• 천문학회보
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• 제37권1호
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• pp.55.2-55.2
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• 2012

Silicate-carbon stars are characterized by oxygen-rich (O-rich) dust features despite their carbon-rich (C-rich) photospheres. While the origin of silicate-carbon stars has been a mystery ever since their discovery, the most widely accepted hypothesis is that the silicate-carbon stars have a low-luminosity companion and the O-rich material is stored in a circumbinary disk or a circumstellar disk even after the primary star becomes a carbon star. In order to study the properties of circumstellar dust envelopes of silicate-carbon stars, we perform radiative transfer model calculations using RADMC-3D with an axi-symmetric dust density distribution (a disk) as well as a spherically symmetric dust distribution. For various dust envelope models with different shapes and chemistry, we calculate the model spectral energy distributions (SEDs) and compare the model results with the observed SEDs of selected 5 silicate-carbon stars. The Circumstellar disk models are fairly well fitted with the observational data of 5 silicate-carbon stars. We find some evidences that the circumbinary disk model could be a better explanation for the origin of silicate carbon stars than the simple detached silicate dust shell model of the transition phase of the stellar chemistry.

• Ocean and Polar Research
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• 제29권4호
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• pp.391-400
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• 2007

To identify the spatial distribution pattern of water quality in Masan Bay, Pearson's correlation as a common statistic method and Moran's I as a spatial autocorrelation statistics were applied to the hydrological data seasonally collected from Masan Bay for two years ($2004{\sim}2005$). Spatial distribution of salinity, DO and silicate among the hydrological parameters clustered strongly while chlorophyll a distribution displayed a weak clustering. When the similarity matrix of Moran's I was compared with correlation matrix of Pearson's r, only the relationships of temperature vs. salinity, temperature vs. silicate and silicate vs. total inorganic nitrogen showed significant correlation and similarity of spatial clustered pattern. Considering Pearson's correlation and the spatial autocorrelation results, water quality distribution patterns of Masan Bay were conceptually simplified into four types. Based on the simplified types, Moran's I and Pearson's r were compared respectively with spatial distribution maps on salinity and silicate with a strong clustered pattern, and with chlorophyll a having no clustered pattern. According to these test results, spatial distribution of the water quality in Masan Bay could be summed up in four patterns. This summation should be developed as spatial index to be linked with pollutant and ecological indicators for coastal health assessment.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 추계 학술논문 발표대회
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• pp.94-95
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• 2016

Calcium Silicate Hydrate (C-S-H), which takes up most of the hydration products of Portland Cement (PC), has the greatest impact on the mechanical behavior and strength development of concrete. The exact mechanism of its deformation, however, has not yet been elucidated. The present study aims to demonstrate the mechanism of nano-deformation behavior of C-S-H in tricalcium silicate paste under compressive loading, unloading and reloading by interpreting atomic pair distribution function (PDF) based on synchrotron X-ray scattering. The strain of the tricalcium silicate paste for a short-range of 0 ~ 20 Å under compressive load exhibited two stages, I) nano-packing of interlayer of C-S-H and II) micro-packing of C-S-H globules, whereas the deformation for a long-range order of 20 ~ 40 Å was similar to that of a calcium hydroxide phase measured by Bragg peak shift. Moreover, the residual strains due to the plastic deformation of C-S-H was clearly observed.

• 천문학회지
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• 제25권2호
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• pp.111-128
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• 1992

Infrared emissions from spherical dust, clouds are calculated using quasi-diffusion method. We have employed graphite-silicate mixture with power-law size distribution for the dust model. The grains are assumed to be heated and cooled by radiative processes only. The primary heating source is diffuse interstellar radiation field. hut the cases with an embedded source are also considered. Since graphite grains have higher temperature than silicate grains, the observed IR emission is mainly due to graphite grains, unless the fraction of graphite grains is negligibly small. The color temperature of Bok globules obtained from IRAS 60 and $100{\mu}m$ data are found to be consistent with the dust cloud with graphite-silicate mixture exposed to average interstellar radiation field. The color temperature is sensitive to the external radiation field, but rather insensitive to the size distribution of the grains. We found that the density distribution can be recovered outside the beam size using the inversion technique that assumes negligible optical depth. However, the information within the beam size is lost for if beam convolved intensity distributions are used in deriving density profile.

• 환경위생공학
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• 제10권3호
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• pp.78-84
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• 1995

Cationic surfactants can be used to modify surface of solids to promote adsorption of hydrophobic organic compounds. This behavior is due to the surfactant forming aggregate structure on the solid surface. Partition coefficients are commonly used to quantify the distribution of organic pollutants between the aqueous and particulate phases of aquatic system Partitioning of hydrophobic compounds to cetyltrimethylammonium bromide ( CTAB ) coated silicate has been investigated as a function of surfactant surface coverage at I=0 and 0.1 ionic strength. Toluene, Xylene, TCI sorption experiments demonstrated that the CTAB coated silicate was able to remove these hydrophobic organic compounds from solution The hydrophobic organic compound with the higher Kow had higher removals than lowest Kow hydrophobic organic compound.

