Search Results (5,423)

Ion-acoustic waves in dense quantum plasmas are strongly influenced by Fermi degeneracy, Landau quantization, and finite-temperature effects, and in many relevant environments, they also experience memory and nonlocal transport processes that cannot be captured within the planar integer Korteweg-de Vries (KdV) paradigm. In the present work, we revisit this problem by considering a two-fluid, partially degenerate electron-ion plasma in which electron trapping in the presence of a quantizing field and finite temperature is taken into account. Starting from the normalized fluid-Poisson system appropriate for such magnetized quantum plasmas, the reductive perturbation technique is used to derive the planar integer KdV equation for weakly nonlinear ion-acoustic disturbances. Within this integer-order KdV framework, we recast the evolution equation as a planar dynamical system, construct the associated Hamiltonian and effective Sagdeev-like potential, and demonstrate the existence of compressive solitary waves and nonlinear periodic modes via homoclinic and periodic phase-space orbits. Exact multi-soliton solutions and interaction states are then obtained by combining Hirota’s direct bilinear method with generalized Wronskian representations, allowing us to describe not only standard one-, two-, and three-soliton profiles but also positon-negaton interactions relevant to magnetized, partially degenerate plasmas. To incorporate hereditary and history-dependent effects that arise from anomalous transport and nonlocal temporal response in dense environments, we extend the model by introducing a Caputo time-fractional derivative, thereby obtaining a time-fractional KdV (FKdV) equation that continuously connects the classical KdV limit to fractional dynamics. The FKdV equation is analyzed using the Tantawy technique. This semi-analytical iterative scheme yields rapidly convergent series approximations for the fractional ion-acoustic soliton and provides explicit control of the approximation error. The fractional solutions show that varying the order of the Caputo derivative modifies the amplitude, width, and temporal relaxation of the solitary structures and can even split the pulse into two distinct lobes, in contrast with the nearly rigid propagation predicted by the integer-order KdV equation. Taken together, these results clarify how Landau quantization, finite electron temperature, and fractional-order memory jointly shape the morphology, robustness, and interaction properties of ion-acoustic structures in strongly magnetized quantum plasmas of astrophysical and high-energy-density laboratory interest. Full article

Titanium alloys exhibit exceptional properties that enable their widespread application. Additive manufacturing (AM) technologies offer significant advantages for titanium alloy components, including rapid prototyping, high forming accuracy, and enhanced performance. Consequently, substantial research and industrial applications have emerged in the field of titanium alloy AM. Nevertheless, a systematic comparison and synthesis of related studies remains lacking. This paper reviews four distinct categories of titanium alloy AM processes classified by energy source (laser, electron beam, electric arc, and compressed air-assisted). Each category is analyzed in detail, with comparative assessments of microstructures, performance, and applications. Secondly, the paper comprehensively discusses current and potential applications of titanium alloy AM across aerospace, medical, and industrial sectors while identifying critical research gaps for future development. Finally, the development of novel titanium alloys for AM, titanium alloy AM assisted by acoustic or magnetic fields, and 4D printing of functional titanium alloys are discussed. Full article

