• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.3-3
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• 2008

21 세기 제 3의 산업혁명을 가져올 것으로 기대되는 나노기술(NT), 정보기술(IT), 바이오기술(BT)은 전 세계 과학자들의 마음을 사로잡고 있다. 이 가운데 나노기술은 전자산업에 응용시 그 기대효과는 우리가 상상하는 이상의 것이라 예상하고 있다. 나노기술에 특히 관심을 가지는 이유는 물질이 마이크로미터 크기로 작아져도 벌크 물질의 물리적 특성이 그대로 유지되지만, 나노미터 크기가 되면서 우리가 경험하지 못했던 새로운 물리적 특성들이 발현되기 때문이다. 그 특성에는 양자구속효과, Hall-Petch 효과, 자기효과 등이 있다. 나노기술의 구현은 양자점과 같은 영차원 나노입자, 나노와이어, 나노막대, 나노리본 등과 같은 직경이 100nm 이하의 일차원 구조의 나노물질 및 나노박막과 기타 100nm 이하의 나노구조물들이 사용된다. 현재 일차원 구조를 이용한 전자디바이스화 연구는 결정성장을 정확하게 조절하는 합성기술 합성된 일차원 나노물질의 물리적 특성을 지배하는 각종 파라미터들과 물리적 특성들과의 상관관계 정립, 나노와이어를 이용한 Bottom-up 방식에 의한 조립기술 확보를 위해 활발히 진행 중이다. 하지만 나노구조의 특성을 확인하는 형태의 연구일 뿐, 실제 디바이스화에는 여전히 많은 과제를 안고 있다. 본 연구에서는 산화아연을 기반으로 한 고품위 능동형 산화물 나노구조의 다양한 성장방법 및 물성 평가에 대해 연구하였다. 성장장비로는 MOCVD와 스퍼터링을 이용하여 대면적 균일 성장을 이룰 수 있었다. 특히 실제 광전소자에 응용요구에 알맞은 Bottom-up 방식에 의한 수직성장 기술, 길이/직경 비 향상 기술, 결정성 향상 기술, 저온성장 기술, Dimension 조절 기술 Interfacial layer 제거 기술 등을 중점적으로 연구하였다. Dimension 조절 기술로 p-Si 기판위에 성장된 나노 LED에서는 밝은 emission을 관찰하였으며, 세계에서 최초로 스퍼터링을 이용하여 4인치 웨이퍼에 대면적 수직 성장하였다. 최근에는 선택적 삼원계 씨앗층을 이용한 길이/직경 비가 매우 향상된 MgZnO 나노와이어를 Interfacial layer 없이 수직으로 성장하여 산화물 전계방출 에미터로서의 가능성을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.8
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• pp.46-51
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• 2012

In this paper, we investigate the power allocation for cognitive relay networks. Cognitive relay networks offer not only increasing spectral efficiency by spectrum sharing but also extending the coverage through the use of relays. For spectrum sharing, conventional works have assumed that secondary users know perfect channel information between the secondary and primary users. However, this channel information may be outdated at the secondary user because of the time-varying properties or feedback latency from the primary user. This causes the violation for interference constraint, and the secondary user cannot share the spectrum of the primary after all. To overcome this problem, we propose the power allocation scheme for the secondary user under the allowable primary user's outage probability constraint. Since the proposed power allocation scheme does not use the instantaneous channel information, the secondary users have lower feedback burden. In addition, the proposed scheme is also robust to the outdated channel environment.

