Search Results (55,887)

To promote the development of long-distance high-speed underwater optical wireless communication (UWOC) based on visible light, this study proposes a high-bandwidth UWOC system based on micro-light-emitting-diodes (micro-LEDs) adopting the Non-Return-to-Zero On-Off Keying (NRZ-OOK) modulation. The numerical simulations reveal that optimizing the structural parameters of gallium nitride (GaN)-based micro-LED through dimensional scaling and quantum well layer reduction may significantly enhance optoelectronic performance, including modulation bandwidth and luminous efficiency. Moreover, experimental validation demonstrated maximum real-time data rates of 420 Mbps, 290 Mbps, and 250 Mbps at underwater distances of 2.3 m, 6.9 m, and 11.5 m, respectively. Furthermore, the underwater audio communication was successfully implemented at an 11.5 m UWOC distance at an ultra-low level of incoming optical power (12.5 µW) at the photodetector (PD) site. The channel characterization yielded a micro-LED-specific attenuation coefficient of 0.56 dB/m, while parametric analysis revealed wavelength-dependent degradation patterns, exhibiting positive correlations between both attenuation coefficient and bit error rate (BER) with operational wavelength. This study provides valuable insights for optimizing underwater optical systems to enhance real-time environmental monitoring capabilities and strengthen security protocols for subaquatic military communications in the future. Full article

Signed networks, which incorporate both cooperative and antagonistic interactions, naturally give rise to symmetric behaviors in multi-agent systems. One such behavior is bipartite containment tracking, where follower agents converge to a symmetric configuration determined by multiple groups of leaders with opposing influence. Moreover, a timely response is critical to ensuring high performance in containment tracking tasks, particularly for high-order multi-agent systems operating in dynamic and uncertain environments. To this end, this paper investigates the predefined-time bipartite containment tracking problem for high-order multi-agent systems affected by external disturbances. A robust tracking control scheme is developed based on the backstepping method to ensure that the tracking errors converge to a predefined residual set within a user-specified time. The convergence time is explicitly adjustable through a design parameter, and the proposed scheme effectively avoids the singularities often encountered in conventional predefined-time control approaches. The stability and robustness of the proposed scheme are rigorously established through Lyapunov-based analysis, and extensive simulation results are provided to validate our theoretical findings. Full article

Food packaging systems play a critical role in reducing resource wastage, extending shelf-life, and enhancing supply chain sustainability. Carbon dots (CDs) have emerged as promising nanofillers for sustainable active and smart packaging due to their exceptional optical properties, biocompatibility, and antimicrobial activity. This review synthesizes recent advances in CD-based food packaging technologies, focusing on their multifunctional applications and performance enhancements. We systematically analyze how CDs improve packaging materials’ mechanical strength, gas barrier properties, and functional performance (antioxidant, antimicrobial, and smart sensing capabilities). Current research demonstrates CDs’ ability to enable intelligent functions such as pH responsiveness and freshness monitoring while maintaining excellent biocompatibility. However, challenges remain in scaling up production, long-term toxicological evaluation, and matrix compatibility. Future research directions should address these limitations while exploring the full potential of CD-based multifunctional films as sustainable alternatives for next-generation food packaging systems. Full article

Carbon dots (CDs) derived from renewable biomass are emerging as sustainable alternatives to traditional nanomaterials for applications in bioimaging, sensing, and photonics. In this study, we reported a one-step synthesis of photoluminescent CDs from Laurus nobilis leaves particularly spread in the Mediterranean area. The resulting nanoparticles (NPs) exhibited average diameters of 3–5 nm and high colloidal stability in water. Structural analysis by X-Rays Diffraction revealed the presence of amorphous graphitic domains, while infrared spectroscopy confirmed oxygenated functional groups on the CD surface. Spectrofluorimetric analysis showed excitation-dependent blue–green emission with a maximum at 490 nm that can be applied also as label agents for cells. The environmental sustainability of the synthetic procedure was evaluated through a Life Cycle Assessment (LCA), highlighting that the current impacts were primarily associated with electricity consumption, due to the laboratory-scale nature of the process. These impacts are expected to decrease significantly with future scale-up and process optimization. Full article

