• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.5
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• pp.452-460
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• 2008

Anti-foaming agents and foam fences have been used to remove the foam at the outfall of power plants, but there are some problems as consumption of maintenance costs and insufficiency of effect. Therefore, development of the methods how to remove the foam by stable coastal structure has been required. In this study, numerical simulation of air entrainment was carried out to design the submerged outlet structure for reducing foam using curtain walls. The air entrainment rate and the discharge of entrained air change according to the shape of weir and curtain wall. Hence, it is necessary to design the optimum section through comparison of each case. The optimum section which has the maximum rate of foam reduction was determined by the simulation results. In addition, it was found that the flow velocity at the submerged outlet is to be smaller than 1 m/s and the submerged depth of curtain wall is to be taller than height of the submerged outlet section.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.98-98
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• 2011

중소규모 하천에서 많이 설치되어 있는 경사형보를 대상으로 하류부 세굴에 대한 수리모형실험과 수치모의를 통하여 경사형보 하류부 세굴특성과 세굴영향인자들에 대한 민감도 분석을 실시하였다. 수리모형실험은 폭 0.8m, 길이 20m의 가변경사 직선 개수로에서 1 : 2(H/L)경사를 가지는 경사형보의 높이, 월류수심, 하류부 수심 변화에 따른 최대 세굴심과 세굴길이의 변화를 관측하였고, 수치모의는 유사이동 모의가 가능한 3차원 수치모형인 FLOW-3D를 이용하여 경사형 보의 경사 변화에 따른 하류부 세굴특성을 모의하였다. 수리모형실험 결과 최대 세굴심 및 세굴길이에 가장 영향을 크게 미치는 인자는 월류고이며, 하류부 수심은 최대 세굴심과 세굴길이의 감소효과 뿐만 아니라 세굴공의 형상에도 영향을 미쳤다. 낙하류의 유입 각도가 예연보에 비하여 작은 경사보는 예연보에 비하여 수평방향 유속이 상대적으로 증가하여 세굴길이가 증가하였으며 이로 인하여 세굴공 하류부 천이영역의 사면경사가 상대적으로 완만하게 형성되었다. 세굴공의 상류부에 재순환 영역이 발생되어 천이영역에서 이송되는 유사의 최대세굴심 발생 위치에 퇴적되는 현상을 방해하며 세굴공의 모양은 완전히 발달된 이중(double) 세굴공을 생성하였으며, 특히 낙하류의 유입각도와 하류부 수위의 영향으로 하류수심($h_t$)과 낙차고(H)의 비($h_t/H$)가 1.0 미만인 경우에 이중(double) 세굴공이 발생하였다. 경사형보의 경사각 영향에 따른 하류부 세굴 영향은 3차원 수치모형을 이용하여 모의하였으며, 경사각을 1V/2H, 1V/3H, 1V/4H로 변화시키며 수치모의를 수행하였다. 수치모의 결과 경사각이 증가할수록 최대 세굴심은 증가하는 경향을 보이고 그에 따른 증가율은 감소하였다. 보 높이, 월류고, 하류부 수심, 경사각 변화에 따른 세굴심의 변화는 상대민감도 방법을 이용하여 비교하였으며 주요 영향인자에 대한 민감도비는 월류고가 보 하류부 세굴에 가장 큰 영향을 미치고, 경사각, 보 높이, 하류부 수심 순이다. 특히 보 하류부의 수심은 음의 민감도를 보이며, 이는 보 하류부 수심이 증가할수록 세굴심이 감소하는 것을 의미한다. 추후 보완 실험 및 수치모의를 추가 활용한다면, 경사형보 하류부 물받이 및 하상보호공 설계를 위한 정량적인 기초자료를 제공할 수 있을 것으로 판단된다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.1
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• pp.33-41
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• 1996

