• Journal of Biosystems Engineering
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• v.39 no.2
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• pp.87-95
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• 2014

Purpose: The purpose of this study was to design a variable frequency LED light system for plant factory which combined red, blue, green, white, and UV lights and controlled the ratio of the light wavelength. In addition, this study evaluated the performance of each combination of LED to verify the applicability. Methods: Four combinations of LED (i.e. Red+Blue, Red+Blue+Green, Red+Blue+White, Red+Blue+UV) were designed using five types of LED. The system was designed to control the duty ratio of each wavelength of LED by 1% interval from 0~100%, the pulse by 1Hz interval from 1~20kHz. Response characteristics of the control system, spectral distribution of each combination, light uniformity and uniformity ratio were measured to test the performance of the system. Results: Clean waveforms were measured from 10Hz to 10kHz regardless of duty ratio. Frequency distortion was observed within 5% of inflection point at frequencies above 10kHz regardless of duty ratio, but it was judged negligible. Spectra showed a normal distribution, and maximum PPF with duty ratio of 100% was $271.4{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ for the Red+Blue combination. PPF of the Red+Blue+Green combination was $258.9{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, and that of the Red+Blue+White combination was $273.9{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. PPF of the Red+Blue+UV combination was $267.7{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. Uniformity ratio for the area excepting border showed 0.90 for the Red+Blue and Red+Blue+White combinations, 0.87 for the Red+Blue+Green combination, and 0.88 for the Red+Blue+UV combination. The light was irradiated evenly at the area excepting border, so it was suitable for plant growing. Conclusions: From the results of this study, response characteristics of the control system, spectral distribution of each combination, light uniformity and uniformity ratio were suitable for applying into the plant factory.

• Horticultural Science & Technology
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• v.30 no.6
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• pp.635-641
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• 2012

In Korea, slurry composted and biofiltered (SCB) liquid fertilizer is produced through the composting and biofiltering of animal waste. An appropriate guidelines involving proper treatment of SCB liquid fertilizer on turfgrass should be considered. An experiment was conducted to determine the optimum application amount, timing, and frequency of SCB liquid fertilizer for Zoysia japonica 'Millock'. The SCB liquid fertilizer was applied in low, medium, and high amount (N at 15, 25, and 40 $g{\cdot}m^{-2}$ per year in 2010, and 10, 20, and 40 $g{\cdot}m^{-2}$ per year in 2011, respectively) and treated during the growing season or dormancy period. During the growing season, SCB liquid fertilizer was applied twice or four times. The greatest improvement in turf quality for both years was in SCB plots applied four times with N at 40 $g{\cdot}m^{-2}$ per year during the growing season (SH4). This treatment exhibited turf color retention in the fall, and enhanced clipping yield during the growing and fall seasons. SCB plots with four times during the growing season (SL4, SM4, and SH4) exhibited higher shoot density relative to the same amount of other SCB treatments. Plots treated during the dormancy period also showed a high turf color index during the next growing season in 2011. The results indicate that SCB with high amount up to N at 40 $g{\cdot}m^{-2}$ per year applied four times during the growing season and dormant application produced high turf quality and growth, and could be recommended as an optimum application guide.

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.304-308
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• 1989

The spectrophotometric determination of $Lu^{3+},\;Eu^{3+}$ and some other rare earths have been investigated using Methyl Thymol Blue(MTB) as spectrophotometric reagent. Rare earth elements form a stable complex with MTB abount pH 6.5 and the ratio of its complex is 1 to 1. MTB has a absorption maxima at 440nm and rare earth MTB complex has absorption maxima 610nm at pH 6.5, respectively. The absorbance of the rare earth MTB complex is stable in 7 hours after color developing and obey the Beer law in the range of $0{\sim}110{\mu}g/50ml$. The ligand such as phosphate, citrate and EDTA decrease the absorbance of its complex considerably, and this method has a poor selectivity of each rare earth element and the molar absorptivity is $1.2{\sim}2.0{\times}10^4mol^{-1}{\cdot}l{\cdot}cm^{-1}$. In methyl alcohol, ethyl alcohol and acetone medium we did not find out any absorption change of the rare earth MTB complex.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.173-177
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• 2015

