• Proceedings of the KSME Conference
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• 2002.08a
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• pp.631-634
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• 2002

The study of the flow characteristics in two types of turbo-fans for a vacuum cleaner was performed in a previous study. In present study an analysis of a new modified model to reduce fan noise was performed by using CFD. The characteristics of three models calculated for various rotating speeds and flow rates are obtained and compared with available measured data. The results show that the modified model gives stable flow characteristics in operating range than the original model, while both models show similar performance characteristics at the range of high flow rate. Since in the modified model it takes much longer for an impeller blade to pass a diffuser blade than in the original model, and thus the peak pressure at BPF can be relieved, it is anticipated that the modified model gives much lower noise level with similar performance than the original one, which remains to be verified by unsteady computation and measurements.

• The Journal of Engineering Geology
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• v.10 no.1
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• pp.79-93
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• 2000

When caverns are excavated, it is very important to understand the distribution and charateristics of geological structures because the structures have an significant effect on grouting, rock reinforcement, and groundwater flow, etc. The main water bearing fractures have an orientation of N50~60W and these fractures are known as tension fractures. Their orientation coincides with a long elliptical axis ofpumping test, and they cross the tension fractures of N10~30E. They have typical fracture systems ofrhombic type in this area.

• Journal of the Korean Geographical Society
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• v.38 no.4
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• pp.591-609
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• 2003

The purpose of this study is to exhibit the characteristics and changes of city network in China through the analyses railway structures and movement of passengers and goods in China. On the basis of accessibility analysis., central China area shows the highest level of accessibility, and it declines toward periphery areas. The center of City network was transfered from the central area to the east. Three main lines from north to south and the central status of main cities remain unchanged. The city network stratum structure of China can be divided into three levels. The first level is in a pattern of linear distribution within provices along main lines. The second level, shows a pattern of strengthened linear distribution and crossed influencial regions. The third level includes 5 areas.

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.6
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• pp.1167-1178
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• 2001

본 연구의 목적은 최근 미국 내에서 교육 개혁의 한 방편으로 공립학교 학생들에게 교복을 착용하도록 하는 도시가 증가함에 따라 교복 정책에 대한 여론은 찬반론이 교차하고 있고, 이를 뒷받침 할 연구는 부족하여 교복 착용에 관련된 요인들간의 관계를 알아보아 교육정책에 제안하기 위하여 시도되었다. 연구 대상자는 미국 미네소타 주, 도심 지역의 세 남녀 공학 고등학교를 대상으로 조사되었다. 세 고등학교는 학교 의복 착용에 대한 서로 다른 규율을 갖고 있었다. School R은 학교에서 지정한 교복만을 착용 해야 하는 규율을 갖고 있고 School F는 학생들에게 학교가 선정한 색상에 일치하는 의복을 통학복 으로 입을 수 있도록 한 매우 유동적인 교복 정책을 갖고 있었다. School N은 특정한 학교 교복은 없고 학생들에게 통학복 착용에 대한 규율은 있었다. 세 학교의 학부모, 교사, 학생을 대상으로 한 연구 결과는 부모, 교사는 교복 착용이 학생들의 행동에 영향을 미칠 것이라고 인지한 반면 학생들은 전체적으로 그렇지 않다는 태도를 보였다. 학생들에게 선호도가 높은 교복은 School F의 교복처럼 통학복에 색상 제한을 하는 약간은 자유로운 형태로 나타났으며 해당 학교 학생들의 교복에 대한 만족도 또한 높게 나타났다. 교복을 입지 않는 School N의 학부모들은 학생들 통학복에 대한 지출이 다른 두 학교 부모 보다 많은 것으로 나타났다. 또한 교복을 착용한 경험이 오래된 학생일수록 교복 착용에 더 긍정적인 관점을 보인 것으로 보아 미국 내에서의 교복 정책은 초등학교부터 실시하는 것이 바람직한 것으로 받아 들여 진다.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.49-57
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• 2005

In this study, in-cylinder flow of the swirl chamber type diesel engine numerically simulated by VECTIS code. The flow fields during the intake and compression process were also investigated in detail. Numerical results revealed that the generation and distortion of the swirling, tumbling vortices and those influences on turbulence kinetic energy by shape of the jet passage, angle and area. It was also found that flow characteristics were affected by inflow velocity that depends on change of the jet passage shape. Swirl ratio was increased according to decrease of jet passage area, and was affected by piston motion according to increase of jet passage angle. Tumbling vortices had the similar in various cases, but tumble ratio was increased with the inflow velocity. The generation of turbulence kinetic energy was considerably influenced by complex effects of swirling and tumbling vortices.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.3
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• pp.126-132
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• 1999

Tritium. a radioisotope of hydrogen, is a constituent of water molecules and, therefore. is a ideal water tracer in hydrology. The tritium level of the precipitation in Korea has been monitored at the Pohang station from 1961 to 1976 by IAEA and has been analyzed from 1987 to present by KAERI. The tritium contents of the precipitation were recorded up to about 1,940 TU owing to world-wide nuclear testing in 1963. The contents have decreased and in present are about 10 TU. of which values are similar to those in pre-thermonuclear period. These data can be usefully applied to hydrological studies such as interpretation of relationship between groundwater and surface water and dating of groundwater.

