• 한국세라믹학회지
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• 제44권7호
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• pp.343-348
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• 2007

Alumina/silver nanocomposites were fabricated using a soaking method through a sol-gel route to construct an intra-type nanostructure. The pulse electric-current sintering (PECS) technique was used to sinter the nanocomposites. Several specimens were annealed after sintering. The microstructure, mechanical properties, critical frontal process zone (FPZ) size, and thermo-mechanical properties of the nanocomposites were estimated. The relative densities of the specimens sintered at 1350 and $1450^{\circ}C$ were 95% and 99%, respectively. The maximum value of the three-point bending strength was found to be 780 MPa for the $2{\times}2{\times}10 mm$ specimen sintered at $1350^{\circ}C$. The fracture toughness of the specimen sintered at $1350^{\circ}C$ was measured to be $3.60 MPa{\cdot}m^{1/2}$ using the single-edge V-notched beam (SEVNB) technique. The fracture mode of the nanocomposites was transgranular, in contrast to the intergranular mode of monolithic alumina. The fracture morphology suggested that dislocations were generated around the silver nanoparticles dispersed within the alumina matrix. The specimens sintered at $1350^{\circ}C$ were annealed at $800^{\circ}C$ for 5 min, following which the maximum fracture strength became 810 MPa and the fracture toughness improved to $4.21 MPam^{1/2}$. The critical FPZ size was the largest for the specimen annealed at $800^{\circ}C$ for 5 min. Thermal conductivity of the alumina/silver nanocomposites sintered at $1350^{\circ}C$ was 38 W/mK at room temperature, which was higher than the value obtained with the law of mixture.

• 한국식품과학회지
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• 제43권6호
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• pp.683-688
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• 2011

국내에서 개발된 유전자변형 프로비타민 A 강화 벼로부터 얻은 쌀을 열탕 또는 증자/볶음처리 방법에 의해 가열조리 했을 때 프로비타민 A 강화 쌀의 주요 영양성분 조성 및 함량에 미치는 영향을 조사하였다. 프로비타민 A 강화 쌀의 일반성분 함량은 모품종 쌀인 낙동 쌀과 유사하였으며 밥 형태로의 열탕처리에 의해 별 차이가 없었으나 증자/볶음 처리에 의해서는 다소 감소하는 결과를 주었다. 프로비타민 A 강화 쌀의 지방산으로 oleic acid, linoleic acid, palmitic acid가 대부분을 차지하고 있었으며 가열조리에 따른 지방산 조성에는 차이가 없는 것으로 나타났다. 열탕 처리에 의해 가열조리한 프로비타민 A 강화 쌀은 아미노산 조성 및 함량에 차이가 없었으나 증자/볶음 처리는 대부분의 아미노산 함량을 약간 감소시켰다. 열탕처리에 의해 가열조리한 프로비타민 A 강화 쌀은 전체적으로 무기질 함량에 큰 차이가 없었으나 증자/볶음처리에 의해 변화가 큰 것으로 나타났다. 프로비타민 A 강화 쌀의 총 카로티노이드 함량은 원곡의 $1.28{\mu}g/g$에서 열탕조리 후 $0.76{\mu}g/g$으로 감소하였으며 증자 및 볶음처리는 $0.40{\mu}g/g$으로 원곡의 약 30% 수준으로 현저한 감소를 초래하였다. 따라서 프로비타민 A 강화 쌀의 조리가공시 가열방법 및 열처리 정도는 카로티노이드를 포함한 영양성분의 손실을 최소화하기 위해 고려해야할 중요한 요소인 것으로 제시되었다.

• 한국가구학회지
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• 제19권1호
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• pp.83-90
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• 2008

Gypsum-wood composites were made by introducing inorganic substances into wood using calcium chloride, first treating solution, and sodium sulfate, secondary treating solution, by double diffusion process under atmospheric pressure at room temperature. The process conducted as follows: water saturated specimens were soaked in calcium chloride solutions at several concentration. Then the specimens were soaked further in saturated sodium sulfate solution, and they were leached in flowing tap water for 24h. To attain sufficient weight percent gain (WPG) values, the suitable concentration of calcium chloride and soaking time in saturated sodium sulfate solution were 20% and 48h, respectively. Inorganic substances were produced mainly in the lumina of tracheides. It was made sure that these substances were dihydrate gypsum($CaSO_4$ $2H_2O$) by X -ray microanalysis (SEM-EDX). The composites had good fire resistance due to low heat transfer rate of gypsum formed in wood. However, the composites had little decay resistances, because they showed high weight losses by test fungi attacks.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.670-674
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• 1997

Semi-solid forging is a compound forging technology to deventional forging process. Among several steps of semi-solid forging process, the heating step of a billet prior to semi-solid forging step is necessarily required to obtain globular microstructure. For the forming operation to work properly, it is also important to heat the billet uniformly for the uniformity of solid-liquid distribution. To satisfy these requirements, induction heating has been generally used for a long time. This paper presents the method to find heating condition and the temperature distribution inside of a billet with a induction heating apparatus by comparing the computer simulation with experiment for aluminum alloys Al2024 and A356.

• 세라미스트
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• 제9권6호
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• pp.49-55
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• 2006

Intra-type alumina-based nanocomposites, in which second-phase nanoparticles are embedded within alumina grains, use dislocation activities to enhance strength and fracture toughness. The dislocations are generated around the nanoparticles by residual stresses during cooling process. In this paper, first, we explain strengthening and toughening mechanisms of alumina-based nanocomposites based on dislocation activities. Second, we propose a soaking method to construct the intra-type nanostructure and fabricate alumina/nickel and alumina/silver nanocomposites. The nanocomposites are then annealed in order to enhance the fracture toughness of the materials. Finally, we discuss the relation between the strength, fracture toughness, and critical frontal process zone size of the materials.

