非晶質 Silicon 薄膜의 製作 및 그 Doping 效果

최범식,김수길,고년규,황정남,정원모,이철주 연세대학교 자연과학연구소 1982 學術論文集 Vol.9 No.-

SiH_4 기체에 PH_3 및 B_2H_6 기체를 0.7% 체적비로 혼합하여 rf glow 방전법으로 n형 및 p형 a-Si:H 박막을 기판온도 120℃에서 제작하여, 광투과도 측정, 열처리에 따른 전기 전도도의 변화 등을 조사하여 이들의 doping 효과를 연구하였다. n형, p형 및 undoped a-Si:H 박막의 optical gap은 각각 1.73eV, 1.86eV 및 1.86eV로 doping이 많이 이루어질수록 줄어 들었다. 250℃에서 열처리한 시료들의 상온에서의 전도도는 각각 2×10^-2Ω^-1㎝^-1, 5×10^-8Ω^-1㎝^-1, 5×10^-7Ω^-1㎝^-1이었고, 활성화 에너지 ??E는 각각 0.16eV, 0.49eV 및 0.48eV이었다. 300℃에서 열처리한 결과, ??E는 줄어 들고 전도도는 증가하였다. 350℃ 및 450℃에서 열처리한 결과 dehydrogenation 효과로 인하여 n형과 p형은 서로 상반되는 결과를 보였다. 즉, n형 시료의 전도도는 감소하고 ??E는 증가하였지만, P형 시료의 전도도는 증가하고 ??E는 감소하였다. 저온 영역에서 구한 n형 시료의 전도도로부터 hopping 활성화 에너지를 구한 결과 0.085eV이었다. Thin n-type and p-type a-Si:H films were prepared by rf glow discharge decomposition of silane mixed with 7×10^-3 parts per volume of phospine or diborane. All specimens were deposited on glass substrates held at 120℃. In order to determine the doping effects the opital absorption and dc conductivity of these specimens were measured after annealing at various temperatures. The optical gap was 1.73eV in the case of the n-type specimens, 1.80eV for the p-type, and 1.86eV undoped. This showed that the gap width decreased as the doping increased. The room temperatuer conductivities of these specimens annealed at 250℃ were 2×10^-2Ω^-1㎝^-1, 5×10^-8Ω^-1㎝^-1, and 5×10^-7Ω^-1㎝^-1, respectively, and the activation energies, ??E, of these specimens were 0.16eV, 0.49eV, and 0.48eV, respectively. For specimens annealed at 300℃, ??E decreased and the conductivity increased. When these specimens were annealed at 350℃ and 450℃, dehydrogenation caused opposite effects on the n-type and p-type specimens; the conductivities of n-type specimens decreased and ??E increased, but the conductivities of p-type specimens increased and ??E decreased.From an investigation of the temperature dependence of the conductivity of the n-type specimen in the low temperature region, we determined that the hopping activation energy was 0.085eV.

유도초음파에 의한 비균질 적층의 접합층두께 평가

조윤호,함효식,최흥호 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.4

비균질 적층 구조물에서의 유도초음파 전파는 이론적 분산성에 기초하여 실험적으로 규명된다. 이는 입사각도와 주파수의 적절한 선택은 적층구조물에서의 유도초음파 발생에 중요하다는 것을 드러낸다. 이론적 분산성은 접착층 두께와 층 두께, 물성치에 크게 의존한다. 실험적으로 분산성의 변화를 관찰하므로 비균질 적층 구조물의 접착층 두께를 측정하는 것이 가능하였다. The guided wave propagation in inhomegeneous multi-layered structures is experimentally explored based on theoretical dispersion curves. It turns out that proper selection of incident angle and frequency is critical for guided wave generation in multi-layered structures. Theoretical dispersion curves greatly depend on adhesive zone thickness, layer thickness and material properties. It was possible to determine the adhesive zone thickness of an inhomogeneous multi-layered structure by monitoring experimentally the change of dispersion curves.

