Search Results (55)

The processing performance of deep narrow grooves by electrical discharge machining (EDM) needs to be further improved, mainly reflected in the serious electrode wear and low processing efficiency. This study firstly conducted a single-factor experiment on electrical parameters to analyze the influence of electrical parameters on electrode length wear and electrode sharp corner wear, respectively. It was found that the increase in pulse width and duty cycle could reduce electrode length wear, but at the same time led to an increase in electrode sharp corner wear. The reason is that bubbles and debris tend to accumulate at the sharp corner of the electrode. It causes short circuits and arcing phenomena, intensifying the sharp corner wear of the electrode. To address this issue, it is proposed to use a rounded corner electrode to facilitate the exclusion of bubbles and debris from the machining gap, reduce the occurrence of short circuits and arcing phenomena, thereby lowering the electrode length and sharp corner wear, and enhancing processing efficiency. Through the simulation of the flow field in the machining gap, it is theoretically proven that the rounded corner electrode can promote the movement of bubbles and debris towards the outlet of the machining gap and slow down the accumulation of bubbles and debris. Through the EDM of deep narrow groove, it is proven that the electrode wear and processing efficiency of the rounded corner electrode are both superior to those of the sharp corner electrode, and the electrode wear and processing efficiency increase with the increase in the rounded corner radius of the electrode. The research results have contributed to improving the performance of deep narrow grooves by EDM. Full article

A novel four-in-one (4-in-series) MicroLED-in-Package (MiP4) architecture is demonstrated for the first time, integrating four sub-85 µm blue micro-LED (µ-LED) dies on a transparent glass substrate through a redistribution-layer (RDL) interconnection process. The MiP4 device operates natively at 16 V, eliminating the need for step-down converters and simplifying high-voltage backlight driving circuits. The transparent glass carrier enables efficient light extraction, excellent thermal dissipation, and uniform emission. Electrical and optical characterization of dual- (B2), triple- (B3), and quad-chip (B4) devices shows ideal voltage scalability (8 V, 12 V, 16 V) and stable emission at 450 ± 2 nm with minimal FWHM broadening (22–29 nm). Compared with a commercial LED, the MiP4 delivers 1.8× higher optical power (~41.8 mW) despite its active area being only ~1/70 that of the reference device (20,000 µm² vs. 1,350,000 µm²), yielding a dramatically enhanced luminous flux density of 64 lm/mm² at 50 mA. Furthermore, pulse-driven measurements under 2%, 5%, and 10% duty cycles verify excellent thermal stability and minimal spectral shift (<1 nm), confirming the device’s robustness and energy efficiency. This first-of-its-kind 4-in-1 high-voltage glass-based µ-LED package provides a scalable and manufacturable route toward next-generation ultra-thin, high-brightness Mini-LED backlight and optical communication systems. Full article

Gallium nitride (GaN) devices are gaining rapid adoption in electric vehicle (EV) power electronics because of their high switching speed, efficiency, and passive size reduction. The remaining gaps concern reliability across real drive cycles, integration with vehicle-level thermal subsystems, and scalability to high-voltage platforms. This review addresses these gaps by synthesizing experimental reports and automotive case studies from 2019 to 2025. We examine reliability through junction stress and derating maps derived from urban/highway duty profiles and temperature extremes, and we link device hot-spots to thermal pathways (TIMs, spreaders, liquid/air cooling) within the EV thermal budget. We then compare GaN-based onboard chargers (OBCs), DC–DC stages (LLC/CLLC/DAB), traction inverters, and EMI strategies against Si/SiC baselines. Results indicate OBC efficiencies of 96–98% at 100–500 kHz, with 30–60% passive reduction; inverter efficiencies > 98% on 400 V platforms; and strong potential for GaN paired with Vienna or T-type rectifiers in 800 V charging, while >900 V traction remains largely SiC-led. We conclude with a topology-selection framework that balances switching and conduction losses, gate-driver complexity, and EMI, plus a roadmap toward EMI-compliant MHz operation and data-driven reliability evaluation. Full article

