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Study of visible-light photocatalytic degradation of 2,4-dichlorophenoxy acetic acid in batch and circulated-mode photoreactors
摘要： Purpose The consumption of pesticides and chemical fertilizers is one of the major environmental and health problems. In this report, 2,4-dichlorophenoxyacetic acid (2,4-D) was chosen to evaluate the impact of photodegradation using LED (Light-emitting diode) (400 and 365 nm) sources in batch and programmable circulated-mode photoreactors respectively. Methods A β-cyclodextrin (β-CD) grafted titanium dioxide P25 (P25/β-CD) and complexation of 2,4-D and β-CD were synthesized via photoinduced and spray-drying methods, respectively. The structures were characterized. Moreover, we investigated the effects of the amount of catalyst, the β-CD amount on bed catalyst, irradiation time, kind of photoreactor on the photocatalytic degradation efficiency. Results Based on the results of experiments in batch reactor, the optimum amount of TiO2, β-CD grafted by catalyst were 1 and 0.1 g/L, respectively. In batch-mode the photodegradation efficiency of 2,4-D after 5 h with P25, P25/β-CD as a photocatalyst and 2,4-D/β-CD complex with P25 photocatalyst were approximately 81, 85 and 95% respectively. After 8 h of irradiation in circulated-mode reactor, degradation yields with P25, P25/β-CD and 2,4-D/β-CD complex along with P25 were 89, 91 and 96% respectively. On the other hand, the circulated-mode photoreactor with high efficiency was appropriate to degradation of the high concentration of 2,4-D solution (200 mg/L). After 5 successive cycles with 25 h of irradiation, P25 and P25/β-CD maintained as high 2,4-D removal efficiency as 82.6, 84% respectively, with excellent stability and reusability. Conclusion The photodegradation method can be used as an effective and environmental friendly process in the degradation of organic compound.
关键词： 2,4-D/β-CD complex,Batch-mode photoreactor,Light-emitting diode (LED),Circulated-mode photoreactor,2,4-Dichlorophenoxyacetic acid (2,4-D)
更新于2025-11-14 15:18:02
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Analysis of Thermal and Optical Characteristics of Light Emitting Diode on Various Heatsinks
摘要： Light emitting diodes (LED) are widely used in today’s world due to its less power consumption and its high luminance capacity. Around 20-30% of energy is converted to light energy and 70-80% of energy is dissipated as heat. The excessive rise in temperature causes failure to the LED. An effective thermal management is required for the proper heat dissipation in LED. In this work, the heat dissipation and the optical characteristics of the 16 W LED are studied using different types of aluminium heat sinks. The variation of case and junction temperature as well as the optical characteristic of LED is measured for different heatsink at different It was observed that heat sink with higher surface area shows the best result in terms of lower case and junction temperature. The higher luminous intensity was observed for the parallel fin type 1 heatsink due to higher surface area.
关键词： Heatsink,Case temperature,Light Emitting Diode (LED),Junction temperature
更新于2025-09-23 15:23:52
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High Speed Wireless Internet Using LiFi
摘要： The internet has become a basic necessity, so with the advancement in technology, people are demanding something faster than WI-FI. Since light is the only medium that can travel fastest than any other source of data transmission else so if we use this medium for internet, it will be the best utilization of medium with a higher data transmission rate. This technology was implemented over and came out with concept of LI-FI Technology. Li-Fi in known for Light-Fidelity, Li-Fi uses an idea of visible light communication (VLC) technology that uses light as a medium to convey fast high-speed communication in a manner like Wi-Fi. Since visible light is present everywhere, the main idea of our review paper is how LI-FI technology can help in security, speed and reliability of internet and even can change our life style. This innovation is actualized utilizing white LED bulbs matched with the Downlink transmitter that can give a higher information transmission rate up to 10Gbps. The main prospective of this paper demonstrates the forthcoming routine of Li-Fi technology innovation and its highlights to expand the execution of information transmission and different applications where Li-Fi has been put to utilize.
