• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.130-136
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• 2004

In the present study, prey preference of juvenile fishes was examined using an experimental approach. Zooplankton composition, as a prey of the fish, was evaluated by taking into account the species as well as body size of juveniles in the aquarium. The predation of juvenile fishes is known to be an important factor in changes of zooplankton communities. In some previous studies at the regulated Nakdong River, the collapse of large cladcoerans and an increase in the rotifer population by selective predation during spring and summer were observed. This study focused on the predation of juvenile fishes such as Hyporhamphus sajori, Rhinogobius brunneus, and Opsariichtys uncirostris amurensis on zooplankton community structure in mesocosm scale experiments. These fishes selected the cladoceran Moina micrura with highest individual preference value (Manly/Chesson index)among zooplankton prey in the experimental aquarium. When the size-selective prey preferences of the juvenile fish were compared, both small (body size <2 cm) and large (body size >2cm) juveniles of O. uncirostris positively selected M. micrura. In the outdoor experimental tanks, juvenile fishes consumed the cladoceran M. micrura, resulting in an high abundance of the rotifer, Polyarthra spp. The results suggest that juvenile fish predation may play an important role in regulating the zooplankton community structure by reducing the cladoceran density and increase of rotifers in the Nakdong River during spring and summer.

• Journal of Korean Society of Transportation
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• v.25 no.4
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• pp.79-87
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• 2007

The interchanges of urban freeways have many problems with traffic operation due to high off-ramp flows and frequent congestion at adjacent intersections. The flow exiting from off-ramps is affected by the operational status and traffic volume conditions of the nearest signalized intersection. As a result, off-ramp flow cannot exit and the queue backs up the freeway mainline when queues from the signalized intersection form up to the junction of the off-ramp and street. The spacing between an off-ramp and an adjacent intersection is likely to determine the traffic conditions at the adjacent intersection. However, the current design guidelines do not consider such a factor. This study is to develop a model calculating the spacing between off-ramps and adjacent intersections considering the signal, traffic, and road conditions. The variables affecting the model in this study are effective green time (g/C), volume-capacity ratio (v/c), the number of lanes, and off-ramp volume. Various scenarios are designed to represent the effects of the variables and the road networks are constructed using VISSIM, which is a common traffic micro-simulation software package. The queue length is derived from VISSIM and this length is considered as the recommended spacing between the off-ramp and the adjacent intersection. Through the simulation analysis, regression models are developed to calculate the queue length reflecting the various conditions such as signals, traffic, and road configurations. The developed model can be used to create road design guidelines to determine the location of off-ramps in the planning stage.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.315-326
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• 2021

The clear-water phase (CWP) is a notable limnological phenomenon in freshwater systems caused by predatory interactions between large filter-feeding zooplankton and phytoplankton. However, the mechanisms and factors that influence the extent of CWP, particularly in complex water systems with both fluvial and lacustrine characteristics, remain poorly understood. The present study evaluated CWP occurrence patterns at different sites in a large reservoir located in a temperate monsoon region (Lake Paldang, Korea); the relationships among factors associated with CWP occurrence, such as transparency, zooplankton diversity, and chlorophyll a concentration were investigated. Transparency exhibited significant correlations with precipitation and retention time, as well as the relative abundance of zooplankton (p<0.01), suggesting that a change in the retention time due to precipitation can alter CWP. Data collected before and after CWP occurrence were analyzed using paired t-test to determine variations in CWP occurrence based on the water system characteristics. The results demonstrated that various factors were associated with CWP occurrence in the fluvial-type and lacustrine-type sites. The correlation between zooplankton biomass and transparency was stronger in the lacustrine-type sites than in the fluvial-type sites. The lacustrine-type sites, where cladoceran emergence is common and is associated with long retention times, favored CWP occurrence. The results suggest that lacustrine-type sites, which are conducive to zooplankton development and have relatively long retention times, enhance CWP occurrence. Furthermore, CWP occurrence was notable in spring, and the present study revealed that site-specific CWP could occur throughout the year, regardless of the season.

