameters, including the mixed convection parameter, power-law index, buoyancy parameters, bioconvection parameters, and needle size parameters, on the velocity, temperature, concentration, and microbe profiles. The results indicate that these parameters significantly affect the surface (wall) temperature, fluid concentration, and motile microbe concentration, as well as the corresponding velocity, temperature, concentration, and microorganism profiles. The findings provide insights into the intricate dynamics of mixed convection flow with bioconvection and have potential applications in diverse fields such as biomedicine and engineering.

Malika Ammari, Mohammed Zerrouk, Imane Zoufri et al.

The use of clinker as a filtering medium is a new method for treating the waste water from olive mills (OMWW), which is a highly toxic effluent for the environment due to its high organic load and its huge concentration of phenolic compounds as confirmed by HPLC analysis. Scanning electron microscopy (SEM), Energy-dispersed X-rays (EDX), Brunauer-Emmet-Teller (BET) and Fourier transformed infrared spectroscopy (FTIR) were used to characterize the prepared clinker. Additionally, adsorption tests were conducted to evaluate the performance of the clinker. The adsorption study was carried out under different conditions such as contact time, pH value, adsorbate concentration and temperature. The adsorption mechanisms are described using the Langmuir, Freundlich, and Temkin isotherms, the pseudo-first-order and pseudo-second-order models represent the kinetics while the thermodynamic study of adsorption examines how thermodynamic properties influence the adsorption process. The results indicate that the pseudo-second-order model and the Freundlich isotherm are most suitable for the adsorption of OMWW. The results showed that the clinker can adsorb 1001.61 mg/g at an initial concentration of 5000 mg/L.

Bharat Gwalani, Andrew Martin, Elizabeth Kautz et al.

Abstract Complex multi-element alloys are gaining prominence for structural applications, supplementing steels, and superalloys. Understanding the impact of each element on alloy surfaces due to oxidation is vital in maintaining material integrity. This study investigates oxidation mechanisms in these alloys using a model five-element equiatomic CoCrFeNiMn alloy, in a controlled oxygen environment. The oxidation-induced surface changes correlate with each element’s interactive tendencies with the environment, guided by thermodynamics. Initial oxidation stages follow atomic size and redox potential, with the latter becoming dominant over time, causing composition inversion. The study employs in-situ atom probe tomography, transmission electron microscopy, and X-ray absorption near-edge structure techniques to elucidate the oxidation process and surface oxide structure evolution. Our findings deconvolute the mechanism for compositional and structural changes in the oxide film and will pave the way for a predictive design of complex alloys with improved resistance to oxidation under extreme conditions.

Jiaojiao Ren, Can Zhao, Jianying Xiao et al.

This paper investigates the problem of exponential <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>H</mi><mo>∞</mo></msub></semantics></math></inline-formula> output control for switching fuzzy systems, considering both impulse and non-impulse scenarios. Unlike previous research, where the average dwell time (ADT: <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>τ</mi><mi>a</mi></msub></semantics></math></inline-formula>) and the upper bound of inter-event intervals (IEIs: <i>T</i>) satisfy the condition <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>τ</mi><mi>a</mi></msub><mo>≥</mo><mfrac><mrow><mo form="prefix">ln</mo><mi>μ</mi><mo>+</mo><mo>(</mo><mi>α</mi><mo>+</mo><mi>β</mi><mo>)</mo><mi>T</mi></mrow><mi>α</mi></mfrac><mo>=</mo><mfrac><mrow><mo form="prefix">ln</mo><mi>μ</mi><mo>+</mo><mi>β</mi><mi>T</mi></mrow><mi>α</mi></mfrac><mo>+</mo><mi>T</mi></mrow></semantics></math></inline-formula>, implying that frequent switching is difficult to achieve, this paper demonstrates that by adopting the mode-dependent event-triggered mechanism (ETM) and a switching law, frequent switching is indeed achieved. Moreover, the question of deriving the normal <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>L</mi><mn>2</mn></msub></semantics></math></inline-formula> norm constraint is solved through the ADT method, although only a weighted <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>L</mi><mn>2</mn></msub></semantics></math></inline-formula> norm constraint was obtained previously. Additionally, by constructing a controller-mode-dependent Lyapunov function and adopting logarithmic quantizers, the sufficient criteria of exponential <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>H</mi><mo>∞</mo></msub></semantics></math></inline-formula> output control problem are presented. The validity of established results is demonstrated by a given numerical simulation.

