• Journal of the Korean Solar Energy Society
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• v.26 no.4
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• pp.93-100
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• 2006

An experimental study of a counterflow heat exchanger was performed. The heat exchanger had an effective heat transfer length of 1000mm and was operated in a counterflow arrangement with hot water($30{\pm}0.5^{\circ}C$, $Re_i=3500{\sim}20000$) in the inner tube(copper tube, $d_0=9.52mm$) and cold water($15{\pm}0.5^{\circ}C$, $Re_{DH}=10700{\sim}39000$) in the annulus(copper tube, $D_0=19.05mm$). Overall heat transfer coefficients were calculated and heat transfer coefficients in the inner tube and the annulus were determined using Wilson plots. The inner Nusselt number was compared with that of Gnielinski's correlation and they agreed within ${\pm}10%$ error. The trends were typical for a fluid-to-fluid heat exchanger with the overall heat transfer coefficient increasing with both inner and annulus flow rates. In the range of this experiment, Nusselt numbers for the inner tube flow were almost identical with those of the annulus flow at the same Reynolds number.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.702-708
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• 2006

This study shows the experimental characteristics of the double pipe inserted liquid pipe with small diameter in the gas pipe with large diameter for circulating of a liquid of high temperature, pressure and a gas of low temperature, pressure at the same time. So the functions of pipe and pipe's expansion and heat transfer are presented simultaneously. In the result, the temperature of gas refrigerant at the inlet of compressor increased about $5^{\circ}C$ by the heat transfer with liquid refrigerant in case of the double pipe. And liquid gas refrigerant which the temperature at the inlet of evaporator decreased about $3^{\circ}C$ comparing with the existing type flows into an evaporator COP of the double pipe increased about $7{\sim}10%$ comparing with that of the conventional pipe. And the noise of the double pipe at capillary tube is less than that of the conventional type about 3dB. Consequently. it is convinced the superiority of the double pipe in the heat loss and soundproofing aspect.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.5
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• pp.687-694
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• 1999

This study was conducted to develop new drying process for automatic control and marine engi-neering system. Air-water tests were carried out to investigate dryer performance. The dispersed flow in he dryer test apparatuses was also simulated by using a numerical code which solves the Dittus-Boelter equation for continuous liquid phase and the Reynolds equation of droplet motion for continuous liquid phase and the Reynolds equation of droplet motion for dispersed phase to predict droplet removal efficiency. Proper conditions for dehumidification were optimized by response ambient conditions. When the selected indexes were constrained in the range of 85-98% moisture content above $15^{\circ}$ and more than mass flow rates of moist air 750kg/h. The numerical results were compared with the experimental data pertaining to the removal effi-ciency at chamber stage and overall pressure drop along concentric tubes Good agreement was obtained as for the efficiency while relatively poor agreement was obtained for the relative humidity. The results also showed that the efficiency depended strongly on the relative humidity at the inlet condition which indicated the importance of estimating the heat exchanger length. Effects of some design parameters in both removal efficiency and breakthrough onset condition are discussed.

• Environmental and Resource Economics Review
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• v.4 no.2
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• pp.197-221
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• 1995

본 논문에서는 산업연관 분석모형을 이용하여 1980년대 수출산업에서의 유가변화의 산업별 파급효과를 분석하고, 1990년대 유가 파급효과를 추정하여 보았으며, 1980년대 산업별 물가상승 요인을 계측하여 1970년대 물가상승요인과 비교분석하여 보았다. 1980년대 상반기의 유가 파급효과가 큰 산업은 석유제품과 에너지 다소비 품종인 화학, 비금속 광물, 전기가스수도, 철강, 금속 등으로 나타났으며 대부분의 산업은 유가인상율의 5% 내외의 인상효과를 나타내었다. 유가 인하기였던 1980년대 하반기에도 인하효과는 산업별로 상반기와 비교할 때 큰 차이는 없었으나, 기계, 전기, 전자통신, 자동차 등 주요 수출산업의 가격인하 효과는 그다지 크지 않은 것으로 분석되었다. 저물가 시대였던 1980년대의 주요 물가변화 요인으로는 임금 등 부가가치 및 원유가격의 변화로서 1970년대와 큰 차이가 없었으나, 중간재 수입가격, 수입계수 및 수업률 변화의 물가변화 기여도는 아주 작아서 1970년대와는 다른 양상을 보였다. 한편 1990년대의 유가파급효과 추정을 위한 모의실험 결과를 보면, 1980년대와 마찬가지로 석유관련 제품의 가격인상 효과가 두드러지겠지만, 1970년대와 1980년대에 비해서 유가파급효과는 상대적으로 낮을 것으로 추정되어 수출산업의 가격경쟁력은 임금, 기타 원자재 가격 등 여타 물가인상 요인에 더 영향을 받을 것으로 예상된다.

