http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Measurement of collective dynamical mass of Dirac fermions in graphene
Yoon, Hosang,Forsythe, Carlos,Wang, Lei,Tombros, Nikolaos,Watanabe, Kenji,Taniguchi, Takashi,Hone, James,Kim, Philip,Ham, Donhee Nature Publishing Group, a division of Macmillan P 2014 Nature nanotechnology Vol.9 No.8
Individual electrons in graphene behave as massless quasiparticles. Unexpectedly, it is inferred from plasmonic investigations that electrons in graphene must exhibit a non-zero mass when collectively excited. The inertial acceleration of the electron collective mass is essential to explain the behaviour of plasmons in this material, and may be directly measured by accelerating it with a time-varying voltage and quantifying the phase delay of the resulting current. This voltage–current phase relation would manifest as a kinetic inductance, representing the reluctance of the collective mass to accelerate. However, at optical (infrared) frequencies, phase measurements of current are generally difficult, and, at microwave frequencies, the inertial phase delay has been buried under electron scattering. Therefore, to date, the collective mass in graphene has defied unequivocal measurement. Here, we directly and precisely measure the kinetic inductance, and therefore the collective mass, by combining device engineering that reduces electron scattering and sensitive microwave phase measurements. Specifically, the encapsulation of graphene between hexagonal boron nitride layers, one-dimensional edge contacts and a proximate top gate configured as microwave ground together enable the inertial phase delay to be resolved from the electron scattering. Beside its fundamental importance, the kinetic inductance is found to be orders of magnitude larger than the magnetic inductance, which may be utilized to miniaturize radiofrequency integrated circuits. Moreover, its bias dependency heralds a solid-state voltage-controlled inductor to complement the prevalent voltage-controlled capacitor.
윤호상(Hosang Yoon),김유겸(Yukyeom Kim),조병룡(Byoungyong Cho) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
It is important that the vehicle parts and system is evaluated by durability test method for fatigue life in order to secure a stability and a reliability of them. As design standard of most of the vehicle parts and system demand a long life, durability test is highly expensive and uneconomical because of taking a long time. Therefore, it is quite important of evaluating ALT(Accelerated Life Testing) in short time.
윤호상(Hosang Yoon),문일동(Ildong Moon),김재원(Jaewon Kim),오재윤(Chaeyoun Oh),이형원(Hyungwon Lee) 한국생산제조학회 2012 한국생산제조학회지 Vol.21 No.4
In this work, the semi-active control of a large-sized bus suspension system with an MR damper was studied. An MR damper model that can aptly describe the hysteretic characteristics of an MR damper was adopted. Parameter values of the MR damper model were suitably modified by considering the maximum damping force of a passive damper used in the suspension system of a real large-sized bus. In addition, a fuzzy logic controller was developed for semi-active control of a suspension system with an MR damper. The vertical acceleration at the attachment point of the MR damper and the relative velocity between sprung and unsprung masses were used as input variables, while voltage was used as the output variable. Straight-ahead driving simulations were performed on a road with a random road profile and on a flat road with a bump. In straight-ahead driving simulations, the vertical acceleration and pitch angle were measured to compare the riding performance of a suspension system with a passive damper with that of a suspension with an MR damper. In addition, a single lane change simulation was performed. In the simulation, the lateral acceleration and roll angle were measured in order to compare the handling performance of a suspension system using a passive damper with that of a suspension system using an MR damper.
Lee, Keundong,Park, Jong-woo,Tchoe, Youngbin,Yoon, Jiyoung,Chung, Kunook,Yoon, Hosang,Lee, Sangik,Yoon, Chansoo,Ho Park, Bae,Yi, Gyu-Chul IOP 2017 Nanotechnology Vol.28 No.20
