• Journal of Radiation Protection and Research
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• v.23 no.4
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• pp.243-249
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• 1998

The methodology for justification and optimization of the countermeasures related with contamination management of milk was designed based on the cost and benefit analysis. The application results were discussed for the deposition on August 15, when pasture is fully developed in Korean agricultural conditions. A dynamic food chain model DYNACON was used to estimate the time-dependent radioactivity of milk after the deposition. The considered countermeasures are (1) the ban of milk consumption (2) the substitution of clean fodder, which are effective in reducing the ingestion dose as well as simple and easy to carry out in the first year after the deposition. The total costs of the countermeasures were quantitatively estimated in terms of cost equivalent of doses and monetary costs. It is obvious that a fast reaction after the deposition is an important factor in cost effectiveness of the countermeasures. In most cases, the substitution of clean fodder was more effective countermeasure than the ban of consumption. A fast reaction after the deposition made longer justifiable/optimal duration of the countermeasure.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.271-272
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• 2003

대기침적은 대기중으로 방출된 오염물질의 이동과 그 영향을 조절하는 중요한 기작으로서, 현상론적인 형태에 따라 습성침착 및 건성침착으로 구분된다. 이러한 대기침착 현상은 수질의 악화, 건강 및 생태학적 약영향을 초래하는 중요한 요소로 작용할 뿐만 아니라, 최근 우리나라를 비롯한 동북아시아지역에서의 대기오염물질의 장거리 이동현상의 정확한 규명을 위한 노력의 일환으로 그 관심이 모아지고 있다. 따라서 건성침적현상에 의한 환경적인 악영향을 줄이기 위한 대처방안을 효과적으로 수립ㆍ시행하기 위해서는 먼저 그 영향 정도를 규명해 낼 수 있는 측정장치의 개발 및 분석평가 방법의 정립이 필수적이다. (중략)

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.387-390
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• 2008

Ni/MgAl 촉매상에서 LPG의 수증기 개질반응을 반응온도 $700{\sim}800^{\circ}C$, 공간속도 $20,000h^{-1}$, 수증기/탄소 비율 $1.0{\sim}3.0$인 조건으로 대기압하에서 수행하였다. 본 연구에서 사용된 촉매들은 공침법으로 제조하였으며, 하이드로탈사이트 구조에서 Ni-MgO 구조로 변환되는 과정에서 활성금속인 니켈이 고분산되는 장점을 지니고 있다. 제조된 촉매는 함침법으로 제조된 촉매보다 활성이 잘 유지되었으며 탄소침적에 대한 내구성 또한 향상되었으나 완벽하게 해결되지는 못하였다. 따라서 이와 같은 문제점을 해결하기 위해 귀금속이 modified된 Ni/MgAl 촉매를 제조하고 반응 특성을 비교하였다. Rh-Ni/MgAl 촉매는 LPG 수증기 개질 반응에서 1024시간동안 활성이 유지됨을 확인하였을 뿐만 아니라 탄소침적 또한 발생하지 않음을 확인하였다.

• Journal of the Korean Institute of Gas
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• v.14 no.2
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• pp.7-14
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• 2010

Synthesis gas was produced by the partial oxidation of methane. For the preparation of catalysts, Ni, known to be active in this reaction and cheap, was used as the active component and $CeO_2$, having high oxygen storage capability and high redox ability, was used as the support. The catalysts were prepared by the impregnation and urea methods. The catalyst prepared by the urea method showed about 11 times higher surface area and finer particle size than that prepared by the impregnation method. The catalysts prepared by the urea method showed higher methane conversion and synthesis gas selectivity than that prepared by the impregnation method. In this reaction, carbon deposition is a problem to be solved, so La was added to the catalyst system to reduce the carbon deposition. TGA analysis results showed that there was 2% carbon deposition with La-added catalysts and 16% with La-free catalysts. It was found that the addition of La decreases the amount of carbon deposition and prevents catalyst deactivation.

• Journal of Radiation Protection and Research
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• v.24 no.2
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• pp.65-72
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• 1999

A methodology for determining the optimal durations of the use of contaminated crops as feedstuffs of cattle was designed based on the cost-benefit analysis method. The results of application for pigs, an omnivorous cattle, were discussed for the hypothetical deposition of radionuclides on August 15 when a number of crops are fully developed in Korean agricultural conditions. For investigating the relative cost-effectiveness of the use of contaminated crops as feedstuffs, the net benefit was compared with the case of the direct disposal of contaminated crops. The time-dependent radionuclide concentration in crops after the deposition was predicted using a dynamic food chain model DYNACON. The net benefit from the actions was quantitatively evaluated in terms of cost equivalent of doses and monetary costs of implementing the action. It depended on a number of factors such as radionuclides, variety of crops supplied as feedstuffs and duration of the actions. The use of contaminated crops as feedstuffs was more cost effective for $^{90}Sr\;or\;^{131}I$ deposition than for $^{137}Cs$ deposition.

