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소석회-광물찌꺼기 고형화의 초기 수화에 미치는 황산염의 영향
이현철,민경원,유환근,Lee, Hyun-Cheol,Min, Kyoung-Won,Yoo, Hwan-Geun 대한자원환경지질학회 2013 자원환경지질 Vol.46 No.6
폐광산의 광물찌꺼기의 고형화처리 시 황산염이 초기 수화에 미치는 영향을 확인하기 위하여 본 연구를 수행하였다. 광물찌꺼기에 소석회를 결합재로 사용하였고, $Na_2SO_4$를 혼합수로 이용하여 9가지 조건의 고화체를 제작하였다. 제작된 고화체를 7일, 14일, 28일 양생 후 압축강도 측정, 중금속 용출시험, XRD 분석을 실시하였다. 증류수를 이용하여 양생을 실시한 고화체는 양생기간이 경과함에 따라 압축강도가 증가하였으며, $Na_2SO_4$를 혼합한 고화체는 양생기간 경과에 따라 압축강도가 감소하였다. $Na_2SO_4$의 농도가 증가할수록 고화체 외부 균열이 확실하게 나타났고, 시간이 경과함에 따라 균열이 내부까지 진행되었다. 고화체의 Cu, Cd, Zn, As 농도는 양생기간 경과에 따라 감소하였고, Pb의 경우 소석회 함량이 10 wt% 이상 혼합될 경우 농도가 증가함을 확인하였다. 균열이 발생된 고화체의 수화 생성물에서 석고와 $MgSO_4$ 피크가 XRD 분석으로 확인되었고, SEM-EDS를 통해 주상의 결정이 Ca, S, O로 구성된 석고임을 확인하였다. 소석회를 이용하여 광물찌꺼기를 고형화시킬 경우 황산염 생성으로 균열이 심하게 발생되므로, 황 함량이 높은 광물찌꺼기의 처리 시에는 이를 보완할 수 있는 대책이 강구되어야 할 것으로 판단된다. Influence of sulfate on the early hydration in the solidification treatment of abandoned mine tailings was characterized. Solidified specimens using hydrated lime as a binder were prepared with various amounts of added $Na_2SO_4$ and different curing days. Unconfined compressive strength measurement, heavy metal leaching test, XRD analysis were performed after 7-, 14- and 28-days curing. According to curing days strength of solidified specimens using only distilled water increased but those with addition of $Na_2SO_4$ decreased. External cracks of specimens developed definitely with increasing $Na_2SO_4$ concentration and curing days. Concentrations of Cu, Cd, Zn, and As in the leached solutions from solidified specimens decreased significantly but Pb was leached readily in cases of hydrated lime dosage more than 10 wt%. Gypsum and $MgSO_4$ were identified in the cracked solidified specimens by XRD analysis, and pillar-shaped crystals of SEM image were identified as gypsum in reference with EDS analysis. Crystallization of sulfate in the process of lime-tailing solidification caused cracking, which should be supplemented for solidification treatment of highly sulfur-contained tailing.
대구-경북지역 광역대도시와 산업도시 환경기준 대기오염물질의 시간적 및 공간적 오염도 특성
이현철(Hyun-Cheol Lee),조완근(Wan-Kuen Jo),김종태(Jong-Tae Kim) 환경독성보건학회 2007 환경독성보건학회지 Vol.22 No.4
This study considers the characteristics of nitrogen dioxide (NO₂), ozone (O₃) and sulfur dioxide (SO₂) in three cities of Daegu-Gyeongbuk Area (Daegu, Pohang, and Gumi), which have different city or industrial characteristics, over a time period of 2 years. The diurnal, weekly, monthly and seasonal concentration variations of criteria air pollutants were attributed to compounds or city types. However, the seasonal variations of O₃ concentrations were dependent on compounds, but not on city types. Lower O₃ concentrations were observed in July when comparing with other summer months. For SO₂ and NO₂, the concentrations were higher in Daegu when compared to Pohang and Gumi, while the concentrations of O₃ were higher in Pohang and Gumi. SO₂ exhibited higher levels in the morning hours, while O₃ and NO₂ exhibited higher levels in the afternoon hours for all cities. For O₃, the concentrations observed during Sunday were higher than those of other week or weekend days. Furthermore, the monthly and seasonal concentration variations of air pollutants depended on compounds or city types. It is noteworthy that the current monthly and seasonal variations were consistent with several previous studies.
