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보로실리케이트 유리의 이온교환에 의한 고강도 투명방탄소재의 제조
김영환,심규인,임재민,최세영,Kim, Young-Hwan,Shim, Gyu-In,Lim, Jae-Min,Choi, Se-Young 한국군사과학기술학회 2010 한국군사과학기술학회지 Vol.13 No.6
Borosilicate glass (81% $SiO_2$-2% $Al_2O_3$-13% $B_2O_3$-4% $Na_2O_3$) was prepared, and the glass was ion exchanged in $KNO_3$ powder containing different temperature and time. The $K^+-Na^+$ ion exchange takes place at the glass surface and creates compressed stress, which raise the mechanical strength of the glass. The depth profile of $Na^+$ and $K^+$ was observed by electron probe micro analyzer. With the increasing heat-treatment time from 0min to 20min, the depth profile was increased from 17.1um to 29.4um, but mechanical properties were decreased. It was also found out that excessive heat treatment brings stress relaxation. The Vickers hardness, Fracture Toughness and bending strength of ion exchanged samples at $570^{\circ}C$ for 10min were $821.8H_v$, $1.3404MPa{\cdot}m^{1/2}$, and 953MPa, which is about 120%, 180%, and 450% higher than parent borosilicate glass, respectively. Transmittance was analyzed by UV-VIS-NIR spectrophotometer. Transmittance of ion exchanged borosilicate glass was decreased slightly at visible-range. It can be expected that transparent bulletproof materials in more light-weight and thinner by ion exchanged borosilicate glass.
전기로 공정에서 슬래그 중 산화철의 환원 회수에 관한 연구
김영환,유정민,Kim, Young-Hwan,Yoo, Jung-Min 한국자원리싸이클링학회 2016 資源 리싸이클링 Vol.25 No.4
전기로 공정에서 슬래그는 Fe를 약 20 ~ 35 wt.% 함유한 채로 슬래그 포트로 배출되어 냉각되고 있다. 슬래그 배출 전에 환원하여 용강으로 회수한다면 제강회수율을 향상할 수 있으며, 슬래그 배출량을 감소할 수 있다. 일반적으로 전기로 공정에서는 슬래그 포밍과 (FetO)의 환원제로 카본계의 환원제가 활용되고 있다. 본 실험은 Metal을 유도용해로에 용해한 후 슬래그와 환원제로 흑연분탄과 저가의 Al dross powder를 Pellet으로 투입하여 (FetO)의 환원 회수와 복인(復燐)에 대한 영향성을 조사하였다. 실험결과 Al dross에 의한 환원 회수율은 흑연분탄에 비해 2.5배 이상의 효과를 나타내었으며, 복인(復燐)에 대한 영향은 50 ppm 이하로 크지 않은 것으로 나타났다. EAF processed slag which contains about 20 ~ 35 weight percent FetO is poured to slag pot and cooled. If we recover Fe from molten slag by the reduction, we will improve steel yield rate and reduce slag quantity poured from the furnace. Usually, carbon is used as a reductant and slag foaming agent in the EAF process. In this experiment, after melt the metal in induction furnace and then add slag with carbon and Al dross powder as a reductant, we investigated the reduction of FetO from slag and change of Phophorus content. As the result, when we use Al dross as a reductant, recovery rate is two times more than carbon. Phosphorus pick up is less than 50ppm with reduction of EAF slag.
동해안 울진원전의 온배수 방출이 주변 해조군집에 미치는 영향
김영환,안중관,이재일,엄희문,Kim, Young-Hwan,Ahn, Jung-Kwan,Lee, Jae-Il,Eum, Hee-Moon 한국조류학회(藻類) 2004 ALGAE Vol.19 No.3
In order to clarify the structure and seasonal dynamics of warm tolerant benthic marine algal community in Korea, the species composition and biomass of marine algae at the discharge canal of Uljin nuclear power plant on the East Coast of Korea were investigated seasonally from February 1992 to October 2000. 107 species of marine algae were found at the discharge canal during the past nine years. In general, the number of species observed was abundant in spring or summer and less in autumn or winter. 27 species (4 blue-green, 5 green, 6 brown and 12 red algae) of marine algae occurred more than 1/ 6 frequency and thus can be categorized as warm tolerant species. Among these, one brown (Dictyota dichotoma) and four red algae (Gelidium amansii, Anphiroa ephedraea, Hydrolithon sargassi, Marginisporum crassissimum) are recorded as warm tolerant marine algae for the first time in Korea. Padina arborescens, Anphiroa zonata and Corallina pilulifera were common species found more than 75% frequency. Seasonal fluctuations of mean biomass were 0-1,330 g dry wt m^(-2) and dominant species in biomass were Corallina pilulifera (contribution to a total biomass proportion 34%), Anphiroa zonata (23%), Padina arborescens (18%) and Sargassum micracanthum (11%). The red algae appeared as predominant algal group at the discharge canal of Uljin nuclear power plant in the qualitative and quantitative aspects. The green algae such as Enterornorpha compressa appeared rather frequently at the discharge canal, but the biomass proportion was very low, in contrast to Kori nuclear power plant where there was definite green algal dominance. Differences in algal communities developed at the discharge canals of Uljin and Kori nuclear power plant on the East Coast of Korea, particularly biomass proportions of green algae, can probably be related to local environmental factors such as water velocity through the canal and natural seawater temperatures.
