Change of photoluminescence property of ferroelectric compounds with the gamma-ray irradiation

Lim, Junhwi,Lee, Y.S.,Yang, Sun A,Choi, Gi Ppeum,Bu, Sang Don Elsevier 2017 Journal of luminescence Vol.188 No.-

<P><B>Abstract</B></P> <P>We investigated the emission properties of Bi<SUB>3.25</SUB>La<SUB>0.75</SUB>Ti<SUB>3</SUB>O<SUB>12</SUB> polycrystals and (K<SUB>0.5</SUB>Na<SUB>0.5</SUB>)(Mn<SUB>0.005</SUB>Nb<SUB>0.995</SUB>)O<SUB>3</SUB> thin films with strong gamma (γ)-ray irradiation by using temperature dependent photoluminescence spectroscopy. At the lowest temperatures, sizable visible emissions were identified for the γ-ray irradiated samples as well as un-irradiated ones. In both kinds of compounds, the visible emission intensity tended to be increased without changing the spectral shape, as the γ-ray dose increased. This indicates that the γ-ray irradiation should increase all kinds of already-existing defects evenly, without preferring the formation of some particular type of defect.</P>

Near-Infrared to Visible Upconversion Emission in Er3+ and Yb3+ Codoped BaHfO3

Junhwi Lim,Donghee Kim,Y. S. Lee 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.7

We report on the upconversion (UC) emission property of Er3+ and Yb3+ codoped BaHfO3 polycrystals. We observed the green ( 540 nm) and the red ( 660 nm) UC emissions in Er3+ in the host material BaHfO3 with 980-nm near-infrared excitation. These emissions exhibited strong temperature evolutions. Interestingly, the UC emissions in Er3+ were found to be controlled with the Yb3+ doping. In Er3+ and Yb3+ codoped BaHfO3, the intensity of the red UC emission increased dramatically while that of the green UC emission showed a non-monotonic temperature dependence. These results suggested that the UC emission process in the Er3+ ion in BaHfO3 should be temperature-sensitive.

Optical Evidence for the Effect of Gamma-ray Irradiation on Ferroelectric Pb(Zr0.52Ti0.48)O3 Thin Films

Junhwi Lim,Y. S. Lee,Sun A Yang,Sang Don Bu 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.11

We investigated the visible emission property of Pb(Zr,Ti)O3 (PZT) thin films irradiated with gammy-ray ( -ray) irradiated at various total doses up to 1000 kGy. The PZT thin films were prepared on Pt/Ti/SiO2/Si substrates by using a sol-gel method with a spin-coating process. The visible emission was found to emerge near 550 nm upon -ray irradiation, and the intensity of the emission increased with increasing dose. The spectrum of the -ray-induced emission was quite narrow, which was quite different from that due to normal defects such as oxygen vacancies. We suggest that the -ray irradiation generates inside the PZT films a specific type of defect state that can be detected by using low-temperature photoluminescence spectroscopy.

전기철도 병렬급전을 위한 루프전류 저감 방안 연구

임준휘(Junhwi Lim),최규형(Kyuhyung Choi),장우진(Woojin Jang) 한국철도학회 2012 한국철도학회 학술발표대회논문집 Vol.2012 No.10

우리나라 전기철도는 편단 급전방식을 표준으로 하고 있다. 편단 급전방식은 변전소 사이에 구분소를 두어 절연구분장치를 설치해야 하고, 열차가 통과할 때 주 회로 차단기를 차단한 상태로 통과하여야 하는 문제가 있다. 병렬 급전방식은 이러한 문제점을 개선하고 전압강하를 경감, 최대전력수요 억제 등의 전력공급 측면에서 유리하다. 그러나 인접 변전소간의 상차각으로 인하여 루프전류가 발생하기 때문에 변전소간 위상 차가 3도 이내일 때로 제한되고 있어 실질적인 적용이 어려운 실정이다. 본 논문에서는 병렬급전 시 루프전류를 감소시키기 위하여 위상보상 장치를 적용하는 방안을 PSIM을 이용해 연구하였다. 이상과 같은 검토를 통하여 전기철도 병렬 급전을 위한 하나의 가능성을 제시하였다. Korean railway feeding system is alternating current Auto-Transformer system called AT which adopts the single power feeding method as the standard. The single power feeding method has some disadvantages such as the necessity of neutral section. and of breaking MCB with loads passing. The parallel power feeding method can resolve those those difficulties and also has advantages in terms of power efficiency by reducing maximum demand power and voltage drops. However, circulating current occurs between substations when voltage phase is different. That is why it is uneasy to apply parallel power feeding under voltage phase differences over3 degrees. This study suggests applying phase control device to reduce the circulating current simulated by PSIM. Through this, a possibility of the parallel power feeding is suggested.