Ketosis is one of the most economically significant metabolic disorders affecting periparturient dairy cows, causing production losses and predisposing animals to secondary complications. Current blood-based diagnostics are invasive and provide limited insight into the underlying metabolic perturbations. This study employed an integrated three-platform metabolomics approach to characterize milk metabolite alterations in ketotic Holstein dairy cows and to evaluate milk-based biomarker panels for early ketosis detection. Milk samples from 20 healthy control (CON) cows and 6 ketotic cows were collected at 2 weeks postpartum and analyzed by direct injection/liquid chromatography–tandem mass spectrometry (DI/LC-MS/MS), proton nuclear magnetic resonance (¹H-NMR) spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS). Ketosis was confirmed by serum β-hydroxybutyrate concentrations ≥ 1400 μmol/L. Principal component analysis, partial least squares-discriminant analysis, and receiver operating characteristic (ROC) curve analyses were applied. All three platforms discriminated ketotic cows from healthy cows, with clear cluster separation validated by 2000 permutation tests (p < 0.05). DI/LC-MS/MS identified 16 significantly altered metabolites (p < 0.05), with butyrylcarnitine (C4), phosphatidylcholine 30:0 (PC 30:0), ether-linked phosphatidylcholine O-38:3 (PC O-38:3), and citrulline identified as the top discriminatory biomarkers (AUC = 0.920; 95% CI: 0.85–0.98; sensitivity = 91.7%; specificity = 93.3%). ICP-MS revealed significantly reduced selenium (Se, p = 0.017), manganese (Mn, p = 0.045), and chromium (Cr, p = 0.037), as well as elevated cobalt (Co, p = 0.014) in ketotic milk (AUC = 0.870). ¹H-NMR detected no individually significant metabolites; however, multivariate analysis distinguished groups (AUC = 0.890), with succinate (numerical fold change: +5.77×; p = 0.059), methanol (−1.94×; not significant), and acetate (+2.88×; not significant) as top VIP contributors. The combined multi-platform biomarker panel (joint classification using top VIP features from all three platforms, without formal data fusion) achieved superior diagnostic performance (AUC = 0.970; 95% CI: 0.93–1.00; sensitivity = 95.0%; specificity = 96.7%). These findings identify coordinated perturbations in glycerophospholipid metabolism, acylcarnitine profiles, amino acid homeostasis, antioxidant mineral status, and energy metabolism during early ketosis, and suggest that milk metabolomics is a promising non-invasive approach for precision dairy health monitoring, pending validation in independent cohorts. We acknowledge the small ketotic group size (n = 6) as a limitation; therefore, these findings should be considered discovery cohort observations requiring prospective validation before clinical translation. Full article

In this work, we report a theoretical study of the energy, momentum, and angular momentum of non-diffracting Tricomi beams. By utilizing the vector potential in the Lorenz gauge, we derive the explicit analytical expressions for the electric and magnetic field components of non-diffracting Tricomi beams. A canonical theory is introduced to describe the energy, momentum, spin angular momentum (SAM), and orbital angular momentum (OAM) of the non-diffracting Tricomi beams. The effects of the asymmetry constants, topological charge, and half-cone angle on the energy, momentum, SAM, and OAM of the non-diffracting Tricomi beams are simulated and analyzed. This study provides fundamental physical insights into the dynamical characteristics of non-diffracting Tricomi beams relevant to potential optical manipulation applications. Full article

This study investigates eddy currents in the dry cool superconducting MRI system by adopting a strong coupling multi-physics analysis method that integrates electromagnetic and mechanical fields. The 3D model is simplified based on the spatial distribution characteristics of the Lorentz force. A set of strong coupling matrix equations is derived by combining mechanical principles with Maxwell’s equations. The weak coupling scheme is implemented by applying displacement boundary conditions and validated through kinetic energy analysis. Through vector analysis, the origin of eddy power is explored, leading to the conclusion that the primary contribution to eddy power stems from the coupling between primary and secondary eddy currents. Furthermore, by analyzing the vector directions of primary and secondary eddy currents at specific mesh elements, the sign (positive or negative) of eddy power at different frequencies is characterized. The results show that the superposition of primary and secondary eddy currents produces positive power when they have a common directional component; conversely, the suppressive effect of secondary eddy currents results in negative power. This research deepens the understanding of the generation mechanism and influence of secondary eddy currents, providing guidance for subsequent dry cool superconducting MRI magnet optimization design. Full article

