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조승재,홍완표,Cho, Seung-Jae,Hong, Wan-Pyo 한국정보통신학회 2008 한국정보통신학회논문지 Vol.12 No.5
본 논문은 $1{\sim}20Ghz$의 대역별 위성통신 신호에 미치는 영향에 대해 예측 모델을 제안하고 기존 황사시 측정한 데이터와 비교 분석하였다. 황사의 감쇠 특성을 분석하기 위해 황사 물질에 대한 이론적 분석을 하였으며 이를 통해 예측 감쇠량을 제시하였다. 예측 감쇠량을 실제 우리나라 황사 강도와 가시거리와 높이 등의 파라미터를 적용한 이론치를 구하여 4년간 측정한 실측치와 비교하였고 이를 토대로 황사로 인한 감쇠를 미리 예측 가능할 것으로 확인되었다. This paper presents the prediction model of attenuation characteristics of satellite communication signals operating in the range from 1 to 20GHz, associated with the effects of the Asian Dust. And this paper analyze the effects of the Asian Dust in theory that dust particles size and density, OPC, signal levels, exponentail distribution and the permittivity. The prediction model of the dust attenuation was got, combining the formula of the complex dielectric constant of Asian dust. Expressions for specific attenuation and attenuation are derived in terms of the height, visibility. Therefore it make an investigate to the prediction model of attenuation characteristics continuously.
전기자동차 모터 회전자의 온도에 따른 자기적 특성 변화
조승재(Seung-jae Cho),김태원(Tae-Won Kim),문기웅(Ki-Woong Moon),조대형(Dae-Hyoung Cho) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.7
전기자동차 모터는 온도가 증가할수록 출력이 감소하는데, 일정 온도 이상 증가하면 회전자의 영구자석에서 회복 불가능한 비가역 감자 (irreversible demagnetization) 현상이 발생, 모터의 출력이 영구적으로 감소한다. 본 논문은 온도 증가에 따른 감자의 영향을 측정하기 위해 회전자의 온도를 -20도, 20도, 60도, 120도, 150도로 증가시키면서 회전자 표면의 자속밀도를 측정하고, 마지막으로 다시 20도로 냉각하여 자속밀도를 측정하였다. 측정 결과는 온도가 증가할수록 고정자의 한 극에 입사하는 자속량이 감소함과 회전자가 다시 냉각되었을 때 비가역 감자가 발생함을 정량적으로 보여준다.
PLC 프로그래밍을 위한 Loader 소프트웨어(pSET) 개발
조승재(Sengjae Cho),구경모(Kyungmo Koo),유병용(Byungyong You),김태욱(Tae-Wook Kim),심태윤(Taeyoon Shim),이진수(Jin S. Lee) 대한전자공학회 2007 대한전자공학회 학술대회 Vol.2007 No.7
The pSET (POSAFE-Q Software Engineering Tool, pSET) is a loader software to program POSAFE-Q PLC and is developed as a part of the KNICS (Korea Nuclear Instrumentation & Control System) project. It satisfies IEC61131-3 standards and supports GUI environment, C language, monitoring/debugging function and simulations. In this paper, we introduce the configuration of pSET software, code conversion procedure to generate assembly code from LD, FBD or CC code and monitoring/debugging function. We discuss what is important in developing PLC loader software.
Chemical Mechanical Planarization of Copper Bumps on Printed Circuit Board
정문기,조승재,이현섭,이아름,강정윤,최진원,김진호,정해도 한국정밀공학회 2011 International Journal of Precision Engineering and Vol. No.
This paper deals with the planarization of copper bumps to improve the bonding performance and reliability of printed circuit board (PCB) manufacturing to improve by using flip chip during the fabrication process of the PCB. Authors tried to develop a novel planarization process using polishing techniques before the continuous process at the PCB fabrication. An experiment was implemented by mechanical polishing (MP) using alumina abrasives mixed with deionizer water (DIW), and by chemical mechanical polishing (CMP) added with oxidizer of HF. CMP showed superior results to MP with mirror surface less than Ra 3nm and minimum step height deviation of 1um, resulting in high bonding performance and reliability. Therefore, CMP is a strong tool for reserving a sufficient margin in the PCB manufacture process.
플래시버트 용접과 연속열간압연법으로 제조된 철근의 기계적 성질과 미세조직에 미치는 합금원소의 영향
김기원,조승재,강정윤,Kim, Ki-Won,Cho, Seung-Jae,Kang, Chung-Yum 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.3
Flash butt welding is applied in many industries. New technology was developed recently for joining billets which called "EBROS (Endless Bar Rolling System)". After reheating billets in furnace, two billets were joined using flash butt welding. The objective of this study was to investigate the effect of alloying elements on mechanical properties of flash butt welded zone of hot rolled steel bar. The tensile properties on welded zone of Fe-Mn steel and Fe-Mn-V steel were dropped as compared with non-welded zone. Fe-Mn-Nb steel was opposed to the former. It was found that the white band at the welded zone had high ferrite volume fraction and large ferrite grain size. The vertical white band between flash butt welded billets was transformed into an arrowhead it of steel bar. According to this band, softening has been appeared. There was a interesting phenomenon with HAZ of Fe-Mn-Nb Steel, 40nm scale of particles were observed and hardness of HAZ was higher than non-welded zone.
SAC 305솔더와 ENIG 기판의 접합강도에 미치는 저주파 수소라디칼처리의 영향
이아름,조승재,박재현,강정윤,Lee, Ah-Reum,Jo, Seung-Jae,Park, Jai-Hyun,Kang, Chung-Yun 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.1
Joint strength between a solder ball and a pad on a substrate is one of the major factors which have effects on electronic device reliability. The effort to improve solder joint strength via surface cleaning, heat treatment and solder composition change have been in progress. This paper will discuss the method of solder ball joint strength improvement using LF hydrogen radical cleaning treatment and focus on the effects of surface treatment condition on the solder ball shear strength and interfacial reactions. In the joint without radical cleaning, voids were observed at the interface. However, the specimens cleaned by hydrogen-radical didn't have voids at the interface regardless of cleaning time. The shear strength between the solder ball and the pad was increased over 120%(about 800gf) when compared to that without the radical treatment (680gf) under the same reflow condition. Especially, at the specimen treated for 5minutes, ball shear strength was considerably increased over 150%(1150gf). Through the observation of fracture surface and cross-section microstructure, the increase of joint strength resulted from the change of fracture mode, that is, from the solder ball fracture to IMC/Ni(P) interfacial fracture. The other cases like radical treated specimen for 1, 3, 7, 9min. showed IMC/solder interfacial fracture rather than fracture in the solder ball.