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Lee, Joonmyoung,Bourim, El Mostafa,Shin, Dongku,Lee, Jong-Sook,Seong, Dong-jun,Park, Jubong,Lee, Wootae,Chang, Man,Jung, Seungjae,Shin, Jungho,Hwang, Hyunsang Elsevier 2010 CURRENT APPLIED PHYSICS Vol.10 No.1
<P><B>Abstract</B></P><P>To analyze the switching mechanism of Nb doped SrTiO<SUB>3</SUB> (Nb:STO) single crystal in a high resistive state (HRS) and low resistive state (LRS), we performed a complex impedance spectroscopy in the frequency domain. We demonstrated the domination of the oxygen vacancies to the resistive switching. Based on the impedance spectroscopy in the HRS and LRS, we concluded that the origin of resistive switching is due to the combination of Schottky junction and a generation of conduction electron from oxygen vacancies. The calculation of activation energies in each resistance state has been performed comparatively, which proposed that a first ionization of oxygen vacancies is responsible for the switching.</P>
Wootae Lee,Jubong Park,Myungwoo Son,Joonmyoung Lee,Seungjae Jung,Seonghyun Kim,Sangsu Park,Jungho Shin,Hyunsang Hwang IEEE 2011 IEEE electron device letters Vol.32 No.5
<P>We have investigated silicon carbide (SiC) as a new programmable metallization cell material for nonvolatile memory applications. Our Cu/SiC/Pt devices showed bipolar resistive switching; the conduction mechanisms can be explained by the formation of a Cu filament and Poole-Frenkel emission in the low-resistance and high-resistance states, respectively. In particular, our devices showed excellent state stability, e.g., nondestructive readout at various stress voltages, excellent retention characteristics at 150°C for 10<SUP>4</SUP> s, and stable memory operation at high ambient temperature. We attribute this state stability to the SiC's high chemical stability and the ability to act as a Cu diffusion barrier.</P>
Lee, Wootae,Park, Jubong,Kim, Seonghyun,Woo, Jiyong,Shin, Jungho,Choi, Godeuni,Park, Sangsu,Lee, Daeseok,Cha, Euijun,Lee, Byoung Hun,Hwang, Hyunsang American Chemical Society 2012 ACS NANO Vol.6 No.9
<P>We demonstrate a high-performance selection device by utilizing the concept of crested oxide barrier to suppress the sneak current in bipolar resistive memory arrays. Using a TaO(x)/TiO(2)/TaO(x) structure, high current density over 10(7) A cm(-2) and excellent nonlinear characteristics up to 10(4) were successfully demonstrated. On the basis of the defect chemistry and SIMS depth profile result, we found that some Ta atoms gradually diffused into TiO(2) film, and consequently, the energy band of the TiO(2) film was symmetrically bent at the top and bottom TaO(x)/TiO(2) interfaces and modified as a crested oxide barrier. Furthermore, the one selector-one resistor device exhibited significant suppression of the leakage current, indicating excellent selector characteristics.</P>
The Role of Civil Society on South Korean Policy toward North Korea
Wootae Lee(이우태),Dongsoo Kim(김동수) 21세기정치학회 2014 21세기 정치학회보 Vol.24 No.2
With democratization, South Korean society has opened up foreign policy issues for debate among the populace. In Kim Dae-jung and Roh Moo-hyun administrations, large proportions of the organizations in South Korean civil society are in favor of cooperation and improving inter-Korean relations. This orientation of groups within South Korean civil society toward the North affects South Korean general people’s perception on North Korea and South Korean engagement policy in Kim Dae-jung and Roh Moo-hyun administrations. However, in Lee Myung-bak administration, the role of South Korean civil society to South Korean policy toward North Korea was rapidly decreased even though the importance and number of civil society was still maintained. The purpose of this paper is to analyze how and why the role of South Korean civil society has been differed between Kim and Roh administrations and Lee administration in the policy making process toward North Korea. The supports from political leadership and trust on the political sector and civil society have an effect to the role of civil society in the inter-Korean relations between Kim Dae-jung and Roh Moo-hyun administrations and Lee Myung-bak administrations.
