• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.33-40
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• 1988

In this study, effects of the density of soil and the confining pressure applied to the soil sample on the elastic moduli of subgrade soils are experimentally analyzed. Through investigation of subgrade materials of domestic expressways, five typical types of subgrade soils are selected for the experiments. A series of unconsolidated undrained triaxial tests is performed on samples prepared with various water contents and densities at the confining pressures of 1.02, 2.04, and $3.06kg/cm^2$. Initial tangent modulus is inferred from the unloading-reloading portion of the stress strain curve obtained during an individual loading-unloading-reloading test. As a result of the analysis, it is found that the effect of the confining pressure on the elastic modulus of subgrade material is well consistent with the equation proposed by Janbu, and that the elastic modulus can be related to the dry unit weight expressing the Janbu constants as exponentiial functions of it. It is also found that the water content has little effect on the elastic modulus for the samples with the degree of saturation less than 70%.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.03a
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• pp.219-219
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• 1999

마직물은 통기성, 흡수성, 투습성이 좋고 건조가 빠른 편이므로 여름철 직물로 많이 사용되어 왔다. 마직물은 또한 뻣뻣하며 몸에 감기지 않고 촉감이 깔깔하여 시원한 느낌을 주며 다른 직물에 비해 강직하고 표면이 거칠고 드레이프성이 떨어지는 등의 독특한 태를 가지고 있다. KES-F 시험기에 의해 여러 물성량들을 종합적으로 계측할 수 있게 됨에 따라 의복의 착용감에 만족을 주는 소재의 성능에 대한 연구가 종래의 주관적평가에서 KES-F 시스템을 이용하여 객관적으로 태를 예측하는 방법으로 진행되고 있다. 그러나 태를 평가하는 객관적 방법에서는 일반적으로 Kawabata와 Niwa에 의해 만들어진 평가식들이 주로 사용되나 이런 식들은 주로 모직물이나 합성섬유직물들을 평가하기에는 적합하지만 마직물의 독특한 태를 평가하기에는 부족하다고 생각된다. 마직물의 태가 기존의 객관적 평가방법만으로는 규명되지 않기 때문에 주관적 태평가방법을 아울러 실시해야 할 필요가 있다고 생각된다. 따라서 본 연구에서는 마직물의 태를 평가하는 방법의 하나로 주관적 평가척도를 개발하고 이 척도를 사용하여 마직물의 주관적인 태 특성을 살펴보았다. 그리고 KES-FB 시스템을 사용한 객관적인 태를 측정하여 주관적 평가치와 객관적 측정치로부터 태 평가의 산출식을 유도하였다. 실험에 사용된 직물은 혼방률, 밀도, 두께 등이 다양한 암, 저마 그리고 마혼방직물과 한산모시, 중국마, 신합섬 직물 등 총 54종을 사용하였다. 마직물의 주관적 태 평가를 위해 26문항의 형용사쌍으로 구성된 9점의 의미미분척도를 개발하였으며 이 척도를 사용해 주관적 평가를 실시하였다. 또 객관적 평가를 위해 KES-FB 시스템을 통해 역학적 특성치를 구하였다. 주관적 평가를 실시한 결과 마직물의 태에 영향을 미치는 7개의 요인이 추출되었다. 이 요인들은 표면성질, 신축성/드레이프성, 중량감, 강연성, 회복성, 수분특성, 밀도감이었으며, 요인들로 설명되는 누적분산값은 67.18%였다.주관적 평가의 결과와 객관적 평가 결과를 이용해 마직물의 태를 평가하는 산출식을 제시하였다. 태 평가치의 경우 16가지 특성치를 모두 넣는 방법과 stepwise 방법, 또 Kawabatark 사용한 순차적 군 회귀법의 세가지 방법의 회귀식 중 16가지 특성치를 모두 넣는 방법의 결정계수가 가장 높았다.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1147-1155
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• 1996

In the spray drying with rotating wheel atomizer of cheese powder, the relationships among variables were analyzed with Response Surface Methodology in which several independent variables such as total solid content, wheel rotation speed, and outlet temperature influenced dependent variables such as particle diameter, moisture content, bulk density, and viscosity of suspended liquid. Significance and correlation were tested according to central composite design. As a results of analyzing the correlations between independent and dependent variables, particle diameter and moisture content of cheese powder were decreased with increasing wheel rotation speed, and bulk density was decreased with increasing outlet temperature. Viscosity of suspended liquid were increased with increasing wheel rotation speed and total moisture content. In correlation among dependent variables, moisture content was proportional to bulk density, and particle diameter was inversly proportional to moisture content and bulk density.

