시간영역반사법을 이용한 유동성 채움재의 특성 연구

한우진(Woojin Han),이종섭(Jong-Sub Lee),변용훈(Yong-Hoon Byun),조삼덕(Samdeok Cho),김주형(Juhyong Kim) 한국지반환경공학회 2016 한국지반환경공학회논문집 Vol.17 No.4

기존 뒤채움재의 대체방안으로 고려되는 유동성 채움재(Controlled Low Strength Material, CLSM)의 경화 특성 및 강도발현은 시공기간을 결정하는 주요 요소이다. 본 연구에서는 시간영역반사법(Time Domain Reflectometry, TDR)을 이용하여 유전상수를 도출함으로써 CSLM의 경화 특성을 모니터링하고, 산정된 유전상수와 일축압축강도간의 관계를 분석해보고자 하였다. CLSM 시료는 시멘트, 비회, 실트, 모래, 급결제 및 물로 배합되었으며 배합된 시료의 플로우, 단위중량, 일축압축강도와 같은 재료 특성을 조사하였다. 양생 기간 동안 CLSM의 유전율 특성을 모니터링하기 위하여 TDR 프로브가 설치된 몰드 및 Reflectometer를 이용하여 측정시스템을 구성하였다. 실험결과 유전상수는 양생 초기에 일정한 값을 유지하다, 시간이 진행됨에 따라 점차 감소하는 것으로 나타났다. 또한, 일축압축강도와 유전상수를 회귀분석한 결과 두 물성 사이에는 반비례적인 거듭제곱함수의 관계가 있음을 보여주었다. 본 연구에서 제안한 시간영역반사법을 이용한 CLSM의 특성 모니터링은 일축압축강도를 추정할 수 있는 현장 비파괴시험기법으로 효과적으로 사용될 수 있을 것으로 기대된다. The hydration process of Controlled Low Strength Material (CLSM) used for backfill is the primary factor to determine the construction period. The objective of this study is to monitor the hydration process of CLSM using the Time Domain Reflectometry (TDR) and to establish the relationship between dielectric constant and compressive strength. The CLSM specimen is composed of cement, flyash, silt, sand, accelerator, and water. The material characteristics of the CLSM including flow, unit weight, compressive strength are investigated. To measure the dielectric constant of the CLSM during the curing time, TDR probe incorporated with a mold and a reflectometer are used. Experimental results show that the dielectric constant remains constant at early stage, and then decreases as the curing time increases. In addition, the dielectric constant is related to the compressive strength in inverse power function. This paper suggests that the TDR technique may be used as a non-destructive testing method in order to estimate the compressive strength of the CLSM mixture under construction.

양생시간에 따른 CLSM의 압축강도 및 압축파 속도 상관성 연구

한우진(Woojin Han),이종섭(Jongsub Lee),조삼덕(Samdeok Cho),김진환(Jinhwan Kim),변용훈(Yonghoon Byun) 한국지반환경공학회 2015 한국지반환경공학회논문집 Vol.16 No.11

다짐이 어려운 지중매설물의 밀실한 충전을 위해 저강도 및 고유동성의 특성을 갖는 유동성 채움재(Controlled Low Strength Materials, CLSM)의 개발 및 현장적용에 대한 연구가 있어 왔다. 본 연구에서는 압축파 속도 및 일축압축강도를 측정하여 양생시간에 따른 CLSM의 강성 및 강도 특성을 비교하고자 하였다. CLSM의 재료는 모래와 실트, 플라이애쉬, CSA계 시멘트, 및 물을 혼합하여 충분한 유동성 및 낮은 강도를 나타내도록 구성하였으며, 플로우, 단위중량, 일축압축강도와 같은 CLSM의 물리적 특성을 분석하였다. 또한 경화되기 전부터 CLSM의 강성특성을 모니터링하기 위하여 압축파 측정용 셀을 제작한 후, 셀에 트랜스듀서를 접하여 압축파를 측정하였다. 실험결과, 일축압축강도는 양생초기에 크게 증가하였고, 기간이 길어질수록 증가량이 줄어드는 것으로 나타났다. 또한 압축파 속도는 양생기간이 길어짐에 따라 증가하였으며, 일축압축강도와 압축파 속도 사이에는 지수함수 관계를 보여주었다. 본 논문에서 제안된 압축파 측정을 통하여 CLSM의 강성변화를 파악할 수 있으며, 경화가 미완료된 양생초기의 일축압축강도 평가에도 효과적으로 활용될 수 있을 것으로 예상된다. The development of Controlled Low Strength Material (CLSM), which is a highly flowable material, has been performed for the application of backfill. The objective of this study is to compare the compressive strength and compressive wave velocity of CLSM according to the curing time. To investigate the characteristics of the CLSM consisting of sand, silt, water, flyash, and CSA cement, uniaxial compression test and flow test were carried out. For the measurement of compressional waves, a cell and a couple of transducers were used. The test results show that the compressive strength increases with the curing time, while the increment of compressive strength decreases with the curing time. In addition, the compressive wave velocity increases with the curing time, and the correlation between the compressive wave velocity and compressive strength is similar to exponential function. This study suggests that the correlation between the compressive wave velocity and compressive strength may be effectively used for the estimation of compressive strength of the CLSM at early curing time.

