크롬계 탄화물의 분포와 형태가 니켈계 합금 600의 염기응력부식에 미치는 영향

김선재,최종호,성진경,김우곤,박순동,이창규,정용환,국일현,Kim, Seon-Jae,Choe, Jong-Ho,Seong, Jin-Gyeong,Kim, U-Gon,Park, Sun-Dong,Lee, Chang-Gyu,Jeong, Yong-Hwan,Guk, Il-Hyeon 한국재료학회 1998 한국재료학회지 Vol.8 No.8

32$0^{\circ}C$, 40%NaOH 용액의 autoclave에서 약 300wppm의 탄소를 함유하고 있는 15Cr-9Fe-balanced Ni 합금 판상시편에 대해 응력부식 저항성을 조사하였다. 부식시편은 $700^{\circ}C$, 100시간 동안의 열처리로 합금내부에 석출될 수 있는 가능한 한 많은 양의 크롬계 탄화물을 석출시킨 후, 다시 재용해에 의해 크롬계 탄화물의 형태를 조절하는 $800^{\circ}C$-$950^{\circ}C$범위의 최종열처리를 시행하고 급냉시킨 다음 U-자형으로 응력을 가하여 준비되었다. 최종열처리 온도가 올라감에 따라 시편들의 입계응력부식균열(IGSCC ) 전파속도는 $900^{\circ}C$까지는 거의 직선적으로 증가하다가 $950^{\circ}C$에서는 $700^{\circ}C$에서 얻은 값보다도 더 낮게 감소하였다. 즉, 크롬계 탄화물이 재용해되어 그 밀도가 감소함에 따라 IGSCC저항성이 감소하다가 완전히 재용해된 $950^{\circ}C$ 열처리 조건에서 오히겨 가장 큰 IGSCC 저항성을 나타내었다. 이와같은 최조열처리 온도에 따른 니켈계 합금 600의 부식거동은 입계에 존재하는 크롬계탄화물의 형태변화 때문이 아니라 입계에서 탄소-크롬계 탄화물-크롬간의 상평형에 의해 이루어지는 탄소의 입계편석량이 크롬계탄화물이 존재할 때에는 열처리 온도에 따라 증가하다가 그것이 완전히 재용해 되었을 때 가장 낮아지기 때문인 것으로 생각된다.

고체산화물 연료전지 기술 및 전망

김선재,황종선 ( Sun Jae Kim,Jong Sun Whang ) 한국전기전자재료학회 1997 전기전자재료학회논문지 Vol.10 No.5

TiCl$_4$ 수용액에서 침전법에 의한 결정상 TiO$_2$ 초미분체 제조

김선재,정충환,박순동,권상철,박성,Kim, Sun-Jae,Jung, Choong-Hwan,Park, Soon-Dong,Kwon, Sang-Chul,Park, Sung 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.4

Crystalline TiO2 ultrafine powders were prepared simply by heating and stirring aqueous TiOCl2 solution with {{{{ {Ti }^{4+ } }} concentration of 0.5 M from room temperature to 10$0^{\circ}C$ under 1 atmoshpere. The crystallinity and the particle shape of TiO2 ultrafine powders obtained by simple precipitation method were analyzed us-ing XRD(X-ray diffractometer). SEM(scanning electron microscopy) and TEM(transmission electron mi-croscopy) TiO2 crystalline precipitate with rutile phases is fully formed at the temperatures of up to $65^{\circ}C$ and then TiO2 crystalline precipitate with anatase phase starts to be formed above temperatures $65^{\circ}C$ showing its full formation at 10$0^{\circ}C$ These behaviors of TiO2 crystalline precipitate directly from an aqueous TiOCl2 solution would be caused due to the existence of {{{{ OMICRON ^2+ }} ions from distilled water which oxydize TiOCl2 to TiO2 not hydrolyzing it to Ti(OH)4 Here thermodynamically stable TiO2 rutile phase generally formed at higher temperature is practically precipitated at lower temperatures in this study This may be due to the precipitation by very slow reaction enough to make TiO2 particles allocated into stable rutile structure.

