• Proceedings of the Materials Research Society of Korea Conference
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• 1994.11a
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• pp.98-98
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• 1994

최근 청색반도체레이저의 실현을 위하여 ZnSe가 대표하는 II-Ⅵ족 화합물반도체와 Gan가 대표하는 III족 질화물반도체분야에서 집중적인 연구가 이루어지고 있으며, 아직까지 실용화 되지 않고 있는 청색반도체레이저의 출현에 대하여 많은관심이 모아지고 있다. III족 질화물반도체는 InM(Eg:1.9eV)부터 AIN(Eg: 6.2eV)에 이르기까지 전 조성영역에서 완전한 고용체를 이루며, 실온에서 직접천이형 에너지 대구조를 가지므로 청색 혹은 자외영역에서 동작하는 발광소자를 제작하는데 있어 유망시 되고 있는 소재이다. 특히 GaN와 InN의 3원흔정인 GaInN를 활성층으로 이용하면 그 발전파장을 370nm부터 650nm까지 즉 가시 전 영역으로부터 근 자외영역을 포함할 수 있게 된다. 이 연구에서는 AIGaN/GaInN 이중이종접합(DH) 구조의 고아여기에 의한 유도방출고아의 편광 특성을 조사하였다. 유기금속기상에피텍셜(MOVPE)법으로 성장한 AIGaN/GaInN DH 구조의 표면에 수직으로 펄스 발진 질소레이저(파장: 337.1cm, 주기 10Hz, 폭: 8nsec) 빔을 조사하고 DH구조의 단면으로부터의 유도방출광을 편광기를 통과 시킨 후 스펙트럼을 측정하였다. 입사고아 밀도가 증가함에 따라 약 402nm의 파장에서 유도발출에 의한 가도가 큰 피크가 나타났고, 그 반치폭은 약 18meV이었다. 실온에서 AIGaN/GaInN DH 구조로 부터의 유도방출에 필요한 입사광밀도의 임계치는 약 130㎾/$\textrm{cm}^2$이었다. 한편 편광각이 90$^{\circ}$일때는 발광스펙트럼의 강도가 매우 낮고 단지 자연방출에 의한 스펙트럼만이 나타났다. 편광각이 0$^{\circ}$일 때 최대의 방출광 강도를 나타내었으며, 편광각이 -90$^{\circ}$로 회전함에 따라 발고아강도의 강도가 감소하였다. 이와 같은 결과는 광여기에 의하여 AIGaN/GaInN DH 로 부터의 유도방출광이 GaInN활성층의 단면에 평행한 전기장의방향으로, 즉 TE모드로 선형적으로 편광됨을 의미한다. AIGaN/GanN DH 로 부터의 유도방출이 선형적으로 TE모드로 편광되는 것은 이 구조를 이용한 청색 및 자외선 반도체 레이저다이오드의 실현에 매우 유익한 것이다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.4
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• pp.241-257
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• 2004

Global prognostic models based on NCOM(NCAR CSM Ocean Model) of NCAR which is generic from Bryan-Cox-Semtner model are established to study the ocean circulation in the neighboring seas of Korean peninsula. The model domain covers areas from $80.6{^\circ}S~88.6{^\circ}N$in meridional direction and the vertical water column is divided into 15 levels taking enhanced grid resolution of $0.3^\circ$ around Korean peninsula. Island option is used for 22 islands to simulate inshore circulation by hole-relaxation method and the restart hydrographic data are taken from NCAR(1998) CSM model that has been run for 300 years. The wind stress data are taken from Choi et al. (2002). Based on the model results, circulation patterns in the NW Pacific and global oceans are investigated. Volume transports calculated at five straits in the neighboring seas of Korean peninsula are compared with the results from Choi et al. (2002) and other observed data.

• Journal of Korea Foresty Energy
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• v.20 no.1
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• pp.73-80
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• 2001

This study was carried out to investigate the strength and technical feasibility of arch type laminated lumber from the domestic small lumbers(Pinus densiflora S. et Z. and Larix kampferi Catt.). Arch type lumbers manufactured with different compositions of laminae. It was designed to improve the strength and stiffness. Strength S. rt Z. U;timate load Carr. laminated lumbers were higher than that of the Pinus densiflora S. et Z. Ultimate load of 7-ply laminated lumbers were 2 times higher than the 5-ply laminated lumbers. The strength of finger jointed lumbers were found to be about 15.8% less than that of the no joint lumber. One solution for this problem is to use veneer as face lamina. The veneer laminated lumbers was considerably greater than that of the non-veneer laminated lumbers. It was suggested that this small lumber may be a candidate for high valued product member to provide the proper combination of laminae.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.21-25
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• 2017

In this study, we have fabricated Schottky barrier diodes (SBD) on single-crystal ${\beta}-Ga_2O_3$ semiconductor that has received much attention for use in next-generation power devices. The SBD had a Pt/Ti/Au Schottky contact on a $2{\mu}m$ Sn-doped low concentration N-type epitaxial layer. The fabricated device exhibited a breakdown voltage of > 180 V, a specific on-resistance of $1.26m{\Omega}{\cdot}cm^2$, and forward current densities of $77A/cm^2$ at 1 V and $473A/cm^2$ at 1.5 V, which proved the potential for use in power device fabrication.

