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김경헌,강주용,최익준,이명철 대한이비인후과학회 부산,울산,경남 지부회 2017 임상이비인후과 Vol.28 No.2
Atypical fibrous histiocytoma is a rare variation of cutaneous fibrous histiocytoma. The histologic features of atypical fibrous histiocytoma include a proliferation of pleomorphic, spindle, and/or polyhedral cells with mainly large, hyperchromatic, irregular, bizarre nuclei, set in a background of classic features of fibrous histiocytoma. It includes spindle cell areas showing a storiform pattern and thickened, hyaline collagen bundles. Generally, atypical fibrous histiocytoma is treated by complete excision, and in most cases, a benign outcome is expected. However it has a tendency to recur locally after excision and there are a few recent reports of occasional distant metastasis. Recently we experienced a case of atypical fibrous histiocytoma in nasal cavity. Therefore we present this case of atypical fibrous histiocytoma with a brief review of literature.
포토리소그래피 공정만을 이용한 단일벽 탄소 나노튜브의 자가 조립 공정에 대한 연구와 단일벽 탄소나노튜브 다중채널 전계효과 트랜지스터 제작
김경헌,김태근,김선호,변영태 한국물리학회 2010 새물리 Vol.60 No.6
In this research, we investigated a selective assembly method of fabricating single-walled carbon nanotubes (SWNTs) on a silicon (Si)surface by using only a photolithographic process; then, we fabricated field-emission transistors (FETs). Photoresist (PR)patterns were made on a silicon-dioxide (SiO₂)-grown Si substrate by using a photolithographic process. This PR-patterned substrate was dipped into a SWNT solution dispersed in dichlorobenzene (DCB). The PR patterns were removed by using aceton. As a result,selectively-assembled SWNT channels could be obtained between two electrodes (source and drain electrodes) without complicated chemical steps using octadecyltrichlorosilane (OTS). Finally, we successfully fabricated SWNT-based multi-channel FETs by using our novel self-assembly method. 본 논문에서 우리는 오직 포토리소그래피 (photolithography) 공정만을이용하여 단일벽 탄소 나노튜브 (single-walled carborn nanotube;SWNT)를 실리콘 기판위에 선택적으로 흡착시키는 공정 방법과 이를이용한 전계효과 트랜지스터 (field emission transistor; FET)의제작방법에 대해 고찰하였다. 산화막(SiO₂)이 형성된 실리콘 기판위에포토리소그래피 공정을 이용하여 임의의 포토레지스트 패턴이형성되었다. 포토레지스트 패턴된 기판은 SWNT가 분산된 다이클로로벤젠(dichlorobenzene)용액 속에 담가진다. 다음은 포토레지스트 패턴이제거되고, 결과적으로 octadecyltrichlorosilane (OTS)를 사용하는기존의 복잡한 화학적 과정 없이도 소오스와 드레인 전극사이에선택적으로 SWNT 채널들이 자기조립 되었다. 이 자기조립공정이이용됨으로서 SWNT가 멀티 채널로 구성된 다중채널 FET가 성공적으로제작되었다.
IoT를 사용한 센서 네트워크 기반의 실시간 토양 습도 모니터링
김경헌,김희동 한국전기전자재료학회 2022 전기전자재료학회논문지 Vol.35 No.5
This paper reports a method to use a wireless sensor network deployed in the field to real-time monitor soil moisture, warning when the moisture level reaches a specific value, and wirelessly controlling an additional device (LED or water supply system, etc.). In addition, we report all processes related to wireless irrigation system, including field deployment of sensors, real-time monitoring using a smartphone, data calibration, and control of additional devices deployed in the field by smartphone. A commercially available open-source Internet of Things (IoT) platform, NodeMCU, was used, which was combined with a 9V battery, LED and soil humidity sensor to be integrated into a portable prototype. The IoT-based soil humidity sensor prototype deployed in the field was installed next to a tree for on-site demonstration for the measurement of soil humidity in real-time for about 30 hours, and the measured data was successfully transmitted to a smartphone via Wifi. The measurement data were automatically transmitted via e-mail in the form of a text file, stored on the web, followed by analyses and calibrations. The user can check the humidity of the soil real-time through a personal smartphone. When the humidity of a soil reached a specific value, an additional device, an LED device, placed in the field was successfully controlled through the smartphone. This LED can be easily replaced by other electronic devices such as water supplies, which can also be controlled by smartphones. These results show that farmers can not only monitor the condition of the field real-time through a sensor monitoring system manufactured simply at a low cost but also control additional devices such as irrigation facilities from a distance, thereby reducing unnecessary energy consumption and helping improve agricultural productivity.
김경헌 한국광학회 2003 광학과 기술 Vol.7 No.2
근래에 들어와 초단 광펄스 생성 기술이 발전되어 다양한 초고속 현상 및 물성 분석 연구에 활용되고 있으며 통신 및 신호처리에 대한 응용 기술에 대해서도 연구되고 있다. 특히 대용량 광통신 기술로는 이미 기술적인 성숙도를 보인 파장분할다중 (WDM) 기술과 더불어 전기적 신호를 다중화하여 광신호로 변환하여 통신하는 전기적 시간분할다중 (ETDM) 기술이 있으며, 초단 광펄스를 이용하는 40 Gbps 급 이상의 고속 광시간분할다중 (OTDM) 광통신 기술도 연구되고 있다. 이 OTDM기술에 있어서는 초단 광펄스 생성 기술과 고속 광신호 다중화 및 역다중화 기술. 광동기신호 재생 기술 등이 주요 핵심 기술을 이루고 있다. 본 글에서는 근래에 들어와 활발히 연구되고 있는 광통신용 펨토초급 초단 광펄스 생성 기술과 이를 이용한 40 Gbps급 이상의 고속 광시간분할다중 (OTDM) 광전송 및 광신호처리에 관련된 기술 현황을 살펴보고자 한다.
Deep Sleep Mode Based NodeMCU-Enabled Humidity Sensor Nodes Monitoring for Low-Power IoT
김경헌,김희동 한국전기전자재료학회 2020 Transactions on Electrical and Electronic Material Vol.21 No.6
In this paper, we provided an effi cient way to reduce the power consumption of sensor nodes in an IoT ecosystem. In many cases, IoT objects are battery powered and need to be energy efficient as the most important requirement in order to have a stable operation over long periods of time. The deep sleep mode is used for low power monitoring of NodeMCU. Commercial humidity sensors normally sleep and wake up once an hour to measure soil humidity. The measured humidity data was transmitted wirelessly to Google Sheets via a NodeMCU Wi-Fi module. The user can check the humidity of the soil by referring to the transmitted data values. The power consumption was reduced by about 83% for 1 h than compared to the always awake mode.