Search Results (7,040)

With the increasing demands for autonomy and coverage efficiency in tasks such as security patrol and post-disaster exploration using mobile robots, achieving random, efficient, and complete coverage path planning has become a critical challenge. Traditional chaotic path planning methods, while capable of generating unpredictable trajectories, still have limitations in terms of randomness strength, traversal uniformity, and convergence coverage. To address this, this study proposes a complete-coverage random path planning method based on a novel four-dimensional fractal-fractional multi-scroll chaotic system. The main contributions of this research are as follows: First, by introducing additional state variables and fractal-fractional operators into the classical Chen system, a fractal-fractional chaotic system with a multi-scroll attractor structure is constructed. The output of this system is then mapped into robot angular velocity commands to achieve area coverage in unknown environments. Key findings include: the novel chaotic system possesses two positive Lyapunov exponents; Spectral Entropy (SE) and Complexity (CO) analyses indicate that when parameter B is fixed and the fractional order α increases, the dynamic complexity of the system significantly rises; in a 50 × 50 grid environment, the robot driven by this system achieved a coverage rate of 98.88% within 10,000 iterations, outperforming methods based on Lorenz, Chua systems, and random walks; ablation experiments further demonstrate that the combined effects of the fractal order β, fractional order α, and multi-scroll nonlinear terms are key to enhancing system complexity and coverage performance. The significance of this study lies in that it not only provides new ideas for constructing complex chaotic systems but also offers a reliable theoretical foundation and practical solution for mobile robots to perform efficient, random, and high-coverage autonomous inspection tasks in unknown regions. Full article

Background/Objectives: This study aimed to evaluate macular choroidal blood flow dynamics and structural alterations in children with hyperopic anisometropic amblyopia and compare these findings with those of the fellow eyes. Methods: This retrospective observational study included 36 eyes from 18 children (mean age: 4.9 years) with unilateral hyperopic anisometropic amblyopia. Central choroidal thickness (CCT) was measured using enhanced depth imaging optical coherence tomography. Macular choroidal hemodynamics were assessed using laser speckle flowgraphy. Mean blur rate (MBR) was used as an index of blood flow, whereas beat strength (BS) was used as a measure of pulsatility. Ocular perfusion pressure (OPP) was also calculated. All parameters were compared between amblyopic and fellow eyes. Results: Amblyopic eyes demonstrated significantly greater CCT compared with fellow eyes (407.6 ± 84.9 µm vs. 326.4 ± 79.1 µm). Conversely, macular MBR was significantly lower in amblyopic eyes (9.28 ± 3.60 AU vs. 10.94 ± 4.68 AU), as was BS (5.73 ± 3.07 AU vs. 7.28 ± 3.59 AU). No significant differences were observed in central retinal thickness or OPP between amblyopic and fellow eyes. In amblyopic eyes, CCT was not significantly correlated with macular MBR or BS. Conclusions: Amblyopic eyes exhibited significant central choroidal thickening accompanied by reduced macular blood flow and pulsatility. These findings suggest that localized macular hemodynamic dysregulation may contribute to the pathophysiology of hyperopic anisometropic amblyopia. Full article

Background: The postpartum period represents a critical transitional phase in which women experience profound changes in identity, meaning, and social roles. This process is often shaped by social vulnerability and existential transformation, yet remains insufficiently explored from a phenomenological perspective. This study aimed to explore how women reconstruct identity and meaning during the postpartum period within the context of social vulnerability and existential transition. Methods: This qualitative study em-ployed an descriptive phenomenological approach in accordance with the COREQ guidelines. Data saturation was achieved with 20 mothers of infants aged 0–12 months who were purposively selected from a province in eastern Türkiye. Data were collected through semi-structured face-to-face interviews and analyzed using Colaizzi’s phenomenological method. Credibility was ensured through participant validation, reflexivity, and team-based analysis. Results: Four themes emerged. Fracturing of Existence indicated an ontological shift from “I” to “we,” reflecting a metaphorical rebirth of the self. Invisible Burdens revealed that societal expectations and insufficient social support intensify psychosocial vulnerability. Re-Tailoring the Self demonstrated that maternal identity is dynamic and continuously negotiated between the past and emerging self. Construction of Silent Resilience showed that women develop strength alongside vulnerability through internal resources, spirituality, and everyday practices of hope. Conclusions: The postpartum period involves a multilayered reconstruction of identity and meaning beyond role adaptation. During this existential transition, women not only give birth to a child but also reconstruct their own existence, metaphorically giving birth to themselves. Full article

