Search Results (16)

This study identifies the optimal conditions for enhancing the performance of the Color Picker System, a device designed for colorimetric sensing using plasmonic paper. A simulation study was conducted toanalyze the transmittance spectra of plasmonic paper embedded in different mixtures, resulting in a comprehensive color chart that includes the chromatic response as well as the RGB values of transmitted light. The filtering properties of the plasmonic paper were evaluated through colorimetric analysis, combining the transmittance characteristics with the spectrum of different light sources. Optimizing the correlation between these filtering properties and the light source enhances both sensitivity and precision. Arrays of nanoparticles with high absorbance, combined with Cold LED light sources, emerge as ideal components for the device set-up. Among the light sources tested, the White LED uniquely generates a red signal while producing the most significant variations in the green channel. In contrast, the Cold LED and Xenon Arc lamp produce the strongest colorimetric signals in the blue channel. This study provides a deep understanding of the filtering properties of plasmonic paper, opening a new way for the implementation of nanoparticle arrays in colorimetric sensing. Full article

This study quantitatively analyzes the influence of the spectral characteristics, reflectance or transmittance, of different materials on the lighting of an interior space with natural and artificial light. For this purpose, a three-dimensional simulated classroom is used, where each of the components is assigned specific materials with an associated reflectance or transmittance. Additionally, two types of lighting are available: 6500 K daylight and light from six continuous spectrum LED luminaires. The lighting is evaluated on two planes: the work plane and the corneal plane (80 cm and 120 cm from the floor, respectively). Three versions of the same classroom were analyzed by varying the walls (white, blue, and red), each with a different neutral-colored floor. Furthermore, calculations were performed in each situation considering two different types of glazing in the windows, with 20% and 88% transmittance. The photopic and melanopic lighting analysis was carried out with the ALFA calculation program to verify the necessary requirements for adequate lighting. The results show that the white classroom is the best lit, followed by the blue and finally the red, due to the reflectance characteristics of the walls and floor although slight differences among them are found. It was found that in some cases, additional auxiliary luminaires would be required for proper lighting depending on the transmittance of the glazing. This study highlights the critical role of material selection in optimizing both photopic and melanopic lighting, with practical implications for energy efficiency and occupant well-being in educational spaces. Full article

This research presents a detailed methodology for indoor positioning using visible light communication (VLC) technology, focusing on overcoming the limitations of traditional satellite-based navigation systems. The system is based on an optical positioning framework that integrates trilateration techniques with a semi-spherical array of photodiodes, designed to enhance both positional accuracy and orientation estimation. The system effectively estimates the receiver’s position and orientation with high precision by utilizing multiple white-light-emitting diodes (LEDs) as transmitters and leveraging angular diversity. The proposed method achieves an average position error of less than 3 cm and an angular accuracy within 10 degrees, demonstrating its robustness even in environments with obstructed line of sight. These results highlight the system’s potential for significant indoor positioning accuracy and reliability improvements. Full article

This paper introduces an approach to enhance the efficiency of urban intersections by integrating Visible Light Communication (VLC) into a multi-intersection traffic control system. The main objectives include the reduction in waiting times for vehicles and pedestrians, the improvement of overall traffic safety, and the accommodation of diverse traffic movements during multiple signal phases. The proposed system utilizes VLC to facilitate communication among interconnected vehicles and infrastructure. This is achieved by utilizing streetlights, headlamps, and traffic signals for transmitting information. By integrating VLC localization services with learning-driven traffic signal control, the multi-intersection traffic management system is established. A reinforcement learning scheme, based on VLC queuing/request/response behaviors, is utilized to schedule traffic signals effectively. Agents placed at each intersection control traffic lights by incorporating information from VLC-ready cars, including their positions, destinations, and intended routes. The agents devise optimal strategies to improve traffic flow and engage in communication to optimize the collective traffic performance. An assessment of the multi-intersection scenario through the SUMO urban mobility simulator reveals considerable benefits. The system successfully reduces both waiting and travel times. The reinforcement learning approach effectively schedules traffic signals, and the results highlight the decentralized and scalable nature of the proposed method, especially in multi-intersection scenarios. The discussion emphasizes the possibility of applying reinforcement learning in everyday traffic scenarios, showcasing the potential for the dynamic identification of control actions and improved traffic management. Full article

