• Journal of Korean Ophthalmic Optics Society
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• v.7 no.2
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• pp.209-215
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• 2002

This study investigated the crystal growth, crystalline structure and the basic optical properties of $SnSe/BaF_2$ epilayers. The SnSe epilayer was grown on $BaF_2$(111) insulating substrates using a hot wall epitaxy(HWE) technique. It was found from the analysis of X-ray diffraction patterns that $SnSe/BaF_2$ epilayer was growing to single crystal with orthorhombic structure oriented [111] along the growth direction. Using Rutherford back scattering(RBS), the atomic ratios of the SnSe was found to be stoichiometric, almost 50 : 50. The best values for the full width at half maximum (FWHM) of the DCXRD was 163 arcsec for SnSe epilarer. The epilayer-thickness dependence of the FWHM of the DCXRD shows that the quality of the $SnSe/BaF_2$ is as expected. The dielectric function ${\varepsilon}$(E) of a semiconductor is closely related to its electronic energy band structure and such relation can be drawn from features around the critical points in the optical spectra. The real and imaginary parts(${\varepsilon}_1$ and ${\varepsilon}_2$) of the dielectric function ${\varepsilon}$ of SnSe were measured. These data are analyzed using a theoretical model known as the model dielectric function(MDF). The optical constants related to dielectric function such as the complex refractive index(n*-n+ik), absorption coefficient (${\alpha}$) and normal- incidence reflectivity (R) are also presented for $SnSe/BaF_2$.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.189-189
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• 2012

Lead sulfide (PbS) nanocrystal quantum dots (NQDs) are promising materials for various optoelectronic devices, especially solar cells, because of their tunability of the optical band-gap controlled by adjusting the diameter of NQDs. PbS is a IV-VI semiconductor enabling infrared-absorption and it can be synthesized using solution process methods. A wide choice of the diameter of PbS NQDs is also a benefit to achieve the quantum confinement regime due to its large Bohr exciton radius (20 nm). To exploit these desirable properties, many research groups have intensively studied to apply for the photovoltaic devices. There are several essential requirements to fabricate the efficient NQDs-based solar cell. First of all, highly confined PbS QDs should be synthesized resulting in a narrow peak with a small full width-half maximum value at the first exciton transition observed in UV-Vis absorbance and photoluminescence spectra. In other words, the size-uniformity of NQDs ought to secure under 5%. Second, PbS NQDs should be assembled carefully in order to enhance the electronic coupling between adjacent NQDs by controlling the inter-QDs distance. Finally, appropriate structure for the photovoltaic device is the key issue to extract the photo-generated carriers from light-absorbing layer in solar cell. In this step, workfunction and Fermi energy difference could be precisely considered for Schottky and hetero junction device, respectively. In this presentation, we introduce the strategy to obtain high performance solar cell fabricated using PbS NQDs below the size of the Bohr radius. The PbS NQDs with various diameters were synthesized using methods established by Hines with a few modifications. PbS NQDs solids were assembled using layer-by-layer spin-coating method. Subsequent ligand-exchange was carried out using 1,2-ethanedithiol (EDT) to reduce inter-NQDs distance. Finally, Schottky junction solar cells were fabricated on ITO-coated glass and 150 nm-thick Al was deposited on the top of PbS NQDs solids as a top electrode using thermal evaporation technique. To evaluate the solar cell performance, current-voltage (I-V) measurement were performed under AM 1.5G solar spectrum at 1 sun intensity. As a result, we could achieve the power conversion efficiency of 3.33% at Schottky junction solar cell. This result indicates that high performance solar cell is successfully fabricated by optimizing the all steps as mentioned above in this work.