Steel slag is a major solid waste generated by the steelmaking industry. Its characteristics, including high hardness and large specific surface area, offer the potential to replace traditional mineral fillers in asphalt mixtures. However, the high alkalinity of unmodified steel slag often leads to unbalanced rheological properties and insufficient moisture stability in asphalt mastic. In this study, a modified steel slag filler was prepared using a process involving crushing and screening, water washing for dealkalization, and surface modification with a silane coupling agent. Using limestone powder and hydrated lime as control groups, the modification effects on base asphalt mastic were systematically investigated. Rheological properties were characterized using a dynamic shear rheometer (DSR) and bending beam rheometer (BBR). Interfacial performance was evaluated through pull-off tests and water immersion dispersion tests. Furthermore, mechanisms were elucidated using X-ray Fluorescence (XRF), BET specific surface area analysis, and surface free energy (SFE) tests. The results indicate that the modified steel slag significantly enhances the high-temperature deformation resistance of the asphalt mastic. At 58 °C, the complex modulus reached 7.3 MPa, representing increases of 43.3% compared to limestone powder mastic. At −18 °C, the creep stiffness increased by only 3.0%, suggesting that low-temperature cracking resistance remained fundamentally stable. The water immersion dispersion loss rate was 2.12%, and the attenuation rate of pull-off strength after water immersion was 12.5%, indicating that its resistance to moisture damage is superior to that of limestone powder and comparable to that of hydrated lime. Mechanism analysis reveals that the large specific surface area of the modified steel slag strengthens physical adsorption, while the basic oxides undergo a weak acid–base reaction with the acidic components of the asphalt. Additionally, surface modification improves compatibility. The preparation process for modified steel slag is simple; it can be used as a standalone substitute for traditional mineral fillers, balancing both performance and environmental benefits. Full article

The large-scale accumulation of titanium-extraction tailing slag (TS) poses environmental concerns, while its application is constrained by high impurity contents and low hydraulic reactivity, which is further exacerbated by the necessary dechlorination process. This study aims to evaluate the effectiveness of synthetic calcium silicate hydrate (C-S-H) nanocrystals in improving the performance of cement pastes incorporating deeply dechlorinated TS (DD-TS). To ensure uniform dispersion and activity, C-S-H seeds with varying crystallinities (55–94%) were prepared via a dynamic hydrothermal method (180 °C for 1–3 h) and incorporated into the composite binder in a wet-powder form at dosages of 0.5–2.0%. Results indicate that C-S-H-1, with the lowest crystallinity, offered the highest efficiency. At 1.5% dosage, the 1 d compressive strength increased by 64.6% to 18.6 MPa, while the initial setting time decreased by approximately 40%. Microstructural analyses reveal that poorly crystalline C-S-H provides abundant nucleation sites, accelerating early hydration and densifying the matrix to levels comparable to 7 d control pastes. These findings demonstrate the potential of C-S-H seeding for enhancing the utilization of DD-TS in cement-based materials. Full article

