• 한국환경과학회지
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• 제11권4호
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• pp.339-346
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• 2002

Physico-chemical properties of the activated sludges(Suyoung and Changlim treatment plant), such as SVI(sludge volume index), absorbance, specific surface area, and specific resistance using Buchener funnel test were investigated with changing anaerobic storage time. This experimental condition was found that it was possible to estimate a linear relationship between their parameters such as specific surface area specific resistance, and sludge volume index(SVI). The specific surface area and the specific resistance to filtration of the activated sludges of Suyoung and Changlim treatment plant were found as 123.6~136.6$m^2$/gDS and 41.5~44.9$m^2$/gDS(dry solid), and 1.09$\times$10$^{14}$ ~5.48$\times$10$_{14}$ m/kg and 1.05$\times$10$^{14}$ ~2.48$\times$10$^{14}$ m/kg, respectively. The results gave a good linear relationship between the specific surface area and the specific resistance, r=2.25$\times$10$^{12}$ s-8.10$\times$10$^{13}$ ($R^2$=0.8885) at Suyoung treatment plant and r=1.26$\times$10$^{13}$ s-4.75$\times$10$^{14}$ ($R^2$=0.8756) at Changlim treatment plant.

• 대한전자공학회논문지
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• 제26권10호
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• pp.1545-1553
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• 1989

The ohmic contact behavior in HEMT structure was compared with that in MESFET one throughout the specific contact resistance and microstructural change in both structures. A Au-Ge-Ni based metallization scheme was used and the alloying temperature of the ohmic materials was changed from 330\ulcorner to 550\ulcorner. The alloying temperature to obtain the minimum specific contact resistance in HEMT structure was 60k higher than that in MESFET. The volume fraction of NiAs (Ge) in MESFET structure increases with alloying temperature and/or the alloying time, which makes the decrease of specific contact resistance at the initial stage of ohmic metallization. In contrast, the volume fraction of NiAs(Ge) in HEMT structure was not dependent upon the specific contact resistance, which implies that the ohmic contacts are dominantly formed by the Ge diffusion to 2-DEG(two dimensional electron gas) layer.

• 한국응용과학기술학회지
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• 제31권2호
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• pp.329-336
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• 2014

The conductive polymer composites have attracted considerable attention in the field of industry due to their electrical properties. To understand electrical properties of the composites, their volume specific resistance was measured. Electrical conductivity results showed percolation phenomena. Percolation theories are frequently applied to describe the insulator-to-conductor transitions in the composites composed of conductive filler and insulating matrix. It was found that the percolation threshold strongly depends on the aspect ratio of filler particles. The critical concentration of percolation formed is defined as the percolation threshold. The purpose of this study was to examine electrical properties of the epoxy resins filled with nickel. The sample was prepared using vehicle such as epoxy resin replenished with nickel powder, and the evaluation on their practical use was performed in order to apply them to electric and electronic industry as well as general field. The volume specific resistance of epoxy resin composites was 4.666~13.074 when using nickel powder. Weight loss of the conductive composites took place at $350^{\circ}C{\sim}470^{\circ}C$.

• 조명전기설비학회논문지
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• 제27권7호
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• pp.82-88
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• 2013

IEC standards do not require to limit the earthing resistance of the concrete-embedded foundation earthing electrode which is installed to a specific value. However, in Korea the value of $5{\Omega}$ and below applies to the earthing resistance for a domestic customer whose receiving voltage is 22.9kV. This paper calculates the minimum area and volume of the concrete-embedded foundation earthing electrode in order to obtain a specific value of the earthing resistance when the electrode of the building's lightning protection system and that of its power system are interconnected. It also suggested the most appropriate method of installing the foundation earthing electrode, taking the electric characteristics of concrete into account.

