Search Results (174)

Tidal turbines represent a promising renewable energy source, generating power from ocean currents. However, due to tidal range variations, they sometimes become partially exposed to the free surface. When this occurs, the turbine experiences reduced power generation and unsteady torque caused by the asymmetric flow. Such conditions can lead to long-term degradation of turbine performance and reliability. From this perspective, a key question arises regarding how significantly power generation differs when turbines are exposed to the free surface. This study was conducted with the objective of quantitatively evaluating the differences in power generation and torque acting on the turbine due to free-surface exposure, in order to address this question. Numerical simulations considering free-surface exposure effects were developed to quantitatively assess these phenomena through Computational Fluid Dynamics (CFD). Additionally, this numerical model was validated by comparison against experimental data and verified by convergence tests. The results revealed that the tidal turbine exhibited power generation differences ranging from a maximum of 45% to a minimum of 0.44%, depending on the degree of free-surface exposure. These findings are expected to serve as valuable indicators for power generation when operating tidal turbines. Full article

This study develops a vibration model for functionally graded material (FGM) plates with embedded planar cracks. Based on thin plate theory and von Kármán-type geometric nonlinear strain assumptions, the kinetic and potential energies of each region are derived. Displacement field trial functions are constructed according to boundary conditions, and the Ritz method is employed to determine natural frequencies and vibration modes under small deformation conditions. The investigation focuses on how crack parameters and material gradient coefficients affect vibration characteristics in exponentially graded FGM plates. The results show that natural frequencies decrease with increasing crack length, while crack presence alters nodal line patterns and mode symmetry. During free vibration, the upper and lower surfaces of the crack region exhibit relative displacement. Material gradient effects induce thickness–direction asymmetry, causing non-uniform displacements between the plate’s upper and lower sections. Full article

Background: Spectacle independence is a key goal in refractive lens exchange (RLE), especially in younger, high-expectation patients. This study evaluates a novel extended monovision approach combining a monofocal aspheric intraocular lens (IOL) in the dominant eye with a rotationally asymmetric bifocal extended-depth-of-focus (EDOF) IOL in the non-dominant eye. The strategy aims to optimize full-range visual performance while minimizing photic phenomena. Methods: In this retrospective cohort study, presbyopic patients underwent bilateral RLE with a monofocal IOL (Hoya Vivinex XC1-SP; target: 0 diopters [D]) in the dominant eye and a rotationally asymmetric bifocal EDOF IOL (LENTIS LS-313 MF15; addition: +1.5 D; target: −1.25 D) in the non-dominant eye. Uncorrected distance visual acuity (UDVA, at 6 m), uncorrected intermediate visual acuity (UIVA, at 66 cm), and uncorrected near visual acuity (UNVA, at 36 cm) were assessed. Additional evaluations included binocular defocus curves, contrast sensitivity, stereoacuity, and photic phenomena. Spectacle independence and satisfaction were measured using the PRSIQ and NEI-RQL-42 questionnaires. Results: A total of 38 patients (76 eyes) were included. The mean postoperative binocular UDVA, UIVA, and UNVA were −0.03 ± 0.08, −0.08 ± 0.09, and 0.04 ± 0.08 logMAR, respectively. The defocus curve peaked at 0.0 D (6 m) with a mean visual acuity of −0.03 ± 0.08 logMAR. Functional vision better than 0.2 logMAR extended over defocus steps from +1.00 to −3.25 D. All patients were spectacle-independent for distance and intermediate vision, and 84% reported complete spectacle independence. Contrast sensitivity was within normal limits for age. Minimal photic phenomena were reported, and stereoacuity was preserved in 97% of patients (≤100 arcseconds). Conclusions: This innovative extended monovision approach, combining two different IOLs in a mini-monovision setup, provides excellent uncorrected visual acuity at all distances, high spectacle independence, and minimal side effects. It represents a compelling alternative to multifocal IOL implantation in presbyopic RLE candidates. Full article

