• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1533-1536
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• 2003

Dynamic model of the rubber-tired AGT light rail vehicle. various load and boundary conditions between vehicle and infrastructures(running track. guidance rail) were defined to analyze vehicular dynamic behaviors occurred by inclement weather(strong wind and earthquake). The dynamic analysis were performed by using a commercialized software RecurDyn. whose results for the magnitudes of wind and earthquake showed the resultant forces and accelerations between car body and bogie, or bogie guidance frame and infrastructures in the various track conditions(straight or curved tracks) and train velocities. Based on these results, speed limitation of tile vehicle were proposed to ensure system stability and passengers safety.

• Journal of Mushroom
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• v.15 no.4
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• pp.259-263
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• 2017

In this study, we investigated the morphological characteristics and antioxidant ability of mushroom cultivar Lentinula edodes 'Nongjingo' fruiting bodies after exposure to various light conditions. Color differences between mushrooms treated with mixtures of LED light revealed that mushrooms displayed lighter color shades when compared to the control group (fluorescent light treated mushrooms). Redness increased and yellowness decreased after exposure to all treatments other than the fluorescent control. Measurement of growth characteristics of 'Nongjingo' fruiting bodies showed increases after exposure to all mixed LED treatments. In addition, the uniformity of fruiting bodies was higher when using LED light compared to fluorescent light. The measurement of stem diameters did not show a significant difference between the treatments, however, diameters were slightly larger with exposure to white-green LED. Moreover, stem length was longer in the mixed LED treatments when compared to those exposed to fluorescent light. Examination of the ratio of stem diameter to stem length revealed that the diameter of the stem was greater than the length. The antioxidant activity of water extracts made from Nongjingo fruiting bodies grown under mixed LED conditions was compared to those from mushrooms grown under fluorescence light conditions. The highest antioxidant activity was observed from mushrooms treated with white LED; however, no significant difference was found between mushrooms exposed to white-green LED compared to white-blue LED. The treatment showed higher antioxidant ability than vitamin C. Our results confirm that treatment of white LED and white-blue LED affects the growth and antioxidant ability of Nongjingo mushroom fruiting bodies.

• Plant Biotechnology Reports
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• v.4 no.4
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• pp.303-309
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• 2010

Endoreduplication is a developmental process that is unique to plants and occurs in all plants. The present study aimed to assess endoreduplication in various explant tissues and regenerated somatic embryos of Doritaenopsis. We further investigated the effects of light quality on endoreduplication and somatic embryo proliferation. To this end, we studied endoreduplication in leaves and root tips from regenerated plantlets and somatic embryos and in developing somatic embryos under 4 types of lighting conditions: red light, red + far-red light, red + blue light, and white light. We found that the degree of endoreduplication varied in different explants, and that the choice of explants used also influenced the ploidy levels of the newly regenerated somatic embryos. The DNA content of the leaf (2C-8C) was less than that of the root tip (2C-16C) and somatic embryo (2C-64C). In terms of light quality, the combination of red and far-red light produced the highest number of somatic embryos, while maintaining a low degree of endoreduplication. The data obtained indicate that this light combination stimulates somatic embryogenesis in Doritaenopsis and may exert some control on endoreduplication during cell division. These findings can be applied to achieve a reduction in somaclonal variations for the purpose of mass proliferation and genetic improvement.

• Environmental Engineering Research
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• v.22 no.4
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• pp.426-431
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• 2017

Some phototoxicity of titanium dioxide nanoparticles ($TiO_2$ NPs) has been reported in recent years in studies with fish embryos or larvae. However, it is necessary to focus on the potential effects of embryonic exposure due to irreversible abnormalities and mortalities observed in sac-fry, and to expand various fish embryos to generate multiple test species. The aim of this study was to evaluate the effects of $TiO_2$ NPs under different irradiation conditions in exposed Oryzias latipes (O. latipes) at the embryonic and sac-fry stages. The effects of different irradiation conditions were observed using ultra-violet (UV) and visible light, and the corresponding effects were monitored by determining cumulative mortality and abnormality. O. latipes were exposed for 8 d to 0, 1, 5, 10, or 50 mg/L $TiO_2$ NPs under UV ($4,818.86mW/m^2$ at the bottom of clear vials) or visible light, after which the embryos were transferred to NP-free embryo-rearing solution until 16 days post fertilization (dpf). Abnormalities of embryos and sac-fry increased at high $TiO_2$ NP concentrations under UV irradiation, compared to control samples treated with visible light or UV irradiation alone. This work provides information regarding the phototoxicity of $TiO_2$ NPs using O. latipes at the embryonic and sac-fry stages.

