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Toroidal-Shaped Coils for a Wireless Power Transfer System for an Unmanned Aerial Vehicle
Jaehyoung Park,Jonghoon Kim,Yujun Shin,Bumjin Park,Won-Seok Kim,Seok-Jong Cheong,Seungyoung Ahn 한국전자파학회JEES 2019 Journal of Electromagnetic Engineering and Science Vol.19 No.1
Unmanned aerial vehicles (UAVs) using communications, sensors, and navigation equipment will play a key role in future warfare. Currently, UAVs are monitored to prevent misfire and accidents, and the conventional method adopted uses wires for data transmission and power supply. The repeated connection and disconnection of cables increases maintenance time and harms the connector. For convenience and stability, a wireless power transfer system to power UAVs is needed. Unlike other wireless power transfer (WPT) applications, the size of the receiving coils must be small, so that the WPT systems can be embedded inside space-limited UAVs. The small size reduces the coupling coefficient and transfer efficiency between the transmitting and the receiving coils. In this study, we propose a toroidal-shaped coil for a WPT system for UAVs with high coupling coefficient with minimum space requirements. For validation, conventional coils and the proposed toroidal-shaped coil were used and their coupling coefficient and power transfer efficiency were compared using simulated and measured results. The simulated and measured results were strongly correlated, confirming that the proposed WPT system significantly improved efficiency with negligible change in the space requirement.
A Resonant Reactive Shielding for Planar Wireless Power Transfer System in Smartphone Application
Jaehyoung Park,Dongwook Kim,Karam Hwang,Hyun Ho Park,Sang Il Kwak,Jong Hwa Kwon,Seungyoung Ahn IEEE 2017 IEEE transactions on electromagnetic compatibility Vol.59 No.2
<P>Demand and interest in wireless power transfer (WPT) have been rapidly increasing lately. However, WPT systems have problems with electromagnetic field (EMF) leakage, which has stimulated interest in methods to suppress EMF leakage levels. In this paper, we propose a compact resonant reactive shielding coil topology for reducing EMF in a near-field WPT mobile device application. The proposed shielding coil employs a closed loop and matching capacitors, and is demonstrated to dramatically reduce the leakage magnetic field from aWPT system. For validation, the proposed shielding was implemented with other shielding topologies and the EMFs were measured and compared. The analytical, simulation, and measurement results were all strongly correlated.</P>
Sequestering carbon dioxide into complex structures of naturally occurring gas hydrates.
Park, Youngjune,Kim, Do-Youn,Lee, Jong-Won,Huh, Dae-Gee,Park, Keun-Pil,Lee, Jaehyoung,Lee, Huen National Academy of Sciences 2006 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.103 No.34
<P>Large amounts of CH4 in the form of solid hydrates are stored on continental margins and in permafrost regions. If these CH4 hydrates could be converted into CO2 hydrates, they would serve double duty as CH4 sources and CO2 storage sites. We explore here the swapping phenomenon occurring in structure I (sI) and structure II (sII) CH4 hydrate deposits through spectroscopic analyses and its potential application to CO2 sequestration at the preliminary phase. The present 85% CH4 recovery rate in sI CH4 hydrate achieved by the direct use of binary N2+CO2 guests is surprising when compared with the rate of 64% for a pure CO2 guest attained in the previous approach. The direct use of a mixture of N2+CO2 eliminates the requirement of a CO2 separation/purification process. In addition, the simultaneously occurring dual mechanism of CO2 sequestration and CH4 recovery is expected to provide the physicochemical background required for developing a promising large-scale approach with economic feasibility. In the case of sII CH4 hydrates, we observe a spontaneous structure transition of sII to sI during the replacement and a cage-specific distribution of guest molecules. A significant change of the lattice dimension caused by structure transformation induces a relative number of small cage sites to reduce, resulting in the considerable increase of CH4 recovery rate. The mutually interactive pattern of targeted guest-cage conjugates possesses important implications for the diverse hydrate-based inclusion phenomena as illustrated in the swapping process between CO2 stream and complex CH4 hydrate structure.</P>
박재형(Jaehyoung Park),김경민(Gyungmin Kim),김우철(Woocheol Kim),임혁(Hyuk Lim) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
연합 학습은 컴퓨팅 자원이 충분한 분산 노드들이 로컬 데이터를 이용하여 개별적으로 학습하여 로컬 모델을 생성하고, 중앙 서버가 학습된 중간 로컬 모델 데이터를 수집하고 결합하여 글로벌 모델을 생성하는 학습 알고리즘이다. 연합 학습에서는 서버가 분산 노드들의 원시 데이터를 수집하는 것 대신 학습된 중간 모델 데이터만 수집하기 때문에 민감한 정보를 포함하는 데이터의 프라이버시를 보호할 수 있다. 그러나 최근에는 중간 모델데이터를 이용하여 프라이버시를 위협하는 기술들이 보고되었다. 본 논문에서는 동형 암호 기술을 이용하여 공유되는 중간 모델 데이터를 보호하는 기술을 설명하고 시뮬레이션을 통해 연합 학습에서 동형 암호를 사용함으로써 발생하는 계산 오버헤드를 측정 및 평가한다.
Video Overlay Board를 이용한 MPEG 영상 부호화기의 구현
박재형(Jaehyoung Park),남명우(Myoungwoo Nam),이재주(Jaeju Lee),노승용(Seungryong Rho) 한국정보과학회 1993 한국정보과학회 학술발표논문집 Vol.20 No.2
동영상 부호화를 위한 소프트웨어 및 하드웨어의 요구가 증가함에 따라, 많은 동영상 압축기술들이 출현하였고, 이 중 MPEG이 표준으로 정착되었다. 본 논문은 PC상에서 Video Overlay를 이용하여, MPEG 부호화기를 구현하였다. 프레임 단위의 처리를 위해, Device Driver를 제작하여 RS-232C가 내장된 VCR 제어에 사용하였다. 동영상 부호화를 구현하기 위하여 이용한 Video Overlay Board는 영상 획득 및 획득한 영상을 다루기에 용이하다. PC상에서 C 언어와 어셈블러를 사용하여 소프트웨어로 구현한 MPEG 부호화기는, 부호화를 실시간으로 할 수는 없지만, 상당한 압축률과 VCR 화질의 동영상을 얻을 수 있었다.