• Journal of Conservation Science
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• v.32 no.3
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• pp.365-375
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• 2016

This study was interpreted the forming process of surface contaminants on ten-story stone pagoda of Wongaksa temple, Seoul. Results of research, we estimated that black contaminants were formed by graphite stuck carbon in air pollution substance after that gypsum was generated by chemical weathering on stone pagoda. White contaminants were built by recrystallization of calcite that were made by decomposition of finishing materials and structure on the stone surface. To preserve a long-term of stone pagoda in Wongaksa temple, there were required that continuous monitoring, anticorrosion treatment and contaminants cleaning of protective facilities.

• Water for future
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• v.27 no.2
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• pp.63-72
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• 1994

In this study, hydraulic characteristics for upstream migration of fish in a pool-and-weir fishway were analyzed through experiment. The results showed that streaming flow was preferable to plunging flow for upstream migration of fish and it was not good to make an orifice beneath the septum since it generates turbulent jet and eddies. Protrusions on the side wall of fishway were preferable to grooves since they decelerate flow velocity and make upstream migration easy. A vertically movable septum was necessary for a flushing of deposited bed material, and net installing over fishway was also needed for birds not to approach the fishway and eat fish.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.248.1-248.1
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• 2010

수송용 바이오연료로써 바이오디젤의 보급 활성화에 따른 원료인 식물성 기름의 가격 상승 및 수급 불안정성 문제를 해결하고자 그동안 활용되지 않았던 폐유지를 바이오디젤 생산 원료로 사용하여 바이오디젤 생산 단가를 낮추고 원료의 수급 안정성도 확보하려는 시도가 이루어지고 있다. 폐유지의 경우 대부분 유리지방산 함량이 높아 염기 촉매를 적용하는 방법으로는 비누의 생성으로 전환이 힘들며 산 촉매를 적용하여 유리지방산을 에스테르화하는 공정을 필요로 한다. 에스테르화 반응에서는 반응 부산물로 물이 생성되며, 생성된 물은 바이오디젤 생산 반응을 저해하고 역반응을 유도하며 촉매의 활성을 감소시킨다. 본 연구에서는 고유리지방산 함량 오일의 에스테르화 반응에서 수분의 영향을 검토하였다. 산 촉매로 액상 촉매인 황산과 고체 산 촉매인 Amberlyst-15를 사용하였다. 초기 수분 함량이 0, 1, 2, 5, 10, 20%로 증가하였을 때, 지방산 메틸 에스테르 함량이 크게 감소하였으며, 1%의 수분 함량에서도 반응이 크게 저해받는 것으로 나타났다. 따라서 고유리지방산 함량 오일의 에스테르화 반응에서 수분에 의한 저해가 중요한 변수라는 것을 알 수 있다. Amberlyst-15는 황산보다 수분의 영향에 의해 지방산 메틸 에스테르 함량이 빠르게 감소하였다. 이는 다공성의 Amberlyst-15에서 생성된 물이 반응물질들이 active site에 접근하는 것을 방해하였기 때문인 것으로 생각된다. 황산을 사용하였을 경우에는 오일 대 메탄올 몰비를 1:3에서 1:6으로 증가시킴으로써 정반응 속도가 증가하여 수분에 대한 영향이 감소하는 현상이 나타났다. 에스테르화 반응 종료 12시간 후에 바이오디젤과 메탄올 내에 수분 함량을 분석한 결과 12%의 수분이 바이오디젤 층에 존재하며 88%의 수분은 메탄올 층에 존재하였다. 반응 중에 생성된 수분을 제거하기 위해, 에스테르화 반응 30분 후에 물을 포함하는 메탄올과 촉매 층을 새 메탄올과 촉매로 교환하는 2단계 반응을 수행함으로써 지방산 메틸 에스테르 함량을 향상시킬 수 있었다. 반응 초기에는 황산이 Amberlyst-15보다 높은 활성을 보였지만, 시간이 지날수록 두 촉매 사이의 에스테르화 성능 차이는 감소하였다. 따라서 2단계 에스테르화 반응이 수분의 저해작용을 줄이는 한 가지 대안으로 제안될 수 있다. 또한 에스테르화 반응에서 물의 저해 작용을 줄이기 위해 앞으로 투과증발막의 적용 또는 물에 저해작용을 받지 않는 구조의 촉매 사용을 검토할 필요가 있다.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.125-130
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• 2011

We describe that the surface and thickness of nanoporous $WO_3$ fabricated by both light-induced and light-absent anodization are affected by pre-annealing process from $200^{\circ}C$ to $600^{\circ}C$. As a result, the nanoporous $WO_3$ with a thickness of $1.83{\mu}m$ can be achieved by anodization for 6 hours after pre-annealing at $400^{\circ}C$ without illumination of light. Moreover, the thickness of nanoporous $WO_3$ fabricated by pre-annealing is thicker than that of $WO_3$ prepared by non-annealing process. However, the light illumination during anodization leads to convert the crystalline structure obtained by pre-annealing, which interfere the growth of nanoporous $WO_3$. In this paper, we discuss about the growth mechanism of these different nanoporous $WO_3$ films.

• Fire Science and Engineering
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• v.22 no.3
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• pp.221-227
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• 2008

In this study, the fire suppression characteristics of a water mist with natural wind in a road tunnel were calculated using the FDS(Fire Dynamic Simulation) code. In addition, the cooling and the chemical kinetic effects of water vapor on fire extinction ere investigated in a counterflow non-premixed flame using a detailed chemistry. As a result, the behavior of fire plume and the spray characteristics of water mist are modified remarkably with the increasing of wind velocity. In the case which is not the external natural wind, small droplets are more efficient in fire suppression than large droplets. However, the large droplets show better results on the fire suppression than the small droplets with the increasing of wind velocity. It can be estimated that the natural wind disturb the penetration of water droplets into the flame region and decrease the effect of oxygen dilution. Finally, it can be identified that the fire into the natural wind can be suppressed with smaller amount of $H_2O$ by flame stretching effect in the flame region than one in an enclosure, and the chemical kinetic effects of $H_2O$ on fire extinction are not affected significantly the velocity of natural wind.