The urgent global issue of climate change caused by rising carbon dioxide (CO₂) levels has led to the widespread use of gas separation processes. Among the available processes, chemical absorption has received more attention due to its maturity and higher efficiency compared to others. However, the high energy consumption during the desorption step poses several technical challenges, limiting its industrial applications. To overcome those challenges, several research studies have been conducted to improve the performance of the desorption process. In particular, various types of catalysts have been tested to improve the performance of the CO₂ desorption process. Among the available catalysts, Titanium Oxyhydrate (TiO(OH)₂) has shown remarkable characteristics for replacing conventional catalysts, mainly due to its stability and the potential for increasing the CO₂ desorption rate. However, limited studies have been conducted to evaluate the performance of the CO₂ desorption process, especially by utilizing commercial solvents such as piperazine (PZ) promoted methyldiethanolamine (MDEA). Hence, this study aims to evaluate the stability of TiO(OH)₂ as a catalyst during the CO₂ desorption process using various characterization techniques. The CO₂ desorption performance is also assessed under different operating conditions. Moreover, the regeneration energy is determined and reported as the sensible heat duty per released CO₂. The results show no significant difference between fresh and cycled TiO(OH)₂, indicating its substantial thermal stability. Furthermore, a notable rise of 19.58% is observed in desorption rate while utilizing TiO(OH)₂ with a mass concentration of 5 wt%, reflecting less energy consumption. These findings suggest that TiO(OH)₂ could serve as a transformative catalyst in industrial-scale CO₂ desorption processes, potentially paving the way for more sustainable CO₂ capture technologies. Full article

This article proposes an improved Visible Light Communication (VLC) solution that, besides the indoor lighting and data transfer, offers an energy-efficient alternative for modern workspaces. Unlike Light-Fidelity (LiFi), designed for high-speed data communication, VLC primarily targets applications where fast data rates are not essential. The developed prototype ensures reliable communication under variable lighting conditions, addressing low-speed requirements such as test bench monitoring, occupancy detection, remote commands, logging or access control. Although the tested data rate was limited to 100 kb/s with a Bit Error Rate (BER) below 10⁻⁷, the key innovation is the light dimming dynamic adaptation. Therefore, the system self-adjusts the LED duty cycle between 10% and 90%, based on natural or artificial ambient light, to maintain a minimum illuminance of 300 lx at the workspace level. Additionally, this work includes a scalability analysis through simulations conducted in an office scenario with up to six users. The results show that the system can adjust the lighting level and maintain the connectivity according to users’ presence, significantly reducing energy consumption without compromising visual comfort or communication performance. With this light intensity regulation algorithm, the proposed solution demonstrates real potential for implementation in smart indoor environments focused on sustainability and connectivity. Full article

Conventional continuous pesticide application remains prevalent in agriculture, but its limitations in addressing the spatial–temporal variability of biotic stressors have led to excessive chemical inputs and inefficiency. The emergence of precision agriculture has catalyzed significant advancements in variable-rate spray systems to optimize agrochemical deployment through real-time modulation. This technology demonstrates critical advantages in minimizing the environmental footprint while maintaining crop protection efficacy. Our systematic review analyzes three foundational variable-rate spray architectures—pressure-regulated, flow rate-regulated, and pesticide concentration-regulated mechanisms—evaluating their maturity and implementation paradigms. Pressure-regulated technology relies on the pressure–flow relationship to achieve regulation, but there is a narrow range in flow regulation, atomization stability is insufficient, and there are other defects. Flow rate-regulated technology achieves precise control through the dynamic adjustment of the nozzle orifice area or Pulse-Width Modulation duty cycles, but this technology faces mechanical wear, a nonlinear flow–duty cycle relationship, and other challenges. Pesticide concentration-regulated technology is centered on real-time mixing, which can avoid the residue of chemicals but is highly dependent on fluid characteristics and mixing efficiency. This study proposes improvement paths from the perspectives of hardware optimization, control strategy integration, and material innovation. Through the summary and analysis of this paper, we hope to provide valuable references for future research on variable-rate spray technology. Full article

High-test peroxide (HTP) monopropellant thrusters are being considered for spacecraft lander missions due to their simplicity and reduced toxicity compared to traditional propellants. Pulse-Width Modulation (PWM) throttling is a key technique for precise thrust control in such systems. However, PWM throttling can lead to pressure surges and oscillations in the propellant feed system, potentially compromising system reliability. This study investigates the influence of PWM parameters, specifically duty cycle and frequency, on pressure surges and oscillations in a 50-newton-class HTP monopropellant thruster. The objective is to identify stable operating conditions that mitigate these effects, thereby enhancing the reliability of PWM throttling for lander applications. An experimental setup was developed, including a 50-newton-class thruster with a ${\mathrm{MnO}}_2{\mathrm{/La/Al}}_2{\mathrm{O}}_3$ catalyst and a solenoid valve for PWM control. Cold flow tests using water characterized the valve response and water hammer effects, while hot fire tests with 90 wt.% HTP were used to evaluate thruster performance under steady-state and PWM conditions. Analytical methods, including Joukowsky’s equation and power spectral density analysis, were used to interpret the data and understand the underlying mechanisms. The results showed that while surge pressures generally aligned with steady-state values, specific PWM conditions led to amplified surges, particularly at low duty cycles. Additionally, high duty cycles induced chugging instability. The natural frequencies of the feed system were found to play a crucial role in these phenomena. Stable operating conditions were identified by avoiding duty cycles that cause constructive interference of pressure waves. This research demonstrates that by carefully selecting PWM parameters based on the feed system’s dynamic characteristics, pressure surges and oscillations can be minimized, ensuring reliable operation of HTP monopropellant thrusters in PWM throttling mode. These findings contribute to the development of more efficient and safer propulsion systems for spacecraft landers. Full article

