• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.606-609
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• 1999

We fabricated white light-emitting diode which have a mixed single emitting layer containing poly(N-vinylcarbazole), trois(8-hydroxyquinoline)aluminum and poly(3-hexylthiophene) and investigated the emission properties of it. It is possible to obtain a blue light from poly(N-vinylcarbazole). green light from tris(8-hydroxyquinoline)aluminum and red light from poly(3-hexylthiophene). The fabricated device emits white light with slight orange light. We think that the energy transfer in a mixed layer occurred from PVK to Alq₃ and P3HT resulted in decreasing the blue light intensity from PVK. We find that the efficiency of the white light electroluminescent device can be improved by injecting electron more effectively and blue light need to improve the color purity of white light.

• Journal of the Korean Society of Visualization
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• v.18 no.1
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• pp.38-43
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• 2020

This paper presents a new type of electrowetting driven tandem light deflector for high performance optical application. To steer an incident light, the proposed light deflector deforms the fluid interface using electrowetting actuation. The performance of the light deflector was experimentally verified by using a prototype of the proposed light deflector. Single and tandem light deflectors were separately prepared using microfabrication processes. The optical tests of the deflectors were conducted using a laser light. The proposed tandem light deflector obtained a 45° beam steering angle with a 5.3° deflection angle while a single light deflector was required for a 10.9° deflection angle to obtain the same beam steering angle. The proposed tandem light deflector with high optical capability can be applied to various optical applications from camera modules in mobile smart devices to advanced future optical systems.

• KIEAE Journal
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• v.16 no.5
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• pp.47-55
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• 2016

Purpose: As the energy consumed by buildings increases, there is a growing need for studies and technology development to address this issue. One of the solutions to excessive energy use by buildings is the light-shelf, which is a natural lighting system enabling efficient reduction in light energy, and research in this area has been intensive. However, most of the studies about the light-shelf are limited to the light environment, and thus the application of their findings to an actual environment in the form of a design may be problematic. Therefore, the purpose of the present study is to provide fundamental data for light-shelf design by carrying out a light-shelf performance evaluation on the basis of the light environment and the heating and cooling environment. Method: In the present study, a testbed was established to conduct a light-shelf performance evaluation by measuring the electric power consumption of lighting and heating and cooling devices depending on the existence of a light-shelf and its angle. Result: The findings of the present study are as follows: 1) With respect to the uniformity of the indoor light environment amenity, the optimum angle of a light-shelf was found to be $30^{\circ}$ for the summer solstice and the winter solstice. 2) With respect to the reduction of electric power consumption by indoor lighting devices, the optimum light-shelf angle at the summer solstice is $30^{\circ}$, at which time electric power consumption may be reduced by 10.2% in comparison with when no light-shelf is applied. However, at the winter solstice, a light-shelf may increase the energy consumption for lighting in comparison with when no light-shelf is applied, and this should be taken into account in the design of a light-shelf. 3) In terms of reducing the electric power consumption of heating and cooling devices, the optimum angle of a light-shelf was found to be $30^{\circ}$ for the summer solstice, while a light-shelf is inappropriate for the winter solstice since a light-shelf creates shade and thus increases the heating energy consumption. 4) To summarize the findings above, the optimum angle of a light-shelf is $30^{\circ}$ for the summer solstice, but the installation of a light-shelf may in some circumstances increase the energy consumed by lighting devices as well as by heating and cooling devices. Therefore, more studies and technology development may need to be performed to solve the problem of increased energy consumption at the winter solstice.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.246-251
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• 2016

