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서하나,김유경,박영선,공병욱,라덕관,정정조 한국환경기술학회 2019 한국환경기술학회지 Vol.20 No.3
The purpose of this study is to investigate most effective cleaning method with the kinds and concentrations of acid and reaction time for reuse of waste ark shell. Whiteness and compressive strength were tested before and after acid cleaning. The whiteness change of ark shell and granular ark shell was showed little difference between HCl and HNO3. Whiteness was the highest when acid : H2O = 1:20. The change of whiteness according to the reaction time was not significantly difference. Compressive strength of the ark shell and granular ark shell was lower HNO3 than HCl. And the compressive strength reduction rate was did not show a clear trend in the ratio of acid concentration and reaction time. Changes in whiteness and compressive strength of acid washing were found that the shells from restaurant were superior. On the other hand, ark shell collected from the B–storage yard was found that the whiteness was improvement only by water washing without acid washing. It is considered that the effective method of improving whiteness and maintaining the compressive strength is when the ratio of HNO3 : H2O = 1:50 for 10 minutes.
서하나,정자현,이만희,이학기 대한건축학회지회연합회 2007 대한건축학회지회연합회 학술발표대회논문집 Vol.2007 No.1
Ministry of construction and transportation has been enforcing extensionally design phase VE(Value Engineering) to the construction costing more than 10 billion won, an importance of design phase VE accordingly is raising to get rid of a waste of cost and noneffective factors previously in construction projects. Although there are legal supports and technical effects, an effect about an introduction of design phase VE can not be applied properly because of several problems at the process. So, in this study, present competency evaluation checklist of design phase VE to highly raise the output through organizing an effective team at the beginning stage of design phase VE. Find out 29 competency factors through characteristics of design VE team for the checklist, classify by team knowledge, team work skill, and team attitude. Get an efficiency regarding importance and find out competency evaluation items of design VE team, present a competency evaluation checklist for indicating an objective standard to competency evaluation by measuring relative importance as to each competency evaluation item.
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서하나,김경일,박상진,공병욱,라덕관,정정조 한국환경기술학회 2020 한국환경기술학회지 Vol.21 No.3
The purpose of this study was to investigate the efficient management of water quality by control of pH and phosphate using loess ball with added calcined ark shell in ornamental fish culture. It was found that a lower shell content and a higher calcination temperature resulted in a higher compressive strength. The porosity increased as the diameter of loss ball increased. The optimum compressive strength, pH increase, and phosphate removal rate were achieved using loess balls with added calcined shell content of 6 % and a calcined temperature of 900 ℃. When loess balls with a diameter of 10 mm were used at a dosage of 25 g/L, the pH increased from 6.5 to 10.5 and the phosphate removal was 93.4 %. At a dosage of 50 g/L or more, the pH increased from 6.5 to 11.0 and phosphate removal was 99.9 %. The increase in pH and phosphate removal was a result of higher shell content, lower calcination temperature, and smaller ball diameter. It is expected that decreasing pH and green algae buildup, which are the problems in ornamental fish culture, can be reduced using loess balls with added calcined shells.