• 도시과학
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• 제9권2호
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• pp.21-30
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• 2020

The purpose of this study is to present a plan to distinguish 229 local governments nationwide by taking into account various characteristics such as population, employment, housing, and industry of the region for customized urban policies in the era of metropolitan areas. The National Statistical Portal (KOSIS) collected and standardized data related to population, housing, industry, and finance by region from 2000 to 2015 for the classification of regional types necessary for customized urban policies, and this was used to classify them into regional types that considered population, employment, housing and industry. The summary of the analysis results is as follows. First, as a result of the regional type classification, 10 key employment sites (4.4%), 5 employment centers (2.2%), 38 residential centers (16.6%), 20 growth areas (8.7%), 26 industrial cities (11.4%), 35 low-fertile farming and fishing villages (15.3%) and 95 stagnant areas (41.5%). Second, the Seoul metropolitan area is the most diverse type of metropolitan area in the country, with most of its core employment sites inside Seoul, residential centers inside and outside Seoul, and growth areas in the southeastern part of the country (Busan, Ulsan, and Gyeongsangnam-do) are mixed with industrial and growth areas centered around Busan, Ulsan and surrounding areas, while the rest of the local governments are found to be low-fertile farming villages or stagnant areas. Daegu (Daegu, Gyeongbuk) is an industrial city in Daegu, and the rest of the local governments are either low-density farming and fishing villages or stagnant areas. The Honam region (Gwangju and Jeolla) was found to be a low-mill farming and fishing village or stagnant area except for Gwangju, while the Chungcheong region (Daejeon, Sejong, and Chungcheong) was seen as a growth area with areas adjacent to Daejeon, Sejong, and the Seoul metropolitan area, and some industrial cities were included. Finally, the Gangwon area was mostly classified as low-density farming and fishing villages and stagnant areas.

• 한국해양공학회지
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• 제6권2호
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• pp.143-150
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• 1992

Numerical simulation is made of a stably stratified salt-water solution due to lateral heating in an equilateral trapezoidal enclosure using boundary-fitted coordinate in grid generation. Results show four types of the global fluid pattern depending on the buoyancy ratio in the enclosure, i.e., unicell flow pattern for the low buoyancy ratio, layered flow pattern for the increasing buoyancy ratio, layered flow pattern with stagnant zone for the relatively high buoyancy ratio and stagnant flow pattern for the much higher buoyancy ratio.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.295-302
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• 2009

The flow in the draft tube cone of Francis turbines operated at partial discharge is a complex hydrodynamic phenomenon where an incoming steady axisymmetric swirling flow evolves into a three-dimensional unsteady flow field with precessing helical vortex (also called vortex rope) and associated pressure fluctuations. The paper addresses the following fundamental question: is it possible to compute the circumferentially averaged flow field induced by the precessing vortex rope by using an axisymmetric turbulent swirling flow model? In other words, instead of averaging the measured or computed 3D velocity and pressure fields we would like to solve directly the circumferentially averaged governing equations. As a result, one could use a 2D axi-symmetric model instead of the full 3D flow simulation, with huge savings in both computing time and resources. In order to answer this question we first compute the axisymmetric turbulent swirling flow using available solvers by introducing a stagnant region model (SRM), essentially enforcing a unidirectional circumferentially averaged meridian flow as suggested by the experimental data. Numerical results obtained with both models are compared against measured axial and circumferential velocity profiles, as well as for the vortex rope location. Although the circumferentially averaged flow field cannot capture the unsteadiness of the 3D flow, it can be reliably used for further stability analysis, as well as for assessing and optimizing various techniques to stabilize the swirling flow. In particular, the methodology presented and validated in this paper is particularly useful in optimizing the blade design in order to reduce the stagnant region extent, thus mitigating the vortex rope and expending the operating range for Francis turbines.

