• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.55-55
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• 2010

We use ab initio density functional theory to determine the effect of bundling on the equilibrium structure, electronic and magnetic properties of $Mo_6S_{9-x}I_x$nanowires with x = 0, 3, 4.5, 6. Each unit cell of these systems contains two $Mo_6S_{6-x}I_x$ clusters connected by S3 linkages to form an ordered linear array. Due to the bi-stability of the sulfur linkages, the total energy of the nanowires exhibits typically many minima as a function of the wire length. We find that nanowires can switch over from metallic to semiconducting by applying axial stress. Structural order is expected in bundles with x=0 and x=6, since there is no disorder in the decoration of the Mo clusters. In bundles with other stoichiometries, we expect structural disorder to occur. We find the optimum inter-wire distance to depend sensitively on the orientation of the wires, but only weakly on x. It is also found that the electronic properties of nanowires are affected strongly due to bundling of nanowires exhibiting very unusual Fermi surfaces. Furthermore, ferromagnetic behaviors are observed in selected stable and many more unstable atomic arrangements in nanowire bundles.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.366-366
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• 2010

Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichorism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spins switch from out-of-plane direction in Fe/NiO/MgO(001) to in-plane direction in Fe/NiO/Ag(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy in Fe/NiO/Ag(001) is due to a 90o-coupling between the in-plane NiO spins and the in-plane Fe spins which causes a switching of the NiO spins during the Fe magnetization reversal.

• 조명전기설비학회논문지
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• 제25권7호
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• pp.105-113
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• 2011

The study about three-phase synthetic making test using DC power has been performed in order to increase the making test capacity on Vacuum Circuit Breaker. And, it made possible to solve the limitations that short-circuit testing facilities can not fulfill the testing requirements of VCB exceeding three-phase 36[kV] 31.5[kA]. By using DC power and high speed spark-gap switch, this method made the equivalence with the pre-arc that occurred during the making process under the fault condition of power system. As results, KERI(Korea Electrotechnology Research Institute) could have capacity to carry out type test for VCB under three-phase 52[kV] 40[kV], which satisfies the IEC Standard.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1769-1771
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• 2002

정전형 펄스파워시스템에서 핵심은 투입 스위치라고 해도 과언이 아니다. 이러한 투입 스위치 중 진공 아크를 이용하는 스위치로는 로렌츠력을 이용 아크를 회전시켜 전극의 손상을 억제한 횡자계형과 전극의 축방향으로 자계를 발생시켜 아크가 확산되도록 함으로써 z-pinch에 의한 전극 손상을 감소시키는 종자계형으로 대별 할 수 있다. 본 논문에서는 고전압/대전류용 횡자계형과 종자계형 진공스위치의 동작특성을 파악하기위해 아크전압-전류 특성에 대해서 기술하였다. 횡자계형 전극과 종자계형 전극을 동크롬(75:25 [wt%])으로 제작하여 진공 챔버 내에서 실험을 통해 아크 전압과 전류를 측정하였으며, 이를 통해 아크 저항과 손실 전력을 구하였다.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권12호
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• pp.511-517
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• 2006

The key issues in high power, high energy applications such as electromagnetic launchers include safety, reliability, flexibility, efficiency, compactness, and cost. To explore some of the issues, a control scheme for a large current wave-forming was designed, built and experimentally verified using a 2.4MJ pulse power system (PPS). The PPS was made up of eight capacitors bank unit, each containing six capacitors connected in parallel. Therefore there were 48 capacitors in total, with ratings of 22kV and 50kJ each. Each unit is charged through a charging switch that is operated by air pressure. For discharging each unit has a triggered vacuum switch (TVS) with ratings of 200kA and 250kV. Hence, flexibility of a large current wave-forming can be obtained by controlling the charging voltage and the discharging times. The whole control system includes a personal computer(PC), RS232 and RS485 pseudo converter, electric/optical signal converters and eight 80C196KC micro-controller based capacitor-bank module(CBM) controllers. Hence, the PC based controller can set the capacitor charging voltages and the TVS trigger timings of each CBM controller for the current wave-forming. It also monitors and records the system status data. We illustrated that our control scheme was able to generate the large current pulse flexibly and safely by experiments. The our control scheme minimize the use of optical cables without reducing EMI noise immunity and reliability, this is resulting in cost reduction. Also, the reliability was increased by isolating ground doubly, it reduced drastically the interference of the large voltage pulse induced by the large current pulse. This paper contains the complete control scheme and details of each subsystem unit.

• 한국항공우주학회지
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• 제40권5호
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• pp.461-466
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• 2012

본 논문에서는 현재 KAIST 인공위성 연구센터(SaTReC)에서 개발 진행 중인 과학기술위성3호(STSAT-3) 위성체의 탑재체 데이터 전송을 위한 X대역 송신기 비행모델 개발 및 시험에 관하여 기술한다. 과학기술위성3호의 통신시스템은 크게 상태정보, 명령 송수신을 위한 통신채널과 임무데이터 전송을 위한 통신채널로 구성되며 상태 정보 및 명령 송수신을 위하여 S대역을 사용하며 임무데이터 전송용으로 X대역 주파수를 사용하고 있다. 과학기술위성 3호에서는 대용량 메모리 유닛(MMU; Mass Memory Unit)에 저장된 탑재체 관측정보가 X대역 송신기의 QPSK 변조기에서 변조를 하고, 변조된 신호는 스위치를 거친 이후에 안테나를 통해 송신된다. 본 논문에서는 과학기술위성 3호 X대역 송신기 내부의 변조방식, 저역통과 여파기, power amp, 스위치 등에 대해서 제작된 특성을 기술한다. X-band 송신기의 비행모델은 성능시험, 환경시험(진동시험, 열진공시험)을 성공적으로 마치고 위성체 조립 단계(Assembly Integration and Test, AIT)에 납품되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1868-1870
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• 2000

