Search Results (411)

To reveal the nonlinear instability mechanism by which the three-degree-of-freedom rotor system of a magnetic-liquid double suspension bearing transforms from stable suspension to periodic vibration, a nonlinear dynamic model considering electromagnetic suspension force, hydrostatic supporting force, rotor unbalance force, and liquid film resistance is established. The equilibrium point of the system is linearized, and the Hopf bifurcation boundary is determined using the Routh–Hurwitz criterion. Numerical simulations are then carried out to investigate the effects of the initial current i₀, supply flow rate q₀, and different initial disturbances on the displacement time histories, phase trajectories, and spatial phase trajectories of the rotor. The results show that, under the given system parameters, the Hopf bifurcation boundary is 0.61 A for the initial current and 9.62 × 10⁻⁵ m³/s for the supply flow rate. Current variation mainly affects electromagnetic stiffness and nonlinear electromagnetic force, whereas flow rate variation primarily changes the hydrostatic load capacity and oil film damping characteristics. Under different initial disturbances, the system may exhibit amplitude attenuation, recovery to stable suspension, or finite amplitude periodic vibration. Experimental results show good agreement with numerical simulations in terms of frequency spectra, displacement time histories, and phase trajectories, thereby verifying the effectiveness of the proposed three-degree-of-freedom dynamic model and Hopf bifurcation analysis method. The results can provide theoretical guidance for parameter matching, stability evaluation, and self-excited vibration suppression of magnetic-liquid double suspension bearings. Full article

Various hydraulic automatic gates play an important role in water resources regulation. This study proposes a novel suspended hydraulic automatic control gate for tidal marine energy generation with adaptive one-sided flow-through characteristics. To evaluate its hydraulic performance and regulation mechanism, model experiments were conducted in a laboratory flume under different upstream and downstream water levels and discharge conditions. Gate opening states, hydraulic parameters, and flow field structures were obtained, while computational fluid dynamics simulations were used to reproduce and analyze the experimental flow field. The results show that the gate opening angle and water level jointly control the discharge capacity, and significant differences exist in the flow structure and discharge behavior between free and submerged outflow conditions. The numerical model further reveals vortex structures, velocity stratification, and gas–liquid two-phase distributions near the gate. Variations in gate structural parameters, discharge, and downstream water level significantly affect moment equilibrium, flow regime, and discharge capacity. The proposed discharge formula effectively predicts variations in gate flow and force characteristics under different hydraulic conditions, showing good applicability and engineering value. The suspended hydraulic automatic control gate has a simple structure, strong adaptability, and promising potential for tidal water regulation and engineering applications. Full article

The Zeta-Minimizer Theorem (ZMT) provides a complete deductive unification of statistical mechanics, number theory, helical geometry, thermodynamics, and electromagnetism from three primitive axioms alone. Starting with the non-proper Archimedean conical helix and the explicit covariant fugacity Hessian, the universal grand-partition function Z(s) is constructed via the integer-gear rule. This functorially invariant object yields gear occupations, Lyapunov exponents, and interaction parameters that govern all subsequent results. Interface matching and marginal stability λ_2,19 (x_2) = 0 trigger superconductivity at solid–fluid boundaries, while the categorical invariance of Z(s) produces exact magnetic and electric equilibrium curves. The Variational Reaction Rate Theorem then projects the framework onto dynamics, yielding Maxwell’s equations, demystified electrical units as helical torque quantities, and a complete classification of electronic phases. Phonons, Cooper pairing, the superconducting gap, and the full BCS correspondence follow without additional postulates. The same marginal-stability condition reproduces the Casimir effect, the Quantum Hall effect, and the entire 115-year experimental history of superconductivity. Generalization of interface matching to arbitrary solid–liquid pairs and introduction of Variational Anchor Cancellation (VAC) self-organizes a shielded superconducting layer. Finally, the first-principles engineering blueprint of the Radial Helical Gear Condenser (RHGC) delivers a modular, self-regulating device that engineers superconductivity at ambient or near-ambient temperature using only a radial pressure gradient and existing pipeline technology. All predictions are zero-parameter and fully deducible from the three axioms. Full article

