Search Results (3,374)

Linear integrators are traditionally used in motion control systems to compensate for static effects and suppress low-frequency disturbances. However, their use is inevitably accompanied by phase delays that limit the performance and robustness of control systems, especially in conditions of parametric uncertainty. In this regard, nonlinear integrators have been considered for several decades as a promising alternative that can weaken phase constraints and improve the quality of transients. In this paper, the concept of nonlinear integrators is reinterpreted in the context of self-organizing motion control of precision stages. In contrast to traditional approaches focused primarily on frequency analysis and the method of describing the function, a method is proposed for the synthesis of a self-organizing control system for nonlinear SISO objects based on catastrophe theory, namely in the class of elliptical dynamics with the property of structural stability. The control action is formed in such a way that transitions between stable modes occur due to bifurcation-conditioned self-organization, without using external switching logic. To ensure strict analytical guarantees of stability, the Lyapunov gradient-velocity vector function method is used, which guarantees aperiodic robust stability, suppression of oscillatory and chaotic modes, as well as monotonic convergence of trajectories under conditions of parameter uncertainty. The parameters of the nonlinear integrator are adapted using Self-Organizing Maps (SOM), while any parameter changes are allowed only within the regions that meet the conditions of Lyapunov stability. This approach ensures the alignment of analytical and data-oriented methods without violating the structural stability of the system. The results of numerical experiments demonstrate the superiority of the proposed method in comparison with classical linear and adaptive regulators in problems of controlling the movement of stages, especially near bifurcation boundaries and with significant parametric uncertainty. The results obtained confirm that the integration of nonlinear integrators with catastrophe theory and self-organization mechanisms forms a promising basis for the creation of robust and high-precision motion control systems of a new generation. Full article

Efficient and low-cost electrocatalysts play a crucial role in hydrogen production through the electrolysis of water. Molybdenum (Mo) carbide with a similar electronic structure to Pt was selected, and both α-MoC_1−x and α-MoC_1−x/β-Mo₂C electrocatalysts were successfully fabricated for electrochemical hydrogen evolution. A continuous optimization of the hydrothermal and carbonization conditions was carried out for the preparation of α-MoC_1−x. The biphasic molybdenum carbide catalysts were further achieved via vanadium doping with a phase transition of molybdenum carbide from α to β, which increased the specific surface area of the electrocatalyst. It was found that the V-Mo_xC catalyst obtained at a Mo/V molar addition ratio of 100:5 exhibited the best hydrogen production performance, with a β to α phase ratio of 0.827. The overpotential of V-Mo_xC at η₁₀ decreased to 99 mV, and the Tafel slope reached 65.1 mV dec⁻¹, indicating a significant improvement in performance compared to the undoped samples. Excellent stability was obtained for the as-prepared electrocatalyst for water splitting over 100 h at a current density of 10 mA cm⁻². Full article

This study addresses the impact-induced failure of drilling pump valves caused by uncontrolled disc–seat collisions by proposing a novel valve design incorporating a two-stage buffering mechanism. The design employs a wave spring as the primary buffer and an elastic sealing ring as the secondary buffer, effectively mitigating impact through staged energy dissipation. A nonlinear stiffness model of the wave spring, accounting for the transition between line and surface contact modes, was developed. Strong fluid–structure interaction transients were simulated using dynamic meshing and user-defined functions. A parametric study was conducted by systematically varying cylindrical spring stiffness (7.7–15 N/mm), preload (110–160 N), and wave spring type (D85 to D110). Results show that, compared to a conventional valve, the two-stage mechanism reduces impact velocity by 24.2%, accelerates opening response by 17.9%, and extends the closing phase by 0.28%. Increasing wave spring stiffness (from D85 to D110) decreases opening delay time by 98.7% and attenuates peak velocity by 44.4%. Optimized hybrid spring parameters can minimize closing delay height by 27.3%. By reducing seat erosion and suppressing vibration-induced failure, the two-stage buffering mechanism effectively extends valve service life and enhances operational reliability in high-cycle drilling operations. Full article

