HVPE 법을 통한 GaN 성장 시 기판 종류 및 V/III 비에 따른 잔류 stress 특성 연구

이주형,이승훈,이희애,강효상,오누리,이성철,이성국,박재화,Lee, Joo Hyung,Lee, Seung Hoon,Lee, Hee Ae,Kang, Hyo Sang,Oh, Nuri,Yi, Sung Chul,Lee, Seong Kuk,Park, Jae Hwa 한국결정성장학회 2020 한국결정성장학회지 Vol.30 No.2

본 연구에서는 HVPE 성장법으로 GaN 성장 시 GaN 내에 잔류하는 stress로 인한 crack 현상을 감소시키고자 기판 종류 및 V/III 비를 조절하여 잔류 stress 특성을 알아보고자 하였다. Sapphire, GaN template 위에 각각 V/III 비 5, 10, 15의 조건으로 GaN을 성장시켜 형성된 hexagonal pit의 분포 및 깊이를 분석하였다. 이를 통해 GaN on GaN template 성장에서 V/III 비가 높을수록 hexagonal pit의 분포 영역 및 깊이가 증가하는 것을 확인하였다. Raman 측정을 통해 hexagonal pit 영역 및 깊이가 컸던 GaN on GaN template 성장에서 V/III 비가 높을수록 stress가 감소하는 것을 확인하였다. 이를 통해 hexagonal pit의 분포 및 깊이가 증가할수록 잔류 stress가 낮아짐을 확인할 수 있었으며, 향후 후막 GaN 성장 시 stress 감소 가능성에 대해 확인하였다. The characteristics of the residual stress on the types of the substrate was investigated with adjusting the V/III ratio during GaN growth via the HVPE method. GaN single crystal layers were grown on a sapphire substrate and a GaN template under the conditions of V/III ratio 5, 10, and 15, respectively. During GaN growth, multiple hexagonal pits in GaN single crystal were differently revealed in accordance with growth condition and substrate type, and their distribution and depth were measured via optical microscopy(OM) and white light interferometry(WLI). As a result, it was confirmed that the distribution area and depth of hexagonal pit tended to increase as the V/III ratio increased. Moreover, it was found that the residual stress in GaN single crystal decreased as the distribution area and depth of the pit increased through measuring micro Raman spectrophotometer. In the case of GaN growth according to substrate type, the GaN on GaN template showed lower residual stress than the GaN grown on sapphire substrate.

이미지 데이터를 모니터링하는 관리도에서 이미지와 ROI 크기 조정의 영향

이주형,윤형욱,이성민,이재헌,Lee, JuHyoung,Yoon, Hyeonguk,Lee, Sungmin,Lee, Jaeheon 한국통계학회 2017 응용통계연구 Vol.30 No.3

A machine vision system (MVS) is a computer system that utilizes one or more image-capturing devices to provide image data for analysis and interpretation. Recently there have been a number of industrial- and medical-device applications where control charts have been proposed for use with image data. The use of image-based control charting is somewhat different from traditional control charting applications, and these differences can be attributed to several factors, such as the type of data monitored and how the control charts are applied. In this paper, we investigate the adjustment effect of image size and region of interest (ROI) size, when we use control charts to monitor grayscale image data in industry. 최근 산업의 생산공정에서는 머신비전시스템을 통하여 제품의 품질특성치에 대한 정보를 이미지 데이터로 제공하는 경우가 많다. 따라서 산업과 의학 현장에서 이미지 데이터의 모니터링을 위해 관리도 절차의 필요성이 많이 대두되고 있다. 이미지 데이터를 모니터링하는 관리도 절차는 전통적으로 사용하는 관리도 절차와 유사한 점도 있지만, 데이터의 구조를 비롯하여 각 이미지에서 ROI를 설정하여 관리도 절차를 적용하는 등 서로 다른 점도 많이 있다. 이 논문에서는 생산공정에서 제공되는 이미지 데이터에 대해 관리도를 사용하는 절차를 소개하고, 이미지 또는 ROI 크기의 확대와 축소가 제품의 이상원인을 탐지하는데 어떠한 영향이 주는지를 모의실험을 통하여 알아보았고 각 관리도의 성능 또한 비교하였다.

