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Ultra Fast Flash Observatory to observe the prompt photons from Gamma Ray Bursts
Jiwoo Nam,Steven Boggs,G. Ripov,Bruce Grossan,Jin-A Jeon,Joo-Young Jin,Ae-Ra Jung,Ji-Eun Kim,Minsoo Kim,Yong-Kweon Kim,P. Klimov,B. Khrenov,Chang-hwan Lee,Jik Lee,Go-Woon Na,Shin-Woo Nam,Il-Heung Park 한국천문학회 2009 天文學會報 Vol.34 No.1
THE UFFO SLEWING MIRROR TELESCOPE FOR EARLY OPTICAL OBSERVATION FROM GAMMA RAY BURSTS
NAM, JIWOO,AHMAD, S.,AHN, K.,BARRILLON, P.,BRANDT, S.,BUDTZ-JØRGENSEN, C.,CASTRO-TIRADO, A. J.,CHANG, S.-H.,CHEN, C.-R.,CHEN, P.,CHOI, Y. J.,CONNELL, P.,DAGORET-CAMPAGNE, S.,EYLES, C.,GROSSAN, B.,HUAN World Scientific 2013 Modern physics letters A Vol.28 No.2
<P> While some space born observatories, such as SWIFT and FERMI, have been operating, early observation of optical after grow of GRBs is still remained as an unexplored region. The Ultra-Fast Flash Observatory (UFFO) project is a space observatory for optical follow-ups of GRBs, aiming to explore the first 60 seconds of GRBs optical emission. Using fast moving mirrors to redirect our optical path rather than slewing the entire spacecraft, UFFO is utilized to catch early optical emissions from GRB within 1 sec. We have developed the UFFO Pathfinder Telescope which is going to be on board of the Lomonosov satellite and launched in middle of 2012. We will discuss about scientific potentials of the UFFO project and present the payload development status, especially for Slewing Mirror Telescope which is the key instrument of the UFFO-pathfinder mission. </P>
남지우(Jiwoo Nam),유홍선(Hong Sun Ryou),조성욱(Seong Wook Cho) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.10
제동 장치는 기계장치의 사용자나 시스템의 안전관점에서 가장 중요한 요소 중 하나이며, 작동 조건 내에서 신뢰성 있는 제동력이 유지 되어야 한다. 일반적으로 브레이크는 운동에너지를 마찰을 통해 열에너지로 변환하여 회전하는 기계장치를 제동한다. 운동에너지가 열에너지로 전환되는 과정에서 고온의 열이 발생하여 기계적 거동에 영향을 준다. 마찰열은 브레이크 시스템의 열팽창 및 마찰계수 변화 등에 영향을 주고 제어되지 않는 고온은 브레이크 성능을 저하시킨다. 따라서 브레이크의 발열을 예측하고 이를 제어하는 것은 중요하다. 마찰열을 예측하기 위한 다양한 수치해석 연구들이 수행되었지만, 계산의 효율 및 재원의 한계로 수치해석의 경계조건을 다양한 형태로 가정하여 마찰열 예측 연구를 수행하였다. 가정된 마찰열 거동은 실제 열전달 온도 분포 경황과 차이가 있고 이를 이용한 냉각 효과나 열응력 수치해석 결과의 신뢰성이 부족하다. 이러한 한계점을 극복하고 마찰열 예측 시뮬레이션 절차를 정립하기 위하여 본 연구에서는 열-구조 결합 요소를 사용하여 브레이크 시스템의 마찰열 발생을 직접적으로 모사하는 시뮬레이션을 수행하였다. 본 논문은 Finite Element Method(FEM)을 이용하여 브레이크 작동에 따른 마찰열 발생을 모사하고 열분포 특성을 분석하기 위해 브레이크 모델을 대상으로 열-구조 연성요소를 적용한 수치해석 연구를 수행하였다. 이 연구는 마찰열 직접 모사의 필요성을 제안하고 시뮬레이션에 필요한 정보를 제공할 수 있다 판단된다. The braking system is one of the most important components in vehicles and machines. It must exert a reliable braking force when they are brought to a halt. Generally, frictional heat is generated by converting kinetic energy into heat energy through friction. As the kinetic energy is converted into heat energy, high temperature heat is generated which affects the mechanical behavior of the braking system. Frictional heat affects the thermal expansion and friction coefficient of the brake system. If the temperature is not controlled, the brake performance will be decreased. Therefore, it is important to predict and control the heat generation of the brake. Various numerical analysis studies have been carried out to predict the frictional heat, but they assumed the existence of boundary conditions in the numerical analysis to simulate the frictional heat, because the simulation of frictional heat is difficult and time consuming. The results were based on the assumption that the frictional heat is different from the actual temperature distribution in a rotating brake system. Therefore, the reliability of the cooling effect or thermal stress using the results of these studies is insufficient. In order to overcome these limitations and establish a simulation procedure to predict the frictional heat, this study directly simulates the frictional heat generation by using a thermal-structure coupling element. In this study, we analyzed the thermo-mechanical behavior of a brake model, in order to investigate the thermal characteristics of brake systems by using the Finite Element method (FEM). This study suggests the necessity to directly simulatethe frictional heating and it is hoped that it can provide the necessary information for simulations.
