• 한국연소학회지
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• 제22권3호
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• pp.47-52
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• 2017

The propellant tile and crack which account for the greatest proportion of solid rockets are profoundly affected by viscosity and mechanical properties of solid propellant. In this paper HTPB/AP/Al system propellant has been researched for the viscosity, mechanical properties and burning properties with type and contents of bonding agents. The viscosity of propellant was changed significantly depending on the type and contents of bonding agents, and mechanical properties of HTPB/AP/Al system propellant were also varied. Considering both lower viscosity and stable mechanical properties, the optimum type and contents of bonding agents can be identified as the main factors to the HTPB/AP/Al system propellant.

• 한국환경과학회지
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• 제20권10호
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• pp.1265-1272
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• 2011

In this study, the extraction characteristics of soluble solid from Rumex crispus(Curled dock) was studied from the investigation of the effects of experimental conditions on extraction rate; extraction ratio, composition of extractants, extraction time and pH of extractant, etc. The proximate composition of Rumex crispus was 2.58% crude lipid, 5.59% crude protein, 7.39% crude ash, 6.13% moisture and 78.31% carbohydrate, respectively. Turbidity of extract by distilled water was higher and increased with extraction time and extraction temperature, where as the turbidity didn't increase by ethanol and methanol in 20 folds of extraction ratio. Turbidity was inversely proportional to the extraction ratio for the three extractants at 25$^{\circ}C$ and 1 hour extraction. But turbidity of extract was highest by composition of 50% methanol-water extractant than any other compositions of extractants. Eighteen and fifteen free aminoacids were detected in extracts with distilled water, methanol and ethanol extractant, respectively, and it's contents were order of glutamic acid>proline>aminobutyric acid>alanine. The extraction rate of soluble solid from Rumex crispus was order of distilled water>methanol>ethanol within experimental extraction ratio. In extraction with distilled water, the contents of soluble solid was inversely proportional to the pH of extractant.

• 한국응용과학기술학회지
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• 제23권1호
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• pp.85-91
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• 2006

Acrylic resins (HSCs : EA/EMA/2-HEMA/CLA) which contain 80% solid content were synthesized by the copolymerization of monomers (ethyl acrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate) and functional monomer (caprolactone acrylate : CLA) which improves the crosslinking density and physical properties of films. The physical properties of the prepared acrylic resins (HSCs) containing CLA, are as follows: viscosity 1440$^{\sim}$2630 cps ; $M_n$ 1590$^{\sim}$1660 ; and conversions, 81$^{\sim}$86%, respectively. From the correlation of $T_g$ values, viscosities, and $M_n$ of the HSCs, it was found thst viscosity and $M_n$ increased with $T_g$ value.

• 한국식품영양학회지
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• 제25권3호
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• pp.612-619
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• 2012

This study was conducted to investigate the physicochemical properties of the ethanol extracts and soluble dietary fiber from Cassia tora L. seed. The proximate composition of Cassia tora, soluble solid contents, color intensity and contents of emodin and rhein of Cassia tora extract, molecular mass distribution, sugar contents and viscosity of soluble fiber from Cassia tora were analyzed. Cassia tora contains 12.6% of moisture, 5.2% of ash, 13.4% of crude protein, 7.2% of crude fat, 8.8% of insoluble fiber and 48.3% of soluble fiber. The effects of extract condition on soluble solid contents, color intensity and contents of emodin and rhein of Cassia tora extract were investigated. The soluble solid contents were higher in 70% or 50% ethanol extracts than those in 100% ethanol extracts and showed highest value in grind sample extracts. In Hunter's color value, 100% ethanol extracts and whole Cassia tora sample extracts were higher in L and b value, but on the contrary, were lower in a value, than those of the other. The highest emodin and rhein contents were observed in 70% and 50% ethanol extracts, respectively, and showed higher value in room temperature extracts than in heating extracts. The molecular mass of soluble fiber from Cassia tora seed was estimated by gel filtration chromatography. Most soluble fiber(80%) exhibited a molecular mass range of between 50~2000 kDa. The major sugars of soluble fiber from Cassia tora seed were identified as xylose, mannose and galactose. The apparent viscosity of 0.5% soluble fiber from Cassia tora seed was 33 mPas showing a higher value than pectin or xanthan gum.

• 콘크리트학회논문집
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• 제26권4호
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• pp.457-463
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• 2014

이 연구는 화학혼화제 인수검사 기준으로 활용할 수 있는 고형분량 변동이 콘크리트 품질에 미치는 영향에 대해 살펴보는데 그 목적을 두었다. 현재 한국도로공사의 잠정기준으로 운용 중인 ASTM C 494 기반의 고형분량 변동범위 ${\pm}12%$는 혼화제의 종류 및 고형분량의 특성을 반영하지 못해 혼화제 종류에 따라 상이하게 나타났다. 고형분량 변동에 따른 콘크리트의 품질 변동을 평가한 결과 리그닌은 감수율이 낮은 관계로 고형분량의 변동범위가 큰 반면 나프탈렌계 및 폴리칼본산계 고성능감수제는 높은 감수율로 인하여 인수검사 기준으로 활용 중인 고형분량의 차이에 대한 허용범위 재조정이 요구되었다.

