고분자 광자결정 나노시스템 기술

최춘기(Choon-Gi Choi),김진태(Jin Tae Kim),한영탁(Young-Tak Han),이우진(Woo-Jin Lee) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.12

다중/역다중 접속기능을 가진 전기적신호-광신호 변환 양방향 전송모듈 개발

최춘기(Choi Choon-Gi),허영운(Heo Young-Un),김중훈(Kim Jung-Hoon),황건(Hwang Gunn) 한국통신학회 2000 한국통신학회 학술대회논문집 Vol.2000 No.7

내방사선 고반응 고감도 습도센서

최춘기(Choon-Gi Choi),이윤식(Yoomsik Yi) 한국유체기계학회 2022 한국유체기계학회 학술대회 논문집 Vol.2022 No.11

편조 윅 히트파이프의 개발과 작동특성에 관한 연구

문석환,최춘기,황건,최태구,Moon, Seok-Hwan,Choi, Choon-Gi,Hwang, Gunn,Choy, Tae-Goo 한국에너지학회 2000 에너지공학 Vol.9 No.1

전자부품 및 시스템의 고속/고밀도화 추세에 따라 발열밀도가 계속증가하고 있다. 최근 팬티엄 II 급이상의 노트북 컴퓨터의 CPU에서는 칩당 발열량이 10W 이상으로 증가하고 있고 패키징 공간의 제한 때문에 소형히트파이프를 이용한 냉각이 많이 적용되고 있다. 본 연구에서는 모세압구동력이 크고 생산성등이 고려된 편조 형태의 새로운 윅을 개발하였으며 , 노트북 컴퓨터의 CPU 등 소형 전자부품냉ㄱ가에 적용가능한 직경 3, 4 mm 히트파이프를 설계 및 제작하였다. 직경 3, 4 mm Miniature Heat Pipe (이하 MHP) 의 작동특성은 일반적인 중형히트파이프와 다르므로 MHP 의 열전달 특성 및 작동성능에 미치는 각종 인자들의 영향을 파악하고자 성능시험을 수행하였다. 고려된 작동인자로는 작동유체 충전률, 전체 파이프길이 및 증발부, 응축부길이, 설치 경사각, 윅의 가닥수, 열부하 등이다. 작동인자의 영향과 관련된 연구결과는 향후 패키징을 위한 응용연구의 기초자료로 활용할 수 있을 것이다.

자동합성장치에 따른 $^{18}F$-FDG의 방사선분해 평가

김시활,김동일,지용기,최성욱,최춘기,석재동,Kim, Si-Hwal,Kim, Dong-Il,Chi, Yong-Gi,Choi, Sung-Wook,Choi, Choon-Ki,Seok, Jae-Dong 대한핵의학기술학회 2012 핵의학 기술 Vol.16 No.1

