• Korean Journal of Ichthyology
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• v.28 no.3
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• pp.186-191
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• 2016

Distribution status and threatened assessment of endangered species, Pungitius sinensis (Pisces: Gasterosteidae), were investigated from March to October 2015 in Gangwon-do and Gyeongsangbuk-do etc., Korea. During the study period, a total of 854 individual P. sinensis were collected from 21 of 71 sampling stations using skimming nets. P. sinensis appeared in 23 streams during the past 30 years. However, it was only collected in 12 streams. Therefore, its habitats and populations were drastically reduced. The preferred habitat of P. sinensis was pool of the lower stream with lots of aquatic plants. Given these evidences of small occupying areas ($84km^2$) and drastic reduction in its habitats and populations, P. sinensis is considered as an endangered (EN) [B2ab(ii,iii,iv,v)] species based on IUCN Red List categories and criteria.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.406-410
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• 2004

The alkaline phosphatase activity (APA) of two dam reservoirs and inflowing streams were measured monthly in 2000. During summer months in 2001, the vertical profiles of APA and related parameters were also examined in one of the reservoirs. The APA was relatively high during the summer season in the epilimnion while it was almost invariable in the hypolimnion. A small increase in APA was observed at just above the bottom. The APA fluctuation was independent of the concentration of soluble reactive phosphorus. It was assumed that APA is not indicative of the phosphorus availability status. An examination of size-fractionated samples suggested that APA in reservoirs was attached to particles larger than $0.4{\mu}m$, whereas in streams it existed in a dissolved form. There was a positive significant correlation between chlorophyll a concentration and APA in the photic zone. In the aphotic zone, APA correlated positively with the colony count of heterotrophic bacteria, but not with microscopic total bacterial counts.

• Journal of Soil and Groundwater Environment
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• v.17 no.3
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• pp.39-48
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• 2012

Visual MODFLOW, a three dimensional groundwater flow model, was used to analyze effects of a weir construction in an alluvial stream on the nearby groundwater flow system. A hypothetical conceptual model was developed to investigate how the groundwater level and the water budget could change after a weir construction depending on the location of tributary streams. A site example, dealing with the Juksan weir installed in the Yeongsan River, was also demonstrated to predict the effects of the weir construction. Model results show that impacts of a weir construction on the groundwater flow system greatly vary depending on how far a tributary is located and whether it is located downstream or upstream from the weir. Therefore, consideration of the location of tributaries in planning the location of a weir could effectively minimize the impacts of a weir construction on the groundwater flow system. It is also demonstrated that model results are highly dependent upon how the model is dealing with small tributaries and agricultural drainage channels, which can be easily found nearby the main streams, acting as major water bodies for groundwater discharge. The model for the Juksan area shows that the weir construction will change the direction of groundwater flow in some areas, leading to changes of groundwater quality and interaction of the Yeongsan River to the aquifer from a gaining to a losing stream. The model also predicted the areas where rise of groundwater level caused by the Juksan weir could adversely affect plant growth, and thereby suggested installing new drainage channels as a countermeasure to drawdown the groundwater level.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.4
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• pp.341-347
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• 2011

This work studies the performance of an injector for a monopropellant thruster, comparing a conventional and new injector types. The conventional injector consists of 8 nozzles on a convex surface allowing the jet to be diverged. The new injector, we suggested, is an impinging type with nozzle holes on a concave surface. The fuel streams through the nozzle holes are collide at a point on an axial direction, which allow to atomize the liquid streams and to spray more uniformly along circular direction. The performance of the injectors is investigated by using computational fluid dynamics, particle image velocimetry and high speed camera visualization.

• Journal of Environmental Science International
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• v.24 no.8
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• pp.969-980
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• 2015

In order to certificate the distribution and pollution of heavy metal of surface sediments in Nakdong River were collected and analyzed for grain size, water content, ignition loss and heavy metal content. Surface sediments mainly composed of sand(avg. 94.6%) and water content and ignition loss were 20.46%, 1.53% on average. Grain size were relatively fine and organic matter content were relatively high in the Hoichun and Sunakdonggang. Most of heavy metal content(Zn > Cr > Pb > Ni > Cu > Hg) in the Deokcheongang and Sunakdonggang were higher than the other streams. The Igeo were non polluted(less than 0) in all streams and the EF were relatively high in the small stream and PLI were non polluted(less than 1). In addition, organic matter, heavy metal content and pollution were highly correlation with grain size. Surface sediments in study area, heavy metal pollution of the Sunakdonggang were relatively high compared to the other stream but these results were not serious pollution that exceed the sediment pollution evaluation standard of river and lake in Korea and pollution levels adversely affected the majority of benthos were not.

