• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.8-9
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• 1997

산업의 발달과 환경에 대한 관심이 높아짐에 따라 고효율, 저공해인 가스터빈의 응용범위가 넓어지고 있는 추세이다. 가스터빈 기관의 효율을 높이기 위해서는 터빈 입구온도를 높이는 것이 필수적인데 이는 재질에 의해 제한 받게 되고 이 때문에 효과적인 냉각방법의 필요성이 대두되었다 충돌제트는 국소적으로 높은 열/물질 전달 효과를 얻을 수 있어서 터빈 블레이드 냉각과 연소기 벽면 냉각에 효과적으로 응용 될 수 있다. 이러한 충돌제트의 냉각효과는 제트출구의 초기조건에 매우 민감한데 Kelvin-Helmholts 불안정은 불안정한 자유전단층에서 자연적인 와류생성(roll up)과 개개의 와류고리 형성의 원인이 되고 이 고리의 성장과 병합(pairing)은 제트의 유동특성에 상당히 영향을 미친다. 제트주위에 생성되는 이러한 와류에 의해 제트중심에서 속도와 난류강도가 변하게 된다. 이러한 제트초기의 불안정성은 하류에서의 와류성장에 영향을 끼치기 때문에 와류의 조절에 의한 충돌 면에의 열 전달 효과 상승을 기대할 수 있다. 이 조절방법은 크게 두 가지로 나눌 수 있는데 하나는 제트주의 환형관에 이차유동을 가하여 와류를 직접 제어함으로써 자유전단류(free shear layer flow)의 안정성 원리를 이용하여 열 전달을 촉진하는 것이고 다른 하나는 음향여기(acoustic exitation)를 사용하여 제트주위의 와류형성을 조절하는 것인데, 자연적으로 형성되는 와류의 주파수(와류의 고유주파수)나 부조화 주파수(subharmonic)로 음향여기 시키는 경우 제트 주위 와류는 더욱 증폭되고 그렇지 않은 경우 제트주위 와류의 형성이 억제되어 더 긴 제트코어의 길이 및 제트코어 주위에서 작은 크기의 와류들이 형성된다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2009.04a
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• pp.540-547
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• 2009

국내도로터널 화재안전성을 확보하기 위하여 FDS를 이용하여 ISO, 도로터널 방재시설기준, Runner Hammer 터널기준의 시나리오에 따라 콘크리트 터널구조물의 내부 열역학적 특성을 예측하였다. 화재로 인한 터널내부의 온도분포를 측정하기 위하여 화염원으로부터 터널입구 방향으로 5m 마다 터널 단면의 온도분포를 추출하였고, 터널의 중심을 지나는 길이방향 단면의 온도분포를 해석하였다. 해석결과 온도는 500${\sim}$950$^{\circ}C$까지의 분포를 나타내었고 가장 높은 온도영향을 받은 Runner Hammer 터널기준의 내부 열환경 조건에서는 터널 단면이 모두 화염에 직접적으로 노출 때문에 단면전체가 800${\sim}$950$^{\circ}C$까지 상승하였다. 특히 상부부분은 900$^{\circ}C$ 이상의 고온에 장시간 노출되고 있어 깊이 50mm 지점의 온도가 250$^{\circ}C$까지 상승하였다.

• Journal of Navigation and Port Research
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• v.37 no.6
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• pp.637-645
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• 2013

Masan bay with a semi-enclosed waters has serious water quality problems due to the low flow and river pollution load from land, and shows the vulnerable locational characteristics to storm surge. We are seeking the way of both operating disaster prevention facilities and water quality improvement measures in the bay. That is, the water was exchanged using the head difference occurred by operating disaster prevention facilities. The location of disaster prevention facilities was assumed to be in the inlet of the bay, in the vicinity of Machang bridge, and in the vicinity of Dot island and the operation time was assumed to be early morning hours(01~05) considering the number of shipping passage and annual tide, and spring tide of the largest head difference. In addition, the experiment case of water exchange including the in-outflow feeder pipe was tested. According to the simulation results, water exchange rate in all experiments has shown a steady increase. Water exchange rate of the whole of Masan bay in the case of present is 38.62%. The water exchange rate of the inside of Masan bay compared with the inlet of bay, appeared to be very low. Thus, we judged that the characteristics of semi-enclosed waters were well reproduced. On the results of the experiment of disaster prevention facilities and in-outflow feeder pipe, the case of the operation of disaster prevention facilities, water exchage rate is high compared with the case of present. And, the higer the operating frequency, the more water exchange is appeared. The cases of water exchange prevention facilities through the in-outflow feeder pipe caused by the head difference, also showed the higest improvement of the water quality. Compared with the south of Machang bridge, the effect of water exchange was better in the inlet of Masan bay and Dot island. On the other hand, the inlet of Masan bay is higer than Dot island as for water exchange of the whole of Masan bay, but opposite, water change rate including Masan inside was higher in the case of Dot island.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.4
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• pp.285-295
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• 2001

