• Journal of Ecology and Environment
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• 제32권2호
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• pp.123-127
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• 2009

Weight loss and nutrient dynamics of Quercus mongolica leaf litter during decomposition were investigated from December 2005 through August 2008 in Mt. Worak National Park as a part of National Long-Term Ecological Research Program in Korea. The decay constant (k) of Q. mongolica litter was 0.26. After 33 months decomposition, remaining weight of Q. mongolica litter was 49.3$\pm$4.4%. Initial C/N and C/P ratios of Q. mongolica litter were 43.3 and 2,032, respectively. C/N ratio in decomposing litter decreased rapidly from the beginning to nine months decomposition, and then showed more or less constant. C/P ratio increased to 2,407 after three months decomposition, and then decreased steadily thereafter. N and P concentration increased significantly during decomposition. N immobilization occurred from the beginning through 18 months decomposition, and mineralization occurred afterwards in decomposing litter. P immobilized significantly from fifteen months during decomposition. K concentration decreased rapidly from the beginning to six months decomposition. However it showed an increasing pattern during later stage of decomposition. Remaining K decreased rapidly during early stage of decomposition. There was no net K immobilization. Ca concentration increased from the beginning to twelve months decomposition, and then decreased rapidly till twenty one months elapsed. However, it increased again thereafter. Ca mineralization occurred from fifteen months. Mg concentration increased during decomposition. There was no Mg immobilization during litter decomposition. After 33 months decomposition, remaining N, P, K, Ca and Mg in Q. mongolica litter were 79.2, 110.9, 36.2, 52.7 and 74.4%, respectively.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.57-61
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• 2014

In this study, carbon aerogel (CA) was synthesized using a soft-template method, and the optimum conditions for the adsorption of carbon dioxide ($CO_2$) by the carbon aerogel were evaluated by controlling the activation temperature. KOH was used as the activation agent at a KOH/CA activation ratio of 4:1. Three types of activated CAs were synthesized at activation temperatures of $800^{\circ}C$(CA-K-800), $900^{\circ}C$(CA-K-900), and $1000^{\circ}C$(CA-K-1000), and their surface and pore characteristics along with the $CO_2$ adsorption characteristics were examined. The results showed that with the increase in activation temperature from 800 to $900^{\circ}C$, the total pore volume and specific surface area sharply increased from 1.2165 to $1.2500cm^3/g$ and 1281 to $1526m^2/g$, respectively. However, the values for both these parameters decreased at temperatures above $1000^{\circ}C$. The best $CO_2$ adsorption capacity of 10.9 wt % was obtained for the CA-K-900 sample at 298 K and 1 bar. This result highlights the importance of the structural and textural characteristics of the carbon aerogel, prepared at different activation temperatures on $CO_2$ adsorption behaviors.

• 대한전자공학회논문지
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• 제22권6호
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• pp.34-40
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• 1985

분자선 에퍼택시 (MBE)방법을 이용하여 (100) GaAs웨이퍼 위에 GaAs에퍼충을 성장시켜 성장된 충에 대한 여러가지 특성을 조사 ·분석하였다. 분자선 에피택시 방법을 이용하여 CaAs에퍼층을 만들 때에는 기판온도와 As와 Ca의 분자선 밀도비 (As/Ga)가 가장 큰 영향을 미친다. 본 실험에서는 좋은 표면상태를 얻기 위해 480℃∼650℃로 유지시키고 As cell의 온도를 230℃, Ga eel함 온도를 917℃로 고정시켜 As와 Ga의 분자선 밀도비를 5∼10 이상으로 유지시켰다. 제작된 GaAs에피층의 표면상태를 SIMS (Seconde,y ion Mass ipectoscopy), AES(Auger Electron Spectroscopy) , SEM (Scanning Elect.on Mic,oscopy) , RHEED (Reflection High Energy Electron Diffraction) 등으로 조사한 결과 기판온도가 540℃일 때 가장 좋은 표면상태를 얻을 수 있었다. 또한 RH-EED관찰 결과 As 안정화된 표면을 관측할 수 있었으며 SIMS로 depth-Profile을 해 본 곁과, Ca 보다 As가 불안정함을 알았다. 또한 반선 회절 검사결과에서 기판온도가 520℃일때와 540℃일때 (400), (200)면에 단결정이 형성되었음을 알 수 있었다.