Adsorption of multicomponent mixtures on solid substrates is essential to numerous technological processes and provides key insights into surface phenomena. Despite advancements in theoretical modeling, many approaches still assume that each adsorbate occupies a single site, thereby neglecting important effects arising from molecules that span multiple adsorption sites. In this work, we broaden the theoretical description of such systems by considering the adsorption of j distinct polyatomic species on triangular lattices. Our approach is based on (i) exact thermodynamic results for polyatomic gases on one-dimensional lattices, extended here to account for substrates with higher coordination numbers, and (ii) the “0D cavity” functional theory originally developed by Lafuente and Cuesta, which reduces to the well-known Guggenheim–DiMarzio model in the limit of rigid rods. As a case study, we explore the behavior of a three-component system consisting of dimers, linear trimers, and triangular trimers adsorbing onto a triangular lattice. This model captures the interplay between structural simplicity, multisite occupancy, configurational diversity, and competition for space, key factors in many practical scenarios involving size-asymmetric molecules. We characterize the system using total and partial isotherms, energy of adsorption, and configurational entropy of the adsorbed phase. To ensure the reliability of our theoretical predictions, we perform Monte Carlo simulations, which show excellent agreement with the analytical approaches. Our findings demonstrate that even complex adsorption systems can be efficiently described using this generalized framework, offering new insights into multicomponent surface adsorption. Full article

Noncoplanar spin textures give rise not only to unusual magnetic structures but also to emergent electromagnetic responses stemming from scalar spin chirality, such as the topological Hall effect. In this study, we theoretically investigate nonreciprocal transport phenomena induced by noncoplanar magnetic orderings through microscopic model analyses. By focusing on meron–antimeron spin textures that exhibit local scalar spin chirality while maintaining vanishing global chirality, we demonstrate that the electronic band structure becomes asymmetrically modulated, which leads to the emergence of nonreciprocal transport. The present mechanism arises purely from the noncoplanar magnetic texture itself and requires neither net magnetization nor relativistic spin–orbit coupling. We further discuss the potential relevance of our findings to the compound Gd₂PdSi₃, which has been suggested to host a meron–antimeron crystal phase at low temperatures. Full article

Span-wise homogeneous supersonic cavity flows display complicated structures due to shear layer breakdown, flow acoustic resonance, and even non-linear hydrodynamic-acoustic interactions. In practical applications, such as aircraft bays, the cavity is of finite width and has doors, both of which introduce distinctive phenomena that couple with the shear layer at the cavity lip, further modulating shear layer bifurcations and tonal mechanisms. In particular, asymmetric states manifest as ‘tornado’ vortices with significant practical consequences on the design and operation. Both inward- and outward-facing leading-wedge doors, resulting in leading edge shocks directed into and away from the cavity, are examined at select opening angles ranging from $22.5°$ to $90°$ (fully open) at Mach 1.6. The computational approach utilizes the Reynolds-Averaged Navier–Stokes equations with a one-equation model and is augmented by experimental observations of cavity floor pressure and surface oil-flow patterns. For the no-doors configuration, the asymmetric results are consistent with a long-time series DDES simulation, previously validated with two experimental databases. When fully open, outer wedge doors (OWD) yield an asymmetric flow, while inner wedge doors (IWD) display only mildly asymmetric behavior. At lower door angles (partially closed cavity), both types of doors display a successive bifurcation of the shear layer, ultimately resulting in a symmetric flow. IWD tend to promote symmetry for all angles observed, with the shear layer experiencing a pitchfork bifurcation at the ‘critical angle’ ($67.5°$). This is also true for the OWD at the ‘critical angle’ ($45°$), though an entirely different symmetric flow field is established. The first observation of pitchfork bifurcations (‘critical angle’) for the IWD is at $67.5°$ and for the OWD, $45°$, complementing experimental observations. The back wall signature of the bifurcated shear layer (impingement preference) was found to be indicative of the 3D cavity dynamics and may be used to establish a correspondence between 3D cavity dynamics and the shear layer. Below the critical angle, the symmetric flow field is comprised of counter-rotating vortex pairs at the front and back wall corners. The existence of a critical angle and the process of door opening versus closing indicate the possibility of hysteresis, a preliminary discussion of which is presented. Full article