• Science of Emotion and Sensibility
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• v.20 no.2
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• pp.117-126
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• 2017

In this study, moisture transport characteristics for the woven and knitted fabrics made of 8 kinds of fiber materials using MMT (moisture management tester) were measured and discussed with the Bireck bt MMT and water evaporating rate (WER) measuring methods, which are vertical moisture transport methods. In addition, the drying property by MMT of the eight kinds of specimens was compared and discussed with the results measured by the vertical drying measurement. MMT experimental result which is horizental moisture transport appeared to be similar to the result of the Bireck method, which is the vertical moisture transport experiment. Absortion time measured from drip method of the fabrics made of the bamboo, linen, and cotton/nylon composite fabrics was short and thus they showed best wicking property, which was attributed to the low contact angle on the fabric surface and high porosity of the fabrics due to the staple yarn structure composed of the hydrophilic staple fibers. In drying property of the fabric specimens by MMT, maximum absorption radius of the dry-zone knit and bamboo woven fabrics were the highest and they showed the best drying property, which was a little different result compared with vertical drying measurement method. Half time of the drying rate in the MMT method was highly correlated with the fabric thickness and saturated moisture absortion rate and their regression coefficients were 0.9 and 0.88, respectively. This means that the knitted and woven fabric design technology for retaining good wicking and drying properties of the fabrics with thin fabric thickness is very important for obtaining high functional wear comfort fabrics. In addition, wicking and drying properties of the fabrics made of different fiber materials and with different yarns and fabric structures showed different results according to the measuring methods.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.65-65
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• 2015

In this talk, I will introduce two topics. The first topic is the polymer light emitting diodes (PLEDs) using graphene oxide quantum dots as emissive center. More specifically, the energy transfer mechanism as well as the origin of white electroluminescence in the PLED were investigated. The second topic is the facile synthesis of eco-friendly III-V colloidal quantum dots and their application to light emitting diodes. Polymer (organic) light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nanomaterial without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence (EL) from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. (Sci Rep., 5, 11032, 2015). New III-V colloidal quantum dots (CQDs) were synthesized using the hot-injection method and the QD-light emitting diodes (QLEDs) using these CQDs as emissive layer were demonstrated for the first time. The band gaps of the III-V CQDs were varied by varying the metal fraction and by particle size control. The X-ray absorption fine structure (XAFS) results show that the crystal states of the III-V CQDs consist of multi-phase states; multi-peak photoluminescence (PL) resulted from these multi-phase states. Inverted structured QLED shows green EL emission and a maximum luminance of ~45 cd/m2. This result shows that III-V CQDs can be a good substitute for conventional cadmium-containing CQDs in various opto-electronic applications, e.g., eco-friendly displays. (Un-published results).

• Korean Journal Plant Pathology
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• v.1 no.1
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• pp.3-11
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• 1985

Three mild mutant strains of tobacco mosaic virus (TMV) were isolated from Nicotiana tabacum var. Samsun incubated at $38^{\circ}C$ for 10 days after inoculation with a wild type of TMV-OM strain. They were designated into Tg 5272, Tw 227 and Tw 333. All mild strains could be distinguished from TMV-OM by their reactions on different indicator plants. The mild strains induced the mild mottling without distinct symptoms, whereas the wild strain produced severe mosaic, rugose and stunting on tobacco and red pepper plants. Tw 227 and Tw 333 produced smaller necrotic spots than those of Tg 5272 and TMV-OM on N. glutinosa and Datura stramonium. The former two strains also produced ring spots and mosaic on Gomphrena globosa compared with necrotic spots by the latter strains. Three mild strains were serologically identical to TMV-OM. Their physical properties were thermal inactivation point $80-85^{\circ}C$, dilution end point between $10^{-4}\;and\;10^{-6}$, and longevity in vitro 7days or longer. Ultraviolet absorption spectra of purified preparations of the mild strains and TMV-OM were identical, with a minimum at 247nm, a maximum at 260nm, and a slight shoulder at 290nm. Electrophoresis of the strains in polyacrylamide-agarose gel showed that all the strains formed one major band and two minor bands, except for one minor band of Tw 333. However, when sodium dodecyl sulfate was added to the purified viruses before electrophoresis, each strain formed only one major band.