• (The) Research of the performance art and culture
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• no.32
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• pp.701-738
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• 2016

The Geomungo(거문고) is a instrument of Gogureoy(高句麗). The instrument had covered a lot of Korea, so it have become a important musical instrument in Korea. Hayasi Genjo(林謙三), Japanese scholar, had maintained his opinion that the Geomungo of Gogureoy is the Wagonghu(臥??), and the Geomungo was formed later, the record of Kimbusik, wrighter of the History of Three Kingdom(三國史記), was incredible. Lee-Hyegu refuted his hypothesis because the introduction on the Wagonghu of Japan have been inaccurate. Since then, many scholars of Korea have studed on the Geomungo of Gogureoy. But their study of the Geomungo was inclined to the topic, relation of the Geomungo and the Wagonghu, or the Wagonghu, the origin of the Geomungo. And They have thought that the record of Kimbusik's was truth. Kimbusik had recorded that Wangsanak(王山岳) had made the Geomungo from the Chilheoyn-Geum(七絃琴, Seven stringed Zither. 古琴). But the Geomungo was different from Geum(琴), but similar to Wagonghu. Many ancient tomb have been unearthed in the old land of Gogureoy, and the were many tomb painting of Gogureoy Geomungo. They were many different style, the form, the size, the number of strings and the position of the musician. So I think that many various type of the Geomungo had been exsited in Gogureoy they had become a prestyle of the Geomungo. The Geomungo was originated from the Wagonghu, its form was similar to the Geomungo. The many scholars considered that it is truth, the Wagonghu was handed down from China, and was spreded to Japan. But there were the Wagonghu in the early Joseon(古朝鮮), The song of the early Joseon, Gongmudohaga(公無渡河歌). The song was accompanied by the Wagonghu. We can read off, at the Song, the Wagonghu had exsisted in the early Joseon. So I think cautiously on that point, the Wagonghu of the Early Joseon was old than that of China, and thd Geomungo of Gogureoy was originated from the Wagonghu of the Early Joseon.

• Korean Journal of Remote Sensing
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• v.34 no.5
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• pp.763-775
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• 2018

In this study, the effects of wind fences on the dispersion of the particles emitted from a constructing site located in the building-congested area in Busan, Korea, using geographic information system (GIS) and a computational fluid dynamics (CFD) model. We averaged the wind speeds observed for 10 years at the Busan automated synoptic observing system (ASOS) and we used the averaged wind speed as the wind speed at the reference height (10 m above the ground level). The numerical simulations were performed for 16 inflow directions, before and after the construction of wind fences with the heights of 5 m and 10 m (total 48 simulations). The detailed flows were analyzed for the northeasterly and south-southwesterly cases which predominantly observed at the Busan ASOS. In the northeasterly case, high concentration appeared at the elementary school next to the construction site due to transport by the airflow coming from the northeast. In the 5-m wind fence case, the wind speeds were slightly weaker and the spread of the fugitive dust was slightly less than those in the no wind fence case. In the 10-m wind fence case, the dust concentration at the elementary school has the maximum reduction of 37%. In the south-southwesterly case, the flow pattern became complicated in the construction site due to the terrain and buildings. Fugitive dust was stagnant at the south side of the construction site but rather spread to the north, increasing the concentration at the elementary school. After the wind fence was built, the concentrations inside the construction site became high as the wind speeds decreased inside, but, the concentrations in the elementary school rather decreased.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1083-1087
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• 2006