This paper introduces a novel approach, Visible Light Communication (VLC), to optimize urban intersections by integrating VLC localization services with learning-based traffic signal control. The system enhances communication between connected vehicles and infrastructure using headlights, streetlights, and traffic signals to transmit information. Through Vehicle-to-Vehicle (V2V) and Infrastructure-to-Vehicle (I2V) interactions, joint data transmission and collection occur via mobile optical receivers. The goal is to reduce waiting times for pedestrians and vehicles, enhancing overall traffic safety by employing flexible and adaptive measures accommodating diverse traffic movements. VLC cooperative mechanisms, transmission range, relative pose concepts, and queue/request/response interactions help balance traffic flow and improve road network performance. Evaluation in the SUMO urban mobility simulator demonstrates advantages, reducing waiting and travel times for both vehicles and pedestrians. The system employs a reinforcement learning scheme for effective traffic signal scheduling, utilizing VLC-ready vehicles to communicate positions, destinations, and routes. Agents at intersections calculate optimal strategies, communicating to optimize overall traffic flow. The proposed decentralized and scalable approach, especially suitable for multi-intersection scenarios, showcases the feasibility of applying reinforcement learning in real-world traffic scenarios. Full article

In recent years, photobiomodulation (PBM) has attracted widespread attention for the treatment of various causes of pain and inflammation. Primary dysmenorrhea (PD) is a common gynecological condition characterized by severe menstrual pain, and the limited effectiveness and side effects of conventional treatments have highlighted the urgent need to develop and identify new adjunct therapeutic strategies. The present study from the perspective of light morphology aimed to bypass the heat risk limitation and evaluate the efficacy and safety of pulsed 630 nm PBM therapy for reducing pain associated with PD. The pulse light parameters were designed according to the transmittance of red light. In this randomized, cross-over design, sham-controlled study, 46 women with PD were included and randomly assigned to either pulsed 630 nm light therapy or white light sham control therapy. The intervention lasted for 20 min per day and was administered for 7 consecutive days before and during menstruation. The results showed that the pulsed 630 nm PBM treatment demonstrated a significant reduction in pain levels compared to the placebo treatment (p < 0.001), with 55.00% of active treatment participants experiencing a pain intensity differential concentration exceeding 50.00%. Moreover, participants reported an improved quality of life during the active treatment phase and generally preferred it as a more effective method for relieving PD. No adverse events or side effects were reported throughout the trial. Based on the results, pulsed 630 nm LED therapy showed significant relief of menstrual pain compared to white light placebo treatment and improved quality of life under certain circumstances. Therefore, this study proposes that pulsed red light PBM therapy may be a promising approach for future clinical treatment of PD. Full article

Dye-sensitized solar cells (DSSCs) can be used as greenhouse glazing materials in agrivoltaic systems because they are translucent, have different colors, and can produce electricity. However, the light quality of DSSCs differs from that of sunlight, and the visible light transmittance is low. Therefore, we compared the plant shape, growth, and leaf color of coleus, a highly photosensitive plant, under transparent glass and red-colored DSSCs. Coleus ‘Highway Rose’ was grown in transparent (T, the control), shaded (S), and DSSC (D) chambers maintained at 23 ± 2 °C. The DSSC chambers were additionally illuminated with blue (B), green (G), white (W), B+G, and R+B+W light-emitting diodes (LEDs) (D+L) at 60 μmol·m⁻²·s⁻¹ photosynthetic photon flux density for 15 h from 05:00 to 20:00. The coleus generally exhibited good growth under the T treatment. However, the light quality of DSSCs differed from that of sunlight, and the visible light transmittance decreased. Coleus exhibited increased growth and leaf color characteristics under the supplemental B lighting treatments (D+L_(RBW), D+L_(B), D+L_(BG), and D+L_(W)). Supplemental lighting with B LEDs using DSSCs improved plant morphology growth and leaf color. On the other hand, supplemental G lighting reinforced the shade avoidance syndrome. Moreover, DSSCs could aid in reducing the energy required to control the environment. Full article