• Journal of Soil and Groundwater Environment
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• v.11 no.5
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• pp.59-66
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• 2006

Optimal method of radon analysis in groundwater was studied using ultra low-level liquid scintillation counter (ULLLSC) which is well known as an analytical instrument for analyzing the alpha and beta radionuclides in environmental materials. Optimization of pulse shape analyzer (PSA) in operating the LSC was performed with $^{241}Am\;and\;^{90}Sr/^{90}Y$ as well as $^{226}Ra$ Also, the chemical quenching of scintillation generation and the color quenching of the generated photon to photomultiplier tubes (PMT) were determined their effects not only to decrease the analytical efficiency but also to change the optimal PSA level and background due to high ion contents of groundwaters. The optimal PSA level was shown in the range of 90 to 110 with less than 5% error. The effects of high ion contents in groundwater for the analytical efficiency show within 10% error from the different ion contents. The chloroform as a quenching agent was used to determine the analytical efficiency with the different amount, showing that the efficiency decreases 20% using the 2% of chloroform.

• Journal of the Mineralogical Society of Korea
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• v.20 no.4
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• pp.267-275
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• 2007

Melting slag generated from municipal-incinerator ash contains lots of impurities which have adverse effects on zeolite synthesis. These impurities are detrimental to zeolite synthesis, and the yield and purity of zeolite was decreased. And thus its performance is lowered. In melting slag, there are lots of components such as $Fe_2O_3$, FeO and CaO. To remove these impurities, we treated the melting slag with hydrochloric acid at initial pH 1, 3, 5, and 7. After the treatment, the $SiO_2,\;Fe_2O_3,\;and\;TiO_2$ ratios increased, but the $Al_2O_3,\;FeO,\;CaO,\;Na_2O$ and MgO ratios decreased. We reacted these treated slag in a NaOH solution under hydrothermal conditions at $80^{\circ}C$. The hydrothermal products from the slag and the slag treated at pH 7 and pH 5 were determined to be tobermorite, whereas those at pH 3 and pH 1, Na-P1 and Na-X zoelite respectively. CaO was found to inhibit the synthesis of zeolite.

• Journal of Conservation Science
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• v.37 no.5
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• pp.411-425
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• 2021

The Stupa of State Preceptor Jigwang from Beopcheonsa Temple Site in Wonju (National Treasure) is a representative stupa of the Goryeo Dynasty, with outstanding Buddhist carvings and splendid patterns, clearly indicating its honoree and year of construction. However, it was destroyed by bombing during the Korean War (1950-1953) and repaired and restored with cement and reinforcing bars in 1957. The surface condition of the original stone shows long-term deterioration due to the m ortar used in past restorations. In order to identify the exact causes of deterioration, the m ortar and surface contaminants on the original stone were analyzed. Portlandite, calcite, ettringite, and gypsum from the mortar were identified, and its ongoing deterioration was observed through pH measurements and the neutralization reaction test. Analysis of surface contaminants identified calcite and gypsum, both poorly water-soluble substances, and their growth in volume among rock-forming minerals was observed by microscopy. Based on those results, semi-quantitative analysis of Ca and S contents significantly influencing the formation of salt crystals was conducted using P-XRF to analyze the basis of surface deterioration, and cross-validation was performed by comparing the body stone affected by the mortar and the upper stylobate stone unaffected by the mortar. Results indicate that the elements are directly involved in the surface deterioration of the body stone.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.4
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• pp.33-42
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• 2004

The usual practice of placing viscoelastic dampers (VED) in the inter-story of building structures frequently interfere with spatial planning and obstruct internal view. These shortcomings can be overcome by installing VED in seismic joints or in expansion joints which are usually hidden under a cover. This study investigates the effect of installing VED in seismic joints to reduce earthquake-induced dynamic reponses. Parametric studies were conducted using 3-DOF systems connected by VED and subjected to earthquake excitations to investigate the effectiveness of the proposed scheme. Nonlinear dynamic analyses were carried out with five-story structures composed of different structure systems and connected by seismic joints. According to the analysis results the use of VED in seismic joints turned out to be effective as long as the natural frequencies of the connected structures are different enough.

• Journal of the Korean Chemical Society
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• v.22 no.3
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• pp.164-172
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• 1978

Carboxypeptidase A-catalyzed hydrolysis of ester substrates was carried out at room temperature in the presence of a number of external reagents. If the acyl-enzyme intermediate, an anhydride, is attacked by the external reagents, products formed by trapping at the acyl portion or at the enzyme portion of the anhydride group can be obtained. Examination of the uv/vis spectral properties of the reaction products and of changes in enzyme activity indicated that such trapping reactions did not occur. Also performed was evaluation of enzymatic rate parameters for the the hydrolysis of O-(o-hydroxyphenylacetyl)-L-${\beta}$-phenyllactate. Detection of 2-coumaranone possibly formed by attack of the o-hydroxy group as an intramolecular trapping group at the acyl-enzyme intermediate was tried, but no evidences for the intramolecular trapping reaction were obtained. Failure to trap the intermediate was discussed in terms of steric hindrance imposed on the approach of the trapping reagents to the anhydride group of the acyl-enzyme intermediate and of the fast enzymatic breakdown of the intermediate.