우수한 기계적 특성과 형상치수 확보를 위한 정밀 압출기술개발
이현철(Lee Hyun-Cheol),이광식(Lee Kwang-Sik),오개희(Oh Kae-Hee),박상우(Park Sang-woo) 한국철도학회 2009 한국철도학회 세미나자료 Vol.2009 No.5
Most advanced countries are researching to apply light weight materials for rolling stock because weight reduction for railway body derives cost-saving, energy-saving, and high-speed. Likewise, current Korea rolling stock field makes arduous efforts of weight-reduction, miniaturization, and high-efficiency to achieve a high-speed railway. Aluminum becomes suitable material for these projects because it is much lighter than steel or stainless. Manufacturing the railway car body by using the Aluminum is increasing because Aluminum is not bringing the corrosion by unique oxidation-passivate. Aluminum extrusion profile for railway body requires a high mechanical property, awn-ate shape dimension, and stable quality because the railway body is composed with many different kinds of extruded profiles. Therefore, it is necessary to research about Aluminum precision-extrusion technology to maintain exit temperature and die load. The goal of this project is applying the Aluminum extrusion profile to next-generation railway car body by developing the Aluminum extrusion profile according to precision-extrusion technology which may maintain isothermal exit temperature.
이현철(Hyun Cheol Lee),조원철(Won Chul Cho),전기준(Gi Joon Jeon) 대한전자공학회 1992 대한전자공학회 학술대회 Vol.1992 No.10
We propose a new control architecture which consists of a PI controller and a neural network(NN) controller connected together in parallel. This architecture is well adapted to a wide range of uncertainties and variations of systems. The NN controller is learned through weights of the emulator which identify the dynamic characteristics of the systems. A performance evaluation level of two NN's decides automatically which controller of the two controllers will be used mainly. The PI controller operates mainly during learning phase of the NN controller whereas a good performance is obtained from the NN controller only, when the NN controller is learned sufficiently.
도시형 자기부상열차에 대한 철도안전법과 도시철도안전법의 충돌안전기준 적용의 비교 연구
이현철(Lee Hyun-Cheol),구정서(Koo Jeong-Seo) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
This paper studied on the application of Korean Railway Safety Law and Urban Transit Safety Law in Crashworthiness Regulations to the urban maglev vehicle of KIMM. The crashworthiness regulations for urban transit vehicle should be satisfied to the urban maglev vehicles according to crash analysis results using the explicit finite element method. However, according to its numerical results, the crashworthiness regulations of Korean Railway Safety Law were partially satisfied except the coupling and shunting condition. When a commercial urban maglev vehicle is developed in the near future, the crashworthiness regulations of Korean Railway Safety Law should be considered and satisfied during its structural design stage in some details
이현철(Hyun Cheol Lee),황계영(Kae Yong Hwang) 대한피부과학회 1994 대한피부과학회지 Vol.32 No.1
We are reporting a case of multiple dermatofibromas which occuired during the treatment of systemic lupus erythematous with prednisolone for 3 years in a 30-yenr-old woman, All of the 26 lesions were 0.5-2cm sized. and had the same appearanes ad usual dermatofibromas coccurring singly. Histopathologic examination showed typical findings of dermatofibroma which were characterized hy proliferation of fibroblasts intermingled with collagen in irregular arrangement and proliferation of small vessels and endothelial cells. (Kor J Dermatol 1994; 32(1): 193-197)
이현철 ( Hyun Cheol Lee ),이숙경 ( Suk Keyong Lee ),이흥렬 ( Heung Ryul Lee ),이원우 ( Won Woo Lee ),김덕하 ( Duck Ha Kim ) 대한피부과학회 1995 대한피부과학회지 Vol.33 No.5
Prurigo pigmentosa is a chror ic pruritic inflammatory dermatosis characterized by erythematous papules in a reticulated pattern that resolve leaving a reticulated, mottled hyperpigmentation and rapidly response to dapsone therapy. Most cases that have been reported are from Japan. We report two cases of prurigo pigmentosa in a 21 year-old female and a 23-year-old female. Histopathologic findings of erythematous papules showed exocytosis, spongiosis, liquefaction degeneration of basal cell layer and perivascular lymphohistiocytic infiltration on the upper dermis. We treated them with dapsone, 100mg daily, which resulted in a remarkable regression of the ery thematous papules and improvenien of pruritus. (Kor J Dermatol 1995;33(5): 945-949)