• ETRI Journal
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• 제37권4호
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• pp.677-684
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• 2015

Recently, orthogonal frequency-division multiplexing (OFDM) was applied to VLC systems owing to its high rate capability. On the other hand, a real-valued unipolar OFDM signal for VLC significantly reduces bandwidth efficiency. For practical implementation, channel estimation is required for data demodulation, which causes a further decrease in spectral efficiency. In addition, the large fluctuation of an OFDM signal results in poor illumination quality, such as chromaticity changes. This paper proposes a spectrally efficient method based on a hidden-pilot-aided precoding technology for VLC with less flickering than a conventional OFDM-based method. This approach can obtain channel information without any loss of bandwidth efficiency while ensuring illumination quality by reducing the flickering effect of an OFDM-based VLC. The simulation results show that the proposed method provides a 6.4% gain in bandwidth efficiency with a 4% reduction in flicker compared to a conventional OFDM-based method.

• 한국통신학회논문지
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• 제37C권10호
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• pp.888-893
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• 2012

Quality of Service (QoS) provisioning is an important issue in the design of next generation wireless network. In visible light communication (VLC) networks, link switching is a solution to maintain or improve the quality of communication. In this paper, we propose a novel link switching scheme using the location of mobile nodes (MNs). The current serving transmitter uses location history of the MN to find out which neighbor transmitter the MN is approaching. This neighbor transmitter is chosen to inform the MN as the next serving transmitter. The simulation results show that our proposed scheme gains better performance than non-predictive link switching scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.72-74
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• 2004

Nowadays there are many kinds of large scale loads and they make the power quality deteriorated. As the uses of nonlinear loads increase, there are the influences on the other kinds of loads (mainly light loads) in the same distribution system. Especially the voltage variation by the loads which draw the large and instantaneous currents can cause the appreciable light flicker. This is called the voltage flicker or, briefly, the flicker. This paper deals with the digital and time domain algorithm of measuring flicker based on IEC 61000-4-15 and the real time measurement of flicker through the proposed power quality monitoring system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.2058-2064
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• 2008

This study is concerned with the quantitative Quality of Service(QoS) of the Light Railway Transit(LRT) System. Generally, the QoS offered to passengers by the Operator of LRT system can be quantified in various ways. In this paper, we assumed that the QoS is a combination of both Train Delivery and Train Punctuality under considering LRT characteristics including core sub-systems such as, rolling stock, signalling, power-supply and PSD(platform screen door), etc. We also, provide a quantitative analysis method to evaluate the QoS related the reliability of LRT system.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 춘계학술대회
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• pp.263-264
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• 2021

산업화의 변화와 환경파괴에 영향중 음용수 수질의 평가 및 관리의 중요성이 대두되고 있다. 현재 우리나라의 탁도에 관한 법 규제가 되어 공정관리에 있어 1.0NTU이하의 저농도 탁도를 유지해야하며, 제어 기술이 필요한 과제로 남아있다. 본 연구는 470nm, 670nm, 850nm를 이용하여 탁도에 따른 흡광도 실험을 하였으며, 850nm의 광원과, 820nm의 수광소자를 이용하여 시료의 90,180도와 따른 반사과 투사광의 관계와 입사광과 수광부의 높이차를 두어 산란광의 영향에 대해 실험을 하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.239-242
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• 2004

This paper presents a novel contrast enhance algorithm for images displayed with bright environment light. This algorithm is designed to preserve local contrast based on the luminance ratio of the pixel to its local surround in attention. This algorithm improves image quality of projectors in a bright room.

• 한국어병학회지
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• 제29권1호
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• pp.7-12
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• 2016

In a previous study on the parasites of cultured rock bream (Oplegnathus fasciatus), we reported the discovery of a new species, Ceratomyxa oplegnathus, obtained from the gallbladder. In the present study, we found another Ceratomyxa species, C. sparusaurati, also from the gallbladder of rock bream. The morphological and ultrastructural characteristics of C. sparusaurati were investigated using light and transmission electron microscopy (TEM).

• 산업경영시스템학회지
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• 제21권45호
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• pp.247-251
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• 1998

From the early 90's TPM(Total Productive Maintenance) plays important roles to improve productivity and quality to keep enterprise's competivity. This study presents the results of an enquiry for the maintenance management of Korean industry in 1996. The response rate was 35.8% (43 companies) that the corporations were divided into four industrial groups, heavy process, light process, heavy assembly and light assembly. 40 question were asked, including maintenance organization, maintenance personnel, maintenance cost, measurement of maintenance performance and improvements achieved. This paper compares the results with those of an earlier Japanese and British enquiry.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2020년도 추계국제학술대회
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• pp.62-62
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• 2020