This study describes the analysis on the dynamic characteristics of model as a fundamental studies for the horn fish Hemiramphus sajor surface pair trawl gear. The model experiments were carried out in a flume tank by using model net for the horn fish surface par trawl gear. The model net was made to the scale of 1/40 by scaling down two surfce par trawl boats of 6.67 and 9.98 ton used for sea experiment in the coast of Jeju Island. Dimensions of the model net were 1.2m for stretch length of net, 1.3m for float line, 1.0m for sinker line, 2.5g for floats, and 0.86g for sinkers. Experiments were conducted in the observation channel of a flume tank with experimental equipments used to change the distance between paired boats and towing velocity. Motion of model net during towing was recorded by two sets of digital camera which were placed in the top and side of the model net. The leading coordinate of net height and net mouth width was captured by the photograph analysis system. Through the experiment, we obtained the following results: 1. The relationship between the net hight(Nh) and towing velocity(Vt) during towing was found to be Nh=(2.39Db-$^{0.62})Vt^{0.56}$ and the relationship between the net mouth width (Nw) and towing velocity during towing was Nw=(0.96Db^{0.62})Vt^{0.11}$, where Db is the distance between paired boats. 2. The relationship between the net tension(Nt) and towing velocity during towing was found to be Nt=106.94Vt+1.43 and the model net becomes parallel to the water surface at the towing velocity larger than 1.5 Knot. 3. The relationship between the net opening area(Na) and towing velocity during towing was found to be Na=(2.28Db0.37)Vt.-0.45, and the relationship between the filtering volume(Fv) and towing velocity during towing was Fv=(69.9Db$^{0.37})Vt^{0.55}$. The net opening area and filtering volume reach maximum value at the distance of 25m between paired boats.

• Journal of Forest and Environmental Science
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• v.15 no.1
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• pp.107-116
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• 1999

For the study on the variation of Pinus densiflora S. et Z. natural populations. 13 stands were selected in Kangwondo region in 1994. They were located in Hyoja-Dong, Chunchon-Si [plot 1]; Sinnam-Myun, lnje-Gun [plot 2]; Buk-Myun, lnje-Gun [plot 3]; Seo-Myun, Yangyang-Gun [plot 4 and 5]; Sonyang-Myun, Yangyang-Gun [plot 6]; Toseong-Myun, Goseong-Gun [plot 7]; Synrim-Myun, Wonju-Si [plot 8]; Dunnae-Myun, Hoengsong-Gun [plot 9]; Jinbu-Myun, Pyungchang-Gun [plot 10]; Sogumgang, Kangneung-Si [plot 11]; Seo-Myun, Ulchin-Gun [plot 12]; and Mitan- Myun, Pyungchang-Gun [plot 13]. The morphological characteristics of needles and cones were investigated for twenty individual trees from each population. The results are summarized as follows: 1. Among needle characteristics, length, the number of serration. and the number of stoma row were significantly different among populations and between individuals within a population. They were 69.3~91.9mm, 25.1~28.7 per 0.5cm, and 4.1~6.2 rows for abaxial side and 2.9~4.6 rows for adaxial side, respectively. 2. Among cone characters surveyed. length and diameter were significantly different among populations and between individuals within a population. They were 31.1~43.7mm and 20.0~24.1mm, respectively. 3. A highly positive correlation was observed between the number of stoma row of abaxial side and that of adaxial side. and between length and diameter of cone. But the number of serration was negatively correlated with all traits. 4. The distance from seashore was positively correlated with needle length and the number of serration, but negatively correlated with the number of stoma row and cone length. However, the altitude was positively correlated with the number of serration, but negatively correlated with the number of stoma row and cone length. 5. Cluster analysis using average linkage method for needle and cone characteristics showed two groups to Euclidean distance 1.0. They were group I consisting of plots 1, 8, 12, and 13 and group II of plots 2, 3, 4, 5, 6, 7, 9, 10, and 11. However, group II was divided again to Euclidean distance 0.8, that is a group including plots 2, 3, 9, and 11 and the other group comprising plots 4, 5, 6, 7, and 10.

• The Journal of Engineering Geology
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• v.24 no.3
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• pp.423-429
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• 2014

Development of a reservoir pressure core sampler (PCS) with a built-in data logging system (DLS) for recording real-time temperature and pressure observations is critical in domestic hydrocarbon production to accurately measure and monitor reserves of shale gas, coalbed methane, and gas-hydrate. Another purpose of this new technology is to minimize the loss of gas from the core as the drill core is collected. This is accomplished by maintaining the pressure of the sample from the moment the drill core is obtained at depth, thus allowing an accurate analysis of shale gas, coalbed methane gas, and gashydrate within the core. Currently, the United States and European countries have monopolized the development and marketability of PCS technologies. We are thus developing a reservoir PCS by analyzing the operating principle and mechanisms of the existing PCS, and by conducting tests on the existing PCS. We further aim to develop a PCS with a maximum operating pressure of 100 bar, a maximum operating temperature of $-20^{\circ}C$ to $40^{\circ}C$, and a pressure loss rate of 10%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6452-6457
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• 2014

