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단위수량 저감에 따른 수화열저감재를 사용한 콘크리트의 수화발열 특성
서동균(Suh, Dong Kyun),김규용(Kim, Gyu Yong),손민재(Son, Min Jae),유하민(Eu, Ha Min),이예찬(Lee, Ye Chan),남정수(Nam, Jeong Soo) 한국콘크리트학회 2021 한국콘크리트학회 학술대회 논문집 Vol.33 No.2
본 연구에서는 수화열저감재 사용에 따른 강도 저하를 보상하기 위해 단위수량을 저감한 고강도 콘크리트의 수화발열 특성을 평가하려고 한다. 간이단열온도 거푸집을 제작하여 시험체 중심부의 온도를 측정하였다. 결과적으로 수화발열 저감과 동시에 강도보상을 위하여 단위수량을 접근하는 방식은 10kg 이내로 하는 것이 워커빌리티를 확보할 수 있을 것으로 기대된다. This study is aim to evaluate the hydration heat characteristics of concrete with a reduced unit water weight in order to compensate for the decreased strength by the use of heat reducer. The simple insulation mold was made, the center temperature was measured. As a result, it is expected that workability can be secured if the method of approaching the unit water weight for strength compensation while reducing hydration fever is less than 10 kg.
초음파를 이용한 온도 및 강도별 콘크리트의 고조파 특성
서동균(Suh, Dong-kyun),김규용(Kim, Gyu-yong),편수정(Pyeon, Su-Jeong),이예찬(Lee, Ye-chan),유하민(Eu, Ha-min),남정수(Nam, Jeong-soo) 대한건축학회 2021 대한건축학회 학술발표대회 논문집 Vol.41 No.1
This study is aim to assess ultrasonic pulse power behavior when concrete is exposed to high temperature in different strength boundary. Test was conducted when specimens were cooled after heating to target temperature in 30, 70, 110 MPa strength level. Ultrasonic pulse wave was generated 50kHz using function generator and AE sensor which were used as transducer and receiver. As a result, fundamental wave power were decreased when temperature is increasing and strength was decreasing. It is because ultrasonic pulse wave power is highly related to matter density, only high strength like 110MPa shows 2<sup>nd</sup>, 3<sup>rd</sup> harmonics and high ultrasonic pulse power is received. To investigate 2<sup>nd</sup>, 3<sup>rd</sup> harmonic in lower strength concrete, further study that considering power of ultrasonic wave and transducer etc. is needed.
2006년 도축장 출하 지육에 대한 항생물질 잔류현황 분석
서동균 ( Dong Kyun Suh ),박대현 ( Dae Hyun Park ),홍주연 ( Ju Yeon Hong ),임현숙 ( Hyun Sook Lim ),김경희 ( Kyung Hee Kim ),이춘식 ( Chun Sik Lee ) 한국동물위생학회 2008 한국동물위생학회지 (KOJVS) Vol.31 No.1
A total of 3,943 samples (beef 698, pork 2,178 and chicken 1,067)were collected from slaughter houses in Daegu from January to December 2006 for analysis of antimicrobial residues. The results were also comparatively analyzed with those carried out from 16 veterinary service laboratories nationwide as a part of national residue program in 2006. The samples from 11 farms (cattle 2, pig 9) were found to exceed the legal limit. Among them 5 were classified as tetracyclines, 3 as β-lactams, 2 as sulfonamides and 1 as quinolone. Nationally a total of 222 farms (241 cases) were found to violate the residual limits, of which 47.3% were detected by screening test, followed by surveillance (38.3%). Failure to observe withholding periods of antimicrobial drugs after treatment was the most significant cause of the non-compliance.
MC1R gene의 PCR-RFLP를 이용한 한우,젖소고기 감별
서동균 ( Dong Kyun Suh ) 한국동물위생학회 2008 한국동물위생학회지 (KOJVS) Vol.31 No.3
The objective of this study was to differentiate the beef species between Hanwoo and Holstein from a total of 1,081 beef samples using PCR-RFLP of MC1R gene. When a PCR product of 403 bp specific band amplified from bovine MC1R gene sequence was digested with restriction enzyme MspA1I, Hanwoo type showed 2 bands, 220 bp and 183 bp size bands. Holstein type, however, showed three bands, 220 bp, 138 bp and 45 bp size band, respectively. The results of the differential test for beef species were as following; 7 samples (0.64%) were determined to Holstein type, of which 4 were submitted from administrative authorities, other 3 from self-collection planing, and none from civilian clients including school.