• 한국해양학회지:바다
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• 제9권4호
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• pp.153-163
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• 2004

In order to estimate the nutrient flux of the Seomjin River into the coastal waters of South Sea, and to understand the estuarine reactions during mixing between river water and seawater, we collected surface water along the salinity gradient in the Seomjin River estuary from Mar. 1999 to Apr. 2001. We found that nitrate and silicate were delivered by fluvial input, while phosphate was, supplied from disposed wastes in the Gwangyang Bay. Mean annual flux of dissolved inorganic nitrogen (DIN), phosphate and silicate into the Gwangyang Bay was estimated 10.9 molesㆍsec$^{-1}$(4,820 tonnesㆍyr$^{-1}$), 0.07 molesㆍsec$^{-1}$(68 tonnesㆍyr$^{-1}$), 13.3 molesㆍsec$^{-1}$(11,747 tonnesㆍy$^{-1}$), respectively. An evident removal of phosphate, silicate and ammonium at the mid-salinity zone during the dry season was attributed to the active uptake of phytoplankton, and consequently nutrient flux into the Gwangyang Bay was low. Whereas, during the flood season in summer, conservative or additional distribution of the nutrients was observed in the estuary. As a rsult nutrient flux into the Gwangyang Bay was maintained high. High concentrations of chlorophyll a and the active removal of nutrient during the dry season at the mid-salinity zone suggest that nutrient distribution in the Seomjin River estuary was mainly controlled by biological processes and nutrient fluxes into the Gwangyang Bay might be significantly modified of by the primary production.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.144-145
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• 2021

Calcium silicate hydrate(C-S-H) is the principal binding phase that controls the strength and thermal stability of concrete. However, the effects of high temperature on the lattice structure and interatomic structure of C-S-H remains poorly understood due to its nanocrystallinity. This study aims to elucidate the change in interatomic distance of synthetic C-S-H with different Ca/Si molar ratios after exposure to high temperature via high energy X-ray scattering experiment which is a powerful analytical tool for amorphous materials.

• 농약과학회지
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• 제4권2호
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• pp.44-49
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• 2000

본 시험은 오이 양액재배시 배양액내 규산칼륨($K_{2}SiO_{3}$) 처리에 의한 생육단계별 규소의 흡수특성, 체내분표 병원균의 침입억제 효과를 검토하기 위하여 수행하였다. 잎에서의 규소 분포는 TEM, SEM 및 EDX-ray를 사용하여 4개(SEM, Ca, Si, K)의 구성원소를 각각 측정하였다. 흡수된 규소는 잎으로 이동하여 모용(毛茸, trichome, hair)을 둘러싸고 있는 기부 세포에 축적되었다. 모용에서의 규소는 고농도의 칼슘 및 칼륨과 혼재하여 분포하였고, 저농도 처리시에는 모용기부를 제외한 표피세포에서는 감지 할 수 없는 수준으로 분포하였다. 잎에서의 규소 축적은 처리 후 24시간에서 48시간 사이에 세포벽 주위에 가장 많이 축적되었고, 그 이후에도 다소 증가하는 경향이었다. 처리된 규소는 발아하고 있는 흰가루병 분생포자의 인접 조직의 세포벽과 병원균 흡기 주변에 다량 축적되어 물리적인 장벽으로 작용하였다. 고농도의 규산 처리된 잎 병반상의 발아관 길이는 낮은 농도의 처리구와 비교하여 현저히 짧았으며, 규산 처리농도와 부의 상관관계를 나타내었다. 배양액내 처리된 규산 농도는 오이가 생장함에 따라 감소하여 뿌리를 통하여 작물체내로 흡수되었으며, 저농도 처리구(0.85 mM이하)에서는 흡수되는 양이 현저히 적었다.

