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Peripheral RAFT polymerization on covalent organic polymer with enhanced aqueous compatibility for controlled generation of singlet oxygen
摘要： The efficient generation of singlet oxygen has attracted a great deal of interest in various fields such as medicine, synthetic chemistry and materials science. In this study, a covalent organic polymer (COP) is prepared by crosslinking the photosensitizer 4,4',4'',4'''-(porphyrin-5,10,15,20-tetrayl)tetraaniline (TAPP) with 4,4'-(anthracene-9,10-diyl)dibenzoic acid (ADDA) via the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/4-dimethylaminopyridine (DMAP) coupling method. The COP is further modified with a hydrophilic polymer i.e. poly(poly(ethylene glycol) methyl ether methacrylate) through grafting-from reversible addition–fragmentation chain transfer (RAFT) polymerization to enhance its solubility in various solvent systems. The modified COP can bind with singlet oxygen through the formation of endoperoxide by ADDA upon the exposure to the red light irradiation. The singlet oxygen incorporated in COP can be then released via the photodynamic mechanism or the cycloreversion by endoperoxide when heated at 110 ℃. Our results have opened new possibilities for simultaneous generation of singlet oxygen by the dual mechanisms, i.e. photodynamic route and singlet oxygen carrier, which demonstrates the promising potential for treating hypoxic tumors.
关键词： RAFT,red LED,photodynamic,grafting from,singlet oxygen,covalent organic polymer,endoperoxides
更新于2025-09-23 15:19:57
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Case Study for Replacement of Conventional Lights by Led Lights
摘要： With the increment in the gap between the demand and supply of energy, various alternatives for decreasing the demand of energy are major concern for the various stakeholders. In order to decrease the energy demand by lighting various energy efficient lights are available in market. However it is difficult to convince the residents to change conventional artificial light sources, since lighting system is an essential part in the building which ensures the comfort, productivity and safety of the occupants in the buildings. Among the various Light Emitting Diode (LED) lights are termed as one of the most efficient energy saving lights which aims to save almost more than 50 % of energy demand than that of CFL lights with same power of illumination. Hence, this study is carried out to calculate energy saving percentage after replacing the conventional lights like florescent, mercury lights and other forms of conventional lights by LED lights. Additionally the study also was focused to evaluate feasibility of the replacement of lights by LED lights in terms of energy saving and return of investment. The research was carried out in building used by Agrotechnology and Food Science (AFSG) science group of Wageningen University in the Netherlands. The results from the study showed that almost 50% of the energy can be saved after replacement by LED lights with around 5 years for return of investment. However, factors like 1) Number of operating hours, 2) Price of lights, 3) Energy cost, 4) Labour cost for replacement and adjustment and 5) Number of replacement and adjustment per hour are the influential features that effects in the performance of various types of lights.
关键词： Energy saving,LED,Energy Consumptions
更新于2025-09-23 15:19:57
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Design and Implementation of 150 W AC/DC LED Driver with Unity Power Factor, Low THD, and Dimming Capability
摘要： This paper presents the implementation of a two-stage light-emitting diode (LED) driver based on commercial integrated circuits (IC). The presented LED driver circuit topology, which is designed to drive a 150 W LED module, consists of two stages: AC-DC power factor correction (PFC) stage and DC/DC power converter stage. The implementation of the PFC stage uses IC NCP1608, which uses the critical conduction mode to guarantee a unity input power factor with a wide range of input voltages. The DC/DC power converter with soft-switching characteristics for the entire load range uses IC FLS2100XS. Furthermore, the design of an electromagnetic interference (EMI) filter for the LED driver and the dimming control circuit are discussed in detail. The hardware prototype, an LED lighting system, with a rated power of 150 W/32 V from a nominal 220 V/50 Hz AC voltage supply was tested to show the effectiveness of the design. The presented LED driver was tested for street lighting, and the experimental results show that the power factor (PF) was higher than 0.97, the total harmonics distortion (THD) was lower than 7%, and the efficiency was 91.7% at full load. The results prove that the performance of the presented LED driver complies with the standards: IEC61000-3-2 and CIRSP 15:2009.