The use of security lighting that emits spill light is considered a cause of light trespass problems in the residential areas. Therefore, a cutoff panel was installed as an alternative way to reduce light trespass. On the other hand, it has another problem in that it is less effective and is not good enough for aesthetics and safety. In this study, a light cutoff panel was designed and manufactured to reduce the light trespass, and the structure of a proper light cutoff panel was studied. Using a goniophotometer, the light distribution file (IES file) was extracted and the characteristics of light distribution were analyzed using the RELUX program. The results showed that the reduction of spilt light in the backward direction was decreased significantly for all types of light cutoff panels except the coated globe. In the case of a black powder coated light cutoff panel, the forward light caused by light reflected from the surface of the light cutoff panel was also reduced, which means that the black powder coated light cutoff panel is effective in the performance of light cutoff in the forward and backward directions. In addition, the coated glove increased the spilt light in the forward and backward directions because it reflects the upward light to go down. A 90 % accuracy between the measurement value of light trespass and the expected value of the light trespass was obtained from a simulation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.60 no.4
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• pp.475-483
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• 2015

We examined the effects of light colors (wavelength) and light quantities on the yield ratio and quality of cultivated cowpea sprouts. All light colors resulted in a lower cowpea sprout yield ratio compared to the untreated condition (darkness), but were similar in hard seed ratio. All light colors promoted the growth of the epicotyl and root when compared to the untreated condition, but limited the growth of the hypocotyl. White light (458 nm) significantly improved grade by increasing the lightness of the cotyledon and the hypocotyl and the yellowness of the hypocotyl. The Fe content of cowpea sprouts was higher in those grown under red light (632 nm), and the total amino acid content was higher for those grown under yellow light (560 nm), white light (458 nm), and blue light (460 nm) compared to plants grown in the untreated condition (darkness). The yield ratio of cowpea sprouts was lower in the yellow light condition (560 nm) at lower light quantity, but no differences were observed at other light colors and quantities. The lightness and yellowness of cowpea sprouts was higher in the yellow light (560 nm) and red light (632 nm) at lower light quantity, redness was lower. No significant differences were observed in the content of normal and inorganic components according to the light quantities of each light color, except that Fe content was higher in sprouts grown under red light (632 nm) as light quantity increased. Total amino acid content was slightly higher in sprouts grown under white light (458 nm) and blue light (460 nm) as light quantity increased.

• Journal of Life Science
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• v.11 no.2
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• pp.166-172
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• 2001

Various types of the seeding of bottle gourd widely used as a rootstock of watermelon has been required to satisfy the farmers need. The study was done to determine the effect of light quality of blue, red and far-red lights treated with light emitting diodes on growth and morphology of bottle goured seeding and chlorophyll content of its cotyledons. The lights were treated in the growth chamber for 7 days to the seeding elapsed 8 days after sowing under natural condition, and 64 hole trays with commercial bedsoil. Plant height, length and diameter of hypocotyl, leaf area of cotyledon and first true leaf, its leaf length, number of true leaves, fraction and total dry weight were measured. Red light shortened and slenderized the hypocotyl, which lengthened by far-red light and thickened by blue light. Plant height was declined in order of far-red light treatment, blue and red lights mainly due to difference of hypocotyl length, Area and length of the first true leaf became smaller and shorter under far-red light than under the other lights. However, blue light increased leaf area of cotyledons. Two cultivars cv. Yongjadaemok and cv. Kunghap had different response to the light treatments in total seedling dry weight(dw); far-red and red light treatments showed the greatest and the least dw of hypocotyl, respectively, while blue and red lights did the greatest dw of the other organs. Among the ratio of each organ dw to total dw, those of hypocotyl and true leaves were different between the light treatments; the highest ratio of hypocotyl dw to total dw was observed in far-red light treatment but the lowest was in red light treatment. Those of the true leaves were the lowest in far-red light and similar response in blue or red light treatment. Chlorophyll content of cotyledons was decreased in order of red light treatment, blue and far-red lights, meaning that short period light treatment may influence photosynthesis of seeding and afterward its growth.