А.А. Karnaukhova, V.Y. Yakovlev

Traditionally, the synthesis of refractory ceramics is a complex and time-consuming process. Some time ago, a new, much faster method was proposed — the method of synthesis of luminescent ceramics in the field of a powerful flux of high-energy electrons. In the synthesis of multicomponent oxide phosphors, it is not an easy task to determine the dependencies of the properties of the resulting material on the composition of the raw mixture and the modes of the synthesis process. In this regard, it seems logical to study the properties of ce- ramics made by radiation synthesis from simple oxides, which are components of more complex phosphors. An investigation of the spectral and kinetic patterns of cathodoluminescence of ceramic samples of metal ox- ides (Ga2O3, Al2O3, Y2O3) and fluorides (MgF2, BaF2) obtained by radiation synthesis method was carried out. The paper presents an analysis of the cathodoluminescence spectra of the studied samples with the allo- cation of elementary bands, conclusions about the dynamics of luminescence decay are made. The obtained results are compared with the known data on single crystal samples. It is shown that, unlike oxide ceramics, the spectral characteristics of MgF2 and BaF2 ceramic samples show good agreement with the data on single crystals of these compounds.

Giovanni Barbero, Luiz. R. Evangelista, Rafael S. Zola et al.

Many fundamental physical problems are modeled using differential equations, describing time- and space-dependent variables from conservation laws. Practical problems, such as surface morphology, particle interactions, and memory effects, reveal the limitations of traditional tools. Fractional calculus is a valuable tool for these issues, with applications ranging from membrane diffusion to electrical response of complex fluids, particularly electrolytic cells like liquid crystal cells. This paper presents the main fractional tools to formulate a diffusive model regarding time-fractional derivatives and modify the continuity equations stating the conservation laws. We explore two possible ways to introduce time-fractional derivatives to extend the continuity equations to the field of arbitrary-order derivatives. This investigation is essential, because while the mathematical description of neutral particle diffusion has been extensively covered by various authors, a comprehensive treatment of the problem for electrically charged particles remains in its early stages. For this reason, after presenting the appropriate mathematical tools based on fractional calculus, we demonstrate that generalizing the diffusion equation leads to a generalized definition of the displacement current. This modification has strong implications in defining the electrical impedance of electrolytic cells but, more importantly, in the formulation of the Maxwell equations in material systems.

Alexander Redkin, Iraida Korzun, Tatyana Yaroslavtseva et al.

The isobaric heat capacity of solid eutectic mixtures LiCl-KCl-CsCl, LiBr-CsBr and LiBr-KBr-CsBr was investigated from room temperature up to melting point. The molar heat capacity of all mixtures under study was found to be close to the additive sum of that of pure salts. The heat accumulated up to melting temperature is directly dependent on the melting point.

Juan Carlos de la Torre, Pablo Pavón-Domínguez, Bernabé Dorronsoro et al.