전자선 증착장치 및 ITO 박막의 제작과 그 특성에 관한 연구

김수길,최범식,우정주,고년규,황정남,정원모,이철주 연세대학교 자연과학연구소 1982 學術論文集 Vol.9 No.-

태양 전지의 제작시 투명 전극막으로 쓰이는 ITO 박막을 제조하기 위하여 cathode 접지 방식의 전자총을 가진 정전 편향 집속형의 전자선 증착 장치를 제작하였다. 가속전압이 0∼15kV, 필라멘트 전류가 0∼28A, 두 전극판 사이의 간격이 11mm, anode와 deflector 사이의 간격이 30mm인 최적 실험조건하에서 생성된 전자선 spot의 크기는 길이가 20mm 폭이 1mm였으며, 전자선의 출력은 약 400W였다. 이 전자선 증착 장치를 이용하여 1600℃까지의 증발 온도를 가진 도체와 절연체 등을 쉽게 증착시킬 수 있었으며, 만드어진 ITO 박막은 약 5000Å의 두께에서 10^-1∼10^-2Ω·㎝의 비저항과 95%의 광투과율을 갖는다. An electron beam evaporator with a cathode grounded type electron gun was designed and constructed in order to deposit ITO thin films for photovoltaic applications. The optimum condition was observed with electode spacing of 11mm, 30mm between anode and deflector, a cathode inner diameter of 3mm and an anode inner diameter of 5mm. As the accelerating voltage varies from 0 to 15kV and ghe filament current from 0 to 28 A, the minimum electron beam spot has a 20mm length, and 1mm width and the output power ranges from 0 to 400W under the above optimum conditions. We can deposit materials whose evaporation temperature is over 1600℃ using this evaporator. And as a result ITO thin film showed a low resistivity of 10^-1∼10^-2Ω·㎝ and the transmittance of 95%.

Glow Discharge 증착법에 의한 a-Si:H 박막의 Doping 효과 및 비정질 Si 태양전지 제작에 관한 연구

지일환,염덕선,최범식,김수길,고년규 연세대학교 자연과학연구소 1983 學術論文集 Vol.12 No.-

GDa-Si:H박막의 전기전도도 σ, 활성화에너지 ΔE, 광흡수계수 α 및 optical oprtical gap energy E_g(opt.)를 측정하여 전기적, 광학적 성질을 조사하였다. 또한 이들 박막의 광전기력 응용으로서 a-Si:H ITO/_(p-i-n)접합 태양전지를 제작하여 광전기력 현상을 관찰하였다. The electrical and optical properties of GD a-Si:H films have been investigated to obtain electric conductivity σ, activation energy ΔE, optical absorption coefficient α, and optical gap energy Eg(opt.). As a photovoltaic application of GD a-Si:H film, amorphous silicon ITO/p-i-n heteroface solar cells have been fabricated and the photovoltaic characteristics of the solar cells have be studied.

형질전환 담배 식물체에서 개똥쑥 Terpene Synthase의 발현

박성길,홍성현,최근원,이윤형,정인식 경희대학교 생명자원과학연구원 2002 硏究論文集 Vol.22 No.-

Expression of Artemisia annua terpene synthase in transgenic tobacco plants was examined. A full length cDNA encoding terpene synthase was cloned into pILTAB357 vector and transgenic tobacco plants were generated. The integration of this gene was analyzed by genomic DNA PCR and Southern blot analysis. The transcription of the terpene synthase gene in tobacco was confirmed by RT-PCR and northern blot analysis.

The mycelial growth of Agaricus bisporus to develop Thermo-tolerance variety

Youn-Lee Oh,Kab-Yeul Jang,Youn-Keol Nam,Young-Bok Yoo,Pyung-Gyun Shin,Won-Sik Kong,In-Gul Choi 한국버섯학회 2014 버섯 Vol.18 No.2

The white button mushroom, Agaricus biporus is commercially the fifth important edible mushroom, accounting for a Korean production of 10,996 tons in Korea, 2012. The button mushroom, A. bisporus, mostly cultivated at mushroom farm controlled 16-19°C temperature during fruiting period in all seasons. For this reason, the production costs including the cost of energy, is very expensive to keep optimal culturing temperature. In this study, mycelial growth of strains collected from various countries was investigated at different cultivation temperature conditions to use baseline data for developing thermo-tolerance varieties. Mycelial growth was recorded strains cultivated in CDA (Compost Dextrose Agar) after two weeks. 12 strains among total 264 strains were cultivated well in high temperature. These strains will be cultivated in high temperature to confirm relationships between mycelial growth and fruit-body formation in same conditions.