This study addresses the long-standing difficulty of predicting the remaining useful life (RUL) of rolling bearings from highly non-stationary vibration signals by proposing WaveAtten, a symmetry-aware deep learning framework. First, mirror-symmetric and bi-orthogonal Daubechies wavelet filters are applied to decompose each raw signal into multi-scale approximation/detail pairs, explicitly preserving the left–right symmetry that characterizes periodic mechanical responses while isolating asymmetric transient faults. Next, a bidirectional sparse-attention module reinforces this structural symmetry by selecting query–key pairs in a forward/backward balanced fashion, allowing the network to weight homologous spectral patterns and suppress non-symmetric noise. Finally, the symmetry-enhanced features—augmented with temperature and other auxiliary sensor data—are fed into a long short-term memory (LSTM) network that models the symmetric progression of degradation over time. Experiments on the IEEE PHM2012 bearing dataset showed that WaveAtten achieved superior mean squared error, mean absolute error, and R² scores compared with both classical signal-processing pipelines and state-of-the-art deep models, while ablation revealed a 6–8% performance drop when the symmetry-oriented components were removed. By systematically exploiting the intrinsic symmetry of vibration phenomena, WaveAtten offers a robust and efficient route to RUL prediction, paving the way for intelligent, condition-based maintenance of industrial machinery. Full article

In integrated permanent magnet synchronous motors (IPMSMs) coupled with mechanical devices such as ball screws and reducers, complex nonlinear friction characteristics often arise, leading to asymmetrical distortions such as position “flat-top” and speed “ramp-up”. These phenomena significantly degrade the system’s positioning accuracy. To address this issue, this paper introduces a symmetry-inspired nonlinear predictive speed control approach based on the Stribeck piecewise linearized friction compensation and a generalized proportional integral (GPI) observer. The proposed method leverages the inherent symmetry in the Stribeck friction model to describe the nonlinear behavior, employing online piecewise linearization via the least squares method. A GPI observer was designed to estimate the lumped disturbance, including time-varying components in the speed dynamics, friction model deviations, and external loads. By incorporating these estimates, a nonlinear predictive controller was developed, employing a quadratic cost function to derive the optimal control law. The experimental results demonstrate that, compared to traditional integral NPC and PI controllers, the proposed method effectively restores system symmetry by eliminating the “flat-top” and “ramp-up” distortions while maintaining computational efficiency. Full article

Cell membranes contain a variety of biomolecules, especially various kinds of lipids and proteins, which constantly change with fluidity and environmental stimuli. Though Helfrich curvature elastic energy has successfully explained many phenomena for single-component membranes, a new theoretical framework for multicomponent membranes is still a challenge. In this work, we propose a generalized Helfrich free-energy functional describe equilibrium shapes and phase behaviors related to membrane heterogeneity via curvature-component coupling within a unified framework. For multicomponent membranes, a new but important Laplace–Beltrami operator is derived from the variational calculation on the integral of Gaussian curvature and applied to explain the spontaneous nanotube formation of an asymmetric glycolipid vesicle. Therefore, our general mathematical framework shows predictive capabilities beyond the existing multicomponent membrane models. A set of new curvature-component coupling Euler-Lagrange equations has been derived for global vesicle shapes associated with the composition redistribution of multicomponent membranes for the first time and specified into several typical geometric shapes. The equilibrium radii of isotonic vesicles for both spherical and cylindrical geometries are calculated. The analytical solution for isotonic vesicles reveals that membrane stability requires distinct bending rigidities among components ($k_{\mathrm{A}}\ne k_{\mathrm{B}}$, ${\overline{k}}_{\mathrm{A}}\ne {\overline{k}}_{\mathrm{B}}$) whose bending rigidities are linearly related, which is consistent with experimental observations of coexisting lipid domains. Furthermore, we elucidate the biophysical implications of the derived shape equations, linking them to experimentally observed membrane remodeling processes. Our new free-energy framework provides a baseline for more detailed microscopic membrane models. Full article