Sn-Zn 공정합금의 응고속도에 따른 조직과 기계적 성질에 관한 연구

이주형,이계완 ( J . H . Lee,K . W . Lee ) 한국주조공학회 1985 한국주조공학회지 Vol.5 No.4

The structures and mechanical properties of undirectionally solidified Sn-Zn eutectic alloys have been examined over the growth range 7㎜/h to 6,000㎜/h. The structures of undirectionally solidified Sn-Zn eutectic alloys were primarily broken-lamellar at growth rates below 760㎜/h and became fibrous at higher growth rates above that. At a growth rate 3,084㎜/h the structures were fibrouse only. There is no dendrites at any growth rates, but occasionally ribbon-like morphologies were seen. The under cooling increased parabolically with growth rate increase. The hardness of specimes increased with growth rates increase but heat-treated specimen decreased after growth rates 760㎜/h and became constant value. The effect of heat-treatment was good at lower growth rate. At room temperature tensile strength increased with growth rates up to R=990㎜/h and then tensile strength became near-constant value. The effect of heat-treatment was well at lower growth rate.

3차원 PCB 채널내에서의 복사-혼합대류 열전달 특성

이주형,박경우,박희용,Lee, J.H.,Park, K.W.,Pak, H.Y. 대한설비공학회 1996 설비공학 논문집 Vol.8 No.4

The interaction of turbulent mixed convection and surface radiation in a three-dimensional channel with the heated blocks is analyzed numerically. Two blocks are maintained at high temperature and the other bottom and horizontal walls are insulated. S-4 method is employed to calculate the effect of the radiative heat transfer. The low Reynolds number k-$\varepsilon$ model proposed by Launder and Sharma is used to estimate the turbulent influence on the heat transfer enhancement. From above modeling, the effects of various channel specifications on the flow and heat transfer characteristics are investigated. The variables used for the present study are Reynolds number, block spacing, the channel height spacing for block and the emissivity. Average Nusselt numbers along the block surfaces are correlated and presented in terms of Reynolds number, emissivity and dimensionless geometric parameters. For the range of conditions in this study, average Nusselt numbers along the block surfaces are strongly influenced by the Reynolds numbers and channel height spacing for block but weakly influenced by the block spacing and the emissivity of the adiabatic walls.

주택규모 선택에 영향을 미치는 가구원수별 특성에 관한 연구

이주형,임종현,강남훈,Lee, Joo-Hyung,Lim, Jong-Hyun,Kang, Nam-Hoon 한국주거학회 2010 한국주거학회 논문집 Vol.21 No.2

The housing market requires customized housing to be supplied according to the various characteristics of households. Multinominal Logistic Regression was used to analyze the effects of variables of household characteristics according to the number of family members on the choice of housing size in the scope of the whole country's housing market. Analysis showed that the number of family members has its own characteristics. When a household has a smaller number of family members, there are more variables affecting choice of housing size. Living and housing expenses variables served as significant variables that affect all household types. Results showed that households with more living and housing expenses are more likely to choose a large sized house and where households have a greater number of family members, there is more influence on that choice. The age of the householder was only found to be a meaningful variable in 1-2 person households and 3-4 person households, particularly in the choice of a small or large sized house. This shows that the age of the householder does not play an important role in choosing medium sized houses for households of under 4 people, but affects the choice of small and large sized houses. The academic ability of household members also served as a significant variable. While 1-2 person households with high academic ability tend to select a large sized house, 3-4 person households with high academic ability tend to select a small sized house. It is observed that members of both 1-2 person households and 3-4 person households tend to select their house between a large sized house and a small sized house in order to own their own houses. The result of this research suggests that there are various and detailed variables on the choice of housing size. Especially, a notable result is that household characteristics more significantly affect the housing size choice of 1-2 person households, while the trend of an aging society will more significantly affect a 3-4 person households' choice of a large sized house. Therefore, a study on the choice of housing size according to characteristics of elderly households and 1-2 person households should be continually analyzed.