In order to obtain the most favourable classification system for fishing gears, the problems in the existing systems were investigated and a new system in which the fishing method was adopted as the criterion of classification and the kinds of fishing gears were obtained by exchanging the word method into gear in the fishing methods classified newly for eliminating the problems was established. The new system to which the actual gears are arranged is as follows ; (1)Harvesting gear \circled1Plucking gears : Clamp, Tong, Wrench, etc. \circled2Sweeping gears : Push net, Coral sweep net, etc. \circled3Dredging gears : Hand dredge net, Boat dredge net, etc. (2)Sticking gears \circled1Shot sticking gears : Spear, Sharp plummet, Harpoon, etc. \circled2Pulled sticking gears : Gaff, Comb, Rake, Hook harrow, Jerking hook, etc. \circled3Left sticking gears : Rip - hook set line. (3)Angling gears \circled1Jerky angling gears (a)Single - jerky angling gears : Hand line, Pole line, etc. (b)Multiple - jerky angling gears : squid hook. \circled2Idly angling gears (a)Set angling gears : Set long line. (b)Drifted angling gears : Drift long line, Drift vertical line, etc. \circled3Dragged angling gears : Troll line. (4)Shelter gears : Eel tube, Webfoot - octopus pot, Octopus pot, etc. (5)Attracting gears : Fishing basket. (6)Cutoff gears : Wall, Screen net, Window net, etc. (7)Guiding gears \circled1Horizontally guiding gears : Triangular set net, Elliptic set net, Rectangular set net, Fish weir, etc. \circled2Vertically guiding gears : Pound net. \circled3Deeply guiding gears : Funnel net. (8)Receiving gears \circled1Jumping - fish receiving gears : Fish - receiving scoop net, Fish - receiving raft, etc. \circled2Drifting - fish receiving gears (a)Set drifting - fish receiving gears : Bamboo screen, Pillar stow net, Long stow net, etc. (b)Movable drifting - fish receiving gears : Stow net. (9)Bagging gears \circled1Drag - bagging gears (a)Bottom - drag bagging gears : Bottom otter trawl, Bottom beam trawl, Bottom pair trawl, etc. (b)Midwater - drag gagging gears : Midwater otter trawl, Midwater pair trawl, etc. (c)Surface - drag gagging gears : Anchovy drag net. \circled2Seine - bagging gears (a)Beach - seine bagging gears : Skimming scoop net, Beach seine, etc. (b)Boat - seine bagging gears : Boat seine, Danish seine, etc. \circled3Drive - bagging gears : Drive - in dustpan net, Inner drive - in net, etc. (10)Surrounding gears \circled1Incomplete surrounding gears : Lampara net, Ring net, etc. \circled2Complete surrounding gears : Purse seine, Round haul net, etc. (11)Covering gears \circled1Drop - type covering gears : Wooden cover, Lantern net, etc. \circled2Spread - type covering gears : Cast net. (12)Lifting gears \circled1Wait - lifting gears : Scoop net, Scrape net, etc. \circled2Gatherable lifting gears : Saury lift net, Anchovy lift net, etc. (13)Adherent gears \circled1Gilling gears (a)Set gilling gears : Bottom gill net, Floating gill net. (b)Drifted gilling gears : Drift gill net. (c)Encircled gilling gears : Encircled gill net. (d)Seine - gilling gears : Seining gill net. (e)Dragged gilling gears : Dragged gill net. \circled2Tangling gears (a)Set tangling gears : Double trammel net, Triple trammel net, etc. (b)Encircled tangling gears : Encircled tangle net. (c)Dragged tangling gears : Dragged tangle net. \circled3Restrainting gears (a)Drifted restrainting gears : Pocket net(Gen - type net). (b)Dragged restrainting gears : Dragged pocket net. (14)Sucking gears : Fish pumps.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.7
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• pp.536-543
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• 2011

In order to find the best design of artificial stream for the riverbed filtration in multi-purpose filtration pond, a mathematical model was developed employing the energy line and the Manning's formula and was analyzed by the Euler's technique. Various design factors were investigated through scenario analyses of the artificial stream using the model. Results showed that the appropriate slope of the stream bottom was 2/10,000 and the appropriate infiltration rate at the streambed was $2.5m^3/m^2-day$ for the pond with the area of 100 ha, and that the Manning's roughness coefficient in this case was expected to be about 0.026 and the maximum water-depth was less than 1m. It was also shown that the longer the artificial stream the more advantageous it became for the riverbed filtration. Furthermore, results showed that it was not an efficient way to prevent clogging of the streambed by increasing the flow velocity of the stream and that the performance was higher near a weir with a large head drop.

• The Journal of the Korea Contents Association
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• v.18 no.8
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• pp.469-482
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• 2018

This research has developed the criteria and index for systematically and objectively assessing the quality of river water by fixing the various factors that affect Gyeongin ARA waterway's water quality through analysis with the Delphi Technique and analytic hierarchy program (AHP) Method. Based on the results, the highest criteria are, in order of importance, physical and environmental factors 28%, administrative factors 26%, natural fixed factors 26% and finally, cultural and social factors 20%. The three dimensions of the criteria show that for the internal physical and environmental factors, the most important are the loss of self-purification capacity, and the external factors are Gulpocheon and the sludge deposit due to Gyulhweon-weir the bridge. The facility factor in management was affected by the coagulation and waste water disposal facilities. The problem for the policy and institutional factors was seen in the regulatory area. The aquatic ecology/ point pollution source for the natural fixed factors show that it is due to the polluted water of Gulpo-cheon and the living environment/ non-point pollution source is shown through the inflow water from other rivers. Cultural and social factors show that the economical causes were due to the cargo and passenger flight operations and the external factors of having a lack of sewage treatment equipment have an importance effect. In order to estimate the order of priority through logical evidence and objectivity, future research must be continued on the evaluation indexes to measure the specific methodology and technique needed to improve the Gyeongin ARA Waterway.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.12
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• pp.821-827
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• 2014

The 4major river project has caused changes in flow and water quality patterns in major rivers in Korea including the Nakdong River where several toxicant release accidents have had occurred. Three dimensional hydrodynamic model, the Environmental Fluid Dynamics Code (EFDC), was applied to evaluate the effect of geomorphological change of the river on the advection and dispersion patterns of a conservative toxic pollutant. A hypothetical scenario was developed using historical data by assuming a toxic release from an upstream location. If there is a toxic release at the Gumi Industrial Complex, the toxic material would be detected after 2.22 and 9.83 days at Chilgok and Gangjung weir, respectively, in the new river system. It was estimated that they took at least 12 times longer than those with the river conditions before the project. Effect of relocation of intake towers for Daegu Metro City to upstream of Gumi City was also evaluated using the developed modeling system. It was observed that hydraulic residence time would be increased due to decreased flow rate and thus due to lowered water level. However, peak concentration differences were found to be about 2% lower in both places due to increased dispersion effect after the relocation.

