• Nuclear Engineering and Technology
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• 제44권8호
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• pp.871-888
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• 2012

This paper aims at presenting the state of the art, the recent progress, and the perspective for the future, in the modelling of two-phase flow in the horizontal legs of a PWR. All phenomena relevant for safety analysis are listed first. The selection of the modelling approach for system codes is then discussed, including the number of fluids or fields, the space and time resolution, and the use of flow regime maps. The classical two-fluid six-equation one-pressure model as it is implemented in the CATHARE code is then presented and its properties are described. It is shown that the axial effects of gravity forces may be correctly taken into account even in the case of change of the cross section area or of the pipe orientation. It is also shown that it can predict both fluvial and torrential flow with a possible hydraulic jump. Since phase stratification plays a dominant role, the Kelvin-Helmholtz instability and the stability of bubbly flow regime are discussed. A transition criterion based on a stability analysis of shallow water waves may be used to predict the Kelvin-Helmholtz instability. Recent experimental data obtained in the METERO test facility are analysed to model the transition from a bubbly to stratified flow regime. Finally, perspectives for further improvement of the modelling are drawn including dynamic modelling of turbulence and interfacial area and multi-field models.

• Computers and Concrete
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• 제21권4호
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• pp.471-484
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• 2018

Refined analysis depicting mass transportation and physicochemical reaction and reasonable computing load with acceptable DOFs are the two major challenges of numerical simulation for concrete durability. Mesoscopic numerical simulation for chloride diffusion considering binder, aggregate and interfacial transition zone is unable to be expended to the full structure due to huge number of DOFs. In this paper, a multiscale approach of combining both mesoscopic model including full-graded aggregate and equivalent macroscopic model was introduced. An equivalent conversion of chloride content at the Interfacial Transition Layer (ITL) connecting both models was considered. Feasibility and relative error were discussed by analytical deduction and numerical simulation. Case study clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Difference for single-scale simulation and multiscale approach was observed. Finally, this paper addressed some worth-noting conclusions about the chloride distribution and rebar corrosion regarding the configuration of rebar placement, rebar diameter, concrete cover and exposure period.

• Transactions on Electrical and Electronic Materials
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• 제11권1호
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• pp.1-10
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• 2010

This is an overview paper reporting our most recent work on processing and microstructure of nano-structured oxides and their photoluminescence and photo-catalysis properties. Zinc oxide and related transition metal oxides such as vanadium pentoxide and titanium dioxide were produced by a combination of magnetron sputtering, hydrothermal growth and atmosphere controlled heat treatment. Special morphology and microstructure were created including nanorods arrays, core-brushes, nano-lollipops and multilayers with very large surface area. These structures showed special properties such as much enhanced photoluminescence and chemical reactivity. The photo-catalytic properties have also been promoted significantly. It is believed that two factors contributed to the high reactivity: the large surface area and the interaction between different oxides. The transition metal oxides with different band gaps have much enhanced photoluminescence under laser stimulation. Use of these complex oxide structures as electrodes can also improve the energy conversion efficiency of solar cells. The mixed oxide complex may provide a promising way to high-efficiency photo emitting materials and photo-catalysts.

• 한국조경학회지
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• 제28권6호
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• pp.29-51
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• 2001

The purpose of this research is to analyze of biotope structure focused on the evaluation for the species and biotope preservation in the case of Soosung District in Daegu metropolitan city. We analyzed the structure of urban biotope, and investigated the disposition of space and several characteristics through the material collection relating to the existing urban ecological material and the field investigation. The results of this study were as follows; 1) The result of biotope type classification was divided into 17 biotope type groups and 90 biotope types belonging to them. 2) The biotope type of mixed forest(QD) has the highest rate in occupation area, 1.764ha and the biotope type of cultivation areas by vinyle-hothouse(KC) has the lowest rate, 0.3ha. 3) In the result of the first evaluation for the species and biotope preservation, biotope types such as QB, QI, PA, PB, NB and NC etc. possess great value. Particulary, these biotope types come from forest areas and transition zone. They have not appeared in the inner of cities. 4) The biotope types such as CA, NA, NB, ND and PB are proved to possess high value in the result of rarity and riskiness evaluation. There appear EE, MA, NB, QC and QD in IV grade which is impossible to have them regenerative. They usually have appeared in forest areas. 5) There emerge 3a biotope type that has the highest value in the result of the second evaluation such as CC, EE, KF, LD, MB, NC, PB, QB and QI etc. Most of them were presented into the large area of site size and were distributed in the forest areas intensively. So, it is certain that the space for the species and biotope preservation connected with residential district is scarce. 6) The detailed biotope plan must be made out specially continuously. It is about biotope spaces that are especially important for the species and biotope preservation from the result of this research. Also, the study on the detailed index settlement of the urban landscape plan based on the biotope map must be continued.

