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Renormalization of spin excitations in hexagonal HoMnO3 by magnon-phonon coupling
Kim, Taehun,Leiner, Jonathan C.,Park, Kisoo,Oh, Joosung,Sim, Hasung,Iida, Kazuki,Kamazawa, Kazuya,Park, Je-Geun American Physical Society 2018 Physical review. B Vol.97 No.20
<P>Hexagonal HoMnO3, a two-dimensional Heisenberg antiferromagnet, has been studied via inelastic neutron scattering. A simple Heisenberg model with a single-ion anisotropy describes most features of the spin-wave dispersion curves. However, there is shown to be a renormalization of the magnon energies located at around 11 meV. Since both the magnon-magnon interaction and magnon-phonon coupling can affect the renormalization in a noncollinear magnet, we have accounted for both of these couplings by using a Heisenberg XXZ model with 1 /S expansions [ 1 ] and the Einstein site phonon model [13], respectively. This quantitative analysis leads to the conclusion that the renormalization effect primarily originates from the magnon-phonon coupling, while the spontaneous magnon decay due to the magnon-magnon interaction is suppressed by strong two-ion anisotropy.</P>
실시간 시뮬레이션 환경 기반 AFS 제어기 설계 및 검증
황태훈(Taehun Hwang),윤경준(Kyoungjun Yoon),강민철(Minchul Kang),오나미(Nami Oh),전대석(Daeseok Jeon),박기홍(Kihong Park) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This paper presents construction of realtime simulation circumstances for designing chassis control system controller. One of various chassis control systems, The AFS(Active Front Steering) system is an active chassis control system that can improve driving stability by controlling yaw motion of vehicle with yaw rate sensor signal. The suggested controller was materialized by special ECU using RCP equipment. As realtime circumstances for controller design, CarSim-RT and RT-LAB were used to construct realtime simulation circumstances. CarSim vehicle model has 27 DOF, and it can reproduce relatively accurate vehicle driving. Besides, realtime-based controller verification ensured reliance. Experiments under the various driving environment were conducted to verify the suggested simulation circumstances and controller.
Park, Jaeman,Oh, Hwanyeong,Ha, Taehun,Lee, Yoo Il,Min, Kyoungdoug Elsevier 2015 APPLIED ENERGY Vol.155 No.-
<P><B>Abstract</B></P> <P>For successful commercialization of a proton exchange membrane fuel cell, the durability requirement must be satisfied. The degradation of a proton exchange membrane fuel cell has been extensively studied, and a number of review papers investigating the durability issue have already been published. However, the gas diffusion layer has rarely been examined, even though it might be a key factor for managing mass transport and two-phase flow while mechanically supporting a membrane-electrode assembly and a bipolar plate. This paper reviews the published works on the durability of the gas diffusion layer of the proton exchange membrane fuel cell. The degradation of the gas diffusion layer can be divided into mechanical degradation, including the compression force effect, freeze/thaw cycle effect, dissolution effect, and erosion effect, and chemical degradation, which consists of the carbon corrosion effect. Following these categories, the methods of accelerated stress tests, the degradation mechanisms, and the influential factors are investigated along with various measurements of gas diffusion layer properties and cell performances.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This paper focuses on the evaluation of the durability characteristics of GDL. </LI> <LI> GDL degradation can be categorized into mechanical and chemical degradation. </LI> <LI> Standardized test protocols need to be established to evaluate GDL durability. </LI> </UL> </P>
Two Phase Flow Boiling Heat Transfer of R410A Inside Horizontal Aluminum Multiport Tube
Jong-Taek Oh(오종택),Nguyen Ba Chien,Pham Quang Vu,Kwang-Il Choi(최광일),Honggi Cho(조홍기),Taehun Kim(김태헌) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Two phase flow boiling heat transfer coefficient of R410A inside multiport tube were investigated in this study. The experimental data were conducted in horizontal aluminum tubes with the hydraulic diameter of 1.14 ㎜. The testing conditions were performed with the mass fluxes from 50 to 150 ㎏/㎡s, the heat fluxes from 3 to 6 ㎾/㎡, the saturation temperature of 6℃ and the vapor quality from 0.1 to dry-out. The effects of mass flux, heat flux on the heat transfer coefficient were analyzed. The experimental data were also compared with some well-known heat transfer coefficient correlations.