Transparent ceramics (Gd_0.975−xLu_xDy_0.025)₃Al₅O₁₂ (x = 0.2, 0.5, 0.975) are fabricated by vacuum sintering with the transmittance of ~60% at 583 nm. The doping of Lu³⁺ was beneficial to stabilize the garnet phase, and the best doping concentration was 20 at.%. All three (Gd, Lu)₃Al₅O₁₂:Dy ceramics display typical Dy³⁺ emission, originating from ⁴F_9/2 → ⁶H_J (J = 15/2, 13/2, 11/2) transition. Temperature-dependent luminescence spectra from 303.15 K to 603.15 K prove that the (Gd, Lu)₃Al₅O₁₂:Dy ceramics had good thermal stability and could be an ideal yellow-emitting candidate in light-emitting diodes. The luminous efficiency of the encapsulated white LED lamp was found to be ~87.9 lm/W when the injection current was 600 mA. The transparent (Gd, Lu)₃Al₅O₁₂:Dy ceramics show great application potential in various optical systems especially in the fields of luminescence and display. Full article

The effectiveness of human security-based guard patrol systems often faces challenges related to the consistency of perimeter checks regarding timing and patterns. Some solutions use autonomous drones for monitoring assistance but primarily optimize their camera-based object detection capabilities for favorable lighting conditions. This research introduces an innovative approach to address these limitations—a flying watchdog designed to augment patrol operations with predetermined flight patterns, enabling checkpoint identification and position verification through vision-based methods. The system has a laser-based data transmitter to relay real-time location and timing information to a receiver. The proposed system consists of drone and ground checkpoints with distinctive shapes and colored lights, further enhanced by solar panels serving as laser data receivers. The result demonstrates the drone’s ability to detect four white dot LEDs with square configurations at distances ranging from 18 to 20 m, even under deficient light conditions based on the OpenCV detection algorithm. Notably, the study underscores the significance of achieving an even distribution of light shapes to mitigate light scattering effects on readings while also confirming that ambient light levels up to a maximum of 390 Lux have no adverse impact on the performance of the sensing device. Full article

Optical wireless power transfer (OWPT) has been employed in the literature as a wireless powering approach for implanted and wearable devices. However, most of the existing studies on this topic have not studied the performances of OWPT systems when light is transmitted through clothing. This research therefore contributes to investigate the effects of clothing on OWPT performances from both theoretical and experimental perspectives. An obtained experimental result indicates that a single light-emitting diode (LED) transmitter is able to perform the OWPT through white cotton clothing, but failed with another dark cotton clothing, even at a small transmitting distance. Hence, this research proposes to employ LED arrays as optical transmitters to improve the OWPT system capability in terms of the wirelessly transmitted power, transmitting distance and system tolerance to misalignments, whilst keeping the system safety, low cost and simplicity. Consequently, a theoretical formula for the power transmission efficiency made by an LED array through clothing is proposed and then is verified with experimental results. Furthermore, the important role of multiple light reflections at the surfaces of clothing and the LED array transmitter is pointed out. Full article

Autonomous unmanned aerial vehicles (UAVs) have attracted increasing academic and industrial attention during the last decade. Using drones have broad benefits in diverse areas, such as civil and military applications, aerial photography and videography, mapping and surveying, agriculture, and disaster management. However, the recent development and innovation in the field of drone (UAV) technology have led to malicious usage of the technology, including the penetration of secure areas (such as airports) and serving terrorist attacks. Autonomous weapon systems might use drone swarms to perform more complex military tasks. Utilizing a large number of drones, simultaneously increases the risk and the reliability of the mission in terms of redundancy, survivability, scalability, and the quality of autonomous performance in a complex environment. This research suggests a new approach for drone swarm characterization and detection using RF signals analysis and various machine learning methods. While most of the existing drone detection and classification methods are typically related to a single drone classification, using supervised approaches, this research work proposes an unsupervised approach for drone swarm characterization. The proposed method utilizes the different radio frequency (RF) signatures of the drone’s transmitters. Various kinds of frequency transform, such as the continuous, discrete, and wavelet scattering transform, have been applied to extract RF features from the radio frequency fingerprint, which have then been used as input for the unsupervised classifier. To reduce the input data dimension, we suggest using unsupervised approaches such as Principal component analysis (PCA), independent component analysis (ICA), uniform manifold approximation and projection (UMAP), and the t-distributed symmetric neighbor embedding (t-SNE) algorithms. The proposed clustering approach is based on common unsupervised methods, including K-means, mean shift, and X-means algorithms. The proposed approach has been evaluated using self-built and common drone swarm datasets. The results demonstrate a classification accuracy of about 95% under additive Gaussian white noise with different levels of SNR. Full article

