• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.3156-3161
• /
• 2007

In the field of yarn dyeing, the most generally employed method is a type of package dyeing which uses a package of cheeses stacked on a spindle made of a perforated tube. In order to understand the process of level dyeing, it is essential to perform a study of the porous flow through the spindle for the cheese dyeing method. In this paper, the axisymmetric, incompressible, Navier-Stokes equations are solved for several spindle configurations using a fully implicit finite volume scheme. For investigating the flow patterns through the spindle, porous diameter and porosity is varied in the present study. The computational results show that the total pressure loss depends only on the velocity of inflow regardless of porous diameter and porosity and a large percentage of the mass flow rate through the spindle is discharged at the upside of the spindle. Therefore, it is required to design a new spindle to obtain the level dyeing.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.456-459
• /
• 2008

In the field of yarn dyeing, the most generally employed method is a type of package dyeing which uses a package cheesesstacked on a spindle made of a perforated tube. Spindles up to now, have been designed without considering the characteristics of dyeing liquid, focusing only on the geometric configuration which cause many problems such as lack of level dyeing. To improve the level dyeing and find the appropriate spindle configuration for the most effective dyeing process, this study examines the spindle flow-field in detail, using a computational method. Flow characteristics inside the spindle have been investigated with varying in porosity, porous diameter and the velocity of the flow. The results show that the total pressure of the flow through the spindle is used to overcome body force. The characteristics of the flow from the porous spindle could also be observed. Based on the results from this study, an effective spindle configuration for level-dyeing has been proposed.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2003년도 총회 및 춘계학술발표회
• /
• pp.63-66
• /
• 2003

This study applied a hydrogeological field survey and isotope investigation to identify source locations and delineate pathways of groundwater contamination by nitrogen compounds. The infiltration and recharge processes were analyzed with groundwater-level fluctuation data and oxygen-hydrogen stable isotope data. The groundwater flow pattern was investigated through groundwater flow modeling and spatial and temporal variation of oxygen isotope data. Based on the flow analysis and nitrogen isotope data, source types of nitrate contamination in groundwater are identified. Groundwater recharge largely occurs in spring and summer due to precipitation or irrigation water in rice fields. Based on oxygen isotope data and cross-correlation between precipitation and groundwater level changes, groundwater recharge was found to be mainly caused by irrigation in spring and by precipitation at other times. The groundwater flow velocity calculated by a time series of spatial correlations, 231 m/yr, is in good accordance with the linear velocity estimated from hydrogeologic data. Nitrate contamination sources are natural and fertilized soils as non-point sources, and septic and animal wastes as point sources. Seasonal loading and spatial distribution of nitrate sources are estimated by using oxygen and nitrogen isotopic data.

• Journal of Mechanical Science and Technology
• /
• 제19권6호
• /
• pp.1347-1357
• /
• 2005

Effects of combustor-level high free-stream turbulence on the blade-surface heat/mass transfer have been investigated in the three-dimensional flow region near the endwall within a high-turning turbine rotor cascade passage. Free-stream turbulence intensity and integral length scale in the high turbulence case are 14.7 percents and 80 mm, respectively. The result shows that there is no considerable discrepancy in the blade heat/mass transfer near the endwall between the low and high turbulence cases. As departing from the endwall, however, the deviation between the two cases becomes larger, particularly in the region where flow separation and re-attachment occur. Under the high turbulence, flow disturbances such as boundary-layer separation and re-attachment seem to be suppressed, which makes the blade heat/mass transfer more uniform. Moreover, there are some evidences that endwall vortices tend to be weakened under the high turbulence.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.1891-1896
• /
• 2003

The bubble motion during nucleate boiling in a microchannel is investigated numerically. The liquid-vapor interface is tracked by a level set method which is modified to include the effects of phase change at the interface and contact angle at the wall. The computations are made for various channel sizes, liquid flow rates, and contact angles. Based on the numerical results, the bubble growth pattern and its effect on the flow and heat transfer are discussed.

• 재무관리논총
• /
• 제10권1호
• /
• pp.249-269
• /
• 2004

Free cash flow is known as a typical type of agency conflict between managers and shareholders in a firm. The insurance industry, which is not growing, is particularly susceptible to such excessive cash flow. We herein investigate the effects of stock ownership plans on reducing agency conflicts. We adopt undistributed cash flow to proxy free cash flow, and size, default risk, group membership, leverage, investment opportunity, and stock options are selected as explanatory variables. We find that stock option plans are effective(at a 10% level) in reducing free cash flow.