디지털 트윈 기반 농업용 사회기반시설물 정보 관리

조준휘 ( Junhwi Cho ),김채현 ( Chaehyeon Kim ),체리로즈고즈 ( Cherry Rose Godes ),임경재 ( Kyoung Jae Lim ),연재흠 ( Jaeheum Yeon ) 한국농공학회 2023 한국농공학회 학술대회초록집 Vol.2023 No.0

농업 지역의 지리 정보는 자원 관리와 농업 생산성에 있어 매우 중요하여 지리 정보 시스템(Geographic Information Systems, GIS)이 활용되고 있다. GIS를 활용하여 토양 조건, 침식, 기저유량 등 다양한 요인을 관리하고 예측이 가능하다. 그러나 기존 GIS는 넓은 지역의 지형, 수리 구조물 등 세밀하게 표현하는 데 한계가 존재하며, 수리 구조물과 같은 농업용 사회기반시설의 크기, 유지관리 이력 등의 정보 표현에 한계가 존재한다. 따라서, 본 연구는 농업용 사회기반시설의 효율적인 관리와 분석을 위해 3차원 모델에 다양한 정보가 포함된 Building Information Model(BIM)의 개념과 Web기반 GIS를 융합하여 새로운 형태의 사회기반시설물 정보관리 방법을 제안한다. 강원도 원주시의 흥업 저수지 수혜 지역을 대상으로, 현장 조사와 UAVs 촬영을 통해 수집된 데이터를 바탕으로 3차원 모델을 생성하고, 이를 Web 기반 지리 공간 시각화 플랫폼인 Cesium을 이용하여 지도상 실제 위치에 시각화하였다. 또한, 3차원 모델과 현장 조사를 통하여 얻어진 각 모델의 세부 정보를 입력하였다. 즉, 특정 모델을 선택하면 해당 모델의 상세 정보가 팝업창을 통해 표시되며, 직관적인 유지관리 정보관리가 가능하도록 하였다. 이러한 방법은 기존 GIS에서는 할 수 없었던 사회기반시설물 이력관리를 가능하게 하도록 하였다. 즉, 수자원 조절 및 관리에 중요한 역할을 하는 수리 시설물의 관리와 유지 보수 이력을 직관적으로 확인하고 분석할 수 있는 실질적인 관리 도구를 제공하며, 사회기반시설물과 수자원 관리 분야의 복잡한 패턴 분석에 체계적으로 기여하며, 현장 방문 없이 실내 환경에서 각 시설물의 정보를 분석과 비교를 가능하게 함으로써 향후 농업과 수자원 관리 분야의 연구와 실용적인 응용에 중요한 발판을 제공할 것으로 기대된다.

CLASSIFICATION OF GENERALIZED PAPER FOLDING SEQUENCES

Yun, Junghee,Lim, Junhwi,Hahm, Nahmwoo The Honam Mathematical Society 2013 호남수학학술지 Vol.35 No.3

Generalized paper folding sequences $X^n_p$ and $(X_pY_q)^n$ where $X,Y{\in}\{R,L,U,D\}$, and $n,p,q{\in}\mathbb{N}$, and with $p,q{\geq}2$ are classified in this paper. We show that all generalized paper folding sequences $X^n_p$ are classified into one type if we classify generalize paper folding sequences along with the numbers of downwards and upwards. In addition, we investigate the numbers of downwards and upwards in $(X_pY_q)^n$ and prove that all generalized paper folding sequences $(X_pY_q)^n$ are classified into two types.