• KSBB Journal
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• 제26권1호
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• pp.13-18
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• 2011

본 연구에서는 $Ca(LA)_2$의 침전조건을 최적화하고 침전된 $Ca(LA)_2$ 용액에 황산을 처리하여 고순도, 고수율의 lactic acid를 회수할 수 있는 방법을 개발하고자 하였다. 특히 $Ca(LA)_2$의 용해도를 낮추기 위하여 여러 종류의 유기용매 첨가에 따른 영향을 평가하였다. 모델용액의 경우 침전을 위한 최적의 석회종류, 석회량, 교반속도, 시간, 온도, 유기용매 첨가량은 각각 CaO, 0.0175 g/mL, 220 rpm, 24 h, $5^{\circ}C$, ethanol 25% (v/v)이었으며 최적 조건 하에서 가장 높은 순도 (98%)와 수율(69%)을 얻을 수 있었다. 발효배양액 (lactic acid 순도: 69%, pH: 7.3)의 경우, 모델용액으로부터 얻은 최적의 조건 하에서 $Ca(LA)_2$ 회수 과정에서 64%, 회수된 $Ca(LA)_2$에 황산을 첨가 ($Ca(LA)_2/H_2SO_4$ molar ratio = 1:1)하여 lactic acid를 회수하는 과정에서 86%의 회수율을 각각 얻어 발효배양액으로부터 총괄 수율 55%로 lactic acid (순도: 88.6%)를 얻을 수 있었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권10호
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• pp.559-563
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• 2000

The $(Sr_{1-x}Ca_x)TiO_3(SCT)$ thin films are deposited on Pt-coated(Pt/TiN/$SiO_2$/Si) using RF sputtering method with substitutional contents of Ca. The maximum grain of thin films is obtained by substitution of Ca at 15[mol%]. Also the composition of SCT thin films were closed to stoichiometry(1.081∼1.117 in A/B/ ratio). The dielectric constant was increased with increasing the substitutional contents of Ca, while it was decreased if the substitutional contents of Ca exceeded over 15[mol%]. The dielectric constant changes almost linearly in temperature ranges of -80∼+90[^${\circ}C$]. The temperature properties of the dielectric loss have a stable value within 0.02 independent of the substitutional contents of Ca. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 2000[kHz]. The current-voltage characteristics of SCT15 thin films showed the increasing leakage current as the measuring temperature increase.

• 한국세라믹학회지
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• 제23권3호
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• pp.27-34
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• 1986

The hydration of flyash-$Ca(OH)_2-CaSO_4$.$2H_2O$ system was stuedied with varing mixing ratio of flyahs $Ca(OH)_2$ and caSO4.2H2O The samples were steam-cured for 1-7 days at 9$0^{\circ}C$. The optimum mixing composition was flyash : Ca (OH)2=65:35 with 15% $CaSO_4$.42H_2O$ added which produced the hardened material having the best compressive strength (300kg/$cm^2$) Also the low specific gravity(1, 2) of the hardened paste suggests the possibility that it can be used as a light-weight building material. The added $CaSO_4$.42H_2O$ constituted calcium-sulfo-aluminate hydrates which activates the formation of C-S-H hy-drates. Both hydrates developed the strength of hardened paste. The amount of calcium-sulfo-aluminate hydrates was increased when the $CaSO_4$.42H_2O$ was added over 15% however the increased amount did not help the development of strength because of the individually grown calcium-sulfo-aluminate hydrates.