To improve temperature uniformity and reduce thermal stress-induced cracking during laser directed energy deposition (laser DED) repair of TiAl blades, this study proposes a refined induction heating coil design based on coupled electromagnetic-thermal finite element simulation. A temperature-dependent model of the induction heating process for a cast 45XD TiAl blade was established and used to compare circular and elliptical coil cross-sectional shapes. The elliptical coil reduced the magnetic field concentration at the leading and trailing edges and decreased the maximum temperature difference across the blade cross-section to below 100 K, thereby improving transverse temperature uniformity. To further improve the temperature distribution along the blade length, a variable-pitch solenoid coil with sparse turns in the middle and dense turns near both ends was designed. This arrangement improved the balance between local heat generation and heat dissipation and reduced the temperature variation within the central 10 cm region of the blade to about 10 K. Experimental validation showed engineering-level agreement with the simulation results, and the blade body was stably maintained at 1020–1030 K, satisfying the preheating requirement for laser DED repair of TiAl blades within the tested design set. Full article

Rare-earth permanent magnet synchronous motors (PMSMs) are commonly used in new energy vehicles, wind power generation, and other relevant fields due to their advantages of small size and high power density. The operation of this type of motor depends on a rare-earth permanent magnet. However, the compatibility between the permanent magnet and the motor under different motor operating conditions is unclear, which is unfavorable for the subsequent selection of motor magnets. In this study, the effects of the permanent magnet on motor performance in different operational environments were analyzed. Three different magnets, namely, N-52M, N-48SH, and SmCo-28H, were selected. Two types of operational conditions were selected: the motor temperature and input current. The load torque, the magnet’s demagnetization behavior, and the magnet’s cost-effectiveness were discussed. The results indicate that the N-52M magnet was suitable for a low temperature and low input current due to its high remanence. However, the SmCo-28H magnet should be used at high temperatures and input currents due to its superior anti-demagnetization properties. The results obtained in this study will enable comparison of the effects of different permanent magnet materials on the motor, thereby guiding the subsequent design of PMSMs. Full article

The optimization of the energy product in permanent magnets presents a complicated multi-parametric problem that encompasses a large variety of intrinsic and microstructural properties. As both high remanent magnetization and coercivity are required, the main concern in optimizing a given material is often how to deal with the trade-off between these two properties. A promising approach is to combine high-anisotropy with high-magnetization phases in chemically synthesized magnetically hard–soft nanoparticles. The magnetization reversal in such systems has been studied by micromagnetics, but most of the solutions are given for a magnetically hard shell surrounding a magnetically soft core, although the inverse configuration may be more accessible from a fabrication perspective and can even help induce tetragonicity in phases such as CoFe. Here we summarize the basic general design rules for such systems, and we present specific calculations for the FePt/CoFe system. Though in larger particles complex reversal modes that are scientifically interesting occur, these are not relevant to the problem of achieving high energy products. Optimal energy products are achieved in small particles in the homogeneous exchange spring regime. Therefore, the optimal size and phase content must be determined under the contradictory requirements of achieving homogeneous reversal and avoiding thermal fluctuations. Full article

In fecal sludges (FSs) from non-sewered sanitation systems, bound moisture constituted 46–67% of total moisture across all sanitation types investigated, yet the energetic basis for its resistance to removal has not previously been characterized. Existing classifications of moisture fractions lack quantitative binding energy data, leaving the thermodynamic limits of solid–liquid separation undefined for FS. This study investigates the distribution and binding energies of bound moisture fractions in FS obtained from ventilated pit latrines, urine-diverting dehydrating toilets, and septic tank systems. Bound moisture fractions were determined using moisture sorption isotherms, low-temperature convective drying, nuclear magnetic resonance, and thermogravimetric–differential scanning calorimetry analyses. Results show that interstitial moisture constituted 37–50% of total moisture, followed by vicinal (6–14%) and intracellular (3–9%) fractions, with net isosteric heat rising sharply below 20–30% moisture content (w.b.). Evaporation enthalpy exceeded that of bulk water at moisture contents below ~30% (w.b.), consistent with EPS-mediated adsorption and capillary confinement contributing to increased energy requirements for moisture removal and indicating a transition from capillary-controlled to structure-influenced retention. These findings provide a thermodynamic basis for interpreting why conventional mechanical dewatering stalls at a residual moisture content that differs systematically between VIP, UDDT, and septic tank sludges. These insights are relevant for improving FS treatment strategies, particularly in selecting appropriate combinations of dewatering, drying, and pre-treatment processes. Full article

