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B-Spline 및 유한요소법을 이용한 자동차 록업클러치의 형상 최적화
현석정(Seok-jeong Hyun),손종호(Jong-ho Son),김철(Cheol Kim),신세현(Se-hyun Sin) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
An efficient method is developed for the shape optimization of arbitrary structures. The sequential linear programming is used for minimization problems. Selected set of master nodes are employed as design variables and assigned to move towards the normal direction. After adapting the nodes on the design boundary, the B-spline curves and mesh smoothing schemes are used to maintain the finite element in good quality. A numerical implementation of optimum design of an automobile torque converter piston subjected to a pressure load is presented.<br/> <br/>
현석균 ( Seok Kyun Hyun ),유승흠 ( Seung Hum Yu ),오현주 ( Hyohn Joo Oh ) 한국병원경영학회 2002 병원경영학회지 Vol.7 No.2
This study was conducted to determine whether follow-up management is carried out continuously following CQI activity and to analyze the factors behind the success and failure of follow-up management. Past presentations from 19941999 of CQI coordinators and lecturers from various institutions who presented at The Korean Society of Quality Assurance in Health Care(KoSQA) on the conditions of follow-up management in each institution were analyzed. The results of this study were as follows; Since the number of subjects on CQI increased each year at symposiums, this has expanded to all medical institutions. Although medical institutions usually conduct 11-20 subjects on CQI per year, there were many such occasions where more than 31 subjects were conducted. Moreover, institutions with less than 800 beds have come up with more projects than those with more than 800 beds, thus 23.3% of these institutions had at least 1 person involved in 4 projects. Tihs had created an overload of responsibilities for specific persons involvement, prompting them to incline toward formahties in their work rather than substantial activities. Among the projects presented at the symposiums, 51.7% demonstrated that follow-up management could be carried out. In particular, 55.3% of the projects from provincial regions could carry out follow-up management compared to 48.8% in Seoul. Moreover, it was demonstrated that 80% of the projects from institutions with 600-799 beds carried out follow-up management most effectively. With regards to previous presentations, the older they were, it was found that follow-up management could not be effectively carried out. Some institutions that responded that follow-up management was carried out effectively in their institutions were found to have conducted follow-up management without any inspection strategies or the appropriate tools. CQI activities were executed and terminated with no consistency and team members had no real concern for it. The most important factors that contribute to an effective follow-up management are the need for concern and interest from the directors of the hospitals, from the relevant departments and team members in addition to the role of the supervising department, follow-up management through management of target goals, consistency in tasks along with communication between all team members. The biggest problems were perceived to be overload of work due to accumulation of proposed projects in addition to lack of awareness pertaining to follow-up management. CQI is beneficial for all staff for the improvement of the mind and business adrmnistration and thus it is believed to be desirable. To carry out follow-up mana-gement effectively, leadership, analysis and application of information, follow-up management and planning, as well as quality management are perceived to be essential, on the other hand, the results showed a significant difference. To prevent CQI activities from becoming just an activity, the basic system should be reconstructed and augmented based on the problems derived from the results of this study. Moreover, we hope this study will be used as reference material that would encourage the administration of follow-up management after CQI activities in most hospitals. Furthermore, various studies on follow-up management should be conducted for CQI activities in the future.
마이크로폰 31개로 이루어진 선형배열 음향렌즈의 구성과 실험
현석봉,민동현,김수용,Hyun, Seok-Bong,Min, Dong-Hyun,Kim, Su-Young 한국음향학회 1994 韓國音響學會誌 Vol.13 No.5
We developed an electronic lens for acoustic imaging systems, which is linear array with 31 microphones equally spaced with distance 34mm. Resonant frequency fo receiver circuit coupled to microphone is 20 kHz. We arranged 16 microphones horizontally and 15 microphones vertically, so that the array allows us to obtain a 2 dimensional angle of source, and to track the motion of source in real time. Due to the problem of aliasing in discrete Fourier Transfrom, the maximum observable angle of the lens is limited to 15${\circ}$. We also employed quadrature phase detection scheme to adjust the focus. We have tested the acoustic lens with a personal computer in an anechoic room and obtained the results agreed with the acoustic imaging theory. 31개의 마이크로폰이 34mm 간격으로 선형배열된 음향영상장치용 전자 렌즈를 제작하였다. 마이크로폰을 이용한 음향센서의 공진주파수는 20kHz이고, 16개의 마이크로폰은 수평으로 나머지 15개의 마이크로폰은 수직으로 배치되어 있어서, 음원의 2차원적인 각도를 알아낼 수 있고 음원의 운동을 실시간으로 추적할 수 있다. 이산 푸리어변환할때 ㅈ나타나는 aliasing 문제 때문에 제작된 렌즈의 최대 관찰가능각도는 15도로 제한된다. 또한 촛점을 맞추기 위해 직각위상 검파방법을 이용하였다. 무향실에서 PC를 이용하여 음향렌즈를 실험하였으며 음향영상이론과 일치하는 결과를 얻었다.
이정남(Jung-Nam Lee),김광선(Kwang Seon Kim),정재호(Jaeho Jung),현석봉(Seok Bong Hyun),조영균(Young-Kyun Cho) 한국전자파학회 2021 한국전자파학회논문지 Vol.32 No.1
본 논문에서는 200 GHz 대역 장거리 전송을 위한 서브 테라헤르츠 고이득 안테나를 설계하고, 이를 제작 및 측정하였다. 혼 반사판 안테나, 카세그레인 안테나 및 빔폭 확장을 위한 타원형 카세그레인 안테나 3종을 제작하였으며, 안테나 성능 측정을 위해 측정환경을 구성하고, 수신파워레벨 및 방사패턴을 측정하였다. 측정결과, 245 GHz 중심주파수에서 각각 37 dBi, 52 dBi, 33.3 dBi의 이득과 2.5도, 0.4도, 30도의 빔폭이 측정되었다. In this study, a sub-terahertz high-gain antenna for long-distance transmission in the 200-GHz frequency band is designed, fabricated, and measured. Three types of antennas are fabricated, namely, a horn reflector antenna, cassegrain antenna, and an elliptical cassegrain antenna for beam-width expansion, and a measurement environment is configured to measure antenna performance. Additionally, the reception power level and radiation pattern are measured. As a result of the measurement, antenna gains of 36, 52, and 33.3 dBi and beam widths of 3.5, 0.4, and 30° are measured at the center frequency of 245 GHz.