• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.2
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• pp.76-93
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• 2013

The hydrodynamics in the Youngsan River Estuary has changed due to coastal developments such as the estuary dam and two tidal barriers. As the freshwater discharge is artificially controlled, the circulation pattern is different from those of natural estuaries and the river-born sediment supply is restricted. 3D numerical modeling system EFDC was applied to investigate the sediment transport pattern and budget in summer with river floods. The real-time driving forces and the fluvial sediment discharges from the watershed modeling were assigned for the simulation period. The size classes of sand, silt and clay were adopted based on the grain-size distribution of bottom sediments. The modeling results were calibrated and validated with the observed tides, tidal currents and suspended sediment concentrations. The suspended sediments are transported to the offshore at surface layer, whereas upstream toward the dam at mid- and bottom layers in August 2011. The characteristic estuarine circulation induced by the freshwater discharge from the dam, causes the deposition of silt-sized sediments on the whole and the sustained suspension of clay-sized sediments.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.462-466
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• 2006

Close-to-nature stream evaluation is one of the processing to make the streams over in order to keep them natural. It is integral to evaluate and make an accurate analysis of them on the purpose of maintaining streams healthy. For many instances, there are, stream organization evaluation for restoration by German government, evaluation for ecosystem protection in natural preserves by New Zealand government, and stream-view evaluation for restoration by Britain government so on. In case of the country there are analysis and evaluation of stream physical organization by Cho, Yong-hyun, Close-to-nature stream evaluation for restoration by Kim, Dong-chan, evaluation of stream properties in korea by Park, Bong-jin. Close-to-nature evaluation by Lim, Chan-uk, that is advanced version of Park, Bong-jin's, shows form of stream including waterway curve, sand bar, diversity of flow, river bed material, diversity of minor bed, minor bed bank protection works, bank protection material. It also does environment of stream including side of minor bed vegetation, width of surface of the water/width of the river etc.. By the way, this evaluation does not have free access to apply those details above in the field, it often happens that you get various outcome from the one spot. so you must need more realistic testing method to obtain more accurate data. Remote sensing method is highly recommended because this is very useful for collecting realistic data of vegetation index. what is more, it can not only scan even the minimum area within its resolving power but also do obtain data anytime. Vegetation index indicates Ratio vegetation index, Normalized difference vegetation index, Soil adjusted vegetation index, Atmospherically resistant vegetation index etc.. The research is focusing on Cheokgwa stream which is the branch of Taehwa river and shows 19 sectioned Close-to-nature stream performed according to the method by Lim, chan-uk. Besides let you know vegetation index came from image data of satellite landsat 7 with the variation of buffering area, of the day 9. may. 2003. Of all, the outcome 0.758 at 200m buffer-zone of NDVI was the best we have got so far.

• Journal of the Mineralogical Society of Korea
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• v.31 no.4
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• pp.257-266
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• 2018

East China Sea (ECS) is known to be supplied with large amounts of sediments form Huanghe, Changjiang and various rivers in Korea. Many studies have been conducted to identify the effects of rivers and deposition process of ECS, but no consensus has been reached. In this study, clay minerals, rare earth elements (REEs) and grain size were analyzed to study the provenance and sedimentation environment of core 99MAP-P63 in ECS. Clay mineral contents of 99MAP-P63 are abundant in order of illite, chlorite, kaolinite, and smectite. The provenance of 99MAP-P63 sediments using clay minerals is interpreted as the Changjiang regardless of depth. As a result of REEs analysis, 99MAP-P63 sediments are very similar to Chinese rivers sediments. Therefore, the provenance of 99MAP-P63 is Changjiang, and the influence of Korean river seems to be insignificant. 99MAP-P63 sediments are generally classified as sandy silt, but the top of the core is divided into sand with a sand contents of 85 %. Compared with surrounding cores, sandy silt sediments arecorresponded to the low stand stage when sea-level was low, and the sediments were thought to have been supplied directly through the paleo-Changjiang. Sandy sediments in uppermost of core are corresponded to transgressive stage. Although distance from estuary was increased due to sea-level rise, it was possible to supply coarse sediments due to high bottom stress, and the paleo-Changjiang sediments deposited in study area were re-deposited.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.1
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• pp.67-73
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• 2012

Coastal erosion and its impact on human activities as well as the economic damage and environmental conservation of coastal area is one of major concern in the national policies. In this study, we conducted physical investigations to evaluate effects of erosion in the Geojin beach, which is located nearby the Geojin Port, for a detecting of shoreline change and beach cross-sectional area. The results showed that significant coastal erosion of the Geojin beach has occurred by the complex resources of natural factor, such as rising sea level, storm surges, high wave, and man-made construction. Especially, due to the sand supplement from Jasan river, the section which is nearby the estuary of Jasan river is maintained as a stable beach, whereas beach erosion of the other site in GW04 section has been increased indeed. Therefore, we suggest that it is need to continuous monitoring using DGPS and various surveying techniques to prevent beach erosion onto the GW04 section.