양생시간에 따른 유동성 채움재의 전단파 특성

한우진(Woojin Han),이종섭(Jong-Sub Lee),변용훈(Yong-Hoon Byun),조삼덕(Samdeok Cho),김주형(Juhyong Kim) 한국지반환경공학회 2016 한국지반환경공학회논문집 Vol.17 No.3

기존의 콘크리트 조기강도의 발현 및 응결특성을 파악하기 위하여 탄성파 기법을 이용한 콘크리트의 모니터링에 대한 많은 연구가 수행되어 왔다. 본 연구에서는 저강도 콘크리트의 일종인 유동성 채움재(CLSM)에 대한 응결특성을 파악하기 위하여 전단파 트랜스듀서인 벤더 엘리먼트를 활용하였으며, 양생시간에 따른 CLSM의 전단파 특성을 조사하였다. 조기강도 및 유동성을 확보하기 위하여 CLSM은 CSA계 시멘트, 비회, 실트 및 모래, 급결제, 물로 구성되었으며 세립분 함량에 따른 전단파 특성 변화를 보기 위해 3종류의 CLSM 시료를 배합하였다. 전단파 측정을 위한 셀은 셀 벽면에 한 쌍의 벤더 엘리먼트가 설치되었고, 배합된 CLSM 시료를 전단파 측정용 셀에 조성하여 양생시작부터 28일간 전단파 변화를 모니터링 하였다. 실험결과 CLSM의 세립분 함량에 상관없이 양생시간이 증가함에 따라 전단파의 공진주파수 및 속도는 증가하였다. 또한, 양생시작부터 약 10시간까지는 전단파의 진폭도 증가하였으며, 동일한 시각에서는 세립분 함량이 적을수록 공진주파수 및 속도가 크게 나타났다. 본 논문에서 제안된 벤더 엘리먼트를 이용한 전단파 측정기법은 양생기간에 따른 CLSM의 응결특성을 평가하는 데 유용하게 사용될 수 있을 것으로 판단된다. The ultrasonic waves for monitoring concrete materials have been used to investigate the setting and hardening process of concrete. This paper presents the application of bender elements for monitoring the hardening properties of Controlled Low Strength Material (CLSM) and the characterization of shear waves in CLSM according to curing time. To ensure the early age properties and flow, the CLSM consists of CSA cement, sand, silt, water, fly ash, and accelerator. In addition, three different type specimens according to fine contents are mixed. A couple of bender elements are installed at the wall of measurement cell and the CLSM specimen are prepared at the measurement cell for 28 days. Experimental results show that the resonant frequency and shear wave velocities increase with an increase in the curing time, regardless of the fine contents. Up to ten hours, the amplitudes of shear waves also increase, and the resonant frequency and shear wave velocities at the same time increase as the fine contents increase. The shear wave measurement technique using the bender elements may be effectively used to evaluate the hardening properties of CLSM along the curing time.