상용화된 자동합성장치는 사용되는 유기용매의 종류가 다르고 합성수율에 차이를 보인다. 따라서 본 연구에서는 자동합성장치에 따른 $^{18}F$-FDG의 방사선분해에 관한 방사화학적순도 변화를 비교하였다. Cyclotron (PETtrace, GE Healthcare)을 사용하여 $^{18}F$를 생산하고, 자동합성장치(FASTlab, Tracerlab MX, GE Healthcare)를 이용하여 FDG로 합성하였다. 방사화화적순도는 Radio-TLC Scanner (AR 2000, Bioscan), GC(Gas Chromatography, Agilent 7890A)를 사용하여 $^{18}F$-FDG에 함유되어 있는 에탄올의 양을 측정하였다. 고정상은 실리카겔로 도포된 유리판($1{\times}10cm$), 이동상은 아세토니트릴과 물 19:1 혼합액을 사용하고, 각각의 합성장치에서 고농도와 저농도의 $^{18}F$-FDG를 생산 후 2시간 간격으로 방사화학적순도를 측정하였다. 저농도 (약 2.59 GBq/mL 이하)에서 순도변화는 Tracerlab MX에서는 99.26%, 98.69%, 98.25%, 98.09%, FASTlab에서는 99.09%, 97.83, 96.89%, 96.62%를 얻었다. 고농도(약 3.7 GBq/mL 이상)에서 순도변화는 Tracerlab MX에서는 평균 99.54%, 96.08%, 93.77%, 92.54%, FASTlab의 경우 99.53%, 95.65%, 92.39%, 89.82%를 얻었다. 그리고 FASTlab에서 생산한 $^{18}F$-FDG의 GC에서는 에탄올이 검출되지 않았으며, Tracerlab MX에서는 100~300 ppm의 에탄올이 검출되었다. 이러한 결과를 비추어 봤을 때 방사선 보호제인 에탄올의 유무보다 방사능농도가 방사선분해에 더 큰 영향을 미치기 때문에 고농도의 $^{18}F$-FDG 생산 후 무균 생리식염수로 희석하여 농도를 낮춘 후 사용해야 한다. Purpose : Among quality control items, the radiochemical impurity must be below 10% of total radioactivity. In this regard, as the recently commercialized automatic synthesis module produces a large amount of 18F-FDG, radiolysis of radiopharmaceuticals is very likely to occur. Thus, this study compared the changes in radiochemical purity regarding radiolysis of $^{18}F$-FDG according to automatic synthesis module. Materials and methods : Cyclotron (PETtrace, GE Healthcare) was used to produce $^{18}F$ and automatic synthesis module (FASTlab, Tracerlab MX, GE Healthcare) was used to achieve synthesis into FDG. For radiochemical purity, Radio-TLC Scanner (AR 2000, Bioscan), GC (Gas Chromatograph, Agilent 7890A) was used to measure the content of ethanol included in $^{18}F$-FDG. Glass board applied with silica gel ($1{\times}10cm$) was used for stationary phase while a mixed liquid formed of acetonitrile and water (ratio 19:1) was used for mobile phase. High-concentration and low-concentration $^{18}F$-FDG were produced in each synthesis module and the radiochemical purity was measured every 2 hours. Results : The purity in low-concentration (below 2.59 GBq/mL) was measured as 99.26%, 98.69%, 98.25%, 98.09% in Tracerlab MX and as 99.09%, 97.83%, 96.89%, 96.62% in FASTlab according to 0, 2, 4, 6 hours changes, respectively. The purity in high-concentration (above 3.7 GBq/mL) was measured as 99.54%, 96.08%, 93.77%, 92.54% in Tracerlab MX and as 99.53%, 95.65%, 92.39%, 89.82% in FASTlab according to 0, 2, 4, 6 hours changes, respectively. Also, ethanol was not detected in GC of $^{18}F$-FDG produced in FASTlab, while 100~300 ppm ethanol was detected in Tracerlab MX. Conclusion : Whereas the change of radiochemical purity was only 3% in low-concentration $^{18}F$-FDG, the change was rapidly increased to 10% in high-concentration. Also, higher radiolysis were observed in $^{18}F$-FDG produced in FASTlab than Tracerlab MX. This is because ethanol is included in the synthesis stage of Tracerlab MX but not in the synthesis stage of FASTlab. Thus, radiolysis is influenced by radioactivity concentration than the inclusion of ethanol, which is the radioprotector. Therefore, after producing high-concentration $^{18}F$-FDG, the content must be diluted through saline to lower concentration.

