• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.4
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• pp.262-267
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• 2014

This study describes that light flicker of LED lamp is improved by placing an AC-powered LED block in each phase of three-phase AC power. Rectified current is considered as an instantaneous luminous flux because the current flowing through the LED block is proportional to the amount of light emitted by the LED block. Percent flicker is calculated simply by modeling the rectified current flowing through the LED block to a triangular wave current. Percent flicker is 100% in single-phase AC powered LED lamp. Percent flicker of the same level as that in an incandescent lamp (6%~14%) is however, achieved if light emission starts before $40^{\circ}$ in each voltage phase of three-phase AC power.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.11
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• pp.729-735
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• 2016

It is highly important issue to use an energy efficiently for sustainable prosperity of mankind. From this point of view, using LED lighting can be a good alternative because it has a lot of advantages such as high efficiency, long life time and eco-friendly manufacturing process. That is the reason why using LED lighting has been encouraged worldwide. However, in situations that LED lighting is replacing traditional lighting quickly, the problem of the flicker of LED lighting has emerged as an important issue. Therefore, in foreign countries like US or Japan in order to ensure the reliability of LED lighting, study for flickering effects of the human body and test methods are have been actively conducted. But related research in domestic situation is an insufficient condition. In this study, a flicker characteristic was measured conventional lamps such as incandescent lamps or fluorescent lamp and 81 items of LED lightings which are distributed in domestic markets.

• Journal of Preventive Medicine and Public Health
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• v.14 no.1
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• pp.23-31
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• 1981

This study was conducted to investigate the effects of passive inhalation of cigarette smoke and the correlation between change of flicker value and active or passive smoking in poorly ventilated room. Forty five male students were tested by divided into four experimental groups composed of active and passive smokers and three control groups. Each four experimental groups were exposed to smoke for Two hours in enclosed room. Vital capacities, flicker values, blood carboxyhemoglobin levels and carbon monoxide concentration in room air were estimated before, during and after the exposure, and amounts of smoking or smoke exposure during two hours were also noted. The results obtained were as follows; 1. Concentration of carbon monoxide in air and increase of blood carboxyhemoglobin level (% COHb) were positively correlated with smoking amount. 2. Increase of blood carboxyhemoglobin in passive smokeres, in average, were about seventy six percent of that in smokers, as 2.2% vs. 2.9%. 3. Comparison with published data showed that Peterson's equation gave most similar result to this study in estimation of increase of blood carboxyhemoglobin level. 4. During the exposure, flicker values fell steadily in both experimental groups and control groups as time passed. Flicker values were, however, elevated again in experimental groups after exposure, despite the fact that values still fell in control groups. 5. Blood carboxyhemoglobin and flicker value were negatively correlated and this correlationship was stronger in passive smoker than in active smoker. 6. Multiple regression equation between flicker value and exposure time and blood carboxyhemoglobin level was expressed as: Flicker value=41.6-0.2 COHb%-0.9Hour, 7. In general, it is suggested that biological criteria would be more preferrable than chemical criteria in establishment of statutory limitation of smoking in enclosed spaces.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.12
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• pp.555-560
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• 2006

As it has been reported that more than 60% of transmission line faults occurs due to lightning strokes, lighting is one of concerned issues in electric power utility company. Most of transmission line is double circuit in Korea. Double circuit outages account for 33.7 percent of total lightning faults from 1996 to 2004. Even though transmission fault might be cleared shortly by protective system, it could deteriorate the power quality accompanied with sag or flicker. Moreover, double circuit fault may lead to more aggravated situation, for instance, blackout. To Protect transmission lines from lightning stroke, reduction of tower footing resistance, multiple ground wires and unbalanced insulation in double circuit lines have been adopted. In this paper, we would like to introduce insulation design standards for lightning protection of Korea Electric Power Corporation.

• Journal of Digital Convergence
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• v.14 no.11
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• pp.241-247
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• 2016

As a domestic traffic control signal system, either the system with which a traffic signal turns into green at regular intervals or the system with which an amber or a red signal flickers on local roads without heavy traffic at midnight has been utilized. However, when the former system is used for roads with light traffic at midnight, delays and congestion can be incurred. Besides, in case of the latter signal system, the risk of vehicle crash is high. This study proposes a response type of flickering green signal system that rearranges signal system after analyzing beacon messages including sensor data. The proposed system, on a trunk road or a branch road at midnight, makes the signal keep flickering in green; When a vehicle enters the range of RSE, the transfer coverage, it transmits beacon messages regularly and Agent System analyzes the messages and alters the signal. It is a system by which vehicles move following the altered signal system, which will not only ensure smooth flow but also prevent vehicles from crashing on a road with light traffic. As a result of a simulation, traffic throughput and the average waiting time displayed 10 to 30 percent better improvement than existing signal systems, in terms of performance.