Currently, there is no existing methodology within commercially available software packages for accurately simulating the gradual evaporation of the aqueous phase in batch thermomechanical dehydration processes involving highly stable water-hydrocarbon emulsions. This limitation constitutes a significant obstacle to the widespread industrial implementation of a promising approach for liquid hydrocarbon waste disposal, which relies on the evaporation of the aqueous phase under intensive stirring conditions, ultimately producing a hydrocarbon product with residual water content. In this study, the widely used Aspen HYSYS V12 software was employed to model these processes. The primary objective was to identify the most appropriate thermodynamic model accurately describing vapor–liquid phase transitions during the boiling of the aqueous phase in highly stable water–hydrocarbon emulsions, with water content ranging from 2 to 60% by weight. The modeling of the gradual boiling process was divided into several sequential stages, each representing a single evaporation step. The initial feedstock temperature was set at 90 °C, with subsequent stages involving temperature increments of 5 °C until the residual water content in the product fell below 0.5% by weight. Four thermodynamic models were evaluated for their ability to predict phase equilibria: Peng–Robinson, Wilson, UNIQUAC, and NRTL. It was observed that the Peng–Robinson model poorly describes the dehydration process, as it predicts water evaporation only at 100 °C, which contradicts experimental evidence indicating that evaporation occurs over a broader temperature range. The Wilson model significantly overestimates boiling points, reaching values up to 290 °C. Although the UNIQUAC model accurately reflects the process at higher water contents, it results in elevated energy consumption, necessitating substantial superheating of the feedstock up to 220 °C. The NRTL model provided the best correlation (among studied thermodynamic models) with experimental data, providing an average relative deviation of 3.68% and effectively capturing the two-stage evaporation mechanism: initial removal of free water at 100–110 °C, followed by bound moisture evaporation at temperatures approaching 160 °C. Vaporization rates were also examined across all models. The Peng–Robinson approach predicted the highest vaporization peaks but was the least representative of actual process conditions. Notably, in the NRTL model, the peak vaporization rates were 1.9 to 2.7 times higher than those estimated using the UNIQUAC and Wilson models. This parameter is critical for the optimal selection and design of subsequent condensation equipment. Based on these findings, the NRTL thermodynamic model is recommended for the industrial-scale implementation of thermomechanical dehydration processes involving heavy hydrocarbon feedstocks, given its accuracy in modeling phase transitions and the temperature-dependent vapor generation rates derived from sequential equilibrium flash calculations. Full article

Calcium leaching is a key degradation mechanism governing the long-term durability of cement-based materials, particularly in marine environments where multi-ionic interactions significantly alter dissolution behavior. In this study, the solid–liquid equilibrium of calcium in hardened Portland cement exposed to NaCl solution and artificial seawater was experimentally established. A wide range of equilibrium states was achieved by varying the liquid-to-solid ratio, and the corresponding aqueous chemistry and phase assemblage were characterized using ICP-AES, XRD, and SEM-EDS. The results show that both NaCl solution and seawater substantially increase the equilibrium calcium concentration compared to deionized water, with a much stronger effect observed in seawater. In NaCl solution, the equilibrium relationship follows a classical three-stage decalcification process. In contrast, seawater induces coupled dissolution–precipitation reactions due to the presence of Mg²⁺ and SO₄²⁻, leading to rapid and extensive decalcification within a narrow calcium concentration range. The findings provide important experimental evidence for improving thermodynamic models and predicting the long-term degradation of Portland cement concrete in marine environments. Full article