• 한국수자원학회논문집
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• 제32권2호
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• pp.153-162
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• 1999

본 연구에서는 정지수체에서 다공확산관을 통해 방류된 연직다중의 혼합 및 희석 특성에 대해 규명하였다. 3차원 실험수조에서 실험을 통해 밝혀진 결과는 다음과 같다. 우선 다공확산관의 병합과정을 살펴보면 흐름의 안정조건에 따라 병합거리가 다소 차이가 있기는 하지만 {{{{ { z}_{ } }}}}/{{{{ {l}_{ } }}}}가 대략 3인 지점부터 병합이 시작되어 그 이후에는 평면부력？의 거동에 서서히 가까워짐을 알 수 있다. 최소희석률에 대해 분석해 본 결과, 방류운동량이 지배적인 영역, 천이영역, 그리고 부력이 지배적인 부력류영역으로 나누어 희석률 특성을 표현할 수 있음을 알 수 있었다. 본 연구의 실험결과 다공확산관의 경우 부력류영역의 희석률 상수가 평면확산관에 비해 15% 더 높게 나왔다. 그 이유는 다공확산관의 경우 병합 이전에는 개별의 경계면에서 주변수의 포획이 발생하여 희석이 증대되기 때문이다.

• 한국환경과학회지
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• 제24권6호
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• pp.731-741
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• 2015

The objectives of study were to evaluate fish species compositions of trophic guilds and tolerance guilds and apply ecological fish assessment (EFA) models to Bekjae Weir, Keum-River Watershed. The EFA models were Stream Index of Biological Integrity (SIBI) used frequently for running water and Lentic Ecosystem Health Assessment (LEHA) used for assessments of stagnant water. The region of Bekjae Weir as a "four major river project" was originally a lotic ecosystem before the weir construction (2010, $B_{WC}$) but became more like lentic-lotic hybrid system after the construction (2011, $A_{WC}$). In the analysis of species composition and ecological bioindicator (fish), fish species with a preference of running water showed significant decreases (p < 0.05), whereas the species with a preference of stagnant water showed significant increases (p < 0.05). After the weir construction, relative abundances of tolerant species increased, and the proportion of insectivores decreased. This phenomenon indicated the changes of biotic compositions in the system by the weir construction. Applications of SIBI and LEHA models to the system showed that the two model values decreased at the same time after the weir construction ($A_{WC}$), and the region became more like lentic-lotic hybrid system, indicating the degradation of ecosystem health. The model values of SIBI were 19 and 16, respectively, in the BWC and AWC, and the health conditions were both "C-rank". In the mean time, the LEHA model analysis showed that the values was 28 in the BWC and 24 in the AWC, thus the health was turned to be "B-Rank" in the BWC and "C-Rank" in the AWC. indicating a degradation of ecological heath after the weir construction.

• 설비공학논문집
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• 제15권12호
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• pp.1078-1087
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• 2003

Kimchi refrigerator is a household electric appliance developed with the wholly domestic technology for maturing and keeping kimchi. However, the principle of keeping is not yet revealed obviously. This numerical study has been conducted to investigate the flow and heat transfer characteristics in a kimchi refrigerator. The effects of arrangement variation of a evaporation tube are examined. Also, the heat transfer characteristics through the insulation material are discussed in detail. The flow and temperature field was simulated using the commercial code of CFX-5.3. A natural convection flow is formed through about 5/6 region from the bottom within the keeping space and accordingly, the 90% region of kimchi containers satisfies the temperature requirement with 0$\pm$0.5$^{\circ}C$. The stagnant flow exists in the upper 1/6 region of the keeping space and accordingly, the stratified high temperature distributions appear in the upper region of kimchi containers. The upward shift of the start location of a evaporation tube improves the temperature concentration toward $0^{\circ}C$ but the pitch variation is of no effect. The heat fluxes on the insulation surfaces show two-dimensional distributions with being higher toward the center. Through the variation of insulation thickness, 3.5% saving of insulation material is obtained under the same heat transfer rate.

