• The Journal of Korean Institute of Information Technology
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• v.16 no.12
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• pp.13-24
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• 2018

Recently, light pollution has become a serious environment issue caused by excessive uses of artificial light. Central and local governments have made efforts to manage light pollution and mitigate light pollution damages. Developing methods to diagnose light pollution is critical to effectively monitor light pollution conditions in Seoul. This study develops a methodology to create a map that presents the status of light pollution in Seoul, using International Space Station(ISS) night-time images. Through the map, we evaluated the areas that show high levels of light intensity and found out local characteristics of light intensity; Commercial area, office building concentrated area, and large sports facilities. The result of study provides basic understanding to present a new way for monitoring light pollution in urban sites.

• Korean Journal of Environment and Ecology
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• v.20 no.1
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• pp.70-74
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• 2006

To study for proper growing conditions of Hydrangea macrophylla var. acuminata, used as ornamental trees or sources of natural sweetenings and biological active compounds, two-year-old cuttings of the plant were subjected to different conditions, light intensity, watering, and fertilizing levels. Photosynthetic rates measured on October 2 differed significantly between two light intensity regimes, but the values measured on September 3 were not significantly different. Mean photosynthetic rates on the plot watered three times a week were higher than the cuttings on the plot watered once a week. Mean photosynthetic rates on the plot fertilized 200grams/cuttings were slightly higher than those of the cuttings on the control plot. Chlorophyll contents measured on August 2 and on September 3 were significantly different between the light intensity regimes. Chlorophyll contents measured on August 2 were significantly different between the moisture regimes, but not significantly different between the fertilizing levels. Means of leaf growth(length and width) measured the highest values on the plot watered three times a week, and on the plot in full-sun lighted.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.7
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• pp.17-22
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• 2008

This paper presents a low-power and small-area pulse width modulator by light intensity for photoflash. Light intensity controller is achieved by using capacitor, photodiode, and comparator. The proposed circuit designs digital circuit to reduce static power consumption except comparator. And IGBT driver has short circuit protection using delay cell. The pulse width modulator has the operating range of $V_{MS}$ from 0.5V to 2.5V and pulse width of output from 0.14ms to 1.65ms at 300Hz. The pulse width modulator fabricated in $0.35-{\mu}m$ CMOS technology occupies $0.85mm{\times}0.56mm$. This circuit consumes 3.0mW at 300Hz and 3.0V.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.2
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• pp.118-122
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• 2000

An extensive investigation has been made for the possible utilization of polypropylene spunbonded fabrics in rice seedling nursery. Considering the cropping systems available in southern part of Korea, sowing dates were fixed at April 5 and April 20 for single cropping and May 6 and May 26 for double cropping. Nursery period was fixed to 35 days for each sowing date. Four different thickness of polypropylene spunbonded fabrics, 40, 60, 80, 100 g/$m^2$, were tested in rice seedling nursery. The temperature and light intensity were not significantly different among the thickness of polypropylene spunbonded fabrics. Light intensity was significantly reduced in polypropylene spunbonded fabric (72.2 Klux) compared with polyethylene mm (85.5 Klux), however, the reduced light intensity was enough for seedling growth. The temperature in the polypropylene spunbonded fabric covering during low air temperature was higher than that in polyethylene mm tunnel. At transplanting, the rice seedlings grown in polypropylene spunbonded fabric condition was shorter (17cm) but healthier than those in polyethylene mm (23cm). The estimated possible nursery periods using the polypropylene spunbonded fabric covering may start from April 1 at Chinju (plain area in Southern Korea, 20m altitude) and April 15 at Susang (mountainous area, 430m altitude). Labour hours and cost were reduced by about 28% and 48%, respectively.