Study on the emission property of YBO3 with co-doping of Ce and Gd ions

Jang, Soyeong,Lim, Junhwi,Lee, Y. S. 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. No.

<P>We investigated the co-doping effect of Ce3+ and Gd3+ ions on the visible emission in vaterite-type orthoborate YBO3. By using photoluminescence and photoluminescence excitation spectroscopy, we found that the co-doping of the Gd3+ ions increased the violet-blue emission of the Ce ions significantly. In basis of the optical spectroscopic data, we discussed our results in terms of the energy transfer between Ce3+ and Gd3+ ions.</P>

Non-contact strain measurement for laterally loaded steel plate using LiDAR point cloud displacement data

Jo, Hyeon Cheol,Kim, Junhwi,Lee, Kangwon,Sohn, Hong-Gyoo,Lim, Yun Mook Elsevier 2018 Sensors and actuators. A Physical Vol.283 No.-

<P><B>Abstract</B></P> <P>Strain measurement in structures provides key information for structural health monitoring (SHM); therefore, researchers have developed various sensing methods for measuring strain in structures. Recently, light detection and ranging (LiDAR) has been studied as a non-contact strain measurement method (NCSMM). LiDAR is a technology for remotely acquiring high precision three-dimensional (3D) coordinate information for a terrain or a structure using a 3D laser scanning system. In recent years, LiDAR applications have expanded to include systems used to monitor structural behavior. Using this technology, structural behavior can be monitored without directly attaching sensors to the surfaces of target structures. It is advantageous to use non-contact 3D laser scanning measuring methods to obtain the 3D coordinates of a specific region or the shape of the target structures. LiDAR technology does not have some of the limitations associated with existing types of measuring sensors used for SHM. Therefore, in this study, we will present a method for estimating deformation and strains for a whole structure by measuring discretized 3D coordinate data of the target structure obtained from the LiDAR. The 3D coordinate data was revised using a regression analysis, and the strain was estimated by developing a finite element model based on the corrected 3D coordinate information. The experimental structural model is a steel plate, which is the primary material used for the outer wall construction of LNG storage tanks. The estimated strains will be compared to the measured values from real strain gauges, and the applicability of the proposed strain measurement method to structural behavior monitoring will be verified.</P> <P><B>Highlights</B></P> <P> <UL> <LI> LiDAR was used to measure the overall deformation of a steel walled structure. </LI> <LI> Strain measurement model represented shapes using a high order polynomial function. </LI> <LI> LiDAR results were verified in comparison with measured strain gauge data. </LI> </UL> </P>

도시철도 기관사 직무부하 평가

임승진(Seung Jim Lim),김남곤(Nam Gon Kim),전기현(Gi Hyun Jeon),박준휘(Junhwi Park),정홍인(Hong-In Cheng) 대한인간공학회 2018 대한인간공학회 학술대회논문집 Vol.2018 No.11

Effect of the Gamma-Ray Irradiation on the Electric and Optical Properties of SrTiO3 Single Crystals

Y. S. Lee,Junhwi Lim,E. Y. Kim,Sang Don Bu 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.10

We investigated the visible emission property of SrTiO3 (STO) single crystals irradiated with gammy-ray ( -ray) at various total doses up to 900 kGy. The electric and optical absorption properties of the irradiated STO samples were hardly changed with the -ray irradiation, compared with those of un-irradiated STO. In contrast, the visible emission near 550 nm increased with the -ray dose increasing. While the development of the visible emission was indicative of the increase of oxygen vacancies inside STO by the -ray irradiation, the newly generated oxygen vacancies were not significantly harmful to the electric and optical properties of STO. We concluded that the STO single crystal should have a good tolerance against the damage by the -ray irradiation.