Search Results (390)

Inspired by the growing demand for small and effective optoelectronic devices, this paper presents a simulation-based analysis of InGaN/GaN quantum dot light-emitting diode, focusing on the effects of systematic variation in both anode and cathode contact regions, as well as overall device size. Two-dimensional simulations using APSYS software were used to examine the impact of scaling the device dimensions as well as the individual contact dimensions on significant performance parameters like internal quantum efficiency (IQE), optical output power, and current-voltage (IV) response. We simulated five LED device sizes that is 50 × 50 µm², 100 × 100 µm², 200 × 200 µm², 300 × 300 µm², and 400 × 400 µm². As device size grows, so does the total current at each voltage. The highest current measurement is achieved by the device with dimensions 400 × 400 µm² while the lowest is observed on the device with dimensions 50 × 50 µm². In addition to changing the device dimensions, we ran extensive simulations on the sizes of p-type and n-type contacts. Notable changes were seen in the efficiency, optical power, and emission profile of the p-contact. The behavior of p-side contacts from 0 to 50 µm was the same, while contacts between 60 and 100 µm showed significant differences. The significant performance parameters were unaffected by changes to n-contact dimensions. The results of this study illustrate how the configuration of contacts and dimensions greatly influences the electrical and optical performance of quantum dot light-emitting diode. The results are believed to be helpful to researchers working on the design of next-generation compact and efficient solid-state lighting devices. Full article

LED diffuse-illumination systems are widely used in industrial inspection and real life because of their scattering properties. However, there has been little research on secondary optical designs for diffuse illumination. Considering the need for diffuse light in real life and work, combined with existing specular-reflection technology, this study proposes a design method for a combined-freeform-surface illumination system with specular and diffuse reflections. Considering that a separate diffusing device cannot effectively control the diffusion area of the light source, the unique properties of the specular-reflective device were utilized in this study. First, the specular-reflection device directs the light from the central portion of the LED to the diffuse-reflection device, and the light collected is then redistributed by the diffuse-reflection device. Two mathematical models were established according to the light-emitting angle of the LED, which corresponded to two freeform surfaces. In addition, when evaluating the uniformity of the target-plane illumination, a set of constraint equations was added to obtain the diffuse freeform surface contour of the target plane. Finally, the ratio of the diameter to the thickness of the resulting illumination system exceeded six, and the illumination uniformity increased to over 56% (with a uniformity improvement ratio of ≥6% compared to traditional single-freeform-surface systems and ≥10% compared to integrating sphere systems). It is specifically designed for industrial precision inspection scenarios, has higher illumination uniformity than other diffuse illumination systems, and has better compactness, making it suitable for high-precision inspection lighting applications. Full article

Background and Objectives: This study aimed to evaluate and compare the effects of immersion and brushing on resins used for temporary crowns, including two 3D-printed resins (Nanolab and PrintaX) and one self-curing resin (Duralay), with different surface finishing protocols. Materials and Methods: Printed specimens were designed using specialized software, followed by slicing and printing. Self-curing resin samples were fabricated using silicone matrices, with the printed specimens serving as references. Square samples (7.0 × 7.0 × 2.0 mm, n = 90) were divided into three groups based on surface finishing: extrinsic pigment with glaze, glaze only, and polish only. The samples were immersed in 15 mL of cola soft drink, energy drink, or distilled water for six days at 37 °C in a dark environment before undergoing a brushing test (180 cycles/minute, 65,700 cycles, 2 N, 37 °C). Color alterations, surface roughness, and Knoop microhardness were then analyzed. Results: Statistical analyses revealed that all factors significantly influenced the tested properties (p < 0.05). Nanolab exhibited the most pronounced color alterations, with ∆E₀₀ values reaching up to 22.21 ± 3.13 in specific conditions (e.g., Glaze, Cola soft drink). It also presented increased surface roughness, particularly when compared to PrintaX. Conversely, Duralay consistently displayed the highest Knoop microhardness changes (e.g., ranging from −1.84 ± 0.36 to 0.47 ± 0.45 in different conditions) across most experimental groups. Polishing consistently provided better outcomes in terms of color stability, surface roughness, and microhardness compared to extrinsic pigment + glaze or glaze-only treatments. The first immersion generally led to the greatest color change. Conclusions: The acidic challenge promoted significant changes in the optical and surface properties of the evaluated resins, increasing ∆E₀₀ and roughness and reducing microhardness to different extents depending on the material. Clinically, these findings highlight the relevance of material selection and limiting exposure to acidic beverages during provisional use. Full article