Expanded polystyrene (EPS) foam concrete is attractive for lightweight building applications, yet its practical use is often limited by weak EPS–cement interfacial bonding, which promotes interfacial debonding and crack propagation and thereby compromises mechanical performance. Although nano-SiO₂ (NS) has been reported to improve EPS–cement compatibility, the interfacial strengthening mechanism is still not fully clarified across scales, especially the molecular-level interactions that govern the formation of a robust interfacial transition zone (ITZ). Herein, EPS particles were modified with NS and a multi-scale framework (macro tests, micro-characterization, and molecular dynamics (MD) simulations) was employed to establish a mechanistic linkage between interfacial chemistry/structure and macroscopic performance. The results show that an optimal NS dosage of 9% (by cement mass) increases the 28-day compressive strength and flexural strength of EPS concrete by up to 18.3% and 11.2%, respectively, compared with the unmodified system. SEM, XRD, and FTIR collectively indicate a denser interfacial microstructure, increased hydration-product accumulation near the EPS surface, refined interfacial porosity, and the occurrence of condensation-related reactions involving NS. MD simulations further reveal that NS facilitates the formation of molecular bridges between EPS and C–S–H through hydrogen bonding and ionic interactions, which enhances interfacial adhesion and contributes to improved ITZ thermal stability. This study provides a cross-scale mechanistic understanding for designing high-performance EPS foam concrete via targeted interfacial engineering. MD simulations further suggest that NS enhances interfacial bonding by increasing the occurrence of hydrogen-bond networks and ionic associations at the EPS/C–S–H interface, as evidenced by the intensified interaction-related distributions and peaks in the simulation outputs. Full article

The differential distribution of cellular towers of Telkomsel, Indonesia’s largest mobile network operator, in Banten Province, Indonesia, poses challenges to network performance and service reliability. Therefore, we developed a novel hybrid framework that integrates geographic information systems, minimum spanning tree modeling, and signal-weighted k-nearest neighbor classification to assess tower utilization and signal coverage. Leveraging geospatial data from 110 Telkomsel cellular towers and 1000 simulated user nodes, it was found that 2.73% of towers were overloaded and 189 signal blank spots were identified in rural and topographically complex areas. By incorporating both spatial topology and signal strength sensitivity, the developed method outperforms conventional spatial or machine learning approaches in preserving spatial fidelity and supporting infrastructure planning. Despite the use of simulated user data, the framework demonstrates high scalability and adaptability for integration with real-time network performance metrics, enabling dynamic and location-specific telecommunication optimization. Full article

Although recent studies have achieved remarkable progress in remote sensing image understanding by fusing spatial- and frequency-domain features to leverage their complementary strengths, they still face two key limitations: frequency modeling remains rigid due to static constraints, limiting adaptability, and spatial–frequency fusion often suffers from poor generalization and instability across tasks and network depths. Our experiments reveal that the relative importance of low- and high-frequency components varies dynamically across feature hierarchies and training stages, indicating that frequency information is inherently task-dependent and stage-aware. Motivated by these observations, we propose the Frequency–Spatial Self-Calibrated Network (FSSC-Net), a task-driven framework for adaptive frequency modeling and collaborative spatial–frequency fusion. FSSC-Net incorporates a lightweight, plug-and-play self-calibrated frequency modeling mechanism, comprising a Dynamic Frequency Selection Module and a Task-Guided Calibration Fusion Module. This mechanism adaptively modulates frequency responses via soft masks, enabling dynamic extraction of task-relevant low- and high-frequency components and effective alignment between spatial- and frequency-domain features. Moreover, we present a systematic analysis of frequency importance across tasks and training stages, providing quantitative evidence for the necessity of task-calibrated frequency modeling. Extensive experiments on various benchmarks demonstrate that FSSC-Net consistently outperforms state-of-the-art methods, exhibiting strong task adaptability and robust cross-task generalization. Full article

