Sb 계면활성제에 의한 p-GaN 박막의 홀농도 향상

김자연,박성주,문영부,권민기,Kim, J.Y.,Park, S.J.,Moon, Y.B.,Kwon, M.K. 한국진공학회 2011 Applied Science and Convergence Technology Vol.20 No.4

본 논문은 고휘도 발광소자의 특성을 높이기 위한 p-GaN 박의 홀농도 향상을 연구하였다. 우리는 metal organic chemical vapor deposition 법을 이용하여 Antimony (Sb)가 p-GaN의 홀농도 향상에 도움을 주는 것을 확인하였다. Atomic force microscope 측정을 통해 Sb가 계면활성제처럼 역할을 함으로써 p-GaN의 2차원 성장이 촉진됨을 알 수 있었다. 또한 X-ray diffraction 결과 [002] 면과 [102] 면의 반폭치가 Sb 도핑과 함께 줄어드는 것을 통해 Edge과 Screw 전위의 감소와 photoluminescence 결과에서 450~500 nm 청색 파장 영역에서 발광의 세기가 현저히 줄어드는 것으로 보아 질소 공극이 감소되는 것이 홀농도 향상의 주된 원임임을 알 수 있었다. Trimethylantimony가 10 ${\mu}mol/min$일 때 홀농도는 최대가 되었고 그때 홀농도는 $5.4{\times}10^{17}cm^{-3}$이었다. The role and effect of Sb surfactant on structure and properties of p type gallium nitride (GaN) epilayers have been investigated. It was found that there was a increase of hole concentration with Sb surfactant, compared to typical Mg-doped p-GaN. The structural and optical quality of p-GaN epilayers were accessed by x-ray diffraction, photoluminescence and atomic force microscope measurements. The results clearly show that the increase in hole concentration with Sb surfactant can be resulted from decrease in the dislocations and nitrogen point defects.

저심도 철도 시스템에서의 열차 및 차량의 이동하중에 의한 동적거동에 관한 연구

김자연,사공명,조국환,Kim. Ja-Yeon,Sagong. Myung,Cho. Kook-Hwan 한국방재학회 2013 한국방재학회논문집 Vol.13 No.4

최근 저심도 경량전철 시스템 사업이 대두됨에 따라, 열차 및 차량 이동하중에 따른 동적거동에 관한 연구의 필요성이 대두되고 있다. 본 연구에서는 유한요소 프로그램인 LUSAS 을 이용하여 열차와 차량이 운행하고 있을 때 지표면에서의 진동 가속도값을 산정하였다. 이 수치를 사용하여 건물에 대한 진동 사용성을 평가하였다. 차량과 열차의 이동하중으로 발생하는 진동 가속도는 1 m 심도일 때 0.0042 g, 3 m 심도일 때 0.0037 g, 5 m 심도일 때 0.00048 g로써 건물의 최소 기준치인 0.102 g에 비해 매우 작은 것으로 나타났다. 이에 심도에 따른 열차주행 진동영향은 매우 적은 것으로 사료된다. As a low depth light rail system is getting issued recently, It is important to understand dynamic effects from train and car moving loads. In this study, Numerical analyses were performed to evaluate ground surface vibrations from train and car operations on low depth track system using LUSAS which is finite-element analysis program. The dynamic serviceability of a building is evaluated using analysis results. The evaluated vibratory acceleration under the moving loads of car and train at the depth of 1.0 m is 0.0042 g, 3.0 m is 0.0037 g and the value of 0.00048 g at the depth of 5.0 m. The research results show that low depth train system can be used with low vibration effect by comparing with the maximum allowable criteria of 0.102 g.

마이크로 LED 핵심 기술과 응용

김자연,사기동,Kim, Ja-Yeon,Sa, Gi-Dong 한국정보디스플레이학회 2018 인포메이션 디스플레이 Vol.19 No.1

비계공사 안전기준 개정에 따른 현장적용 실태에 관한 연구

김자연,조윤희,Kim, Ja Yeon,Cho, Youn Hee 한국안전학회 2020 한국안전학회지 Vol.35 No.4

Scaffolding works are demolished after this structure is completed, and safety accidents often occur because they are installed differently from legal standards or frequently change during work. Therefore, in order to strengthen the safety of scaffolding, the Ministry of Land, Infrastructure and Transport required a need for design standards for temporary facilities that can systematically prevent and solve large-scale safety accidents that are repeatedly increasing during temporary construction. It has been enacted, and some contents have been revised for the past three years. However, construction site personnel do not know or know the revised matters, but often install scaffolding by the installer's experience rather than complying with relevant laws and regulations. It is the situation that the ground strength test of the foundation ground for the load applied to the floor of the column is omitted in most sites. Therefore, this study grasped the actual situation on the degree of recognition of the revised laws and regulations of the construction site and the foundation-based treatment of the floor working load of the scaffolding column, and derived problems. In addition, we intend to provide reference materials for the endurance test according to the ground conditions to small-scale small sites where it is difficult to conduct the test by carrying out the endurance test of the scaffolding ground according to the revised standards.