Audit Pricing of Shared Leadership

Youn-Sik Choi,JiwonHyeon,TaejinJung,Woo-JongLee 한국회계정보학회 2016 한국회계정보학회 학술대회발표집 Vol.2016 No.2

This study explores audit implications of shared leadership in client firms. Shared leadership via co-CEO appointments may lead to either suboptimal or optimal managerial decisions, depending on the conflicting or complementary dynamics between multiple CEOs. Analyzing data from 2002 to 2013 of Korean listed companies where co-CEO structure is widespread, we find that auditors spend fewer audit hours and charge lower audit fees for clients with multiple CEOs. Additional tests reveal that hourly fees are not significantly different across clients with or without co-CEOs. Collectively, our findings suggest that the lower audit fees for co-CEO clients are likely attributable to reduced audit effort rather than to a reduced hourly fee. In further searches of specific channels through which audit fees are reduced for the co-CEO clients, we present evidence that firms with co-CEOs exhibit better reporting quality than do firms with a solitary CEO. In sum, the findings of this paper suggest that mutual monitoring via co-CEO appointments assures high quality financial reporting of audit clients, and thus leads to reduced audit fees.

MountainStill in Stereo_110

Choi, Youn Sik 한국콘텐츠학회 2012 ICCC International Digital Design Invitation Exhib Vol.8 No.1

Symptoms of North Korea`s Economic System: Now is the Time to Open up Economically

( Youn Sik Choi ),( Hyung Rok Jung ),( Sung Man Yoon ) 한국국방연구원 2013 The Korean Journal of Defense Analysis Vol.25 No.1

Since suffering economic difficulties, particularly from the 1990s onwards, North Korea, even implicitly, has taken several actions based on the nature of its limited market economy system. North Korean scholars seem to have attempted to practice economic reform and a more open-door policy by learning the capitalistic mark eteconomy system. This paper investigates the current state of trends of North Korean studies associated with economics and management. It is found that even though directly praising and idolizing "Kim Il Sung" and/or "Kim Jong Il" are consistently accomplished, studies on new and subtle issues such as an open-door policy, the global (international) monetary system, compensation, wage (salaries),and self-financing (financing a giupso, in itself, without external financing such as borrowing or issuing shares) drastically increased in the 2000s, especially before and after the announcement of the ``7.1 Economic Management Improvement Measures`` implemented in July 2002. This paper`s findings suggest that North Korea has tried to learn capitalistic market economy system before it takes any steps regarding economic reform. This paper also identifies the political implications in drawing up initiatives in preparation for the era of unification of the two Koreas.

Complementary and Alternative Medicine Use among Cancer Patients at the End of Life: Korean National Study

Choi, Jin-Young,Chang, Yoon-Jung,Hong, Young-Seon,Heo, Dae-Seog,Kim, Sam-Yong,Lee, Jung-Lim,Choi, Jong-Soo,Kang, Ki-Mun,Kim, Si-Young,Jeong, Hyun-Sik,Lee, Chang-Geol,Choi, Youn-Seon,Lim, Ho-Yeong,Yun, Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.4

Objectives: To investigate in depth the use of complementary and alternative medicines (CAMs) by cancer patients at the end-of-life (EOL) and how they communicate with physicians about them. Design and location: In 17 hospitals in Korea between January and December 2004 we identified 4,042 families of cancer patients. Results: The prevalence of CAM use among cancer patients at the EOL was 37.0%, and 93.1% had used pharmacologic types of agents. The most frequent motive for CAM use was the recommendation of friends or a close relative (53.4%) or a physician (1.6%). Only 42.5% discussed CAM use with their physicians. Satisfaction with CAMS was recalled for 37.1%. The most common reason given for that satisfaction was improvement of emotional or physical well-being, while ineffectiveness was the most common reason given for dissatisfaction. The average cost of CAM during the last month of life was $US 900. CAM use was associated with longer disease periods, primary cancers other than liver, biliary, and pancreatic, and need of support from physicians or religion. Conclusions: CAM use among cancer patients at the EOL was common, not discussed with physicians, and associated with expectation of cure. Expectations were generally unmet while the treatments were a financial burden. Further studies evaluating the effects of CAM at the EOL and factors that enhance communication with the physician are needed.