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이정희,Jae-Hee Park,Jae-Hoon Lee,Jae-Seung Lee,Jong-Wook Kim,Kye-Seok Lee,Sung-Bum Bae,Sung-Ho Hahm 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
Based on investigating the effects of isoelectronic Al-doping on GaN film, a new layer structure is proposed for a heterostructure field effect transistor (HFET) including an isoelectronic Al-doped channel. The electron mobility measured at 77 (300) K significantly increased from 145 (130) cm$^2$/V$\cdot$s in the undoped sample to 823 (440) cm$^2$/V$\cdot$s in the Al-doped sample grown with a trimethylaluminum flow rate of 3 $\mu$mol /min, while maintaining the background doping concentration below $\sim$ 6 $\times$ 10$^{16}$ cm$^{-3}$. Two-dimensional electron gas mobilities of 1690 and 9280 cm$^2$/Vs were measured for a 25-nm Al$_{0.3}$Ga$_{0.7}$N/1-nm AlN/70-nm Al-doped channel/GaN heterostucture at 300 and 77 K, respectively. The improved results are explained based on a decrease in the compensating acceptors or other defects associated with the formation of screw dislocation due to the incorporation of Al in the channel layer, plus a decrease in the alloy disorder scattering in the heterostructure based on introducing a binary thin AlN layer between the Al$_{0.3}$Ga$_{0.7}$N and Al-doped channel layers.
A Study on the Incorporation of Sulfate-sulfur into Sulfur-containing Protein
이정희,전세열,신상주,Lee, Chung-Hee,Chun, Sea-Yull,Shinn, Sang-Joou 생화학분자생물학회 1971 한국생화학회지 Vol.4 No.1
고등동물에 있어서 황산염 유황의 단백질 전환은 소화관내에 기식하는 미생물의 도움으로만 가능한 것으로 알려져 있으나 본 실험에서는 고등 동물자체가 독자적으로 그와 같은 기능을 가졌는가를 구명하고져 반추초식덩물 아닌 토끼를 이용하여 표지된 황산염을 여러가지 방법으로 투여하여 그것이 단백질 합성에 이용됨을 구명하였고 토끼가 그와 같은 능력을 독자적으로 지녔음을 확인하였다. 각 기관에 있어서의 방사능 분포 상태도 아울러 조사하였다. Hinted by a symbiotic relationship between rumen microorganisms and host ruminant in utilization of inorganic sulfur compounds such as sodium sulfate and ammonium sulfate, an investigation was conducted to determine a similar symbiotic effect between ceacum microflora and host rabbit, for ammonium sulfate. Radioactivity of fecal emission was detected from the first day of administration but the radioactive compound(s) was not precipitated by barium chloride. A similar fact was found when the labelled sulfate-sulfur was administered by intraperitoneal injection. When urinary ejection was fractionated into 3 parts, namely, trichloroacetic acid precipitate, barium chloride precipitate and supernatant fractions, radioactivity was almost equally distributed into barium chloride precipitable and supernatant fractions with a minor beta-ray emission from TCA precipitated fraction. Radioactivity was detected in hairs of experimental subjects regardless the mode of drug administration. Our finding shows that angola rabbit possesses per se the capacity of such utilization independent to its ceacum microflora. Liver homogenates made 48 hours after the suspension of drug administrations showed no radioactive emission from its barium chloride precipitated fracton. Majorities of beta-ray emission was detected in the TCA precipitated fraction. A minor amount of count, detected from supernatant is interpreted as an evidence that in the liver, transformation of inorganic sulfate sulfur into other sulfur compound (s) is a pre-requisite for protein incorporation or other physiological or metabolic process. The results of in vitro test for microbial incorporation of labelled sulfate-sulfur show that when ceacum microfiora are incubated under anaerobic conditions the microorganisms can incorporate the labelled element into their cellular protein. The capacity of doing so seems to be increased by a prolonged exposure to or contact with such compound expressed otherwise, they can be trained to do so.
이온전리함 기반의 컨테이너 검색용 고에너지 X-선 선량 측정장치 개발
이정희,임창휘,박종원,이상헌,Lee, Junghee,Lim, Chang Hwy,Park, Jong-Won,Lee, Sang Heon 한국정보통신학회 2020 한국정보통신학회논문지 Vol.24 No.12
X-ray of up to 9MeV are used for container inspection. X-ray intensity must be maintained stably regardless of changes in time. If dose is not constant, it may affect the image quality, and as a result, may affect the inspection of abnormal cargo. Therefore, to acquire high-quality images, continuous dose monitoring is required. In this study, the ion-chamber based device was developed for monitoring the dose change in high-energy x-ray. And to estimate the performance of signal-processing device change according to the environmental change, the output changing due to the change of temperature and humidity was observed. In addition, verification of the device was performed by measuring the output change. As a result of the measurement, there was no significant difference in performance due to changes in temperature and humidity, and the change in output according to the change in exposure was linear. Therefore, it was found that the developed device is suitable for the dose monitoring of high-energy x-ray. 일반적으로 컨테이너 내부검사를 위해서는 최대 9MeV의 X-선을 사용한다. 이때 사용되는 X-선은 선형가속기를 통해 생성되며 일정한 세기의 X-선량이 시간의 변화에 관계없이 안정적으로 유지되어야 한다. 만약 발생되는 X-선의 세기가 일정하지 않다면 영상의 해상도와 대비도 등에 영향을 미칠 수 있으며 결과적으로 컨테이너 내부의 이상화물에 대한 검사에 영향을 미칠 수 있다. 그러므로 고화질의 영상을 획득하기 위해서는 발생되는 X-선 선량에 대한 지속적인 모니터링이 요구된다. 이와같은 선량 모니터링을 위하여, 본 연구에서는 고에너지 X-선 선량의 변화 측정을 위한 이온전리함 기반의 선량변화 측정장치를 개발하였고 환경변화에 따른 신호처리부의 성능변화를 확인하기 위하여 온도와 습도 변화에 의한 측정값의 변화를 관찰하였다. 또한, 고에너지 X-선 발생장치에서 발생되는 선량의 변화에 따른 응답특성변화를 측정함으로써 개발한 X-선 선량측정장치의 검증을 수행하였다. 측정결과 온도와 습도의 변화에 따른 성능의 차이가 크게 나타나지 않았으며 입사되는 선량의 변화에 따른 출력의 변화가 선형적이었다. 그러므로 개발한 이온전리함 기반의 선량변화측정장치는 고에너지 X-선의 선량변화의 측정에 적용하기에 적합함을 알 수 있었다.
이정희,Se-Yeong Lee,곽재섭 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.12
A rotational electro-magnetic finishing (REMF) was an effective way to minimize burr and improve edge quality on the surface. This study conducted two stages of explicit dynamic simulations: signle collision analysis and multiple collision analysis to verify the effect of abrasives’ behavior on the deburring processes. From observed results, successful deburring depended on the total amount of abrasives and the collision angle. Based on the simulated results and response surface methodology, it was found that the accuracy was reached approximately 95.4 %. Additionally, the maximum deburring area from the predictive model and simulation were similar to 2.27 mm 2 and 2.37 mm 2 , respectively, at rotational speed of 1800 rpm, abrasive diameter of 0.7 mm, and abrasive weight of 2.0 kg. In the experimental verification, the results were in good agreement with the experimental data, although specific values did not correspond exactly. Thus, the suggested approach adopting explicit dynamic simulations could effectively evaluate deburring performance in the REMF process.