과거 50 년 동안 국내 보 설치 수는 매년 증가하여 왔으나, 그 증가비율은 근래 들어 감소하는 추세로, 이는 보 보다는 용수공급능력이 큰 양수장, 저수지 등 타 시설물에 의존하는 것으로 판단 할 수 있다. 더욱이 인구의 도시 집중화에 따른 농경지의 도시화, 경작 방식의 변화에 의한 비닐하우스 단지로의 변화, 시설의 노후화 등으로 매년 $50{\sim}150$개 정도의 보가 폐기되고 있다. 그러나 이렇게 폐기되는 보는 하천에 그대로 존치되어 하천생태통로의 단절, 수질악화, 수변 서식처 악화 등의 문제를 지속적으로 야기 시키고 있다. 실험은 문산천 검전보, 안양천 안양대교보, 기철거된 경안천 무명보에서 자연시료를 채취하여 실행 하였다. 문산천 검전보는 하천환경이 안정되고 양호한 대조구간으로 선정하였다. 안양 대교보는 도심화로 인하여 원기능을 상실하였으며 수차례에 걸친 개수가 이루어졌고 수년전까지만 해도 러브보로 인한 수질정화장치가 있었으나 효능이 약화되어 철거할 계획을 가지고 있는 것으로 알려져 있다. 경안천 무명보는 현재는 완전 철거된 상태이다. 경안천 무명보는 기 철거된 보의 대조구간으 로 선정하였다. 보 상류의 수질 오염도가 높은 것은 정체구역에 의한 용존산소 부족과 오염저니에 의한 것으로 판단되므로, 각각의 대상보의 퇴적물 오염도를 조사하였다. 각각의 조사 지점은 검전보의 경우, 만장교를 최상류 지점으로, 검전보 상/하류, 광탄교를 최하류 지점으로 선정하여, 총 4 지점에서 채취했으며, 안양대교보의 경우 최상류지점, 보 상/하류 지점으로 총 3지점, 무명보의 경우 보 상/하류로 총 2 지점에서 채취했으며, 실험은 $\ulcorner$Soil Method$\lrcorner$에 준하여, 각각 입도분포, 함수율, 강열감량, COD, T-N, T-P 등을 시행하였다. 문산천 검전보 퇴적물 오염도 조사 결과, 강열감량, COD, T-N, T-P 항목에서 보 상류가 보 하류에 비해 높게 나타났으며, 각각 하류에 비해 상류가 30.76%, 16.69%, 73.13%, 18.91% 더 높게 나타났다. 안양대교보 퇴적물 조사 결과, 검전보와 마찬가지로, 강열감량, COD, T-N, T-P 항목에서 보 상류가 보 하류에 비해 33.33%, 9.23%, 24.78%, 18.56% 높게 나타났다. 기 철거된 무명보의 경우, 무명보 상류, 무명보 하류 2개 지점을 채취하였으며, 강열감량, COD, T-N 항목에서 보 상류가 보 하류에 비해 18.75%, 412.6%, 25.75% 높게 나타났다. 퇴적물 조사 결과, 강열감량, COD, T-N 항목에서 검전보, 안양대교보, 무명보 모두 보 상류의 오염도가 높게 나타났으며, 무명보를 제외한 검전보, 안양대교보는 T-P 항목에서도 보 상류의 오염도가 높게 나타나, 보 상류의 퇴적물 오염농도가 심화된 것으로 나타났다. 그러나 기철거된 무명보의 경우, 강열감량, COD, T-N, 항목에서 보 상류가 높게 나타났으나, 철거되지 않은 검전보나 안양대교보에 비해 그 차이가 크지 않은 것으로 나타났다.

• Journal of Korean Society of Transportation
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• v.20 no.3
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• pp.17-30
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• 2002