This study presents an innovative approach for the selective extraction of Co(II) and its separation from Ni(II) using ethyl ester glycine–betaine derivatives, specifically tri(n-pentyl)[2-ethoxy-2-oxoethyl]ammonium dicyanamide, as extractants in combination with continuous-mode liquid–liquid contact. Semi-pilot-scale implementation requires non-equilibrium conditions, characterized by short contact times between effluent and extractant phases. To address this, we propose dissolving analog of glycine–betaine ionic liquid (AGB-IL) in low-viscosity MIBK solvents to enhance mass transfer while reducing dependence on fossil-based solvents. Liquid–liquid extraction and continuous-flow stripping experiments were designed based on prior batch results and conducted in a saline environment, employing a chaotropic electrolyte for extraction and a kosmotropic electrolyte for stripping. Both open and closed systems were tested to compare extractive performance with batch conditions and with scenarios representative of industrial operations. Results indicate that continuous-flow systems achieve performance comparable to batch systems in terms of extraction efficiency, Co/Ni separation coefficients, and recyclability. These findings provide proof of concept for the development of semi-pilot and pilot-scale processes for efficient cobalt recovery. Full article

Making 1 $\mathrm{k}$$\mathrm{t}$ of cheese produces 9 $\mathrm{k}$$\mathrm{t}$ of cheese whey permeate, a waste with 5% lactose, which is either discarded or dried for animal feed. One pathway to add value to this waste is to convert it to lactic acid (LA), a monomer for polylactic acid, the largest bioplastic produced in the world. Lactose hydrolyses to glucose and galactose. While Brønsted acidity enhances lactose hydrolysis, Lewis acidity favours the formation of lactic acid. For the first time, we tested both industrial whey permeate and purified lactose as feedstocks for LA over a heterogeneous catalyst–Er₂O₃/Al₂O₃. LA Yield from whey permeate reached 14%, while the maximum yield with purified lactose was 22%. LA yield was invariant with respect to mixing speed while increasing temperature accelerates the time it takes to reach quasi-equilibrium. Yield was also independent of pressure with either air, He, N₂, or H₂ in the vapour space above the liquid phase in the autoclave. LA yield over spent catalyst with fresh lactose was only 11%, which indicates that the catalyst deactivates. Based on XRF analyses, the Er₂O₃ mass fraction dropped from 15% to 5%, with 6.4% leaching into the aqueous phase after the first step but only 0.8% after the second test. Full article

The rapid global transition toward electric vehicles (EVs) demands lithium-ion battery (LIB) systems that ensure both extreme performance and uncompromising safety. However, the inherent thermal asymmetry within battery packs—driven by non-uniform heat generation and localized hotspots—remains a critical bottleneck, accelerating degradation and triggering thermal runaway. Phase change materials (PCMs) have emerged as pivotal thermal buffers due to their high latent heat capacity and ability to maintain passive thermal symmetry. This review provides a comprehensive analysis of recent advancements in PCM-based battery thermal management systems (BTMSs), transitioning from material-level nanostructural enhancements to system-level hybrid architectures. Unlike traditional reviews, we critically evaluate how the integration of multidimensional conductive fillers and advanced encapsulation technologies resolves the trade-offs between energy density and thermal response rates. Furthermore, the synergistic coordination between PCMs and active cooling strategies (liquid, air, and heat pipes) is synthesized to provide a roadmap for achieving global thermal equilibrium under extreme fast-charging (XFC) conditions. Full article

Red mud discharged during alumina production via the Bayer process is characterized by high contents of sodium carbonate, sodium sulfate, and other soluble salts, and it remains poorly utilized and accumulates in long-term stockpiles. Sodium percarbonate has found extensive industrial applications, and its synthesis via the salting-out method represents one of the dominant industrial routes. In this context, sodium sulfate was employed as a salting-out agent. On the basis of relevant ternary systems, the phase equilibrium of the quaternary system Na₂CO₃–Na₂SO₄–H₂O₂–H₂O at 5 °C was systematically investigated and calculated. The objective was to utilize red mud as a waste resource and develop a novel integrated process that favored the wet synthesis of sodium percarbonate while enabling the efficient separation of sodium salts. The solubility data for the ternary subsystems constituting the above quaternary system were correlated using the Pitzer model, yielding the corresponding ion interaction parameters and activity coefficients. The validated model was then applied to predict the phase equilibrium data of the quaternary system. Verification results indicate that the calculated values are in satisfactory agreement with the experimental data. On the basis of the phase equilibrium data of the Na₂CO₃–Na₂SO₄–H₂O₂–H₂O system at 5 °C, a phase diagram was constructed. Along with five solid-phase crystallization fields, three invariant points were identified: the co-saturation point of Na₂SO₄·10H₂O, Na₂CO₃·10H₂O, and Na₂CO₃·1.5H₂O₂·H₂O; the co-saturation point of Na₂SO₄·10H₂O, Na₂CO₃·1.5H₂O₂·H₂O, and Na₂SO₄·0.5H₂O₂·H₂O; and the co-saturation point of Na₂CO₃·1.5H₂O₂·H₂O, Na₂SO₄·0.5H₂O₂·H₂O, and Na₂CO₃·2H₂O₂·H₂O. From phase diagram analysis, a novel wet process route for sodium percarbonate production using waste red mud is proposed. The process involves chemical reaction, crystallization, separation, and drying to obtain the final product. A new process flow diagram for the value-added production of sodium percarbonate is also presented. Full article

