Search Results (3,073)

The synthesis of thin films in multilayer structures on different textiles is of interest due to their potential use in flexible solar absorber coatings and thin-film solar cells. The aim of the study was to deposit bismuth(III) sulphide and copper(II) sulphide thin films on various textiles at the same time. This was achieved using the sustainable and cost-effective successive ionic layer adsorption and reaction (SILAR) method. The study examined how the elemental distribution, phase composition, crystallinity, surface morphology, and optical features of the resulting films are determined by the intrinsic structure and material makeup of structural textiles. The analysis used data from scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD), as well as ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy. Depending on the textiles used, the formed films were polycrystalline and rich in copper. According to the findings, the normalised atomic percentages were as follows: Cu, 57.66–68.75%; Bi, 1.19–5.26%; S, 30.06–38.63%. The direct transition optical energy gap values varied from 1.3 to 2.88 eV, while the indirect varied from 0.9 to 2.25 eV, and the refractive index from 1.3 to 1.8. These properties were influenced by the composition of the textiles and the films themselves. These properties directly impact the films’ applications. Full article

A sliding mode predictive control (SMPC) scheme integrated with an extreme learning machine (ELM) disturbance observer is proposed for the trajectory tracking of a flexible air-breathing hypersonic vehicle (FAHV). To streamline the controller design, the longitudinal model is decoupled into a velocity subsystem and an altitude subsystem. For the velocity subsystem, a proportional-integral sliding mode surface is designed, and the control law is derived by minimizing a cost function that weights the predicted sliding mode surface and the control input. For the altitude subsystem, a backstepping control framework is adopted, with the SMPC strategy embedded in each step. Multi-source disturbances are modeled as composite additive disturbances, and an ELM-based neural network observer is constructed for their real-time estimation and compensation, thereby enhancing system robustness. The semi-globally uniformly ultimately bounded (SGUUB) stability of the closed-loop system is rigorously proven using Lyapunov stability theory. Simulation results demonstrate the comprehensive superiority of the proposed method: it achieves reductions in Root Mean Square Error (RMSE) of 99.60% and 99.22% for velocity and altitude tracking, respectively, compared to Prescribed Performance Control with Backstepping Control (PPCBSC), and reductions of 98.48% and 97.12% relative to Terminal Sliding Mode Control (TSMC). Under parameter uncertainties, the developed ELM observer outperforms RBF-based observer and Extended State Observer (ESO) by significantly reducing tracking errors. These findings validate the high precision and strong robustness of the proposed approach. Full article

This paper introduces the Lambert-Lindley distribution, a two-parameter extension of the Lindley model constructed through the Lambert-F generator. The new distribution retains the non-negative support of the Lindley distribution and provides additional flexibility by incorporating a shape parameter that controls skewness and tail behavior. Structural properties are derived, including the probability density function, cumulative distribution function, quantile function, hazard rate, and moments. Parameter estimation is addressed using the method of moments and maximum likelihood, and a Monte Carlo simulation study carried out to evaluate the performance of the proposed estimators. The practical applicability of the Lambert–Lindley distribution is demonstrated with two real datasets: stress rupture times of Kevlar/epoxy composites and hospital stay durations of breast cancer patients. Comparative analyses using goodness-of-fit tests and information criteria demonstrate that the proposed model can outperform classical alternatives such as the Gamma and Weibull distributions. Consequently, the Lambert–Lindley distribution emerges as a flexible alternative for modeling positive unimodal data in contexts such as material reliability studies and clinical duration analysis. Full article

Flexible pressure sensors are essential for wearable electronics, human–machine interfaces, and soft robotics. However, conventional Polydimethylsiloxane (PDMS)-based sensors often suffer from limited conductivity, poor filler dispersion, and low structural integration with textile substrates. In this work, we present a robotic drop-coating approach for fabricating graphite–copper nanoparticle (G-CuNP)/PDMS composite pressure sensors with textile-integrated electrodes. By precisely controlling droplet deposition, a three-layer sandwiched structure was realized that ensures uniformity and scalability while avoiding the drawbacks of conventional full-line coating. The effects of filler loading and graphite nanoparticle (GNP) and copper nanoparticle (CuNP) ratios were systematically investigated, and the optimized sensor was obtained at 40 wt% total fillers with a graphite content of 55 wt%. The fabricated device exhibited high sensitivity in the low-pressure region, stable performance in the medium- and high-pressure ranges, and an exponential saturation fitting with R² = 0.998. The average hysteresis was 7.42%, with excellent cyclic stability over 1000 loading cycles. Furthermore, a hand-shaped sensor matrix composed of five distributed sensing units successfully distinguished grasping behaviors of lightweight and heavyweight objects, demonstrating multipoint force mapping capability. This study highlights the advantages of robotic drop-coating for scalable fabrication and provides a promising pathway toward low-cost, reliable, and wearable soft pressure sensors. Full article