김영환,서형주,김진만,정연훈,문경환,Kim, Young-Hwan,Suh, Hyung-Joo,Kim, Jin-Man,Jung, Yeon-Hoon,Moon, Kyong-Whan Korean Society for Food Science of Animal Resource 2008 한국축산식품학회지 Vol.28 No.5
This study was undertaken to determine the concentrations of airborne bacteria, fungi, particles, and endotoxin in swine and chicken houses. Six swine buildings and seven chicken houses were randomly selected in southern Gyonggi Province, South Korea. The geometric mean concentrations of airborne bacteria in swine and chicken houses were $2.7{\times}10^5\;CFU/m^3$ and $5.6{\times}10^7\;CFU/m^3$, respectively. The airborne bacteria concentrations in chicken houses were significantly higher than those of swine houses (p<0.05). The geometric mean concentration of airborne fungi in swine houses was $4.9{\times}10^3\;CFU/m^3$, which was higher than the value of $2.1{\times}10^3\;CFU/m^3$ found in chicken houses. The mean concentrations of airborne particles and endotoxin in swine houses were $3.48\;mg/m^3$ and $943.1\;EU/m^3$, and they were $15.43\;mg/m^3$ and $1,430.5\;EU/m^3$ in chicken houses, respectively. A significant difference between swine and chicken houses was found for total dust (p<0.05), but not for endotoxin. In this study, the concentrations of endotoxin in both swine and chicken houses as well as particles in chicken houses were high, and in about 50% of the samples exceeded the worker health safety levels of $614\;EU/m^3$ suggested in previous studies. These results may indicate a considerable respiratory hazard for workers in these environments.
UO$_{2}$ 펠릿 산화로의 분말 비산 방지를 위한 최종속도 측정
김영환,윤지섭,정재후,진재현,홍동희,Kim Young-Hwan,Yoon Ji-Sup,Jung Jae-Hoo,Jin Jae-Hyun,Hong Dong-Hee 한국방사성폐기물학회 2005 방사성폐기물학회지 Vol.3 No.2
A voloxidizer for a hot cell demonstration, that handles spent fuels of a high radiation level in a limited space should be small and spent fuel powders should not be dispersed out of the equipment involved. In this study a density rate equation as well as the Stokes'equation has been proposed in order to obtain the theoretical terminal velocity of powders. The terminal velocity of U$_{3}$O$_{8}$ has been predicted by using the terminal velocity of SiO$_{2}$, and then determination has been the optimum air flow rate which is able to prevent powders from scattering. An equation which has shown a relationship between theoretical terminal velocities of U$_{3}$O$_{8}$ and SiO$_{2}$ has been derived with the help of the Stokes'equation, and then an experimental verification made for the theoretical Stokes' equation of SiO$_{2}$ by means of an experimental device made of acryl. The theoretical terminal velocity based on the proposed density rate equation has been verified by detecting U$_{3}$O$_{8}$ powders in a filter installed in the mock-up voloxidizer. As the results, the optimum air flow rates seem to be 20 LPM by the Stokes'equation while they are 14.5 L/min by the density rate equation. At the experiments with the mock-up voloxidizer, a trace amount of U$_{3}$O$_{8}$ seems to be detectable at the air flow rate of 14.5 L/min by the density rate equation, but U$_{3}$O$_{8}$ powders of 7$\mu$m diameter seem detectable at the air flow rate of 20 L/min by the Stokes'equation. It is revealed that 14.5 L/min is the optimum air flowe rate which is capable of preventing U$_{3}$O$_{8}$ powders from scattering in the UO$_{2}$ voloxidizer and the proposed density rate equation is proper to calculate the terminal velocity of U$_{3}$O$_{8}$ powders.