Wootae Lee,Siddik, M.,Seungjae Jung,Jubong Park,Seonghyun Kim,Jungho Shin,Joonmyoung Lee,Sangsu Park,Myungwoo Son,Hyunsang Hwang IEEE 2011 IEEE electron device letters Vol.32 No.11
<P>We have investigated the effect of a Ge<SUB>2</SUB>Sb<SUB>2</SUB>Te<SUB>5</SUB> (GST) thermal barrier on the reset operations in TiN/Cu/SiC/Pt devices. When the GST film was introduced as a thermal barrier, the device showed a lower reset voltage and a lower reset current than a device without the GST layer. In particular, the reset speed of the device with the GST layer was significantly faster at room temperature compared to the device without the GST layer. We attribute the improved resistive switching to the GST thermal barrier, which induces thermally assisted electrochemical reduction of the Cu filament.</P>
이우태(Lee, Wootae) 한국정치정보학회 2016 정치정보연구 Vol.19 No.1
1953년 한미상호방위조약으로 태동된 한미동맹은 지난 60년 동안 대한민국 외교 및 안보에 있어서 중요한 핵심 축으로 작동해오고 있다. 그러나 한미동맹의 형태는 동맹이 성립되었던 시기부터 강대국인 미국이 약소국인 한국에게 안보를 제공하고 한국은 미국에게 정책적 자율성을 일정부분 양보하는 전형적인 비대칭 동맹의 형태였다. 동맹의 비대칭성에도 불구하고 이명박 정부 이후의 한미동맹관계는 단순한 군사안보 동맹에서 ‘가치동맹’, ‘포괄적 전략 동맹’으로 발전되었고, 박근혜 정부에 들어서는 ‘글로벌 파트너십’ 관계로 격상되었다. 본 논문은 이명박 정부 이후 한미동맹관계가 외향적으로 격상된 만큼 내용적으로 얼마나 동맹의 비대칭성이 완화되었는지 또한 동맹의 비대칭성을 줄이고 건설적인 발전을 하기 위한 방안을 비대칭동맹과 관련한 후견-피후견 관계이론, 안보-자율성 교환동맹 이론, 그리고 포기와 연루의 딜레마를 통해 살펴보았다. Korea-U.S. alliance which is begun from the ROK-U.S. Mutual Defense Agreement in 1953 has played a role as the linchpin of the security and diplomacy of Korea over the past 60 years. However, since the alliance was established, Korea-U.S. alliance has been the typical asymmetric alliance that the United States guarantee Korea"s security and Korea waive in some degree its autonomy to the U.S. Notwithstanding asymmetric feature of the alliance, Korea-U.S. alliance developed from the just security-military alliance to "valued alliance" or "comprehensive strategic alliance" in the Lee Myung-bak presidency and it was also upgraded to "global partnership" in the Park Geun-hye administration. In this paper, author tries to analyze how the asymmetry of alliance relationship between Korea and the United States is mitigated in the Lee Myung-bak and Park Geun-hye administrations as well as upgraded diplomatic rhetoric. To analyze the asymmetry of alliance in the Lee Myung-bak and Park Geun-hye administrations, three asymmetric alliance theories such as patron-client state relation theory, security-autonomy tradeoff theory, and abandonment-entrapment dilemma are used as theoretical frameworks.
이우태 ( Lee Wootae ) 한국접경지역통일학회 2020 접경지역통일연구 Vol.4 No.2
2018년 남북관계가 평창올림픽을 계기로 개선되고, 이후 지속된 남북 체육교류가 남북관계의 발전을 이끌었듯이, 2032년 남북 올림픽 공동개최는 남북관계의 재도약을 위해 전환점이 될 것으로 보인다. 남북 올림픽 공동개최는 단순히 ‘올림픽’ 이라는 대회 개최뿐만 아니라 체육분야 남북교류협력이 활성화될 때 공동개최의 진정한 효과를 얻을 수 있을 것이다. 따라서 남북 체육교류를 활성화시키고 2032년 남북 올림픽 공동개최라는 목표를 달성하기 위해서는 체육분야 교류협력이‘올림픽’이라는 목표를 두고 ‘올림픽 유치’와 ‘체육교류 확대’라는 투 트랙(two-track)으로 전개되어야 한다. Co-hosting 2032 Summer Olympics by South and North Korea will be a turning point for the reform of inter-Korean relations, as 2018 Pyongchang Olympics and sports exchange led an improvement of strained inter-Korean relations. Jointly hosting Olympics between two Koreas can achieve its real goal when sports exchange revitalizes with hosting a mega sports event like Olympics. Therefore, the future inter-Korean sports exchange should go on two-track approach; ‘hosting the 2032 Summer Olympic Games’ and ‘expanding inter-Korean sports exchange’.
Nonlinear Modeling and Sliding Mode Control of a Vane-Type Variable Valve Timing System
Myeong-hyeon Son,Minkwang Lee,Kangyoon Lee,Myoungho Sunwoo,Seungwoo Lee,Chunwoo Lee,Wootae Kim 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The Variable Valve Timing (VVT) system for high performance has become a key technology used in newly developed engines. In this paper, model-based control is proposed to make a fast and precise VVT control system that has robustness to manufacturing tolerances and aging. The VVT system is modeled by a third-order nonlinear state equation, which in particular accounts for nonlinearities of the system. Based on the model, a controller is designed for position control of the VVT system. The sliding mode theory is applied to controller design in order to overcome model uncertainties and unknown disturbances. The experimental results suggest that the proposed sliding mode controller is capable of improving the tracking precision. In addition, the proposed controller seems to be robust against change in magnitude of the cam timing inputs.