• 한국가스학회:학술대회논문집
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• 2003.10a
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• pp.120-125
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• 2003

본 연구는 원자력 발전소에 있는 방화벽의 케이블 관통부위에 설치된 CPFS(Cable Penetration Fire Stop)시스템 안에서 일어나는 동적열전달 현상을 3 차원으로 나타낼 수 있는 시험시뮬레이터에 사용될 수학적 모델과 수치계산 알고리즘의 개발에 관한 것이다. CPFS 내에서 일어나는 열전도 현상을 나타내는 지배방정식은 주어진 조건들 하에서 포물선형 편미분방정식(Parabolic PDE)으로 나타난다. 문제를 단순화하기 위해 열의 흐름을 두 성분으로 나누었다 즉, 케이블과 평행한 선을 따라서 일어나는 열전도와 벽면과 평행한 평면 위에서 일어나는 열전도로 나누었다. 먼저 선을 따라 일어나는 동적 열전도 현상을 나타내는 PDE를 연속과완화(SOR: Successive Over-Relaxation)를 적용하여 유한한 불연속점들에 대한 연립 상미분방정식(ODE)으로 전환했고, 그 연립방정식은 ODE Solver 를 이용하여 풀 수 있었다. 둘째로, 각 불연속 점에 위치한 평면 위에서 일어나는 열전도를 계산하기 위해서, 유한요소의 합을 근사식으로 이용하여 PDE를 ODE로 전환해서 계산하는 유한요소법(Finite Element Method)이 이용된다. 여기서 시간과 공간의 함수 T(x, y, z, t)인 온도는 각 선의 점들과 각 평면의 요소들에 대해서 일정한 시간간격으로 초기온도와 경계온도를 업데이트하여 계산을 반복한다. 이러한 일련의 계산결과를 바탕으로 CPFS 시스템 내에서의 온도분포의 동적인 변화를 해석한다. 결론적으로 관통하는 케이블이 CPFS 시스템의 온도분포에 매우 중요한 역할을 한다는 것을 알 수 있다. 시뮬레이션 결과는 CPFS 내의 온도분포를 쉽게 이해할 수 있도록 3 차원 그래픽으로 나타냈으며, 상용소프트웨어 FEMLAB 으로 계산한 결과와 비교해서 개발된 모델과 계산 알고리즘의 정당성을 보였다. 맞이하고 있음을 볼 수 있다. 국내광업이 21C 급변하는 산업환경에 적응하여 생존하기 위해서는 각종 첨단산업에서 요구하는 소량 다품종의 원료광물을 적기에 공급 할 수 있는 전문화된 기술력을 하루속히 확보해야 하며, 이를 위해 고품위의 원료광물 확보를 위한 탐사 및 개발을 적극 추진하고 가공기술의 선진화를 위해 선진국과의 기술제휴 등 자원산업 글로벌화 정책이 절실히 요구되고 있음을 알 수 있다. 또한 삶의 질을 향상시키려는 현대인의 가치관에 부합하기 위해서는 각종 소비제품의 원료를 제공하는 광업의 본래 목적 이외에도 자연환경 훼손을 최소화하며 개발 할 수밖에 없는 구조적인 어려움에 직면할 수밖에 없다. 이처럼 국내광업이 안고 있는 여러 가지 난제들을 극복하기 위해서는 업계와 정부가 합심하여 국내광업 육성의 중요성을 재인식하고 새로운 마음가짐으로 관련 정책을 수립 일관성 있게 추진해 나가야 할 것으로 보인다.의 연구 결과를 요약하면 다음과 같다. 첫째, 브랜드 이미지와 서비스 품질과의 관계에서 브랜드이미지는 서비스 품질의 선행변수가 될 수 있음을 증명하였으며 4개 요인의 이미지 중 사풍이미지를 제외한 영업 이미지, 제품 이미지, 마케팅 이미지가 서비스 품질에 영향을 미치고 있음을 알 수 있다. 둘째, 지각된 서비스 품질과 가격 수용성과의 관계에서, 서비스 품질은 최소 가격에 신뢰서비스 요인에서 정의 영향을 미치고 있으나 부가서비스, 환경서비스에서는 역의 영향을 미침을 알수 있고, 최대 가격에 있어서는 욕구서비스 요인은 정의 영향을 미치지만 부가서비스의 경우에는 역의 영향을 미치고 있음을 알 수 있다. 셋째, 서비스품질과 재 방문 의도와의 관계에 있어서 서비스품질은 재 방문 의도에 영향을 미침을 알 수 있다. 따라서 브랜드 이미지는 서비스품질의 선행변수가 될 수 있으며, 서비스품질은 가격 수용성과 재방문 의도에 영향을 미치고 있음을 알 수