• Journal of the Korean Geotechnical Society
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• v.22 no.12
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• pp.25-31
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• 2006

This paper studies the field applicability of the Special Chemical grouting Method (SCM) in reinforcing and reducing permeability of the back of an existing continuous wall. SCM uses double rod which imposes intermediate pressure ($981{\sim}9,810kPa$) to disturb, cut, discharge, and mix the ground. It is observed that a bulb is formed by using cement paste and environmentally friendly injection materials with minimal alkali leaching. Uniaxial compression tests, test for chemical properties and fish poison test are performed. Test results indicate that the method results in higher durability, less leaching through the use of the environmentally friendly injection material and faster mobilization of the strength. In addition, field tests confirm the formation of the bulb and the seepage cutoff wall.

• Journal of Convergence for Information Technology
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• v.9 no.8
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• pp.155-163
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• 2019

Laminar mixed convection of a nanofluid consists of water and $Al_2O_3$ in a horizontal circular tube has been studied numerically. Two-phase mixture model has been used to investigate hydrodynamic and thermal behaviors of the nanofluid with variables physical properties. Three dimensional Navier-Stokes, energy and volume fraction equations have been discretized using the finite volume method. The Brownian motions of nanoparticles have been considered to determine the thermal conductivity and dynamic viscosity of $Al_2O_3$-Water nanofluid, which depend on temperature. The calculated results show good agreement with the previous numerical data. Results show that in a given Reynolds number (Re), increasing solid nanoparticles volume fraction and Richardson number (Ri) increases the convective heat transfer coefficient and wall shear stress.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.615-618
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• 2003

This paper presents Bi thin films have been fabricated by atomic layer-by-layer deposition and co-deposition at an IBS method. The growth rates of the films was set in the region from 0.17 to 0.27 nm/min. MgO(l00) was used as a substrate. In order to appreciate stable existing region of Bi 2212 phase with temperature and ozone pressure, the substrate temperature was varied between 655 and 820 $^{\circ}C$ and the highly condensed ozone gas pressure(PO$_3$) in vacuum chamber was varied between 2.0$\times$10$^{-6}$ and 2.3$\times$10$^{-5}$ Torr. Bi 2212 phase appeared in the temperature range of 750 and 795$^{\circ}C$ and single phase of Bi 2201 existed in the lower region than 785 $^{\circ}C$. Whereas, PO$_3$ dependance on structural formation was scarcely observed regardless of the pressure variation. And high quality of c-axis oriented Bi 2212 thin film with T$_{c}$(onset) of about 90 K and T$_{c}$(zero) of about 45 K is obtained. Only a small amount of CuO in some films was observed as impurity, and no impurity phase such as CaCuO$_2$ was observed in all of the obtained films.lms.

• Journal of the Korean GEO-environmental Society
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• v.6 no.4
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• pp.65-71
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• 2005

Recently, difficulties in soft ground improvement that caused by effectiveness of the ground improvement, the durability and environmentally friendliness of the injection material come to the fore. This paper studies the field applicability of the SCM in reinforcement and seepage cutoff of the back of an existing continuous wall. SCM uses double rod which imposes heavy pressure($10-100kgf/cm^2$) to disturbed, cut, discharge, and mix the ground. It is observed that a bulb is formed by using cement paste and environmentally friendly injection materials with minimal alkali leaching. Unconfined compression test and fish poison tests are performed. Test results indicate that the method results in higher durability, less leaching through use of the environmentally friendly injection material, and faster mobilization of the strength. In addition, field tests confirm the formation of the bulb and the seepage cutoff wall.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.2 no.3
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• pp.103-122
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• 2007

Innovation clusters developed or evolved around a specific region IS the key element of national innovation system and determine national competitiveness. Recognizing the importance of innovation clusters, Korean government has made "Daedeok Special R&D Zone" in 2005. This paper examines the success factors of famous Cluster in advanced countries and China, and proposes the strategy for regional development in Daejeon through boosting Daedeok Innovation Cluster. Although 30.5% of government R&D investment is being concentrated in Daedeok along with 10% of the country's doctorate degree holders, it is lack of increasing revenue by linking corporate R&D with a creative and challenging entrepreneur spirit. The core of the innovation cluster is the integration and mutual networking of the main participants. This paper suggests strategies for developing as a world class innovation cluster, global networking and clustering, venture ecosystem formation, commercialization the knowledge by interacting with market. It also explains the necessity of regional integration for cluster to cluster linkages in the East Asia Region.

• Geotechnical Engineering
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• v.12 no.4
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• pp.33-46
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• 1996

When structures are constructed in ground with poor bearing capacity, deformation of ground may induce foundation settlements and cracks of structures. Recently, high pressure jet grouting is widely used to improve the engineering properties of such foundation. Sometimes, the grouting columns are built in the ground by jet grouting method. They are used as in -situ piles to increase the bearing capacity of existing foundation. In this paper, as for the grouting columns built in ground by high pressure jet grouting with double tube rod, the effects on reinforcement and bearing capacity of ground are investigated. A series of laboratory tests has been performed on the specimens sampled from the grouting columns and a pile load test has been performed on a grouting column. The test results show that high pressure jet grouting has a sufficient effect on reinforcement of ground and restraint of settlement of structure.