Understanding the dynamics of public opinion formation in digital environments is crucial for managing technological communications effectively. This study investigates stance interactions and opinion reversal phenomena in technical discourse through analysis of the Manus AI controversy that generated approximately 36,932 social media interactions during March 2025. Employing an integrated methodology combining Large Language Model (LLM)-enhanced stance detection with agent-based modeling (ABM), we reveal distinctive patterns challenging traditional public opinion theories. Our cross-correlation analysis identifies significant lagged interaction effects between skeptical and supportive stances, demonstrating how critical expressions trigger amplified counter-responses rather than inducing silence. Unlike prior conceptualizations of counter-silencing that emphasize ideological resistance or echo chambers, our notion of the “counter-spiral of silence” specifically highlights lagged emotional responses and reactive amplification triggered by minority expressions in digital technical discourse. We delineate its boundary conditions as arising under high emotional salience, asymmetrical expertise, and platform structures that enable real-time feedback. The agent-based simulation reproduces empirical patterns, revealing how emotional contagion and network clustering mechanisms generate “counter-spiral of silence” phenomena where challenges to dominant positions ultimately strengthen rather than weaken those positions. These findings illuminate how cognitive asymmetries between public expectations and industry realities create distinctive discourse patterns in technical contexts, offering insights for managing technology communication and predicting public response trajectories in rapidly evolving digital environments. Full article

In recent years, flexible piezoresistive sensors based on polydimethylsiloxane (PDMS) matrix materials have developed rapidly, showing broad application prospects in fields such as human motion monitoring, electronic skin, and intelligent robotics. However, achieving a balance between structural durability and fabrication simplicity remains challenging. Traditional methods for preparing PDMS flexible substrates with high porosity and high stability often require complex, costly processes. Breaking through the constraints of conventional material systems, this study innovatively combines the high elasticity of polydimethylsiloxane (PDMS) with the stochastically distributed porous topology of a sponge-derived biotemplate through biomimetic templating replication technology, fabricating a heterogeneous composite system with an architecturally asymmetric spatial network. After 5000 loading cycles, uncoated samples experienced a thickness reduction of 7.0 mm, while PDMS-coated samples showed minimal thickness changes (2.0–3.0 mm), positively correlated with curing agent content (5:1 to 20:1). The 5:1 ratio sample demonstrated exceptional mechanical stability. As evidenced, the PDMS film-encapsulated architecturally asymmetric spatial network demonstrates superior stress dissipation efficacy, effectively mitigating stress concentration phenomena inherent to symmetric configurations that induce matrix fracture, thereby achieving optimal mechanical stability. Compared to the pre-test resistance distribution of 10–248 Ω, after 5000 cyclic loading cycles, the uncoated samples exhibited a narrowed resistance range of 10–50 Ω, while PDMS-coated samples maintained a broader resistance range (10–240 Ω) as the curing agent ratio increased (from 20:1 to 5:1), demonstrating that increasing the curing agent ratio helps maintain conductive network stability. The 5:1 ratio sample displayed the lowest resistance variation rate attenuation—only 3% after 5000 cycles (vs. 80% for uncoated samples)—and consistently minimal attenuation at all stages, validating superior electrical stability. Under 0–6 kPa pressure, the 5:1 ratio device maintained a linear sensitivity of 0.157 kPa⁻¹, outperforming some existing works. Human motion monitoring experiments further confirmed its reliable signal output. Furthermore, the architecturally asymmetric spatial network of the device enables superior conformability to complex curvilinear geometries, leveraging its structural anisotropy to achieve seamless interfacial adaptation. By synergistically optimizing material composition and structural design, this study provides a novel technical method for developing highly durable flexible electronic devices. Full article

The present study investigates the control strategy of a novel doubled-fed induction generator (DFIG) with a series grid-side converter (SGSC) during grid faults. The rotor-side inverter is subject to a control strategy derived from the Model Predictive Current Control (MPCC) theory, which is implemented during periods of fault occurrence; for the series grid-side converter, the positive and negative sequence component control is implemented during both steady state and fault periods to enhance system stability and performance. The proposed coordinated control strategy is implemented on a doubly fed turbine with SGSC, while taking into account different degrees of symmetric and asymmetric faults to further evaluate the efficacy of the proposed method. The results of the simulations demonstrate the efficacy of the model-predictive current control scheme applied to the rotor-side converter under conditions of asymmetric faults. This enables the suppression of a range of phenomena, including rotor overcurrent, stator overcurrent, and overvoltage, electromagnetic torque ripple, and DC bus voltage during low-voltage ride-through (LVRT), among others. The present study confirms the viability of implementing positive and negative sequences of voltage separation control in the SGSC during both grid faults and steady state. This approach is expected to minimize the switching of SGSC control strategies and thereby reduce output power fluctuations. The Rotor Side Converter (RSC) and SGSC can perform coordinated control during faults, and the proposed method is able to improve low-voltage ride-through performance compared to existing methods, thereby preventing damage to the converter under multiple fault conditions. Full article

