• 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 Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.11
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• pp.2160-2169
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• 1994

Main components of phase time error of synchronous network are flicker noise and random walk noise. This paper describe computer simulation of clock error characterized by a statistical model recommended as a standard measure. Flicker noise sequences are generated from white noise sequences by means of a algorithm developed by Barnes. Random-walk noise sequence are obtained by integration of a white noise sequence. Especially for flicker noise, relation between stage number N, time constant ratio K and bandwidth of flicker noise generated was defined by using some examples.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.41-46
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• 2012

Visible light communication(VLC) system based on LED devices has some specific advantages compared with RF system. First, visible light is harmless to human and there is no limit to using frequency band. Also, VLC system has good security performance, and it can use the very wide frequency band for data transmission. However, for simultaneously using the illumination and data transmission in VLC systems, degradation of code rate is occurred. So, in this paper, we proposed the novel line coding scheme for flicker free and efficient dimming control in VLC systems. From the simulation results, it is confirmed that proposed scheme has good flicker, dimming, and transmission performance compared to conventional variable pulse position modulation(VPPM) scheme.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.12
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• pp.1163-1168
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• 2009

The power quality of wind energy becomes more and more important in connecting wind-farms to the grid, especially weak grid. This paper presents the simulation of a wind farm of a permanent magnet synchronous generator (PMSG) and a doubly fed induction generator (DFIG). Flicker mitigation is performed by using PMSG as a static synchronous compensator (STATCOM) to regulate the voltage at the point of common coupling (PCC). A benefit of the measure is that integrating two function of to control the active power flow and to reduce the voltage flicker in a wind farm. Simulation results show that controlling PMSG is an effective and economic measure in reducing the flicker during continuous operation of grid connected wind turbines regardless of short circuit capacity ratio, turbulence intensity and grid impedance angle.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.6
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• pp.123-133
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• 2017

In this paper, we developed an optimal flicker-free control algorithm operating within 16 luminance implementation bits and 512 brightness implementation pulses irrespective of LPM(LED Pixel Matrix) module configuration on dynamic driving method of LED display system. As an implementation method, we turned the refresh rate up by increasing the number of scans through multiple shift-latches which were devised from conventional shift-latch scheme for full color representation. As a result, the LED display system of this method has no flicker phenomenon because of the novel refresh rate higher than 2,040[Hz] incomparable to 240~480[Hz] of conventional system.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.327-331
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• 2014

LED(Light Emitting Diode) is a semiconductor device utilizing electroluminescent effect is a phenomenon in which a type of P-N junction diode, the light of short wavelength which a voltage is applied in the forward direction is released. LED is advantageous in reducing the energy as environmentally materials that can greatly reduce the carbon emissions, recent it has attracted attention IT(Information Technology) and GT(Green Technology) industry. In addition, there are advantages long life, high efficiency, and excellent response speed, LED have come into the spotlight as the illumination means to replace the existing fluorescent light and incandescent light bulb. When connecting to MR16 electronic transformer for existing LED driver circuit, due to malfunction of the dimmer and the electronic transformer, flicker occurs and linear dimming is not possible. Therefore, in this paper, we suggest an LED drive circuit there is no flicker with the corresponding dimming MR16 electronic transformer. Further, we explain the principles of the LED current control technique and the principle of the drive circuit of the LED, in order to validate the proposed circuit through prototyping and simulation.

• Journal of Industrial Technology
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• v.30 no.B
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• pp.109-112
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• 2010

Unlike the general lighting systems, stage lighting system requires accurate dimming control and reduction of flicker phenomenon. In this paper, we studied PWM dimming control and linear voltage level control methods. PWM Dimming is easy control and flicker phenomenon of linear voltage level dimming does not happen by experiment result. We concluded that stage lighting dimming system required to combine two techniques of the PWM and linear voltage level dimming control method.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.143-149
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• 2018

In this paper, we introduce an edge-spike modulation method for visible light communication (VLC). This method is effective in preventing LED flicker and 120 Hz noise interference in base-band VLC. In the VLC transmitter, edge-spikes are generated by passing the digital data through a simple RC-high pass filter (HPF). The LED modulation of the edge-spikes does not change the average power of the LED light; thus it prevents LED flicker. In the VLC receiver, the 120 Hz noise from other lighting lamps is easily eliminated by RC-HPF, while the edge-spike signal is detected normally. In our experiment, the message of an air-quality sensor was successfully transmitted using edge-spike modulation. This structure is useful in constructing, e.g., wireless gas monitoring sensor systems to warn and prevent harmful gas leakage accidents in buildings using LED light.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.75-81
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• 2020

We introduce a new visible light communication (VLC) method in which three-level return-to-zero (RZ) modulation is used for flicker-free transmission. In the VLC transmitter, the three-level RZ modulation ensures that the average optical power is constant; thus, a flicker-free light-emitting diode (LED) light is achieved. In the VLC receiver, a resistor-capacitor high-pass filter is used for generating spike signals, which are used for data recovery while eliminating the 120 Hz optical noise from adjacent lighting lamps. In transmission experiments, we applied this method for wireless transmission of an air quality sensor message using the visible light of an LED array. This configuration is useful for the construction of indoor wireless sensor networks for air pollution monitoring using LED lights.

• Journal of Power Electronics
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• v.12 no.2
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• pp.333-343
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• 2012

This paper proposes a strategy of flicker mitigation for doubly-fed induction generator (DFIG) wind turbine systems. In the weak grid system where the grid impedance ratio is low, the reactive power compensation only cannot suppress the flicker sufficiently due to the limited power capacity of the converters or the DFIG. For the full suppression of flickers, the active power smoothening using the energy storage system (ESS) needs to be utilized together with the reactive power compensation. The effectiveness of the proposed method is verified by PSCAD/EMTDC simulation results for a 2[MW] DFIG wind turbine system and by experimental results for a 3[kW] wind turbine simulator.