• 한국토양비료학회지
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• 제11권2호
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• pp.89-95
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• 1979

규산질비료(珪酸質肥料)를 이앙(移秧) 전년(前年) 추시(秋施)했을 때와 이앙(移秧) 직전(直前) 춘시(春施)했을 때의 시용시기(施用時期) 및 입도(粒度)의 차이(差異)가 밀양 23호와 진흥의 수량(收量)에 미치는 효과를 검토할 목적(目的)으로 포장시험(圃場試驗)을 수행(遂行)하였다. 규산질비료(珪酸質肥料)의 시용(施用)(250kg/10a)에 의(依)하여 정조수량(正租收量) 및 고중(藁重)의 증가는 현저하였으나 시용시기(施用時期)에 대한 유의성(有意性)은 없었다. 입시(秋施)에 의(依)한 규산시용(珪酸施用)의 효과는 춘시(春施)한 것에 비(比)하여 다소 떨어지는 경향(傾向)을 나타낼 뿐이었다. 규산질비료(珪酸質肥料)의 입도(粒度)가 클수록 수도(水稻)의 수량(收量)에 미치는 규산시용(珪酸施用)의 효과는 떨어지는 경향(傾向)이었으나 8-25(60%)와 현행규산질비료(現行珪酸質肥料)는 대등한 것으로 평가(評價)되었다. 규산질비료(珪酸質肥料)의 시용(施用)에 의하여 대체로 주당수수와 수당입수가 증가된 반면(反面) 등숙률(登熟率)과 천립중(千粒重)은 떨어지는 경향(傾向)이었으나 추시구의 진흥에서는 입도(粒度)에 따라 수량구성요소(收量構成要素)의 변화경향이 일정(一定)치 않았다. 경엽의 규산함량(珪酸含量)은 진흥에서 높고 정조(正租)의 규산함량(珪酸含量)은 밀양23호에서 높았으며 품종간(品種間) 규산함량(珪酸含量)의 차(差)는 수확기(收穫期)보다는 이앙(移秧)50일후(日後) 식물체(植物體)에서 현저하였다. 규산함량(珪酸含量)에 미치는 시용시기(施用時期) 및 입도(粒度)의 영향은 이앙(移秧)50일후(日後) 식물체의 규산함량(珪酸含量)에서 유의성(有意性)이 인정(認定)되었으며 수확기(收穫期)의 규산함량(珪酸含量)에서는 진흥의 고중(藁中) 규산함량(珪酸含量)에 대한 입도(粒度)의 영향만이 인정(認定)되었다. 토양(土壤)의 유효규산함량은 시험전 36.7ppm에서 규산시용(珪酸施用)에 의하여 수확후(收穫後)에 춘시구에서는 159.5~273.8ppm, 추시구에서는 80.3~134.4ppm으로 증가되었다. 춘시구에서는 8-25(60%)를 시용(施用)한 경우에 가장 높았으며 추시구에서는 현행규산질비료(現行珪酸質肥料)와 8-25(60%)를 시용(施用)한 경우의 차(差)가 적었다. 결론적(結論的)으로 8-25(60%)는 현행규산질비료(現行珪酸質肥料)와 대등한 것으로 평가(評價)되며 추시(秋施)에 의(依)해서도 규산질비료(珪酸質肥料)의 효과를 충분(充分)히 얻을 수 있으나 규산질비료(珪酸質肥料)의 잔효에 대하여는 새로운 연구검토가 요구(要求)됨을 지적(指摘)하였다.

• Ocean and Polar Research
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• 제27권4호
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• pp.359-379
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• 2005

In order to understand the spatial and temporal variations of nutrients and factors controlling their distribution in Gwangyang Bay, this study was carried out bimonthly from June 2001 to July 2003, Inorganic silicate and nitrate concentrations ranged from $0.04{\mu}M\;to\;69.5{\mu}M(avg.\;12.9{\mu}M)$, and from $0.12{\mu}M\;to\;42.2{\mu}M\;(avg.\;7.83{\mu}M)$, respectively. Silicate concentrations measured just after the typhoon were the highest with an average of $43.2{\mu}M$ at the surface layer in June 2001, whereas the highest nitrate concentration $(avg.\;37.0{\mu}M)$ was observed in the surface layer in July 2003. River runoff apparently influenced variations in silicate and nitrate concentrations (r=0.701 and 0.728, p<0.000, respectively) as well as salinity (r=-0.628, p<0.000). Phosphate concentrations ranged from $0.24{\mu}M\;to\;5.70{\mu}M\;(avg.\;1.34{\mu}M)$ and were highest at stations 5, 6, and 7, near a fertilizer plant with an average of $2.01{\mu}M$. On the basis of N/P and Si/N molar ratios, limiting nutrients have varied temporary and spatially. During 2001-2002, nitrogen was a limiting nutrient in the study area, and Phosphate was limited when a large volume of freshwater flowed into the bay. Silicate was limited when the high standing crops of phytoplankton occurred in the whole study area throughout 2003, and in the inner bay in February and August 2002. During the study period, factors controlling the distribution of nutrients might be summarized as follows; 1) inflow of freshwater by heavy rain accompanied by typhoons and frequent rainfall in summer, showing high concentrations of silicate and nitrate, 2) release of high phosphate concentrations from the fertilizer plant located in the south of Moydo to adjacent stations, 3) release of nutrients from bottom sediment, 4) magnitude of occurrence of phytoplankton standing crops.