• Journal of the Korean Society of Food Culture
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• v.32 no.2
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• pp.135-143
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• 2017

This study evaluated the quality characteristics of semi-dried noodles prepared with different water contents (wet noodles; 32, 24, 22, 20%, dry noodles; 12%). The drying process was carried out in a drying chamber at $13{\sim}18^{\circ}C$ temperature and 75~95% humidity. The proximate composition of Korean wheat flour was as follows: water $22.1{\pm}3.64%$, protein $8.6{\pm}0.13%$, fat $1.3{\pm}0.10%$, ash $0.7{\pm}0.02%$, carbohydrates $67.3{\pm}0.10%$. As water contents decreased, both L and b values significantly decreased before cooking of noodles, whereas L, a, and b values were not significantly different after cooking of noodles. Weight, water absorption, and volume of cooked noodles significantly increased as water content decreased, whereas turbidity of soup was not significantly different. Cutting hardness before cooking of noodles significantly increased as water content decreased. Sections of noodles after cooking by SEM (scanning electron microscopy) showed roughness and fewer round starch particles as water content decreased. For overall preferences according to the sensory evaluation, noodles prepared with different water contents were not significantly different. According to the results, semidried noodles have development potential to complement the disadvantages of both wet noodles and dry noodles.

• Polymer(Korea)
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• v.32 no.1
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• pp.1-6
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• 2008

The adhesion behaviors and processability of NBR as a sealing material were investigated. In order to find the optimum formulation, the adhesive properties and processability were observed as the change of the contents of acrylonitrile (ACN) in NBR. Effects of Mooney viscosity, filler, plasticizer and crosslinking agent on the adhesion behaviors were also studied. The contents of ACN in NBR have great effects on adhesion behaviors and processability in NBR sealing. To know the optimum condition of roll mixing, degree of dispersion was investigated. It was confirmed that degree of dispersion was influenced by various factors such as mixing order, time, and temperature. The crosslinking system was studied as the observation of sulfur system, peroxide system, crosslinking density, and structure. From the variation of the dry condition and hexamine contents, the relation between adhesive and NBR was studied. These results show the adhesion properties and processability are dependent on the contents of ACN and crosslinking system.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.170-172
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• 2018

지구 온난화로 인해 여름철 북극해의 해빙이 점차 감소함에 따라서 북극항로를 이용한 선박의 화물운송이 점차 증가하고 있다. IMO에서는 극지해역운항선박의 안전성과 해양오염방지를 위하여 2014년에 Polar Code를 개정하였으며, 2017년 1월부터 SOLAS협약과 MARPOL73/78협약에 추가되어 시행되고 있다. 본 연구는 해양수산부 해양안전 및 해양교통시설기술개발 사업으로 1) Polar Code 강제화에 따라 '극지해역 운항선박용 항해안전지원시스템의 개발'의 필요성과 2) 북극항로에 대한 국적선의 안전 운항 확보를 위한 '북극권 국가와의 국제협력 및 공조체계 구축'과 '극지 구난, 구조 및 환경보호 관련 국내법 및 규정 제정'을 위한 기반 연구의 필요성에 의거하여 2014년 11월 10일에 시작되었으며 2018년 12월 31일에 종료될 예정이다. 연구내용은 1) 고정밀도 북극항로 빙상정보 수치예측 시스템 개발, 2) 북극항로 안전속도 예측, 평가, DB구축 및 항행 모델 개발, 3) 북극항로 안전운항을 위한 항해계획 기술 개발, 4) 북극항로 운항선박 건조 및 안전항해 가이드라인 개발이다. 본 논문에서는 개발 중인 KRISO Arctic safe Routing System (KARS)에 대한 소개와 활용 결과 및 향후 계획에 대해서 설명하고자 한다. 본 KARS는 향후 지속적인 수정보완 작업을 통해서 완성도를 높여갈 예정이며, 검증단계를 거쳐서 최적하고 안전한 항로와 운항 관련 정보를 선사와 해기사에게 제공함으로서 북극항로 중 단기 운항계획 수립과 안전 운항을 지원할 수 있을 것으로 기대된다.