• 농촌계획
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• 제9권1호
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• pp.65-75
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• 2003

As a pre-step research to make land-use planning in the region level, this study aims to analyze some probability pattern representing transition probabilities from farmland to others using the sequential detailed digital land-use maps. Kinki and Chubu regions of Japan, which have Osaka and Nagoya cities as their center places respectively, were selected as test regions in this study. The 10m grid land-use maps for four time series at every 5 year from 1977 to 1992 were used. In this study, the regions were divided into three sub-areas 10km, 20km, and 30km according to distance from center cities, respectively. The correlation coefficient (CC) between sub-areas with same distance in the two regions was calculated to analyze whether or not the two regions have common points in the pattern of land-use conversion probability from farmland to other types. The probability distribution of the converted areas which were moved to the urbanized area (residential, commercial, industrial, road, park and public facility areas) was about $40{\sim}70%$ for both all periods and sub-areas. According to distance from city centers, the probability moved to the urbanized area was about 60% at 10km area, and 40% at the 30km area, which means that the values we decreased gradually, while in the case moved to the forest and the etc areas, the values were increased slightly. The CC analysis from the paddy field and the dry field to the others separately showed that there is high correlation in the probability pattern between the two regions.

• 한국농공학회논문집
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• 제63권3호
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• pp.59-73
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• 2021

The purpose of this study is to investigate transition of pumping technology, irrigation water requirement, and unit area drainage discharge at the Pumping station-based Irrigation Associations (PIAs) in South Korea during Japanese colonial period (1910-1945). The PIAs established pumping stations and embankments along rivers for the purpose of irrigation, drainage and flood prevention until the mid-1920s. From the late 1920s after major river improvement projects, newly established PIAs did not include the flood prevention in their purpose of establishment. The design criteria of the irrigation and drainage projects, such as irrigation water requirements, design rainfall, and allowable ponding duration were decided according to the circumstances of PIAs. The gross irrigation water requirement of paddy fields increased from the 1920s to the 1940s, and reached the level of 0.0020 m³/s/ha (19 mm/d) in the 1940s for the fairly good irrigation status in the drought. The great floods of 1930, 1933, and 1934 triggered the increase in drainage discharge in the late 1930s, leading to the unit area drainage discharge of 0.9-2.6 m³/s/km² for natural drainage and 0.3-1.1 m³/s/km² for pump drainage. Therefore, several PIAs near the major rivers could avoid repetitive floods damage.

• 한국환경복원기술학회지
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• 제13권6호
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• pp.1-12
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• 2010

This study aims at analyzing the development status of surroundings of natural environment conservation areas and securing an adequate distance from development activities to conserve natural environment conservation areas efficiently or developing an improvement plan for setting conservation areas. Findings from the study shows that 1) rather than simply designating a legal natural environment conservation area, a conceptual scope approach of a "core area", "buffer area", and "transition area" such as in zoning of a "biosphere reserve" by UNESCO is recommended; 2) when setting an adequate range in a natural environment conservation area, it should be set by fully considering locational situation and the regional and environmental features of surroundings rather than setting a certain distance uniformly; 3) instead of designating wetlands only as a conservation area, entry and exit areas should be also included as buffer areas and in the case of wild animals, not only habitats but also feeding areas should be designated as conservation areas; and 4) an adequate horizontal separation space is important in the case of ground development, but for natural resources related to subterranean water and geological situation such as wetlands, an adequate vertical separation space should be fully considered.