고온이력을 받은 콘크리트의 강도별 기본파와 고조파 특성
서동균 ( Suh Dong-kyun ),김규용 ( Kim Gyu-yong ),손민재 ( Son Min-jae ),사수이 ( Sasui Sasui ),유하민 ( Eu Ha-min ),남정수 ( Nam Jeong-soo ) 한국건축시공학회 2021 한국건축시공학회 학술발표대회 논문집 Vol.21 No.1
The non-destructive method using ultrasonic waves has been applied in many studies due to its low damage to the structure and its simple evaluation method and high precision. On the other hand, if the concrete is subjected to a high-temperature, the mechanical properties may be deteriorated due to the micro-crack network and the damage may be severe depending on the strength of the concrete. Therefore, this study attempts to evaluate the fundamental wave behavior of different strength ranges using the ultrasonic non-destructive method for concrete that has been subjected to high-temperature. As a result, the relative power of the fundamental wave was decreased as temperature increase. And it was confirmed that the 2nd and 3rd harmonics were generated at 110 MPa. However, to check the 2nd, 3rd harmonics 110 MPa or less, there is a need for further research considering the ultrasonic output, the output of the sender and receiver, and the appropriate frequency accordingly.
석회석 혼합재의 화학특성이 시멘트 모르타르에 미치는 영향
서동균 ( Suh Dong-kyun ) 한국건축시공학회 2022 한국건축시공학회 학술발표대회 논문집 Vol.22 No.2
Using the limestone powder as material that can substitute the clinker, it seems to get positive effect as filler and enhance workability of cement but the substitution amount and chemical properties of it can affect mechanical properties of cement. Thus, in this study, the effect limestone powder that has other properties on cement is evaluated. As a result, the workability enhancing effect was confirmed but deterioration of compressive strength was also checked. Later, with the view of workability, the experiment that the possibility of strength compensation by decreasing unit water weight of limestone powder cement is planned when the limestone powder is used.
고온에서 폴리프로필렌섬유와 비정질강섬유를 보강한 150MPa급 초고강도 콘크리트의 수증기 압력특성
서동균 ( Suh Dong-kyun ),김규용 ( Kim Gyu-yong ),이상규 ( Lee Sang-kyu ),황의철 ( Hwang Eui-chul ),유하민 ( Eu Ha-min ),남정수 ( Nam Jeong-soo ) 한국건축시공학회 2020 한국건축시공학회 학술발표대회 논문집 Vol.20 No.1
The aim of this study is to evaluate the combination effect of amorphous steel fiber and polypropylene fiber on spalling of the 150MPa level ultra high strength concrete. Considering spalling has a great relationship with water vapor pressure, this paper is focusing on water vapor pressure. The test specimens were heated accordance with ISO-834 Standard Curve using electric heating furnace, the depth of 10mm water vapor pressure formation was tend to get faster and spalling damage become severe when the mixing proportion of amorphous steel fiber increase. When using ultra high strength concrete reinforced with amorphous steel fiber, further research about proper mixing proportion of polypropylene fiber.
비정질강섬유 보강 고강도 콘크리트의 온도별 잔존 역학적 특성 평가
서동균 ( Suh Dong-kyun ),김규용 ( Kim Gyu-yong ),이상규 ( Lee Sang-kyu ),황의철 ( Hwang Eui-chul ),유하민 ( Eu Ha-min ),남정수 ( Nam Jeong-soo ) 한국건축시공학회 2020 한국건축시공학회 학술발표대회 논문집 Vol.20 No.2
This study is aim to assess mechanical properties which is highly related to structural safe and durability of 100MPa high strength concrete mixed with amorphous metallic fiber. All specimens were heated with low velocity heating rate(1℃/min.), residual compressive strength and residual flexural strength was evaluated. The specimens were cooled down to room temperature after heating. As a result, in the case of 100MPa high-strength concrete, the residual compressive strength enhancing effect of amorphous metallic fiber has showed with the mix proportion of fiber. In addition, residual flexural strength showed more regular pattern before 300℃ then residual compressive strength, but simillar decreasing behavior was shown after 300℃ like residual compressive strength. Further study about fiber pull-out behavior and fiber mechanical, chemical property change due to temperature is needed.