R1234yf has been developed as an alternative refrigerant to R134a, which has been associated with global warming. The capillary tubes as expansion valves control the mass flow rate and balance system pressure in the refrigeration cycle. The present numerical model used the governing equations including the law of conservation of mass, momentum, and energy in a capillary tube. The mass flow rate of R1234yf decreased by 47.0% as the capillary tube length was increased from 1 to 4 m. As the inner diameter of the capillary tubes was changed from 1.3 to 1.7 mm, the mass flow rate of R134a and R1234yf increased by 117.9% and 121.0%, respectively. The mass flow rate of the R134a and R1234yf increased by 28.3% and 29.1% with subcooling increasing from 0 to $7^{\circ}C$. In addition, when the inlet temperature of the capillary tubes was changed from 35 to $60^{\circ}C$, the mass flow rate of R134a and R1234yf increased by 31.0% and 45.4%, respectively.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.9-15
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• 2009

In this study, the l/35 reduced-scale model experiment were conducted to investigate designed ventilation system performance at rescue station in tunnel fire. A model tunnel with 2 mm thick of steel, 10 m long, 0.19 m high and 0.26m was made by using Froude number scaling law. The cross-passages installing escape door at the center. were connected between accident tunnel and rescue tunnel. The n-heptane pool fire, $4cm\times4cm$, with heat release rate 698.97W were used as fire source. The fire source was located in the center and portal of accident tunnel as Worst case.. An operating ventilation system extracted smoke amount of 0.015 cms. The smoke temperature and carbon monoxide. concentration in cross-passage were measured to verify designed ventilation system. The results showed that, in center fire case without ventilation in accident tunnel, smoke did not propagated to rescue station. In portal tire case, smoke spreaded to rescue station without ventilation. But smoke did not propagated to rescue station with designed ventilation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.294-294
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• 2008

동시 증발 증착법 화합물의 구성원자를 독립적으로 증발시켜서 기판에 증착하는 방법이다. 각 물질은 온도에 따른 증기압을 가지는데 각 물질의 온도를 조절하여 증착률을 조절한다. 보트에서 떠난 원자가 기판에 도달할 확률은 챔버의 진공도, 보토와 기판과의 거리 등에 의하여 영향을 받는다. 진공도가 나쁠수록, 보트와 기판과의 거리가 멀수록 기판에 도달할 확률이 떨어진다. 동시증발 증착법을 이용한 SmBCO 초전도층 증착에서 각 물질의 기판에 도달하는 원자비를 조절하기 위하여 QCM(증착률 측정장치), QCM 가이드를 사용하였다. QCM sensor 입구에 튜브형태의 QCM 가이드를 설치하고 QCM 가이드가 특정한 물질의 증발보트를 향하도록 배치하였다. 따라서 각 보트에서 떠난 원자들은 특정한 QCM sensor에 도달하게 되고 결국 3원소(Sm, Ba, Cu)의 증착률의 비를 조절함으로써 조성비를 조절할 수 있게 된다. QCM 증착률의 비와 실제 조성비는 여러 가지 변수에 의하여 영향을 받는 다. 대표적인 변수는 챔버의 진공도, QCM 가이드의 직경 및 길이, QCM 센서와 보트와의 거리 등이 있다. 진공도가 높을수록 특정 보트에서 떠난 원자들이 QCM 가이드 입구에 도달할 확률이 낮아지고, QCM 가이드의 직경이 좁을수록 가이드 내벽에 흡착될 확률이 높아진다. 또한 QCM센서와 보트와의 거리가 멀수록 챔버내 잔류가스의 원자들과 충돌확률이 높아지므로 도달확률이 줄어들게 된다. 동시 증발 증확법에서 조성비의 재현성을 높이기 위해서는 매회 증착실험에서 진공도가 일정해야 하며, QCM 가이드와 보트와의 거리를 되도록 최소화 하고, QCM 직경을 크게 하는 것이 유리하다.

• Korean Journal of Plant Taxonomy
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• v.35 no.3
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• pp.201-209
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• 2005

Two new naturalized species, Amaranthus hybridus and Crepis tectorum, are reported here. Descriptions and illustrations of the species and comparison of morphology with related species are provided. Amaranthus hybridus was first found at Nanjido, Seoul and is widely distributed in the central and southern part of Korean peninsula. New Korean name is given as "Ginteolbireum". It is well distinguished from the related species, A. retroflexus and A. patulus, by its late flowering time (September to October), sparse hair on the leaves, similar length between tepal and fruit, and long inflorescence without division. Crepis tectorum was first found at the entrance of Weoljeongsa Temple in Pyongchang-gun, Gangwon-do and spreads rapidly to other areas. New Korean name is given as "Nadomindulle".