• Proceedings of the KSME Conference
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• 2002.08a
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• pp.443-446
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• 2002

Wake downstream of an object in the stratified flow has been of long-standing interest in fluid dynamics because of its similarity to geophysical flow over topographical terrains and more recently, concerns about the wake left behind a body moving through the ocean thermocline. Decades of studies of geophysical flow have unveiled that the flow downstream of obstacles in stratified flow consists of attached wake and strong internal waves, or separated, fluctuating wake and persistent late wakes, all of which depend on the flow conditions. Among unique and interesting characteristics of the stratified flow past obstacles is the generation of coherent vortex structure in the late wake far downstream of the object. Without the density stratification, the flow field downstream becomes undisturbed after relatively fast diminishing of the near wake. However, no matter how small the stratification is, the flow field downstream self-develops coherent vortex structures even after diminishing of the near wake. This paper present a computational approach to simulate the generation mechanism of the coherent vortex and analysis of the vortical structure.

• Korean Journal of Social Welfare
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• v.68 no.2
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• pp.27-51
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• 2016

This paper is about the NOOMP(Not Out of My Pocket) phenomenon, the inconsistent welfare attitude for an expansion of welfare system and increase of financial resources. By analyzing the scale and influential factors of the NOOMP to the main welfare programs, focusing on the class, gender, and age group, the paper tries to investigate the relationship between the NOOMP and the inherent stratification structure of each programs. This paper uses the Additional Survey of Welfare Attitude in 2013 Korea Welfare Panel Survey. As a result of analysis, low level of NOOMP phenomenon has been observed in welfare programs for whole society members such as health policies, pension, employment policies, compared to those of targeted programs for the poor, aged, or disabled. In addition, high probability of each group of 'low incomer', 'female', and '20s or less'to the NOOMP phenomenon has been appeared, therefore, high relevance of the NOOMP and the stratification structure of welfare programs have been confirmed. These results indicate that the transition to the universal welfare programs and the improvement of welfare programs for more equal structure are needed to reduce the NOOMP phenomenon.

• Korean Journal of Environment and Ecology
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• v.12 no.3
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• pp.224-235
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• 1998

Floristic composition of Kyongpo Provincial Park area were investigated from June, 1997 to June, 1998. Vascular plants were composed of 87 families, 240 genera, 281 species, 51 varieties, and 7 formae, totaling 339 taxa. Among them, three taxa such as Vicia venosissima, Paulownia coreana, Aster ciliosa were Korean endemic species. Pteridophyta calculation(Pte-Q) was investigated, 0.61. A naturalized plants were 12 species, corresponding to 5.5％ of totaling 218 species in South Korea by Lee and Chon(1995). The dominant species could be represented by Pinus thunbergii and P. densiflora. And its stratification structure were composed as follows : Pinus thunbergii and P. densiflora in tree and subtree layer, Pinus thunbergii, P. densiflora. and Prunus sargentii in shrub layer, and Spodiopogon sibiricus, Festuca ovina, Melandryum firmum, Artemisia princeps, Rumex acetosella, Commelina communis and Plantago depressa in herb layer, respectively. But stratification structure of dominant species appeared very unstable in subtree and shrub layer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.3
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• pp.303-309
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• 2004

In order to improve thermal comfort in the Rotunda, which is high and wide visiting space of the new national museum of Korea, eight ventilating fans were installed near the ceiling of Rotunda. It has been analyzed thermal comfort of Rotunda with/without ventilating fans by numerical simulation. To evaluate thermal comfort of the Rotunda, well-known indices, PMV and PPD were introduced. The results of present investigation show that temperature distribution of the case with fans is closer to target temperature than the case with-out fans at the breathing zone. In the case without fans, thermal stratification with 16$^{\circ}C$ of temperature difference occurs along the height of the Rotunda which makes the thermal environment worse and the PPD values reach up to 50% in the 6th floor connection passage. In the case with fans, however, the vertical temperature difference were reduced to 9$^{\circ}C$ and the PPD values were lower below 20%. Consequently, the ventilating fans adopted on this study are effectively used for improving the thermal comfort in large space structure with thermal stratification.

• The Korean Journal of Petroleum Geology
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• v.4 no.1_2 s.5
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• pp.12-19
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• 1996

Directional sedimentary structures (channel structure, cross stratification, and current ripple) were observed in fine to gravelly ye.y coarse sandstones of the Cretaceous Mayans Group (lljig, Hupyeongdong, and Jeomgok formations) in the northeastern part of Euiseong subbasin of Kyongsang basin, Southeast Korea. Large and small scale channel structures are common in all formations. Trough cross-stratification and channel structure frequently occur in the lljig formation (proximal fluvial deposit), whereas planar cross- stratification, cross lamination, and current ripple occur abundantly in the Hupyeongdong and Jeomgok formations (distal braided fluvial to marginal lacustrine deposits). The paleocurrent directions inferred from a statistical analysis of total 43 directional sedimentary structures show a mean azimuth of $290^{\circ}C$ with a standard deviation of $\pm68$. It suggests that the main flow of the paleocurrents moved toward the WNW direction and the source area of the sediments would be located somewhere in the ESE direction beyond the study area.

