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김기복(Ki-Bok Kim),이복희(Bok-Hee Lee),조정현(Jeong-Hyeon Joe) 한국조명·전기설비학회 2009 조명·전기설비학회논문지 Vol.23 No.9
뇌전류와 같이 고주파성분을 함유한 서지전류나 전자통신기기의 전자기장해를 유발하는 고주파 이상전류에 대하여 접지전극은 주파수에 의존적인 상당히 복합적인 임피던스의 특성을 보인다. 접지전극의 접지임피던스는 접지전극의 크기를 증가시켜도 낮아지지 않고, 대지의 특성과 주파수 조건에 따라 접지임피던스가 최소값을 보이는 접지전극의 길이가 존재하며, 이 접지전극의 길이를 대지의 특성과 주파수 조건에 대한 임계길이라 정의한다. 본 논문에서는 분포정수회로모델을 이용하여 수직접지전극과 수평접지전극의 임계길이를 산정하였으며, 실험결과와의 비교를 통해 타당성을 확인하였다. For the surge currents like lightning currents containing high frequency components and the abnormal currents having high frequencies which cause the EMI(Electromagnetic interference) problems for the electronic devices and communication instruments, the linear grounding electrodes have the significantly composite impedance characteristics which are dependent on the frequency of the applied current. The impedance of a grounding electrode is not lowered by expanding the dimension of the grounding electrode, and the length of grounding electrode having the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical length. In this paper, the critical lengths for the vertically and horizontally-buried grounding electrodes are calculated by using the distributed parameter circuit model. The propriety of the simulations has been confirmed by comparing the simulated results with the measured results.
김기복(Ki-Bok Kim),안봉영(Bongyoung Ahn),박해원(Haewon Park),김영주(Young-ju Kim),이승석(Seung-Seok Lee) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8
In this study, the capacitive micromachined ultrasonic transducer (cMUT) was developed. Theoretical analysis and finite element analysis of the behavior of membrane (such as resonance frequency, membrane deflection, collapse deflection and collapse voltage) of the cMUT were performed. The design parameters of the cMUT were estimated and are the dimension and thickness of membrane, thickness of sacrificial layer, thickness and size of electrode, size of active element and so on. With the micro-fabrication process, the cMUT was fabricated on the silicon wafer. To measure the membrane displacement of cMUT, the Michelson phase modulation fiber interferometer was constructed. The measured membrane displacement was good agreed with the result of finite element analysis. To estimate the ultrasonic wave generated by the cMUT, the ultrasonic transceiver system was constructed. The developed cMUT shows a good performance and hence will be widely used to the filed of non-contact ultrasonic application.
SAW 온도센서용 음향 반사판 분석 및 무선 온도 측정
김기복(Ki-Bok Kim),김성훈(Seong-Hoon Kim),정재기(Jae-Kee Jeong),신범수(Beom-Soo Shin) 한국비파괴검사학회 2013 한국비파괴검사학회지 Vol.33 No.1
본 연구는 비접촉 무전원 표면탄성파(surface acoustic wave, SAW) 온도센서를 개발하기 위하여 수행 되었다. 단일전극 구조의 IDT(inter-digital transducer)와 434 MHz의 공진주파수를 가지는 SAW 소자를 128˚ rot-X LiNbO₃ 압전기판위에 반도체 공정으로 제작하였다. SAW 온도센서의 음향 반사판에 따른 반사 신호의 특성을 분석하기 위하여 다양한 형태의 음향 반사판을 제작하여 표면탄성파 신호의 반사특성을 분석한 결과 빗살형 전극형태의 반사판이 가장 양호한 반사특성을 나타내었다. SAW 온도센서를 구동하기 위한 신호를 송신하고 온도에 따른 SAW 센서의 출력신호를 수신하기 위하여 다이폴 안테나와 마이크로프로세서에 기반한 무선 송수신 시스템을 제작하였다. 40∼80 ℃의 온도 범위에서 개발된 SAW 온도센서와 무선 송수신 시스템을 평가한 결과 온도증가에 따라 SAW 온도센서의 공진 주파수가 선형적으로 감소하였으며 결정계수가 0.99 이상으로 정확한 무선 온도측정이 가능한 것으로 나타났다. In this study, a wireless and non-power SAW (surface acoustic wave) temperature sensor was developed. The single inter-digital transducer (IDT) of SAW temperature sensor of which resonance frequency is 434 MHz was fabricated on 128˚ rot-X LiNbO₃ piezoelectric substrate by semiconductor processing technology. To find optimal acoustic reflector for SAW temperature sensor, various kinds of acoustic reflectors were fabricated and their reflection characteristics were analyzed. The IDT type acoustic reflector showed better reflection characteristic than other reflectors. The wireless temperature sensing system consisting of SAW temperature sensor with dipole antenna and a microprocessor based control circuit with dipole antenna for transmitting signal to activate the SAW temperature sensor and receiving the signal from SAW temperature sensor was developed. The result with wireless SAW temperature sensing system showed that the frequency of SAW temperature sensor was linearly decreased with the increase of temperature in the range of 40 to 80℃ and the developed wireless SAW temperature sensing system showed the excellent performance with the coefficient of determination of 0.99.
김기복 ( Ki-bok Kim ),노희영 ( Hee-young No ) 한국미용예술경영학회 2011 미용예술경영연구 Vol.5 No.3
As the modern society develops and the importance of lifestyle increases, the service provision of wedding industry is recognized as a necessary item, so that it fits the structure and personality of product and the emotion of customers. Especially because wedding service is recognized as one of the most important events in their lives for the customers, various efforts should be made to increase the satisfaction of the customers. Because it also includes all items, such as a wedding dress, photographs, make up, hair styling, wedding hall, home furnishing, honeymoon destination, etc. commercializing and strategical providing the service are expected to be the cornerstone for the development of wedding industry. Furthermore, considering that the size of domestic wedding industry is significant, and the Southeast Asian countries, such as Vietnam, are interested in the domestic wedding industry, the reorganization of the wedding service at this point will become the foundation for the further development of the wedding service industry.