• Elastomers and Composites
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• v.41 no.4
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• pp.252-259
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• 2006

A new route for making rubber/clay nanocomposites was suggested based on skim natural rubber latex (SNRL), which is a protein rich by-product obtained during the centrifugal concentration of natural rubber (NR) latex. NR/acrylonitrile butadiene rubber (NBR) based nanocomposites were prepared from SNRL and NBR latex of 26 % acrylonitrile content by blending of aqueous dispersion of organoclay (OC) followed by coagulation, drying, mill mixing and vulcanization. X-ray diffraction(XRD) studies revealed that NR/NBR blend nanocomposites exhibited a highly intercalated and exfoliated structure, especially for NBR-rich blends. Dynamic mechanical studies showed that more compatible behavior was observed for NBR-rich blends. The 25/75 NR/NBR blend nanocomposite showed the best mechanical properties.

• Journal of the Korean Geosynthetics Society
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• v.18 no.2
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• pp.1-10
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• 2019

This study was intended to evaluate the water permeability and structure for calcium bentonite-sand mixtures to utilize calcium bentonite as a liner. This study conducted physico-chemical properties tests, compaction tests, permeability test and Scanning Electron Microscopy analysis (SEM) analysis. It was found the higher the ratio of calcium bentonite, the lower the dry density with coefficient of permeability, and the higher the optimum moisture content. In particular, SEM analysis was found the higher the ratio of calcium bentonite, the higher the area of the montmorillonite particles. In conclusion, the optimum coefficient of permeability that finds the landfill liner condition (must be less than $1{\times}10^{-7}cm/sec$) was obtained when the ratio of calcium bentonite was 40% or higher. These findings may improve the understanding of the calcium bentonite as a liner. Calcium bentonite shows a similar permeability to sodium bentonite 7% when mixed at 40% or more. Therefore, it is considered that calcium bentonite can be utilized as a liner.

• Journal of the Korean Geotechnical Society
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• v.25 no.11
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• pp.5-15
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• 2009

Dynamic shear properties of Nak-Dong river sand were investigated to build a soil property database for Nak-Dong delta region. Samples were taken from the estuary and the midstream of the river. Laboratory specimens were prepared by air pluviation method, and were tested by using RC/TS apparatus at various confining stresses, relative densities and numbers of cycles. Shear modulus reduction and damping curves were developed using Ramberg-Osgood and Modified Hyperbolic Models. The developed curves, compared to those reported by other investigators, show only a slight difference. The outcome of this RC/TS experiments can be very important resources when accessing the dynamic response of sandy soils in Nak-Dong delta region in the future.

• Composites Research
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• v.20 no.5
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• pp.49-55
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• 2007

Nanocomposite blade for dicing semiconductor wafer is investigated for micro/nano-device and micro/nano-fabrication. While metal blade has been used for dicing of silicon wafer, polymer composite blades are used for machining of quartz wafer in semiconductor and cellular phone industry in these days. Organic-inorganic material selection is important to provide the blade with machinability, electrical conductivity, strength, ductility and wear resistance. Maintaining constant thickness with micro-dimension during shaping is one of the important technologies fer machining micro/nano fabrication. In this study the fabrication of blade by wet processing of mixing conducting nano ceramic powder, abrasive powder phenol resin and polyimide has been investigated using an experimental approach in which the thickness differential as the primary design criterion. The effect of drying conduction and post pressure are investigated. As a result wet processing techniques reveal that reliable results are achievable with improved dimension tolerance.