The proper classification of the origins of food products is a crucial issue all over the world nowadays. In this paper, the authors present a device—a multispectral portable fibre-optic reflectometer and signal processing patch—together with a machine-learning algorithm for the classification of the origins of chicken eggshells in the case of Mycoplasma synoviae infection. The sensor device was developed based on previous studies with a continuous spectrum in transmittance and selected spectral lines in reflectance. In the described case, the sensor is based on the integration of reflected spectral data from short spectral bands from the VIS and NIR region, which are produced by single-colour LEDs and introduced to the sample via a fibre bundle. The measurement is carried out in a sequence, and the reflected signal is pre-processed to be put in the machine learning algorithm. The support vector machine algorithm is used together with three different types of data normalization. The obtained results of the F-score factor for classification of the origins of samples show that the percentages of eggs coming from Mycoplasma synoviae infected hens are up to 87% for white and 96% for brown eggshells. Full article

Indoor positioning systems based on visible light communication (VLC) using white light-emitting diodes (WLEDs) have been widely studied in the literature. In this paper, we present an indoor visible-light positioning (VLP) system based on red–green–blue (RGB) LEDs and a frequency division multiplexing (FDM) scheme. This system combines the functions of an FDM scheme at the transmitters (RGB LEDs) and a received signal strength (RSS) technique to estimate the receiver position. The contribution of this work is two-fold. First, a new VLP system with RGB LEDs is proposed for a multi-cell network. Here, the RGB LEDs allow the exploitation of the chromatic space to transmit the VLP information. In addition, the VLC receiver leverages the responsivity of a single photodiode for estimating the FDM signals in RGB lighting channels. A second contribution is the derivation of an expression to calculate the optical power received by the photodiode for each incident RGB light. To this end, we consider a VLC channel model that includes both line-of-sight (LOS) and non-line-of-sight (NLOS) components. The fast Fourier transform (FFT) estimates the powers and frequencies of the received FDM signal. The receiver uses these optical signal powers in the RSS-based localization application to calculate the Euclidean distances and the frequencies for the RGB LED position. Subsequently, the receiver’s location is estimated using the Euclidean distances and RGB LED positions via a trilateration algorithm. Finally, Monte Carlo simulations are performed to evaluate the error performance of the proposed VLP system in a multi-cell scenario. The results show a high positioning accuracy performance for different color points. The average positioning error for all chromatic points was less than 2.2 cm. These results suggest that the analyzed VLP system could be used in application scenarios where white light balance or luminaire color planning are also the goals. Full article

Visible Light Communications (VLC) have gained much popularity lately. In such a system, a white LED (Light-Emitting Diode) plays a double role as a light source and a transmitter. The main problem here is that the LED exhibits a low bandwidth and high nonlinearity, so the equalization of the LED nonlinear dynamic response is necessary. For this, various equalizers are used. This paper compares the pre- and post-equalizer performance in terms of the received signal quality for a channel that includes a nonlinear element of limited bandwidth, such as an LED. Multilevel Pulse Amplitude Modulation (PAM) was selected as the signal format, as well as a variant of the Volterra series equalizer as the compensating element. The results obtained may be used for the correction of the dynamic characteristics of LEDs applied in VLC systems. For the sake of comparison, we used Modulation Error Ratio (MER) values at the receiver output. The dynamic nonlinear behavior was modeled by a Wiener–Hammerstein device, whereas the post/pre-equalizer was based on the dynamic deviation reduction-based Volterra series. The obtained results indicate that the post- and pre-equalizer performed comparably for the linear/moderately nonlinear channels and for a high noise level. In the case of high nonlinearity and a large SNR (Signal–to–Noise Ratio) values, the post-equalizer performed somewhat better in terms of MER by a few dB at maximum. Full article

In this paper, a new method to regulate the correlated color temperature (CCT) of white light-emitting diodes (LEDs) is proposed for the single-chip packaging structure, in which the blue light distribution emitted from the chip in the red/yellow phosphor layer was modulated through changing the paraffin-polydimethylsiloxane (PDMS) film transparence and haze. The results show that the transmittance of the paraffin-PDMS film can be modulated from 49.76% to 97.64%, while the haze of that ranges from 88.19% to 63.10%. When the thickness of paraffin-PDMS film is 0.6 mm, and the paraffin-PDMS film concentration is 30 wt%, the CCT of white LED decreases from 15177 K to 3615 K with the increase of thermal load in the paraffin-PDMS film. The modulating range of its CCT reaches 11562 K. The maximum CCT variation at the same test condition is only 536 K in the repeated experiments within one week. Full article