PMMA / PVDF 혼합물의 물성 및 광학적 성질

김병철(Byeong Cheol Kim),최춘기(Choon Gi Choi),한상필(Sang Pil Han),윤근병(Keun Byoung Yoon),정명영(Myung Yung Jeong),이대수(Dai Soo Lee) 한국고분자학회 2002 폴리머 Vol.26 No.4

Sol-Gel 법으로 제작한 Zn_1-xCo_xO 박박의 미세조직 및 자기적 특성

고윤덕,태원필,김응권,김기출,최춘기,김종민,송준태,박태석,서수정,김용성,Ko, Yoon-Duk,Tai, Weon-Pil,Kim, Eung-Kwon,Kim, Ki-Chul,Choi, Choon-Gi,Kim, Jong-Min,Song, Joon-Tae,Park, Tae-Seok,Suh, Su-Jeung,Kim, Young-Sung 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.7

Zn$_{l-x}$Co$_{x}$O (x = 0.05 - 0.20) films were grown on Coming 7059 glass by sol-gel process. A homogeneous and stable Zn$_{l-x}$Co$_{x}$O sol was prepared by dissolving zinc acetate dihydrate (Zn(CH$_{3}$COO)$_{2}$$\cdot$2H$_{2}$O), cobalt acetate tetrahydrate ((CH$_{3}$)$_{2}$$\cdot$CHOH) and aluminium chloride hexahydrate (AlCl$_{3}$ $\cdot$ 6H$_{2}$O) as solute in solution of isopropanol ((CH$_{3}$)$_{2}$$\cdot$CHOH) and monoethanolamine (MEA:H$_{2}$NCH$_{2}$CH$_{2}$OH). The films grown by spin coating method were postheated in air at 650°C for 1 h and annealed in the condition of vacuum (5 $\times$ 10$^{-6}$ Torr) at 300$^{\circ}C$ for 30 min and investigated the nature of c-axis preferred orientation and physical properties with different Co concentrations. Znl_xCOxO thin films with different Co concentrations were well oriented along the c-axis, but especially a highly c-axis oriented Zn$_{l-x}$Co$_{x}$O thin film was grown at 10 at$\%$ Co concentration. The transmittance spectra showed that Zn$_{l-x}$Co$_{x}$O thin films occur typical d-d transitions and sp-d exchange interaction became activated with increasing Co concentration. The electrical resistivity of the films at 10 at$\%$ Co had the lowest value due to the highest c-axis orientation. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster was formed, and the ferromagnetic properties appeared, respectively. The characteristics of the electrical resistivity and room temperature ferromagnetism of Zn$_{l-x}$Co$_{x}$O thin films suggested the possibility for the application to dilute magnetic semiconductors.

나노임프린트된 폴리머 광결정

기철식(Chul-Sik Kee),최춘기(Choon-Gi Choi),윤근병(Keun Byoung Yoon),한상필(Sang-Pi Han),정명영(Myung Yung Jeong) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11

We present that two-dimensional periodic nano-patterns can be embossed on a polymer thin film using the nano-imprint process. The silicon masters with triangular arrays of rods such as square, hexagon, dodecagon and circle were successfully fabricated using the e-beam lithography and inductively coupled plasma etching. We also show that the polymer thin films with two-dimensional periodic patterns, polymer photonic crystals, can exhibit electromagnetic stop bands and the line defects introduced in the periodic patterns can serve as low loss waveguides from the photonic band calculations and the finite difference time domain simulations.

방사성의약품 합성에서 발생하는 방사성기체의 효율적 차단

지용기,김동일,김시활,원문희,최성욱,최춘기,석재동,Chi, Yong Gi,Kim, Dong Il,Kim, Si Hwal,Won, Moon Hee,Choe, Seong-Uk,Choi, Choon Ki,Seok, Jae Dong 대한핵의학기술학회 2012 핵의학 기술 Vol.16 No.2