We show that recent numerical findings of universal scaling relations in systems of noisy, aligning self-propelled particles by Rüdiger Kürstencan robustly be explained by perturbation theory and known results for the Mathieu equation with purely imaginary parameter. In particular, we highlight the significance of a cascade of exceptional points that leads to non-trivial fractional scaling exponents in the singular-perturbation limit of high activity. Crucially, these features are rooted in the Fokker–Planck operator corresponding to free self-propulsion. This can be viewed as a dynamical phase transition in the dynamics of noisy active matter. We also predict that these scaling relations depend on the symmetry of the alignment interactions and discuss the relevance of this structure in the free propagation for self-alignment and cohesion-type interactions. Full article

Mn-based layered oxide cathodes are pivotal for advancing sodium-ion batteries, yet their practical deployment is hindered by structural instability and complex phase transformations during cycling. This review provides a systematic overview of recent strategies aimed at rational design and performance enhancement of these materials. It begins with fundamental thermodynamic principles governing phase formation, particularly P2/O3 structural dichotomy, and highlights the critical roles of sodium content, transition metal chemistry, and ionic potential in determining crystal stability. The emergence of high-entropy engineering is examined as a powerful approach to suppress detrimental phase transitions through configurational entropy stabilization, lattice distortion, and synergistic multi-element interactions. Furthermore, the integration of machine learning with multidimensional descriptors including electronegativity-weighted entropy and cationic potential enables more accurate predictions of phase behavior in complex compositional spaces. The review also highlights the decisive influence of synthesis protocols, where precise control over calcination conditions, atmosphere, and local elemental distribution enables the formation of targeted phase architectures, such as P2/O3 intergrowth, which exhibit superior electrochemical robustness. Collectively, these advances illustrate a shift from empirical trial and error toward a theory-guided, data-informed framework for designing high-performance layered oxide cathodes. Full article

The formation of hard/brittle layers (HBLs) forming in proximity to the transition-layer interface during the welding process of stainless steel clad plates constitutes a pivotal element in determining the limitations on joint homogeneity and toughness. In order to elucidate their formation mechanisms and develop viable suppression routes, S31603/Q420qENH clad plates were utilised to fabricate five butt joints. This was achieved by varying the carbon content of the welding consumables and the heat input in the transition layer. A programme was conducted that combined microstructural and microhardness characterisation, mechanical testing, and numerical welding simulations. The findings indicate that base-layer consumables with comparatively elevated carbon content (w(C) ≥ 0.06%) expeditiously engender a constricted, localised hardened band in close proximity to the transition-layer interface. This is characterised by the predominance of martensite and Cr-rich compounds of the M_xCr_y type, which function as the principal genesis of bending cracks. Conversely, the utilisation of low-carbon welding consumables has been shown to markedly reduce interfacial carbon activity and C-Cr segregation, thereby suppressing the precipitation of M_xCr_y phases and effectively decreasing the overall thickness of the HBLs. Further numerical analysis shows that moderately increasing the transition-layer heat input lowers the T_8/5 cooling rate and shifts the cooling path away from the martensite region. This transforms the interfacial microstructure from a localised hardened band into a more uniform, graded structure. These findings provide an engineerable process-control strategy for enhancing both microstructural uniformity and toughness in stainless steel clad joints. Full article

