• Nuclear Engineering and Technology
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• 제41권3호
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• pp.287-294
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• 2009

Due to thermal hydraulics phenomena, such as thermal stratification, various events occur to the parts of a nuclear power plant during their lifetimes: e.g. cracked and dislocated pipes and thermally fatigued, bent, and damaged supports. Due to the operational characteristics of the parts of the steam generator feedwater inlet horizontal pipe, thermal stratification takes place particularly frequently. However, the thermal stress due to thermal stratification at the steam generator feedwater inlet horizontal pipe was not reflected in the design stage of old plants(Kori Unit No.1, 2, 3 and 4, Yeonggwang Unit No. 1 and 2, and Uljin Unit No. 1 and 2; referred to as old-style power plants hereinafter). Accordingly, a verification experiment was performed for thermal stratification in the horizontal inlet nozzle steam generator of old-style plants. If thermal stratification occurred in the horizontal pipe of an old-style power plant, numerical analysis of the temperature distribution of the pipes and fluids was conducted. The temperature distributions were compared at the curved part of the pipe and the horizontal pipe before and after the installation of the improved thermal sleeves designed to alleviate thermal stress due to thermal stratification. The thermal stress reduction measure was proven effective at the steam generator inlet horizontal pipe and the curved part of the pipe.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.735-740
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• 2001

In the nuclear power plant, emergency core coolant system(ECCS) is furnished at reactor coolant system(RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, it occurs thermal stratification phenomena in case that there is the mixing of cooling water and high temperature water due to valve leakage in ECCS. This thermal stratification phenomena raises excessive thermal stresses at pipe wall. Therefore, this phenomena causes the accident that reactor coolant flows in reactor containment in the nuclear power plant due to the deformation of pipe and thermal fatigue crack(TFC) at the pipe wall around the place that it exists. Hence, in order to fundamental identification of this phenomena, it requires the experimental research of modeling test in the pipe flow that occurs thermal stratification phenomena. So, this paper models RCS and ECCS pipe arrangement and analyzes the mechanism of thermal stratification phenomena by measuring of temperature in variance with leakage flow rate in ECCS modeled pipe and Reynold number in RCS modeled pipe. Besides, results of this experiment is compared with computational analysis which is done in advance.

• 대한설비공학회지:설비저널
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• 제17권4호
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• pp.382-394
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• 1988

Dynamic characteristics of thermally-forced stratification process in a square enclosure with a linear temperature profile at the side walls have been investigated through flow visualization experiment and numerical analysis. The experiment was performed on air with the Rayleigh numbers of order $10^5$. A particle tracer method is used for the flow visualization and to obtain a sudden linear temperature profile at the side walls copper blocks which already have a linear temperature profile are come into contact with the thin copper plates of the test section. Immediately a meridional circulation is developed and heat transfer takes place from the wall to the interior region by circulation of fluid and finally a thermal stratification is achieved. In the numerical study, QUICK scheme for convective terms, SIMPLE algorithm for pressure correction, and the implicit method for the time marching are adopted for the integration of conservation equations. Comparison of flow visualization and numerical results shows that the developing flow patterns are very similar in dynamic nature even though there is a time lag due to the inevitable time delay in setting up a linear temperature profile. For high Rayleigh numbers, the oscillatory motion is likely to take place and stratified region is extended. However, initial temperature adjustment process is much slower than that for low Rayleigh numbers.

• 대한지리학회지
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• 제43권4호
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• pp.511-525
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• 2008

거주지 분화(residential segregation)는 도시 불평등을 심화하는 요인 중 하나이다. 본 연구는 거주지 분화의 원인에 대한 상이한 주장들을 살펴보고 사례분석을 통해 현실 적합성을 검증하고자 한다. 이론적 고찰은 일찍이 논의가 활발했던 미국도시의 인종 민족별 거주지 분화에 대한 것으로 한정하였으며, 거주지 분화가 소수민족의 주류사회로의 낮은 동화에 기인한다고 주장하는 지리적 동화론(spatial assimilation), 주택금융시장의 인종차별에 기인한다는 층화론(place stratification), 그리고 거주지선택에 있어 타민족에 대한 선입관과 자기민족에 대한 선호에 기인한다는 재기되는 민족성론(resurgent ethnicity)을 살펴보았다. 사례 연구로 시카고에 거주하는 아시아인의 거주패턴의 변화를 출신국가별로 지도로 그려 분석하였다. 1990년대를 통한 가장 큰 변화는 교외화와 재집중화로 요약될 수 있으며 이는 민족성론을 그리고 부분적으로 마나 동화론을 뒷받침한다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.131-136
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• 2003