关键词： Data utilization,Visible Light communication,Wi-Fi,server,Light-emitting diode (LED),Light-Fidelity (Li-Fi),Video LAN Client (VLC)
更新于2025-09-23 15:22:29
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Indoor Localization Using K-Pairwise Light Emitting Diode Image-Sensor-Based Visible Light Positioning
摘要： A great deal of research has been devoted to studying indoor localization schemes for the development of location-based services. This study investigated an indoor localization system, including subsystems of non-line-of-sight (NLOS) image-sensor-based visible light communications (IS-VLC) and the proposed ??-pairwise light emitting diode (LED) image-sensor-based visible light positioning (IS-VLP), in a unified lighting environment. A smartphone received multiple LED identifiers through the designed NLOS IS-VLC and successfully performed the proposed ??-pairwise LED IS-VLP with ?? = 3 to achieve localization, with maximum localization errors of 2.92 cm and 3.54 cm being obtained for ceiling heights of 100 cm and 150 cm, respectively.
关键词： visible light communications (VLC),Image-sensor-based visible light positioning (VLP),light emitting diode (LED)
更新于2025-09-23 15:21:21
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Evaluation of Lighting Parameters at the Workplace with the use Replacements for Incandescent Lamps
摘要： The article evaluates the possibility of using halogen lamps, compact fluorescent lamps and LED lamps as direct substitutes of traditional 100 W incandescent lamps for selected residential lighting applications. A single halogen lamp, six compact fluorescent lamps and six LED light sources were examined. A traditional light bulb was also examined for comparison. All lamps operated in three luminaires. The basic evaluation criterion was the illuminance, uniformity and glare limitation in the place of work. It was found that not all light sources can be considered substitutes of traditional light bulbs. In the case of a luminaire made from a translucent material and one luminaire with a reflector, not all lamps allowed to obtain at least the same lighting parameters in the place where visual work was performed, as when a traditional light bulb was used.
关键词： light-emitting diode (LED),bulb's replacement,lighting parameters at the workplace,light sources for household
更新于2025-09-23 15:21:21
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A Lifetime Performance Analysis of LED Luminaires Under Real-Operation Profiles
摘要： Light-emitting diode (LED)-based lighting is the most dominant lighting solution in the current era since it is energy-efficient and long-lasting. Hence, performance analysis of the LEDs throughout its lifetime is of prime importance. The work presented in this article provides insight on degradation analysis of the LED luminaire inclusive of the LED driver in real operating ambient conditions and investigates the performance of both LED light engine and LED driver throughout the period of its lifetime. To represent the practical scenario of LED lighting system usage in commercial applications, analysis of switching cycles on the performance of LED luminaires is also studied. The outcome of this article suggests that LED luminaire under study tends to fail due to lumen degradation, followed by color shift represented by Duv and then lastly by driver failure. Scanning electron microscope and energy-dispersive spectroscopy (SEM-EDS) analysis suggests the corrosion of Ag mirror resulting in lumen output reduction and, thus, is the main reason for the failure of LED luminaire. This provides an insight into the LED manufacturing companies to have better estimate on lifetime of LED luminaires and also the necessity to improve the LEDs’ performance such that luminaires will have longer lifetime as claimed.
关键词： Life estimation,operating cycles,light-emitting diode (LED) luminaire,lumen degradation
更新于2025-09-23 15:21:01
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Evaluation of a Ultraviolet B Light Emitting Diode (LED) for Producing Vitamin D <sub/>3</sub> in Human Skin
摘要： Aim: A commercially available light emitting diode (LED) that transmitted narrow band ultraviolet B (UVB) radiation was evaluated for its efficacy and efficiency to produce vitamin D3 in human skin. Materials and Methods: Human skin samples were obtained from surgical procedures. The LED had peak emission wavelength of 295 nm. Skin samples were exposed to the UVB-LED for varying times and then were analyzed by high-pressure liquid chromatography (HPLC) to determine the vitamin D3 content. Results: There was a statistically significant time- and dose- dependent increase in the percent of 7-dehydrocholesterol that was converted to vitamin D3 in the skin type II samples; 1.3%±0.5, 2.3%±0.6 and 4.5%±1.67 after exposure to 0.75 (11.7 mJ/cm2), 1.5 (23.4 mJ/cm2) and 3 (46.8 mJ/cm2) minimal erythemal doses (MEDs), respectively. Conclusion: The UVB-LED was effective and efficient in generating vitamin D3 in human skin, in vitro. The amount of vitamin D3 production increased in a dose-dependent fashion with increased UVB energy. UVB-LEDs can be developed for devices that can efficiently produce vitamin D3 in human skin.