• The Korean Journal of Mycology
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• v.47 no.4
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• pp.385-392
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• 2019

Currently, plastic bags are being used for sawdust cultivation of shiitake mushroom. However, due to serious environmental problems caused by the use of plastic bags, we studied the efficacy of bottle cultivation method to replace the sawdust bag method. Small detachable plastic bottles (400 g capacity) filled with Quercus spp. sawdust and wheat bran (4:1 w/w) media were incubated for 80 and 120 days. The weight loss (%) of the media was higher for the NIFoS 2464 strain at an approximate light intensity of 300 Lux than light intensity of 500 Lux; the light intensity was associated with the loss of sawdust medium-weight during the cultivation period. The highest yield was observed when the strain was cultivated for 80 days under dark conditions, 40 days under 500 Lux light, and air circulation fan speed of 30 rpm. When incubated for 120 days, mushroom yield in the bottle media was higher at 40 days of light exposure than 20 days of light exposure. In the bottle media incubated for 80 days under dark conditions, the mushrooms fruited due to repetitive water spraying on the top of the media and light stimulation during the fruiting period. The media could be separated from the bottles because the media shrank after the first harvest. These separated plastic bottles could be re-used for mushroom cultivation, thereby reducing the amount of plastic waste.

• Journal of Korea Foresty Energy
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• v.21 no.3
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• pp.46-53
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• 2002

The study was carried out to determine the growth and biomass production of deciduous trees including Betula pendula, Fraxinus rhynchophylla, Cornus controversa subjected to artificial shade treatment of three levels in nursery field. The results were as follows; The height growth of seedlings was no difference subjected to artificial shade treatment. The root collar diameters of the relative growth rates of seedlings grown in full sun showed 29-32% as compared with those subjected to the shade treatment of 7-10% light intensities of full sun. Corrus controversa of the root collar diameters of the relative growth rates were better in the seedlings grown in 26-34% light intensities of full sun. Total dry mass including the dry mass of leaves, shoot and root were as a whole decreased with shade treatment. The ratio of the dry mass of leaves and stem increased the dry mass of root. T/R ratio of the seedlings increased by decreasing the relative light intensity. And the T/R ratio of 7-10% light intensities of full sun was ranged from 1.00~2.27 were greater in the full sun light was ranged from 0.51~l.13. Light intensity by artificial shade treatment decreased in deciduous trees when compared on the whole, it showed tendency that SLA increases, increased that seeing resemblant tendency in LAR and LWR and changed of light intensity is strong, it increased that showed difference as statistical.

• Journal of Environmental Science International
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• v.15 no.7
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• pp.677-688
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• 2006

Currently, the application of $TiO_2$ photocatalyst has been focused on purification and treatment of wastewater. However, the use of conventional $TiO_2$ slurry photocatalyst results in disadvantage of stirring during the reaction and of separation after the reaction. And the usage of artificial UV lamp has made the cost of photocatalyst treatment system high. Consequently, we studied that solar light/$TiO_2$ film system was designed and developed in order to examine disinfection characteristics of sewage wastewater treatment. The optimum conditions for disinfection such as solar light intensity, characteristic of sewage wastewater, amounts of $TiO_2$ and comparison of solar ligth/$TiO_2$ systems with UV light/$TiO_2$ system was examined. The results are as follows: (1) photocatalytic disinfection process with solar light in the presence of $TiO_2$ film more effectively killed total coliform (TC) than solar light or $TiO_2$ film absorption only. (2) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with remain resistant material. (3) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with the increase of amounts of $TiO_2$. (4) TC survival ratio decreased linearly with increasing UV light intensity. (5) The disinfection effect of solar light/$TiO_2$ slurry system decreased more than UV light/$TiO_2$ film systems. (6) The disinfection reaction followed first-order kinetics. We suggest that solar light instead of using artificial UV light was conducted to investigate the applicability of alternative energy source in the disinfection of TC and the degradation of organic material.

