Search Results (1,838)

The maneuvering flight of future aircraft which employ morphing variable camber wings (VCWs) requires rapid and accurate aerodynamic regulation. However, the dynamic lift responses during fast morphing deflection exhibit unsteady hysteresis effects, hindering shape and flight control performance. This study proposes a novel modeling and feedforward compensation algorithm based on the Prandtl–Ishlinskii (PI) model to identify and mitigate such unsteady hysteresis effects from a control perspective. First, unsteady lift responses of a two-dimensional trailing-edge VCW under periodic and non-periodic morphing motions are analyzed, and the influences of morphing trajectories on lift characteristics are investigated. The results reveal that the maximum lift decreases significantly as the morphing frequency increases. Under point-to-point non-periodic morphing conditions, pronounced hysteretic lift responses are observed and are strongly influenced by the morphing trajectories. A forward model mapping “morphing trajectory-lift response” is developed using PI hysteresis operators and log(t)-creep operators, identified using time-domain data from two-dimensional computational fluid dynamics (CFD) calculations. From this, an inverse model of the “expected lift response-compensated morphing trajectory” is derived using a hysteresis compensation function. Simulations indicate that periodic lift hysteresis is effectively compensated, yielding a quasi-steady linear relationship. For fast terminal morphing, compensated trajectories enable lift to reach targets rapidly, smoothly, and stably without lag. Robustness is validated for varying lift targets and terminal times. This work offers new insights into fast morphing-wing and high-maneuverability control of future smart aircraft. Full article

Akerlof’s classical theory of the “Market for Lemons,” which conceptualizes adverse selection driven by information asymmetry, established the foundation of information economics. While the traditional model assumes static equilibria among a limited number of agents, analyzing its behavioral dynamics within large-scale, complex network environments remains a highly relevant task in computational social science. This study extends the classical lemon market model into a nonlinear dynamical system on adaptive networks. We mathematically elucidate macro-level social phase transitions—specifically structural exclusion such as scapegoating and collective ostracism—induced by computational cognitive limits, and evaluate optimal intervention strategies to mitigate these systemic failures. Multi-agent simulations utilizing large-scale tensor operations demonstrate that autonomous edge rewiring under incomplete information does not merely result in the uniform displacement of high-quality goods as predicted by static theory. Instead, the network self-organizes into an irreversible structural division: a core group of influential agents monopolizes high-quality information, while marginalized agents are isolated into a peripheral “lemon echo chamber” where only low-quality information circulates. To address this structural pathology under a resource constraint limiting intervention to 10% of the total agents, we evaluated two distinct approaches. The results indicate that providing informational support to influential hubs functions as a trap that exacerbates systemic inequality, superficially elevating the overall market evaluation but permanently fixing the exclusion gap. Conversely, the forced maintenance and protection of “weak ties” bridging disconnected clusters constitutes the mathematically optimal solution to dissolve fragmentation, effectively eliminating the price gap and facilitating social inclusion. Furthermore, this study demonstrates that the mechanism of social exclusion exhibits strong hysteresis effects. A distinct tipping point governs the progression toward a fragmented lemon echo chamber. Interventions implemented after crossing this critical threshold fail to restore the system to its baseline state despite identical resource expenditure, confirming the presence of an irreversible phase transition. These findings establish that the collapse dynamics outlined in the classical lemon market serve as a generalized model for explaining contemporary collective ostracism driven by information cascades. Consequently, the analysis highlights the necessity of early intervention prior to critical thresholds and the systemic preservation of structural bypasses rather than post-hoc remediation. Full article