Understanding the motion parameters of floating ice is very important for characterizing the ice water dynamics of rivers during freezing periods. Due to the low spatiotemporal resolution of satellite images, limited observation range of unmanned aerial vehicles, and deformation of shore-based camera images, it is difficult to simultaneously quantify the translational and rotational motion characteristics of floating ice and long-distance transportation. This study used the unmanned aerial vehicle GPS joint observation method to observe and obtain various motion parameters such as local translation, rotation, and long-distance transportation in the curved section of the upper reaches of the Yellow River and the straight section of the middle reaches of the Yellow River during the winter of 2024–2025 under conditions of ice density of 50–90%. The velocity field obtained by the drone shows an average ice velocity of 1.27 m/s at the bend and 1.18 m/s in the straight section, with lateral velocity gradients of −0.245 to 0.050 s⁻¹ and −0.141 to 0.222 s⁻¹, respectively. The angular velocity of a single floating ice block is 0.008–0.016 rad/s at bends and 0.010–0.036 rad/s in straight sections. The angular velocity is positively correlated with the local shear strength, and the rotation direction is consistent with the sign of the velocity gradient. GPS tracking provides long-distance transportation trajectories, and the average difference between the speeds obtained by GPS and drones is 0.10 m/s, confirming the reliability of speed estimation based on drones. These results indicate that integrated unmanned aerial vehicle GPS observation can quantitatively characterize local floating ice movement and long-distance floating ice transport behavior, providing on-site parameters for river ice water dynamics research and hazard assessment, and has the potential to be applied to rivers in other cold regions. Full article

This study investigates the durability performance of bamboo fiber recycled aggregate concrete (BFRAC) in a sulfate attack environment by simulating harsh conditions through dry–wet cyclic tests. It compares the sulfate attack resistance of steel fiber recycled aggregate concrete (SFRAC) and BFRAC, analyzing their durability performance. The experiments were designed with bamboo fiber admixtures (by volume) of 1%, 1.5%, and 2%, using a 5% Na₂SO₄ solution for dry–wet cycling. The tests evaluated the mass loss rate, microstructure evolution, compressive strength corrosion resistance coefficient, split tensile strength, and dynamic modulus at cycles 0, 30, 60, 90, and 120. A damage model was established to predict the concrete’s damage life. The results showed that as the number of wet and dry cycles increased, the specimens developed cracks, mortar detachment, and fiber rusting on the surface. The mass loss initially increased and then decreased, while the relative dynamic modulus of elasticity and compressive strength exhibited a trend of increasing followed by a decrease. Bamboo fiber concrete demonstrated better durability in terms of compressive strength and splitting tensile strength. Among the BFRAC specimens, those with a 1.5% bamboo fiber admixture had the longest predicted service life, as determined by the Weibull distribution model. Full article

Chitosan, a biocompatible and biodegradable polysaccharide, exhibits notable antibacterial properties. However, its practical applications are often constrained by inherent limitations such as poor solubility (restricted to acidic media) and suboptimal mechanical strength. By constructing dynamic covalent networks with QCS and green crosslinkers (e.g., genipin, dialdehyde cellulose), materials acquire excellent pH-responsive intelligence. This review elaborates on the molecular design, crosslinking strategies, and applications in intelligent packaging and targeted therapy. The synergistic Schiff-base/hydrogen-bonding mechanism enables dual (pH/enzyme) responsive release. We clarify the relationship between quaternization degree and cytotoxicity as a key challenge for clinical translation and analyze how green crosslinkers are molecular bridges to tailor network properties. The ‘perception-response’ integrated design principle of QCS demonstrates significant potential for intelligent packaging and antibacterial−anticancer synergistic therapy, while addressing key biosafety considerations. Full article

Parents of children with special educational needs (SEN) experience elevated stress, anxiety, and depression, a challenge compounded by insufficient emotional support services. This study developed and evaluated a culturally adapted online counselling programme for Hong Kong Chinese parents of adolescents with SEN, integrating Solution-Focused Brief Therapy (SFBT) and Mindfulness Training. The 8-week programme aimed to reduce parental distress and improve family dynamics by emphasising strengths, fostering self-compassion, and enhancing empathetic interactions. A mixed-methods approach was used, combining standardised self-report measures such as the Parental Stress Scale (PSS), Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI), and Child Behaviour Checklist (CBCL), with qualitative interviews and behavioural observations. Quantitative analysis of pre–post data via paired samples t-tests indicated significant within-group reductions in anxiety across all groups and in depression for the active control group. However, between-group comparisons of post-test scores did not show clear superiority of the experimental intervention. Qualitative findings highlighted perceived benefits, including increased emotional regulation, a shift towards a strengths-based perspective, and enhanced self-compassion, with the programme’s cultural adaptation deemed crucial for engagement. The study addresses a significant service gap and provides preliminary evidence for the acceptability and potential mechanisms of an integrative online model, while highlighting the need for further research with larger samples. Full article