Achieving a stable color output across wide temperature ranges in automotive LED applications is challenging, especially when using cost-sensitive chips with limited computational resources. This study proposes an improved temperature model that integrates Fourier heat conduction and thermal resistance concepts to more accurately capture self-heating and power dissipation effects. To accommodate the constraints of low-cost automotive-grade microcontrollers (MCUs), the associated optical algorithm is converted from floating-point to a 16.16 fixed-point format, reducing both memory usage and computational overhead. Experimental results conducted from −40 °C to 120 °C show that the improved model predicts LED temperatures within 5 °C of measured values, reducing errors by up to 30% compared to conventional PN-junction-based methods. Furthermore, by comparing the chromaticity points generated under the new and traditional models—and implementing an additional three-duty-cycle offset at 1% brightness—the improved approach reduces chromaticity drift by approximately 0.0052 in the CIE 1931 xy color space. These findings confirm the superior stability and accuracy of the new model for both thermal management and chromaticity compensation, offering a cost-effective solution for automotive LED systems requiring precise color control under constrained MCU resources. Full article

A photoplethysmography (PPG) sensor is a cost-effective and efficacious way of measuring health conditions such as heart rate, oxygen saturation, and respiration rate. In this work, we present a hybrid PPG sensor system working in a reflective mode with an optoelectronic module, i.e., the combination of an inorganic light-emitting diode (LED) and a circular-shaped organic photodetector (OPD) surrounding the LED for efficient light harvest followed by the proper driving circuit for accurate PPG signal acquisition. The performance of the hybrid sensor system was confirmed by the heart rate detection process from the PPG using fast Fourier transform analysis. The PPG signal obtained with a 50% LED duty cycle and 250 Hz sampling rate resulted in accurate heart rate monitoring with an acceptable range of error. The effects of the LED duty cycle and the LED luminous intensity were found to be crucial to the heart rate accuracy and to the power consumption, i.e., indispensable factors for the hybrid sensor. Full article

Portable and wearable sensor systems implemented in the paradigm of the Internet of Things (IoT) are part of our daily activities as well as commercial and industrial products. The connection of measurement devices has led to not only a sharp increase in information sharing, but also to the frequency of cyber-attacks, in which system vulnerabilities are exploited to steal confidential information, corrupt data, or even make the system unavailable. Physical unclonable function (PUF)-based devices exploit the inherent randomness introduced during device manufacturing to create a unique fingerprint. They are widely used to generate passwords and cryptographic keys to mitigate security issues in IoT applications. Among the existing different PUF structures, ring oscillator (RO)-based PUF devices are very popular due to their simple structure and their potential easy integration onto chips. In this paper, the possibility of increasing the number of challenge–response pairs (CRPs) of RO-based PUF devices by measuring two different parameters (the oscillation frequency and the duty cycle) is investigated. The results achieved by the performed circuit level simulations and experimental measurements show that these two parameters feature a weak correlation. The proposed PUF device can be used to increase the number of CRPs to improve device security while achieving a high uniqueness value (49.77%). Full article

A novel prototype based on the combination of a multi-junction, high-efficiency photovoltaic (PV) module and a supercapacitor (SC) able to self-power a wireless sensor node (WSN) for outdoor air quality monitoring has been developed and tested. A PV module with about an 8 cm² active area made of eight GaAs-based triple-junction solar cells with a nominal 29% efficiency was assembled and characterized under terrestrial clear-sky conditions. Energy is stored in a 4000 F/4.2 V supercapacitor with high energy capacity and a virtually infinite lifetime (10⁴ cycles). The node power consumption was tailored to the typical power consumption of miniaturized, low-consumption NDIR CO₂ sensors relying on an LED as the IR source. The charge/discharge cycles of the supercapacitor connected to the triple-junction PV module were measured under illumination with a Sun Simulator device at selected radiation intensities and different node duty cycles. Tests of the miniaturized prototype in different illumination conditions outdoors were carried out. A model was developed from the test outcomes to predict the maximum number of sensor samplings and data transmissions tolerated by the node, thus optimizing the WSN operating conditions to ensure its self-powering for years of outdoor deployment. The results show the self-powering ability of the WSN node over different insolation periods throughout the year, demonstrating its operation for a virtually unlimited lifetime without the need for battery substitution. Full article