Flexible pressure sensors serve as core sensing components for wearable health monitoring systems, electronic skins for soft robots, and flexible human–machine interaction devices. Benefiting from the interfacial electric double-layer polarization effect, iontronic sensing delivers far higher pressure response sensitivity than conventional parallel-plate capacitive sensors, endowing it with distinctive advantages in the detection of weak physiological signals. Nevertheless, current dense ionic thin-film dielectric layers suffer from limited deformation space under compression and poor low-pressure sensing capability. Mainstream high-precision micropillar arrays are fabricated via photolithography, 3D printing, and metal etching molds, which require costly equipment and complicated fabrication procedures, making large-area mass production unfeasible. Random frosted concave-convex microstructures feature disordered dimensions, leading to severe device hysteresis and narrow linear ranges, which fail to achieve ultrahigh sensitivity alongside a wide pressure detection range simultaneously. To address the aforementioned multiple bottlenecks, this paper proposes a low-cost resin template replication process to fabricate TPU-based ionic thin-film dielectric layers with ordered micropillar array microstructures. Combined with inkjet-printed silver conductive PI flexible electrodes, an iontronic flexible pressure sensor with a sandwich layered structure is constructed. Multi-dimensional investigations including microscopic morphology characterization, electromechanical sensing performance calibration, and human wearable application tests are systematically implemented to thoroughly elucidate the synergistic enhancement mechanism of the arrayed micropillars. Test results demonstrate that the effective pressure detection range of the sensor spans 0–1038 kPa, accommodating ultra-low pressures such as pulse signals as well as medium-to-high-pressure loads including joint bending. The sensitivity reaches 23.27 kPa⁻¹ within the low-pressure range of 0–200 kPa and remains stable at 3.52 kPa⁻¹ in the high-pressure range of 200–1038 kPa, with piecewise linear fitting correlation coefficients of 0.93 and 0.96 respectively. Both the response time and recovery time of the device are 40 ms, and the hysteresis error throughout the loading-unloading cycle is merely 2.62%. After 20,000 consecutive cyclic loading-unloading tests, the peak capacitance output only decays by 5.1%, verifying outstanding mechanical fatigue resistance and electrical stability. Validations in multi-scenario applications prove that the sensor can accurately capture human physiological and motion signals including radial artery pulses, laryngeal deformation induced by multi-syllable vocalization, and multi-angle bending of fingers and elbow joints, suitable for home-based health monitoring, quantitative rehabilitation training, flexible tactile interaction and other scenarios. The entire fabrication process eliminates high-precision micro-nano processing equipment such as photolithography systems, plasma etchers and 3D printers; only general chemical raw materials and conventional laboratory instruments are adopted. The reusable templates enable low manufacturing costs and large-area coating forming, offering a novel low-cost technical solution for the engineering implementation and industrialization of high-performance iontronic flexible pressure sensors. Full article

In this paper, we propose a layered structure composed of Weyl semimetal (WSM) and one-dimensional photonic crystal (1D-PhC) to achieve low-threshold and tunable optical bistability (OB). By exploiting the bandgap characteristics of the photonic crystal and the strong third-order nonlinearity of WSM in the terahertz regime, reflective OB is realized within the photonic bandgap. It is shown that at certain frequencies inside the bandgap, the reflectance exhibits a jump with an increasing incident electric field, manifesting a clear hysteresis loop. The bistable threshold and hysteresis width can be effectively tailored by adjusting the Fermi energy and the thickness of the WSM layer. In addition, the influence of the incident angle and the parameters of the spacer layer on the OB threshold has also been elucidated. After parameter optimization, the incident electric field threshold is reduced to the order of 10⁶ V/m. We believe that this structure can provide a reference for constructing optical bistable schemes with simple structures and low thresholds. Full article

Brush seals using compliant bristle packs can reduce turbomachinery leakage more effectively than conventional labyrinth seals, but their coupled structural and flow behavior makes design difficult. Under large pressure loading, bristles can deflect, lose contact with the rotor, and generate clearance, causing the sharp leakage increase known as blow-out. This study develops a model linking nonlinear bristle deflection, rotor–bristle contact loss, and leakage response. The bristle is treated as an inextensible nonlinear elastic member subjected to distributed pressure loading, backing-plate support, and frictional rotor contact. Contact and separated states are solved iteratively using boundary-value and initial-value solvers. Leakage through the bristle pack is calculated using a random bristle-bed formulation, and leakage through generated clearance is evaluated with an orifice-flow model. The model agrees well with published bristle-deflection predictions. Increasing pressure load reduces normal contact force until lift-off occurs, producing clearance and a sharp rise in leakage. Increasing front-plate free height shifted lift-off from pressure ratio ≈4 to ≈2, while clearance flow contributed up to 36.5% after lift-off. Brush-seal blowout is therefore governed by the transition from rotor–bristle contact to separation. Lower back-plate height can delay blow-out, but hysteresis and durability tradeoffs must be considered. Full article