• 한국습지학회지
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• 제14권4호
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• pp.537-545
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• 2012

낙엽활엽수인 상수리나무 낙엽의 지역에 따른 분해율 및 분해과정에 따른 영양염류의 함량 변화를 파악하기 위해 2008년 12월 공주의 상수리나무림과 진주지역의 낙엽-상록침엽수 혼효림 임상에 낙엽주머니를 설치하고 2011년 3월까지 33개월 동안 분해율, 분해상수 (k), 그리고 분해과정에 따른 C/N 비, C/P 비의 변화와 영양염류의 동태를 조사하여 비교하였다. 33개월경과 후 공주와 진주에서 상수리나무 낙엽 잔존률은 각각 $41.2{\pm}0.4%$와 $28.3{\pm}0.6%$, 분해상수 (k)는 각각 0.39와 0.61로 진주지역이 공주지역에 비해 분해가 빠른 것으로 나타났다. 이것은 진주지역이 공주에 비해 연중 기온과 강수량이 높기 때문인 것으로 판단된다. 상수리나무 낙엽의 분해과정에 따른 C/N. C/P 비율은 초기에 각각 46.8, 270.9 이었으나 33개월경과 후에는 공주지역에서 각각 22.0과 106.8, 진주지역에서는 각각 19.2와 170.2로 낮아졌다. 낙엽의 초기 N, P, K, Ca, Mg 함량은 각각 8.31, 0.44, 4.18, 9.38, 1.37 mg/g이었으며, 33개월경과 후 N, P, K, Ca, Mg의 잔존률은 공주지역에서 각각 91.0, 85.4, 30.2, 47.9, 11.7 %, 진주지역에서는 각각 67.0, 54.2, 19.9, 30.0, 40.8%로 Mg을 제외하고 진주지역의 잔존률이 낮았다. 조사기간 동안에 질소와 인은 부동화 후 무기화가, 칼륨, 칼슘, 마그네슘은 지속적인 무기화가 진행되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.160-161
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• 2005

The $(Sr_{1-x}Ca_x)TiO_3$(SCT) thin films are deposited on Pt-coated electrode (Pt/TiN/$SiO_2$/Si) using RF sputtering method with substitutional contents of Ca. The optimum conditions of RF power and $Ar/O_2$ ratio were 140[W] and 80/20, respectively. Deposition rate of SCT thin film was about 18.75$[{\AA}/min]$. The dielectric constant was increased with increasing the substitutional contents of Ca, while it was decreased if the substitutional contents of Ca exceeded over 15[mol%]. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 200[kHz].

• The Korean Journal of Ceramics
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• 제6권3호
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• pp.286-290
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• 2000

The hydration behavior of fly ash and slag on cement paste were investigated. Early stage of hydration reaction was delayed by mixing fly ash and/or slag with cement, but production of C-S-H hydrates by pozzolanic reaction densified the microstructure. The Ca/Si ratio of C-S-H hydrates in OPC and blended cement of fly ash 50%, slag 50%, fly ash+slag 50% were 2.24, 1.80, 1.82 and 1.97, respectively. The C-S-H gel with low Ca/Si ratio showed rather reticulate than needle-like structure.

• 자원리싸이클링
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• 제5권1호
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• pp.3-8
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• 1996

석회석슬럿지, 폐주물사, 석탄회 및 폐유리병 등의 산업폐기물을 용융처리하여 시멘트 클링커 상의 일부인 $C_2$S(2CaO.$SiO_2$)를 얻고, 폐기물 원료의 배합비율을 변화시킬 때 각 폐기물의 최종 생성물에 미치는 영향을 조사하였다. 일정한 염기도를 갖도록 혼합된 폐기물을 $1370^{\circ}C$에서 용융 처리한 결과 $\beta$-C$_2$S 및 $C_2$AS(2CaO.$Al_2$$O_3$.$SiO_2$)상으로 이루어진 용융물을 얻을 수 있었고, 2가지 상의 분율은 폐기물 원료의 조합방법에 따라 변하였다. 직교배열표를 이용하여 각 폐기물의 함량이 최종 용융물의 상에 미치는 영향을 조사한 결과, $\beta$-$C_2$S 상의 분율을 증가시키기 위해서는 석탄회의 함량을 감소시키고 폐유리병의 함량을 증가시켜야 함이 밝혀졌다. 분산분석을 행한 결과 석탄회의 함량조절이 최종 용융물의 상을 조절하는데 있어서 가장 중요한 인자임을 알 수 있었다.