• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.108-111
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• 2001

ZnO thin films on (001) sapphire substrates have been deposited by pulsed laser deposition(PLD) technique for light emitting device applications. We have controlled the emission intensity of UV and visible light, depending on film thickness and various post-annealing time. UV emission became strong as the thickness of ZnO thin films increased. The intensity of visible light was strong as post-annealing temperature increased. The optical properties of the ZnO thin films were characterized by PL(photoluminescence) and the structural properties of the ZnO were characterized by XRD for the application of ZnO light emission device.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.108-111
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• 2001

ZnO thin films on (001) sapphire substrates knave been deposited by pulsed laser deposition(PLD) technique for light emitting device applications. We have controlled the emission intensity of UV and visible light, depending on film thickness and various post-annealing time. UV emission became strong as the thickness of ZnO thin films increased. The intensity of visible light was strong as post-annealing temperature increased. The optical properties of the ZnO thin films were characterized by PL(photoluminescence) and the structural properties of the ZnO were characterized by XRD for the application of ZnO light emission device.

• 천문학회지
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• 제50권4호
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• pp.105-109
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• 2017

The well-known solar cycle controls almost the entire appearance of the solar photosphere. We therefore presume that the continuous emission of visible light from the solar surface follows the solar cyclic variation. In this study, we examine the solar cyclic variation of photospheric brightness in the visible range using solar images taken by the Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI). The photospheric brightness in the visible range is quantified via the relative intensity acquired from in the raw solar images. In contrast to total solar irradiance, the relative intensity is out of phase with the solar cycle. During the solar minimum of solar cycles 23-24, the relative intensity shows enhanced heliolatitudinal asymmetry due to a positive asymmetry of the sunspot number. This result can be explained by the strength of the solar magnetic field that controls the strength of convection, implying that the emission in the visible range is controlled by the strength of convection. This agrees with the photospheric brightness increasing during a period of long spotless days.

• 대한전자공학회논문지TC
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• 제48권3호
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• pp.60-67
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• 2011

가시광 무선 통신은 반도체로 제조된 LED (light emitted diode)의 발광을 제어하여 데이터를 송신하고, 수광 소자인 PD (photo diode)를 통하여 데이터를 수신하는 차세대 무선통신 기술이다. 가시광 무선 통신 시스템의 전송 능력은 LED의 발광 세기, PD의 수신 감도, 송수신기 간의 거리 및 송수신기가 이루는 수신각에 의해 결정된다. 특히, 수신기의 수직적 및 수평적 이동에 따라 송수신기가 거리와 수신각의 변화가 발생하고, 이러한 변화는 수신기의 수신 감도에 영향을 주어 시스템의 전송 능력이 저하될 수 있다. 이에 본 논문에서는 실내 가시광 무선 통신 시스템에서 LED AP (access point)의 통신 영역 내 수신 광도에 따른 위치별 수신 광도 특성화 곡선과 주기적으로 측정된 단말기의 수신 광도 변화를 비교하는 특징을 가진 단말기의 위치와 수신각 추정 알고리즘을 제안한다. 제안 알고리즘에 대한 성능 분석을 위해 모의실험을 수행하였고, 그 결과 수신 광도 정보를 이용한 위치 및 수신각 추정이 가시광 무선통신 시스템의 성능을 향상 시킬 수 있음을 확인하였다.

• The Journal of Korean Physical Therapy
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• 제11권1호
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• pp.71-77
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• 1999

The purpose of this study was to investigate the changes of muscle power by transcutaneous electrical nerve stimulation(TBNS), low frequency-low intensity(20pps, invisible muscle contraction intensity), low frequency-high intensity(20pps, visible muscle contraction), high frequency-low intensity(100pps, invisible muscle contraction intensity) and high frequency-high intensity(100pps, visible muscle contraction). The results were as follows. 1. Increased muscle power after 30 minutes of treatment by low frequency-low intensity TENS, and post-treatment 30 minutes muscle power were increased more than pre-treatment power(p<0.05). 2. Decreased muscle power after a 30 minute treatment by low frequency-high intensity TENS, and after the 30 minute treatment was terminated muscle power didn't recover to pre-treatment levels. 3. Decreased muscle power after 30 minute treatment by high frequency-low intensity TENS, but post-treatment 30 minute, muscle power didn't recover to pre-treatment levels. 4. The muscle power was remarkably decreased by high frequency-high intensity TENS after 30 minute treatment, in addition treatment terminated after 30minutes didn,t recover to pre-treatment power(p<0.05). 5. Lower frequency-low intensity TENS are good methods for preventing muscle fatigue, buty high intensity (TENS) are increased muscle fatigue. 6. Traditional TENS by high frequency-low intensity is a good method for preventing muscle fatigue.