• Journal of the Korean Society of Marine Environment & Safety
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• v.5 no.2
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• pp.57-65
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• 1999

The in situ observations and the seawater analyses were conducted at all seasons from July 1996 to April 1999 for the purpose of describing the characteristics of seasonal variations of water quality in Mokpo harbour, Korea. Vertical stratification started to be formed in water column in spring, developed in summer and disappeared in fall. In summer, vertical density distribution of water column was found to be in stable structure with lower temperature and higher salinity of bottom water, and the vertical mixing of water between surface and bottom layers was restricted. In winter, however, surface water was found to be similar to bottom water in temperature and salinity, and water column was in unstable structure and in well-mixed condition between surface and bottom waters. The saturation percentage of dissolved oxygen(DO) in bottom water of inner part of Mokpo harbour at all seasons was shown to be decreased to the third grade or under the third grade of Korean standards of seawater quality. In particular, dissolved oxygen was oversaturated in surface water and undersaturated in bottom water in summer, due to stratification and organic pollution. The difference of DO concentration between surface and bottom waters was found to be greater in spring and summer than in fall and winter, due to stratification and photosynthesis of phytoplankton. The concentrations of chemical oxygen demand(COD) over the entire waters of Mokpo harbour were found to fluctuate from below the third grade to the first grade of Korean standards through all seasons and COD concentrations of same seasons were shown to be different year after year. In particular, in view of COD, the annual average seawater quality of Mokpo harbour was evaluated to be in third grade of Korean standards, due to organic pollution. The average COD of surface water was greater than that of bottom water in spring and summer, due to the autochthonous COD caused by production of phytoplankton in surface waters, while the average COD of surface water was similar to that of bottom water in fall and winter, due to the vertical mixing of water between surface and bottom layers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.6
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• pp.419-423
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• 2015

The flowing caused by artificial upwelling structure occurs ascending water flowing and vortex of rear side. In this moment, plentiful nutrient in the bottom water moves to the surface of the water and makes those plankton and fishing ecology promoted so that the fishing productivity can be enhanced. In this study, the changes of the upwelling flowing is included in consideration of the conditions of stratification by using CFD. In the conclusion, the closer upwelling effect is from the artificial upwelling structure, the better effectiveness comes out. Regardless of the conditions of stratification, only the upwelling feature from the bottom to the surface was shown up. But considering the conditions of stratification, the repeated flowing feature between upwelling and downwelling was verified.

• Journal of Ocean Engineering and Technology
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• v.21 no.4
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• pp.21-27
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• 2007

The multiplication equipment of marine products with artificial upwelling structures could be useful in the fishing grounds near coastal areas. Artificial upwelling structures could move the inorganic nutrients from the bottom to the surface. Artificial upwelling structures have been used to improve the productivity of fishing grounds. Until now, research on artificial upwelling structures has been related to the distribution of the upwelling region, upwelling structures, and the marine environment. However, little work on the optimum design of the rubber-mound artificial upwelling structures has been done to increase the efficiency of drawing up the inorganic nutrients. This study investigated the optimum cross-section of rubber-mound artificial upwelling structures by means of hydraulic experiments. The hydraulic experiments include the falling test of rubber. Based on the results of the falling test, the relationship between the length of the rubber mound and water velocity, and the relationship between the shape of the rubber and the stratification parameter were established. In addition, the effect of the void ratio of various artificial structures on the stratification parameter was studied. From the experiment, it was found that upwelling could be enhanced when the ratio of structure height to water depth was 0.3 and stratification parameter was 3.0. The upwelling was not improved when the void ratio exceeded 0.43. The optimum size of rubber mounds was determined when the incident velocity was influenced by the mean horizontal length rather than size of block.

• Korea journal of population studies
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• v.24 no.1
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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.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.922-934
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• 2009

The transport of contaminants and spatial variation in a deep reservoir are certainly governed by the thermal structure of the reservoir. There has been continuous efforts to utilize three-dimensional (3D) hydrodynamic and water quality models for supporting reservoir management, but the efforts to validate the models performance using extensive field data were rare. The study was aimed to evaluate a 3D hydrodynamic model, ELCOM, in Daecheong Reservoir for simulating heat fluxes and stratification processes under hydrological years of 2001, 2006, 2008, and to assess the impact of internal wave on the reservoir mixing. The model showed satisfactory performance in simulating the water temperature profiles: the absolute mean errors at R3 (Hoenam) and R4 (Dam) sites were in the range of $1.38{\sim}1.682^{\circ}C$. The evaporative and sensible heat losses through the reservoir surface were maximum during August and January, respectively. The net heat flux ($H_n$) was positive from February to September, while the stratification formed from May and continued until September. Instant vertical mixing was observed in the reservoir during strong wind events at R4, and the model reasonably reproduced the mixing events. A digital low-pass filter and zero crossing method was used to evaluate the potential impact of wind-driven internal wave on the reservoir mixing. The results indicated that most of the wind events occurred in 2001, 2006, 2008 were not enough to develop persistent internal wave and effective mixing in the reservoir. ELCOM is a suitable 3D model for supporting water quality management of the deep and stratified reservoirs.