• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.1
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• pp.15-23
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• 2002

In this study, metal/ZnO contacts were thermally annealed at different temperatures (as-dep., 400$^{\circ}C$, 600$^{\circ}C$, 800$^{\circ}C$, 1000$^{\circ}C$) for the investigation of electrical properties, and surface and interface characteristics. The analysis of the element composition and the chemical bonding state of the surface was made by the XPS(X-ray photoelectron spectroscopy). An attempt was made to establish the electrical property-microstructure relationship for the (Ti, Au)/ZnO. The Ti/ZnO contact exhibits an ohmic characteristics with a relatively high contact resistance of 4.74${\times}$10$\^$-1/ $\Omega$$\textrm{cm}^2$ after an annealing at 400$^{\circ}C$. The contact showed a schottky characteristics when the samples were annealed at higher temperature than 400$^{\circ}C$. The transition from the ohmic to schottky characteristics was contributed from the formation of the oxide layers as was confirmed by the peaks for O-O and Ti-O bondings in XPS analysis. For the Au/ZnO contact the lowest contact resistance was obtained from the as-deposited sample. The resistance was slowly increased with annealing temperature up to 600$^{\circ}C$. The ohmic characteristics were maintained eden fort 600$^{\circ}C$ annealing. The XPS analysis showed that the Au-O intensity was dramatically decreased with temperature above 600$^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.124-124
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• 2010

Much interest has been focused on InGaN-based materials and their quantum structures due to their optoelectronics applications such as light emitting diode (LED) and photovoltaic devices, because of its high thermal conductivity, high optical efficiency, and direct wide band gap, in spite of their high density of threading dislocations. Build-in internal field-induced quantum-confined Stark effect in InGaN/GaN quantum well LED structures results in a spatial separation of electrons and holes, which leads to a reduction of radiative recombination rate. Therefore, many growth techniques have been developed by utilizing lateral over-growth mode or by inserting additional layers such as patterned layer and superlattices for reducing threading dislocations and internal fields. In this work, we investigated various characteristics of InGaN multiple quantum wells (MQWs) LED structures grown on selectively wet-etched porous (SWEP) GaN template layer and compared with those grown on non-porous GaN template layer over c-plane sapphire substrates. From the surface morphology measured by atomic force microscope, high resolution X-ray diffraction analysis, low temperature photoluminescence (PL) and PL excitation measurements, good structural and optical properties were observed on both LED structures. However, InGaN MQWs LED structures grown on SWEP GaN template layer show relatively low In composition, thin well width, and blue shift of PL spectra on MQW emission. These results were explained by rough surface of template layer, reduction of residual compressive stress, and less piezoelectric field on MQWs by utilizing SWEP GaN template layer. Better electrical properties were also observed for InGaN MQWs on SWEP GaN template layer, specially at reverse operating condition for I-V measurements.

• Korean Journal of Organic Agriculture
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• v.19 no.spc
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• pp.190-193
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• 2011

Organic and chemical fertilizer amendments are an important agricultural practice for increasing crop yields. In order to maintain the soil sustainability, it is important to monitor the effects of fertilizer applications on the shift of soil microorganism, which control the cycling of many nutrients in the soils. Here, culture-dependent and culture-independent approaches were used to analyze the soil microorganism and community structure under six fertilization treatments, including green manure, rice straw compost, rapeseed cake, pig mature compost, NPK +pig mature compost, NPK and control. Both organic and chemical fertilizers caused a shift of the cultural microorganism CFUs after treatments. Bacterial CFUs of the organic fertilization treatments were significantly higher than that of chemical fertilization treatments. The DGGE profiles of the bacterial communities of the samples showed that the green manure treatment was a distinct difference in bacterial community, with a greater complexity of the band pattern than other treatments. Cluster analyses based on the DGGE profile showed that rice straw compost and pig mature compost had a similar banding pattern and clustered together firstly. Rapeseed cake, NPK, NPK +pig manure compost and control clustered together in other sub-cluster and clearly distinguished from green manure.

• Journal of Surface Science and Engineering
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• v.47 no.5
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• pp.239-243
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• 2014

The electrical and optical properties of amorphous In-Tin-Zinc-Oxide(ITZO) deposited at room temperature using rf-magnetron sputtering were investigated. The amorphous ITZO thin films were obtained at the composition of In:Sn:Zn = 6:2:2, 4:3:3, and 2:4:4, but the ITZO (8:1:1) showed a crystalline phase of bixbyite structure of In2O3. The resistivity of ITZO could be controlled by oxygen pressure in the sputtering ambient. The resistivity of post-annealed ITZO thin films exhibited the dependence on the amount of Indium. Optical energy band gap and transmittance increased as the amount of indium in ITZO increased. For the device application with ITZO, the bottom-gated thin-film transistor using ITZO as a active channel layer was fabricated. It showed a threshold voltage of 1.42V and an on/off ratio of $5.63{\times}10^7$ operated with saturation field-effect mobility of $14.2cm^2/V{\cdot}s$.