Uncertain systems are those wherein some variability is observed, meaning that different observations of the system will produce different measurements. Studying such systems demands the use of statistical methods over multiple measurements, which allows overcoming the uncertainty, based on the premise that a single measurement is not representative of the system’s behavior. In such cases, the current multifractal detrended fluctuation analysis (MFDFA) method cannot offer confident conclusions. This work presents multi-signal MFDFA (MS-MFDFA), a novel methodology for accurately characterizing uncertain systems using the MFDFA algorithm, which enables overcoming the uncertainty of the system by simultaneously considering a large set of signals. As a case study, we consider the problem of characterizing software (Sw) consumption. The difficulty of the problem mainly comes from the complexity of the interactions between Sw and hardware (Hw), as well as from the high uncertainty level of the consumption measurements, which are affected by concurrent Sw services, the Hw, and external factors such as ambient temperature. We apply MS-MFDFA to generate a signature of the Sw consumption profile, regardless of the execution time, the consumption levels, and uncertainty. Multiple consumption signals (or time series) are built from different Sw runs, obtaining a high frequency sampling of the instant input current for each of them while running the Sw. A benchmark of eight Sw programs for analysis is also proposed. Moreover, a fully functional application to automatically perform MS-MFDFA analysis has been made freely available. The results showed that the proposed methodology is a suitable approximation for the multifractal analysis of a large number of time series obtained from uncertain systems. Moreover, analysis of the multifractal properties showed that this approach was able to differentiate between the eight Sw programs studied, showing differences in the temporal scaling range where multifractal behavior is found.

Siyi Huang, Qi Lu, Xiaorui Ma et al.

Hexavalent chromium (Cr (VI)), an anthropogenic heavy metal pollutant, is harmful to human beings, due to its carcinogenicity. In this study, a tourmaline–biochar composite (TMBC) was synthesized to remove Cr (VI) from an aqueous solution. The effects of different ratios (TM:BC) and pyrolysis temperatures on TMBC adsorption performance were compared. The TMBC samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscope–energy-dispersive spectrometry (SEM-EDS). The kinetics and thermodynamics were analyzed to investigate the sorption mechanism. The results showed that the proper pyrolysis temperature was 650 °C, and the ratio of TM:BC was 1:3. SEM results showed the TM was well attached to the BC which assisted tourmaline dispersion. The adsorption kinetics were well fitted by the pseudo-second-order model, indicating that the sorption was related to chemical absorption. Langmuir adsorption isotherms suggested monolayer adsorption between the Cr (VI) and the TMBC, and the maximum adsorption capacity of the TMBC for Cr (VI) was 43.64 mg/g, which was more than twice the amount for the pristine TM (17.84 mg/g). The automatic polarization of water caused by tourmaline was the unique adsorption property of the TMBC. Therefore, TMBCs can be used as an economic adsorbent in the remediation of heavy metal pollution.

D. Spanner

Nagamanickam Nagajothi, Vadivel Sadhasivam, Omar Bazighifan et al.

In this paper, we investigate the existence results for nonlinear fractional q-difference equations with two different fractional orders supplemented with the Dirichlet boundary conditions. Our main existence results are obtained by applying the contraction mapping principle and Krasnoselskii’s fixed point theorem. An illustrative example is also discussed.

Andreas Y. Troumbis

The application of the mass-energy-information equivalence principle developed after the experimentally demonstrated Landauer's principle on thermodynamics, entropy, and information is an unexplored but promising path in search of objectivity and compatibility between strict physical and mathematical entities and relative human behavior in biodiversity conservation issues. Conservation culturomics is proposed as the epistemic methodology and programme to trace the evolution in cultural human-nature relationships. Historically, controversies do persist between pro- vs. non- environmental opinions and policies. The proposed combination of physics and culturomics is feasible, although complex, multileveled, and depending on a series of academic, technical, and political prerequisites. In the era of staggering information technologies, Internet use proliferation and cultural relativism, reliable information on conservation knowledge vs. often unfounded story-tellings is a sine qua non for the development of badly needed modern global conservation strategies, targets, and goals.

Nadezhda S. Bondareva, Mikhail A. Sheremet

The constant growth of urban agglomerations with the development of transport networks requires the optimal use of energy and new ways of storing it. Energy efficiency is becoming one of the main challenges of modern engineering. The use of phase change materials in construction expands the possibilities of accumulating and storing solar energy, as well as reducing energy consumption. In this study, we consider the problem of the effect of natural convection on heat transfer in a building block containing a phase change material. Heat transfer, taking into account melting in brick, was analyzed at various temperature differences. The mathematical model was formulated in the form of time-dependent equations of conjugate natural convection using non-dimensional stream function, vorticity, and temperature. The equations describing melting, taking into account natural convection, were solved using the finite difference method. Smoothing parameters were used to describe phase transitions in the material. As a result of calculations, local characteristics of heat and mass transfer at various points in time were obtained, as well as changes in temperature profiles on the side surfaces. It is shown that with a large volume of melt, natural convection increases heat loss by more than 10%.