• 한국해양학회지
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• v.26 no.2
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• pp.155-168
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• 1991

In order to study the community structure and distribution patterns of primary producers and their relations to abiotic environmental factors, phytoplankton and environmental parameter were determined during the five times from October, 1989 to July. 1990. 159 taxa of phytoplankton have been identified and the most important species group is diatom which contributes to 70.4% of the total number of species. Ratios of phytoplankton group (neritic species, fresh water species, oceanic species) clustered by habitats were 52%, 18%, 12%, respectively, suggesting study area be the typical estuarine environment which is strongly affected by both fresh water discharge and sea water penetration. Species composition could be governed by the variations of salinity. the standing stocks of primary producer in the study area vary with space and time, showing close correlation with water transparency, and exhibit relatively larger than those of other coastal regions in the Yellow Sea. Spectransies diversity also showed large variation with space and time. According to the cluster analysis, the study area could be divided into two regions (inner part and outer part): in fall and winter, outer area affected by the oceanic water, but in spring and summer, inner estuarine area heavily influenced by fresh water.

• Journal of Chest Surgery
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• v.31 no.1
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• pp.46-51
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• 1998

Treatment of esophageal perforation when diagnosed late remains controversial. Ten consecutive patients since 1990 were treated late(later than 24 hours) for esophageal perforation with primary repair. Four perforations were iatrogenic, 3 were spontaneous, 2 were foreign body aspiraton and 1 was trauma. The interval from perforation to operation was 116 hours in mean and 48 hours in median value. The principles of repair included (1) a local esophagomyotomy proximal and distal to the tear to expose the mucosal defect and intact mucosa beyond, (2) debridement of the mucosal defect and closure, (3) reapproximation of the muscle, and (4) adequate drainage. The repair was buttressed with parietal pleura or pericardial fat in 9 patients. Associated distal obstruction was treated with dilation and esophagomyotomy intraoperatively. There was one mortality and cause of death was massive gastric bleeding due to gastric ulcer on 33rd day after operation. Five patients had leak at the site of repair and these cases were treated completely with conservative treatment except a mortality case. In conclusion, in the absence of malignant or irreversible distal obstruction, meticulous repair of perforated esophagus and adequate drainage are preferred approach, regardless of the duration from the injury to the operation.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.142-149
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• 1996

Pyramid type three roll bending machines are widely used in roll-bending process to produce singly curved plate. In forming singly curved plate, controlling the vertical displacement of the center roller is most important to acquire the shape required and automation system of the process. In this paper roller bending process is modeled as an elastic-plastic phenomenon and analyzed using beam theory and finite element method. In finite element analysis the workpiece is modeled by using beam elements and plane strain elements respectively. Through the analyses vertical center roller displacement is obtained to get constant curvature distribution along arc length. The relationship between center roller displacement and curvature in steady state as well as residual stress and strain along plate thickness direction are calculated through finite element analysis.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.304-308
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• 1995

In order to measure magnetic field difference, we have constructed a fluxgate magnetometer which is based on the measurement of apparent coreci ve field strength from the magnetizing current of two sensors. 'Co-based amorphous ribbon, which has square shape of ac hysteresis loop, was used as core material. Two sensors have 315 turns of the primary and the secondary windings respectively, and core size of 2 mm wide and 30 mm long. The primary windings are connected parallel to measure external magnetic field difference and the secondary windings serieally for the averaged magnetic induction of the cores. The constructed magnetometer could measure magnetic field difference with sensitivity of $1.6{\times}10^{6}V/T$ and resolution of 1 nT at 1 Hz bandwidth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.4718-4725
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• 2011

Intake-air flow and distribution characteristics of the 1600cc gasoline engine intake manifold have been studied using the computer simulation. Simulation has been conducted using both one-dimensional performance simulation and three-dimensional CFD software. Steady state flow simulation result of the intake manifold shows good distribution characteristics that the standard deviation of flow coefficients is below 1.0 percentage for both one- and three-dimensional simulation. Even though one-dimensional simulation result slightly overestimates compared with three-dimensional simulation result, both results show very good agreement in flow coefficient trend. Also, unsteady state simulation result shows consistent distribution characteristics with that of steady state. It is shown that unsteady state distribution characteristics might be able to be predicted through the steady state mass distribution result.