DCA-MOD 방법으로 제조된 YBCO 박막의 미세조직에 미치는 열처리 효과

김병주,김혜진,조한우,유석구,유정희,이희균,홍계원,Kim, Byeong-Joo,Kim, Hye-Jin,Cho, Han-Woo,Yu, Seok-Koo,Ryu, Jung-Hee,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2007 Progress in superconductivity Vol.9 No.1

[ $YBa_2Cu_3O_{7-{\delta}}$ ] films have been prepared on $LaAlO_3$ (100) single-crystal substrates by a metalorganic deposition using dichloroacetate precursors (DCA-MOD). Calcination conditions were varied in order to optimize the microstructure and the superconducting properties of YBCO film. Coated films were calcined at various temperatures ranging from $400{\sim}700^{\circ}C$ in flowing humid oxygen atmosphere. Ramping rate to calcination tempertures was $2.22^{\circ}C/min$. Conversion heat treatment was performed at $800^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. Observations of surface and cross sectional SEM microstructure showed that the particle size in the calcined film increased in the range of 100-200 nm with heating rate and the calcination temperature. SEM EDS analysis showed that 13 a/o of chlorine was contained in the calcined film. It was also observed that the porosity increased with the heating rate and temperature. Porous microstructure was developed when YBCO films were prepared using porous calcined film. Dense microstructure and high $J_c$ over $1\;MA/cm^2$ was obtained when calcination was carried out at the temperature of $500^{\circ}C$ with a heating rate of $2.22^{\circ}C/min$.

DCA-MOD 법으로 YBCO 박막 제조시 하소열처리의 승온속도 효과

김병주,김혜진,조한우,권연경,유정희,이희균,홍계원,Kim, Byeong-Joo,Kim, Hye-Jin,Cho, Han-Woo,Kwon, Youn-Kyung,Ryu, Jung-Hee,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2007 Progress in superconductivity Vol.8 No.2

High $J_c\;YBa_2Cu_3O_{7-x}$ superconducting films have been fabricated $LaAlO_3(100)$ substrate by MOD method using dichloroacetic acid(DCA) as chelating solvent for preparing precursor solution. Heating rate was varied in order to optimize the calcination heat treatment condition in DCA-MOD method. Coated films were calcined at lower temperature up to $500^{\circ}C$ in flowing humid oxygen atmosphere. The heating rate was calcined from $13.3^{\circ}C/min\;to\;0.28^{\circ}C/min$. Conversion heat treatment was performed $800^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. Surface and cross sectional SEM microstructures showed that particle sizes were increased with heating rate at a calcination step. The amount of pores was increased with heating rate in the calcined films. Dense microstructure and sharp texture were developed in an YBCO films after conversion heat treatment. A high critical current density (Jc) of $1.26MA/cm^2$ (@77 K and self-field) was obtained for the YBCO film which was prepared with a heating rate of $0.28^{\circ}C/min$.

2009 H1N1 influenza virus infection and necrotizing pneumonia treated with extracorporeal membrane oxygenation

지선태,이옥정,양지혁,안강모,조중범,한우식,김예진 대한소아청소년과학회 2011 Clinical and Experimental Pediatrics (CEP) Vol.54 No.8

A 3-year-old girl with acute respiratory distress syndrome due to a H1N1 2009 influenza virus infection was complicated by necrotizing pneumonia was successfully treated with extracorporeal membrane oxygenation (ECMO). This is the first reported case in which a pediatric patient was rescued

질산염 무기금속 화합물의 분무열분해법에 의한 High-$J_c$ YBCO 박막 제조

홍석관,김재근,김호진,조한우,유석구,안지현,주진호,이희균,홍계원,Hong, Suk-Kwan,Kim, Jae-Gun,Kim, Ho-Jin,Cho, Han-Woo,Yu, Seok-Koo,Ahn, Jin-Hyun,Joo, Jin-Hoo,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1

High $J_c$ over 1 $MA/cm^2$ YBCO film has been successfully prepared using nitrate precursors by spray pyrolysis method. Aerosol drolpets generated using a concentric spray nozzle were directly sprayed on a $LaAlO_3$(100) single crystal substrate. The cation ratio of precursor solution was Y:Ba:Cu=1:2.65:1.35. The distance between nozzle and substrate was 15 cm. Deposition temperature was ranging from $750^{\circ}C\;to\;800^{\circ}C$. Deposition pressure was 100 Torr, and oxygen partial pressure was varied from 10 Torr to 50 Torr. The microstructure, phase formation, texture development and superconducting properties of deposited films were largely changed with oxygen partial pressure. Deposited films showed a texture with(001) planes parallel to substrate plane. High quality film was obtained when film was deposited at $760^{\circ}C$ with an oxygen partial pressure of 30 Torr. The critical current density($J_c$) of the YBCO film was 1.75 $MA/cm^2$ at 77 K and self-field.