We fabricated TiO₂ thin films using the sol–gel method, incorporating TiO₂ nanoparticle sizes of 25 nm on the fluorine-doped tin oxide (FTO) substrates by spin coating and annelation at 600 °C. The influence of incorporating TiO₂ particles on the surface morphology, optical properties, and photovoltaic performance of TiO₂ thin-film dye-sensitized solar cells (DSSC) was examined. Structural characterization was analyzed using X-ray diffraction (XRD), while the morphologies were analyzed using scanning electron microscopy (SEM). The transmittance and absorbance of films were measured using an ultraviolet (UV)–visible (VIS)–near-infrared (NIR) spectrophotometer. The current–voltage (I-V) property was evaluated under simulated solar irradiation. The results demonstrated that the incorporation of TiO₂ particles enhanced the efficiency of DSSCs. The photovoltaic performance of DSSCs was improved with TiO₂ nanoparticle incorporation. The optimized DSSC incorporated TiO₂ films (TIFNA). TIFNA achieved a Jsc of 14.49 mA/cm², Voc of 0.69 V, fill factor of 60.5%, and efficiency of 6.05%, compared to 4.23% for the DSSC with unincorporated TiO₂ thin film. The improved performance was attributed to increased dye adsorption, better crystallinity, and enhanced electron transport. Full article

Optical frequency domain reflectometry (OFDR) is one of the key diagnostic tools for fiber optic components and circuits built on them. A low signal-to-noise ratio, resulting from the low intensity of backscattered signals, prevents the correct quantitative description of the medium parameters. Known methods of signal denoising, such as empirical mode decomposition, frequency filtering, and activation function dynamic averaging, make the signal smoother but introduce errors into its dynamic characteristics, changing the intensity of reflection peaks and distorting the backscattering level. We propose a method to reduce OFDR trace noise using elliptical arc fitting (EAF). The obtained results indicate that this algorithm efficiently processes both areas with and without contrasting back reflections, with zero distortion of Fresnel reflection peaks, and with zero attenuation error in regions without Fresnel reflections. At the same time, other methods distort reflection peaks by 14.2–42.6% and shift the correct level of Rayleigh scattering by 27.2–67.3%. Further work will be aimed at increasing the accuracy of the method and testing it with other types of data. Full article

This work develops a novel phosphate-functionalized extraction resin (HEHEHP + Cyanex272)/SiO₂-P via the vacuum impregnation method for efficient separation of light rare earth element impurities from lanthanum (La³⁺) in nitric medium through synergistic extraction. Batch experiments have demonstrated superior adsorption selectivity toward impurity ions over La³⁺ in a pH 4 nitric acid solution. Column studies confirmed exceptional performance under ambient conditions, achieving a lanthanum treatment capacity of 120.6 mg/g and over 98% impurity removal, which surpasses most reported values. Notably, this purification process enables direct production of purified La³⁺ solutions through a single-column system without desorption, significantly enhancing efficiency and reducing costs. Mechanistic insights revealed combined ion exchange and coordination interactions between metal ions and P-OH/P=O groups, corroborated by advanced characterization and density functional theory calculations. These findings indicate a higher binding affinity of light rare earth compared with La³⁺. This strategy provides a scalable approach for ultra-high-purity lanthanum compound production in advanced optical and electronic applications. Full article

Digital holography enables the reconstruction of both 2D and 3D object information from interference patterns captured by digital cameras. A major challenge in this field is speckle noise, which significantly degrades the quality of the reconstructed images. We propose a novel speckle noise reduction method based on 3D adaptive filtering. Our technique processes a stack of holograms, each with an uncorrelated speckle pattern, using an adapted 3D Frost filter. Unlike conventional filtering techniques, our approach exploits statistical adaptivity to enhance noise suppression while preserving fine image details in the reconstructed holograms. Both numerical simulations and optical experiments confirm that our 3D filtering technique significantly enhances reconstruction quality. Specifically, it reduces the normalized standard deviation by up to 40% and improves the structural similarity index by up to 60% compared to classical 2D, 3D median, BM3D, and BM4D filters. Optical experiments validate the method’s effectiveness in practical digital holography scenarios by local and global image quality estimation metrics. These results highlight adaptive 3D filtering as a promising approach for mitigating speckle noise while maintaining structural integrity in digital holography reconstructions. Full article