As a key energy-conversion component of tower gravity energy storage systems (T-SGESs), the hoisting structure is susceptible to large-amplitude coupled vibrations when the dominant frequency of a continuous external excitation approaches one of its natural frequencies, potentially compromising operational stability and safety. To characterize this behavior, a two-degree-of-freedom nonlinear dynamic model is developed based on Hamilton’s principle. Eigenvalue and modal analyses are performed to determine the natural frequencies and modal characteristics of the coupled system, while the second-mode primary resonance is further analyzed using the method of multiple scales and validated through numerical frequency-sweep simulations. Near the second-mode primary resonance, the system exhibits a pronounced hardening-type nonlinear response characterized by multistability, saddle-node bifurcations, jump transitions, and hysteresis. Parametric analysis indicates that greater attention should be paid to short-rope and low-payload operating conditions, under which the system tends to exhibit stronger nonlinear responses and larger payload swing amplitudes near the second-mode primary resonance. Meanwhile, the nonlinear resonance response of the hoisting structure can be effectively mitigated through enhanced equivalent stiffness and damping, which substantially narrow the multistable frequency interval. At a damping ratio of 0.04, the system transitions from a multivalued response to a single stable branch, with a marked reduction in payload swing amplitude. These findings identify the second-mode primary resonance as a critical nonlinear operating regime and provide a quantitative basis for resonance avoidance and parameter regulation in T-SGES hoisting systems. Full article

Proton exchange membrane fuel cell (PEMFC) durability under dynamic operation remains a major challenge because the observed voltage decay may combine persistent and transient performance changes. This study presents a condition-aware and data-driven analysis of PEMFC degradation under a dynamic fuel cell load cycle (FC-DLC). A public single-cell PEMFC dataset was reconstructed into 3076 dynamic cycles over 1008.24 h of operation and complemented with polarization curves measured directly after dynamic operation and after 12 h of shutdown rest. Load-resolved voltage indicators, polarization descriptors, direct-to-after-rest difference metrics, hysteresis indices, and uncertainty-evaluated short-horizon forecasting models were developed. The dynamic analysis showed that voltage degradation was strongly current-dependent, with the early-to-late voltage drop increasing from 23.09 mV at 0 A to more than 76 mV at the highest current levels. Over the common 100–1000 h comparison window, maximum power decreased by 9.31% in the direct condition and by 12.00% in the after-rest condition, whereas the voltage–current area decreased by 11.79% and 10.40%, respectively. Therefore, the after-rest temporal losses were not uniformly smaller and depended on the selected indicator and current region. The comparison between direct and after-rest curves revealed persistent after-rest minus direct voltage differences of 30–45 mV in medium- and high-current regions even after 1000 h. A sensitivity analysis showed that the voltage-cleaning threshold had no measurable effect on the reported dynamic indicators. For high-load voltage forecasting, Ridge regression achieved RMSE values of 0.00936 V and 0.01134 V at 50- and 100-cycle horizons, improving upon the persistence baseline by 29.7% and 23.5%, respectively. These error reductions were statistically significant, although the corresponding $R^2$ values remained negative on the late-life temporal holdout. The ablation analysis further showed that the complete feature set was not systematically optimal, and the best-performing feature group depended on the target and forecasting horizon. Nominal 90% conformal coverage was adequate at 50 cycles (91.25%) but decreased to 55.03% at 100 cycles, indicating loss of calibration under the longer temporal horizon. Overall, the proposed framework integrates load-dependent voltage-loss characterization, direct and after-rest measurement conditions, feature-group ablation, persistence benchmarking, and uncertainty evaluation without assigning the observed measurement-condition difference to a unique reversible or irreversible mechanism or claiming a validated remaining-useful-life or maintenance-decision system. Full article

The moisture sorption isotherms of corn extrudates fortified with ultrafiltration (UF) concentrate derived from rose wastewater (RWW) were examined. Two formulations containing 4 g (sample S4) and 11 g (sample S11) of retentate, respectively, per 100 g of semolina were prepared and subsequently extruded. Adsorption and desorption isotherms of both samples were determined at 10 °C, 25 °C and 40 °C using the static gravimetric method within a water activity range of 0.11–0.85. The experimental data of equilibrium moisture content (EMC) were fitted using modified GAB, modified Oswin, and modified Halsey equations. The monolayer moisture content of the samples was determined using the BET model. The results showed that the sorption isotherms exhibited a typical sigmoidal (Type II) shape and a pronounced hysteresis effect between adsorption and desorption. The hysteresis effect decreased with increasing temperature. Based on the combined evaluation of error analysis and residual distribution, the modified Oswin model provided the most balanced overall performance and was determined as suitable for the description of the sorption isotherms of the extrudates studied. The effect of UF-retentate level on EMC was not uniform and depended on temperature, water activity, and sorption direction. The monolayer moisture content of the extrudates varied from 4.08 to 8.39% d.b. The higher retentate level was generally associated with higher monolayer moisture values. Packaging and storage at the theoretically estimated range of water activities from 0.09 to 0.24 may be expected to maintain EMCs close to the monolayer. Full article