• Food Science and Preservation
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• v.6 no.2
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• pp.161-166
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• 1999

In order to increase the Korean wheat-cultivators' incomes as well as to promote their consumptions, the native wheat of 11 varities (Chokwangmil, Geurumil, Eunpamil, Tapdongmil, Woorimil, Olgeurumil, Alchanmil , Gobunmil, Geungangmil Seodunmil and Suwon 265) were investigated on dough properties to compared with those of two imported wheat varieties, DNS (Dark Northern Spring Wheat) and ASW (Austrlian Standard White). In dough stickiness, Chokwangmil was highest as 81.78, and the mean value of native wheat was 53.98 g. ASW and DNS showed the stickiness values of 58.7 g and 52.9 g, respectively. Tapdongmil was highest in the tensile tone of dough as 87.6 g. In the texture test, the highest elasticity, gumminess, firmness and chewiness were observed in Woorimil as values of 0.980, 1,022.8, 1,562.7 and 1,001.9, respectively, while the highest cohesiveness and adhesiveness were obtained from Suwon 265 and Geurumil, respectively, as 0.710 and -609.4. In amylogram properties, the initial gelatinization temperature was ranged from 65$^{\circ}C$ to 69$^{\circ}C$, and maximum, minimum and final viscosities were highest in Woorimil as 1,140, 1,100 and 1,730 BU, respectively. In farinogram, water absorption rate was highest in Suwon 265 as 65.1%, which required the longest dough arrival time of 3.5 min. Dough developing time, weakening and stability were longest in Gobunmil as 9.7. 32.1 and 29.9 min., respectively. The resistance of dough was highest in Olgeurumil as 110 BU.

• Journal of Korea Foresty Energy
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• v.25 no.1
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• pp.18-23
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• 2006

pH dependent K/S values, Hue, Value, and Chroma change of the hot-water and alkali extract of Boehmeria tricuspis have investigated as a part of the studies on natural dye resources. Maximum optical absorption of the dyed cotton, Korean paper, and silk with the extract were observed at 400 nm. According to the result of pH dependent K/S values change, it tended to increase as pH decreased except for the silk and there was no change near pH 7. For Hue, the materials dyed with hot-water and alkali extract indicated YR and R color, respectively. The change in Value of the dyed materials tended to increase, whereas Chroma of them decreased as the pH moved to alkali conditions although there were no significant changes near pH 7. As a result, it is considered that the optimum pH would be 7 when the mentioned materials are dyed with Boehmeria tricuspis extract.

• Horticultural Science & Technology
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• v.35 no.4
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• pp.431-438
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• 2017

This study investigated the effect of pre-planting nitrogen (N) fertilization levels added to a soilless root medium on the growth of 'Dotaerang Dia' tomato seedlings. The N levels were varied for a total of 7 treatments: 0, 100, 250, 500, 750, 1,000, or $1,500mg{\cdot}L^{-1}$. The pH of the root media gradually rose in all treatments as the seedlings grew; however, the differences in the pH were not significant among the treatments. The electrical conductivity (EC) of the root media was significantly different among the treatments from sowing to week three, then drastically decreased after week four, which diminished the differences in the EC among the treatments. At week six, plant height, leaf length, leaf width, number of leaves, and fresh and dry weights of the shoot were highest for the treatment with $500mg{\cdot}L^{-1}N$. In contrast, the treatment with $1,500mg{\cdot}L^{-1}N$ had the lowest results for all growth measurements. The fresh weight was 67% heavier in the $500mg{\cdot}L^{-1}N$ treatment compared to the $1,500mg{\cdot}L^{-1}N$ treatment. The total N content in the tissues was lowest in the treatment with $0mg{\cdot}L^{-1}N$ and highest in the treatment with $1,000mg{\cdot}L^{-1}N$. The contents of calcium (Ca), magnesium (Mg), and metal micronutrients in the tissues were highest in the $250mg{\cdot}L^{-1}N$ treatment. A previous study demonstrated that adjusting the fertilization level to promote growth to over 90% of the maximum growth is a good strategy for lowering production costs and preventing damage due to excessive fertilizer absorption by crops. Our results indicated that the optimal pre-planting N fertilization level for tomato plug seedlings should be lower than $500mg{\cdot}L^{-1}$ and the optimum tissue N contents should be around 3.21% to 4.60%.