The cemented backfill mining method has progressively become the preferred mining technique for underground metal extraction due to its advantages such as environmental friendliness, high efficiency, and economic viability. The mechanical properties of the backfill are fundamental to ensuring effective strata control and structural stability within backfilled stopes. Hydration reaction serves as the critical factor in the formation of backfill mechanical properties, while temperature influences these properties by governing the progression of the hydration process. This paper systematically reviews five fundamental hydration models (NG, CEMHYD 3D, Krstulovic-Dabic, Heat of Hydration and Thermodynamic Phase Equilibrium), critically analyzing their limitations in predicting performance under extreme geothermal and cryogenic conditions. Distinct from previous reviews, this study reveals the nonlinear mapping between dynamic temperature fields and microstructural evolution. Furthermore, it incorporates recent advancements in multi-field coupling mechanisms and AI-driven strength prediction. Ultimately, this study establishes that with the emergence of advanced modeling software and machine learning algorithms, the investigation of temperature effects on backfill is poised to move toward a more comprehensive, intelligent, and refined direction. Full article

In grid-connected inverter systems, the Phase-Locked Loop (PLL) is fundamental for achieving and maintaining precise synchronization between the inverter and the electrical grid. Developing an efficient and robust PLL is essential to ensure reliable operation, particularly in the presence of abnormal grid conditions. Among the existing synchronization methods, the Synchronous Reference Frame-based PLL (SRF-PLL) is widely adopted due to its robust performance; however, it suffers from degraded accuracy under unbalanced voltage conditions. To address this limitation, the Second-Order Generalized Integrator-Quadrature Signal Generator (SOGI-QSG) was proposed in previous studies as an alternative approach. Despite its advantages, the SOGI-PLL exhibits weak filtering capability for lower-order harmonics and remains sensitive to DC offset, both of which can affect synchronization quality. As a result, numerous advanced PLLs based on SOGI-QSG have been proposed in the literature to address SOGI-QSG limitations by enhancing DC offset rejection, filtering capability, and dynamic response. This article provides a comprehensive assessment of various three-phase PLLs based on SOGI-QSG under unbalanced grid conditions, focusing on peak-to-peak frequency error, filtering performance, and DC offset rejection. The operational principles and mathematical models of each technique are discussed, and their performances are validated using MATLAB/Simulink (R2025b). The results show that the SRF-PLL exhibits oscillatory behavior under unbalanced conditions, whereas the PLLs based on SOGI-QSG demonstrate stable synchronization with different trade-offs between filtering strength and dynamic response. Therefore, the selection of the appropriate PLLs based on SOGI-QSG depends on the priorities of the specific application. Full article

This study examines the seismic stability of an underground powerhouse cavern located in the Lesser Himalayan region of Nepal. Both static and seismic loading conditions are analyzed using the finite element method (FEM) and the distinct element method (DEM). Rock mass properties are derived from field investigations and laboratory testing, while empirical correlations are applied to estimate rock mass strength and deformation modulus. Pseudo-static analyses are performed using the FEM-based software Rock and Soil-2-Dimensionsl (RS²) Version 11.027, and dynamic analyses are conducted using the DEM-based software Universal Distinct Element Code (UDEC) Version 5.0 to evaluate deformation and stress redistribution around the cavern. Seismic fragility curves are developed to quantify the probability of damage under varying seismic intensities. Results indicate that a peak ground acceleration (PGA) of 0.25 g increases cavern wall deformation by approximately 15–20 mm compared to static conditions. Fragility analysis shows a probability exceeding 68% for slight damage, while the probability of collapse remains low at approximately 1.7%. Seismic loading also significantly alters stress redistribution along the cavern boundary. Overall, the combined use of numerical modeling and fragility analysis provides a probabilistic framework for assessing seismic risk in underground caverns, offering valuable insights for the design and safety evaluation of hydropower projects in seismically active Himalayan regions. Full article