• 한국안광학회지
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• 제4권1호
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• pp.15-20
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• 1999

상용전원을 사용한 평행판전극 방전장치에서 수소플라스마로부터 방사되는 가시광선의 스펙트럼을 분광기로 조사하였다. 기체압력과 방전전력에 따라 수소플라스마로부터 방사되는 가시광선의 세기를 조사하고, 같은 조건에서 탐침으로 플라스마밀도를 측정하여 가시광선의 세기와 비교하였다. 측정결과, 가시광선의 세기는 플라스마의 밀도에 영향을 받으며, 플라스마 밀도는 기체압력과 방전전력에 영향받았다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.102-102
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• 1999

Visible photoluminescence(PL) in si-implanted SiO2 films on crystaline silicon were observed. Thermal oxide films of 1 ${\mu}{\textrm}{m}$ thickness on P-type crystal silicon were made and si+ ions were implanted with 200keV acceleration voltage on ti. Argon laser (wavelength 488nm) and PM tube were used for PL measurements. As annealing time increased at low temperature, the visible PL intensity are increased and the peak positions are changed. On the other hand, with increasing annealing time at high temperature, the visible PL intensity are disappeared. From the PL peaks and intensity changes, XRD results, and TEM observations, we will discuss the origin of PL in Si+-implanted SiO2 films with oxygen righ defects and silicon rich defects.

• Journal of Astronomy and Space Sciences
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• 제14권1호
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• pp.87-93
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• 1997

Radiometers in UV and visible wavelengths were onboard the Korean Sounding Rocket(KSR)-1 and 2 which were launched on June 4th and September 1st, 1993. These radiometers were designed to capture the solar radiation during the ascending period of the rocket flight. The purpose of the instrument was to measure the vertical profiles of stratospheric ozone densities. Since the instrument measured the solar radiation from the ground to its apogee, it is possible to investigate the altitude variation of the measured intensity and to estimate the effect of atmospheric scattering by comparing the UV and visible intensity. The visible channel was a reference because the 450-nm wavelength is in the atmospheric window region, where the solar radiation is transmitted through the atmosphere without being absorbed by other atmospheric gases. The use of 450-nm channel intensity as a reference should be limited to the altitude ranges above the certain altitudes, say 20 to 25km where the signals are not perturbed by atmospheric scattering effects.

• Current Optics and Photonics
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• 제2권6호
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• pp.532-539
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• 2018

Multiple LED arrays can be utilized in visible-light communication (VLC) to improve communication efficiency, while maintaining smart illumination functionality through dimming control. This paper proposes a modulation scheme called "Spatial Intensity Modulation" (SIM), where the effective number of turned-on LEDs is employed for data modulation and dimming control in VLC systems. Unlike the conventional pulse-amplitude modulation (PAM), symbol intensity levels are not determined by the amplitude levels of a VLC signal from each LED, but by counting the number of turned-on LEDs, illuminating with a single amplitude level. Because the intensity of a SIM symbol and the target dimming level are determined solely in the spatial domain, the problems of conventional PAM-based VLC and related MIMO VLC schemes, such as unstable dimming control, non uniform illumination functionality, and burdens of channel prediction, can be solved. By varying the number and formation of turned-on LEDs around the target dimming level in time, the proposed SIM scheme guarantees homogeneous illumination over a target area. An analysis of the dimming capacity, which is the achievable communication rate under the target dimming level in VLC, is provided by deriving the turn-on probability to maximize the entropy of the SIM-based VLC system. In addition, a practical design of dimmable SIM scheme applying the multilevel inverse source coding (MISC) method is proposed. The simulation results under a range of parameters provide baseline data to verify the performance of the proposed dimmable SIM scheme and applications in real systems.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.171-174
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• 2000

This study uses neon and xenon gas mixture discharges to determine the effects of the neon plasma emission on the characteristics of visible emission from the stimulation of the red, green, blue(RGB) phosphor layers in a surface-type alternate current plasma display panel(AC PDP). With a mixture of less than 2% xenon to neon, it is found that the luminance changes in the visible emission of the phosphor layers are similar to those of the neon plasma emission. In the range of xenon mix ratio from 2 to 5%, the luminance of the red, green, blue(RGB) phosphor layers decreases with a decrease in the neon plasma emission intensity. However, with a mixture of above 5% xenon to neon, the luminance of the red, green, blue(RGB) phosphor layers increases regardless of a decrease in the neon plasma emission intensity. Furthermore, the color purity of the red, green, blue(RGB) phosphor layers improve as the neon plasma emission intensity decreases. Accordingly, it is concluded that the optical properties of the phosphor layers, including color purity and luminance, depend on the neon plasma discharge emission as well as the visible emission from the stimulation of the phosphor layers.