This study examines the effects of incorporating recycled carbon fibers obtained from decommissioned wind turbine blades into cementitious composites. An extensive experimental program was carried out, varying fiber content (0–8 kg/m³), fiber length (25, 38, 50 mm), water-to-cement ratio (0.4, 0.5), and cement type (CEM I 42.5, CEM II 42.5R/A-V). The mechanical properties of the fiber-reinforced concretes, including compressive strength, flexural strength, splitting tensile strength, and modulus of elasticity, were evaluated. The addition of recycled carbon fibers significantly improved flexural and splitting tensile strengths, with increases exceeding 60% and 100%, respectively, at the highest fiber dosage (8 kg/m³), attributed to efficient crack-bridging capability. Compressive strength was mainly influenced by the water-to-cement ratio, while the modulus of elasticity showed slight reductions in some mixes due to fiber clustering and increased micro-porosity. Regression analysis indicated that shorter fibers (25 mm) were more effective in enhancing flexural strength, whereas longer fibers (50 mm) improved splitting tensile strength. Classical predictive models generally underestimated the flexural capacity of recycled-carbon-fiber-reinforced concretes, highlighting the need for recalibration. Optical microscopy confirmed uniform fiber dispersion at lower dosages and a dominant pull-out failure mechanism. The findings demonstrate the feasibility of using recycled carbon fibers to enhance the mechanical performance of concrete while supporting sustainability through waste diversion and circular economy strategies. Full article

Low-cost sensors have demonstrated their advances in acquiring hyper-localized data compared to traditional, high-maintenance air quality monitoring stations. The study aims to leverage the mobility of participants equipped with low-cost wearable monitors (LWMs) by comparing their exposure to particulate matter (PM) across indoor-home, outdoor-walking, and hybrid-commuting micro-environments. The LWMs would be calibrated first through field co-location and the multiple linear regression models. The coefficient of determination (R²) of PM_1.0 and PM_2.5 increased to over 0.85 after calibration, along with the reduced root mean square error of 2.25 and 3.46 , respectively. The 26-day PM data collection with geographic locations could identify individual exposure patterns, local source contributions, and hotspot maps. Commuting constituted a small fraction of daily time (4–8%) but contributed a disproportionate impact, accounting for 11% of individual PM exposure. Indoor-home PM_2.5 exposure varied significantly among the urban districts. Based on the PM_2.5 hotspot map, the elevated concentration was mainly concentrated in dense residential areas and historical industrial areas, as well as interchanges of major roads and the highway system. LWMs acting as non-regulatory instruments can complement monitoring stations to provide missing short-term and hyper-localized air pollution data. Future studies should integrate long-term monitoring and citizen science across seasons and geographical regions to address pollutant spatiotemporal variability for building and city sustainability. Full article

Molecular imaging and precision therapies are transforming ophthalmology, enabling earlier and more accurate diagnosis and targeted treatment of sight-threatening diseases. This review focuses on age-related macular degeneration, diabetic retinopathy, glaucoma, and uveitis, examining high-resolution imaging techniques such as optical coherence tomography (OCT), OCT angiography, MALDI-MSI, and spatial transcriptomics. Artificial intelligence supports these methods by improving image interpretation and enabling personalized analysis. The review also discusses therapeutic advances, including gene therapies (e.g., AAV-mediated RPE65 delivery), stem cell-based regenerative approaches, and biologics targeting inflammatory and neovascular processes. Targeted molecular therapies targeting specific signaling pathways, such as MAPK, are also explored. The combination of single-cell transcriptomics, proteomics, and machine learning facilitates the development of personalized treatment strategies. Although these technologies hold enormous potential, their implementation in routine clinical care requires further validation, regulatory approval, and long-term safety assessment. This review highlights the potential and challenges of integrating molecular imaging and advanced therapies in the future of precision ophthalmic medicine. Full article