Adaptive feedback can destabilize a loop that would be stable under any fixed gain, so the speed at which the gain adapts is itself a design parameter. We study this effect in a minimal three-dimensional model motivated by the photocatalytic degradation of microplastics: a pollutant concentration is driven toward a setpoint by an ultraviolet (UV) actuator whose gain adapts online. The model has a single bilinear nonlinearity, so the local analysis can be carried out in closed form. Under an explicit feasibility condition, the system has a unique positive equilibrium. The Routh–Hurwitz criterion shows that this equilibrium is locally asymptotically stable below an explicit critical adaptation speed ${\kappa }_c$ and unstable above it. At $\kappa ={\kappa }_c$, a purely imaginary eigenvalue pair crosses the imaginary axis transversally, and a Hopf bifurcation occurs, with an explicit onset frequency. The first Lyapunov coefficient is computed in closed form; it separates a supercritical onset, for well-damped actuators, from a subcritical onset with hysteresis, for weakly damped actuators. Numerical experiments confirm the predicted limit cycle and the classification. All the stability results established here are local. Full article

This study investigates the temperature-responsive thermodynamic behavior of a zinc-based flexible metal–organic framework for ethylene/ethane C₂H₄/C₂H₆ separation. Isothermal adsorption suggested a highly sensitive, temperature-dependent guest-induced structural transition. At 273 K, C₂H₄ triggers a pronounced gate-opening effect at low pressures with a broad desorption hysteresis loop, while C₂H₆ shows only a marginal stepwise uptake increase at about 0.6 bar. Crucially, elevating the temperature to 298 K shifts the C₂H₄ transition threshold to higher pressures and completely suppresses the C₂H₆ response. This divergence enables the selective triggering of the framework expansion exclusively by C₂H₄ at room temperature. Further heating to 323 K entirely suppresses phase-transition characteristics for both gases. Dynamic mixed-gas breakthrough experiments confirm that precise thermal regulation strikes an optimal balance, achieving maximized fixed-bed separation selectivity while preserving a substantial capacity. This work demonstrates temperature as a key parameter to tailor the dynamic separation performance of flexible adsorbents in practical PSA/TSA applications. Full article

We present a brief review that highlights the importance of III-Nitride semiconductor compounds according to their structural, compositional, morphological, and optical properties, which have significant applications in new semiconductor devices and play a fundamental role in modern electronic and optoelectronic technologies. The importance of sputtering as a viable alternative for obtaining III-Nitride semiconductor compounds is discussed. This is due to its versatility, cost, ease of handling, and advantages provided by the physics of its operation in obtaining thin films compared to techniques such as metal–organic chemical vapor deposition (MOCVD), atomic layer deposition (ALD), and molecular beam epitaxy (MBE). The physics of the sputtering method is briefly and clearly described, including magnetron configurations, plasma generation, energy dependence of sputtering, reactive sputtering, hysteresis effects, target types, and the importance of temperature and working distance between the substrate and target. In addition, the review of the literature on the application of sputtering for obtaining III-Nitride semiconductor compounds is presented. Furthermore, this review also highlights the future of sputtering, which is moving towards high-power pulsation, atomic-level precision, and AI-driven automation due to the miniaturization of electronics, advances in green technology, and innovations in plasma control to increase film density and reduce target material loss. Full article

Transparent conducting oxides and electron transport layers are central to optoelectronic devices, yet their interfacial electronic behavior remains strongly dependent on substrate chemistry, defect states, and surface potential alignment. Here, we compare ITO and FTO transparent electrodes coated with ZnO and TiO₂, combining ab initio simulations, surface potential mapping, Hall effect measurements, sheet resistance, microscopy, and optical spectroscopy. Density functional calculations show that both ITO and FTO behave as degenerately doped n-type transparent conducting oxides, but with distinct work functions, surface dipoles, and donor-state distributions, leading to different interfacial charge-transfer tendencies. ZnO- and TiO₂-coated substrates display markedly different temperature-dependent transport, including resistance hysteresis and carrier-type switching, with FTO-based heterojunctions showing more clearly defined transitions due to the greater thermal stability of FTO. Scanning Kelvin probe (SKP) measurements reveal that ZnO more effectively accepts electrons from ITO or FTO, whereas TiO₂ shows weaker electron accumulation and more resistive interfacial behavior. Optical measurements and HSE06-based simulations confirm that TiO₂ behaves as a wider-gap ultraviolet absorber, while ZnO exhibits a lower-energy absorption onset, with real spectra additionally shaped by substrate, thickness, scattering, and defect contributions. The results show that transparent conducting oxide substrates are active electronic participants, not passive supports, in ZnO- and TiO₂-based optoelectronic interfaces. Full article