Beichuan Hong, Varun Venkataraman, Andreas Cronhjort

Energy carried by engine exhaust pulses is critical to the performance of a turbine or any other exhaust energy recovery system. Enthalpy and exergy are commonly used concepts to describe the energy transport by the flow based on the first and second laws of thermodynamics. However, in order to investigate the crank-angle-resolved exhaust flow enthalpy and exergy, the significance of the flow parameters (pressure, velocity, and temperature) and their demand for high resolution need to be ascertained. In this study, local and global sensitivity analyses were performed on a one-dimensional (1D) heavy-duty diesel engine model to quantify the significance of each flow parameter in the determination of exhaust enthalpy and exergy. The effects of parameter sweeps were analyzed by local sensitivity, and Sobol indices from the global sensitivity showed the correlations between each flow parameter and the computed enthalpy and exergy. The analysis indicated that when considering the specific enthalpy and exergy, flow temperature is the dominant parameter and requires high resolution of the temperature pulse. It was found that a 5% sweep over the temperature pulse leads to maximum deviations of 31% and 27% when resolving the crank angle-based specific enthalpy and specific exergy, respectively. However, when considering the total enthalpy and exergy rates, flow velocity is the most significant parameter, requiring high resolution with a maximum deviation of 23% for the enthalpy rate and 12% for the exergy rate over a 5% sweep of the flow velocity pulse. This study will help to quantify and prioritize fast measurements of pulsating flow parameters in the context of turbocharger turbine inlet flow enthalpy and exergy analysis.

Lim Jun An, Mohammed Abdul Hannan

Greenwater (splashing of water on the deck) loading is a classical problem faced by designers of ship-shaped vessels, which becomes even worse when the vessel operates in harsh weather conditions for an extended period of time. Installation of breakwaters on the deck can play a crucial role in minimizing this impact. However, research on the design and optimization of the breakwater is still in its infancy, and this study aims at shedding further light on this area by proposing and analysing the effectiveness of three breakwater designs on a fixed box-shaped vessel. The commercial CFD software ANSYS Fluent is used for this investigation. The design model (without breakwater) was validated at first against experimental results of greenwater splashing, before performing the actual simulations with the proposed breakwater design. A vertical plate is used as the deck structure, and the greenwater pressure at several locations on that plate is measured to compare the effectiveness of various breakwater designs. Overall, breakwaters with openings (perforations, grillages, etc.) were found to be more effective in minimizing the pressure generated by the greenwater. Nevertheless, there is significant room for improvement on breakwater designs, and some topics for further research are also suggested in this regard.

Pavlos Alexias, Kyriakos C. Giannakoglou

In this paper, the continuous adjoint method is used for the optimization of a static mixing device. The CFD model used is suitable for the flow simulation of the two miscible fluids that enter the device. The formulation of the adjoint equations, which allow the computation of the sensitivity derivatives is briefly demonstrated. A detailed analysis of the geometry parameterization is presented and a set of different parameterization scenarios are investigated. In detail, two different parameterizations are combined into a two-stage optimization algorithm which targets maximum mixture uniformity at the exit of the mixer and minimum total pressure losses. All parameterizations are in conformity with specific manufacturability constraints of the final shape. The non-dominated front of optimal solutions is obtained by using the weighted sum of the two objective functions and executing a set of optimization runs. The effectiveness of the proposed synthetic parameterization schemes is assessed and discussed in detail. Finally, a reduced length mixer is optimized to study the impact of the length of the tube on the device&#8217;s performance.

S. Safran