The development of reproducible and stable plasmon-free substrates for surface-enhanced Raman scattering (SERS) is critical for practical applications in analytical chemistry. Transition metal dichalcogenides (TMDCs) have emerged as promising candidates due to their unique electronic properties, yet their performance is often constrained by the chemical inertness of their pristine basal planes. This work presents a systematic comparison of crystalline flakes and nanoparticles of tungsten diselenide (WSe₂) and tungsten ditelluride (WTe₂), prepared via liquid-phase ultrasonic exfoliation and non-equilibrium femtosecond pulsed laser ablation in liquid (PLAL), respectively. The results demonstrate that nanoparticle-based substrates consistently outperform their flake-based counterparts, achieving enhancement factors in the range of ${10}^4$. The superior performance of the nanoparticles is hypothesized to originate from the synthesis-induced defects and high-curvature regions in the nanoparticles shell which facilitates efficient, defect-mediated charge transfer between the substrate and the analyte. At the same time, the inner polycrystalline volume conserves the important characteristics of the bulk counterparts like excitons in semiconducting WSe₂ and broadband absorption in semimetallic WTe₂, which unblocks the tunable photothermal colloidal response. The study establishes morphology engineering through non-equilibrium synthesis as a powerful and generalizable strategy for designing high-performance, dual-function colloidal platforms, offering a pathway toward robust and reproducible analytical systems. Full article

High-entropy MAX (HE-MAX) phases represent a new class of layered ceramics that combine the multi-principal-element chemistry of high-entropy materials with intrinsic damage tolerance, electrical conductivity, and multifunctionality of conventional MAX phases. Despite their promise, the synthesis of HE-MAX phases remains fundamentally constrained by sluggish multicomponent diffusion, narrow thermodynamic stability windows, and strong competition from thermodynamically favored binary and ternary carbides, borides, and nitrides. These challenges are further exacerbated by the volatility of A-site elements under near-equilibrium processing conditions. This review positions self-propagating high-temperature synthesis (SHS) as an energy-efficient, non-equilibrium processing route capable of stabilizing selected entropy-driven MAX chemistries through ultrafast thermal excursions and rapid quenching. A unified thermodynamic–kinetic framework is developed to elucidate the interplay among reaction enthalpy, configurational entropy, combustion wave sustainability, and phase evolution in HE-MAX systems. Predictions of thermochemical adiabatic temperature are systematically correlated with experimental SHS studies to delineate phase stability boundaries, stoichiometric sensitivity, and the roles of diluents and transient liquid formation. Finally, practical design principles for scalable SHS synthesis of HE-MAX phases are outlined, alongside strategies for their selective exfoliation into high-entropy MXenes and a critical assessment of their emerging functional applications. Full article