• 한국식품영양과학회지
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• 제40권6호
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• pp.853-859
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• 2011

검정콩의 기능적, 영양적으로 매우 유용한 성분을 손쉽게 섭취할 수 있는 편리성을 갖춘 형태인 스낵 타입의 검정콩 제품을 개발하였다. 부드러운 조직감과 높은 기호도를 위해서 1차 당침지 조건/2차 당침지 조건을 달리하였으며 수분함량, 조직감, 관능평가 등을 고려하여 1차 당침지 당액농도 $40^{\circ}brix$, 2차 당침지 당액농도 $50^{\circ}brix$로 침지하여 제조한 당침지 콩스낵 제조공정을 확립하였고 그에 따른 최적 조건하에 제조된 당침지 검정콩 편이식 시제품에 대한 일반성분 분석을 실시한 결과 수분함량은 $5.50{\pm}0.39%$, 조단백질은 $16.25{\pm}0.07%$, 조지방은 $34.26{\pm}3.95%$, 조회분은 $0.51{\pm}0.05%$, 탄수화물은 $43.48{\pm}0.01%$이었으며 최종제품의 잔존당 함량은 $10.20{\pm}0.10^{\circ}brix$로 나타났다. GABA 함량은 $15.24{\pm}1.47\;mg$/g으로 9배 정도 증가되었으며, 이소플라본은 당이 분리된 alycon 형태로써의 daidzein($695.7{\pm}6.08\;{\mu}g$/g), genistein($810.6{\pm}3.9\;{\mu}g$/g) 함량보다 배당체 형태인 daidzin($755.8{\pm}39.6\;{\mu}g$/g)과 genistin($1640.7{\pm}390.8\;{\mu}g$/g) 형태로 많이 함유되어 있으며 페놀성분과 플라보노이드 함량은 각각 $0.16{\pm}0.01\;mg$/g과 $2.33{\pm}0.40\;mg$/g이 함유되어 있는 것으로 분석되었다.

• 한국주조공학회지
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• 제22권4호
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• pp.174-183
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• 2002

Twin-roll process is a relatively new continuous casting process which can produce high-quality strip products directly, and solidification rate can reach $10^3$ to $10^4$ K/s, leading to fine and uniform microstructures with enhanced mechanical properties. The strip casting condition for producing fine Al-Sn alloy strip was obtained experimentally, and defects appearing on the strip was examined. Crack formation and surface quality of the strip was found to depend mainly on process parameters such as melt temperature, roller gap and rolling speed. Sn structure of network type was observed in Al-20Sn and Al-40Sn alloy strips, and cell spacing of Al-40Sn alloy was smaller than that of Al-20Sn. Banding strength of the heat treated specimens increased with increasing of soaking time and temperature, and bonding strength of Al-20Sn alloy was more superior than that of Al-40Sn alloy. However wear resistance of Al-40Sn alloy contained large amount of soft Sn which possess good anti-friction characteristics was superior than that of Al-20Sn alloy.

• Journal of the Optical Society of Korea
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• 제20권2호
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• pp.314-320
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• 2016

The glass thermal forming process provides a high volume, low cost approach to producing aspherical reflectors for x-ray optics. Thin glass sheets are shaped into mirror segments by replicating the mold shape at high temperature. Heating parameters in the glass thermal slumping process are crucial to improve surface quality of the formed glass. In this research, the heating process of a thermal slumping glass sheet on a concave parabolic mold was simulated with the finite-element method (FEM) to investigate the effects of heating rate and soaking temperature. Based on the optimized heating conditions, glass samples 0.5 mm thick were formed in a furnace with a steel concave parabolic mold. The figure errors of the formed glass were measured and discussed in detail. It was found that the formed glass was not fully slumped at the edges, and should be trimmed to achieve better surface deviation. The root-mean-square (RMS) deviation and peak-valley (PV) deviation between formed glass and mold along the axial direction were 2.3 μm and 4.7 μm respectively.

• 대한안전경영과학회지
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• 제21권1호
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• pp.17-23
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• 2019

The diesel engine generate many pollutants such as PM(Particulate matter) and NOx(Nitrogen oxide). So the SCR(Selective catalytic reduction) must be required to meet the emission standard. The SCR catalyst market is growing rapidly, and the automobile markets using alternative energy sources are growing rapidly. This study deals with optimization of the calcination process the manufacturing process of SCR catalyst to be competitive. The calcination process is a bottleneck and it is required to optimize productivity and accept to be safety, But we cannot trade off anything in terms of safety. We applied DOE(Design of experiments) among many research methods performed in various fields. In order to achieve quality and productivity optimization. The dependent variables in the DOE were selected as NO Conversion(%). The independent variables were selected as the calcination temperature, soaking time and fan speed RPM. the CCD(Central composite designs) constructs response surface using the data onto experience and finds optimum levels within the fitted response surfaces. Our tests are our stability guarantee and efficient together with operation.

• 한국분말재료학회지
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• 제26권5호
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• pp.369-374
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• 2019

The properties of powder metallurgy products are related to their densities. In the present work, we demonstrate a method to apply artificial neural networks (ANNs) trained on experimental data to predict the bulk density of barium titanates. The density is modeled as a function of pressure, press rate, heating rate, sintering temperature, and soaking time using the ANN method. The model predictions with the training and testing data result in a high coefficient of correlation (R2 = 0.95 and Pearson's r = 0.97) and low average error. Moreover, a graphical user interface for the model is developed on the basis of the transformed weights of the optimally trained model. It facilitates the prediction of an infinite combination of process parameters with reasonable accuracy. Sensitivity analysis performed on the ANN model aids the identification of the impact of process parameters on the density of barium titanates.