• Proceedings of the Ginseng society Conference
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• 2002.10a
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• pp.266-276
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• 2002

A red ginseng acidic polysaccharide(RGAP) with immunomodulating antitumor activities was isolated from Korean red ginseng, The molecular weight of RGAP was estimated to be 12-450 kDa by gel filtration chromatography, RGAP was found to increase survival rate and to inhibit of tumor growth significantly in a dose dependent manner in mice transplanted with tumor cells. RGAP significantly promoted nitric oxide(NO) production from peritoneal macrophages bothin vivo and in vitro. Western blot analysis exhibited a newly synthesized inducible nitric oxide synthase(iNOS) protein band in the RGAP treated group. It seems likely that immunomodulating antitumor activities of RGAP are mainly mediated by NO production of macrophage. RGAP was further purified by ultrafiltration and anion exchange chromatography on DEAE-sepharose, followed by gel filtration on Sephacryl S-300 to give an active fraction(GFP) with stronger NO production in murine macrophages. GFP increased survival rate ten times compared to RGAP in male ICR mice transplanted with sarcoma 180 and also showed more potent tumoricidal activities of natural killer cells than RGAP. Sugar $composition(mol\%)$ of GFP was found to be arabinose:rhamnose:xylose:galacturonic acid:mannose:galactose:glucose(10:9:1:25:8:20:27) by GC/MS. The results suggest that clinical trials of RGAP in immunotherapy against cancer are highly feasible.

• Korean Journal of Materials Research
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• v.29 no.9
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• pp.553-558
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• 2019

$Cu_2ZnSn(S,Se)_4(CZTSSe)$ thin film solar cells areone of the most promising candidates for photovoltaic devices due to their earth-abundant composition, high absorption coefficient and appropriate band gap. The sputtering process is the main challenge to achieving high efficiency of CZTSSe solar cells for industrialization. In this study, we fabricated CZTSSe absorbers on Mo coated soda lime glass using different pressures during the annealing process. As an environmental strategy, the annealing process is performed with S and Se powder, without any toxic $H_2Se$ and/or $H_2S$ gases. Because CZTSSe thin films have a very narrow stable phase region, it is important to control the condition of the annealing process to achieve high efficiency of the solar cell. To identify the effect of process pressure during the sulfo-selenization, we experiment with varying initial pressure from 600 Torr to 800 Torr. We fabricate a CZTSSe thin film solar cell with 8.24 % efficiency, with 435 mV for open circuit voltage($V_{OC}$) and $36.98mA/cm^2$ for short circuit current density($J_{SC}$), under a highest process pressure of 800 Torr.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3855-3863
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• 2022

An evaluation of the radiation shielding performance of high-Z-particle-loaded polylactic acid (PLA) composite materials was pursued. Specimens were produced via fused deposition modeling (FDM) using copper-PLA, steel-PLA, and BaSO₄-PLA composite filaments containing 82.7, 75.2, and 44.6 wt% particulate phase contents, respectively, and were tested under broad-band flash x-ray conditions at the Sandia National Laboratories HERMES III facility. The experimental results for the mass attenuation coefficients of the composites were found to be in good agreement with GEANT4 simulations carried out using the same exposure conditions and an atomistic mixture as a model for the composite materials. Further simulation studies, focusing on the Cu-PLA composite system, were used to explore a shield design parameter space (in this case, defined by Cu-particle loading and shield areal density) to assess performance under both high-energy photon and electron fluxes over an incident energy range of 0.5-15 MeV. Based on these results, a method is proposed that can assist in the visualization and isolation of shield parameter coordinate sets that optimize performance under targeted radiation characteristics (type, energy). For electron flux shielding, an empirical relationship was found between areal density (AD), electron energy (E), composition and performance. In cases where ${\frac{E}{AD}}{\geq}2MeV{\bullet}cm{\bullet}g^{-1}$, a shield composed of >85 wt% Cu results in optimal performance. In contrast, a shield composed of <10 wt% Cu is anticipated to perform best against electron irradiation when ${\frac{E}{AD}}<2MeV{\bullet}cm{\bullet}g^{-1}$.