Poultry farming is important from a food point of view, as it provides products for the population. Waste resulting from poultry farming and processing is environmentally sensitive, which is why treatment technologies are crucial for sustainability. Conventional pre-treated wastewater originating from the poultry sector, combined with innovative methods of using substances with antimicrobial effects constitute another approach to eliminating health risks. This research aimed to evaluate the behavior of bacterial strains isolated from water samples treated by reverse osmosis (RO), ultrafiltration (UF), and ultraviolet disinfection (UV). To choose our antimicrobial substances, we surveyed the population using the Google Forms platform and the official questionnaire. Using a factorial design, the concentration of antibiotic or antiseptic, as well as the duration of their action on bacterial strains isolated in pure culture, was varied. The optical densities of bacterial cultures reflect the efficiency of treatments with antibacterial or antiseptic substances. Factorial design, corroborating the experimental results, led to the following: 4.84 mg·L⁻¹ antibiotic for 7.6 h and 4.23 mg·L⁻¹ chloramine for 16.23 h. The results obtained from mathematical modeling correspond to a decrease in the bacterial population. In perspective, combining purification technologies with antimicrobial substances, adapted to the volume of water through mathematical modeling, will reduce the risk of microbiological contamination, with bacterial recovery rate values ranging between 0.58 and 1.21 in the case of antiseptic using, and between 0.60 and 0.92 in the case of antibiotic using. Full article

Numerous road accidents involving vulnerable road users result from their insufficient visibility to drivers. To increase the appeal of warning clothing and motivate consumers to use it, particularly in non-professional settings, an innovative high-visibility vest with an active lighting system (ALS) and phosphorescent elements was developed. The effectiveness of the vest’s visibility-enhancing elements was assessed by examining two factors: the intensity of the light emitted by the phosphorescent tapes and the luminance of the optical fibers in the ALS. Studies have shown that thermal-transfer phosphorescent tapes are approximately 42% more effective in terms of luminescence than sewn-on tapes. The ALS demonstrated high durability, withstanding up to 15 washing cycles at 40 °C in a mild process. The luminance of optical fibers decreases significantly with increasing distance from the light source (LED). The difference between the luminance at the light source and at the end of the 1 m optical fiber was about 6 cd/m², representing approximately 68% of the maximum luminance value. This finding can assist in designing luminous clothing. Tests in real-world conditions in a tunnel have shown that the ALS allows the visibility of vest user to be increased to over 430 m, which is a 67% increase compared to retroreflective tapes. Laboratory performance testing confirmed the high acceptability of the vest model, including its aesthetics, by potential users. Full article

Aniline (ANI) was electropolymerized on ITO substrates with different surface resistivities. The process was performed by cyclic voltammetry from an aqueous, homogeneous solution containing sulfuric acid and the aniline monomer using various numbers of cycles and scan rates. The resulting polymer films (PANI) were characterized by ATR-IR spectroscopy, spectroscopic ellipsometry and atomic force microscopy. The influence of ITO surface resistivity on the electropolymerization process, the quality of the obtained PANI layers, and their optical properties was evaluated. Homogeneous PANI films were produced on ITO substrates with surface resistivities of 15–25 Ω/sq, encompassing both emeraldine salt and emeraldine base forms. Although the film’s growth was rapid, it also led to adhesion issues. In contrast, for ITO substrates with surface resistivities of 70–100 Ω/sq and 80–100 Ω/sq, the resulting films showed improved adhesion but were less homogeneous. Nevertheless, the conductive emeraldine salt form of polyaniline was successfully obtained. The conductive form of polyaniline was obtained without any additional modifications to the electropolymerization procedure. Notably, the literature provides no systematic analysis of electropolymerization on ITO substrates with different surface resistivities, which opens up new research opportunities and provides a basis for the rational design and optimization of PANI-based electro-optical coatings for advanced sensing applications. Full article