• Journal of Animal Science and Technology
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• v.47 no.3
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• pp.397-408
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• 2005

This study, consisting of three experiments, was conducted to determine the effects of feeding feather meal (FM), feather meal digest (FMD), L-cystine and methionine hydroxyl analogue (MHA) on taurine content of milk and milk production of Holstein dairy cows. In experiment 1, FM or FMD was supplemented at 0, 1, 3 and 5% of dry matter intake (DMI), respectively. Taurine concentration of 3% FM and 5% FMD treatment were increased by 14% and 220/0, respectively. The 5% FM treatment had a negative effect on milk yield and FM and FMD treatments had no significant or consistent effects on milk fat, protein, lactose, milk urea nitrogen (MUN) and somatic cell count (SCC). In experiment 2, Lcystine or MHA was supplemented at 0, 1, 3, and 5g or ml/d along with 5% FMD, respectively. Milk yield decreased at 3 and 5g or ml Lcystine or MHA supplementation along with 5% FMD. Fat and lactose in milk were not significantly affected by treatments. However, milk protein level increased significantly in the 5 ml HMA with 5% FMD treatment. SCC decreased significantly in 1ml MHA with 5% FMD supplemented treatment but increased in 5g Lcystine with 5% FMD and 5 ml MHA with 5% FMD treatments. Increase of milk taurine concentration of L'cystine with 5% FMD treatments was not significant but those of MHA with 5% FMD treatments were significantly higher than the control. The highest increase of milk taurine concentration was 65% shown in 1 ml MHA with 5% FMD treatment. In experiment 3, 5% FM, 5% FM+3% molasses or 5% FM+3% molasses+l ml MHA was supplemented to the based TMR diet. The molasses treatments (5% FM+3% molasses and 5% FM+3% molasses+l ml MHA) showed significantly higher milk taurine content than the 5% FM treatment. The molasses treatments significantly reduced MUN but increased SCC. It was concluded that FMD is more effective than FM in enriching taurine in milk. Maximum taurine enrichment (65%) in the milk was obtained by supplementation of 5% FMD/DM1+1 ml MHA/d/cow. Molasses supplementation to 5% FM diet increased milk taurine content. However, MHA supplementation in dairy cows increased ruminal escape, gastrointestinal absorption and response of serum methionine.

• Journal of Food Hygiene and Safety
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• v.16 no.4
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• pp.315-323
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• 2001

This study was concentrated that the contents of heavy metals were estimated from 782 samples of sold fisheries in Seoul(33 species in fishes, 15 in bivalves, 12 in crustaceans and 10 in others) by Atomic Absorption Spectrometer. The contents of As, Cd and Pb [minimum~maximum (mean)] were N.D.~0.162 mg/kg(0.021),0.001~0.120 mg/kg(0.014) and 0.015~0.499 mg/kg(0.111) in fishes, 0.003~0.311 mg/kg(0.052), N.D.~1.905 mg/kg(0.182) and 0.013~0.462 mg/kg(0.138) in bivalves, N.D.~0.328 mg/kg(0.042), 0.002~1.113mg/kg(0.079) and 0.006~-.510 mg/kg(0.109) in crustaceans, N.D. ~0.181 mg/kg(0.024), 0.001~0.214 mg/kg(0.033) and 0.010~0.877 mg/kg(0.118) in others respectively, bivalves were the highest than others. The average weekly intakes of three metals from sold fisheries took about 1.4~26.4% of PTWI (provisional tolerable weekly intakes) that FAO/WHO Joint Food Additive and Contaminants Committee had set to evaluate their safety.