Ginseng is a shade-plant cultivated using shading facilities. However, at too low light levels, root growth is poor, and at high light levels, the destruction of chlorophyll reduces the photosynthesis efficiency due to leaf burn and early fall leaves. The ginseng has a lightsaturation point of 12,000~15,000 lux when grown at 15 to 20℃ and 9,500 lux at 25℃. This study was conducted to select the optimal light intensity of 3-year-old ginseng grown in blue-white film plastic house. The seeds were planted in the blue-white film plastic house with different light receiving rate (March 17, 2020). Between April and September, the average air temperature in the house was 20.4-20.7℃. Average soil temperature was 18.3℃-18.5℃. The chemical properties of the test soil was as follows. The pH level was 7.0-7.4, EC was 0.5-0.6 dS/m, OM was at the levels of 33.6-37.7 g/kg, P₂O₅ was 513.0-590.8 mg/kg, slightly higher than the allowable 400 mg/kg. The amount of light intensity, illuminance, and solar radiation in the blue-white film house was increased as the light-receiving rate increased and the amount of light intensity was found to be 9-14% compared to the open field, 8-13% illuminance and 9-14% solar irradiation respectively. The photosynthesis rate was the lowest at 3.1 µmolCO²/m²/s in the 9% light blue-white plastic house and 4.2 and 4.0 µmolCO²/m²/s in the 12% and 14% light blue-white plastic house, respectively. These results generally indicate that the photosynthesis of plants increases with the amount of light, but the ginseng has a lower light saturation point at high temperatures, and the higher the amount of light, the lower the photosynthetic efficiency. The SPAD (chlorophyll content) value decreased as the increase of light-receiving rate, and was the highest at 32.7 in 9% light blue-white plastic house. Ginseng germination started on April 11 and took 13-15 days to germinate. The overall germination rate was 82.9-85.8%. The plant height and length of stem were long in the 9% light-receiving plastic house. The diameter of stem was thick in the 12-14% light-receiving plastic house. In the 12% and 14% light-receiving plastic house, the length and diameter of taproot was long and thick, so the fresh weight of root per plant was 20 g or more, which was heavier than 16.9 g of the 9% light-receiving plastic house. The disease incidence (Alternaria blight, Gray mold and Damping-off etc.) rate were 0.9-2.7%. The incidence of Sclerotinia rot disease was 7.5-8.4%, and root rot was 0-20.0%. The incidence ratio of rusty root ginseng was 34.4-38.7% level, which was an increase from the previous year's 15% level.

• 생물환경조절학회지
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• 제21권3호
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• pp.220-227
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• 2012

폐쇄형 묘생산 시스템에서 청색LED, 적색LED, 백색형광등을 인공광원으로 이용한 가운데 파프리카의 육묘시 생장 특성과 정식 후 생장 및 초기 수량을 분석하고자 본 연구가 수행되었다. 폐쇄형 시스템에서 파프리카 육묘용 환경조건은 광주기 16/8h, 평균 PPF $204{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, 기온 26/$20^{\circ}C$, 상대습도 70%이었다. 육묘 후 21일째에 백색형광등과 LED 하에서 생장된 파프리카 묘의 엽장, 엽폭, 엽면적 등 잎 관련지표뿐만 아니라 지상부 생체중과 건물중, 엽록소함량 등이 자연광 처리구에 비해서 크게 나타났다. 청색 LED, 적색LED 및 자연광 처리구에서의 엽면적은 대조구인 형광등 처리구와 비교할 때 각각 63%, 63%, 28%에 해당하였다. 또한 청색LED, 적색LED 및 자연광 처리구의 지상부 건물중은 각각 대조구의 64%, 50%, 22%로 나타났다. 정식 후 18일째에 엽수는 대조구에서 44매로 가장 크게 나타났다. 적색LED, 청색LED 및 자연광 처리구의 엽수는 대조구에 비해서 각각 86%, 81%, 48%로서 정식 시기와 비교할 때 엽수의 차이가 줄어들었다. 정식 후 114일째에 초장은 청색LED와 적색LED 처리구에서 상대적으로 작게 나타났다. 이러한 결과는 단색LED 하에서 육묘된 파프리카의 줄기 신장이 정식 후에 억제된 것으로 판단된다. 초기 4주 동안 수확된 파프리카는 청색LED 3.5개/plant, 적색LED 3.3개/plant, 자연광 1.0개/plant으로서 대조구 2.2개/plant에 비해서 각각 159%, 150%, 45%로 나타났다. 초기수량은 적색LED 453g/plant, 청색LED 403g/plant, 자연광 101g/plant으로서 대조구 273g/plant와 비교할 때 각각 166%, 148%, 37%로 나타났다. 한편 적색LED 처리구에서의 평균 중량은 136g으로서 다른 처리구와 비교할 때 상대적으로 큰 과실이 생산되었다. 한편 정식 후 온실에서의 재배기간이 길어짐에 따라 인공광 처리구와 자연광 처리구에서 수량 차이가 없었다. 이러한 결과를 종합하면 LED 또는 형광등을 인공광원으로 이용한 조건에서 육묘된 파프리카의 정식 후 초기 생육이 양호하였으며, 초기 수확이 자연광 처리구에 비해서 1주 정도 빠르게 이루어졌음을 알 수 있다. 따라서 LED 또는 형광등과 같은 인공광원이 파프리카 육묘에 이용될 경우 묘소질의 향상, 조기 수확 및 초기 수량의 증대가 기대된다.