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String을 이용한 원형실린더 주위의 수평력 감소에 관한 연구
백동일(Dong-Il Baek),조효제(Hyo-Jae Jo),이민준(Min-Jun Lee),임재환(Jae-Hwan Lim),이태경(Tae-Kyung Lee),김재희(Jae-Heui Kim),오태원(Tae-Won Oh) 한국해양공학회 2018 韓國海洋工學會誌 Vol.32 No.4
Recently, it was predicted that the size of offshore markets will grow as gas prices edge up. This paper presents experimental results for using strings as a suppression device on a circular cylinder and discusses the various data. A test model was used to investigate the role of strings by varying the thickness of the strings used to suppress a cylinder’s lateral force taking into account the effect of turbulence promoted. A substantial amount of experimental data were taken from experiments performed on cylinders at Reynolds number up to a maximum value of 105. The suppression of vortex shedding and a lateral force reduction of up to 70% were observed for the cylinder with strings.
히트파이프를 이용한 매스콘크리트의 수화열 제어에 관한 실험 연구
백동일(DONG-IL BAEK) 한국해양공학회 2007 韓國海洋工學會誌 Vol.21 No.6
In order to eliminate the hydration heat or mass concrete, this paper reports the results of hydration heat control in mass conrete using the OCHP (Oscillating capillary tube heat pipe). In the summarized results of the mock up experiments, distributing the heat pipe at 300 ㎜ intervals based on the center of the test specimen was the most effective. A 200 ㎜ turn interval the heat pipe was measured to be the most appropriate, taking into account the reinforcement placing at the actual site. Therefore, when the hydration heat control method using the heat pipe developed in this study is applied, not only canconstruction efficiency ?? a reduction in the necessary construction time be expected, but so can outstanding economical effects.
황산염 침해를 받는 부순모래 모르타르의 단위중량 및 압축강도 특성
김명식(Kim Myung-Sik),백동일(Baek Dong-Il) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.4A
본 연구는 부순모래를 사용한 시멘트 모르타르가 황산염 침해를 받을 경우 단위중량 및 압축강도 특성을 파악하고자 한다. 잔골재는 강모래와 부순모래를 사용한 두 종류의 실험을 실시하였다. 또한 시멘트 모르타르에 실리카흄과 플라이애쉬의 치환율을 변화시켜 시편을 제작한 다음 수중, 10% 황산나트륨 수용액, 10% 황산마그네슘 수용액, 해수에 재령 28일, 60일, 90일, 180일 동안 침적 시켰다. 그리고 침적 기간에 따라 시편의 압축강도의 변화, 단위중량의 변화, SEM과 EDS 분석을 통하여 황산염 수용액에 침적된 시편의 미세구조를 파악하였다. 그 결과 부순모래 모르타르에 적절한 비율로 혼화재를 치환할 경우 강모래와 비교하여 좋은 저항성을 가짐을 알 수 있었다. The aim of this study is to estimate characteristic of compressive strength and unit weight when cement mortars using crushed sand under sulfate attacks. Besides tests have been performed using river sand and crushed sand, respectively. The cement mortars were made with replacement ratios of silica fume and fly ash. The cement mortar were immersed in fresh water, 10% sodium sulfate solution, 10% magnesium sulfate solution, and seawater for 28days, 60days, 90days and 180days. This study, investigate change of compressive strength and unit weight of cement mortars about immersion time and replacement of mineral admixtures. Additionally SEM and EDX analysis was performed to identify the microstructure under sulfate solution. It was observed from the test results that the cement mortar using crushed sand was found to have a good resistance against sulfate compared with river sand.