As a drive for an ETC (Electro-thermal Chemical) launcher, a large pulse power system of a 2.4MJ energy storage was designed, constructed and tested. The overall power system consists of eight capacitive 300kJ energy storage banks. In this paper we describe the design features, setup and operation test result of the 300kJ pulsed power module. Each capacitor bank of the 300kJ module consists of six 22kV 50kJ capacitors. A triggered vacuum switch (TVS-43) was adopted as the main pulse switch. Crowbar diode circuits, variable multi-tap inductors and energy dumping systems are connected to each high power capacitor bank via bus-bars and coaxial cables. A parallel crowbar diode stack is fabricated in coaxial structure with two series 13.5kV, 60kA avalanche diodes. The main design parameters of the 300kJ module are a maximum current of 180kA and a pulse width of 0.5 - 3ms. The electrical performances of each component and current output variations into resistive loads have been investigated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.343-344
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• 2012

It has been known since the mid 1960s that Ag can be photodissolved in chalcogenide glasses to form materials with interesting technological properties. In the 40 years since, this effect has been used in diverse applications such as the fabrication of relief images in optical elements, micro photolithographic schemes, and for direct imaging by photoinduced Ag surface deposition. ReRAM, also known as conductive bridging RAM (CBRAM), is a resistive switching memory based on non-volatile formation and dissolution of a conductive filament in a solid electrolyte. Especially, Ag-doped chalcogenide glasses and thin films have become attractive materials for fundamental research of their structure, properties, and preparation. Ag-doped chalcogenide glasses have been used in the formation of solid electrolyte which is the active medium in ReRAM devices. In this paper, we investigated the nature of thin films formed by the photo-dissolution of Ag into Ge-Se glasses for use in ReRAM devices. These devices rely on ion transport in the film so produced to create electrically programmable resistance states. [1-3] We have demonstrated functionalities of Ag doped chalcogenide glasses based on their capabilities as solid electrolytes. Formation of such amorphous systems by the introduction of Ag+ ions photo-induced diffusion in thin chalcogenide films is considered. The influence of Ag+ ions is regarded in terms of diffusion kinetics and Ag saturation is related to the composition of the hosting material. Saturated Ag+ ions have been used in the formation of conductive filaments at the solid electrolyte which is the active medium in ReRAM devices. Following fabrication, the cell displays a metal-insulator-metal structure. We measured the I-V characteristics of a cell, similar results were obtained with different via sizes, due to the filamentary nature of resistance switching in ReRAM cell. As the voltage is swept from 0 V to a positive top electrode voltage, the device switches from a high resistive to a low resistive, or set. The low conducting, or reset, state can be restored by means of a negative voltage sweep where the switch-off of the device usually occurs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.326-326
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• 2014

It has been known since the mid 1960s that Ag can be photodissolved in chalcogenide glasses to form materials with interesting technological properties. In the 40 years since, this effect has been used in diverse applications such as the fabrication of relief images in optical elements, micro photolithographic schemes, and for direct imaging by photoinduced Ag surface deposition. ReRAM, also known as conductive bridging RAM (CBRAM), is a resistive switching memory based on non-volatile formation and dissolution of a conductive filament in a solid electrolyte. Especially, Ag-doped chalcogenide glasses and thin films have become attractive materials for fundamental research of their structure, properties, and preparation. Ag-doped chalcogenide glasses have been used in the formation of solid electrolyte which is the active medium in ReRAM devices. In this paper, we investigated the nature of thin films formed by the photo-dissolution of Ag into Ge-Se glasses for use in ReRAM devices. These devices rely on ion transport in the film so produced to create electrically programmable resistance states [1-3]. We have demonstrated functionalities of Ag doped chalcogenide glasses based on their capabilities as solid electrolytes. Formation of such amorphous systems by the introduction of Ag+ ions photo-induced diffusion in thin chalcogenide films is considered. The influence of Ag+ ions is regarded in terms of diffusion kinetics and Ag saturation is related to the composition of the hosting material. Saturated Ag+ ions have been used in the formation of conductive filaments at the solid electrolyte which is the active medium in ReRAM devices. Following fabrication, the cell displays a metal-insulator-metal structure. We measured the I-V characteristics of a cell, similar results were obtained with different via sizes, due to the filamentary nature of resistance switching in ReRAM cell. As the voltage is swept from 0 V to a positive top electrode voltage, the device switches from a high resistive to a low resistive, or set. The low conducting, or reset, state can be restored by means of a negative voltage sweep where the switch-off of the device usually occurs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.232.1-232.1
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• 2014

The green displays are the human friendly displays, the nature friendly displays, and the economical displays. Electrochromic displays are low cost and environmental devices because they do have more choice of colours and use much less power. The elements of the electrochromic devices consist of at least two conductors, an electrochromic material and an electrolyte. The optical properties were obtained using the optical contrast between the transparency of the substrate and the coloured state of the electrochromic materials. These devices can be fully flexible and printable. Due to the characteristics of the high coloration efficiency and memory effects, the electrochromic devices have been used in various applications such as information displays, smart windows, light shutters and electronic papers. Among these technical fields switchable mirrors have been received much attention in the applicative point of view of various electronic devices production. We have developed a novel silver (Ag) deposition-based electrochromic device for the reversible electrodeposition (RED) system. The electrochromic device can switch between transparent states and mirror states in response to a change in the applied voltage. The dynamic range of transmittance percent (%) for the fabricated device is about 90% at 550 nm wavelength. Also, we successfully fabricated the large area RED display system using the parted electrochromic cells of the honey comb structure.