Transforming industrial by-products into new resources is a fundamental principle of sustainable agriculture and circular bioeconomy. Waste products from rosemary (Rosmarinus officinalis L.) essential oil extraction, such as exhausted biomass and water residues (WRs), are rich in bioactive compounds like phenols and terpenes. These by-products may represent a promising and economically viable option for agricultural management, particularly in weed control. This study evaluates the potential use of WR as a bioherbicide. In vitro experiments were conducted to assess the inhibitory effects of WR on the germination and seedling morphology (root and shoot development) of four detrimental weed species for temperate cropping systems: two monocotyledonous (Alopecurus myosuroides and Lolium multiflorum) and two dicotyledonous (Sinapis alba and Amaranthus retroflexus). WR was tested at four concentrations (0, 25, 50, and 100), corresponding to an increasing gradient of WR, with 100 representing pure WR. The results showed that WR did not significantly inhibit germination in A. myosuroides, L. multiflorum and S. alba, whereas A. retroflexus exhibited a dose-dependent inhibition, with germination reduced by 37.5%, 64.5%, and 91.6% at doses of 25, 50, and 100, respectively, compared with the control (dose 0). Furthermore, germination delays were observed across all tested species with promising application of WR for regulating weed–crop competitive interactions in the early crop growth stages. Results on the morphological traits of weed seedlings showed that WR application affected root more than shoot growth inhibition. In particular, WR demonstrated a pronounced root inhibitory effect in A. myosuroides, L. multiflorum, and A. retroflexus. In contrast, a dose-dependent increase in root length was observed for S. alba (21.41 mm at dose 0 and 25.77 mm, 30.97 mm and 35.96 mm, respectively, at doses 25, 50, and 100). The results of this study highlight the potential application of WR as a sustainable solution to be included in an integrated weed management (IWM) toolbox and underscore their role in promoting the valorization of waste from essential oil production. Full article

Highly efficient shielding materials, transparent in the visible and IR ranges are becoming important in practice. This stimulates the development of cheap methods for creating transparent conductors with low sheet resistance and high optical transparency. This work presents a complex approach based on preliminary modeling of the shielding characteristics of two-layer sandwich structures based on irregular aluminum mesh (IAM) formed by the cracked template method. Experimentally measured spectral dependences of the transmission coefficient of single-layer IAM are used as a reference point for modeling. According to the simulation results, two types of sandwich structures were designed using IAM, with varying filling factors and a fixed PMMA layer thickness of 4 mm. The experimentally measured shielding characteristics of the sandwich structures in the range of 0.01–7 GHz are in good agreement with the calculated data. The obtained structures demonstrate a shielding efficiency of 55.96 dB and 65.55 dB at a frequency of 3.5 GHz (the average range of 5G communications). At the same time, their optical transparency at a wavelength of 550 nm are 84.07% and 75.78%, respectively. Our sandwich structures show electromagnetic shielding performance and uniform diffraction pattern. It gives them an advantage over structures based on regular meshes. The obtained results highlight the prospect of the proposed comprehensive approach for obtaining highly efficient, low-cost optically transparent shielding structures. Such materials are needed for modern wireless communication systems and metrology applications. Full article

We present the conceptual framework of the Astronomical Hub (AstroHub), a unified platform combining various optical instruments at a single observatory. Its major approach lies in arranging conditions for research groups to install telescopes and equipment and participate in joint projects. AstroHub is planned to integrate Virtual Observatory (VO) tools, FAIR data principles, and a telescope network to create a powerful and attractive ecosystem for both robust near-Earth object (NEO) monitoring and diverse deep space research. We provide an overview of the AstroHub development directions in the case study of the Assy-Turgen Observatory. Full article

Port maintenance causes large quantities of dredged sediment throughout the world. The disposal of this material in authorised landfills is economically disadvantageous, as well as being at odds with a circular economy model with a reduced impact on the environment. The application of stabilization/solidification treatment to dredged marine sediments allows an improvement of their physical and mechanical properties, together with the production of cement-based materials that can be used for road construction, as well as for making blocks and bricks. In this study, an experimental laboratory investigation is carried out on two samples of sandy sediments collected from the Mola di Bari harbour (Southern Italy), to identify sustainable management options for recovering materials that will be dredged. To assess the influence on mortars made from sediments with variable organic matter content and seawater, these were characterised from a chemical–physical point of view before and after washing treatment and oxidative processes. The products of the Stabilization/Solidification (S/S) treatment were evaluated in terms of workability, flexural and compressive strengths, and, furthermore, a microstructural study was conducted using SEM-EDX and optical microscopy to analyse the internal structure of the materials. The mechanical performance evaluation clearly demonstrated organic matter’s negative impact on strength development, resulting in a 16% reduction. Pre-treatments, such as sediment washing, effectively improved the performance of treated sediments (e.g., 24% increase in compressive strength). This study aims to demonstrate the benefits of recycling marine sediments in cement-based materials, highlighting how this process can enhance circularity and sustainability while reducing the environmental impact of dredging activities. Full article