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황대원,김동표,장희동,김헌창,이병윤 한국공업화학회 2002 응용화학 Vol.6 No.2
Cobalt nanoparticles were synthesized by the hydrogen reduction of cobalt chloride in the gas phase. Concentration of CoCl_2, Reaction temperature, and residence time were chosen as key experimental variables for the control of the particle size. Cobalt nanoparticles ranged from 50 to 90nm in average particle diameter were produced by through all the experiments. As the CoC1_2 concentration in the flame increased, the average particle diameter increased. Average particle diameter increased with the increase of reaction temperature. Smaller particles were produced with decrease of the residence time of reactant in the reaction zone.
샌드위치형 GFRP 아치의 구조적 거동 및 현장 적용성
황대원,김광우,김용성,연규석 한국농공학회 2018 한국농공학회논문집 Vol.60 No.2
This study investigated the structural behavior and field applicability of sandwich type GFRP arches with polymer mortar in core. As a result, in case of crack loading and failure loading, total strains at crown were the highest; the fracture strain at crown was 0.01690, which is 4.2 times greater than the fracture strain (0.004) of cement concrete. The 3 % deflection load was 17.42 kN, the flexural strength was 163.98×10 -3 GPa, and the flexural elastic modulus was 11.884 GPa. From load-deflection relationship up to 3.5 % deflection, 3D analysis results and experimental values were observed to be almost identical. It was considered reasonable to set a deflection rate limit to be 3 % for structural safety purpose. The standard external flexural strength of semicircular arch used in this study was approximately 2.64 times higher than that of hume pipe (2 type standard) and tripled composite pipe. The external pressure strength at fracture was approximately 1.57 times higher than that of hume pipe. It was confirmed that the implementing semicircular arch had mechanically more advantage than the circular pipe. Optimum member thickness was 8~53 mm according to arch radius of 450~1,800 mm and cover depth of 2~10 m. It was found that the larger strength could be obtained even if the thickness of member was smaller than that of concrete structure. In field application study, figures and equations were derived for obtaining applicable cover depth and optimum member thickness according to loading conditions. These would be useful data for design and manufacture of sandwich type semicircular arch.
황대원 ( Hwang Dae Won ),한금선 ( Han Kuem Sun ) 한국정신간호학회 2023 정신간호학회지 Vol.32 No.4
Purpose: The purpose of this study was to understand the process of adapting to daily life after discharge of self-injury adolescents and to develop a substantive theory that can explain their experiences. Methods: Data collection and analysis were conducted through interviews with 9 participants who returned to their daily life after discharge, and data analysis was conducted according to the grounded theory approach. Results: As a result of the analysis, a total of 31 concepts and 9 categories were derived, and were classified into the areas of conditions, actions-interactions, and consequences according to the grounded theory paradigm. As a core category that can explain all these concepts and categories, ‘balance oneself in a precarious daily life’ was derived. Conclusion: In this study, a theory in which this process was composed in the order of return stage, crisis stage, and transformative stage, was presented. Finally, the discussions and suggestions of this study based on these results were described.
고전압 GaN 쇼트키 장벽 다이오드의 완충층 누설전류 분석
황대원(Dae Won Hwang),하민우(Min-Woo Ha),노정현(Cheong Hyun Roh),박정호(Jung Ho Park),한철구(Cheol-Koo Hahn) 大韓電子工學會 2011 電子工學會論文誌-SD (Semiconductor and devices) Vol.48 No.2
본 논문에서 실리콘 기판 위에 성장된 GaN 에피탁시를 활용하여 고전압 쇼트키 장벽 다이오드를 제작하였으며, 금속-반도체 접합의 열처리 조건에 따른 GaN 완충층 (buffer layer) 누설전류와 제작된 다이오드의 전기적 특성 변화를 연구하였다. Ti/Al/Mo/Au 오믹 접합과 Ni/Au 쇼트키 접합이 제작된 소자에 설계 및 제작되었다. 메사를 관통하는 GaN 완충층의 누설전류를 측정하기 위하여 테스트 구조가 제안되었으며 제작하였다. 700℃에서 열처리한 경우 100 V 전압에서 측정된 완충층의 누설전류는 87 ㎁이며, 이는 800℃에서 열처리한 경우의 완충층의 누설전류인 780 ㎁보다 적었다. GaN 쇼트키 장벽 다이오드의 누설전류 메커니즘을 분석하기 위해서 Auger 전자 분광학 (Auger electron spectroscopy) 측정을 통해 GaN 내부로 확산되는 Au, Ti, Mo, O 성분들이 완충층 누설전류 증가에 기여함을 확인했다. 금속-반도체 접합의 열처리를 통해 GaN 쇼트키 장벽 다이오드의 누설전류를 성공적으로 감소시켰으며 높은 항복전압을 구현하였다. We have fabricated GaN Schottky barrier diode (SBD) for high-voltage applications on Si substrate. The leakage current and the electrical characteristics of GaN SBD are investigated by annealing metal-semiconductor junctions. Ohmic junctions of Ti/Al/Mo/Au and Schottky junctions of Ni/Au are used in the fabrication. A test structure is proposed to measured buffer leakage current through a mesa structure. When annealing temperature is increased from 700℃ to 800℃, measured buffer leakage current is also increased from 87 ㎁ to 780 ㎁ at the width of 100 ㎛. The diffusion of Au, Ti, Mo, O into GaN buffer layer increases the leakage current and that is verified by Auger electron spectroscopy. Experimental results show that the low leakage current and the high breakdown voltage of GaN SBD are achieved by annealing metal-semiconductor junctions.