본 연구에서는 Monopile 방식 풍력발전기 강구조물의 부식을 방지하기 위하여 S355 steel의 표면 거칠기에 따른 용사 코팅 상태에 관한 연구를 수행했다. 일차적으로는 시편별 서로 다른 표면거칠기를 부여하기 위해 밀링머신에 페이스 커터를 결합하여 시편별로 다른 조건의 Ra값 기준 표면거칠기를 부여했다. 실험 조건으로는 시편 가공 시 4가지의 회전속도(60, 400, 1200, 2000 rpm), feed rate 150(mm/min) 조건을 선정했다. 2차로는 와이어 용융 방식의 아크 용사 코팅을 실시했다. 코팅 조건으로는 분사 거리 200mm, 전압 24V, 전류 120A, 분사 압력 5bar, 와이어 삽입 속도 30g/mm, 와이어 직경 2mm이다. 용사 코팅 후 FE-SEM으로 표면을 관찰한 결과 모든 시편의 S355 면과 코팅층(아연-알루미늄) 사이에 유격이 발생하지 않고 성공적으로 안착이 되었음을 확인할 수 있었다.

In this research, the a novel finishing machine was used for hight-precision surface of spherical ball products that have been widely used for on/off valve for hydrogen energy flowing system and in medical field such as artificial hip joint component. The spherical balls products are the workpiece that made by Co-Cr-Mo alloys with 32-mm in diameter and Sa≈ 0.30μm in surface roughness. Their surface roughness was successfully improved via the magnetic abrasive tools that controlled the magnetic field of permanent magnets. The critical input conditions were selected as rotational speed: 800rpm, gap: 3mm, tool grain size: 1-μm finishing time: 0, 3, 6, 9, 12, and 15min. The results of this research showed that under the given finishing conditions, the high surface quality in the terms of surface precision of spherical ball products are successfully achieved, in which the surface roughness is reduced from 0.30-μm to 0.04-μm within the short finishing time at 12min. Therefore, it can be concluded that a novel finishing machine is feasible to be used for improving the surface roughness of spherical ball products, resulted in high surface precision of materials.

A study on the possibility of recycling by solidification using tailings from abandoned metal mine were studied. The study was carried out on testing compressive strength of concrete made by different ratio of various mine tailing, chemical speciation of Cd, Cu, Pb and Zn in the tailing by sequential extraction procedure and SPLP leaching test. Mixing of mine tailings with cement or asphalt and aging of mortar gave strong influence on compressive strength of concrete. Marshal's stability of asphalt with tailing waste were higher of 98.0~101.0% than not added one. Therefore it was recommended to use of the tailings to low the infiltlation of the water to protect the bank in the abandoned mine region. Total metals in concrete and asphalt with tailing waste were lower than that of tailing waste. The amount of adsorbed fraction and carbonate fraction which were labile in the aquatic environment were very lower in the concrete and asphalt specimen than mine tailing waste.Leachabilityof studied metals are under the waste management standard.

Fractional composition of surface and core sediment samples were analysed to collect quality improvement and weed control in eutrofied brackish Lake Kyungpo. Fractional scheme for sediment phosphorus was made for four chemically defined phosphorus forms as adsorbed phosphorus, nonapatite inorganic phosphorus, apatite phosphorus and residual phosphorus. The analysis of surface sediment samples shows that Lake Kyungpo sediments have high labile phosphorus fraction and thus have high water pollution potential. It was found that no significant water quality improvement could be expected by dredging down to 1.0m depth of sediments.