• 재활치료과학
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• 제11권3호
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• pp.23-36
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• 2022

목적 : 본 연구는 전환프로그램 연구동향과 장애청소년을 대상으로 국내외 전환프로그램의 중재 및 효과를 체계적으로 분석함으로써 학교 및 지역사회 관련 기관들과 협력하여 성인생활의 모든 측면을 포함할 수 있는 중재 전략에 대한 기초자료를 제공하는 것을 목적으로 한다. 연구방법 : 학술연구정보서비스(Research Information Sharing Service: RISS), Pubmed, Web of Science(WoS) 데이터베이스를 사용하여 2006년부터 2021년까지의 게재된 논문을 검색하였다. 주요 검색어는 'Disability' AND ('Adolescents' OR 'Young adult') AND ('Transition education' OR 'Transition program')를 사용하였다. 최종적으로 7편의 국내외 논문을 본 연구의 분석 대상으로 선정하여 전문을 검토하였다. 또한, WoS(Web of Science) 플랫폼과 VOSviewer(version 1.6.16, CWTS, Netherlands, 2020) 프로그램을 이용하여 키워드와 국가 관계를 분석하고 시각화하였다. 결과 : 7개의 논문에서 참여한 대상자를 유형별로 분석한 결과, 대상자는 ASD, ADHD, ID, DD, physical disability 총 5가지로 분류되었다. 중재에 사용된 영역은 크게 직업(학업), 자기관리(시간), 상호작용(대인관계, 의사소통) 3가지 범주로 혼합되어 실시되었다. 중재 결과 7편 중 1편을 제외하고는 사회성 및 적응, 삶의 질, 일상생활활동 세 가지 분류 중 적어도 하나 이상의 부분에서 유의미한 향상을 보였다. 결론 : 본 연구는 전환프로그램의 연구동향을 파악하면서 프로그램의 적용과 그 효과를 정리하여 다양한 전문가와의 교류하는 방향성을 제시하는 동시에 단편적인 측면이 아닌 성인생활의 모든 측면을 확대하는 기초자료로 활용될 수 있을 것이다.

• 대한토목학회논문집
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• 제37권2호
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• pp.397-407
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• 2017

본 연구는 고속도로 졸음쉼터 현황 조사 및 문제점 도출을 통해 졸음쉼터의 제원 산정 및 설계기준 수립을 위한 개선안 제시를 목적으로 한다. 고속도로 졸음쉼터 진입부를 감속변이구간, 감속차로, 진입연결로로 분류하고, 진출부는 진출연결로, 가속차로, 가속변이구간으로 분류하여 차량의 본선 주행속도, 진출입연결로의 시 종점부 주행속도, 감속도 및 가속도 등을 고려하여 구간별 적정길이를 산정하였다. 또한 졸음쉼터 주차부를 주차형태, 횡단구성 주차공간의 길이 등으로 구분하고, 실제 졸음쉼터를 이용하는 차량의 이용률, 중차량 비율, 졸음쉼터 내 설계속도 등을 고려하여 합리적인 설계기준을 정립하였다. 본 연구를 통해 제시된 고속도로 졸음쉼터 설계기준은 향후 졸음쉼터 계획 및 재정비 시 유용하게 활용될 수 있을 것으로 판단된다. 또한, 고속도로 졸음쉼터의 규정 및 산정 결과를 고려한 졸음쉼터의 설치기준 정립은 휴게시설 및 고속도로 교통사고 예방은 물론 이용률 증가 및 안전성 측면의 향상을 가져올 것으로 판단된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1839-1842
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• 1999

We have synthesized carbon nanotubes by thermal chemical vapor deposition of $C_2H_2$ on transition metal-coated silicon substrates. Carbon nanotubes are uniformly synthesized on a large area of the plain Si substrates, different from Previously reported porous Si substrates. It is observed that surface modification of transition metals deposited on substrates by either etching with dipping in a HF solution and/or $NH_3$ pretreatment is a crucial step for the nanotube growth prior to the reaction of $C_2H_2$ gas. We will demonstrate that the diameters of carbon naotubes can be controlled by applying the different transition metals.