• Analytical Science and Technology
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• v.18 no.4
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• pp.271-277
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• 2005

Urea in blood has been measured as an effective marker for diagnosis of renal function. Urea which is e end-product of nitrogen containing metabolites such as proteins is filtered through glomeruli of kidneys and then excreted as urine. If the renal function is deteriorated, the urea concentration in blood will be increased, from which the healthiness of renal function is judged. In order to improve the confidence of diagnosis results, the results must keep traceability chain to certified reference materials, which was certified by primary reference method. In this study, we proposed isotope dilution-liquid chromatography/mass spectrometry (ID-LC/MS) as a candidate primary method, in which $15^N_2$-urea is used as an internal reference material. The developed method is highly accurate in principle and is convenient as it does not require cumbersome derivatization. 0.1 mmol/L ammonium chloride was selected as a mobile phase for HPLC because it provided low interference in MS analysis of relatively low molecular weighted urea. HPLC and MS were connected with an electrospray ionization (ESI) interface of positive mode, which provided high sensitivity and reproducibility. The developed method was validated with internationally recognized reference materials, and we have obtained satisfactory results in an international ring trial. The expanded uncertainty calculated according to ISO guide was 1.8% at 95% confidence interval. The developed method is being used as a primary reference measurement method such as for certification of serum certified reference materials (CRMs).

• Journal of Applied Biological Chemistry
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• v.66
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• pp.424-435
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• 2023

As a result of this study, DPPH radical scavenging activity was 81.8% at a concentration of 100 ㎍/mL of Alpinia galanga L. rhizome 70% ethanol extract (AG.E), and ABTS⁺ radical scavenging activity was confirmed to be 99.8%, similar to L-Ascorbic acid (AA), at a low concentration of 50 ㎍/mL AG.E. To measure anti-aging activity, collagenase and elastase inhibitory activities were measured and AG.E showed higher inhibitory effects than epigallocatechin gallate (EGCG) starting at a low concentration of 50 ㎍/mL. In particular, AG.E showed inhibitory effects more than three times that of EGCG at a concentration of 500 ㎍/mL. In order to verify anti-aging effect of AG.E in CCD-986sk cell, good anti-aging effect was obtained in various experiments stimulated with UVB. In a gene expression analysis experiment using RT-PCR, the COL1A mRNA expression level was found to increase 2.90 times compared to no addition at a low concentration of 20 ㎍/mL AG.E, confirming the possibility of developing it as a good functional material related to anti-aging. As a basic study on temporal biological activity preservation ratio of material when applied to formulations, AG.E, and AA were added to a stable W/O type emulsion and stored in a thermostat at 25 ℃ for 60 days. As a result of measuring DPPH and ABTS⁺ radical scavenging activities on the 1st, 30th, and 60th days, it was confirmed that antioxidant effects are maintained at a high level over time in formulations.

• Food Science of Animal Resources
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• v.29 no.3
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• pp.382-390
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• 2009

This study was carried out to determine the effects of tomato powder (TP) as nitrite (NT) on pork patties. The following treatments were made: 0.01% NT (Tl), 0.01% NT and 1.0% TP (T2), 0.5% TP (T3), 1.0% TP (T4), and 0.01% NT and 1.0% TP (T5) were in basal formula (C). The following observations were made: T5 displayed lower gumminess and adhesiveness values than those of C and T1 (p<0.05) on Day 1 of storage; the hardness and surface hardness of T3 and T4 were relatively lower and the surface hardness and gumminess of T3 were relatively higher than the others (p<0.05) on Day 21 of storage; Y4 had significantly lower TBARS values than the others during storage; VBN values of the tested groups were significantly lower than the control samples on Day 7 and 21 of storage; T3 and T4 samples displayed lower pH values (p<0.05) than the control samples on Day 21 of storage; T3, T4 and T5 revealed lower CIE $L^*$ and W than those of C and T1 during storage; T2 had the highest CIE $a^*$ (p<0.05); T4 had significantly higher CIE $b^*$ and chroma values than those of others; T3 and T4 had significantly lower total plate counts than the others; T1 had significantly lower yeast and mold and Staphylococcus sp. counts than the other groups'; and T1 and T2 displayed significantly higher color acceptability than the others.