고효율 LED 개발 기술

김자연,Kim, Ja-Yeon 한국전기전자재료학회 2016 전기전자재료 Vol.29 No.3

결측되었거나 구간중도절단된 중간사건을 가진 준경쟁적위험 자료에 대한 가산위험모형

김자연,김진흠,Kim, Jayoun,Kim, Jinheum 한국통계학회 2017 응용통계연구 Vol.30 No.4

본 논문에서는 사망과 같은 종말사건의 발생 유무는 알고 있지만 치매 발병과 같은 중간사건이 구간중도절단 되었거나 연구 기간 도중에 추적이 끊겨 결측된 준경쟁적위험 자료에 대해 다중상태모형을 적용하여 모수를 추정하는 방법을 제안하였다. 이를 위해 본 논문에서는 상태 간의 전이강도는 로그정규 프레일티를 랜덤효과로 가진 Lin과 Ying(1994)의 가산위험모형을 따른다고 가정하였다. 다섯 가지 상태를 가진 다중상태모형에서 가능한 여섯 가지 경로별로 조건부우도를 정의하였고, 주변우도를 구하기 위해 조정중요표본추출법을 적용하였으며 반복유사뉴튼 방법으로 최적해를 구하였다. 소표본 모의실험을 통해 모수의 95% 신뢰구간 포함률이 명목값에 얼마나 가까운지 살펴보았으며, 제안한 모형을 Persones $Ag{\acute{e}}es$ Quid (PAQUID) 자료 (Helmer 등, 2001)에 적용하고 그 결과를 해석하였다. We propose a multi-state model to analyze semi-competing risks data with interval-censored or missing intermediate events. This model is an extension of the three states of the illness-death model: healthy, disease, and dead. The 'diseased' state can be considered as the intermediate event. Two more states are added into the illness-death model to incorporate the missing events, which are caused by a loss of follow-up before the end of a study. One of them is a state of the lost-to-follow-up (LTF), and the other is an unobservable state that represents an intermediate event experienced after the occurrence of LTF. Given covariates, we employ the Lin and Ying additive hazards model with log-normal frailty and construct a conditional likelihood to estimate transition intensities between states in the multi-state model. A marginalization of the full likelihood is completed using adaptive importance sampling, and the optimal solution of the regression parameters is achieved through an iterative quasi-Newton algorithm. Simulation studies are performed to investigate the finite-sample performance of the proposed estimation method in terms of empirical coverage probability of true regression parameters. Our proposed method is also illustrated with a dataset adapted from Helmer et al. (2001).

국도하부 풍화대구간 패널공법 적용구간 수치해석 안정성 해석 연구

김자연(Kim, Ja-Yeon),엄기영(Eum, Ki-Young),김효영(Kim, Hyo-Young),김지현(Kim, Ji-Hyeon),윤태영(Yoon, Tae-Young) 대한토목학회 2021 대한토목학회 학술대회 Vol.2021 No.10

한국 폐경여성에서 저밀도 지단백 수용체 관계 단백 5 유전자의 단일염기유전자다형성과 골량 사이의 연관성에 관한 연구

김자연 ( Ja Yeun Kim ),이동옥 ( Dong Ock Lee ),지병철 ( Byung Chul Jee ),서창석 ( Chang Suk Suh ),김석현 ( Seok Hyun Kim ),최영민 ( Young Min Choi ),문신용 ( Shin Yong Moon ),김정구 ( Jung Gu Kim ) 대한폐경학회 2007 대한폐경학회지 Vol.13 No.1