This study investigates how young children’s geometric reasoning develops through the act of drawing, examining how their eye movements, actions, and verbal explanations interact to reveal emerging structural awareness. Grounded in a developmental framework of structural reasoning, the study extends this model from static visual products to the dynamic processes involved in constructing geometric figures. Using an exploratory qualitative case study design, three children (ages 5.5–7.5) completed line, circle, and rectangle drawing tasks while their gaze and actions were recorded using mobile eye-tracking. Gaze data, video recordings, drawing product, and verbal responses were synchronized and analyzed frame by frame to examine gaze–action coordination. Analysis revealed a progression from partial structural awareness, where gaze remained embedded in action, to structural awareness, where gaze projected multiple steps ahead to coordinate global shape structure. Between these, an intermediate, process-oriented phase was identified, characterized by alternating gaze-in-activity and anticipatory fixations supporting local planning. These fine-grained gaze patterns reveal micro-level transitions in geometric reasoning that are not observable from final drawings alone. The study refines current models of geometric development by revealing how perceptual, representational, and embodied processes dynamically integrate during drawing, offering a more nuanced understanding of early structural reasoning and its implications for teaching geometry. Full article

Contemporary urbanisation in hot-arid cities presents coupled challenges related to sustainability, spatial efficiency, and climate resilience. This study applies Research by Design as a preliminary methodological approach to adapt the superblock typology for Riyadh’s Al-Raed neighbourhood, integrating GIS-based territorial diagnosis with Grasshopper parametric iterations. Sixteen geospatial layers, including land use, density, road hierarchy, transit access, service distribution, green cover, and climatic exposure, inform attractor-based scenario generation and a structured comparative evaluation framework assessing regulatory compliance, human scale, connectivity, and environmental and economic feasibility. The resulting loop-and-courtyard configuration reorganises local streets to strengthen first- and last-mile access, shaded pedestrian continuity, and microclimatic comfort, while supporting Saudi Vision 2030 programs, such as the Quality of Life Program, National Transport and Logistics Strategy, Riyadh Public Transport Program, and Saudi Green Initiative. Quantitative spatial indicators are interpreted alongside design-based morphological reasoning to inform spatial decisions, acknowledging climatic and cultural constraints. This study contributes a reproducible, policy-relevant digital workflow for neighborhood-scale urban transformation in Riyadh and comparable hot-arid contexts. As a preliminary Research by Design phase, it structures iterative scenarios and a structured comparative evaluation framework, providing a foundation for subsequent quantitative and empirical validation. Full article

The Asian migratory locust (Oedaleus decorus asiaticus) is a major grassland pest in northern China, with outbreak dynamics closely linked to phase transition mediated by chemical communication. This study focused on a chemosensory protein, OasiCSP12, to explore its potential role in this process. We analyzed its expression patterns via qRT-PCR, purified the recombinant protein, and identified potential ligands through fluorescence competitive binding assays. Structural insights were gained through homology modeling, molecular docking, and molecular dynamics simulations, with binding energetics assessed using MM/PBSA. Results showed that OasiCSP12 expression is phase- and sex-specific, being significantly upregulated in gregarious adult antennae. The protein bound selectively to 15 locust body-surface volatiles, including aldehydes and esters. Its structure features a hydrophobic binding cavity where van der Waals interactions, primarily predicted to be mediated by residues Val86, Leu71, and Trp101, likely stabilize ligand complexes. These findings indicate that OasiCSP12 is potentially associated with both chemical perception and phase regulation in O. d. asiaticus, providing a candidate target for developing behavior-based green control strategies against this pest. Full article

Weakly nonlinear oscillators display complex behavior that perturbation methods struggle to analyze, particularly near critical thresholds. The non-perturbation approach (NPA) offers a unified, parameter-agnostic approach that is effective in strongly resonant situations, accurately capturing global phase space structures, and directly addressing chaotic transitions, providing predictive insights where traditional methods fail. The NPA as a novel technique successfully converts the nonlinear weakly oscillator of the ordinary differential equation (ODE) into a linear issue. Theoretical findings are confirmed through a numerical comparison using Mathematica Software (MS). The results of the numerical solution (NS) show excellent agreement. It is commonly acknowledged that all conventional perturbation methods utilize Taylor expansion to augment restoring forces, hence optimizing the usual conditions. A comprehensive analysis of the issue’s stability is easily achievable via NPA. Accordingly, when evaluating NS estimates of weakly nonlinear oscillators, NPA occupations serve as a more useful form of responsibility. Additionally, the stability analysis is easily accomplished via NPA. The system’s dynamics are examined by chaotic analyses, incorporating bifurcation diagrams (BDs), Poincaré maps (PMs), and Lyapunov exponents (LEs). This analysis identifies transitions between regular and complicated behavior and thoroughly examines the system’s stability features. The results provide a comprehensive understanding of the fundamental nonlinear dynamics and offer significant insights for future research on analogous systems. Full article

