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Electron Spin Resonance of Atoms on a Surface
Yujeong Bae 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
Combining the spin-polarized scanning tunneling microscopy (STM) with electron spin resonance (ESR) [1] enables us to investigate spin states of single atoms and inter-atomic coupling with unprecedented spatial and energy resolution. Employing ESR-STM, we have characterized the magnetic dipolar [2], exchange [3,4], and even hyperfine interactions [5] of atoms on a surface. Such ESR experiments in STM have been performed measuring the ESR signals of atoms positioned directly under the tip. Beyond this single atom level, we present a new approach to control two electron spins simultaneously and independently. We found that it is possible to remotely control a spin, which is not directly under the tip, if we place a single-atom magnet next to it. This way to control the remote spin allowed us to control two spins in weakly coupled atoms. Our development widens the approaches to the multi-spin control in tailored spin structures on a surface.
이유정(Yujeong Lee),김민주(Minju Kim),정소미(Somi Jung),나원배(Won-Bae Na) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.10
본 연구는 부산 가덕도 인근의 유의파와 태풍의 극한 조건에서 방갈로 인공어초의 안정성을 평가하였다. 모리슨 방정식을 이용하여 인공어초의 안정성(활동, 전도)을 평가했다. 모리슨 방정식의 변수인 항력계수는 총 7개의 유향 조건을 고려하여 ANSYS-CFX로 계산하였고, 정밀한 유동장과 격자 크기를 결정하기 위해 독립성 시험을 수행하였다. 흐름의 투과성이 높은 0°에서 상대적으로 다른 유향에 비해 높은 안전율을 보였으나, 유의파 조건에서는 활동에서, 태풍 조건에서는 활동과 전도에서 모두 불안정하였다. This study evaluated the stability of an bangalow-typed artificial reef (AR) under significant wave and extreme condition (e.g., typhoon) near Gadeokdo in Busan. Using the Morison equation, we evaluated the stability of the AR and examined if the AR secures the safety from sliding and overturning. The drag coefficients, used in the Morison equation, were calculated as ANSYS-CFX by considering seven flow directions (0°, 15°, 30°, 45°, 60°, 75°, and 90°). To precise the numerical results, independence tests were conducted to determine the appropriate flow field and mesh size. In overall, the safety factors are better at the incident angle of 0° (or 180°) than the other angles. However, it was shown that the better case is neither stable for sliding under the significant wave and nor stable for sliding and overturning under the typhoon conditions.
이유정(Yujeong Lee),정소미(Somi Jung),나원배(Won-Bae Na) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.10
물의 흐름은 자유낙하 하는 물체를 이동시키고 결국에는 해저에 도달하는 위치를 결정 짓는 데 영향을 준다. 본 연구에서는 수평 유동의 영향을 받으며 자유낙하 하는 정육면체 모델의 이동 거리를 추정한다. 이를 위해, 정육면체 모델의 이동 거리를 추정하는 모형실험과 수치해석을 수행하였다. 방법론의 검증을 위해 실험 결과와 수치해석 결과를 비교하였고, 약 5% 이내의 오차가 발견되었다. 연구 결과는 물속에서 중력과 수평 유동의 영향을 받는 고체의 이동거리 또는 낙하 거리를 예측하는 데 사용할 수 있다. It is important to consider horizontal water flow because it makes a free-falling body move horizontally and eventually determines its arriving location in the seabed. Therefore, we estimated the movement distance of a free-falling cube model in the presence of horizontal water flow. Experimental and numerical works have been performed to estimate the movement distance of the cube model. Those eresults were compared for the verification of the methodologies, and the errors were found within 5%. As a result, the results can be used to predict either of movement distance or falling distance of underwater moving solids subjected to gravity and horizontal water flow.
배창한(Changhan Bae),장예지(Yeji Jang),최진영(Jinyoung Choi),전재우(Jaewoo Jeon),한기돈(Gidon Han),이유정(Yujeong Lee),이수진(Sujin Lee),주나영(Nayeong Joo),하주형(Juhyeong Ha),이지환 (Jihwan Lee),백창대(Changdae Baek),고세진(Sejin Ko) 한국추진공학회 2020 한국추진공학회 학술대회논문집 Vol.2020 No.11
본 논문에서는 KNSB MOTOR를 이용하여 목표고도 400m, 무게 3kg 미만의 로켓을 제작하는 과정을 서술하였다. NURA 입회 후 첫 대회인 만큼 비행 안정성에 초점을 두고 설계를 하였다. 사출 방법은 낙하산에 손상을 가할 수도 있는 화약 사출 대신, 용수철을 이용한 물리적 사출로 설계하였다. 사출은 아두이노와 MPU-6050 6축 자이로 가속도 센서를 이용하여 제어하였다. 미션은 GPS센서, GY-68 대기압 센서, 먼지센서, 자이로센서로 데이터를 수집해 Xbee 모듈을 이용하여 지상으로 실시간 데이터 전송을 하도록 설계하였다. This paper describes the process of building a rocket with a target elevation of 400 m and a weight of less than 3 kg using KNSB MOTOR. As it was the first competition since joining NURA, the design focused on flight stability. The ejection method was designed as a physical ejection using a spring, instead of a chemical ejection that could damage the parachute. The ejection was controlled using Arduino and MPU-6050 6-axis gyro acceleration sensors. The mission is designed to collect data with GPS sensors, GY-68 atmospheric pressure sensors, dust sensors and gyro sensors and send real-time data to the ground using Xbee modules.
Hyperfine interaction of individual atoms on a surface
Willke, Philip,Bae, Yujeong,Yang, Kai,Lado, Jose L.,Ferró,n, Alejandro,Choi, Taeyoung,Ardavan, Arzhang,Ferná,ndez-Rossier, Joaquí,n,Heinrich, Andreas J.,Lutz, Christopher P. American Association for the Advancement of Scienc 2018 Science Vol.362 No.6412
<P>Taking advantage of nuclear spins for electronic structure analysis, magnetic resonance imaging, and quantum devices hinges on knowledge and control of the surrounding atomic-scale environment. We measured and manipulated the hyperfine interaction of individual iron and titanium atoms placed on a magnesium oxide surface by using spin-polarized scanning tunneling microscopy in combination with single-atom electron spin resonance. Using atom manipulation to move single atoms, we found that the hyperfine interaction strongly depended on the binding configuration of the atom. We could extract atom-and position-dependent information about the electronic ground state, the state mixing with neighboring atoms, and properties of the nuclear spin. Thus, the hyperfine spectrum becomes a powerful probe of the chemical environment of individual atoms and nanostructures.</P>
Electrically controlled nuclear polarization of individual atoms
Yang, Kai,Willke, Philip,Bae, Yujeong,Ferró,n, Alejandro,Lado, Jose L.,Ardavan, Arzhang,Ferná,ndez-Rossier, Joaquí,n,Heinrich, Andreas J.,Lutz, Christopher P. Nature Publishing Group 2018 Nature nanotechnology Vol.13 No.12