This study investigated factors predicting cognitive flexibility in Chinese–English bilinguals, with a comprehensive focus on demographic and language-related variables. Cognitive flexibility was assessed using reaction times (RTs) and maximum absolute deviation (MAD) in a mouse-tracking nonverbal task-switching paradigm, capturing both mix and switch costs. Regression analyses revealed that bilingual experience explained a larger proportion of variance in mix costs than in switch costs, with stronger effects for MAD than RTs. Higher composite factor scores (CFS) were positively associated with mix costs, whereas balanced language use across life stages, activities, and interlocutors predicted smaller mix costs, suggesting a move to multi-dimensional, experience-based approaches. In contrast, switch costs were largely unrelated to CFS, but balanced language use across situational contexts, which predicted reduced switch costs in MAD, indicating enhanced reactive control. Moreover, bilingual experiences in the home environment appeared to be positively associated with cognitive flexibility. These findings highlight the multidimensional nature of bilingual experience and underscore the value of movement trajectory measures in capturing subtle effects on sustained and transient cognitive control. Full article

Flexible upconversion (UC) devices, owing to their unique combination of high–efficiency optical energy conversion and mechanical flexibility, have attracted increasing attention in the fields of optoelectronics, wearable devices, flexible displays, and biomedical applications. However, significant challenges remain in balancing optical performance, mechanical adaptability, long–term stability, and scalable fabrication, which limit their practical deployment. This review systematically introduces five representative upconversion mechanisms—excited–state absorption (ESA), energy transfer upconversion (ETU), energy migration upconversion (EMU), triplet–triplet annihilation upconversion (TTA–UC), and photon avalanche (PA)—highlighting their energy conversion principles, performance characteristics, and applicable scenarios. The article further delves into the flexible transition of upconversion devices, detailing not only the evolution of the luminescent layer from bulk crystals and nanoparticles to polymer composites and hybrid systems, but also the optimization of electrodes from rigid metal films to metal grids, carbon–based materials, and stretchable polymers. These developments significantly enhance the stability and reliability of flexible upconversion devices under bending, stretching, and complex mechanical deformation. Finally, emerging research directions are outlined, including multi–mechanism synergistic design, precise nanostructure engineering, interface optimization, and the construction of high–performance composite systems, emphasizing the broad potential of flexible UC devices in flexible displays, wearable health monitoring, solar energy harvesting, flexible optical communications, and biomedical photonic applications. This work provides critical insights for the design and application of high–performance flexible optoelectronic devices. Full article

Dental enamel exhibits a unique combination of high hardness and high toughness. This outstanding mechanical property is closely tied to its multi-scale hierarchical structure. In this study, rat tooth enamel was selected as the research object, the different structural layers and mechanical properties of tooth enamel were investigated and characterized experimentally. The multi-scale mechanical models with different structural layers were developed and analyzed using numerical simulations. The research results indicate that, regarding the load-bearing mechanism, the outer layer of tooth enamel consists of hydroxyapatite crystal bundles arranged in parallel and inclined orientations, and this structural feature enables it to exhibit excellent elastic modulus and resistance to deformation, while the inner layer with cross-arranged crystal bundles shows different mechanical response characteristics. In terms of crack propagation behavior, the outer layer is more prone to crack initiation due to the consistency of crystal orientation, and the cracks tend to extend in a straight line, while the unique cross arrangement of crystals in the inner layer can effectively inhibit crack propagation by inducing crack deflection and branching mechanisms, thus demonstrating more excellent fracture toughness. This “outer hard and inner flexible” gradient structure design elucidates the synergistic mechanism between crystal orientation and crack propagation behavior in tooth enamel, offering significant design insights for biomimetic composite materials. Full article