• Journal of Ecology and Environment
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• v.46 no.3
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• pp.161-171
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• 2022

Background: Epilobium hirsutum L. is designated as an endangered plant in South Korea located in Asia, due to the destruction of its habitats through the development of wetlands. Therefore, in this study, in order to find a light condition suitable for the growth and ecophysiological responses of Epilobium hirsutum L., those of this plant under treatment with various light qualities in a smart farm were measured. Results: In order to examine the changes in the physiological and growth responses of Epilobium hirsutum L. according to the light qualities, the treatment with light qualities of the smart farm was carried out using the red light: blue light irradiation time ratios of 1:1, 1:1/2, and 1:1/5 and a red light: blue light: white light irradiation time ratio of 1:1:1. As a result, the ecophysiological responses (difference between leaf temperature and atmospheric temperature, transpiration rate, net photosynthetic rate, intercellular CO₂ partial pressure, photosynthetic quantum efficiency) to light qualities appeared differently according to the treatments with light qualities. The increase in the blue light ratio increased the difference between the leaf temperature and the atmospheric temperature and the photosynthetic quantum efficiency and decreased the transpiration rate and the intercellular CO₂ partial pressure. On the other hand, the white light treatment increased the transpiration rate and intercellular CO₂ partial pressure and decreased the temperature difference between the leaf temperature and the ambient temperature and photosynthetic quantum efficiency. Conclusions: The light condition suitable for the propagation by the stolons, which are the propagules of Epilobium hirsutum L., in the smart farm, is red, blue and white mixed light with high net photosynthetic rates and low difference between leaf temperature and atmospheric temperature.

• Journal of Satellite, Information and Communications
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• v.11 no.1
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• pp.51-54
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• 2016

This paper present a method which resolves an optical discontinuity in bezel of digital signage using light guide film. On a polycarbonate film, a light guide film is bonded to produce refraction, reflection, diffraction of light. Arc shaped light guide film is assembled on the top LED light sources (red and green) to see light propagation through the film. When the two light sources (red and green) are mechanically attached at the end of the film, optical convergence brings new colors which have light wavelength between red and green. This result indicates that the light waveguide method could solve the light discontinuity on bezel of the digital signage system.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.5
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• pp.571-574
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• 2013

To determine an efficient growth system for algal cultivation and to develop adequate culture system utilizing LED light, we investigated the effects of fluorescent and light emitting diode (LED) light source on the growth of Ulva pertusa. U. pertusa was cultured at $17^{\circ}C$ under a light intensity of 35 ${\mu}mol$ photons $m^{-2}s^{-1}$ and a 10L:14D photoperiod using either fluorescent or LED lamps. After 1 week of incubation under the same environmental condition, the length and width of Ulva pertusa grown under LED light were 1.5- and 1.9-fold greater, respectively, than the length and width of algae grown under fluorescent light. After two weeks, length and width were 2.6- and 2.0-fold greater, respectively, in algae grown under LED light. Total length and width of Ulva pertusa after three weeks of incubation were 1.7- and 1.2-fold greater in algae grown under LED light than those grown under fluorescent light. Therefore, the LED light induced significantly higher growth of Ulva pertusa than fluorescent light.

• Korean Institute of Interior Design Journal
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• v.20 no.5
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• pp.13-22
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• 2011

The purpose of this study is to analyze Alva Aalto's libraries for understanding his efficient induction of natural light. To fulfill this purpose, Alvar Aalto's thought about library and natural light are examined through his working years and building types. The comparison of his libraries on usage of natural light shows different ways of natural light induction based on different locations and programs of libraries. Similarities and differences of Alvar Aalto's library architecture have strong relationship to the usage of natural light in libraries because Alvar Aalto himself regard reading as the core function of library and the efficient use of natural light is the main key of reading. In his natural light planning, regional characteristics including environmental factors and programmatic differences act as a basic standard for natural light plan. Especially, altitude of sun and its path, seasonal features affect the induction way of natural light. While conical skylights used at Viipuri library shows the characteristics of universality in Modernism architecture, later libraries presents not only various kinds of pan-shape plan but different ways of inducing natural light in according to appropriate function. From conical skylight to monitor with curved reflection wall make it possible shed diffused light to reading space and this affects to form Alvar Aalto's organic architecture. As a result, using natural light in Alvar Aalto's library architecture act as the core of forming library concepts and their development.