분무 열분해 CVD법으로 이동 중인 LaAlO_3(100) 단결정 위에 증착시킨 YBCO 박막의 특성

김재근,홍석관,김호진,유석구,조한우,안지현,주진호,이희균,홍계원,Kim, Jae-Gun,Hong, Suk-Kwan,Kim, Ho-Jin,Yu, Seok-Koo,Cho, Han-Woo,Ahn, Jin-Hyun,Joo, Jin-Hoo,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1

YBCO films were deposited on a moving substrate by a spray pyrolysis method using nitrate aqueous solution as precursors. Deposition was made on $LaAlO_3$(100) single crystal substrate by spraying precursor droplets generated by a concentric nozzle. The cation ratio of precursor solution was Y:Ba:Cu=1:2.65:4.5. The distance between nozzle and substrate was 15 cm. Substrate was transported with a speed ranging from 0.23 cm/min to 0.5 cm/min. Films were deposited at the pressure ranging from 10 Torr to 20 Torr and the deposition temperature was ranged from $740^{\circ}C\;to\;790^{\circ}C$. Oxygen partial pressure was controlled between 1 Tow and S Torr. Superconducting YBCO films were obtained from $740^{\circ}C\;to\;790^{\circ}C$ with an oxygen partial pressure of 3 Torr. Scanning electron microscope(SEM) and X-ray diffraction(XRD) observation revealed that films are smooth and highly texture with(001) plans parallel to substrate plane. Highest Jc was 0.72 $MA/cm^2$ at 77K and self-field for the film with a thickness of 0.15 m prepared at a substrate temperature of $740^{\circ}C$ and $PO_2$=3 Torr.

분사열분해 CVD 법으로 증착된 YBCO 박막의 특성에 미치는 기판 온도의 영향

김재근,홍석관,유석구,조한우,김병주,안지현,홍계원,이희균,Kim, Jae-Geun,Hong, Suk-Kwan,Yu, Seok-Koo,Cho, Han-Woo,Kim, Byung-Joo,Ahn, Ji-Hyun,Hong, Gye-Won,Lee, Hee-Gyoun 한국초전도학회 2007 Progress in superconductivity Vol.9 No.1

YBCO films have been synthesized using a spray pyrolysis method. We used nitrates of Y, Ba, Cu as precursors. Deposition was made on $LaAlO_3$ (100) single crystal substrate by spraying the mist of aqueous precursor solution generated by a concentric nozzle. The distance between concentric nozzle and substrate was 15 cm. C-axis oriented films were obtained at deposition temperature of $740{\sim}800^{\circ}C$ and working pressure of 20 Torr. Oxygen partial pressure was 3 Torr and substrate was transported with the speed ranging from 0.23 cm/min to 0.7 cm/min by reel to reel. Scanning electron microscope (SEM) and X-ray diffraction (XRD) observation revealed that films are smooth and highly textured with (001) planes parallel to substrate. Highest critical current density (Jc) was $1.38\;MA/cm^2$ at 77K and self-field for the film with a thickness of $0.5\;{\mu}m$ prepared at a substrate temperature of $780^{\circ}C$ and $PO_2\;=3\;Torr$. The effect of temperature on the microstructure and YBCO phase formation will be discussed.

쾌적한 병실 제공을 위한 병실 실시간 모니터링 시스템의 제안

곽수민(Soo Min Gwak),한우성(Woo Sung Han),조유리(Yoo Ree Cho),최관해(Gan Hae Choe),이회문(Hoe Mun Lee),정연만,조동욱(Dong Uk Cho) 한국통신학회 2018 한국통신학회 학술대회논문집 Vol.2018 No.1