关键词： vitamin D3,human skin,ultraviolet B radiation,Previtamin D3,ultraviolet radiation light emitting diode (LED)
更新于2025-09-23 15:21:01
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[IEEE 2020 Moscow Workshop on Electronic and Networking Technologies (MWENT) - Moscow, Russia (2020.3.11-2020.3.13)] 2020 Moscow Workshop on Electronic and Networking Technologies (MWENT) - Measurement of the Dynamic Characteristics of Separate Spectral Bands of the LEDs Electroluminescence Spectra
摘要： A method for measuring the 3 dB frequency of the full modulation of separate spectral components of electroluminescence spectrum of light-emitting diodes (LEDs) is described. The method consists in passing through the LED a series of current pulses having the shape of a meander, and the emission spectrum of the LED is measured by a spectrometer OceanOptics USB2000+ in the mode of signal accumulation. As the pulse frequency increases, the intensity of all spectral components of the LED emission spectrum decreases. The frequency at which the optical signal decreases 1.19 times relative to the level measured at a low frequency is taken as the 3 dB frequency of the separate spectral component of the LED electroluminescence spectrum. By using the pulse signal it is possible to increase the sensitivity of the measuring means compared to the measuring means using the harmonic test signal. A description of the hardware-software complex implementing said measurement method is presented. The results of testing the measuring complex by the electroluminescence spectra of commercial green InGaN-based LEDs at the current range of 10-5...10-2 A and the current frequency range of 0.001...10 MHz are presented. The developed hardware-software complex and the method for estimating the spectral recombination parameters of heterojunction LEDs can be used both for the purpose of diagnosing the quality of LEDs and in developing structural and technological solutions for creating new light-emitting structures.
关键词： electroluminescence spectra,measuring complex,measurement method,3 dB frequency,light-emitting diode (LED),radiative and nonradiative charge carriers lifetime
更新于2025-09-23 15:21:01
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A High-Power-Factor Dimmable LED Driver with Integrated Boost Converter and Half-Bridge-Topology Converter
摘要： This paper proposes a dimmable light-emitting diode (LED) driver featuring a high power factor and zero-voltage switching on (ZVS). The circuit is obtained by integrating a boost converter and a dc-dc converter with half-bridge topology. The high power factor is achieved by operating the boost converter in discontinuous current mode (DCM). The LEDs are dimmed by the control scheme of asymmetrical pulse-width modulation (ASPWM). The developed circuit eliminates the inherited dc-o?set current of the transformer in a conventional asymmetrical half-bridge converter by introducing a balance capacitor. Both active switches can operate at ZVS by freewheeling the boost inductor current and the transformer magnetizing current to discharge the energy stored in their parasitic capacitance. The circuit operation is analyzed in detailed, and mathematical equations are derived. Finally, a 115-W prototype circuit for driving high brightness LEDs was built and tested. The experimental results verify the feasibility of the proposed LED driver with satisfactory performance. It can achieve a high power factor and ZVS operation.
关键词： power-factor correction,half-bridge converter,zero-voltage switching on (ZVS),asymmetrical pulse-width modulation (ASPWM),light-emitting diode (LED)
更新于2025-09-23 15:21:01
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Closed Loop Control of a Series Class-E Voltage-Clamped Resonant Converter for LED Supply with Dimming Capability
摘要： In this work, a new closed-loop control system is applied to a class-E resonant DC–DC converter with voltage clamp used for light-emitting diode (LED) supply. The proposed power topology was first described by Ribas et al. in a recent work. In the present paper, the LED current is sensed and used to implement a feedback control loop instead of the simplified feedforward scheme used in this previous reference. To design the control, a novel, simplified small-signal model is presented. This model is used to analyze the converter behavior as a function of the output power. The proposed approximation is significantly simpler than the multifrequency averaging technique normally used to analyze resonant converters. The feedback control loop is designed to reduce the LED low frequency current ripple while providing dimming control. Both the model and the control are verified by simulation and laboratory experimentation and the results obtained are in good accordance with the expected values.
关键词： small-signal dynamic model,light-emitting diode (LED) driver,high efficiency LEDs,resonant DC–DC converter,Class-E inverter,single-switch topology,closed-loop control,voltage clamp
更新于2025-09-23 15:19:57