• Advances in concrete construction
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• v.5 no.3
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• pp.201-219
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• 2017

With the rapid growth in construction sector, it becomes all the more important to assess the amount of Construction and Demolition (C&D) waste being generated and analyze the practices needed to handle and use this waste before final disposal. This serves waste management and disposal issues, paving way to waste utilization in construction industry from the sustainability point of view. C&D waste constitutes a major bulk of total solid waste produced in the world. In this work, an attempt is made to study the performance of concrete using water soaked Recycled Coarse Aggregates (RCA) in replacement levels of 0%, 25%, 50%, 75% and 100% to Natural Coarse Aggregates (NCA). Experiments were designed and conducted to study the performance of RCA based concrete. Further suitable performance enhancement techniques to RCA based concrete were attempted, to achieve compressive strength at least equal to or more than that for no RCA based concrete (control concrete). Performance enhancement study is reported here for 50% and 100% RCA based concretes. All four techniques attempted have given favorable results encouraging use of RCA based concretes with full replacement levels, to adopt RCA based concrete in structural applications, without any kind of concern to the stake holder. Further attempts have also been made to use Recycled Fine Aggregates (RFA) with appropriate modifications to serve as fine aggregates in mortar and concrete. Using RFA blended with river sand fractions as well as RFA with Iron Ore Tailings (IOT) fractions, have given good results to serve as fine aggregates to the extent of 100% replacement levels in mortars and concretes.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.12a
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• pp.79-79
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• 2020

Halophyte is a plant that has evolved to grow well in salty places, and is mainly distributed in coastal wetlands, sand dunes, salt fields, and reclaimed lands in tidal flats and river estuaries. Because it grows in the soil where seawater enters and exits, it is very abound in natural minerals and produces certain metabolites to survive sustainably in the surrounding environment. In this study, anti-inflammatory studies were conducted using 15 kinds of halophyte to secure data on halophytes of infinite value as functional materials. The aim of this study was to select a group of halophytes that regulate iNOS expression, which is involved in the secretion of inflammatory cytokines and nitric oxide production in LPS-induced macrophages. Among the 15 species of halophyte, except for Triglochin maritimum, Suaeda japonica, and Carex pumila, NO production was reduced in 12 species of halophytes, and 7 species of halophyte (Suaeda asparagoides, Artemisia fukudo, Spergularia marina, Aster tripolium, Suaeda australis, Atriplex subcordata, Calystegia soldanella) significantly decreased the expression levels of TNF-α and IL-1β.

• Korean Journal of Ichthyology
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• v.36 no.3
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• pp.240-252
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• 2024

The distribution status of the nature monument species, Hemibarbus mylodon, was investigated from 2021 to 2024 in Geumgang River and Mujunamdae Stream (a tributary of the Geumgang River). In 2021 to 2023, five individuals from Gemgang River upstream were collected by Geumsan-gun, Chungchangnam-do. In 2021 to 2024, 1,592 induviduals juvenile from seven sites were collected by surveying 15 sites from Mujunamdae Stream. The main habitat of juvenile was about 0.3~1.5 meters water deep, 0.14~0.16 meters per second in the middle-upper stream of rock and sand bottom with slow rapids and pools. The age groups for H. mylodon estimated by the frequency distribution of total length in after spawning season (May) to October indicated the 10~65 mm is 0-year old, 75~90 mm is 1-year old group. In addition, over the 120 mm group is 2-years old, the 190~250 mm is more than 3-years old group. In 2024, we identified 35 spawning place from six sites were sites were collected by surveying 15 sites. Spawning place at the river bottom were top of the rapids, 30~60 cm (mean 48.2 cm) water deep, and the place was covered with stone and gravel, water velocity was 0.13~0.34 (mean 0.25 m/sec) meter per second. The spawning place size of the gravel piles was as follows: length 35~48 cm (mean 40.7 cm), width 25~37 cm (mean 34.5), and height 5~12 cm (mean 8.6 cm). Thus, H. mylodon reintroduced to Mujunamdae Stream has successfully settled down and increase in abundance within the natural habitat.