• 한국식품조리과학회지
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• 제31권1호
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• pp.18-25
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• 2015

This study investigated the baking properties of sorghum with the addition of xylanase or Pentopan, which is a baking additive containing xylanase. The control bread was made with a 30% substitution for wheat flour and the optimum level of enzyme addition was 0.75 mg/g flour for Pentopan and 5 mg/g flour for xylanase. The water binding capacity of wheat flour increased with the addition of sorghum, but decreased with the addition of either xylanase or Pentopan. The resistance of dough increased while extensibility decreased with the addition of sorghum; however, resistance decreased while extensibility increased with the addition of the enzyme. Specific volume of bread decreased significantly with the addition of sorghum. However, the specific volume was significantly recovered with the addition of enzyme. Crumb firmness was higher in the sorghum-added sample, but crumb firmness of the bread decreased with the addition of the enzyme. The crumb firmness of bread with added xylanase decreased significantly in 24 hours. These results demonstrated that adding sorghum with either xylanase or Pentopan that included xylanase increased specific volume and decreased crumb firmness whereas sorghum decreased the quality of fermented bread when added to wheat flour. The firmness rate of fermented bread particularly decreased with the addition of pure xylanase.

• Journal of Welding and Joining
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• 제20권3호
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• pp.54-59
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• 2002

Overlays is a treatment of the surface and near-surface regions of a material to allow the surface to perform functions that are distinct from those frictions demanded far the bulk of the material. Welding, thermal spray, quenching, carburizing and nitration have been used as the surface treatment. Especially, weld overlay is a relatively thick layer of filler metal applied to a carbon or low-alloy steel base metal for the purpose of providing a wear resistant surface. In this study, weld overlay was performed by MAG welding on the base metal(SS400) with filler metal which contain composite powders($Cr_3C_2+Mn+Mo+NbC$) and solid wire(JIS-YGW11). Characteristics of hardness and wear resistance on overlays were analyzed by EDS, EPMA, XRD and microstructures. Carbide formations were $M(Cr, Fe)_7C_3$ and NbC phases. And carbide volume fraction, hardness and specific wear resistance of overlays were increased with increasing powder feed rate and decreasing wire fred rate. Hardness and wear resistance were almost proportioned to carbide volume fraction of overlay.

• Tuberculosis and Respiratory Diseases
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• 제45권1호
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• pp.99-106
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• 1998

연구배경: 기관지 천식은 다양한 원인에 대한 기도 협착과 과민 반응을 특정으로 하는 기도 질환으로, 그 병인에 대한 연구를 임상적으로 시행하는 데에는 한계가 있어, 동물 천식 모형을 이용한 연구가 필요하다. 동물에서의 기도 저항의 측정은 주로 마취나 삽관 상태에서 침습적으로 측정되었으나, 최근 비침습적으로 의식이 있는 상태에서 일상호흡 중의 specific 기도 저항을 측정하는 방법들이 고안되었다. 이에 저자들은 기니픽에 allergen인 ovalbumin을 피하 주사하여 감작시킨 후, 의식이 있는 상태에서 ovalbumin과 methacholine을 각각 흡입시켜, 비침습적인 방법으로 specific 기도 저항을 측정함으로써 즉시형 기관지 수축 정도와 methacholine에 대한 기도 과민성의 변화를 연구하여 동물 천식 모형을 만들고자 하였다. 연구방법: 기니픽 30마리를 천식군 20마리, 대조군 10마리로 나누어, 천식군에서는 ovalbumin을 피하 주사하여 감작시킨 후, ovalbumin을 흡입(1% wt/vo1)으로 노출시켰고, 대조군은 생리 식염수를 동일한 방법으로 감작, 노출시켰다. specific 기도 저항(airway resistance $\times$ thoracic gas volume)은 의식이 있는 상태에서 비침습적으로 동물 body plethysmography를 사용하여, Pennock법으로 allergen 노출 3분전부터, 노출후 27분까지 3분 간격으로 30분간 측정하였다. Methacholine은 지속적으로 2배씩 농도를 증가하여, 각 농도에 대하여 3분 간격으로 흡입시킨 후, 통일한 방법으로 specific 기도 저항을 측정하여 기도 저항이 200% 이상 증가될 때의 methacholine 농도 ($EC_{200}R_L$)를 구하였다. 결 과: 천식군 20마리 중 65%인 13마리에서 ovalbumin 흡입에 대한 specific 기도 저항이 3분부터 증가하여 6분에 231.5%로 최고를 보이고 실험 측정 종료까지인 30분까지 대조군에 비하여 유의하게 증가된 상태로 지속되어 (p<0.001), 천식 모형이 형성되었다. Methacholine에 대한 기관지 과민 반응은 $EC_{200}R_L$가 대조군에서 평균 $0.446{\pm}0.287mg/ml$, 기하평균 $-1.429{\pm}0.976$였고, 천식군에서 형성된 천식 모형에서의 평균은 $0.149{\pm}0.075mg/ml$, 기하평균 $-2.923{\pm}0.760$으로 천식 모형에 있어서 methacholine에 대한 기관지 과민 반응이 대조군에서보다 2 배 높았다(p<0.0013).