• Current Optics and Photonics
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• v.3 no.6
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• pp.516-521
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• 2019

The electrical leakage levels of GaN-based light-emitting diodes (LEDs) containing leakage paths are estimated using photoluminescence (PL) and photovoltaic properties under photoexcitation conditions. The PL intensity and open-circuit voltage (V_OC) decrease because of carrier leakages depending on photoexcitation conditions when compared with reference values for typical LED chips without leakage paths. Changes of photovoltage-photocurrent characteristics and PL intensity due to carrier leakage are employed to assess the leakage current levels of LEDs with leakage paths. The current corresponding to the reduced V_OC of an LED with leakage from the photovoltaic curve of a reference LED without leakage is matched with the leakage current calculated using the PL intensity reduction ratio and short-circuit current of the LED with leakage. The current needed to increase the voltage for an LED with a leakage under photoexcitation from V_OC of the LED up to V_OC of a reference LED without a leakage is identical to the additional current needed for optical turn-on of the LED with a leakage. The leakage current level estimated using the PL and photovoltaic properties under photoexcitation is consistent with the leakage level measured from the voltage-current characteristic obtained under current injection conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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• pp.711-715
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• 2007

Properties of organic light-emitting diodes (OLEDs) with aluminum-doped zinc oxide (ZnO:Al) anodes showed different behaviors from OLEDs with indium tin oxide (ITO) anodes according to driving conditions. OLEDs with ITO anodes gave higher current density and luminance in lower voltage region and better EL and power efficiency under lower current density conditions, However, OLEDs with ZnO:Al anodes gave higher current density and luminance in higher voltage region over about 8V and better EL and power efficiency under higher current density over $200mA/cm^2$. These seemed to be due to the differences in conduction properties of semiconducting ZnO:Al and metallic ITO. OLEDs with ZnO:Al anodes showed nearly saturated efficiency under high current driving conditions compared with those of OLEDs with ITO anodes. This meant better charge balance in OLEDs with ZnO:Al anodes. These properties of OLEDs with ZnO:Al anodes are useful in making bright display devices with efficiency.

• Horticultural Science & Technology
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• v.30 no.1
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• pp.6-12
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• 2012

Early growth, pigmentation, protein content, and phenylalanine ammonia-lyase (PAL) activity of red curly lettuces (Lactuca sativa L.) grown under different lighting conditions were investigated. Fluorescent lamps (control), blue, red, and blue plus red light-emitting diodes (LEDs) were used as light sources for 10 days. An equal proportion (1:1) of blue and red LEDs was used in the mixed radiation condition. Compared with the control, monochromic red or blue lighting increased fresh and dry weights of 'Ttuksum' and 'Jaju' lettuces. Anthocyanin synthesis was also significantly promoted by the mixed radiation of blue and red LEDs. The mixed radiation also increased the protein content and PAL enzyme activity of 'Ttuksum' leaves by about 200% compared to other treatments. Anthocyanin content was the highest in lettuces subjected to the mixture radiation of blue and red light treatment, while anthocyanin synthesis was inhibited by monochromic red light. The results of the present study indicate that growth and pigment synthesis in lettuces are significantly enhanced by exposure to mixed radiation from blue and red LEDs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8901-8907
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• 2015

Conventional streetlight with the not-adjustable light distribution characteristic is generating light pollution such as glare, damage to the crops and disturbed sleep, because beam of streetlight is not distributed evenly according to the surrounding areas and road conditions. In this paper, we proposed the new structure LED streetlight controlled light irradiation angle according to the surrounding areas and road conditions. Proposed LED streetlight are available to the adjustable light distribution characteristic using the half-circle angle control device. Result of measurement and simulation, beam angle is made available to control at least from $100^{\circ}$ up to $154^{\circ}$, average illumination exceeded 15% of KS regulation and overall uniformity exceeded more than 50% of KS regulation. the Developed large capacity LED streetlight luminaire is considered to minimize glare and light pollution and optimize uniformity ratio of illuminance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.762-767
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• 2010

This paper describes characteristic of a light triggered thyristor investigated by experiment to adopt it into a main switch of a pulsed power unit. Triggering principle of the light triggered thyristor are referred with its structure and equivalent circuit. Operational principle and simulation result of a capacitive pulsed power circuit are explained. A variety of triggering conditions of triggering circuit and characteristics on turn-on, turn-off, voltage dividing in series operation, overvoltage protection function of the light triggered thyristor are investigated by experiments. Experimental result of 40 kJ pulsed power unit using the light triggered thyristor is presented.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.1
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• pp.79-84
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• 2003

A light guide panel is an element of the LCD backlight module that is often used for the display of compact electronic devices. In this study, a laser marking system is proposed to fabricate light guide panel, which can replace other manufacturing methods such as silk printing, stamping, or v-cutting methods. The objective of this research is to evaluate the process parameters of the laser marking system. Light guide patterns were marked with a 50W $CO_2$ laser (CW) to understand the effects of average power and scanning speed on the geometry and quality of groove pattern. The width of the fabricated grooves increases with increasing laser power and decreasing scan speed. In order to analyze surface characteristics and optical properties (luminance, uniformity), SEM photography and BM7 (luminance measuring system) were used. As a result, the optimal conditions of the process parameters were determined.