关键词： EMI filter,power factor correction,LED driver,LLC resonant converter
更新于2025-09-23 15:19:57
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A level shifted asymmetric duty cycle controlled half-bridge series resonant LED driver configuration
摘要： This paper proposes an e?cient LED lamp converter circuit incorporating dimming feature and multiple lamp independent control. The converter consists of a half-bridge resonant converter in series with a DC source. This converter operates at 200 kHz. Soft switching is employed with resonant power conversion. With modulation of the low frequency pulse width, the dimming feature is incorporated. The proposed con?guration provides lower voltage stress for switching devices as well as lower switching losses resulting in increased e?ciency. It is possible to independently control the current of each lamp. For two lamps operating in parallel with a total power of 25 W, a laboratory prototype has been designed. It can be used in residential applications. The proposed circuit is presented with detailed operation of the circuit, simulation and experimental results.
关键词： ADC Control,soft switching,series resonance,led driver,dimming
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 15th Brazilian Power Electronics Conference and 5th IEEE Southern Power Electronics Conference (COBEP/SPEC) - Santos, Brazil (2019.12.1-2019.12.4)] 2019 IEEE 15th Brazilian Power Electronics Conference and 5th IEEE Southern Power Electronics Conference (COBEP/SPEC) - A Resonant-Switched-Capacitor Step-Down DCa??DC Converter in CCM Operation as an LED Driver
摘要： This paper proposes a analysis of a LED driver. The driver consists of a resonant switched capacitor converter designed to operate in CCM and fed from nanogrid. This mode of operation allows the reduction of current peaks and, consequently, reduction of conduction losses. There is ZVS in the turn-off of the switches due to the full charge and discharge of the switched capacitor. Therefore, switching losses are also reduced. The inductor operates at twice the switching frequency, contributing to the reduction of the magnetic elements. In addition, this converter has the advantage of stabilizing the power of the LED by adjusting the switching frequency, without the needing sensors and control circuit, which reduces the cost of the circuit. In order to validate the comparative analysis, a 10W prototype was designed in a laboratory, operating with a switching frequency of approximately 58 KHz, and presenting an overall ef?ciency of 92.8% in nominal conditions.
关键词： CCM,LED Driver,Resonant Switched Capacitor (RSC) Converter,ZVS
更新于2025-09-23 15:19:57
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Application of Response Surface Methodology to Evaluate Photodynamic Inactivation Mediated by Eosin Y and 530 nm LED against Staphylococcus aureus
摘要： Photodynamic antimicrobial chemotherapy (PAC) is an efficient tool for inactivating microorganisms. This technique is a good approach to inactivate the foodborne microorganisms, which are responsible for one of the major public health concerns worldwide—the foodborne diseases. In this work, response surface methodology (RSM) was used to evaluate the interaction of Eosin Y (EOS) concentration and irradiation time on Staphylococcus aureus counts and a sequence of designed experiments to model the combined effect of each factor on the response. A second-order polynomial empirical model was developed to describe the relationship between EOS concentration and irradiation time. The results showed that the derived model could predict the combined influences of these factors on S. aureus counts. The agreement between predictions and experimental observations (R2 adj = 0.9159, p = 0.000034) was also observed. The significant terms in the model were the linear negative effect of photosensitizer (PS) concentration, followed by the linear negative effect of irradiation time, and the quadratic negative effect of PS concentration. The highest reductions in S. aureus counts were observed when applying a light dose of 9.98 J/cm2 (498 nM of EOS and 10 min. irradiation). The ability of the evaluated model to predict the photoinactivation of S. aureus was successfully validated. Therefore, the use of RSM combined with PAC is a promising approach to inactivate foodborne pathogens.
关键词： photodynamic inactivation,xanthene dye,foodborne pathogen,green LED light,mathematical model
更新于2025-09-23 15:19:57
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Proof-of-Principle Experiment of a 20-kW-Average-Power Ka-Band Gyro-Traveling Wave Tube With a Cut-Off Waveguide Section
摘要： This paper summarizes recent work on the use of optical wireless links as a robust outdoor backhaul solution for small radio cells, such as WiFi, LTE and 5G, over distances between 20 and 200 m. Results of a 5-month outdoor field trial in Berlin, Germany, indicate that the visibility range was never below 180 m, with more than 1 km in 99% of all times during this period. Rate-adaptive transmission proved to improve the availability remarkably in the occasional presence of fog or sunlight. A mathematical model of the backhaul link including these impairments is presented and implemented to obtain an optimized link design. A prototype was realized, accordingly, using low-cost optoelectronic components and a 1 Gb/s baseband chipset. Gross data rates of 800, 500, and 225 Mb/s have been achieved in real-time operation over 20, 100, and 215 m outdoor link distance, respectively, with 2 ms latency at 95% load. Finally, we discuss further evolution towards 5G mobile networks.