이지우 ( Jiwoo Lee ),남소혜 ( So Hye Nam ),이장호 ( Jang Ho Lee ),유동열 ( Dong Ryeol Yoo ),김진희 ( Jin Hee Kim ),김미정 ( Mee Jeong Kim ),김명환 ( Myung-hwan Kim ) 대한내과학회 2019 대한내과학회지 Vol.94 No.5
Primary lymphoma of pancreatic mucosa-associated lymphoid tissue (MALT) is extremely rare. Initial suspicion of primary pancreatic lymphoma is hampered by its low incidence. However, it should always be included in a differential diagnosis of pancreatic mass with unusual features, because an accurate diagnosis can avoid unnecessary surgical intervention. A 70-year-old woman presented with melena associated with a mass on the pancreatic head. Endoscopic ultrasonography-guided core-needle biopsy of the pancreatic mass revealed MALT lymphoma. The patient is currently undergoing radiation therapy. We present a case of primary lymphoma of the pancreatic MALT with a review of the literature. (Korean J Med 2019;94:443-448)
Yu, Jiwoo,Nam, Dae-Hyun,Lee, Young-Joo,Joo, Young-Chang The Korean Microelectronics and Packaging Society 2016 마이크로전자 및 패키징학회지 Vol.23 No.2
We developed a flexible and micro-thick electromagnetic interference (EMI) shielding nanofabric layer that also functions as a water resisting and heat sinking material. Electrospinning followed by a simple heat treatment process was carried on to produce the EMI-shielding Ni/C hybrid nanofibers. The ambient oxygen partial pressure ($pO_2$ = 0.1, 0.7, 1.3 Torr) applied during the heat treatment was varied in order to optimize the effectiveness of EMI-shielding by modifying the size and crystallinity of the magnetic Ni nanoparticles distributed throughout the C nanofibers. Permittivity and permeability of the nanofibers under the electromagnetic (EM) wave frequency range of 300 MHz~1 GHz were measured, which implied the EMI-shielding effectiveness (SE) optimization at $pO_2$ = 0.7 Torr during the heat treatment. The materials' heat diffusivity for both in-plane direction and vertical direction was measured to confirm the anisotropic thermal diffusivity that can effectively deliver and sink the local heat produced during device operations. Also, the nanofibers were aged at room temperature in oxygen ambient for water resisting function.
코로나19와 불평등 -코로나19가 아동의 인적자본투자에 미치는 영향-
김지우(Kim, Jiwoo),김나영(Kim, Nayoung),남재현(Nam, Jaehyun) 한국아동복지학회 2021 한국아동복지학 Vol.70 No.2
본 연구는 코로나19의 영향으로 인하여 아동의 인적자본투자에 어떤 변화가 발생하였는지를 파악하기 위하여 수행되었다. 소득계층에 따른 차이를 고려하여 빈곤가구와 비빈곤가구로 구분하여 분석을 진행하였으며, 2019-2020년의 가계동향조사 분기 자료를 활용하여 이중차이분석을 적용하였다. 분석결과, 코로나19로 인하여 빈곤 아동 가구와 비빈곤 아동 가구 모두 교육 지출에 대한 감소를 경험하였다. 하지만, 디지털 장치와 문화 오락에 대한 지출은 비빈곤 아동 가구에서만 유의한 증가를 보였다. 이와 같은 결과는 아동의 발달에 영향을 미칠 수 있는 교육 및 문화생활과 같은 인적자본에 대한 투자가 코로나19로 인해 소득계층에 따라 그 격차가 벌어지고 있음을 의미한다. 따라서 빈곤 아동 가구를 대상으로 교육격차 및 디지털 격차를 완화할 수 있는 공교육 및 지원서비스 확대가 요구되며, 코로나19로 인해 등한시 되고 있는 아동의 문화권을 보장하기 위한 노력이 요구된다. The purpose of this study was to examine the effects of COVID-19 on inequality in children’s human capital investment. For this purpose, we used Household Income and Expenditure Survey (HIES) quarterly data for 2019-2020, and employed a difference-in-differences method to compare child-related expenditures between households with and without children after classifying families into those living in poverty and those that are not. The analyses revealed that households with children, regardless of poverty status, experienced a decline in expenditures on children’s education due to COVID-19. However, expenditures on the digital equipment and cultural entertainment increased significantly only in households with children not living in poverty. These results indicate that, depending on income class, COVID-19 contributed to widening gaps in parental investments in children’s human capital, such as education and cultural life, which can affect children’s development. Based on the results, we discuss various aspects of the policy implications for improving public education and related services to reduce the educational and digital divides, and for ensuring children’s cultural rights neglected due to COVID-19.