• Food Science of Animal Resources
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• v.43 no.2
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• pp.305-318
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• 2023

This study investigated the protein digestibility of chicken breast and thigh in an in vitro digestion model to determine the better protein sources for the elderly in terms of bioavailability. For this purpose, the biochemical traits of raw muscles and the structural properties of myofibrillar proteins were monitored. The thigh had higher pH, 10% trichloroacetic acid-soluble α-amino groups, and protein carbonyl content than the breast (p<0.05). In the proximate composition, the thigh had higher crude fat and lower crude protein content than the breast (p<0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of myofibrillar proteins showed noticeable differences in the band intensities of tropomyosin α-chain and myosin light chain-3 between the thigh and breast. The intrinsic tryptophan fluorescence intensity of myosin was lower in the thigh than in the breast (p<0.05). Moreover, circular dichroism spectroscopy of myosin revealed that the thigh had higher α-helical and lower β-sheet structures than the breast (p<0.05). The cooked muscles were then chopped and digested in the elderly digestion model. The thigh had more α-amino groups than the breast after both gastric and gastrointestinal digestion (p<0.05). SDS-PAGE analysis of the gastric digesta showed that more bands remained in the digesta of the breast than that of the thigh. The content of proteins less than 3 kDa in the gastrointestinal digesta was also higher in the thigh than in the breast (p<0.05). These results reveal that chicken thigh with higher in vitro protein digestibility is a more appropriate protein source for the elderly than chicken breast.

• Fisheries and Aquatic Sciences
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• v.26 no.9
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• pp.535-547
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• 2023

Sea cucumbers (Holothuria scabra), also known as beche-de-mer, are highly valued as a luxurious food item and have been utilized as a traditional tonic food in various Asian countries for centuries. The body walls of sea cucumbers are the main edible part, which are primarily composed of glycosaminoglycan (GAG). The rehydration of dried sea cucumber is a crucial step prior to further processing. The aim of this study was to assess the impact of ultrasound-assisted rehydration (UAR) on the quality of dried sea cucumbers. The experiment used four different rehydration methods, including conventional methods at 27℃ (KV27℃) and 15℃ (KV15℃), as well as a combination of ultrasound at 27℃ with conventional at 15℃ (UAR27 + KV15℃) and ultrasound at 15℃ with conventional at 15℃ (UAR15 + KV15℃). Results indicated that the rehydration rate (RR) was significantly affected by both the rehydration method and the temperature used (p < 0.05). UAR27 + KV15℃ was identified as the most effective method in terms of rehydration behavior and quality characteristics of dried sea cucumber, with a RR of 0.58 ± 0.53 gH₂O/hour and reduced rehydration time of up to 28 hours. Moreover, the UAR27 + KV15℃ method demonstrated superior rehydration potential, nutritional value (proximate composition and sulfate content), color, lower energy, and microstructure properties compared to the other methods. The sulfate content and yield of sulfated GAGs were determined to be 89.4 mg/g and 52.8 ㎍/g, respectively. Confirmation of the absorption band of the sulfate group showed the presence of 3-N-acetyl galactosamine at a wavelength of 1,269 cm^-1 and C-O-S at 860 cm^-1. The sea cucumbers treated with UAR exhibited a GAG content approximately 2.9 times higher than those rehydrated with the conventional method. Eventually, the combination of UAR at 27℃ with conventional at 15℃ methods can significantly accelerate the rehydration of sea cucumber without negatively affecting its physical quality properties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.400-406
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• 2024

Next-generation wide-bandgap semiconductors such as SiC, GaN, and Ga2O3 are being considered as potential replacements for current silicon-based power devices due to their high mobility, larger size, and production of high-quality wafers at a moderate cost. In this study, we investigate the gradual modulation of chemical composition in multi-stacked metal oxide semiconductor thin films to enhance the performance and bias stability of thin-film transistors (TFTs). It demonstrates that adjusting the Ga ratio in the indium gallium oxide (IGO) semiconductor allows for precise control over the threshold voltage and enhances device stability. Moreover, employing multiple deposition techniques addresses the inherent limitations of solution-processed amorphous oxide semiconductor TFTs by mitigating porosity induced by solvent evaporation. It is anticipated that solution-processed indium gallium oxide (IGO) semiconductors, with a Ga ratio exceeding 50%, can be utilized in the production of oxide semiconductors with wide band gaps. These materials hold promise for power electronic applications necessitating high voltage and current capabilities.