• Journal of Advanced Navigation Technology
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• v.15 no.6
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• pp.1111-1117
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• 2011

We was designed the portable LED light which can shadowless shooting and developed using a high-power LED that medical attention as a new lighting components for structural confirmation of oral dental area, medical and surgical lesions in the local area. LED which applied to the development, was used the 3-color LEDs for possible of implement a variety of colors and adjusted the light intensity. It is being magnified of delicacy expressiveness and three-dimensional for tone of the subject-specific. It has been developed a highly efficient light module that LED is used to consider the electrical characteristics and optical properties. SMPS has We was designed the portable LED light which can shadowless shooting and developed using a high-power LED that medical attention as a new lighting components for structural confirmation of oral dental area, medical and surgical lesions in the local area. LED which applied to the development, was used the 3-color LEDs for possible of implement a variety of colors and adjusted the light intensity. It is being magnified of delicacy expressiveness and three-dimensional for tone of the subject-specific. It has been developed a highly efficient light module that LED is used to consider the electrical characteristics and optical properties. SMPS has produced for use in mobile that can be driven at low voltage. In addition, it was also possible to implement a variety of colors from monochromatic Light to polychromatic light using by PWM control method and were available 32,768.

• Journal of Bio-Environment Control
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• v.21 no.4
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• pp.305-311
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• 2012

To investigate the influence electrical conductivity (EC) of nutrient solution and light intensity on growth of red leafy lettuce, fresh and dry weights, number of leave, chlorophyll concentration and production efficiency were evaluated through nutrient film technique system. The levels of EC were 0.5, 1.0, 1.5, 2.0, 3.0, and $6.0dS{\cdot}m^{-1}$, and those of light intensity were 120, 150, and $180{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. Under photoperiod of 16 h/day, the temperature was maintained in the range of $20{\sim}25^{\circ}C$. Planting density was $10{\times}10cm$ (100 plants/$m^2$). When red leafy lettuce were grown in the EC range of $0.5{\sim}1.5dS{\cdot}m^{-1}$, the fresh and dry weights decreased as the EC levels and light intensity were lowered, however, Hunter's a value showed no significant differences among the treatments of EC and light intensity levels (Ex. 1). The fresh and dry weights and production efficiency ($g{\cdot}FW/kw$) were the highest in the treatment of $3.0dS{\cdot}m^{-1}$ and $180{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ when crops were grown under the EC range of EC $1.5{\sim}6.0dS{\cdot}m^{-1}$ (Ex. 2). But the fresh and dry weights, number of leaves, and production efficiency of $2.0dS{\cdot}m^{-1}$ were the highest when the light intensity was $180{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ (Ex. 3). The SPAD value increased gradually as EC levels were elevated. From the above results, we concluded that optimum levels of EC and light intensity were $2.0dS{\cdot}m^{-1}$ and $180{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, respectively, for production as well as production efficiency of red leaf lettuce in plant factory.

• Korean Journal of Environmental Agriculture
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• v.31 no.3
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• pp.224-228
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• 2012

BACKGROUND: This experiment was conducted to investigate the effects of red light on inhibition of flowering and vegetative growth of perilla (Perilla Frutescens. L). METHODS AND RESULTS: To determine red light intensity for inhibiting floral induction of perilla 6h light plus daylength extension (17:00-23:00) with three different intensity of red lights 0.046, 0.114 and $0.177{\mu}mol/m^2/s$ were treated respectively, and control plants were grown under 11(06:00-17:00)/13(17:00-06:00)h light/dark environment. Red(660nm) and far-red(730nm) light were irradiated for night break treatment subsequently to investigate photoreversible flowering response of perilla 'Manchu'. The flowering was inhibited by night break with red light, but sequential far-red light induced floral induction of perilla. Perilla not flowered by red light intensity over $0.177{\mu}mol/m^2/s$. Red light of $0.2{\mu}mol/m^2/s$ was irradiated for 6 hours (20:00-02:00) with LEDs device in plastic house. Perilla not flowered and continued the vegetative growth by red light treatment and the plant length, number of leaves, fresh weight, and leaf area of perilla were increased by 3%, 7%, 21%, and 19%, respectively, compared to incandescent control. CONCLUSION: These results showed that red(660nm) light for daylength extension could be used to control flowering and to enhance production of perilla leaf.