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.

스펙트럼 상관관계를 이용한 ATSC 지상파 DTV의 고속 주파수 동기 방법

이주형,송현근,남완주,김재명,김승원,Lee Joo-Hyung,Song Hyun-Keun,Nam Wan-Ju,Kim Jae-Moung,Kim Seung-Won 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.9a

본 논문에서는 ATSC 지상파 DTV 시스템에서 스펙트럼 상관관계를 이용한 주파수 동기 방법을 제안한다. 파일럿 신호를 이용하는 기존 알고리즘은 다중경로와 이동수신 환경에 의해 파일럿 주변의 스펙트럼 왜곡이 심하면 주파수 옵셋 추정 오류가 발생한다. 제안하는 알고리즘은 파일럿을 사용하지 않고 기준 스펙트럼과 수신된 스펙트럼 사이의 상관관계를 이용하여 주파수 동기를 획득하기 때문에 기존의 동기 방식에 비해 빠르고 정확하게 주파수 동기를 획득할 수 있다. 또한 파일럿을 사용하지 않는 새로운 ATSC 주파수 동기 방식을 제시한다. This paper proposes the method of frequency synchronization using the spectrum correlation in ATSC terrestrial DTV system. If the spectrum around pilot is severely distorted by multipath or mobile reception environment, the conventional algorithm using the pilot signal makes the estimation error of the frequency offset. Because the proposed algorithm acquires frequency synchronization using the correlation between the received specalm and the standard spectrum without the use of pilot, the proposed method can acquire frequency synchronization faster and more accurate than conventional algorithm. And this paper proposes new method for ATSC frequency synchronization without the use of pilot.

노후 콘크리트 구조물의 실용적 유지관리를 위한 콘크리트 구조물 안전진단 지침 분석

이주형,조재열,Lee, Joo-Hyung,Cho, Jae-Yeol 한국토지주택공사 토지주택연구원 2020 LHI journal of land, housing, and urban affairs Vol.11 No.3

In South Korea, problems caused by material deterioration of time-worn concrete structures have been increased recently. Because severe material deterioration could damage the structure's safety, it's important to evaluate the old structure's condition and structural capacity regularly to keep its proper performance. The safety evaluation of concrete structures has been initiated and performed periodically since 1995 according to a guideline in accordance with a law in Korea. The guideline prescribes the evaluation types, intervals and methods of the target structure. A lot of cost and labor have been invested every year to carry out the regular safety evaluation. However, it's not clear that the current manual could inspect the old structure's condition and assess the structural capacity precisely. Thus, the verification study initiated to figure out the Korean safety evaluation manual's practicalness. First, the Korean manual was analyzed and then compared with that of other countries for concrete bridges which are representative concrete structure. After that, the previously written evaluation reports were collected and analyzed to find out how the safety evaluation has been carried out. Based on the study results, the parts requiring verification of the manual were drawn. A research program is in progress in order to verify the parts by performing tests with actual structural members from decommissioned concrete bridges.

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.

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.

콘크리트 내부 고해상도 이미지 획득을 위한 Near-field UWB SAR 알고리즘

이주형 ( Lee Joo-hyung ),조창빈 ( Joh Chang Bin ) 한국구조물진단유지관리공학회 2024 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.28 No.1

고강도 철근 최적 활용을 위한 휨 및 사용성 최적 설계조건 검토

이주형(Lee, Joo Hyung),김경민(Kim, Kyung Min),조재열(Cho, Jae-Yeol) 대한토목학회 2016 대한토목학회 학술대회 Vol.2016 No.10

채점규칙 변경 후 기계체조 마루운동의 기술 동향 분석

이주형(Lee, Joo-Hyung),황용재(Hwang, Yong-Jae) 한국체육과학회 2022 한국체육과학회지 Vol.31 No.5

The purpose of this study analyzed the contents of the performance of eight people in each of the middle, high, university, and general divisions who participated in the final match of the floor exercise at the 77th National Classification Championships in 2022. First, Korean players prefer lower D difficulty, but in order to compete with the top players, they need to acquire E difficulty and F difficulty skills, and all players have enough potential with 2.0 EG scores, but they need to adapt physical preparation and lower difficulty skills to develop them. Second, EGI is considered to be a basic and stable element. Since it must be performed, it is judged that it would be good to select a non-acrobatic element that can be performed stably or can reduce the deduction. Third, it is judged that it is necessary to carefully select a skill that can be performed with connection skill and a single skill as a skill that can satisfy essential elements while increasing the difficulty score in EGII by deleting the limit on connection addition. Fourth, EG III has relatively stable skills as it can land while looking at the mat, and it is judged that practice is necessary to select a skill that can develop to a high level even if a low level of difficulty is acquired. Fifth, the limit on connection points is deleted, so all connection points can be obtained within 10 skills, and it is considered advantageous to connect as many high-level skills as possible, and it is considered that better performance can be expected only when connecting skills with D difficulty or higher with 0.2 points.

철봉 KOVACS 동작의 운동학적 분석

이주형(Lee, Joo-Hyung),김종수(Kim, Jong-Soo) 한국체육과학회 2011 한국체육과학회지 Vol.20 No.5

The purpose of this paper was to investigate the effect from rotations and air-flights caused by kinematic differences according to phases of Kovacs-performance in high bar. For this study, four national man-gymnasts were selected and two Kovacs -performances performed from the first and final game to choose members of Olympic gymnastic team were analyzed. Two digital video cameras(Sony, PD-l50) were used to used to capture images for 3D analysis and Kwon3D 3.1 was used to process data and analyze for factors. The results were as follows: First, a horizontal displacement of the third phase increased, but a vertical displacement decreased because the spent-time of the 1st trial was longer than the 2nd trial during the second phase. That made a CoM-height of body low at the 4th event(at top). In comparison with the 2nd trial, a low velocity and a small scapular angle from the 1st trial at the 3rd event(at release) could cause an an unstable landing without sufficient air-rotation force. Second, a vertical velocity of the 3rd event(at release) and the 4th event(at top) from the 2nd trial was faster than the 1st trial during the third phase. That made body quickly upward and gave them a stable and high position for putting their hand to connect a next technique and reducing factors of penalty count. The vertical velocity of the 4th event(at top) and the 3rd event(at release) from the 2nd trial were faster than the 1st trial during the third phase. That made body quickly upward and gave them a stable and high position for putting their hand to connect a next technique and reducing factors of penalty count. Third, the hip joint angle of the 4th event(at top) from the 2nd trial was greater than the 1st trial. The reason was that the rapid rotation force acquired from a whip swing increasing the moment of inertia not to rotate excessively at putting their hand to the high bar.

휨실험을 통한 700MPa급 고강도철근 적용 RC보의 연성지수 및 사용성 평가

이주형(Lee, Joo-Hyung),안준용(An, Jun Long),조재열(Cho, Jae-Yeol) 한국콘크리트학회 2018 한국콘크리트학회 학술대회 논문집 Vol.30 No.2