• 한국콘텐츠학회논문지
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• 제22권8호
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• pp.367-376
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• 2022

본 연구는 도시재생사업으로 인한 지역 활성화로 영도구 도시재생사업 대상지의 상권변화를 살펴보고자 한다. 도시쇠퇴로 인한 지역 침체의 심화는 도심 상업 기능의 쇠퇴를 가속할 수 있기에, 경제활동이 저하된 원도심을 활성화하기 위한 상권 활력 증진 측면에서 이해할 수 있다. 도시재생사업 대상지의 상권변화 분석을 위해, 상업 활성화를 살펴보는 상점 밀도, 업종 다양성을 지표로 산출하여 비교 분석하였다. 또한, 인구의 유입과 집객에 영향을 미치는 음식점업과 카페 비율을 통해 대상지 상권의 동태적 변화를 확인하였다. 연구 결과 영도구 내 도시재생사업 대상지에서 상점 밀도와 업종 다양성이 증가하는 추세를 보였다. 음식점업과 카페 비율의 경우 큰 차이를 발견하기는 어려우나, 영선2동(흰여울문화마을)의 경우 상업적 변화가 상대적으로 크게 나타나는 것으로 확인하였다. 본 연구는 영도구 도시재생사업 대상지의 상업적 변화를 정량적으로 평가 분석하였다는 데 그 의의가 있다.

• 한국연소학회지
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• 제22권1호
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• pp.32-38
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• 2017

This paper shows the dynamics of the Burke-Schumann flame. To show flame dynamics, this paper measures the flame surface and heat release rate. The flame shape is divided into three types with forcing frequencies. When the forcing frequency is lower than 120 Hz, the upper region of flame is cut. The flame is stagnant with 220 to 280 Hz forcing frequencies. The rest conditions of forcing frequencies make the connected wave shape of flame. The heat release rate is expressed by the flame transfer function. The gain of the flame transfer function is similar with the oscillation magnitude of the flame area except for flame cutting conditions. The flame is cut because the fuel is not supplied to upper flame region.

• 한국지구과학회지
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• 제43권1호
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• pp.77-90
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• 2022

최근 동아시아 지역에서 인위적 배출량의 감소에도 불구하고, 봄철에 한국에서는 잦은 연무 사례가 발생하고 있다. 북동 태평양에서 자주 발생하는 대기 블로킹은 지구 규모 대기 변동과 동아시아 지역의 서풍 기류를 정체시키기도 한다. 2019년 3월 동아시아 지역의 온난하고 정체적인 종관 기상 특성이 알래스카 대기 블로킹이 발생한 6-7일 후에 일어나고 있었다. 특히, 2019년 3월 18-24일에 발생한 알래스카 대기 블로킹은 3월 25-28일 동안 한국에서 일평균 미세먼지(particulate matter; PM₁₀) 질량농도가 50 ㎍ m^-3을 넘는 고농도 PM₁₀ 연무 사례가 발생하는 데 영향을 미치고 있었다. 한편, WRF-Chem 모델을 활용하여 한국의 고농도 PM₁₀ 연무 사례에 대한 인위적 배출의 장거리 수송 기여도는 30-40%를 나타내고 있었다. PM₁₀ 에어로졸 구성 성분인 황산염, 질산염, 암모늄, 블랙 카본, 유기 탄소, 기타 무기물의 장거리 수송 기여도는 각각 10-15, 20-25, 5-10, 5-10, 5-10, 15-20%를 나타내었다. 질소 산화물이 온난하고 정체적인 대기에서 암모늄과의 광화학 반응으로 형성된 질산암모늄은 한국의 고농도 PM₁₀ 연무 사례에 대한 장거리 수송 기여도가 PM₁₀ 에어로졸 중 가장 큰 비중을 나타내고 있었다.

• 한국안전학회지
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• 제10권1호
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• pp.64-73
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• 1995

A preliminary study is performed in order to design an effective ventilation equipment for the control of possible pollutants in a workshop. To this end, the Patankar's SIMPLE methodology is used to investigate the flow characteristics of the contaminated thermal deflected jet which is encounted often in practical hood system. SIMPLE-Consistent algorithm is employed for the pressure-velocity coupling appeared in momentum equations. A two equation, k-$\varepsilon$ model is used for Reynolds stresses. The prediction data is compared well against the experimental results by Chang(1989). Considering the control of the wake due to its high turbulence together with the stagnant feature has been investigated in term of major parameters such as temperature and magnitude of the discharge velocity. Detailed discussions are made to reduce the size of the wake region which give rise to pollutant concentration stratification.