• 한국콘텐츠학회논문지
• /
• 제17권2호
• /
• pp.535-542
• /
• 2017

우리나라는 갈수기와 홍수기의 유량차이가 극심하여 수자원 관리에 대한 중요성이 대두되고 있는 실정이다. 하천의 특성을 파악하기 위해 정확한 유량을 산정해야 한다. 유량을 산정하기 위해서는 유량을 구하고자 하는 하도의 단면적을 산정하고, 해당 단면에서의 유속을 측정해 연속방정식을 이용하여 유량을 산출해야 한다. 보편적으로 수위-유량관계식으로부터 유량을 산정하지만, 이 경우에는 동일한 수심 동일한 유량만을 산출할 수밖에 없다는 단점이 있다. 그래서 본 연구에서는 낙동강 교량 강창교 지점의 성서관측소의 수심과 ADVM를 이용하여 측정된 수심을 이용한 수면경사와 ADVM지점의 수심을 이용하여 유량산정식을 개발하였다. 자연하천의 흐름은 정류나 등류가 아닌 부정류 흐름이기 때문에 하상경사가 아닌 수면경사를 반영하고자 본 연구에서는 두 지점의 측정된 수심으로부터 손쉽게 유량을 산정하는 방법을 제안하였다.

• 한국지리정보학회지
• /
• 제9권2호
• /
• pp.115-126
• /
• 2006

본 연구의 목적은 도시지역에서의 침수시뮬레이션에 필요한 도시침수해석모형을 개발하고, 이를 GIS(geographic information system)와 연계 운영할 수 있는 시스템을 구축함에 있다. 이를 위해서 미국환경보호청(EPA)의 SWMM(storm water management model)모형을 이용하여 도시지역 배수 시스템에서의 도시유역 유출량 및 월류량을 계산하고, 지표면으로 월류된 유량에 대해 GIS를 이용한 침수해석을 실시하였다. GIS를 이용한 침수해석 모형으로는 Level-Pool 침수해석모형과 DEM 기반 침수해석모형을 개발하고 도시지역에서의 시간별 침수위 및 침수범위 등을 계산 할 수 있게 하였다. 도시배수시스템과 지표침수해석모형을 GIS를 이용하여 통합시킨 도시침수해석 모형을 통해서 배수 시설에서의 유출량 예측과 지표면에서의 월류유량의 전파특성을 예측할 수 있도록 구성하였다. 본 연구결과는 도시지역에서의 배수 시설의 설계 및 운영의 문제, 침수 예상도의 작성 및 각종 홍수 예경보 수립에 기여할 수 있을 것으로 판단된다.

• 한국환경과학회지
• /
• 제17권7호
• /
• pp.743-753
• /
• 2008

Gwangyang Bay is often severely confronted by photochemical pollutants due to its location and dense emissions. It is located in a basin on the south coast of the Korean peninsula and is crossed by a remarkable cluster of hills and mountains of a small horizontal scale that forms a channel. Clearly, the air flow field has a great influence on the dispersion of air pollutants. The characteristics of the wind flow patterns have an important effect on the dispersion of pollutants emitted. In these situations, the distribution of the ozone concentration is extremely complicated because of the superposition of circulations of the air flow fields, especially in complex coastal region. In this study, we examined the distribution of the high level ozone on Gwangyang Bay particularly during the episode day (for 5 years). Among these days, A high level ozone was induced by the development of a sea/land breeze local circulation system, as well as by an anabatic/catabatic flow from the mountains and valley with weakening of the synoptic wind. High level ozone distribution pattern(6 types) on Gwangyang bay is analyzed and the comparison of each pattern reveals substantial localized differences in intensity and distribution of ozone concentration from the site coherence and UPA analysis of ozone concentration. The observed VOC concentration had much difference in concentrations and daily variations between Jungdong and Samil.

• 터널과지하공간
• /
• 제27권4호
• /
• pp.205-216
• /
• 2017

지하수위 변동은 석회석 폐광산에서 발생하는 지반침하의 주된 요인이다. 본 연구에서는 지하수로 포화된 석회석 채굴공동에서 발생하는 지하수 유동을 자연상태와 골재 충전, 임시배수로 구분하여 지반 안정성에 미칠 영향을 3차원 지하수 유동 해석을 통해 평가하였다. 해석 결과 골재 충전시 지반 및 소류지의 지하수위가 상승하였지만 강우나 소류지 농업용수 사용으로 발생하는 수위차 보다 작고 유속 또한 자연상태의 유속과 유사하게 나타났다. 임시배수시에는 지반 및 소류지의 지하수위가 급격하게 하강하고 공동 내 유속이 최대 25배 이상 증가하는 것으로 나타나 지반침하 위험성이 증가하는 것으로 나타났다.