경시적 자료의 주의력 결핍 과잉행동 장애를 종점으로 한 납의 벤치마크 용량 하한 도출

이주형,김시연,하미나,권호장,김병수,Lee, Juhyung,Kim, Si Yeon,Ha, Mina,Kwon, Hojang,Kim, Byung Soo 한국통계학회 2016 응용통계연구 Vol.29 No.7

본 연구의 목적은 아동 건강에 미치는 환경의 영향을 평가하기 위하여 우리나라 환경부에서 구축한 경시적 자료인 CHEER 자료를 바탕으로 납의 벤치마크 용량 하한(BMDL)을 도출하여 Kim 등 (2014)의 결과를 재현하는 것이다. 본 연구에서는 CHEER 자료의 2005년 동집단을 사용하였는데, 벌점화 선형 스플라인을 이용한 변환공식으로 2005년 동집단의 ADHD 평가 척도를 통일하고, 경시적 자료의 특성을 반영한 두 개의 선형혼합모형을 구축하였다. 이후 구축된 모형을 바탕으로 혈중 납 농도의 BMDL을 도출하였다. 이 과정에서 Kim 등 (2014)에서 발견한 ADHD 점수의 평균으로의 회귀 현상이 재확인되었고, 2005년 동집단과 2006년 동집단의 분포 상의 특징적 차이가 발견되었다. 결과적으로 이 차이를 감안했을 때, Kim 등 (2014)과 일치적인 결과를 얻을 수 있었다. This paper is to reproduce the result of Kim et al. (2014) by deriving a benchmark dose lower bound (BMDL) of lead based on the 2005 cohort data set of Children's Health and Environmental Research (CHEER) data set. The ADHD rating scales in the 2005 cohort were not consistent along the three follow-ups since two different ADHD rating scales were used in the cohort. We first unified the ADHD rating scales in the 2005 cohort by deriving a conversion formula using a penalized linear spline. We then constructed two linear mixed models for the 2005 cohort which reflected the longitudinal characteristics of the data set. The first model introduced the random intercept and the random slope terms and the second model assumed the first order autoregressive structure of the error term. Using these two models, we derived the BMDLs of lead and reconfirmed the "regression to the mean" nature of the ADHD score discovered by Kim et al. (2014). We also noticed that there was a definite difference between the sampling distributions of the two cohorts. As a result, taking this difference into account, we were able to obtain the consistent result with Kim et al. (2014).

극소수 샘플에서 유의발현 유전자 탐색에 사용되는 순열에 근거한 검정법

이주형,송혜향,Lee, Ju-Hyoung,Song, Hae-Hiang 한국통계학회 2009 응용통계연구 Vol.22 No.5

마이크로어레이 극소수 샘플(array) 자료의 분석에서는 유의한 발현수치를 나타내는 유전자를 검정통계량에 의해 결정하는 것이 주요과제이다. 이 때 수 천 또는 수 만개인 유전자의 발현수치로부터 귀무분포(null distribution)의 생성이 필수적이며, 극소수 샘플 자료의 경우에는 순열방법(permutation methods)에 의해 귀무분포를 생성하는 것이 가장 바람직하다. 본 논문에서는 귀무분포 생성에 사용될 수 있는 매우 단순한 검정통계량을 제시하면서 더불어 귀무분포 생성에 적절한 순열방법도 제안한다. 모의실험으로 기존의 검정통계량으로 생성된 귀무분포와 본 논문에서 제안하는 검정통계량의 귀무분포를 비교하며, 실제 자료에 적용하여 유의 유전자를 탐색한다. In the analysis of microarray data with a small number of arrays, the most important task is the detection of differentially expressed genes by a significance test. For this purpose, one needs to construct a null distribution based on a large number of genes and one of the best way for constructing the null distribution for a small number of arrays is by means of permutation methods. In this paper we propose simple test statistics and permutation methods that are appropriate in constructing the null distribution. In a simulation study, we compare the null distributions generated by the proposed test statistics and permutation methods with the previous ones. With an example microarray data, differentially expressed genes are determined by applying these methods.