• Journal of Environmental Policy
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• v.14 no.4
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• pp.45-61
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• 2015

The river environment in Korea has changed significantly after the completion of the Four Major Rivers Project due to the outdated river management methods and thus, it is necessary to modify the current river management process. A typical example of this management is dredging but it is a method that usually results in socio-environmental side effects. Therefore, in order to minimize the socio-environmental impacts of dredging, Korea is currently applying the Environmental Windows, a management practice currently being used in the United States that eliminates the risk of potentially harmful impacts of dredging. The use of statistical methods was suggested to address the issue of data insufficiency and this methodology was applied in the downstream part of the Gangjeong-Goryeong weir located within the Nakdong river basin. The results show that when performing a month of dredging, the optimal period is March whereas the optimal month to start dredging is August in case of an eight-month dredging project. If Korea's flood season is also considered for an eight-month dredging process, then October is the optimal month to start dredging. Non-structural methods such as the Environmental Windows reduce maintenance costs and also bring only short-term side effects to the environment, as opposed to structural methods such as the development of environmentally-friendly dredging machine. Given that few studies have explored this topic in Korea, the findings and suggestions could serve as basic data in studying river dredging in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.2
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• pp.113-128
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• 1990

In recent years, various types of coastal protection scheme have been studied around the coastal region. Among them, so-called zonal protection systems are being watched with interest from various points of view. In this paper, wave overtopping rate from overflowing the vertical seawall is investigated by conducting two dimensional model on the horizontal bed experiment. Hereafter this system is referred to as a artificial reef system. One is the foundation to control wave height near the surfzone and the other is function to prevent coastal disaster by suppressing net overtopping rate. The main results obtained in this study are summarized as follows. 1) Wave attenuation taken place on the artificial reef can be predicted numerically by using energy dispersion model due to wave breaking proposed by Battjes. 2) To evaluate the wave overtopping rate from a vertical seadike on various coastal constructions by weir model, a numerical procedure for prediction of overtopping is confirmed.

• Korean Journal of Ecology and Environment
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• v.46 no.2
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• pp.192-204
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• 2013

Fish community structure and inhabit status of endangered fish species were investigated during April to November 2011 in Baebong Stream, Gangwon do, Korea. The number of fish species inhabiting the upper section (Stations 1~3, 5) was 14 and the stream bottoms were mostly composed of cobbles and boulders (Aa-type). Meanwhile, the number of fish species inhabiting the lower section (Stations 4, 6, 7) was 26 and the stream bottoms were mostly composed of pebbles, cobles and sand (Bb-type). A total of 26 species belonging to ten families were found in the stream during the survey period. The dominant and subdominant species were Rhynchocypris steindachneri (31.1%) and Squalidus multimaculatus (13.3%), respectively, and others such as Pungitius kaibarae (11.0%), Zacco koreanus (7.8%), Misgurnus anguillicaudatus (7.0%), Iksookimia pacifica (5.5%) and Z. platypus (5.3%) were followed in the order. Four species of Squalidus multimaculatus, Z. koreanus, I. pacifica and Liobagrus andersoni were endemic to Korea. And, Lethenteron japonica, L. reissneri, Pungitius sinensis and Cottus hangiongensis were endangered fish species in this stream. Oncorhynchus keta, L. japonica and Tribolodon hakonensis were anadromous species, and Plecoglossus altivelis was an amphidromous species. The similarity index based on species composition and abundance clearly divided the fish community structure of the Baebong Stream into two sections fragmented by a weir installed into the stream. It is necessary to install a fish ways on the weirs for a fish migration and movements.

• Korean Journal of Ecology and Environment
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• v.53 no.3
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• pp.255-264
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• 2020

The use of fishway has been investigated up to 2~9 years, continuously each month and over the long term that installed in 6 domestic rivers. The fish's use of fishway has been investigated as direct collection by trap in exit section of the fishway. The population structure of fish using 6 fishway and the fish that live in the river showed difference. About 2 to 7 species of fish took possession of more than 80% of total use of fish in fishways. This seems to be not the results of attraction flow in fishway but specialized result of physiology characteristic followed by species of fish. In addition, the distribution of fish species using fishway was different with the fishways installed in river. This difference seems to be consequence of the place that of the river and fishway types. Generally, the fish species were less and had high ratio of home migratory fish in vertical slot type fishway, which shows relatively fast velocity of water flow. This analysis result of major fish species using fishway can be used in planning fishway and to choose major targeted species for the planning.