<P>We report flexible resistive random access memory (ReRAM) arrays fabricated by using NiO<SUB> <I>x</I> </SUB>/GaN microdisk arrays on graphene films. The ReRAM device was created from discrete GaN microdisk arrays grown on graphene films produced by chemical vapor deposition, followed by deposition of NiO<SUB> <I>x</I> </SUB> thin layers and Au metal contacts. The microdisk ReRAM arrays were transferred to flexible plastic substrates by a simple lift-off technique. The electrical and memory characteristics of the ReRAM devices were investigated under bending conditions. Resistive switching characteristics, including cumulative probability, endurance, and retention, were measured. After 1000 bending repetitions, no significant change in the device characteristics was observed. The flexible ReRAM devices, constructed by using only inorganic materials, operated reliably at temperatures as high as 180 °C.</P>
Yoon, Taeho,Kim, Daesoo,Park, Kern H.,Park, Hosang,Jurng, Sunhyung,Jang, Jihyun,Ryu, Ji Heon,Kim, Jae Jeong,Oh, Seung M. The Electrochemical Society 2014 Journal of the Electrochemical Society Vol.161 No.4
<P>The evolution of surface film on aspect of chemical composition and thickness is monitored on a nickel-doped manganese spinel positive electrode (LNMO, LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB>) for lithium-ion batteries. In the first charging from 4.2 to 4.9 V (vs. Li/Li<SUP>+</SUP>), large amount of lithium fluoride (LiF) deposits at lower potentials (4.2 V) but it is removed when the electrode potential moves to the charging end (4.9 V). The phenomenon of LiF deposition at lower potentials and removal at higher potentials is repeated in the continuing cycles, but the overall LiF concentration becomes progressively lower for the surface films to be enriched by the carbon-containing organic species in the later cycles. Due to the highly resistive nature of LiF, the film resistance shows a strong correlation with the LiF concentration in the films. From the finding that LiF formation is the most significant at 4.2 V in every cycle, under which circumstances LNMO itself is fully lithiated to provide lithium source for LiF formation, hydrogen fluoride (HF) attack on the LNMO surface has been proposed to be the major route for LiF formation.</P>
무선 ATM환경에서의 효과적인 핸드오버를 위한 새로운 크로스오버 스위치 검색 기법
윤호상(Hosang Yun),윤현수(Hyunsoo Yoon) 한국정보과학회 1999 한국정보과학회 학술발표논문집 Vol.26 No.1A
Wireless ATM network의 handover에서 중요한 문제중의 하나가 이동한 switch로의 새로운 connection의 설정이다. 연결 지향적인(connection-oriented) ATM network에서는 새로운 connection의 설정에 많은 시간이 소요된다. Connection 설정시간이 길어지게 되면, hanover 시간이 길어지게 되고 이로 인한 QoS, cell lose, cell miss ordering등의 문제가 발생하게 된다. 본 논문에서는 효과적이고 빠른 handover를 수행하기 위한 방안 중에서 기존의 path를 재 사용하는 Incremental path re-establishment 기법의 핵심인 Crossover Switch 검색 기법을 제시한다. 본 연구에서 제안하는 Crossover Switch 검색 알고리즘은 Wireless ATM의 backbone network은 구성이 고정되어 있고 현재의 switch에서 핸드오버 가능한 스위치들을 미리 알 수 있으므로 이들에 대한 Crossover switch를 미리 계산하여 핸드오버가 발생할 때 CX를 찾지 않고 미리 계산한 CX를 사용하므로 핸드오버 시간을 줄이는 방안이다. 따라서 이와같은 CX list preparing 방법을 이용하면 CX discovery overhead를 줄여 효과적인 path rerouting이 가능하다.
Park, Hosang,Yoon, Taeho,Kim, Youngjin,Lee, Jae Gil,Kim, Jongjung,Kim, Hyun-seung,Ryu, Ji Heon,Kim, Jae Jeong,Oh, Seung M. The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.6
<P>The thermal degradation of surface films (solid electrolyte interphase, SEI) and their repairing behaviors are examined on graphite electrodes that have different states-of-charge (SOC). In detail, a fully passivating SEI layer is generated in advance and then stored at 85°C for a prolonged time. The surface films (SEI) are thermally degraded upon high-temperature exposure. The damaged films are repaired by electrolyte decomposition and concomitant film deposition, during which Li<SUP>+</SUP> ions/electrons are supplied from the graphite electrodes, which appears as an increase in the open-circuit voltage (OCV) of the graphite electrodes. The repaired surface films show a comparable passivating ability along with a similar morphology and chemical composition to that of the initial SEI layers. The degradation/repairing continues until the graphite electrodes are fully de-lithiated (OCV = 3.0 V vs. Li/Li<SUP>+</SUP>). Once the graphite electrodes are fully de-lithiated, the damaged surface films cannot be repaired because the Li<SUP>+</SUP> ions/electrons are exhausted in the graphite electrodes. Because of the incomplete repairing, the graphite surface becomes poorly covered by surface films, which leads to a loss of passivating ability.</P>
VOCs 센서 제작을 위한 그래핀옥사이드-산화아연 전기영동적 코팅
안호상(Hosang Ahn),정병권(Byeongkwon Jung),주민(Min Ju),윤영한(YoungHan. Yoon) 한국산학기술학회 2015 한국산학기술학회 학술대회 Vol.2015 No.1
본 연구에서는 우수한 전기적, 화학적, 기계적 특성으로 다양한 분야에서 각광받고 잇는 그래핀과 기존의 반도체식 센서의 주된 소재로 활용이 된 산화아연을 실내공기질 센서로의 적용을 위해 경제적이고 빠른 시간내에 센싱레이어 적용이 가능한 전기영동법 방식으로 실내공기내 VOCs를 감지할 센싱레이어로의 적용에 관한 결과를 정리하였다. 전기영동법의 실험적 조건에 따라 센싱레이어로의 적용이 가능한 최적의 조건이 도출되었고 실내공기질 센서 제작의 경제적 방법으로 적용이 타당함을 확인할 수 있었다.