Bluetooth기반의 센서네트워크를 이용한 효율적인 심전도 측정시스템 설계

김선재,오원욱,이창수,민병묵,오해석,Kim, Sun-Jae,Oh, Won-Wook,Lee, Chang-Soo,Min, Byoung-Muk,Oh, Hae-Seok 한국정보처리학회 2009 정보처리학회논문지 C : 정보통신,정보보안 Vol.16 No.6

유비쿼터스 컴퓨팅 기술의 발전과 IT-BT-NT를 포함한 기술간 컨버전스 경향은 유비쿼터스 헬스케어(u-Healthcare)의 실현을 가속화하고 있다. u-Healthcare 시스템은 센서 네트워크로부터 수집된 대량의 생체신호를 신속히 처리 분석하여 의료진에게 전달함으로써 시간과 장소에 관계없이 환자에게 적절한 의료 서비스를 제공할 수 있다. 기존의 u-Healthcare 시스템은 지그비(Zigbee) 프로토콜을 사용하여 센서 노드가 수집한 데이터를 전부 전송함으로써 베이스 노드의 처리 부담이 컸으며 센서 노드의 통신 빈도수가 많았다. 본 논문에서는 지그비 프로토콜 대신 블루투스(Bluetooth)를 사용하여 생명과 직접적 연관이 있는 생체신호 전달에 있어 보다 뛰어난 전송속도를 제공하며 유비쿼터스 환경에서 다양하게 사용되는 모바일 기기들에 효율적으로 적용시킬 수 있는 u-Healthcare 시스템을 설계하였다. 또한 미리 정의된 이벤트에 속하는 데이터만 선별하여 베이스 노드로 전송하는 EEF(Embedded Event Filtering) 기법을 적용하여 통신 빈도수와 처리 비용을 줄였다. 시뮬레이션 결과를 통해 기존의 심전도 측정시스템보다 효율적인 시스템임을 확인하였다. The convergence tendency accelerates the realization of the ubiquitous healthcare (u-Healthcare) between the technology including the power generaation and IT-BT-NT of the ubiquitous computing technology. By rapidly analyzing a large amount of collected from the sensor network with processing and delivering to the medical team an u-Healthcare can provide a patient for an inappropriate regardless of the time and place. As to the existing u-Healthcare, since the sensor node all transmitted collected data by using with the Zigbee protocol the processing burden of the base node was big and there was many communication frequency of the sensor node. In this paper, the u-Healthcare system in which it can efficiently apply to mobile apparatuses it provided the transfer rate in which it is superior to the bio-signal delivery where there are the life and direct relation which by using the Bluetooth instead of the Zigbee protocol and in which it is variously used in the ubiquitous environment was designed. Moreover, by applying the EEF(Embedded Event Filtering) technique in which data in which it includes in the event defined in advance selected and it transmits with the base node, the communication frequency and were reduced. We confirmed to be the system in which it is efficient through the simulation result than the existing Electrocardiogram Measurement system.

SF₆ 가스절연에서 부분방전의 특성분석

김선재,왕국명,박서준,길경석,안창환,Kim, Sun-Jae,Wang, Guoming,Park, Seo-Jun,Kil, Gyung-Suk,An, Chang-Hwan 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.7

This paper deals with the characteristics of partial discharge (PD) for the purpose of a condition based maintenance (CBM) of gas insulated switchgears (GIS) in power equipment. Four types of electrode systems such as a protrusion on enclosure (POE), a particle on spacer (POS), a free particle (FP) and a Floating were designed and fabricated. PD pulses were measured using UHF sensor with a frequency range of 300 MHz~1.4 GHz and a DAQ with a sampling rate of 250 MS/s. Discharge inception voltage (DIV), discharge extinction voltage (DEV), and phase resolved partial discharge (PRPD) were analyzed depending on electrode systems. The average DIV in the POS was 28.8 kV. It was about 1.7 times higher than that in the FP, which was the lowest value of 17.2 kV. The FP shuffled and jumped at the applied voltage of 23.5 kV. Over 95% of PD pulses in the POE were generated in the negative polarity ($181^{\circ}{\sim}360^{\circ}$) of applied voltage. The results showed the phase (${\Phi}$)-magnitude (dBm) of PD pulses by UHF sensor, a cluster was formed separately depending on electrode systems.

SF₆ 압력에 따른 결함별 부분 방전 펄스의 분포 분석

김선재,조향은,정기우,길경석,김성욱,Kim, Sun-Jae,Jo, Hyang-Eun,Jeong, Gi-Woo,Kil, Gyung-Suk,Kim, Sung-Wook 한국전기전자재료학회 2015 전기전자재료학회논문지 Vol.28 No.1

