• Proceedings of the Korean Society of Crop Science Conference
• /
• 2022.10a
• /
• pp.184-184
• /
• 2022

This study was aimed to evaluate the antioxidant activity and bioactive property of extracts from a purple-colored wheat variety 'Arriheuk' (Triticum aestivum L.) wheatgrass, affected by light emitting diode irradiation (LED). The wheatgrass was cultivated for 10 days after sowing in a growth chamber under the following LED conditions: R1B1 (Red:Blue = 1:1), R7B3 (Red:Blue = 7:3), and R3B7 (Red:Blue = 3:7). We examined antioxidant activity of the hot water extracts of wheatgrass using DPPH and ABTS free radicals scavenging assays. At the concentration of 10,000 ㎍/ml, the extract from R1B1 showed the highest DPPH free radical scavenging activity(79.29%), but its ABTS free radical scavenging activity was the lowest(32.0%). To evaluate bioactive property of the wheatgrass, we examined the change of natural killer (NK) cell activity affected by the wheatgrass extracts in vitro. At the concentration of 500㎍/ml, NK cell activity was most highly enhanced by the extract from R1B1(181.6%), and the activity was 176.1% (R7B3) and 144.6%(R3B7), respectively. These results suggest that the functional property of 'Arriheuk' wheatgrass would be enhanced by LED irradiation condition.

• Journal of the Korean Chemical Society
• /
• v.47 no.4
• /
• pp.370-375
• /
• 2003

$BaMg_2Al_16O_27:Eu,\SrGa_2S_4:Eu$, and ZnCdS:Ag,Cl phosphors were chosen to produce blue, green, and red emissions, respectively, under excitation from a violet light emitting diode (LED). A four-band white LED was obtained by a combination of nonabsorbed violet emission from a violet LED and blue, green, and red emissions from $BaMg_2Al_16O_27:Eu,\SrGa_2S_4:Eu$, and ZnCdS:Ag,Cl phosphors. The luminescent properties of the four-band white LED were also discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.2
• /
• pp.145-151
• /
• 2001

In this study, blue light emiting, soluble PPV copolymers were synthesized by Witting reaction and characterized. ITO/copolymer/Ca and ITO/copolymer/A1 structured light emitting diodes(LED) were fabricated and their I-V characteristics were examined. Copolymers showed $\pi$-$\pi$ transition in UV-Vis./NIR spectra. The PL and abosorption spectrum showed the symmetric vibration modes with mirror images which means that copolymers are highly aligned. By introducing aliphatic hydrocarbon group on polymer main chain, the solubility of copolymers was improved and no significant effects of substituent were observed. The band offset of copolymers are well suited as light emitting material for LED application than monomer or oligomer does. THe band offset of copolymers is ∼3eV in PL spectrum and the threshold voltages of ITO/copolymer/Ca and ITO/copolymer/Al structured LED 3V, 12V respectively. In the case of ITO/copolymer/Ca LED, it is believed that the amount of electrons and holes is well balanced and the recombination of opposite charges occurs easily because the work functions of Ca and Al electrodes are 2.9 and 4.3eV respectively and the difference in barrier height between polymer and electrode was small.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.13 no.4
• /
• pp.121-129
• /
• 2014

This study was carried out to develop an efficient plant growth system that can be controlled by altering the wavelength and illumination using a LED module. If it is possible to develop a system that can be controlled in this manner, utilizing different characteristics in the meaningful wavelength band depending on the growth time or type of plant, the plant growth conditions can be optimized. In order to this, red, green, blue and white LEDs are arrayed in a rectangle, consisting of LED modules which can be combined with each other. Consequently, the array can be used to select the optimal light conditions with monochromatic red, green, blue and white LEDs, or mixed LEDs, for plant growth. Experiments on the characteristics of the wavelengths to evaluate the efficiency of the plant growth system were performed. The usefulness of the system was demonstrated through a cultivation test involving several special plants.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.8
• /
• pp.2523-2528
• /
• 2012