The presence of metals and microplastics in the water environment is a threat to the environment and human health. The development of analytical strategies to remove both pollutants simultaneously is very important. Iron-based adsorbents are environmentally friendly and have a high capacity to remove pollutants from the environment. In this work, Fe₃O₄ magnetic nanoparticles were applied to eliminate microplastic polyethylene from water and, because of the capacity of MPs to absorb metals, lead and arsenic were simultaneously removed in a single step. All experimental conditions were optimized to achieve the highest removal efficiency of the three pollutants. The optimal experimental parameters were 210 min of contact time at room temperature and pH 7 using Fe₃O₄ NPs as an adsorbent, achieving removal efficiencies of 98% of PE-MPs, 80% of Pb(II) and 96% of As(III). Although the adsorption steps occur sequentially—first the adsorption of Pb(II) and As(III) onto the surface of the PE-MPs, followed by the magnetic capture of the metal-loaded microplastics using Fe₃O₄ nanoparticles—the proposed methodology achieves the simultaneous removal of all three pollutants in a single magnetic separation step. The thermodynamics of the process were characterized, revealing a spontaneous Langmuir-type physisorption, and the adsorbents were characterized before and after the removal process by employing field-effect scanning electron microscopy and energy-dispersive X-ray spectroscopy. Full article

BL Lacertae objects (BL Lacs) are active galactic nuclei notable for beamed emission generated in the relativistic jets, forming a small angle with respect to our line-of-sight. The broadband spectra of BL Lacs show a two-component spectral energy distribution (SED). The group of high-energy-peaked BL Lacs (HBLs) exhibit their lower-energy SED peak at the UV to X-ray frequencies. Consequently, these objects are generally bright in the 0.3–10 keV band (compared to other blazar subclasses) and allow us to carry out intense timing/spectral studies on the wide range of timescales (from years down to a few minutes). Although X-ray emission of HBLs is widely accepted to have a synchrotron origin (along with the occasional presence of the inverse-Compton component), many problems associated with the jet particle content, their acceleration up to ultra-relativistic energies and unstable mechanisms responsible for the extreme flux/spectral variability still remain to be solved. This review highlights the basic timing and polarimetric and spectral results obtained in the framework of the numerous studies of HBLs in the 0.3–10 keV band, which was covered by the X-ray instruments operating onboard the different space missions. Moreover, the plausible physical processes responsible for the observed HBL features (relativistic shocks, magnetic reconnection, turbulence etc.) are also addressed. Full article

The grid-forming (GFM) wind turbine with energy storage is regarded as a promising solution for the integration of renewable energy sources (RESs) into power systems. However, the system faces the risk of instability during large grid disturbances, such as grid voltage sags and frequency variations. To address this issue, this paper proposes a coordinated control method to enhance the transient stability of GFM wind turbines with energy storage. First, a permanent magnet synchronous generator (PMSG)-based wind turbine employing grid-forming control and integrated with an energy storage system is introduced. Then, transient stability cases are identified based on the equal area criterion (EAC) within the virtual synchronous generator (VSG) control framework. On this basis, a low-voltage ride-through (LVRT) method is developed by coordinately adjusting inertia, damping, and active power reference according to fault severity, thereby ensuring system stability under low-voltage grid fault. Furthermore, a frequency fluctuation mitigation (FFM) is proposed to suppress power oscillations under frequency disturbances. The coordinated LVRT and FFM methods enable effective stabilization of the system under grid voltage and frequency faults. Finally, simulation results validate the theoretical analysis and demonstrate the effectiveness of the proposed control strategy. Full article