연구목적: 한국 폐경여성에서 저밀도 지단백 수용체 관계 단백 5 (low density lipoprotein receptor-related proteins 5; LRP5) 유전자 다형성양상과 골밀도사이에 연관성이 있는가를 알아보고자 하였다. 연구재료 및 방법: 자연폐경여성 261명에서 LRP5 유전자 내 A314G, T2268C, GInv17-30A 다형성 양상을 제한절편길이다형성 (restriction fragment length polymorphism; RFLP)으로 분석하고 혈청 CrossLaps (CTX), osteocalcin, bone alkaline phosphatase (BAP), calcitonin, 부갑상선호르몬 (parathyroid hormone; PTH), 칼슘, 인 농도를 각각 효소면역법, 면역측정법, 원자흡광법으로, 요추 및 대퇴 근위부에서의 골밀도를 이중에너지 엑스레이 흡수계측기 (DXA)로 측정하였다. 결 과: LRP 유전자 내 A314G, T2268C 다형성양상에 의한 유전자형은 AA 83.1%, AG 14.9%, GG 1.9%, CC 50.2%, CT 43.3%, TT 6.5%이었으며, GInv17-30A의 경우 GG 76.2%, GA 20.7%, AA 3.1%이었다. 이러한 다형성양상에 의한 단일 유전자형 또는 haplotype 유전자형에 따른 요추 및 근위 대퇴부에서의 골밀도에서는 차이가 없었다. 혈청 PTH 농도가 A314G 다형성의 GG 유전자형에서 AA 유전자형 또는 AG 유전자형 보다 높다는 것 이외에 다른 단일 유전자형 또는 haplotype 유전자형과 골의 생화학적 인자 농도사이에는 연관성이 없었다. 결 론: 한국 자연폐경 여성에서 LRP5 유전자 내 A314G, T2268C 및 GInv17-30A 다형성양상은 골밀도에 영향을 주지 않는다. Objectives: To investigate the relationship between low density lipoprotein receptor-related protein 5 (LRP5) gene polymorphisms and bone mineral density (BMD) in postmenopausal Korean women. Methods: The A314G, T2268C, and G Inv17-30 A polymorphisms in LRP5 gene were analyzed by restriction fragment length polymorphism in 261 postmenopausal Korean women. Serum CrossLaps (CTX), bone alkaline phosphatase (BAP), osteocalcin, parathyroid hormone (PTH), calcitonin, calcium, and phosphorus levels were measured by enzyme linked immunosorbent assay, immunoassay and by atomic absorptiometry respectively. The BMD at the lumbar spine and proximal femur was determined by dual energy X-ray absorptiometry. Results: The distributions of A314G, T2268C, and G Inv17-30 A polymorphisms in LRP5 gene were as follows; AA 83.1%, AG 14.9%, GG 1.9%, CC 50.2%, CT 43.3%, TT 6.5%, GG 76.2%, GA 20.7%, and AA 3.1%. No significant differences in adjusted BMD of lumbar spine and femoral neck were noted among single or haplotype genotypes of LRP5 gene polymorphisms. No statistical significances in associations between serum levels of bone biochemical markers except PTH and single or haplotype genotypes were observed. Serum PTH levels in women with GG genotype of A314G polymorphism was significantly higher than those in women with AA or AG genotype. Conclusion: The A314G, T2268C, and G Inv17-30 A polymorphisms in LRP5 gene do not affect BMD at the lumbar spine and proximal femur in postmenopausal Korean women.

질화갈륨 기반 다각형 발광다이오드의 광추출 효율 향상

김자연 ( Ja-yeon Kim ),조유현 ( Yu-hyun Cho ),박현선 ( Hyun-sun Park ),김두형 ( Doo-hyung Kim ),김민우 ( Min-woo Kim ),박종락 ( Jong-rak Park ),권민기 ( Min-ki Kwon ) 조선대학교 공학기술연구원 2016 공학기술논문지 Vol.9 No.2

GaN based LEDs have gradually replaced traditional light sources in various applications including backlight display units, traffic signals, automotive lighting, architectural lighting, and general lighting. However, improvements to the external quantum efficiency (EQE) are required for these various application. The EQE of LED is correlated to the internal quantum efficiency (IQE) and the light extraction efficiency (LEE). Although the IQE of GaN-based LEDs has reached more than 80% due to the rapid development of growth techniques for high-quality epi-layers, the LEE of the LEDs is still low because of the large refractive index difference between the GaN (nGaN=2.5) and air (nair=1). Herein, various polygon shaped(triangle, parallelogram, pentagon, hexagon, circle shaped) LEDs are compared with those of a traditional quadrangular LED to enhance LEE of LED. To estimate the enhancement of LEE, we simulated the various shaped LEDs with ray-trace simulation tools. In addition, to measure the total amount of photons emitted from LEDs in all directions, the various polygon LEDs were encapsulated and packaged with To-can. Their optical output power of polygonal shaped LED is significantly improved, compared to that of traditional quadrangular LED due to increase in LEE along to lateral direction.

국내 하수 시료로부터 검측된 SARS-CoV-2 정량을 실험실별 비교하는 방법과 COVID-19 발생 예측 연구

김자연(Jayun Kim),정우식(Woosil Jung),김수빈(Subin Kim),김윤지(Yoon-Ji Kim),엄재구(Jae-Ku Oem),로이데바난다(Debananda Roy),박준홍(Joonhong park) 대한환경공학회 2022 대한환경공학회 학술발표논문집 Vol.2022 No.11