• Journal of the Korean Wood Science and Technology
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• v.34 no.4
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• pp.1-8
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• 2006

Anatomy of Quercus variabilis charcoal was investigated by scanning electron microscopy. Charcoal was prepared in an electric furnace under nitrogen gas atmosphere at $400^{\circ}C$, $600^{\circ}C$, $800^{\circ}C$, and $1000^{\circ}C$ for 10 min. The structure of charcoal was significantly affected by charring temperature. In cross section, charcoal prepared at $400^{\circ}C$ exhibited a smooth clean surface. As the charring temperature increased, the surface became more rough and increasingly disrupted. The cell walls appeared homogeneous and glass-like. Ray parenchyma cells showed very little separation from each other in radial section at $400^{\circ}C$. At $600^{\circ}C$ and above there is an apparent disintegration of the middle lamella, resulting in a separation of the ray cells. The $2{\sim}4{\mu}m$ wart-like protuberances were observed on the surfaces of the parenchyma cells. These structures were seen in charcoal prepared at all temperatures. Distinctive features can be seen in multiseriate rays as large crack and split. Rhomboidal crystals in crystalliferous cells had a smooth surface at $400^{\circ}C$ and $600^{\circ}C$, but the crystals had a sponge like appearance at $800^{\circ}C$ and $1000^{\circ}C$.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.570-575
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• 2015

The green algae have cellulose as a main structural component of their cell wall and the cellulose content in green algae is much higher than other marine algae such as brown algae and red algae. Furthermore, green algae do not contain lignin in their cell wall and store starch as food in their plastids. Thus, it was investigated that the effect of hydrothermal pretreatment process utilizing microwave irradiation for Ulva pertusa Kjellman, a division of green algae, which is expected to be utilized for bioenergy production, on the enzymatic hydrolysis. The hydrothermal temperature have an effect on the pretreatment of Ulva pertusa Kjellman, but the effect of power of microwave irradiation is negligible. The rate of enzymatic hydrolysis was increased as the hydrothermal temperature increased until $140^{\circ}C$. The enzymatic hydrolysis of pretreated Ulva pertusa Kjellman under the optimum pretreatment conditions (50 W of microwave irradiation power and $150^{\circ}C$ of hydrothermal temperature) with cellulase, ${\alpha}$-amylase, and Novozyme 188 having ${\beta}$-glucosidase acitivity resulted in the saccharification of 96 wt% of total carbohydrate in Ulva pertusa Kjellman during 3 hrs, while it took 24 hrs for the enzymatic hydrolysis of untreated Ulva pertusa Kjellman. It confirmed that the hydrothermal pretreatment was effective on Ulva pertusa Kjellman for the enzymatic hydrolysis.