Electrode systems: a protrusion on conductor (POC), a protrusion on enclosure (POE), a crack in epoxy plate and a free particle (FP) were fabricated to simulate insulation defects in a gas insulated switchgear (GIS). $SF_6$ gas was filled in the electrode systems by 3 bar and/or 5 bar, respectively. Partial discharge (PD) pulses were detected through a $50{\Omega}$ non-inductive resistor. A calibration test was carried out according to IEC 60270, and the sensitivity was 0.25 pC/mV. PD pulses were distributed in the phase of $50^{\circ}{\sim}135^{\circ}$ and over 95% of them existed in the phase of $55^{\circ}{\sim}120^{\circ}$ for the POC. PD pulses were distributed in the phase of $230^{\circ}{\sim}310^{\circ}$ and over 90% of them existed in phase of $220^{\circ}{\sim}300^{\circ}$ for the POE. PD pulses occurred in the phase of $40^{\circ}{\sim}60^{\circ}$ and $220^{\circ}{\sim}300^{\circ}$ for the crack, and pulse counts were 25% higher in negative polarity than in positive polarity. PD pulses were distributed in every phase unlike to other three electrode systems and the peak magnitude was measured at $118^{\circ}$ and $260^{\circ}$ for the FP. As described above, PD pulses were observed in positive polarity for the POC, in negative one for the POE, in both one for the crack and the FP. In conclusion, it is expected that the identification rate of defect type can be improved by considering the polarity ratio of PD pulses on the PRPDA method.

Brookite TiO₂ 코팅용 졸의 제조 및 광촉매 효과

김선재,이남희,이강,최창주,Kim, Sun-Jae,Lee, Nam-Hee,Lee, Kang,Choi, Chang-Joo 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.7

Transparent TiO$_{2}$ sols were prepared by hydrothermal synthesis to heat Ti precursor solutions, from Ti hydroxides obtained with neutralizing aqueous TiOCl$_{2}$ solutions having various concentrations of NaCI by aqueous NaOH solution, in the autoclave at 120$^{\circ}C$ The photocatalytic abilities of glass beads coated with the sol for gaseous benzene were evaluated. As a result, it was found that due to the increase of brookite phase in TiO$_{2}$ by controlling the concentration of Na ion the optical absorption of TiO$_{2}$ increases toward long wavelength but that in the area of short wavelength becomes relatively low and consequently the photocatalytic performance of TiO$_{2}$ thin film for benzene gas rather decreases, compared to that of composite film of anatase and brookite phases. These results suggest that in order for coated TiO$_{2}$ thin film to have high dissociation performance for benzene gas it is effective to form anatase and brookite phases compositely in TiO$_{2}$.

잠수함용 LED 등기구의 제작과 평가

김선재,김세진,길경석,안창환,송동영,Kim, Sun-Jae,Kim, Se-Jin,Kil, Gyung-Suk,An, Chang-Hwan,Song, Dong-Young 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.10

In order to develop a LED luminaire for naval-submarines which can replace a conventional one with two-compact fluorescent lamp (CFL) of 18 W, we analyzed the electrical and optical performance of the conventional luminaire. A LED luminaire was fabricated as compact as possible based on the analyzed data. The weight of the prototype LED luminaire is 1.8 kg, reducing up to 58% of the conventional one. The use of LED package for the submarine luminaire could reduce the power consumption from 38 W to 14.5 W with the same optical performance. The reason is that the optical efficacy of the LED luminaire improved by 2.47 times as 61.9 lm/W, compared to 25.1 lm/W for the conventional one.

SF₆가스 중 파티클 형태에 따른 부분방전의 특성

김선재(Sun-Jae Kim),왕국명(Guoming Wang),윤민영(Min-Young Yun),길경석(Gyung-Suk Kil) 한국철도학회 2015 한국철도학회 학술발표대회논문집 Vol.2015 No.10

본 논문에서는 SF6가스의 절연 시스템에서 발생 가능한 결함의 위험성을 분석하기 위하여 파티클 형태에 따른 부분방전의 특성을 기술하였다. 파티클은 볼, 사다리꼴, 직사각형 및 Twist로 분류하였다. 파티클이 설치된 전극계에 직류고전압을 최대 25 ㎸ 인가하였다. 각각의 파티클에 대하여 방전개시전압(DIV), 방전소멸전압(DEV) 및 TRPD(Time Resolved Partial Discharge)를 분석하였다. 실험결과, 네 종류의 파티클 중 Twist의 방전개시전압이 가장 낮게 검출되었기 때문에 위험성이 가장 높을 것으로 판단된다. 또한 TRPD가 파티클의 형태에 따라 상이하게 분석되었다. This paper described the characteristics of partial discharge depending on particle types to analyze the risk of defects in SF6 gas insulation system. The particle types were classified into ball, trapezoid, rectangle, and twist. HVDC was applied to the electrode system including a particle up to 25 ㎸max. We analyzed discharge inception voltage(DIV), discharge extinction voltage(DEV), and the time resolved partial discharge(TRPD). The risk probability of the twist was the highest due to its lowest DIV. Also, TRPD of the particles were compared.

SOFC의 전해질재료를 위한 20㏖% Gd-doped CeO₂ 소결체의 재열처리 온도에 따른 전기전도도의 변화

金宣在(Sun-Jae Kim),黃宗善(Jong-Sun Hwang),崔昌柱(Chang-Joo Choi) 대한전기학회 1998 전기학회논문지 Vol.47 No.11