• Journal of the Korean Vacuum Society
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• v.13 no.1
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• pp.1-8
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• 2004

The SOI wafer fabrication technique has been developed by using ion-cut process, based on proton implantation and wafer bonding techniques. It has been shown by TRIM simulation that 65 keV proton implantation is required for the standard SOI wafer (200 nm SOI, 400 nm BOX) fabrication. In order to investigate the optimum proton dose and primary annealing condition for wafer splitting, the surface morphologic change has been observed such as blistering and flaking. As a result, effective dose is found to be in the 6∼$9\times10^{16}$ $H^{+}/\textrm{cm}^2$ range, and the annealing at $550^{\circ}C$ for 30 minutes is expected to be optimum for wafer splitting. The depth distribution of implanted hydrogen has been experimentally confirmed by ERD and SIMS measurements. The microstructure evolution in the damaged layer was also studied by X-TEM analysis.

• Journal of Life Science
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• v.10 no.3
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• pp.229-235
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• 2000

The absorption characteristics of Korean yam powder according to different drying methods were investigated. The physical properties of yam powder by different drying methods were showed the biggest porosity in freeze drying sample, while the smallest in hot air drying sample. No difference was founded in proximate compositions of yam powder by various drying methods. The amount of total phenolic compound and Vit C were showed the bigger decrement in freeze dried sample than other drying methods. The time reaching to equilibrium moisture content were determined in 12 days. Monolayer moisture contents were predicted to 0.0508∼0.0588 by BET equation and 0.0705∼0.0811 g H2O/g solid by GAB equation. BET equation for isothermal absorption curve showed over 0.95 R-square for every drying methods. GAB equation showed over 0.99 in vacuum and freeze drying but a poor R-square in hot air drying.

• Journal of Welding and Joining
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• v.6 no.4
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• pp.44-53
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• 1988

The mechanical strengths of buried lamellar tears located near the weld toe in the welded tee joints were evaluated in terms of the loss of load carrying capacity as a function of tear area. In static loading, the load carrying capacity was significantly reduced when tear intercepted over 10% of the cross-sectional area of the welded joints. However, the welded joints containing buried tears still failed at stresses over the yield strength of the base metal in the through-thickness direction in spite of the presence of tears up to 20-25% of the area. Fatigue strength of welded joints containing tears markedly reduced with increasing tear areas. Lehigh lamellar tearing test used in this study to produce speicmens was described in detail. The load carrying cpapacity in static loading was influenced by the reduction of supporting area whereas that in fatigue loading was influenced by the stress-concentration effects of lamellar tears and the reduction of supporting area. In bend tests, the pre-existing lamellar tears always grew up toward the weld toe. However, in fatigue loading, cracks grew up and down simultaneously form both the weld toe and the top of lamellar tears because of stress concentration. In fatigue loading, delaminations and decohesion of inclusion/matrix interface generated in multipass welds provided crack propagation paths and enhanced crack propagation because the tips of delaminations and deconhesios acted as stress raisers.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.109-118
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• 1996

Al$_2$O$_3$-TiO$_2$powders of six different compositions were plasma-sprayed on Ti substrate. The spray powders and the spray coated layers were analysed and compared using SEM and X-RD. The elastic properties (specific elastic constant and damping coefficient) of the coated specimens were measured in order to select the optimum composition range of ceramics for use in a speaker diaphragm. A correlation between the microstructure and elastic properties was also investigated. When $Al_2$O$_3$powders with 0- 13% TiO$_2$were plasma sprayed, the coated layers were composed of metastable y-Al$_2$O$_3$with small amount of $\alpha$-Al$_2$O$_3$and the content of $\alpha$-Al$_2$O$_3$was increased with TiO$_2$content. Specific elastic constant was rapidly increased with 2 and 13% TiO$_2$addition to $Al_2$O$_3$. The internal damping was nearly unchanged with TiO$_2$content The specific elastic constant seemed to be dependent on the content of $\alpha$-Al$_2$O$_3$in the coated layer.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.42-45
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• 1999

The room temperature optical transmission spectra of GaN /InGaN/GaN single quantum wells (SQW) and InGaN/GaN heterostructures grwon by low pressure metalorganic chemical vapor deposition have been measured. The dependence of the absorption edges of the GaN/InGaN/GaN SQW on the well width has been determined from the transmission spectra. The result shows that the absorption edge of GaN/InGaN/GaN SQW shifts towards lower energy as increasing the well width. The dependence of the absorption edges of the InGaN/GaN heterostructures on InN mole fraction has also been determined from the transmission spectra. The result is compared with calculated values obtained from Vegards's laws. Our result shows a good agreement with the calculated values.

• Conservation Science in Museum
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• v.13
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• pp.59-69
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• 2012

The flower type ornament of the gilt bronze palace-type sarira reliquary among those sarira reliquaries of the East Pagoda at the Gameunssa Temple Site, which is the Treasure No. 1359 owned by the National Museum of Korea, was separated from the sarira reliquary in November 2010, thus conducting conservation treatments to be done on two items including the gilt bronze palace-type sarira reliquary during the period of March-October 2011. Those conservation treatments were carried out by following the process of removing the coated areas having excessive gross and bubbles, re-coating with Incralac, and then strengthening both the cracked areas and the separated flower-type ornaments with woven glass fiber after rejoining. For those areas where removal of gloss and bubbles at the coating and adhesive areas was not possible, the gloss and bubbles were made less perceivable through matting treatment and coloring.