Landslide is a natural disaster frequently noticed In korea during monsoon season in flicting nationwise damages on human lives, properties, transportation networks, construction sites, etc. This study is about landslide characteristic in rainfall. This study selects seven sites that occured in 2001 and 2002. So elect areas divide and studied special quality by carcinoma by igneous rock, metamorphic rock, sedimentary rock. According to study finding, because igneous rock area is very thin into 1m interior and exterior soil layer, failures happened much rock and soil interface. There was place that depth of soil layer becomes about 2∼3m being area that receive serious weathering case of metamorphic rock. Therefore, at collapse much debriflow occurrence expect. Case that sedimentary rock area is broken through stratification looked. When see such results, it may become many helps to study characteristics of landslide occurrence area grasping collapse special quality by rock type.

• 한국조경학회지
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• 제30권2호
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• pp.50-62
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• 2002

From modernism to post-modernism, the practice in the design field often reduced the complexity of environment and to remove variety. However, contemporary ideas of space have been changed. The current thought premise is that the environment is mutable and is evolving according to inner and outer forces and elements. Therefore, leading designers recognize that the environment is complex in itself while anticipating a new theory explaining on-going trends. The idea of fold formulated by Gilles Deleuze can provide a theoretical base for new environmental design in constrat to current design practices. The fold is a hybrid by accommodating complex relations within an object. It carries a dynamic world view through continual process and yields a topological space against absolute space like Euclid geometry. The characteristics of the fold can be paraphrased as rhizome, stratification and smooth space. Rhizome forms a non-hierarchial connection like networking in internet space. Stratification is a kind of superimposition of autonomous potential layers within a single object. Smooth space is a free space and event oriented space keeping non-linear form. This study tried to incorporate the idea of fold to environmental design methods and design process in order to make space which can correspond with complex environment and topological form. In the design process adapted to fold theory, rhizome analysis accepts the complexity of environment and stratification strategy embraces the possibility of accidental use. As a result, the designed park carries a monadic image and produces an ambiguous space. Lastly, smooth space makes topological space unlike Euclid geometry and is free space comosed by the user themselves. Transporting the idea of fold into environmental design could be an alterative way for indeterminate and flexible design to accept new identity of place. Therefore, this study accepts the concept of incidental morphogenesis to make space based on the complexity of environment. The designed space based on the idea of fold searches to create free event space determined by user rather than designated by designer.

• 한국인구학
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• 제24권1호
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• pp.41-65
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• 2001

This study aims a comparative analysis of social stratification in the Great Seoul area using two types of population. One type of population is a resident population(常住人口), and the other is a daytime population주간인구(晝間人口). In most demographic studies, only resident population have been considered. There has been less attention to daytime population. However, a resident population have a character of night population야간인구(夜間人口). In fact, most people move and work in the areas where they do not live in everyday life in the contemporary period, which indicates that the concept of a daytime population is more significant than that of a resident population. This study reveals that a number of people, on the one hand. come together to the downtown area to work or study while they live in other areas. On the other hand, resident population in downtown area do not move so much. When we analyze the social stratification structure of the Great Seoul area using a resident population, we find that the resident population of downtown area consist of those of low social status. On the contrary, the daytime population of downtown area in Seoul consist of those of high social status. This means that most people of high social status live in the southern area of Seoul or outside Seoul, but make a living in downtown area in everyday life. From this study, we find that the concept of a daytime population is as important as that of a resident population. The more residence becomes separate from work place, the more the significance of the concept of a daytime population grows in making policy as wall as in demographic studies. This study implies that we need to pay more attention to the concept of daytime population in demographic and sociological Studies.