As a finite strategic resource, helium is extracted from natural gas (NG). The concentration of helium in NG is very low, which makes helium hard to separate. The hydrate-based gas separation (HBGS) was proposed as a promising method for the separation of the NG with low helium content in this work. This work systematically investigated the HBGS of helium from simulated NG. The thermodynamic analysis reveals that the existence of 5.00 mol% tetrahydrofuran (THF) in the liquid phase decreased the gas–liquid–hydrate equilibrium pressure by 92.11%, compared to the deionized water system. The single-stage HBGS experimental results show that high THF concentration, low temperature, and high pressure benefited the gas processing capacity and helium purification, but they led to a low helium recovery rate. The best HBGS performance was limited by the “hydrate shell effect”. The decrease in gas–liquid ratio led to an increase in helium concentration without losing the gas processing capacity, but it caused a decrease in the helium recovery rate. Through three-stage HBGS optimization, the helium concentration was increased from 0.54 mol% to 13.54 mol% (a 25.07-fold enrichment), and a total helium recovery of 87.34% was achieved. The mathematical model proposed in this work accurately predicts the performance of HGBS with 2.09% average relative error compared to the experimental data. Full article

Fully compressible two-phase flow configurations present many challenges for numerical modelling, requiring the development of Real Fluid Models (RFMs) able to simulate flows in subcritical, transcritical and supercritical regimes. Such an RFM has been recently developed at IFPEN based on physical properties lookup tables, mainly for binary and ternary chemical systems. This paper proposes an Artificial Neural Network (ANN) approach to overcome the limitations of lookup tables of thermodynamic properties and to apply RFM to multi-species combustion. A methodology for generating an optimized data set by combining a vapor–liquid equilibrium (VLE) thermodynamic solver and the in situ adaptive tabulation (ISAT) method is developed. It aims to improve the neural network training process for two-phase combustion simulations where many species are present. This ANN methodology has been implemented in the CONVERGE CFD solver and validated using a mixing layer (LOX/GH₂) benchmark from the literature relevant to rocket conditions, and an academic gaseous (H₂/O₂) case relevant to hydrogen combustion. The results show that this ANN approach makes H₂ combustion simulation possible when coupled to the RFM framework and using a 10-species kinetic mechanism. Full article

The present work investigated the thermodynamic behaviors of oxygen in a liquid Fe–Ti alloy over a wide Ti concentration range of 11.6–71.2 wt% at 1873 K by integrating equilibrium experiments with thermodynamic modeling. To prevent excessive oxidation during the equilibrium experiments, the liquid alloys were equilibrated in a purified Ar atmosphere with an oxygen partial pressure below ~10⁻²⁰ atm. Two quenching methods—furnace quenching with He gas injection and water quenching via quartz tube suction—were employed to evaluate the effect of cooling rate on total oxygen measurements. While He gas quenching led to higher measured oxygen contents owing to the formation of secondary Ti oxides, the quartz tube suction quenching method consistently yielded significantly lower oxygen values. The dissolved oxygen content increased with increasing Ti content. Electron probe microanalysis identified TiO as a stable equilibrium oxide phase above 11.6 wt% Ti, which was characterized as a face-centered cubic (FCC) rock-salt structure via electron backscatter diffraction analysis. Based on these results, a thermodynamic assessment of oxygen behavior in a liquid Fe–Ti alloy in equilibrium with TiO was performed for the first time using a modified quasichemical model. Consequently, the present model successfully reproduced the Ti–O relationship in the liquid Fe–Ti alloy across both the high-Ti concentration region saturated with TiO and the low-Ti concentration region saturated with Ti₂O₃ and Ti₃O₅. Full article

Spatial confinement strongly affects matter by altering structural stability, relaxation times, and equilibrium properties. Interest in hydrogen storage within carbon nanotube bundles has grown because it addresses practical energy needs while revealing rich confined-fluid physics. Understanding how geometry and defects influence hydrogen structure and dynamics is essential to the development of effective storage materials. Here, we investigate how confinement in single-walled carbon nanotube (SWCNT) bundles with vacancies alters the spatial distribution and phase behavior of physisorbed hydrogen. At low temperature, hydrogen forms solid-like, cylindrical layered structures both inside and outside the tubes. Raising the temperature broadens these layers and produces a liquid-like arrangement within the confined regions. This confined solid-to-liquid crossover controls storage capacity and release behavior and can be tuned by temperature, confinement dimensions, and vacancy defects. Full article