Cyanate ester resins are widely recognized for their excellent thermal stability, low dielectric loss, and high glass transition temperature, making them attractive for advanced electronic and communication applications. However, their inherent brittleness and limited filler compatibility restricts broader use. In this study, cyanate ester composites were developed by incorporating transparent and opaque borosilicate glass powders modified with silane coupling agents—3-Triethoxysilylpropyl isocyanate (TESPI) and 3-Isocyana-topropyl trimethoxysilane (IPTMS)—to enhance interfacial adhesion and crosslink density. The transparent (CTF) and opaque (COF) composite systems were fabricated with varying filler contents (5–20 wt%), and their structural, mechanical, and dielectric performances were systematically characterized through X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Energy-Dispersive X-ray Spectroscopy (EDX) and dielectric performance analyses. The results revealed that both filler types enhanced the dielectric and mechanical stability of the cyanate ester matrix; however, the COF-15 composite, containing 15 wt% opaque glass, exhibited the highest tensile strength of approximately 125.70 ± 1.50 MPa, and the dielectric constant increased from 2.86 ± 0.1 (neat matrix) to about 5.0 ± 0.1 while maintaining a low loss tangent (0.007@1 MHz). These improvements were attributed to the zirconium-enriched opaque glass phase, which promoted strong interfacial bonding, compact microstructure, and effective polarization control. Full article

This study presents a reliable methodology for analyzing reinforced ultra-high-performance fiber-reinforced concrete (UHPFRC) elements by linking material behavior to structural performance. A non-linear finite element model (NLFEM) is proposed to simulate the tensile response of reinforced UHPFRC elements, with particular emphasis on shrinkage effects. The model operates in two phases: the first simulates shrinkage during specimen storage and the second simulates the mechanical tensile test, using the internal stresses from the first phase as initial conditions. The model was validated through an experimental program involving reinforced UHPFRC ties. The NLFEM accurately reproduced the load–displacement response using average UHPFRC tensile parameters obtained from a simplified Four-Point bending test Inverse Analysis method (4P-IA). It reliably predicted the shrinkage strain range and its impact on stiffness loss during microcrack initiation and stabilization, where tension-stiffening behavior is critical. Additionally, the simulation from the model captured the transition from microcracking to macrocrack formation and the role of fiber bridging in maintaining stiffness. The predicted shrinkage strain aligns with values reported in the literature and represents a conservative upper bound, neglecting the potential effects of creep and relaxation. Overall, the NLFEM effectively simulates the full tension-stiffening behavior of reinforced UHPFRC, including three-dimensional effects, and provides a reliable tool for structural analysis and design. Full article