• 한국수산과학회지
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• 제31권3호
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• pp.437-446
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• 1998

제주도 북부연안역의 해황 및 조석전선의 변동특성을 파악하기 위하여 $1991\~1993$년까지 CTD에 의한 해황조사를 실시하고, 조석전선의 위치 Energy를 계산하여 분석하였다. 1 제주도 북부연안역의 국소지역에서는 해협의 중앙부 및 주변해역보다 상대적으로 저온v고염한 해수가 자주 출현하여 주변수 사이에는 국지적 수온 $\cdot$염분전선을 형성하는 경우가 많았다. 이와 같은 현상은 제주도 북부연안역에서의 용승 혹은 조석전선에 의해 발생하는 것이며, 위치는 지형이 다소 돌출된 곳과 수심이나 해저지형이 해$\cdot$조류의 흐름에 영향을 줄 수 있는 곳으로 제주도 서쪽의 차귀도와 비양도 연안, 애월북부 연안역과 제주시 부근 및 함덕 북부해역, 제주도 동쪽의 우도 북부와 행원부근해역에서 자주 출현하고 있다. 2. 제주해협내에는 성질이 서로 다른 이질수괴가 마주치고 있으므로 안장형 (Saddle)의 수온$\cdot$염분분포가 거의 매월 출현하여 안장형의 중앙역이나 이질수괴간의 경계역에서 수온$\cdot$염분전선이 형성된다. 3. 제주도 연안역을 대상으로 계산된 조석전선의 성층계수 (stratification parameter-V ($J/m^3$) )는 6월이 $8.4\~209.8\;J/m^3$의 범위이며, 8월이 $201.9\~634.9\;J/m^3$. 9월 $0.18\~680\;J/m^3$, 10월 $2.7\~462\;J/m^3$의 분포범위로 제주도 북부연안역 약 $1\~2$해리 범위내의 수심변화가 심한 해역에서 위치에너지 10$J/m^3$정도의 등치선이 출현해 조석전선이 형성되고 있으며 이는 대략 50m등심선과 일치했다.

• 천문학회지
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• 제49권1호
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• pp.1-8
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• 2016

The aim of this study is to describe the physical processes taking place in the solar photosphere. Based on 3D hydrodynamic simulations including a detailed radiation transfer scheme, we investigate thermodynamic structures and radiation fields in solar surface convection. As a starting model, the initial stratification in the outer envelope calculated using the solar calibrations in the context of the standard stellar theory. When the numerical fluid becomes thermally relaxed, the thermodynamic structure of the steady-state turbulent flow was explicitly collected. Particularly, a non-grey radiative transfer incorporating the opacity distribution function was considered in our calculations. In addition, we evaluate the classical approximations that are usually adopted in the onedimensional stellar structure models. We numerically reconfirm that radiation fields are well represented by the asymptotic characteristics of the Eddington approximation (the diffusion limit and the streaming limit). However, this classical approximation underestimates radiation energy in the shallow layers near the surface, which implies that a reliable treatment of the non-grey line opacities is crucial for the accurate description of the photospheric convection phenomenon.

• 한국조사연구학회지:조사연구
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• 제5권2호
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• pp.3-30
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• 2004

출구조사에서 투표소 표집방법으로는 지금까지 판단표집의 일종인 대표구 추출방법과 층화 대표구의 두 가지 방법이 주로 사용되고 있지만 아직 어느 방법이 더 효과적인가에 대해서 체계적인 연구가 이어지지 않았다. 본 연구는 지금까지 논의되어 온 네가지 투표소 추출방법 중에서 어느 방법을 사용할 때 오차가 가장 적을것인지 그리고 어느 정도의 투표소를 추출하는 것이 적절한지에 대해서 분석해 보았다. 17대 총선에서 1위와 2위간의 격차가 8% 이내로 경합을 보인 50개 선거구를 대상으로 투표소 추출방법과 추출규모를 달리했을 때 예측오차가 어떻게 달라지는가를 분석한 결과, 과거 선거결과를 토대로 투표소를 정치성향별로 정렬한 후 체계적으로 추출하는 '종단적 체계적 추출방법'이 지금까지 주로 사용되었던 대표구 혹은 층화후 대표구 방법보다 우수한 것으로 나타났다. 그리고 표집규모는 9개에서 11개 정도의 투표소 추출이 적절한 것으로 나타났다.