방사성의약품 제조 시 휘발성 기체의 경우에 완전 차폐가 되지 않고, Hot cell 외부로 그리고 배기덕트를 통해 작업자에게 외부피폭은 물론 호흡을 통해 내부피폭을 가져오게 한다. 처음에는 Hot cell 자체의 배출구를 막아서 방사성기체를 차단하려하였으나 장치에 맞는 기체 밀폐형 댐퍼의 제작이 어렵고, 크기가 맞지 않아서 설치 후에 여전히 문제점이 개선되지 않았다. 그러나 Tedlar gas sampling bag의 사용으로 합성 장치의 가스 배출구를 연결하여 방사성 기체를 저장하고 10반감기가 지난 후에 배출함으로써 작업자의 피폭을 확연히 줄이게 되었으며 $^{18}F$ 방사성 기체는 Hot cell 배출구에 활성탄 필터를 연결하고 최종 배출구에 2차 활성탄 필터를 사용함으로써 배출되는 방사능 농도를 90% 이상 줄여주었다. 단 반감기의 핵종인 경우는 위와 같은 경우를 이용하여 다음날 작업을 할 수 있지만 반감기가 긴 핵종들 같은 경우는 다음날 처리 할 수 없는 문제점들이 발생한다. Decay tank의 추가적인 문제점들을 보완하거나 기체상의 여러 방사성 입자들을 포집 할 수 있는 물질들이 만들어져야 할 것이다. 현재 우리나라는 최종 배출 공기 중 방사능 농도만을 규제하고 있으나 유럽 같은 경우 일일 배출 양과 연간 배출도 규제를 하고 있다. 방사성의약품 합성 시 발생하는 많은 방사성 물질들을 보다 효과적으로 친환경적으로 처리할 수 있는 여러 연구들이 이루어져야 할 것이다. Purpose : Methode an effective block was investigated to deal with volatile radioactive gas, short lived radioactive waste generated as a result of the routinely produced radiopharmaceuticals FDG (2-deoxy-2-[$^{18}F$]fluoro-D-glucose) and compound with $^{11}C$. Materials and Methods : All components of the radiation stack monitoring and data management system for continuous radioactive gas detection in the air extract system purchase from fixed noble gas monitor of Berthold company. TEDLAR gas sampling bags purchase from the Dongbanghitech company. TEDLAR gas sampling bags (volume: 10 L) connected via paraflex or PTFE tubing and Teflon 3 way stopcock. When installing TEDLAR gas sampling bags in Hot cell on the inside and not radioactive gas concentrations were compared. According to whether the Hot cell inside a activated carbon filter installed, compare the difference in concentration of the radioactive gas $^{18}F$. Comparison of radiation emission concentration difference of module a FASTlab and TRACElab. Results : Activated carbon filter are installed in the Hot cell, a measure of the concentration of radioactive gas was 8 $Bq/m^3$. Without activated carbone filter in the hot cell was 300 $Bq/m^3$. Tedlar bag prior to installation of the radioactive gases a measure of the concentration was 3,500 $Bq/m^3$, $^{11}C$ synthesis of the measured concentration was 27,000 $Bq/m^3$. After installed a Tedlar bag and a measure concentration of the radioactive gases was 300 $Bq/m^3$ and $^{11}C$ synthesis was 1,000$Bq/m^3$. Conclusion : $^{11}C$ radioactive gas that was ejected out of the Hot cell, with the use of a Tedlar gas sampling bag stored inside. A compound of 11C is not absorbed onto activated carbon filter. But can block the release out by storing in a Tedlar gas sampling bag. We was able to reduce the radiation exposure of the worker by efficient radiation protection.

레이저 표면용융에 의한 Al-12% Si 합금의 미세조직 형성

최춘기 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.12

The surface of Al-Si 12% alloys has been modified by laser surface melting process. A 5 kW CO₂ laser has been used to melt the surface of casting alloy. The dimension and microhardness of molten zone have been investigated for mono- and multi-pass. The dimension of molten zone depends on the parameters (power, scanning velocity......) of laser beam. The microhardness increases as the crystalline size and interdendritic space decrease and the scanning velocity increases. A substantial reduction of silicon particle size has been achieved from about 50 microns before laser melting to about 1 micron after laser melting with scanning velocity of 1 m/min. The relationship between solidification rate and scanning velocity has been also studied. The solidification rate begins to zero at the interface between substrate and molten zone, and rapidly increases up to a value equivalent to the scanning velocity at the surface. Interdendritic space depends on the quenching rate. It decreases with the speed of treatment and it is about 1 micron with a scanning velocity of 10 m/min.