• Journal of the Korean Wood Science and Technology
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• v.36 no.6
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• pp.138-146
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• 2008

The chemical compositions, cell wall biopolymers and non-isothermal behavior of the stem biomass of Nicotiana Tabacum originated from tobacco industry were investigated in depth. On a weight basis, the contents of total ash and total sugar are 19.1% and 20.7% respectively. Lignin content was around 3% of tobacco stem biomass while pectin was over 7%. The holo-cellulose content in cell wall biopolymer was around 13% and the $\alpha$-cellulose constitutes 60% of the total holo-cellulose. The thermal behavior of stem biomass showed different patterns depending on either inert (nitrogen) or oxidizing (air) atmospheric condition. In the air atmosphere, the rapid thermal decompositions at around $473^{\circ}C$ and $581^{\circ}C$ were recorded as the peaks in DTG curve, while the peaks were not shown in the nitrogen atmosphere condition. The thermal analysis of the freeze dried soluble obtained from hot water extraction of tobacco stem biomass showed that the rapid thermal decomposition at around $581^{\circ}C$ in the air atmosphere was due to the residual char originated from the soluble fraction. The distinct difference in thermal decomposition between hemicellulose and cellulose were easily found in the DTG curve obtained in the nitrogen atmosphere.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.3
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• pp.391-395
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• 2009

To materialize anti-inflammatory compounds from dandelion leaves, we studied optimal conditions of hot water extraction and concentration. We investigated the properties of extracts on various temperatures between 60 and $90^{\circ}C$. Extraction yields at $60^{\circ}C$ were the highest at $39.2{\pm}1.3%$ and flavonoid contents were increased by heating. However, anti-inflammatory activities were remarkably decreased by increasing temperature. According to the results that the highest anti-inflammatory activities of water extract were demonstrated at $60^{\circ}C$, cell wall degrading enzyme treatment was carried out to increase extraction yield of anti-inflammatory compounds. The enzyme treatment resulted in increased yields and flavonoids from dandelion leaves of 1.5-fold and anti-inflammatory activities were not decreased. Also, column chromatography was used for concentration of anti-inflammatory compounds from extract of dandelion leaves treated with enzyme. Anti-inflammatory activities of adsorbed compounds on Amberlite XAD-2 and Sepabeads SP-850 were significantly increased. However, yields of adsorbed compounds were increased over two-folds on Sepabeads SP-850 compared to Amberlite XAD-2. Thus Sepabeads SP-850 was more effective than Amberlite XAD-2 to concentrate the anti-inflammatory compounds of dandelion leaves.

• Fire Science and Engineering
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• v.31 no.5
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• pp.37-43
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• 2017

Domestic sandwich panel buildings are widely used on walls and roofs of factories and warehouse facilities. Factory and warehouse facilities have high fire load and rapid spread of fire due to their use characteristics, leading to large fires. Due to the characteristics of materials, walls and roofs are collapsed, resulting in life damage and property damage. In this regard, this study examined domestic and international standards of sprinkler facilities to prevent ignition of sandwich panel walls. Also, in order to check whether the fire was prevented by installing the head on the wall of the sandwich panel, the fire test was carried out with 10 cm, 60 cm, and 120 cm from the wall along the sprinkler head installation standard of domestic fire safety standards. As a result of the fire test, it was confirmed that the sandwich panel was prevented from igniting when the head of water pressure 0.1 MPa and water quantity K-80 was installed. According to the separation distance, it was impossible to measure the temperature at 10 cm, but at 60 cm, At the maximum temperature of $525^{\circ}C$ and 120 cm, the maximum temperature of the wall of the sandwich panel was measured as $276^{\circ}C$. As a result of the fire test, considering the fire point of 450 degrees Celsius in the fire test of the sandwich panel, the distance from the sandwich panel wall to the combustible is more than 120 cm.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.21-31
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• 2018