The remarkable growth of high-frequency electronic systems has raised concerns about electromagnetic interference (EMI), emphasizing the need for lightweight and efficient shielding materials. In this study, ternary composites based on polypyrrole (PPy), graphene oxide (GO), and silver nanowires (AgNWs) were synthesized through chemical oxidative polymerization of pyrrole monomer and embedded into polycaprolactone (PCL) matrices to create flexible films. Structural and morphological analyses confirmed the successful incorporation of all components, with scanning electron microscopy showing granular PPy, sheet-like GO, and fibrous AgNWs, while spectroscopic studies indicated strong interfacial interactions without damaging the PPy backbone. Thermomechanical analysis revealed that GO increased stiffness and defined the glass transition, whereas AgNWs improved toughness and energy dissipation; their combined use resulted in balanced properties. EMI shielding effectiveness (SE) was tested in the X-band (8–12 GHz). Pure PPy exhibited poor shielding ability, while the addition of GO and AgNWs significantly enhanced performance. The highest EMI SE values were observed in PPy/GO–AgNWs composites, with an average SE of 16.05 dB at 20 wt% of the composite in the PCL matrix, equivalent to about 84.4% attenuation of incident waves. These results demonstrate that the synergistic integration of GO and AgNWs into PPy matrices enables the creation of lightweight, flexible films with advanced EMI shielding properties, showing great potential for next-generation electronic and aerospace applications. Full article

The article focuses on floor composite beams used in buildings. Within the scope of the conducted analytical and numerical studies, the authors compared the typical solution—namely, the T-shaped reinforced concrete beam—with various types of composite beams, the height of which could not exceed the predetermined usable depth of the beam cross-section. The analyses focused on traditional steel–concrete composite beams, which are widely used in civil engineering, as well as modern solutions, such as timber–timber and steel–timber composite beams. A new type of a steel–timber composite beam with a cold-formed girder made of two channels was presented in this study. Due to the flexibility of the connections, the timber–timber and steel–timber composite beams were examined under three different connection conditions: full composite action, partial composite action, and no composite action (friction only). Composite beams with timber slabs are consistent with the principles of sustainable construction, which makes their comparison with conventional solutions particularly relevant. The load-deflection curves and the bending resistance of the analysed elements were obtained using numerical simulations. In the numerical analyses, advanced material models were used. Composite beams with timber elements had lower stiffness than the steel–concrete composite beam. For this reason, meeting the serviceability limit state can be more challenging for such structures. Furthermore, the degree of shear connection in the composite beams with timber elements had a strong impact on their load-bearing capacity and end-slip. The steel–timber composite beam with a cold-formed girder had the most favourable resistance-to-mass ratio. The analytical results, and especially the numerical findings, provide a foundation for future experimental investigations. Full article

Urban green spaces (UGS) are pivotal to urban sustainability, yet their morphology—patch size, shape, and configuration—remains insufficiently linked to institutional drivers. We investigate how land tenure strength shapes UGS morphology across 36 cities in nine countries. Using OpenStreetMap data, we delineate UGS and compute landscape metrics (AREA, PARA, SHAPE, FRAC, PAFRAC) via FRAGSTATS; we develop a composite index of land tenure strength capturing ownership, use-right duration, expropriation compensation, and government land governance capacity. Spearman’s rank correlations indicate a scale-dependent coupling: stronger tenure is significantly associated with micro-scale patterns—smaller patch areas and more complex, irregular boundaries—consistent with fragmented ownership and higher transaction costs, whereas macro-scale indicators (e.g., overall green coverage/connectivity) show weaker sensitivity. These findings clarify an institutional pathway through which property rights intensity influences the physical fabric of urban nature. Policy implications are twofold: in high-intensity contexts, flexible instruments (e.g., transferable development rights, negotiated acquisition, ecological compensation) can maintain network connectivity via embedded, fine-grain interventions; in low-intensity contexts, one-off land assembly can efficiently deliver larger, regular green cores. The results provide evidence-based guidance for aligning green infrastructure design with diverse governance regimes and advancing context-sensitive sustainability planning. Full article

Heavy metal ions (HMIs) threaten ecosystems and human health due to their carcinogenicity, bioaccumulativity, and persistence, demanding highly sensitive, low-cost real-time detection. Electrochemical sensing technology has gained significant attention owing to its rapid response, high sensitivity, and low cost. Molybdenum disulfide (MoS₂), with its layered structure, tunable bandgap, and abundant edge active sites, demonstrates significant potential in the electrochemical detection of heavy metals. This review systematically summarizes the crystal structure characteristics of MoS₂, various preparation strategies, and their mechanisms for regulating electrochemical sensing performance. It particularly explores the cooperative effects of MoS₂ composites with other materials, which effectively enhance the sensitivity, selectivity, and detection limits of electrochemical sensors. Although MoS₂-based materials have made significant progress in theoretical and applied research, practical challenges remain, including fabrication process optimization, interference from complex-matrix ions, slow trace-metal enrichment kinetics, and stability issues in flexible devices. Future work should focus on developing efficient, low-cost synthesis methods, enhancing interference resistance through microfluidic and biomimetic recognition technologies, optimizing composite designs, resolving interfacial reaction dynamics via in situ characterization, and establishing structure–property relationship models using machine learning, ultimately promoting practical applications in environmental monitoring, food safety, and biomedical fields. Full article