Free-space optical (FSO) communication is a promising alternative to radio-frequency (RF) and optical fiber systems due to its high data rates and large bandwidth. However, its performance is highly susceptible to atmospheric conditions such as fog, rain, snow, and haze. This paper analyzes fog-induced signal attenuation in the Morogoro and Mbeya regions of Tanzania using the Kim and Kruse attenuation models. To improve link performance, a quadrature amplitude modulation (QAM) multiple-input multiple-output (MIMO) FSO link was designed and analyzed using OptiSystem 22.0. In Mbeya, light fog conditions with 0.5 km visibility resulted in an attenuation of 32 dB/km, a bit error rate (BER) of 4.5 × 10⁻²³, and a quality factor of 9.79 over a 2.62 km link. In Morogoro, dense fog with 0.05 km visibility led to an attenuation of 339 dB/km, a BER of 1.12 × 10⁻¹⁵, and a maximum link range of 0.305 km. Experimental measurements were further conducted under clear, moderate, and dense fog conditions to systematically evaluate the FSO link performance. The results demonstrated that MIMO techniques significantly enhanced link performance by mitigating fog effects. Moreover, a dedicated application was developed to analyze transmission errors and evaluate system performance metrics. Additionally, a mathematical model of the FSO link was developed to describe and forecast the performance of the MIMO FSO system in atmospheric conditions impacted by fog. Full article

The strategic selection of lens geometry—spherical versus plane—decisively shapes the opto-thermal performance boundary of deep ultraviolet light-emitting diodes (DUV-LEDs), thereby governing their efficacy in application-specific photochemical processes. This study demonstrates that spherical lenses, by virtue of their superior light-collecting geometry, significantly enhance optical extraction efficiency and thermal management performance compared to conventional plane lenses. These engineered performance characteristics translate directly into divergent functional outcomes: spherical lenses enable rapid, high-intensity processing, while plane lenses are better suited for controlled, sustained operation. The findings establish a fundamental principle for DUV-LED packaging design: lens geometry can be tailored to optimize efficiency for distinct photochemical tasks, providing a clear pathway from device engineering to application-driven performance. Full article

Organic optoelectronic devices receive appreciable attention due to their low cost, ecology, mechanical flexibility, band-gap engineering, brightness, and solution process ability over a broad area. In this study, we designed and studied organic light-emitting diodes (OLEDs) consisting of an assembly of natural dyes, extracted from noble fir leaves (evergreen) and blue hydrangea flowers mixed with poly-methyl methacrylate (PMMA) as light emitters. We experimentally demonstrate the effective conversion of blue light emitted by an inorganic laser/photodiode into longer-wavelength red and green tunable photoluminescence due to the excitation of natural dye–PMMA nanostructures. UV-visible absorption and photoluminescence spectroscopy, ellipsometry, and Fourier transform infrared methods, together with optical microscopy, were performed for confirming and characterizing the properties of light-emitting diodes based on natural dyes. We highlighted the optical and physical properties of two different natural dyes and demonstrated how such characteristics can be exploited to make efficient LED devices. A strong pure red emission with a narrow full-width at half maximum (FWHM) of 23 nm in the noble fir dye–PMMA layer and a green emission with a FWHM of 45 nm in blue hydrangea dye–PMMA layer were observed. It was revealed that adding monolayer MoS₂ to the nanostructures can significantly enhance the photoluminescence of the natural dye due to a strong correlation between the emission bands of the inorganic–organic emitters and back mirror reflection of the excitation blue light from the monolayer. Based on the investigation of two natural dyes, we demonstrated viable pathways for scalable manufacturing of efficient hybrid OLEDs consisting of assembly of natural-dye polymers through low-cost, purely ecological, and convenient processes. Full article