Freezing rain poses a substantial hazard to the operation and safety of unmanned aerial vehicles (UAVs) in cold-weather environments. In the present study, a comprehensive experimental campaign was conducted to investigate the effect of surface icephobicity on ice accretion and shedding from rotating UAV propellers under freezing-rain conditions. A novel, durable, slippery liquid-like surface (SLLS) coating, characterized by low contact-angle hysteresis and low ice adhesion, is utilized as a passive strategy for UAV icing mitigation. The coating was assessed through wettability and ice-adhesion measurements, phase-locked high-speed imaging of supercooled large-droplet impingements, rotating-propeller ice accretion experiments, accelerated rain erosion testing, and surface-topography characterization. The measurement results revealed distinct normal and oblique droplet impingement regimes and demonstrated that the evolving leading-edge ice geometry substantially altered droplet deformation, liquid redistribution, and subsequent ice growth. Compared with the uncoated, baseline propeller, the SLLS-coated propeller was found to promote earlier ice shedding and reduce the ice-induced power consumption by approximately 36%. These findings highlight the potential of SLLS coatings as a promising strategy for UAV propeller icing protection to ensure safer and more efficient UAV operations under adverse weather conditions. Full article

Upper-limb motor dysfunction resulting from neurological disorders severely limits patients’ activities of daily living and social participation. Pneumatic upper-limb rehabilitation robots have emerged as a promising intervention owing to their inherent compliance, lightweight design, and high power-to-weight ratio, which facilitate safe, repetitive, and home-based training. Despite these advantages, extensive clinical translation remains hindered by challenges including actuator hysteresis, nonlinear dynamics, limited accuracy in intention recognition, and inconsistent clinical evaluation metrics. This review systematically examines recent advancements in pneumatic upper-limb rehabilitation robots across four critical dimensions: structural design, human–robot interaction, control strategies, and clinical translation. We comparatively analyze rigid exoskeletons, soft wearable devices, and rigid–soft hybrid configurations based on output capability, motion accuracy, comfort, and clinical applicability. The findings suggest that while rigid systems offer high precision and soft systems maximize safety, rigid–soft hybrid architectures represent a critical developmental trend for balancing motion accuracy with interaction compliance. Furthermore, the review evaluates multimodal sensing techniques (e.g., EMG, EEG, and IMUs) for motion intention decoding and training state monitoring, alongside conventional, adaptive, and artificial intelligence-driven control methods aimed at compensating for pneumatic nonlinearity and improving real-time response. Current clinical evidence indicates that these systems effectively enhance upper-limb function and muscle strength, particularly in post-stroke rehabilitation; however, existing trials are frequently constrained by small sample sizes, short interventions, and heterogeneous protocols. Future research must prioritize rigid–soft hybrid architectures, robust multimodal sensor fusion, digital twin-assisted assessment, adaptive intelligent control, and standardized home-based rehabilitation platforms. Ultimately, this comprehensive review provides a concise reference for the design optimization and clinical deployment of next-generation pneumatic rehabilitation systems. Full article

Flexible capacitive humidity sensors are pivotal for next-generation wearable electronics and Internet of Things (IoT) applications. However, conventional devices suffer from severe salt leaching and delamination of hygroscopic sensing materials, alongside poor interfacial adhesion and mechanical fragility of metallic electrodes. Herein, an innovative in situ strategy is reported for constructing LiCl-CH₃COOK/laser-induced graphene (LIG) composite flexible electrodes via single-step laser direct writing. This approach simultaneously patterns three-dimensional (3D) porous LIG interdigitated networks on polyimide substrates and drives deep infiltration of the LiCl-CH₃COOK hygroscopic phase within the graphene pores. The 3D interconnected LIG skeleton not only provides abundant physical anchoring sites and rapid water vapor transport channels but also effectively suppresses the physical loss and leaching of the deliquesced salts through micro-nanoscale spatial confinement, yielding remarkable interfacial stability and cycling lifetime. Benefiting from the synergistic deliquescence of the composite salts, the sensor delivers an exceptional sensitivity of 65,570% (ΔC/C₀), moderate response/recovery times of 75/90 s, and ultralow hysteresis of 0.981%. Furthermore, the streamlined laser-scribing route replaces conventional costly microfabrication sequences, enabling low-cost, high-precision customization. Demonstrations in human respiration monitoring and smart agriculture validate the sensor’s superior reliability and practical applicability, establishing a novel pathway for miniaturized, highly integrated, and robust flexible humidity detection systems. Full article