Electrical Characteristics of AlxGa1-xN/GaN Heterostructure withIsoelectronic Al-Doped Channel for HFET Application

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.

세계화와 상호공존의 시민정신: 하퍼 리의 『앵무새 죽이기』

이정희 ( Chung Hee Lee ) 한국현대영미소설학회 2004 현대영미소설 Vol.11 No.1

교류전위차법에 의한 강자성체의 응력확대계수 결정

이정희,Lee, Jeong-Hee 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.9

In order to determine the Mode I stress intensity factor ($K_1$) experimentally by means of the alternating current potential drop(ACPD) technique, the change in potential drop due to load for a ferromagnetic material containing a two-dimensional surface crack was examined. The cause of the change in potential drop and the effect of the magnetic flux on the change in potential drop were clarified by using the measuring systems with and without removing the magnetic flux from the circumference of the specimen. To remove the magnetic flux, a new measuring system was made by utilizing the characteristic of coaxial transmission line. The change in potential drop in the case without magnetic flux in the air was caused by the change in electromagnetic properties near the crack tip due to magnetization. The relationship between the change in potential drop and the change in $K_I$ was linealized by demagnetization and was found to be independent of the crack length.

직류전위차법 자료에 대한 통계적 자료분석

이정희,이우동,Lee, Jeong-Hee,Lee, Woo-Dong 한국데이터정보과학회 2010 한국데이터정보과학회지 Vol.21 No.1

비파괴검사방법 중 직류전위차법은 표면균열 측정에 유효한 수단으로 알려져 있다. 이차원 표면 균열을 가진 시험편에서 전류입출력점사이의 거리가 직류전위차에 미치는 영향을 알아보는 실험을 실시하여 자료를 얻었다. 이 자료로부터 전위차 값은 일정 전위차계측점사이의 거리에 있어 전류입출력점사이의 거리가 증가함에 따라 반비례적으로 감소하고, 노치의 길이에 비례하고 있었다. 이 실험에서 관찰된 자료를 통계적 모형에 적합시키고, 적합된 모형에서 전위차에 영향을 주는 유의한 변수를 알아보는 것은 비파괴검사에서 중요하다고 할 수 있다. 본 연구에서는 관찰된 자료를 적절하게 설명할 수 있는 통계적 모형을 제안하고, 제안된 모형에서 유의한 독립변수를 찾아보는 것이 목적이다. It was verified that the effect of the distance between current input point and output point on direct current potential drop (DCPD) in the material with two-dimensional surface notch. If the distance between potential drop measuring points was fixed at a certain distance, the potential drop was decreased with increasing the distance between current input and output points. DCPD technique was a useful method for surface crack sizing because the potential drop was proportional to the length of notch. In this paper, we suggest a statistical model to describe the data and want to find a significant variables to effect to potential drop. We use R program to analyze the data.

홀 형상이 막 냉각 유동에 미치는 효과에 대한 수치 해석적 연구

이정희,최영기,Lee, Jeong-Hui,Choe, Yeong-Gi 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.7

In this study, the effect of hole geometry of the cooling system on the flow and temperature field was numerically calculated. The finite volume method was employed to discretize the governing equation based on the non-orthogonal coordinate with non-staggered variable arrangement. The standard k-.epsilon. turbulence model was used and also the predicted results were compared with the experimental data to validate numerical modeling. The predicted results showed good agreement in all cases. To analyze the effect of the discharge coefficient for slots of different length to width, the inlet chamfering and radiusing holes were considered. The discharge coefficient was increased with increment of the chamfering ratio, radiusing ratio and slot length to width and also the effect of radiusing showed better result than chamfering in all cases. In order to analyze the difference between the predicted results with plenum region and without plenum region, the velocity profiles of jet exit region for a various flow conditions were calculated. The normal velocity components of jet exit showed big difference for the low slot length to width and high blowing rate cases. To analyze the flow phenomena injected from a row of inclined holes in a real turbine blade, three dimensional flow and temperature distribution of the region including plenum, hole and cross stream with flow conditions were numerically calculated. The results have shown three-dimensional flow characteristics, such as the development of counter rotating vortices, jetting effect and low momentum region within the hole in addition to counter rotating vortex structure in the cross stream.