• Journal of the Korean Institute of Rural Architecture
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• v.22 no.4
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• pp.71-78
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• 2020

Today, the whole world is going through a big chaos due to the COVID-19, but paradoxically, the emergence of COVID-19 has been leading to the need for sustainable development, such as Green New Deal that can improve global warming and carbon emissions, and the need for sustainable architecture is growing bigger and bigger in the architectural field as well. The level of CLT buildings in Korea is at a very rudimentary stage, while CLT buildings remedying existing wooden buildings are getting the spotlight among European countries for sustainable architecture. This study was conducted to categorize structure layer compositions of overseas CLT buildings and analyze architectural techniques and materials applied by collecting and analyzing information about CLT structure layer compositions of overseas CLT building-related institutions, companies and cases. When classifying structure layer compositions of foreign CLT buildings depending on the roles of layers. it was revealed that exterior wall structure layers were combined and organized within a sequence of external finishing, ventilation, waterproof, board, external insulation, airtightness, structure, airtightness, interior insulation, interior finishing, sloped roof structure layers were external finishing, ventilation, waterproof, board, external insulation, airtightness, structure, airtightness, interior insulation, interior finishing, flat roof structure layers were external finishing, ventilation, waterproof, planking wood, external insulation, waterproof, external insulation, airtightness, structure, airtightness, interior insulation, interior finishing.

• New & Renewable Energy
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• v.16 no.4
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• pp.41-48
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• 2020

This study performed a single hole operation method using a balancing well-cross-mixed underground heat exchanger, and conducted thermal performance studies of an SCW-type underground heat exchanger using a two-well. The study attempted to change the existing operating method of the two adjacent SCW underground heat exchangers with one ball each. The SCW-type geothermal heat exchanger is considered to enable up to 20% of bleed discharge at maximum load, which makes groundwater usage unequal. The efficiency factor of the geothermal system was improved by constructing the discharged water by cross-mixing two balancing wells to prevent the discharge of groundwater sources and keep the temperature of the underground heat exchanger constant. As a result of the cooling and heating operation with the existing SCW heat exchange system and the balancing well-cross-mixed heat exchange system, the measured performance coefficient improved by 23% and 12% in cooling and heating operations, respectively. In addition, when operating with a balanced cross-mixing heat exchange system, it has been confirmed that the initial basement temperature is constant with a standard deviation of 0.08 to 0.12℃.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.11
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• pp.755-762
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• 2022

The wind tunnel test data for the missile configuration were compared with analysis results using various semi-empirical code and CFD analysis code. The three types of configurations were used for comparison including 2 types of main wing, inline and interdigitate configuration that the main wing and tail intersect. Additionally, it was confirmed that the vortex flow was accurately predicted by comparing the CFD analysis result with the flow visualization test result.

• Economic and Environmental Geology
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• v.50 no.1
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• pp.61-71
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• 2017

The effects of joint density and size distribution on the hydrogeologic characteristics of jointed rock masses are addressed through numerical experiments based on the 2-D DFN (discrete fracture network) fluid flow analysis. Using two joint sets, a total of 51 2-D joint network system were generated with various joint density and size distribution. Twelve fluid flow directions were chosen every $30^{\circ}$ starting at $0^{\circ}$, and total of 612 $20m{\times}20m$ DFN blocks were prepared to calculate the directional block conductivity. Also, the theoretical block conductivity, principal conductivity tensor and average block conductivity for each generated joint network system were determined. The directional block conductivity and chance for the equivalent continuum behavior of the 2-D DFN system were found to increase with the increase of joint density or size distribution. However, the anisotropy of block hydraulic conductivity increases with the increase of density discrepancy between the joint sets, and the chance for the equivalent continuum behavior were found to decrease. The smaller the intersection angle of the two joint sets, the more the equivalent continuum behavior were affected by the change of joint density and size distribution. Even though the intersection angle is small enough that it is difficult to have equivalent continuum behavior, the chance for anisotropic equivalent continuum behavior increases as joint density or size distribution increases.