PMSM-based flywheel energy storage systems require fast and robust speed regulation in the presence of parameter uncertainty, load disturbances, and measurement noise, while avoiding the cost and reliability limitations associated with mechanical encoders. This paper proposes a sensorless control framework that combines a fractional-order sliding-mode speed controller with a fractional-order sliding-mode observer. To improve dynamic performance, an improved hybrid Aquila Optimizer–African Vulture Optimization Algorithm (IHAOAVOA) is employed to tune the controller parameters, while the observer follows the proposed robust sensorless design. Simulation results show that at the 1000 rpm operating point under a 20 N·m load disturbance, the proposed method limits the startup overshoot to about 0.24%, compared with 8.02% for the PI control and 9.74% for the conventional sliding-mode control. After the disturbance is introduced at $\mathrm{t}=1.0$ s, the speed drop of the proposed method is limited to 2.80%, whereas those of the PI control and conventional sliding-mode control reach 7.20% and 5.60%, respectively. At the 8000 rpm operating point under an 80 N·m load disturbance, the proposed method maintains the same advantage, with an overshoot of about 0.04% and a speed drop of 1.88%, both lower than those of the two benchmark controllers. In sensorless operation, the sensorless scheme with the IHAOAVOA-tuned speed controller also improves transient estimation performance. At the 1000 rpm operating point, the maximum startup speed estimation error is reduced from 41.8 r/min to 34.8 r/min. At the 8000 rpm operating point, the estimation error enters the ±10 r/min band at 0.0671 s, compared with 0.0718 s for the PSO-tuned case. The electromagnetic torque responses further indicate that the proposed tuning strategy improves transient torque smoothness while maintaining comparable steady-state torque behavior. These results demonstrate that the proposed control framework provides an effective balance among fast dynamic response, disturbance rejection, sensorless estimation accuracy, and electromechanical transient smoothness for PMSM-based flywheel energy storage applications. Full article

Freezing effectively extends the shelf life of food and maintains product quality by inhibiting microorganisms, enzyme activity, and chemical reactions. However, issues such as ice crystal formation, protein denaturation, lipid oxidation, and the low-temperature adaptability of psychrophilic microorganisms during the freezing process can directly affect the final quality of frozen foods. Among these, the size and distribution of ice crystals are key factors determining the extent of tissue damage. Therefore, this review aims to identify innovative and optimized freezing and frozen storage strategies. In order to save energy and improve product quality, various new technologies have emerged in recent years, such as ultrasonic-assisted freezing, high-pressure freezing, and magnetic-field-assisted freezing. This study systematically discusses the principles, applications, and impact mechanisms of these technologies on frozen foods. Furthermore, this study proposes the future development trends of frozen foods, filling the gap in the current food industry where there is a lack of systematic discussion and evaluation of frozen foods. It provides technical support and research directions for continuous development and innovation in the field of frozen foods. Full article

The dominance of inexpensive ferrites and high-performance rare-earth-based magnets on the global market causes a significant performance gap between these materials. Fe${}_2$P-based materials are promising rare-earth-free candidates to bridge this gap, offering high magnetization and uniaxial anisotropy. In this study, density functional theory was employed to systematically analyze the influence of Si and Co substitution on the phase stabilities of such Fe${}_{2-y}$Co${}_y$P${}_{1-x}$Si${}_x$ compounds. At 0 K, Si substitution destabilizes the compounds; however, this trend is reversed at elevated temperatures, where Si significantly enhances phase stability. In contrast, Co substitution reduces competition energies at 0 K but promotes instability with increasing temperature. For quaternary Fe${}_{2-y}$Co${}_y$P${}_{1-x}$Si${}_x$ compounds, the combined presence of Si and Co leads to a pronounced expansion of the stability range of the hexagonal crystal structure, in reasonable agreement with available experimental observations. Starting from temperatures above 1000 K, several quaternary compounds exhibit negative competition energies, indicating thermodynamic stability. Among all investigated compositions, Fe${}_{1.84}$Co${}_{0.16}$P${}_{0.84}$Si${}_{0.16}$ stands out, combining particularly low competition energies with a previously reported mean-field Curie temperature of 557 K and a high magnetic hardness factor. These results identify Fe${}_{1.84}$Co${}_{0.16}$P${}_{0.84}$Si${}_{0.16}$ as a highly promising rare-earth-lean hard magnetic material for future applications. Full article