This experiment was conducted to determined the optimum planting density for the production of high quality bitter gourd (Momordica charantia L.) adapted in spring cultivation with the unheated greenhouse condition. 'Erave' variety was planted at three different planting densities (235, 305, $380plants{\cdot}10a^{-1}$) on March 26. The training method was six lateral vines with pinching the main one. The light intensity was lower in the higher planting density than the lower one. Net photosynthetic rates of the bitter gourd leaves in the higher density were significantly lower (41 to 71%) than the lower one. There was no difference in the fruit characteristics among treatments. But the root weight was heavier in the lower planting density ($235plants{\cdot}10a^{-1}$) as 113.1g than 96.0g of the higher planting density ($380plants{\cdot}10a^{-1}$). The number of the harvested fruit also higher in the lower planting density ($235plants{\cdot}10a^{-1}$) with 60.7 than 39.9 of the higher planting density ($380plants{\cdot}10a^{-1}$). The average fruit weight was the highest in the plot of $305plants{\cdot}10a^{-1}$ as 338.7g and lowest in the lower planting density ($235plants{\cdot}10a^{-1}$) as 285.2g. The total yield of $305plants{\cdot}10a^{-1}$ density was $5,359kg{\cdot}10a^{-1}$, which was higher than $4,068kg{\cdot}10a^{-1}$ of the lower planting density ($235plants{\cdot}10a^{-1}$). Marketable yield was increased by 24% in the planting density of $305plants{\cdot}10a^{-1}$($4,767kg{\cdot}10a^{-1}$) as compared to the lower density in $235plants{\cdot}10a^{-1}$($3,629kg{\cdot}10a^{-1}$) and increased by 13% in the planting density as $380plants{\cdot}10a^{-1}$($4,137kg{\cdot}10a^{-1}$). Therefore, the planting density of bitter gourd was desirable in $305plants{\cdot}10a^{-1}$ density for the higher yield and quality in the protected cultivation.

• Journal of the Korean Ceramic Society
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• v.51 no.1
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• pp.43-50
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• 2014

We fabricated undoped and Sb-doped $SnO_2$ thin films on glass substrates by a pulsed laser deposition (PLD) process. Undoped and 2 - 8 wt% $Sb_2O_3$-doped $SnO_2$ targets with a high density level of ~90% were prepared by the spark plasma sintering (SPS) process. Initially, the effects of the deposition temperature on undoped $SnO_2$ thin films were investigated in the region of $100-600^{\circ}C$. While the undoped $SnO_2$ film exhibited the lowest resistivity of $1.20{\times}10^{-2}{\Omega}{\cdot}cm$ at $200^{\circ}C$ due to the highest carrier concentration generated by the oxygen vacancies, 2 wt% Sb-doped $SnO_2$ film exhibited the lowest resistivity value of $5.43{\times}10^{-3}{\Omega}{\cdot}cm$, the highest average transmittance of 85.8%, and the highest figure of merit of 1202 ${\Omega}^{-1}{\cdot}cm^{-1}$ at $400^{\circ}C$ among all of the doped films. These results imply that 2 wt% $Sb_2O_3$ is an optimum doping content close to the solubility limit of $Sb^{5+}$ substitution for the $Sb^{4+}$ sites of $SnO_2$.

• Journal of Bio-Environment Control
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• v.23 no.2
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• pp.144-147
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• 2014

It was intended to closely examine an effect that a change in the concentration of culture medium had on the potato(Solanum tuberosum L.) plantlet growth in the microponic system so as to mass-produce the virus-free plant of new variety 'Saebong' for potato processing. The adjusted concentration of potato culture medium was 0.2, 0.6, 1.0, 1.4, 1.8, and $14.0dS{\cdot}m^{-1}$. And potato seedling was cut into pieces of 1.5 cm in length, which included 2 growth points and leaves. And each was explanted in glass vial of 50 mL. And experiments were carried out twice for 18 days or 21days. Culture medium of 2ml was put in the container respectively. And 1 mL was added after 10 days. And in terms of cultivation environment, the experiment was carried out at the day length of 16 hours at the temperature of $23{\pm}1^{\circ}C$ under the white LED light of $40{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. The concentration of culture medium in the experiment I was EC 0.2, 1.0, $14dS{\cdot}m^{-1}$ and was adjusted to 0.6, 1.0, 1.4, $1.8dS{\cdot}m^{-1}$ in the experiment II. The results showed that the survival rate of plantlet was 90% at $0.2dS^2m^{-1}$, 100% at $0.6dS^2m^{-1}$, 100% at $1.0dS^2m^{-1}$. 0% at $1.4dS{\cdot}m^{-1}$, 0% at $1.8dS{\cdot}m^{-1}$. and 0% at $14.0dS{\cdot}m^{-1}$ after 7 days. With regard to the explanted potato seedling, in case of the treatment where the electrical conductivity of culture medium was adjusted to $1.0dS{\cdot}m^{-1}$, root developed 2 days after transplantation. And the plantlet vigorously grew into strong plant that had 7 leaves, length of 5cm, and fresh weight of 0.5 g after 18 days. In case of the treatment where the concentration of culture medium was adjusted to $0.6dS{\cdot}m^{-1}$, the root plantlets developed 4 days after transplantation. And those grew into plant that had 7 leaves and fresh weight of 0.2 g after 21 days. Therefore, we found that it is effective to control potato culture medium by adjusting its electrical conductivity to $0.6{\sim}1.0dS{\cdot}m^{-1}$ for the mass production of virus-free potato seedling in the microponic system.