关键词： Backhaul,optical wireless communications,small cells,Fronthaul,LTE,LED,5G
更新于2025-09-23 15:19:57
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The Active Power Losses in the Road Lighting Installation with Dimmable LED Luminaires
摘要： In accordance with the requirements of PN EN 13201-5 standard for road lighting installation, energy performance indicators should be descripted. In order to calculate energy performance indicators, it is necessary to know the active power of the road lighting system. The above standard does not specify whether active power losses should be taken into account in calculations. The main purpose of the article is to estimate the active power losses in the road lighting installation. The article presents methods for calculating active power losses, taking into account losses in all main elements of the installation. The obtained calculation results show the relationship between active power losses and the power of luminaires, their number and spacing between poles. Calculations of active power losses were made for single-phase and three-phase installations. The active power losses in a three-phase system do not exceed 1.5% and in a single-phase installation they may be greater than 7%. Therefore, in order to obtain exact values of energy performance indicators (and also predict electricity consumption), active power losses should be taken into account in calculations. In addition, a comparative analysis of the effect of luminaires dimming and active power losses on annual CO2 emissions was made. Not taking into account the active power losses in the calculation of the lighting installation’s power, for single-phase installations in particular, understates the calculated value of CO2 emissions by more than 6%.
关键词： power losses,road lighting,LED luminaires
更新于2025-09-23 15:19:57
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Plant Factory || LED advancements for plant-factory artificial lighting
摘要： Growing food crops without stressful environmental factors (e.g., drought, ?ooding, extreme heat or cold, growth-limiting light) typically enables shorter production cycles and higher yields per cycle, leading to an order of magnitude higher annual crop-productivity rate on an area-footprint basis for protected cultivation compared to open-?eld agriculture (Mitchell, 2004), and two orders of magnitude more productive for multitiered indoor crop production (Kozai et al., 2015). Variously termed worldwide as “indoor agriculture,” “urban farming,” “vertical farming,” or “plant factories” (PFs), such controlled-environment agriculture (CEA) enterprises have great potential to provide fresh, healthy produce year-round without long-distance transport, especially in view of urbanization and climate change caused by unchecked fossil-fuel use. All platforms of CEA, including greenhouse as well as warehouse-based food production, will play increasingly important roles in feeding a rapidly growing world population as we progress through the 21st century. In fact, it is anticipated that agricultural productivity will have to expand as much as 70% above current production levels over the next 30 years to keep pace with projected increases in food demand worldwide (Agrilyst, 2017). Although the productivity potential of CEA is clear, the heavy up-front capital investments for technology and high operational energy costs to grow crops productively indoors causes the indoor agriculture industry to struggle with near-term pro?tability and carbon-footprint issues. For this reason, quick-turning leafy greens and culinary herbs with low light requirements are the present crop types of choice for PF crop production in warehouses and converted shipping containers.
关键词： energy efficiency,plant factory,artificial lighting,controlled-environment agriculture,LED
更新于2025-09-23 15:19:57
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Susceptibility of LED street lamps to voltage dips
摘要： There is an ongoing transition from high-pressure sodium lamps to LED street lamps that offer higher efficiency, cost saving and better photometric performance. This transition could lead to unintended consequences such as light flicker and extinguishing in street lighting applications when they are exposed to voltage dips. The goal of this paper is to analyse the light intensity variation of various street lamps when they are exposed to voltage dips. Several performance metrics for quantifying immunity of lamps have been proposed. Values for these metrics are obtained by applying artificial voltage dips to lamps. For voltage dips with residual voltage above 38%, lamps are immune in terms of a short-term light flicker metric. For residual voltage above 25%, light intensity reduces but without extinguishing. Compared to an incandescent lamp and high-pressure sodium lamp, LED street lamps exhibit longer zero-light intensity duration. Most of the studied LED street lamps exhibit uncoordinated light intensity drops, longer or shifted, with respect to the applied voltage dip. Individual characteristics of LED street lamps require testing before installation to prevent unexpected consequences. Recommendations are given for standardisation committees to implement an assessment method for lighting equipment.
关键词： voltage dips,LED street lamps,light intensity variation,immunity,performance metrics
更新于2025-09-23 15:19:57