• Journal of KIISE:Databases
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• v.36 no.3
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• pp.235-246
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• 2009

As demands intending to treat an access control on a client side that was conventionally controlled at a server are surged. it needs a way to treat query processing in effective and secure manners in an environment that has limited resources. Because the access control having been previously performed was only focused on safety, there was little effort to consider the access control in terms of efficiency. Researches about security including access control are started as the security issues are cropped up in a recent stream environment. This paper proposes a method for efficient and secure query processing of XML data streams like a PDA and a portable terminal at the client that is in limited resources. Specifically, this study suggests (1) an access control processing that possesses small overhead for attaining a secure result in a limited memory and (2) a way to enhance the performance, finding the parts being capable of optimizing in each processing step for offsetting the overhead caused by an addition of the access control processing. Superiority of the new method was analyzed by experiment.

• Advances in Energy Research
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• v.2 no.2
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• pp.85-95
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• 2014

Small Hydro-Power (SHP) is an environmental friendly technology. Usually hydro power generation projects are viewed as constructing large dams and reservoirs but available new research and engineering techniques have helped hydro power generation without large dams and without large reservoirs. In India, there are several water installations, irrigation dams, canals, streams or running rivers not tapped to generate power. In these cases the existing system and facilities can help in generating power with less investment and time. This area is yet unexplored. Harnessing a stream for hydroelectric power is a major undertaking for the energy crises and the global issues to go green. In this technical note a potential site for mini hydro power plant nearby Shoolini University is identified and examined for the economic feasibility.

• Animal Systematics, Evolution and Diversity
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• v.33 no.4
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• pp.262-266
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• 2017

Flies of the genus Scatella are small and dark-gray, and many species have distinctive whitish spots on their gray wings. Most species are found in damp environment, such as the borders of marshes, seashore areas, swamps, lakes, ponds, streams, and paddy fields. The Korean shore fly genus Scatella Robineau-Desvoidy has been taxonomically noted. A total of five species have been identified: S. calida Matsumura, 1915, S. nipponica Miyagi, 1977, S. obsoleta Loew, 1861, S. paludum (Meigen, 1830), and S. tenuicosta Collin, 1930. This is the first report of S. calida Matsumura, 1915 from Korea. A key to the Korean Scatella species and photographs of the external features have been provided.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.369-370
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• 2015

본 연구는 농경유역 중소하천에서 실측된 유량과 총유사량의 분포특성을 분석하고 이들 간의 관계식을 도출하고자 한다. 유량과 유사량 자료 측정에는 프로펠러 유속계, 전자파 표면유속계와 DH-48, D-74 부유사 채취기 및 BL-84, BLH-84 소류사 채취기를 각각 사용하였다. 4개 하천을 대상으로 국가 지방하천 수로구간의 7개 측점을 선정하고, 2012년 8월부터 2014년 9월까지 유량과 부유사 및 소류사를 각각 측정하였다. 측정결과는 수리특성의 분포분석과 유량-총유사량 간의 관계식을 멱함수 형으로 유도하였으며, 이들 관계식은 수공실무에 유용한 도구로 사용할 수 있을 것이다.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1111-1115
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• 2008

The relative magnitudes of the individual terms of the momentum equation are analyzed and compared by the analytical methods in open channel flow. The temporal variations of each term(local acceleration term, convective acceleration term, pressure force term, gravity force term, and friction force term) are analyzed for the influence factors to runoff expressed by the parameters of the momentum equation, stream slopes and roughness coefficients. The magnitudes of each term vary with the channel characteristics, especially when the roughness coefficients are dominant or for the mild stream slopes the pressure term can not be negligible. As a result of the characteristics of momentum equation in open channel flow, the acceleration terms are very small compared with the other terms. The magnitudes of local acceleration and convective acceleration offsets each other. The peak time of each term except the gravity term coincides with inflection point of the hydrograph rising limb each other.