• 한국초등수학교육학회지
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• 제21권1호
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• pp.161-194
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• 2017

본 연구는 초등학교 수학에서 입체도형의 공간 감각에 해당하는 쌓기나무 단원과 관련된 공간 감각 요인들을 살펴보고, 이를 바탕으로 우리나라와 핀란드, 네덜란드 교과서의 입체도형의 공간 감각 관련 내용의 특징을 분석함으로써 앞으로 입체도형의 공간 감각 지도 개선을 위한 시사점을 제공하는 데 그 목적이 있다. 이를 위해 이론적 고찰을 통해 공간 감각의 의미와 하위 요인을 알아보고, 입체도형의 공간 감각과 관련된 공간 감각의 하위 요인과 활동 예들을 제시하고, 이를 기초로 우리나라, 핀란드, 네덜란드 교과서의 입체도형의 공간 감각 지도 내용의 특징을 분석하였다. 이론적 고찰과 교과서 비교 분석 결과 입체도형의 공간 감각 지도 개선을 위한 시사점으로 교육과정에서 공간 감각 요인의 포괄적 제시와 학년간의 연속성, 공간 시각화뿐만 아니라 공간 방향의 포함, 정신적 회전과 정신적 변형의 강화, 정신적 차원 변형의 다양한 방법들의 비교, 다양한 현실적인 공간 상황과 공간 대상의 활용을 제안하였다.

• 한국토양비료학회지
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• 제48권6호
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• pp.697-704
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• 2015

This study was carried out to assess bioenergy conversion efficiency by biogas and solid fuel production in the cattle feedlot manure discharged from beef cattle barn. Feedlot manure was sampled from the cattle farmhouse located in Yong-in, Gyeonggi during the mid-fattening stage, periodically. The chemical characteristics, BMP (Biochemical methane potential) and HV (Heating values) of feedlot cattle manures were analyzed. Total solid contents of cattle feedlot manure were in the range of 29.98~44.28%, and volatile solid contents were in the range of 23.53~24.47%. In the anaerobic digestion of cattle feedlot manure, the methane production potential has increased from 0.141 to $0.187Nm^3kg^{-1}-VS_{added}$. The methane production of fresh cattle feedlot manure showed the range $0.141{\sim}0.187Nm^3kg^{-1}$-Manure (average $0.047Nm^3kg^{-1}$-Manure), the LHVs (lower heating values) of the produced methane were in the range of $316{\sim}560kcalkg^{-1}$-Manure (average $400kcalkg^{-1}$-Manure). In the direct combustion of fresh cattle feedlot manure, the LHVs were measured in the range of $747{\sim}1,271kcalkg^{-1}$-Manure (average $916kcalkg^{-1}$-Manure), and LHVs of solid fuel which have the water content of 20% were in the range of $2,694{\sim}2,876kcalkg^{-1}$-Manure (average $2,791kcalkg^{-1}$-Manure). Then, the drying energy of average $443kcalkg^{-1}$-Manure was consumed in the production of solid fuel which has a water content of 20%. Therefore, the direct combustion of cattle feedlot manure showed about 2.3 times higher LHV than the LHV of methane produced by anaerobic digestion. And LHV of solid fuel was about 6.0 times higher than the LHV of methane produced by anaerobic digestion. Then, the production of solid fuel presented more bioenergy conversion efficiency than the biogas production in the bioenergy use of cattle feedlot manure.

• 한국연소학회:학술대회논문집
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• 한국연소학회 제26회 KOSCO SYMPOSIUM 논문집
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• pp.119-127
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• 2003

In this study we propose an unsteady I-dimensional model of bed combustion with multiple solid phases, which confers a phase on each solid material. This model can be applied to a variety of bed combustion cases of various configurations and ignition methods. It contains fuel combustion, gaseous reaction, heat transfers between each phase, and geometric changes of the solid particles. An iron ore sintering pot is selected for verifying the model validity and simulation results are compared with the limited experimental data set of various coke contents and air supply rates. They predict the experimental results well and show applicabilities to the various system of the fuel bed with various solid materials.

• 한국세라믹학회지
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• 제49권3호
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• pp.253-259
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• 2012

In this study, crystal structural changes and dielectric properties of $(1-x)Pb(Yb_{1/2}Nb_{1/2})O_3-xPbTiO_3$ ((1-x)PYN-xPT) solid solutions were measured and analyzed with respect to the $PbTiO_3$ (PT) contents ($0.40{\leq}x{\leq}0.60$). From X-ray diffraction (XRD) measurements, (1-x)PYN-xPT solid solutions showed changes of the crystal structure from pseudocubic ($0.40{\leq}x{\leq}0.44$) to tetragonal ($0.52{\leq}x{\leq}0.60$) on increasing PT contents and exhibited the coexistence of pseudocubic and tetragonal phase near the morphotropic phase boundary (MPB) composition ($0.46{\leq}x{\leq}0.50$). The dielectric constant showed a maximum value at x = 0.46 and the maximum values in (1-x)PYN-xPT decreased with higher PT contents. The phase transition temperatures of (1-x)PYN-xPT solid solutions increased over the whole composition ranges tested ($0.40{\leq}x{\leq}0.60$).

• 한국세라믹학회지
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• 제32권2호
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• pp.234-238
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• 1995

MgFe2O4 formation, grain growth in Fe2O3, Fe solid-solution limit in MgO for MgO-Fe2O3 mixture were studied by means of investigating the distribution of phases and compositions in reaction area between MgO and Fe2O3. The reaction area at equlibrium was composed with MgO-FexO matrix and MgFe2O4 precipitation, MgFe2O4 was formed by precipitating from MgO-FexO matrix dependent on oxygen partial pressure. Fe contents was exponentially decreased with diffusion distance in MgO single crystal, and thus Fe solid-solution limitation in MgO was about 4mol%. The grain growth rate in Fe2O3 base was increased with Mg contents diffused from MgO single crystal.