• Clean Technology
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• v.15 no.3
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• pp.194-201
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• 2009

Reductive reactivity of zero-valent iron nanoparticles was investigated for removal of nitrate-nitrogen which is considered one of the major water pollutants. To elucidate the difference in reactivity between preparation methods, iron nanoparticles were synthesized respectively from microemulsion and aqueous solution of ferric ions. Iron nanoparticles prepared from microemulsion were deposited on aluminum by electrophoretic method, and their reaction kinetics was compared to that of the same nanoparticles suspended in aqueous batch reaction. With an approximation of pseudo-first-order reaction, rate constants for suspended nanoparticles prepared from microemulsion and dilute aqueous solution were $3.49{\times}10^{-2}min^{-1}$ and $1.40{\times}10^{-2}min^{-1}$, respectively. Iron nanoparticles supported on aluminum showed ca. 30% less reaction rate in comparison with the identical nanoparticles in suspended state. However, supported nanoparticles showed the superior effectiveness in terms of nitrate-nitrogen removal per zero-valent iron input especially when excess amounts of nitrates were present. Iron nanoparticles deposited on aluminum maintained reductive reactivity for more than 3 hours, and produced nitrogen gas as a final reduction product of nitrate-nitrogen.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.19-24
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• 2009

The purpose of this study was to investigate the formation of apatite layer on two different titanium substrate treated with biomimetic method, Titanium plates were heat-treated at different temperatures of $400^{\circ}C$, $600^{\circ}C$, and $800^{\circ}C$ for 5 h in air atmosphere, And then, that plates were chemically treated with an alkali solution of 1 M sodium hydroxide (NaOH), The pre-treated titanium plates were soaked in the simulated body fluid (SBF) of Kokubo's recipe, After soaking for 7 days and 21 days in SBF, the coated layers formed on the titanium plates were characterized and compared with the morphology and chemical composition, The apatite formation was more activated on the titanium plates chemically treated with NaOH compared with the only heat-treated titanium plates.

• Journal of Aquaculture
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• v.9 no.2
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• pp.141-149
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• 1996

Effects of $17{\alpha}$-methyltestosterone ($17{\alpha}-MT$) in rearing water on sex reversal of Nile tilapia (Oreochromis niloticus) were investigated and optimum conditions as initial treatment time, concentrations and treatment durations of hormone were evaluated in this study. For the study of the optimum initial treatment time, 0 to 20-day-old fry were treated by immersion in a 500 ppb solution of $17{\alpha}-MT$. Desirable results were obtained at 12-day-old fish as $86.4\%$ of male induction rates and this frequency was obviously higher than the other age groups. Twelve-day-old fry were immersed in $17{\alpha}-MT$ solutions at concentrations of $0\~2,000$ ppb for 24 hours for the study of dose dependent relationship between sex ratios and concentrations of $17{\alpha}-MT$, Male induction rates of all treated groups were higher than $80\%$, $X^2$ values against the sex ratio of control group indicate that sex reversal has taken place effectively in all experimental groups (P<0.001). Futhermore, 500 ppb treated groups showed highest male incidence of $86.4\%$. Effects of 5 different durations (0, 12, 18, 24 and 30 hours) treated with 1,000 ppb of $17{\alpha}-MT$ were also evaluated. Male induction rate from 0 to 24 hours treated group was increased with treatment durations. However, male incidence of 30-hour treated group ($84.0\%$) was sligthly decreased compare to the 24-hour treated group ($85.2\%$). It is concluded that immersion treatment using $17{\alpha}-MT$ on O. niloticus is possible on sex reversal at low concentration of 500 ppb and short treatment durations within 24 hours with 12-old-day fry.

• Journal of Biomedical Engineering Research
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• v.18 no.3
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• pp.217-222
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• 1997

Hydroxyapatite(HA)-coated metal composites were made by the dipping method. The specimen substrates were Ti plates with a thickness of 2 mm. The HA coating was carried out in HA-sol for 1 min by the dipping method. The concentration of HA-sol for the coating ranged from 3.28 to 9.99 wt%. Excellent coating was observed on Ti substrate dipped once in 9.99 wt% sol. Preparation of Ti plates by sandblasting provided the better environment for coating HA on Ti surface than non-treated surface. As the concentration of sol increased, the weight change and the coating thickness increased. Above 7 wt% sol, they increased sharply.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.1-10
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• 1999

In this paper, we have investigated the effects of the environmental factors on Low Molecular Weight (LMW) silicone fluid contents existing in high temperature vulcanized (HTV) silicone rubber sample, using dipping method and contact angle, current measurement. Artificial treatments such as immersion in water, elevated temperature, UV irradiation and dry band arcing under salt-fog condition are selected as the environmental factors. This results will be helpful to investigate the degradation with time and to expect a life time, because the LMW silicone content, which is important to recovery the hydrophobicity of silicone rubber surface, show different results by each environmental factors.