This work examined the influence of UV-A light modulation on the photocatalytic process coadjuvated with H₂O₂ to mineralize phenol in an aqueous solution. A fixed-bed batch photocatalytic reactor with a flat-plate geometry, irradiated by UV-A LEDs, was employed. The successful deposition of commercial TiO₂ PC105 on a steel plate (SP) was achieved, and the structured photocatalyst was characterized using Raman spectroscopy, specific surface area (SSA) measurements, and UV–vis DRS analysis. These analyses confirmed the formation of a titania coating in the anatase phase with a bandgap energy of 3.25 eV. Various LED-dimming techniques, with both fixed and variable duty cycle values, were tested to evaluate the stability of the photocatalyst’s activity and the influence of operating parameters during the mineralization of 450 mL of a phenol solution. The optimal operating parameters were identified as an initial phenol concentration of 10 ppm, a hydrogen peroxide dosage of 0.208 g L⁻¹, and triangular variable duty cycle light modulation. Under these conditions, the highest apparent phenol degradation kinetic constant (0.39 min⁻¹) and the total mineralization were achieved. Finally, the energy consumption for mineralizing 90% phenol in one cubic meter of treated water was determined, showing the greatest energy savings with triangular light modulation. Full article

An adaptive high-efficiency light-emitting Diode (LED) backlight driver scheme has been proposed to address the issue of additional power loss caused by LED forward voltage variation. In this scheme, the peak current and the duty cycle of each LED channel are adjusted separately through an adaptive control algorithm to minimize the voltage drop on the linear current regulator (LCR) of each LED channel to reduce the excessive power loss in each LED channel and enhance the total power efficiency. A linear current regulator, suitable for adaptive control, is designed on a 0.18 μm 5V complementary metal-oxide-semiconductor (CMOS) process. Simulation results demonstrate that the linear current regulator can achieve a linearly adjustable channel current ranging from 0 to 48 mA with a current resolution of 0.2 mA. Across different process corners and temperatures, the maximum error for the full current range is less than 0.1%. The core area of chip layout is about 0.1 mm². The complete driver prototype comprises the LCR chips, external power MOS transistors, digital module, and LED chains. The test results show that the power loss of the linear current regulator has been significantly reduced, and the power efficiency of each LED channel has been measured at around 98.1%. Full article

In this paper, a novel ultraviolet (UV) scatter communication scheme is presented, designed to dynamically adjust the signal duty cycle to optimize on–off keying (OOK) modulation and reduce the bit error rate (BER), particularly under varying rate settings. This approach addresses the significant challenge posed by LED tailing effects, which cause signal fluctuations and increase BER in high-speed communications. This BER suppression scheme is proposed for the first time in UV communication research, enhancing communication performance without the need for additional hardware or complex algorithms. A UV communication model that incorporates both path loss and LED tailing effects is introduced, with the probability density function of the signal from transmitter to receiver derived. By varying the signal duty cycle, tailing-induced BER is effectively minimized. Additionally, a closed-form expression for signal transmission BER using a single-scattering model is provided, and the proposed UV communication system is validated through comprehensive simulations and experimental tests. The results indicate that LED tailing has a pronounced impact on BER at higher communication speeds, while its effects are less significant at lower speeds. By optimizing the duty cycle parameters for various communication rates, findings demonstrate that lower duty cycle settings significantly reduce the BER at higher speeds. This further demonstrates the excellent performance of the proposed UV communication solution for OOK-modulated optical communication. Full article

The micro-arc oxidation (MAO) technique was employed to produce calcium phosphate coatings on titanium surfaces using an electrolyte composed of hydroxyapatite and calcium carbonate in an aqueous solution of orthophosphoric acid. The coatings’ morphology and composition were regulated by adjusting electrical parameters, specifically the duty cycle and voltage. This study examined the effects of the duty cycle and voltage during the MAO process on the microstructure and composition of calcium phosphate coatings on VT1–0 titanium substrates. Scanning electron microscopy (SEM) was utilized to analyze the microstructure and thickness of the coatings, while X-ray diffraction (XRD) was employed to determine their phase composition. The findings reveal that the surface morphology of the calcium phosphate coatings transitions from a porous, sponge-like structure to flower-like formations as the duty cycle and voltage increase. A linear increase in the voltage within the applied duty cycles led to a rise in the size of the forming particles of amorphous/crystalline structures containing phases of monetite (CaPO₃(OH)), monocalcium phosphate monohydrate (Ca(H₂PO₄)₂·H₂O), and calcium pyrophosphate (γ–Ca₂P₂O₇). Full article