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곽동희,전훈,정팔진 ( Dong Heui Kwak,Hoon Jeon,Paul Gene Chung ) 한국물환경학회 1998 한국물환경학회지 Vol.14 No.2
Many water bodies used for water supply may contain solid particles with a lower density. These solids are hardly removed in the sedimentation unit due to the own tendency of floating. In order to treat this type of water, the dissolved air flotation (DAF) unit is known to be an effective method. A series of laboratory experiments has been performed to investigate the characteristics of solid separation followed by simplification of DAF models in water treatment processes. Results of DAF treatment studies show that total solids removal efficiency depended on the amount of solids attached to bubble on the water surface and residual floating solids in the water. For the enhancement of solid removal efficiency, It is to be desired that surface loading should be operated less than rising velocity of residual floating particles as well as air volume concentration enough.
정수장 float 를 형성하는 미세기포의 실채와 영향인자
곽동희,김영철,이성우,정팔진 ( Dong Heui Kwak,Youngchul Kim,Sung Woo Lee,Paul Gene Chung ) 한국물환경학회 1998 한국물환경학회지 Vol.14 No.2
General type of processes treating a water for its public use in Korea, are chemically aided sedimentation tanks followed by rapid sand filters. Settled sludge from a coagulation/flocculation and sedimentation process is easily drained into the sludge treatment train from the bottom of tanks but sludge floated along with numerous micro-bubbles on the surface of coagulation/flocculation tanks and head-part of sedimentation tanks, initially built and operated without a skimmer and barrier against moving floats, has caused serious aesthetic and operational problems. In this study, sources of the micro-bubbles combining with floc particles and causing floating sludge, and factors affecting formation of those bubbles were investigated. There are several factors which can produce gas bubbles in the water treatment plant. Pumps and conduits highly pressurized during water intake and transport to the water treatment plant might be one of the possibilities which can produce micro-bubbles due to the pressure differences. The amounts of nitrogen and carbon dioxide gases evolved during prechlorination and coagulation processes were calculated by using actual plant operational data. Changes of interfacial properties of coagulated water were examined as a possibility of enhancing micro-bubbles production. Among these three factors, it was found that changes of surface characteristics had a significant and direct effect on the formation of micro-bubbles at this plant.
충만 디스크의 면내 진동 해석을 위한 1차원 환상 평판 요소
곽동희(Kwak, Dong-Hee),임정기(Lim, Jung-Ki),김창부(Kim, Chang-Boo) 한국소음진동공학회 2009 한국소음진동공학회 논문집 Vol.19 No.12
We present a one-dimensional annular plate element with which the in-plane vibration of full disks can be analyzed efficiently and accurately by using the FEM. Its elementary mass matrix and stiffness matrix are derived, respectively, from the virtual work by effective forces and the virtual strain energy. The static deformation modes obtained from an integration of the differential equilibrium equations of the annular plate are used as interpolation functions of the one-dimensional annular plate element. The in-plane natural vibration characteristics of a 2-step full disk and a uniform full disk are analysed. Its results are compared with the results obtained by utilizing two-dimensional 8-node quadrilateral plane elements and cyclic symmetry of the disk. And also, by comparing with the theoretical results of previous researchers, the efficiency and accuracy of the presented element are verified.