• Korean Journal of Ichthyology
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• v.26 no.2
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• pp.99-111
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• 2014

Community structure of fish and inhabiting status of natural monument and endangered species, Cobitis choii were investigated in the Baekgok Stream, a tributary of the Geum River drainage system of Korea from May to November 2012. Ten-15 fish species inhabited upper stream (St. 1~St. 3) with a Aa or Aa-Bb river type composed of mostly pebble and cobble bottoms. 15~21 species did middle stream (St. 4~St. 5) with Aa or Aa-Bb type composed of mostly cobble, boulder and pebble bottoms. Nine species did Reservoir Baekgok (St. 6) with composed of mostly mud bottoms, and Seven species did Reservoir Baekgok outflow (St. 7) with Aa-Bb type composed of mostly boulder and cobble bottoms. And 20~23 species did lower stream (St. 8~St. 9) with a Bb-Bc type composed of mostly cobble and sand bottoms. A total of 35 species belonging to ten families were found in the stream during the survey. The dominant species were in the order of Zacco platypus (34.7%), Pungtungia herzi (9.4%) and Microphysogobio yaluensis (9.0%). Other abundant species included Tridentiger bifasciatus (8.2%), Pseudogobio esocinus (5.9%), Carassius auratus (4.6%), Squalidus chankaensis tsuchigae (3.7%), Rhinogobius brunneus (3.0%). Among residing species, ten (28.6%) species were endemic to Korea, one (Cobits choii) was endangered, and two (Micropterus salmoides and C. cuvieri) were non-indigenous. Natural monument and endangered species, C. choii were only inhabited St. 5, and they are inhabited 30~100 cm in water depth, sand bottom and slowly velocity. Using the mark-recapture method, populations were estimated at $7,838{\pm}6,290$ individuals. Age group in May estimated from total length indicated that the 38~45 mm group is 0 year old, the 46~60 mm group is 1 years old, the 61~80 mm group is 2 years old, and the 81~93 mm group is more than 3 years old. Condition factor (${\times}10^5) was 0.36~0.39 and 0.35~0.38 for female and male, respectively, and they are 13.5% were infected with parasites (digenea). We are discussed the health status, threats and conservation strategies of C. choii in the Baekgok Stream.

• Korean Journal of Ecology and Environment
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• v.50 no.3
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• pp.275-285
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• 2017

To investigate the changes of dominant species of benthic macroinvertebrates according to the changes of temperature and precipitation, we surveyed twenty sites of the main Seomjin River in May and September in 2013 and 2014. The temperature, precipitation, water quality factors and substrate composition, which are important factors in benthos habitat environment, were collected and measured. The average temperature of the Seomjin River increased by $0.2^{\circ}C$ in 2014 compared to 2013, and the temperature increased from upstream to downstream, showing a difference of more than $3^{\circ}C$. Also, the annual cumulative precipitation (ACP) was increased toward low latitude. The temperature of Seomjin River increased more than twice in September ($21.7{\sim}24.5^{\circ}C$) after rainfall compared to May ($7.6{\sim}11.3^{\circ}C$) before rainfall, and CP (cumulative precipitation) increased about 3 times before rainfall (263 mm~287.5 mm) and after rainfall (756.3 mm~882 mm). Due to washing effect by summer precipitation, total number of species and individuals for benthic macroinvertebrates were higher in May than in September. Chironomidae sp. and Choroterpes altioculus were dominated in May, Ecdyonurus levis, Macrostemum radiatum and Choroterpes altioculus were dominated in September. As a result of correlation analysis between community indices and environment factors, it was found that there is a high correlation with boulder and sand among substrate compositions. According to the results of cluster analysis based on temperature, CP and the dominant species of benthic macroinvertebrates in Seomjin River, it was divided into two groups following temperature and CP, and the dominant species and geographical position were reflected and divided into detailed groups.

• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.17-33
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• 2011

Recently, the utilization of recycled aggregates for backfilling a power transmission pipeline trench has been considered due to the issues of eco-friendly construction and a lack of natural aggregate resource. It is important to identify the physical and thermal properties of domestic recycled aggregates that can be used as a backfill material. This paper evaluated thermal properties of concrete-based recycled aggregates with various particle size distributions. The thermal properties of the recycled aggregates and river sand provided by local vendors were measured using the transient hot wire method and the transient needle probe method after performing the standard compaction test. The needle probe method considerably overestimated the thermal resistivity of recycled aggregates especially at the dry of optimum water content because of experiencing disturbance while the needle probe is being inserted into the specimen. Similar to silica sand, the thermal resistivity of recycled aggregates decreased when the water content increased at a given dry density. Also, this paper evaluated some of the existing prediction models for the thermal resistivity of recycled aggregates with the experimental data, and developed a new prediction model for recycled aggregates. This study shows that recycled aggregates can be a promising backfill material substituting for natural aggregates when backfilling the power transmission pipeline trench.