• FLOWER RESEARCH JOURNAL
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• v.19 no.3
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• pp.127-138
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• 2011

Four different plant growth retardants (PGRs), paclobutrazol, flurprimidol, daminozide, and chlormequat, were applied to potted Saxifraga rosacea 'Kumoma' and 'Kumoma-Gusa' plants for control of the growth and flowering. Paclobutrazol (10, 20, 40, $80mg{\cdot}L^{-1}$), flurprimidol (5, 10, 20, $40mg{\cdot}L^{-1}$), daminozide (500, 1000, 2000, $4000mg{\cdot}L^{-1}$), and chlormequat (50, 100, 200, $400mg{\cdot}L^{-1}$) were applied to the plants by a foliar spray or drenching. In 'Kumoma', application of $40mg{\cdot}L^{-1}$ paclobutrazol by a foliar spray or drenching reduced plant height by 12.5 and 12.6 cm, and flower length by 3.4 and 3.3 cm, respectively. On the other hand, in 'Kumoma-Gusa', drenching of paclobutrazol reduced plant height by 10.7 to 12.6 cm and flower length by 2.0 to 3.9 cm with increasing concentration, but the number of florets almost fell to 20 as compared to 40.5 in the control. 'Kumoma-Gusa' plants drenched with $80mg{\cdot}L^{-1}$ paclobutrazol and sprayed with $40mg{\cdot}L^{-1}$ flurprimidol had the shortest heights of 10.7 and 9.9 cm, and floral length of 2.0 and 1.5 cm, respectively. A flurprimidol drenching at $40mg{\cdot}L^{-1}$ delayed the harvest by 3-13 days as compared to the control and the smallest number of florets, 15.6, was observed in this treatment. In both cultivars, chlormequat and daminozide did not effectively influence the growth and flowering. However, number of florets increased to more than 41 at all concentrations and up to 63, the greatest floret number, with chlormequat drench in 'Kumoma-Gusa'. These results demonstrated that over $40mg{\cdot}L^{-1}$ of paclobutrazol or 5 to $20mg{\cdot}L^{-1}$ of flurprimidol could be used as PGRs to control the growth of floral length and flowering for improving potted plant quality in S. rosacea 'Kumoma' and 'Kumoma-Gusa'.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.11
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• pp.911-914
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• 2011

We optimize electrical and optical properties of thermal and SF6 plasma treated indium tin oxide (ITO)/Al based reflector for high-power ultraviolet (UV) light-emitting diodes (LEDs). After thermal and $SF_6$ plasma treatments of ITO/Al reflector, the specific contact resistance decreased from $1.04{\times}10^{-3}\;{\Omega}{\cdot}cm^2$ to $9.21{\times}10^{-4}\;{\Omega}{\cdot}cm^2$, while the reflectance increased from 58% to 70% at the 365 nm wavelength. The low resistance and high reflectance of ITO/Al reflector are attributed to the reduced Schottky barrier height (SBH) between the ITO and AlGaN by large electronegativity of fluorine species and reduced interface roughness between the ITO and Al, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.1
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• pp.56-63
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• 2013

IGZO thin films have been prepared by RF magnetron sputtering. The structural, electrical and optical properties of the IGZO thin films have been investigated as a function of deposition condition. XRD analysis of IGZO thin films showed a typical crystallographic orientation with c-axis perpendicular regardless of deposition conditions. The carrier mobility, carrier concentration and resistivity of the IGZO films sputtered at 200 W, 1mTorr and $300^{\circ}C$ were $28.5cm^2/V{\cdot}sec$, $2.6{\times}10^{20}cm^3$, $8.8{\times}10^{-4}{\Omega}{\cdot}cm$ respectively. The optical transmittance were higher than 80% at visible region regardless of the deposition conditions under the experiments above, and specifically higher than 90% at wave length over 500 nm. The absorption edge was shifted to shorter wavelength with increase of carrier concentration.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.1
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• pp.28-31
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• 2004

The results of investigations of Ag2Se single crystal are presented. $Ag_2Se$ crystal was grown by the Bridgman method. The $Ag_2Se$ single crystal was an orthorhombic structure with lattice constance $a=4.333{\AA}$, $b=7.062{\AA}$, $c=7.764{\AA}$. Hall effect shows a n-type conductivity in the $Ag_2Se$ single crystal. The electrical resistivity was $1.25{\times}10^3ohm^{-1}^cm{-1}$ and electron mobility was $-5.48{\times}10^3cm^2/V{\cdot}sec$ at room temperature(RT).