HCI 이론에 기반한 게임형 학습 프로그램 평가 준거 개발 및 적용

이정희,이재무,Lee, Jeong-Hee,Lee, Jae-Mu 한국정보교육학회 2007 정보교육학회논문지 Vol.11 No.1

The purpose of this study is to develope a criterion for evaluation on game-type learning programs by the application of HCI(Human Computer Interaction) theory. And to analyze game-type learning programs for elementary students on the criterion developed in this study. The HCI theory, which deals with principles or methods for developing systems people can use conveniently and pleasantly, has been applied to overall area of program development. And it also has been widely used to evaluate learning programs. However, there have been few studies on a game-type learning program evaluation on the basis of the HCI theory. This paper shows that evaluation criteria are developed on three viewpoint bases : usefulness, usability, and affect which are as elements in HCI. And analyzes the game-type learning programs from these three points of view. The evaluation criteria developed in this study can be applied to a basis for evaluation on game-type learning programs, and the analysis will be able to be a useful guide to game programers as well as its users.

얼굴 특징점 추적 및 움직임 측정도구

이정희,이영희,차의영,Lee, Jeong-Hee,Lee, Young-Hee,Cha, Eui-Young 대한임베디드공학회 2011 대한임베디드공학회논문지 Vol.6 No.5

This paper proposes facial feature tracking based on modified ART2 neural networks. And we also suggest new measurement devices such as 'Persistence Exponent' and 'Moving Space Exponent' for the criterion of input vector which consists features. The proposed methods have been applied to classify 48 students by 2-class (ADHD positive, ADHD negative). The results of the experiment have shown that the proposed methods are effective for ADHD Behavior Pattern Classification based on the Image Processing.

국내 쯔쯔가무시증의 감염자 분포와 유병자수 추정

이정희,박정수,Lee, Jung-Hee,Murshed, Sharwar,Park, Jeong-Soo 한국데이터정보과학회 2009 한국데이터정보과학회지 Vol.20 No.1

쯔쯔가무시증은 가을철 유행성 출혈열 중 80%이상을 차지하는 질병으로 1주에서 2주의 잠복기를 가지는 것으로 알려져 있다. 우리는 그 잠복기간의 확률분포가 감마분포라 가정하고 후향연산식을 이용하여, ${\hat{\mu}}=309.92$$, ${\hat{\sigma}}=14.154$인 정규분포를 따르는 감염자 분포를 추정하였다. 감염자는 10월에 집중적으로 분포하는 것으로 나타났다. 이러한 감염자 분포형태는 발병자 수가 11월동안 급격하게 증가하는 것에 기인한다. 본 연구에서 추정한 감염확률에 의해 미래의 유병자수를 계산한 결과 최대 1200명이었고 이는 매년 증가하는 발병자 수의 경향을 반영하지 못한 한계가 있다. 또한 우리는 전염병 모형으로 잘 알려져 있고 전염발전 단계간의 상호작용을 고려하는 SIRS 모형을 적용해 보았다. 모수는 초기값으로부터 잘 근사되어 수렴하는 값으로 추정하였다. Tsutsugamushi fever occupies more than 80% of total fall epidemic diseases and has an incubation period of 1 or 2 weeks as well. We have assumed that the incubation period distribution is gamma and therefore, reach an agreement that the infected distribution is normal with ${\hat{\mu}}=309.92$, ${\hat{\sigma}}=14.154$ by back calculation method. The infection cases are found severely large around the month of October. The infection case distribution demonstrates the incidence number increasing rapidly and progresses fast during the month of November. In this study, we have calculated the future prevalence number of maximum 1,200 people by inferred infection probability and incubation period distribution with some sort of limitation that the trend of increasing incidence number is not taking into an account. We considered the SIRS model which is also known as epidemic model, familiar to interaction between epidemiological classes. Our estimated parameters converged well with the initial parameter values.

표지된 황산염 유황의 유황단백질에 대한 이용에 관한 연구

이정희,전세열,신상주 ( Chung Hee Lee,Sea Yull Chun,Sang Joou Shinn ) 생화학분자생물학회 1971 BMB Reports Vol.4 No.1

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 fraction. 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 microflora 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.

학교도서관과 독서지도의 문제

이정희,Lee, Jeong-Hui 한국도서관협회 1976 圖協月報 Vol.17 No.7