This paper studies a generalized class of linear operators acting on spaces of analytic functions, defined by $P_n^{\psi ,\phi }\left(f\right)\left(z\right)={\displaystyle \sum _{j=0}^n}{\psi }_j\left(z\right)f^{\left(j\right)}\left(\phi \left(z\right)\right)$, where $\psi =\{{\psi }_0,{\psi }_1,\dots ,{\psi }_n\}\subset H\left(\mathbb{D}\right)$ and $\phi \in S\left(\mathbb{D}\right)$. This formulation encompasses several classical operators, including composition, weighted composition, differentiation–composition, and the Stević–Sharma operator. We focus on the action of $P_n^{\psi ,\phi }$ from $BMOA$ and analytic Besov spaces ${\mathcal{B}}_p$ into the Bloch space $\mathcal{B}$, and provide necessary and sufficient conditions for boundedness and compactness. These results unify and extend many previously known characterizations and demonstrate the flexibility of the $P_n^{\psi ,\phi }$ framework in the context of analytic operator theory. Full article

Carbon nanotubes (MWCNTs) were synthesized in situ on para-aramid fabrics (gCPO) via a low-temperature (450 °C) chemical vapor deposition (CVD) process to enhance interfacial pull-out, frictional, and fracture toughness characteristics. FESEM analysis confirmed CNT coverage on fiber surfaces, while FTIR, Raman, and XRD results indicated limited structural modification without significant polymer degradation. The CNT-functionalized fabrics exhibited a 66.19% increase in maximum pull-out force, 55.32% improvement in interlacement rupture strength, and a three-fold rise in intra-yarn shear resistance compared with control fabrics (KPO). The static and kinetic friction coefficients increased by 26.67% and 16.67%, respectively, due to CNT-induced surface roughness, enhancing inter-fiber load transfer and reducing slippage. Single-yarn pull-out tests revealed notable gains in energy dissipation and fracture toughness (up to 1769 J/m²), whereas multi-yarn pull-out performance decreased due to excessive friction surpassing filament strength. The study demonstrates that low-temperature MWCNT growth enables effective interfacial reinforcement of soft para-aramid fabrics, establishing a novel framework for meso-scale mechanical screening of flexible nano-ballistic composites. Full article

The shift towards renewable resources has positioned agar, a natural seaweed polysaccharide, as a pivotal and sustainable material for developing next-generation energy storage technologies. This review highlights the transformative role of agar-based composites as a game-changing and eco-friendly platform for supercapacitors, batteries, and fuel cells. Moving beyond the traditional synthetic polymers, agar introduces a novel paradigm by leveraging its natural gelation, superior film-forming ability, and inherent ionic conductivity to create advanced electrolytes, binders, and matrices. The novelty of this field lies in the strategic fabrication of synergistic composites with polymers, metal oxides, and carbon materials, engineered through innovative techniques like electrospinning, solvent casting, crosslinking, 3D printing, and freeze-drying. We critically examine how these innovative composites are breaking new ground in enhancing device efficacy, flexibility, and thermal stability. Ultimately, this analysis not only consolidates the current landscape but also charts future pathways, positioning agar-based materials as a pivotal and sustainable solution for powering the future. Full article

In this work, we investigated the use of a piezoelectric flexible device for energy harvesting. The main goal of the study was to fill the nanostructured pores of anodic aluminum oxide (AAO) films with piezoelectric polymer (PVDF-TrFE) via a modified conventional screen printing technique using blade printing. In this way, it is possible to obtain a composite from nanostructured thin films of polymer nanorods that shows improved charge generation ability compared to other non-nanostructured composites or pure (non-composite) aluminum with similar dimensions. This behavior is due to the effect of the highly developed surface of the material used to fill in the AAO nanopore template and its ability to withstand the application of higher mechanical loads to the structured piezoelectric material during deformation. The contact blade print filling technique can produce nanostructured piezoelectric polymer films with precise geometric parameters in terms of thickness and nanorod diameters, at around 200 nm, and a length of 12 μm. At a low frequency of 17 Hz, the highest root-mean-square (RMS) voltage generated using the nanostructured AAO/PVDF-TrFE sample with aluminum electrodes was around 395 mV. At high frequencies above 1700 Hz, the highest RMS voltage generated using the nanostructured AAO/PVDF-TrFE sample with gold electrodes was around 680 mV. The RMS voltage generated using a uniform (non-nanostructured) layer of PVDF-TrFE was 15% lower across the whole frequency range. Full article