Green phosphors $(Zn_{1-a-b}M_aM^{\prime}_b)_xGa_yS_{x+3y/2}:Eu^{2+}$ (M, M' = alkali earth ions) with x = 2 and y = 2-5 were prepared, starting from ZnO, MgO, $SrCO_3$, $Ga_2O_3$, $Eu_2O_3$, and S with a flux $NH_4F$ using a conventional solidstate reaction. A phosphor with the composition of $(Zn_{0.6}Sr_{0.3}Mg_{0.1})_2Ga_2S_5:Eu^{2+}$ produced the strongest luminescence at a 460-nm excitation. The observed XRD patterns indicated that the optimized phosphor consisted of two components: zinc thiogallate and zinc sulfide. The characteristic green luminescence of the $ZnS:Eu^{2+}$ component on excitation at 460 nm was attributed to the donor-acceptor ($D_{ZnGa_2S_4}-A_{ZnS}$) recombination in the hybrid boundary. The optimized green phosphor converted 17.9% of the absorbed blue light into luminescence. For the fabrication of light-emitting diode (LED), the optimized phosphor was coated with MgO using magnesium nitrate to overcome their weakness against moisture. The MgO-coated green phosphor was fabricated with a blue GaN LED, and the chromaticity index of the phosphor-cast LED (pc-LED) was investigated as a function of the wt % of the optimized phosphor. White LEDs were fabricated by pasting the optimized green (G) and the red (R) phosphors, and the commercial yellow (Y) phosphor on the blue chips. The three-band pc-WLED resulted in improved color rendering index (CRI) and corrected color temperature (CCT), compared with those of the two-band pc-WLED.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.5
• /
• pp.3007-3013
• /
• 2014

The objectives of this study was to evaluate the validity of 3D digital models made from blue LED dental scanner. Twenty same cases of stone models and 3d digital models were manufactured for this study. Intercanine distance, intermolar distance, two dental arch lengths(right, left) and two diagonal of dental arch lengths(right, left) were measured for evaluation of validity. The nonparametric Wilcoxon rank sum test was used for statistical analysis (${\alpha}$=0.05). Although stone models showed larger than digital models in all measured distances(p<0.05), none exceeded the clinically acceptable range.

• Journal of Plant Biotechnology
• /
• v.42 no.2
• /
• pp.104-110
• /
• 2015

We analyzed the effects of various LED light treatments (red 655 nm, blue 456 nm, white and mixed light) on growth pattern, gene expression and flavonoid contents in lettuce leaf. Plants treated with mixed light (red+blue+white) showed better growth performance than those treated with single LED and fluorescent lamp (FL). Expression analysis of the eight genes involved in flavonoid biosynthesis in plants treated with LED light was examined. Results showed that red lettuce grown under mixed light showed high expression levels of LsC4H, LsF3H and LsDRF genes. Morever, the same treatment plants possessed higher content of gallic acid, chlorogenic acid and quercetin contents than those in plants exposed to single light. However, the highest total anthocyanin content was identified in plants treated with red+blue light and the lowest content was identified in plants exposed to white fluorescent lamp and single LED light condition. Thus, this study indicates that the ratio of blue to red LEDs is important for the morphology, growth, and phenolic compounds with anthocyanin properties in the two lettuce cultivars tested.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.10
• /
• pp.64-71
• /
• 2020

This study evaluated the effects of the culture media and light sources on the growth of microalgae Haematococuus pluvialis. Limited ingredient medium, Modified Bold's Basic Medium (MBBM), commercial liquid fertilizer medium Neo, and seven different light sources with different wavelengths were used to incubate H. pluvialis for 39 days, and the growth rates were compared. As a result, the growth of H. pluvialis, a limited ingredient medium, produced the highest cell growth in the fluorescent light source while cell growth was the lowest in the blue+red LED. The growth of H. pluvialis in commercial medium Neo was highest in the fluorescent light source, and cell growth was lowest in the blue LED. In this study, the MBBM culture medium showed better results than the Neo culture medium. Microalgae grown in the fluorescent light source using the MBBM culture medium showed the best cell growth result in this study. The results were optimized for the culture medium, light source, and light quantity in H. pluvialis culture for the production of secondary metabolites and provide basic data for the mass culture of microalgae.

• Journal of Conservation Science
• /
• v.36 no.4
• /
• pp.236-243
• /
• 2020

In this study, an accelerated aging experiment for fabric and paper was conducted using two light emitting diode(LED) sources with different wavelength characteristics, and the discoloration under each lighting type was examined. Hanji(Korean traditional paper) and related textiles showed more discoloration under blue LEDs, while the blue wool standard showed more discoloration under white LEDs. This, indicated that the deterioration varied depending on the sample color. The the effect of the light source on artifact deterioration was primarily related to the total radiation flux(expressed in mill watts), rather than the total luminous flux(expressed in lumens). In addition, the discoloration of the investigated artifacts was dependent on the color rendering of the lighting.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.11a
• /
• pp.274-277
• /
• 1996

This paper describes the realization of the full-color to the degree of nearest white light by compounding high brightness Red, Green and Blue LEDs with appropriate proportional index. Once these three colors; red, green and blue are mixed, they are genearlly additive mixing and produce white light color contrasted to negative mixing. The luminous efficiency is defined as the product of the efficiency(lm/w), which indicates the degree of perceptual response by the human eye to unit energy(W) of light emitted by an active display devises and as the conversion efficiency of the device from electric power consumed to optical energy produced. We will deduce the each number of LEDs theoretically and design several shapes of LED displays for the full-color. Finally theoretical predictions will be compared with the measured data with different type of display designs.