보령댐 가뭄 대응을 위한 수자원시스템 모델 적용 사례

이주형,김연주,김기주,Lee, Ju-Hyeong,Kim, Yeon-Ju,Kim, Gi-Ju 한국수자원학회 2022 물과 미래(한국수자원학회지) Vol.55 No.9

전방십자인대 손상으로 인한 슬관절 불안정성에 따른 경골 골단 해면골 미세구조 변화 : 내방과 외방에서의 해면골 미세구조 패턴 변화

이주형,전경진,김한성,임도형,Lee, Joo-Hyung,Chun, Keyoung-Jin,Kim, Han-Sung,Lim, Do-Hyung 대한의용생체공학회 2012 의공학회지 Vol.33 No.2

Knee joint instability by anterior cruciate ligament(ACL) rupture is allowing the abnormal loading condition at the tibial epiphysis locally, resulting in producing locally different bone bruise. The study examined difference between local alteration patterns of trabecular bone microarchitecture at medial and lateral parts of the tibial epiphysis by ACL rupture. Fourteen SD rats were divided into Control(CON; n = 7) and Anterior Cruciate Ligament Transection(ACLT; n = 7) groups. The tibial joints were then scanned by in vivo ${\mu}$-CT at 0, 4, and 8 weeks post-surgery. The results showed that alteration pattern on trabecular bone microarchitecture at medial part was significantly higher than that at lateral part of the tibial epiphysis in ACLT group from 0 to 8 weeks(P < 0.05). Tb.Th and Tb.Sp distributions were well corresponded with differences between aforementioned trabecular bone microarchitectural alteration pattens at medial and lateral parts of the tibial epiphysis in ACLT group from 0 to 8 weeks(P < 0.05). These findings suggest that the alteration patterns of trabecular bone microarchitecture should be locally and periodically considered, particularly with respect to the prediction of bone fracture risk by ACL rupture. Improved understanding of the alteration patterns at medial and lateral trabecular bone microarchitectures at the tibial epiphysis may assist in developing more targeted treatment interventions for knee joint instability secondary to ACL rupture.

정규화 포락선 검파기와 얼리-레이트 필터를 적용한 새로운 홉 타이밍 예측기

이주형,Lee, Ju-Hyung 한국통신학회 2007 韓國通信學會論文誌 Vol.32 No.4C

본 논문에서 정규화 포락선 검파 기법(NED ; Normalized Envelop Detection)과 얼리-레이트 필터(ELF ; Early-Late Filter)가 적용된 새로운 홉 타이밍 예측기를 제안하였다. 제안한 구조의 성능 검증을 위해 컴퓨터 시뮬레이션으로 제안한 시스템과 기존 시스템의 동기 오차 측정 결과를 비교하였다. 시뮬레이션 결과를 통해서 부분 대역 재밍 환경에서 제안 구조가 기존 구조보다 정확하게 동기오차를 예측하는 것을 확인할 수 있었으며, 이러한 경향은 $E_b/N_j$와 재밍점유대역비(rho)가 낮을수록 더욱 뚜렷하였다. In this paper, the hop-timing estimator, which NED and ELF are adopted to, has been proposed. The estimation performance of the proposed scheme and the conventional scheme is compared through computer simulations. The simulation results show that the new system has less hop-timing error than the conventional system in partial band noise jamming channel. The lover Eb/Nj and ratio of jamming bandwidth(rho) we, the bigger performance enhancement of the proposed system is.