Incident duration prediction is one of the most important steps of the overall incident management process. An accurate and reliable estimate of the incident duration can be the main difference between an effective incident management operation and an unacceptable one since, without the knowledge of such time durations, traffic impact can not be estimated or calculated. This research presents several multiple linear regression models for incident duration prediction using data consisting of 384 incident cases. The main source of various incident cases was the Traffic Incident Reports filled out by the Motorist Assistant Units of the Korea Highway Corporation. The models were proposed separately according to the time of day(daytime vs. nighttime) and the fatality/injury incurred (fatality/injury vs. property damage only). Two models using an integrated dataset, one with an intercept and the other without it, were also calibrated and proposed for the generality of model application. Some findings are as follows ; ?Variables such as vehicle turnover, load spills, the number of heavy vehicles involved and the number of blocked lanes were found to significantly affect incident duration times. ?Models, however, tend to overestimate the duration times when a dummy variable, load spill, is used. It was simply because several of load spill incidents had excessively long clearance times. The precision was improved when load spills were further categorized into "small spills" and "large spills" based on the size of vehicles involved. ?Variables such as the number of vehicles involved and the number of blocked lanes found not significant when a regression model was calibrated with an intercept. whereas excluding the intercept from the model structure signifies those variables in a statistical sense.

• Journal of Korean Home Economics Education Association
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• v.17 no.4 s.38
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• pp.1-26
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• 2005

The Purpose of this study was to investigate the eating habits, nutrition and dietary fiber intakes of middle school students from urban areas, Jinju city and rural areas, Hadong and Namhae Gun in Gyeongnam province. Data were collected by using a survey questionnaire. The result of this study are as follows: In the respects of eating habits, the eating habits of girl students ware worse than those of boy students Regardless of region and subjects, the intakes of energy, calcium, iron, riboflavin, dietary fiber were poor. In all the regions the intakes of dietary fiber was far less than $20\~25g$ of daily intakes level. Mental education should also be emphasized to form teenagers' self-identity and the sense of value. Also, the nutritionists of each school should try to focus on the composition of group meals containing fish, vegetables, Kimchi and boiled rice and cereals, not satisfying with the group meals centered on hygiene. Health and nutrition depends on the food people take, teenagers' health is the basis of their future health. The continuous study about teenagers' eating habits and dietary fiber needs to be emphasized.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.914-921
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• 2017

The experimental research on a high-altitude environment simulation of space launch vehicle is important for securing independent technologies with launching space vehicles and completing missions. This study selected an altitude of 65 km for the experiment environment where it exceeded Mach number of 6 after the launch of Korean Space Launch Vehicle(KSLV-II). Shock tunnel was used to replicate the flight condition. After flow establishment, in order to confirm aerodynamic characteristics and normal and oblique shockwaves, the flow verification was carried out by measuring stagnation pressure and heat flux of a forebody model, and shockwave stand-off distance of a hemispherical model. In addition, a shock-free technique to recover free-stream condition has been developed and verified. From the results of the three verification tests, it was confirmed that the flow was replicated with the error of about ${\pm}3%$. The error between the slope angle of inclined shockwave of the scaled down transition section model using the shock-free shape and the slope angle of the horizontal plate model, and between the theoretical and the experimental value of the static pressure of the model were confirmed to be 2% and 1%, respectively. As a result, the efficiency of the shockwave cancellation technique has been verified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.3
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• pp.575-583
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• 2017

Various types of flow patterns around the stepped weir and spillway, such as the skimming flow over such structures and the wave-type flow with a standing undular hydraulic jump and roller downstream of the structures, are developed in open channels. Unsteady three-dimensional numerical simulations are carried out using a hybrid RANS-LES turbulence modeling approach and the volume of fluid method for resolving free surface fluctuations to represent the turbulent flow including the skimming flow and wave-type flow over a stepped weir installed in a rectangular channel. The comparison of numerical results with an existing experimental measurement reveals that the present numerical simulations reasonably well reproduce the turbulent flow passing the stepped weir, in terms of time-averaged velocity profiles at selected locations downstream of the weir, flow topology characterized by the wave-type and skimming flows, the maximum height and length of the standing wave and the length of reattachment of recirculating zone. The numerical result further elucidates the distinct flow behaviors of the wave-type and skimming flow by presenting instantaneous intense variations of free surface and velocity vectors, the distributions of Reynolds shear stress and turbulent kinetic energy and three-dimensional complex features of coherent structures and total pressure distribution.