Molybdenum disulfide (MoS₂) films are promising solid lubricants for aerospace and other advanced applications, yet their tribological performance is highly sensitive to environmental conditions. To enhance environmental adaptability, Zr-doped MoS₂ composite films were prepared by magnetron co-sputtering, and their composition, microstructure, mechanical properties, and tribological behavior were systematically investigated. The results showed that the as-deposited MoS₂ films exhibited a nearly stoichiometric sulfur-to-molybdenum ratio (S/Mo ≈ 2), while the Zr-doped MoS₂ composite films showed sulfur-deficient, sub-stoichiometric ratios (S/Mo < 2). Pure MoS₂ films displayed a porous columnar structure, whereas with the incorporation of Zr, the columnar structure becomes progressively more compact. Moreover, the film structure transitions from a purely crystalline form to a two-phase structure with both crystalline and amorphous phases coexisting. The hardness and elastic modulus of the films increased with the addition of Zr, mainly due to the densification of the structure and the disorder introduced in the film. Moderate Zr doping markedly improved the friction and wear performance of composite films across vacuum, atmospheric, and humid environments. The optimal film achieved a coefficient of friction (COF) of 0.02 and wear rate of 6.23 × 10⁻⁸ mm³/N·m in vacuum and COFs of 0.10 with low wear rates in both atmospheric and humid conditions. By adjusting the Zr target power to modulate Zr content, the crystallographic orientation and microstructure of MoS₂-Zr composite films could be tailored, thereby regulating their mechanical and tribological properties. This study provides theoretical guidance for the application of metal-doped MoS₂ composite films under alternating environmental conditions. Full article

Accurately characterizing spatiotemporal patterns of carbon emissions and their driving mechanisms is essential for advancing regional low-carbon transitions. Focusing on northeast China, a representative old industrial base, this study develops a spatialized carbon emission estimation framework using an XGBoost model that integrates nighttime light data, land-use information, population, and economic indicators. A 1 km resolution carbon emission dataset spanning 2000 to 2021 is generated, and the SHAP method reveals nonlinear responses and stage-dependent evolutions of key driving factors. The results demonstrate three key findings. Carbon emissions in northeast China increased from 636 Mt in 2000 to 1131 Mt in 2021, exhibiting three distinct phases: rapid expansion (2000–2010, +36%), peak stabilization (2010–2015, +13%), and localized contraction (2015–2021, +3%). Liaoning Province contributed 46% of total emissions in 2021, while Jilin showed the fastest growth rate at 92%. County-level Moran’s I values (0.292–0.349) remain substantially lower than city-level values (0.642–0.700), revealing scale-dependent spatial clustering. High–high clusters concentrated persistently in southern Liaoning, encompassing eight cities by 2010, whereas low–low clusters dominated northern Heilongjiang. Population and GDP exhibited saturating marginal effects after 2015, with SHAP values plateauing beyond thresholds of approximately 450,000 persons and 420 billion CNY respectively, indicating gradual decoupling between economic growth and emissions. Industrial mining land influence declined by 68% from 2005 to 2020, while urban land-use ratio maintained stable contributions. This high-resolution spatiotemporal dataset provides empirical evidence for designing threshold-based emission reduction policies, identifying regional transfer risks, and implementing county-level differentiated strategies in old industrial bases undergoing low-carbon transition. The XGBoost–SHAP framework demonstrates transferability to other heavy industrial regions facing similar structural transformation challenges. Full article

The annual soccer training cycle consists of preparatory, competitive, and transition periods. The transition phase is usually characterized by a decrease in training volume, which may lead to detraining and declines in physical fitness. The aim of this study was to examine the effects of a structured transitional training program on anthropometric characteristics, aerobic capacity, and jumping performance in young soccer players. Twenty-three under-17 players participated in the study and, following a two-week period of training cessation, completed a three-week program that included aerobic training three times per week (continuous and interval running sessions) and strength progressive resistance training twice per week. Pre- and post-intervention measurements were analyzed using paired-samples t-tests, with statistical significance set at p < 0.05. The results revealed significant reductions in body fat percentage (p = 0.016, d = 0.547), body fat mass (p = 0.018, d = 0.535), and resting systolic blood pressure (p = 0.024, d = 0.507). Additionally, time to reach the anaerobic threshold (p = 0.022, d = −0.515) and movement speed at the anaerobic threshold (p = 0.029, d = −0.487) significantly increased. No significant changes were observed in the remaining variables. These findings indicate that a three-week transition-period training program combining structured aerobic running drills with progressive resistance training can induce favorable adaptations in selected anthropometric and physiological parameters in youth soccer players. However, the lack of a control group should be considered when interpreting the magnitude of the program’s effects. Full article