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Failure rates among metal brackets cured with two high-intensity LED light-curing lamps: an in vivo study
摘要： The objective of this split-mouth clinical trial was to compare bonding failure rates of metal brackets bonded with two different light-emitting diode (LED) light-curing lamps with different high-intensity power outputs. Forty patients were included for a total of 800 brackets that were randomly bonded (left and right sides in a 1:1 ratio) in maxillary and mandibular arches using two different LED devices. An LED of 3200 mW/cm2 and an LED of 5000 mW/cm2 were used in this split-mouth clinical trial. Bonding failures during the initial 6 months of orthodontic treatment were recorded as maxillary versus mandibular, anterior teeth versus posterior teeth, and left side versus right side. Five dropouts were recorded for discontinuing orthodontic treatment and 700 brackets were analysed in total. The bonding failure rates for 3200 and 5000 mW/cm2 LEDs were 6.0 and 7.4 per cent, respectively (P = 0.450), which were not statistically significantly different. There were no significant differences in bracket survival rates between the LEDs used (P = 0.866). The posterior teeth presented a higher index of bond failures (odds ratio, 3.14; 95% confidence interval, 1.68–5.87; P < 0.001). Similar bonding failures were recorded using both LED devices (3200 and 5000 mW/cm2). Significantly more bonding failures occurred in premolar teeth than in anterior teeth.
关键词： LED light-curing lamps,bonding failure rates,metal brackets,orthodontic treatment
更新于2025-09-19 17:13:59
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Influence of smart lighting control on the lifetime of high power LED luminaires
摘要： LED lighting and smart controlling can decrease the consumption of electric power in zero or positive energy buildings. This study demonstrates that cyclic dimming, which appears in smart controlling, e.g. through occupancy sensing, might have an effect on the luminaire lifetimes and failure rates. Two different types of LED luminaires were aged in 30-s cycled dimming and undimmed modes. The manufacturer-specified lifetimes for both luminaire types were 100 000 hours. For one of the luminaire types, four out of five cycled units failed before 30 000 operating hours. For the uncycled luminaires, the lifetimes estimated from the measurements were over 100 000 hours. For the other type, the estimated lifetimes were 75 000 hours and 64 000 hours for uncycled and cycled luminaires, respectively.
关键词： LED lighting,failure rates,luminaire lifetimes,smart controlling,cyclic dimming
更新于2025-09-16 10:30:52
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Impact of Subsystems on the Overall System Availability for the Large Scale Grid-connected Photovoltaic Systems
摘要： This paper demonstrates the impact of subsystem availability on a large scale grid-connected photovoltaic (PV) systems’ performance. Subsystem denotes to the installation of some subassemblies, which can be very small or gigantic in size, that serve this subsystem and the overall system. The analysis is largely based on a huge worldwide dataset of failures and repairs of various subassemblies, derived from different large scale grid-connected solar-PV systems. Major subsystems, such as a photovoltaic inverters (PVI), are also included, which are shown to have a signi?cant impact for improving on the overall system availability. An improved reliability block diagram (RBD) with an exponential probability distribution function is presented for estimating the reliability and availability performance of seven practical grid-connected solar-PV systems. In addition, availability importance measures are employed to rank various subsystems with regards to their impact on the overall system availability. Accordingly, it will be helping in identifying the subsystems that the planned maintenance should focus on in order to achieve the desired level of the availability. The secure operation of the system will be achieved by this approach. The implementation demonstrates the efficiency and the effectiveness of the proposed approach which may significantly contribute to enhancing the system availability.
关键词： reliability block diagram,failure rates,availability importance measures,repair rates,reliability,Photovoltaic systems,availability
更新于2025-09-12 10:27:22