The non-uniform deformation and failure phenomena encountered in steeply inclined coal seams during roof-cutting and gob-side entry retaining operations demand urgent resolution. Taking the haulage roadway of the 3131 working face in Longmenxia South Coal Mine as the research background, the theoretical analysis method is adopted to explore the mechanical state of the main roof in inclined coal seams and the design of roadside support resistance. According to the structural evolution characteristics of the main roof, it is divided into four periods. Based on the elastic theory, corresponding mechanical models are established, and the mechanical expressions of the main roof stress and deflection are derived. The distribution characteristics of the main roof’s mechanical state in each zone and the influence law of the coal seam dip angle on the main roof’s mechanical state are studied. This study reveals a critical transition from symmetric to asymmetric mechanical behavior in the main roof structure due to the coal seam dip angle and roof structure evolution. The results show that, in the absence of roadside support, during the roadway retaining period, the upper surface of the main roof is in tension, and the lower surface is under compression. The stress value increases slowly from the high-sidewall side to the middle, while it increases sharply from the middle to the short-sidewall side. Under the inclined coal seam, as the dip angle of the coal and rock strata increases, the component load perpendicular to the roof direction decreases, and the roof deflection also decreases accordingly. On this basis, the design formula for the roadside support resistance of gob-side entry retaining with roof cutting in inclined coal seams is presented, and the roadside support resistance of the No. 3131 haulage roadway is designed. Building upon this foundation, a design formula for roadside support resistance in steeply inclined coal seams with roof-cutting and gob-side entry retaining has been developed. This formula was applied to the No. 3131 haulage roadway support design. Field engineering tests demonstrated that the maximum roof-to-floor deformation at the high sidewall decreased from 600 mm (unsupported condition) to 165 mm during the entry retaining period. During the advanced influence phase of secondary mining operations, the maximum deformation at the high sidewall was maintained at approximately 193 mm. Full article

Microswimmers are key for unveiling new physical phenomena underlying their propulsion, especially when driven inside complex fluids. Liquid crystals are anisotropic complex fluids that feature long-range orientational order. The propulsion of non-charged dielectric particles can be accomplished in these systems by breaking the particles’ fore-aft symmetry thanks to anisotropies in the conductivity and dielectric permittivity parameters of the liquid crystal. Under the application of an AC electric field, asymmetric osmotic flows are generated to propel non-spherical particles, whose direction of motion depends on the orientational order of the liquid crystal molecules around the inclusions. This means that, by controlling the LC orientation, one will be able to steer driven colloidal inclusions. In this experimental work, we show that a homogeneous magnetic field that is able to control the orientation of the liquid crystal molecules also allows us to determine the direction of motion of driven particles without significant changes in the propulsion mechanism. Additionally, we show that a radial configuration of the magnetic field lines can be used to generate topological defects in the liquid crystal orientational field that attract colloidal particles, leading to their clustering as rotating mills. The generated clusters were tested to study the collective motion of particles, suggesting the presence of particle–particle interactions. Full article

Compared with the traditional brushless doubly-fed generator (BDFG), the BDFG with double stator (BDFG-DS) architecture achieves enhanced configurability by physically decoupling the power and control windings onto independent stator assemblies. The design offers benefits such as expanded slot dimensions and enhanced power density, yet it remains constrained by inherent asymmetry in three phases, which causes large harmonics and torque ripples. In this paper, the working mechanism of the BDFG-DS is introduced. Then the root cause of the asymmetric phenomena is discussed. And based on the analysis, an optimization method with complementary skewed stators is developed to enhance the performance of the BDFG-DS. By adopting the appropriate combination of pole slot and skewing slot angles of the two stators, the asymmetry and performance, including harmonics and torque ripples, are improved. Meanwhile, unlike the traditional skewing slot method, the torque density and power density are not decreased. Finally, a finite element analysis model is built and simulations are conducted to demonstrate the electromagnetic optimization efficacy of the proposed skewed-stator topology. Full article