This paper analyzes the displacements of CFRD which was completed by field measurement. It is to understand the deformation behavior of the dam body according to the water level change from the impounding time. And it was compared with numerical analysis results. As a result of measuring the behavior of the dam crest and downstream slope according to impounding, horizontal displacements in axis direction of the dam, upstream and downstream displacements and settlements occurred mostly when the water level reaches about half of the dam height. The displacements continued until the water level reached its maximum. After that, it showed a constant convergence regardless of the water level. Horizontal displacements of the face slab which is the most important in CFRD were similar at all locations. The Horizontal displacements of the face slab showed the trends of increasing in winter and decreasing in summer due to the effect of the outside temperature before impounding. Also, the displacements increased until the water level reached about half of the dam height. After that, they decreased with rising in water level. As a result, the face slab behaviors according to seasonal change after impounding as well as water level condition. It is judged because of the material characteristics of the concrete slab. Numerical analysis showed slightly different maximum settlement and depth of occurrence from the measuring data after construction of the dam. It is considered that this is due to various design and construction differences such as the estimation of input parameters in analysis, construction period, and the layer thickness of construction. For the overall period of the dam, the settlements were mostly completed during the construction period and some settlements occurred in the early days of impounding and then converged.

• Microbiology and Biotechnology Letters
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• v.9 no.2
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• pp.83-89
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• 1981

Several kinds of organic acids, alcohols, aromatic compounds and sugars as carbon sources were tested in order to produce the cell mass of Rhizopus oryzae which is used in part of food processing or organic acid fermentation. Sodium acetate among them was good enough for carbon source as well as glucose under the concentration of one percent. All nitrogenous substances tested such as ammonium, nitrate or organic nitrogen compounds were well used by this strain of Rhizopus oryzae as nitrogen source. Ammonium sulfate among inorganic nitrogen compounds was most utilized as a nitrogen source in glucose or acetate medium. This strain did not require any growth factors such as yeast extract. The following composition of medium was therefore determined in order to produce the cell mass of Rhizopus oryzae: Na-acetate 1 %, (NH$_4$)$_2$SO$_4$ 0.2%, $K_2$HPO$_4$ 0.05%, MgSO$_4$.7$H_2O$ 0.01%, NaCl 0.01% (PH 5.5). The cell wall of mycelium grown in above medium was lysed optimally at pH 6.5 and 5$0^{\circ}C$ by the action of Strepzyme 115-5. On producing protoplast from mycelium by enzymatic action, almost all of the mycelium was damaged after 4hrs of treatment.

• Composites Research
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• v.23 no.2
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• pp.1-9
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• 2010

This study analyzes the apparent fracture toughness of a thick-walled cylinder with a functionally graded material (FGM) coating at the inner surface of the cylinder. The cylinder is assumed to have a single radial edge crack emanating from its inner surface. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion as a result of cooling from sintering temperature is taken into account. Based on a method of evaluating stress intensity factor introduced in our previous study, an approach is developed to calculate apparent fracture toughness. The approach is demonstrated for a cylinder with a TiC/$Al_{2}O_{3}$ FGM coating and some numerical results of apparent fracture toughness are presented graphically. The effects of material distribution profile, cylinder wall thickness, application temperature, and coating thickness on the apparent fracture toughness are investigated in details. It is found that all of these factors play an important role in controlling the apparent fracture toughness of the cylinder.

• Conservation Science in Museum
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• v.4
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• pp.71-78
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• 2003

The wooden striker on the Divine Bell of King Seongdeok was examined to identify the species of the wood and the outdoor wood weathering caused by solar light, moisture, temperature and air. The species of the wooden striker was identified to Zelkova serrata. When observed the striker with naked eyes, the results were surface discoloration (graying), cracking and roughness. In order to examine the morphological changes according to deterioration type, the specimen were separated to three part(I, II,III-spot). The I-spot was discolored to gray and at the same time entirely covered with dust. So the observation was impossible. The II-spot was also discolored but its texture could be observed. On it could observe numerous fungal hypae and dirts like dust flown into the cell lumens. The cell wall has been so weakened by weathering that it lost the physical intensity. This have made microchecks and splits on the cell wall. Although fungal hypae covered the cell, they did not result in wood decay. The III-spot, located just 0.5 mm below the surface, was maintaining the natural red-brown color of the wood. Its cell wall was similar to that of sound wood. These changes are different from wood decay, and limited only to the surface of the striker-less than or equal to 0.5 mm below.