This investigation examines the optical degradation of 260 nm and 265 nm UVC LEDs subjected to varying drive current conditions, simulating real-world deployment in consumer and professional disinfection systems. The primary aim was to assess lifetime trends and degradation behaviour based exclusively on radiometric and spectral data. A total of 24 devices (12 per wavelength group) were operated for 2000 h under a broad range of thermally stabilised current levels, from low-standby to maximum-rated operation. The results demonstrated distinct current-dependent ageing characteristics, wherein, for the tested device sets and operating conditions, 260 nm LEDs exhibited faster optical power degradation than the investigated 265 nm LEDs under nominal drive conditions. Notably, a moderate current derating of approximately 20% resulted in a more than fourfold increase in L70 lifetime and over a threefold extension in the number of effective disinfection cycles. Despite a stable spectral power distribution throughout ageing, significant statistical variation in lifetime metrics (L90, L80, L70, L50) was observed even among identically operated devices, underscoring the need for population-level reliability qualification. Optical lifetime estimates based on empirical model fitting indicated that the Ruschel logarithmic function most accurately captured the long-term degradation trends for the analysed datasets. These findings provide practical guidance for the design of durable and efficient UVC LED systems within the investigated device class and operating regimes, supporting sustained germicidal performance and long-term operational reliability across diverse use cases. Full article

A receipt information extraction task requires both textual and spatial analyses. Early receipt analysis systems primarily relied on template matching to extract data from spatially structured documents. However, these methods lack generalizability across various document layouts and require defining the specific spatial characteristics of unseen document sources. The advent of convolutional and recurrent neural networks has led to models that generalize better over unseen document layouts, and more recently, multi-modal transformer-based models, which consider a combination of text, visual, and layout inputs, have led to an even more significant boost in document-understanding capabilities. This work focuses on the joint use of a neural multi-modal transformer and a rule-based model and studies whether this combination achieves higher performance levels than the transformer on its own. A comprehensively annotated dataset, comprising real-world and synthetic receipts, was specifically developed for this study. The open source optical character recognition model DocTR was used to textually scan receipts and, together with an image, provided input to the classifier model. The open-source pre-trained LayoutLMv3 transformer-based model was augmented with a classifier model head, which was trained for classifying textual data into 12 predefined labels, such as date, price, and shop name. The methods implemented in the rule-based model were manually designed and consisted of four types: pattern-matching rules based on regular expressions and logic, database search-based methods for named entities, spatial pattern discovery guided by statistical metrics, and error correcting mechanisms based on confidence scores and local distance metrics. Following hyperparameter tuning of the classifier head and the integration of a rule-based model, the system achieved an overall F1 score of 0.98 in classifying textual data, including line items, from receipts. Full article

Underwater marine and freshwater environments are vast and mysterious, but our ability to explore them is limited by the inflexibility and inconvenience of monitoring systems. To overcome this problem, in this work, we present a proof-of-concept deployment of a real-time Internet of Underwater Things (IoUT) using blue light-emitting-diode-based visible light communication (VLC). Pulse-amplitude modulation with four levels is employed. To relax the focus point and increase the received power, four avalanche photodiodes (APDs) are adopted. Moreover, to reduce the error rate, the convolutional code with constraint-7 is used, which is the simplest to implement. Encoding and decoding are implemented by a field-programmable gate array. The results are verified by experimental demonstration. A baud rate of 9600 is used, but, unfortunately, we only have a 2 m long tank. System performance is improved when the number of APDs is increased; we investigated the effects of up to four APDs. Notably, bit error-free data transmission can be achieved. Additionally, this method would make underwater monitoring very conventional and dependable, and low-cost real-time monitoring would be possible, with data shown on the Grafana dashboard tool. Full article