• 한국응용과학기술학회지
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• 제27권3호
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• pp.310-317
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• 2010

The electrochemical properties of electric double layer capacitor(EDLC) was studied by controlling pore size distribution and specific surface area of the activated carbon fiber(ACF). The mesoporous ACF, which was prepared by the iron exchange method, showed the tendency of increasing average pore size and decreasing total surface area. The mesoporous ACF (surface area = 2225 $m^2$/g, pore size=1.93 nm) showed increased mesopore(pore size=1~3nm) volume from 0.055 cc/g to 0.408 cc/g compared to its raw ACF. The charging capacity of the EDLC which uses the prepared mesoporous ACF also increased from 0.39 F/$cm^2$ to 0.55 F/$cm^2$. From these results, it can be known that the electrochemical properties of EDLC are mainly dependent on the specific surface area, but above the surface area 2200 $m^2$/g, it is the mesopore volume that affects the performance of the capacitor considerably. Because the increased mesopore volume results in a decreased ion mobility resistance, the charge capacitance is enhanced.

• 한국응용과학기술학회지
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• 제30권3호
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• pp.472-479
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• 2013

The conductive polymer composites recently became increasingly to many fields of industry due to their electrical properties. To understand these properties of composites, electrical properties were measured and were studied relatively. Electrical conductivity measurements showed percolation phenomena. Percolation theories are frequently applied to describe the insulator-to-conductor transitions in composites made of a conductive filler and an insulating matrix. It has been showed both experimentally and theoretically that the percolation threshold strongly depends on the aspect ratio of filler particles. The critical concentration of percolation formed is defined as the percolation threshold. This paper was to study epoxy resin filled with copper. The experiment was made with vehicle such as epoxy resin replenished with copper powder and the study about their practical use was performed in order to apply to electric and electronic industry as well as general field. The volume specific resistance of epoxy resin composites was 3.065~13.325 in using copper powder. The weight loss of conductive composites happened from $350^{\circ}C{\sim}470^{\circ}C$.

• 콘크리트학회지
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• 제9권2호
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• pp.137-144
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• 1997

발수제의 유무와 알루미늄분말의 분말도 및 첨가량을 조절하여 비중을 0.4에서 0.7로 변화시켜 비중과 ALC의 기초물성, 내동해성 및 내구성과의 관계를 조사하였다. 압축 및 인장강도는 비중이 0.4에서 0.7로 증가함에 따라 발수제의 첨가량에 관계없이 증가하였고 발수제의 첨가량이 증가하면 내동해성은 개선되었으며 흡수율은 감소하였다. 입경이 작은 AI분말을 이용항 제조한 ALC의 박리에 의한 체적감소율은 낮게 나타났으며 일면동결지속시험 및 기중동결수중융해시험에서도 내동해성이 우수한 것으로 나타났다.