Energy efficiency in road lighting is increasingly critical for sustainable urban development, yet numerical indicators essential for objective evaluation are often misunderstood or misapplied. This paper addresses fundamental misconceptions in interpreting the Power Density Indicator (PDI), a key metric for assessing lighting system efficiency. Through analysis of Romanian street lighting modernization projects and extensive literature review, we demonstrate widespread misunderstanding of PDI’s properties, including inappropriate summation across streets and failure to recognize its independence from road class. We present a comprehensive methodology for PDI interpretation and optimization through spatial visualization of Luminous Intensity Distribution Curves (LIDCs) using MATLAB’s MESH function. The theoretical framework derives minimum achievable PDI values as a function of LED-specific efficacy and system utilance. Case studies from 181 streets in Romanian cities reveal significant optimization potential. Finally, we demonstrate, through computational simulation, the theoretical ideal: a perfectly adapted LIDC achieving unitary utilance, confirming that minimum PDI depends solely on LED efficacy and optical efficiency. These findings provide practical guidance for designers to optimize energy efficiency while meeting photometric requirements. Full article

Optical Wireless Communication (OWC) technologies are emerging as promising complements to radio-frequency systems, offering high bandwidth, spatial confinement, and license-free operation. Within this domain, Visible Light Communication (VLC) and Optical Camera Communication (OCC) represent two distinct paradigms with divergent performance and security profiles. While VLC leverages LED-photodiode links for high-speed data transfer, OCC exploits ubiquitous image sensors to decode modulated light patterns, enabling flexible but lower-rate communication. Despite their potential, both remain vulnerable to various attacks, including eavesdropping, jamming, spoofing, and privacy breaches. This work applies—and extends—the Risk Matrix (RM) methodology to systematically evaluate the security of VLC and OCC across reconnaissance, denial, and exploitation phases. Unlike prior literature, which treats VLC and OCC separately and under incompatible threat definitions, we introduce a unified, domain-specific risk framework that maps empirical channel behavior and attack feasibility into a common set of impact and likelihood indices. A normalized risk rank (NRR) is proposed to enable a direct, quantitative comparison of heterogeneous attacks and technologies under a shared reference scale. By quantifying risks for representative threats—including war driving, Denial of Service (DoS) attacks, preshared key cracking, and Evil Twin attacks—our analysis shows that neither VLC nor OCC is intrinsically more secure; rather, their vulnerabilities are context-dependent, shaped by physical constraints, receiver architectures, and deployment environments. VLC tends to concentrate confidentiality-driven exposure due to optical leakage paths, whereas OCC is more sensitive to availability-related degradation under adversarial load. Overall, the main contribution of this work is the first unified, standards-aligned, and empirically grounded risk-assessment framework capable of comparing VLC and OCC on a common security scale. The findings highlight the need for technology-aware security strategies in future OWC deployments and demonstrate how an adapted RM methodology can identify priority areas for mitigation, design, and resource allocation. Full article

In the field of non-imaging optics, the use of freeform lenses for achieving uniform illumination is of significant research importance. However, existing studies have primarily focused on uniform illumination design for planar targets and have made remarkable progress, while relatively less attention has been paid to uniform illumination on curved surfaces. To address this, this paper proposes a design method for freeform lenses aimed at uniform illumination on curved surfaces. The key to this method lies in utilizing the first kind of surface integral Equation to transform the problem from the Cartesian coordinate system on the target surface into a planar coordinate system, thereby significantly reducing computational complexity. Simulation results confirm the feasibility of the proposed lens design method in enabling the realization of high-efficiency, high-uniformity illuminance distribution on a curved surface via secondary optics for LEDs. Full article